Mechanisms of CO and COS Formation in the Claus Furnace

Abstract

The aim of this study was to determine the major pathways leading to COS and CO formation and consumption during the processing of H2S and CO2 in the partially oxidizing conditions of the Claus furnace. Both species were found to be produced by a multitude of pathways, which include the direct reaction of H2S with CO2 to form COS and H2O and the reaction of CO2 with S2, one of the major primary products in a Claus furnace. This last reaction produced SO2 and CO as the major products, with COS being formed in lesser quantities. The dissociation of H2S to H2 and S2 at high temperatures (>1000 °C) was shown to promote a further cascade of reactions stemming from the reduction of COS and CO2, both of which lead to CO. Because of the known formation of CS2 from hydrocarbon carry-over into the furnace, the reactions of CS2 with CO2, H2O, and SO2 were also studied as potential CO- and COS-forming reactions. Reaction with CO2 was slow at <1200 °C, but reaction with either H2O or SO2 was fast above 900 °C. Conversion of CS2 by H2O led to CO, H2, H2S, S2, and CO2, whereas reaction with SO2 resulted in CO2 and S2 as the major products. Similar observations were made for the reactions of COS with H2O and SO2. The summary of pathways presented in Scheme shows a complex interlinkage among many reactions involving H2S, CO2, CO, COS, SO2, and S2, leading to the conclusion that previous explanations of the production of COS from CO + S2 and CO from incomplete combustion dramatically oversimplifies the formation/consumption for these compounds. It also shows that modeling of individual kinetic rate expressions is somewhat impractical.

Oxidation of Reduced Sulfur Species: Carbon Disulfide

“…Experimental results for oxidation of CS 2 These data sets were obtained in an overlapping temperature and pressure range but under conditions of low (300 ppm 7 ) and high (25% 8,14 ) concentrations of CS 2 , respectively. Figure 6 compares the measured and calculated explosion limits.…”

“…In the experiments, the reactants CS 2 and O 2 were preheated separately and mixed at the entrance to the reaction zone. Atomic oxygen, formed from O 2 at the heating elements in the preheating oven, was suggested to promote onset of reaction.…”

“…17,18,20,24,25 No reported chemical kinetic models are found to satisfactory describe experimental data across a wider range of mixture composition, temperature, and pressure as the mechanism is complex and accurate kinetic data have been unavailable for several important reactions. The objective of the present study is to develop a detailed chemical kinetic model for oxidation of CS 2 and evaluate it over a broad range of conditions. The work is a continuation of a recent study by Glarborg and Marshall 26 on the oxidation chemistry of carbonyl sulfide.…”

Ionic liquids for metal extraction from chalcopyrite: solid, liquid and gas phase studies

“…The presence of carbon and oxygen in the chalcopyrite, and formation of CS 2 and CO 2 in the gas phase during leaching, is reminiscent of a Stock-like reaction mechanism (4). 44,45 …”

Investigation of Inlet Gas Streams Effect on the Modified Claus Reaction Furnace

“…Paskal et al gives a summary of the main reactions thought to occur within the Claus furnace [6,7]. Clark et al discussed the mechanisms behind the formation of key sulfur containing species found within the furnace, and in a subsequent study outline primary reaction pathways for the principal components in the furnace [8,9]. While there have been numerous attempts to model the Claus process based on simplified kinetic expressions, the complexity of the chemistry and the number of involved reactions has precluded the accurate prediction of outlet compositions.…”