Analysis of heat pump flue gas waste heat recovery and nitrogen reduction system

doi:10.16085/j.issn.1000-6613.2023-0091

Abstract

Abstract:

To solve the heat loss and pollution caused by the exhaust gas of gas boilers, this paper proposed a synergistic system for waste heat recovery and low nitrogen oxides combustion. The system used heat exchanger and heat pump evaporator to recover waste heat of flue gas in different stages to realize deep waste heat recovery and waste water recovery of flue gas, and achieve the effect of "wet plume removal". Meanwhile, the recycled hot water was used to heat the humidified and combustion air, achieving nitrogen reduction effect of flue gas. A heat pump flue gas waste heat recovery and nitrogen reduction experimental bench was built. The results showed that when the return temperature and the return flow of the heating network were respectively 40℃ and 1853L/h, experimental system could reduce nitrogen oxides emissions by 60.6%, and the exhaust gas temperature could be reduced to 24.5℃. The system could recover 6.9% of the heat while maintaining a minimum nitrogen oxides emission of 39.7mg/m³, which meant that the system could meet the high-efficiency and clean production requirements of the energy system at the same time. In addition, the annual amount of residual water recovery was 20.2—31.2t/a, which proved that the system can synergistically deal with condensing waste heat recovery, nitrogen emission reduction, residual water recovery and whitening of gas boilers. The minimum payback period of the system investment was about 4.0 years.

Key words: gas boiler, waste heat recovery, heat pump, low nitrogen emission, combustion-air humidification

摘要：

为解决燃气锅炉烟气冷凝余热回收效率低和氮氧化物（NO _x ）排放浓度高的问题，本文提出一种热泵型烟气冷凝余热回收与降氮协同处理系统。该系统利用换热器和压缩式热泵分级回收烟气高温显热和冷凝余热，以实现烟气余热深度回收；并利用吸收余热的热水对助燃空气进行加热加湿，实现烟气降氮效果。搭建了热泵型烟气余热回收及降氮系统试验台，研究了助燃空气含湿量、空气加湿塔液气比、热网回水温度及流量对系统余热回收和低氮排放性能的影响规律。结果表明：在热网回水温度为40℃、流量为1853L/h工况下，系统余热回收效率可达6.9%，排烟温度可降至24.5℃，NO _x 排放浓度可降至39.7mg/m³，减排效率可达60.6%。此外，试验工况下的系统供热效率均大于未加湿时锅炉的热效率，余水回收量为20.2~31.2t/a，证明该系统能够协同处理好燃气锅炉的冷凝余热回收、降氮排放、余水回收和消白问题。该系统的最短投资回收期约为4年，具有良好的节能、环保与经济效益。

关键词: 燃气锅炉, 余热回收, 热泵, 低氮排放, 助燃空气加湿

CLC Number:

TK11⁺5

ZHANG Qunli, WANG Yushi, ZHAI Hongbao, GUO Yingjie, ZHANG Qiuyue, HUANG Haotian. Analysis of heat pump flue gas waste heat recovery and nitrogen reduction system[J]. Chemical Industry and Engineering Progress, 2023, 42(12): 6600-6608.

张群力, 汪玉诗, 翟洪宝, 郭颖杰, 张秋月, 黄昊天. 热泵型烟气余热回收及降氮系统性能[J]. 化工进展, 2023, 42(12): 6600-6608.

Figures/Tables 14

References 18

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测量参数	测试仪器	型号	精度
烟气温度	烟气分析仪	Testo340	±0.5%
NO浓度			±5mg·m^-3
NO₂浓度			±10mg·m^-3
热网水温度	热电偶	T型	±0.75%
热网水流量	电磁流量计	LDYD-3-032-16-1-1	±0.5%
助燃空气温度	温湿度记录仪	WWSZY-1	±0.2℃
助燃空气湿度	温湿度记录仪	WWSZY-1	±2%RH
—	数据采集器	Agilent34972A	±0.004%

测量参数	测试仪器	型号	精度
烟气温度	烟气分析仪	Testo340	±0.5%
NO浓度			±5mg·m^-3
NO₂浓度			±10mg·m^-3
热网水温度	热电偶	T型	±0.75%
热网水流量	电磁流量计	LDYD-3-032-16-1-1	±0.5%
助燃空气温度	温湿度记录仪	WWSZY-1	±0.2℃
助燃空气湿度	温湿度记录仪	WWSZY-1	±2%RH
—	数据采集器	Agilent34972A	±0.004%

热网回水温度/℃	冷凝器侧热网回水流量/L·h^-1	投资回收期/a
40	400	12.8
	800	5.3
	1200	4.0
	1800	4.2
45	1200	6.0

热网回水温度/℃	冷凝器侧热网回水流量/L·h^-1	投资回收期/a
40	400	12.8
	800	5.3
	1200	4.0
	1800	4.2
45	1200	6.0

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