DE1594674A1 - Process for removing sulfur oxides from gases containing them - Google Patents

Description

Process for removing sulfur oxides from such containing Gases

The invention relates to a method for removing sulfur oxides from such gases and gases containing oxygen and water vapor, in particular from smoke gases, by means of carbonaceous gases Adsorbents.

To keep the air clean it is necessary to remove sulfur oxides from gases containing such, in particular from smoke gases and other exhaust gases, urgently required.

Numerous proposals have already been made to meet this requirement, but none of them have proven themselves technically. It is known, for example, from German Auslegeschrift 1 181 682 and German Patent 1 046 818 to free flue gases ^{from sulfur oxides in the presence of oxygen and water vapor at temperatures up to 180 °} C. with the aid of carbon-containing adsorbents. In addition to activated carbon, the adsorbents used are mainly semi-cokes made from peat, lignite, hard coal or from oxidized hard coal. This known method is based on the adsorption of SOg

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on the coal, which then increases with the oxygen content of the gas SO., Is oxidized and converted to sulfuric acid with the steam.

It is also known from British patent specification 1 050 942, SO ^ initially catalytically to SO, to oxidize, which then as such or as HpSO, of carbonaceous adsorbents is bound.

The regeneration of the adsorbents takes place in the above-mentioned processes by heating them to about 450 ^° C., the SO. However, this type of regeneration is associated with a considerable loss of substance.

It is also from the German patent specification 854 205 and the German Auslegeschrift 1 171 404 known the implementation of SOp-Grelialtes of exhaust gases with the likewise contained oxygen to be carried out in the presence of water on carbon contacts to obtain dilute sulfuric acid. This is going to be special Value placed on an excess of water or dilute sulfuric acid. The big disadvantage of this method is the lack of it thermal lift of the cooled exhaust gases, which go to the ground in the immediate vicinity of the chimney and there to Damage to vegetation.

In all of the aforementioned known processes, the oxidation of SOp to SO, the slowest step in the overall reaction, is like this that, in technical processes, residence times of 20 to 40 seconds have to be used, provided that the degrees of desulphurisation are satisfactory should be achieved. Substantial volumes of apparatus are therefore required for the technical implementation of these processes / who cast doubt on the economic viability of these processes.

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It is finally from British patent specification 826 221 smoä, feeäannt to inject ammonia _{into the flue gas to bind SO 2} and to separate the ammonium salts formed in electric filters. The ammonium sulphate-sulphite mixture produced cannot be used because of the impurities, the predominantly ammonium sulphite that is formed is easy so that, due to its low concentration, it is separated from the gas and easily enters the soli chimney with the flue gases. In addition, our own experiments have shown that a reaction between ammonia and the sulfur oxides ΐ6ϊ exhaust gases is technically effective only when large excess ammonia is added.

The invention is based on the object of improving the binding of the sulfur oxides with ammonia so significantly that it can be used for the desulphurisation of flue gases in the Netherlands.

This object is achieved according to the invention in that the Ammonia in the flue gases before they enter the adsorbent or introduced directly into the adsorption bed

Me applicable for the process of this invention carbonaceous adsorbents can cokes made from wood, peat, lignite, bituminous coal, which in Kokungsendtemperaturen 500-1300 ⁰ O oxidative with or without pretreatment of the training | good materials are made. In addition, eoks of this type can also be used, which are activated by a rapid gasification process or by chemical activation. Activated carbon or high-temperature coke (metallurgical coke) have proven to be particularly useful adsorbents.

Adsorption, sulfur oxides from gases containing them

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can be carried out at temperatures in the adsorbent bed below 200 ⁰ G, it is preferably to Ibo performed ⁰ C at temperatures in the range of 80 s.

During the adsorption of the sulfur oxides on the carbonaceous ones Adsorbents is in the adsorbent bed between the introduced ammonia and the sulfur oxides present a molar ratio between 1: 1 and 1: 4 is maintained.

The adsorbents loaded with sulfur compounds can be regenerated by dry means in a manner known per se. For this dry regeneration preferably temperatures between 300 and 55O ⁰ C. The suitable for the temperature control can be obtained between different products. At a high heating rate, the ammonium salts, which are mainly present as ammonium sulfate, essentially decompose to SO2, HpO and Np. At a slow heating rate (under I ⁰ C per minute) on the other hand the DeSorptionsreaktors considerable mass forms in the cool zones ammonium bisulfate.

In addition, you can also carry out a wet regeneration by washing out with steam or hot water. It is expedient to work at water temperatures of up to 100 ^° C. This gives a concentrated ammonium sulfate solution which can contain up to about 25 to 30% ammonium sulfate.

The process according to the invention can be carried out in per se known way, for example, by adding the SOg-containing Exhaust gases are passed through containers or towers that contain the adsorbent. The adsorbent can here for example in the solid layer, in a moving layer or in the trickle cloud. The Adsortio * is expediently carried out in one

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Wandering layer in which the adsorbent slowly descends migrates »while the exhaust gas moves from the bottom to the top of the adsorbent flows in the opposite direction. This way of working is therefore special, important to use abrasion-resistant adsorption material. For this purpose, specially shaped products such as activated carbons and low-temperature coke have been found from coal or high temperature coke oxidized with air.

After the adsorbent has emerged from the towers or containers, the flue dust retained in the bed and the abrasion can be sifted dry, whereupon the granular material is freed from ammonium sulfate by showering or immersing it in water. The wet bed can be introduced to the adsorber after dripping% once again.

The invention will be explained in more detail on the basis of exemplary embodiments:

example 1

a) Through an adsorber tower with a height of 5 m and a diameter of 0.2 m, 15 Nnr flue gas per hour from a heating oil furnace, which has the following composition: 15 Vol .- # GO ₂ , 2 to 4 Vol.-Ji · O ₂ , 8 Vol .- $ έ H ₂ O and 0.08 to 0.1 Vol.-Jt SO ₂ -

The adsorber tower is filled to a bed height of 1 m with activated carbon with a grain size of 2 to 3 mm. Before entering the adsorber, a stoichiometric amount of gaseous ammonia _{based on the S0 2 content is added to the flue gas.} The residence time dee exhaust gas in the reactor is about 20 seconds and the temperature 120 ⁰ C. Nach.über OEO hours gas passage through the adsorber, a desulfurization of about 90 j6 is still obtained. The loading of the adsorbent is then over 20 wt .- ^

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Even "with a dwell time of 2 seconds" is that achieved Degree of desulphurization after tfO hours of gas passage still over $ 60.

b) is not introduced into the ammonia Rauohgas for comparison during the adsorption of the sulfur oxides, as is at a Verweiizeit of 20 seconds and a! temperature of 120 ⁰ C of Intschwefelungsgrad only 25 #. With a residence time of 2 seconds, only a desulphurization of about $ 5 is obtained.

c) If no activated carbon is filled into the adsorber tower for comparison, but the same stoichiometric amount of gaseous ammonia can be added under the same conditions no ^ desulphurisation effect observed. This also applies to the Pail that an inert filling material, e.g. Raschig rings, creates a intensive mixing of the gas streams is achieved.

Example 2

a) The Adsorba ± urm described in Example 1 is filled up to a layer height of 1 m with metallurgical coke with a grain size of less than 10 mm and the same flue gas is passed through under the same conditions. With a residence time of the flue gas of 7 seconds in the bed, the desulfurization after introduction of a stoichiometric amount of ammonia is about $ 55. If, on the other hand, a double stoichiometric amount is introduced, the degree of desulphurization is even over $ 70>.

b) If no gaseous ammonia is introduced for comparison, the degree of desulfurization is with a residence time of 7 seconds only about 5%.

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Claims (5)

Patent claims: 1) Process for removing sulfur oxides from such gases and gases containing oxygen and water vapor, in particular from Flue gases, by means of carbonaceous adsorbents, thereby characterized in that in the flue gases before they enter the adsorbent or directly in the Adsorptionsmittelohüttung Ammonia is introduced. 2) Yeri'ahren according to claim 1, characterized in that the adsorption of the sulfur oxides is carried out at a temperature in the .Schüttung of below 200 ⁰ G, preferably in the range from QQ to IbO ⁰ G. 3; Process according to Claims 1 and 2, characterized in that a molar ratio between 1: 1 and 1: 4 between ammonia and sulfur oxides is maintained in the adsorber bed. 4; Method according to claim 1 to 3 »characterized in that activated carbon is used as the carbon-containing adsorbent. 5) Method according to claim 1 to 3 _f, characterized in that times high-temperature coke is used as the carbon-containing adsorbent. " Π ORIGINAL 109817/021 1