DESIGN AND SIMULATION OF HYDRO-DESULPHURIZATION UNIT IN AN AMMONIA PLANT

The research work considered the design and simulation of 200 tons per year hydro-desulphurization plant for the removal of sulfur in the form of H2S in the cracked natural gas. The process flow diagram for the hydro-desulphurization plant consists of an absorber column and two fixed bed reactors in series aimed at absorbing the H2S using the MDEA/H2O as solvent and then removal of the sulphide from the absorbent through the series fixed bed reactors respectively. The models were simulated with plant data using MATLAB and Aspen HYSYS. The results from the various simulations showed that the absorber height, diameter, number and height of transfer units, and pressure drop gave values of 7.06m, 2.36m, 6 and 0.843m, and 18.43kN/m2 respectively. The cost results for the absorber gave $44,000 while cost for fixed bed reactor 1 gave $12,000 as well as cost for fixed bed reactor 2 gave $100,000. Finally, the models were validated with plant data and result showed that the models developed were reliable and good predictor of the process since the percentage deviations are of range 0 to 5, except H2S component which gave 66.7 when compared the final value with the plant composition. The design results for the absorber column and the reactors gave the diameters and heights of 2.36m and 5.06m; 2.3m and 6.74m; and 1.8m and 6.74m respectively. It was observed that the pressure drop of the fixed bed reactors were 0.7bar. Simulated models performed better and reliable as the models developed predicted the process well since the results from the simulations gave good values.