Evaluation of SO2 capture efficiency of combustion gases using commercial limestone

According to the World Energy Balance, coal is the most used source for electricity generation in the world, accounting for 41% of total production. It is known that one of the main problems of the generation of energy from the coal burning is the emission of polluting gases, as the sulfur dioxide (SO2), which cause several negative impacts to the environment. Thus, the main motivation of this work is to reduce the environmental impacts caused by coal burning in power generation thermoelectric plants, by capturing the sulfur dioxide present in the flue gases. In view of the problem outlined above, several techniques have been developed and improved for desulfurization (removal of SO2) from the flue gases. Among them, the absorption by limestone is one of the most used methods, mainly due to the low cost of the raw material and the generation of a product with added value, and also mainly for the efficiency of the sulfur removal. Thus, this work had as main objective to evaluate the influence of airflow and burning temperature in the SO2 capture efficiency from flue gases, through its absorption in aqueous suspension of commercial limestone. The SO2 capture tests were carried out on the prototype developed on a bench scale, which consists of a coal-burning furnace coupled to a washer bottle responsible for the absorption of the sulfur dioxide from the combustion. To evaluate the percentage of SO2 absorbed by limestone and yield, the capture tests were done according to a factorial design, whose objective was to evaluate the influence of the most relevant variables and the interaction between them. Thus, a two-factor factorial design was done with central points, and the parameters selected for evaluation were the airflow and the maximum burning temperature of the coal. New methods of calculating the absorbed SO2 content were developed using thermal analysis curves of the residual product up to 1000 °C prior to the decomposition of the formed product (CaSO4). Yield of 99% was obtained using 4.5 L min−1 of air flow and 600 °C of maximum firing temperature, indicating that there should be an optimum point near this flow and temperature, in which the SO2 absorption of the combustion is maximal.