JPS59223222A - Manufacture of light granular alkali carbonate - Google Patents

Abstract

PURPOSE:To manufacture a light granular alkali carbonate having a low apparent specific gravity, a large surface area, superior flowability and mechanical strength by mixing an alkali carbonate with a thermally decomposable substance, granulating the mixture with a granulating agent, and calcining the resulting granules. CONSTITUTION:An alkali carbonate such as sodium carbonate is mixed with a thermally decomposable substance such as ammonium hydrogencarbonate or ammonium carbonate, and the mixture is granulated with an alkali silicate such as sodium silicate or an alkali hydroxide such as sodium hydroxide as a granulating agent. The resulting granules are calcined to obtain a light granular alkali carbonate such as sodium carbonate having <=0.6 apparent specific gravity and 200-1,000mum average grain size. high mechanical strength can be provided to the product by grinding the alkali carbonate and/or the thermally decomposable substance as starting materials to <=100mum average grain size before mixing them.

Description

[Detailed description of the invention] The present invention relates to a method for producing light granular alkali carbonate,
More specifically, the present invention relates to a method for producing especially light granular soda carbonate having an extremely small apparent specific gravity, excellent fluidity, a large surface area, and good mechanical strength.

Generally, when soda ash is used in the form of an aqueous solution, it is required to have a fast dissolution rate and little dusting. However, the current commercially available dense soda ash (apparent specific gravity 1.2)
Light soda ash (apparent specific gravity 0.8) has the disadvantage that it clumps when dissolved in cold water, although it produces less powder.
Although it has better solubility than dense soda ash, it has the disadvantage that it is difficult to dust because the particle size is smaller than that of dense soda ash.

In addition, soda ash is widely used because it is effective for desulfurization and dephosphorization of hot metal used in steelmaking, but when using dense soda ash by lance blowing, the particle specific gravity is large, so N2
This causes the problem that the water collects in the piping and is transported, causing it to become warm. On the other hand, when commercially available light soda ash is used, the disadvantage is that the particle size is small and the inertia of the particles is small, so they accumulate locally and the reaction ends rapidly, reducing the reaction efficiency. There is. Therefore, there is a demand for soda ash having a small true specific gravity, a large particle size, and a large surface area. Furthermore, in the detergent industry, there is a demand for soda ash with a lower apparent specific gravity and a larger specific surface area in order to reduce the bulk density of laundry detergents or to increase the dissolution rate.

Therefore, in view of the above, the present inventors have conducted extensive research in order to obtain a soda ash that has a small apparent specific gravity, excellent fluidity, a large surface area, and good strength. the result,
It has been discovered that the desired light granular alkali carbonate can be obtained by mixing a thermally decomposable substance with an alkali carbonate, granulating it with a granulating agent, and then completely firing the granulated product,
This has led to the provision of the present invention.

That is, according to the present invention, the apparent specific gravity is 0.6 or less, especially 03 to 0.5, compared to the conventional light soda ash, which has an apparent specific gravity of about 0.8, and the current dense soda ash. It is possible to obtain light granular soda ash having a total mechanical strength of the same order of magnitude.

The alkali carbonate that is the raw material of the present invention may be selected depending on the type of light granular alkali carbonate that is intended. Alternatively, dense soda ash can be easily used. Further, as the thermally decomposable substance, it is preferable to use a substance that is stable at room temperature, and is dispersed as a gas by decomposition and does not remain. Generally, thermally decomposable substances having a decomposition temperature of 40'' to 120'O are recommended, and specifically, ammonium dioxide, ammonium carbonate, etc. are suitable.

′! In addition, in the present invention, it is extremely effective to use all of the raw materials for the alkali carbonate and/or thermally decomposable substances by pulverizing them to an average particle size of 100 μm or less.

That is, when using raw materials with an average particle size of 100μ,
By using a granulating agent, it is possible to produce a good granulated product, and even if the granulated product is completely burnt, it does not disintegrate easily, and it is possible to produce a light granular alkali carbonate having full mechanical strength. However, if a raw material with an average particle size larger than 100 μm is used, even if a granulated product can be produced, the strength of the light granular alkali carbonate obtained by baking is insufficient and tends to collapse.

The granulating agent used in the present invention is not particularly limited as long as it can completely pulverize the mixture of the above-mentioned alkali carbonate and heat-decomposable substance, and has a strength that at least does not disintegrate the resulting light granular alkali carbonate. It is desirable to have something that can maintain this.

Furthermore, the granulating agent may be selected depending on the intended use of the obtained light granular alkali carbonate, taking into consideration the remaining impurities. In general, inorganic granulating agents are preferably used, such as alkali silicate and caustic alkali. For example, when producing light granular carbonate jeep from soda carbonate, liquid sodium silicate or caustic soda is preferably used as the granulating agent. Sodium silicate is generally SiO2/Ha2
Sodium orthosilicate whose molar ratio of 0 is 0.5 to 3.5,
Sodium metasilicate and No. 1 to No. 3 sodium silicate are used. Further, as the caustic soda, it is preferable to use an aqueous solution of 4 to 48 wt%.

In order to obtain a good light granular form of sodium carbonate by granulating it with the above-described total sodium silicate solution, L1
The sodium silicate is 1 to 50% by weight as total SiO□, especially 1
It is preferable to contain it in a proportion of 0 to 30% by weight. In this case 1. As the SiO□ contained in the granular soda carbonate increases, the strength increases, but the apparent specific gravity also tends to increase. Further, depending on the use, the SiO□ content of light granular soda carbonate may become a problem as an impurity. Therefore, the content of sodium silicate in granular soda carbonate is determined based on the intended use of light granular soda carbonate.
It may be arbitrarily determined in advance from the above range, taking into consideration the apparent specific gravity and strength.

On the other hand, when caustic soda is used as a granulating agent, it is more effective than the above-mentioned sodium silicate because the resulting light granular soda carbonate can avoid containing impurities.

When caustic soda is used, the apparent specific gravity tends to decrease and the strength tends to increase as the amount added increases, contrary to the case of silica. However, beyond a certain amount, the apparent specific gravity increases. In order to granulate such carbonated soda well,
Caustic soda 1.5-100% based on the bicarbonate of soda
, it is preferable to contain ψ in an amount of 3 to 20%.

However, when caustic soda is used as a total granulating agent, the strength of the light granular soda carbonate obtained is slightly inferior to that of sodium silicate. Therefore, by using a mixture of caustic soda and sodium silicate as a granulating agent, it is possible to appropriately adjust the 13102 content and strength of the desired light granular soda carbonate.

In the present invention, the ratio of the thermally decomposable substance/material to be mixed with the alkali carbonate varies depending on the type of the two, and is generally not determined. Generally, by increasing the ratio of the thermally decomposable substance to soda carbonate, the apparent specific gravity of the target light granular alkali carbonate can be reduced. However, if the mixing ratio of the thermally decomposable substance is too large, a problem arises in that the strength of the light granular soda carbonate decreases. So, for example, carbonated soda.

Generally, it is desirable to mix 25 to 100% of the company's thermally decomposable material with respect to the amount of the powder.

In the granulated product of the above-mentioned alkali carbonate and thermally decomposable substance of the present invention, the average particle size is generally maintained at 0.2 to 10s+15, preferably 0.5 to 5im, to obtain the desired light granular alkali carbonate. This is extremely important. That is, when the average particle size of the granulated material is smaller than 0.2n,
Not only is there a lot of granulation, which deteriorates the overall workability, but also the apparent specific gravity of the resulting light granular alkali carbonate cannot be made sufficiently small. In addition, the average particle size of the granulated material is ・10g
When it is larger than m, not only does it require pulverization and classification of the resulting light granular alkali carbonate, but it also has the disadvantage of being easily disintegrated in terms of strength.

The method of granulation and firing in the present invention is not particularly limited, and it may be granulated in advance and then fired, or it may be a method in which granulation and firing are performed simultaneously, and various known granulation methods can be applied. can. Particularly, in order to industrially obtain the desired uniform granulated product, the atomization granulation method, the fluidized bed granulation method, and the rolling granulation method are recommended. The calcination temperature must be at least the temperature at which the thermally decomposable substance decomposes, and is generally 120°C or higher, particularly 150 to 250°C (04°C) to form the desired light granular charcoal. You get soda.

According to the present invention, the light granular alkali carbonate obtained is
Since the alkali carbonate is fired and made porous while maintaining its strongly granulated form using a granulating agent, the alkali carbonate has an extremely low apparent specific gravity and has mechanical strength that prevents disintegration.

Therefore, the light granular alkali carbonate of the present invention has an average particle size of 10 to 1000μ, an apparent specific gravity of generally 0.6 to 0.06,
In particular, it has the advantage of having a small size of 0.3 to 0.5, excellent fluidity, good mechanical strength, and little scattering loss.

Examples of the present invention will be shown below, but the present invention is not limited thereto. In addition, the apparent specific gravity and disintegration property in Examples were measured as follows.

(1) Apparent specific gravity (according to J Engineering 5K-1462) Apparent specific gravity,
Sample 450m~500m Total weight known measuring cylinder 5
00 MIK (measured with IJF accuracy), tap the cylinder lightly on a rubber plate and find that there is no difference in capacity.
The capacitance TtV (1) was calculated using the following formula.

Apparent specific gravity = □ 8; Weight of sample V (2J Disintegration (US military standard M engineering IPL-202
13D) Sample 50.019 (classified to 250 to 1000μ), 15 steel balls of 8- are placed in a test container and vibrated for 30 minutes using a Rotatub sieve tester. After finishing sample 1 in the container, classify it again at 125μ for 5 minutes, measure the weight under 125μ (accuracy of 0.1g), and double that value to get the weight 2.
The disintegration value was calculated as a weight percent.

The smaller the number, the stronger and desirable it is.

Example 1 Soda carbonate and ammonium carbonate, each pulverized to an average particle size of 100μ or less, were mixed at a ratio of 1:1 by weight and placed in a rotating drum, and a silica solution was blown off with hot air at 100°C. 81 using transfer granulation method to spray
Granules of bicarbonate soda having a content of 0□ varied as shown in Table 1 were prepared and baked at Yt200°C for 3 hours to obtain the desired light granular soda ash. The apparent specific gravity of this material and the disintegrating tube are shown below.

Table 1 Comparative Example 1 In Example 1, light granular soda ash was obtained by changing the 8102 content by using only soda carbonate without mixing ammonium carbonate. The apparent specific gravity and disintegration properties of this material are shown in Table 2.

Table 2 Example 2 Under the same conditions as in Example 1, only the granulating agent was changed from sodium silicate to caustic soda and the amount added to soda carbonate was varied to obtain the desired light granular soda ash. Table 3 shows the apparent specific gravity and disintegration properties of this product.

Table 3

Claims (1)

[Claims] l) A method for producing a light granular alkali carbonate, which comprises mixing an alkali carbonate with a thermally decomposable substance, granulating it with a granulating agent, and firing it. 2) A method for producing a light granular alkali carbonate, which comprises mixing an alkali carbonate with a thermally decomposable substance, granulating it with a granulating agent, and firing it. 3) The thermally decomposable substance is ammonium bicarbonate. The manufacturing method according to claim 1, wherein the noodles are ammonium carbonate. 4) The granulating agent is silicic acid. 5) The manufacturing method according to claim 4, where the alkali silicate is sodium silicate; 6) The manufacturing method according to claim 4, where the granulating agent is a caustic alkali. 7) Caustic Alkaline Lika 1 Caustic Soda Patent Claim 0II
8) The manufacturing method described in claim 1, wherein the apparent specific gravity of the light granular alkali carbonate is 9) The average particle size of the light granular alkali carbonate is 200 to 10.
10) The manufacturing method according to claim 1, in which the average particle size of the alkali carbonate is 100 μm or less 11) The average particle size of the thermally decomposable substance is 100 μm Claim 1 which is as follows:
Manufacturing method described in section