Evaluation of SO2 capture efficiency of combustion gases using commercial limestone
- 63 Downloads
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.
KeywordsLimestone Coal Sulfur Capture Thermal analysis
The authors acknowledge the experimental assistance of the Federal University of Rio de Janeiro, School of Chemistry, Thermal Analysis Laboratory, and the financial support of the Coordination for the Improvement of Higher (CAPES) and of the Brazilian National Research Council (CNPq).
- 1.Nacional Electric Power Agency (ANEEL). Atlas of electric energy in Brazil. 2008. http://www2.aneel.gov.br/arquivos/pdf/atlas3ed.pdf. Accessed 26 Oct 2017.
- 2.Kohl A, Nielsen R. Gas purification. 5th ed. Houston: Gulf Publishing Company; 1997.Google Scholar
- 9.European Integrated Pollution Prevention and Control Bureau (EIPPCB). Reference document on best available techniques for large combustion plants (BREFs). 2006. http://eippcb.jrc.ec.europa.eu/reference/BREF/lcp_bref_0706.pdf. Accessed 18 Oct 2017.
- 15.Martin AE, editor. Emission control technology for industrial boilers. Park Ridge: Noyes Data Corporation; 1981.Google Scholar
- 16.Pinheiro PCC, Valle RM. Control of combustion: optimization of air excess. Publication at the 2nd congress of equipment and automation of the chemical and petrochemical industry, vol 1. Rio de Janeiro, RJ: ABIQUIM; 1995. p. 157–62.Google Scholar
- 17.Costa MCD. Effect of temperature on the conversion and coefficient of reaction rate on the absorption of SO2 by limestone in a fluidized bed reactor. M.Sc. dissertation, Graduate Course on Mechanical Engineering, São Carlos School of Engineering, São Paulo University, São Carlos, Brazil, 2000.Google Scholar
- 18.Leckner B, Amand LE. Emissions from a circulating and a stationary fluidized bed boiler: a comparison. In: 9th international conference on fluidized bed combustion, ASME; 1987. p. 891–97.Google Scholar
- 21.Dweck J, Souza PS. Prototype system for thermogravimetric analyses. Ceramics. 1989;35:l69–175.Google Scholar
- 23.Dweck J. Factors affecting thermogravimetric analysis results. Internal publication of the Material and Process Thermal Analysis Course, Chemical and Biochemical Process Engineering Course for Graduates, School of Chemistry, Rio de Janeiro Federal University, 2014.Google Scholar
- 25.Földvári M. Handbook of thermogravimetric system of minerals and its use in geological practice. Budapest: Occasional Papers of the Geological Institute of Hungary; 2011.Google Scholar
- 27.Castellán JL, Chazan DT, D’Ávila ML. Desulphurisation in coal thermoelectric plants: the case of the Candiota II Power Plant. Publication at the 2nd congress of technological innovation in electric energy (CITENEL). Salvador: BA, ANEEL; 2003. p. 330–8.Google Scholar
- 28.Barboza FH. Capture of SO2 from coal-burning process of lithothamnium type marine limestone. Dissertation, Graduate Course on Chemical and Biochemical Process Technology, School of Chemistry, Rio de Janeiro Federal University, Rio de Janeiro, Brazil, 2017.Google Scholar