JPH0763581B2 - Manufacturing method of flue gas treatment agent - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to a method for producing a flue gas treatment agent, and more specifically, flue gas accompanying combustion, roasting, drying, etc. of fuels such as coal heavy oil and various wastes. The present invention relates to a method for producing a flue gas treatment agent for treating methane.

[Prior Art] Sulfur oxides, nitrogen oxides, halogens, halides, sulfuric anhydride contained in exhaust gas generated by combustion of fuels such as coal and heavy oil, industrial waste, municipal waste and sludge,
It is known that hydrogen sulfide, etc. not only harms buildings, structures, etc., but also exerts an extremely large effect on plants and animals as well as on the human body. Various methods have been developed.

For example, Japanese Unexamined Patent Publication (Kokai) No. 58-95551 discloses a desulfurizing agent for a fluidized bed in which alumina alumina cement or a mixture of alumina cement and a barium compound is kneaded with water, hydrated and hardened, and heated and dehydrated.

In addition, the applicant of the present application has already applied for a patent, and is disclosed in JP-A-61-2090.
In the method for producing lime, gypsum, silica, and alumina-based desulfurization denitration agents disclosed in 38 and 62-97640, it is described that after mixing the raw materials, water is added to perform room temperature room air curing or steam curing. .

All of these obtained by hydration hardening or curing are hardened bodies, and it was necessary to make them into a shape suitable for flue gas treatment by operations such as pulverizing and granulating and granulating after that.

[Problems to be solved by the invention]

An object of the present invention is to improve a method of hydration treatment in a conventional method for producing a flue gas treatment agent of lime, silica, or alumina so that it can be applied to various exhaust gas treatment processes. To provide.

[Means for solving problems]

This invention relates to a method for producing an flue gas treatment agent in which a substance capable of supplying calcium sulfate is added to and mixed with a substance capable of supplying calcium oxide, silicon dioxide and aluminum oxide. This is a production method in which it is dispersed in water.

Examples of substances that can supply calcium oxide in the present invention include quick lime, slaked lime, lime carbonate, cement, slag, by-product such as dolomite plaster (containing lime) and acetylene slag.

Examples of substances that can supply silicon dioxide include silicic acid, hydrous silicic acid, metasilicic acid, aluminum silicate, calcium silicate and cristobalite, tridymite, kaolin, bentonite, talc, perlite, shirasu, diatomaceous earth, and glass. Examples thereof include compounds containing silicon dioxide.

Examples of substances that can supply aluminum oxide include compounds containing reactive aluminium, such as alumina, aluminum hydroxide, aluminum silicate, calcium aluminate, bentonite, kaolin, diatomaceous earth, zeolite, perlite, bauxite, and cryolite. can give.

In addition, examples of other substances that can simultaneously supply 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, second Table shows one example), cement and cement clinker (calcium oxide, silicon dioxide, aluminum oxide source), slag and shirasu, andesite, chert, quartz trachyte, opal, zeolite,
Feldspar, clay minerals, ettringite (calcium sulfate, silicon dioxide, aluminum oxide, calcium oxide source), in-furnace desulfurized ash such as fluidized bed combustion ash and ash desulfurization agent after flue desulfurization, sludge incineration ash, municipal waste incineration ash , Cement waste, acetylene slag, and other waste materials.

In addition, two or more kinds of the above-mentioned four compounds may be used in the production of the flue gas treatment agent of the present invention, scraps, pulverized unused flue gas treatment agent, flue gas treatment agent in which unreacted substances remain. Can be a substance that can be supplied at the same time. Therefore, the loss of material in the manufacturing process can be extremely reduced.

Table 2 shows an example of the chemical composition of these typical substances.

In the exhaust gas treatment by the flue gas treatment agent of the present invention, the basic substances involved in the exhaust gas treatment are CaO, Al ₂ O ₃ , SiO ₂ and CaSO ₄ .

The basic substances involved in the flue gas treatment are not simply composed of a mixture of pure substances, but unexplained XCaO ・ Al ₂ O ₃・ ZSiO ₂・ YSO ₃・ nH ₂ O It is suggested that it may be a substance very similar to the sulfuric acid / calcium aluminate complex compound represented by.

In this formula, X = 4 to 7, Y = 2 to 4, X is greater than Y and Z = 0.1 to 3, preferably 0.3 to 1, or n is 5
Nos. 22 to 22 are reported in the process for the production of synthetic pigments (UK patent 1115482), but nothing is said about flue gas treatment.

The ettringite used in the form of a paper coating aqueous paste is composed of the following formula without SiO ₂ .

3CaO ・ Al ₂ O ₃ / 3CaSO ₄・ 31-32H ₂ O However, this ettringite has a low ability to purify flue gas, and the strength of the compound is low, so that it has little value as a flue gas treatment agent. However, the CaO, Al ₂ O ₃ , SiO ₂ and CaSO ₄ based compound into which SiO ₂ is incorporated according to the present invention is hard and can be made into fine particles, and the performance of desulfurization and the like is dramatically improved. Crystals of Ca (OH) ₂ cannot be detected by the X-ray diffraction method in the flue gas treatment agent at this time.

Absorbing and fixing acidic substances such as SO ₂ is CaO in the oxide display.
However, the effect of each pure substance on the performance of the flue gas treatment agent created is that SiO ₂ contributes to the sustainability of the performance, and Al ₂ O
₃ helps increase the reaction rate with SO _2, etc.
_{O 2, CaO, Al 2 O} 3, the hard material by CaSO ₄ is obtained, CaSO ₄ at this time is believed to play a role to promote the synthesis reaction mixture.

The most important thing in this reaction system is that these reactions have useful effects in the presence of nitrogen oxides. The presence of H ₂ O and O ₂ also has the power to accelerate the reaction.
That is, for example, in the desulfurization reaction, the presence of NO and NO ₂ significantly accelerates the reaction. In other words, the presence of NO, NO ₂ , SO _{2, and the} like in the exhaust gas to be treated makes it possible to expect the excellent effects of the treatment agent of the present invention.

There are many unclear points about these reaction mechanisms, but for example, in the reaction with Ca (OH) ₂ in a relatively low temperature range (30 to 500 ° C), NO or NO ₂ proceeds first, and Ca (NO ₂ ) ₂ To generate. Next, SO ₂ is instantly oxidatively fixed as CaSO ₄ , and part of the desorbed NO, NO ₂ reacts with Ca (OH) ₂ as Ca (NO ₃ ) ₂ and NO, NO _2. It is estimated that

_{2Ca (OH) 2 + 4NO 2} → Ca (NO 2) 2 + Ca (NO 3) 2 + H 2 O 2Ca (OH) 2 + 4NO + O 2 → 2Ca (NO 2) 2 + 2H 2 O 2Ca (NO 2) 2 + SO 2 + 1 / 2O ₂ → CaSO ₄ + Ca (NO ₃ ) ₂ + 2NO However, for example, the desulfurization ability of the flue gas treatment agent used in the present invention is not all specific effects due to the presence of NO and NO ₂ .

In addition, when viewed as a whole, the simple Ca (OH) ₂ + SO ₂ + 1 / 2O ₂ → CaSO ₄ + H ₂ O or Ca (OH) ₂ + SO ₂ → CaSO ₄ + H ₂ O CaSO ₃ + NO ₂ → It seems that the reactions of CaSO ₄ + NO and CaSO ₂ + 1 / 2O ₂ → CaSO ₄ are also proceeding.

Therefore, the flue gas treatment agent of the present invention has, for example, a catalytic effect of appropriately fixing NO as NO ₂ (NO → Ca (NO ₂ ) ₂ ), S
Properties to oxidize and fix substances such as O ₂ (SO ₂ , Ca (NO
₂ ) ₂ → CaSO ₄ ), and is composed of a substance having the property of fixing a part of NO, NO ₂ as Ca (NO ₃ ) ₂ and is characterized by simultaneous desulfurization and denitration.

However, the reaction mechanism for absorbing and removing HCl, HF, and Cl in the coexistence of NOx is considered to be slightly different from that of SO ₂ and SO ₃ . This is because as the flue gas treatment reaction proceeds, the halogenation rate is faster than Ca (OH) ₂ fixing nitrogen oxides as Ca (NO ₃ ) ₂ as in the case of SO _2. The preferential element-mediated oxidation reaction results in the formation of only small amounts of Ca (NO ₃ ) ₂ . For this reason, the denitrification capacity is inevitably lower than that of SO ₂ .

What is important in the flue gas treatment of the present invention is that NOx is contained in the flue gas.
When present, the oxidation by an intermediate substance represented by the formation of Ca (NO ₂ ) ₂ plays a dominant role, the decomposition reaction of the intermediate substance was found, and the substance that significantly advances this reaction is It is that it is the most important constituent substance of the flue gas treatment agent of the present invention, and that the coexistence of H ₂ O and O ₂ promotes the above-mentioned reactions.

The hydration treatment in this invention means the above-mentioned substances (raw materials).
The treatment required to promote the hydration reaction between
Wet air curing and steam curing were already known. These conventional curing should be called curable hydration treatment, so that the solid-liquid ratio at the time of kneading is small, for example, by promoting the bonding between the material particles by setting it to 1: 0.2 to 1: 0.80, the cured body is It was a hydration treatment to obtain.

On the other hand, the hydration treatment of the present invention should be called, as it were, a non-consolidating hydration treatment, which is a treatment for preventing the material particles from binding to each other during the hydration treatment and growing into coarse particles. The solid-liquid ratio at the start is set to a large value, for example, 1: 1 to 1:20. If the solid-liquid ratio is less than 1: 1, sufficient dispersibility of the particles is lost, particles tend to combine to grow into coarse particles, and problems such as inability to stir occur. If the solid-liquid ratio exceeds 1:20, the amount of substances that elute from the material particles will increase, so the performance of the finishing treatment agent may deteriorate.In addition, the power used when spraying it as it is into a flue gas as a high water content slurry is used. And the cost for separation and drying when used after solid-liquid separation are increased, which is not preferable. Specifically, it is a treatment in which the raw material is dispersed in water and stirring, bubbling, circulation, shaking, etc. are carried out for several minutes to several days so that the raw material does not precipitate and harden in the lower part. The liquid temperature during the treatment is preferably 40 ° C to 180 ° C.

In these curing processes, 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 flue gas purification is completed, and during this period, a part of the water or Most are consumed in the compound formation reaction.

The ultrafine particles that have been hydrated while being dispersed in water can be directly sprayed into the exhaust gas as a highly water-containing slurry for use in the exhaust gas treatment.

Further, the slurry may be subjected to solid-liquid separation by a conventional method and dried to form ultrafine particles, or may be further pressure-molded to form coarse particles.

In compression molding, particles of several millimeters such as ultrafine particles, fine particles, and coarse particles, and particles of about 10 mm can be similarly molded without adding a binder.

The molding pressure varies depending on the application of the agent and the shape of the molded product (tablet shape, plate shape, honeycomb shape, Raschig ring, etc.), but in the case of relatively large particles that are packed in layers, 10 kg / cm ^{2 to} 10 t /
cm ² , 0.01 to several mm When manufacturing particles, several kg / cm ² to several t /
It is cm ² .

When the coarse and fine particulate flue gas treatment agent is dried by dielectric heating, the treatment can be performed from the inside. Therefore, for example, the drying time can be completed several times earlier than the hot air treatment. Further, in the case of a coarse, fine particulate flue gas treatment agent used in a method of suspending flue gas in a dry state, the molded product after curing is 30 ° C. or higher, preferably in the range of 50 ° C. to 500 ° C., 0.1
Although the performance of the treating agent can be further improved by drying for 10 hours, the preferable upper limit of the water content of the treating agent varies depending on the symmetrical product. For example, desulfurization is 10
%, De-HCl, de-HF is 25%, de-H ₂ S is 20%, etc.

In order to bring the flue gas treatment agent of the present invention into contact with the exhaust gas, the gas is filled by layering a coarse or particulate flue gas treatment agent of a few mm to a few tens mm that is wet or dried into a layer such as a moving layer or a fixed layer. Pass through and make contact. In the case of dry ultrafine particles, the contact area is increased by suspending the agent by the force of the flow of exhaust gas, and the collision between agent particles induces the exposure of a new surface of the agent,
Improve performance. At this time, the agent must be dispersed in the exhaust gas as widely as possible.

When spraying a high water content slurry into the exhaust gas as it is, it is possible to increase the contact area with the exhaust gas and to synergize the SO ₂ uptake effect by the liquid by spraying with a general method to make the droplets as fine as possible. Exhaust gas can be effectively treated.

In the treatment of flue gas that is dispersed and suspended in flue gas, the reacted portion of the treatment agent is peeled and abraded by the mutual contact and collision of particles, and the particle size of the agent decreases as the treatment reaction proceeds. The flue gas treatment is preferred so that the strength and form of the flue gas treatment agent and the agent to be extracted after completion of the reaction have a difference in particle size from the agent newly supplied. The treatment agent dispersed or suspended in the gas after the exhaust gas treatment can be collected by collecting particles that are wet or dried at the exhaust gas temperature by a cyclone, an electrostatic precipitator, a filter type precipitator, or other general methods. The collected flue gas treating agent can be repeatedly used until there is no unreacted material.

The treatment temperature of the exhaust gas of the flue gas treatment agent can be carried out by a conventional method in a wide temperature range, that is, 10 ° C to 1200 ° C, preferably 30 ° C to 1000 ° C for desulfurization, 50 ° C to 400 ° C for desulfurization, and dehydrochlorination.
Is 30 ° C to 1000 ° C, and HF and H ₂ S are 30 ° C to 1000 ° C. The pressure may be normal pressure, but the performance can be further improved by pressurizing the region where the smoke and the smoke treatment agent contact.

Examples will be described below.

〔Example〕

Example 1 Various materials shown in Table 2 are mixed by adding water according to the formulation shown in Table 3. Then, it was aged in hot water of 98 ° C. for 2 hours and 12 hours so as not to precipitate, and kept floating in the liquid for curing. The thus obtained slurry as it was was used as the treating agent of Example 1-1 (2-hour curing product) and Example 1-2 (12-hour curing product). Further, the slurry of Example 1-2 was subjected to solid-liquid separation and then dried to obtain a white ultrafine particle particle as it was, which was molded at a pressure of 640 kg / cm ² in Example 1-3 (particle size: 1.7 to 2.5 mm). The obtained coarse particles were used as the treating agent of Example 1-4. In the case of ultra-fine particles obtained by drying the slurry as it is, after spraying (floating) the ultra-fine particulate flue gas treatment agent into the flue gas, it is solid and vaporized by the filtration type dust collector installed on the downstream side. Separated. The performance was ascertained by measuring the target component in the separated gas. In the case of coarse particles, the treatment agent was layeredly filled in the reaction tube to perform exhaust gas treatment.

The flue gas treatment performance test was conducted under the conditions shown in Tables 4 and 5 with SO ₂ , NO
It was conducted for x, SO ₃ , HF, HCl, Cl _2, etc.

The specific surface area was measured by the BET method after degassing the sample at 200 ° C. (the same applies to the following Examples and Comparative Examples). The test results are shown in Table 6.

Example 2 According to the formulations shown in Table 3, various materials shown in Table 2 were prepared.
In the same manner as in Example 1-4, molding was carried out at a pressure of 640 kg / cm ² , the particle size was adjusted to 1.7 to 2.5 mm, and gas was passed through the flue gas treatment agent packed in layers to confirm the performance.

The flue gas treatment performance test was conducted under the conditions shown in Table 5 under the conditions of SO ₂ , SO ₃ , NO
For x, HF, HCl, Cl, etc., the results are shown in Table 6 together with the specific surface area.

Comparative Example 1 According to the formulations shown in Table 3, various materials shown in Table 2,
Add water and mix. 95-100 ℃ in the presence of water
Heat to 12 hours and cure. Exhaust gas treatment was carried out by pulverizing the hardened material and spraying (floating) the flue gas treatment agent into fine particles with a particle size of about 1 mm or less in the exhaust gas.

The flue gas treatment performance test was conducted under the conditions shown in Table 4 with SO ₂ , SO ₃ , NOx,
The results of HF, HCl, Cl ₂ etc. are shown in Table 6 together with the specific surface area.

[Effects of the Invention] The flue gas treatment agent of the present invention comprises CaO, SiO ₂ , Al ₂ O ₃ and CaSO ₄
Since it is mainly composed of substances that can supply ash, raw materials include coal ash, cement, volcanic ash, slag, shirasu, fluidized bed combustion ash, used flue gas treatment agent (including unused desulfurization agent), clay, etc. A wide range of raw materials can be used and can be used.

Further, the obtained flue gas treatment agent can be subjected to spray treatment with slurry of exhaust gas, floating treatment with dry fine particles, moving bed treatment with compression molded particles, fixed bed treatment, etc. The method suitable for the smoke generating facility can be adopted. Further coal ash, slag, spent desulfurization agent, waste glass, etc. can be utilized wastes such as fluidized bed combustion ash, SO ₂ not only useful as a resource technology,
The acid substances and other harmful components contained in the flue gas such as SO ₃ , NOx, HF, HCl and Cl ₂ can be removed with high efficiency and at low cost, which is extremely important in contributing to pollution prevention.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication B01D 53/68 53/74 53/81 B01D 53/34 132 Z 134 C (72) Inventor Toshiya Kodama 6 461 Satotsuka, Toyohira-ku, Sapporo, Hokkaido, Hokkaido Research Institute of Electric Power Company (72) Inventor, Takeshi Murayama 461-6, Satozuka, Toyohira-ku, Sapporo City, Hokkaido (56) Reference: Japanese Patent Laid-Open No. 62-97640 (JP, A) JP 61-209038 (JP, A) JP 58-95551 (JP, A) JP 56-91824 (JP, A) JP 51-90991 (JP, A) Kai 56-500837 (JP, A) JP 52-138079 (JP, A)

Claims (2)

[Claims] 1. A method for producing an flue gas treatment agent, wherein a substance capable of supplying calcium sulfate is added to a substance capable of supplying calcium oxide, silicon dioxide and aluminum oxide, and the hydration treatment is performed by using a raw material as water. And a solid-liquid ratio of the dispersion liquid is 1: 1 to 1:20. 2. The production method according to claim 1, wherein the temperature of the dispersion liquid is 40 ° C. to 180 ° C.