Development of Carbon Dioxide Capture Technologies in Coal-Fired Power Plants

Development of Carbon DioxideCapture Technologiesincoa fired power plantsRowerresearcillnsAbstract: With a particular reference to China Huaneng Group's practices in CO, capture, this article presentsa briefing on the current development of CO, capture technologies in coal-fired power plants both in China andabroad. Sooner or later. the integration ofCO, capture and storage (CCS) facility with coal-fired power plantwill be ineitably put on the agenda of developerKeywords: coal-fired power plant. emission control: carbon diaxide capture2007, CO, emissions from China's coal-fired power plantsIntroductionexceeded 2 700 million tons. The power sector is destinedto play a central role in CO, emission reduction since it isWhile fossil fuels underpin social and economic currently a major source of CO, emission, coupled withactivities of the world, they are blamed for global the fact that it produces a concentrated stream of cowarming for the fact that their consumption is building up suitable for capturecarbon dioxide, a kind of greenhouse gas(GHG)in thethe Intergovernmental Improving heat conversion efficiency and therebyPanel on Climate Change(IPCC)under the United Nations, cutting coal consumption is a practical approach forto maintain a safe temperature rise within 2 C, the co, power plants to reduce CO, emissions in the near termconcentration in the air must be controlled within 455 ppm. Highcr efficiency helps to rcducc unit consumption ofIn November 2009, China announced its firm commitment fuel in power generation and consequently decreaseto reduce its carbon dioxide emissions per unit of GDP, or CO, emissions. In recent years, Chinas power sectorcarbon intensity, by 40 to 45 percent by 2020, as compared has cut coal consumption significantly by replacingwith the level of 2005small generating units with larger ones and installinghigh-capacity supercritical and even ultra-supercriticalThe largest sources of CO, emission in China are gener中国煤化工traffic vehicles and power plants that consume a majorityof the primary energy. For the power sector alone, itCNMH Ge energies like windaccounts for about half of the total co, emissions In power, solar power hydropower and biomass powerELECTRICITY 2010.4ECTRICITcan help reduce the dependence on power generation The resulting syngas from the Co shift reactionfrom fossil fuels and slow down the increase in Co, features high sulfur and co, content and high partialcmission. However, China's demand on encrgy has been pressure of CO, and H, S. As appropriate to the gasificationincreasing so sharply over an enormous basis that, in the process, physical absorption of Co, is preferable. Typicalnear term, the goal of new energy development is just to methods of Co, physical absorption are Selexol Methodmaintain the current share of coal power in the total power and Rectisol Method Both methods are based on lowconsumptiontemperature absorbing process. The Selexol Methodoperates at-10-15C and Rectisol Method at-75-0CRestricted by the total potential, enhancing efficicncy Either method can serve to remove CO, and H, S by onend developing new energies is hard to meet the Co, step with high degree of purification, and thus has nocontrol objective. With the huge demand of CO, control need for FGD unit. Nevertheless, the conversion processin the future, the most effective approach is to develop a equipment must be sulfur resistantcost-effective, energy-efficient capture technology andstore CO, deeply under the ground on a large scaleThe Selexol Method involves the use of solventdeveloped by America's Norton Corporation, and theCO, is the main GHG causing greenhouse effect. relevant commercial application data are still not madeMeanwhile, CO, itself is a valuable resource. The Co, publicly available. Since its capital cost and operatingcaptured can be used for carbonate drink, tobacco expense are high, it can be advantageous only in the casesswelling, arc welding, organic compound fabrication, fire of high CO, concentration and pressure as in IGCC PCDCstopping and cooling as well as enhanced oil recovery process(EOR)and enhanced coal-bed methane recovery(ECBM)The Rectisol Method has been in industrial applicationCO, capture in coal-fired power plants for many years in chemical sector. Its major disadvantagesare the use of sophisticated equipment system and highAccording to the combustion stage during which the methanol vapor pressure in the absorption proccss,separation happens, CO, capture technologies for coal- resulting in high loss of solvent. Most studies on CCS forfired power plants fall into three broad categories, i.e. IGCC are based on Selexol Methodpost-combustion capture, pre-combustion decarbonizationand oxy-fuel combustion. No matter which one is Besides the above, membrane separation techniqueaccepted, it has little or nothing to do with the selection is recognized as highly potential in reducing energyof CO, compression, transport or storage technologies. consumption and realizing compacted equipment arrangeSince the high capital cost and operation expenditure kills ment. Various inorganic membranes for gas separationfind ways to reduce capital cost and energy consumption membrane is the most promising prouf oalladium-basedoff the prospective, the path forward undoubtedly is to are under development. In particular, theduring operation.A variety of clean coal power programs aiming atPre-combustion decarbonizationreducing CO, emissions has been proposed, includingPre-combustion decarbonizationPCDC) technology America's Future Gen Program, China's Green Gerfers to processes that take out the chemical energy from Program and Australia,s ZeroGen Program. Most of themcarbon, and separate carbon from other energy-bearing are based on IGCC and integrate fuel cell, H, turbine ansubstances before combustion takes place. Integrated CCS for the ultimate purpose of close-to-zero emission,application, which is a new power generation technoloy Lgasification combined cycle(IGCC)is a typical PCDc even COcombining coal gasification with combined-cycle power The Green Gen Program(Fig. I)will be implementedgeneration. In this case, the fossil fuel is partially oxidized by three stages in a time framework of over ten years. Asin a gasifier. The resulting syngas(Co and H) )is shifted final output, a 250-MW iGCC pilot plant and a 400-MWinto CO, and more H2, carrying over the chemical energy Green Gen pilot plant will be established. As a part of theof the fuel to H2. The resulting CO, can be captured from Stageneng Giroun's 250-MW IGCC powera relatively pure exhaust stream. Finally, the H, can be plant中国煤化工 Iction and installationused as fuel, while the co, is removed before combustion phaseCN MH Gal operation at the endtakes placef202010.4 ELECTRICITY 51R&D for key technologiesmprove IGCC technologyIGCC plantImprove the IGCC polygenerationturbine combined cycle generation andAs boR AaReBuild a 400 MW Green Gen demonstration-engincen(power-beat-syngas) technologyEconomic and technical comparisonbetween 3 500 t/d and 2 2 000 vd gasifers Operate the Green Gen plant2 000 t/d gasificationH, productionProve the Green Gen economie viability250 MW IGCC polygenerationCCs(power-heat-syngas)Fuel cell power generation technologyrepare and extend for commercial systemBuild the Green Gien LaboratoryStage IStage IItge Ill2010201320142017Fig 1 Green Gen Program roadmapIn addition, trans-national and trans- institutional some chemical absorption methods suited to high partialjoint R&D initiatives have been launched. What are pressure, a general approach for chemical process systems,notable in China are the Sino-EU COACH Program and don' t work in this context. Therefore, other chemicalSino-British NZEC Program. COACH aims at laying absorption methods, suited to low partial pressurea solid foundation for establishing high-capacity multi- naturally become the prevailing roadmap for capturinggeneration demonstration projects with CCS. The CCs CO,. Amine method and chilled ammonia method are twosolution(including enhanced oil gas recovery rate)will be major PCC methods that have been demonstrated on aprecedent to the implementation of COACH. Three topics large scale in commercial power plants, and are pursuedhave been established for COACHwith a high level of R&D activities ongoing globallyCoal-based multi-geneartion coal gasification and CCS Amine scrubbing, typically based on MonoethanolInvestigation into China's geological reliability for amine(MEA). is featured in strong alkalinity andCO, storagequick reaction with CO,, achieving quick and effectiveStudy of an overarching framework, covering legal, absorption of CO,. MEA system can operate at both highregulatory, financial and economic dimensionspressure and nomal pressure environment. The operatingtemperature can be adapted to the flue gas tempcraturePost-combustion capturTherefore, the MEA solution is most applicable to coJust as its name implies, post-combustion capture recovery from flue gas. Drawbacks of the MEa method(PCC)is a kind of end-of-pipe solution that involves the include high energy consumption and severe MEAinstallation of a facility downstream the combustion unit oxidative degradation. Researches into renovated amine(boiler or gas turbine)to capture or strip CO, in the flue solvents are under way both in China and abroadgas. This roadmap is applicable to substantially all existing Meanwhile, R&D initiatives are ongoing globally tocoal-fired power plants and requires less modification to optimize the absorption/regeneration processes andthe existing power plant facilities. However, the flip side enhance the integration of CCs with power generationof that coin is that high capital costs and operational costs system so as to cut the energy consumption and make theare required to separate CO, from large-volume fluc gas at system more cost-effcctivea very low CO, partial pressure.中国煤化工。 nd Xi'an ThermalIn a conventional coal-fired power plant, the CO, PoweCN M H Gn pushing ahead withpartial pressure in the flue gas is very low, merely the development of amine-based Co, capture process10%-15% of the total. Physical absorption mcthod and In July 2008, Huaneng Beijing Cogeneration PlantELECTRICITY 2010.4LECTRICITYcommissioned a flue gas CO, capture pilot project with Alstom has performed lab experiments and field testsa capacity of 3 000 tyr. The entire system is 100% based and established six demonstration projects in Americaon domestic equipment and is recognized as Chinas Sweden and Norway in collaboration with partnersfirst CO, capture system for coal-fired power plant InIn October 2009, a 100kt/yr cO, capture facility wasDecember 2009. the world's largest Co, capture pilot established at Mountaineer Power Station, New Havensystem for coal-fired power plant(see Fig. 2 below) was West Virginia with Alstoms chilled ammonia technologycommissioned at Huaneng's Shanghai Shidongkou Il The Co, as captured is compressed, transported andPower Plant. The system outputs 120 kt/yr of liquid Co, stored. Therefore, the Mountaineer Power Station isat food-class purityrecognized as the first of its kind in the world to captureand store cO on the site-fuel combustion is also known as air separationflue gas recirculation technology. The system producesenriched oxygen or pure oxygen by use of an air sepa-ration unit, then feed the fuel and oxygen into an oxy-fuelboiler for combustion. Major components of the fluegas will be Co, and water vapor. Certain portion ofthe flue gas is fed back to the combustion chamberlower the combustion temperature and increase the COconcentration in the nue gas. As nue gas comprisesmainly CO, and H, O, the separation is easy, significantlyreducing the energy consumption for CO, captureFig 2 Huaneng's Shanghai Shidongkou 120-ktyrThe oxy-fuel combustion system is applied in threecO, capture facilitiesmaJor ways.Besides China Huaneng Group's power plants, MEA Oxy-fuel combustion system adapted from conventdecarbonization technology is also applied at Americas ional pulverized coal boilerWarrior Run Power Station and shady point powerIGCC system, where the gas from a coal gasificationStation Warrior Run Power Station is based on 180-Mwprocess is burnt at an oxy-fuel environment andCFB boilers. The CO, capture system, commissioned in the combustion output(mainly CO, is used as the2000, employs ABB Lummus's amine washing process working media of gas turbine and waste hcat boilerand produces 150 vd of food-class CO,. Shady Point Power generation with higher efficiency, for example,Power Station in Oklahoma runs with 4x80 MW CFB fuel cell driven with new fossil fuelboilers and also employs ABB Lummus's amine washingprocess, producing 200 t/d of Co, at purity of 99%In such new fuel cell application, coal gas reacts at theanode of the cell. The flue gas, mostly CO, resulted fromChilled ammonia method is another chemical the fuel combustion at the oxy-fuel environment furtherabsorption solution. Compared with MEA, ammonia reacts at the cathodehas prominent advantages, i.e. absorbing capacity ashigh as 1.2 kg CO/kg NH, and ammonia solvent costs The oxy-fucl combustion system adapted from con-as low as 1/6 of MEA. The disadvantages are that the ventional pulverized coal boiler is one of the technologiesammonium carbonate is apt to volatilization, causing the most likely to put into industrial application. the key isCO, to return to the air, and that the absorbing reaction study on the characteristics of the oxy-fuel combustionoccurs at a temperature below 10C, causing high energy system and design/manufacturing of burns, in particularconsumption for fluc gas cooling. Studies outside China the materials to be used. Certain pilot facilities of oxy-to overcome the above disadvantages have made certain fuel combustion for induetrial heating or power plantindire中国煤化工 ned to test mainly thecheCNMH Gas as oxy-fuel systemAlstom is at the forefront of technical development in combustion, neat conduction, pollutants formation andnd application of co, capture with chilled ammonia. control010. 4 ELECTRICITYSEEIn September 2009, the oxy-fuel combustion systemat Schwarze Pumpe Power Station in Germany was Conclusionscommissioned. Alstom supplied oxy-fuel combustionboilers running at a capacity of 40 t/h(30 MW, )and 1)Sooner or later, the integration of Co, capture andbuming brown coal with an oxygen consumption of 215 th storage facility with coal-fired power plant will be inev-and a co. capture of ll thstably put on agenda of the developerst the second quarter of 2009, the 30-MW, pilot 2)IGCC would lay an important foundation for near-natural gas oxy-fuel combustion systcm at Lacq Power zero emission of pollutants(including Co, )at coal-firedStation in France was commissioned. This is a joint power sectorventure project between Total and Alstom. with a steamoutput of 40 th and an oxygen consumption of 240 td, 3)It will become increasingly mandatory forit is anticipated that 150 kt of co, will be stored at an conventional coal-fired power plants to be retrofitted withabandoned gas fieldCO, capture systems. Such systems shall be designed andintegrated with power generation systems so that theirIn China, studies on the oxy-fuel combustion of energy consumptions and capital costs can be reduced topulverized coal have also been made at universities and acceptable levels.research institutes like Huazhong University of ScienceTechnology, Zhejiang University and North ChinaTranslated by Liu Lianbo andElectric Power Universityedited by Li Shulan)Continued from P49Soot blowerBeijing: Chemical Industry Press, 2001According to the dust characteristic in Yuhuan SCR [2] GB13223-2003. Emission Standard of Air Pollutantsproject, four retractable steam soot blowers are installedfor Thermal Power Plants [S]for cach SCR reactor and cach catalyst layer. The steam [3] EPA. Air pollution control cost manual EPA/452/in soot blowers is at 1.0-1.6 MPa and 350 C, the steamB0200[R]2002,(4):31-46.consumption is 5 th for each, the operation time of each [4]Kathelecn C T. Nitric oxide catalysts in automotivesoot blower lasts 20 minutes, and the operation frequencyexhaust systems []. Catalysis Review: Science andis once every 8 hoursEngineering,1993(35):457-481.[5]Zhang Qiang. Engineering Application and Flue GasConclusionSCR Denitrification Technique in Coal Fired PowerPlant[M]. Beijing: Chemical Industry Press, 2007r The DeNO, system of Huaneng Yuhuan Power Plant [6] Zhang Q, Zhang X T. Choice of key technology forthe first such system of domestically-made ultraimplementing SCR denitrification technique in coalsupercritical 1 000 MW units for China Huaneng Group.fired power plant [J]. Thermal Power Generation,It is also the first De-NO, retrofit project with 1 000-Mw2007,36(4)1-5class capacity undertaken by Beijing Guodian Longyuan [7] Bosch H, Janssen F Catalytic reduction of nitrogenEnvironmental Engineering Co, Ltd. The accomplishmentoxides, a review in the fundamental sand technology小] Catalyst Today,1988(2∷369-532.for the SCR modification of domestically-manufactured [8] GB/ 21509-2008. Denitration Equipment of Coal-ultra-supercritical units with 1 000-Mw class capacity.Fired Flue Gas [S]Therefore, it has strategic significance to the sustainable [9] Shen D, Zhong Z P, Guo X L. Numerical simulationdevelopment of power environment protection in China.of different guide plates in selective catalyticreduction denitrification reactor of 600 Mw powerReferences中国煤化工 onmental ProtectionCNMHG[1] Hao J M, Wang SX, Lu Y Q. Pollution ControlTechnical Manual of Coal-Fired Sulfur Dioxide [M](Edited by Liu Wenying)20104