The retrofit of the calcium chloride production by Pinch approach and process modifications

In this paper, the analysis of an existing calcium chloride evaporation unit was performed to cut primary energy use and harmful emissions. This paper proposes the use of several approaches for retrofit of existing calcium chloride production. The existing process's energy efficiency was examined to identify drawbacks and bottlenecks and provide the pathways for proper process modification. The methodology is based on a systematic analysis and step-by-step reduction of energy use. It uses a Pinch approach, process unit simulation and vapour recompression considering existing process constraints, e.g. product quality, process capacity etc. Two retrofit options of heat exchanger network were proposed with the simulation and design of additional equipment. Energy recovery was increased by identifying vapour recompression potential and its proper application and retrofitted exchanger network. All process changes were simulated by commercial software to prove the robustness of proposed energy-saving measures. The case study analyses a chemical plant that exploits the Solvay process and distilled liquid of ammonia production as a feedstock. In the result of retrofit, the energy cost was cut by about 400,000 USD/y and emissions reduction by 18,818 tCO2/y. Steam consumption was reduced by 51%, and the cooling water flow rate is decreased by 69%. The economic efficiency of proposed energy-saving measures demonstrates the payback period up to 1.5 years. The madmap of the step-by-step application of process changes was proposed.