JPS60233183A - Method for reducing alkalinity of alkaline powder - Google Patents

Abstract

PURPOSE:To increase the rate of reaction of an alkaline powder remarkably, and to enable the lowering of the alkalinity to an arbitrary level by the adjustment of the water content, by adding water to the alkaline powder, and contacting the mixture with carbon dioxide gas to lower the alkalinity of the powder. CONSTITUTION:(A) 100pts.(wt.) of a powdery industrial waste exhibiting strong alkalinity such as ash is added with (B) 0.1-10pts. of water preferably in the form of mist. The mixture is mixed externally with (C) 0.1-10pts. of carbon dioxide gas under agitation to lower the alkalinity of the component A. The water may be fresh water or sea water, and the source of CO2 is preferably liquefied carbon dioxide, dry ice, or combustion gas of a fuel.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is aimed at reducing the alkalinity of particles such as ash, which exhibit strong alkalinity, by an industrial method.
This invention relates to a method for producing alkaline powder that is convenient for use in the food processing industry and agriculture.

Alkaline powder such as ash is used to extend the shelf life of foods by mixing them with seaweed such as young cloth and root vegetables such as potatoes, and to increase the product value by adding vivid colors. It is used for a variety of purposes, including mixing to adjust the alkalinity of soil.

When ash or the like is used for each purpose, there is an alkaline range suitable for each purpose, so it is necessary to find a powder with an alkalinity suitable for each purpose.

However, alkaline powders that exist in nature are
- There are few products with alkalinity suitable for the above uses, and many have too strong alkalinity, so in most cases they cannot be used effectively as they are. Therefore, it is necessary to adjust the alkalinity to the optimal value for the usage conditions. As a method for adjusting the alkalinity of alkaline powder, the following three methods have been put into practical use.

■ Mix ash with strong alkalinity and ash with weak alkalinity to produce ash with a specified alkalinity.

■ An acidic substance neutralizes a portion of the alkaline powder and lowers the overall alkalinity.

■ Leave ash with a strong alkalinity in the atmosphere for a long time and wait for the alkalinity to naturally decrease before using it. etc. method.

However, even if methods ① and ① above yield an aqueous solution of powder with a moderate average alkalinity, the powder particles with varying degrees of alkalinity will be mixed in and will not adhere to the surface of foods, etc. If it is, it will not be possible to give a uniform alkaline effect and it cannot be said to be used correctly.

In addition, it is difficult to obtain powder and granular materials having appropriate alkalinity, resulting in expensive products.

Also, according to method ① above, several months to several years', 4
) It has been said that it is extremely difficult to obtain ash with the necessary alkalinity when needed.

Therefore, in the industry that utilizes alkaline powder such as ash, there has been a strong desire for an industrially inexpensive supply of alkaline powder such as ash whose alkalinity is uniformly adjusted to an appropriate level.

In order to solve these problems, the present inventors discovered that strong alkaline powder absorbs carbon dioxide and becomes weakly alkaline, and that if carbon dioxide is mixed in after adding an appropriate amount of water to the powder, Focusing on the fact that the reaction rate is dramatically accelerated, we developed a method that allows the alkalinity to be freely lowered and adjusted by taking advantage of both properties, and an industrial production method.

Furthermore, by controlling the amount of water added to the alkaline powder, we have found a method that allows the alkalinity to be easily and accurately adjusted within a predetermined range.

On the other hand, in order to obtain uniform alkaline ash etc. at low cost, it is appropriate to use ash collected by an electrostatic precipitator from the flue gas emitted from a large combustion furnace, for example, coal ash from a coal-fired power plant, We have developed a method to use ash, which is normally discarded as industrial waste, such as plant ash from pulp factories, as a raw material.

Therefore, the present invention can easily and easily adjust the alkalinity of alkaline powder to an appropriate alkalinity in a short period of time. Furthermore, by controlling the amount of water added, the alkalinity can be adjusted accurately to the desired alkalinity, and at low cost. To provide a method for industrially adjusting the alkalinity of a large amount of alkaline powder.

Another important objective of the present invention is to develop a method for reducing the alkalinity of alkaline granules that can adjust the alkalinity of a huge amount of ash, which is industrial waste that is difficult to dispose of, and effectively reuse it. It is on offer.

EXAMPLES Hereinafter, examples of the present invention will be shown and the invention will be specifically explained, but the present invention is not limited by these examples.

The apparatus used in the present invention is shown in FIG.

The apparatus for reducing the alkalinity of powder and granular material shown in Fig.
, a stirring blade 2 for stirring the alkaline powder in the mixing and stirring tank 1, a water spray nozzle 3 for spraying water in a mist onto the alkaline powder in the mixing and stirring tank 1, and a mixing and stirring A carbon dioxide sludge discharge nozzle 4 that supplies carbon dioxide gas into the tank 1, a raw material ash supply conveyor 5 that sends alkaline powder, which is raw Fl, to the mixing and stirring tank 1, and an alkaline powder whose alkalinity has been adjusted. and a carry-out conveyor 6 for sending out.

This equipment is a batch production method, in which a certain amount of alkaline powder is stored in a mixing tank 1, and water and carbon dioxide are added to it and stirred to maintain a constant alkalinity of the alkaline powder. After the value is adjusted, stirring is stopped and the alkaline powder is then transported out.

In order to reduce the alkalinity of alkaline powder using the apparatus shown in FIG. 1, the following steps are performed. First, the raw material ash is fed into the mixing and stirring tank 1 by the raw material ash supply container 5, and then the stirring blade 2 is operated, and the amount of water is measured with the water flow meter 7 through the water spray nozzle 3 from the upper part. Provide adequate amount of water. After that, without further operating the stirring blade 2, carbon dioxide gas is continuously injected into the mixing stirring tank 1 from the carbon dioxide gas discharge nozzle 4 while using a flow meter 8 to increase the alkalinity of the alkaline powder. decrease. The ash whose alkalinity has been reduced by the above step 1- is carried out to the outside by a product carrying-out conveyor 6 at the bottom of the mixing and stirring tank 1.

Using the apparatus shown in FIG. 1, alkalinity was adjusted according to the methods of Examples 1 to 4 below.

(7) Example 1 Coal ash with an alkalinity of 15.8 is fed into the mixing tank 1, and 100 g of raw material is mixed over 72 hours without spraying water.
About 50 g of carbon dioxide gas was mixed into the solution, and the decrease in alkalinity was measured over time.

Example 2 Plant ash with an alkalinity of 95.3 was supplied to the mixing tank 1, and without spraying water, only about 50 g of carbonate scum was mixed into 100 g of the raw material over 72 hours, and the alkali increased over time. The decrease in the degree of

Example 3 Coal ash with an alkalinity of 15.0 was supplied to the mixing stirring tank 1,
Add 2 g of water to 100 g of ash, and then mix about 10 g of carbon dioxide gas to 100 g of raw material for 48 hours.
The alkalinity was measured after 8 hours of incubation.

Example 4 (8) Coal ash and plant ash were mixed to make ash with an alkalinity of 28.5, and this was supplied to the mixing tank 1, and 1.5 g of water was sprayed to 100 g of ash. 5 g of carbon dioxide gas was mixed into 100 g of ash and stirred, and the alkalinity was measured over time.

Table 1 shows the alkalinity of the ashes in Examples 1 to 4.

(Left below) As is clear from Table 1, Example 1. In a normal method such as in Example 2, no matter how much carbon dioxide gas is mixed into the ash etc., if no moisture is mixed in, the alkalinity is only a small degree that is indistinguishable from measurement error. Does not decrease.

It is a result of our tests that no significant alkalinity reduction trend is observed even after this test is continued for several months.

In addition, the present inventors either added only water to the ash and stirred it without mixing carbon dioxide gas, or the alkalinity of the ash hardly decreased in this state.

Figure 2 shows how the alkalinity of the ash decreases over time by adding water to the ash and then stirring without continuously adding carbon dioxide gas.

In creating this figure, a total of 1000 kg of ash was prepared by mixing plant ash and coal ash at a weight ratio of 1:3 and the alkalinity was adjusted to 35. 2
The time was supplied at a rate of 251/min, and then continuously at a rate of 10/min.

Curve AH1 shows the decrease in alkalinity of ash with 1 g of water added to 100 g of ash, curve B6-j-1 shows the decrease in alkalinity of ash with 1.5 g of water added to 100 g of ash, Curve C shows the change in alkalinity of the ash without adding water.

As is clear from this figure, the alkalinity of the ash that was stirred with carbon dioxide gas without adding water hardly decreased, whereas the alkalinity of the ash that was added with water decreased rapidly.

This characteristic curve demonstrates that the alkalinity of the ash can be easily and precisely controlled with the exact amount of water added. This is because ash to which about 1% water has been added has an alkalinity of 8 to the curve.
As shown by the asymptote approaching , even if the mixing time of carbon dioxide gas is increased, the alkalinity (l 1) hardly changes from 8 to 9, and the water content is about 1.5%.
The added ash changes little from alkalinity 3.

Therefore, it has been found that even if the supply amount of carbon dioxide gas and the contact time with carbon dioxide gas are significantly changed, the alkalinity of the ash hardly changes, and the alkalinity of the ash is determined by the added moisture.

If we were to lower the alkalinity of the ash to 10-8, if we added 1.5% water, we could adjust it to the specified value in 5-7 hours; however, if we supplied more carbon dioxide, the alkalinity would further increase. After 10 hours, the alkalinity is about 6.5.
has declined to.

On the other hand, the alkalinity of ash with 1% moisture added cannot be reduced to below 10 unless carbon dioxide gas is supplied for about 18 hours, but even if carbon dioxide gas is supplied for 50 hours after that, the alkalinity drops below 8. It can be adjusted within a predetermined range.

With reference to the characteristic curve in FIG. 2, preferable water (l 2
) Addition amount is determined.

That is, if the amount of water added to the ash is too small, for example 0.1 g or less of water per 100 g of ash, the alkalinity of the ash will hardly decrease even if the amount of carbon dioxide gas mixed is increased. On the other hand, if there is too much, for example 100g of ash to 10g of water.
If it exceeds 1.5 g, the alkalinity will decrease or the stickiness of the ash will increase, making it difficult to handle as powder. Furthermore, if the amount of water added is too small, the decrease in alkalinity is small and the variation is large, making it difficult to control the alkalinity. Also, if too much water is added, the alkalinity will drop too quickly and the time to reach the appropriate alkalinity will be very short, making it difficult to accurately control the alkalinity since it is necessary to accurately control the amount of carbon dioxide gas supplied. Control becomes difficult. Therefore, the amount of water added to the ash is determined to be 0.1 to 10 g per 100 g of ash.

The amount of carbon dioxide supplied is optimal depending on the amount of water added and the alkalinity required for the ash [although it is directly determined, it is usually guaranteed to be in the range of 0.1 to 10 g per 100 g of ash]. I was caught.

Historically, a third device was developed that could continuously reduce the alkalinity of ash.
As shown in the figure.

This alkalinity lowering device inputs powder raw materials such as ash from the left end of an inclined rotary mixing and stirring drum 9, and sprays water onto the ash from a water spray/spool 3 that opens near the input port.
Carbon dioxide gas is supplied from the carbon dioxide gas discharge nozzle 4 opened at the right end of the mixing and stirring drum 9, and the ash is transferred from the product delivery conveyor 6 connected to the lower end of the mixing and stirring drum 9 to the outside of the rotary mixing and stirring drum 9. It is constructed so that it can be taken out to the department.

In the alkalinity lowering method using this device, in the process -I-, nine rotary mixing and stirring drums are continuously rotated, and water and carbon dioxide are also measured by a water flow meter 7 and a carbon dioxide gas flow meter 8, respectively. Since it is possible to adjust the amount to be continuously supplied in a constant amount, by continuously supplying raw materials such as ash in a constant amount, the product can also be continuously taken out in a constant amount.

Although the above embodiments have been described in detail for the case where the alkaline powder is ash, the alkalinity of other powders can be reduced in the same manner.

In the present invention, water is added to alkaline powder and brought into contact with carbon dioxide gas to lower the alkalinity.

This method has the advantage of being able to save electricity and quickly adjust the alkalinity to an appropriate level compared to conventional methods, and to process a large amount of alkaline powder at low cost. Furthermore, since the alkalinity can be controlled extremely accurately by adjusting the amount of water added, it is not necessary to precisely control the supply of carbon dioxide gas and the contact time, and the great effect of adjusting the alkalinity extremely accurately is realized.

(l 5) Furthermore, by utilizing the present invention, alkaline powders such as coal ash and dancing wood ash, which have been industrial wastes that had limited disposal locations due to their strong alkalinity, can be industrially made into alkalis. Adjustments have been made to enable effective reuse.

[Brief explanation of drawings]

Fig. 1 is a schematic sectional view showing an example of the apparatus used in the present invention, Fig. 2 is a graph showing the state in which the alkalinity of powder or granular material is reduced by the present invention, and Fig. 3 is a schematic cross-sectional view showing an example of the apparatus used in the present invention. FIG. 2 is a schematic cross-sectional view showing an example of the device. 1. Mixing stirring tank, 2. Stirring blade, 3. Spray nozzle, 4. Discharge nozzle, 5e. Supply conveyor, 6. Unloading conveyor, 7. Water flow meter, 8. Flow meter, 9 ...Mixing stirring drum, applicant Kyoei Zoki Co., Ltd. agent patent attorney Yasuhiro Toyosu (l 6) Coo-d

Claims (9)

[Claims] (1) In the method of lowering the alkalinity of alkaline powder by bringing carbon dioxide gas into contact with the powder, water is added in a weight ratio of 0.1 to 10 to 100 parts of alkaline powder to reduce the alkalinity. How to reduce the degree. (2) The method for reducing the alkalinity of an alkaline powder or granule according to claim (1), wherein the amount of carbon dioxide mixed is in a weight ratio of 0.1 to 1o per 1oo of the powder or granule. (3) A method for reducing the alkalinity of an alkaline powder or granule according to claim (1), which comprises mixing the alkaline powder with water in the form of a spray without stirring the alkaline powder. (4) The method for lowering the alkalinity of alkaline powder as set forth in claim (1), wherein carbon dioxide gas is mixed from the outside while stirring the alkaline powder in a container. (5) A method for lowering the alkalinity of an alkaline powder according to claim (1), wherein water is first mixed into the alkaline powder and then carbon dioxide is mixed therein. (6) A method for reducing the alkalinity of an alkaline powder according to claim (1), which comprises simultaneously mixing water and carbon dioxide into the alkaline powder. (7) The method for reducing the alkalinity of alkaline powder according to claim (1), wherein fresh water or seawater is used as the mixed water. (8) The alkali of the alkaline powder according to claim (1), which is either a source of carbon dioxide gas mixed into the alkaline powder or liquefied carbon dioxide, dry ice, or combustion gas of fuel. How to lower the degree. (9) The method for reducing the alkalinity of an alkaline powder according to claim (1), wherein part or all of the alkaline powder is coal ash.