Simulation of off-design performance of an efficient power generation system with cold-ends optimization using hot air recirculation

doi:10.16085/j.issn.1000-6613.2021-1196

Abstract

Abstract:

The boiler-turbine coupling power system based on hot air recirculation (HAR) process can improve the efficiency of a thermal power plant significantly, and has the advantages of low investment and high operation safety. In order to solve the problem of safe and efficient operation of the HAR system in the whole load variation range, an in-service 600MW hard-coal-fired power unit was taken as the reference unit, and the variable load simulation of the HAR system was carried out by using the Ebsilon software. The results showed that, the exhaust gas temperature of the waste heat recovery system decreases with the decrease of power load, which might lead to serious low temperature corrosion risk for air preheater under low load. For the existing HAR system, under low load it is difficult to remain a safe cold-end metal temperature for the rotary air-preheater against low-temperature acid corrosion by adjusting the heat absorption of the high-pressure and low-pressure economizers. In order to ensure the safe and reliable operation of the heating surfaces of the HAR system in the whole load variation range, an optimized HAR system was proposed by adding a heat-bypass pipe into the waste heat recovery system. In the load range of 50%—100%THA (turbine heat acceptance), the application of the optimized HAR system could reduce the standard coal consumption of the reference unit by 1.94—3.32g/(kW·h), thereby achieving marked energy-savings in the whole load variation range. To promote the novel technology into practice, a method of controlling the operation of the optimized HAR system was proposed.

Key words: thermal power plant, energy saving, waste heat recovery, thermal economy, hot air recirculation

摘要：

基于热风再循环回收烟气余热的机炉耦合发电（HAR）系统具有高效节能、受热面投资少、运行安全性高等优点。为解决其在全负荷范围安全又高效运行的问题，本文以某600MW烟煤机组为例，利用Ebsilon软件对HAR系统进行变负荷仿真研究。结果表明：烟气余热回收系统的排烟温度随负荷减小而降低，使锅炉空气预热器在低负荷下面临严重低温腐蚀风险；在低负荷下，现有的HAR系统难以通过调节高压、低压省煤器吸热量控制空气预热器冷端金属温度从而控制低温腐蚀；为在全负荷范围保证HAR系统内受热面安全可靠运行，提出了在余热回收系统中增设热量旁通管的HAR优化系统；在50%~100%热耗率验收工况（THA）负荷范围，应用该系统可使实例机组的标煤煤耗降低1.94~3.32g/(kW·h)，在全负荷范围保持显著节能效益。为进一步推进该技术付诸应用，文章提出了HAR优化系统的运行控制方法。

关键词: 火力发电厂, 节能, 余热回收, 热经济性, 热风再循环

CLC Number:

TM611

MA Youfu, WANG Ziwen, LYU Junfu. Simulation of off-design performance of an efficient power generation system with cold-ends optimization using hot air recirculation[J]. Chemical Industry and Engineering Progress, 2022, 41(5): 2340-2347.

马有福, 王梓文, 吕俊复. 热风再循环机炉耦合高效发电系统变负荷性能仿真及优化[J]. 化工进展, 2022, 41(5): 2340-2347.

Figures/Tables 9

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负荷/MW	空预器出口排烟温度/℃	空预器一次风进口温度/℃	空预器二次风进口温度/℃	高省出口水温/℃	低省出口水温/℃	热风再循环率/%	高省旁通水率/%	低省旁通水率/%	暖风器旁通水率/%
300	90	50	49.7	244.6	—	18.5	5.6	0	2.2
360	90	50	50	254.9	175.1	19.4	5.9	0.2	1.4
420	90	50	50	263.9	163.7	20.1	6.2	1.0	0.9
480	90	50	50	271.9	168.9	20.9	6.4	2.6	0.5
540	90	50	50	279.2	173.6	21.5	6.6	3.9	0.2
600	90	50	50	285.7	151.5	22.8	7.2	20.4	0

负荷/MW	空预器出口排烟温度/℃	空预器一次风进口温度/℃	空预器二次风进口温度/℃	高省出口水温/℃	低省出口水温/℃	热风再循环率/%	高省旁通水率/%	低省旁通水率/%	暖风器旁通水率/%
300	90	50	49.7	244.6	—	18.5	5.6	0	2.2
360	90	50	50	254.9	175.1	19.4	5.9	0.2	1.4
420	90	50	50	263.9	163.7	20.1	6.2	1.0	0.9
480	90	50	50	271.9	168.9	20.9	6.4	2.6	0.5
540	90	50	50	279.2	173.6	21.5	6.6	3.9	0.2
600	90	50	50	285.7	151.5	22.8	7.2	20.4	0

负荷/MW	空预器出口排烟温度/℃	空预器一次、二次风进口温度/℃	高省出口水温/℃	低省出口水温/℃	热风再循环率/%	调温风率 /%	高省旁通水率/%	低省旁通水率/%	暖风器旁通水率/%
300	90	50	244.6	131.2	18.6	35.5	3.8	9.6	2.2
360	90	50	254.9	136.4	19.4	26.5	4.4	11.6	1.4
420	90	50	263.9	140.9	20.1	19.1	5.0	13.6	0.9
480	90	50	271.9	144.9	20.9	12.6	5.7	15.6	0.5
540	90	50	279.2	148.4	21.6	7.5	6.1	17.5	0.2
600	90	50	285.7	151.5	22.8	0	7.2	20.4	0

负荷/MW	空预器出口排烟温度/℃	空预器一次、二次风进口温度/℃	高省出口水温/℃	低省出口水温/℃	热风再循环率/%	调温风率 /%	高省旁通水率/%	低省旁通水率/%	暖风器旁通水率/%
300	90	50	244.6	131.2	18.6	35.5	3.8	9.6	2.2
360	90	50	254.9	136.4	19.4	26.5	4.4	11.6	1.4
420	90	50	263.9	140.9	20.1	19.1	5.0	13.6	0.9
480	90	50	271.9	144.9	20.9	12.6	5.7	15.6	0.5
540	90	50	279.2	148.4	21.6	7.5	6.1	17.5	0.2
600	90	50	285.7	151.5	22.8	0	7.2	20.4	0

负荷/MW	热风再循环回收热量 /MW	高省利用热量 /MW	低省利用热量 /MW	发电标煤煤耗 /g·kW^-1·h^-1	HAR优化系统标煤节煤量 /g·kW^-1·h^-1	现有HAR系统标煤节煤量 /g·kW^-1·h^-1
300	4.8	3.2	1.6	276.2	1.94	2.74
360	7.2	4.8	2.4	273.1	2.22	2.87
420	9.9	6.6	3.3	271.0	2.49	2.97
480	13.2	8.8	4.4	269.6	2.74	3.08
540	16.7	11.0	5.7	268.7	2.98	3.16
600	22.6	15.0	7.6	267.9	3.32	3.32