HYDRAULIC ANALYSIS IS KEY TO EFFECTIVE LOW-COST DEMETHANIZER DEBOTTLENECK

摘要

Eastman's demethanizer was bottlenecked by flooding, that was apparent just above the tower swage. A hydraulic analysis based on simulation of plant operating data was used as a basis for a detailed hydraulic analysis. The hydraulic analysis indicated absence of a bottleneck above the swage, but diagnosed the bottleneck to be caused by downcomer backup flooding just below the swage. It also revealed that all the trays below the swage operated close to the downcomer backup flooding limit. The analysis identified the root cause of the downcomer backup flooding to be low open hole areas on the trays below the swage. Increasing hole area by replacing all tray panels below the swage with new panels containing more holes completely eliminated the flooding and enhanced column capacity. Demonstrated capacity went up by more than 20%, and no limit has been reached. After the hydraulic limitation was eliminated, the temperature in the coldest tower feed drum could be significantly lowered, which reduced ethylene losses in the tower overhead. A good understanding of the equipment limitations, and a correct hydraulic analysis combined with field measurements and simulation, held the key for successfully identifying and eliminating the tower bottleneck.