JPH10202042A - Acidic gas removing agent and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent leaching of heavy metals in fly ash, etc., produced by neutralizing and removing acidic gas by producing an acidic gas removing agent in the form of an aq. slurry contg. a basic alkaline earth metallic compd. and a heavy metal, fixing agent and having a specified solid concn. SOLUTION: This acidic gas removing agent is made of an aq. slurry contg. a basic alkaline earth metallic compd. and a heavy metal fixing agent and having 0.1-50wt.% solid concn. The basic alkaline earth metallic compd. is, e.g. an alkaline earth metallic hydroxide such as calcium hydroxide or magnesium hydroxide or basic carbonate of an alkaline earth metal such as basic calcium carbonate or basic magnesium carbonate and it is preferably calcium hydroxide. The heavy metal fixing agent is not especially limited if it can fix heavy metals and it is, e.g. phosphoric acid such as metaphosphoric acid, pyrophosphoric acid or orthophosphoric acid or an inorg. phosphate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for producing acidic substances, especially acidic gas components, particularly sulfur oxides, from a wide range of waste gases containing acidic gas components, especially waste gas discharged from waste incineration equipment. Acidic gas that can neutralize and remove harmful acidic gas components such as hydrogen halide, and has the ability to immobilize heavy metals by suppressing the elution of heavy metals contained in its removal products, for example, fly ash from garbage incineration. The present invention relates to a remover and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, acidic gases in waste gas incineration waste gas are neutralized by calcium hydroxide and collected as fly ash together with dust, but at the same time, harmful heavy metals such as lead are also collected and fly ash. included. Therefore, fly ash is designated as "Specially managed municipal waste", and new plants are disposed of by landfill after intermediate treatment by the four methods specified by the Minister of Health, Labor and Welfare.

[0003]

SUMMARY OF THE INVENTION Under such circumstances, the present invention provides a method for removing fly ash and the like generated by neutralizing and removing acidic gas such as waste gas in a flue of a garbage incineration facility or the like. It is an object of the present invention to provide an acid gas remover capable of suppressing elution of heavy metals.

[0004]

The inventor of the present invention has conducted various studies to develop an acidic gas removing agent having the above-mentioned preferable characteristics, and as a result, has found that a basic alkaline earth metal compound and a heavy metal fixing agent, in particular, It has been found that an aqueous slurry containing a phosphorus-based inorganic compound and having a predetermined solid content concentration can be suitable for the purpose, and the present invention has been completed based on this finding.

That is, the present invention provides an acidic gas removing agent comprising an aqueous slurry containing a basic alkaline earth metal compound and a heavy metal fixing agent and having a solid content of 0.1 to 50% by weight. It is.

[0006]

DETAILED DESCRIPTION OF THE INVENTION The acid gas remover of the present invention comprises an aqueous slurry containing a basic alkaline earth metal compound and a heavy metal fixing agent. Examples of the basic alkaline earth metal compound include alkaline earth metal hydroxides such as calcium hydroxide and magnesium hydroxide, and alkaline earth metal basic carbonates such as basic calcium carbonate and basic magnesium carbonate. Among them, calcium hydroxide is particularly preferable.

[0007] The heavy metal fixing agent is not particularly limited whether it is organic or inorganic as long as it can fix heavy metals. Examples of such a fixing agent include phosphoric acid, inorganic phosphates and chelating agents. Examples of commercially available products include Ashnite R (manufactured by Kurita Water Industries Ltd.). Particularly advantageous as the heavy metal fixing agent is at least one phosphorus-based inorganic compound selected from phosphoric acid and inorganic phosphates.

Examples of the phosphoric acid include metaphosphoric acid, pyrophosphoric acid, orthophosphoric acid (which is usually referred to as phosphoric acid), triphosphoric acid, tetraphosphoric acid, and the like. A combination of more than one species may be used.

The inorganic phosphate is not particularly limited as long as it is an inorganic salt of the above-mentioned phosphoric acid. Examples of such an inorganic phosphate include hydroxyapatite, carbonate apatite, fluorinated apatite, and ammonium dihydrogen phosphate. , Diammonium hydrogen phosphate, ammonium phosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate, sodium phosphate,
Potassium dihydrogen phosphate, dipotassium hydrogen phosphate, potassium phosphate, calcium dihydrogen phosphate, calcium hydrogen phosphate, tricalcium phosphate, magnesium phosphate, magnesium ammonium phosphate, octacalcium phosphate, ammonium metaphosphate, Sodium metaphosphate, ammonium pyrophosphate, sodium pyrophosphate, potassium pyrophosphate, sodium hydrogen pyrophosphate, and the like,
These may be used alone or in combination of two or more.

The basic alkaline earth metal compound and the heavy metal fixing agent are usually contained in a mixture of a basic alkaline earth metal compound and a heavy metal fixing agent, a basic alkaline earth metal compound-heavy metal fixing agent composite. Or a mixture of a basic alkaline earth metal compound and a basic alkaline earth metal compound-heavy metal fixing agent complex, preferably in such a form and the basic alkaline earth metal compound is an alkaline earth metal compound. When the metal-like hydroxide, especially calcium hydroxide, is, for example, a mixture of calcium hydroxide and heavy metal fixing agent, calcium hydroxide-heavy metal fixing agent complex, calcium hydroxide and calcium hydroxide-heavy metal fixing agent complex and In particular, a mixture of calcium hydroxide and a phosphorus-based inorganic compound, a calcium hydroxide-phosphorus-based inorganic compound complex, Calcium oxide and calcium hydroxide - If a mixture of phosphorus-based inorganic compound complex is advantageous.

The aqueous slurry constituting the acid gas removing agent of the present invention needs to have a solid content concentration of 0.1 to 50% by weight, and this concentration is preferably 1 to 30% by weight, particularly preferably Advantageously, it is in the range from 5 to 15% by weight. If the solid concentration is less than 0.1% by weight, the acid gas removing ability is reduced, and if it exceeds 50% by weight, the viscosity of the suspension is undesirably increased. In the acid gas remover of the present invention, the content ratio of alkaline earth metal to phosphorus is preferably in the range of alkaline earth metal / phosphorus = 10 to 3000 in molar ratio, and this ratio is more preferably in molar ratio. It is advantageous to select from a range of preferably 30 to 1000, particularly 100 to 300. If this ratio is 10 or less, the reactivity with the acidic gas decreases, which is disadvantageous in terms of cost, and if it exceeds 3000, the ability to fix heavy metals decreases.

This aqueous slurry has a solid content uniformly dispersed in an aqueous medium. As the aqueous medium, water or a mixed medium of water and an organic solvent is advantageously used. Examples of the organic solvent include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol,
Examples thereof include alcohols such as butanol, isobutyl alcohol and tert-butyl alcohol, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, and ethers such as diisopropyl ether, dibutyl ether, tetrahydrofuran and dioxane.

The acid gas removed by the acid gas removing agent of the present invention is not particularly limited as long as it is a gas containing an acidic substance, for example, an acidic gas component. Examples include incineration waste gas, combustion waste gas generated by thermal power generation, waste gas from a boiler, and combustion waste gas of combustible waste such as old tires. By treating an acidic gas with the acidic gas remover of the present invention, it is possible to neutralize and remove acidic substances, especially acidic gas components, particularly harmful acidic gas components such as sulfur oxides and hydrogen halides, from the acidic gas. . As the removal treatment, a method of spraying an acidic gas remover on an acidic gas is preferably used.

The acidic gas remover of the present invention is prepared by uniformly mixing a basic alkaline earth metal compound, a heavy metal fixing agent and a suitable aqueous medium at a solid concentration of 0.1 to 50% by weight. It can be produced by dispersing into an aqueous slurry. The following production method is suitable for the acidic gas remover of the present invention in which calcium hydroxide is used as the basic alkaline earth metal compound. Calcium oxide or calcium hydroxide is converted into an aqueous solution or an aqueous suspension comprising at least one phosphorus-based inorganic compound selected from phosphoric acid and an inorganic phosphate and an aqueous medium, in a molar ratio of calcium / phosphorus. = A method of adjusting and processing in the range of 10 to 3000. As the aqueous medium, water or a mixed medium of water and an organic solvent is preferably used. At least one phosphorus-based inorganic compound selected from phosphoric acid and an inorganic phosphate is added to a calcium hydroxide aqueous suspension in a molar ratio of calcium / phosphorus = 10 to 3000.
Adjusting to the range and mixing. The aqueous calcium hydroxide suspension is preferably composed of calcium hydroxide and water, but a mixed medium of water and an organic solvent may be used instead of the water. In an aqueous medium, a powder of a complex of at least one phosphorus-based inorganic compound selected from phosphoric acid and inorganic phosphate and calcium hydroxide is mixed in a molar ratio of calcium / phosphorus =
A method in which the amount is adjusted in the range of 10 to 3000 and then added. A mixture of at least one phosphorus-based inorganic compound selected from phosphoric acid and inorganic phosphates and calcium oxide or calcium hydroxide powder is added to an aqueous medium in a molar ratio of calcium / phosphorus = 10 to 3000. Adjusting to the range described above and adding.

Among the above methods, calcium oxide is used in particular in an aqueous solution or an aqueous suspension comprising a phosphorus-based inorganic compound and an aqueous medium, in a molar ratio of calcium / phosphorus = 10 to 10%.
A method of adjusting to a range of 3000, uniformly mixing and digesting is preferred. The amount of aqueous medium used exceeds the digested amount,
The obtained acid gas remover is adjusted to have a predetermined solid content concentration. For example, when calcium oxide is reacted with an aqueous solution of a phosphorus-based inorganic compound, water / calcium oxide is usually 5 to 4500 in a molar ratio. , Preferably 20 to 100
Is adjusted to the range. As the aqueous medium, water or a mixed medium of water and an organic solvent is preferably used. The organic solvent is preferably one that delays the reaction, such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, tert-butyl alcohol, and the like. Examples thereof include ketones such as alcohol, acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, and ethers such as diisopropyl ether, dibutyl ether, tetrahydrofuran, and dioxane.

When calcium oxide is used as a raw material, the calcium oxide is not particularly limited, but is preferably dry-pulverized, for example, limestone is calcined in a rotary kiln, Beckenbach furnace, fluidized roasting furnace, or the like. After pulverization with a dry pulverizer such as a cage mill, a vibration mill, a ball mill, and a disk mill, the powder is classified. Such a calcium oxide powder has a cumulative 50% average particle diameter of usually 20 to 300 μm, preferably 20 to 110 μm.

The water used for producing the acid gas remover of the present invention is preferably fresh water, but may contain some impurities as long as the object of the present invention is not impaired. is there.

[0018]

Next, the present invention will be described in more detail by way of examples, which should not be construed as limiting the present invention. In addition, each gas concentration of each comparative example and an example is an average value of the one-hour integrated value.

First, a comparative example will be described for comparison. Comparative Example 1 17832 mol of quicklime was added to 500000 mol of water at 20 ° C and stirred until the digestion reaction was completed. Water was added to the obtained suspension, and a solid content concentration adjusted to 8% by weight was used as an acid gas remover, and a waste gas treatment was performed at the time of operation of a garbage incinerator with a treatment capacity of 200 tons / day. . The concentration of waste gas at the entrance to the waste gas flue of the waste gas treatment tower is 5 HCl.
80 ppm, SO ₂ is 40 ppm, HCl and SO ₂
The acid gas remover was sprayed in such an amount that the calcium hydroxide concentration was about 4 equivalents with respect to the total inlet concentration of. The gas concentration at the outlet of the tower was 20 ppm for HCl and 12 ppm for SO ₂ , and the removal rates were 97% for HCl and 70% for SO ₂ . At this time, fly ash was well collected by a bag filter, and the waste gas temperature was 175 to 185 ° C. When the content of each heavy metal in fly ash was measured, lead was 650 m
g / kg, cadmium 24 mg / kg, arsenic 6.9
5. mg / kg, total chromium 73 mg / kg, total mercury 6.
1 mg / kg was contained. As a result of carrying out the dissolution test of the fly ash as notified by the Environment Agency No. 13, the elution amount of each heavy metal was
Lead was 5 mg / l and mercury was 0.0007 mg / l. Cadmium, arsenic and hexavalent chromium were not detected.

Comparative Example 2 The specific surface area adjusted to a solid concentration of 8% by weight was 13 m ² /
The waste gas treatment was performed in the same manner as in Comparative Example 1 except that a suspension of g special slaked lime (manufactured by Okutama Industry Co., Ltd.) was used as an acid gas remover. The outlet gas concentration of the HCl was 21 ppm for HCl,
SO ₂ is 10 ppm, the removal rate is 96% for HCl,
SO ₂ was 75%. At this time, dust collection of fly ash is performed well with a bag filter, and the waste gas temperature is 175 to 175.
185 ° C. When the content of each heavy metal in the fly ash was measured, lead was 620 mg / kg and cadmium was 28 mg.
/ Kg, 8.9 mg / kg arsenic, 82 mg total chromium
/ Kg, and 5.8 mg / kg of total mercury. As a result of conducting an elution test of the fly ash as notified by the Environment Agency No. 13, the elution amount of each heavy metal was 7 mg / liter for lead and 0.0006 mg / liter for mercury. Cadmium, arsenic and hexavalent chromium were not detected.

[0021] was adjusted to Comparative Example 3 solid concentration of 8 wt%, a specific surface area of 40 m ² /
g of high specific surface area slaked lime (manufactured by Okutama Kogyo Co., Ltd.) was used as an acid gas remover, and the injection amount was adjusted to HCl and SO _2.
Waste gas treatment was carried out in the same manner as in Comparative Example 1 except that the amount of slaked lime was set to be about 2 equivalents to the total inlet concentration. The gas concentration at the outlet of the tower was 20 ppm for HCl and 20 ppm for SO ₂
There are 8 ppm, removal rate HCl 97%, the SO ₂
80%. At this time, dust from fly ash is favorably collected by a bag filter, and the waste gas temperature is 175 to 185 ° C.
Met. When the content of each heavy metal in the fly ash was measured,
1250mg / kg lead and 62mg / k cadmium
g, arsenic 12 mg / kg, total chromium 103 mg / k
g, total mercury was 8.9 mg / kg. The fly ash was subjected to the dissolution test of Notification No. 13 of the Environment Agency, and as a result, the elution amount of each heavy metal was 22 mg / liter for lead and 0.1 for mercury.
003 mg / l. Cadmium, arsenic and hexavalent chromium were not detected.

Example 1 17832 mol of quicklime was added to a mixed solution of 500000 mol of water and 17.8 mol of orthophosphoric acid at 20 ° C., and stirred until the digestion reaction was completed. The resulting suspension was used as an acid gas removing agent. Except for using, waste gas treatment was performed in the same manner as in Comparative Example 1. The gas concentration at the outlet of the tower was 20 ppm for HCl and 20 ppm for SO ₂
Was 8 ppm, and the removal rates were 97% for HCl and 80% for SO ₂ . At this time, dust from fly ash is favorably collected by a bag filter, and the waste gas temperature is 175 to 185 ° C.
Met. When the content of each heavy metal in the fly ash was measured,
650 mg / kg lead, 23 mg / kg cadmium,
It contained 8 mg / kg of arsenic, 78 mg / kg of total chromium, and 4.8 mg / kg of total mercury. As a result of performing a dissolution test of the fly ash as notified by the Environment Agency No. 13, the amount of lead dissolved was 0.2 mg / liter. Mercury, cadmium, arsenic and hexavalent chromium were not detected.

Example 2 17832 mol of quicklime was added to a mixed solution of 500000 mol of water and 59.4 mol of orthophosphoric acid at 20 ° C., and water was added to a suspension obtained by stirring until the digestion reaction was completed. Exhaust gas treatment was performed in the same manner as in Comparative Example 1 except that the solid content concentration adjusted to 8% by weight was used as an acid gas remover. The gas concentration at the outlet of the tower was 19 ppm for HCl and 9 for SO _2.
ppm, the removal rate was 97% for HCl and 78 for SO _2.
%Met. At this time, fly ash was well collected by a bag filter, and the waste gas temperature was 175 to 185 ° C. When the content of each heavy metal in the fly ash was measured, it was found that lead contained 620 mg / kg, cadmium 18 mg / kg, arsenic 11 mg / kg, total chromium 73 mg / kg, and total mercury 4.5 mg / kg. . As a result of performing a dissolution test of the fly ash as notified by the Environment Agency No. 13, the lead elution amount was 0.1 mg / liter. Mercury, cadmium, arsenic and hexavalent chromium were not detected.

Example 3 17832 mol of quicklime was added to a mixed solution of 500,000 mol of water and 178 mol of orthophosphoric acid at 20 ° C., and water was added to a suspension obtained by stirring until the digestion reaction was completed. Exhaust gas treatment was carried out in the same manner as in Comparative Example 1 except that the one adjusted to a partial concentration of 5% by weight was used as an acid gas remover. The gas concentration at the tower outlet was 23 ppm for HCl and 6 for SO _2.
ppm, the removal rate is 96% for HCl and 85% for SO _2.
%Met. At this time, fly ash was well collected by a bag filter, and the waste gas temperature was 175 to 185 ° C. When the content of each heavy metal in the fly ash was measured, it was found that lead contained 620 mg / kg, cadmium 31 mg / kg, arsenic 7 mg / kg, total chromium 65 mg / kg, and total mercury 4.5 mg / kg. . As a result of performing a dissolution test of the fly ash as notified by the Environment Agency No. 13, the lead elution amount was 0.1 mg / liter. Mercury, cadmium, arsenic and hexavalent chromium were not detected.

Example 4 17832 mol of quicklime was added to a mixed solution of 500,000 mol of water and 594 mol of orthophosphoric acid at 20 ° C., and water was added to a suspension obtained by stirring until the digestion reaction was completed. Exhaust gas treatment was carried out in the same manner as in Comparative Example 1 except that the component concentration adjusted to 8% by weight was used as an acid gas remover. The gas concentration at the outlet of the tower was 20 ppm for HCl and 1 for SO _2.
The removal rate was 97% for HCl and 7 for SO _2.
3%. At this time, fly ash was well collected by a bag filter, and the waste gas temperature was 175 to 185 ° C. When the content of each heavy metal in the fly ash was measured, it was found that lead contained 620 mg / kg, cadmium 21 mg / kg, arsenic 7 mg / kg, total chromium 75 mg / kg, and total mercury 4.3 mg / kg. . The fly ash was subjected to the dissolution test of No. 13 notified by the Environment Agency. As a result, the amount of lead dissolved was 0.01 mg / liter. Mercury, cadmium, arsenic and hexavalent chromium were not detected.

Example 5 To a mixed solution of 500000 moles of water and 17.8 moles of orthophosphoric acid at 20 ° C., 17832 moles of slaked lime (Okutama Kogyo Co., Ltd.) having a specific surface area of 13 m ² / g was added and mixed with stirring. Waste water treatment was carried out in the same manner as in Comparative Example 1 except that water was added to the suspension thus obtained, and a solid content concentration adjusted to 8% by weight was used as an acid gas remover. The gas concentration at the outlet of the tower was 15 ppm for HCl and 8 ppm for SO ₂ , and the removal rates were 97% for HCl and 80% for SO ₂ . At this time, fly ash was well collected by a bag filter, and the waste gas temperature was 175 to 185 ° C. When the content of each heavy metal in the fly ash was measured, it was found that lead contained 680 mg / kg, cadmium 28 mg / kg, arsenic 11 mg / kg, total chromium 71 mg / kg, and total mercury 5.1 mg / kg. . As a result of performing a dissolution test of the fly ash as notified by the Environment Agency No. 13, the amount of lead dissolved was 0.2 mg / liter. Mercury, cadmium, arsenic and hexavalent chromium were not detected.

Example 6 To a mixed solution of 500000 moles of water and 59.4 moles of orthophosphoric acid at 20 ° C., 17832 moles of slaked lime having a specific surface area of 13 m ² / g (manufactured by Okutama Kogyo Co., Ltd.) were added, followed by stirring and mixing. Waste water treatment was carried out in the same manner as in Comparative Example 1 except that water was added to the suspension thus obtained, and a solid content concentration adjusted to 8% by weight was used as an acid gas remover. The gas concentration at the outlet of the tower was 18 ppm for HCl and 10 ppm for SO ₂ , and the removal rates were 97% for HCl and 75% for SO ₂ . At this time, dust collection of fly ash is performed well with a bag filter,
The waste gas temperature was 175-185 ° C. When the content of each heavy metal in the fly ash was measured, the lead was 720 mg / kg,
Cadmium is 29mg / kg, arsenic is 14mg / kg,
Total chromium 78 mg / kg, total mercury 6.8 mg / kg
It was contained. As a result of performing a dissolution test of the fly ash as notified by the Environment Agency No. 13, the amount of lead dissolved was 0.2 mg / liter. Mercury, cadmium, arsenic and hexavalent chromium were not detected.

Example 7 A specific surface area of 13 m ² / g in 500,000 mol of water at 20 ° C.
No. 17832 mol of slaked lime was added, and 17.8 mol of orthophosphoric acid was added to the suspension obtained by stirring and mixing. The suspension obtained by stirring and mixing was used as the acid gas removing agent. Waste gas treatment was performed in the same manner as in Example 1. The gas concentration at the outlet of the tower was 23 ppm for HCl and 10 ppm for SO ₂ , and the removal rates were 96% for HCl and 75% for SO ₂ . At this time, fly ash was well collected by a bag filter, and the waste gas temperature was 175 to 185 ° C. When the content of each heavy metal in fly ash was measured, lead was 680 m
g / kg, cadmium 25mg / kg, arsenic 14m
g / kg, total chromium 78 mg / kg, total mercury 6.8
mg / kg. As a result of conducting a 13th dissolution test of the fly ash as notified by the Environment Agency, the lead elution amount was 0.2 m.
g / liter. Mercury, cadmium, arsenic and hexavalent chromium were not detected.

Example 8 To a mixed solution of 500000 moles of water and 594 moles of orthophosphoric acid at 20 ° C., 17832 moles of slaked lime (Okutama Kogyo Co., Ltd.) having a specific surface area of 13 m ² / g was added, followed by stirring and mixing. Waste gas treatment was carried out in the same manner as in Comparative Example 1, except that water was added to the suspension and the solid content was adjusted to 8% by weight, and the resulting suspension was used as an acid gas remover. The gas concentration at the tower outlet was 11 ppm for HCl and 5 ppm for SO ₂ , and the removal rates were 98% for HCl and 88% for SO ₂ . At this time, fly ash was well collected by a bag filter, and the waste gas temperature was 175 to 185 ° C. When the content of each heavy metal in the fly ash was measured, it was found that lead contained 800 mg / kg, cadmium 33 mg / kg, arsenic 12 mg / kg, total chromium 82 mg / kg, and total mercury 7.8 mg / kg. . The fly ash was subjected to the dissolution test of No. 13 notified by the Environment Agency. As a result, the amount of lead dissolved was 0.01 mg / liter. Mercury, cadmium, arsenic and hexavalent chromium were not detected.

Example 9 To a mixed solution of 500000 moles of water and 178 moles of orthophosphoric acid at 20 ° C., 17832 moles of slaked lime (Okutama Kogyo Co., Ltd.) having a specific surface area of 13 m ² / g was added, followed by stirring and mixing. Exhaust gas treatment was carried out in the same manner as in Comparative Example 1 except that the obtained suspension was used as an acid gas remover. The gas concentration at the tower outlet was 19 ppm for HCl and 10 ppm for SO ₂ ,
The removal rate was 97% for HCl and 75% for SO ₂ . At this time, fly ash was well collected by a bag filter, and the waste gas temperature was 175 to 185 ° C. When the content of each heavy metal in the fly ash was measured, the lead was 780 mg / k.
g, cadmium 27 mg / kg, arsenic 8 mg / k
g, total chromium 72 mg / kg, total mercury 4.2 mg / kg
kg. About this fly ash notification 13
As a result of conducting a number elution test, the amount of lead eluted was 0.1 mg / liter. Mercury, cadmium, arsenic and hexavalent chromium were not detected.

Example 10 To a mixed solution of 500,000 mol of water and 17.8 mol of orthophosphoric acid at 20 ° C., 17832 mol of slaked lime having a specific surface area of 40 m ² / g (manufactured by Okutama Industry Co., Ltd.) was added, followed by stirring and mixing. water was added to the obtained suspension which was, using those having a solid fraction concentration of 5 wt% as an acidic gas removing agent, hydrated lime concentration of about the injection amount with respect to the total inlet concentrations of HCl and SO ₂ Exhaust gas treatment was performed in the same manner as in Comparative Example 1 except that the amount was 2 equivalents. The gas concentration at the tower outlet is HCl
Is 22 ppm, SO ₂ is 8 ppm, and the removal rate is HC.
l is 96%, SO ₂ was 80%. At this time, fly ash was well collected by a bag filter, and the waste gas temperature was 175 to 185 ° C. When the content of each heavy metal in the fly ash was measured, it was found that lead contained 1380 mg / kg, cadmium 62 mg / kg, arsenic 12 mg / kg, total chromium 105 mg / kg, and total mercury 5.8 mg / kg. . As a result of performing a dissolution test of the fly ash as notified by the Environment Agency No. 13, the amount of lead dissolved was 0.2 mg / liter. Mercury, cadmium, arsenic and hexavalent chromium were not detected.

Example 11 To a mixed solution of 500000 moles of water and 59.4 moles of orthophosphoric acid at 20 ° C., 17832 moles of slaked lime (manufactured by Okutama Kogyo Co., Ltd.) having a high specific surface area of 40 m ² / g were added and mixed with stirring. Water was added to the resulting suspension, and a solid content concentration adjusted to 8% by weight was used as an acid gas remover, and the injection amount was adjusted so that the slaked lime concentration was about the total inlet concentration of HCl and SO _2. Exhaust gas treatment was performed in the same manner as in Comparative Example 1 except that the amount was 2 equivalents. The gas concentration at the tower outlet is HCl
Is 22 ppm, SO ₂ is 8 ppm, and the removal rate is HC.
l is 96%, SO ₂ was 80%. At this time, fly ash was well collected by a bag filter, and the waste gas temperature was 175 to 185 ° C. When the content of each heavy metal in the fly ash was measured, it was found that lead contained 1220 mg / kg, cadmium 68 mg / kg, arsenic 10 mg / kg, total chromium 101 mg / kg, and total mercury 5.3 mg / kg. . As a result of performing a dissolution test of the fly ash as notified by the Environment Agency No. 13, the amount of lead dissolved was 0.2 mg / liter. Mercury, cadmium, arsenic and hexavalent chromium were not detected.

Example 12 To a mixed solution of 500,000 mol of water and 178 mol of orthophosphoric acid at 20 ° C., 17832 mol of slaked lime (manufactured by Okutama Kogyo Co., Ltd.) having a high specific surface area of 40 m ² / g was added, followed by stirring and mixing. Water was added to the obtained suspension, and the solid concentration was 8% by weight.
Was used in the same manner as in Comparative Example 1 except that the injection amount was adjusted so that the slaked lime concentration was about 2 equivalents to the total inlet concentration of HCl and SO _2. Gas treatment was performed. The gas concentration at the tower outlet was 23 ppm for HCl and 6 ppm for SO ₂ , and the removal rate was HCl.
But 96%, SO ₂ was 85%. At this time, fly ash was well collected by a bag filter, and the waste gas temperature was 175 to 185 ° C. When the content of each heavy metal in the fly ash was measured, it was found that lead contained 1270 mg / kg, cadmium 57 mg / kg, arsenic 11 mg / kg, total chromium 111 mg / kg, and total mercury 6.8 mg / kg. . As a result of performing a dissolution test of the fly ash as notified by the Environment Agency No. 13, the lead elution amount was 0.1 mg / liter. Mercury, cadmium, arsenic and hexavalent chromium were not detected.

Example 13 To a mixed solution of 500,000 mol of water and 594 mol of orthophosphoric acid at 20 ° C., 17832 mol of slaked lime having a high specific surface area of 40 m ² / g (manufactured by Okutama Industry Co., Ltd.) was added, followed by stirring and mixing. Water was added to the obtained suspension, and the solid concentration was 8% by weight.
Was used in the same manner as in Comparative Example 1 except that the injection amount was adjusted so that the slaked lime concentration was about 2 equivalents to the total inlet concentration of HCl and SO _2. Gas treatment was performed. The gas concentration at the tower outlet was 16 ppm for HCl and 6 ppm for SO ₂ , and the removal rate was HCl.
But 97%, SO ₂ was 85%. At this time, fly ash was well collected by a bag filter, and the waste gas temperature was 175 to 185 ° C. When the content of each heavy metal in the fly ash was measured, it was found that lead contained 1410 mg / kg, cadmium 70 mg / kg, arsenic 10 mg / kg, total chromium 102 mg / kg, and total mercury 6.3 mg / kg. . The fly ash was subjected to the Environment Agency Notification No. 13 dissolution test. As a result, the amount of lead dissolved was 0.02 mg / liter. Mercury, cadmium, arsenic and hexavalent chromium were not detected.

Example 14 Calcium / phosphorus = 30 in 500,000 mol of water at 20 ° C.
0 (molar ratio) and slaked lime having a specific surface area of 11 m ² / g
17832 mol of calcium phosphate composite powder was added,
Waste gas treatment was carried out in the same manner as in Comparative Example 1 except that water was added to the suspension obtained by stirring and mixing, and a solid content concentration adjusted to 8% by weight was used as an acid gas remover. The gas concentration at the outlet of the tower was 14 ppm for HCl and 8 ppm for SO ₂ , and the removal rates were 98% for HCl and 80% for SO ₂ . At this time, fly ash was well collected by a bag filter, and the waste gas temperature was 175 to 185 ° C. When the content of each heavy metal in fly ash was measured, lead was 600m
g / kg, cadmium 25 mg / kg, arsenic 6 mg
/ Kg, total chromium is 65mg / kg, total mercury is 3.1m
g / kg. As a result of conducting a 13th dissolution test of the fly ash as announced by the Environment Agency, the lead elution amount was 0.03 m.
g / liter. Mercury, cadmium, arsenic and hexavalent chromium were not detected.

Example 15 Calcium / phosphorus = 30 in 500,000 mol of water at 20 ° C.
0 (molar ratio) and slaked lime having a specific surface area of 42 m ² / g
17832 mol of calcium phosphate composite powder was added,
Water was added to the suspension obtained by stirring and mixing, and a solid content concentration adjusted to 8% by weight was used as an acid gas remover, and the injection amount was adjusted to the concentration of slaked lime with respect to the total inlet concentration of HCl and SO _2. The waste gas treatment was carried out in the same manner as in Comparative Example 1 except that the amount was adjusted to about 2 equivalents. The gas concentration at the tower outlet is HC
1 is 12 ppm, SO ₂ is 6 ppm, and the removal rate is H
Cl is 98%, SO ₂ was 85%. At this time, fly ash was well collected by a bag filter, and the waste gas temperature was 175 to 185 ° C. When the content of each heavy metal in the fly ash was measured, it was found that lead contained 1220 mg / kg, cadmium 78 mg / kg, arsenic 14 mg / kg, total chromium 103 mg / kg, and total mercury 7.3 mg / kg. . The fly ash was subjected to the Environment Agency Notification No. 13 dissolution test. As a result, the amount of lead dissolved was 0.02 mg / liter. Mercury, cadmium, arsenic and hexavalent chromium were not detected.

Example 16 17832 mol of quicklime was added to a mixed solution of 300,000 mol of water and 17.8 mol of orthophosphoric acid at 20 ° C., and the mixture was stirred until the digestion reaction was completed. Except for using, waste gas treatment was performed in the same manner as in Comparative Example 1. The gas concentration at the outlet of the tower was 20 ppm for HCl and 20 ppm for SO ₂
Was 8 ppm, and the removal rates were 97% for HCl and 80% for SO ₂ . At this time, dust from fly ash is favorably collected by a bag filter, and the waste gas temperature is 175 to 185 ° C.
Met. When the content of each heavy metal in the fly ash was measured,
680 mg / kg lead, 22 mg / kg cadmium,
It contained 5 mg / kg of arsenic, 76 mg / kg of total chromium, and 4.1 mg / kg of total mercury. As a result of performing a dissolution test of the fly ash as notified by the Environment Agency No. 13, the amount of lead dissolved was 0.2 mg / liter. Mercury, cadmium, arsenic and hexavalent chromium were not detected.

Example 17 17832 mol of quicklime was added to a mixed solution of 500,000 mol of water and 178 mol of pyrophosphoric acid at 20 ° C., and the mixture was stirred until the digestion reaction was completed. Exhaust gas treatment was performed in the same manner as in Comparative Example 1 except that the concentration adjusted to 8% by weight was used as an acid gas remover.
The gas concentration at the outlet of the tower is 16 ppm for HCl and 6 pp for SO ₂ .
m, and the removal rates were 97% for HCl and 85% for SO ₂ . At this time, fly ash was well collected by a bag filter, and the waste gas temperature was 175 to 185 ° C. When the content of each heavy metal in the fly ash was measured, lead was found to be 6%.
It contained 70 mg / kg, cadmium 24 mg / kg, arsenic 8 mg / kg, total chromium 54 mg / kg, and total mercury 3.5 mg / kg. As a result of performing a dissolution test of the fly ash as notified by the Environment Agency No. 13, the lead elution amount was 0.1 mg / liter. Mercury, cadmium, arsenic and hexavalent chromium were not detected.

Example 18 17832 mol of quicklime was added to a mixed solution of 500,000 mol of water and 30 mol of hydroxyapatite at 20 ° C., and water was added to a suspension obtained by stirring until the digestion reaction was completed. Exhaust gas treatment was carried out in the same manner as in Comparative Example 1 except that the component concentration adjusted to 8% by weight was used as an acid gas remover. The gas concentration at the outlet of the tower was 15 ppm for HCl and 7 for SO _2.
ppm, and the removal rate was 97% for HCl and 83% for SO _2.
%Met. At this time, fly ash was well collected by a bag filter, and the waste gas temperature was 175 to 185 ° C. When the content of each heavy metal in the fly ash was measured, it was found that lead contained 610 mg / kg, cadmium 21 mg / kg, arsenic 5 mg / kg, total chromium 51 mg / kg, and total mercury 3.7 mg / kg. . As a result of performing a dissolution test of the fly ash as notified by the Environment Agency No. 13, the amount of lead dissolved was 0.2 mg / liter. Mercury, cadmium, arsenic and hexavalent chromium were not detected.

Example 19 To a mixed solution of 500000 moles of water at 20 ° C. and 30 moles of hydroxyapatite was added 17832 moles of slaked lime having a specific surface area of 13 m ² / g (manufactured by Okutama Industry Co., Ltd.), followed by stirring and mixing. Exhaust gas treatment was carried out in the same manner as in Comparative Example 1 except that the obtained suspension was used as an acid gas remover. The gas concentration at the tower outlet was 17 ppm for HCl and 10 ppm for SO ₂ ,
The removal rate was 97% for HCl and 75% for SO ₂ . At this time, fly ash was well collected by a bag filter, and the waste gas temperature was 175 to 185 ° C. When the content of each heavy metal in the fly ash was measured, the lead was 730 mg / k.
g, cadmium 25 mg / kg, arsenic 10 mg / k
g, total chromium 71 mg / kg, total mercury 3.2 mg / kg
kg. About this fly ash notification 13
As a result of conducting a number elution test, the amount of lead eluted was 0.2 mg / liter. Mercury, cadmium, arsenic and hexavalent chromium were not detected.

Example 20 17832 mol of slaked lime (manufactured by Okutama Kogyo Co., Ltd.) having a high specific surface area of 40 m ² / g was added to a mixed solution of 500000 mol of water at 20 ° C. and 30 mol of hydroxyapatite, followed by stirring and mixing. Water was added to the obtained suspension, and the solid concentration was 8% by weight.
Was used in the same manner as in Comparative Example 1 except that the injection amount was adjusted so that the slaked lime concentration was about 2 equivalents to the total inlet concentration of HCl and SO _2. Gas treatment was performed. The gas concentration at the outlet of the tower was 23 ppm for HCl and 8 ppm for SO ₂ , and the removal rate was HCl.
But 96%, SO ₂ was 80%. At this time, fly ash was well collected by a bag filter, and the waste gas temperature was 175 to 185 ° C. When the content of each heavy metal in the fly ash was measured, it was found that lead contained 1280 mg / kg, cadmium 69 mg / kg, arsenic 11 mg / kg, total chromium 105 mg / kg, and total mercury 6.3 mg / kg. . As a result of performing a dissolution test of the fly ash as notified by the Environment Agency No. 13, the amount of lead dissolved was 0.2 mg / liter. Mercury, cadmium, arsenic and hexavalent chromium were not detected.

[0042]

Since the acid gas remover of the present invention has an ability to fix heavy metals, it can remove acid gas from a wide range of waste gas containing acid gas components, especially waste gas discharged from waste incineration equipment. It can neutralize and remove substances, especially acidic gas components, especially harmful acidic gas components such as sulfur oxides and hydrogen halides, and remove elution of heavy metals contained in the removed products, for example, fly ash from garbage incineration. It has a remarkable effect that it can be suppressed. In addition, it is practically difficult to uniformly disperse the acid gas remover of the present invention uniformly in a conventional heavy metal fixing agent used for suppressing elution of heavy metals in industrial waste such as fly ash. On the other hand, by using the heavy metal fixing agent together with the original acid gas remover such as slaked lime at the time of acid gas treatment, the heavy metal fixing agent can be uniformly dispersed in the acid gas removal treated material such as fly ash, Elution can be more effectively suppressed.

Claims (9)

[Claims] 1. An acid gas remover comprising an aqueous slurry containing a basic alkaline earth metal compound and a heavy metal fixing agent and having a solid content of 0.1 to 50% by weight. 2. The acid gas remover according to claim 1, wherein the basic alkaline earth metal compound is calcium hydroxide. 3. The acid gas remover according to claim 1, wherein the heavy metal fixing agent is at least one kind of a phosphorus-based inorganic compound selected from phosphoric acid and an inorganic phosphate. 4. The acid gas remover according to claim 3, wherein the phosphoric acid is at least one selected from metaphosphoric acid, pyrophosphoric acid, orthophosphoric acid, triphosphoric acid, and tetraphosphoric acid. 5. The method according to claim 1, wherein the inorganic phosphate is hydroxyapatite,
Carbonate apatite, fluorapatite, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium phosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate, sodium phosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate , Potassium phosphate, calcium dihydrogen phosphate, calcium hydrogen phosphate, tricalcium phosphate, magnesium phosphate, magnesium ammonium phosphate,
The acid gas removal according to claim 3 or 4, wherein the acid gas is at least one selected from octacalcium phosphate, ammonium metaphosphate, sodium metaphosphate, ammonium pyrophosphate, sodium pyrophosphate, potassium pyrophosphate and sodium hydrogen pyrophosphate. Agent. 6. An aqueous solution or suspension containing at least one phosphorus-based inorganic compound selected from phosphoric acid and inorganic phosphates in a molar ratio of calcium oxide or calcium hydroxide. Calcium / phosphorus = 10-300
6. The method for producing an acidic gas remover according to claim 3, wherein the treatment is performed after adjusting to a range of 0. 7. An aqueous calcium hydroxide suspension containing at least one phosphorus-based inorganic compound selected from phosphoric acid and inorganic phosphates in a molar ratio of calcium / phosphorus = 10.
6. The method for producing an acid gas remover according to claim 3, wherein the mixture is adjusted to a range of from 3,000 to 3,000 and mixed. 8. A powder of a composite of at least one phosphorus-based inorganic compound selected from phosphoric acid and an inorganic phosphate and calcium hydroxide is added to an aqueous medium in a molar ratio of calcium / phosphorus = 10. 6. The method for producing an acid gas remover according to claim 3, wherein the acid gas is added after being adjusted to a range of from 3,000 to 3,000. 9. A mixture of at least one phosphorus-based inorganic compound selected from phosphoric acid and an inorganic phosphate and calcium oxide or calcium hydroxide powder in an aqueous medium is mixed with calcium / molar in a molar ratio. 6. The method for producing an acidic gas remover according to claim 3, wherein phosphorus is adjusted to a range of 10 to 3000 and added.