EP0790291A2 - Process for operating a high-temperature reactor for the treatment of waste products - Google Patents

Abstract

The invention relates to a method for operating a high-temperature reactor for the treatment of heterogeneous waste products, in which the waste goods are introduced into the reactor via a charging point and form a loose, poured gasification bed below the charging point, in which the inorganic or organic components of a melting process are caused by oxygen or gasification and homogenization are subjected and the gaseous gasification products for the formation and stabilization of synthesis gas are subjected to a high-temperature treatment with the addition of oxygen above the charging point, water-cooled oxygen lances being used for the high-temperature treatment.

Description

The invention relates to a method for operating a high-temperature reactor for the treatment of waste materials, in which these waste materials such as e.g. Household and / or industrial wastes are subjected to high-temperature treatment in a reactor, with specially oriented oxygen lances being used for the high-temperature treatment of both the gaseous, liquid and the solid components.

A wide variety of methods and devices for the high-temperature treatment of disposal goods such as household and industrial waste of all kinds are known from the prior art. A process in which the waste materials of all kinds are first compacted and then all further process steps such as drying, degassing, gasification and melting are carried out without interruption has become known to experts in the field as the "Thermoselect process" (DE 41 30 416, as well as reference from Günther Häßler: "Thermoselect - The new way to treat residual waste in an environmentally friendly way", Verlag Karl Goerner, Karlsruhe, 1995).

(Wassergasreaktion) ab. Das insgesamt entstehende Synthesegas, das stofflich und/oder energetisch sehr wirtschaftlich nutzbar ist, besteht bei einer solchen Temperaturführung überwiegend aus CO, H₂ und geringen Anteilen an CO₂. Organische Schadstoffe, insbesondere auch die hochgiftigen Dioxine oder Furane, sind in dem fraglichen Temperaturbereich nicht mehr stabil und werden mit Sicherheit gecrackt. Die metallischen und/oder mineralischen Bestandteile des Mülls werden hingegen in der unteren Brennzone aufgeschmolzen und aus dem Hochtemperaturreaktor abgezogen.In this process, the thermally pretreated waste materials are introduced into the high-temperature reactor without interruption via a charging point. The waste materials pretreated in this way form a gas-permeable bed in the reactor itself. By adding oxygen or air enriched with oxygen to the pouring column of the gasification bed, the carbon contents present are oxidized or gasified at temperatures in the core of the gasification bed of more than 2000 ° C. The resulting CO ₂ is mainly reduced to CO in a calming room above the bed, ie in the top area of the high-temperature reactor, above the gasification bed at temperatures of at least 1200 ° C. At these temperatures the reaction equilibrium (Boudouard equilibrium) is shifted towards the CO. Due to the waste moisture brought into the high-temperature reactor, the reaction runs parallel to the Boudouard equilibrium reaction $${\text{H}}_{\text{2nd}}{\text{O + C → C}}_{\text{O}}{\text{+ H}}_{\text{2nd}}$$

(Water gas reaction). The resulting synthesis gas, which can be used very economically in terms of material and / or energy, mainly consists of CO, H ₂ and small amounts of CO ₂ at such a temperature control. Organic pollutants, especially the highly toxic dioxins or furans, are no longer stable in the temperature range in question and are cracked with certainty. The metallic and / or mineral components of the waste, however, are in the melted lower firing zone and withdrawn from the high temperature reactor.

It is further intended to homogenize the melted inorganic components with simultaneous separation of the minerals from the metals, phase separation in a temperature range from approx. 1600 ° C to above 2000 ° C, before the melted and homogenized inorganic components solidify after shock cooling with water jets . The cracking of the pollutants in the free gas space, the so-called calming space above the gasification bed of the high-temperature reactor, requires precisely defined temperature conditions in each section of the room and defined dwell times.

In particular, there are two conditions that can affect the process. Firstly, because of the possible, very different garbage composition - especially with a high moisture content - the temperature of the synthesis gas in the dwell room above the gasification bed can temporarily drop, and secondly, laminar flow areas can form in the dwell room above the gasification bed, which reduce the residence time of the synthesis gas for partial areas. This so-called lane or lane streak formation must be avoided in the calming room under all circumstances. In both cases it cannot be ruled out that traces of pollutants remain in the synthesis gas and are released when it is used.

The possibility that the non-gasified carbon, for example in the form of fine particles carried along, is in the synthesis gas in the calming room mentioned to justify the need for gasification in the gas space.

From DE 195 12 249.6 it is known that specially designed oxygen lances are used for the process described above for melting the inorganic constituents. These oxygen lances are equipped with a permanently burning pilot flame of high flame temperature and high burning speed in such a way that the lance oxygen is accelerated to at least approximately the speed of sound. This should improve the melting process. However, to solve all problems occurring in the high-temperature reactor - especially for the optimization of the processes in the calming area above the bed - it is not sufficient to only improve the conditions in the bed below the loading point.

High demands must be placed on the high-temperature treatment of waste materials due to the heterogeneity of the waste supply. The lances described above were also unable to provide a complete remedy, so that even with these lances no optimal operating conditions for operating such a high-temperature reactor could be achieved, in particular with regard to the gasification in the upper part of the reactor.

Proceeding from this, it is therefore the object of the present invention to develop the method described in more detail above in such a way that conversion of both the inorganic and the gaseous constituents is as optimal as possible.

In particular, it is also the object of the invention to reliably rule out any contamination of the synthesis gases with organic pollutants and to improve the quality of the mineral residues.

The object is achieved by the characterizing features of claim 1. Advantageous further developments are specified in the subclaims.

It is thus proposed according to the invention to carry out both the high-temperature gasification of the gasifiable constituents in the upper region of the reactor and the melting or melting of the inorganic constituents in the lower part of the reactor by means of oxygen lances, the oxygen lances in the lower region being oriented so that they are in the direction of flow of the melting or melted inorganic constituents, and in the upper region so that they face the direction of flow of the gasification constituents, so that inhibition occurs.

The combination fuel / oxygen lance is preferably designed so that a portion of the oxygen required for the combustion of the heating gas flows through the oxygen lances. As a result, the nozzle of the lance, which is exposed to the high temperature, is constantly cooled by this oxygen flow, even if no lance oxygen would be required. This measure protects the burner from damage or contamination of the UV monitoring glass by preventing the backflow or diffusion of the pressurized gas from the high-temperature reactor into the interior of the oxygen lance. where an explosive mixture would otherwise form when the lance is out of order.

The fact that in the upper region of the reactor, i.e. Above the charging point, the oxygen lances are arranged opposite to the direction of flow of the gasifying constituents, i.e. the rising flow of the synthesis gases is slowed down, their dwell time in the calming zone increases, which makes it possible to re-gasify any carbon components that are also carried along, as well as the decomposition of all organic pollutants is ensured.

The oxygen lances oriented in the flow direction of the mineral and metal components to be melted out within the bed in the reactor area below the charging point promote the desired separation of components there, in particular when oxygen is used at high flow rates.

Characterized in that oxygen is also temperature-controlled injected into the calming space in the form of a free gas space of the high-temperature reactor in such subsets, the temperature can be kept absolutely constant here by partial combustion of the synthesis gas. The injection of additional oxygen also offers the possibility of swirling the gas flow in the high-temperature range in such a way that laminar flow areas, which could form the “thoroughfares” mentioned for pollutants, no longer arise. Additional turbulence can be achieved in a simple manner in that several oxygen nozzles for injecting the partial oxygen quantity are used, which are arranged axially and / or radially inclined. Through the use of the oxygen lances in connection with the swirling of the gasifiable constituents, constituents that are partially or not fully gasified are simultaneously also subjected to gasification. It has been shown that when operating the reactor it cannot be ruled out that the pure gaseous constituents also carry in the upper reactor part those which have not yet or only partially gasified. These components are now also whirled up by the alignment of the lances according to the invention, detected and oxidatively converted and gasified by the oxygen lances supplied. As a result, the combustion process is further optimized and guided in the direction of complete synthesis gas formation. It has been shown that with this orientation of the oxygen lances according to the invention not only does "post-gasification" of components which have not yet been partially or not fully gasified take place, but at the same time there is a cracking of traces of organic pollutants still present in the gasification chamber under these operating conditions. This also contributes to optimal synthesis gas formation. For high-temperature gasification, at least two oxygen lances are aligned in the manner described above.

Of course, it is also possible to provide more than two oxygen lances, it being possible for some of the oxygen lances to have a different orientation than that described above. The oxygen lances do not have to be arranged on one level but can be spatially distributed over the gasification room.

If oxygen lances are used with at least one permanently burning, controllable pilot flame, the temperature necessary for the removal of pollutants can be maintained in any case, that is to say regardless of other parameters.

These oxygen lances are preferably operated stoichiometrically with in-process synthesis gas or also externally supplied fuels, so that it can be set for the respective high-temperature treatment, the minimum temperature required. For high-temperature gasification, the reactor room above the charging point is kept at> 1000 ° C. The dimensioning of the reactor space is carried out in such a way that there is sufficient residence time for the equilibrium ratio to reach the reactor outlet until the synthesis gas is shock-cooled to avoid the formation of new organic compounds.

The oxygen lances in the lower region, ie for the melting or melting of the inorganic constituents, are oriented according to the invention in such a way that they support the direction of flow of the melt flowing away. Here, too, it is necessary according to the present invention that at least two lances are aligned in this direction. The preferred procedure is that several lances are provided following the elliptical reactor bottom. The lances used for this essentially correspond to the lances as are known from DE 195 12 249.6. On the revelation content this document is therefore expressly referred to. It is essential that the lance oxygen is accelerated to at least approximately the speed of sound, so that it is also able to penetrate the melting or melting inorganic components with sufficient pressure. The high speed also prevents clogging of the oxygen lance. This high temperature treatment is preferably carried out at temperatures below 2000 ° C.

A further development provides that, in addition to the oxygen lances described above, further burners are arranged in the area of the homogenization in the area of the melting and melting. In the method according to the invention, it is provided that the area for the homogenization be designed in such a way that the molten inorganic constituents can be homogenized almost completely. To provide support, it is provided that additional burners are arranged on the outlet side in the homogenization part of the reactor, these burners not necessarily having to be equipped with oxygen lances, but rather can be conventional burners. These burners are arranged so that they face the direction of flow of the flowing melt. It is thereby achieved that any solid agglomerates still present are pushed back by the directed burner or prevented from flowing, so that there is a sufficiently long dwell time for melting and thus homogenization of these residual solid agglomerates still present. According to the invention the shock-like cooling of the melt for solidification takes place by means of water jets only when complete homogenization of the melt has occurred in the manner described above.

If at least one burner is overstoichiometric in the area of melt homogenization, i.e. operated with excess oxygen, the homogenization takes place in an oxidizing atmosphere. Post-oxidation improves the stability of the melted minerals.

In the method according to the invention, the oxygen supply to the oxygen lances and / or fuel supply to the pilot flames is regulated as a function of the calorific value of the materials to be disposed of, so that an almost constant synthesis gas composition and / or quantity results in each case. This procedure thus compensates for different calorific values of the supply goods fed through the loading opening. As described at the beginning in the prior art, the method according to the invention also starts from heterogeneous waste. However, the calorific values of heterogeneous waste vary greatly, because the waste can have a large number of organic components and thus a high calorific value or more inorganic components or moisture and thus a low calorific value. In the process according to the invention, the composition of the synthesis gas mixture is determined at the gas-side outlet and the oxygen supply to the oxygen lances is regulated as a function of the calorific value, i.e. the oxygen lances are operated in such a way that a constant synthesis gas composition is achieved at the gas-side outlet.

Claims (13)

Process for operating a high-temperature reactor for the treatment of heterogeneous disposal goods such as industrial, special and domestic waste, in which the disposal goods are optionally pretreated thermally and / or compressed into the reactor via a loading point and form a loose, poured gasification bed below the loading point to which the inorganic or organic constituents are subjected to melting or gasification and homogenization by means of oxygen and the gaseous gasification products for the formation and stabilization of synthesis gas are subjected to a high-temperature treatment with the addition of oxygen above the charging point,
characterized by
that water-cooled oxygen lances are used for the high-temperature treatment, at least two oxygen lances being arranged below the charging point in such a way that they support the flow direction of the melting or melted disposal goods, and that at least two oxygen lances are arranged above the charging point so that they flow the rising gaseous gases Inhibit components. Method according to claim 1,
characterized in that the oxygen is injected in a temperature-controlled manner into the free gas space of the high-temperature reactor, which is designed as a dwell zone in a manner known per se, in such a way that a partial combustion of the synthesis gas which is thereby possible keeps the temperature above the gasification bed constantly above about 1000 ° C, and that the oxygen injection takes place in such a way that it leads to a swirling of the gases, with the formation of alleys / streaks being excluded and complete, homogeneous gas mixing being ensured. The method of claim 1 or 2
characterized in that the high-temperature reactor is additionally supplied with heat to maintain the minimum temperatures of the thermal processes by using oxygen lances which have at least one permanently burning pilot flame which is operated stoichiometrically with process-specific synthesis gases and / or externally supplied fuels. Method according to at least one of claims 1 to 3,
characterized in that the oxygen lances are operated in such a way that gasification of partially not or not fully gasified components takes place and / or that existing traces of organic pollutants are cracked from the gasification process. Method according to claim 4,
characterized in that the high temperature treatment is carried out at temperatures> 1000 ° C. Method according to at least one of claims 1 to 5,
characterized in that the lance oxygen of the oxygen lances arranged below the loading point is accelerated to at least approximately the speed of sound. Method according to at least one of claims 1 to 6,
characterized in that a portion of the fuel oxygen continuously flows through the oxygen lance, so that the nozzle of the lance is cooled by this flow of oxygen and protected from contamination, even if no lance oxygen would be required. Method according to claim 7,
characterized in that the high temperature treatment takes place at temperatures above> 1600 ° C. Method according to at least one of claims 1 to 8,
characterized in that the reaction space above the charging point is dimensioned so large that there is sufficient residence time until the gas-side outlet to set the equilibrium ratio, until the synthesis gas is shock-cooled to avoid the formation of new organic compounds. Method according to at least one of claims 1 to 9,
characterized in that the reactor below the feed point is designed such that it has a homogenization area dimensioned on the outlet side which enables complete homogenization and phase separation of the flowing melt before it is cooled to solidification. A method according to claim 10,
characterized in that the temperature in the homogenization area is kept at> 1500 ° C by at least one additional burner, at least one burner being oriented such that its flame is directed in the direction of flow of the melt flowing away. A method according to claim 11,
characterized in that at least one burner is used, the flame of which is operated above stoichiometrically in such a way that an oxidizing atmosphere prevails in the homogenization region. Method according to at least one of claims 1 to 12,
characterized in that the oxygen supply of the oxygen lances is controlled so that an almost constant amount and composition of synthesis gas results.