Process integration study for increased energy efficiency of a PVC plant
|Chalmers tekniska högskola / Institutionen för energi och miljö
|Chalmers University of Technology / Department of Energy and Environment
|Increasing energy prices combined with the need to reduce greenhouse gas emissions makes energy efficiency important both for economical and environmental reasons. In the energy-intensive industry, such as the process industry, there is a substantial potential for energy savings. INEOS ChlorVinyls, a major chlor-alkali producer, has a PVC production site in Stenungsund, on the West coast of Sweden. The site is a large consumer of both electricity and different fuels, and it is therefore relevant to perform a systematic energy efficiency study of the site. This master’s thesis has investigated the possibilities for increasing the energy efficiency of INEOS’ PVC production site by increased internal heat recovery. The production of PVC is divided into three sub-processes. In this study focus has been on the second sub-process, which is the VCM production plant. Since the site is to be retrofitted in a near future, and the production capacity will be extended, the study was made for a future scenario with increased production. To identify options for increasing the energy efficiency of the site, pinch analysis has been used. Pinch analysis is a systematic method for identifying opportunities for improving the integration of processes in order to decrease the amount of external heating and cooling needed. The results show that theoretically 7.8 MW of steam and the same amount of cooling water could be saved by internal heat exchange in the future VCM plant. This corresponds to 37% of the steam use. The pinch violations in the heat exchanger network were identified, and different retrofits are proposed, aiming to eliminate the five largest pinch violations in the system. Both direct heat transfer and the use of a heat transfer media such as water have been investigated. The suggested retrofits lead to steam savings between 4.5 and 6.5 MW, and an economic evaluation shows that the annual savings could reach 20 MSEK with a short pay-back period of about one year. Both in the existing and future VCM-plant, there is a large excess of low-grade heat below the pinch, which could be used for heating at other parts of the site. This would enable additional steam savings of the same size as in the proposed retrofits for increased internal heat transfer.
|Process integration study for increased energy efficiency of a PVC plant
|Examensarbete för masterexamen