JP2641401B2 - Activation method of slaked lime flue gas treatment agent - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to high activation of dry flue gas treatment using calcium hydroxide, which was conventionally considered to have low desulfurization and denitration performance.

[0002]

2. Description of the Related Art Sulfur oxides, nitrogen oxides and the like contained in flue gas generated by the combustion of coal, heavy oil and the like not only harm buildings and structures, but also extremely affect animals, plants and the human body. It has been found that it has a great effect, and methods for removing the above substances in flue gas, that is, desulfurization and denitration methods have been studied, and various methods have been developed. Desulfurization methods are roughly classified into dry, semi-dry and wet methods.
The methods shown in Table 1 are known for the dry and semi-dry processes to which the present invention belongs.

[0003]

[Table 1] In the absorption method shown in Table 1, expensive NH ₃ is required for the regeneration of the reactants (recovery of sulfur or a sulfur compound) (active manganese oxide method), or a valuable reducing gas is required (alcalizing). (Alumina method), or the reaction temperature is high (alkaline alumina method, lime blowing method). The adsorption method has the drawback that the activated carbon used is expensive and easily deteriorates.The catalytic oxidation method has the problems that the vanadium-based catalyst used is expensive and easily deteriorates, and the reaction temperature is relatively high. .

Heretofore, calcium hydroxide has not been actively used, particularly in the dry process, because of its low reaction efficiency despite its high cost. For this reason, various techniques for further increasing the activity of calcium hydroxide have been studied. As one of them, a method of adding calcium chloride to slaked lime has been proposed (JP-A-3-161102).
However, when only calcium chloride is added to calcium hydroxide, no improvement in desulfurization activity is observed.

[0005]

An object of the present invention is to improve the desulfurization activity of calcium hydroxide,
It is an object of the present invention to solve various problems of the conventional dry desulfurization method, to provide an inexpensive and high-performance flue gas treating agent, and to provide a flue gas treating method using the flue gas treating agent.

[0006]

As a result of various studies to achieve the above object, as described below, the activity is remarkably improved by further adding calcium carbonate to a system in which calcium chloride is added to slaked lime. I found that. The flue gas treating agent obtained by mixing and drying the above three components in a slurry state has many theoretically unknown points,
No improvement in the desulfurization activity was observed, but it was found that the desulfurization activity was improved by further adding a small amount of powdered calcium hydroxide.

That is, the present invention provides: Water characterized by adding 1 to 20% by weight of powdered calcium chloride to calcium hydroxide and 0.1 to 20% by weight of powdered calcium carbonate on a dry mixture basis, and drying as it is or as water 1. A method for activating a powdery or particulate flue gas treating agent using calcium oxide as a reactant. A method for activating a flue gas treating agent using calcium hydroxide as a reactant, comprising preparing a slurry mixture of calcium hydroxide, calcium chloride and calcium carbonate, drying and then adding powdered calcium hydroxide to the mixture. And
Based on the obtained mixture of calcium hydroxide, calcium chloride and calcium carbonate, calcium chloride in the mixture is 1 to 20% by weight, calcium carbonate is 0.1 to 20% by weight, and the remainder is calcium hydroxide. The added powdery calcium hydroxide is 10 to 5 based on the mixture.
Said activation method characterized in that the content is adjusted to 0% by weight. 3-20% by weight of powdered calcium chloride and 0.1-20% by weight of powdered calcium carbonate based on a dry mixture of calcium hydroxide and calcium hydroxide. %, And using a powdery or particulate flue gas treating agent having calcium hydroxide obtained as it is or dried as a reactant, at 60 ° C to 20 ° C.
A method for treating flue gas, comprising treating flue gas at a temperature of 0 ° C. And 4 preparing a slurry mixture of calcium hydroxide, calcium chloride and calcium carbonate, drying and further adding powdered calcium hydroxide and mixing, based on the obtained mixture of calcium hydroxide, calcium chloride and calcium carbonate. The calcium chloride in the mixture is 1 to 20% by weight, the calcium carbonate is 0.1 to 20% by weight, and the balance is calcium hydroxide. The powdery calcium hydroxide added later is 10 to 10% by weight based on the mixture. Using a powdery or particulate flue gas treating agent containing calcium hydroxide as a reactant obtained by adjusting to 50% by weight, the temperature is from 60 ° C to 20 ° C.
This is a method for treating flue gas, wherein the flue gas is treated at a temperature of 0 ° C.

The purity of calcium hydroxide, calcium chloride and calcium carbonate used in the present invention is not particularly limited, and any one can be used as long as it is generally available on the market. If the purity is high, even by-products can be accepted.

The amounts of calcium chloride and calcium carbonate to be added are 1 to 20% by weight of calcium chloride, 0.1 to 20% by weight of calcium carbonate, and the balance is calcium hydroxide, based on the dry mixture after addition. Outside this range, the effect of the activation will be impaired.

As to the method of addition, it is possible to mix in a solid state, but the powder or slurry of the remaining material is added to at least one slurry of calcium hydroxide, calcium chloride and calcium carbonate, and calcium hydroxide, chloride It is preferable to prepare a slurry-like mixture containing calcium and calcium carbonate, and after drying, further add powdered calcium hydroxide. In this case, the weight ratio of calcium chloride and calcium carbonate based on the finished dry mixture is the same as above (1 to 20% by weight and 0.1 to 20% by weight, respectively), The weight ratio of calcium is 1 based on the finished dry mixture.
What is necessary is just to adjust so that it may become 0 to 50 weight%. Any known apparatus can be used for addition, drying, and mixing.

The mixture obtained by the above-mentioned addition method can be used as a flue gas treating agent in powder or granular form. When used in powder form, it can be used by methods such as flue spray, fluidized bed or spouted bed. When used in a granular form, a powdery substance can be formed by a known method such as a disk pelletizer and used in a moving bed, a fixed bed, a fluidized bed, and a spouted bed. Applicable smoke emissions include:
In addition to flue gas from coal and oil-fired boilers, it can also treat flue gas containing acidic gas such as HCl, and more specifically, flue gas from refuse incineration boilers and the like. Exhaust gas treatment temperature is from room temperature to 300
° C, preferably 60 to 200 ° C.

[0012]

【Example】

Example 1 A predetermined amount of commercially available calcium carbonate and commercially available particulate anhydrous calcium chloride were powdered and mixed with commercially available calcium hydroxide to activate the calcium hydroxide. A performance evaluation test was performed under the test conditions shown in Table 2, and the time required for the desulfurization rate to exceed 80% was determined by the amount of Ca (O
Table 3 shows the values converted to Ca equivalents in H) ₂ .

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

Example 2 A predetermined amount of commercially available anhydrous calcium chloride was used as an aqueous solution at 95 ° C., and commercially available calcium hydroxide and calcium carbonate were added thereto in the proportions shown in Table 3 to reduce the slurry concentration to 16.
After stirring for 30 minutes, the mixture was dried at 200 ° C. for 2 hours, and powdered calcium hydroxide was mixed to obtain an activated flue gas treating agent. The same performance evaluation test as in Example 1 was performed, and the results are shown in Table 3.

Example 3 A predetermined amount of commercially available anhydrous calcium chloride was powdered and mixed with powdered industrial slaked lime (CaCO ₃ content: 7%) to obtain an activated flue gas treating agent. The same performance evaluation test as in Example 1 was performed, and the results are shown in Table 3.

Example 4 Commercially available mixture of calcium carbonate and coal (mixing ratio 8: 2)
Was calcined at 900 ° C., and a hydration reaction was performed with water at 65 ° C. so that the slurry concentration was 16.7%. This is 200
After drying at 2 ° C. for 2 hours, a predetermined amount of commercially available particulate anhydrous calcium chloride was powdered and mixed to obtain an activated flue gas treating agent. The same performance evaluation test as in Example 1 was performed, and the results were shown in Table 3.
It was shown to.

Example 5 A predetermined amount of a used slaked lime absorbent (the composition is shown in Table 4) used in the semi-dry method was added to a slaked lime slurry at 95 ° C immediately after the digestion reaction was completed, and the mixture was added at 200 ° C for 2 hours After drying, a predetermined amount of commercially available particulate anhydrous calcium chloride was powdered and mixed to obtain an activated flue gas treating agent. The same performance test as in Example 1 was performed, and the results are shown in Table 3.

Comparative Example 1 A commercially available calcium hydroxide was subjected to the same performance evaluation test as in Example 1, and the results are shown in Table 3.

Comparative Example 2 A performance evaluation test was performed on commercially available anhydrous calcium chloride, and the results are shown in Table 3.

Comparative Example 3 A performance evaluation test was performed on commercially available calcium carbonate, and the results are shown in Table 3.

Comparative Example 4 A powdery industrial hydrated lime (CaCO ₃ content: 7%) was subjected to the same performance evaluation test as in Example 1, and the results are shown in Table 3.

Comparative Example 5 A commercially available calcium hydroxide was mixed with a predetermined amount of commercially available particulate anhydrous calcium chloride in powder form. The same performance evaluation test as in Example 1 was performed, and the results are shown in Table 3. Comparative Example 6 A predetermined amount of commercially available anhydrous calcium chloride was used as an aqueous solution at 95 ° C., and commercially available calcium hydroxide and calcium carbonate were added thereto in the proportions shown in Table 3 to reduce the slurry concentration to 16.
After stirring for 30 minutes, the mixture was dried at 200 ° C. for 2 hours to obtain a smoke emission treating agent. The same performance evaluation test as in Example 1 was performed, and the results are shown in Table 3.

[0023]

[Table 2]

[0024]

[Table 3]

[0025]

[Table 4]

[0026]

According to the present invention, the activity of slaked lime as a flue gas treatment agent can be improved, and a dry or semi-dry type, relatively inexpensive, highly active flue gas treatment agent can be provided. became.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Takeshi Murayama 4-1, 9-9, Migaoka, Toyohira-ku, Sapporo, Hokkaido Hokkaido Electric Power Company Research Institute (56) References JP-A-5-57139 (JP, A)

Claims (4)

(57) [Claims] 1. A method in which powdered calcium chloride is added to calcium hydroxide in an amount of 1 to 20% by weight and dry powdered calcium carbonate in an amount of 0.1 to 20% by weight based on a dry mixture, and dried as it is or as it is. A method for activating a powdery or particulate flue gas treating agent comprising calcium hydroxide as a reactant. 2. A method for activating a flue gas treating agent comprising calcium hydroxide as a reactant, comprising preparing a slurry mixture of calcium hydroxide, calcium chloride and calcium carbonate, drying the mixture, and then powdering calcium hydroxide. Are further added and mixed, and based on the obtained mixture of calcium hydroxide, calcium chloride and calcium carbonate, 1 to 20% by weight of calcium chloride and 0.1% of calcium carbonate are contained in the mixture.
-20% by weight, the balance being calcium hydroxide, wherein the powdery calcium hydroxide added later is adjusted to 10-50% by weight based on the mixture. 3. A powdered calcium chloride is added to calcium hydroxide in an amount of 1 to 20% by weight and a powdered calcium carbonate in an amount of 0.1 to 20% by weight based on a dry mixture, and the calcium hydroxide is dried as it is or as it is. Using a powdery or particulate flue gas treating agent containing the obtained calcium hydroxide as a reactant, 6
A method for treating flue gas, comprising treating flue gas at a temperature of 0 ° C to 200 ° C. 4. A slurry mixture of calcium hydroxide, calcium chloride and calcium carbonate is prepared, and after drying, powdery calcium hydroxide is further added and mixed, and the resulting calcium hydroxide, calcium chloride and calcium carbonate are mixed. 1 calcium chloride in the mixture, based on the mixture
-20% by weight, 0.1-20% by weight of calcium carbonate,
The remainder is calcium hydroxide, and powdery or particulate form containing calcium hydroxide obtained by adjusting the amount of powdered calcium hydroxide added later to be 10 to 50% by weight based on the mixture, as a reactant. Using a flue gas treatment agent
A method for treating flue gas, comprising treating flue gas at a temperature of 0 ° C to 200 ° C.