A feasibility study of improved heat recovery and excess heat export at a Swedish chemical complex site

Artikel i vetenskaplig tidskrift, 2018

New ambitious targets for reduced greenhouse gas emissions and increased energy efficiency in industry and in the stationary energy sector provide incentives for industrial plants to investigate opportunities for substantially increasing recovery and use of excess heat from their operations. This work investigates the economic feasibility of recovering industrial excess heat at a Swedish chemical complex site for increased site internal heat recovery or export to a regional district heating (DH) network. The work is based on investment cost data estimated in previous work by the authors. A site-wide heat collection and distribution system based on circulating hot water was envisioned, which is also connected to a regional DH network. With the help of multiobjective optimization, the optimal heat contributions from the individual plant sites were identified that minimize the total system cost for a large range of options involving different quantities of internally recovered heat and heat export to the DH system. A payback period analysis was conducted together with a risk assessment to take into account uncertainty regarding utility steam production cost and heat sale price. The results of the study indicate that a payback period of around 3 years can be achieved for a number of cases in which 30% to 50% of the total excess heat produced by the site plants is recovered. Although it seems more profitable to recover heat at the site rather than exporting heat to the DH system only, profitability appears to be maximized by hybrid solutions that allow a share of the excess heat to be sold to the DH system and some heat to be recovered at the site simultaneously.