DE19745191A1 - Material for purifying gas to remove mercury and other pollutants - Google Patents

Abstract

A material for purifying gases comprises finely-powdered inorganic substances, e.g. bentonite, clay, flue dust, etc., and/or carbon-containing substances such as active carbon, with a content of sintered-on or melted-on sulfur. A material comprising finely powdered inorganic substances such as trass, trass lime, bentonite, bauxite, activated aluminum oxide, silica gel, powdered clay, fired clay, fuller's earth, aerated concrete dust, swelling clay, cements, calcium or sodium aluminate, flue dust, calcium sulfate or sulfide, and/or carbonaceous substances such as active carbon, open-hearth furnace coke or pulverized lignite, with a content of sintered-on and/or melted-on sulfur. Independent claims are also included for (a) materials consisting of finely-powdered basic substances and the above materials; (b) a process for the production of materials (a) by mixing the substances in the dry state and using the mixture for gas purification or by injecting the separate components into a gas stream to be purified so that mixing takes place in the gas; (c) a process for the production of granules from these mixtures by adding water and binders such as Portland cement, clay, bentonite, silicates and/or water glass; (d) a process for purifying off-gas and gases to remove volatile heavy metals, chlorinated dioxins and furans, chlorinated aromatic and aliphatic hydrocarbons, toxic organic compounds, hydrogen chloride and/or sulfur dioxide, by introducing the above material into the gas stream and trapping the reaction products (from material plus pollutants) on fibrous filters and/or electrostatic filters.

Description

The invention relates to a means, a method for production the means and the use of the means for gas cleaning.

In thermal processes, e.g. B. metallurgical processes, coal firing, Waste incineration and numerous industrial processes who the exhaust gases generated with volatile heavy metals, e.g. B. Cad mium, mercury, thallium, arsenic, antimony and lead are. These are elementary heavy metals or Salts, preferably chlorides and oxides. They also contain in many cases organic pollutants such. B. Dioxins, Fu rane, aromatics and the like.

Usually the gases are cooled and the pollutants wet washed out. Often this is not sufficient if the Heavy metals exist in elemental form. Mercury z. B. is often emitted as an element. It can then also be over do not separate a wet wash from the gas. On top of that there is Problem that volatile heavy metal salts even after wet washing emitted as aerosols and / or hard-to-collect fine dust will. Also the dioxins, aromatics and halogenated hydrocarbons are only insufficiently deposited.

Another method is to use activated carbon Filter to direct. This leads to a reduction in the salary of volatile pollutants, e.g. B. of mercury, but it is This process is burdened with considerable costs, since large quantities Highly active coal must be used and always the danger the smoldering fire exists in the coal bed. About the always available In addition, fine dust containing pollutants is emitted during abrasion, which is difficult to separate.

Another method is to add sulfur to activated carbon apply and direct the gas flow over it. The mercury over separation and the separation of organic pollutants quite effective, but the problems of self-ignition remain generation and the emission of abrasion. In addition, there is that the use of sulphided coal at the exorbitant price the same fails.

There has therefore been no lack of further attempts that volatile heavy metals with sulfur or sulfides in to implement low-volatility sulfides and from the gas stream to be deposited.

For this purpose, calcium hydroxide is often used alone or with the well-known additives activated charcoal and stove coke with sulfur mixed and used in exhaust gas cleaning. The mercury separation is with the use of calcium hydroxide and sulfur unsatisfactory. One explanation could be that sulfur is associated with the reactive basic compounds, e.g. B. Ca (OH) 2, reacts and thus no longer available for binding the mercury stands.

The mixture of calcium hydroxide, activated carbon and sulfur provides Although good values, there is always the risk of inflammation of the Mixture with insufficient heat dissipation.

There is therefore a need to emerge from the gas streams, posh Lich from waste incineration plants, volatile heavy metals, especially mercury, in its various forms of connection men and also as elements, targeted, simple and inexpensive to be separated, but also organic pollutants such as dioxins and To capture furans and also to separate them. Still exists the task of a simple and inexpensive method for common deposition of volatile inorganic and organic pollutants and acidic components from gas streams to develop. There must be a reduction in the pollutant content be so high in the exhaust gas flow that the existing limit values, e.g. B. for Hg, Cd, Tl and dioxins / furans, are safely adhered to can. It is also an object of the invention to provide a non-combustible sorbent made from sulfur and inorganic To propose substances, preferring the volatile Heavy metals, but also organic pollutants on their own or in combination with other substances or sorbents separates.

There is also a need to use the flammable carbonaceous sorbents, e.g. B. activated carbon or Furnace coke, modified with sulfur so that their Mercury binding capacity is increased so much that the required amount of activated carbon can be significantly reduced. In order to can also determine the flammability of the residue products after Gas cleaning can be reduced significantly.

The invention achieves the objects by the means consisting of fine-powdered inorganic substances such as trass, trass lime, Bentonites, bauxite, activated aluminum oxide, silica gel, Powdered clay, burnt clays, bleaching earth, aerated concrete dust, expanded clay, Cements, calcium aluminates, fly ash, sodium aluminates, Calcium sulfates, calcium sulfides and / or carbonaceous Substances such as activated charcoal, stove coke, lignite dust, and a content of sintered and / or melted Sulfur.

The preparation of the funds is done in a simple manner Mixing the finely powdered substances with sulfur, preferably Sulfur bloom, and heating the mixture to the melting point of sulfur of 119 ° C or higher. Temperatures higher than 200 ° C are not required. Low temperatures are better than higher temperatures. Suffice it to add the sulfur to the to sinter the listed substances. Hence a thermal Treatment time of a few seconds with small amounts of sulfur up to 45 minutes with high contents sufficient.

Furthermore, funds are claimed that result from the above mentioned felt substances and fine powdery basic substances. In this combination, both toxic pollutants, volatile heavy metals, chlorinated dioxins and furans, chlorinated and non-chlorinated hydrocarbons, organic Acids, phenols, aromatic hydrocarbons, etc., as well the acidic inorganic substances hydrogen chloride, sulfuric acid oxide, sulfur trioxide, hydrogen fluoride and nitrogen oxides, deposit.

The preferred agents contain calcium hydroxide, one inexpensive basic substance. It can be considered normal Calcium hydroxide or as calcium hydroxide with a large surface can be used. Substances with a Grain size <50 µm. It's not technically a problem that Grain distribution of basic and sulphurized substances To coordinate means so that none in moving media Segregation occurs.

Sodium hydrogen carbonate (NaHCO3) can then be used with advantage Use a mixture with the claimed sulphurized agents, when a high deposition of sulfur dioxide and Hydrogen chloride is required and the temperature of the exhaust gas should not be lowered.

The sulphurized agents and the finely powdered basic ones Substances can be mixed in a wide range. The amount the basic substances depends on the load on the Gases and exhaust gases with the acidic reacting substances. Will only Residual amounts of acids separated out, then contents of 5 are sufficient up to 30% by weight of basic substances in the mixtures. In the Treatment of exhaust gases from waste incineration plants e.g. B. be Mixtures with more than 70% by weight of basic substance are used.

A major advantage of the invention is that the funds from the sulphurized agents and the basic substances before the Application in the exhaust gas cleaning can be mixed. With With the help of a suitable mixer, you can create very precise mixtures getting produced. This is especially useful for small systems of Meaning. On the other hand, it is also within the scope of the invention the means by mixing the individual substances with separate ones Injection at the same point or at different points to produce exhaust gas cleaning. With the latter method mixing and the start of the reaction are then carried out in one step.

Provide when using calcium hydroxide as a basic substance different ways of mixing with the sulphurized agents. Since calcium hydroxide from quicklime with Water is produced, the sulfurized agent can be used before Extinguishing the quicklime, during the extinguishing the water and after be mixed with the finely powdered calcium hydroxide before extinguishing.

Of course, the sulfurized agents can also be used in any mixing ratio with fine powder surface-active substances such as activated charcoal, hearth furnace coke, activated alumina, silica gel, kieselguhr, artificial and natural zeolites are mixed. The Fine powdery basic substances are added. Basically all substances can be added that are in the Exhaust gas cleaning are effective.

For some purposes it is desirable to use the means as To use granules. The production of the granules takes place on known way by adding water and binding agent. the best-known binders are Portland cement, clays, bentonites, Silicates and / or water glass. The use of Bentonite and cement.

The agents are preferred for gas and exhaust gas cleaning used. All known cleaning devices be used. They are used to clean gases and exhaust gases of 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. Thereby the funds are in the gas stream introduced, the pollutants treated with the means and the with pollutants loaded with airborne dust and the unreacted agents to filters, e.g. B. fabric filter, or at Electrostatic precipitator deposited and removed from the gas flow.

The agents are preferred for dry sorption, the conditioned dry sorption and spray sorption used. Depending on the structure of the cleaning process, the Means at various points in the exhaust gas purification system Gas stream are introduced. The addition is preferably carried out together with the basic substances.

In the case of spray sorption, there are several options for adding. It has proven useful to add the agent after the spray has been injected Milk of lime in the exhaust stream if the water of the milk of lime has evaporated. On the other hand, the sulfurized agents can also can be added to the milk of lime. It is technically simple Adding the agent to the quicklime with the subsequent implementation to milk of lime.

There are also no obstacles to the means in wet washing apply. You can do this in the gas stream before washing given and then transferred to the wash water or with the Wash water are injected into the gas stream. Technically proven the addition of the agent in the cleaned exhaust gas flow has changed still residual amounts of pollutants, especially mercury and the organic pollutants to remove. In this case it can the addition of basic substances is reduced, d. H. it suffices 20 to 70 wt .-%, or it is made with sulfurized agents only worked.

The claimed funds are preferred for exhaust gas purification used. They are in the temperature range from 20 to 400 ° C applicable. Above 400 ° C there is a risk of burns of sulfur. The means can preferably be im Use temperature range from 60 ° C to 250 ° C. E.g. work Wet process above 60 ° C. Particularly preferred can Means in the spray sorption, dry sorption and conditioned dry sorption processes can be used.

Examples example 1

9.5 g of finely powdered Ca (OH) 2 and 0.5 g of finely powdered trass were intensely mixed.

27 l of the following gas mixture were passed over 250 mg of this mixture at 140 ° C:

- nitrogen 90% by volume - oxygen 10% by volume - HCl 18.1 mg / l - humidity 0.15 g / l

Of a total of 8 µg of mercury dosed in (dosed in In the form of HgCl2), 6.8 µg were found. This means one 15% mercury deposition.

Example 2

Over 250 mg of a finely powdered mixture of 94.5% by weight Ca (OH) 2.5 wt% trass and 0.5 wt% sulfur were according to example 1 at 140 ° C again 27 l of the above Gas mixture passed.

Of a total of 8 µg of mercury dosed in (dosed in In the form of HgCl2), 5.6 µg were found. This means one Hg separation of 30%.

Example 3

5 g of finely powdered trass and 0.5 g of sulfur bloom became intense mixed and heated to 150 ° C for 30 minutes.

Made from 9.45 g of finely powdered Ca (OH) 2 and 0.55 g of sulphurized trass became a homogeneous mixture by intensive mixing manufactured.

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

Of a total of 8 µg of mercury dosed in (dosed in In the form of HgCl2), 2.8 µg were found. This means one Hg separation of 65%.

Compared to Example 2, the result is more than 100% Increase in Hg separation.

Example 4

This experiment was carried out according to experiment 3. It however, 2 g of sulfur bloom were melted onto 5 g of trass. A mixture of 93% by weight Ca (OH) 2.5% by weight was used Trass and 2 wt% sulfur. The experimental conditions were not changed.

There was a Hg deposition of 80%.

If the sulfur is not melted on Trass, then it occurs considerable sulfur discharge.

Example 5

4.5 g of fine powdery tassel and 0.5 g of sulfur bloom became intense mixed and then heated at 150 ° C for 30 minutes.

Made from 9.5 g of finely powdered Ca (OH) 2 and 0.5 g of sulphurized trass a homogeneous mixture was obtained by intensive mixing represents.

About 250 mg of this mixture were according to Example 1 at 150 ° C again 27 l of the above gas mixture passed.

Of a total of 8 µg of mercury dosed in (dosed in In the form of HgCl2), 3.1 µg were found. This means one Hg separation of 62.3%.

Compared to Example 2, the result is a slope of more than 100% tion of the Hg deposition.

Example 6

9 g of finely powdered trass and 1 g of sulfur blossom were intensively ge mixed and heated to 130 ° C for 5 minutes.

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

Of a total of 8 µg of mercury dosed in (dosed in In the form of HgCl2), 0.6 µg were found. This means one Hg separation of 92.5%.

Despite the high level of sulfur in Traß, there was no sulfur out wear to watch.

This experiment shows that sulfurized trass is excellent It is a sorbent for separating mercury.

The Traß (Schwaben-Traß) used in all examples had the following key parameters:
Grain size distribution (passage in%):
64 µm 98
24 µm 70
10 µm 43.

Chemical characterization (expressed as oxides):

SiO2 63-69% Al2O3 12-16% CaO 3.5-9% Fe2O3 4-6% MgO 2-4% SO3 <1.5-%

Example 7

9.5 g calcium hydroxide and 0.5 g kieselguhr (commercial product Celaton MNS from Chemag AG) were mixed.

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

Of a total of 8 µg of mercury dosed in (dosed in In the form of HgCl2), 5.8 µg were found. This means one Hg separation of 27.5%.

Was over 250 mg of a mixture of 93% calcium hydroxide, 5% Diatomaceous earth and 2 sulfur at 140 ° C gelei the gas from Example 1 tet, then the experiment had to be broken off because of the strong sulfur content carried out of the reaction tube and into the absorption bottle and the other measuring devices arrived.

For another experiment with diatomaceous earth according to the inventor 5 g of kieselguhr and 2 g of sulfur bloom were intensively used mixed and heated to 130 ° C for 5 minutes.

From 9.3 g of finely powdered Ca (OH) 2 and 0.7 g of the sulphurized Brick meal became homogeneous through intensive mixing Mixture made.

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

Of a total of 8 µg of mercury dosed in (dosed in In the form of HgCl2), 1.9 µg were found. This means one Hg separation of 76.3%.

Characteristic values of the diatomite Celaton MN 5:

Particle size <44 µm <Tracks Average particle size 5.5 µm Surface area m2 / g (BET) 26.5 SiO2 89.1% Al2O3 3.9% Fe2O3 1.4% CaO 0.5%

Example 8

9.0 g calcium hydroxide and 1.9 g brick dust (grain size 100% <63 µm) were mixed.

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

Of a total of 8 µg of mercury dosed in (dosed in In the form of HgCl2), 5.5 µg were found. This means one Hg separation of 31.3%.

For another attempt with brick dust according to the Er 9.9 g brick powder and 0.1 g sulfur bloom were intensive mixed and heated to 130 ° C for 5 minutes.

From 9 g of finely powdered Ca (OH) 2 and 1 g of the sulphurized Brick meal became a homogeneous mixture by vigorous mixing manufactured.

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

Of a total of 8 µg of mercury dosed in (dosed in In the form of HgCl2), 2.5 µg were found. This means one Hg deposition of 86.7%.

This experiment clearly shows how by sintering on Sulfur on brick dust is an excellent sorbent for that Mercury separation can be produced from exhaust gases.

If instead of brick dust, under the same conditions, calcium Aluminum silicate, as is the case with the incineration of paper waste in the paper industry is used, then the Hg- Deposition 54%.

Good separation results are also achieved with flue dust from a Domestic waste incineration plant achieved. Used instead of brick dust under the same conditions flue dust from the household waste disposal Bamberg incineration plant is used, 69% of the The mercury used is deposited.

Claims (18)

1. Means consisting of fine powdered inorganic substances, such as trass, trass limestone, bentonite, bauxite, activated Alumina, silica gel, powdered clay, calcined clays, bleachers den, aerated concrete dust, expanded clay, cements, calcium aluminates, Fly ash, sodium aluminate, calcium sulfate, potassium sulfide, and / or carbonaceous substances such as activated charcoal, hearth furnace coke, lignite dust, and a content of sintered and / or. melted sulfur. 2. Means according to claim 1, consisting of the finely powdered anor ganic and / or organic substances with a grain size of 1 µm to 200 µm, preferably 1 µm to 100 µm, in particular <50 µm. 3. Agent according to the preceding claims with a sulfur content from 0.01 to 60% by weight. 4. Composition according to claim 3 with a sulfur content of 1 to 40 % By weight, preferably 10 to 30% by weight. 5. Means according to the preceding claims, produced by Mixing the finely powdered substances with finely powdered sulfur, especially sulfur bloom, and heating the mixture to tem temperatures <119 ° C, preferably <119 to 200 ° C, in particular 119 to 160 ° C, preferably 120 to 130 ° C. 6. Composition according to claim 5, produced by heating during 10 seconds to 45 minutes, preferably 15 seconds to 15 Wed utes, especially 30 seconds to 2 minutes. 7. Means made from fine powdery basic substances and the means according to the preceding claims. 8. Agent according to claim 7 with calcium hydroxide, calcium carbonate, Quicklime, sodium carbonate and / or sodium hydrogen carbonate as basic substances. 9. Means according to claims 7 and 8 with a proportion of fine powdery basic substances from 1 to 99% by weight, preferably se, 5 to 90% by weight, in particular 20 to 80% by weight. 10. A method for producing the agent according to claims 7 to 9, characterized in that the agents and substances mixed dry and then used for gas cleaning or separately injected into a gas stream to be cleaned and to be mixed there. 11. Process for the preparation of the means, characterized thereby net that the means according to claims 1 to 6 before deletion to quicklime, to extinguishing water during extinguishing and afterwards be added to the calcium hydroxide for quenching. 12. Means according to the preceding claims with a proportion on the finely powdered surface-active substances activated carbon, Furnace coke, activated aluminum oxide, silica gel, kieselguhr as well as artificial and / or natural zeolites in the range of 0.5 to 90% by weight, preferably from 1 to 40% by weight. 13. Process for the production of a granulate from the above mit by adding water and binding agents such as Portlandze ment, clays, bentonites, silicates and / or water glass. 14. Process for cleaning exhaust gases and gases from volatile Heavy metals, chlorinated dioxins and furans, chlorinated aromatic and aliphatic hydrocarbons, chlorinated Biphenylene, aromatic hydrocarbons, toxic organi chemical compounds, hydrogen chloride and / or sulfur dioxide, characterized in that the above agents enter the gas stream brought the pollutants treated with the means and the re action products as well as the unreacted funds on tissue fil tern and / or electrostatic precipitators are deposited. 15. The method according to claim 14, characterized in that the Agents in dry sorption, conditioned dry sorption, Spray sorption and / or gas scrubbing can be used. 16. The method according to claim 15, characterized in that the O.a. means before adding the basic substances of the indicated performed sorptions, along with the basic substances and / or after the addition of the basic substances to the rice Nigenden gas flow are introduced. 17. The method according to claim 16, characterized in that the o.a. Agent before the gas scrubbing, during the gas scrubbing, in the scrubbing water, after the gas scrubbing and / or in the waste water of the Gaswä cal be introduced. 18. The method according to the preceding claims, characterized ge indicates that the purification of gases and exhaust gases in tempera ture range from 20 to 400 ° C, in particular in the range from 60 to 250 ° C, preferably from 120 to 2110 ° C is carried out.