Abstract
The organic rankine cycle (ORC) has been widely used to convert low-grade thermal energy to electricity. The selection of the cycle configuration, working fluid, and operating parameters is crucial for the economic profitability of the ORC system. In the methanol to olefin (MTO) process, multi-stream low-temperature waste heat has not been effectively utilized. The previous study mostly focused on the optimization of a single stream system and rarely considered the comprehensive optimization of multi-stream ORC systems which have multi-temperature heat sources. This paper proposes five kinds of system design schemes, and determines the optimal output work and the highest exergy efficiency through the selection of working fluid and optimization of system parameters. In addition, the influence of mixed working fluid on the thermodynamic performance of the system was also investigated. It is found that there is an optimal evaporation temperature due to the restriction of pinch temperature. At the optimal temperature the ORC system obtains the maximum net output power of 4.95 MW. The optimization results show that the working fluid R227EA selected from seven candidate working fluids shows the optimal thermodynamic performance in all the five design schemes, and obtains the maximum output work and exergy efficiency.
Highlights
Energy is an important guarantee for human social and economic development
In the recent research on the recovery of low-temperature waste heat by the organic rankine cycle (ORC) system, the heat sources are often considered as single stream, and most of them are directly condensed by cooling water or cooling air
The output work of the expander is mainly determined by three parameters: The flow rate of the circulating working fluid, the inlet pressure of the expander, and the outlet pressure of the expander
Summary
Energy is an important guarantee for human social and economic development. Driven by rapid industrialization and urbanization, the energy problems are becoming increasingly acute, especially in the fields of geotherm, metallurgy, chemistry, electrical, and machinery [1]. As for the application of ORC in chemical industry, Song et al [14] analyzed and optimized a comprehensive ORC recovery system utilizing five waste heat sources distributed in different temperature levels, from a 1.2 million ton-level reforming and extraction unit in Shijiazhuang Refining & Chemical Company of China. In the recent research on the recovery of low-temperature waste heat by the ORC system, the heat sources are often considered as single stream, and most of them are directly condensed by cooling water or cooling air. This paper is based on the current energy utilization status of the MTO process, and introduces bteheenOuRseCd erneaesrgoynarbelcyovfreormy ttehcehpnoerlospgeycitnivtoe othf etheenfiergstylarewcoovfetrhyerinmoMdTyOnapmrioccseassn.dAtchceosrdecinogndtolatwhe oafbthoveremliotedryantuarme,icths.ere is currently no ORC energy recovery for the low temperature waste heat of the MTOInpthroecreescse.nAt rnedselaerscshroensetahrechreoconvtehrey ofvleorwal-lteomptpimeriaztautrieonwaosfteOhReCatebnyerthgey OreRcCovseyrsytesmch, ethmeehsefaotr somuurclteis-satreaomftehnecaotnssoiudrecresd. The outpAust msheocwhanniincaFl iwgourrke i1s,ptrhoeceOsRseCd sbyysttheme exinpcalnuddeers dfouurirngmtahienicsoenmtrpoopnicenetxsp: aAnsnioenvpaproocreastso.rN, aenxt etxhpeanexdpera,nadceodndoregnasneri,cawndorakipnugmflpu;iadnvdafpoourr fmloawins tihnetormthoedycnoanmdeicnsperrocwehsseerse: tihseensttreoapmic icsomcoporleesdsiaonnd (1c-o2n)d, iesnosbeadriicnthoelaiqtiunigdibnytihseosptaretihcehaeteart tarnandsefevra.pFoinraatlloyr, (t2h-e4l)i,qiuseidntorrogpainciecxwpoarnksiinognfilnuitdhiesesxepntantodtehre (4p-u5m), apnfdorisothbearnicexctooclyinclge.inHtohwe ecvoenrd,einnseprra(5c-t1ic)a. lSoO,RwCe aapsspulmicaetitohnast,ththeerehiseantotrparnesssfeurreanddropwoinrkthineg pprerohceeasteser,seavraepnoortatsotrr,icotrlycoisnednetrnospeirc
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