Most of lower grade heat is directly rejected to the environment by Chinese steel, cement, and chemical industry in recent years. Lower grade heat is commonly considered as waste heat in Chinese industry. With the increased demand for energy in China and under great pressure of environment emission, low grade energy should be reasonably used in Chinese industry. Organic Rankine cycle is a good way to use the huge amount of lower grade thermal energy in China.
Several organic Rankine cycles is designed for different energy source in this paper. The lower grade heat in the process industry is divided into three type of energy source according its temperature. The temperature of waste heat is below to 300°C, such as residual heat from the cement industry. This kind of heat can be used both in Organic Rankine cycle and steam Rankine cycle. Calculation is done for those cycle parameters. The analysis shows that those cycles has similar performance. But for organic working fluid the exhausted gas is dry and it is very helpful for turbine designing. So the degree of super heat can be low to sufficiency use low grade thermal energy. The temperature of waste heat is below to 200°C, the organic Rankine cycle show the advantage from the analysis of thermodynamics property. The temperature of heat source is about to 100°C, the organic Rankine cycle is only available way to generate electricity, especially for geothermal, solar, and biomass sector. The performance for the cycle with regenerator and without regenerator is carried out in this research. Several working fluid is selected for the research, such as isopentane.
From the research, some conclusion can be seen that organic Rankine cycle has high performance to use low grade residual energy in Chinese industry. From the thermodynamic point of view, isopentane can be a right working fluid in such cycle. The performance of organic cycle with regenerator is greater than without cycle. The potential available for using low grade thermal energy with organic Rankine cycle in big scale in China show its good future.