ENERGY CONSERVATION IN SULPHURIC ACID PLANT

Abstract

This thesis presents a theoretical' investigation on various aspects of energy conservation in sulphuric acid plants. It mainly includes the effect of shifting the blower position with respect to the drying tower, role of excess air in the combustion of sulphur, and the effect of decre-asing the converter inlet temperature on the energy conser-vation as well as the economics of the plant. As a result, necessary changes in the sulphuric acid plant have been pro-posed, which are economically viable in terms of reduction in energy consumption as well as higher recovery of heat. The arrangement having the blower after the drying tower has been compared with the one employing blower before it for their energy consumption and capital investment. This analysis has been carried out for plants of various capaL, cities employing air at various temperatures and humidities., Calculations have indicated that by changing over the blower position from pre—to post—drying tower location, power consumption and the capital requirement can be reduced drastically. Using the method of minimization of free energy, equilibrium composition of the gases leaving the combustion chamber has been determined. It has been found that the amount of sulphur dioxide in the burner gases remains unaffected irrespective of the amount of excess air introduced in the combustion chamber. In fact, supply of excess air affects the plant economy adversly by increasing the size of com-bustion chamber, ducts and waste heat boiler as well as by limiting the recovery of therMal energy to a lower value. Temperature of the gases entering the converter has been observed to be a vital•parameter influencing the degree of conversion, weight of the catalyst, converter size, and the amount of heat recovered in waste heat boiler and the economiser. Decrease in the converter inlet temperature hac resulted in an increase in heat recovery as well as the degree of conversion of sulphur dioxide. However, capital investment for the catalyst and the converter becomes higher when the converter inlet temperature is lowered. Based on the economic analysis, a reduction in converter inlet temperature has been found to improve the overall economics of the plant.