Performance Assessment of a Sulphur Recovery Unit

A refinery plant in the middle east started its official production in 2020. All the refinery plant acidic gas is fed to the Sulphur recovery unit plant to produce sulphur and prevent any acidic emissions against environmental regulations. The Sulphur recovery unit was simulated via special package named SULSIM. The results were validated, then the simulation was used in case studies to understand some important parameters of Sulphur recovery plants. The effect of decreasing the combustion air inlet temperature, the effect of decreasing the Claus reactor 1 inlet temperature and the effect of decreasing the thermal reactor feed were studied. Decreasing combustion air outlet temperature on the thermal reactor decreases the thermal reactor burning temperature, increases the concentration of COS and CS 2 by-products. Decreasing Catalytic reactor 1 inlet temperature decreases the hydrolysis reactions of COS and CS 2 but increases the Sulphur conversion efficiency. Decreasing AAG feed to the thermal reactor decreases the waste heat boiler duty.

Performance Monitoring of a Sulphur Recovery Unit: A Real Start- up 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 (H 2 S/SO 2 ) 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 279.73 o C to 314.34 o 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 24 o C, respectively. 0.04, 0.14, and 0.04 kg/cm 2 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.

Modeling, Evaluating and Scaling up a Commercial Multilayer Claus Converter Based on Bench Scale Experiments

Industrial scale reactors work adiabatically and measuring their performance in an isothermal bench scale reactor is faced with uncertainties. In this research, based on kinetic models previously developed for alumina and titania commercial Claus catalysts, a multilayer bench scale model is constructed, and it is applied to simulate the behavior of an industrial scale Claus converter. It is shown that performing the bench scale isothermal experiments at the temperature of 307 ºC can reliably exhibit the activity of catalytic layers of an industrial Claus converter operating at the weighted average bed temperature (WABT) of 289 ºC. Additionally, an adiabatic model is developed for a target industrial scale Claus reactor, and it is confirmed that this model can accurately predict the temperature, and molar percentages of H2S and CS2. Based on simulation results, 20% of excess amount of Claus catalysts should be loaded to compensate their deactivation during the process cycle life. Copyright © 2020 BCREC Group. All rights reserved

A Comparative CFD Simulation Study of Two-Channel and Three-Channel Claus Reactors

The Claus reactors is widely used to recover elementary sulfur from hydrogen sulfide that is contained in fresh natural gas. It involves thermal oxidation of hydrogen sulfide and its reaction with sulfur dioxide to form sulfur and water vapor. To improve the efficiency of the process, we built two kinds of 3-dimensional Claus reactor models to explore the key factors that affect the combustion reactions. The two-channel Claus reactor consisted of an air channel and an acid gas channel (60% H2S, 33% CO2, 7%H2O) while the three-channel Claus reactor consisted of two air channels and an acid gas channel (60% H2S, 33% CO2, 7%H2O). The two-channel model was built according to the devices used in the factory while the three-channel model was improved by us from the two-channel model. In both the two models, air and acid gas turned into swirling flow in their channels respectively before their mixture. Then air and acid gas mixed and burned at the throat of the models. The most remarkable difference between the two kinds of Claus reactors was that the three-channel reactor had an additional inner air channel inside the acid gas channel that can be helpful to the mix of the acid gas and air. The second difference was that the two kinds of reactors had different deflectors to swirl in the flow fields. In this study, we compared the flow fields and concentration fields of the two kinds of Claus reactors by using a computational fluid dynamics (CFD) tool. The simulation results indicated that the swirling intensity and the mix intensity played an important role in the combustion reactions. The efficiency of sulfur recovery in Claus reactors increased with an increase of the swirling intensity or the mix intensity. The stronger the swirling intensity or the mix intensity was, the sooner the mixture of air and acid gas reached to the best stoichiometric ratio. The three-channel reactor had a better performance than that of the two-channel reactor due to the additional inner air channel which can strengthen the mix of the acid gas and air from the inside of the acid gas. Moreover, the helix deflectors in the three-channel reactor had a better swirling performance than that of the vane deflectors in the two-channel reactor. From the comparison of the two models, we can obtain a way to improve the process of elementary sulfur recovery in the industry, which can be helpful to reduce pollution emissions and improve economic performance.