Synthesis of waste heat recovery using solar organic Rankine cycle in the separation of benzene/toluene/p-xylene process

Abstract

Current energy intensification measures of dividing wall columns are mainly based on vapor recompression and organic Rankine cycle technologies. Vapor recompression can achieve self-heat recovery of the dividing wall column to use a large part of the waste heat. And the organic Rankine cycle recovers the surplus low-temperature waste heat. However, the efficiency of such low-temperature waste heat recovery by organic Rankine cycle is always low. Additionally, the current design of such energy systems is based on conventional fossil fuels, which are not conducive to long-term development. This paper proposes using solar energy to improve the efficiency of low-temperature waste heat recovery. Based on this concept, a novel waste heat recovery combined solar organic Rankine cycle is established, which is integrated into a vapor recompression assisted dividing wall column system to simultaneously recover waste heat and produce electric power. In addition, the organic Rankine cycle and solar organic Rankine cycle assisted systems were compared. Furthermore, a robust solar-energy design and optimization procedure was used to optimize the three proposed schemes by considering the actual solar fluctuations in Islamabad. Performance analysis and techno-economic evaluation were executed under nominal and actual conditions. The results show that solar radiation can increase the waste heat recovery efficiency and reduce the actual total annual cost.