DE3443686A1 - Process for the elimination of nitrogen oxides and sulphur oxides from gases - Google Patents

Abstract

On the basis of the known catalysts for reacting nitrogen oxides with ammonia, the use of brown coal low-temperature carbonisation coke is proposed. Comparable catalyst bodies based on activated charcoal or activated coke are significantly more expensive and therefore require expensive regeneration plants. The frequently undesired effect of the sulphur oxide absorption can be expediently utilised by use of brown coal low-temperature carbonisation coke as a disposable catalyst. The use of brown coal low-temperature carbonisation coke in conjunction with other gas purification plants and the use of brown coal low-temperature carbonisation coke from brown coal pressed pieces or as pressed coke are also proposed.

Description

Patent description

Process for removing nitrogen oxides and sulfur oxides from gases.

The invention relates to a method for the simultaneous reduction of Nitrogen and sulfur oxides from gases, depending on the nature of the gas, too the reduction of only one of these pollutants is possible.

There are numerous for the desulfurization and nitrogen oxide reduction of gases Procedure known. The sulfur oxides are mainly extracted from the water with water Gas washed out, with the water for binding the sulfur oxides basic components can be added. Also known are dry or semi-dry processes in which the sulfur oxides on dry, pasty or liquid bases injected into the gas stream be bound. Another way to reduce sulfur oxide is that Addition of basic material directly to the combustion chamber of incineration plants (direct desulphurisation). In contrast, mainly catalytic processes are used to reduce nitrogen oxides, in which the nitrogen oxides are reduced to molecular nitrogen with ammonia. Numerous metallic and ceramic materials in different ways are used as catalysts Shape usage.

Activated carbon and activated coke are also used or tested on the one hand itself can act as a catalyst, on the other hand as a carrier material for other catalysts are used (e.g. DE-09 23 50 498, DE-09 26 35 652, DE-09 30 14 934). Activated carbons and activated cokes have catalysts over most other the advantage that the catalytic conversion takes place at much lower temperatures is possible. The usual range of application for many catalysts is around 300-400 (C, while activated carbons and cokes are already effective at temperatures of approx. 100 C.

In addition to the catalytic effect, activated carbons and cokes also have very good adsorptive properties for other gas components, especially for sulfur oxides. However, this adsorption usually leads to a decrease in the catalytic properties Effect, as a result, the activated carbons or cokes have to be replaced frequently. Because of their relatively high price, they generally become technically complex Regeneration supplied, the inevitably occurring losses must be through fresh produce be replaced.

The adsorptive properties of these catalysts also in relation to Ammonia and nitrogen oxides also have significant control engineering advantages Adsorption of the various gas components makes breakthroughs easier Avoiding and peaks in concentration can be reduced, an aspect that can be of considerable weight, especially in systems that are not operated in a stationary manner (Buffer effect).

The invention was based on the object of an inexpensive catalyst to find, which has the advantages of activated charcoal or activated coke, namely at relative low temperatures for the catalytic conversion of nitrogen oxides with ammonia to be effective, but because of its low price and / or its other reusability can be dispensed with a regeneration.

A further advantage of such a catalyst is that it is used for regeneration mandatory and therefore often perceived as annoying adsorption of other pollutant components, especially the sulfur oxides, can be used sensibly.

According to the invention, the task is achieved through the use of lignite coke solved. Lignite coke is an economic good, the price of which is roughly its Corresponds to the calorific value, when used according to the invention in gas cleaning it when it slackens the catalytic or adsorptive effect dem System can be taken and fed to an incineration plant, the ecological Effect with regard to the sulfur oxides, of course, a corresponding desulfurization system presupposes. All others mentioned for the use of activated carbons or cokes Advantages in particular with regard to the temperature range and the control behavior remain fully preserved.

The use of the lignite welded coke can in different, technach known reactor types take place. The use of fixed bed reactors is possible, one reactor can be refilled while the second is in operation is. Another possibility is a moving bed reactor, in which the exchange of the Brown coal coke takes place continuously. Use can also be an advantage of fluidized bed reactors, with the use of pipelines or gas ducts as a reactor is possible.

To avoid pressure loss and dust generation in the reactor can, depending on the type of reactor used, the use of lignite coke in be sensible in a certain form, lignite coke can also be omitted, for example Produce pressed lignite or molded coke.

The technical and economic advantages resulting from the invention Use of brown coal coke as a catalyst to reduce nitrogen oxides follows, result from the elimination of the complex regeneration system. That in this Respect disruptive adsorption behavior of activated carbons or cokes for sulfur oxides can, however, be economically and technically possible when using lignite coke use it sensibly.

In addition to being used to reduce nitrogen oxides, the lignite coke can also be used used simultaneously or exclusively in a targeted manner will the Reduce residual emissions of sulfur oxides behind gas desulfurization systems. the Targeted utilization of the sulfur oxide adsorption also makes it possible to only use a partial flow to promote the gases through a gas desulphurization system and after mixing with the feed untreated electricity to a brown coal coal coke reactor. For wet washes or spray absorption method, this circuit has the advantage that not the entire Gas stream is cooled and so with a sufficient total degree of desulphurization on the otherwise required reheating of the flue gases is completely or partially omitted can be.

Likewise, the utilization of the sulfur oxide binding capacity of Advantage behind desulphurisation systems which, due to the process, are not the desired ones Fall below residual emission values, this can e.g.

be the case with direct desulphurization or dry sorption systems.

Similar advantages for reducing residual emissions of sulfur oxides also result when used behind systems, the exhaust gases of which are already a relative have low levels of sulfur oxide, but exceed the relevant limit values. This often applies, for example, to waste incineration plants, even if they are equipped with a Wet scrubbers are equipped for hydrogen chloride, as can the use behind Rolling firing systems can be an advantage.

This results in the possibility, for example, of systems that use the Only exceed sulfur oxide limits relatively slightly with nitrogen oxide reduction systems to equip on the basis of lignite coke, which at the same time reduce the sulfur emission to the required values without the need for a disproportionately expensive desulphurisation system must be erected. The loaded catalyst is called sulfur-containing fuel fed to a suitable incineration plant. It can also be advantageous to have several Equip plants with lignite coke reactors and another plant to be provided with a conventional flue gas desulphurization system, which the consumed Catalysts are then fed as fuel.

Claims (7)

Process for removing nitrogen oxides and sulfur oxides from gases. Claims 1. A method for removing nitrogen oxides and sulfur oxides from gases, the nitrogen oxide reduction through catalytic reduction with ammonia and the sulfur oxide reduction takes place by adsorption, characterized in that that the gas mixed with ammonia a reactor filled with lignite coke flows through. 2. The method according to claim 1, characterized in that the method in gases that are not or only slightly contaminated with sulfur oxides, mainly for catalytic purposes Reduction of nitrogen oxides is used. 3. The method according to claim 1, characterized in that the method With no ammonia dosage, mainly for the adsorption of sulfur oxides Is used. 4. The method according to any one of the preceding claims, characterized in, that it is in connection with a spray absorption, dry sorption or direct desulphurization system or a wet gas scrubber is used. s 5. The method according to any one of claims 1 to 4, characterized in that that the method is used in combination with another gas cleaning system finds that only a partial flow of the gas to be treated through this gas cleaning system is performed, the two substreams are brought together and jointly the lignite coke reactor are fed. 6. The method according to one or more of the preceding claims, characterized in that lignite coke coke as molded coke or from lignite compacts is used. 7. The method according to one or more of the preceding claims, characterized in that the lignite coke is the gas-carrying lines is added continuously, is carried along by the gas and in a dust collector is removed from the gas stream after the reaction has taken place.