Flexible heat exchanger network design for low‐temperature heat utilization in oil refinery

Abstract

Oil refinery is an energy-intensive industry. To reduce the utility cost, there is an increasing need to utilize low-temperature heat available in the system. The use of heat exchanger network (HEN) can facilitate this low-temperature heat utilization. Normally, in a refinery, a good design of low-temperature HEN can reduce the energy cost by 10-15%. During the operation, process conditions may alter at different periods. To ensure feasible operation and avoid deprivation of the system's economics, a flexible HEN design is essential. However, flexibility consideration to handle process parameter deviations has not yet been discussed for the low-temperature HEN design. In this study, a systematic approach considering both process flexibility and system economics is proposed and demonstrated through a case study. 

Optimization of Heat Exchanger Networks for the Utilization of Low-Temperature Process Heat

“…Initial water flow rate (F w0 ) for the LTHEN model is obtained from temperature−enthalpy composite curves for the hot and cold process streams, using a 10°C approach temperature. 9 This provides a feasible region of operation for the heat capacity flow rate of water. Using this initial water flow rate, the LTHEN model with HE capital costs, but without pressure drop, piping, and other equipment costs, is solved first for minimizing TAC.…”

“…A good design of LTHEN can reduce the total energy cost by 10−15%. 9 There are several challenges in the development of a model for a LTHEN. The majority of the HEN problems have their process stream temperatures, heat capacity flow rates, or heat duties specified.…”

“…However, these are unknown for the circulating medium at the design phase of the problem. Lai et al 9 proposed a nonsmooth mixed-integer nonlinear programming (MINLP) model to minimize the total cost (which includes capital cost of new HEs and utility costs for the operation of water heater and cooler) for designing a new LTHEN. However, they did not consider capital cost for piping, water tanks, and pumps and also the operating cost of pumps required for LTHEN operation.…”

Recent advances in resource conservation and planning—a review

“…emission, wastewater and paper) via efficient product and process design. This group also covers available tools such as software, models and heuristic techniques 7–13 The second group emphasises on the transformation of waste to wealth by converting it into useful products 14…”

“…emission, wastewater and paper) via efficient product and process design. This group also covers available tools such as software, models and heuristic techniques 7–13…”