HRP970030A2 - Process for the separation of copper and heavy metals from incinerated garbage residue and slag - Google Patents

Description

The invention relates to a process for separating copper and heavy metals from waste and slag incineration residues.

In conventional waste incineration devices as well as waste pyrolysis devices, residues are deposited in the form of pyrolysis residues or waste incineration residues, i.e. slag. As a rule, such slags are acidic and depending on the origin of the waste, especially when using industrial waste, such slags are most often heavily contaminated with heavy metals. Direct utilization of such slag without more or less expensive purification is only possible with high apparatus costs.

The aim of the invention is therefore to make such waste incineration residues containing heavy metals suitable for further processing, where, for example, in combination with steel slag, environmentally compatible hydraulic binders or other valuable substances can be obtained again. It is especially necessary to be able to process such slags, which are not directly suitable for metallurgical processes, or such residues, into synthetic blast furnace slag with hydraulic properties as well as into valuable iron alloys saturated with carbon. For the solution of this task, the procedure according to the invention essentially consists in the fact that residues from burning waste, that is, residues from pyrolysis and slag together with substances containing chlorine or chlorides, such as residues from flue gas purification, CaCl2 from the production of soda, table salt, organic solvents containing chlorine or galvanic sludge are heated under reducing conditions to above 650°C, after which Cu-chlorides and volatile chlorides of heavy metals, such as e.g. PbCl2 or ZnCl2, extracted in the gas phase. By roasting residues from the burning of waste or slag, i.e. residues from pyrolysis together with substances containing chlorine, i.e. chlorides and maintaining reducing conditions during this roasting, it is possible to separate heavy metals in the form of volatile chlorides and carry them out through the gas phase. The gas phase can be purified in the usual way, whereby copper, chloride, lead chloride and zinc chloride can be retained quantitatively in filters. At the same time, such a procedure allows the processing of other difficult-to-dispose products, such as organic solvents containing chlorine, as well as residues from flue gas purification or calcium chloride from soda production, whereby a large number of problematic substances can be disposed of at the same time. The mentioned chlorides of heavy metals generally have a relatively low vapor pressure at low temperatures. The vapor pressures of the relevant chlorides of heavy metals show the following values at 600 'C:

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In order to achieve safe volatilization at relatively low temperatures, the respective partial pressure must be lowered, for example with the use of a cleaning gas, or to work with the application of at least a partial vacuum. The process according to the invention is conveniently carried out in such a way that, at temperatures between 650°C and 1400°C, a cleaning gas is used to remove volatile chlorides, especially the hot exit gas from incineration, which ensures sufficient volatilization of heavy metal chlorides. Alternatively or additionally to the application of such a cleaning gas, it is possible to work in a partially evacuated vertical furnace, or to apply a cleaning gas under negative pressure. At a pressure of 1 bar and without the use of cleaning gas, chlorination would have to follow at temperatures of around 1400°C, that means at the melting temperature.

The process according to the invention ensures that sufficient depletion of heavy metals is achieved in conventional vertical furnaces with exit gases from incineration, as well as with cleaning gas, already at temperatures of around 850°C, whereby the heating of incineration residues is conveniently handled of waste and slag is performed at temperatures of around 850°C in a vertical furnace or a rotary furnace.

Recovery of heavy metals from the gas phase can be carried out in a particularly simple way by passing the gas phase containing volatile heavy metal chlorides through a filter and the filter dust containing heavy metal chlorides being dissolved in water and/or cemented with Fe-waste. after which heavy metal chlorides are extracted and/or heavy metals are separated by fractional electrolysis and/or fractionally distilled. When cementing with scrap iron, oxides of heavy metals are reduced and iron chloride is formed. In fractional electrolysis, copper, tin, nickel and other metals are separated and of high purity.

In order to ensure adequate partial pressures and at the same time maintain reducing conditions, it is convenient to proceed in such a way that heating in a vertical furnace is carried out in countercurrent with the exit gases from incineration. It is especially economically expedient to further process properly exhausted waste incineration residues, i.e. pyrolysis residues and slag , succeeds then if, as it is in accordance with convenient further development, the heated solid residues in the amount of 10 to 40 wt.%, primarily about 20 wt.%, are mixed with grain steel slag or limestone marl to the mixed slag, whereby the remaining volatile heavy metals such as Pb and Zn are separated from the gas phase, and in the given case, dissolved chlorides in the mixed slag, such as e.g. CaCl2, are oxidized with the expulsion of Cl2, and the mixed slag is reduced via a turbulent Fe-bath with a C content between 3 and 4 wt.%.

Since the heated residues react with acid, when mixed with steel slag, it is possible to at least partially neutralize the very basic steel slag, while at the same time reducing the viscosity. With the heat of mixing and neutralization, any remaining heavy metals can safely evaporate. At the same time, an iron bath is sedimented from the steel slag, and it is convenient to proceed in such a way that the turbulent Fe bath is subjected to fractional reduction to separate the alloy of iron and chromium. This turbulent iron bath must be kept at the required carbon content between 3 and 4 wt.%, to ensure that the desired reduction takes place, where for example from about 0.4 t of roasted slag and 1.6 t of steel slag can be get a total of 1 t of synthetic blast furnace slag and 0.9 t of pig iron. To ensure that a usable cement addition is formed, the chlorides must first be expelled.

It is particularly convenient to combine the process for the reduction roasting of residues from the burning of waste and slag with the appropriate process for the production of synthetic blast furnace slag, since the CO created through the required carbon content in the iron bath can be used particularly well energetically. This is done in such a way that during the reduction of the slag mixture, the CO generated due to the carbon dissolved in the Fe-bath is used for further burning and annealing of the mixed slag, i.e. the residues.

In order to further improve the quality of synthetic blast furnace slag and to be able to produce particularly good cement additives, or to be able to produce cement directly, it is convenient to add bauxite, or Al2O3, to the grain mixed slag.

As already mentioned at the beginning, the required partial pressures for volatile chlorides can be adjusted either with appropriate amounts of cleaning gas, or with the application of negative pressure.

In the following, the invention is explained in more detail on the basis of an exemplary embodiment.

A mixed slag with the following composition was applied:

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The remaining part from the analysis is the unburned and unusable residue.

Such waste slag was added together with 10% CaCl2 (3.6% Ca + 6.4% Cl) to a vertical furnace and heated in a reduced process with a lack of oxygen (counter-current). The outlet gas temperature of the vertical furnace was 850°C. The fried, melted waste slag had the following analysis:

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Fried waste slag is mixed with 80% steel slag in a liquid state with the following composition:

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The mixed slag had the following composition:

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During the mixing process, Zn and Pb evaporate practically quantitatively and could be obtained from the outlet gas.

This mixed slag is reduced in an OBM-converter above a turbulent iron bath using carbon dissolved in the iron bath. The heat for reduction, as well as the waste heat losses, were compensated in the gas phase very economically for the process, by partial combustion of the generated CO in the upper part of the converter.

The reduced slag showed the following composition:

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The heavy metals Cu and Ni could no longer be proven using X-ray-fluorescent-analysis in the reduced slag (provable limit approx. 100 ppm).

In water, granulated -broska proved to be a good hydraulically active component of mixed cement. In order to increase the early strength of the mixed cement, approximately 10% of bauxite (Al2O3) was added to the fine slag melt.

The obtained regulus (crude iron) showed the following composition:

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The procedure was conducted in such a way that the carbon content of the iron bath was always between 3 and 4% by weight. The pig iron thus obtained is a valuable raw material for the steel industry. Alternatively, a highly concentrated carbon-free ferro-chromium alloy can be obtained again by fractional reduction.

Claims (10)

1. Process for separating copper and heavy metals from waste incineration residues and slags, characterized by the fact that waste incineration residues, i.e. pyrolysis residues and slags, are heated under reducing conditions to above 650°C together with substances containing chlorine, i.e. chlorides , such as residues from flue gas purification, CaCl2 and soda production, kitchen salt, organic solvents containing chlorine or galvanic sludge, after which they are drained and separated in the gas phase, Cu-chlorides and volatile chlorides of heavy metals, such as e.g. PbCl2 or ZnCl2, and solid residues are processed separately. 2. The process according to claim 1, characterized by the fact that at temperatures between 650°C and 1400°C, cleaning gas, especially hot exhaust gas from combustion, is used to release volatile chlorides. 3. The process according to claim 1 or 2, characterized by the fact that the gas phase, which contains volatile chlorides of heavy metals, is led through a filter and that the filter dust containing chlorides of heavy metals is dissolved in water and/or cemented with Fe-waste, after which heavy metal chlorides are extracted and/or heavy metals are separated by fractional electrolysis and/or fractionally distilled. 4. The process according to claim 1, 2 or 3, characterized by the fact that the heating is carried out in a vertical furnace in countercurrent with the exit gases from combustion. 5. The process according to one of the claims 1 to 4, characterized in that the heated solid residues are mixed in an amount of 10 to 40 wt.%, preferably about 20 wt.%, with grain steel slag or limestone marl to the mixed slag, whereby the remaining volatile heavy metals, such as Pb and Zn, are separated from the gas phase and, in this case, dissolved chlorides in the mixed slag, such as e.g. CaCl2, are oxidized with the expulsion of Cl2, and the mixed slag is reduced via a turbulent Fe-bath with a C content between 3 and 4 wt.%. 6. Process according to one of claims 1 to 5, characterized in that the turbulent Fe-bath is subjected to fractional reduction to separate the iron-chromium alloy. 7. The process according to one of claims 1 to 6, characterized in that the heating of the residues is carried out at temperatures of about 850°C in a vertical furnace or a rotary furnace. 8. The process according to one of the claims 1 to 7, characterized by the fact that during the reduction of the mixed slag, the CO formed due to the carbon dissolved in the Fe-bath is used with further combustion and heating of the mixed slag, i.e. the residues. 9. Process according to one of claims 1 to 8, characterized in that bauxite, or Al2O3, is added to the grain mixed slag. 10. The method according to one of claims 1 to 9, characterized in that the heating is carried out at atmospheric pressure.