WO1998003250A1

WO1998003250A1 - Process for treating waste gases produced in an organic waste incineration plant

Info

Publication number: WO1998003250A1
Application number: PCT/DE1997/001515
Authority: WO
Inventors: Heinz HÖLTER
Original assignee: Hoelter Heinz
Priority date: 1996-07-18
Filing date: 1997-07-18
Publication date: 1998-01-29
Also published as: CN1230133A; EP0912230A1; CN1128654C; AU3846097A; AU736661B2

Abstract

The invention concerns a process for treating waste gases which contain organic pollutant compounds and are produced in waste-incineration plants. Without being pre-treated, the waste gases are mixed with hot flue gases from the fossil fuel-burning furnaces of industrial boiler plants and so heated to above 1200 °C.

Description

Process for the treatment of waste gases in an organic waste incineration plant

The invention relates to a method for the treatment of the waste gases which still occur in a waste incineration plant and which still contain organic pollutant compounds.

For thermal recycling of organic waste materials, such as. B. of household and / or commercial garbage, a number of processes in the field of pyrolysis, gasification and in particular the combustion of waste have become known.

In practice, the thermal utilization of the waste continues to take place predominantly in incineration plants, in particular in incineration plants that are equipped with grate firing.

The exhaust gases generated in these systems are similar to the flue gases from fossil fuels from industrial boiler systems, such as. B. coal-fired power plants, dust removal, desulfurization and mostly also subjected to denitrification.

The disadvantage here is that the organic hydrocarbon compounds which are usually still present in the waste gases from waste incineration plants, owing to the inhomogeneous composition of the waste, including highly toxic furans and dioxins, are not detected by the cleaning plants mentioned or lead to contamination of the separated flight dust. In addition to the impairment of dust recycling, it is therefore necessary in waste incineration plants, additional very complex separation devices, These are usually activated carbon filters to separate the hydrocarbon compounds still present in the exhaust gas.

The object of the invention is to significantly reduce the technical and thus also the economic outlay for the separation, in particular of toxic hydrocarbon compounds, from the exhaust gases of waste incineration plants.

This object is achieved according to the invention in a method of the type mentioned in that the exhaust gases are mixed with hot flue gases from the fossil furnace of one or more industrial boiler systems without prior separation of pollutants and are heated to a temperature> 1200 ° C.

As a result of the heating of the exhaust gases of a garbage incineration plant to temperatures above 1200 ° C., the organic compounds still contained in the exhaust gas are either afterburned or split. Experiments have shown that highly toxic dioxins and furans are no longer detectable in the flue gas from fossil industrial boiler plants, to which the flue gas from the incineration plant was added. Surprisingly, it has also been shown that even when the flue gas is cooled, neither dioxins nor furans form again.

The mixed waste gases from the waste incineration plant can now be subjected to the usual pollutant separation (dedusting, desulphurization, denitrification) together with the flue gas from the fossil industrial boiler plant and then discharged into the atmosphere. According to a further feature of the method according to the invention, it proves to be particularly advantageous to mix the exhaust gases from the incineration plant with the hot flue gases from the kiln of a cement plant.

With flue gas temperatures in the cement plant of up to 2000 ° C, it is no problem to heat the waste gases from the garbage incineration plant to the required temperature of 1200 ° C.

On the other hand, and this is a particular economic advantage, the heat content can now also be treated by untreated, i.e. H. Use unprepared waste directly in a cement plant.

While in the previous procedure for using waste as fuel in cement plants, the waste is mixed directly with the feed fuel, which places very high demands on the quality of the waste treatment and basically only allows the recycling of about 30% of the waste generated in order to process quality-related qualitative To avoid impairment of cement production, the combustion of waste and fossil fuel in the area of the cement plant is now completely decoupled. The warm content of the waste is coupled into the process for cement production via the hot exhaust gas, which usually leaves the waste incineration plant at temperatures between 800 and 1000 ° C. The residues resulting from waste incineration, such as. B. the majority of the slag remain in the waste incineration plant and can not prove harmful with regard to the process parameters to be observed in cement production.

The waste gas produced in the waste incineration plant is expediently mixed directly with the combustion air required for the fossil combustion of the cement plant. This ensures homogeneous mixing of exhaust gas and flue gas directly behind the burner. Of course, the exhaust gas can also be introduced directly into the cement kiln at a corresponding point.

According to a further feature of the method according to the invention, it proves useful in connection with cement plants to use the hot cooling air of the clinker cooler as combustion air for the waste incineration plant. Due to the high temperature of the clinker cooler exhaust air of approx. 800 ° C, optimal firing conditions are created in the waste incineration plant. If the waste incineration plant under reducing conditions, i.e. H. as a waste gasification plant, at least some of the heat required for gasification can also be injected from the hot flue gas of the cement kiln. In this case, the waste gas from the waste incineration plant still contains chemically bound heat, which is released by combustion in the cement kiln.

The residues resulting from waste incineration or gasification can be carried out in the usual manner, e.g. B. for road and path construction or, in processed form, for the cement process itself as additives.

According to a further feature of the invention, the hot exhaust gas from the waste incineration plant can expediently also be mixed with the even hotter flue gas from a coal-fired power plant. In both coal-fired power plants with dust and melt furnaces, i.e. both dry and wet-deslagged coal boilers, the temperature level of the flue gases produced is sufficient to achieve the required minimum temperature of 1200 ° C after mixing with the waste gas from the waste incineration plant to destroy toxic ones Hydrocarbon compounds such as B. dioxins and furans. The waste gas from the waste incineration plant is expediently introduced into the lower region of the boiler of the coal-fired power plant, as a result of which particularly long dwell times and thus also heating times of the waste gas in the coal boiler are achieved.

In coal-fired power plants in particular, to which a waste incineration plant, so to speak, as a satellite plant, is subsequently connected, it can also make sense to mix the waste gases from the waste incineration plant directly into the combustion air for the coal burner's coal burners and to enter them into the power plant boiler.

However, it is also possible to introduce the waste gases from the garbage incineration plant together with the fresh coal into the boiler via the grinding / drying plant for the fresh coal. This procedure has the further advantage that the heat content of the hot exhaust gases from the waste incineration plant can now be used thermally for drying the fresh coal.

Further variants for introducing the waste gases of the waste incineration plant into the boiler of the coal-fired power plant are discharges into the coal drop shaft of the coal mill, into the suction shaft of the smoke gas used for grinding and drying, i.e. in front of the coal mill, as well as in the presence of mill air blowers in the air duct in front of or behind the Mill air duct.

In the event that, for reasons of the existing infrastructure, the waste incineration plant can only be set up at a greater distance from the power plant boiler, it can also be expedient for the hot flue gases of the exhaust gases, for example in indirect or direct heat exchange with combustion air for the coal boiler , so far to cool down that a complex lining of the exhaust gas connection line between the waste incineration plant and the power plant boiler can be omitted.

According to a further feature of the method according to the invention, it proves to be expedient to prepare the waste intended for the waste incineration plant beforehand into a coarse fraction with a higher calorific value, which is then fed to the incineration plant, and into a fine, low calorific value fraction which is first subjected to a rotting process and then burned together with the fossil fuel in an industrial boiler, preferably a coal-fired power plant boiler.

In particular, e.g. B. Household waste separated by a drum screen with a separating cut of about 100 ± 40 mm in a high calorific value and a low calorific value fraction. The latter contains a lot of organic material with high moisture (food residues) and the mostly inert fine waste. The high calorific fraction consists largely of wood, cardboard, paper, foils, textiles and is contaminated with coarse contaminants.

The high calorific value fraction is burned in a grate furnace after sorting out the largest contaminants and passing through a magnetic separation either directly or after transport with press containers. Transport in baled bales is also possible, although this requires a crushing stage. The flue gas from the grate furnace is fed into the coal-fired large boiler and passes through the boiler together with the flue gas from the furnace. Due to the high combustion chamber temperatures of well over 1200 ° C, pollutants are destroyed or evaporated and separated by condensation or sublimation on the fly dust in the filter or in the washer. The low calorific value fraction is converted into a biologically stable state in an intensive rot, whereby a rotting loss due to carbon dioxide and water vapor of about 30% arises. The rotting material is not pathogenic, the smell is slight, the residual moisture is 10 - 15%, landfill gas formation and leachate formation are minimized, and the material can be used for landfill construction, as a landfill cover or as a soil conditioner in certain areas. This material also contains approx. 30% calorific substance, which can be separated by sieving at approx. 40 ± 20 mm. According to the fraction thus obtained is directly, with container or baling z. B. led to a coal-fired power plant, placed in the grinding dryer together with the design fuel and then burned in the large boiler.

In total, around 55% of household waste is used thermally with a high power plant efficiency in the process variant according to the invention. A remaining remainder of approx. 25% is a degassed, leachate-free material and therefore very well suited for landfill construction. The rest of 20% represents the loss of rotting. When a post-rotting is set up, the quality of the rotting material can be increased to compost quality, which considerably expands the area of application as a soil improver.

Claims

P a t e n t a n s r u c h e

Process for the treatment of waste gases in a waste incineration plant which still contain organic pollutant compounds, characterized in that the waste gases are mixed with hot flue gases from the fossil furnace of one or more industrial boiler plants without prior separation of pollutants and at a temperature> 1200 ° C be heated.

2. The method of claim 1, d a d u r c h g e k e n n z e i c h n e t that the exhaust gases are mixed with the hot flue gases of a cement plant.

3. The method according to claim 2, d a d u r c h g e k e n n z e i c h n e t that the hot exhaust gases are mixed with the combustion air required for the kiln of the cement plant and introduced into the kiln with this.

Method according to claims 3 or 4, characterized in that at least part of the hot cooling air obtained in the clinker cooler of the cement plant is fed as combustion air to the furnace of the waste incineration plant.

5. The method of claim 1, d a d u r c h g e k e n n z e i c h n e t that the exhaust gases of the waste incineration plant are mixed with the hot flue gases of a coal-fired power plant.

6. The method according to claim 5, that the exhaust gases are introduced into the lower region of the power plant boiler.

Method according to Claim 6, that the exhaust gases are mixed with the combustion air for the coal burners and are introduced into the power plant boiler with them.

8. The method according to claim 5, characterized in that the exhaust gases are introduced together with the fresh coal in the power plant boiler.

9. The method according to claim 8, d a d u r c h g e k e n n z e i c h n e t that the exhaust gases are introduced into the power plant boiler via the grinding and drying system for the fresh coal

10. The method according to any one of claims 1 to 9, characterized in that the waste provided for the incineration plant is processed into a coarse, high calorific value fraction, which is fed to the waste incineration plant, and in a low calorific value, fine fraction, which is first subjected to a rotting process and then is burned in an industrial boiler plant together with the fossil fuel intended for the boiler plant.

11. The method according to claim 10, d a d u r c h g e k e n n z e i c h n e t that the fine fraction from the rotting process of the coal mill of a coal-fired power plant or other fossil-fueled industrial boiler is fed.

12. The method according to claims 10 or 11, so that the coarse fraction preferably has a grain size between 60 and 140 mm and the freer fraction has a grain size preferably <60 mm.