Modeling and Simulation of the 1,3-Butadiene Extraction Process at Turndown Capacity

As cracker feed around the globe is trending towards lighter feedstocks, butadiene production facilities worldwide are now run at turndown capacities. Models are developed to study how operation at turndown ratios of feed rates affects the purity of 1,3-butadiene. The optimal solvent-to-feed ratio was found to be in the range of 6-7 when the plant is run at normal throughput; however, it is necessary to change the solvent-to-feed ratio in the range of 10-11 when the plant is operating at turndown capacity. Dynamic simulations indicate that the effect of fluctuations in the feed flow rate on product purity can be minimized by a ratio controller to change the solvent flow rate and a composition controller to alter the side-draw flow rate.