JP3854652B2 - Method for producing calcium hydroxide - Google Patents

Description

【００２３】
これより、熟成機での好適条件に欠ける比較例では水及びアルコールの含有率が製品とするには高いのに対し、本発明の実施例ではいずれもこれらの含有率が比較例の数分の１に低減されることが分る。
【図面の簡単な説明】
【図１】 本発明方法の実施態様を示す系統図。[0001]
BACKGROUND OF THE INVENTION
The present invention neutralizes acidic exhaust gases such as sulfur oxides such as sulfurous acid gas, hydrogen halides such as hydrogen chloride and hydrogen fluoride, hydrogen sulfide, acidic exhaust gases and wastewater from garbage incinerators and factories. -It is related with the manufacturing method of the calcium hydroxide excellent in reaction activity used suitably as a removal agent.
[0002]
[Prior art]
Conventionally, calcium hydroxide has been used as a neutralizing / removing agent for acidic exhaust gas, but this calcium hydroxide has a low reaction activity with SOx and hydrogen halide and is 2 to 5 times equivalent to that of acidic exhaust gas. It is inevitable that a large amount is required.
Therefore, recently, as a method for producing calcium hydroxide rich in reaction activity, a method using an organic solvent such as alcohol has been proposed (for example, Japanese Patent Publication No. 6-8194 and Japanese Patent Application Laid-Open No. H5-193997).
However, this method has a problem that the reaction aging step and the step of removing the solvent by vacuum or purge gas are performed separately, and thus the process becomes complicated and the manufacturing cost increases.
[0003]
[Problems to be solved by the invention]
The present invention has been made for the purpose of providing a method for easily and efficiently continuously producing calcium hydroxide excellent in reaction activity, overcoming such conventional drawbacks.
[0004]
[Means for Solving the Problems]
The present inventors have conducted various researches to develop an industrial production method of calcium hydroxide having excellent reaction activity with acidic exhaust gas and the like, and as a result, inert gas and / or dry air is introduced into the aging machine. It was found that the purpose can be achieved by continuously supplying while adjusting the supply amount, the internal temperature of the aging machine, and the residence time of the calcium hydroxide in the aging machine. It came to be completed.
[0005]
That is, in the present invention, a dry pulverized mixture of calcium oxide, water and alcohol is digested with a digester, and the resulting digestion reaction product is aged with an aging machine, and water and alcohol are vaporized and removed. By adjusting the supply amount of the inert gas and / or dry air in the aging machine, the internal temperature of the aging machine, and the residence time of the digestion reaction product in the aging machine in the method of continuously producing calcium hydroxide However, the present invention provides a method for producing calcium hydroxide characterized in that it is continuously supplied and water and alcohol are vaporized and removed.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Calcium oxide used as a raw material in the present invention is not particularly limited as long as it is dry pulverized, but preferably calcined limestone in a rotary kiln furnace, Beckenbach furnace, fluid roasting furnace, then cage mill, vibro mill, ball mill, disk Examples thereof include those pulverized by a dry pulverizer such as a mill and classified by sieving.
This dry-milled calcium oxide has a cumulative 50% average particle size of usually 20 to 300 μm, preferably 20 to 110 μm.
[0007]
The digestive fluid used to digest this calcium oxide is a mixture of water and alcohol. The water is preferably fresh water, but may contain some impurities as long as the object of the present invention is not impaired, and industrial water is sufficient. The alcohol is preferably in a liquid state, and among them, lower alcohols having a boiling point lower than that of water, particularly methanol, ethanol, methanol-modified ethanol, isopropyl alcohol-modified ethanol, and various industrial alcohols are preferable. The ratio of water and alcohol in the digestive fluid is usually selected in the range of 1: 0.8 to 1: 3, preferably 1: 1.2 to 1: 2, by weight. If there is too much water, a digestive reaction will occur abruptly, slaked lime will remain in a non-uniform state, and reactive slaked lime will not be obtained. take time.
[0008]
The use ratio of calcium oxide and water in the digestive fluid is usually selected in the range of 1: 0.3 to 1: 2, preferably 1: 0.3 to 1: 1.0 by weight. If there is too much calcium oxide, some calcium oxide will remain in the calcium hydroxide, and if there is too much water, moisture will remain and agglomerate.
[0009]
It is preferable to mix the calcium oxide and the digestion solution well before subjecting them to digestion reaction.For example, both are supplied to the mixer at a predetermined ratio and mixed uniformly in the mixer, and the resulting mixture, usually a suspension, is added. It is preferable to supply to a digester and perform a digestion reaction. This mixing treatment is usually performed at a temperature of 45 ° C. or lower, preferably 30 ° C. or lower. When the mixing treatment temperature exceeds 45 ° C., the reaction rapidly occurs and the viscosity increases, so that it becomes difficult to mix uniformly. Examples of the mixer include a plow blade mixer, a single paddle screw mixer, and a double paddle screw mixer.
[0010]
As digestion reaction conditions, the reaction temperature is usually 70 to 120 ° C., preferably 75 to 110 ° C., and the reaction time is 5 to 180 minutes, preferably 10 to 120 minutes.
[0011]
The digestion reaction product of the digester is then fed to the aging machine. The aging machine is continuously supplied with inert gas and / or dry air. For example, nitrogen or argon is used as the inert gas. The inert gas and / or dry air is supplied into the aging machine while adjusting the supply amount, the internal temperature of the aging machine, and the residence time of the digestion reaction product in the aging machine.
[0012]
This adjustment is preferably performed with respect to the amount of inert gas and / or dry air supplied to the aging machine, 5 to 120 liters per kg of calcium hydroxide in the digestion reaction product, preferably 10 to 80 liters. The internal temperature is 80 to 110 ° C., and the residence time of the digestion reaction product in the aging machine is 5 to 60 minutes, preferably 10 to 50 minutes.
[0013]
In order to maintain such an internal temperature of the aging machine, it is preferable to fill a jacket attached to the aging machine with heating steam, and it is practical to conduct heating steam through the jacket.
[0014]
In this way, water and alcohol are vaporized and removed. This treatment is preferably performed continuously. For example, the inert gas and / or dry air is supplied from the lower part of the aging machine, and the inert gas and / or dry air, dust, water and alcohol are supplied to the upper part of the digester and / or. Alternatively, there may be mentioned a method of filtering and collecting with a filtering dust collecting device such as a bag filter provided at the upper part of the aging machine, and separating and collecting the dust.
[0015]
Et al of water and alcohol such has passed through the filtration dust collector as bag filter, an inert gas and / or dry air is separated into water and alcohol and an inert gas and / or dry air, water and alcohol It is preferably reused as digestive liquid, and the inert gas and / or dry air is preferably supplied to the aging machine after passing through the air dryer. In order to separate the water and alcohol from the inert gas and / or dry air, the water and alcohol are preferably condensed using a condenser.
As mentioned above, although the manufacturing method of the calcium hydroxide of this invention was explained in full detail, the one embodiment is shown in FIG. 1 with a systematic diagram.
[0016]
【The invention's effect】
According to the method of the present invention, calcium hydroxide excellent in reaction activity can be obtained simply and efficiently continuously, the content of water and alcohol in the produced calcium hydroxide can be greatly reduced, and inert gas And / or the partial pressure of alcohol falls by blowing in dry air, it becomes easy to vaporize alcohol, alcohol can be collect | recovered at a high rate, and there exists a remarkable effect of helping cost reduction.
[0017]
【Example】
EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.
[0018]
Example 1
100 parts by weight of calcium oxide (cumulative 50% average particle size: 75 μm) calcined in a rotary kiln oven, dry pulverized in a cage mill, and coarse particles removed with an air separator were mixed with a screw feeder and a mixed digestion solution of water and ethanol (59 (Weight%: 25 ° C.) 90 parts by weight were respectively supplied to the mixers by a metering pump and mixed well with stirring. While supplying this mixture to the digester with a jacket for a heating, it heated by letting a steam flow through a jacket so that the inside of a digester might be 100 degreeC, and it was made to digest reaction for 30 minutes. The obtained digestion reaction product is supplied to a maturing machine with a jacket for heating, and heated by passing steam through the jacket so that the inside of the maturing machine is 100 ° C., and nitrogen gas is supplied at a rate of 30 liters per kg of slaked lime. It is supplied from the lower part of the aging machine (inlet temperature: nitrogen gas temperature 25 ° C), aged so that the residence time in the aging machine is 30 minutes, water and ethanol are vaporized, and water is passed through the bag filter provided at the upper part of the aging machine Then, alcohol, dust, inert gas and / or dry air was sucked, filtered and collected, and dust was separated and collected to obtain dry calcium hydroxide powder. Table 1 shows the water content and alcohol content of the obtained calcium hydroxide.
[0019]
Example 2
A calcium hydroxide dry powder was obtained in the same manner as in Example 1 except that the temperature in the aging machine was 110 ° C., the supply amount of nitrogen gas was 40 liters, and the residence time of the aging machine was 15 minutes. Table 1 shows the water content and alcohol content of the obtained calcium hydroxide.
[0020]
Example 3
A calcium hydroxide dry powder was obtained in the same manner as in Example 2 except that instead of nitrogen gas, a mixture of nitrogen gas and dry air (weight ratio 80:20) was used. Table 1 shows the water content and alcohol content of the obtained calcium hydroxide.
[0021]
Comparative Example A dry calcium hydroxide powder was obtained in the same manner as in Example 1 except that the temperature in the aging machine was 75 ° C. and the supply amount of nitrogen gas was 50 liters. Table 1 shows the water content and alcohol content of the obtained calcium hydroxide.
[0022]
[Table 1]

[0023]
From this, in comparative examples lacking suitable conditions in the aging machine, the content of water and alcohol is high to make a product, whereas in the examples of the present invention, these contents are all a few minutes of the comparative examples. It can be seen that it is reduced to 1.
[Brief description of the drawings]
FIG. 1 is a system diagram showing an embodiment of the method of the present invention.

Claims (7)

A mixture of dry pulverized calcium oxide, water and alcohol is digested with a digester, and the resulting digestion reaction product is aged with a maturing machine, and water and alcohol are vaporized and removed continuously. In the method for producing calcium hydroxide, inert gas and / or dry air is supplied into an aging machine maintained at an internal temperature of 80 to 110 ° C. , the supply amount thereof, the internal temperature of the aging machine, and the retention of digestion reaction products in the aging machine. A method for producing calcium hydroxide, characterized in that water and alcohol are vaporized and removed continuously while adjusting time.   The method for producing calcium hydroxide according to claim 1, wherein the digestion reaction is carried out in a digester after mixing in a mixer. The supply amount of inert gas and / or dry air is adjusted to 5 to 120 liters per kg of calcium hydroxide in the digestion reaction product, and the residence time of the digestion reaction product in the aging machine is adjusted to 5 to 60 minutes, respectively. A method for producing calcium hydroxide according to 1 or 2. The method for producing calcium hydroxide according to claim 1, 2 or 3, wherein the jacket attached to the aging machine is filled with heated steam so that the internal temperature of the aging machine is maintained at 80 to 110 ° C.   The method for producing calcium hydroxide according to any one of claims 1 to 4, wherein water and alcohol are continuously removed.   A filtration dust collector that supplies inert gas and / or dry air from the lower part of the aging machine and installs inert gas and / or dry air, dust, water, and alcohol at the upper part of the digester and / or the upper part of the aging machine. The method for producing calcium hydroxide according to any one of claims 1 to 5, wherein the dust is collected by filtration and the dust is separated and collected.   Water and alcohol, inert gas and / or dry air that has passed through the filter dust collector are separated into water and alcohol and inert gas and / or dry air, and the water and alcohol are reused as digestive fluid and inert. The method for producing calcium hydroxide according to any one of claims 1 to 6, wherein the gas and / or dry air is supplied to the aging machine after passing through the air dryer.

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