Analysis on the reconfiguration of the control system of the heat exchanger in response to the slow and time-varying fouling

Heat exchanger as an important heat transfer equipment in the chemical process, generally needs to continue to run for a long time, during which due to the continuous accumulation of fouling resistance, heat transfer efficiency of the heat exchanger will gradually decline with time, until it cannot meet the process requirements. In the actual industrial heat exchange process, the process personnel usually carry out margin design on the heat exchanger. However, the heat exchanger needs to run longer or the allowance design is insufficient, the regulating effect of the commonly used flow control strategy gradually deteriorates at the end of the heat exchanger operation while the bypass control scheme cannot realize the continuous control of the whole cycle in the face of the inevitable fouling growth. Therefore, an integral asymptotic model of fouling accumulation was established based on the asymptotic grouth model, which considered the influence of process parameters on the fouling rate. Secondly, taking a small area heat exchanger used for water circulation as an example, the regulating effect of flow control and bypass control under the condition of considering fouling growth is analyzed. Finally, according to the characteristics of slow time-varying and continuous fouling process, a reconstruction control strategy based on heat carrier flow and bypass opening was designed. The operation results of the example show that for the same heat exchanger with limited area margin, this control scheme can prolong its service life and achieve its goal of continuous control throughout the whole cycle. © 2021, Editorial Board of CIESC Journal. All right reserved.