Remoção de compostos sulfurados a partir de Syngas obtido por hidrogaseificação do carvão mineral

Abstract

The current concern about clean sources of energy generation has led to a growing research on the gasification of coal. Gasification consists of the thermochemical conversion of organic material into gaseous fuel, also called synthesis gas (syngas). Mineral coal is an unexplored national wealth, whose application is reduced only to its burning for electricity generation. Emissions from sulfur compounds from coal combustion pose a risk to the environment and the population, with emphasis on hydrogen sulfide (H2S) and sulfatic sulfur (SO42-). The objective of this work was focused on the removal of H2S and SO42- from the syngas through the chemical absorption technology in redox solution. This process was chosen for economic viability, through the possibility of reducing operating costs and reagents. The experiments were carried out in the Laboratory of Energy and Carbochemistry (LEC) and in the Laboratory of Spectroscopy of UNIPAMPA, campus Bagé, where the sulfur compounds were produced by hydrogasification of the coal from the Candiota-RS deposit and analyzed the products. The gas produced was subjected in situ to the chemical absorption process by redox solution of Fe3+, obtained from the ferric chloride salt (FeCl3), with and without EDTA chelator. During the process, there was precipitation of particulate in the solution without chelating, due to the reduction reaction of Fe with SO42- forming ferrous sulfate (FeSO4). The solid part was separated by centrifugation and filtration, and in conjunction with the liquid samples were subjected to qualitative titration, Raman spectroscopy and FT-IR analyzes. The liquid samples underwent titration analysis of SO42- by barium hydroxide (Ba(OH)2) solubilized in methanol (CH3OH), with alizarin red as indicator. The two liquid samples showed turbidity and precipitation, indicating the presence of the ion. In the EDTA liquid sample, when excess titrant was added, there was precipitation of barium sulfate (BaSO4) which was also separated for analysis. The solid and liquid samples were subjected spectrometric analyzes by Raman, with wavelength 532 nm, 785 nm and 1064 nm. The solid samples did not present definite results due to their luminescence. All liquid samples showed peaks in the region of 980 cm-1 to 1200 cm-1, characteristic of the presence of SO42-, and the titrated samples also showed high intensity peaks at 1017 cm-1 owing to the asymmetric stretching vibration of the BaSO4 molecule. The solid samples were also submitted to FT-IR spectrometric analysis presenting results consistent with the literature for FeSO4 and BaSO4 at 625 cm-1, 997 cm-1 and 1271 cm-1. It is possible to imply the presence of sulfates in the liquid samples and in the solid samples, showing qualitatively the efficiency of the chemical absorption by redox solution of iron. The addition of EDTA did not add better results to the process, nor the selectivity of the reaction. Future work proposals can quantitatively demonstrate the efficacy of the method, in addition to producing and comparing the efficiency of the iron-based catalyst in the same process.