炼油厂低温余热有机朗肯循环工艺参数选择

Selection of ORC process parameters for refinery low-temperature waste heat

炼油厂低温余热具有热量大、取热方便等特点,适合采用有机朗肯循环发电方式进行回收利用。从工程设计角度看,膨胀机型式、工质类型和最佳蒸发温度等参数是确定工艺方案的重点参数。根据炼油厂低温余热参数进行热力计算,对重点参数进行比选,即可得出不同热源条件下的最佳工艺参数。研究表明,向心式膨胀机适用于热源热量较大的场合,单机功率可达500~10 000 k W,螺杆式膨胀机适合于小流量、小膨胀比、单机功率100~1 000 k W的场合;循环工质R600,R600a和R245fa在热源温度90~130℃时热力性能相近,热源温度较高时R245fa的热力性能更好。选择工质时应着重考虑系统配套措施和工质价格因素,工质价格对大容量系统一次投资影响较大;系统温差和冷热源温度确定后,即可通过模拟计算得出其最佳蒸发温度,热源温度为130,120,110,100,90℃时,系统的最佳蒸发温度依次为85,80,75,70,65℃附近。

The refinery low-temperature waste heat has the characteristics of being large in quantity and convenient in recovery and utilization. It is suitable for recycling Organic Rankine Cycle（ ORC） power generation. In view of project engineering design,the expander model,the working fluid type and optimum evaporation temperature are the important parameters for determining process scheme. Through thermal calculation of refinery＇s low-temperature waste heat and comparison of important parameters,the optimal process parameters under different heat source conditions are obtained. The study shows that the centripedal expander is suitable for larger heat sources,and its single machine power should be 500 to 10 000 k W; The screw expander is suitable for the condition with small flowrate and small expansion ratio,and its single machine power is between 100 to 1 000 k W. Working fluids R600,R600 a and R245 fa have similar thermal performance at a heat source temperature of 90 - 130 ℃. The R245 fa has a better thermal performance at a higher heat source temperature. Various factors especially the price and system facilities should be considered when selecting working fluids. The price of working fluids has a greater impact on the initial investment of large system; After the system temperature difference and temperature of cold heat sources are determined,the optimum evaporation temperature can be calculated through simulation; When the heat source temperature are 130/120/110/100/90 ℃,the corresponding optimum evaporation temperatures of the system are 85/80/75/70/65 ℃ respectively.