Abstract
Carbonyl sulfide (COS) are usually yielded from the petrifaction industry or steel-making plants. In this study, a low-temperature radio-frequency (RF) plasma approach was used to destruct COS for removing sulfur. The results showed that at an inlet O2/COS molar ratio of 3, the removal efficiency of COS reached 98.4% at 20 W and 4000 N/m2, with the major product being SO2 with small amounts of sulfur deposition. The removal efficiency of COS was lower in the H2-containing condition than in the O2-containg one. However, when H2 was added into the COS/N2 mixtures, the products, including major elemental sulfur with CS2 as a minor product, were easily collected and recovered.
Highlights
Carbonyl sulfide (COS) is an odourless, tasteless and colourless polar gas molecule with a boiling point of -50.2°C, which is relatively different from other sulfur-containing impurities of hydrocarbon feedstocks (Adewuyi and Carmichael, 1987)
Removal efficiency of COS at various inlet H2/COS molar ratios and operating pressures In order to examine the influences of the inlet H2/COS molar ratios (RH2) at two levels of operating pressure on the removal efficiency of COS (RECOS), the experiments were carried out at a fixed 30 W
As RH2 increased from 0 to 4.5 at 30 W, RECOS decreased slightly from 99.8% to 97.7% at a lower pressure (1333 N/m2), whereas the RECOS reduced significantly from 89.2% to 73.4% at a higher pressure (4000 N/m2) (Fig. 2)
Summary
Carbonyl sulfide (COS) is an odourless, tasteless and colourless polar gas molecule with a boiling point of -50.2°C, which is relatively different from other sulfur-containing impurities of hydrocarbon feedstocks (Adewuyi and Carmichael, 1987). During the high temperature stage of the Claus process, the formation of COS results from hydrocarbons being present in the flue gas according to the following reactions. COS that is emitted into the atmospheric environment will contribute to the formation of SO2 and promote photochemical reactions, but will have an effect on the climate (Lelieveld and Heintzenberg, 1992). The tail gas from Cluas Plants is usually incinerated and COS and CS2 are converted to the harmful SO2. An alternative method of reducing the levels of COS involves hydrogenation, which takes advantage of the hydrogen present in the Claus process via reaction (3) by using a Co-Mo-Al2O3 type catalyst (Tong et al, 1992; Rhodes, et al, 2000)
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