Design of multivariable control structure for crude oil distillation column: effect of capacity change

This paper presents control structure design and dynamic modeling of atmospheric distillation column using relative gain array (RGA) and relative normalized gain array (RNGA). Nonsquare control structure selection for atmospheric distillation has not been addressed in the literature. The column has been modeled and simulated for 40,000 and 60,000 bbl/day capacities in order to examine the control performance of the column. Output performances of control structure were examined by ±5% step change in feed rate. Based on the results, the output responses for both RGA and RNGA methods show good control performance for 60,000 bbl/day capacity, while the output responses for 4,000 bbl/day capacity suggest change in control structure for both methods.