All these together, pose a formidable challenge of producing affordable electricity with minimum impact to the environment.

Transcription

1 Message by CTO Mr. Debabrata Guha Dear Colleagues, Today, progress is synonymous with urbanization, higher consumption of goods and services, industrialization etc. Per capita electricity consumption is often used as a measure of progress or growth. Unfortunately all the above comes with an adverse impact on the environment, specifically when it comes to fossil fuel based (thermal) power generation. We, as responsible professionals, have to be sensitive towards the environment. "Responsible growth" and not "growth at any cost", has to be our priority. We owe it to our future generations. In the developed countries electricity generation and consumption has reached a level of saturation. In India, we are still way behind the required energy generation (and consumption) to sustain the intended economic growth rate. On personal consumption front, 'electricity for all' is yet some distance away. Therefore, in India we need to add power generation capacity. Coal based power plants will have to be built, as the renewable form of energy has its limitations of predictability and continuity. India being a developing country, electricity should also be available at an affordable cost. All these together, pose a formidable challenge of producing affordable electricity with minimum impact to the environment. This edition of Wattsup, touches on the measures / technologies related to minimizing the adverse environment impact of thermal power generation. In days to come with newer technologies, I am sure more effective measures will be put in place. Happy reading and all the best!!!

2 Message by Chief CE Ms. Anjali Kulkarni Dear Colleagues, One of the greatest problems that the world is facing today is that of environmental pollution, increasing with every passing year and causing grave and irreparable damage to the earth. Power plants, if not designed carefully, are major contributors to environment pollution. Emissions from thermal power plants include sulfur dioxide (SO₂), nitrogen oxides (NOx), carbon monoxide (CO), particulate matter (PM) etc. Tata Power constantly strives for utilizing technologies that can minimize the emissions of these harmful components and protect the environment. Hence, the ninth issue of Wattsup is dedicated to the Environment Protection Technologies. In the technical section of this issue, we present to you a number of technical papers, which will cover various technologies being utilized as well as being studied further by Tata Power, for reducing the environmental impacts like reduction in SOx, NOx, particulate matter etc. We hope these technical articles interest you and provide an update on current developments in this area. In an effort to provide knowledge sharing platforms, the Corporate Engineering Teams have been arranging technical workshops, knowledge sharing sessions etc. Some of the outcomes have been brought out in this magazine under section key highlights. The sections, 'Employee corner' and 'Fun at work' bring to you team's enthusiastic engagement in various organizational initiatives and fun activities. We again bring you a 'Technical quiz' on the topics covered in the current Wattsup issue, which awaits your attention! We have received an overwhelming response from the readers for the Quizzes included in the last two issues. I thank all the readers for their great participation and congratulate the winners of the first three correct entries. I look forward to your active participation this time too! Happy reading!!

3 Technologies for reduction in Particulate Matter from Existing Thermal Power Plant By Sanjay Raut, PE. 1. Preface The Thermal Power Plants using coal as primary fuel face the challenge of suspended particulate matter (SPM) through flue gas. The society felt the illeffects of pollution and therefore the authorities had to tighten the particulate emission within limit. The pollution control legislation keeps on getting stricter continually with the availability of better technology and resource. A need has arisen to bring up the old pollution control equipment to the latest level and the concept retrofitting evolved. The retrofitting concept have revolutionized from the simple Part to Part replacement to renovation, refurbishment, enhancement, upgradation, life extension, total replacement and incorporation of latest techniques of energisation of TR sets for effective dust collection. This article details the various technologies and retrofitting of old pollution control equipment for reduction of SPM. 2. Methods available for capturing SPM There are many methods available for capturing the SPM from the flue gas: Cyclone separators: This technology uses inertial energy of suspended particles to separate them from the medium. Cyclone separators are simple to operate and maintain and do not require any auxiliary power. However, cyclone separators are not effective for capturing fine or sticky particles. Fabric filter (baghouses): This technology uses mechanical filters made of fine fabric to capturing the particles from the flue gas. This technology has very high efficiency (99.9%) for both coarse and fine particles. However, fabric filter requires high maintenance, frequent replacement and high auxiliary power consumption. Fabric material possess fire hazards during operation. Wet scrubbers: This technology is based on the scrubbing of flue gas with spray of water. With addition of chemicals to spray water this technology can be used for SOx control also. Electrostatic precipitators (ESP): Electrostatic precipitators use electrostatic attraction to control particulate matter and can handle large volume of gases at low pressure drops. Electrostatic Precipitators (ESP) is important device used to control the pollution by collecting dust particles present in the flue gases. This technology has efficiency of >=99.5% up to 99.8%. It can capture particles up to 10 microns size, below which it is difficult to capture. To renovate the existing pollution control equipment, following methods are being practiced: Filling the dummy fields (casing without internals were installed at the initial stage) Introducing intermittent charging. Adding series fields to the existing ESPs. Addition of one more ESP pass parallel to the existing ESP. Replacing the internals and adding new internals by increasing the casing height. Introducing bag filter in the existing ESP casings. 3. Present Emission Norms Ministry of Environment and Forest (MOEF) has updated environmental regulations applicable to coal fired thermal power plants effective Dec The brief summary of present and revised norms, as applicable to our power plants, is mentioned below. CGPL (Coastal Gujarat Power Limited) 5x 800 MW Year of Commissioning Param eters Present Norms (mg/nm 3 ) Revised Norms (mg/nm 3 ) 2012 and 2013 SPM Trombay Unit MW 1984 SPM Trombay Unit MW 1990 SPM Maithon Power Limited (2 x U MW) U SPM Jojobera Unit 1 to 3 1x 67.5 and 2x 120 MW U U SPM Jojobera Unit 4 and 5-2 x 120 MW U U U SPM 50 50

4 4. Need for Retrofitting Precipitator is a static, effective dust-capturing device. After a passage of time, the emission is more than what it is supposed to limit. It is acknowledged that the reasons could be one or multiples of the factor outlined below: Change in environmental legislation. Change in fuel properties. Poor quality of fuel, alteration of fuel with respect to design. Change in boiler behaviour. Deterioration of boiler performance, use of multifuel firing, conversion of firing type and change in the plant rating. Degradation of Precipitators performance due to: Poor electrical and mechanical condition like improper gas distribution, unstable operating condition of precipitator, plant beyond serviceable conditions and ineffective maintenance. 5. Basics of Electrostatic Precipitators (ESP) The first patent for ESP was obtained by F.G.Cottrell in the year 1907 with application in chemical industry. The latest ESP have evolved since then. The ESP consists of series of positively charged electrodes (also known as Collecting Electrodes) which are in the form of plates. The negatively charged electrodes also known as Emitting Electrodes, are placed in between two collecting electrodes. The Emitting Electrodes are charged with very high voltage (80 to 110 KV) through Transformers Rectifier set. This high voltage in the Emitting Electrodes with negative pressure prevailing inside the ESP causes ionization of dust/ash particles of the flue gas. The negatively charged ions (ash particles) gets attracted and deposited on the Collecting Electrode. The ash accumulated on Electrodes need to be dislodged periodically. This is achieved by rapping the electrodes based on the magnetic impulse or tumbling hammer system. The ash dislodged from the electrodes is collected in the hoppers below and evacuated periodically. The performance of an electrostatic precipitator is largely influenced by the following parameter like inlet dust loading, resistivity of ash, flue gas temperature, sulphur content in coal, Na 2 O content, moisture content in flue gas etc. Flue gas temperature Resistivity Vs Flue gas temperature Resistivity Vs Na 2 O Resistivity Vs Moisture Content 6. Renovation and Modernization (R&M) of ESP's to address Emission norms Methods for R&M of the existing ESP are mentioned below: 6.1 Renovation of mechanical and electrical system. Filling of dummy fields: A number of earlier precipitator installations have been provided with an added feature of dummy field either at inlet or outlet so that during later stages, these empty sections can be filled with active components to provide additional collection area. Also, anticipating the futuristic tough legislation, many plant owners for the green field application, today specify the present emission with one field out of service per pass. This means, there will always be one extra live field available and this may meet the future emission norms. Introducing intermittent charging: The precipitators installed in the early days were energized with full wave TR sets. Most of the power supplies are provided with automatic spark limit control, which uses SCR phase control to limit the power input to precipitators to the point of sparking. This works well for low resistivity ash whereas there was a deficiency in the performance for high resistivity dusts due to back corona. Increasing the power input beyond the onset of corona power, not only wastes power but also degrades the precipitator emission. The intermittent charging technique block certain cycles and allows current flow for a few cycles to achieve current limit. Its aim is to produce high peak voltages and currents for a short time, while maintaining low average current through the dust layer below the onset of back corona. This automatic optimization process adjusts the charge ratio to eliminate back corona and results in better performance than the conventional waveform. Refurbishment of existing ESP. The existing ESP components are replaced with improved collecting electrodes or discharge electrodes or rapping system.

5 7. R&M of Jojobera Unit 1 ESP The ESP of Jojobera Unit 1 was commissioned in December This ESP consists of 'Two Pass' of capacity 60% each. The design emission from Unit 1 ESP is at 150 mg/nm 3. The performance of the ESP got deteriorated due to ageing of components. The particulate emission norm applicable to Jojobera generating station was revised by MOEF as 75 mg/nm 3 while granting EC (Environmental Compliance) for Unit 5 in the year The Tata Power management has decided to go beyond compliance requirement and adopt stringent norm of 30 mg/nm 3. The necessary work for R & M of Unit 1 ESP includes following: Addition of New stream which is necessary for enhancing the performance of ESP. The ESP was designed for Indian coal with ash content of 45% and inlet dust loading of gm/nm 3. Due to deterioration in coal quality and mines availability, the ash content in coal has increased to 60.15% (IB Valley Coal) which has resulted in increase in inlet dust loading on the ESP. This requirement has to be met by providing an additional pass. Considering the above, it was decided to add new stream parallel to the existing passes. Conventional single phase TR set to be upgraded with 3 phase TR set and controller system. Complete replacement of internals for existing streams of ESP including its associated electrical and control system. Energy Performance Management System (EPMS) will help in optimising the power consumption based on the SPM as measured at stack (opacity signal). An outlet emission signal, 4-20 ma is connected to the number of ESP-rectifiers selected for this control. 8. Conclusion This paper outlines briefly the various options available for Renovation & Modernization of the existing ESP's being implemented. Based on the technology available and in-situ site condition, options need to be evaluated and considered for retrofitting the existing ESPs to enhance the performance

6 Flue Gas De-sulphurisation technologies- Making air cleaner than before 1. Preface Due to rapid industrialization and improved standard of the living of the people, energy demand has increased significantly in last few years. Considering major contribution of coal based thermal power generation in India, the coal consumption has increased, so has air pollutant emissions such as SOx, NOx and PM (Particulate Matter). Coal naturally contains a significant amount of sulfur content which during combustion process gets converted to sulfur dioxide (SO 2 ) compound and released though flue gas exhaust. This paper discusses the various abatement techniques used for SO 2. By Vaibhav Korgaonkar, PE. 2. SOx emission by thermal power plants and its impact As per CSE(Center for Science and Environment) report ( ), Coal-fired power plants are major source of air borne pollution including SOx, NOx and PM. The graph below indicates the contribution of coal based thermal power plants in industrial pollution due to these pollutants. Out of these pollutants, SO 2 is one of the most hazardous pollutant as it can have several ill effects on the human health and environment/ecology. Some of the hazardous effects of the SO 2 emissions are as follows: Impact on Human health: Long time exposure of SO 2 in air may lead to diseases of eyes, nose, bronchus etc. Bad effects on vegetation: Decrease in growth and production of plants by interruptions in photosynthesis process. This also leads to stunted plant growth, species decline etc. as long term impacts. Bad effects on ecology: Destruction of ecosystem by acidifying land or river due to acid rain or acid snow. Decreased visibility in surroundings: Decrease visibility by absorption or diffraction of sun light in atmosphere along with floating particles. Creates corrosive environment: Corrosion of architecture, structures, buildings, equipment, historical statues/ monuments which are national heritage. 3. Environmental norms for SOx abatement at Thermal Power Plants Considering the impact of the coal based thermal power plant on the air borne pollution, the Ministry of Environment, Forest & Climate Change (MoEF&CC) announced in December 2015 stringent standards for coal-based thermal power plants. The new standards aim to drastically curtail emissions of particulate matter (PM), Sulphur dioxide (SO 2 ), oxides of nitrogen (NO x ) and mercury. The emission norms are per MoEF notification in December 2015 are summarized in below table: Emission norms Particulate for Thermal power SO2 plants (MoEF notification NOx dated Dec 2015) Mercury. Standards Matter (mg/nm3) (mg/nm3) (mg/nm3) (ppm) Current Standards None None None New Standards Units installed till 100 <500MW: >=500 MW: 2003 >= 500 MW: Units installed MW: between 2004 to >= 500 MW: Units installed after Jan 2017 The newly introduced norms for SO 2 emissions would necessitate FGD (Flue Gas Desulphurization) system installation for thermal power plants where the current emission levels are above applicable norms.

7 4. Various technologies for SOx abatement 4.1 Wet FGD: The wet FGD makes use of reagent slurry for flue gas scrubbing process. Usually used reagent chemicals are- Limestone (Ca(OH)2), Ammonia (NH3), Magnesium carbonate or Sodium bicarbonate. Limestone based wet FGD generates gypsum as a by-product which can be used by cement industry and other gypsum applications. Similarly FGDs based on Ammonia as reagent for scrubbing flue gases generates Ammonium sulphate as byproduct which finds application as fertilizer. The most popular reagent is Limestone due to easy availability, low cost and gypsum generation as byproduct. Among Wet FGD installations globally, majority are limestone based designs. Chemical Reaction- Limestone based FGD: CaCO 3 + SO 2 + 2H 2 O+ ½O 2 CaSO 4 2H 2 O (Gypsum) + CO 2 Ammonia based FGD: 2NH 3 +SO 2 +2H 2 O (NH 4 ) 2 SO 4 (Ammonium Sulphate) Typical process flow diagram of Wet FGD process using Limestone 4.2 Dry FGD Dry FGD uses Quick Lime (CaO) in dry powdered form for flue gas scrubbing process This technology is not very popular in thermal power plants due to difficulty in disposal and no reuse of waste byproduct (Calcium sulphite). Chemical Reaction: CaO (Dry Lime) + H2O Ca (OH)2 Ca(OH)2 + SO2 CaSO3 (Calcium Sulphite) + H2O 4.3 Sea water based FGD This technology makes use of naturally available alkalinity of the Sea water for scrubbing the flue gases for absorbing the SO 2. The seawater discharge post scrubbing passes through aeration and dilution stage. The ph and dissolved oxygen levels of seawater are maintained prior to discharge back to sea. The SO2 is absorbed and converted to sulphate which is natural constituent of seawater. Typical process flow diagram of Sea-water FGD 4.4 Other new technologies- Amine based FGD and activated coke based FGD are two newly developed technologies. Both of these regenerative reagent type processes produce the Sulphur rich gas or solution which form Sulphuric acid as a byproduct. The Sulphuric acid can be stored and supplied for use in for industrial processes. 5. Selection of FGD technology Selection of FGD technology as a retrofit option mainly depends on following factors: Technical: Existing SO 2 emission levels, SO 2 removal efficiency, location of the plant (inland/coastal/access to reagent source), space requirements, process water requirement, wastewater quality/quantity & treatment required, outage requirements, layout feasibility, quality/quantity of waste byproduct generated & its disposal/reuse, provenness of technology etc. Commercial: Cost of reagent chemical sourcing, availability of reliable suppliers for reagent, feasibility of disposal/reutilization of waste byproduct generated, off-takers for byproduct, selling price expected from waste by product, logistics arrangement for reagent & waste byproduct generated.

8 Economical: Capital cost, Operating cost (Cost of reagent chemical, cost of utilities required and cost of increased Aux. power consumption), Impact on tariff, Development of techno-economically feasible model for reuse of waste byproduct. Considering the Sulphur absorption required to meet the new regulations, reagent availability, saleability of by product, footprint, proven nature of technology and cost effectiveness, limestone based wet FGD is generally considered techno-commercially optimum option for desulphurization of flue gas for at inland power plants in India. For coastal power stations having access to seawater, the Sea water FGD is optimum technology option for desulphurization of flue gas considering the proven nature of technology, no reagent sourcing/handling concerns, moderate footprint requirements, moderate to low auxiliary power consumption, no issues with waste disposal and lower CAPEX/OPEX compared to other reagent chemical based FGD technologies etc. Tata Power has been pioneer in the SOx abatement using FGD system with it's Seawater FGD installed at Trombay Unit 5 which is India's first FGD installation in thermal power plant. Various other installations of Tata Power such as 2x525 MW Maithon Power Limited and 5x 800 MW CGPL plant had maintained space provision for FGD retrofit. 6. Challenges in FGD retrofit in existing plants Limited area within existing unit and Layout Constraints: In case of limestone based wet FGD substantial area is required for facilities like limestone handling/storage, gypsum handling/storage, slurry preparation system, gypsum dewatering system, waste water treatment plant etc. Absorber tower and GGH (Gas to Gas Heat Exchanger) need space close to chimney which becomes difficult if sufficient space is not provided in original layout. The installation of seawater FGD as well needs substantial footprint for scrubber tower and auxiliary systems, seawater supply and seawater treatment scheme etc. Sourcing of seawater for FGD: Seawater for FGD scrubber requirement is usually about 20-25% of total CW flow rate of the unit. In case of OTC (Once Through Cooling) system based on seawater it is generally possible to tap it from CW outlet by suitable means. Treatment of FGD outlet seawater: The seawater treatment needs an elaborate system for dilution and aeration. Construction of the dilution and aeration basin alongside the existing outfall channel/ seal well and its connection would be challenging task. Sourcing and Logistics of Limestone:The plant would need access to the limestone on continuous basis for the operation of FGD. The same may be constrained in many areas due to logistical issues / availability issues (For 1000 MW limestone requirement would be approx. 300 TPD) Disposal of gypsum: Large quantity of Gypsum will be generated on a daily basis that would need large storage pond and evacuation facility (For 1000 MW Gypsum generated daily would be approx TPD). Waste water treatment: The waste water from limestone FGD would require the treatment system to effectively treat the effluent and maintain ZLD condition for plant. The waste water bleed from FGD process will generally be less than 5-10 cum/hr for typical 500 MW unit FGD. Increase in Aux. power requirement (approx. 0.8 to 1.5% depending on the technology and plant constraints) and may need major augmentation in electrical power supply system to meet this Aux power requirement Increased OPEX for sourcing reagent for reagent scrubbing based FGD (Limestone). Some portion of reagent cost can be offset by selling of the waste by-product if suitable means of off take and reuse are established. 7. Way forward and conclusion As the FGD technology has not been widely used in Indian power sector, the CAPEX and OPEX requirements in the Indian context are yet to be established and may vary site to site. However the recent movement of power industry towards implementation of SOx abatement technologies will play a vital role in minimizing the impact of thermal power plants on environment and build cleaner future. For inland power plants the limestone based wet FGD is most popular choice considering the techno- commercial advantages such as availability of Limestone and reusable byproduct Gypsum whereas for coastal power plants seawater FGD is generally considered most optimum solution. There are several other alternate technologies such as Ammonia based FGD, Amine based FGD and Activated coke based FGD which may also become feasible in future, if the means for disposal/consumption of waste byproduct (ammonium sulphate or sulphuric acid) are established. The choice of techno-commercially best suited technology needs to be made considering technoeconomic analysis for the specific plant. Presently Engineering is finalizing the techno - commercially best suited and optimum design solution for FGD implementation at our operating thermal power stations

9 NO x - Emission & Abatement in Thermal Power Plants 1. Preface Ministry of Environment, Forest & Climate Change (MOEF & CC) issued notification on 07 th December 2015 in which Environment (Protection) Rule 1986 has been amended. As per notification, limit of Nitrogen Oxides (NO X ) emissions from Thermal Power Plants (TPPs) have been notified. Due to above notification, NO X emission has become an important consideration in design and operation of Boilers installed in TPPs. This paper discusses about basics of NO X, National & International norms for NO X emission from Thermal Power Plants (TPPs), Type of NO X, Technologies for NO X abatement and effect of NO X on human health & atmosphere. By C P Tiwari, CTDS. 2. Nitrogen Oxides (NO X ) Nitrogen Monoxide (NO) and Nitrogen Dioxide (NO 2 ) are byproduct of combustion process of any fossil fuel collectively referred to as Nitrogen Oxides (NO X ). NO X is formed by the reaction of atmospheric nitrogen or fuel nitrogen at high temperature. At ambient conditions, nitrogen and oxygen in air are stable and non-reactive. 3. National & International limit for NOx emission from TPPs As per notification dated 07 th Dec 2015, NOx limit for TPPs in India is as under: TPPs installed before 31st December mg/nm3 International limit for NO X emission is as under: TPPs installed after 1st Jan 2004 till 31st December mg/nm3 TPPs installed after 1st Jan mg/nm3 China: for unit installed before 2004, 200 mg/ Nm 3 and for unit after 2004, 100 mg/ Nm 3. World Bank: with Volatile Matter > 10%, 750 mg/ Nm 3 and with Volatile Matter <10%, 1500 mg/ Nm 3 International NOx Standard USA: 117 mg/ Nm 3 European Standard: for MW Unit mg/ Nm 3, for more than 100 MW mg/ Nm 3 4. Type of NO X Depending on origin of formation, NO X can be categorized as Fuel NO X and Thermal NO X. Fuel NOX Thermal NOX N2 for NOX formation originates from originally bound compound of fossil fuels and account for up to 80% of total NOX in uncontrolled combustion. Fuel NOX is high for coal having high reactive nitrogen generally in proportion to volatile matter. N2 for NOX formation originates from atmospheric air. Thermal NOx is dependent on combustion temperature, N2 and O2 concentration & time and increases with increase of any of these parameters. 5. Factors affecting NO x formation Factors affecting Fuel and Thermal NOx formation are as under: Coal with lowest fuel nitrogen content and lowest fuel oxygen / nitrogen ratio will generally produce lowest NO X. Fuel NO X formation depends on availability of oxygen to react with the fuel nitrogen during combustion. The compound that evolves from coal particle like HCN or NH 3 will convert to NO X in air rich atmosphere. Fuel NOX can be minimized by controlling the quantity of air permitted to mix with the fuel in early stages of combustion. Low NO X burners are designed to minimize volatile Nitrogen conversion to NOx by establishing early ignition and O 2 staging. The contribution of Thermal NO X to total NO X can be minimized by operating boilers at lowest permitted excess air & minimizing gas temperature throughout furnace by using low turbulence diffusion flame and large water cooled furnaces.

10 6. Technologies for NOx Abatement Technologies for NOx abatement can be broadly classified into following categories: Combustion Control like Combustion Tuning, Low NOx Burners & Air Staging Post Combustion Control like Selective Non Catalytic Reduction (SNCR), Selective Catalytic Reduction (SCR) & Hybrid System 6.1 Combustion Control like Combustion Tuning, Low NOx Burners (LNBs) & Air Staging Low NO x Burners (LNBs) regulate the initial fuel-air mixture, velocities, and turbulence to create a fuel-rich flame core, and control the rate at which additional air required to complete combustion is mixed. This ensures early de-volatilization of coal & avoids highly oxidized environment conducive to NO x formation. Air Staging & Advanced Over fire Air (AOFA) technology involves injection of air above the primary combustion zone to allow the primary combustion to occur without amount of oxygen needed for complete combustion. This oxygen deficiency reduces fuel NO x formation. Over fire air injected at high velocity, creates turbulent mixing to complete the combustion in a gradual fashion at lower temperatures to mitigate thermal NOx formation. Usually, AOFA is used in combination with LNBs and can reduce NO x up to 60% when system is supplied and installed in new Boilers. In retrofit, maximum possible NO x reduction using combustion control techniques depends of furnace size, furnace height, coal quality etc. In general, in applying combustion control techniques, unburnt carbon in fly ash increases. Increase in unburnt carbon due to use of combustion control technologies for NO x control shall be one of the important consideration. 6.2 Selective Non Catalytic Reduction (SNCR), Selective Catalytic Reduction (SCR) & Hybrid System The SCR and SNCR technologies can be used alone or in combination with combustion control technologies or SNCR along with SCR (Hybrid System). These processes use ammonia or urea in a reducing reaction with NOx to form elemental nitrogen and water. The SNCR system can only be used at high temperatures (800 ºC 1200 ºC) where a catalyst is not needed. Generally, SNCR systems alone can achieve NOx emission reductions of 30% 50% percent. Use of SNCR system was limited to smaller unit size. However with new technologies of ammonia injection into furnace (like Umbrella SNCR System developed by Alstom / GE), SNCR System can be used in large unit also. The SCR system is typically applied at temperatures between 300 ºC 400 ºC. The SCR system is located between downstream of the boiler economizer and upstream of the Air Preheater. In SCR catalyst is utilized which promotes a chemical reaction between nitrogen oxides (NO x ) and ammonia (NH 3 ) to produce nitrogen (N 2 ) and water vapor (H 2 O). The NO x SNCR System reduction reaction takes places as the flue gas passes through the catalyst in the SCR reactor. In addition to NOx reduction process, certain undesirable reaction also take place like formation of Ammonium Bisulphate. Ammonium Bisulphate will foul in air preheaters and will reduce its efficiency. Ultimate Goal of SCR designer is to minimize undesirable reaction and ammonia slip. SCR System SCR catalyst of varying configurations and formulations are available from a number of manufacturers worldwide and must be selected to meet the specific performance requirements.

11 SCR catalyst for Indian coal ash is not yet proven and different types of catalyst are being tested in one of the NTPC project for deciding type of catalyst to be used for Indian coals. SCR Catalyst Ammonia storage and injection system is required in both SCR and SNCR System. SCR System NOx reduction - 80% to 95% Aux Power Increase - up to 0.5% Reagent - Ammonia or Urea Reaction Temperature C C Capital Cost - High compared to SNCR Catalyst - Required, contains heavy metal. Disposal and recycling of catalyst is required. Life of Catalyst - 6 to 10 years SNCR System NOx reduction - 30% to 50% Aux Power Increase - up to 01% - 0.3% Reagent - Ammonia or Urea Reaction Temperature C C Capital Cost - Low compared to SCR Catalyst - Not Required Comparison of SCR and SNCR System 7. Effect of Nitrogen Oxides (NO X ) In atmosphere, NO X and volatile organic compound (VOCs) react in presence of sunlight to form ground level ozone, the major constituent of photochemical smog. Unlike ozone in the stratosphere, ozone at ground level has strong negative impact on human health and environment. It impairs lungs function and aggravates heart diseases, respiratory diseases such as Asthma and Bronchitis. NO X reacts with oxygen and other compound of air to form nitrates which coalesces into fine particles which is also a main cause for respiratory diseases. NO X also contributes to acid rains which can destroy fish and other form of fresh and coastal water life and damage building, material, forest and agricultural crops. 8. Conclusion NO X emission in TPPs is becoming an important issue due to focus on reduction of gaseous emission across globe. It has become an important issue in Indian context due to recent environmental norms. NO X generated in TPPs consist of Thermal and Fuel NO X. NO X reduction in TPPs is possible by using combustion control technologies like Low NO X Burner, air staging etc. or by using post combustion technologies like SCR and SNCR. SCR technology is widely viewed as most effective NO x abatement technology with NO x removal efficiency 80% - 95% especially for future units with NO x limit of 100 mg/nm 3. However for existing units in India for which NO x limit is 300 mg/nm 3, low cost combustion control technologies like LNBs, air staging etc. shall be used for reducing NO x level to lowest value possible. Incase even after using combustion control technologies, NO x emission is not reduced to desired limit, other NO x abatement technologies will be used. Measurement of NO X is also an important issue. It is very important to use right conversion factor for converting NOX usually measured in ppm to mg/nm3

12 ReACT - Integrated Gaseous Emission abatement Technology 1. Preface In the recent environmental notification, Ministry of Environment and Forest (MOEF) has specified limits for emission of Nitrogen Oxides (NO x ) and Sulfur Oxides (SOx) and Mercury (Hg) from Thermal Power Plants (TPPs) emission. As per this notification more stringent limit for Suspended Particulate Matter (SPM) will be applicable for existing as well as new plants. The new MOEF notification necessitates requirement of Integrated Gaseous Emission abatement technology for existing as well as new TPPs. By C P Tiwari, CTDS. ReACT - Regenerative Activated Coke Technology is an integrated gaseous emission abatement technology, developed by J Power Japan. Hamon Research-Cottrel is Licensee of ReACT since This paper discusses how ReACT technology can be utilized to reduce the environmental impact of TPPs. 2. Brief of Technology ReACT is Integrated Multi-pollutant Control Technology in which Flue Gas (FG) flows over moving bed of Activated Coke (AC) having very high specific surface area up to 300 m 3 /gm. Contact of FG with AC provides mechanism for efficient absorption of SO x, Hg, SPM and surface promoted catalytic and non-catalytic NO x reduction (low temperature SCR reaction). In order to promote the reaction and absorption process, ammonia is also injected in FG stream. SO x is absorbed in AC as H 2 SO 4 or Ammonium Bisulphate (NH 3 ) 2 SO 4. AC also absorbs all forms of Hg and other acidic gases. In presence of Ammonia, NO x is reduced to N 2. Absorption Stage Generation Stage By-Product Recovery Stage During regeneration, AC is heated, absorbed species leaves and decomposes. H 2 SO 4 decomposes to H 2 O and SO 3. Ammonium Bisulphate (NH 4 ) 2 SO 4 decomposes into NH 3 and SO 2. NH 3 is reabsorbed in AC & improves later activity of NO x reaction. Sulfur rich gas is feedstock for acid plant. Sulfuric acid is by product of process. During the regeneration process, fines of AC is generated which can be used in boiler as fuel or some other purpose. Make-up of fresh AC is required to compensate the loss due to fines. 3. Benefit of Technology ReACT Technology has following benefits: Integrated Multi-pollutant Control Technology - Control of SO x, NO x, and Hg. System also works as flue gas polisher. Little or no water use. Acid - Saleable by product. No change in existing Ash Handling System, Boiler and ESPs No change in flue gas temperature. Lining in stack is not required. Avoidance of Limestone and Gypsum (By Product) handling system & its related pollution associated with wet lime stone FGD

13 Small foot prints - Estimated space requirement for 2 x 525 MW Maithon project is 6000 to 7000 m 2 (less than 2 acres) System is designed for full load flue gas flow with maximum SO x concentration. At part load, system efficiency further improves. Minimum waste from system - closed loop for purged gas, AC fines used in boilers, No solid waste. Acid is by product of process. Need not to consume chemicals for neutralization of Sulfur captured during process. Technology can be used for >95% SO x control, 20% to 80% NO x control, flue gas polishing and >95% Hg Control. 4. Operating Cost Components Operating Cost in ReACT system includes: Ammonia consumption Activated Coke make-up Higher ID Fan Power Consumption (applicable in Green Field s) Booster Fan Power (applicable in retrofit projects) LDO consumption for regeneration. Auxiliary Power Consumption for Regeneration 5. Operating Plants with ReACT Technology & Demonstration s ReACT Technology is already operating in J Powers 2 x 600 MW Isogo (First unit 2002, Second Unit 2009) in Japan. Hamon USA are in final stages of commissioning of ReACT system for 1 x 360 MW coal fired power plant as Wisconsin, USA. 6. ReACT System for 2 x 525 MW Maithon Plant Feasibility of installing ReACT System for 2 x 525 MW Maithon Plant is being studied along with Hamon-Research Cottrell India Pvt Limited. Following design parameters are being considered for preliminary design of ReACT System: Inlet concentration of SO x : 1400 mg/nm3 Inlet concentration of NO x : 529 mg/nm3 Flue Gas Flow Nm 3 / sec Flue Gas Temp C Outlet concentration of SO x and NO x for design of ReACT: 180 mg/nm3 and 280 mg/nm3 respectively. Presently Maithon Boilers are designed for NO x emission up to 880 mg/nm 3 which will be reduced below 500 mg/nm 3 using various in furnace control like combustion optimization, low NOx burner etc. Design outlet SOx and NOx level have been considered 20 mg/nm 3 less than the new environment norm. Details of Proposed ReACT System for each 525 MW Unit Moving Bed Absorption Cartridge for each 525 unit: No of regenerator per unit: AC required (first fill) AC make-up requirement: Ammonia Consumption H2SO4 Production Rate System Pressure Drop 3 x 12 (size 4.2m x 4.2m x 18m) 3 Nos 4500 T 0.5 T/hr 642 kg/ hr TPH 3 Kpa Budgetary capital cost, Operating Cost including cost of AC, source of AC etc. is being discussed with Hamon-Research Cottrell for completing techno-economic analysis of ReACT System for Maithon. 7. Conclusion ReACT is a promising technology as this can be used for integrated SO x, NO x, Hg control and FG Polishing. For optimum sizing of ReACT system, NO x at inlet of ReACT system shall be less than 529 mg/nm3 to get outlet NO x level less than 280 mg/nm3. This will be achieved by combustion optimization, using Low NO x Burners (LNBs) and air staging. Major consumables in ReACT system is activated coke for which domestic supplier is not available and presently we need to depend on Chinese supplier. Hamon Research Cottrell is already in discussion with Indian manufacturers for manufacturing activated coke of required specification in India. Once such suppliers are available, cost of activated coke as well as techno-economic of ReACT system may be viable and competitive compared to SCR & FGD System for Indian s

14 Air Cooled Condenser By Dheeraj Pareek,. 1. Preface Is there enough potable water to fuel India's power expansion? Avoid usage of more water and start conserve water. The production of electricity requires reliable, abundant, and predictable source of freshwater, a precious resource which is limited throughout the world. The process of power generation from fossil fuels such as coal, oil, and natural gas are all water intensive. Particularly in country like India, which has nearly 330 GW installed power generating capacity, out of which nearly 220 GW are thermal power plants. A huge amount of water is required only for cooling purpose. Water is one of the key input requirements for thermal power generation, for process cooling in the condenser, ash disposal, removal of heat generated in plant auxiliaries, and various other plant consumptive uses. For power plants located on main land, the raw water is generally drawn from fresh water source such as river, lake, canal, reservoir, and barrage. For power plants located in coastal areas, water for cooling of condenser and auxiliaries is drawn from the sea or creek which provides for water requirement of the wet ash handling system also. The requirement of water for other plant consumptive uses is met from an alternative source or by installing desalination plant. Coal bearing states like Orissa, Jharkhand and Chhattisgarh are already facing difficulties in siting thermal power plants due to non-availability of water. Also, in states like Rajasthan, the land is available in plenty but there is scarcity of water. Naturally drinking and irrigation uses of water have got priority over industrial uses. Thus, there is a need to minimise consumptive water requirement for thermal power plants. In such areas where there is acute shortage of water, use of dry cooling system for condenser cooling can be explored as it helps us to save huge quantity of water with respect to conventional cooling system. This articles discusses the use of dry cooling system to minimise water usages in power plants. 2. Conventional cooling water system Cooling water is required for condensing of steam in a surface condenser and for secondary cooling in heat exchangers of equipment cooling system for plant auxiliaries. Typically, 3.5 m 3 /hr water is required for a coal based thermal power plant with cooling towers. For a typical 500 MW coal fired unit, the amount of cooling water required for condenser and auxiliary cooling is of the order of 60,000 m3/h with temperature rise across the condenser about C. Once through type cooling systems were installed in only coastal thermal power plants using sea water with max temperature rise of 7 0 C. 3. Water minimisation by use of dry cooling system In a conventional wet cooling tower, hot water is cooled by direct mixing with ambient air resulting in evaporation of a part of circulating water, and make up water is required to compensate for loss of water due to evaporation, drift and blow down water. Dry cooling systems do not require any make up water as rejection of power cycle waste heat from condenser to atmosphere takes place by sensible cooling in finned tubes by ambient air and no evaporative cooling is involved. Dry cooling systems can be broadly classified in two categories viz. Direct dry cooling system Indirect dry cooling system In direct dry cooling system (refer fig.1), exhaust steam from turbine is directly cooled in a system of finned tubes by ambient air using mechanical draft fans or natural draft hyperbolic tower. In an indirect dry cooling system (Heller system), exhaust steam from the turbine is cooled by water in a surface or jet condenser and hot water is cooled by air in finned tube bundles using mechanical draft fans or natural draft hyperbolic tower.

15 In case dry cooling system is adopted for the condenser, wet cooling tower is required only for ACW (auxiliary cooling water) flow and requirement of plant make- up water is considerably reduced. Since Cooling Tower (CT) make up water constitutes major part of plant consumptive water, use of dry cooling system results in reduction of plant consumptive water by about 70%. The requirement of plant consumptive water can be further reduced by adopting dry cooling mode for ACW flow also, using air cooled heat exchangers. Direct dry cooling system: In direct dry cooling system, exhaust steam from LP turbine is directly cooled in a system of finned tubes by ambient air. Mechanical draft or natural draft in a hyperbolic tower can be used to move the air through fin tube heat exchange elements. Majority of direct dry cooling installations employ mechanical draft fans and are termed as air cooled condensers (ACC). A typical schematic of direct dry cooling ACC is indicated below (refer fig.2). The finned tubes are generally arranged in the form of an A frame (or delta) over a forced draft fan with steam distribution manifold connected horizontally along the apex of A frame. An ACC for a typical power plant consist of several such A frame structures each comprising of several cells. Each cell consists of a number of finned tube bundles arranged in parallel along two walls of A frame cell. Steam flowing down inside the tubes condenses due to the cooling effect of ambient air drawn over external finned surface of the tubes by the fans. The condensate drains from finned tubes into condensate manifolds and then drains into a condensate tank before being pumped to the conventional condensate cycle. To reduce pressure drop in steam conveying system, ACC needs to be installed close to the turbine hall. Fig.2 Schematic of an Air Cooled Condenser The inclined exhaust duct routing reduces the steam side pressure drop between turbine and condenser and saves duct material as well as man power for manufacturing and erection. The supporting structure of the Air Cooled Condenser platform was derived from nature and therefore called bionic design. This design reduces the number of foundations and saves structure material as well. Some of finned tubes used in ACC: Alex tube Flat shape steel with aluminium coating. Meandering form of aluminium fins. Connection by brazing. A tube Elliptical core steel tube. Rectangular steel fins. Connection by hot dip galvanizing

16 4. Benefits of ACC: No need for water availability on site, Good amount for water saving. Flexibility in the selection of the power plant site (grid proximity, land cost, fuel source proximity) High performance finned tubes with excellent cleaning ability for long term availability. A-Frame supported tube bundles, allowing heat exchanger free thermal expansion for maximum reliability. Long-term mechanical and thermal integrity. Reduction of operating floor height 5. Challenges of ACC Large capacity steam condensing for maximum electrical output. Coal mine areas are dusty with corrosive environment. Diverse and challenging climates, from hot to freezing conditions with risks of mechanical wear. Base load operation requiring high availability. Higher CAPEX, therefore higher tariff. Note: The condenser pressure achievable in dry cooling system is considerably higher than in wet cooling system and consequently dry cooling systems result in reduced power output (about 7%) and increased heat rate by 7% (lower efficiency) of the unit besides higher capital cost (estimated Rs.190 Cr to Rs. 250 Cr). Auxiliary power consumption as percentage of gross unit output is 6.25 to 6.5 %, with Turbine Driven BFPs (TDFP). Figures/Nos. indicated above are for typical 500MW size unit. ACC installations at some coal fire power plants 4 x 600 MW, Jinjie, China 2 x 600 MW SP Datong Gen. Co. Ltd., China 4 x 600 MW, Zhenglan, China 6 x 800 MW, Medupi, South Africa 6. Conclusion There are considerable number of dry cooling installations including for large size units ( 600 MW) operating in different parts of the world. In India also, some small size combined cycle plants, captive power plants and industrial units have been provided with air cooled condensers. Recently, NTPC has also ordered 3 x 800 MW units with ACC for their Jharkhand project. Exploring this technology for preserving water sources for higher capacity power plants can be studied further.

17 CFB Technology: A Better Alternative for Meeting New MoEFCC Norms for NOx 1. Preface Govt. Of India, Ministry of Environment, Forest & Climate Change (MoEFCC) has revised the Environmental norms for Thermal Power Plants (TPPs). The norms mentions that all the Thermal power plants which are to be installed post Dec 2016 shall meet gaseous emission SOx, NOx less than 100 mg/nm 3, PM less than 30 mg/nm 3 and Mercury less than 0.03 mg/nm 3. By Dipankar Das, PE. The revised MoEF norms issued for gaseous emissions had originated discussions between OEMs & Plant Owners for evolving a feasible and techno - economical solution. The recent emission norm for SOx, NOx of <100mg/Nm3 makes it essential for a plant user to analyze both pollution control equipment as well as the source of Coal. Generally the Plant owners often have less control on the coal quality except for calorific value and moisture. There are various technologies available for Fossil fuel fired Boilers viz. PF Boilers, CFBC Boilers etc, Circulating fluidized bed is a relatively new technology with the ability to achieve lower emission of pollutants. In CFB, the furnace is pressurized and furnace gas is recirculated to capture the unburnt carbon and to increase the thermal efficiency of the boiler. The fluidized action promotes complete coal combustion at relatively low temperatures, and provides a means to transfer combustion heat efficiently from the bed to the steam tubes. Limestone is added in the furnace for achieving the desired SOx limit. Circulating fluidized bed (CFB) offers fuel flexibility, Low temperature combustion, In-furnace Sorbent addition and effective Ca/S utilization which needs moderate investment on tail end Pollution equipment and operating expenditure. In the present scenario, for larger size units, adoption of supercritical PF (pulverized fuel) firing technology with FGD for external desulfurization and SCR/SNCR for De NOx system is preferred. However in mid-range utility segment CFB has been a decent alternative due to capability of infurnace emission control, low temperature combustion resulting low NOx emission, better air staging, in furnace SOx reduction (up to 95% reduction) due to limestone addition in furnace etc. The paper discusses how CFB boilers are helpful in NOx emission in thermal plants 2. NOx Emission The predominant form of NOx is NO, NO 2 with traces of other forms of NOx is also present. NOx emissions from the fired process are typically 90-95% NO and balance NO 2. However when flue gas leaves the stack most of the NO is eventually oxidized to NO 2.There are two principal mechanism of NOx formation in steam generation i.e. Thermal NOx and Fuel NOx. Thermal NOx refers to the NOx formed through high temperature oxidation of nitrogen found in the combustion air. Normally thermal NOx formation increases significantly above a temperature of 1150 deg C. Fuel NOx refers to conversion of fuel bound nitrogen to NOx during combustion process. Nitrogen found in the fuel is typically bound to the fuel as an organic compound. The majority of NOx formation from fuel bound nitrogen occurs through a series of reaction which can be broadly described in two separate paths. The first path involves the oxidation of volatile nitrogen species during the initial phase of combustion. During the release and prior to the oxidation of the volatile compound, nitrogen reacts with several intermediate compound in the fuel rich flame region which then oxidized to NO and reduced to N 2 in the post combustion zone. However the formation of NO or N 2 strongly depends on fuel/ air ratio. The second path involves release of nitrogen radicals during combustion of char fraction of the fuel. The fuel bound nitrogen releases free radicals viz. HCN, NH 3, NH which participates in series of reaction to form NOx. It may be noted that hardly 15-20% of fuel bound Nitrogen is eventually converted into NOx and remaining gets reduced into molecular nitrogen due to presence of large amount of char present in the Bottom furnace. It is also evident that fuel with more volatile matters (VM) evolves more NOx. CFBC Boiler operates at a bed temperature of C wherein PF Boilers operates at a temperature of C. The thermal NOx formation is high in PF Boilers due to high operating temperature which is negligible in CFBC Boiler due to lower operating temperature.

18 Below Table gives an approximate idea for NOx emission w.r.t VM. Indian Coal Indonesian Coal Petcoke Lignite Washery Rejects Volatile Content 16-20% 20-30% <8% >30% 16-20% Fuel Bound Nitrogen % % < % % NOx* Emission (mg/nm3) O2 vol.dry New MoEF Norm mg/ Nm3 NOx reduction in CFB can be possible (without external system) by methods like Air staging, Reducing the combustion temperature, Reducing Excess air etc. Air staging is a common technique in boilers, however achieving a perfect balance between NOx reduction and CO reduction and unburned combustible is highly empirical in nature. Based on fuel quality changes operation changes may be required to achieve the best of all the three. Typically the primary air to total ratio is maintained between 50-70% based on the fuel reactivity. It was proven that the air staging technique is effective when the fuel has higher amount of Volatiles. The bottom portion of CFB is operated below Stoichiometric limits which generates CO and Char. The NO formation from fuel volatiles are partially reduced by unreacted char. Strong intensity of air staging affects CO formation also. Figure 1 below shows the relation of NOx, CO with equivalence ratio. Equivalence Ratio is the ratio of actual fuel/air ratio to the stoichiometric fuel/air ratio. NOx is found to be lower, when the equivalence ratio is more than 1. It is obvious that fuel rich zone can encourage lower NOx formation, however after a particular limit of excess air (fuel lean zone), the NOx stops reducing due to the reason that the higher dilution air restricts combustion and combustion temperature. Thus the CFB bottom zone is operated below Equivalence ratio of 1 and the remaining Fig.2 Schematic of an Air Cooled Condenser stoichiometric and excess air is admitted well above the PA zone to reduce overall NOx emission. Fig 1. Emission Vs Equivalence Ratio 3. Effect of CaO on NOx formation With new environmental norms, it is imperative to maximize the SOx control to reduce the requirement of external flue gas desulphurization (FGD) system. However it is to be noted that after 92% Sulphur capture the requirement of Limestone exponentially increases which leads to increase in CaO in bottom ash. The CaO catalyzes the fuel volatile release viz. NH3 and forms NO and HCN converts to NO 2 as mentioned in Figure (2). Therefore a tradeoff to be done for high Sulphur fuel for optimized NOx & SOx emission. Fig 2. Fuel NOx release 4. Conclusion Systems like SCR, SNCR are available for external NOx control. SCR is a catalyst based system with substantial investment and higher CAPEX. Additionally SCR systems are yet to be proven for high ash Indian coals in terms of Erosion, Catalyst plugging etc. In CFBC Boiler due to low combustion temperature, better air staging the NOx formation is comparatively lower than PF Boilers and the current environmental norms can be met with combination of SNCR

19 Environmental friendly technologies for Coal handling system dust control. By Debasish Biswal, PE. 1. Preface Coal handling plant (CHP) is a major source of fugitive emissions including coal particles, dust etc. due to multiple handling (unloading, unloading and transfer) of coal. Coal, which is received within the plant, contains some amount of fines (about 3 to 4% of total coal received), defined as coal particles which are less than 1 mm size to few microns. During handling of coal within the plant, these fines escape into the nearby atmosphere due to surrounding wind and cause nuisance. Also, the coal carrying equipment are not water tight and are prone to leakages with usage, and hence, some amount of coal leak during the process of handling. This results in wastage of coal and since, these fines are very vulnerable to fire, creates potential fire hazard. Fine coal dust can settle in nearby households, thus creating nuisance value and posing a health hazard. This is also applicable for employees within the plant premises, who spend considerable amount of time breathing the dust contaminated air. In order to avoid the above damages to health and environment, loss of coal and unsafe conditions, different environmental friendly technologies, primarily aiming at minimizing the fugitive emissions and spillage, are utilized in the coal handling plant and a brief in-sight to them has been included in this article 2. Environmental friendly technologies for minimizing the coal spillages and fugitive emissions The precautions that could be taken while designing coal handling system as well as various technologies that could be used to minimise the spillage as well as fugitive emissions are detailed below: 2.1 Avoiding multiple and manual handling of coal: As a common practice, coal is received within the plant through various logistics solutions viz wagons, trucks and for a power plant through nearby port or jetty, through barges. All the above logistics solutions demand well-defined mechanical handling system for minimizing manual handling of coal (with the help of mobile yard equipment like dozers, pay-loaders, labourers etc.). For example, a wagon tippler system or a barge unloader eliminates the need of manual handling of coal. The coal from wagons or barges are mechanically unloaded and directly fed to the coal conveying system. This avoids spillage of coal with a well-designed conveyor system and fugitive emissions are controlled with the help of dust suppression systems. On the other hand, unloading of wagons along a railway siding, with the help of labourers, mobile yard equipment would result into spillage of coal, which is a direct loss of asset and source of fugitive emissions. The trucks which would carry coal from siding to plant will be additional source of fugitive emissions as the carrier is open to atmosphere. The design of the CHP (Coal Handling Plant) must ensure the following to minimize loss of coal and fugitive emissions: a) The conveying system is designed as per relevant standards and practical experiences to avoid spillage of coal while conveying from one place to other. Adequate skirt length must be provided to contain coal on the conveyors when coal is received from a chute to a belt conveyor. b) The length of chute (height from one transfer point to another) must be optimized and design of the chute must ensure that the velocity of coal at the end of the chute is same to that of receiving conveyor. A chute must also ensure centre-line feeding of coal onto the chute to avoid spillage from edges. c) System design must also ensure that rate of feeding of a chute must be same as the evacuation rate of the receiving conveyor. Also the storage in the chute must be decided considering the stoppage time of the feeding and receiving conveyor. d) As far as possible, conveyors must be housed within enclosed galleries with sufficient mechanical ventilation systems while restricting contact of coal with natural strong winds. e) Coal must be stocked at minimum number of locations which are well accessible through mechanical yard equipment like the stacker, stacker cum re-claimers. Transfer of coal from one location to other location, again adds to loss of coal and emissions. f) In case, stocking and handling of coal at multiple locations within the plant is essential, it must be designed with suitable and sufficient type of dust suppression systems.

20 g) While deciding the coal stockyard location, the wind-rose must be referred to minimize exposure of coal with strong winds for maximum duration of a year. h) Stock yards must be located away from nearby habitats to minimize the risk of carrying over of fugitive emissions. i) The maximum height of coal stock-pile must not exceed the height specified by local pollution control board (max 10 metres in most areas in India). j) In case, the above conditions are not achievable, due to certain constraints, a wind barrier must be designed (at least 3 metre high than highest height of coal stockpile) and installed, surrounding the CHP, in the dominant direction of wind. This would reduce carrying over of fugitive emissions to nearby areas. 2.2 Pipe Conveyors: As a significant jump in minimizing spillage and loss of coal during the process of conveying from one location to another, the technology of pipe conveyors is being adopted. In contrast to trough type conveyors, which is open and provides a possibility of spillage of coal (beyond its edges) due to defined width and profile, the pipe conveyor carries the coal in a completely enclosed pipe like structure, wherein both the edges of the conveyor overlap to create a closed containment, thus containing the entire load of coal, eliminating contact of coal to wind and chances of spillage of coal beyond the edges. It is possible to achieve zero loss of coal (spillage or emissions) with a pipe conveyor. The pipe conveyor is similar to a trough conveyor for initial 45 metres to 65 meters at its receipt and discharge end, depending on the tonnage of pipe conveyor. However, the above lengths are, generally, located, within enclosed conveyor galleries and hence, emissions during transfer of coal are minimized. Due to zero spillage from these conveyors, it is suitable to carry coal over environmentally sensitive areas like open water resources, forest land etc. Pipe conveyors also allow coal to be carried at steeper angles and can change direction with certain minimum radius, thus, sometimes, allowing optimization of CHP layouts, reducing the requirement of land for the power plant. The cross-section of a troughed conveyor and pipe conveyor is provided below: Pipe conveyor C/S Trough conveyor C/S 2.3 Screw type Barge Unloaders: For power plants, which receive coal through barges, grab type unloader are put to use. It s a technology that has been put to use due to its ruggedness as it is not highly dependent on the type of coal, size of coal, foreign material and has long life. However, these grabs, though, designed as water tight enclosures, leak coal from the mating surface of the either halves of the grab, within few days of operation. This leaked coal, mostly, drops into water, thus polluting the water body. Hence, as a more environmentally friendly technology of unloading coal from barges, screw type continuous unloaders have been developed and installed. The screw type unloader uses a specially designed rotating feeding head and a screw conveyor, called as the vertical screw, followed by horizontal and gantry screw conveyors to unload coal from barges. All the above screw conveyors are completely enclosed within casings and hence, no coal can escape the machine unless the final discharge is reached. This completely eliminates possibility of leakage of coal at any point of conveying coal from barge to conveyor. Though, these type of unloaders demand coal size of - 50 mm, free from any foreign material with maximum moisture of 35%, they provide a much cleaner and intensively environment friendly methodology for unloading coal from barges. 2.4 Dust Suppression system: Complete elimination of fugitive emissions while handling of coal is not possible. This is because of presence of fines and generation of fines during handling of coal. It is essential that coal is transferred from one place to another in some or other way of conveying/handling. This demands that the coal is passed through numerous transfer points, wherein it is dropped from a height to a receiving conveyor or equipment. Also, coal is crushed to achieve a definite size which further increases percentage of fines. Hence, to contain and control fugitive emission of fines, water based dust suppression systems are provided. Dust suppression systems are typically provided at every unloading and handling point/location in the CHP viz the wagon unloading facility, receiving

21 and discharge point of conveyors, on the boundary coal stockpiles, discharge of boom conveyors of yard equipment, truck unloading hoppers etc. The water based dust suppression system can be implemented in following ways: The clearance is kept in-order to prevent damage to belt surface Plain water based dust suppression system: It is provided with the help of water jet nozzles, sprinklers wherein the amount of fugitive emissions are significantly higher viz the wagon/truck unloading stations, stockpiles etc. High pressure water (low flowrate) is discharged through sprinklers/jet nozzles to create a blanket of water to contain the fugitive emissions. The droplets are heavier than the fugitive particles and hence help in settling them down. The system is designed to cover the complete stock pile/coal unloading station with the help of a network of nozzles. During the process, the coal is also wetted, reducing further possibility of emissions in the downstream handling process. Dry Fog Type Dust suppression (DFDS) system: It is provided with the help of air-water jet nozzles. Water and air are introduced into the same nozzles and the high pressure air atomizes the water into very fine droplets (less than 1 microns) to form a blanket of atomised water. This contains the minute fugitive particles and prevents emissions. This type of system is installed wherein the amount and size of fugitive emissions are relatively smaller viz at the discharge and receipt end of conveyors. Combination of above two technologies: After prolonged use of only DFDS system at the receiving and discharge end of conveyors, it has been observed that its efficacy is limited and significant emissions occur during transfer of coal through conveyors. Hence, as a new trend, specially designed plain dust water system is installed at the discharge of conveyor and DFDS type system is installed at the receipt end. A combination of these systems have proven to be highly efficient in minimizing emissions. Also the system does not require any electrical valve operations, instrumentations and power etc. to operate. Most of the dust suppression systems fail, due to premature failure of the supporting operating systems and hence lead to the complete system unavailable after a few days of installation. However, the newly installed system is completely mechanical and operates with tap off from service water and service air system provided along the conveyors. The actuating mechanism is a runner wheel which remains in contact with the non-carrying side of the conveyor and actuates the dust suppression system as soon as the conveyor is in motion. This helps in wetting the belt and reduce emission of dry coal, which gets stuck to the conveyor when the conveyor is stopped after operations. A schematic of the system is provided below: PWS and DFDS Schematic 2.5 Belt Wash Box System: Belt wash box is an equipment which cleans the carrying surface of the belt during return travel. It so happens that minute particles of coal which are not heavy enough to be discharged into the discharge chute, remain attached with the surface of the belt due to adhesive forces within coal and the top rubber surface. Though scrappers are provided before and after the bend pulleys, they are not in complete contact with the surface of the belt and hence, cannot completely clean the belt.

22 due to continuous scrapping of belt. The wash box is installed in the path of return conveyor wherein the carrying surface of the conveyor is scrapped by an inbuilt acrylic scrapper and washed with the help of high pressure (3 bar) water jet nozzles. The high pressure water ensures dislodging of the sticky coal on the surface while the acrylic scrapper, which is in absolute contact along the surface of the belt, cleans the belt more efficiently than other scrapers. The discharge of the wash box is routed to nearest drains. This system, ideally, ensures a completely clean and wetted belt in the return side avoiding any emissions that could occur due to coal sticking onto surface of the belt. 2.6 Junction tower sealing, cleaning and ventilation system: Junction tower are the technological structures wherein the transfer of coal takes place from one conveyor to other, sometimes through certain equipment viz the screens, samplers, crushers etc. and hence are the major source of fine fugitive emissions. Therefore it is essential to contain the fugitive within these towers and handle them suitably. To achieve the same, two methodologies are to be adopted: Sealing and cleaning of junction towers: The junction towers must be sealed at all locations for except the doors and access points. Proper and sufficient sheeting must be ensured to cover the junction towers all around. The monorail doors, the access doors must be kept shut when not in use. The conveyor entry and exit points may also be concealed with doors. The windows must be fixed with non-openable glass with proper access to all windows to replace the window glass in case of damage. Proper service water system with drains on all floors of the junction towers must be provided to clean the junction tower of any spillages which might occur during transfer of coal. As a whole, it must be endeavoured not to leave unnecessary openings in the junction tower to allow coal dust to escape the junction tower. Ventilation system: Junction tower ventilation system has been used for the 1 st time in CGPL Mundra Pipe conveyor to pull the fine dust particles which still manage to escape despite installation of the already discussed water based dust suppression systems. Suction air ducts, which are connected to an induced draft fan, creates a low pressure zone on the working floors of the junction towers and hence, suck the coal fines. The fines are collected through a bag filter system and through a rotary air lock valve, is discharged into a container, which may be put back to stockpiles or conveyors. 3. Conclusion The combination of the above mentioned technologies certainly helps in making the coal handling plant more environmentally friendly and will lead to more conducive and healthy working conditions

23 Environment Friendly Transformer Oil - Ester fluid By Pramod Tupe, CTDS. 1. Preface Power transformers are the key elements in any electrical power network and developed significantly in design and insulating material used, since their invention over a century ago. However, the use of mineral oil as an insulating and cooling medium remained virtually unchanged till the global oil crisis in 1970s which triggered the search for alternative fluids and driven by growing desire for environmentally-friendly solutions over recent decades. Many companies in Transformer manufacturing as well as Insulating oil industries have taken lead in this area and developed ESTER fluid as dielectric insulating oil. Likewise, many power utilities are focusing their attention on enhancing the environmental, safety and operational performance of both new and existing power transformers; in order to deliver more reliable, cleaner power to their customers. In this article, an attempt is made to collate development of environmentally-friendly Ester oil and its field experience in brief. 2. Mineral Oil & its environment impact Mineral oils are composed of saturated hydrocarbons called "paraffins", whose general molecular formula is CnH2n+2. Other hydrocarbon compounds like "naphtenic" CnH2n and "aromatic" CnHn are also used as insulating oil. However, all above Mineral oils are obtained from petroleum crude oil products. Unfortunately, the Mineral oil is having limited biodegradability and can impact on environment heavily, in case of careless spillage or inappropriate disposal. Additionally, quantity of oil used in Transformers (for example, 90MVA, 110/22kV Power Transformer is having KL while 250MVA 220/110kV ICT is having KL) intensifies the hazard. Commonly used mineral transformer oil has an ecological threat index twice higher than water and the same may be increased up to three times due to presence of polycyclic aromatic compounds in some aged / long operated Transformers. The Mineral oil leaked from Transformer to the soil are major source of its contamination (Degradation of oil-soaked layer) and in consequence, the contamination of water bodies occurs. As per OECD 301 standard, the biodegradability factor is only 10% which indicates that after 28 days from the entering the oil to the environment, only small part of this fluid surrenders to selfdegradation. Moreover, the mineral oil need to be disposed-off after its useful life, certain precautions are necessary to avoid risk of environmental pollution and legal requirements as applicable to industrial and other lubricants. Another environmental issue associated with Mineral oil is combustibility property due to its low flash point. Fire in failed transformer are very dangerous and cause air pollution. 3. Alternative solution for Transformer insulating oil Environmentally friendly insulating fluids, which are an alternative to Mineral oils, are the Synthetic Esters and Natural Esters. The base of Natural Esters are vegetable oils produced from plants. Ester fluid is not listed as hazardous by international authorities such as EPA (Environmental Protection Agency) and OSHA (Occupational Safety and Health Administration). Thus emerging as one of the cleanest types of product available on the market today, which is safe for people and the environment. The term "Ester" comes from chemical linkage formed from the reaction of an alcohol & an acid. Synthetic esters are manufactured from organic acids and alcohol to give chosen properties. Natural esters are derived from refined seed oils (examples rapeseed, Soya, Sunflower, canola and corn). In past, Synthetic Ester fluids have used in traction, wind turbines, offshore platform etc. and having service history of more than 35 years. Natural ester only marketed since late 1990 s Properties of Ester Fluid In the Table 1, the basic physical-chemical and dielectric parameters for both esters and mineral oil are summarized (Ref. FR3 Data Sheet 2008, Midel 7131 Data Sheet 2010). From Table -1, it is important to notice that biodegradability and flash point properties of both types of Ester oil are superior to Mineral oil on account of ecological aspects, thereby ester fluid offers alternative solution as insulating oil in the places having restricted environmental regulation.

24 The better properties of esters are also visible looking at the intensity of the smoke emitted by the burned liquids. In the case of Mineral oil, smoke is black and very dense while for Property Table 1: Basic parameters of synthetic ester, natural ester and mineral oil. Physical - Chemical properties Unit Synthetic ester Natural ester Mineral oil Density at 20 o C Kg / cm Specific Heat at 20 o C J / kg K Thermal Conductivity at 20 o C W/m Kinematic Viscosity at 20 o C mm2 / s Pour point o C Fire point o C Flash point o C Fire Hazard classification to IEC / IEC K3 K2 -- Biodegradability % Oxidation Stability -- Excellent stability Oxidation susceptible Good stability Dielectrical Properties Breakdown voltage kv >75 >75 70 Dielectric dissipation factor at 90 o C -- <0.008 <0.003 <0.002 Permittivity at 20 o C the both esters smoke is emitted in smaller amounts and its density is also much lower. In percentages, the volume of waste gases emitted by the burned Ester oil in comparison to the gases emitted by burned Mineral oil is only about 15%. Ester fluids are classified under Less Flammable Insulating Fluids (K Class Liquids) with a fire point greater than 300 C and are manufactured in accordance with IEC (for synthetic esters) and IEC (for natural esters). From the insulating property point of view, the most important parameter for transformer oil is breakdown voltage. For the Mineral oil, its strength goes down with increase of moisture content, whereas Ester oil delivers constant value of breakdown voltage for moisture content up to 600 ppm. The higher value of electrical permittivity of the Ester oil than the Mineral oil, thus help in the stress distribution in Transformer insulation (cellulose - oil) system. Its unique ability to absorb moisture contained in aging paper without deterioration of dielectrical strength, can extend insulation life by a factor of as much as five. It also chemically helps to prevent long cellulose paper molecules from aging due to heat exposure. These properties can result in an increase of overloading capability and longer transformer insulation life. The results are lower lifecycle costs and better use of your assets. In past, the transformer industry has reported the failure of Transformer units due to the presence of corrosive sulphur. Ester fluid have been tested by independent laboratories and found to be non-corrosive as per ASTM D1275 and IEC Although there are many positive properties of the Ester fluids, their lightning impulse strength is not as good as Mineral oil. Therefore necessary electrical clearances need to be considered while design stage. Moreover, Ester fluids are characterized by higher density and viscosity, thereby contact with the surface of heating elements (used during production process) is much longer. This leads to overheating of Ester fluid and resulting into increase in dielectric dissipation factor. Thus, production of Ester fluid becomes complex in relation with Mineral oil. On other hand, the higher density of Ester fluid impacts free circulation of insulating oil in the cooling ducts as compare to Mineral oil. Thereby, during designing of power transformer filled with Ester fluid should consider this property to provide the correct circulation of the cooling fluid both in the natural and forced type construction. This leads to wider cooling ducts and high auxiliary power requirement with respect to Mineral oil. 4. Cost Benefits of Ester Fluids As a result of higher raw material & production costs, the initial cost of Ester fluid is higher than Mineral oil and the same can be compensated by taking advantages in optimized transformer

25 design, extended insulation / asset life and reduced maintenance. The benefit of Ester fluid's dielectric properties allow smaller transformer design for transformer ratings, which may result in a lower cost per KVA. For utility or industry customers who have to install transformers in urban areas where land is expensive, reducing the land required will provide significant savings. Present Central Electricity Authority (CEA) regulations in India mandates use of fire protection systems for transformer capacity more than 10 MVA and above or with capacity more than 2000 Ltrs. In addition to that only dry type transformers are allowed for indoor applications. IEC also allows reduced minimum separate clearance for K class liquid filled transformers and The US NEC (NFPA 70) allows for indoor installations of less flammable liquid filled transformers without fire suppression systems. Such guidelines for ester filled transformers are at present not available in India and there is an emerging need for that. Incidentally, BIS is shortly coming out with National standard for Distribution transformers up to 2500 kva, 33 kv filled with Ester liquids. 5. Field experience of Easter filled transformers Natural and synthetic Esters have built up experience in distribution and small power transformers. Presently, Transformer manufactures / Utilities are moving towards higher voltage classes and larger power transformers with realisation of installation advantages from fire safety and environmental benefits. The below table -2 shows a selection of power transformers with synthetic and natural ester installed over the past 25 years. Table 2: Power Transformer installed over the past 25 years (Source : MIDAL database) Tata Power Delhi Distribution Limited (TPDDL) has already carried out trials with both types of Ester fluid for small single phase distribution transformers and standardized on natural Ester oil. The biodegradable oil retro-fill has helped them in addressing issues like overloading, safety, mineral oil dispose-off problems and other environmental concerns. In our Distribution system, four 20/28MVA Natural Ester filled transformers were installed in Mumbai as green initiative. Such transformer design provides increased capacity by 8 MVA, while reducing the footprint by 17%; it yields cost-savings of about 16% and reduces noise level from 73 db to 59 db. In EHV Power Transformer category, an attempts are made to introduce Ester fluid filled transformer, however cost run-over is around 20%. 6. Conclusion Biodegradable ester fluids are good alternative to mineral oil, especially in the situations when the power transformer has to be installed in urban areas with catastrophic consequences in case of fire. With the many positive aspects like the higher biodegradability, high flash point and good breakdown strength, its negative parameters like worse cooling property, concentrated heat flux, low lightning impulse strength etc. should be taken into account in the design phase and during operation & maintenance of the transformer with Ester fluids. Power utility companies that have used Ester fluid in transformers, have reported major benefits like reduction of installation costs, higher transformer reliability and availability as a result of reduced maintenance requirements. In the longer term, they can expect extended operational lifetime, as well as reduced risk of fire and explosion and lower costs related to environmental compliance

26 Key Highlights Presentation on "Protection and Automation - Tata Power Perspective by Mr. Amok Agarwala and Mr. T Murlikrishna Mr. Amok Agarwala and Mr. T Murlikrishna made a presentation at National Seminar on 'Smart Grid Technologies and Standards' in march 2017 at Vadodara. The seminar was organized by IEEE and hosted by GETCO. The presentation highlighted the issues concerning the utilities in upgrading Protection & Automation. The presentation was well appreciated by the attendees. Workshop on Communication Technologies Technical workshop on communication technologies was organized by Communication team at Khopoli for Engineers and staff from Khopoli, Bhira and Bhivpuri. Training on 23rd June 2017 on various communication technologies and introduction to different fiber optic testing instruments along with hands on demo of Optical time domain reflectometer, Power meter, Fusion splicing was given. The session has increased awareness level of the team on communication technologies and cyber security and would help them in effectively managing hydro centralization automation network. Release of report on compendium of Boiler tube leaks FY 16 & 17 " A report on "Compendium of Boiler tube leaks FY 16 & 17" prepared by CTDS was released by COO & ED Mr. Ashok Sethi on 9th June'17. Lecture on ' Commissioning & Operating Experience of India's first 830 MW units at super critical units " Mr. Unni Gopalakrishnan delivered a lecture on Commissioning & Operating Experience of India's first supercritical 830 MW units', during the NTPC Operations Heads' Conference on 29th May'17 at PMI, Noida.

27 Training on Hydro maintenance and operations A two days training on Hydro Maintenance and Operations was given by experts from CTDS Mr. A. K. Sinha, Mr. Himanshu Marmat and External Hydro expert Mr. R.C. Sharma on 7 th and 8 th June 2017 at Khopoli. A session on Adoption of good practices in power industry at NCQM Ms. Anjali Kulkarni, Chief-Corp delivered session on Adoption of good practices in power industry at NCQM (National Centre for Quality Management) AGM (Annual General Meeting) on 12th August, The session covered good practices adopted by corporate engineering s various verticals for addressing several business challenges and achieving improved performance. Session was widely appreciated by professionals from various industry. A training session on " Design of Wind Turbine Foundation " A training session Design of Wind Turbine Foundation was organized for civil group. Dr. Sanjay Chakarmane, Professor, Structural Engineering, IIT Roorkee was invited. The training session mainly delved into inputs required, design philosophy and expected results for the foundation. A case study was taken up for further understanding and deliberation.

28 "Technical Paper on "Challenges in Restoration of Transmission Lines" Mr. Sandeep Deshmukh presented Technical Paper on "Challenges in Restoration of Transmission Lines - Case Study in Mumbai" during 5 th National Conference on "Innovations & Best Practices in Design, Construction O&M & Environmental Considerations for EHV & UHV Transmission Lines". The conference was conducted by CBIP New Delhi on 22 nd June.17. Knowledge Sharing session on Basics of Protection & Relay co-ordination and Condition Monitoring of switchgear & Transformer A Knowledge sharing session on Basics of Protection & Relay coordination and Condition Monitoring of switchgear & Transformer was conducted by Ms. Shraddha Mahurkar & Mr. Binoy Kalaria on 30 th June 2017 at Godrej premises for Godrej O&M engineers upon their request. The session was coordinated by Mr. Mattoo from Distribution East team and covered protection, relay coordination & condition monitoring aspects as applicable to Godrej. A case study for Relay coordination of Godrej 22 kv network was explained. Godrej officials appreciated team's initiative and inputs. ISO 9001: Transition Auditors certificate course QA&I team arranged Transition Auditors Certificate Course to enhance their knowledge on ISO edition. The course was conducted by faculty Mr. B. Banerjee, Registered QMS Lead Auditor from National Centre for Quality Management (NCQM). Entire QA&I team attended the two days training program organized on 28 th and 29 th June 2017 which will help team to improve their skills and make themselves aware with the amendments made in latest edition of ISO 9001:2015.

29 Employee Corner Mr. Sheshrao Suryawanshi (CTDs), Mr. Dayanand Wanmore (PE) and Mr. Paresh Gohil (QA&I) participated in Customer Acquisition & Retention drive as company's initiative to support Distribution division and received the reward for excellent contribution towards "Best performing zone Operation Grounding" on 29th March 17 at R & R function held at Dharavi. Mr. Paresh Mestri and Mr. Aniket Rajoba obtained Associate membership and Chartered Engineer Certificate from Institute of Engineer. Mr. Dhawal Pandya (QA&I) represented Tata Power in Tata Inter-Company Badminton Tournament held at Andheri Sports Complex on 24th to 26th March Tata Power team played well and reached up to quarter finals of the tournament

30 SARGAM is a company wide initiative for encouraging the music talent within the organization. Annual show of Sargam Nite was held at Y B Chavan auditorim on 16th June Mr. Anand Buddhiwant, Ms. Madhura Korantak, Ms. Deepa Joshi (PE) participated in the show. Traditionally seniors have been recognizing their juniors for their efforts. PE decided to go for a 360 degree turn. A poll was conducted for judging seniors under various categories. Mr. Sandeep Deshmukh & Mr. Shivprasad Lakhapati were chosen as role models and were facilitated by SAMMAN trophy & Certificate in PE Department meeting. Mr. Sujit Jha (QA&I) successfully completed his Post Graduate Diploma in Management from IMT Ghaziabad. His specialization in one year course was Operation Management. Mr. Sanjay Prasad (Electrical Testing) and Ms. Shruti Marathe (QA&I) qualified in Silver Level for TBEM Assessment training.

31 Farewell of Mr. Rajendra Shintre on 29th June 2017 Vishal weds Shubhangi Asha weds Abhit Aarush son of Mr. Amar Chavan Daughter of Mr. Jitendra Shinde

32 Fun At Work F u n a t w o r k p r o g r a m a t T r o m b a y. H o l i C e l e b r a t i o n a t C E N T E C B i r t h d a y C e l e b r a t i o n a t C E N T E C

33 Earth Day Walk was conducted at CENTEC on 21st April 2017 in Technopolis premises. Lunch with MD was organised for 11 Employees at CENTEC on 11th May CEO & MD Mr. Anil Sardana Interacted with the employees. Evacuation mock drill was conducted in Fire Service Week- 14th to 20th April 2017 at CENTEC in presence of Mr. Sanjay Kale Head Fire & Safety.

34 Fun At Work Team members from Testing, PE and other department of Tata Power participated in hiking to Gorakhgad on 25th June 2017 Team members from Testing and PE went on a family Monsoon Picnic to Kondeshwar. Everyone enjoyed mesmerising beauty of waterfall and nature around. A sapling plantation drive was also conducted on the way back.