JPH07185320A - Activated desulfurization and denitration method by using new flue gas treating agent - Google Patents

Abstract

PURPOSE:To inexpensively produce a new flue gas treating agent high in performance by adding calcium chloride to a flue gas treating agent consisting of alkaline earth metal carbonate in a specified ratio. CONSTITUTION:This new flue gas treating agent is characterized by adding 1-10wt.% of calcium chloride to a conventional treating agent consisting of alkaline earth metal carbonate. Various methods can optionally be adopted to prepare this new treating agent. For example, a powdery calcium chloride is mixed with a powdery alkaline earth metal carbonate. Or, the calcium chloride in solid, slurry or aq. soln is added to the alkaline earth metal carbonate in slurry form. Further, the slurry mixture is dried and solidified. In this way, the alkaline earth metal carbonate which have been conventionally considered to be active only at high temp. or in water can be activated even at a far lower temp.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for activating a flue gas treatment agent comprising a carbonate of an alkaline earth metal, which is conventionally effective only at high temperatures or in water.

[0002]

2. Description of the Related Art Sulfur oxides, nitrogen oxides, etc., contained in the exhaust gas generated by the combustion of coal, heavy oil, etc., not only harm buildings, structures, etc., but are also extremely large for animals, plants and human bodies. It has been found that it has an influence, and methods for removing the above substances in exhaust gas, that is, desulfurization and denitration methods have been studied, and various methods have been developed.

The desulfurization method is roughly classified into a dry method, a semi-dry method and a wet method. The methods shown in Table 1 are known as the dry method and the semi-dry method to which the present invention belongs.

[0004]

[Table 1] In the absorption method shown in Table 1, expensive NH ₃ is required for the regeneration of the reactant (sulfur or sulfur compound recovery) (active manganese oxide method), or a valuable reducing gas is required (Alkalisation). Doalumina method) or high reaction temperature (alkalized alumina method, lime blowing method).

The adsorption method has drawbacks in that the activated carbon used is expensive and easily deteriorates. In the catalytic oxidation method, the vanadium-based catalyst used is expensive and easily deteriorates, and the reaction temperature is relatively high. There is a point.

On the other hand, the semi-dry desulfurization method mainly uses Ca (OH) ₂ as an absorbent, and is simpler and less expensive than the dry method and wet limestone gypsum method (hereinafter abbreviated as wet method). Is low in desulfurization performance and expensive Ca (OH)
There are problems such as an increase in running cost due to the use of ₂ .

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to solve various problems of conventional dry and semi-dry desulfurization methods by activating desulfurization and denitrification ability of alkaline earth metal carbonates. The purpose is to provide an inexpensive and high-performance flue gas treatment agent and a desulfurization and denitration method.

[0008]

According to the present invention, a flue gas treating agent comprising an alkaline earth metal carbonate and calcium chloride
It is a desulfurization and denitration activation method for a flue gas treatment agent, which is characterized by adding 10 to 10% by weight.

Ca used in the semi-dry or dry method
It is considered that (OH) ₂ reacts as shown in the following formula (1) or (2).

Ca (OH) ₂ + SO ₂ → CaSO ₃ + H ₂ O ... (1) Ca (OH) ₂ + SO ₂ +1/20 ₂ → CaSO ₄ + H ₂ O ... (2) Even though the main component is alkaline earth metal carbonate, the same reactions as in formulas (1) and (2) proceed as shown in formulas (3) and (4), and alkaline earth metal sulfate or S in the exhaust gas as sulfite
O ₂ can be fixed and removed.

[0011] _{CaCO 3 + SO 2 → CaSO 3} + CO 2 ... (3) CaCO 3 + SO 2 +1/20 2 → CaSO 4 + CO 2 ... (4) Conventionally, an alkaline earth metal carbonate, with SO ₂ in the flue gas Due to its low reactivity, it has been thought that it mainly reacts with SO ₂ in a high temperature range of 700 to 800 ° C. or higher (in-furnace desulfurization method) or water (thermal method). The present invention can provide a flue gas treatment agent capable of removing SO ₂ at a relatively low temperature even in the gas phase by adding calcium chloride.

In the present invention, the alkaline earth metal carbonate has calcium and magnesium as the alkaline earth metal, and the raw materials to be actually used are limestone, calcium carbonate, magnesium carbonate, dolomite, cement, slag, and used. Examples thereof include substances containing an alkaline earth metal carbonate such as a desulfurizing agent.

The addition ratio of calcium chloride to the alkaline earth metal carbonate is preferably 100: 1 to 10 by weight. If the addition amount is less than 1%, the effect of addition is not sufficiently exhibited, and if it exceeds 10%, the effect of addition is not improved.

As a method of addition, a method of mixing both in a powder form, a method of simultaneously pulverizing and mixing, a method of adding calcium chloride in the form of a solid, a slurry or an aqueous solution to a slurry of an alkaline earth metal carbonate. Etc., any method can be adopted. When water is used for the adding operation, the amount of water after mixing is appropriately 10 to 500 parts by weight per 100 parts by weight of dry matter. After addition, if necessary, dry and solidify,
Alternatively, it is granulated by a known method. Drying condition is 50 ~
It is preferably several seconds to 10 hours at 500 ° C.

The mixture obtained by the above addition method is
It can be used as a smoke treatment agent in the form of slurry, powder or granules.

When it is used as a slurry, it is sprayed into a flue passage through which the exhaust gas to be treated passes or a spray dryer, and is collected and discharged by a known dust collecting device such as a bag filter.

When it is used in the form of powder, it may be carried out in accordance with the slurry, or a method of supplying it to a fluidized bed or a spouted bed can be adopted. When a granular material is used, a powdery material can be molded by a known method such as a disk pelleter and used in a moving bed, a fixed bed, a fluidized bed or a spouted bed.

The treatment temperature of the exhaust gas is room temperature to 300 ° C, preferably 60 to 250 ° C.

[0019]

Example 1 Water was added to commercially available calcium carbonate to adjust the slurry concentration to 1
It was adjusted to 6.7% and kept at 95 ° C., and commercially available calcium chloride was added at the ratio shown in Table 2, and after stirring for 30 minutes, 20
It was dried at 0 ° C. for 2 hours to obtain a flue gas treatment agent. A performance evaluation test was conducted using these agents under the test conditions shown in Table 3,
The desulfurization rate and the denitration rate after 5 hours were obtained and shown in Table 2.

The measurement results of the specific surface area are also shown in the table. The specific surface area was measured by the BET method after degassing the sample at 300 ° C. for 1 hour.

Example 2 Commercially available magnesium carbonate was made into a slurry having a concentration of 16.7%, kept at 95 ° C., commercially available calcium chloride was added at the ratio shown in Table 2, and after stirring for 30 minutes, at 200 ° C. It is dried for 2 hours, and a performance evaluation test is conducted under the conditions shown in Table 3,
The results are shown in Table 2.

Example 3 Commercially available limestone pulverized to 200 mesh or less and commercially available calcium chloride were mixed with each other at a ratio shown in Table 2 to obtain an flue gas treatment agent. The same performance evaluation test as in Example 1 was performed, and the results are shown in Table 2.

Example 4 Commercially available calcium chloride was added to the limestone slurry kept at 95 ° C. in the ratio shown in Table 2, and after stirring for 30 minutes,
It was dried at 200 ° C. for 2 hours to obtain a flue gas treating agent. The same performance evaluation test as in the previous example was conducted, and the results are shown in Table 2.

Comparative Example 1 A performance evaluation test was conducted on a sample of calcium carbonate alone obtained by the same operation as in Example 1 except that calcium chloride was not added, and the results are shown in Table 2.

Comparative Example 2 A performance evaluation test was conducted on a sample of magnesium carbonate alone obtained by the same procedure as in Example 2 except that calcium chloride was not added, and the results are shown in Table 2.

Comparative Example 3 Commercially available calcium chloride was subjected to a performance evaluation test under the same conditions as in Example 1, but no activity related to desulfurization and denitration was observed under any temperature condition.

[0027]

[Table 2]

[0028]

[Table 3] * Magnesium carbonate type is 30g and calcium carbonate type is 60g

[0029]

According to the present invention, it is possible to provide an flue gas treatment agent which is active at a much lower temperature by activating an alkaline earth metal carbonate which was conventionally considered to be active only at a high temperature or in water. It became possible.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location B01D 53/74 C01F 11/46 9040-4G (72) Inventor Hiroaki Doi 4 Migamioka, Toyohira-ku, Sapporo-shi, Hokkaido Article 9-2-1 No. 1 in Hokkaido Electric Power Co., Inc. Research Institute (72) Inventor Hideki Nakamura 4-9-2, Miyoshioka, Toyohira-ku, Sapporo, Hokkaido Hokkaido Electric Power Co., Inc. Research Institute (72) Inventor Kunihiro Mori Hokkaido Sapporo City Toyohira-ku Mihogaoka 4-92-1 Hokkaido Research Institute of Electric Power Company (72) Inventor Tsutomu Yatani Hokkaido Mihogaoka Mihogaoka 4-92-1 Hokkaido Electric Power Company Research Institute

Claims (4)

[Claims] 1. A method for desulfurization and denitration activation of a flue gas treating agent, which comprises adding 1 to 10% by weight of calcium chloride to the flue gas treating agent composed of an alkaline earth metal carbonate. 2. The activation method according to claim 1, wherein powdery calcium carbonate is mixed with powdery alkaline earth metal carbonate and added. 3. The activation method according to claim 1, wherein the alkaline earth metal carbonate is slurried and calcium chloride in a solid, slurry or aqueous solution is added. 4. The activation method according to claim 3, wherein the added slurry is further dried and solidified.