Abstract: Analyses of multiple steady states of a fluid catalytic cracking unit (FCCU) with high-efficiency regenerator with the riser reaction temperature under open loop and closed loop control were performed based on the theory of output multiplicity and input multiplicity. The multiple steady states under these two conditions were determined with respect to the amount of the added CO combustion promoter. The heat removal curve was found monotonously increasing with riser reaction temperature under open loop control, which resulted in the existence of three multiple steady states because of weak coupling between regenerator temperature and riser reaction temperature. On the other hand, the heat feedback of regenerator and riser reactor changed under closed loop control because regenerated catalyst flow rate could be used as an extra measure to compensate the difference between regenerator temperature and riser reaction temperature to enhance coupling between regerator temperature and riser reactor temperature. Multiple steady states would exist only when CO promoter was extremely insufficient. Otherwise, only one steady state existed under current operating condition which avoided multiple steady states with riser reaction temperature under open loop control.

Key words: systems engineering, process systems, control, FCCU, multiple steady states

摘要： 针对催化裂化反应-再生系统在提升管反应温度开环和闭环控制条件下的输出与输入多稳态问题，分析了烧焦罐式高效再生催化裂化反应-再生系统在两种条件下随着CO助燃剂添加量变化时的多稳态分布。在反应温度开环条件下，因再生温度与反应温度的耦合程度较低，使系统移热曲线呈单调递增，导致了系统出现3个稳态操作点。在反应温度闭环控制条件下，提升管反应器和再生器间热反馈机制发生改变，由于再生剂循环量可以作为额外的自由度对再生温度和反应温度之差进行补偿，再生器和提升管反应器的耦合程度增强，使得系统只会在助燃剂添加量极低时才会出现多个稳态点，而在基准操作条件下只有一个稳态点，规避了系统在提升管反应温度开环时的多个稳态点的问题。

关键词: 系统工程, 过程系统, 控制, 催化裂化, 多稳态