EP0523815A1 - Process for fabrication of synthesis or fuel gases from pasty or solid refuse or waste materials or from low-grade fuels in gasification reactor - Google Patents

Abstract

For a process for producing synthesis gases and/or fuel gases from residues and waste materials containing organic constituents and/or low-grade fuels (feedstocks) by means of oxygen-containing gases, using a pneumatic gasifier or shaft gasifier, the object is to ensure the most uniform product gas quality possible, in spite of the difficulties in handling the feedstock, which can especially also be light shredder material from motor vehicle recycling. For this purpose, a pyrolysis treatment stage is provided upstream of the gasification reactor, the solid material obtained downstream of the pyrolysis treatment stage being gasified in the gasification reactor to give a product gas and the gas fraction obtained downstream of the pyrolysis treatment stage being used in the production process for introducing process heat and/or for the production of further product gas. <IMAGE>

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 as well as low-quality fuels 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, wet brown or hard coal with a high tar content, old tires and many others. These substances have in common that they contain organic components.

Inferior fuels, such as wet brown coal or hard coal with a high tar content, old iron, etc., can already be gasified today - even without undesirable emissions in the extracted product gas; in particular, the product gas can be free or almost free of impurities which reduce the calorific value and restrict further use and pollute the environment. For this purpose, a shaft-shaped gasification reactor, among other things, has been developed, the special feature of which is that the bulk material bed in the primary gas chamber is constructed in two layers. A first layer of the bulk bed consists of a relatively high quality coke. The second layer of the bulk bed is stored as a relatively thin layer on the first bulk layer and is formed by the inferior fuel. The free bulk surface of the second bulk material layer faces the primary gas burner in the primary gas chamber. A fuel, oxygen or air and possibly water vapor are applied to the primary gas burner and provide the sensible heat required for the endothermic gasification process. As a fuel, the primary gas burner z. B. used oils and a pasty residue from a paper mill. The primary gas generated by the combustion in the burner occurs at a temperature of 1500 to 1800 ° C. Upon contact with the cargo to be gasified (low-quality fuel, e.g. a mixture of used tires and deinking sludge), the primary gas reacts with this cargo to form raw gas. The raw gas has z. B. 1,864 ° C and then flows through the second bed of coke and leaves it as a finished product gas at the top of the shaft gasifier. On the thickness of the (second) bed of bulk goods, ie the batch to be gasified (low-quality fuel) and the setting of the primary gasification, it depends on whether the batch lying behind the second bed of bulk goods, e.g. B. the higher quality coke, also gasified or used only or primarily as a filter for the raw gas passing through. The primary gasification is set either via the ratio of oxygen to carbon carrier in the burner, or via the total amount of primary gasification substances or - if pure oxygen is introduced via the burner instead of air - via the ratio of oxygen to water vapor (EP 0 194 252 B1).

Experiments with the aforementioned shaft gasifier have now shown that a number of high-temperature gasification of starting materials, such as. B. the shredder light fraction from motor vehicle recycling considerable problems occur; in particular, it is difficult in some cases, and in particular in the case of the shredder light fraction from vehicle recycling, to introduce this charge material so uniformly into the gasification zone, ie specifically into the primary gas space, that the product gas has a sufficiently uniform quality. To solve this problem, previously unpublished efforts have been made to briquette the low-quality fuel and then to give it to the shaft gasifier in a lumpy form by means of 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 starting material is ground, as z. B. 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 inferior fuel. This procedure is also very expensive.

Proceeding from this, the object of the invention is to ensure as uniform a product gas quality as possible in the gasification of inferior and / or difficult to handle feedstocks and / or residues and waste materials containing organic constituents, in particular in the gasification of the shredder light fraction during motor vehicle recycling.

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 Schachtvergasers oder 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 die Sekundärfraktion im Vergasungsreaktor (festes Chargiergut) nur noch aus der Festfraktion des thermisch behandelten minderwertigen Einsatzstoffes besteht; im Falle der Verwendung eines Schachtvergasers benötigt dieser also nicht mehr zwei unterschiedliche Chargiergüter und kann mithin einfacher aufgebaut sein, wie etwa in der DE 29 20 922 C3 oder in der EP 0 143 106 B1 beschrieben;
• 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, falls sie im Brennstoff des Primärgasbrenners vorhanden sind, bei den relativ hohen Verbrennungstemperaturen 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 necessary for operating a shaft gasifier or entrained-flow gasification reactor is (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 in the gasification on the use of z. B. metallurgical coke can be dispensed with entirely, so that the secondary fraction in the gasification reactor (solid charge) consists only of the solid fraction of the thermally treated low-quality feedstock; if a shaft gasifier is used, it no longer needs two different charging goods and can therefore be of simpler construction, as described, for example, in DE 29 20 922 C3 or in EP 0 143 106 B1;
• 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, if they are present in the fuel of the primary gas burner, are destroyed at the relatively high combustion 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 compared to other recycling processes and are therefore less toxic;
• Dietary fiber contained in the feed, such as. B. 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.

Gasification reactors operating according to the preferred entrained flow principle (entrained flow gasifier) are sufficiently 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. While the use of a gasification reactor working according to the entrained flow principle (also known as the fly dust principle) is preferred according to the invention, alternatively there is also a gasification reactor working according to the fluidized bed principle, as described u. a. is addressed in EP-B1-0 011 151, for use according to the invention. While the so-called fluidized bed gasifiers use a relatively wide and coarse grain size range for the solid to be gasified in the gasifier (typical values are 0.1 mm to 100 mm), grain size ranges of around 0.001 mm to 5 mm are used for the 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 (claim 2).

In contrast, when using a shaft gasifier, which is also preferred according to the invention, the solids obtained after the pyrolysis treatment stage can preferably be used can be used directly in the shaft gasifier without a special adjustment of the grain size range and without great handling problems when charging the solid fraction; A relatively uniform product gas quality is also ensured with this driving style. The above-mentioned shaft carburetors (EP-B1-0 194 252) are basically suitable for such an application. Such a shaft gasifier has a shaft-shaped container for receiving the solid cargo to be obtained behind the pyrolysis treatment stage, forming a traveling layer with a passage for the cargo at the lower end of the container. Connected to the passage is a primary gas chamber arranged under the container and fired by a primary gas burner, in which a bed surface facing the primary gas burner of a bed of bulk material formed by the solid cargo below the passage is formed, the product gas and the slag from the gasification process be deducted in a suitable manner. In particular, if such a shaft gasifier is used according to the invention, it is advantageous to supply the fraction which is gaseous behind the pyrolysis treatment stage and which is gaseous under operating conditions of the pyrolysis treatment to the primary gas burner in order to supply the endothermic gasification process with heat of gasification. In this case, the gas fraction and, if appropriate, further fuels are preferably fed in by forming an entrained flow in the primary gas chamber.

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

The liquid fraction obtained behind the condensation stage can possibly be used in another process, but is preferably fed to the gasification reactor for gasification and / or for the introduction of heat for the endothermic gasification process. According to a preferred embodiment of the invention (claim 3), the solid fraction obtained after the pyrolysis treatment stage and the liquid fraction obtained after the condensation stage are mixed and fed to the gasification reactor together, depending on the consistency of the mixture, preferably a pump or a screw machine being used. 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 4.

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 (claim 5).

Further process variants within the scope of the invention result in connection with the block diagram to be explained (FIG. 1). While the feedstocks to be processed according to the invention are either essentially solid or pasty, with pasty not only solid / liquid mixtures but also more or less thickened Liquids are to be understood, in principle liquid feedstocks, ie residues and waste materials and / or inferior fuels containing organic constituents, can also be used or also used for the production process of synthetic and / or fuel gases according to the invention. As a rule, however, liquid feedstocks of the aforementioned type can also be converted into synthesis and / or fuel gases in other processes.

With regard to the type of gasification reactor used, other types of gasifier can also be used in accordance with the invention in addition to those which, as is preferred, work on the entrained flow principle or are designed as shaft gasifiers. An example of this are the fluidized bed gasifiers already mentioned.

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 negative pressure (if suction fans are used).

The invention is therefore based on the basic idea of producing synthetic and / or fuel gases from residual and waste materials and / or inferior fuels (feedstock) containing organic constituents with oxygen or oxygen-containing gases and possibly water vapor, first by subjecting the feedstock to a thermal pretreatment Supply of heat and essentially avoiding the burning of constituents of the feed (pyrolysis treatment) into a gaseous and a solid fraction under operating conditions to separate the solid fraction by producing the synthesis and / or fuel gas in the To gasify the gasification reactor and to process the gas fraction at least partially in the manufacturing process for introducing process heat and / or for producing additional amounts of synthesis gas and / or fuel gas.

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

The thermal pretreatment with the supply of heat and essentially avoiding combustion of constituents of the fuel with separation into a gas and a solid fraction can be carried out in a wide variety of ways. So-called pyrolysis plants are generally known for this; Because of their knowledge of their structure and their process conditions, these need not be explained in detail here. Typical examples of pyrolysis plants which can be used according to the invention and other inferior fuels are e.g. B. the pyrolysis of waste wood in the fluidized bed reactor or the pyrolysis of chemical production residues in the rotary tube reactor.

The size, shape, material selection, technical conception and process conditions of the aforementioned components and process steps to be used according to the invention and described in the following exemplary embodiment and subject to the invention are not subject to any special exceptions, so that the selection criteria known in the respective field of application are used without restriction can.

• Fig. 1 ein Blockschaltbild sowie
• Fig. 2 eine vereinfachte Verfahrensskizze für den Anwendungsfall eines Schachtvergasers.

Further details, features and advantages of the subject matter of the invention result from the following description of the accompanying drawing. The drawing shows:

• Fig. 1 is a block diagram as well
• Fig. 2 is a simplified process sketch for the application of a shaft gasifier.

The block diagram shown in FIG. 1 applies in principle to every type of gasification reactor, but is explained below primarily in connection with the preferred 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.

1, a residual or waste material and / or inferior fuel containing organic components, hereinafter referred to as feed, is subjected to a pyrolysis treatment stage 101, such as e.g. 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 supply of heat, extraneous gas, product gas obtained behind the gasification reactor 102 and / or behind a condensation stage 103 downstream of the pyrolysis stage, preferably occurring in a pyrolysis gas purification stage 104, can be used.

The intermediate product obtained from the feed material in the pyrolysis treatment stage 101 is separated as steam (Gas fraction) and coke (solid fraction) removed. The solid fraction is adjusted, if necessary after setting the grain size range in a grinding, sieving and / or screening stage 105, to the level which is compatible with the respective gasification reactor type (gasification reactor 102) and fed to the gasification reactor 102, for example pneumatically. Recyclables contained in the solid fraction, e.g. B. metals can in a separation stage 106, z. B. a screening device, be removed 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 steam to the gasification reactor for gasification and / or introduction of heat of reaction or first passed through a condensation stage 103. The residual gas deposited therein, which occurs 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 pyralysis gas can be fed 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 after 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.

Inorganic components occur behind the gasification reactor, which no longer have to be deposited, but instead can be used as recyclables. 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 used.

The product gas accumulating 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.

The shaft carburetor 100 shown in detail in FIG. 2 is known from DE 29 20 922 C3. A pressure vessel 1, which has external insulation 33, forms the shaft carburetor 100. The pressure vessel 1 has a vertical upper section and a laterally angled section. In the upper section of the pressure vessel 1, the solid charge is fed through a lock 4, which after each cycle with an inert gas, for. B. steam is flushed through a line 5. The lumpy, solid charge passes into a basket 3, which is accommodated in the pressure vessel 1, from cooling water pipes and forms a bed 11 in the latter with a pouring cone having an upper free surface 12. The lines of the basket 3 are supplied via a lower ring distributor 31, to which down pipes 30, which lie in the space between the basket 3 and the pressure vessel 1, lead from an upper ring distributor 29, to which a cooling water supply line 7 is connected.

The basket 3 has in the lower third an inward projection 20 which forms the upper boundary of an underlying primary gas chamber 21. Because of the narrowing (passage) present in the basket 3, an inclined embankment-like free bed surface 13 is inevitably formed at the lower end of the bed 11, which bounds the primary gas chamber 21 on this side.

At the bottom, the bed 11 stands on a slag pan 22 also formed by coolant lines on the lower part of the basket 3. In the lower area, ie below the projection 20, the inside of the basket 3 including the slag tray 20 is provided with a refractory ramming compound 32. The embankment forming the lower free fill surface 13 of the fill 11 is at a distance from one of the overflow weir 16 formed from the corner of the slag tray 22 facing away from the fill 11.

During the operation of the shaft gasifier 100, the liquid slag with a free surface can collect between the lower free bed surface 13 and the overflow weir 16 in a slag bath 14 taken up by the slag pan 22. The outer part of the primary gas chamber 21 is delimited by the refractory mass 32 of the basket 3.

Directly opposite the overflow weir 16 in the wall of the pressure vessel 1 is a primary gas burner 2, to which the gas fraction from the thermal pretreatment of the inferior fuel, oxygen or oxygen-containing gas and possibly steam are fed. The primary gas jet 15 formed by the primary gas burner 2 is inclined downwards in the direction of the lower free bed surface 13 and the free surface of the slag bath 14 directed. In this way, intensive gasification is achieved at the lower free bed surface 13 and also the constituents containing carbon floating on the slag bath 14 and a blockage of the overflow weir 16 is prevented, because the primary gas jet 15 is directed against the slag flow flowing to the overflow weir 16.

For the other details, reference is made to DE 29 20 922 C3. The arrangement (shaft carburetor) for two charging goods which can also be used according to the invention as one of the possible alternatives is described in detail in EP 0 194 252 B1. Full reference is made to these two documents, it being noted that in DE 29 20 922 C3 the bed 11 consists of a relatively high-quality fuel, while the shaft gasifier described there in the case of the present invention for the solid fraction of the thermally treated inferior Fuel is used.

As shown in FIG. 2 for the rest, the feed material referred to as "waste" is first fed to a plant for thermal pretreatment designated "pyrolysis". This takes place with the addition of heat and essentially avoiding the burning of constituents of the starting material (low-quality fuel), the process being carried out in a manner known per se in such a way that a gas and a solid fraction are formed, which are separated from one another and in FIG. 2 on the one hand as "pyrolysis gas" (gas fraction) and on the other hand as "pyrolysis coke and valuable materials" (solid fraction). It goes without saying that any liquid fraction that occurs can be a component of the “solid fraction” and / or “gas fraction”. In this thermal pretreatment z. B. the following process conditions are set:
Temperatures approx. 300 - 650 ° C and a degassing pressure of approx. 0.9 X 10⁵ to1.2 X 10⁵ Pascal.

The "solid fraction" can be separated into its components "pyrolysis coke" and "recyclable materials" in a separating apparatus, such as an air classifier, a sieve or other. The "pyrolysis coke" is then fed to the shaft gasifier 100 via the lock 4.

The "pyrolysis gas" (gas fraction) obtained in the thermal pretreatment is fed to the primary gas burner 2.

While the slag accumulating in the shaft gasifier 100 is discharged at the discharge lock 26, the product gas is obtained after flowing through the bed 11 at the gas outlet 6 and from there after further cleaning of gas and solid impurities (H₂S, HCL, dust) with CHP designated cogeneration plant as a gaseous fuel for machines such. B. gas engines or gas turbines, a flue gas being produced during the combustion of the product gas taking place in the combined heat and power plant, which is usually released into the atmosphere via a chimney. The pyrolysis drum can be heated either directly by burning pyrolysis gas or indirectly by removing flue gas from the CHP.

Claims (5)

Process for the production of synthesis and / or fuel gases from solid or pasty residues and waste materials and / or inferior fuels (feedstocks) containing organic constituents with oxygen or oxygen-containing gases and possibly water vapor using a traction gas principle or a shaft gasifier Gasification reactor at temperatures of about 800 ° C to about 1,700 ° C and possibly higher,
characterized in that a) is first separated by thermal pretreatment with the addition of heat and essentially avoiding the burning of constituents of the starting material (pyrolysis treatment), in particular in a heated rotary tube, into a gaseous, in particular vaporous, and a solid fraction under operating conditions, b) the solid fraction is fed to the gasification reactor as a solid charge to be gasified, if appropriate after separation of valuable materials, and c) the gas fraction is also added to the gasification reactor or, after a condensation step, is used in the manufacturing process in such a way that the gas fraction obtained behind the condensation stage is combined directly as part of the synthesis and / or fuel gas with the product gas stream occurring behind the gasification reactor or the gasification reactor or is fed to the pyrolysis treatment stage for introducing heat for the endothermic process and the liquid fraction obtained after the condensation stage is used in another process or the gasification reactor for gasification and / or for introducing heat for the endothermic gasification process. A method according to claim 1, characterized in that the grain size range of the solid fraction obtained after the pyrolysis treatment stage is reduced before the gasification in an entrained-flow gasification reactor by grinding, sieving and / or classifying. Process according to Claim 1 or 2, characterized in that the solid fraction obtained after the pyrolysis treatment stage and the liquid fraction obtained after the condensation stage are mixed and fed, preferably by means of a pump or screw machine, to the gasification reactor together. Method according to one of claims 1 to 3, characterized in that the product gas occurring behind the gasification reactor and possibly the product gas downstream of the condensation stage, if appropriate after removal of any existing pollutants (pollutant gas components) as gaseous fuels for the operation of a possibly already existing Power plant, in particular a combined heat and power plant, is used. Method according to one of claims 1 to 4, characterized in that inorganic residues or waste materials are admixed to the starting material.

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