DE2758813A1 - Gasification of carbonaceous matter in fluidised bed reactor - under conditions of controlled temp. determined by reactive agents - Google Patents

Abstract

Solid materials containing carbon are gasified by means of oxygen-contg. gases and/or water vapour or steam, CO2 or other gases, in a fluidised bed reactor having above the fluidised bed a post-reaction chamber. The distribution of temp. along the axis of the reaction chamber and/or transversely to it, is influenced by the feeding of the reactive agents. These are introduced into >=2 zones spaced some distance apart along the reactor axis, outside the zone of the fluidised bed, and also in the central and/or the topmost zone of the post-reaction chamber. The gasification is carried out under increased pressure, pref. at 30 bar. Oxygen contg. gases and/or steam are blown into the central and/or topmost zone of the post reaction chamber. The reactor can be operated much more flexibly both relatively to the characteristics of the carbonaceous material to the characteristics of the carbonaceous material to be gasified and to the constitution of the resulting gas mixt. The temp. along the reactor is controlled to give the desired results. The emission of sulphur into the atmos is also prevented at little expense.

Description

Process for gasifying solid, carbonaceous material

Addition to patent application P 27 41 805.9 The main application concerns a process for gasifying solid, carbonaceous material with oxygenated ones Gases and / or steam, carbon dioxide or other gases, preferably in a fluidized bed reactor with a post-reaction space arranged above the fluidized bed, the temperature distribution along the reactor axis and / or across it by adding reactants can be influenced.

The main application also claims that in the reactor releasing CaO and / or MgO or, at higher temperatures, CaO and / or MgO Connections, d. H. CaCO3 and / or MgC03. These aggregates are supposed to influence the softening point of the ashes on the one hand and to one on the other Desulfurization of the product gas at least contribute, since that is present in the fuel Sulfur in the course of the gasification process as calcium sulfate or magnesium sulfate or calcium sulfide or

Magnesium sulfide is bound. Calcium sulfide and magnesium sulfide are environmentally harmful. You can therefore not z. B. on a Dump tilted will.

A method is already known - see DE-PS 1 770 602 as well as US Pat. No. 3,784,676 - in which of the sulfur-containing calcium or magnesium compounds the sulfur is recovered and the regenerated CaO and / or MgO in the circuit be returned to the reactor. The effort involved is reasonable large, so that this method is only applicable in practice when it comes to the removal of large amounts of sulfur is possible, for which a correspondingly large amount is possible Sulfur production corresponds to the regeneration of the additives.

The invention is based on the object of the method according to Design the main registration in such a way that it can be disposed of in a way that is harmless to the environment of sulfur is possible without the aforementioned, time-consuming and cumbersome State-of-the-art regeneration processes must be used.

To solve this problem, the invention proposes that the in the reactor Sulphides of calcium and / or magnesium formed under reducing conditions an oxidizing aftertreatment for the purpose of conversion into calcium sulfate or magnesium sulfate be subjected. The end product can be dumped without endangering the environment or the like. Tilted.

In general, there is the option to use the To procure the additives required for the procedure at low cost, so that the process can at least always be used where the in to be gasified Fuel-containing amounts of sulfur are too large to be in the product gas could be left, but on the other hand are too small for a Extraction of this amount of sulfur would be worthwhile.

The method according to the invention is in its practical implementation extremely easy. The above-mentioned sulfides coming out of the reactor In addition to ash, solid residues containing solid residues also have a considerable share of unreacted carbon. This residual carbon can easily with excess oxygen can be burned in such a way that the residue in the residue is called sulfide The sulfur contained is mixed with that which is also strongly superstoichiometric Ca0 or MgO connects to CaS04 or MgS04. It can be assumed here that anyway only a small part of the aggregates inside the reactor for absorption of the sulfur is used, so there is still so much in the solid residue Calcium oxide or magnesium oxide are present that under all circumstances the one you want Reaction occurs with the formation of sulfates.

In a fluidized bed reactor, part of the solid gasification residues is consisting of residual carbon, ash and aggregates or the resulting from them Compounds withdrawn from the bottom of the reactor. Another part of this solid residue is discharged at the top with the product gas and from the gas flow by means of separators removed. The main login here sees the Possibility before that the outlet of the reactor for the product gas is a separation device for the coarse cleaning of the gas as well as a second separator in series for fine cleaning are connected downstream and the output of the first separator for the separated Solid is connected to the reactor, so that this solid is recycled again is, whereas the - finer-grained - solids from the second separation device is led out of the system.

In particular, this solid is responsible for the above-described oxidizing Treatment in question because the sulfur it contains is predominantly in the form of Sulphides is bound to the aggregates. A treatment of the first Separation device - coarser - solids in relation to the contained therein Sulfur is generally not required, as the vast majority of the sulfur content in the solids discharged with the product gas are in the finer-grained fraction is located.

A treatment of the test residues that are withdrawn from the reactor below is normally not required as it is in the lower part of the reactor is generally driven with excess oxygen, so that the sulfur with The aggregates are already converted there to CaS04 and / or MgS04.

These residues can thus be tipped over without further treatment will.

In the drawing, the scheme of a system is an exemplary embodiment shown for gasifying solid fuels.

In the lower area of a fluidized bed reactor, coal and aggregates are placed entered. This is indicated by the arrow 12. It is convenient to use the coal and the aggregates, for example dolomite, calcite or the like, with one another to mix and feed them together to the reactor 11.

In the lower part of the reactor 11 are in three cross-sectional areas 13, 14, 15, which are vertically spaced from one another, nozzles 16, 17, 18 arranged, which are connected to a feed line 19 for gasification agent. The one supplied at 12 Coal with the aggregates forms a fluidized bed in the lower area of the reactor, the upper limit of which is around 21. Inside the fluidized bed and also in that The post-reaction space located above the coal is reacted with the gasification agent. In addition to the additives supplied with the coal 12, in the area CaO or MgO or CaCO 3, dolomite or the like are also added above the fluidized bed will.

The reducing gas is in the upper part of the reactor 11 over a line 22 is fed to a first separator 23, in which a first cleaning of the gas takes place. Here the coarser particles are separated from the gas, which can still contain significant amounts of carbon. You will have a Line 24 returned to the reactor 11 and in the lower area same abandoned again.

The gas pre-cleaned in the first separator 23 passes through a line 25 into a second separator 26, in which the fine dust still in the gas Will get removed. This fine dust contains high proportions of fuel ash and aggregates, those with the sulfur contained in the fuel fed into the reactor, predominantly sulfidic compounds has entered.

The latter applies in any case when in the upper part of the reactor bed and in the post-reaction chamber it is operated predominantly under reducing conditions. This fine dust is via a pipe or in some other suitable way a Aftertreatment system 10 supplied, in which with the supply of oxygen-containing gases the sulfide compounds are converted to calcium sulfate and / or magnesium sulfate. The resulting mixture of ash, CaO and / or MgO, sulfates and possibly carbonaceous Residues can then be dumped in a landfill without endangering the environment.

The gasification residue not discharged from the reactor 11 with the product gas is at the lower end of the conical section 20 of the reactor 11 z. B. using a screw 29 or some other suitable device out of the reactor. These residues also contain to the aggregates and possibly - at Corresponding quality of the ash - amounts of sulfur bound to the ash. However, these will normally be mostly sulfates, see above that these residues can easily be dumped. In the other case If post-treatment would also be necessary or possible here, that in the separator 26 experiences fine dust separated from the product gas.

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Claims (3)

Claims 1. A method for gasifying solid, carbonaceous Material with gases containing oxygen and / or steam, carbon dioxide or others Gases, preferably in a fluidized bed reactor with one above the fluidized bed arranged post-reaction space, the temperature distribution along the reactor axis and / or can be influenced across this by the addition of reactants and in the reactor CaO and / or MgO or at higher temperatures CaO and / or MgO releasing compounds, e.g. CaC03 and / or Mg03, are given according to patent application P 27 41 805.9, characterized in that the in the reactor under reducing conditions resulting sulphides of calcium and / or magnesium from an oxidizing aftertreatment for the purpose of conversion into calcium sulphate or magnesium sulphate. 2. The method according to claim 1, characterized in that the implementation the sulphide to sulphate using the solid residues withdrawn from the reactor of the residual carbon contained in them are converted with excess oxygen. 3. The method according to claim 1 or 2, characterized in that with a coarse cleaning and a subsequent fine cleaning of the from the reactor coming product gas for the purpose of the solid separated in the fine cleaning Conversion of the sulfide into Sulphate is treated oxidizing.