Performance assessment and process optimization of a sulfur recovery unit: a real starting up plant

Abstract

Sulfur recovery units (SRU) have an important role in the industrial production of elemental sulfur from hydrogen sulfide, whereas the generated acidic gas emissions must be controlled and treated based on local and international environmental regulations. Herein, Aspen HYSYS V.11 with Sulsim software is used to simulate the industrial and treatment processes in a refinery plant in the Middle East. In the simulation models, in temperature, pressure, flow, energy, and gas emissions were monitored to predict any expected change that could occur during the industrial processes. The simulation models were validated by comparing the obtained data with actual industrial data, and the results showed low deviation values. The simulation results showed that the current process temperature conditions can work efficiently for sulfur production without causing any environmental consequences. Interestingly, the simulation results revealed that sulfur can be produced under the optimized temperature conditions (20° less than design temperatures) with a total amount of steam reduction by 1040.12 kg/h and without any negative impact on the environment. The steam reduction could have a great economic return, where an average cost of 7.6 $ per ton could be saved with a total estimated cost savings by 69,247.03 $ per year. The simulation revealed an inaccurate production capacity calculated by real data in the plant during the performance test guarantee (PTG) where the real data achieved around 1 ton/h higher capacity than the simulation result, with an overall recovery efficiency of 99.96%. Based on this significant result, a solution was raised, and the level transmitters were calibrated, then the test was repeated. The simulation models could be very useful for engineers to investigate and optimize the reaction conditions during the industrial process in sulfur production facilities. Hence, the engineers can utilize these models to recognize any potential problem, thereby providing effective and fast solutions. Additionally, the simulation models could participate in assessing the performance test guarantee (PTG) calculations provided by the contractor.

Keywords: Environment; Optimization; Performance test guarantee; Sulfur recovery unit.

Fig. 1

A representation for the main processes in the SRU plant

Fig. 2

Scheme for methodology

Fig. 3

Detailed block diagram for the plant

Fig. 4

Process simulation (thermal, catalytic, tail gas treatment, degasser, and incinerator sections)

Fig. 5

Effect of decreasing air inlet temperature to thermal reactor on outlet temperature from thermal reactor

Fig. 6

Effect of decreasing air inlet temperature to thermal reactor on thermal reactor sulfur conversion

Fig. 7

Effect of decreasing air inlet temperature to thermal reactor on COS outlet from thermal reactor

Fig. 8

Effect of decreasing air inlet temperature to thermal reactor on CS₂ outlet from thermal reactor

Fig. 9

Effect of decreasing inlet temperature of catalytic reactor1 on CS2 outlet

Fig. 10

Effect of (H₂S/SO₂) ratio on catalytic reactor1 sulfur conversion efficiency

Fig. 11

Effect of (H₂S/SO₂) ratio on catalytic reactor2 sulfur conversion efficiency