JPH10139501A - Slaked lime composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a slaked lime composition small in reduction of a specific surface area with the lapse of time and excellent in storage stability by adding a specified amount of an alkali metal hydroxide to the slaked lime. SOLUTION: In this slaked time composition, 0.1-0.7 pts.wt. of an alkali metal hydroxide is incorporated in 100 pts.wt. slaked lime. NaOH and/or KOH is preferable as the alkali metal hydroxide. In the production of the slaked lime composition, a prescribed amount of NaOH and/or KOH are added preferably. For example, NaOH and/or KOH may be added at a grinding stage or may be dissolved previously in water for hydrating calcium oxide. The method is effective for preventing deterioration with the lapse of time of a pulverized slaked lime large in absorption of moisture and CO2 and having >=30m<2> /g specific surface area, and especially effective in the case when the slaked lime composition is stored for 1-2 week in an atmosphere of 30-70% relative humidity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slaked lime composition, and more particularly to a slaked lime composition excellent in storage stability which prevents the specific surface area of slaked lime from decreasing over time.

[0002]

2. Description of the Related Art One of the main uses of slaked lime (calcium hydroxide) is for purification of combustion exhaust gas from incinerators.
Slaked lime used for this purpose is desired to be a fine powder having a large specific surface area from the viewpoint of reactivity with hydrogen chloride and sulfur oxide in exhaust gas.

[0003] However, slaked lime does not contain moisture in the air or C
The specific surface area gradually decreases by absorbing O ₂ . Especially,
Slaked lime with a large specific surface area has a high absorption rate of water and CO ₂ and a large decrease in the specific surface area during storage, so it varies depending on the storage environment. It halves over time.

[0004]

It usually takes one to two weeks for slaked lime produced in a factory to be used by a user. For this reason, at present, slaked lime whose specific surface area is considerably smaller than that at the time of production, and therefore, reactivity is considerably reduced is used.

An object of the present invention is to solve the above-mentioned conventional problems and to provide a slaked lime composition having a small amount of decrease in specific surface area with time and excellent storage stability.

[0006]

The slaked lime composition of the present invention comprises NaOH and / or K based on 100 parts by weight of slaked lime.
It is characterized in that 0.1 to 0.7 parts by weight of an alkali metal hydroxide such as OH is mixed.

A predetermined amount of NaOH and / or KO is added to slaked lime.
By mixing H, the absorption of moisture and CO _{2 in} slaked lime can be prevented, and the decrease in the specific surface area over time can be reduced.

[0008]

Embodiments of the present invention will be described below in detail.

The slaked lime composition of the present invention is obtained by mixing 0.1 to 0.7 parts by weight of an alkali metal hydroxide such as NaOH and / or KOH with 100 parts by weight of slaked lime. If the ratio of NaOH and / or KOH is less than 0.1 part by weight with respect to 100 parts by weight of slaked lime, the effect of the present invention caused by mixing NaOH and / or KOH cannot be sufficiently obtained. If the ratio of NaOH and / or KOH exceeds 0.7 parts by weight with respect to 100 parts by weight of slaked lime, the rate of decrease in specific surface area over time is small, but excessive N
If the aOH and / or KOH enter the gaps between the aggregated particles formed by the fine slaked lime particles of slaked lime and close them, the initial specific surface area of the slaked lime itself becomes small, which is not preferable. Further, particularly when NaOH is large, Na
OH easily causes adhesion inside the equipment during the mixing and grinding processes,
In addition, Na ₂ C produced by the reaction of NaOH and CO ₂
O ₃ absorbs water, which may accelerate the specific surface area reduction.

A particularly preferred ratio of NaOH and / or KOH is 0.1 to 0.5 part by weight per 100 parts by weight of slaked lime.

[0011] Such a slaked lime composition of the present invention is prepared by adding a predetermined amount of NaOH and / or KO to the slaked lime produced.
Although H can be added and mixed for production, preferably, it is produced by adding a predetermined amount of NaOH and / or KOH in the slaked lime production process. In this case, the step of adding NaOH and / or KOH is not particularly limited, and NaOH and / or KOH may be added to the step of pulverizing slaked lime, as shown in Examples described later. NaOH and / or KOH may be previously dissolved in water.

The slaked lime composition of the present invention contains water and CO ₂
It is effective in preventing the deterioration of fine powder slaked lime having a specific surface area of 30 m ² / g or more with the lapse of time, which is particularly effective in reducing the specific surface area at a relative humidity of 30 to 70%. Is effective for preventing deterioration when stored for about 1 to 2 weeks.

[0013] The slaked lime composition of the present invention comprises activated carbon,
It may contain clay minerals and other additives. For example, activated carbon 5 to 2 with respect to 100 parts by weight of slaked lime
It is also effective for a slaked lime composition having a dioxin adsorption ability containing 0 parts by weight.

[0014]

The present invention will be described more specifically below with reference to examples and comparative examples.

Examples 1 to 4 and Comparative Examples 1 to 3 A predetermined amount of flake-like NaOH was added to a pulverizing step of a test plant having a slaked lime production capacity of 15 kg / hour, and mixing and pulverizing were simultaneously performed to reduce the amount to 100 parts by weight of slaked lime On the other hand, a slaked lime composition mixed with the amount of NaOH shown in Table 1 was produced (however, in Comparative Example 1, NaOH was not added).

The obtained slaked lime composition is 18 cm wide and 2 cm long.
A test sample was placed in a 3 cm bat at a thickness of 1 cm.
The test sample was left open in a room with a constant humidity of 35% and 65% relative humidity, respectively, with the top open. Immediately after production (0 days)
The specific surface area of the slaked lime composition after 3 days, 7 days, 14 days and 28 days after standing was measured using a monosoap specific surface area measuring device manufactured by Yuasa Ionics, and the results are shown in Table 1.

[0017]

[Table 1]

Examples 5 to 8, Comparative Examples 4 and 5 In Example 1, KOH was used in place of NaOH, and a slaked lime composition was prepared by mixing KOH in an amount shown in Table 2 with 100 parts by weight of slaked lime. did.

With respect to this slaked lime composition, the change with time of the specific surface area was examined in the same manner as in Example 1, and the results are shown in Table 2.

Table 2 also shows the results of Comparative Example 1.

[0021]

[Table 2]

Examples 9 to 11 In Example 1, NaOH and KOH were used instead of NaOH.
Was used to produce a slaked lime composition in which NaOH and KOH were mixed in the amounts shown in Table 3 with respect to 100 parts by weight of slaked lime.

With respect to this slaked lime composition, the change with time in the specific surface area was examined in the same manner as in Example 1, and the results are shown in Table 3.

[0024]

[Table 3]

As described above, since the time required for slaked lime produced at the factory to be used is 1-2 weeks,
Slaked lime is desired to have a small decrease in the specific surface area in the period of one to two weeks or less.

As shown in Tables 1 to 3, in Comparative Example 1 containing neither NaOH nor KOH, the amount of decrease in the specific surface area was large, and in particular, when the relative humidity was 65%, it was less than half in two weeks.

On the other hand, NaOH and / or KOH
In Examples 1 to 11 in which 0.1 to 0.7 parts by weight was mixed with 100 parts by weight of slaked lime, the decrease in the specific surface area was small, and in particular, the decrease in the specific surface area after 1 to 2 weeks was significantly improved. ing.

In Comparative Examples 2 and 4 in which the amount of NaOH or KOH was small, the effect of adding NaOH and KOH was not sufficient, and the amount of decrease in the specific surface area was large.

In Comparative Examples 3 and 5 in which the amount of NaOH or KOH is large, the specific surface area decreases with time, but the specific surface area immediately after production is small.

[0030]

As described in detail above, the slaked lime composition of the present invention has a small decrease in specific surface area with time and maintains high reactivity even after long-term storage.

Therefore, according to the slaked lime composition of the present invention,
Due to the high reactivity, it is possible to reduce the amount used in exhaust gas treatment and the like.

Claims (2)

[Claims] 1. A slaked lime composition comprising 100 parts by weight of slaked lime and 0.1 to 0.7 parts by weight of an alkali metal hydroxide. 2. The slaked lime composition according to claim 1, wherein the alkali metal hydroxide is NaOH and / or KOH.