Organic Rankine Cycle Power Generation System With Low Temperature Water Heat From The Process Of Oil Shale In-situ Hot Exploitation

Oil shale is the conventional energy supplement. Its pyrolysis can receive shale oil similar to crude and substitute for natural gas. It has very important strategy sense to change the energy structure of our country.Oil shale in-situ hot exploitation is the safe and effective means for mining and the technical way in the future. But in the finality of the thermal process, a large number of low temperature and waste heat steam was wasted because of the unusefulness to oil shale pyrolysis effect. Recovering this part of heat to power generation can not only save energy, but also improve the economic factor in Oil shale in-situ hot exploitation. In this paper, the purpose is to recover the low temperature waste heat stream of Oil shale in-situ hot exploitation. On that basis, we carry out the study of using low temperature waste heat stream to power generation. On the basis of investigating the domestic and international research, the paper combined with the actual engineering situation of Oil shale in-situ hot exploitation, made comparisons with the current low temperature waste heat power generation system and finally chosen the organic Rankine cycle (ORC) generation system model consist of the evaporator, condenser, refrigerant pump, turbine and other main components.Considering the safety and environmental protection and other aspects, we selected five refrigerant for the ORC.Aiming at the components of ORC and basing on the thermodynamic theory, we has carried on the detailed thermal analysis and established the system thermodynamic equation. And then, we took the net output power and heat efficiency of the system as the performance measures and used the engineering calculation software--EES to study the influence to cycle parameters.We also analyzed the distinction between different working mediums and thereby determined the optimum cycle parameters and optimum circulating refrigerant. Through analyzing the influence to the system from the same refrigerant cycle parameters, we found that the influence of parameters to the system was different and the evaporation temperature on net output power had the greatest effect. When the waste heat fluid temperature and steam pressure was in a certain way, there exited a "best evaporating temperature" to make the net output power maximum and the "best evaporation temperature" increased with the increasing of the waste heat fluid temperature and steam pressure. Comparing with the cycle parameters between different refrigerant, we analyzed in the best evaporation temperature of different refrigerants corresponding to the parameters. Considering comprehensive economic and environmental, we finally selected R245fa as the most suitable cycle refrigerant.By using the engineering calculation software--EES, this paper carried on the exergy efficiency and exergy loss analysis to the system, and analyzed the position, type and quantity of the exergy loss. Then we found that the preheater evaporator and condenser exergy loss accounted for the largest proportion. Basing on this conclusion, we optimized the system, increased the heat regenerator, reduced the transfer temperature difference and the exergy loss of condenser and the preheater evaporator heat and reduced the system irreversibility.The study of experimental model can not only recovery on the Oil shale in-situ hot exploitation and gas low temperature waste heat recycling, but also be referenced by other engineering or projects to the low temperature waste heat.