400MW整体煤气化联合循环机组脱硝方案比较

Comparison of Denitration Schemes in 400 MW IGCC Plant

整体煤气化联合循环(integrated gasification combined cycle,IGCC)电厂是我国洁净煤发电的主要方向之一。为了合理选择NO x排放方案,基于流程模拟软件Thermoflex建立了400 MW级IGCC系统模型,采用回注氮气或蒸汽法降低燃气轮机燃烧温度以减少热力型NO x排放,回注所需稀释剂不足时结合余热锅炉+选择性催化还原(selective catalytic reduction,SCR)法,保证各脱硝方案下排烟中NO x含量均为50 mg/m3;在燃气轮机功率为286 MW工况下比较各系统的热力性能,并结合工程实际计算各方案初始投资。结果表明:回注氮气脱硝效果不如注蒸汽,但回收利用来自气化岛氮气可提高能量利用效率,增加燃气轮机出力,系统效率有所提高;在目前IGCC电厂关键设备的技术水平下,增大SCR脱硝比例可改善IGCC系统热力性能,而IGCC电厂单位投资和运行成本也将增加。随着IGCC系统关键技术的提升,回注氮气法将会是最具环保节能潜力的脱硝方案。

IGCC （ integrated gasification combined cycle） plant is one of the main way of clean coal power generation in China. In order to choose a reasonable NOr emission control scheme, the model of 400 MW IGCC was constructed with using process simulation software Thermoflex, in which nitrogen injection and steam injection were used to decrease the burning temperature then reduce thermal NOx emissions, SCR （ selective catalytic reduction） in the HRSG （ heat recovery steam generator） was adopted under the diulent inadequate condition to ensure that the NOx emission approached about 50 mg/m3. The thermal performance of different systems under 286 MW turbine power were studied, and the initial investment of each scheme was calculated combined with practical engineering. The results show that the denitration effect of steam injection is superior to the nitrogen injection, however, the nitrogen injection scheme recycles the nitrogen from Gasification Island, which can improve energy efficience, increase gas turbine power, and enhance system efficiency. The thermal performance of IGCC can he improved by using SCR under the current technology level of key equipments in IGCC units except the highest invstment and operation cost. After all, the nitrogen injection scheme will be the most potential denitration scheme with environment protection and energy saving, along with the promotion of key technology for IGCC.