JPH07102320B2 - Exhaust gas treatment agent manufacturing method and exhaust gas treatment method - Google Patents

Description

TECHNICAL FIELD The present invention relates to treatment of exhaust gas, particularly to a method for producing a treatment agent for exhaust gas containing SO ₂ and / or HCl and NOx and a method for treating exhaust gas.

[Problems to be Solved by Conventional Techniques and Inventions]

Nitrogen in the air is oxidized during combustion of various fuels in the air, and various nitrogen oxides, so-called NOx, are generated, which has a large effect on the environment.
Various methods of removing x, that is, denitration have been studied.

As a dry denitration method to which the present invention belongs, a novel denitration method using a hardened composition obtained from an inexpensive raw material by a relatively simple production method has been disclosed (JP-A-63-69523). However, it has been desired to improve the life of the denitration agent. It is an object of the present invention to provide a method for producing an exhaust gas treating agent having the same system and improved denitration performance, and an exhaust gas treating method using the same.

[Means for Solving the Problems]

The present invention provides (1) calcium oxide and / or calcium sulfate,
Aluminum oxide and silicon dioxide, or one or more substances selected from the group of substances capable of supplying a sulfuric acid compound, a halogen element compound, a sulfide and a hydroxide of an alkali metal, and powdered them (2 ) Mixing with water and hydration treatment to obtain a cured product, (3) SO ₂ and / or H
A method for producing an exhaust gas treating agent, which comprises treating with a gas containing Cl, and then (4) treating with ammonia, and SO ₂ and / or HCl and NOx using the cured product obtained in (2) above. This is an exhaust gas treatment method in which the exhaust gas contained is treated, then the cured product is treated with ammonia, and then mainly NOx in the exhaust gas is removed.

The substance capable of supplying calcium oxide and / or calcium sulfate in the present invention is, for example, quick lime, slaked lime, lime carbonate, gypsum, cement, slag, dolomite plaster (containing lime), and by-products such as acetylene slag.

The substance capable of supplying aluminum oxide is, for example, alumina, aluminum hydroxide, aluminum silicate, alum sulfate, alum, aluminum sulfide, aluminum sulfate,
Aluminum chloride, calcium aluminate, bentonite, kaolin, diatomaceous earth, zeolite, perlite,
Examples thereof include compounds containing reactive aluminum such as bauxite, sodium aluminate, cryolite, and aluminum cleaning residue (alcite).

The substance that can supply silicon dioxide is, for example, silicic acid, hydrous silicic acid, metasilicic acid, aluminum silicate, water glass, calcium silicate and cristobalite, tridymite, kaolin, bentonite, takule, perlite, shirasu, diatomaceous earth, glass. , Compounds such as fir-husk ash and incineration ash of charcoal containing reactive silicon dioxide.

In addition, examples of substances capable of simultaneously supplying at least two or more of the above-mentioned four types of compounds include coal ash and volcanic ash, coal fluidized bed combustion ash (calcium oxide, silicon dioxide, aluminum oxide, calcium sulfate source), cement And cement clinker (calcium oxide, silicon dioxide, aluminum oxide source), slag and silas, andesite, chert, quartz trachyte, opal, zeolite, feldspar, clay mineral, ettringite (calcium sulfate, silicon dioxide, aluminum oxide, calcium oxide) Source) such as reactive silicon dioxide, and oxides such as aluminum and calcium,
Minerals containing chlorides and sulfates, spent desulfurization ash such as fluidized bed combustion ash and used desulfurization agents for flue desulfurization, sludge incineration ash, municipal waste incineration ash, cement waste, acetylene slag, used wastewater treatment Examples include agents. Here, the used desulfurizing agent is shown in Japanese Patent Application Laid-Open No. 61-209038, which is a used desulfurizing agent such as CaO, Ca (OH) ₂ and CaCO _2.
It refers to a used desulfurizing agent composed of a CaO, Al ₂ O ₃ , SiO ₂ , and CaSO ₄ type composition.

Table 1 shows examples of chemical compositions of these representative raw materials.

The group of substances capable of supplying a sulfuric acid compound, a halogen element compound, a sulfide and a hydroxide of an alkali metal, magnesium sulfate, calcium chloride, magnesium chloride, sodium sulfate, calcium sulfite, calcium hydrogen sulfate, sodium chloride, strontium chloride, Calcium bromide,
Examples include calcium iodide, potassium chloride, sodium thiosulfate, sodium hydrogen carbonate, calcium hydrogen carbonate, calcium sulfide, iron sulfide, zinc sulfide, sodium hydroxide and potassium hydroxide.

The ratio of the above components in the cured product is ₁ to 90% of Ca and / or CaSO ₄ as CaO, ₂ to 70% of Al ₂ O ₃ , ₂ to 90% of SiO ₂ , and preferably 2 to 80% of CaO, CaSO ₄ is 0.1 to 70%, Al ₂ O ₃ is 5 to 70%, and SiO ₂ is 5 to 80%.

Selected from the group of substances capable of supplying sulfuric acid compounds, halogen element compounds, sulfides and alkali metal hydroxides 1
When more than one substance is added, one or more of Na ₂ SO ₄ , CaCl ₂ , and NaCl is 0.1 to 50% as a sulfide, preferably calcium sulfide is 0.1 to 50%, as an alkali metal hydroxide, preferably NaOH and /
Or KOH is 0.1-10%.

The hydration treatment of (2) means a treatment necessary for proceeding the hydration reaction between the above-mentioned substances (raw materials), as disclosed in, for example, JP-A-64-38130. It includes high-pressure room temperature water or hot water curing, wet air curing, steam curing, etc., and is classified into a hardening hydration treatment and a non-consolidating hydration treatment.

Curable hydration treatment is a small mixing ratio (solid-liquid ratio) of the raw materials and water at the time of treatment, for example, 1: 0.2 to 1: 0.99 to promote bonding between material particles, A hydration treatment for obtaining a cured product.

Non-consolidating hydration treatment is a treatment that prevents the material particles from binding to each other during the hydration treatment to grow into coarse particles, and the solid-liquid ratio at the start of treatment is increased, for example, 1: 1 to. It is set to 1:20, and in hot water curing, the raw material is dispersed in water at 40 ° C to 180 ° C, and stirring, bubbling, circulation, shaking, etc. are performed for several minutes to several days so that the raw material does not precipitate and harden at the bottom. is there.

In the hydration treatment process, after a sufficient amount of water necessary for the production of the active substance in the treatment agent is given, the important step of active compound formation necessary for exhaust gas purification is completed, Alternatively, most is consumed in the compound formation reaction.

Wet air curing in the curable hydration treatment is performed at a temperature of 10 ° C to 40 ° C.
Relative humidity of 50% to 100% for a few minutes or tens of days is preferable, and steam curing is performed at a temperature of 40 ° C to 180 ° C and a relative humidity of 1%.
At 00%, it is preferably several minutes to several days.

The treatment with the gas containing SO ₂ and / or HCl in (3) is performed at a temperature of 20 ° C. to 500 ° C. containing 100 ppm to 90% of these gases.
The above gas may be treated at a SV of 5 to 50,000 h ⁻¹ for a time sufficient to contact at least 1 mol of SO ₂ and / or HCl gas per 1 kg of the exhaust gas treating agent, and the exhaust gas to be usually treated can be used.

The treatment with ammonia in (4) uses ammonia gas or aqueous ammonia. There is no particular limitation on the concentration of the ammonia gas or ammonia water used, the treatment time, the specific method of treatment, etc., and the saturated retention amount of the cured product (exhaust gas treatment agent) (about 5 mg /
It is preferable to hold 10% or more of g).

It is not clear whether the ammonia retained by the ammonia treatment is simply physically adsorbed on the cured product or chemically reacted with the components of the cured product to be bonded.
Furthermore, whether this treatment promotes the reaction between NOx and the constituents of the treating agent or the adsorption of NOx to the treating agent, or whether the retained ammonia reduces NOx to N ₂ and so on, is there any conclusive evidence? However, in any case, it is obvious that it is effective in removing NOx as in the examples described later.

Further, treatment with a substance which produces ammonia by thermal decomposition or chemical reaction, such as urea and its derivatives, pyridine, hydrazine, ammonium sulfate or ammonium chloride aqueous solution, is also effective in removing NOx.

In addition to NOx, this exhaust gas treatment agent is used as SO ₂ and / or HCl.
When used in the exhaust gas processing including, SO ₂ of the (3)
And / or treatment of the cured product with a gas containing HCl
The gas to be processed may be used. The cured product before the ammonia treatment has already been disclosed by the applicant in JP-A-61-209038, 62-9764.
0,62−213842,62−254824,63−69523,64−38130,64−80
As disclosed in 425, since it has the performance of exhaust gas treatment such as desulfurization and denitration, it can be assembled into the exhaust gas treatment system shown in FIGS.

That is, in FIG. 1, the cured product S is first
The abatement device 1 removes the treated exhaust gas G containing SO ₂ and / or HCl in addition to NOx, and the treated gas is treated with this treated exhaust gas, and then treated with ammonia A in the ammonia treatment device 3. , The exhaust gas treating agent R of the present invention,
Further, it is effective in removing harmful gas remaining in the exhaust gas to be treated, which is filled in the second abatement device 2, mainly in denitration.

In FIG. 2, the cured product S is first charged in the second abatement device 2, and the abatement process of the treated exhaust gas containing NOx and SO2 ₂ and / or HCl remaining through the first abatement device 1 is performed. Then, the exhaust gas is treated with this exhaust gas to be treated, then treated with ammonia A in the ammonia treatment device 3 to become the exhaust gas treatment agent R of the present invention, and then filled in the first abatement device 1 to enhance the denitration ability. The treated agent is subjected to primary detoxification of the exhaust gas to be treated.

In FIG. 3, the exhaust gas to be treated passes through the abatement device in the order of the first, second and third abatement devices. The cured product S is first filled in the second abatement device 2 to perform a secondary abatement treatment of the remaining treated exhaust gas of NOx and SO ₂ and / or HCl that has passed through the first abatement device, and from this itself It is treated with a treatment gas, and then treated with ammonia A in the ammonia treatment device 3 to become the treatment agent R of the present invention, which is then filled in the first abatement device 1 to be treated as a treatment agent having an enhanced denitration capability. Performs primary removal of exhaust gas. Further, a process in which the denitrification ability and the treatment agent having decreased are subjected to ammonia treatment in the ammonia treatment device 3 ', the denitration capability is restored, and the third time detoxification device 4 is filled to perform the third detoxification of the gas to be treated.

The exhaust gas treating agent will be described in detail below with reference to examples.

〔Example〕

Example 1 51 parts by weight of coal ash (overseas coal) (AlO ₃ 22%, SiO ₂ 64%), Ca
(OH) ₂ 30 parts by weight, CaSO ₄ 19 parts by weight To a powdery material, 45 parts by weight of water was added and kneaded, steam-cured at 95 to 100 ° C for 12 hours, and 130 ° C.
After being dried for 2 hours, it was crushed to obtain a cured product having a particle size of 1.7 to 25 mm.

This cured product was treated with the gas shown in Table 2 at SV1000 (h ^-1 ) at a temperature of 130 ° C for 170 hours, then cooled to room temperature, 40 g of which was diluted with air to 10% NH ₃ gas. It was put in a container containing No. 2 for 10 minutes and taken out to obtain an exhaust gas treating agent of the present invention. The amount of ammonia retained was 3 mg per 1 g of the treating agent. 30 ml of this treating agent (bulk specific gravity 0.9) was filled in a test device, and the gas shown in Table 2 was passed through at SV2000 (h ^-1 ) at a temperature of 130 ° C, and the concentration of NOx and SO ₂ in the inlet and outlet gases was increased. Was measured to determine the denitration and desulfurization rate. The test results are shown in Table 3.

Table 2 SO ₂ (ppm) 900 NOx (ppm) 450 O ₂ (%) 6 CO ₂ (%) 13 H ₂ O (%) 10 N ₂ (%) Balance Example 2 The exhaust gas treating agent obtained in Example 1 was subjected to an exhaust gas treating test under the same test conditions as in Example 1 except that the SO ₂ concentration and the NOx concentration in the gas composition to be treated were changed to 800 ppm and 100 ppm, respectively, The results shown in Table 4 were obtained.

Example 3 An exhaust gas treating agent was obtained in the same manner as in Example 1 except that the treatment time with the gas having the composition shown in Table 2 of the cured product was changed to 62 hours. The ammonia retention of this treating agent was 1.6 mg / g. An exhaust gas treatment test was conducted on this sample under the same test conditions as in Example 1, and the results are shown in Table 5.

Example 4 An exhaust gas treating agent of the present invention was obtained in the same manner as in Example 1 except that the composition of the treatment gas for the cured product was changed to that shown in Table 6 and the treatment time was changed to 44 hours. Ammonia retention amount is 2 mg /
In g, the bulk density did not change. About this treatment
Except that 500 ppm of HCl gas was added to the composition of the gas to be treated,
An exhaust gas treatment test was conducted under the same test conditions as in Example 1, and
The results shown in the table were obtained.

Table 6 HCl 910ppm NO ₂ 80ppm SO ₂ 60ppm CO ₂ 6% O ₂ 14% N ₂ balance [Effects of the Invention] Although the denitration rate by the exhaust gas treating agent of the present invention is not high at 50% or less, it is possible to increase the denitrifying ability of the conventional used treating agent with a simple device and operation, and Since the temperature during denitration may be low, its practical value is extremely large.

[Brief description of drawings]

1 to 3 show conceptual diagrams of an exhaust gas treatment system incorporating the method of the present invention. 1 ... First abatement device, 2 ... Second abatement device, 3,3 '... Ammonia treatment device, 4 ... Third abatement device G ... Exhaust gas to be treated, S ... Cured product, R …… Exhaust gas treatment agent, A …… Ammonia.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location B01D 53/68 53/81 B01J 20/30 B01D 53/34 134 A (72) Inventor Takeshi Murayama Hokkaido 461-6, Satozuka, Toyohira-ku, Sapporo, Hokkaido Research Institute of Electric Power Company (72) Inventor, Kunihiro Mori Hokkaido, Toyohira-ku, Sapporo, Hokkaido 461-6, Research Institute of Hokkaido Electric Power Company (72) Toshiya Kodama, Toyohira-ku, Sapporo, Hokkaido 461-6 Satozuka, Hokkaido Research Institute of Electric Power Company (72) Inventor Hideki Nakamura 461-6, Satozuka, Toyohira-ku, Sapporo, Hokkaido Research Institute of Hokkaido Electric Power Company

Claims (4)

[Claims] 1. A material capable of supplying calcium oxide and / or calcium sulfate, aluminum oxide and silicon dioxide is pulverized, (2) mixed with water and hydrated to obtain a cured product, and (3) SO. _A method for producing an exhaust gas treating agent, which comprises treating with a gas containing ₂ and / or HCl and then treating with (4) ammonia. 2. (1) One selected from the group of substances capable of supplying calcium oxide and / or calcium sulfate, aluminum oxide, silicon dioxide, and a sulfuric acid compound, a halogen element compound, a sulfide and a hydroxide of an alkali metal. The above substances are pulverized, (2) mixed with water and hydrated to form a cured product, (3) treated with a gas containing SO ₂ and / or HCl, and then (4) treated with ammonia. A method for producing an exhaust gas treating agent, which is characterized. 3. A method for treating an exhaust gas containing SO ₂ and / or HCl and NOx, wherein (1) calcium oxide and / or calcium sulfate, aluminum oxide and a powder of a substance capable of supplying silicon dioxide are used as water. Exhaust gas is treated with a cured product obtained by mixing and hydration, and then (2) the cured product is treated with ammonia, and (3) the ammonia-treated cured product is mainly used.
An exhaust gas treatment method characterized by removing NOx. 4. The powdery substance mixed with water is further added with one or more substances selected from the group of substances capable of supplying a sulfuric acid compound, a halogen element compound, a sulfide and a hydroxide of an alkali metal. The method for treating exhaust gas according to claim 3, wherein