WO1999019051A1

WO1999019051A1 - Agent for purifying gas, a method for the production thereof, and the application of the same

Info

Publication number: WO1999019051A1
Application number: PCT/EP1998/006446
Authority: WO
Inventors: Konrad Fichtel
Original assignee: Ftu Gmbh Forschung Und Technische Entwicklung Im Umweltschutz
Priority date: 1997-10-13
Filing date: 1998-10-12
Publication date: 1999-04-22
Also published as: DE19745191A1

Abstract

The invention relates to an agent for purifying gas comprised of at least one finely powdered inorganic material with an active surface. Said inorganic material is inert against melted sulphur and contains or consists of sulphur which is sintered and/or melted thereon. The inventive agent can additionally contain a finely powdered basic substance, especially calcium hydroxide, burnt lime, calcium carbonate, dolomite, sodium carbonate and/or sodium hydrogen carbonate.

Description

Gas purification agent, process for its manufacture and use of the agent

description

The invention relates to an agent for gas purification, a method for its production and the use of the agent.

In thermal processes, e.g. Smelter processes, coal firing, waste incineration and numerous industrial processes produce exhaust gases that are mixed with volatile heavy metals, e.g. Cadmium, mercury, thallium, arsenic, antimony and lead are contaminated. They are mostly present in the exhaust gases in elemental form or as salts, preferably chlorides and oxides. Furthermore, the exhaust gases still contain organic pollutants in many cases, e.g. Dioxins, furans, aromatics and the like.

To remove these pollutants, the gases are usually cooled and the pollutants are washed out wet. If the heavy metals are in elemental form, this is often not sufficient. Mercury e.g. is often emitted as an element. It cannot then be separated from the gas even with wet washing. In addition, there is the problem that volatile heavy metal salts are also emitted as aerosols and / or fine dust that is difficult to remove after wet washing. A u c h d i e D i o x i n e, A ro m a ts and halocarbons are only insufficiently separated by wet washing.

Another method is to route exhaust gas flows through activated carbon filters. This leads to a reduction in the volatile content

Pollutants, such as mercury, but this process is associated with considerable costs because large amounts of highly active coal are used and there is always the risk that smoldering fires can occur in the coal bed. The always present coal dust also emits pollutant-containing fine dust, which is difficult to separate.

Yet another method is to apply sulfur to activated carbon and pass the gas stream over it. This method is quite effective for mercury separation and the separation of organic pollutants, but the problems of spontaneous combustion and the emission of abrasion remain. In addition, the use of sulfided activated carbon fails because of its exorbitant price.

There has been no lack of further attempts to convert the volatile heavy metals with sulfur or sulfides into low-volatility sulfides and to separate them from the gas stream.

For this purpose, calcium hydroxide alone or with the known additives activated carbon or hearth coke are mixed with sulfur and used in exhaust gas purification. However, mercury separation is unsatisfactory when using calcium hydroxide and sulfur.

A mixture of calcium hydroxide, activated carbon and sulfur gives good values, but there is a risk of the mixture igniting if there is insufficient heat dissipation.

Accordingly, there is still the task of separating volatile heavy metals, in particular mercury, in their various forms of connection and also as elements from the gas streams, primarily from waste incineration plants, in a targeted, simple and inexpensive manner, but also to detect and remove organic pollutants such as dioxins and furans to be able to separate as well. Another job is a to create a simple and inexpensive process for the joint separation of volatile inorganic and organic pollutants and acidic constituents from gas streams. The reduction in the pollutant content in the exhaust gas flow must be so high that the existing limit values, in particular for Hg, Cd, Ti and dioxides / furans, can be safely adhered to. It is also an object of the invention to provide a non-combustible sorbent which preferentially separates volatile heavy metals, but also organic pollutants on their own or in combination with other substances or sorbents.

The invention achieves the objects by an agent which contains or consists of at least one finely powdered inorganic substance which is inert to molten sulfur and has an active surface with a content of sulfur sintered or / and melted thereon. Preferably, the inorganic substance which is inert to molten sulfur and has an active surface consists of at least one substance from the group consisting of tress, lime, bentonite, bauxite, aluminum oxide, diatomaceous earth, clay powder, burnt clays, bleaching earth, calcium carbonate, dolomite, perlite, pumice, broken from Lime sandstone production or yali stone production, aerated concrete dust, expanded clay, cements, calcium aluminates, flying dust, sodium aluminates, calcium sulfates, calcium sulfide and / or brick powder. Traß, diatomaceous earth and brick flour are particularly preferred. The active surfaces range from 5 to 200 m ² / g.

The agent according to the invention can be prepared by mixing the finely powdered substances with sulfur, preferably sulfur bloom (particle size 90% <20 μm), and heating the mixture above 1 20 ° C. (melting point of the sulfur 1 19 ° C.). Temperatures higher than 200 ° C are not required. Temperatures in the lower part of this range, in particular from 1 20 to 1 60 ° C and in particular from 1 20 to 1 30 ° C, are preferred. It is sufficient to sinter the sulfur onto the substances listed. Therefore, a thermal treatment time of a few Seconds with small amounts of sulfur are sufficient. With high levels of sulfur, times of up to 45 minutes are sufficient.

According to a preferred embodiment of the invention, agents according to the invention contain, in addition to the sulfurized inorganic substances specified above, finely powdered basic substances such as alkaline earth metal hydroxides, carbonates, alkali carbonates, in particular calcium hydroxide, calcium carbonate or sodium carbonates. This combination can be used for toxic pollutants, volatile heavy metals, chlorinated dioxins and furans, chlorinated and non-chlorinated hydrocarbons, organic acids, phenols, aromatic hydrocarbons and the like. and also remove the acidic inorganic substances hydrogen chloride, sulfur dioxide, sulfur trioxide, hydrogen fluoride and nitrogen oxides.

Agents which contain calcium hydroxide as the basic substance are particularly preferred. It can be used as normal calcium hydroxide or as a large surface area calcium hydroxide. The basic substances preferably have a grain size of <50 μm. The particle size distribution of the basic substances and the sulfurized inorganic substances can be coordinated so that no segregation occurs in moving media.

Another preferred embodiment of the agent of the invention contains sodium bicarbonate (NaHC0 ₃ ) as the basic substance. This can be used advantageously in a mixture with the sulfurized inorganic substances if a high separation of sulfur dioxide and hydrogen chloride is required and the temperature of the exhaust gas should not be reduced.

The sulfurized inorganic substances and the fine powdered basic substances can be mixed in a wide range. The The amount of basic substances depends on the pollution of the gases and exhaust gases with the acidic substances. If only residual amounts of acids have to be separated off, contents of 5 to 30% by weight of basic substances in the mixtures are sufficient. In the treatment of waste gases with a higher acid content, such as waste gases from waste incineration plants, mixtures of up to 95% by weight and more of basic substance can be used.

A major advantage of the invention is that the agents can be mixed from the sulfurized inorganic substances and the basic substances before use in exhaust gas purification depending on the desired composition. With the help of suitable mixers, certain mixtures can be produced very precisely. This is particularly important for small systems. On the other hand, in the context of the invention, the agents can also be produced by mixing the individual components with separate injection at the same location or at different locations in the exhaust gas cleaning system. In the latter procedure, mixing and the beginning of the reaction then take place in one step.

When using calcium hydroxide as a basic substance, there are various options for mixing with the sulfurized inorganic substances. Since calcium hydroxide is produced from quicklime by adding water, the sulphurized agents can be mixed with quicklime, quick-fire extinguishing water and after extinguishing with fine powdered calcium hydroxide.

In addition, other agents effective in exhaust gas purification can be added to the agent of the invention, provided that they do not interfere with the other components of the agent.

The agent according to the invention is preferably used for gas and exhaust gas purification. All known cleaning devices can be used become. They are used to purify gases and exhaust gases from volatile heavy metals, chlorinated dioxins and furans, chlorinated aromatic and aliphatic hydrocarbons, chlorinated biphenyls, aromatic hydrocarbons, toxic organic compounds, hydrogen chloride and / or sulfur dioxide. The agent is introduced into the gas stream in such a way that the pollutants come into contact with the agent and then the agent loaded with pollutants, together with fly dust and unreacted agent, is separated off on filters, for example fabric filters or electrostatic filters, and removed from the gas stream.

The agent is preferably used in dry sorption, conditioned dry sorption and spray sorption. Depending on the structure of the cleaning process, the components of the agent or the entire agent can be introduced into the gas stream at various points in the exhaust gas cleaning system. The addition is preferably carried out together with the basic substances.

There are several ways to add spray sorption. The addition of the sulfurized inorganic substance after the injection of lime milk into the exhaust gas stream has proven itself when the water of the lime milk has evaporated. On the other hand, the sulfurized inorganic substances can also be added to the lime milk and introduced with it. It is technically simple to add the sulfurized inorganic substance to quicklime with the subsequent conversion to milk of lime.

There are also no obstacles to using the product in wet laundry. For this purpose, it can be added to the gas stream before washing and then transferred to the washing water or injected into the gas stream with the washing water. The addition of the agent to the prepurified exhaust gas stream to remove residual amounts of pollutants, in particular mercury and the organic pollutants, has proven to be technically very successful to remove. In this case, the addition of basic substances can be reduced, ie mixtures with 0 to 70% by weight of basic substance are sufficient.

The agent according to the invention is preferably used in exhaust gas purification. It can be used in the temperature range from 20 to 400 ° C. Above 400 ° C there is a risk of sulfur burning. The agent can preferably be used in the temperature range from 60 ° C. to 250 ° C. For example, wet processes work above 60 ° C. The agents are particularly preferably used in the spray sorption, dry sorption and conditioned dry sorption processes.

However, in the sense of the invention it is also possible to apply sulfur to the above-mentioned inorganic substances in granular form (0.25-5 mm) and to guide the gases to be cleaned through the solid layer. Furthermore, granules can also be produced with the basic substances listed, which are used as a fixed bed.

Examples: Example 1 (comparative example)

9.5 g of finely powdered Ca (OH) 2 and 0.5 g of finely powdered stew were mixed intensively.

About 250 mg of this mixture were passed at 1 40 ° C. 27 l of the following gas mixture, mercury also being metered in as the NgCl ₂ solution.

- Nitrogen 90% by volume - Oxygen 1 0% by volume - HCl 1 8, 1 mg / l

- Moisture 0.15 g / l From a total of 8 μg of mercury co-dosed (dosed in the form of HgCI2), 6.8 μg were found. This means a mercury separation of 1 5%.

Example 2 (comparative example)

About 250 mg of a finely powdered mixture of 94.5% by weight of Ca (OH) 2.5% by weight of tress and 0.5% by weight of sulfur were again 27 liters of the above-mentioned gas mixture at 140 ° C. in accordance with Example 1 headed.

Of a total of 8 μg of mercury co-dosed (dosed in the form of HgCI2), 5.6 μg were found. This means a mercury separation of 30%.

Example 3 5 g of finely powdered Tras and 0.5 g of sulfur flower were mixed intensively and heated to 150 ° C. for 30 minutes.

A homogeneous mixture was prepared from 9.45 g of finely powdered Ca (OH) 2 and 0.55 g of sulphurized tress by intensive mixing.

About 250 mg of this mixture were passed according to Example 1 at 1 40 ° C again 27 l of the above gas mixture.

Of a total of 8 μg of mercury co-dosed (dosed in the form of HgCI2), 2.8 μg were found. This means a mercury separation of 65%.

Compared to Example 2, there is a more than 100% increase in the Hg deposition. Example 4

This experiment was carried out in accordance with experiment 3. However, 2 g of sulfur bloom were melted onto 5 g of the feed according to Example 3. A mixture of 93% by weight of Ca (OH) 2.5% by weight of tress and 2% by weight of sulfur was used. The test conditions were not changed.

There was an Hg deposition of 80%.

If the sulfur is not melted on the trass, then a significant sulfur discharge occurs.

Example 5

4.5 g of finely powdered trass and 0.5 g of sulfur bloom were mixed intensively and then heated at 150 ° C. for 30 minutes.

A homogeneous mixture was prepared from 9.5 g of finely powdered Ca (OH) 2 and 0.5 g of sulphurized ressum by intensive mixing.

About 250 mg of this mixture were passed again according to Example 1 at 1 50 ° C 27 l of the above gas mixture.

Of a total of 8 μg of mercury also metered in (metered in in the form of HgCl 2), 3.1 μg were found. This means a mercury separation of 62.3%.

Compared to Example 2, there is a more than 100% increase in the Hg deposition.

Example 6

9 g of finely powdered trass and 1 g of sulfur bloom were mixed intensively and heated to 1 30 ° C. for 5 minutes. About 250 mg of this substance were passed according to Example 1 at 140 ° C 27 I of the above gas mixture.

Of a total of 8 μg of mercury also dosed in (dosed in the form of HgCl 2), 0.6 μg was found again. This means an Hg separation of 92.5%.

In spite of the high sulfur content of Traß, no sulfur discharge was observed.

This experiment shows that sulfurized trass is an excellent sorbent for the separation of mercury.

The Traß (Schwaben-Traß) used in all examples had the following essential parameters:

Grain size distribution (passage in%): 64 μm 98

24 μm 70 1 0 μm 43

Chemical characterization (given as oxides):

Si02 63 69%

AI203 12 16%

CaO 3.5 - 9% Fe203 4 6%

MgO 2 4%

S03 <1.5%

Example 7 a) 9.5 g of calcium hydroxide and 0.5 g of diatomaceous earth (commercial product Celaton MN5 from Chemag AG) were mixed. About 250 mg of this mixture were passed according to Example 1 at 1 40 ° C 27 I of the above gas mixture.

From a total of 8 μg of mercury (metered in in the form of HgCl 2), 5.8 μg were found. This means a mercury

Deposition of 27.5%.

b) About 250 mg of a mixture of 93% calcium hydroxide, 5% diatomaceous earth and 2 sulfur at 1 40 ° C, the gas from Example 1 was passed. The attempt had to be stopped because it was stronger

Sulfur discharge from the reaction tube occurred and got into the absorption bottle and the other measuring devices.

c) 5 g of diatomaceous earth and 2 g of sulfur bloom were mixed intensively and heated to 130 ° C. for 5 minutes.

A homogeneous mixture was produced from 9.3 g of finely powdered Ca (OH) 2 and 0.7 g of the sulfurized kiesigur by intensive mixing.

About 250 mg of this mixture were passed according to Example 1 at 1 40 ° C 27 I of the above gas mixture.

From a total of 8 μg of mercury (metered in in the form of HgCl 2), 1.9 μg were recovered. This means an Hg separation of 76.3%.

Characteristic values of the Celaton MN 5 Kiesigur:

Particle size> 44 μm> traces Average particle size 5.5 μm

Surface m2 / g (BET) 26.5

Si02 89, 1% AI203 3.9%

Fe203 1.4%

CaO 0.5%

Example 8

9.0 g calcium hydroxide and 1.0 g brick flour (grain size 100% <63 μm) were mixed.

About 250 mg of this mixture were passed according to Example 1 at 140 ° C 27 I of the above gas mixture.

5.5 μg of a total of 8 μg of mercury co-dosed (dosed in the form of HgCI2) were found. This means a mercury separation of 31.3%.

For a further experiment with brick flour according to the invention, 9.9 g of brick flour and 0.1 g of sulfur flower were mixed intensively and heated to 130 ° C. for 5 minutes.

A homogeneous mixture was prepared from 9 g of finely powdered Ca (OH) 2 and 1 g of the sulfurized brick powder by intensive mixing.

Of a total of 8 μg of mercury also metered in (metered in in the form of HgCl 2), 2.5 μg were found. This means an Hg separation of 68.8%.

This experiment clearly shows that an excellent sorbent for mercury separation can be produced from exhaust gases by sintering sulfur onto brick powder. Example 9

Instead of brick powder, sulfurized calcium aluminum silicate was used under the same conditions as in Example 8, as is the case when paper waste is incinerated in the paper industry. The mercury deposition was then 54%.

Example 10

Instead of brick powder, sulfurized fly dust from a domestic waste incineration plant (Bamberg) was used under the same conditions as in Example 8. This removed 69% of the mercury used.

Claims

Expectations

1. Means for gas cleaning, because of the fact that it contains or consists of at least one finely powdered inorganic substance with an active surface and inert to molten sulfur with a content of sulfur sintered and / or melted thereon.

2. Composition according to claim 1, d a d u rc h g e k e n n ze i c h n et that the inorganic substance with an active surface and inert to molten sulfur from at least one substance from the group Traß, Traßkalke, bentonite, bauxite, aluminum oxide, silica gel,

Clay powder, burnt clays, bleaching earth, calcium carbonate, dolomite, perlite, pumice, broken stone from the production of sand-lime brick or yali stone, gas concrete dust, expanded clay, cements, calcium aluminates, flying dust, sodium aluminates, calcium sulfates, calcium sulfide and / or brick powder.

3. Composition according to claim 1 or 2, d a d u rc h g e k e n n z e i c h n et that the finely powdered inorganic substances have a grain size of 1 to 200 microns.

4. Means according to claim 3, d a d u rc h g e k e n n ze i c h n et that the grain size is less than 50 microns.

5. Agent according to one of the preceding claims, dadu rc hgekenn ze ichn et, that the sulfur content is 0.01 to 60 wt .-%, based on the total agent.

6. Composition according to claim 5, g e k e n n z e i c h n et d u rc h a sulfur content of 1 to 40 wt .-%, based on the fine powdery inorganic substance with an active surface and inert to molten sulfur.

7. Means according to claim 6, d a d u rc h g e k e n n z e i c h n et that the sulfur content is 10 to 30 wt .-%.

8. Composition according to one of the preceding claims, obtainable by mixing the finely powdered inorganic substance with active

Surface and inert to molten sulfur or mixtures of such substances with finely powdered sulfur and heating the mixture to temperatures above 120 ° C and, if necessary, subsequent mixing with finely powdered basic substances.

9. Composition according to claim 8, d a d u rc h g e k e n n ze i c h n et that a temperature above 120 ° C to 200 ° C is applied.

10. Means according to claim 8 or 9, d a d u rc h g e ke n nze i c h n et that the heating in a period of 10 seconds to 45

Minutes.

11. Agent according to one of the preceding claims, dadu rc hgekennzeichn et, that it additionally contains at least one fine powdered basic substance.

12. Composition according to claim 10, d a d u rc h g e k e n n z e i c h n et that the finely powdered basic substance is selected from calcium hydroxide, quick lime, calcium carbonate, dolomite, sodium carbonate and / or sodium hydrogen carbonate.

13. Composition according to one of claims 1, 11 and 12, d a d u rc h g e k e n n z e i c h n et that it contains 1 to 99 wt .-% of the fine powdered basic substance.

14. Composition according to claim 13, d a d u r c h g e k e n n ze i c h n et that the content of fine powdered basic substance 5 to 90

% By weight, in particular 20 to 80% by weight.

15. A process for the preparation of an agent according to any one of claims 11 to 14, d a d u rc h g e k e n n ze i c h n et that the components thereof are mixed dry or injected separately into a gas stream to be cleaned and mixed there in situ.

16. The method according to claim 15, dadurchgekennzeichn et that an agent according to one of claims 1 to 10 with quicklime before its extinguishing or the extinguishing water or after its extinguishing are added to the calcium hydroxide formed.

17. Process for removing volatile heavy metals, chlorinated dioxins and furans, chlorinated aromatic and aliphatic hydrocarbons, chlorinated biphenyls, aromatic hydrocarbons, toxic organic compounds, hydrogen chloride and / or sulfur dioxide from gases in particular

Exhaust gases, d a d u r c h g e k e n n z e i c h n et that an agent according to one of claims 1 to 14 is introduced into the gas stream, the gases are treated with the agent at a temperature of 20 to 400 ° C and the reaction products and unreacted agent are separated on fabric filters and electrostatic filters.

18. The method according to claim 17, so that the agent is used in dry sorption, conditioned dry sorption, spray sorption and / or gas scrubbing.

19. The method of claim 18, d a d u rc h g e k e n n ze i c h n et that the content of the agent of basic substance, the components of the agent as a mixture or separately, simultaneously or in any order in succession, are introduced into the gas stream to be cleaned.

20. The method according to claim 19, dadu rc hgekennzeichn et that the agent or its components are introduced before the gas scrubbing, during the gas scrubbing, in the washing water, after the gas scrubbing and / or in the waste water from the gas scrubbing.

21. The method according to any one of the preceding claims 17 to 20, that the cleaning of the gases and exhaust gases is carried out in the temperature range from 60 to 250 ° C, preferably 120 to 210 ° C.

22. A process for removing volatile heavy metals, chlorinated dioxins and furans, chlorinated aromatic and aliphatic hydrocarbons, chlorinated biphenyls, aromatic hydrocarbons, toxic organic compounds, hydrogen chloride and / or sulfur dioxide from gases, in particular

Exhaust gases, d a d u rc h g e k e n n e i c h n et that an agent according to one of claims 1 to 14 is brought into contact with the gas stream in granular or granular form and the gases are treated with the agent at a temperature of 20 to 400 ° C.