DE19509626A1 - Heat treatment of waste contg. combustible components giving fluid slag and hot flue gas - Google Patents

Abstract

In the thermal treatment of waste material contg. combustible components in which a fluid slag and a hot flue gas at 1,200-1,800 deg C are formed by the direct thermal treatment of combustion or gasification of waste gas contg. combustible components obtd. in the thermal treatment, the flue gas is cooled and freed from dust, then chloride and S cpds. are (partly) removed by a wash liq. giving a suspension contg. chloride and S cpds. which is dewatered to give a solid mixt.. The fluid slag is mixed at 1,200-1,500 deg C in a mixing zone with the solid mixt. and a fluid slag contg. Fe oxides in a mol. ratio of CaO:SiO2 of 0.4-1.2. Fe content of 5-20 wt. % is withdrawn, cooled and solidified.

Description

The invention relates to a method for thermal Treating flammable constituents Waste materials, being directly at the thermal treatment or when burning or gasifying a at the formed thermal treatment, combustible components exhaust gas containing liquid slag and hot Flue gas with a temperature in the range of 1200 to 1800 ° C arise, where the hot flue gas cools and dedusted and removed from the flue gas by direct contact with at least one washing liquid chlorides and Sulfur compounds at least partially removed and a Chloride and sulfur compounds containing suspension arises, which is drained to a solid mixture.

In DE-A-42 35 412 and DE-A-44 12 004 is the thermal Treatment of waste materials in the circulating Fluidized bed described, with a hot flue gas is formed, which under formation of liquid slag burned or gassed. When burning you take care of superstoichiometric oxygenation while at Gasification with just under stoichiometric oxygen supply is working. In the method according to DE-A-44 24 583 and 44 24 707 the waste is put into a slag bath a reactor, and you can do that with something substoichiometric to stoichiometric or else can work superstoichiometric O₂ supply. The Slag bath consists of 50 to 100 wt .-% of residues waste and a hot flue gas is formed, which is withdrawn from the slag bath reactor.  

In the mentioned methods for gasification or combustion of waste materials, the hot flue gas contains chlorine, fluorine and chlorine Sulfur compounds. Fall in the flue gas cleaning these substances in dry form and also in the necessary Wet cleaning in suspensions or sludges. The Invention is the object of the at Gas cleaning accumulating pollutants in the likewise to integrate formed liquid slag. It should be a Slag arise after solidification so is environmentally neutral that it continues to be used or can be easily deposited. According to the invention succeeds this in the aforementioned method in that the liquid slag in a mixing zone with the dehydrated, Containing chlorides and sulfur compounds Solids mixture at temperatures of 1200 to 1500 ° C. mixes and from the mixing zone iron oxide-containing liquid Slag with a molar ratio CaO: SiO₂ of 0.4 to 1.2 and subtracts a FeO content of 5 to 20 wt .-%, which it cools and solidifies. Elution experiments have shown that a slag with these criteria as practical can be considered environmentally neutral.

For the waste materials eligible for the process is it z. As to municipal or industrial waste or even waste sludge. If the iron content of the Waste is too low, ferrous waste be mixed. Likewise, the calcium or SiO content especially in the formation of the liquid Slag to be adjusted.  

If you have the waste in the slag bath reactor processed, falls both liquid slag and hot Flue gas with temperatures in the range of 1200 to 1800 ° C on. This flue gas is cooled and dedusted and the Removal of chlorides, fluorides and sulfur compounds subjected to at least one wet wash. This is what happens pollutant-containing mixture, which is in the slag integrates. For this purpose one pulls continuously or batchwise from the slag bath reactor liquid slag and gives them into a mixing zone, which one also the pollutant-containing solid mixture from the Flue gas cleaning gives up. One then cares in the already mentioned way that a liquid slag formed is a molar ratio CaO: SiO₂ of 0.4 to 1.2 and has a FeO content of 5 to 20 wt .-%. Preferably is the molar ratio CaO: SiO in the range of 0.4 to 0.8 and the FeO content is at least 10 wt .-%. Generally contain ashes from the gasification or Burning of garbage relatively much SiO₂, so that the Basicity is usually considerably less than 0.4. In the Slag from such ashes are the pollutants the flue gas cleaning only insufficiently involved. The FeO content should not be too high, especially because otherwise the inclusion of pollutants also deteriorates and because of the aggressiveness of the slag rises towards a refractory lining.

Further refinements of the method will be explained with the help of the drawing. It shows Flow chart of the process, the waste in a circulating fluidized bed are thermally treated.  

A fluidized bed reactor ( 1 ) through the line ( 2 ) waste and through the line ( 3 ) O₂-containing gas, ie air, oxygen-enriched air or technically pure oxygen supplied. If necessary, oxygen-containing gas can also be passed through the secondary feed ( 3 a) in the reactor ( 1 ). At temperatures of 750 to 1000 ° C, the waste gases in the reactor gas or burn ( 1 ) and a solids-containing exhaust gas is passed through the channel ( 5 ) to the cyclone ( 6 ). Deposited solids are at least partially recycled through line ( 7 ) to the bottom of the reactor ( 1 ).

Ashes are drawn through the channel ( 8 ), which starts from the grate ( 9 ) and leads down to the line ( 10 ). In a screening device ( 11 ) separated coarse grain, which is discharged in the line ( 12 ) of fine grain, which is fed through the line ( 13 ) of a possibly necessary grinder ( 14 ), which may also be coupled with a magnetic separation ,

Fine-grained ash, which is still carbonaceous, is on the transport path ( 15 ) in a cleavage reactor ( 16 ). This cleavage reactor is also led to the dusty exhaust gas leaving the cyclone ( 6 ) in the conduit ( 17 ). It is also possible to divert a portion of the solids of the line ( 7 ) in the line ( 7 a) and also to lead these solids in the reactor ( 16 ).

Oxygen-containing gas, in particular oxygen-enriched air or technically pure oxygen is fed to the cleavage reactor ( 16 ) through the line ( 19 ). It is possible to meter the supply of oxygen in the reactor ( 16 ) so that either gasification conditions, ie sub-stoichiometric mode of operation, or combustion conditions in superstoichiometric O₂ supply complies. In any case, temperatures in the range of 1200 to 1800 ° C in the reactor ( 16 ), so that liquid slag is formed. Through line ( 20 ) one can introduce additional fuel and / or additives into the reactor ( 16 ) which are desired in the formed slag. These additives may, for. B. be calcium or iron compounds.

The fission reactor ( 16 ) produces a hot flue gas which contains dust and pollutants, in particular chlorides, fluorides and sulfur compounds. This hot flue gas is first passed through the line ( 22 ) for cooling in a waste heat boiler ( 23 ), in which a part of the dust is deposited. The cooled flue gas is then passed through various types of wet scrubbing for further purification. In the drawing, first a wash with water in the column ( 24 ) is shown, in which the gas enters through the conduit ( 25 ). Fresh water is introduced in the line ( 26 ), mixed with recirculated liquid from the line ( 27 ) and sprayed into the column ( 24 ). The water wash is used in a known manner, in particular the removal of chlorides and fluorides from the flue gas. Pollutant-containing liquid, which is obtained in the bottom of the column ( 24 ), is withdrawn through the conduit ( 28 ), wherein a portion is recycled through the conduit ( 27 ). The remaining liquid reaches a drainage device ( 30 ). Here, a thickened sludge is first formed in a known manner, not shown, the z. B. further drained in a filter press. Dehydrated solids are removed in line ( 31 ). Notwithstanding the drawing, the water wash can also be designed in multiple stages.

The flue gas, which leaves the scrubbing column ( 24 ) in line ( 34 ), then passes to the desulfurization column ( 35 ). There is washing solution, the z. B. contains calcium hydroxide, sprayed. Used washing solution is partially recycled in the line ( 36 ), fresh washing solution comes out of the line ( 37 ), purified gas withdraws in the line ( 39 ). The scrubbing solution withdrawn from the bottom of the column ( 35 ) in the line ( 38 ) passes partly into the dewatering device ( 40 ), wherein dewatered solids also occur here in the line ( 41 ). Notwithstanding the drawing, the desulfurization can be done in several stages.

In the mixing vessel ( 44 ), a liquid slag is produced, which is cooled and solidified environmentally neutral. In this container is added through the line ( 18 ) in the cleavage reactor ( 16 ) resulting liquid slag and this in the waste heat boiler ( 23 ) resulting dust, which is introduced in the conduit ( 29 ). Further, to the container ( 44 ) the dewatered solids of the lines ( 31 ) and ( 41 ). The container ( 44 ) can be heated in a manner known per se, not shown, in order to maintain a bath ( 45 ) of liquid slag. In the bathroom, the slag is moved to mix what z. B. by the supply of gas through the lance ( 46 ) can be done. The gas may, for. For example, it may be an inert gas (eg, nitrogen), or a combustible gas may be introduced together with oxygen, with combustion additionally being the slag bath ( 45 ) at the desired temperature in the range of 1200 to 1500 ° C and usually at most 1400 ° C C holds. From the container ( 44 ) is withdrawn through the line ( 48 ) liquid slag, which is cooled in a known manner, not shown, for. B. by introducing into a water bath. Exhaust leaves the container ( 44 ) through the line ( 47 ) and can be mixed in a manner not shown the flue gas of the line ( 22 ).

The slag in the line ( 48 ) has a molar ratio CaO: SiO₂ of 0.4 to 1.2 and preferably up to at most 0.8. Their FeO content is in the range of 5 to 20 wt .-% and preferably at least 10 wt .-%. Usually, the slag contains 0.5 to 2 wt .-% chlorine, 1 to 3 wt .-% fluorine and 0.5 to 3 wt .-% sulfur. To prove that the slag can be reused or easily dumped, cooled, granulated slag is subjected to an eluate test. Here, 100 g of slag granules are shaken in 1 liter of distilled water in a glass container of 2 l capacity at a temperature of 20 ° C for 24 hours. The filtered water separated after this usually has the following data:

• - electrical conductivity: 50 to 500 mS (permissible after DIN: 10,000 mS),
• pH-value: 8 to 10 (permissible according to DIN: 5.5 to 13),
• - Fluorine content: 0.08 to 0.6 mg / l (permissible according to DIN: 5 mg / l),
• - Solid residue after boiling the water: <1 g (permissible according to DIN: maximum 3 g).

example

In a plant as shown in the drawing, but without the line ( 7 a), 7500 kg sorted household garbage are gasified per hour. The details of the example were partially calculated. The garbage has the following composition:

C 25.8% by weight H 3.3% by weight O 15.1% by weight S 0.2% by weight Cl 0.5% by weight F 0.1% by weight SiO₂-containing ash 26.0% by weight humidity 29.0% by weight

By magnetic separation together with the grinder ( 14 ), the iron content of the ash is adjusted so that a FeO content in the slag of the line ( 48 ) of 12 wt .-% results. The gasification in the fluidized bed reactor ( 1 ) is carried out at 900 ° C in the cleavage reactor ( 16 ), the temperature is 1450 ° C. Through the line ( 20 ) 195 kg / h CaO are introduced into the reactor ( 16 ) through the line ( 19 ) leads to technically pure oxygen. The column ( 35 ) is fed to a Ca (OH) ₂-liquor.

The container ( 44 ) through the line ( 18 ) 2150 kg / h slag with 1400 ° C abandoned, through the line ( 29 ) come 50 kg / h of dust through the line ( 31 ) are dust and 68 kg / h of chlorides introduced and through the line ( 41 ) 80 kg / h sulfur compounds. Through the lance ( 46 ) leads to 100 Nm³ / h of gas from the line ( 39 ) and 20 Nm³ / h of oxygen, so that in the exhaust gas of the line ( 47 ) adjusts a CO / CO₂ ratio of 2. Under these conditions, the formation of metallic iron in the container ( 44 ) is prevented.

The cooled slag coming from line ( 48 ) has the following characteristics:

Molar ratio CaO: SiO₂ = 0.6

FeO content 12.0% by weight Cl content 1.7% by weight F content 0.5% by weight S content 0.7% by weight

The eluate test described above gives an electrical Conductivity of the filtered water of 230 mS and a Solid residue after boiling the water of 0.6 g.

Claims (5)

1. A method for the thermal treatment of waste containing combustible constituents, wherein liquid slag and a hot flue gas having a temperature in the range of 1200 to 1800 ° directly in the thermal treatment or combustion or gasification of an exhaust gas formed during the thermal treatment, flammable constituents C arise, wherein the hot flue gas is cooled and dedusted and at least partially removed from the flue gas by direct contact with at least one washing chlorides and sulfur compounds and a chlorides and sulfur compounds containing suspension is formed, which is dewatered to a solid mixture, characterized in that the liquid slag in a mixing zone with the dehydrated, chlorides and sulfur compounds containing solid mixture at temperatures of 1200 to 1500 ° C mixed and from the mixing zone iron oxide-containing liquid slag with a molar ratio CaO: SiO₂ vo n 0.4 to 1.2 and a FeO content of 5 to 20 wt .-% deducted, which is cooled and solidified. 2. The method according to claim 1, characterized in that the thermal treatment of waste by Gasification or incineration in a fluidized bed reactor takes place and the exhaust gas formed in a Cleavage reactor at temperatures ranging from 1200 to 1800 ° C is burned or gasified, the liquid Slag and the hot flue gas are formed.   3. The method according to claim 1, characterized in that the waste materials for thermal treatment in a Slag bath are introduced, the slag to 50 to 100 wt .-% of residues of the waste exists and temperatures in the range of 1200 to 1800 ° C and that over the slag bath the hot one Flue gas with temperatures of 1200 to 1800 ° C subtracts. 4. The method according to claim 1 or one of the following characterized in that one in the liquid slag in the mixing zone combustible gas and O₂-containing gas blows. 5. The method according to claim 1 or one of the following characterized in that the cooled flue gas first by a wet wash to remove Chlorides and fluorides and then by a Gas scrubbing to remove sulfur compounds by means of a washing solution leads.