EP0600923B1 - Process for producing synthetic or fuel gasses from solid or pasty residues and waste or low-grade fuels in a gasifying reactor - Google Patents

Abstract

A process is disclosed for producing synthetic and/or fuel gasses from organic elements-containing residues and waste and/or low-grade fuels (charging materials) with oxygen-containing gasses by means of a flying stream or shaft gasifyier. In order to obtain a product gas of a quality as uniform as possible, in spite of the handling difficulties presented by the charging materials, that may in particular be shredder-produced light materials from car recycling, a pyrolytic stage is arranged upstream of the gasifying reactor. The solid materials that leave the pyrolytic stage are gasified into product gas in the gasifying reactor and the gaseous fraction leaving the pyrolytic stage is used to supply heat to the production process and/or for further producing product gas.

Description

The invention relates to a method according to the preamble of patent claim 1.

Since the deposition of solid or pasty residues and waste materials is no longer justifiable, the recycling of these materials is becoming increasingly important. These substances include e.g. B. Shredder light goods from motor vehicles, plastics, oil, paint and solvent sludges, partially dewatered sewage sludges and many others. These substances have in common that they contain organic components.

Experiments with so-called shaft gasifiers have shown that in high-temperature gasification a number of feedstocks, e.g. the shredder light fraction from motor vehicle recycling encounter considerable problems; in particular, it is difficult in some cases, and in particular in the case of the light shredder fraction from motor vehicle recycling, to feed this cargo evenly into the gasification zone, i.e. to be introduced specifically into the primary gas space so that the product gas has a sufficiently uniform quality. To solve this problem, previously unpublished efforts have been made to briquette the feedstock and then to give it to the shaft gasifier in a lumpy form by conventional lock systems. The briquetting as such turned out to be very complex and not yet mature enough.

Another previously unpublished solution has also not led to success. According to this approach, the feed is milled, e.g. is known for the use of fuels in an entrained-flow gasification reactor. This grinding proves to be problematic insofar as wear-intensive substances such as glass, stones, iron and others can be contained in the residual or waste material. This procedure is also very expensive.

The disposal of carbon-containing waste materials of varying composition, such as domestic and industrial waste, is known from EP-A3-0 120 397. The aim of this process is the production of fuel gas. For this purpose, the carbon-containing waste material is smoldered in a rotary tube reactor above 200 ° C to obtain a carbonization gas and a pyrolysis coke. The pyrolysis coke is then gasified in a fluidized bed or fluidized bed gasifier. The gasification products leave the carburetor at relatively low Temperatures between 400 ° C and 1000 ° C. The liquid and gaseous components released from the smoldering stage and the gasification stage are subsequently burned, while the ashes that have to be disposed of have to be disposed of. - This process is unsatisfactory for environmentally friendly disposal of the input materials, since both the final incineration and the disposal of the ashes lead to new environmental problems.

A process similar to that described in EP 0 120 397 A3 is also known from WO 90/02162, in which essentially the same problems as described in connection with EP 0 120 397 A3 arise. In the process known from WO 90/02162, both the pyrolysis step and the gasification step are carried out allothermally. WO 90/02162 also provides for the combustion of the solid gasification residue in a gasification residue combustion chamber, the step of burning the gasification residue being an essential step for the overall process. In addition to the production of a synthesis gas, the process management there aims at a particularly advantageous use of heat within the overall process, and in order to provide sufficient quantities of heat in the individual process stages, it is also intended to supply the process with coal as well as waste as a raw material.

Proceeding from this, the object of the invention is to ensure the most environmentally compatible disposal of residues and waste materials which are difficult to handle and contain organic constituents, in particular the light shredder fraction, in the recycling of motor vehicles, and thereby to obtain a synthesis gas.

To achieve this object, the method with the features of claim 1 is proposed.

• Bei dem thermischen Vorbehandlungsschritt (Pyrolysebehandlungsschritt) des Einsatzstoffes fallen die Gasfraktion und die Festfraktion, insbesondere dann, wenn es sich bei dem Einsatzstoff um eine Shredderleichtfraktion handelt, in einem Mengenverhältnis an brenn- bzw. vergasbaren Material an wie es zum Betrieb eines Flugstromvergasungsreaktors erforderlich ist (etwa 60 % Gasfraktion und etwa 40 % Festfraktion); ein Zufeuern anderer Brennstoffe in einem Primärgasbrenner ist daher so gut wie nicht erforderlich;
• die Festfraktion aus der thermischen Vorbehandlung hat Eigenschaften wie etwa ein Hüttenkoks; deshalb kann bei der Vergasung auf den Einsatz von z.B. Hüttenkoks ganz verzichtet werden, so daß das feste Chargiergut nur noch aus der Festfraktion des thermisch behandelten Einsatzstoffes besteht;
• bei der erfindungsgemäßen Vergasung der Einsatzstoffe fallen Umweltgifte wie Dioxine und Stickoxide nicht an, da die Dioxine bei der unter unterstöchiometrischen Bedingungen durchgeführten Vergasung nicht existieren können und bei den relativ hohen Vergasungstemperaturen zerstört werden; Stickoxide aus der Primärgasverbrennung werden unter den Vergasungsbedingungen reduziert; außerdem weisen etwa anfallende Metalloxide einen im Vergleich zu anderen Verwertungsverfahren geringeren Oxidationsgrad auf und sind somit weniger toxisch;
• in dem Einsatzstoff enthaltene Ballaststoffe, wie z.B. Metalle können nach dem thermischen Vorbehandlungsschritt aus der Festfraktion durch einen üblichen Trennschritt abgeschieden werden, bevor die Festfraktion dem Vergasungsreaktor als Chargiergut aufgegeben wird;
• der Eintrag des festen Chargiergutes in den Vergasungsreaktor wird wesentlich vereinfacht und vergleichmäßigt.

A number of significant advantages are achieved by the invention. These include:

• In the thermal pretreatment step (pyrolysis treatment step) of the feedstock, the gas fraction and the solid fraction, in particular if the feedstock is a light shredder fraction, are obtained in a quantity ratio of combustible or gasifiable material as is required to operate an entrained-flow gasification reactor ( about 60% gas fraction and about 40% solid fraction); adding other fuels in a primary gas burner is therefore hardly necessary;
• the solid fraction from the thermal pretreatment has properties such as that of a cottage coke; Therefore, the use of, for example, smelting coke can be dispensed with entirely in the gasification, so that the solid charge only consists of the solid fraction of the thermally treated feedstock;
• In the gasification of the feedstocks according to the invention, environmental toxins such as dioxins and nitrogen oxides do not occur, since the dioxins cannot exist in the gasification carried out under substoichiometric conditions and are destroyed at the relatively high gasification temperatures; Nitrogen oxides from primary gas combustion are reduced under the gasification conditions; in addition, metal oxides that occur have a lower degree of oxidation than other recycling methods and are therefore less toxic;
• Dietary fibers contained in the feed, such as metals, can be separated from the solid fraction by a conventional separation step after the thermal pretreatment step before the solid fraction is fed to the gasification reactor as a charge;
• the entry of the solid charge in the gasification reactor is considerably simplified and evened out.

Surprisingly, it has been found that the advantages which can be achieved by the invention with the known disposal methods which, as described in EP-A1-0 120 397, carry out the gasification in the fluidized bed, i.e. cannot be achieved in a defined stationary to circulating fluid bed. In these known disposal methods, a solid residue is formed, in particular a cyclone ash separated after the fluidized bed, which mostly contains higher proportions (e.g. 5%) of unreacted carbon and which, according to today's stricter environmental laws, may no longer be disposed of. This residue has the disadvantage that solid gases which are not gasified can be eluted very easily.

It has also been found that not every combination between pyrolysis treatment of material to be disposed of and subsequent gasification in the entrained flow achieves the considerable success achieved by the presently claimed invention. In particular, the disposal process described in US Pat. No. 4,497,637 is neither suitable for such heterogeneous starting materials as are to be disposed of in accordance with the present invention, nor is it possible to carry out such disposal in the desired environmentally compatible manner. In this known method, synthesis gas is produced from a biomass; this includes US-A-4,497,637 wood shavings, sawdust and the like from trees and other land plants, algae, agricultural and forestry residues and waste, the coal-containing fraction of municipal waste and the like. First, a mechanical and thermal (drying) pretreatment of the biomass is carried out. After the pretreatment, a combined process of entrained flow pyrolysis takes place and entrained-flow gasification, both of which are carried out in the so-called downdraft, the entrained-flow pyrolysis taking place in an outer zone and the gasification in an inner zone of a common, concentrically constructed entrained-flow reactor in which the pyrolysis is carried out at a temperature of up to 1600 ° F, corresponding to 870 ° C is done. The temperature of the pyrolysis step is therefore extremely high. In addition to nitrogen, the hot carrier gas for pyrolysis also contains water vapor and CO ₂ . In connection with the reaction pressure between 1 and 5 atmospheres in the entrained-flow pyrolysis chamber, process conditions are achieved in which gasification of the mechanically and thermally pretreated biomass already begins. - Apart from the complex pretreatment and the biomass which is relatively easy to handle compared to the shredder light fraction from motor vehicle recycling, this method cannot be compared with the concept of the present invention because of its special process management in the combined pyrolysis / gasification entrained flow reactor.

The same applies to GB-A-2 109 400, which describes synthesis gas production from a fibrous biomass, such as wood chips. In this connection, a so-called slurry gasification is carried out after a pyrolytic pretreatment of the starting material. This type of gasification requires a relatively high liquid carrier content of approx. 40%. The gasification apparently takes place at relatively low process temperatures, namely below the ash softening. This known process is not very suitable for feedstocks of the type that are to be disposed of in accordance with the present invention.

Other combination processes for the disposal of carbon-containing feedstocks also start from process concepts which do not meet the requirements set out in the present invention: this is the case in WO 81/00112 known to further treat bituminous hard coal, lignite, wood, straw and the like after an upstream rotary tube pyrolysis in a coupled cracking and shaft gasification process with partial combustion of the coke from the pyrolysis stage. - Difficult feedstocks, as they should be disposed of according to the present invention, can not be treated with the desired result in this known combination process.

Gasification reactors operating according to the entrained flow principle (entrained flow gasifiers) are well known and therefore do not require any special description at this point; reference is made, for example, to DE-C2 27 21 047 and EP-B1-0 011 151. Grain bandwidths of approximately 0.001 mm to 5 mm are used for use in so-called entrained flow gasifiers. The particle size of the solid fraction obtained after the pyrolysis treatment stage according to the invention is adjusted after the pyrolysis treatment and before the entrained flow gasification by grinding, sieving and / or sifting, the particle size range being reduced.

The gas fraction obtained after the pyrolysis treatment stage is preferably first subjected to a condensation step. The gas fraction obtained after the coding stage is then further used in the synthesis gas production process according to the invention. For this purpose, this gas fraction is fed to the gasification reactor or the pyrolysis treatment stage for introducing heat for the endothermic pyrolysis or gasification step or admixed to the product gas obtained behind the gasification reactor as part of the synthesis gas.

The liquid fraction obtained after the condensation stage can possibly be used in another process, but is preferably used in the gasification reactor for gasification and / or supplied for the introduction of heat for the endothermic gasification process. According to a preferred embodiment of the invention, the solid fraction obtained after the pyrolysis treatment stage and the liquid fraction obtained after the condensation stage are mixed and fed together to the gasification reactor, a pump or a screw machine being used, depending on the consistency of the mixture. Suitable funding bodies and procedures for this are known from DE-C2-27 21 047 and EP-B1-0 011 151 as examples.

A particularly advantageous use of the gases produced according to the invention results from claim 7.

It is also possible to add inorganic residues or waste materials to the feedstock in order to remove contaminating substances contained therein from the residue or waste material in the pyrolysis treatment stage or in the gasification stage.

Further method variants within the scope of the invention result in connection with the block diagram to be explained (FIG. 1).

In the production process according to the invention, the gasification is generally carried out under a pressure of preferably 10 to 100 bar. Basically, higher gasification pressures are possible. The gasification can also be carried out at atmospheric pressure or in a slightly reduced pressure (if suction fans are used).

With regard to the gas or liquid fraction to be fed to the gasification reactor from the thermal pretreatment of the starting material, it goes without saying that these can also have solid constituents in the form of fine-grained, in particular dust-like material.

The size, shape, material selection, technical conception and process conditions of the above-mentioned components as well as those claimed and described in the following exemplary embodiment and to be used according to the invention are not subject to any special exceptional conditions, so that the selection criteria known in the respective field of application are used without restriction can.

Further details, features and advantages of the subject matter of the invention result from the following description of the associated drawing. The drawing shows:
Fig. 1 is a block diagram.

The block diagram shown in FIG. 1 is explained below in connection with the use of an entrained-flow gasification reactor. Alternative procedures are shown in dashed lines. Process steps that are preferably used are additionally outlined with a dashed line.

According to FIG. 1, a residual or waste material containing organic constituents, hereinafter referred to as feed material, is fed to a pyrolysis treatment stage 101, such as an indirectly heated rotary kiln (drum wall temperature up to 900 ° C.). In this, the feed material is pretreated, largely without oxygen, with the addition of heat and essentially avoiding the burning of constituents of the feed material at temperatures between approximately 300 and 650 ° C. For the heat supply, extraneous gas, product gas accumulating behind the gasification reactor 102 and / or pyrolysis gas accumulating behind a condensation stage 103 downstream of the pyrolysis stage, preferably accumulating in a pyrolysis gas purification stage 104, can be used.

The intermediate product obtained in the pyrolysis treatment stage 101 from the starting material is discharged separately as steam (gas fraction) and coke (solid fraction). The solid fraction is adjusted, if necessary after setting the grain size range in a grinding, sieving and / or classifying stage 105, to the level which is compatible with the respective gasification reactor type (gasification reactor 102), and the gasification reactor 102, e.g. B. pneumatically supplied. Recyclables contained in the solid fraction, e.g. Metals can be separated in a separation stage 106, e.g. a screening device, before the solid fraction is fed to the gasification reactor 102.

The gas fraction obtained behind the pyrolysis treatment stage 101 is either fed as vapor to the gasification reactor for the gasification and / or introduction of heat of reaction or is first passed through a condensation stage 103. The residual gas deposited therein, which is obtained under the condensation conditions, is fed to the pyrolysis treatment stage for introducing process heat either, preferably after passing through a pyrolysis gas purification stage 104. As an alternative or in addition, the pyrolysis gas can be supplied to the gasification reactor 102 or the product gas stream occurring behind it to introduce gasification heat. In these cases, a pyrolysis gas cleaning stage may not be necessary.

The oil (liquid fraction) obtained behind the condensation stage 103 is recycled in other processes or, as is preferred, introduced into the gasification reactor 102. Especially when this oil is to be gasified together with the solid fraction from the pyrolysis treatment stage 101, the two fractions can first be combined and fed to the gasification reactor 102 by means of a pump or screw machine 107.

After the gasification reactor, there are inorganic components that no longer have to be deposited, but can be used as valuable materials. The product gas obtained behind the gasification reactor 102 will generally be cleaned in a gas cleaning stage 108. The constituents removed from the product gas can be fed to the gasification reactor 102 at least as a partial stream, so that they are divided there into product gas or inorganic constituents. In addition, enriched harmful gas components such as sulfur, salts and heavy metals can be reused.

The product gas obtained behind the gas purification stage 108 can, as is preferred, be fired in a power plant 109, which may be already present, or, if appropriate partially, in the pyrolysis treatment stage 101 or used as synthesis gas or other fuel gas.

Claims (8)

1. A process for producing synthetic gas from solid or pasty residues and waste - difficult to handle and containing organic components - in particular the shredder light fraction from vehicle utilisation with oxygen or oxygen-containing gases and, optionally, water vapour by using an entrainment gasifying reactor at temperatures of from 800°C to 1700°C and. optionally, higher, during which

   a) first of all as a result of thermal pre-treatment by supplying heat and, substantially, by avoiding combustion of components of the feed (pyrolysis treatment) there is separation in a heated revolving tube into a gaseous, in particular vapour-like, fraction and a solid fraction,

   b) the solid fraction is fed to the entrainment gasifying reactor as a solid feed material to be gasified, optionally after separation off of valuable substances, for changing into the synthetic gas, and

   c) the gas fraction is utilised at least partially in the production process, in particular for introducing heat for the endothermic gasification process.
2. A process according to Claim 1, characterised in that the gas fraction which is obtained during pyrolysis undergoes a condensation step before being utilised.
3. A process according to Claim 2, characterised in that the gas fraction obtained after the condensation stage is combined immediately as part of the synthetic and/ or fuel gas with the product gas stream obtained downstream of the gasifying reactor, or is added to the gasifying reactor or the pyrolysis treatment stage for the purpose of introducing heat for the endothermic process.
4. A process according to Claim 2 or 3, characterised in that the liquid fraction obtained after the condensation stage is utilised in another process or is added to the gasifying reactor for gasification and/or introduction of heat for the endothermic gasification process.
5. A process according to any one of Claims 1 to 3, characterised in that the grain size range, obtained after the pyrolysis treatment stage, of the solid fraction is reduced before gasification in the entrainment gasifying reactor by grinding, sifting and/or classification.
6. A process according to any one of Claims 1 to 4, characterised in that the solid fraction obtained after the pyrolysis treatment stage and the liquid fraction obtained after the condensation stage are mixed and, are added, preferably by means of a pump or screw machine, to the gasifying reactor.
7. A process according to any one of Claims 1 to 5, characterised in that the product gas obtained downstream of the gasifying reactor and, optionally, after the condensation stage, is used, where necessary after removing for example pollutants present (pollutant gas components), as a gaseous fuel for the operation of a power station, optionally already available, in particular, a block-type thermal power station.
8. A process according to any one of Claims 1 to 6, characterised in that inorganic residues or waste are added to the feed.

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