JPH0416235A - Purification agent for harmful substance from gas and exhaust gas and method for purification thereof and for production of said agent - Google Patents

Abstract

PURPOSE: To remove volatile harmful substances in a high efficiency by using a purifying agent comprising a dry powder having a reactive calcium hydroxide as its main component and a water soluble salt of sulfur-containing substances. CONSTITUTION: The agent for purifying harmful substances such as heavy metals or the like from gasses and waste gasses is composed of a dry powder having a reactive calcium hydroxide as its main component and 0.01 to 5 wt.% of a water soluble salt of sulfur containing substances. Also, the said purifying agent is composed of a dry powder containing a reactive calcium hydroxide as its main component, 0.5 to 10 wt.% of surface active substances and 0.5 to 5 wt.% of sulfur powder, wherein the said sulfur powder is either carried on the surface active substance or mixed with the calcium hydroxide and the surface active substance. As the water soluble salt of sulfur-containing substance, mercaptan, sulfide, polythionic acid, polythionic acid and thiosulfuric acid salt and alkalimetal compounds of these are exemplified.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention provides a purification agent for purifying gas or waste gas by removing harmful substances such as volatile heavy metals or organic substances from gas or waste gas. and methods, methods for producing this agent, and uses of this agent.

[Conventional technology]

In thermal processes such as metallurgy 7 coal combustion or waste incineration, small volatile metals such as cadmium,
Waste gas containing mercury, thallium, arsenic, antimony or lead is generated. Here, the interlayer is an elemental heavy metal or a salt thereof, especially a chloride or an oxide.

These gases are usually cooled and the heavy metals wet-scrubbed to remove them. When heavy metals are present in elemental form,
This is often insufficient. For example, mercury is often released as an element.

In that case, mercury cannot be separated from the gas by wet cleaning. In addition, volatile heavy metals also pose a problem after wet cleaning, since they are released as aerosols and/or fine dusts that are difficult to separate.

Another known method is to pass the waste gas stream through an activated carbon filter. In this case, the content of volatile heavy metals, such as mercury, is reduced, but costs are increased due to the need to use large amounts of highly active activated carbon and smoldering combustion in the activated carbon bed. Furthermore, not only wear occurs constantly, but also fine dust containing heavy metals, which is difficult to separate, is also generated.

Therefore, attempts have also been made to remove volatile heavy metals from the gas stream by converting them into less volatile sulfides using sulfur or sulfides.

According to this method, sulfur is supported on activated carbon.

A gas stream is directed above it. In this case, separation of the mercury is certainly achieved, but problems arise with self-ignition and release of debris.

Another method according to the prior art involves suspending sulfur or sulfur compounds in an aqueous solution of a thiourea compound, such as thiourea. The solution or suspension is atomized by spraying into a gas stream, and the mercury and sulfur compounds formed are separated by an electrostatic precipitator.

However, mercury separation of 70% is insufficient to maintain the limit of 0.200 mg/rn'. This poor mercury separation may be due to the addition of water to the gas stream and the high content of strong acids, especially when treating waste gas from waste incinerators.

Sulfur or a water-soluble sulfur compound such as ZnS with Ca(OH
) It has already been proposed to separate mercury by injecting it into the waste gas of a waste incinerator together with the powder. 200-250
lff1g/rr at a temperature of °C? Even if ZnS is used,
To achieve the mercury limit of 0.2 mg/rn', 60% mercury separation is insufficient.

[Problem to be solved by the invention]

Therefore, in particular, the removal of volatile hazardous substances (in particular heavy metals such as mercury) from gas streams from waste incinerators, in the form of their various compounds or in the form of elements, in particular or sometimes without a cooling process, and It is also desired to remove organic substances such as dioxins, chlorofluorocarbons, and furans. It would also be desirable to develop a simple and inexpensive method for simultaneously separating both volatile hazardous substances and acidic components from a gas stream. In that case, the reduction of harmful substances in the waste gas stream is 3
For example, the values must be sufficient to ensure that the limit values for Hg, Cd, Tl and As are met.

The present invention aims to meet these demands.

[Means and effects for solving the problem] According to the invention, this problem is solved by a purification agent for removing and purifying harmful substances from gases and waste gases according to claim 1. That is, according to the present invention, it consists of a dry powder mainly composed of 9-reactive calcium hydroxide, and 0.01 to 5% by weight of a water-soluble salt of a sulfur-containing substance. The above objective is achieved by a purifying agent for harmful substances such as heavy metals and organic substances from gas and waste gas. A preferred embodiment of this purifying agent is as follows.

It is described in claims 2-9.

The invention further provides for the production of dry powders based on calcium hydroxide or powders containing small amounts of water for cleaning gases and waste gases.

A manufacturing method according to claim 9 is provided. That is, 1. The method for producing a purifying agent such as gas according to the present invention includes (a) adding the ingredients to quicklime before slaking the quicklime, (b) adding slaked water during the slaking, and (c)
After slaked, calcium hydroxide is added with at least one of (a) to (c), a water-soluble salt of a sulfur-containing substance, or a surface-active substance and a water-soluble salt of a sulfur-containing substance, or sulfur itself or a surface-active substance. It is characterized by the addition of sulfur supported on a substance.

Preferred implementation of this manufacturing method! ! The third aspect is described in claims 10 and 11.

According to another aspect of the invention, claims 12.17 and 18
It was written in. A method for purifying gas and waste gas from harmful substances is proposed. Preferred embodiments of the method of claim 12 are described in claims 13-16.

According to the present invention, the solution to the above problem is achieved in two steps: in the first step, calcium hydroxide containing a water-soluble salt of a sulfur-containing substance is produced; In this process, volatile or vaporous toxic substances such as heavy metals in the waste gas are acted upon by a dry or semi-dry process and then separated again from the waste gas stream.

The great advantage of water-soluble salts of sulfur-containing substances is that they can act on calcium hydroxide in the most finely divided form, either during or after the slaking process, while dissolved in water. It is in. Supporting (or attachment) to surface-active substances is also very easy. The finest division is very favorable for reactions with double metals and volatile organic pollutants. From the same point of view, the particle size of the purifying agent containing calcium hydroxide as a main component is preferably less than 200 μm.

Furthermore, water films are formed on the calcium hydroxide and on the surface-active substances, and these water films dissolve the salts accordingly. Heavy metals, which are volatile as salts, dissolve in the water film and react quickly with the salts of sulfur-containing compounds.

The separation of volatile heavy metals is greatly facilitated by this mechanism.

As a modification of the original inventive idea of the present invention, water-insoluble sulfur is used and this sulfur is combined with two surface-active substances for better distribution and finely divided during the process of slaked lime. It may also be supported on calcium hydroxide in divided form.

[Preferred embodiments and effects]

According to the invention, mercaptans, sulfides, polysulfides, polythionates and thiosulfates are used as water-soluble salts of sulfur-containing substances, in particular in the form of compounds of alkali metals or alkaline earth metals. . Sulfides also include hydrogen sulfide. Thiosulfates and polysulfides form a special group, since they release sulfur under the action of acid or heat or both, and thus under reaction conditions.

This sulfur is formed in the most finely divided form and is very well suited to combine with a large variety of volatile heavy metals. Waste gas streams from waste incinerators and other incineration systems always contain acids, thus ensuring the separation of sulfur from thiosulphate.

Another form of bonding is a water-soluble mercaptan, an organic compound containing a hydrogen sulfide group.

One important group of water-soluble sulfur-containing compounds includes hydrogen sulfide and water-soluble sulfides. These react with volatile heavy metals to form insoluble-hardly volatile sulfides.

Among the water-soluble sulfides, sodium hydrogen sulfide and sodium sulfide are preferred, but other alkali metal and alkaline earth metal sulfides are also suitable.

A disadvantage of sulfides is that they are severely oxidized at high temperatures, for example 200° C., so that they cannot be used for the separation of volatile heavy metals.

As a group of sulfur-releasing compounds, the general formula M2Sn (in the formula n
can take values of 2.3.4.5 and higher 1
Also preferred are polysulfides with M representing a metal. These polysulfides, under the action of acids, liberate sulfur, which, together with the highly active hydrogen sulfide that is likewise liberated, acts on volatile heavy metals.

As the sulfur-releasing compound, salts of polythionic acids can be used. Salts of polythionic acids are decomposed into sulfur, sulfite and sulfuric acid under the action of acids. The liberated sulfur is particularly suited for binding volatile heavy metals in gas and waste gas streams.

A preferred embodiment of the cleaning method according to the invention for cleaning gases and waste gases from volatile heavy metals is to prepare water-soluble sulfur compounds by supporting or mixing them with calcium hydroxide. It consists in being used with.

According to the manufacturing method according to the present invention of a dry powder or water-containing powder containing calcium hydroxide as a main component for cleaning gas and waste gas from heavy metals, (a) before slaked the quicklime, (b) ) in the slaked water during slaking; (c) in calcium hydroxide after slaked; A salt and a surface-active substance, or sulfur itself or supported on a surface-active substance, are added.

The combination of the sulfur-containing compound and the calcium hydroxide is preferably made by adding the sulfur-containing compound to the water required for slaking.

According to one embodiment of the invention, a solution of thiosulfate in slaked water is used for slaked quicklime. In that case, the thiosulfate, in its finest form, -like
The distribution on the calcium hydroxide makes it available for subsequent reactions, especially in highly active form.

Here, the slaked process can also be carried out by first partially slaked with pure water and then completely slaked with water containing a water-soluble salt of the sulfur-containing substance.

However, the sulfur-containing compounds may also be supported on the calcium hydroxide in solid form, especially as a finely divided powder, or in dissolved and concentrated form.

When later supported on calcium hydroxide by solution, preferably 0.5 to 3% by weight and 0.1 to 5% by weight.
A powder of calcium hydroxide is obtained which contains % water by weight.

Another possibility for combining sulfur-containing compounds and calcium hydroxide is to add these to the quicklime and then slake the quicklime. In all these cases, the sulfur-containing compounds are present in the most finely distributed □ state in the calcium hydroxide. The great advantage of this production method is that the quicklime and the sulfur-containing compounds can be thoroughly premixed, for example in a lime factory, and then slaked by the user, in particular to produce milk of lime, which can then be used This eliminates the need for auxiliary equipment for the person.

This manufacturing method is specified in detail in claims 1-8. It is controlled so that an agent containing calcium hydroxide as a main component is obtained.

This means that the content of water-soluble salts of sulfur-containing substances is between 0.01 and 5.
% by weight, preferably in the range of 0.1 to 1% by weight, more preferably in the range of 0.2 to 0.6% by weight.

Depending on the loading (content) of volatile heavy metals in the waste gas, use highly doped calcium hydroxide or doped Ca(OH)2 agents in amounts that vary in a controlled manner during operation. I can do it.

The combination of sulfur-containing compounds with calcium hydroxide is particularly suitable when using hydrogen sulfide or hydrogen sulfide-forming substances such as polysulfides or polythionic acids, or when using hydrogen sulfide and water-soluble sulfides. . Calcium hydroxide is used in such a large excess over the sulfur-containing compounds that the liberated hydrogen sulfide compounds are immediately neutralized by the calcium hydroxide to form the acid. Further action of acid at elevated temperatures converts the sulfides into odorless compounds, especially sulfites and sulfates.

Besides containing water-soluble salts of sulfur-containing substances.

Also containing 0.5 to IO weight percent of surface-active substances.

It is also possible to produce and use cleaning agents according to the invention.

Surface-active substances include activated carbon, lignite-open-hearth coke,
Silicate gel, diatomaceous earth and/or activated aluminum oxide are used.

The sulfur-containing substance may be supported on the surface-active substance via an aqueous solution or may be further mixed mechanically.

The loading on the surface-active substance is most preferably carried out during a suitable treatment step, but it may also be carried out during the slaked process.

This loading can also be carried out by mixing water-soluble salts of sulfur-containing substances and surface-active substances with quicklime and slaking this quicklime. However, this slaking may also be carried out by mixing the quicklime with the surface-active substance and then slaking it with water containing the salts of said substance.

For example, water-soluble sulfides, polysulfides, mercaptans,
After thiosulfate and polythionic acid are sufficiently supported on lignite-open hearth coke, water can be evaporated to produce a dry form. If necessary, these sulfur-releasing compounds may be pretreated with acid so as to distribute the most finely divided form of sulfuric acid on the surface-active material.

Surface-active substances are highly preferred for separating volatile heavy metals. Surface-active substances are often combined alone with one heavy metal, but this effect can be further enhanced by the presence of sulfur-containing compounds.

Surface-active substances are also effective in separating most volatile organic pollutants. Such harmful substances include, in particular, chlorinated dioxins, furans, chlorofluorocarbons, or hexachlorbenzole.

Chlorinated hydrocarbons such as hexachlorocyclohexane, trichlorethylene and perchlorethylene, polyaromatic hydrocarbons such as benzanilene2 and
(Technischen Anleitung Lu
rt) class 1~ of hazardous substances listed in the 1986 edition.
There are other volatile hazardous substances, such as class I~■ of cancer-inducing substances and class I~■ of organic hazardous substances.

Another form of combining surface-active substances with water-soluble salts of sulfur-containing substances is that they can be combined in finely divided form with solid surface-active substances by grinding or mixing.

Combinations of calcium hydroxide, surface-active substances and finely divided sulfur are also particularly preferably used. The content of sulfur is 0,5
~5% by weight. This combination is produced either during the process of slaking the quicklime or by subsequently adding a mixture of sulfur powder and surface-active substances.

The use of Ca(OH)2/surface-active substance/sulfur mixtures offers significant advantages over prior art methods. Especially the big advantage.

The combustion of sulfur at gas cleaning temperatures of 150-400° C. does not lead to adverse results. generated S
The O□ is immediately absorbed by Ca(OH)2, and the sulfur burning on the cloth filter does not perforate the filter because the Ca(OH)2 powder forms a protective layer.

According to a preferred embodiment of the invention, the gas stream or waste gas stream is treated with a sulfur compound in a temperature range from 0 to 400C, preferably from 20 to 300C, more preferably from 80 to 250C.

If the temperature is higher than 400° C., there is a high possibility that the sulfur-containing compound will be rapidly combusted. The main range of use is 20
to about 300°C. At 200-250 °C, most of the waste gas from the incinerator.

After passing through the boiler, it is led to a cleaning device. Therefore.

It is particularly advantageous to separate volatile pollutants from waste gases at high temperatures of 200-250°C. For this, sulfur,
Particular preference is given to salts of periosulfates, polysulfides and polythionic acids. In particular, sulfur and periosulfate are most preferred because they are stable with respect to temperature and can quickly react with volatile heavy metals at high temperatures.

What is the ratio of sulfur compounds to heavy metals to be separated?

It is provided that the heavy metals present in very small amounts can be treated with a significant excess of sulfur-containing compounds without any particular outlay. According to the invention, the ratio of sodium thiosulfate to mercury is between 1 and 1000 times, preferably 25 times
~500 times the amount. The amount used herein means that for every 1 weight unit of mercury, the same weight unit of sodium 1,000 sulfate is used.

The preferred usage range is 25 to 500 times the amount. Such a stoichiometric ratio allows reliable separation of volatile heavy metals without making the process uneconomical.

When using sulfur, the amount is 50 to 2000 times, preferably 2
A quantity ratio of 5 to 500 times has proven advantageous.

What are the benefits of sulfur-releasing compounds such as 100sulfate?

Sulfur is present in its most finely divided form upon decomposition under the action of acids.

A particular advantage of the cleaning method according to the invention is that the salts of the sulfur-containing substances used for binding the volatile heavy metals of the waste gases or the powder of relatively large amounts of Ca(OH)2 are used as carriers.
The advantage is that it can be delivered into a gas stream. This means that the sulfur-containing substances are reliably distributed in the gas stream. Particularly when using cloth filters, a reaction layer is formed which necessarily passes through the waste gas to be cleaned.

Ca(OH)2 thus performs not only the function of an acid binder, but also the function of creating a surface and the possibility of 9 reactions for sulfur-containing substances.

Ca(OH)2 also performs the function of collecting and neutralizing oxidation products generated from sulfur or sulfur-containing substances, such as SO2 or S03.

Since no release of S02 or S03 should be expected, the S-containing material can be used in very excess with respect to volatile heavy metals. Therefore, volatile heavy metals can be separated to LOO% without any problems.

Even at reaction temperatures as high as 200° C., volatile heavy metals are separated with a resolution higher than 70%.

The features according to the invention can also be significantly transferred to spray adsorption. This means that one can suspend the agent prepared according to the invention in water and atomize it into the gas stream or waste gas stream to be cleaned. Quicklime to which water-soluble salts of sulfur-containing substances have been added may also be used. In this case, when producing the milk of lime in the apparatus, a suspension is obtained, which can likewise be used in the sense of the invention.

Reaction products formed from sulfur compounds and volatile heavy metals as well as harmful substances bound to surface-active substances can be removed using known filters, in particular cloth filters, electrostatic filters (dust collectors).
, cyclone or wet cleaning equipment.

The method according to the invention uses gases and waste gases from production processes 9 such as metallurgical chloralkali electrolysis or blast furnaces, as well as 1 power plants, waste incinerators.

It is advantageously used for the treatment of gases and waste gases from special waste incinerators, installations of the glass-ceramic industry, combustion plants, aluminum smelters, incinerators, etc.

The method of the invention is advantageously used in waste gas treatment processes such as dry adsorption, dry adsorption, including water conditioning, as well as spray adsorption.

〔Example〕

Example 1 11111 g of sodium thiosulfate was dissolved in 17 mm of water. This slaked 28 g of quicklime. The dry calcium hydroxide thus obtained was used for cleaning waste gases.

The following composition Nitrogen 80% by volume Oxygen 20% by volume Moisture 289 g/i! HCβ 12. La+g/f! HgCjl!
20.7% g/R 2 of waste gas lO,5f was passed at a temperature of 192° C. onto 265 mg of the abovementioned product.

HgCj of 7.4 tlg in total! 5.7 u out of 2
g was separated. Therefore, the separation rate was 76.8%.

Example 2 After mixing 28 g of quicklime with 0.37 g of sulfur, 17 g of water was added.
quenched with m(!). A pale yellow anhydrous product was obtained.

The following composition Nitrogen 80% by volume Oxygen 20% by volume Moisture 273*g/, g HC, e 11.5mg/ JHg CR
20,6LR/j! of the waste gas 11 (at a temperature of 186°C, the product 26
8 mg.

The total amount of HgCj is 7.4■! 5.4 ug of z was separated from the waste gas. Therefore, the separation rate was 73.3%.

Example 3 1.85 g of finely powdered lignite-open hearth coke was mixed with 0.85 g of sulfur flower.
37 g. This mixture was then mixed with 28 g of quicklime.

28 g of quicklime was slaked with 17 mff of water to obtain an anhydrous product.

The following composition Nitrogen 80% by volume Oxygen 20% by volume Moisture 292ff1g/, 9HCi'
12.3mg/j! Hg C41' 2
0.72ug/j! 10.3 J of waste gas,
At a temperature of 190° C., 283 mg of the product were introduced.

The total amount is 7.4 ug of HgCj! 6.2tIg out of 2
was separated. Therefore, the separation rate was 84.2%.

〔Effect of the invention〕

The gas purifying agent of the present invention contains activated calcium hydroxide powder as a main component and a water-soluble salt of a sulfur 8N substance.

Preferably by supporting and including on a surface active substance,
It is possible to purify waste gas by removing volatile harmful substances (volatile harmful heavy metals such as mercury, six volatile harmful substances) with high efficiency, inexpensively, and in a simple manner. Further, the gas purifying agent of the present invention can be easily produced by two simple steps using the method of the present invention. Furthermore, the present invention is effective in removing an extremely wide variety of harmful substances, and can be applied to a wide variety of waste gases.

In any case, the present invention is effective in achieving predetermined emission standards, and is extremely significant in that it contributes to simple and inexpensive waste gas purification.

Applicant: F.T.L.K.M.Beher, Representative Patent Attorney: Asa Kato Written amendment to legal proceedings (voluntary) Date: 30th, 1990

Claims (18)

[Claims] (1) A purifying agent for harmful substances such as heavy metals from gas and waste gas, consisting of a dry powder mainly composed of reactive calcium hydroxide and a water-soluble salt of a sulfur-containing substance of 0.01 to 5% by weight. . (2) The purifying agent according to claim 1, wherein the particle size is less than 200 μm. (3) The cleaning agent according to claim 1 or 2, wherein the dry powder containing reactive calcium hydroxide as a main component further contains 0.5 to 10% by weight of a surface active substance. (4) The purifying agent according to claim 3, characterized in that a water-soluble salt of a sulfur-containing substance is supported on a surface-active substance. (5) The cleaning agent according to claim 3, characterized in that a water-soluble salt of a sulfur-containing substance is mixed with a surface-active substance. (6) that the water-soluble salt of the sulfur-containing substance is selected from the group consisting of mercaptans, sulfides, polysulfides, polythionic acids and thiosulfates, and alkali metal and alkaline earth metal compounds thereof; Claim 1
5. The purifying agent according to any one of 5 to 5. (7) Dry powder mainly composed of reactive calcium hydroxide, 0.5 to 10% by weight of a surface active substance, and 0.5 to 5% by weight of a surface active substance.
% by weight of sulfur powder, which sulfur powder is free of heavy metals from gases and waste gases, supported on surface-active substances or mixed with calcium hydroxide and surface-active substances.
A purifying agent that removes harmful substances such as organic matter. (8) The purifying agent according to any one of claims 1 to 7, wherein the water content is 0.1 to 5% by weight. (9) The surface active substance is activated carbon, lignite-open-hearth coke,
A cleaning agent according to any one of claims 2 to 8, characterized in that it is selected from the group consisting of activated aluminum oxide, silicic acid gel and diatomaceous earth. (10) Calcium hydroxide as a main component according to any one of claims 1 to 9, for purifying gas and waste gas by removing harmful substances such as heavy metals and organic substances from gas and waste gas. In the method for producing dry or hydrated powder, (a)
(a) to quicklime before slaking the quicklime, (b) to slaked water during slaking, and (c) to calcium hydroxide after slaking.
At least one of (c) is a water-soluble salt of a sulfur-containing substance;
Or a manufacturing method characterized by adding a surface-active substance and a water-soluble salt of a sulfur-containing substance, or sulfur itself or sulfur supported on a surface-active substance. (11) Claim 10 characterized in that a water-soluble salt of a sulfur-containing substance is dissolved in water and supported on calcium hydroxide.
Manufacturing method described. (12) In a method for purifying gas and waste gas by removing harmful substances such as heavy metals and organic substances using a sulfur-containing substance, the amount of dry or water containing water-soluble salts of the sulfur-containing substance is 0.1 to 5 weight. % of finely powdered calcium hydroxide, a water-soluble salt of a sulfur-containing substance or a sulfur-supported surface-active substance, or a surface-active substance mixed with sulfur and calcium hydroxide, in a gas stream or A method for purification, characterized in that it is added to a waste gas stream and the sulfides of harmful substances, such as heavy metals and organic substances, are collected from the gas stream or the waste gas stream by suitable collection devices. (13) A purification method according to claim 12, characterized in that the purification agent according to claims 1 to 8 is used. (14) Process according to claim 12 or 13, characterized in that the gas stream or waste gas stream is treated with a sulfur compound in a temperature range from 0 to 400°C. (15) A water-soluble salt of a sulfur-containing substance, particularly sodium sulfate, is used in an amount ratio of 1 to 1000 times that of a volatile heavy metal such as mercury. purification method. (16) 5 to 2 sulfur to volatile heavy metals such as mercury
The purification method according to any one of claims 12 to 14, characterized in that the method is used at a quantitative ratio of 1,000 times. (17) In a method for purifying gas and waste gas by removing harmful substances such as volatile heavy metals and organic substances contained therein, a water-soluble salt of a sulfur-containing substance or sulfur is supported on a surface-active substance, or Claim 15 or 16 in a temperature range of 0 to 400°C in a state where it is mixed with a surface-active substance.
A purification method characterized in that it is used in the stoichiometric ratios described in . (18) The purifying agent according to any one of claims 1 to 9 or claim 1
Carbonization of chlorinated dioxins, furans, fluorocarbons, chlorinated hydrocarbons and/or polyaromatics, characterized by treating gas or waste gas using a purification agent produced by the method described in items 0 to 16. How to remove hydrogen.