固体氧化物燃料电池联合发电系统性能计算与优化研究

【作者】 卢立宁；

【导师】 李素芬；

【作者基本信息】 大连理工大学 ， 热能工程， 2004， 硕士

【摘要】 固体氧化物燃料电池(SOFC)是一种高效低污染的新型能量转换装置。SOFC工作温度高(800～1000℃)，可以使用多种燃料作为原料气；其能量转化率不受“卡诺循环”的限制，可达到50％～60％。另外，SOFC还具有寿命长、成本低、综合热电效率高等优点，有非常好的发展前景，很多国家都很重视对SOFC的研究开发工作。 本文从SOFC的工作机理出发，利用电化学和热力学知识建立SOFC本体的能量平衡分析模型和(火用)分析模型。将SOFC组成以天然气为原料的带直接内部重整的SOFC发电系统，应用Visual Basic编程技术进行实例计算。结果表明：SOFC发电系统的发电效率和(火用)效率均可超过45％，优于传统的发电方式。影响SOFC性能的主要原因在于各种过电位的存在，其中欧姆过电位所占比重最大。因此应改进SOFC的结构和材料，提高电池工作电压，增加电池发电量。 研究显示：由于SOFC的工作特点，其排气温度较高，有非常高的余热利用价值。因此本文将SOFC与传统的蒸汽轮机(ST)和燃气轮机(GT)分别组成联合发电系统，建立系统物理模型并进行性能分析计算。计算结果表明：SOFC-ST联合发电系统的发电效率可达58.933％，(火用)效率56.98％。SOFC-GT联合发电系统的能量利用率超过80％，(火用)效率高达70.263％，充分说明将SOFC与传统发电方式组成联合发电系统将是一种性能良好的发电方式。文中还研究了各种系统参数对系统性能的影响。减小SOFC的电流密度和提高燃料利用率有助于系统性能的提高；提高电池工作压力和原料进入电池的初温，均可提高系统发电效率和(火用)效率。 本文利用能量系统的(火用)分析辨识法，找出SOFC-GT联合发电系统的薄弱环节为换热器和SOFC。以提高系统发电效率和(火用)效率为目标，文中提出两种SOFC-GT优化方案。经计算：方案一发电效率提高了8.61％，(火用)效率提高了4.79％；方案二发电效率提高了11.11％，(火用)效率提高了6.63％。系统性能确实得到改善。 文中还研究计算了SOFC-ST-GT联合发电系统。结果表明：此SOFC-ST-GT系统的性能好于SOFC-ST系统，但比SOFC-GT发电系统略差。考虑到经济性问题，小容量机组不建议使用这种系统。更多还原

【Abstract】 Solid oxide fuel cell (SOFC) is a new energy conversion device. Because of its highly efficiency, fuel adaptability and long term stability, the research and development of SOFC have been emphasized in many countries.Energy balance model and exergy analysing model of SOFC are established in this thesis. A SOFC power system, which is fed by natural gas, is calculated. Results show that the electrical efficiency and exergy efficiency of this power system can all exceed 45%. There are several sources that contribute to the irreversible losses in an operating SOFC. The performance of SOFC can be improved by improving SOFC structure and using advanced material.Owing to its working features, SOFC cannot convert all fuel. At the same time, SOFC has highly exit gas temperature. So SOFC can be combined with other power systems. In this paper, energy analysis and exergy analysis of hybrid power systems are given. A combined cycle system with SOFC and steam turbine can achieve an electrical efficiency of 58.933% and an exergy efficiency of 56.98%. For hybrid SOFC and gas turbine power system, the capacity usage ratio and exergy efficiency are, respectively, more than 80% and 70%. It can be find that decreasing the current density and increasing the fuel utilization of SOFC will improve the performance of system. In addition, the increase in operating pressure and inlet temperature of SOFC will increase the electrical efficiency and exergy efficiency of whole power system.Using exergy analysing identification, weak links of SOFC-GT power system can be find. In this paper, main weak links are heat exchanger and SOFC. In order to increase the electrical efficiency and exergy efficiency, two optimization schemes are researched. The electrical efficiency of first scheme is increased by 8.61% and exergy efficiency by 4.79%. For the second scheme, the electrical efficiency and exergy efficiency are increased respectively by 11.11% and 6.63%.At last, a SOFC power system combined both with steam turbine and gas turbine is calculated. Its performance is better than SOFC-ST power system, but not as good as SOFC-GT power system. Considering the investment cost, this system is not suggested when capacity is small.更多还原