火电厂石灰石——石膏湿法脱硫系统优化运行的策略改进
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摘要
21世纪随着中国经济的飞跃前行,拉动了全国电力工业的长足发展,尤其是火力发电厂迅猛投建。电力工业实现将一次能源向二次能源高效转换,为社会生产了洁净、高效、传输方便的电能,但同时必然消耗了大量的化石燃料,并生产了大量SO_2等大气污染物。SO_2不仅破坏全球生态环境,威胁人类生存健康,还制约了国家的国民经济发展,因此对燃煤电厂实行SO_2脱排与治理已刻不容缓。
本论文基于萧山发电厂两炉一塔式石灰石——石膏湿法脱硫系统,针对烟气脱硫设施运行中常见问题:运行稳定性差、GGH堵塞及结垢、主机与脱硫系统之间缺乏协调控制、系统经济低下等,采取设备改造、技术革新、试验数据、软件设计等方面的研究,旨在提高脱硫系统运行的可靠性、经济性、稳定性,探求主机与脱硫系统之间的协调控制运行方式,为企业达到脱硫系统高投运率、高脱除率及低经济指标之间新的平衡点。本文的主要工作和成果如下:
1、针对目前企业以牺牲设备或降低系统经济性为代价,追求脱硫投运率、脱硫效率双95%门槛值的问题,采用对系统多年的运行数据分析及试验研究,得出提高脱硫精度的方法:控制浆液pH值在5.45～5.6相对狭小的范围,确保吸收塔内部化学反应的良好环境;合理安排浆液循泵运行组合,使吸收塔内部的液气比与系统经济性取得最佳;控制浆液排放最佳密度1120～1130kg/m~3,不仅提高石灰石浆液的使用效率,也保证了石膏结晶品质。
2、针对系统存在GGH结垢的顽疾,通过对GGH在线吹灰器改造、GGH抽箱换热面清洗、更换L型换热元件、人工冲洗等措施,寻找暂时解决GGH易结垢、堵塞而造成GGH压差大、脱硫系统阻力大的方法;针对增压风机电耗高,利用变频新型技术对增压风机电机进行调速改造,实现增压风机的转速随原烟气流量变化而变化,避免了挡板开关时风道压流损失、风道磨损、噪声大的问题,降低了系统对风道密封性能的破坏,改善了系统的经济性。
3、针对脱硫系统串接入主机与烟囱之间,改变原来的烟气回路,存在脱硫系统与主机如何协调运行与控制的问题。在分析脱硫串接前后的烟气流向变化,分析烟气流量与主机负荷之间的关系,提出在增压风机与主机锅炉之间设计一个联合控制程序,以稳定增压风机出口压力-220Pa,实现炉膛内部负压P1、P2控制在-30～-50Pa,避免主机在烟气排出不当时引起锅炉MFT动作,影响机组的安全稳定运行。还利用实验证实增压风机采用变频器控制时,对增压风机前导叶开度k的最佳值为80%。
4、本论文针对萧山电厂脱硫系统提出优化运行的一系列改进策略,虽然存在一定的局限性,但对提高同类型脱硫系统的运行可靠性、经济性、稳定性,以及主机与系统之间的联控运行等具有一定的参考价值。
Inspired by the rapid development of China' s economy in the 21st century, the electricity industry has developed greatly, particularly the vast investment and construction of thermal power plants. The electricity industry converts primary energy to the secondary energy and provides clean, high efficiency and convenient transfer power for the society, but consumes a lot of fossil fuels and produces a great deal of SO_2 and other atmospheric pollutants. It is well known that SO_2 not only wrecks the global environment as well as a threat to human health and survival, but also constrains the economic development. Therefore, it is essential for coal-fired power plant to implement the emission and governance of SO_2 after desulfurization.
To date, there are still many problems existing in the flue gas desulphurization process, including (1) poor stability; (2) GGH block and scaling; (3) lacking coordination between host and the desulfurization control system; (4) low economic benefit of system, etc. In order to solve these problems, and improve reliability, economical efficiency and stability of system operation, and explore the compatible operation mode between the host and the desulfurization control system, and provide a new balance between high investment/operation ratio, high removal ratio and low economic indicators for the company, in the present paper, based on two furnaces-one tower limestone-gypsum wet flue gas desulfurization system of Xiaoshan coal-fired Power Plant, we draw a series of meaningful conclusions after careful investigation via equipment modification, technological innovation, data test, software design.
1. Improving desulfurization precision. Nowadays, a lot of companies pursue investment/operation ratio of 95 % and removal ratio of 95 % at the expense of equipment and system economical efficiency. In order to solve these problems, after long-time analysis of operation data and test of system, we propose some effective ways to improve the desulfurization precision as follows: (1) Reasonable pH value. The pH value of slurry in the narrow range of 5.45 to 5.6 can provide a favorable environment for chemical reactions in absorption tower; (2) Reasonable combination of slurry pump to obtain the optimal combination point between liquid/gas ratio and economical efficiency in absorption tower; (3) Controlling emission density. Control the optimal emission density in the range of 1120～1130kg/m~3 to improve the utility efficiency of limestone slurry and ensure the quality of gypsum crystal.
2. Removing GGH scaling and reducing power consumption of booster fan. We explored temporary methods to solve the excessive pressure difference and big resistance of desulfurization system caused by GGH scaling and block, including on-line soot blowers modification, heat-transfer cleaning of pump box, replacing the L-type heat transfer element and manual washing, etc. On the other hand, we reduced the power consumption of booster fan by transforming the motor frequency of booster fan, by which the speed of the booster fan can change with the original gas flow and avoid the air duct press flow loss, air duct wear and big noise when the baffle switches, reduce the duct sealing performance of damage caused by systemand improve economical efficiency of system.
3. Enhancing the coordination controllability between the host and the desulfurizationsystem. After analyzing the flue gas before and after tandem connection of desulfurization and the relationship between the flue gas flow and the host load, we proposed to design a joint control procedure between the booster fan and the host boiler to stabilize the booster fan outlet pressure at-220Pa and obtain the negative pressure P_1 and P_2 in chamber in the range of -30～-50 Pa, and avoid the MFT action of boiler as the flue gas emissions inappropriately by the host and ensure safe and stable operation of crew. It is also confirmed that the optimal K value of front guide vane of booster fan should be 80 % when the booster fan is under frequency control.
4. In this paper, we have proposed a series of methods for the optimal system operation of Xiaoshan coal-fired power plant. Despite some limitations, these methods are meaningful and provide reference values for the improvement of system operation reliability, economical efficiency, stability as well as joint control between host and system.
本论文基于萧山发电厂两炉一塔式石灰石——石膏湿法脱硫系统,针对烟气脱硫设施运行中常见问题:运行稳定性差、GGH堵塞及结垢、主机与脱硫系统之间缺乏协调控制、系统经济低下等,采取设备改造、技术革新、试验数据、软件设计等方面的研究,旨在提高脱硫系统运行的可靠性、经济性、稳定性,探求主机与脱硫系统之间的协调控制运行方式,为企业达到脱硫系统高投运率、高脱除率及低经济指标之间新的平衡点。本文的主要工作和成果如下:
1、针对目前企业以牺牲设备或降低系统经济性为代价,追求脱硫投运率、脱硫效率双95%门槛值的问题,采用对系统多年的运行数据分析及试验研究,得出提高脱硫精度的方法:控制浆液pH值在5.45～5.6相对狭小的范围,确保吸收塔内部化学反应的良好环境;合理安排浆液循泵运行组合,使吸收塔内部的液气比与系统经济性取得最佳;控制浆液排放最佳密度1120～1130kg/m~3,不仅提高石灰石浆液的使用效率,也保证了石膏结晶品质。
2、针对系统存在GGH结垢的顽疾,通过对GGH在线吹灰器改造、GGH抽箱换热面清洗、更换L型换热元件、人工冲洗等措施,寻找暂时解决GGH易结垢、堵塞而造成GGH压差大、脱硫系统阻力大的方法;针对增压风机电耗高,利用变频新型技术对增压风机电机进行调速改造,实现增压风机的转速随原烟气流量变化而变化,避免了挡板开关时风道压流损失、风道磨损、噪声大的问题,降低了系统对风道密封性能的破坏,改善了系统的经济性。
3、针对脱硫系统串接入主机与烟囱之间,改变原来的烟气回路,存在脱硫系统与主机如何协调运行与控制的问题。在分析脱硫串接前后的烟气流向变化,分析烟气流量与主机负荷之间的关系,提出在增压风机与主机锅炉之间设计一个联合控制程序,以稳定增压风机出口压力-220Pa,实现炉膛内部负压P1、P2控制在-30～-50Pa,避免主机在烟气排出不当时引起锅炉MFT动作,影响机组的安全稳定运行。还利用实验证实增压风机采用变频器控制时,对增压风机前导叶开度k的最佳值为80%。
4、本论文针对萧山电厂脱硫系统提出优化运行的一系列改进策略,虽然存在一定的局限性,但对提高同类型脱硫系统的运行可靠性、经济性、稳定性,以及主机与系统之间的联控运行等具有一定的参考价值。
Inspired by the rapid development of China' s economy in the 21st century, the electricity industry has developed greatly, particularly the vast investment and construction of thermal power plants. The electricity industry converts primary energy to the secondary energy and provides clean, high efficiency and convenient transfer power for the society, but consumes a lot of fossil fuels and produces a great deal of SO_2 and other atmospheric pollutants. It is well known that SO_2 not only wrecks the global environment as well as a threat to human health and survival, but also constrains the economic development. Therefore, it is essential for coal-fired power plant to implement the emission and governance of SO_2 after desulfurization.
To date, there are still many problems existing in the flue gas desulphurization process, including (1) poor stability; (2) GGH block and scaling; (3) lacking coordination between host and the desulfurization control system; (4) low economic benefit of system, etc. In order to solve these problems, and improve reliability, economical efficiency and stability of system operation, and explore the compatible operation mode between the host and the desulfurization control system, and provide a new balance between high investment/operation ratio, high removal ratio and low economic indicators for the company, in the present paper, based on two furnaces-one tower limestone-gypsum wet flue gas desulfurization system of Xiaoshan coal-fired Power Plant, we draw a series of meaningful conclusions after careful investigation via equipment modification, technological innovation, data test, software design.
1. Improving desulfurization precision. Nowadays, a lot of companies pursue investment/operation ratio of 95 % and removal ratio of 95 % at the expense of equipment and system economical efficiency. In order to solve these problems, after long-time analysis of operation data and test of system, we propose some effective ways to improve the desulfurization precision as follows: (1) Reasonable pH value. The pH value of slurry in the narrow range of 5.45 to 5.6 can provide a favorable environment for chemical reactions in absorption tower; (2) Reasonable combination of slurry pump to obtain the optimal combination point between liquid/gas ratio and economical efficiency in absorption tower; (3) Controlling emission density. Control the optimal emission density in the range of 1120～1130kg/m~3 to improve the utility efficiency of limestone slurry and ensure the quality of gypsum crystal.
2. Removing GGH scaling and reducing power consumption of booster fan. We explored temporary methods to solve the excessive pressure difference and big resistance of desulfurization system caused by GGH scaling and block, including on-line soot blowers modification, heat-transfer cleaning of pump box, replacing the L-type heat transfer element and manual washing, etc. On the other hand, we reduced the power consumption of booster fan by transforming the motor frequency of booster fan, by which the speed of the booster fan can change with the original gas flow and avoid the air duct press flow loss, air duct wear and big noise when the baffle switches, reduce the duct sealing performance of damage caused by systemand improve economical efficiency of system.
3. Enhancing the coordination controllability between the host and the desulfurizationsystem. After analyzing the flue gas before and after tandem connection of desulfurization and the relationship between the flue gas flow and the host load, we proposed to design a joint control procedure between the booster fan and the host boiler to stabilize the booster fan outlet pressure at-220Pa and obtain the negative pressure P_1 and P_2 in chamber in the range of -30～-50 Pa, and avoid the MFT action of boiler as the flue gas emissions inappropriately by the host and ensure safe and stable operation of crew. It is also confirmed that the optimal K value of front guide vane of booster fan should be 80 % when the booster fan is under frequency control.
4. In this paper, we have proposed a series of methods for the optimal system operation of Xiaoshan coal-fired power plant. Despite some limitations, these methods are meaningful and provide reference values for the improvement of system operation reliability, economical efficiency, stability as well as joint control between host and system.
引文
[1]孙克勤,钟秦.火电厂烟气脱硫系统设计、建造及运行[M],北京:化学工业出版社,2005.
[2]中国环境年鉴编辑委员.中国环境年鉴2005[M].北京:中国环境年鉴社,2005.
[3]何昌群,谢敬东,魏萍.电力行业节能减排是国家重要战略举措[J].华东电力,2008,36(9):67-70.
[4]国家电力监管委员会,国家发展和改革委员会,国家能源局.2007年电力企业节能减排情况通报[R].北京:国家电力监管委员会网站,2008-9-17.
[5]王琼.火电厂石灰石/石膏湿法烟气脱硫系统的设计及优化[D].武汉:武汉大学硕士学位论文,2005.
[6]Tarvis Thoms.developments for the precombustion removal of inorganic sulfur from coal.Fuel processing Thchology[J],1995,Vol(43):123-128.
[7]Gottlicher,G,Schneider,J.,Baue r,H.Biomass solutions for heat and Power egneration[J].VGB Poewrtech,2004,84(10):100-104.
[8]Jozewicz,W.,Gostomczyk,M.A.Multi Pollutant control for power Plants[J].Inzynieria Chemican I Porcesowa,2004,25(4):75-81.
[9]杨巧云.火电厂脱硫技术综述[J].环境保护科学,2008,34(3):8-11.
[10]Selvaraj P T,Little M.Analysis of mobilized cell bioreactor for desulfurization of flue gases and sulfite/sulfate-laden wastewater[J].Biodegradation,1997,(8):227-236.
[11]Lee K H,SubleRe K L.Simultaneous combined microbial removal of sulfur dioxide and nitric oxide from a gas stream[J].Bio—chem..Biotehnol,1991,28(Aprl):623-625.
[12]Cork D J,Jenger B E and manka A.Biocatalytic production of sulfur from process waste streams[J].Biotechnol.Bioeng,1986,23(16):149-151.
[13]张驰.国外湿法脱硫技术进展[J].化学工业与工程技术,2007,(28):51-54.
[14]岳涛,庄德安,杨明珍,邓九兰,张迎春.我国燃煤火电厂烟气脱硫脱硝技术发展现状[J].能源研究与信息,2008,24(03):125-129.
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[18]冯静,刘向东.模糊控制在湿法脱硫烟气系统中的应用[J].环境科学与技术,2008,31(10):135-136.
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[2]中国环境年鉴编辑委员.中国环境年鉴2005[M].北京:中国环境年鉴社,2005.
[3]何昌群,谢敬东,魏萍.电力行业节能减排是国家重要战略举措[J].华东电力,2008,36(9):67-70.
[4]国家电力监管委员会,国家发展和改革委员会,国家能源局.2007年电力企业节能减排情况通报[R].北京:国家电力监管委员会网站,2008-9-17.
[5]王琼.火电厂石灰石/石膏湿法烟气脱硫系统的设计及优化[D].武汉:武汉大学硕士学位论文,2005.
[6]Tarvis Thoms.developments for the precombustion removal of inorganic sulfur from coal.Fuel processing Thchology[J],1995,Vol(43):123-128.
[7]Gottlicher,G,Schneider,J.,Baue r,H.Biomass solutions for heat and Power egneration[J].VGB Poewrtech,2004,84(10):100-104.
[8]Jozewicz,W.,Gostomczyk,M.A.Multi Pollutant control for power Plants[J].Inzynieria Chemican I Porcesowa,2004,25(4):75-81.
[9]杨巧云.火电厂脱硫技术综述[J].环境保护科学,2008,34(3):8-11.
[10]Selvaraj P T,Little M.Analysis of mobilized cell bioreactor for desulfurization of flue gases and sulfite/sulfate-laden wastewater[J].Biodegradation,1997,(8):227-236.
[11]Lee K H,SubleRe K L.Simultaneous combined microbial removal of sulfur dioxide and nitric oxide from a gas stream[J].Bio—chem..Biotehnol,1991,28(Aprl):623-625.
[12]Cork D J,Jenger B E and manka A.Biocatalytic production of sulfur from process waste streams[J].Biotechnol.Bioeng,1986,23(16):149-151.
[13]张驰.国外湿法脱硫技术进展[J].化学工业与工程技术,2007,(28):51-54.
[14]岳涛,庄德安,杨明珍,邓九兰,张迎春.我国燃煤火电厂烟气脱硫脱硝技术发展现状[J].能源研究与信息,2008,24(03):125-129.
[15]刘国瑞.湿法烟气脱硫技术研究[D].杭州:浙江大学硕士学位论文,2003.
[16]孔华.石灰石湿法烟气脱硫技术的试验和理论研究[D].杭州:浙江大学博士学位论文,2001.
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