Uniformity Control of Parallel Streams Temperatures: a Modified DCT Method

A furnace with multiple parallel passes is an important unit in petroleum refineries. In order to maintain the furnace running in a safe, stable and high-efficiency state, it is necessary to control the outlet temperatures of the multiple passes to be as identical as possible. Some advanced control methods, including adaptive control, predictive control, and robust control, are usually too complex for convenient use. Based on conventional control scheme, the difference control technique (DCT) has been proposed to solve such problem and successfully applied to a preheat furnace with four passes. However, in some cases, the DCT technique might encounter some problems. In this paper, a modified version of difference control technique, called modified difference control technique (mDCT), is proposed. The proposed technique can keep away from the problem of the DCT while retaining its advantages. The principle of the proposed mDCT technique is explained and demonstrated, and some of the simulation results are reported.