SUSPENDED PARTICULATE MATTER ATTENUATION BY FLUE GAS CONDITIONING

Transcription

1 DATE OF PUBLICATION: JULY 5, 014 ISSN: OLUME 0 ISSUE 06 JULY 014 SUSPENDED PARTICULATE MATTER ATTENUATION BY FLUE GAS CONDITIONING 1 NITIN G. PUNEKAR, S. Y. KAMDI, R.E.THOMBARE 1 Chandrapur Super Thermal Power Station, Chandrapur (India), Rajiv Gandhi College of Engineering, Research & Technology, Chandrapur 4440 (India) Corresponding Author s E mail: nitin.punekar@gmail.com ABSTRACT Increasing population and industrial development insist sustainable electricity, which, in India, mainly depends on based thermal power stations for the generation of electricity. However, the combustion of high ash results in production of large quantity of ash, which essentially comprises bottom and fly ash. Fly ash particles that are in the form of suspensions in the flue gas contribute to an increased suspended particulate matter (SPM) in the surrounding environment. As such, for safeguarding the environment, reduction in the emission levels of the SPM becomes essential. To achieve this, ammonia flue gas conditioning is explored in the manuscript. KEYWORDS: SPM, Flue Gas, Ammonia, AFGCS 1. INTRODUCTION Increasing population and industrial development demand sustainable electricity, which, in India, mainly depends on based thermal power stations for the generation of electricity. However, the combustion of high ash results in production of large quantity of ash, which essentially constitutes bottom and fly ash. Fly ash particles that are in the form of suspensions in the flue gas contribute to an increased suspended particulate matter (SPM) in the surrounding environment. Coal is usually delivered by trains. Modern train unloaders use rotary devices that swivels each carriage upside down to dump the, while all the train is still coupled together. If the plant is built close to a mine, pipeline or conveyors are used to deliver the. Highway trucks can be used as an additional way to support smaller amount of combustible, typically wood chips or INTERNATIONAL JOURNAL OF SCIENCE, ENGINEERING AND TECHNOLOGY

2 DATE OF PUBLICATION: JULY 5, 014 ISSN: OLUME 0 ISSUE 06 JULY 014 biomass. Large collier ships may be also used in favorable locations. The from unloaders is then stored on the yard with large reserve to bridge a possible gap between the deliveries. The is prepared for use in mills by crushing the rough to pieces less about 5 cm in size. Then is the transported by conveyor belts from the yard to silos. The silos feed pulverizers that grind the to powder consistency. The powder is then mixed and preheated with primary combustion air which transports it to the boiler furnace. Figure 1: Electrostatic Precipitator For starting up, the plant usually uses fuel oil as well. The oil is usually stored in vertical cylindrical steel tanks. The energy released from the combustion processes in the furnace can be expressed with equations of the complete combustion. Also calorific value, amount of oxygen and the stechiometric air to fuel ratio are defined by stechiometric equations 1, and. C O CO 1mol 1mol 1mol mol 1mol mol 4,0g,9dm 88,5kJ 1g,9dm,6dm [1] H O H O kJ S O SO 1mol 1mol 1mol,06g,9dm 44,8dm 950kJ 1,89dm [] [] Except the combustible components, the also contains significant volume of INTERNATIONAL JOURNAL OF SCIENCE, ENGINEERING AND TECHNOLOGY

3 DATE OF PUBLICATION: JULY 5, 014 ISSN: OLUME 0 ISSUE 06 JULY 014 ashmatter and water. If the amount of oxygen is lower than the stechiometric air to fuel ratio, incomplete combustion occurs. This is very unpleasant effect that decreases the efficiency and increases the fuel consumption. Some components remain unburnt and further contaminate the flue gas. 1 C O CO 847kJ 1 1mol mol 1mol 1g 11,dm,4dm [4] Combustion is a complex set of exothermic chemical reactions between a combustible and an oxidant agent. In fact, the combustion process runs as a chain reaction in several stages. For most fuels ( including) pyrolysis occurs before combustion and partial incomplete combustion can occur. This fact is important only during the initiation phase of the burning process, while for ordinary calculations, the stechiometric equations give sufficient results. The amount of is defined by the average thermal power of the power station P t during the period and the calorific value of the q. Thermal power can be calculated from the electric power P el and the efficiency η. m Pt Pel [kg] [5] q q Large air fans blow the combustion air into the fireplace where it serves as the oxidizing agent for burning processes. The amount of dry air can be calculated from the oxygen volume in the air (1 %) and the stechiometrical amount of oxygen O calculated from the stechiometric equations 7.1., 7.. and 7,. [4] min 0, 1 O [m kg 1 ] [6] The atmospherical air contains some amount of water vapors increasing its volume. This volume depends on the relative humidity φ, atmospherical pressure P A and the pressure of saturated steam at given temperature P S. PS atm min vapor min PA PS [m kg 1 ] [7] The amount of oxygen is primary defined by chemical structure of the combustible. Because of the nonhomogeneity of burned mixture formed from air and pulverized, some additional air is necessary to allow complete combustion of all fuel. This amount α is typically 0 % of the stechiometric air to fuel ratio. INTERNATIONAL JOURNAL OF SCIENCE, ENGINEERING AND TECHNOLOGY- 81

4 DATE OF PUBLICATION: JULY 5, 014 ISSN: OLUME 0 ISSUE 06 JULY 014 [m kg 1 ] [8] when in one of its heavy water [8] plants air atm having a fired captive co generation To avoid complicated calculations plant had an excess of SPM emission according to stechiometrical equations, approximate Rosin equations can be used for various combustibles. The calorific value of the combustible q can be measured in a calorimeter. levels during its initial days ( mg/nm compared to a limiting value of 115 mg/nm). The most appropriate solution was to externally alter the resistivity of the ash particles in the atm atm atm q charged flue gas medium through weak 0,5 1,01 [m 4187 kg 1 ] [9] [9] alkali conditioning agents. A pilot level study with ammonia as a conditioning qoil 1,7 0,88 [m 4187 kg 1 ] [10] agent was followed by actual [10] plant set up based on in house design and qgas engineering. A fully fledged technology 0,8 1,09 [m m ] [11] [11] 4187 demonstration plant was set up for the. EXPERIMENTAL first time in 1999 in the Captive Power Plant with spectacular success. The SPM The grace of Ammonia Flue Gas which was hovering nearly at Conditioning technology is that it is simple, robust and can be implemented with minimum downtime once the mg/nm came down to less than 70 mg/nm making the stack exhaust almost invisible. initial characterization and system Subsequent to the demonstration of this design is finalized scientifically based on technology and completing the the site specific conditions. That this formalities of patenting (patent is likely technology can be incorporated in new to be available in near future), the or existing installations makes it really a technology was demonstrated at some boon to this country where thermal more power stations within the country power stations still continue to be our with successful results. A systematic main stay in power generation and scientific approach followed at all these where unfortunately contains high places in terms of selection of dosing ash in some cases, excess of 40 rate, types of distributor of the ammonia 45%.This spin off technology was and air mixture resulted in bringing developed by the Heavy Water Board INTERNATIONAL JOURNAL OF SCIENCE, ENGINEERING AND TECHNOLOGY- 81

5 DATE OF PUBLICATION: JULY 5, 014 ISSN: OLUME 0 ISSUE 06 JULY 014 down the SPM concentration in all these power stations. The comparison with other flue gas conditioning chemicals indicated that ammonia or its derivatives would be the most appropriate flue gas conditioning chemical for Indian conditions. After successful commissioning of this system at HWP, Manuguru, this technology was demonstrated at the power plants of Punjab State Electricity Board, Bhatinda and the Gujarat Electricity Board, Ukai through technology transfer channel. In all these power stations the technology was demonstrated as a retrofit option to existing ESPs, and could bring down the SPM concentration to well below 100 mg/nm without any retrofit of ESP itself.. RESULTS & DISCUSSION Results fly ash resistivity and SPM level are summarized below Figure : Fly Ash Resistivity s Gas Temperature INTERNATIONAL JOURNAL OF SCIENCE, ENGINEERING AND TECHNOLOGY

6 DATE OF PUBLICATION: JULY 5, 014 ISSN: OLUME 0 ISSUE 06 JULY 014 Table 1: AFGCS Analysis SR. NO. PARAMETER MAGNITUDE 1 Load(MW) 189 Coal Analysis Wt.% Carbon 41.6 Moisture 1.09 Sulphur 0.89 Ash 9.6 GC(Kcal/kg) 491 Temperature at ESP 19 4 Ammonia Injection Flow (kg/hr) 1 5 SPM level before injection (mg/nm) 6 SPM level after injection (mg/nm) CONCLUSION SPM levels can be easily controlled to the desired level by simply adjusting the dosing amount of the ammonia flue gas conditioning. These agents are quite helpful in improving the dielectric characteristics of fly ash particles, which results in enhanced ash collection efficiency of the ESP. REFERENCES Sengupta I (007) Regulation of suspended particulate matter (SPM) in Indian based thermal power plants: A static approach. Energy Economics 9: Singh DN, Kolay PK (00) Simulation of ash water interaction and its influence on ash characteristics. INTERNATIONAL JOURNAL OF SCIENCE, ENGINEERING AND TECHNOLOGY

7 DATE OF PUBLICATION: JULY 5, 014 ISSN: OLUME 0 ISSUE 06 JULY 014 Progress in Energy and Combustion Science 8: Sahu JN, Mahalik KK, Patwardhan A, Meikap BC (008) Equilibrium studies on hydrolysis of urea in a semibatch reactor for production of ammonia to reduce hazardous pollutants from flue gas. Journal of Hazardous Materials 164: Sahu JN, Mahalik K, Patwardhan A, Meikap BC (008) Equilibrium and kinetic studies on the hydrolysis of urea for ammonia generation in a semi batch reactor, Industrial & Engineering Chemistry Research 47: Sahu JN, Gangadharan P, Patwardhan A, Meikap BC (009) Catalytic hydrolysis of urea with fly ash for generation of ammonia in a batch reactor for flue gas conditioning and NOx reduction. Industrial & Engineering Chemistry Research 48: Jaworek A, Krupa A, Czech T (007) Modern electrostatic devices and methods for exhaust gas cleaning: A brief review. Journal of Electrostatics 65: INTERNATIONAL JOURNAL OF SCIENCE, ENGINEERING AND TECHNOLOGY