DE2155320A1 - Sulphur dioxide removal from waste gas by adsorption - and reduction to elementary sulphur - Google Patents

Abstract

is removed from waste gases, before discharge, in an economic absorption process which quantitatively extracts the SO2 and converts it to elementary S. The SO2 is removed on an adsorption medium of activated charcoal. The loaded adsorption agent is regenerated by contact with a hot, inert, heat carrier (e.g. quartz-sand), pref. at 750-1000 (800-850)degrees C whilst hydrocarbon gas or vapour are passed through. The amount of HC supplied is controlled so that the ratio SO2; (1/2 CS2 + COS + H2 + CO + H2S) in the evolved gases = 1:2. The evolved gases are subjected to one-or several-stage catalytic treatment, to yield S. The adsorption medium is recycled for further use.

Description

Process and device for the reduction of gases containing sulfur dioxide to elemental sulfur The invention relates to a method for removing sulfur dioxide from such containing gases with the help of carbonaceous adsorbents and regeneration of the loaded adsorbents with the help of hot inert heat carriers, Efforts are made to produce sulfur dioxide from flue gases, roasting gases and the like Gases remove the sulfur dioxide to the population from its harmful To preserve influences. For this purpose, numerous methods are known in which the sulfur dioxide either by solid adsorbents or by liquid absorbents Will get removed.

However, the procedure can only be carried out economically if when the sorbent materials are subjected to a regeneration process and reused will. This results in regeneration gases containing a high percentage of sulfur dioxide exhibit. Up until now it was common for these gases to reach sulfuric acid to process. Attempts have also been made to reduce the sulfur dioxide with the help of carbonaceous Compounds such as natural gas and liquid hydrocarbons, a partial reduction to subject and then to process elemental sulfur.

A common method for removing sulfur dioxide from flue gases or other gases containing sulfur dioxide is the adsorptive cleaning with the help of carbonaceous sorbents, e.g. B. activated carbon, coke, etc .. This is the sulfur dioxide is adsorbed at temperatures between about 100-2000C, whereby at the same time an oxidation of the sulfur dioxide wit that in the flue gas or the like. Existing Oxygen is made to sulfur trioxide. This is due to the moisture in the gases Sulfur trioxide is then converted into sulfuric acid.

The subsequent regeneration of the loaded carbon-containing adsorbents takes place, among other things, through the action of heat that is introduced by external heat transfer media. Such a heat transfer medium is, for example, highly heated quartz sand. In this type of regeneration, the sulfuric acid in the hot environment is reduced to sulfur dioxide by the carbon in the adsorption bed. A mixture of sulfur dioxide, carbon dioxide and water vapor is produced as the regeneration gas. Like the reaction equation shows, this reduction is associated with a consumption of the carbonaceous adsorbent.

The present invention seeks to regenerate the loaded adsorbents so improve that once instead of sulfur dioxide, elemental sulfur is the reaction product and secondly, the consumption of carbonaceous adsorbents is reduced will.

In a method of the type mentioned at the outset, this is achieved by that during the regeneration process the adsorption material except for the heat transfer medium Gaseous or vaporous hydrocarbons are supplied and the resulting Regeneration exhaust gases from a single or multi-stage catalytic treatment for conversion subjected to the sulfur-containing ingredients of the regeneration gas in elemental sulfur will.

As a heat transfer medium for the regeneration, hot inert gas, e.g. B.

Nitrogen can be used. Use hot quartz sand instead and admixed with the adsorbent as it travels through a desorption chamber, 80 the gaseous or vaporous hydrocarbons in the Passed countercurrent.

In the case of the invention, a reductive regeneration takes place, d'e carried out in a temperature range of 75.degree.-1000.degree. C., preferably at 800-83000 will.

The sulfuric acid bound to the activated carbon settles with it the hydrocarbons to a mixture of carbon oxysulphide, hydrogen sulphide, Carbon disulfide and elemental sulfur U. Appear as further reaction products Hydrogen and carbon monoxide.

This gas mixture is expediently first fed to a waste heat plant1 in which a cooling down to approx. 25U - 2000C takes place.

A large part of the elemental sulfur that has already formed falls into this liquid form.

The gases cooled in this way then pass through a single-stage or two-stage catalytic plant, the one. Part of a well-known Claus system modeled is. Both the hydrolysis of the carbon oxysulphide takes place on Al2O3- containing catalysts and the carbon disulfide to hydrogen sulfide as well as the further conversion formed hydrogen sulfide with sulfur dioxide after elemental sulfur.

The remaining sulfur, carbon sulfide, carbon disulfide and Hydrogen sulfide components are used in a thermal or catalytic aftertreatment again oxidized to sulfur dioxide. These residual gases with 400 - 3000C become the treated gas supplied upstream of the adsorption unit.

In the drawing is an embodiment of a device for Carrying out the method using quartz and as a heat transfer medium for the Regeneration is shown schematically, which is described below.

In an adsorber 1, the carbon-containing adsorbent filled and flows from top to bottom through the adsorption device. Above a discharge 2, the loaded adsorbent is introduced into the desorber 3, in which it is freed from the adsorbate. Arrived via a discharge device 4 the adsorbent in a cooler 5, in which it is back to the adsorption temperature is cooled. A conveyor 6 then conveys the cooled adsorbent back into the adsorber 1.

from via line 7 the adsorber 1 is the / sulfur dioxide to be liberated Gas supplied. The exhaust gas cleaned of sulfur dioxide leaves the adsorber Line 8.

At the same time in a vortex chamber 9, which at 9a vortex air can be supplied that contains the inert heat transfer medium required for regeneration, here quartz sand, with the help of the hot flue gases from burner 9b via 9c to the desorber 3 funded. The exhaust gases from the heating of the inert heat transfer medium are via the Line 11 discharged. The hot, inert heat transfer medium mixes in the desorber 3 with the loaded adsorbent.

At the same time, in countercurrent to that from top to bottom through the Desorptionskanmer is a moving mixture of hot, inert heat transfer medium and adsorption material gaseous or vaporous hydrocarbon in stoichiometric amount supplied at 10, so that in the regeneration gas a ratio of SO, (1/2 CS2 + CO + lI2 + COS + H2S) as 1 s 2 is present. This regeneration gas is over the line 12 fed to a waste heat boiler 13. Here part of what has already been formed is separated Elemental sulfur in liquid form, which is fed to the sulfur collecting tank 21 will.

The regeneration gas, cooled to 200 - 250 C, passes through the first catalytic conversion stage 14, which is carried out with an aluminum oxide-containing catalyst is loaded. This is where the further conversion takes place between the oxygen-free, sulfur-containing gases and the S02 to elemental sulfur.

Via the heat exchanger 15, a waste heat boiler 16, a sulfur separator 17 the gas is freed from sulfur. In the heat exchanger 15, the gas is again heated to process temperature and fed to the second contact stage 18.

The gas leaving the contact stage 18 is then again in the Waste heat boiler 16 and sulfur separator 19 largely freed from elemental sulfur and then a catalytic resp.

thermal post-combustion 20 fed. This is where the oxidation takes place the sulfur compounds that do not contain oxygen and the sulfur compounds that are still present Sulfur to sulfur dioxide. The exhaust gas leaving this stage becomes the one to be cleaned Exhaust gas flow is fed back at 7.

The method according to the present invention shows over the heretofore known method has the advantage that a universally usable product accrues that can easily be stacked safely for a long time.

It also shows the advantage that the carbon-containing adso large sorbent materials not subject to / consumption during the regeneration process are.

The sulfur yield is based on the amount of adsorbed sulfur dioxide approx. 100%.

Literature taken into account VDI report 149, keeping the air clean 1970, Pages 135 - 136 VDI report 149, Keeping the air clean 197U, Pages 116 - 121 Dust - Cleanliness of the air, Volume 28, 1968, No. 3, Pages 89 - 93 Title: Newer research results in the field of exhaust gas desulfurization Chem.-Ing.-Technik, 38th year, 1966, issue 7, page 734 - 736 title: Process for the dry separation of sulfur dioxide from exhaust gases Zhurnal Prikladuoi Khimii, Vol. 43, No. 1, Pages 35 - 43 (1970) Title: Thermodynamics of Reduction of Sulfur Dioxide by Methane.

Claims (5)

P a t e n t a n s p r ü c h e 1. Process for removing sulfur dioxide from such containing Gases with the help of carbon-containing adsorbents and regeneration of the loaded adsorbents with the help of hot inert heat carriers, characterized in that, that during the regeneration process the adsorption material apart from the heat carrier Gaseous or vaporous hydrocarbons are supplied and are formed in the process Regeneration exhaust gases from a single or multi-stage catalytic treatment for conversion subjected to the sulfur-containing ingredients of the regeneration gas in elemental sulfur will. 2. The method according to claim 1, characterized in that the exhaust gas from the catalytic treatment of a catalytic or thermal afterburning subjected and from there the gas to be cleaned before the adsorption treatment be fed. 3. The method according to claim 1, characterized in that the for the amount of gaseous or vaporous hydrocarbons to be supplied to the regeneration process is dimensioned so that a ratio SO, s (t / 2 CS2 + COS + H2 + CO + H2S) is 1: 2. 4. The method according to claim 1, characterized in that the reductive Regeneration in a temperature range of 750-1000 ° C, preferably at 800 - 850 ° C. 5. The method according to claim 1, characterized in that the regenerated hot adsorbent by the hydrocarbon stream fed in at the bottom of the desorbent be pre-cooled. L e r s e i