Thermal Energy Integration Using Pinch Analysis Technology in Case of Finchaa Sugar Production Plant, Finchaa, Ethiopia

Abstract

This study focused on heat exchanger network and thermal heat integration in the Finchaa sugar production plant using the Aspen Energy Analyzer v11.0 software through the principle of pinch analysis techniques. The aim of this retrofit heat exchanger network design is to reduce the use of external utilities by increasing energy recovery and shifting heat from available hot process stream to cold process streams which needs heating by applying the principles of the first and second law of thermodynamics, the increasing cost of energy and environmental concerns are forcing industries to look for methods of reducing energy consumption and wastage. Identifying the optimum heat exchanger network that was achieved the minimum energy target (supreme heat recovery) and economic savings were realized in the study area. Both primary and secondary data sources were collected for this investigation. Primary data were collected from operators of the company through an interview at each stage unit operations, and secondary data were collected from the manual document of the production section, journals, and textbooks of related articles. In this design, the problem is a threshold problem that requires only hot utility. The network was designed for maximum energy recovery and optimized at the minimum total cost with further relaxation of breaking ten loops. The trade-off production (utility) cost with capital cost obtained an optimal heat exchanger network topology designed was not too changed from the existing plant network. The analyses exposed that the number of heat exchanger units was significant with target value but, the number of shells designed was above target value by 48.5%. In the study area, the amount of hot utility requirement is 25,960kW and it remains constant as ΔTmin varies up to the threshold temperature (5℃), which is the optimum approach temperature change value. The heat exchanger network design resulted in energy savings of 100% for cold utilities, 47.91% for hot utilities and 64.92% from total utility compared with the current energy consumption of the plant. Profitability analysis of the designed heat exchanger network was made in both discount and non-discount cash flow methods. The non-discount criteria found with a payback period and accounting rate of return of 0.91years (nine months) and 90.40% respectively. Similarly, the discount criteria found with net present value (NPV) and internal rate of return (IRR) of $2,369,786.297 within 20 years and 18.0609% respectively, which indicates this project has an acceptance. The results show that the design of the heat exchanger network with a new heat exchanger arrangement proves that energy integration can lead to a minimum energy (utility) consumption, maximum energy recovery, and financial savings of the plant