基于稳定性的循环物流系统流程模拟——以催化裂化反应-再生系统为例

过程流程模拟中广泛应用的序贯模块法处理循环物流系统存在很多困难，如断裂流股的选择、迭代方程的收敛性等。基于稳定性理论解决循环物流系统的流程模拟问题，首先根据化工单元装置的模型方程将其分为正向模型和反向模型，并将循环物流中的变量定义为迭代变量和收敛变量；然后在收敛变量处将循环物流的流股断裂，迭代变量分别通过正向模型和反向模型计算收敛变量，二者的偏差通过增益系数对迭代变量进行修正，进而得到迭代方程；最后，利用控制理论中的稳定性理论来确定迭代方程的增益系数，将迭代方程线性化，采用劳斯判据确定增益系数的稳定范围，当增益系数位于稳定范围以内时，迭代方程必然收敛。催化裂化装置反应-再生系统因催化剂循环的存在而成为典型的循环物流系统，本文将反应器作为正向模型，再生器作为反向模型，以再生温度和再生催化剂含碳量作为迭代变量，构造了催化裂化装置反应-再生系统流程模拟的迭代方程，利用稳定性理论找到增益系数的稳定范围，保证流程模拟计算必定达到收敛，验证了该方法的可行性和有效性。

Process simulation of stream circulation system based on stability:FCCU reaction and regeneration system as an example

The sequential modular method, which is widely used in process simulation, has many difficulties in dealing with stream circulation system, such as the selection of tearing stream and the convergence of iterative equations. Based on the stability theory, this paper solves the process simulation problem of stream circulation system. First, according to the model equation, chemical plants are identified as forward model and backward model, and the variables in stream circulation are defined as iterative variables and convergence variables respectively. Then, the stream circulation is broken at the convergence variables, and the convergence variables are calculated from the iterative variables by the forward model and the backward model respectively; the convergence errors are used for the correction of iterative variables through the gain coefficients, and then the iterative equation is obtained. Finally, the stability theory in control theory is used to determine the gain coefficient of the iterative equation, the iterative equation is linearized, and the Routh criterion is used to determine the stable range of the gain coefficient; when the gain coefficients is within the stable range, the iterative equation must converge. The reaction and regeneration system of FCCU is a typical stream circulation system because of catalyst circulation. The reactor is treated as the forward model and the regenerator is treated as the backward model. The temperature and carbon content of regenerator are treated as iteration variables to build the iterative equation of process simulation for FCCU reaction and regeneration system. The stability range of the gain coefficients is found by using the stability theory to ensure the convergence of the simulation calculation, and the feasibility and effectiveness of this method are verified.