EP0563777B1 - Process for production of synthesis gas by thermal treatment of raw materials containing metallic and organic substances - Google Patents

Abstract

A process was to be developed, by means of which the residual materials arising in the separate collection and sorting of packaging materials and the like can be utilized for producing a synthesis gas and at the same time the pollution potential inherent in the residual materials is destroyed and the formation of new pollutants is prevented. This is effected in such a way that, after a pyrolysis reaction at temperatures from 300-500 DEG C, the metallic constituents are separated off and the remaining solid phase is charged to a gasification stage and gasified at temperatures between 1450 and 1850 DEG C with oxygen-enriched air or oxygen under reducing conditions. The ash fractions arising in the gasification stage are taken off in the form of a vitrified slag, and the gas phase leaving the pyrolysis is converted to synthesis gas together with the gases formed in the gasification stage at temperatures between 800 and 1250 DEG C, with simultaneous addition of steam. Apparatus for carrying out the process consists of a rotary pipe reactor which has a gas outflow line for the pyrolysis gases formed at the end opposite the charging side. On the solids take-off side, the rotary pipe is connected to a metal separator device and a gasification reactor which is connected via a gas outlet to a decomposition reactor, the pyrolysis gases taken off from the rotary pipe reactor and steam also being introduced into the decomposition reactor. The crude synthesis gas formed is discharged from the decomposition reactor via a cooling and scrubbing device.

Description

Process for the production of synthesis gas by thermal treatment of residues containing metallic and organic components Introduction to the description

The invention relates to a process for the production of synthesis gas by thermal treatment of residues containing metallic and organic constituents, in particular for the treatment of packaging materials made of aluminum and plastic, the residues being broken down in a pyrolysis reaction, separated into a gas and solid phase, the separated solid phase enters into a gasification stage and is gasified with oxygen-enriched air or oxygen.

Residual materials of the type mentioned at the outset occur, for example, in the separate collection and sorting of packaging materials from the household sector or as production residues and usually consist of plastics of different compositions in connection with thin metal foils made of, for example, aluminum.

Packaging materials are usually provided with varnishes and / or adhesive layers which, when processed, result in products containing harmful substances, which make recycling to a great extent difficult. Particularly noteworthy is an organically bound chlorine content, which can be attributed to polyvinyl chloride PVC contained in the mixed plastics, as well as to polychlorinated hydrocarbons such as PCB (polychlorinated biphenyls) and other, sometimes very toxic, compounds.

Furthermore, sulfur compounds of various compositions but also heavy metals can be found in such residues. Finally, the problem of the adherent ingredients pointed out, which, depending on the field of application of the packaging material, can consist of pharmaceutical residues, food, but also of various chemicals, for example from the photo industry.

The generation of synthesis gas as well as the gasification of solid materials as a whole have been tried and operated in a variety of ways. The energy sources used so far consisted primarily of hard coal and coke but also of so-called "inferior" substances with a lower calorific value, e.g. Lignite, peat and wood. The nature of such feed materials differs significantly in terms of their physical consistency as well as in terms of their chemical composition, in particular with regard to the hydrogen, oxygen and pollutant content, from the residues mentioned at the beginning. Therefore, the known methods and devices cannot be directly applied to the thermal treatment of packaging materials and production residues.

A process for the production of synthesis gas and other gaseous products by processing residues in a pyrolysis stage with subsequent separation of the residues into a gas and solid phase is known from W091 / 04306. The solid leaving the pyrolysis is introduced into a gasification stage and gasified there at the temperatures required for the desired product streams. The gases from the pyrolysis stage and from the gasification stage are passed through a separator and divided into the various product streams (tar, oil and fuel gas). Furthermore, processes are known which use the gas phase obtained in the pyrolysis process in combustion devices, in individual cases together with the solids from the fractionation which cannot be used directly, and utilize them energetically. The associated "dioxin problem" (dioxin formation, regression and destruction) leads to a considerable effort in the cleaning of the flue gases. The use of waste heat generated in the process, e.g. for heating the pyrolysis furnace can only be realized with complex plant equipment.

According to FR-A-2 261 974, in a process for producing a gas containing hydrogen and carbon monoxide, the feedstock from carbon powder, oxygen-containing gas and steam is divided into two substreams and, in a first reaction zone, the feedstock from substream 1 at temperatures from 1200 ° to 1700 ° C converted to a product gas mixture of hydrogen and carbon monoxide. The product gas mixture is then reacted with the second partial stream of the starting mixture in a second reaction zone at temperatures of 600 ° to 1400 ° C. The process is intended to increase the yield of carbon monoxide and hydrogen.

From DE-A 24 32 504 a method is known in which waste is pyrolyzed at a temperature of 300 to 600 ° C with the exclusion of air and the carbonization gas obtained is continuously passed through a hot coke bed. The carbonization gas is converted into a fuel gas in the coke bed.

The blazing coke bed is replaced by the smoldering coke and / or other carbon carriers, e.g. Charcoal or brown coal smoked coke and supplied preheated fresh air are formed. So much preheated fresh air is supplied to the coke bed that a temperature level of 1000 to 1200 ° C. is maintained and the longer molecular chains contained in the carbonization gas can be split. It is disadvantageous for the environmental compatibility of such a system that the remaining solids in the coke bed are not melted and pollutants, such as heavy metal compounds, are not incorporated into them in an eluate-safe manner, so that they are washed out or leached out over time in an open landfill can.

The object of the present invention is to provide a method for producing synthesis gas by thermal To create treatment of residues containing metallic and organic constituents in which the pollutant potential contained in the residues is destroyed and the formation of new pollutants is prevented, the resulting process products being usable as fillers, for example in construction, or at least capable of landfill and the chemical contained in the residues Energy at the highest possible level is used to produce a high-quality synthesis gas.

This object is achieved by the features specified in claim 1. Further preferred process variants can be found in the subclaims.

Surprisingly, with the process according to the invention, a complete destruction of the organic hydrocarbons with simultaneous formation of a valuable hydrogen-rich synthesis gas could be achieved in a decomposition and a gasification stage, the decomposition and waste products resulting from the conversion being able to be withdrawn as slag from the decomposition process and solidify with the possibly occurring heavy metals to mineral vitreous bodies. They can be used with advantage as fillers or building materials. However, they can also be stored temporarily because the pollutants are firmly integrated and cannot be leached out.

The invention is explained in more detail below using an exemplary embodiment.

1 shows the basic sequence of the process according to the invention for the production of synthesis gas.

In the pyrolysis stage, the residual materials are first thermally separated into a gas and a solid stream at 300-500 ° C. The temperature in the pyrolysis stage is set so that, depending on the amount of chlorine or organochlorine compounds present in the feed, all polychlorinated hydrocarbons are completely converted into the gas phase. The treatment time is also to be controlled that no new pollutants can arise under the conditions prevailing in the pyrolysis. To ensure this task, a sufficient treatment time is required, which takes about 45-60 minutes when carried out, for example, in a rotary tube reactor. is.

Following the pyrolysis, the gas and solid streams are fed separately for further treatment. In the case of the solid stream, the reusable constituents are comminuted and separated, e.g. of metals. This is done in a metal separator 4, from there the metal parts reach the melting furnace 5 in cleaned form.

In addition to minerals, the non-metallic parts of the pyrolysis solids also contain heavy metals and salts, as well as elementary carbon and also non-volatile hydrocarbon parts. These enter a gasification zone, where CO, CO2, H2 and H2O are formed as gaseous products and liquid slag when oxygen-enriched air or oxygen is added at temperatures above 1450 ° C. The slag is withdrawn from the gasification zone, cooled and can be used as filler material or fed to the landfill.

The gaseous products withdrawn from the gasification stage are mixed in the decomposition stage with the gaseous constituents from the pyrolysis, the amount of steam required for the production of synthesis gas being fed in at the same time. The stoichiometrically required amounts can be calculated from the analysis of the starting materials as well as the remaining solids from the pyrolysis and the oxygen content of the air blown in. They are to be calculated in such a way that the cracking and decomposition reactions required for the complete conversion of the hydrocarbons contained in the pyrolysis gases take place automatically, and the result is a synthesis gas with the desired composition.

An essential idea of the invention is that the feed contains metallic and organic components is gasified in several temperature levels, namely first at low temperatures in the pyrolysis (degassing) and then - separated from the pyrolysis gases - in a gasification zone at very high temperatures, while the pyrolysis gases at much lower temperatures, for example at 1000 ° C in the presence of water vapor to be converted into a gas mixture with a high proportion of 2 and CO. Under these conditions, a regression of the polychlorinated hydrocarbons (denovo synthesis) is also ruled out, so that the raw synthetic gases coming from the decomposition stage only have to be subjected to wet cleaning in order to remove pollutants such as hydrogen chloride, ammonia and inorganic sulfur compounds from the gas.

Another important feature of the synthesis gas production method according to the invention is that the oxygen is added at a location where neither organochlorine components nor hydrogen chloride are present. In addition, at this point at temperatures counteracted a formation of dioxin above 1450 ° C, so that even in the oxygen-containing gasification stage, the requirements set out above with regard to an environmentally friendly and energetically favorable synthesis gas process are met.

This is also made possible by the fact that the low-volatility hydrocarbons obtained with the solid from the pyrolysis can be used in the gasification, in that they contribute to an acceleration of the process step and thus the desired reactions can take place completely and without residue under the action of the high temperatures.

The idea on which the invention is based, of a multi-stage, temperature-adapted digestion of the residues can be completed by a pressure control described below. It is assumed here that the energy required for the synthesis gas generation essentially depends on the temperatures at which a complete separation of the supplied water vapor is possible.

It has now surprisingly been found that an increase in pressure in the second gasification stage can be used to advantage for a complete conversion of the pyrolysis gases withdrawn from the pyrolysis and introduced into the decomposition stage.

For example, steam jet compressors can advantageously be used for the task described, which compress the gas removed from the pyrolysis into the second gasification stage inject under pressure. This has the further advantage that the pyrolysis gases containing tar and oil vapor can be introduced into the gasification chamber in a very finely divided form. In a preferred embodiment, the inlet openings for the pyrolysis gases and the water vapor feed are arranged opposite one another, so that complete mixing of the gas components into a homogeneous reaction mixture is made possible.

1.

Menge des zugegebenen Sauerstoffs bzw. Luft in die Vergasungsstufe

2.

Menge des in den Pyrolysefeststoffen enthaltenen Kohlenstoffanteils bzw. Kohlenwasserstoffverbindungen

3.

Menge des in die Zersetzungsstufe eingeleiteten Wasserdampfes

4.

Menge und Zusammensetzung der Pyrolysegase

The method according to the invention can be controlled by the following parameters:

1.

Amount of oxygen or air added to the gasification stage

2nd

Amount of carbon or hydrocarbon compounds contained in the pyrolysis solids

3rd

Amount of water vapor introduced into the decomposition stage

4th

Amount and composition of the pyrolysis gases

These parameters are set according to the following criteria:

First of all, the process according to the invention is started at medium temperatures. This means that a final temperature of approximately 400 ° C. is set in the pyrolysis, a temperature of approximately 1750 ° C. in the gasification stage and a temperature of approximately 1100 ° C. in the decomposition stage. Then the composition of the raw synthesis gas is examined and more or less water vapor is introduced into the decomposition stage as required. If the temperature falls below 800 ° C, the temperature in the gasification stage must be raised. This is done by regulating the amount of oxygen supplied.

If a temperature limit of 1250 ° C is exceeded in the decomposition stage, the temperature in the gasification stage must be reduced if the amount of water vapor in the decomposition stage cannot be increased. However, there is a risk that the slag flowing out of the gasification stage will still have an excessively high carbon content or an insufficient viscosity. In this case, the conditions in the pyrolysis must be changed in such a way that the carbon content is reduced by increasing the pyrolysis temperature. However, this can only be done satisfactorily up to an upper temperature limit of 500 ° C. In addition, with a further increase in temperature, the composition of the pyrolysis gases would be changed so that they could no longer be completely broken down to CO and H₂ in the decomposition stage at the temperatures of 800 to 1250 ° C.

An exemplary embodiment of the method according to the invention is explained in more detail below:

The amount of oxygen required for the complete gasification of the pyrolysis residues is adjusted by regulating the gasification temperature in the range between 1700 and 1850 ° C. In the subsequent decomposition stage, the pyrolysis gases are decomposed in an endothermic reaction, the temperature being regulated between 800 and 1250 ° C. by a controlled addition of steam. The optimum composition of the raw synthesis gas generated is used as a control means for regulation.

Fluctuating residual material compositions can be compensated for by their temperature control in the gasification and decomposition stage by regulating the temperature of the pyrolysis process. This is done in an advantageous manner by controlling the content of "low-volatility hydrocarbons", the proportion of which is varied depending on the pyrolysis temperature in the pyrolysis solid. The content of low-volatility hydrocarbons in turn influences the temperature of the gasification process and the composition of the raw gases leaving the gasification.

According to the proposed procedure, a regression of the polychlorinated hydrocarbons (denovo synthesis) is prevented with certainty, since the oxygen is added at a place where neither organochlorine components nor hydrogen chloride are present. For example, the raw synthetic gases coming from the decomposition stage only have to be subjected to wet cleaning in order to remove the pollutants which may have formed in the decomposition stage, such as hydrogen chloride, ammonia and inorganic sulfur compounds from the raw gas.

When pyrolysis gas is fed into the decomposition stage, the pressure energy of the water vapor can be used to increase the pressure of the pyrolysis gas. The introduction of the pyrolysis gas into the decomposition stage is facilitated by the excess pressure. Furthermore, advantageous operation of the gasification and decomposition stage under increased pressure is possible.

Here, I can advantageously use steam jet compressors that inject the gas removed from the pyrolysis into the decomposition stage under pressure. By means of the injection, the tar and oil-containing pyrolysis gases can be introduced into the decomposition space in a very finely divided form.

The basic diagram of synthesis gas production is explained in more detail below. The input materials E or residual materials such as packaging materials and plastic / metal composites are entered in pyrolysis 1. After a temperature treatment between 300 and 500 ° C, the pyrolysis gases PG and the pyrolysis solids PFM leave the pyrolysis 1 via separate lines.

The pyrolysis solid PFM is very homogeneous and well prepared by the pyrolysis treatment, so that metal deposition can be carried out in the metal separator 4, with the result that the metal portion is fed to an oven 5, while the remaining constituents are fed into the gasification zone 3.1 as pyrolysis solid PF . Oxygen O also enters the gasification zone 3.1, which regulates the temperature in the gasification zone between 1700 ° C. and 1850 ° C.

As soon as the carbon content of the pyrolysis solid PF has been converted into carbon monoxide CO, this gas is introduced into the decomposition stage 3.2 together with the pyrolysis gas PG and water vapor WD. At temperatures between 800 and 1250 ° C., a raw synthesis gas SR is generated, which is cleaned in a gas purification 6 and then leaves the system after a gas scrubbing 8 as a purified synthesis gas SG.

As is known, the washing water can be passed through evaporator 9, the vapors B being advantageously introduced into the decomposer 3.2. The salts SA leave the evaporators 9 with the evaporated water. Furthermore, from the gasification stage 3.1, slag SC and from the furnace 5, a metal melt can be obtained, which can be processed to secondary metal in an advantageous manner.

Feed water W is used for gas cleaning, which is introduced into gas cleaning 6 and leaves it as water vapor WD. The water vapor is input into the decomposition stage 3.2 to form synthesis gas and can advantageously also be used for the production of pressure energy in a steam jet compressor 2.

Claims (8)

1. A process of producing synthetic gas by thermally treating residual materials containing metallic and organic constituents, especially for treating packaging materials consisting of aluminium and plastics, with the residual materials being opened up in a pyrolysis reaction, being separated into a gas phase and solid substance phase and with the separated solid substance phase being fed into a gasification stage and being gasified with oxygen-enriched air or oxygen,

   characterised in

   that the residual materials are heated in a pyrolysis reaction at a temperature of 300-500 °C until the chloro-organic hydrocarbons have been transferred completely into the gas phase; that after separation of the metallic constituents, the remaining solid substance phase is gasified in the gasification stage at temperatures ranging between 1450 and 1850 °C under reducing conditions; that the ash components occurring in the gasification stage are extracted in the form of a vitrified slag; and that, in a decomposition stage, with water vapour being added simultaneously, the gas phase leaving the pyrolysis, together with the gases which occurred in the gasification stage, are converted into synthetic gas at temperatures ranging between 800 and 1250 °C.
2. A process according to claim 1,

   characterised in

   that, after separation of the metallic constituents, the solid substances originating from the pyrolysis stage, during the first gasification stage, are heated to a temperature which is sufficient for completely converting the organic part into a gas phase consisting of CO, CO₂, H₂ and H₂O.
3. A process according to any one of the preceding claims, characterised in
   that transformation of the gases in the decomposition stage takes place under increased pressure.
4. A process according to any one of the preceding claims, characterised in
   that the pyrolysis gases are introduced into the decomposition stage at an increased pressure and directly brought into contact with the water vapour.
5. A process according to any one of the preceding claims, characterised in
   that the synthetic gas is cleansed, that the washing water is evaporated and that part of the water-vapour containing exhaust steam contained therein is used for decomposing the pyrolysis gases.
6. A process according to any one of the preceding claims, characterised in
   that the water vapour required for decomposing the pyrolysis gases is used to operate a steam jet compressor.
7. A process according to any one of the preceding claims, characterised in
   that the slag extracted from the first gasification stage is used for heating the water vapour needed for the decomposition of the pyrolysis gases.
8. A process according to any one of the preceding claims, characterised in
   that oxygen-enriched air is introduced in the gasification stage and that the resulting gases are transferred into a decomposition reactor, whereas the ash parts are extracted in the form of a liquid gas slag, cooled and consolidated; that the pyrolysis gases are introduced into the decomposition reactor together with the water vapour; and that the resulting synthetic gases are guided through a cooling and washing device.

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