DE2419103C2 - Process for removing sulfur oxides from gases by adsorption - Google Patents

Description

The invention relates to a method for removing sulfur oxides from gases by adsorption a large surface, with oxides of cobalt and molybdenum or tungsten, or of nickel and molybdenum or tungsten impregnated adsorbent until the sulfur oxides break through and regenerate of the impregnated adsorbent with heated gas.

From DE-AS 10 84 248 a hydrogenation catalyst is known in which clay minerals are used as carrier material will. This catalyst is impregnated with oxides of cobalt, molybdenum, nickel and / or tungsten. For regeneration, the impurities deposited on it are burned with air, then takes place the reduction of the catalyst to make it usable again.

The invention is based on the object to work easily and economically with the possibility that to convert desorbed sulfur compounds into elemental sulfur. With the method mentioned at the beginning this is done by using activated carbon as the adsorbent and regenerating the adsorbed sulfur oxides are desorbed by hydrogen or hydrogen-containing gas, the adsorption the sulfur oxides in the temperature range from normal temperature to about 120 ° C and the desorption in Temperature range from about 200 to 450 ° C takes place. In this desorption treatment, the consumption of Avoided activated carbon because the carbon does not oxidize. The adsorbed compounds SO2 and SO3 are already partially reduced to H2S during the desorption.

According to a preferred embodiment of the invention, the activated carbon is impregnated up to 10% by weight their own weight with the oxides of cobalt, nickel, tungsten and molybdenum with a composition, the molar ratio of CoO or NiO to MO2O3 or W2O3 of about 1: 1.5 corresponds. Preference can be given to adsorption of the sulfur oxides as well as also carry out their desorption in moving adsorbent beds.

When using the method according to the invention, it is possible to use the desorption gas, which consists of hydrogen as the carrier gas and contains the desorbed sulfur compounds in the form of H ₂ S and SO ₂ , to carry out the Claus reaction and work up to elemental sulfur at temperatures between 100 and 300 ° C to cool over granular large-area solids acting as a catalyst, such as. B. to conduct activated carbon or aluminum oxide and then condense out the sulfur formed in this way. The hydrogen freed from elemental sulfur during cooling can be used for the further desorption of sulfur oxides from activated carbon loaded therewith, the hydrogen expediently being circulated. By circulating the desorption water substance, which at the beginning of the desorption, as long as the temperature is still low, _{initially desorbs the SO 2} as such, the latter is completely reduced _{to H 2 S.} In this way, a _{gas mixture consisting only of H 2} S and H ₂ is obtained, in which the hydrogen sulfide is enriched up to concentrations of 30% by volume and more.

If the amount of desorption hydrogen circulated is reduced, not all of the SO _{2 is} reduced to H2S and a gas mixture with a volume ratio of H2S: SO2 = 2: 1 can be obtained, that of a Claus contact at temperatures of approx. 230 to 28O ⁰ C can be converted to elemental sulfur. After the elemental sulfur has condensed out, the hydrogen is obtained for reuse as a desorption gas.

example

A flue gas with an SO ₂ content of 0.5 vol .-%, a residual oxygen content of 4.2 vol .-% and a water vapor content of 3 vol .-% is at a temperature of 69 ° C over a granular activated carbon with a Grain diameter of 4 mm passed. The activated carbon is impregnated with cobalt molybdenum oxide. The amount of impregnation of oxide, expressed as the sum of Co metal + Mo metal, is 2.9% by weight. The stoichiometric ratio Co: Mo corresponds to the ver ()
After uptake of around 10 Nl = 29 g of SO ₂ per 1 kg of coal until the SO ₂ breakthrough, the gas loading is interrupted and the loaded coal is heated to a temperature of 370 ° C. with heated hydrogen _{for the purpose of desorption of the adsorbed SO 2.} When the temperature rises, the desorption of SO ₂ begins. As the temperature continues to rise, H ₂ S takes its place. The gas is completely free of CO ₂ , which could have been formed by oxidation of the carbon by SO3, which is produced catalytically even when SO.- is adsorbed on carbon in the presence of O2.

By circulating the predominantly hydrogen desorption gas over

This hot adsorbent completely hydrogenates the SO2 still present in the first gas fractions to H ₂ S. A desorption gas is obtained, the total sulfur content of which is increased to 29% by volume of H ₂ S by repeated circulation

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Claims (3)

Patent claims: 1. A method for removing sulfur oxides from gases by adsorption on a large-surface adsorbent impregnated with oxides of cobalt and molybdenum or tungsten, or of nickel and molybdenum or tungsten until the sulfur oxides breakthrough and regenerating the impregnated adsorbent with heated gas, characterized in that, that one uses as an adsorbent activated charcoal and regenerating desorbs the absorbed sulfur oxides with hydrogen or hydrogen-containing gas, wherein the adsorption of the sulfur oxides in the temperature range from normal temperature to about 120 ⁰ C and desorption in the temperature range of 200 is carried out to 450 ° C 2. The method according to claim 1, characterized in that the activated carbon is impregnated up to 10 wt .-% of its own weight with the oxides of cobalt, nickel, tungsten and molybdenum in a composition that corresponds to the molar ratio of CoO or NiO to MO2O3 or W ₂ O ₃ of about 1: 1.5. 3. The method according to claim 1 or 2, characterized in that the adsorption and the desorption Performs in moving adsorbent beds.