The Research Of Low Temperature Waste Heat Recovery Of Thermodynamic System Of Power Plant Based On Organic Rankine Cycle

With the rapid development of China’s economy, energy demand is gradually increasing,and there is a huge amount of low grade energy in our country, especially in places like thermal power plant. Organic Rankine cycle technology will become a development trend in the future. So how to choose a suitable organic working fluid and how to optimize a cycle when the working fluid has been selected have become a key research in this filed. Because its structure is simple and thermal efficiency is high in terms of the recovery of low temperature waste recovery, the organic Rankine cycle(ORC)has attracted wide attention of scholars worldly.In view of the characteristics of low temperature waste heat recovery of thermodynamic system of power plant, taking the boiler continuous blowdown flash steam as an example, the economic model and thermodynamic model of the organic Rankine cycle system under constraint condition have been set up.The Aspen( Advanced System for Process Engineering) Plus software is used to calculate the thermodynamic properties of organic working fluid and simulate the cycle properties. The thermal characteristics of heat source side and organic working fluids side have been discussed and analyzed.First, for a fixed low temperature waste heat inlet temperature, the choice of organic working fluid has been discussed. Based on different working fluid, the impact of the evaporation temperature, flowrate and condensing temperature on the thermal efficiency, the net power output have been discussed and analyzed.Results indicate that the net system output power, thermal efficiency show a rising trend with the increase of evaporating temperature, but with the mass flow goes down. So there is no organic working fluid that can satisfy all evaluation indexes at the same time. For the recovery of the latent heat is a major proportion of the waste heat, the working fluids with high latent heat are recommended. In this study task, the R134 a have been proposed as working fluid of the ORC cycle, eventually the thermal efficiency of ORC reaches a max value.Then, for a fixed organic working fluid, based on different heat source parameters, the impact of the heat source inlet temperature, flowrate and evaporator outlet temperature on the thermal efficiency, the net power output have been discussed and analyzed. And according to the characteristics of the working fluid on both sides, evaporator and condenser are designed.Results indicate that for a fixed the working fluid, the net system output power, thermal efficiency show a rising trend with the increase of heat source temperature, but with evaporator outlet temperature goes down.At last, using 4 type of working fluids as the working fluid, the characteristics of regenerative ORC have been discussed and analyzed, and compares the two kinds of circulation ability of work. The results show that the cycle thermal efficiency and output power have improved with the internal heat exchanger, but the cost of the total capital will increase simultaneously.