Large-scale Gas Absorption Heat Pump Applied for Distributed Heating: a Preferred Alternative to Gas Boilers
Boilers are the main heating methods in building and industry fields at present. In the process of carbon neutrality, the replacement of gas boilers with high energy consumption and carbon emission is of vital importance. However, recent electric heat pumps are confronted with application problems such as difficulties in electrical power expansion, lower heating capacity of single unit, higher investment and operating costs, making it difficult to directly replace fuel boilers. Gas-fired absorption heat pump is a new heating technology with high efficiency and low carbon emission. It can be driven by high-grade heat of natural gas combustion, and recover low-grade heat from the ambient air, ground or waste water. Therefore, the gas efficiency can far more higher than boilers. In this paper, large-scale gas absorption heat pump with new configurations were designed and built, using self-developed vertical falling film generator with winding tube type, solution-spray absorber with plate type, and integrated multistage centrifugal pump. Moreover, intermediate evaporation and absorption processes were introduced to improve the internal heat recovery under higher temperature lifts, and enhance heat utilization of exhaust gas. Performance testing were carried out to replace conventional gas boilers. Results showed that the heating efficiency was over 1.4, and the maximum heating capacity was nearly 1200kW. Moreover, benefits from the strategy of absorption heat for defrosting during normal operating, the defrosting time was less than 15 minutes, and did not have significant impacts on the return water temperatures. The consumption of natural gas and carbon emission is reduced by more than 37% compared with conventional gas boilers, and the payback period is only 3.6 years. It was proven that the proposed large-scale gas absorption heat pump has significant advantages in distributed heating, and is a preferred alternative to gas boilers.