Research On Double-effect Evaporation Concentration System Based On High Temperature Heat Pump

Evaporative-concentration is a typical chemical unit operation in the industry,so improving the operating efficiency of the evaporative-concentration system plays an important role in reducing energy consumption.The high-temperature heat pump doubleeffect evaporation system is a new type of evaporation-concentration system.It introduces a heat pump circulation subsystem in a conventional double-effect evaporation-concentration system to replace the high-energy steam heat source,achieving efficient energy application and recovery.At the same time,it also avoids the problem that the compressor manufacturing process is complicated,the volume is large,and the cost is high in the MVR system.Based on the analysis and research of the system operation process,this paper tests the operation effect of the system and evaluates the energy conservation and economy of the system.The optimization design and operation simulation method of the system are studied.(1)In order to achieve efficient recycling of steam condensation heat,the hightemperature heat pump double-effect evaporation system was constructed.According to the actual working conditions,the energy budget of each component is simply estimated,the energy utilization efficiency of the system is compared and analyzed,and the direction and magnitude of energy transfer in the system are specified,which provides a basis for the establishment of the system model.Considering the principle of evaporation concentration process and the universality of heat pump working fluid,R245 fa is selected as the refrigerant working medium of high-temperature heat pump.(2)Mathematical models are a prerequisite for thermal system design and performance analysis.Based on the system energy flow diagram,the relationship between mass conservation and energy conservation,the paper has completed the thermal calculation model,calculation heat transfer model and system evaluation model of the high-temperature heat pump double-effect evaporation system.They include: double-effect evaporation subsystem equipment model,high-temperature heat pump subsystem equipment model,phase-change heat transfer coefficient calculation model,energy-saving and economic evaluation indicators.(3)Based on the mathematical model of the system,the optimization design and operation simulation of the high-temperature heat pump double-effect evaporation system were completed.In order to optimize the system economy,the evaporation under the system unit cost is the optimization goal,and the genetic algorithm is used to optimize the system,and the maximum evaporation under the system unit cost is 16.656kg/yuan.In order to study the operating characteristics of the system,an iterative calculation method was used to solve the running simulation model of the system.The heat transfer characteristics of the heat exchanger,the proportion of non-condensable gas and the influence of the compressor volume flow on the system operation were studied.When the proportion of non-condensable gas increased from 0 to 30%,the total evaporation decreased by 16.01%,and the unit electricity consumption evaporation decreased by 11.11%.(4)In order to master the performance of the high-efficiency heat pump double-effect evaporation system,and verify the achievability of the system,a test bench was built to test the performance of the system under design conditions and variable design conditions.The experimental conclusions are as follows: the total evaporation of the system can reach 1917 kg / h,the heat pump COP is 4.62,the unit power consumption evaporation is 11.62 kg / kW · h;When the compressor load increases,it will increase the total evaporation and reduce the unit power consumption evaporation;The system performance of the evaporator adopts dual process is better than that of the three process system;The energy-saving and economy of the new system are all better than the conventional system,and the total annual cost of the new system is 735,300 yuan,and the total annual evaporation can reach 16600 tons.In this paper,the thermal characteristics and influencing factors of the high-efficiency heat pump double-effect evaporation system are studied,which provides theoretical basis and guidance for the practical engineering application,efficient design and optimization of the system.