JP3864443B2 - Method for producing high-fluidity calcium hydroxide - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing calcium hydroxide which is fine and has high fluidity and is therefore easy to handle.
[0002]
[Prior art]
As is well known, calcium hydroxide is industrially produced by adding water to digestion of quick lime obtained by calcining limestone, that is, calcium oxide. When a fine powder is required, calcium hydroxide is classified and, if necessary, ground and classified to meet this requirement.
[0003]
However, the finely powdered calcium hydroxide provided in this way is generally difficult to handle due to problems such as strong adhesion and cohesion and difficulty in dropping from the hopper due to low powder fluidity. Factors that cause poor fluidity when a metal hydroxide such as calcium hydroxide is made into a fine powder are that it is easily affected by moisture in the atmosphere due to its large molecular polarity, and static electricity between particles. It is conceivable that an interaction due to the above works.
[0004]
Among the various uses of calcium hydroxide, especially in the field of treating waste gas containing HCl and SOx from garbage incinerators, which are expanding in recent years, it is required that the powder is fine and therefore highly reactive. Is done. On the other hand, it is desirable that the powder has high fluidity and is easy to handle, not limited to this field.
[0005]
As a measure to obtain calcium hydroxide with high fluidity while being relatively fine powder, it is conceivable to suppress the hydration reaction in the digestion of calcium oxide, and the use of digested water containing alcohol as its means Has been tried. For example, a method of producing calcium hydroxide having a high specific surface area and excellent jet properties using a mixed solution with water containing 50 to 70% by volume of ethanol (Japanese Patent Publication No. 6-8194), an interface in addition to alcohol For example, a method of obtaining calcium hydroxide having excellent fluidity using digested water containing an activator (Japanese Patent Laid-Open No. 5-193997).
[0006]
However, since these methods use a large amount of alcohol, it is necessary to recover and reuse the alcohol, which is complicated by the addition of a process for that purpose, and has the disadvantages of high energy consumption. In addition, since these alcohols are highly volatile and flammable, it is necessary to take measures against breath problems, combustion, and explosion.
[0007]
[Problems to be solved by the invention]
It is an object of the present invention to provide a high fluidity calcium hydroxide, in particular, a calcium hydroxide that can maintain fluidity even when classified into fine powders without complicating the process or increasing energy consumption. It is to provide a method of manufacturing.
[0008]
[Means and Actions for Solving the Problems]
The method for producing high-fluidity calcium hydroxide of the present invention is a method for producing calcium hydroxide by adding water to calcium oxide for digestion, and the following (a) water solution having 3 to 8 carbon atoms as digestion water: Polyhydric alcohol (b) polyglycol surfactant (c) amino-modified dimethyl silicone oil
(A) + (b), (b) or (c) is characterized by using water containing 0.05 to 5%.
[0010]
A hydration inhibitor such as ethanol, which has been attempted to be used conventionally, has a boiling point lower than that of water, and has no effect unless used in a large amount. If you use a substance that can suppress the molecular polarity in a small amount and has a boiling point higher than that of water, and therefore adheres to the surface of the product calcium hydroxide and does not interfere with odor or toxicity, Based on the idea that high-fluidity calcium hydroxide can be obtained without having to go through a complicated process as in the case of using a low-boiling alcohol, the inventors have advanced research and are useful. What has been confirmed is the above-mentioned additive to digestion water.
[0011]
All of these additives are readily available and can be used economically, and there are no problems such as corrosiveness to the apparatus. Therefore, the present invention is carried out by using equipment such as conventional digesters and aging machines as they are. can do.
[0012]
Specific examples of the polyhydric alcohol having 3 to 8 carbon atoms include glycerin, propylene glycol, 1,3-butanediol, hexylene glycol and the like. In particular, glycerin and propylene glycol are easily available and inexpensive. It is useful because there is. From the viewpoint of the effect and economy, it is appropriate to add about 2 to 4% to digested water.
[0013]
It is appropriate to use the polyglycol-based surfactant in a smaller amount of about 0.05 to 1%.
[0014]
Organosilicon compounds are used in various applications as dispersants and water repellents. It is known that adding a small amount of an organosilicon compound to an inorganic powder improves the fluidity of the powder, but when applied to calcium hydroxide, it is thought to have a significant effect on the chemical properties of the particles. It was. For this reason, attempts have not been made to add it to the digested water of calcium oxide or the product calcium hydroxide, but the inventors have found that amino-modified dimethyl silicone oil is useful for improving fluidity. I understood it. This is suitably used as a 0.5-2% aqueous solution or emulsion.
[0015]
【Example】
Using a conventional digester and aging machine, calcium hydroxide was produced using 60 parts by weight of the following digested water for 100 parts by weight of quicklime. No. Nos. 1 and 2 are reference examples. 3 to 5 are examples.
[0016]
No. 14 4% glycerin aqueous solution
No. 2 2% aqueous propylene glycol solution
No. 3 0.05% polyglycol derivative surfactant aqueous solution
No. 4 0.5% amino-modified dimethylpolysiloxane emulsion
No. 5 Combined use of 2% glycerin and 0.05% polyglycol derivative surfactant.
[0017]
For comparison, a JIS special slaked lime and a powder obtained by classifying the JIS slaked lime with an air classifier were added to the sample. The former is A and the latter is B. Sample No. In addition to measuring the average particle diameters of 1 to 6 and A and B, a hopper test and a vibration drop test were performed as a measure of fluidity, and a hydrogen chloride gas removal rate was measured as a measure of reactivity. Each test method is as follows.
[0018]
(Hopper test)
A 1 kg sample that has been kept sealed for at least one day is placed in a hopper model of a specific shape and size, the lower valve is opened, the vibrator is vibrated by the vibrator, and the time until the entire sample falls is measured. If the total amount does not fall after 30 seconds, stop the vibration and measure the amount remaining in the hopper.
[0019]
(Vibration drop test)
A sample (100 g) is placed on a sieve having an opening of 1 mm through a cylinder. The platform on which the sieve is placed is vibrated up and down five times at regular time intervals, and the amount of passage through the sieve is measured.
[0020]
(Hydrogen chloride gas removal rate)
A tube with an inner diameter of 8.5 mm is filled with about 50 mg of sample, and a mixed gas containing 0.4% by volume of HCl and 50% by volume of water vapor is placed at 200 ° C. under a gas flow rate of 4.4 m / min. Circulate for 20 minutes and measure the removal rate of HCl.
[0021]
The results obtained by performing the above test on each sample are as shown in the following table:
Table sample Average particle size Hopper Vibration drop HC1 removal rate
No. ( μm ) ( Seconds ) ( % ) ( % )
Reference Examples and Examples 1 2.9 3.9 75.2 94.4
2 3.5 6.0 63.9 89.0
3 3.5 3.7 49.5 92.4
4 3.4 8.1 55.6 94.0
5 3.3 2.5 77.2 92.8
Comparative Example A 6.0 4.8 45.6 79.0
B 3.3 370 g residual 29.0 88.0
Calcium hydroxide ( No. 3-5) produced by the method of the present invention has a reactivity equivalent to or higher than fine powder obtained by classification from JIS special slaked lime, while having a much higher fluidity. This is evident from the data above. In particular, No. 5 in which the additives (a) + (b) were used in combination showed the best fluidity.
[0022]
【The invention's effect】
With the method of the present invention, the calcium oxide is digested using equipment consisting of a conventional digester and an aging machine without complicating the process or increasing energy consumption, and even if it is a fine powder, it has high fluidity Therefore, calcium hydroxide having high reactivity can be produced.

Claims (1)

In the method for producing calcium hydroxide by adding water to calcium oxide and digesting, the following (a) water-soluble polyhydric alcohol having 3 to 8 carbon atoms (b) polyglycol surfactant (c) ) Amino modified dimethyl silicone oil
(A) + (b), (b) or water containing 0.05 to 5% of (c) is used, A method for producing highly fluid calcium hydroxide,