JPH03213143A - Preparation of exhaust gas treatment agent and treatment of exhaust gas - Google Patents

Abstract

PURPOSE:To enhance the denitration capacity of a used treatment agent by treating exhaust gas containing SO2 and/or HCl and NOx using a cured substance obtained on the way of the manufacturing of a specific exhaust gas treatment agent and treating the cured substance with ammonia. CONSTITUTION:To calcium oxide and/or calcium sulfate, aluminum oxide and silicon dioxide, one or more kinds of a substance selected from among a group consisting of substances capable of supplying a sulfuric acid compound, a halogen atom compound, sulfide and alkali metal hydroxide thereto is added and the resulting mixture is ground into a powdery form. Next, the powdery mixture is mixed with water to be subjected to hydration treatment to form a cured substance which is, in turn, treated with gas containing SO2 and/or HCl. Subsequently, the cured substance is treated with ammonia. Exhaust gas containing SO2 and/or HCl and NOx is treated using the obtained cured substance and, subsequently, the cured substance is treated with ammonia to be mainly used in the removal of NOx in exhaust gas. By this simple operation, the denitration capacity of a conventional used treatment agent can be enhanced.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention is applicable to the treatment of exhaust gas, especially SO2 and/or H
The present invention relates to a method for producing a treatment agent for exhaust gas containing Cl and NOx, and a method for treating exhaust gas.

[Prior art and problems to be solved by the invention] When various fuels are burned in the air, nitrogen in the air is oxidized and various nitrogen oxides, so-called NOx, are generated, which has a large impact on the environment. Various studies have been conducted on the removal of NOx from combustion exhaust gas, that is, denitrification methods.

As a dry denitrification method to which the present invention belongs, a novel denitrification method using a cured composition obtained by a relatively simple manufacturing method from low-grade raw materials has been disclosed (Japanese Patent Laid-Open No. 63-69523).

However, there was still a desire for improvement in the lifespan of the denitrification agent. The object of the present invention is to provide a method for producing an exhaust gas treatment agent having improved denitrification performance and an exhaust gas treatment method using the same.

[Means for Solving the Problems] This invention provides: (1) calcium oxide and/or calcium sulfate;
Aluminum oxide, silicon dioxide, or one or more substances selected from the group of substances capable of supplying sulfuric acid compounds, halogen element compounds, sulfides, and alkali metal hydroxides are added thereto and pulverized (2 ) A method for producing an exhaust gas treatment agent, which comprises mixing with water and hydrating it to form a cured product, (3) treating it with a gas containing SO2 and/or HCl2, and then (4) treating it with ammonia; An exhaust gas treatment method in which exhaust gas containing SO□ and/or HCl and NOx is treated using the cured product obtained in (2) above, and then the cured product is treated with ammonia, and then mainly NOx in the exhaust gas is removed. It is.

In the present invention, substances capable of supplying calcium oxide and/or calcium sulfate include by-products such as quicklime, slaked lime, carbonated lime, gypsum, cement, slag, dolomite plaster (containing lime), and acetylene slag.

Substances that supply aluminum oxide include, for example, alumina, aluminum hydroxide, aluminum silicate, sulfuric acid, alum, aluminum sulfide, aluminum sulfate,
Aluminum chloride, calcium aluminate, bentonite, kaolin, diatomaceous earth, zeolite, perlite,
These include compounds containing reactive aluminum such as bauxite, sodium aluminate, cryolite, and aluminum cleaning residue (alcite).

Substances that supply silicon dioxide include, for example, silicic acid, hydrous silicic acid, metasilicic acid, aluminum silicate, water glass, calcium silicate, cristobalite, tridymite, kaolin, bentonite, talc, perlite,
These include compounds containing reactive silicon dioxide, such as incineration ash such as whitebait, diatomaceous earth, glass, rice husk ash, and wood ash.

In addition, examples of substances that simultaneously supply two or more of the four types of compounds mentioned above 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 sources), slag and shirasu, andesite, chert, quartz trachyte, opal, zeolite, feldspar, clay minerals, ettringite (calcium sulfate, silicon dioxide, aluminum oxide, Minerals containing reactive silicon dioxide such as calcium oxide sources), oxides such as aluminum and calcium, chlorides, sulfates, etc., in-furnace desulfurization ash such as fluidized bed combustion ash, and used desulfurization agents for flue desulfurization Examples include sludge incineration ash, municipal waste incineration ash, cement waste, acetylene slag, and used wastewater treatment agents. Here, the used desulfurization agent refers to used calcium-based desulfurization agents such as Cab, Ca(OH)2, CaC0z, and JP-A-61
-Cab shown in 209038.

It refers to used desulfurization agents made of Al2203, S102, and CaSO4-based compositions.

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

The group of substances that can supply sulfuric compounds, halogen element compounds, sulfides, and alkali metal hydroxides are magnesium sulfate, calcium chloride, magnesium chloride, sodium sulfate, calcium sulfite, calcium hydrogen sulfate, sodium chloride, strontium chloride, calcium bromide,
These include calcium iodide, potassium chloride, sodium thiosulfate, sodium bicarbonate, calcium bicarbonate, calcium sulfide, iron sulfide, zinc sulfide, sodium hydroxide, and potassium hydroxide.

The proportions of the above components in the cured product are 1 to 90% as CaO for Ca and/or CaS04, 2 to 70% as Aβ203, and 2 to 70% as SiO2.
2-90%, preferably as CaO 2-80%, as CaSO3 0.1-70%, as 8β203
5-70%, as SiO2 5-8
It is 0%.

1 selected from the group of substances capable of supplying sulfuric compounds, halogen element compounds, sulfides, and alkali metal hydroxides;
When adding more than one species, Na 2 S O4C
a Cl 2 One or more types of NaCl 0.1-50% as sulfide, preferably calcium sulfide, 0.1-50% as alkali metal hydroxide, preferably NaOH and/or K
OH is 0.1-10%.

The hydration treatment (2) is, for example, disclosed in Japanese Patent Application Laid-Open No. 64-38130.
As disclosed in , it refers to the treatment necessary to advance the hydration reaction between the various substances (raw materials) mentioned above, such as normal pressure or high pressure room temperature water or hot water curing, humid air curing, steam curing, etc. It is classified into hardening hydration treatment and non-caking hydration treatment.

Curing hydration treatment refers to reducing the mixing ratio (solid-liquid ratio) of the various raw materials and water during treatment, for example, from 1:0.2 to 1:0.99.
This refers to a hydration treatment that promotes bonding between material particles and obtains a cured product.

Non-caking hydration treatment refers to a treatment that prevents material particles from bonding together and growing into coarse particles during the hydration treatment, and the solid-liquid ratio at the start of the treatment is increased, for example from l:1 to 1.20,
Hot water curing is a process in which raw materials are dispersed in water at 40°C to 180°C, and stirring, bubbling, circulation, shaking, etc. are performed for several minutes to several days to prevent the raw materials from settling and hardening at the bottom.

In the hydration treatment process, the important step of forming active compounds necessary for exhaust gas purification is completed after providing sufficient moisture necessary for the production of active substances in the treatment agent. Alternatively, most of it is consumed in the compound formation reaction.

Humid air curing in hardening hydration treatment is performed at a temperature of 10°C to 40°C.
It is preferable to carry out steam curing at a temperature of 50% to 100% relative humidity for several minutes or several tens of days.
Preferably, the temperature is 0°C and 100% relative humidity for several minutes to several days.

(3) The treatment with a gas containing SO2 and/or HCJ2 is a gas containing 1100pp to 90% of these gases at a temperature of 20℃ to 500℃, S
-' should be treated for a time sufficient for contacting at least 1 mole of S 02 and/or HCρ gas per Ikg of exhaust gas treatment agent, and exhaust gas to be normally treated can be used.

For the ammonia treatment (4), ammonia gas or ammonia water is used. There are no particular restrictions on the concentration of ammonia gas or ammonia water used, the treatment time, or the specific treatment method.
g/g) is preferably maintained at 10% or more.

It is not clear whether the ammonia retained by this ammonia treatment is simply physically adsorbed to the cured product or chemically reacts and bonds with the components of the cured product.

Furthermore, there is no certainty as to whether this treatment promotes the reaction between NOx and the constituent components of the treatment agent, the adsorption of NOx to the treatment agent, or whether the retained ammonia reduces NOx to N2. However, in any case, it is clear that this method is effective in removing NOx, as shown in the examples described later.

Furthermore, treatment with a substance that generates ammonia through thermal decomposition or chemical reaction, such as urea and its derivatives, pyridine, hydrazine, ammonium sulfate, or an aqueous solution of ammonium chloride, is equally effective in removing NOx.

When this exhaust gas treatment agent is used to treat exhaust gas containing SO2 and/or HCl2 in addition to NOx, the treatment of the cured material with the gas containing SO2 and/or HCl2 in (3) above does not require the treatment of the gas to be treated. Just use it.

The cured product before ammonia treatment was already developed by the applicant in JP-A No. 6
1-209038゜62-97640.62-2138
42.62-254824.63-69523.64-
As disclosed in 38130.64-80425, 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. 1-3.

That is, in FIG. 1, the cured product S is first
In addition to NOx, the abatement device 1 also collects SO2 and/or HC.
The exhaust gas G to be treated containing R is removed, and the exhaust gas G to be treated is treated with this exhaust gas to be treated, and then treated with ammonia A in the ammonia treatment device 3 to obtain the exhaust gas treatment agent R of the present invention.
Furthermore, it is filled into the second detoxification device 2 and is effective in removing harmful gases remaining in the exhaust gas to be treated, mainly in denitrification.

In FIG. 2, the cured material S is first filled into the second abatement device 2, and then passed through the first abatement device 1 to produce NOx and SO.
2 and/or HCfi, the remaining exhaust gas to be treated is treated with the treated exhaust gas, and then treated with ammonia A in the ammonia treatment device 3 to produce the gas treatment agent. R, then the first
It is filled into the abatement device 1 and performs primary abatement of the exhaust gas to be treated as a treatment agent with enhanced denitrification ability.

In FIG. 3, the exhaust gas to be treated is in the first. It passes through the second and third abatement devices in this order. The cured product S is first filled into the second abatement device 2, and performs a secondary abatement treatment on the remaining exhaust gas including NOx, SO□ and/or HCl2 that has passed through the first abatement device. treated with a processing gas, and then treated with ammonia A in an ammonia treatment device 3.
The treatment agent R of the present invention is then filled into the first abatement device 1 to perform primary abatement of the exhaust gas to be treated as a treatment agent with enhanced denitrification ability. Further, the processing agent whose denitrification ability has decreased is subjected to ammonia treatment in the ammonia treatment device 3' to restore the denitrification ability and is then charged into the third abatement device 4 to perform tertiary abatement of the gas to be treated.

This exhaust gas treatment agent will be explained in detail below with reference to Examples.

〔Example〕

Example 1 Coal ash (overseas coal) (8β0322%, 5ift64%)
51 parts by weight, 230 parts by weight of Ca(OH), CaSO3
45 parts by weight of water was added to 19 parts by weight of the powder and kneaded.
After steam curing at 5 to 100°C for 12 hours and drying at 130°C for 2 hours, the mixture was crushed to obtain a cured product with a particle size of 1.7 to 2.5 mm.

This cured product was treated with the gas shown in Table 2 at 5v100o (h
-'), was treated at a temperature of 130°C for 170 hours, then cooled to room temperature, and 40g of it was placed in a container containing NH3 gas 2β diluted with air to make 10% for 10 minutes and taken out. An exhaust gas treatment agent was obtained. The amount of ammonia retained was 3 mg per 1 g of treatment agent. This treatment agent 30m
j2 (bulk specific gravity 0.'l) was filled into the test apparatus, and the gas shown in Table 2 was heated at 5V2000 (h-') at a temperature of 13
The denitrification and desulfurization rates were determined by passing through the gas at 0° C. and measuring the concentrations of NOx and S02 in the inlet and outlet gases. The test results are shown in Table 3.

SO□ Ox 2 O2 2O 2 2nd (ppm) (ppm) (%) (%) (%) (%) Table 00 50 3 0 Remainder Table *At the end of the treatment with the gases shown in Table 2 of the cured product ,Sv
2000hr" is shown.

Example 2 Regarding the exhaust gas treatment agent obtained in Example 1, the S02 concentration in the composition of the gas to be treated was set to 800 ppm, and the NOx concentration was set to 110 ppm.
An exhaust gas treatment test was conducted under the same test conditions as in Example 1, except that the test conditions were changed to 0 pp, and the results shown in Table 4 were obtained.

Table 4 *The values obtained by testing the cured product under the same conditions as in Example 2 at the final stage of treatment with the gases shown in Table 2 are shown.

Example 3 Table 2 shows the cured product in Example 1! An exhaust gas treatment agent was obtained in the same manner as in Example 1 except that the treatment time with the gas was changed to 62 hours.

The ammonia retention amount of this treatment agent was 1.6 mg/+. An exhaust gas treatment test was conducted on this sample under the same experimental conditions as in Example 1, and the results are shown in Table 5.

Table 5 *At the end of the treatment with the gases shown in Table 2 of the cured product, 8■
The measured value is expressed by changing 2000hr-,' to 2000hr-,'.

Example 4 An exhaust gas treatment 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 as shown in Table 6 and the treatment time was changed to 44 hours.

The amount of ammonia retained was 2 mg/g, and the bulk specific gravity did not change. Regarding this treatment agent, an exhaust gas treatment test was conducted under the same test conditions as in Example 1, except that 500 ppm of HCl2 gas was added to the composition of the gas to be treated, and the results shown in Table 7 were obtained.

Table 6 10ppm 0ppm 0ppm 6% 14% Remaining CI2 O2 02 O2 2 2 Table *The values obtained by testing the cured product under the same test conditions as in Example 4 at the end of treatment with the gas shown in Table 6. show.

[Effect of the invention 1 Although the denitrification rate of the exhaust gas treatment agent of this invention is less than 50% and cannot be said to be high, it is possible to increase the denitrification ability of the conventional used treatment agent with a simple device and operation. Since the temperature during denitrification may be low, its practical value is extremely large.

[Brief explanation of drawings]

1 to 3 show conceptual diagrams of an exhaust gas treatment system incorporating the method of the present invention. l...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.

Claims (1)

[Claims] 1. (1) A substance capable of supplying calcium oxide and/or calcium sulfate, aluminum oxide and silicon dioxide is pulverized, (2) it is mixed with water and subjected to hydration treatment to form a hardened product, ( 3) A method for producing an exhaust gas treatment agent, which comprises treating with a gas containing SO_2 and/or HCl, and then (4) treating with ammonia. 2. (1) One or more substances selected from the group of calcium oxide and/or calcium sulfate, aluminum oxide, silicon dioxide, and substances capable of supplying sulfuric compounds, halogen element compounds, sulfides, and alkali metal hydroxides. (2) mixed with water and hydrated to form a hardened product, (3) treated with a gas containing SO_2 and/or HCl, and then (4) treated with ammonia. Method for manufacturing processing agent. 3. In a method for treating exhaust gas containing SO_2 and/or HCl and NOx, (1) a powder of a substance capable of supplying calcium oxide and/or calcium sulfate, aluminum oxide and silicon dioxide is mixed with water; An exhaust gas characterized in that the exhaust gas is treated using a cured product obtained by Japanese processing, then (2) the cured product is treated with ammonia, and further (3) NOx is mainly removed with the ammonia-treated cured product. Processing method. 4. The powder to be mixed with water is further added with one or more substances selected from the group of substances capable of supplying sulfuric compounds, halogen element compounds, sulfides, and alkali metal hydroxides. The exhaust gas treatment method according to claim 3.