economical–environmental evaluation of so3/so2 elimination from acid sulphoric plants in petrochemical industry

sulfuric acid production plants are one of the main sources of sulfur oxides, emission to the atmosphere. in the present study to control sulfur oxides of sulfuric acid plant two methods have been selected. the first method is desulfurization by ammoniac (plant a) and the second one is a combination of the first method and dry scrubbing process with calcium hydroxide as the absorbent material) plant b). concerning economical investigation two techniques were carried out regarding the conclusion of the simulation. considering the simulation results by hysys v3.1 software, 110 tones of sulfur oxides production were eliminated daily in two methods. as elimination of sulfur oxides was nearly the same (110 tones daily) in both methods, the external costs of production reduction of sox as a pollutant substance is the same, too. therefore, economic index of these two methods were calculated through comfar ? software with two presuppositions i.e. considering the external costs and not considering the external costs, the internal rate of return (irr) in the first method was about 46% which is more than that of the second method (18%). moreover, the payback period in the first method was 3 years which is less than that of the second method (5 years). net present value (npv) as a major criterion in economics was calculated, too. in the first method npv was more than that of the second method which is a sign of an appropriate flow of cash in the first method. in cash flow of implementation of the second presupposition, there would be 541286 million rials save as the result of reduction of external costs. consequently, the first method has economic priority over the second method for desulfurization of sulfuric acid production plants.