Circulating Fluidized Bed Technology for Large Scale Power Generation Using Coal and Petroleum Coke

Transcription

1 Circulating Fluidized Bed Technology for Large Scale Power Generation Using Coal and Petroleum Coke Timo Jäntti Kalle Nuortimo Foster Wheeler Energia Oy Finland Presented at Russia Power Moscow, Russia March 5-7, 2012

2 Abstract Based on some estimates global consumption of coal in 2030 is projected to be about the same as today. Coal consumption is increasing strongly in China, India and South-East Asia. In Europe coal consumption is estimated to not grow but still about 170GW of new power generation capacity based on fossil fuels will have to be installed by There is also a growing interest towards firing petroleum coke and other refinery byproducts to produce steam with high efficiency and availability in CFB boilers. Efficiency and environmental performance, especially CO 2 emissions will be one of the key issues to consider when planning the new capacity. The proven high efficiency circulating fluidized-bed (CFB) technology offers good solutions for high efficiency electricity production and CO 2 reduction. Foster Wheeler is the world s leading supplier of high-efficiency, low-emission circulating fluidized bed (CFB) boilers for coal and petroleum coke firing. First high efficiency CFB power plants to utilize the supercritical steam parameters in coal firing with once-though steam cycle technology are Lagisza, 460MW e in Poland, and Nocherkasskaya, 330 MW e Russia. As a next step, Foster Wheeler has been given a full notice to proceed by Hyundai Engineering and Construction for the design and supply of four 550 MWe (gross megawatt electric) supercritical circulating fluidized-bed (CFB) steam generators for the Samcheok Green Power Project for Korea Southern Power Co., Ltd. (KOSPO). For petroleum coke firing, commercial scale of 300 MWe is achieved with 2 x 300 MW e and 2 x 330 MW e references in USA. Latest European deliveries include 100 MWe Deven JSCo in Bulgaria and 70 MWe Lukoil Energy & Gas in Romania s.r.l.. These CFB boilers are now in commercial operation. Furthermore, Foster Wheeler has developed its CFB technology to commercially offer the MW e size, with a net efficiency of about 45 %(LHV). INTRODUCTION The target for high efficiency in modern power plants is set not only because of economical reasons but also for enhanced environmental performance in terms of reduced fuel needs, quantity of ash generated and pollutants emitted. Cutting CO 2 emission has become increasingly important after the Kyoto Protocol and European Union emission trading. As coal will remain an important source of energy, the focus has been set to improve the

3 efficiency of coal fired power plants. To achieve this goal, supercritical steam parameters have been applied. Most large European thermal power plants built for fossil fuels such as coal and brown coal over the last decade have had supercritical steam parameters and have been based on pulverized coal (PC) fired once-through boiler technology. Circulating Fluidized Bed (CFB) boiler technology has been growing in size and number over the past three decades and it has established its position as utility scale boiler technology. Plant sizes up to 460 MW e are in commercial operation today, including the 460 MW e Łagisza CFB plant with supercritical steam parameters. When the Łagisza power plant began commercial operations in late June 2009, it marked a new era in the evolution of circulating fluidized bed (CFB) technology. At the heart of the 460 megawatt electric (MWe) Łagisza power plant is the world s largest CFB boiler, which is also the world s first once-through unit (OTU) supercritical CFB boiler. Large enough to produce electricity at utility scale, the Łagisza plant has met or exceeded all emissions and performance expectations since coming online. Figure 1 is a picture of the plant, located in the Katowice area of southern Poland. Figure 1 - Łagisza Power Plant The adoption of the Kyoto Protocol for reducing greenhouse gas (GHG) emissions has increased the urgency of reducing CO 2 emissions in fossil fuel power plants. Since coal will remain an important source of energy, the focus has been on improving the efficiency and

4 environmental performance of new or repowered older coal-fired power plants. Foster Wheeler addresses this need with its proven CFB boiler technology, a clean-coal platform with a unique low-temperature combustion process that cleanly and efficiently burns both traditional fuels and carbon-neutral fuels. Originally developed more than 30 years ago, CFB boilers have maintained a market leadership position through ongoing technical innovation. The Lagisza CFB produces electricity at an efficiency level well above that of typical coal plants. The unit incorporates a number of advanced design features such as compact solid separators, INTREX super heaters, and low-temperature flue-gas heat recovery that captures valuable heat that would otherwise be lost. The unit incorporates also for the first time ever in any CFB highly efficient BENSON vertical once-through technology developed and licensed by Siemens AG, Germany. Foster Wheeler s CFB technology with its low and uniform furnace heat flux is very well suited for the BENSON technology. The once through (OTU) supercritical CFB unit combines high plant efficiency with the well-known benefits of CFB technology, such as superior fuel flexibility, inherently low emissions and high availability. Since all emission requirements can be met without the need for wet desulfurization and selective catalytic reduction (SCR) systems, total plant investment cost was lower for a CFB boiler, compared to the traditional pulverized coal (PC) alternative also investigated for the Łagisza plant. In addition, plant efficiency has increased from about 35 percent to nearly 44 percent based on the fuel s lower heating value (LHV). Compared to the original plant, nitrogen oxide (NOx) has been reduced by 71 percent and CO2 by 28 percent due to the CFB repowering. The gaseous emissions from the plant meets the requirements of the new European Union Large Combustion Plant Directive (LCP), Table 1. Table 1 Emission limits Emission (6% O 2, dry) mg/m 3 n SO NO x 200 Particulates 30

5 The Łagisza plant, owned by Polish utility company Południowy Koncern Energetyczny SA (PKE), replaced old power blocks of the existing 1960 s-era Łagisza Power Plant. The existing blocks consisted of seven units ( MW e each). The new boiler is located adjacent to the old boilers and many of existing plant systems like coal handling and water treatment have been renovated and utilized for the new CFB unit. The PKE Łagisza CFB boiler design The boiler design for Łagisza plant is based on well proven Foster Wheeler CFB technology. It utilizes the experience of over 350 reference units. The fuel data is shown in Table 2. The main fuel for the boiler is bituminous coal. The fuel is sourced from 10 local coal mines with wide range of coal parameters, proving once more the fuel flexibility of the CFB technology. Table 2 Fuel specification Bituminous Coal Design fuel Range LHV (a.r.) MJ/kg Moisture % Ash (a.r.) % Sulfur (a.r.) % Chlorine (dry.) % < 0.4 < 0.4 a.r. = as received The steam parameters for the boiler were specified by the PKE. The selected steam pressure and temperature are proven in other supercritical units and conventional boiler steel materials can be used. Table 3 presents main design steam parameters of this 460 MW e CFB boiler. Table 3 Design Steam parameters at 100 % load SH flow kg/s 361 SH pressure MPa 27.5 SH temperature C 560

6 RH flow kg/s 306 RH pressure MPa 5.48 Cold RH temperature C 315 Hot RH temperature C 580 Feed water temperature C 290 The plant net efficiency is naturally dictated by the selected steam parameters, steam cycle configuration, cooling tower conditions and boiler efficiency. In Łagisza design the boiler efficiency is improved by flue gas heat recovery system, which cools the flue gases down to 85 C thus improving the plant net efficiency. The calculated LHV net plant efficiency for Łagisza is 43.3 % and net power output is 439 MW e. Figure 2 Steam circuitry In the Łagisza CFB boiler, the feed water enters the boiler at a temperature of 290 C for preheating in a bare tube economizer (Figure 2). Water is then fed to the enclosure walls of the INTREX fluidized bed heat exchangers and further to the distribution headers of the evaporator (furnace) walls. The water is heated in the evaporator wall tubes, and dry steam exits at the evaporator outlet. As the boiler operates in sliding pressure mode, dry-out will occur in the subcritical region, as in all once-through designs, at a certain elevation of the evaporator, causing a reduced internal heat transfer coefficient and locally increased tube and fin temperatures. In CFB boilers, the furnace heat flux is considerably lower than in PC

7 boilers, and the highest heat flux occurs in the lower furnace, where water is always subcooled. From the flue gas side, Łagisza s furnace design is based on extensive analysis of all the fuels and limestones that are going to be used. These have given the required data for the design models to make predictions for circulating material particle size distribution, solids densities and finally the heat transfer with gas temperatures. The design resulted with a furnace cross section of 27.6 x 10.6 m and height of 48.0 m. The Łagisza CFB boiler is presented in figure 3. Figure 3 Łagisza CFB Boiler Design A single fluidizing grid is utilized in the bottom of the furnace under which there are separate air plenums introducing primary air to furnace. The primary air flow for these air plenums is measured and controlled separately to insure equal air flow to all sections of the grid and uniform fluidization. The single continuous fluidizing grid ensures simple control as well as a stable and uniform operation of the furnace.

8 Fuel is introduced to the side walls of the furnace via feeding points giving the same grid area per feed point as used in other boilers. Secondary air is introduced also on long furnace walls at different elevations to provide staged combustion for minimizing the NO x emissions. Lagisza Commercial Operation Operation experience of the Łagisza boiler has been excellent. Over the whole load range boiler has performed as designed and operation has been steady and easily controllable. Basic process parameters on different levels of load are shown on table 4. Table 4 Process parameters on different load levels 40 %MCR 65 %MCR 80 %MCR 100 %MCR Main steam flow kg/s Main steam pressure Bar Main steam temperature C Reheat temperature C Flue gas exit temperature C Peak heat fluxes in a CFB boiler are clearly lower than experienced in PC boilers. Because of the low heat fluxes in a CFB furnace, the full load water-steam mass flow rate can be in the kg/m 2 s range. This low mass flux creates a natural circulation characteristic that together with stable circulation of the solids giving more uniform heat flux distribution, will result in reduced tube tube temperature differentials. Based on the analysis result from Łagisza CFB, heat flux profiles to furnace walls have been low and uniform during coal firing. Due to uniform heat fluxes to furnace walls, steam temperature variation after evaporator has been minimal when operating above Benson-point. Emissions have been lower than set by the Large Combustion Plant (LCP) directive and a low flue gas exit temperature together with good combustion efficiency are guaranteeing high thermal efficiency. Control concept chosen for the Łagisza boiler has turned out to be a success. The CFB is behaving well on transient conditions and on the other hand all the parameters are stable as the boiler is operated on steady state conditions.

9 Łagisza plant provides base for scale up to larger CFB units The Lagisza boiler s general layout was based on the conventional in-line arrangement that has been applied in Units 4 6 at the Turów power plant. Mechanical scale up was also reasonable modest since physical size of the Łagisza boiler is not significantly larger than boilers already in operation for lower grade fuels like brown coal in the Turów units. No problems regarding mechanical scale up of the boiler occurred during commissioning. Boiler auxiliary equipments functioned without major problems from minimum up to maximum boiler load. As Foster Wheeler is heading for larger boiler sizes and higher efficiencies it is important to collect all possible information from Łagisza to achieve a better understanding of large CFB boilers. As planned during the boiler commissioning and trial operation, Foster Wheeler carried out an extensive testing program on the Łagisza boiler. Performance of the boiler was tested on steady state operation as well as in dynamic conditions and data from the measurements will be used for validation of the process and dynamic models for large scale CFB. Operating experiences of the world s first CFB utilizing supercritical steam parameters have been excellent. Boiler operation has been stable and easily adjustable while heat fluxes to furnace walls on coal firing have been low and uniform- as was expected. This provides a good knowledge base for Foster Wheeler to propose CFB technology with super-critical steam parameters up to the 800 MWe scale in the near future. NOVOCHERKASSKAYA PROJECT General In year 2007 The Sixth Wholesale Power Producer OGK-6 made a decision to take a step forward in their power producing capacity in terms of combustion technology and steam parameters. A selection of supercritical CFB combustion technology with 565/565 oc steam temperatures was made to be used in a new Novocherkasskaya GRES Unit No 9 (Figure 5).

10 Figure 5: Novocherkasskaya GRES Unit No 9 Foster Wheeler was selected as a supplier of the 330 MWe CFB boiler(table 5) to PJSC Energo Mashinostroitelny Alliance (EM Alliance). Manufacturing of pressure parts within FW s scope of supply furnace walls, grid and wingwall superheaters took place on FW s Fakop workshop in Sosnowiec (Poland), cyclones, furnace roof and Intrex superheaters were manufactured in WarkausWorks (Finland). The boiler is capable of combusting wide selection of fuels including anthracite, bituminous coal and coal slurry. Table 5.Design values of Novocherkasskaya GRES Unit No 9 Plant Electrical Output (Gross/Net) MWe 330/312 Net Plant Efficiency (LHV/HHV) % 41,5/39,9 Net Plant Heat Rate (LHV/HHV) kj/kwh 8681 SH flow kg/s 278 SH pressure bar(g) 247 SH temperature C 565 RH flow kg/s 227 RH pressure bar(g) 37 RH temperature C 565 Feed water temperature C 280 Current status

11 Basic design, followed by detail design as well as purchasing procedures is ready and all engineering activities have been finished. Manufacturing of pressure parts was completed in April Pressure parts' as well as other equipment's deliveries to customer have been completed on May SAMCHEOK GREEN POWER 4 X 550 MW E SUPERCRITICAL CIRCULATING FLUIDIZED-BED STEAM GENERATORS IN SOUTH KOREA Foster Wheeler has been given a full notice to proceed by Hyundai Engineering and Construction for the design and supply of four 550 MWe (gross megawatt electric) supercritical circulating fluidized-bed (CFB) steam generators for the Samcheok Green Power Project for Korea Southern Power Co., Ltd. (KOSPO). Contract includes the design and supply of four 550 MWe advanced vertical tube, once-through supercritical CFB steam generators feeding two steam turbines. The CFB steam generators will be designed to burn coal mixed with biomass while meeting stringent environmental requirements. When these CFB units enter commercial operation in 2015, they will be the world's largest and most advanced CFB s providing KOSPO with a new level of fuel flexibility, reliability and environmental performance. DESIGN STUDY OF A 800 MW E CFB Łagisza has validated Foster Wheeler s supercritical CFB design platform providing a solid base for the further scale-up of the CFB technology. Foster Wheeler is offering today supercritical CFB up to scale 800 MW e in size for bituminous coal, meeting the highest requirements for plant efficiency and environmental performance. Specially, India and South- East Asia are potential areas for large scale supercritical CFB technology in near future. PETROLEUM COKE FIRING IN UTILITY SCALE Petroleum coke, a solid residue by-product of the crude oil refining processes, mostly delayed coking, is a very attractive fuel for large-scale power production due it s high carbon content, low hydrogen and almost free of ash qualities. Foster Wheeler is the market leader in petcoke-fired CFB-boilers with over 45 references and over 60 % market share in petroleum coke fired boilers. CFB is suitable technology also for firing other refinery by-products. For petroleum coke firing, commercial scale of 300 MWe is achieved with 2 x 300 MWe and 2 x

12 330 MWe references in USA. Latest European deliveries include 100 MWe Deven JSCo in Bulgaria and 70 MWe Lukoil Energy & Gas in Romania s.r.l.. These CFB boilers are now in commercial operation. Deven JSCo, Bulgaria Foster Wheeler recently replaced two Russian PC boilers at Deven s soda ash plant in Devnya, Bulgaria (Figure 6). Figure 6: Deven 100MWe CFB boiler in Bulgaria Value added seen by Deven in Coke Fired CFB Technology (Table 6) is gained from flexible fuel sourcing, where coke is supplied from nearby Foster Wheeler cokers and also local limestone is used. Deven CFB boiler is designed to burn up to 80% (7.5% sulfur) coke with Russian semi-anthracite coal. FW Full Release for the project was received in 2006 and CFB plant start-up was in June Table 6:Design values of Deven JSCo, CFB boiler Total Heat Output 312 MWth Plant Electrical Output 100 MWe Steam Flow 111 kg/s Steam Pressure 100 bar Steam Temperature 540 C Fuel Petroleum Coke FW Full Release 2006

13 Commercial Operation 2009 Lukoil Energy & Gas For petroleum coke firing, Foster Wheeler recently replaced oil boilers at Lukoil s refinery in Ploiesti, Romania (Figure7). Delivery included a 70 MWe boiler in November 2007, which entered into commercial operation in October Dependency on crude oil as boiler fuel was decreased (Table 7), plant capacity increased (Table 8), emissions were lower (Table 9) and fuel sourcing capabilities flexible. Figure 7: Lukoil CFB boiler in Romania Table 7:Design fuel for Lukoil boiler Design fuel: Petroleum Coke LHV (a.r.) MJ/kg 31,14 Moisture % 10,2 Ash (a.r.) % 0,55 Sulfur (a.r.) % 3,53 Table 8:Design steam data for Lukoil boiler

14 Total Heat Output 185 MWth SH flow 72 kg/s SH pressure 100 bar SH temperature 540 C Feed water temperature 214 C Table 9:Emissions for Lukoil boiler Emission (6% O 2, dry) mg/m 3 n SO NO x 200 Particulates 30 Summary Circulating fluidized bed (CFB) technology has established its position as a utility-scale boiler technology. When considering either new plants or repowering old plants, efficiency and environmental performance are the key issues. High efficiency means lower fuel consumption, and lower levels of ash and air emissions, including lower emissions of carbon dioxide (CO 2 ). To achieve these goals, supercritical steam parameters have been applied. First high efficiency CFB power plants to utilize the supercritical steam parameters in coal firing with once-though steam cycle technology are Lagisza, 460MW e in Poland, and Novocherkasskaya, 330 MW e Russia. As a next step, Foster Wheeler has been given a full notice to proceed by Hyundai Engineering and Construction for the design and supply of four 550 MWe (gross megawatt electric) supercritical circulating fluidized-bed (CFB) steam generators for the Samcheok Green Power Project for Korea Southern Power Co., Ltd. (KOSPO). Contract includes the design and supply of four 550 MWe advanced vertical tube, once-through supercritical CFB steam generators feeding two steam turbines.. Initial operating experiences of the world s first CFB utilizing supercritical steam parameters have been excellent. Extensive development work combined with Lagisza experiences provides a good knowledge base for Foster Wheeler to propose CFB technology with supercritical steam parameters up to scale 800 MW e.

15 For petroleum coke firing, commercial scale of 300 MWe is achieved and latest deliveries include 100 MWe Deven JSCo in Bulgaria and 70 MWe Lukoil Energy & Gas in Romania s.r.l..

16 REFERENCES /1/ T. Jäntti et al.; Łagisza 460 MWe Supercritical CFB - Design, Start-up and Initial Operation Experience Presented in P-GEN Europe 2009, Cologne, Germany, May, 2009 /2/ T. Jäntti et al.; Circulating Fluidized-bed Technology Towards Zero CO 2 Emissions Presented in P-GEN Europe 2006, Cologne, Germany, 31 May, 2006