关键词: 换热网络, 扰动, 负荷迁移, 瓶颈, 解瓶颈

Abstract:

For the heat exchanger network (HEN) with source/sink parameter variation, a systemic disturbance response/parameter adjustment method is proposed to maintain the heat balance of the system, identify the bottleneck restricting energy recovery and propose corresponding debottlenecking strategy. Based on topology analysis, feasible response objects and disturbance propagation paths of the system are enumerated, and the load-shift laws of heat exchangers are clarified. The relationship between heat exchanger thermal resistance requirement (R^req), area increment (∆A), total annual system cost (Ct) and heat capacity flow rate fluctuation coefficient (α) is derived. The thermal resistance demand change trend diagram and economic change diagram are constructed. With the optimal cost taken as the goal, the best response object is selected, and its heat load change value is determined. The system energy bottleneck caused by thermal resistance restriction during the adjustment of the response variable is located, and the area increment required to solve the bottleneck is determined. The proposed method can determine the change of the heating/cooling medium’s flow rate and that of each heat exchanger’s area demand under the disturbance state without complex simulation calculation, which is intuitive and efficient and can guide the design, optimization, or retrofit of chemical processes. A benzene alkylation process is analyzed to illustrate its application. When α locates in the interval [0.75, 0.88] and [0.88, 1.35], two heaters are the optimal response objects, saving the total annual cost up to 19400 USD∙a^-1 and 24024 USD∙a^-1, respectively.

Key words: heat exchanger network, disturbance, load-shift, bottleneck, debottleneck