CN1161424A

CN1161424A - Method of operating high-temp. reactor for treatment of waste material

Info

Publication number: CN1161424A
Application number: CN97100722A
Authority: CN
Inventors: 冈特·H·基斯
Original assignee: Thermoselect AG
Current assignee: Thermoselect AG
Priority date: 1996-02-16
Filing date: 1997-02-14
Publication date: 1997-10-08
Anticipated expiration: 2017-02-14
Also published as: EP0790291A2; EP0790291A3; CA2196649C; CN1143982C; BR9700982A; EP0790291B1; ATE203267T1; JPH09314100A; JP3121555B2; CA2196649A1

Abstract

The invention relates to a process for operating a high temp. reactor for treating disposable material, wherein, waste pass via a charging point into the reactor. A loose gasifying bed is formed, in which the inorganic and organic components are melted and gasified and then homogenised. Above the charging site, the gaseous products are then subjected to high temp. treatment with addition of oxygen to form and stabilise the synthesis gas. The novelty is that water-cooled oxygen lances are used in the high temp. treatment.

Description

Method for operating a high-temperature reactor for treating waste

The invention relates to a method for operating a high-temperature reactor for treating waste materials, in which method these waste materials, such as household and/or industrial waste materials, are subjected to a high-temperature treatment in the reactor, in particular oxygen lances which are aligned not only for the high-temperature treatment of gaseous and liquid components but also for the high-temperature treatment of solid components.

Various methods and devices for the high-temperature treatment of various types of waste, such as household and industrial waste, are known from the prior art. Experts entitled thermal treatment (Thermoselectprocess) are known with a process in which various types of waste arefirst compressed and from this point onwards all further processing steps such as drying, degassing, gasification and melting are carried out without interruption (DE 4130416, and Gunther Hasler document: "Thermoselect, the new way of treating waste in environmental disposal prepropressional maner" Verlag Karl Goerner, Karlsruhe, 1995).

In this process, thermally pretreated waste is continuously fed into a high temperature reactor via an inlet. The waste thermally pretreated in this manner forms a gas-permeable waste heap within the reactor. The carbon component present is oxidized or gasified at a temperature of up to 2000 ℃ in the center of the gasification bed by feeding oxygen or oxygen-enriched air into the stacked gasification bed column. In a modulation chamber (i.e. the top zone of the high temperature reactor) above the waste heap above the gasification bed, at a temperature of at least 1200 ℃, CO₂Is reduced and CO is mainly formed. At these temperatures, the equilibrium of the reaction (reactant-gas equilibrium) tends to form CO. Since the water in the waste is also introduced into the high-temperature reactor, the reaction The water gas reaction is carried out simultaneously with the reactant-gas equilibrium reaction. The resulting synthesis gas is extremely economical and practical in terms of materials and/or energy, and is composed mainly of CO, H₂And a small amount of CO₂And (4) forming. Organic contaminants, in particular the very toxic bis 8-hydroxyquinoline (dioxin) or furan, are no longer stable in this temperature range and are reliably cleaved off. On the other hand, the metallic and/or mineral components of the waste material are melted in the lower burner zone and removed from the high temperature reactor.

There is also provided a method of homogenizing a molten inorganic component while separating minerals from metals by phase separation at a temperature range of about 1600 to 2000 c before the molten and homogenized inorganic component is quench hardened by spraying with water. The cracking of contaminants in the free gas space above the gasification bed of the high-temperature reactor, called the conditioning chamber, requires precise definition of the temperature conditions and the respective delay times of the individual chamber sections.

In particular, there are two conditions that can impair the process. First, the temperature of the synthesis gas in the delay chamber above the gasification bed will temporarily drop due to the extreme variation in the composition of the waste (first having a high water content); second, in the delay chamber above the gasification bed, a laminar flow zone is formed which reduces the delay time of the synthesis gas in a partial region. In each case the formation of such so-called channels or channel hinges in the modulator chamber must be avoided. In both cases it cannot be avoided that traces of contaminants remain in the synthesis gas and are released during use.

Mention should be made of the possibility that non-gasified carbon, for example carbon introduced in the form of fine particles, will enter the synthesis gas in the conditioning chamber, in order to provide the basis for having to carry out a re-gasification in the gas chamber.

It is known from DE 19512249.6 that in the above described process for melting inorganic components, specially designed oxygen lances are used which are equipped with permanent combustion ignition tips having a high flame temperature and a fast combustion speed, so that the lance oxygen is accelerated to at least approximately the speed of sound. This is to improve melting. However, merely improving the conditions of the waste heap below the inlet is not sufficient to solve all the problems generated in the high temperature reactor, above all to optimize the process layout of the conditioning zone above the waste heap.

High temperature treatment of waste is a demanding requirement for the inhomogeneity of the fed waste. The lances described above also do not provide all the assistance, and therefore these lances do not receive the optimum operating conditions for operating such high temperature reactors, particularly with respect to the gasification in the upper reactor section.

Starting from this point, it is therefore an object of the present invention to further develop the process described in detail above in such a way that the best possible conversion of the inorganic and gaseous components is achieved.

In particular, it is a further object of the invention to reliably separate organic pollutants from synthesis gas and to improve the quality of mineral residues.

The object of the invention is achieved by the features of the characterizing portion of claim 1. Further advantageous developments are described in the dependent claims.

The invention therefore proposes to gasify the gasifiable components at high temperatures in the upper part of the reactor and to melt or fuse the inorganic components in the lower part of the reactor by means of oxygen lances, the lower oxygen lances being calibrated so as to intensify the flow direction of the molten or fused inorganic components, and the upper oxygen lances being counter-directed to the flow direction of the gasified components in order to produce an inhibiting effect.

The combination of combustion/oxygen lances is preferably designed so that a partial amount of oxygen necessary to combust the heating gas flows through the oxygen lances. Even in the absence of lance oxygen, the lance nozzle thus exposed to the highest temperature is continuously cooled by this oxygen flow. By taking this measure, the burner is protected from damage or the UV monitoring mirror from soiling, and the compressed gas in the high-temperature reactor is not recirculated or diffused in the oxygen lance, which would otherwise form an explosive mixture when the lance is shut down.

In fact, the oxygen lances are installed in the upper part of the reactor (i.e. above the inlet) in a direction opposite to the flow direction of the gasification components, thus suppressing the upward flow of synthesis gas, increasing the delay time of these gases in the modulation section, so as to re-gasify any carbon components that are entrained and to ensure that all organic pollutants are decomposed.

The placement of the oxygen lance in the region of the reactor below the inlet in the direction of flow of the mineral and metal components being removed from the heap facilitates the desired separation of the components, particularly when oxygen is used at high flow rates.

In fact, under temperature control, oxygen is additionally introduced in partial quantities into the modulation zone in the form of a free gas chamber of the high-temperature reactor, at which point an absolute constant temperature can be maintained by partial combustion of the synthesis gas. The additional oxygen addition provides an opportunity for turbulent flow to form in the gas stream in the high temperature reaction zone, such that turbulent flow causes no laminar flow regions to form, so-called "channels" for contaminants. Additional turbulence can be achieved in a simple manner by using a plurality of oxygen nozzles for introducing a partial quantity of oxygen, which nozzles are inclined axially and/or radially. By the use of oxygen lances and the turbulent flow of the vaporized components, partially or incompletely vaporized components may be simultaneously vaporized. It has become apparent that during operation of the reactor it cannot be excluded that unvaporised or only partially vaporised components are brought into the upper part of the reactor together with the pure gaseous components. According to the invention, these components are subjected to turbulence by aligning the lance so that they are melted, oxidatively transformed and gasified by the lance supplied with oxygen. In this way the combustion process is further optimized and improved in the direction of complete formation of synthesis gas. It has become apparent that by the alignment of the oxygen lances according to the invention, not only can partially or not yet completely gasified components be "re-gasified", but also under these operating conditions, the simultaneous cracking of traces of residual organic contaminants still present in the gasification zone can take place. This also contributes to the optimal formation of synthesis gas. For high temperature gasification, at least two oxygen lances are aligned in the manner described above.

Naturally, more than two oxygen spray guns can be arranged; multiple oxygen lances may be aligned in a different manner than described above. For this purpose, the oxygen lances do not have to be arranged on a plane, but they can be distributed over the space of the gasification zone.

If an oxygen lance with at least one permanently burning adjustable ignition plume is used, the temperature necessary for pollutant removal can be maintained in each case, whatever the other parameters.

The oxygen lances are preferably operated in stoichiometric fashion in combination with the synthesis gas produced by the process itself or even with externally supplied fuel, so that they can be adjusted to the minimum temperature required for the respective high-temperature treatment. For high temperature gasification, the temperature of the reactor space above the inlet is kept above1000 ℃. The reactor is dimensioned in space so that a sufficient delay time remains until the reactor outlet for the adjustment of the equilibrium ratio until the synthesis gas is quenched to prevent new formation of organic compounds.

The lower oxygen lances (i.e., lances for fusing or melting inorganic components) are aligned so that they enhance the direction of the exiting molten stream. Here too, according to the invention, at least two oxygen lances must be directed in this direction. The alignment step preferably provides a plurality of lances along the contour of the oval reactor base. The spray gun used for this purpose substantially corresponds to the spray gun known from DE 19512249.6. This document is hereby incorporated by reference as if fully set forth herein. The basic factor is to accelerate the oxygen of the lance to at least near sonic velocity to enable it to penetrate with sufficient pressure into the inorganic compound to be melted or fused. Due to the high velocity, clogging of the oxygen lance is also prevented. The high temperature treatment is preferably carried out at a temperature of 2000 ℃.

In addition to the oxygen lances described above, a further development requires a further arrangement of burners in the homogenization zone, in the melting and melting zone. In the process according to the invention, the homogenization zone is designed such that an almost complete homogenization of the molten inorganic components is achieved. For this purpose, additional burners may be arranged in the homogenization zone at the outlet of the reactor, these burners not necessarily being matched to the oxygen lance, but being burners of the type previously known. The burners are arranged so as to be directed in the opposite direction to the direction of the outgoing melt flow. In such a position, the aligned burner forces back or prevents the flow of any solid agglomerates still present, so that there is adelay time long enough for these solid agglomerates still remaining to melt and thus be homogenized. According to the present invention, only when the melt is completely homogenized in the manner described above, the water jet is abruptly cooled to harden the melt flow.

If at least one burner is operated in a substoichiometric manner in the melt homogenization zone, i.e. in the presence of an excess of oxygen, homogenization takes place in an oxidizing atmosphere. By re-oxidation in this way, the stability of the outflowing molten mineral is improved.

In the method according to the invention, the oxygen supply of the oxygen lance and/or the fuel supply of the ignition flare are adjusted in dependence on the calorific value of the waste material, so that in each case an almost constant synthesis gas composition and/or quantity is obtained. Therefore, this step compensates for the difference in the calorific value of the waste material fed from the feedwell. As is known in the art, the process of the invention also starts from heterogeneous waste. However, heterogeneous waste materials vary greatly in caloric value, which is high if the waste material contains a large amount of organic components; if the waste material contains more inorganic components or moisture, its calorie value is lower. In the method according to the invention, this step consists in determining the composition of the synthesis gas mixture at the outlet on the gas side and in adjusting the oxygen supply to the oxygen lance as a function of the calorific value, i.e. in operating the oxygen lance in such a way that a constant synthesis gas composition is obtained at the gas outlet.

Claims

1. A method of operating a high-temperature reactor for the treatment of heterogeneous waste, such as industrial waste, specialty waste, and household waste, inwhich the waste is thermally pretreated and/or compressed if necessary and is passed into the reactor via an inlet, under which a loosely piled gasification bed is formed, in which inorganic or organic constituents are melted or gasified and homogenized by oxygen, and above which the gaseous gasification products are subjected to a high-temperature treatment by supplying oxygen to form and stabilize synthesis gas, characterized in that the high-temperature treatment is carried out using water-cooled oxygen lances, at least two oxygen lances being arranged below the inlet so that they intensify the flow direction of the molten or melted waste, and at least two oxygen lances being arranged above the inlet so that they suppress the flow of rising gaseous constituents.

2. A method according to claim 1, characterized in that oxygen is introduced under temperature-controlled conditions into the free gas space of the high-temperature reactor, which space forms a delay zone in a known manner, in such an amount that the resultant combustible gas is partially combusted, that the temperature above the gasification bed is maintained always above 1000 ℃, and that the oxygen is introduced in such a manner that it causes turbulence in the gas, prevents the formation of channels or kinks and ensures the formation of a completely homogeneous gas mixture.

3. Method according to claim 1 or 2, characterized in that, in order to maintain the minimum temperature of the heat treatment, an oxygen lance with at least one permanent combustion ignition plume, which is stoichiometrically manipulated by the gases synthesized by the process itself and/or externally supplied fuel, is used to supply additional heat to the high-temperature reactor.

4. Method according to at least one of claims 1 to 3, characterized in that the oxygen lance is operated in such a way that partly non-gasified or partly incompletely gasified components are gasified and/or residual traces of organic contaminants are cracked by the gasification treatment.

5. A method according to claim 4, characterized in that the high-temperature treatment is carried out at a temperature above 1000 ℃.

6. The method according to at least one of claims 1 to 5, characterized in that the oxygen in the oxygen lance placed below the inlet is accelerated to at least approximately the speed of sound.

7. Method according to at least one of claims 1 to 6, characterized in that even if lance oxygen is not required, a partial quantity of the combustion oxygen stream is continuously passed through the oxygen lance in order to cool the nozzle of the lance by this oxygen stream and prevent clogging.

8. A method according to claim 7, characterized in that the high-temperature treatment is carried out at a temperature above 1600 ℃.

9. Process according to at least one of claims 1 to 8, characterized in that the reaction chamber above the inlet is so large that a sufficient delay time is left before the gases are discharged to establish the equilibrium ratio until the synthesized gases are quenched to prevent new synthesis of organic compounds.

10. The process according to at least one of claims 1 to 9, characterized in that the reactor is designed below the inlet so that it has a homogenization zone at the outlet end, which homogenization zone is of such a size that the exiting melt stream is completely homogenized and phase separated before cooling and hardening.

11. The method according to claim 10, characterized in that at least one burner is aimed, by means of at least one further burner, so that the flame is directed against the direction of the outgoing melt flow and the temperature of the homogenization zone is higher than 1500 ℃.

12. The method according to claim 11, characterized in that at least one burner is used, the flame of which is manipulated in a substoichiometric manner, so that an oxidizing atmosphere is obtained in the homogenization zone.

13. Method according to at least one of claims 1 to 12, characterized in that the supply of oxygen to the oxygen lance is controlled so that a synthesis gas of almost constant and constant composition is produced.