Performance Research And Equipment Development Of Direct Evaporative Heat Pump Steam Generator System

It is one of the important measures to promote the smooth implementation of the Carbon Peak and Neutrality Goal to build a new power system based on non-fossil energy and deepen the reform of electrification replacement of terminal energy equipment.At present,the industrial steam market is huge,that mainly relies on the supply of Coal-Boiler and Gas-Boiler.Their utilization rate of primary energy is relatively low,and a lot of CO2 and NOx are emitted in the using process,which seriously hindering the realization of the goal of carbon neutrality.A new direct evaporation heat pump steam generator system(DE-SGHP)was proposed in this paper,according to the situation of industrial wasteheat emission and industrial heating demand.Exergic efficiency and thermal performance of the new system were analyzed under different working conditions.And the test equipment was developed for performance verification and typical scene demonstration application.First of all,a mathematical model of circulating flash heat pump generator system(CF-SGHP)that widespread adoption was established.The exergy efficiency analysis and thermal performance research were carried out,it found that the system exergy efficiency(ηex,sys)is 62.02%under the typical working condition of heat source temperature(Thsw)was 60℃ and outlet steam temperature(Tout)was 165 ℃.The greatest exergy loss occurred in vapor compression process,refrigerant compression process and circulating flash process,whose exergy loss accounts for 21.89%.As a result,a direct evaporation heat pump generator steam system was proposed in this paper.A bilateral phase transtion steam generation device was used to replace flashing cycle.It was found that under different intermediate condensation temperature(Tcond),steam outlet temperature(Tout)and heat source temperature(Thsw),the exergy efficiency and thermal performance of DE-SGHP system were both higher.The ηex,sys was increased by 7.5%,the system COP was increased by 9.5%.Then,the adaptability of the high temperature refrigerant used in the heat pump steam system was studied,and the refrigerant meeting the requirements of steam production was selected as R245fa,R1224yd(E),R1233zd(E),R1234ze(Z)and R1336mzz(Z).It was found that several kinds of refrigerants were wet compression working medium.In order to avoid the compressor liquid strike,the suction superheat should be set separately,6-14℃ for R1336mzz(Z)system,and 5℃ for other refreigerants.After comparative analysis of the thermal performance of several refrigerants adopted in the heat pump steam system,it is found that the thermal performance of several types of refrigerant is not much different under the same Thsw and Tout,among which R1233zd(E),R1336mzz(Z)performance were better.However,the selection of refrigerant in the developed equipment also needs to consider the applicability of the compressor and the stability of the system.On the basis of the above research,the heat pump steam technology was developed productively.Two heat pump.steam generators of 120℃ and a vapor compressor equipment of 150℃ were developed in this paper,to meet the market heating demands of low temperature steam,high temperature hot water and medium temperature steam.Through the structural design of the key steam generator,the optimization of water spraying of the vapor compressor,the automatic control design of the system and the integrated processing of the equipment,the 100kW heat pump steam generator 1#unit with a vertical steam generator and 400kW heat pump steam generator 2#unit with a horizontal steam generator are obtained,both of which can meet the goal of producing 100-120℃ saturated steam.The performance test platforms were built for the equipments,A linear fitting relation was obtained using isentropy-efficiency(ηrefc)and compressor pressure ratio(πrefc)of compressor with R245fa refrigerant.The test also showed that the heating capacity could meet the requirements under rated working conditions,with systems COP of the two products were 2.34 and 2.4,respectively.The accuracy of the heat pump cycle part in the mathematical model in this paper was verified through the comparative analysis of the test results and the model simulation.A vapor compressor equipment of 500kg/h was also developed,and the flow rate of 152℃ steam was 0.513t per hour,the rate of injection liquid gasification was 10%-20%,and the average power consumption of generate a ton steam was 146kWh,which verified the accuracy of the vapor compression part of the mathematical model in this paper.At the same time,the combined cycle performance of the two developed products was predicted.It is predicted that when the evaporation temperature of the combined unit is 45℃,the COPcomb of the unit to generate steam of 151℃ is 1.96,and when the evaporation temperature of the combined unit is 45 ℃,The COPcomb is abov 2.0.Then,the economic efficiency of two heat pump steam systems(SGHP)was analyzed.The results showed that compared with bolier system,the emission reduction effect of SGHP system was only related to system COP.In most areas of China,the supply of 130-170℃ steam had a certain emission reduction effect.In addition,with the promotion of carbon neutrality strategy,the proportion of renewable energy in the power generation side is increasing,and the carbon reduction effect of using SGHP system for steam supply will be more and more significant.It is expected that by 2060,the carbon reduction amount of SGHP system for steam supply will reach more than 64%.The energy saving effect of SGHP system was also related to the gas-electricity ratio and coal-electricity ratio of the project location.The larger the gas-electricity ratio and coal-electricity ratio,the better the energy saving effect of SGHP system for steam supply.Combined with the climate characteristics and energy prices of typical Chinese cities,it was found that in most Chinese cities,when the steam supply is 130℃-170℃,using SGHP supply for steam has better energy-saving effect compared with Gas-B system.But it only had a certain energy-saving performance in South and East China compared with Coal-B system.Therefore,it is recommended to take the lead in the application and popularization of heat pump steam technology in South and East China.Finally,the demonstration and application research of heat pump steam generator was carried out.In this paper,the 1#heat pump steam generator was applied to the production process of molecular distillation monglyceride.Through the actual operation test,the average steam supply capacity of the equipment was 3.74t/d,the electric energy consumption was 1301kWh/d,and the average COP of heat pump steam generator cycle was 2.47.The average COP of the whole steam supply system was 2.33,which reduced the cost of steam supply by 11.74%compared with purchased steam and by 24.33%compared with gas boiler.Considering the gas emission penalty,the static payback period was 5.0 years and 2.4 years,respectively.Meanwhile,the energy saving analysis of heat pump steam generators in other typical scenarios was also carried out.For example,the operating cost was reduced by 40.7%when it applied in the heating transformation of oil-water separation process in petrochemical industry.The operating cost was reduced by 20.6%when it applied in the heating transformation of packaging process in beer industry.The operation cost was reduced by 22.7%when it applied in the heating transformation of drying process in linen washing industry.All these had a good prospect of popularization and application.