Comparison of the Steady-State Performances of 2 × 2 Regulatory Control Structures for Fluid Catalytic Cracking Unit

摘要

The closed-loop steady-state performances of 2x2 regulatory control structures are evaluated and compared for a side-by-side FCC unit under partial combustion (PC) and complete combustion (CC) mode. Aspen HYSYS (R) CatCracker module is used for this purpose. Three types of disturbances are selected, namely feed flow rate change, feed temperature change and the variation in air blower discharge temperature. The control structures in which reactor plenum temperature is controlled by catalyst flow rate have exhibited favourable and superior closed-loop steady-state performances. The successful regulation of conversion is seen as the key for preserving the product yields at their design values. The best workable control structures are identified for both PC and CC modes of operation. For the two modes, the control structures in which regenerator temperature is controlled by catalyst flow rate suffer from closed-loop steady-state multiplicity, infeasible set point or unfavourable closed-loop steady-state performance.