Performance Monitoring of a Sulphur Recovery Unit: A Real Startup Plant

A Sulphur recovery unit at a refining plant in the Middle East, which began official production in 2020, treats all acid gas to elemental Sulphur. Acid gas cannot be released into the atmosphere because of stringent environmental regulations. To test some essential parameters, the plant was simulated using a special Sulphur package in HYSYS called SULSIM. One of the most critical keys, the (H2 S/SO2 ) ratio, was checked after simulation validation. The optimal ratio is 2. Any deviation from this ratio results in serious issues in the process, such as catalyst ageing in the reactors. The effect of reducing the ratio from 2 to 0.22 was investigated in a case study. The temperature of the reduction reactor's outlet rose from 279.73o C to 314.34o C, which was higher than normal. The performance of the catalyst was measured on six separate days. The temperature difference and the pressure difference through the bed are the two most important parameters in catalyst monitoring. The ΔT designs for the first Claus reactor, second Claus reactor, and Reduction reactor are 51, 20 and 24o C, respectively. 0.04, 0.14, and 0.04 kg/cm2 g are the ΔP designs in the first Claus reactor, second Claus reactor, and Reduction reactor, respectively. The actual parameters were found to be in the normal range. Sulphur production is calculated in two ways: by the level of the Sulphur production tank and by calculating the material balance by laboratory analysis. Based on a comparison in four days the calculations are precise because of the levels, and large deviations are revealed by laboratory analysis. The percentage deviation error was found to be (-36.4, 70.7, -7.6, -10.5) percent by the laboratory analysis.