Condensate Stabilizer Flooding Diagnosis

Abstract

Condensate stabilizers at PDO Saih Rawl Central Processing Plant experienced severe pre-mature flooding causing process upsets and Operational difficulties. Conventional steady state simulations and tray hydraulics could not suggest actual causes. The purpose of the proposed paper is to present the methods followed in analyzing the flooding issue and identified solutions. Initially, the flooding issue was analyzed by carrying out steady state process simulation with latest feed composition and tray adequacy checks in consultation with the tray supplier. The study concluded the existing hardware is adequate, jet flooding limit and down comer flooding levels well within acceptable limits. The study recommended only few adjustments in Operating conditions to resolve the issue. As part of verification, alternate tray suppliers were also approached to carry out tray hydraulic checks and found no concerns. Subsequently, the column was subjected to gamma ray scan during normal operation and a scanning was repeated after simulating a flooding inside the column. Coupled with gamma ray scanning results, a tray by tray by simulation was carried out to ascertain the flooding the phenomena. Gamma ray scan revealed the condition of the column internals, liquid heights and froth level during normal operation as well as during simulated upset conditions. Even though the trays were in good conditions, bottom few trays showed higher liquid height during normal operation itself. Along with the results from Gamma ray scanning, process simulation results and investigation of Operating conditions revealed the possible reasons for the flooding issue. The study predicted a temperature dip in few trays and further rise somewhere near the column top, which is unusual for a distillation column. This is the resultant of different feed ratios from the original design and one of the feed to the column is estimated to be below 5 °C, which is too cold compared to column profile. Based on the results, options were developed to alleviate the flooding issue without compromising the production capabilities of the column profile. The nature of flooding experienced inside the column handling different feeds and large variation in temperatures is unique with the condensate stabilizers. Conventional full column steady state simulation and tray sizing were not adequate for investigating problem. It needed, gamma ray scanning while the column is in normal operation and during simulated flooding condition.