基于吸收式换热的燃气锅炉烟气余热回收技术的节能效益分析

Energy Efficiency Analysis of the Waste Heat Recovery of Flue Gas from Natural Gas Boiler based on the Absorption Heat Exchange

锅炉是供热系统的主要热源形式,其供热能力约占全国总供热能力的58%。鉴于供热行业煤改气工程的快速推进,燃气锅炉供热能力较高,且排烟温度偏高,具有较大的节能潜力。就常规燃气锅炉区域供热系统的排烟余热回收率低、经济性较差的问题,本文从系统的角度探讨燃气锅炉排烟余热回收利用方法,提出了基于吸收式换热的燃气锅炉烟气余热回收及区域供热技术方案,并从热力学和经济学角度将该系统与目前存在的2种燃气锅炉供热系统进行对比分析,结果表明:该技术方案可将一次热网回水温度降低至20℃;提高一次热网输送能力约47%;与常规燃气锅炉区域供热系统相比,基于吸收式换热的燃气锅炉烟气余热回收及区域供热技术具有系统用能方式较合理、节能效益显著和经济效益较好的特征,是高效、经济回收燃气锅炉排烟余热的主要供热技术方案,适用于供热半径大或既有一次热网输热能力不足的供热工程。

Natural gas-fired boilers are main heat source of district heating systems. The heating capacity of boilers is about 58% of the total heating capacity in China. With the rapid progress of conversion from coal-fired boilers to natural gas-fired boilers,the heating capacity of natural gas-fired boilers increases and it has large potential of energy-saving because of its higher temperature of exhausted gas. In view of a smaller rate of exhausted gas waste heat recovery and poor economic benefit,a natural-gas fired district heating system with waste heat recovery unit based on the absorption heat exchangers（ DH-WHR-AHE） is presented from view of the whole district heating system. And the DH-WHR-AHE and two conventional district heating systems with natural gas boilers are studied according to the theory of both thermodynamics and economics. The studied results indicate that the DH-WHRAHE can decrease the return water temperature of the primary heating network（ PHN） to 20 ℃,and the heating capacity of the existing PHN can be increased by about 47%. Compared with the other two district heating systems with natural gas boilers,the DH-WHR-AHE has the characteristics of more optimum mode of energy utilization,higher energy efficiency and better economic benefit. As the main technical solution to efficiently recover the waste heat of exhausted gas from natural gas-fired boilers,the DH-WHR-AHE could be applied more appropriately to district heating projects with heat transmission over a long distance or with poor heating capacity of the PHN.