WO1983000046A1

WO1983000046A1 - Device for manufacturing a storable, odourless solid fuel from waste material

Info

Publication number: WO1983000046A1
Application number: PCT/DE1981/000100
Authority: WO
Inventors: Kommunal-Anlagen Miete Gmbh Deutsche
Original assignee: Hillekamp, Klaus; Berghoff, Rolf
Priority date: 1981-06-25
Filing date: 1981-06-25
Publication date: 1983-01-06

Abstract

The waste material, of which the organic portion contains as an average more than 50 % by weight of cellulose or cellulose derivatives, particularly household and/or industrial waste materials, and of which the dampness content does not exceed 40 % by weight, are degased in a continuous, indirectly heated furnace during 30 to 120 minutes, particularly 40 to 80 minutes, by bringing the waste materials to a temperature of at least 250<o>C, and at a maximum 500<o>C. The pyrolisis gas thus obtained is tapped from the continuous furnace preferably in the counter-current direction or in the direction of the waste stream.

Description

Process for the production of solid, storable and odorless

Fuels from waste

The invention relates to a method for producing solid, storable and odorless fuels from waste, in which the waste is thermally treated.

The disposal of waste, in particular household waste and household-type waste, is an increasingly urgent problem because of the growing population and the exhaustion of the landfills. Attempts have therefore been made several times to treat the waste in order to use its components in a meaningful manner.

A process for the treatment of organic waste materials and the product obtained are described in DE-OS 25 13 767. However, this procedure leads to a high environmental impact when burning the fuels produced.

Furthermore, various processes are known in which waste materials are subjected to pyrolysis, particular attention being paid to the generation of gas and the production of pyrolysis oils and tars. An example of such a pyrolysis process is described in US Pat. No. 4o 38 152. All of the waste materials are ultimately heated to a temperature of around 540 ° C in order to achieve a high yield of gas and

To produce smoldering oil, whereby the solid residues are also processed and divided into various usable products. In addition to dietary fiber, non-magnetic and magnetic metals are separated, and two batches of charcoal, one in powder form and one in dust form, are not given about their further use in the application in question.

The present invention has for its object to provide a method which enables the production of solid, storable and odorless fuels from waste, which are combustible without high environmental pollution and enable a good yield in terms of the energy content contained in the waste. This object is achieved according to the invention in that wastes, the organic components of which contain on average more than 50% by weight of cellulose or cellulose derivatives, in particular household waste and / or household-type commercial waste, and whose moisture content is not more than 40% by weight, over a period of time degassed in an indirectly heated continuous furnace for 30 to 120 minutes, and that the waste was reduced to at least 250 ° C, to a maximum

500 ° C, heated. The process according to the invention gives a solid fuel which is not only storable and easy to transport due to its neutral odor, but which, moreover, can be burned particularly advantageously due to its largely water-free nature, since the hydrolysis reactions of the alkali contained in it at temperatures above 800 ° C and alkaline earth chlorides are not used. The combustion of the solid fuels according to the invention thus results in an almost hydrogen chloride-free exhaust gas which does not require additional flue gas scrubbing. This advantage has a particular effect in the case of a joint combustion of coal and the solid fuel produced according to the invention, since coal likewise has a very low water content, so that the alkaline earth metal and alkali metal halides remain in the ash.

Due to the low temperature to which the waste is heated to the maximum, it is achieved that in the solid residue of the pyrolysis process, which supplies the solid fuel, a relatively high total energy content is achieved in relation to the total energy content of the waste materials used. If the pyrolysis temperature, ie. the temperature to which the waste is heated to the maximum, according to a preferred embodiment, is between 250 ° C. and 480 ° C., the process takes place in a range in which the energy required to carry out the pyrolysis is low. If, in a particularly preferred embodiment, this temperature is between 300 ° C and about 450 ° C, the pyrolysis takes place in a range in which the heat of decomposition reaches its maximum, while the heat of coking decreases to a minimum. This means that at these temperatures the pyrolysis has to be carried out with minimal energy consumption. If the pyrolysis is carried out in conventional continuous furnaces, in particular in so-called rotary kilns, a period of time for the passage of the waste of 40 to 80 minutes is usually sufficient under the specified process conditions in order to degas the waste materials to such an extent that the desired embrittlement occurs. which makes it unnecessary to use special chemical embrittlement agents or to carry out energy-intensive pre- or post-shredding.

According to a particularly preferred procedure, the pyrolysis gas formed is drawn off from the continuous furnace in countercurrent to the waste. By flowing the pyrolysis gas through the continuous furnace against the direction of flow for the waste, it supports the drying of the waste that initially enters the continuous furnace when it is moist. Furthermore, it is not necessary with this procedure that the water vapor generated is heated up to the maximum temperature prevailing in the continuous furnace.

According to an alternative procedure, the pyrolysis gas that is produced is drawn off from the continuous furnace in cocurrent to the waste. This procedure has the advantage that additional cracking occurs in the gaseous products inside the continuous furnace, which leads to an additional loss of carbon and thus to an increase in the calorific value of the solid discharge materials. In addition, this procedure avoids the risk that the carbonization gases cool down prematurely before or after they emerge from the continuous furnace below the condensation point of the low-boiling components contained in the carbonization gas, so that there is an undesirable precipitation of aqueous and / or oily or tar-containing components

Condensate comes, which can clog the system. It has proven to be particularly favorable if the pyrolysis gas produced is used at least in part for heating the continuous furnace. The terrroerature at which the waste is degassed is expediently chosen depending on the composition and the moisture content of the waste materials in such a way that the energy content of the pyrolysis gas produced is just sufficient for heating the continuous furnace. This means that only as much gas with sufficient energy content is generated in the pyrolysis process as is necessary for the self-sufficient progress of the entire pyrolysis process. In this way, it is achieved that the processing of the waste does not require external energy to maintain the pyrolysis process, nor does excess gas or carbonization oil, which is difficult to utilize in energy terms, result.

For reasons of simple operation and operation of the pyrolysis plant, however, it is sometimes advisable to generate a small amount of excess pyrolysis gas in order to be able to react to fluctuating energy demands of the pyrolysis process, such as those caused by different moisture contents and different sulfur energy requirements of the different wastes. The excess pyrolysis gas can be burned like the gas required for heating the pyrolysis reactor. The sensible heat from the combustion of the excess gas and the required heating gas can be used to preheat the combustion air.

In principle, however, it is also possible to cover briefly occurring increased energy requirements of the pyrolysis process with external energy. In this case, the pyrolysis gas provides the basic energy load and the external energy only the energy peaks. As mentioned above, the choice of pyrolysis temperature is influenced by the amount of energy required in the carbonization gas. If the amount of energy required to maintain the pyrolysis process is small, which is the case, for example, with the degassing of dry waste, then the pyrolysis temperature can be selected to be low. Conversely, substances with a high pyrolysis energy requirement require a higher energy input, which is conveyed to the carbonization gas by an elevated pyrolysis temperature.

It has proven to be particularly favorable if the pyrolysis gases are burned at temperatures above 800 ° C., preferably above 1,000 ° C. This procedure guarantees a complete destruction of odor-forming substances, ie. it leads to a complete deodorization of the flue gases produced, while at the same time the chlorinated aromatic compounds, e.g. chlorinated dioxins, chlorinated biphenyls and the like, and also the condensed aromatic compounds are completely oxidatively broken down and rendered harmless. This is a considerable advantage of the method according to the invention compared to the classic domestic waste incineration on grates.

If the pyrolysis gases - with the exception of dedusting - do not undergo any additional cleaning before they are burned, it is expedient to separate hydrogen chloride, hydrogen fluoride, hydrogen sulfide and SO ₂ from the flue gases, which can be done dry or by means of a flue gas scrubber. However, it is preferable if dry hydrogen chloride, hydrogen fluoride and hydrogen sulfide as well as SO _{2 are} separated from the hot pyrolysis gases before they are burned, which can be done according to known techniques (so that this will not be dealt with in more detail), which usually involves dust separation. The dry separation of the above The advantage of pollutants is that they can be carried out at higher temperatures, at which the dew point of the lowest-boiling components of the carbonization gas is not yet undershot, so that condensation of volatile organic constituents, which could lead to considerable wastewater pollution, is effectively avoided. In order for this advantage to be fully effective, it is recommended according to a particularly advantageous embodiment of the invention to keep the pyrolysis gas formed at and after it emerges from the continuous furnace until it is burned at a temperature which prevents such volatile products from condensing out. The lower limit for this temperature is generally 200 ° C. for the wastes to be processed by the method according to the invention.

Since hydrogen chloride, hydrogen fluoride, hydrogen sulfide and SO ₂ pass from the waste into the pyrolysis gas when carrying out the process according to the invention, from which, as mentioned above, they can be separated easily and without great environmental pollution, the chlorine, fluorine and Sulfur content of the solid discharge materials to be used as solid fuels from the continuous furnace. The one obtained by the process according to the invention

Fuel therefore has a lower content of chlorides, fluorides and sulfur compounds than fuels from domestic waste, as they are produced without pyrolytic decomposition.

It has also proven to be expedient if the solid fuels formed are separated into at least two fractions of different particle sizes. This can be done, for example, by means of a grinding and / or screening stage. The sieve stage offers the Possibility of separating very fine dust from carbon, which due to its large surface has an increased content of heavy metals and chlorides, fluorides and sulfur compounds. The separation of the fine dust thus leads to a reduction in the pollutant content in the fuel itself. It is facilitated if calcium compounds, such as hydrated lime and lime, are present during the degassing, which cause the fine particles to agglomerate, which then separate even more easily from the coarser parts to let.

The fractions with a particle size above 0.3 mm are preferably used as the desired commercial form of the solid fuel or are further processed to this, which can be done, for example, by pressing into briquettes.

The solids, metals and / or heavy inert substances emerging from the continuous furnace, which are not further changed during pyrolysis in the low temperature range used, such as Fe, Cu, Al etc., as well as glass, stones and ash are advantageously separated off by means of an inert substance separation , which leads to an increase in the calorific value of the solid fuel formed, which then essentially consists only of carbon-containing material. Elimination is particularly easy since the pyrolysis treatment means that the waste is water-free, dry and easy to handle after it has left the continuous furnace.

For use in power plants with blow-in firing, after the metals and the other inert substances have been separated off, comminution is carried out in a grinding circuit, which brings the fuel into a fineness that can be fired with normal dust firing. In this way the solid fuel generated can be burned particularly advantageously in existing conventional large-scale power plants, and there is no need to resort to the poorer efficiency of the grate firing of old power plants or waste incineration plants.

However, it is also possible to use the degassed waste in the cement industry without further treatment. In this case, the iron and inert substances even represent usable components.

According to a further advantageous embodiment of the method, the waste is subjected to a gentle coarse comminution or sieving for the separation of fine material before it is fed into the continuous furnace. The purpose of this procedure is, on the one hand, to prevent the inlet to the continuous furnace from being accidentally blocked, and, on the other hand, to prevent portions of the inert material, such as glass, from being comminuted too much. The screening for the separation of fine material causes an increase in the calorific value of the waste introduced into the continuous furnace, since this removes ash components.

To increase the performance of the plant and to avoid the risk of condensation in the reactor, ie. in the

Continuous furnace comes, it is advisable to pre-dry the waste before it is fed to the continuous furnace and to set a moisture content which is preferably between 5% by weight and 15% by weight of water.

If one compares the method according to the invention with the techniques used hitherto, the advantages achieved thereby become particularly clear. Compared to the BRAM process, the waste to be processed does not have to be pretreated, or only slightly. In particular, the energy-intensive and material-wasting fine grinding and the energy-intensive predrying are no longer necessary.

There are also significant advantages compared to conventional pyrolysis of waste. This aims at the extraction of gases or oils, whereby a carbon-containing residue of a certain calorific value arises as a sometimes annoying by-product. However, the cleaning of the gases and oils from the inorganic and water-soluble organic substances presents considerable problems with this method. These serious problems are eliminated when the method according to the invention is used, since only as much carbonization gas is generated here as is necessary to maintain the pyrolysis process. This small amount can be freed from the acidic constituents hydrogen chloride, hydrogen fluoride, hydrogen sulfide and SO ₂ dry without any special technical effort.

In addition, energy accumulates in the pyrolysis process according to the invention, which is not the case with the household garbage pyrolysis processes which are being tested and which are designed for direct use of the main product pyrolysis gas. Since no direct use of the main product is thus required in the method according to the invention, there is also no need here to combine the pyrolysis part of the system with a heat part or heat power part. This coupling of the pyrolysis part and the energy utilization part makes the usual pyroysis processes expensive and prone to failure. When the process according to the invention is used for the pyrolysis of normal household waste, solid residue is discharged with an average of 45% by weight to 60% by weight and gas is discharged on average from 35% by weight to 55% by weight. %, each based on the waste materials used. A discharge of solid fuel of an average of 55% by weight with normal household waste is an unprecedented discharge, which is one of the reasons for the particular economy of the process.

The invention is explained in more detail below with the aid of a schematic method family tree, from which further advantageous details can be found. The individual devices already known in the art, such as rotary tube furnaces, devices for dry cleaning, etc., are reproduced in the process family tree as labeled blocks.

The delivered household waste first goes to a pre-shredding device 1, e.g. a chain hammer mill or a roller cutter, which causes a good loosening of the various waste components and shreds the bulky parts, while the remaining components are not shredded if possible. It is therefore a gentle pre-shredding.

From the pre-comminution device 1, the pre-comminuted waste passes into a sieve 2 for the separation of fine raw material fractions such as ash, sand, fine vegetables and the like. Sieve drums and / or tensioning shaft sieves with a mesh size of lo am to 30 mm are suitable.

Instead of pre-shredding with additional screening, it is also possible to carry out the treatment in a screening drum with internals. The fixtures in the feed section then break the bulky parts while the internals in the screening drum tear open the garbage cans. Pre-screening increases the calorific value of the degassed waste by removing the inert component. The household waste pretreated in this way now passes into the externally heated pyrolysis reactor 3, which in the example shown should be an externally heated rotary tube. There, the waste is heated to at least 250 ° C. and at most 500 ° C., but preferably to 250 ° C. to 480 ° C., preferably 300 ° C. to 450 ° C., in the absence of air, and is pyrolytically decomposed in the process. The resulting volatile products are withdrawn from the pyrolysis device, which, as shown in broken lines, can take place in countercurrent or, as shown in solid lines, in cocurrent to the direction in which the waste flows through the rotary tube.

They are then fed to the device 4 for the dry separation of HC1, HF, H ₂ S and SO ₂ .

Salts are formed from HC1, HF, H ₂ S and SO ₂ during dry cleaning. These can be deposited or used for further use.

From the device 4 for the dry separation of pollutants, the cleaned pyrolysis gas passes into a reactor muffle 5, where it is burned together with preheated combustion air, which has been preheated in an exhaust gas heat exchanger 6, at temperatures above 800 ° C. Suitable insulation of the pipelines, which lead from the pyrolysis reactor 3 to the device 4 and from there to the reactor muffle 5 or to an auxiliary combustion chamber 10, ensures that the pyrolysis gases are kept above a temperature which prevents the volatile products from condensing out. Too much carbonization gas generated can be burned in the auxiliary combustion chamber 10. After leaving the reactor muffle 5, the exhaust gas enters the exhaust gas heat exchanger 6. With an exhaust gas temperature of approx. 200 ° C., it leaves this heat exchanger and can be released into the atmosphere without further aftertreatment due to the dry gas cleaning of the raw gas.

The residue is discharged gastight. Sealing takes place via the residue itself.

Since the residue is in bulk as a result of the pyrolytic treatment and the dry discharge, the coarser hard materials, such as iron, glass, stones, non-ferrous metals, wire mesh and the like, can be separated in a simple manner by a device 7 for screening or for screening become. The further separation can be carried out magnetically to obtain valuable materials and by using the different special weights.

If the use of the solid fuel in the cement production is intended, then the pre-treatment step screening of the raw waste fine material and the post-treatment of the degassed waste can be dispensed with, since the inert components do not interfere in the cement production process but even, e.g. Iron, desired components.

In order to further increase the calorific value of the fuel, the inert substances still present are broken down into a fraction with a high calorific value and a low calorific value by sieving 8 with subsequent sorting via a setting machine. At the same time, a fine substance fraction is separated off in this process, which due to its specifically high surface area and the absorption properties given by carbon with heavy metals and chlorides is enriched. The separation of the fines content means that the fuel fraction is less contaminated with these pollutants. The fuel produced has a calorific value H of 3,500 to 4,500 kcal / kg. The yield of fuel, based on the average household waste, is 250 to 300 kg.

Claims

1. A process for the production of solid, storable and odorless fuels from waste, in which the waste is thermally treated, characterized in that waste, the organic content of which contains on average more than 50% by weight of cellulose or cellulose derivatives, in particular household waste and / or domestic refuse-like commercial waste, and the moisture content of which is not more than 40% by weight, is degassed in a indirectly heated continuous furnace over a period of 30 to 120 minutes, and the waste is heated to at least 250 ° C, maximum to 500 ° C.

2. The method according to claim 1, characterized in that the waste is heated to a maximum temperature which is between 250ºC. and 480 ° C, preferably between 300 ° C and 450 ° C.

3. The method according to claim 1 or 2, characterized in that the waste is passed through the continuous furnace in a period of 40 to 80 minutes.

4. The method according to any one of the preceding claims, characterized in that the pyrolysis gas is drawn off in countercurrent to the waste from the continuous furnace.

5. The method according to any one of claims 1 to 3, characterized in that the pyrolysis gas formed is withdrawn from the continuous furnace in co-current with the waste.

6. The method according to any one of the preceding claims, characterized in that the pyrolysis gas formed is used at least in part for heating the continuous furnace.

7. The method according to claim 6, characterized in that the temperature at which the waste is degassed, depending on the composition and the moisture content of the waste materials, is selected such that the energy content of the pyrolysis gas produced is just sufficient for heating the continuous furnace.

8. The method according to any one of the preceding claims, characterized in that the pyrolysis gases are burned at temperatures above 800 ° C, preferably above 1000 ° C.

G. Method according to one of the preceding claims, characterized in that one separates dry from the hot pyrolysis gases hydrogen chloride, hydrogen fluoride and hydrogen sulfide and SO ₂ .

10. The method according to any one of the preceding claims, characterized in that the pyrolysis gas formed is kept at and after it emerges from the continuous furnace until it is burned at a temperature which prevents condensation of volatile products.

11. The method according to any one of the preceding claims, characterized in that the solid fuels formed are separated into at least two fractions of different particle sizes.

12. The method according to claim 11, characterized in that the fractions with a particle size above 0.3 mm are used as the desired commercial form of the solid fuel or are processed to this.

13. The method according to any one of the preceding claims, characterized in that exiting from the continuous furnace. Solids metals and / or heavy inert materials are separated.

14. The method according to any one of the preceding claims, characterized in that the waste is subjected to a gentle coarse comminution and / or screening for the separation of fine material before it is fed into the continuous furnace.

15. The method according to any one of the preceding claims, characterized in that the waste is pre-dried before being fed into the continuous furnace in order to obtain a moisture content between 5% by weight and 15% by weight.