JPS5826028A - Manufacture of anhydrous sodium carbonate crystal - Google Patents

Abstract

PURPOSE:To stably obtain dense, hard and excellent anhydrous sodium carbonate crystals from an aqueous sodium carbonate soln. by deposition by specifying the relation between the deposition speed and the concn. of a slurry in the deposition vessel. CONSTITUTION:When anhydrous sodium carbonate crystals are deposited from an aqueous sodium carbonate soln., the crystals are deposited while keeping the deposition speed and the concn. of a slurry in the deposition vessel in the region X of the diagram using the difference DELTAt between the temp. of the aqueous sodium carbonate soln. and the temp. of transition of sodium carbonate monohydrate anhydrous sodium carbonate as a parameter. The region bounded by lines A, B, C is X, and the line A changes in accordance with DELTAt. When crystals are deposited in a region Y above the line A, the crystal surfaces are made rough and crystal nuclei are newly generated to deposit fine crystals among the desired crystals. As the value of DELTAt is increased, such phenomena are liable to occur, so it is required to reduce the deposition speed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing anhydrous sodium carbonate crystals of uniform particle size, hardness, and high bulk specific gravity from an aqueous sodium carbonate solution.

A commonly used method for producing anhydrous soda crystals with a large bulk specific gravity is to add water to porous anhydrous soda carbonate, which is called light ash and has a bulk specific gravity of about 0.4. Anhydrous soda crystals are obtained by heating.

However, the bulk specific gravity of anhydrous soda carbonate obtained by this method is only about 1.0, and the crystals are still porous and have an angular shape.
It is easy to crush, so contamination with fine particles is unavoidable, and
The particle size usually varies over a wide range and has poor fluidity when handled. In addition, since this crystal is porous, it has a high hygroscopic property, and also has the property of being easily converted into sodium sesquicarbonate by carbon dioxide gas in the air.

The present invention overcomes these drawbacks of the conventional method and can provide spherical anhydrous soda crystals that have a truly large bulk specific gravity, are dense, hard, transparent, and have uniform particle sizes. . When precipitating anhydrous sodium carbonate crystals from an aqueous solution of sodium carbonate, the crystals can be precipitated by simply limiting the temperature difference between the temperature of the aqueous solution and the transition temperature of anhydrous sodium carbonate #sodium carbonate hydrate (hereinafter simply referred to as transition temperature). In some cases, it is not always possible to obtain crystals with the above-mentioned properties,
The shape may be fine crystals, or the shape may be an aggregation of fine crystals, the spherical shape may be distorted, or the surface may have a rough surface with small crystals stuck to it. The cause of this is not clear, but it is possible that the supersaturation concentration in the precipitation tank was too high overall or in some areas, resulting in the generation of new nuclei or inhibiting the uniform growth of the crystal surface. Furthermore, it is thought that too low supersaturation concentration promotes differences in the growth properties of the crystal growth surface, resulting in distortion, but it is difficult to limit and control these individually.

The present invention has been made based on the discovery of specific conditions within the crystal precipitation tank to consistently obtain well-formed crystals as a result of numerous experiments and studies.

That is, in order to prevent slurry crystals from depositing and to eliminate uneven distribution of supersaturation, the flow rate of the anhydrous soda carbonate crystal slurry was set at son/h to 4000! El/h
It has been discovered that in a crystal precipitation tank which is stirred and flowed at a rate of 1000 s, it is possible to obtain crystals with good properties as described above when the precipitation rate and the slurry concentration in the precipitation tank exhibit a certain relationship. It is. That is, FIG. 1 is a graph showing the preferable relationship between the precipitation rate in the precipitation tank and the slurry concentration in the precipitation tank using the temperature difference Δt between the solution temperature and the transition temperature as a parameter. It has been found that by creating a relationship between the precipitation rate and the slurry concentration in the region X surrounded by O, the above-mentioned good crystals can be stably obtained.

FIG. 1 will be explained in more detail.

In FIG. 1, 2im changes in a sodium carbonate aqueous solution depending on the difference Δt between the liquid bottom body temperature and the transition temperature of sodium carbonate monohydrate/sodium carbonate anhydrous salt. In the region Y above the line, when crystals are precipitated, the crystal surface becomes rough, new crystal nuclei are generated, and fine crystals are mixed. In particular, as Δt increases, it becomes necessary to slow down the crystal precipitation rate in order to prevent such phenomena from occurring.

As a result, in FIG. 1, a group of lines with Δt as a parameter is shown.

Line B1 Line 0 indicates the slurry concentration conditions in the precipitation tank. When the slurry concentration is lower than line B, new crystal nuclei are likely to be generated and fine crystals are likely to be formed. In addition, scale is likely to adhere to the inner wall of the precipitation tank.
It becomes difficult to obtain stable and good crystals.

In addition, when the slurry concentration is higher than Twin 0, there is a lot of wear between the crystal particles, and the size of the obtained crystal particles fluctuates over time, making it difficult to obtain stable and good crystals. It is inconvenient for

The specific method that satisfies the conditions in the precipitation tank described above is not particularly limited, and may be carried out in an appropriate and optimal manner.

For example, the precipitation rate may be adjusted by adjusting the amount of sodium carbonate monohydrate supplied to the precipitation tank, or by adjusting the supply rate of the solid form 1 and the caustic soda solution. Furthermore, the rate at which water is evaporated may be adjusted.

Moreover, the adjustment of the message is done by using the Mail contained in the solution.

This may be done by adjusting the concentration of NaOH or the like, or of course by adjusting the temperature of the solution itself.

Next, a more specific explanation will be given with reference to Examples.

Example internal volume 1 with internal circulation pump and steam heating jacket
- Prepare a crystal precipitation tank, and add sodium carbonate monohydrate crystals to it uniformly in the tank so as to maintain the mother liquor composition, temperature, Δt1 slurry 17- concentration, and precipitation rate shown in Table 1. supplied.

In the Mata and Kono processes, solid Na01.4
81 NaOH aqueous solution was fed. In addition, maintaining the temperature is
By adjusting the amount of steam supplied to the steam jacket, the measurement was carried out within a range of ±0.2°C. Further, the slurry concentration is maintained by taking out the crystals when the slurry concentration is high, and by taking out the mother liquor when the slurry concentration is low. The characteristics and operating conditions of the obtained anhydrous carbonated soil are also listed in Table 1.9.

[Phase] 1: Comparative Example @ 2: 200j (D sample powder' was placed in a measuring cylinder of zoornt, and the volume was calculated based on the volume when there was no change in volume by vibrating it with a pipe lake.

@13: The powder sog after removing 80 pieces of gourd from the sample powder after drying before the test has an internal volume of 250 rnl,
The mixture was placed in a pulverizer together with 15 agate balls (5 sl in total) and pulverized at 170 r, p, m for 30 minutes. The powder under 200 meshes of the sample after pulverization was separated in an assay section, and the weight of this powder was expressed as a percentage of the original sample weight.

[Brief explanation of the drawing]

FIG. 1 is a graph showing a preferable relationship between the slurry concentration and the precipitation rate of anhydrous sodium carbonate crystals in the anhydrous sodium carbonate crystal precipitation right, and shows the relationship between the precipitation tank concentration and the transition temperature of anhydrous sodium carbonate and sodium carbonate monohydrate. The temperature difference Δt is shown as a parameter. Procedural amendment (method) Haruki Shimada, Commissioner of the Japan Patent Office, 2//1980 Relationship with the case of the person making the amendment Patent applicant address: 2-1-2 Marunouchi, Chiyoda-ku, Tokyo Name
(004) Asahi Glass Co., Ltd. January 26, 1980 (shipment date) 6 Number of inventions increased by amendment

Claims (1)

[Claims] A manufacturing method for producing anhydrous soda carbonate in which anhydrous sodium carbonate crystals are precipitated from an aqueous sodium carbonate solution, characterized in that the precipitation is carried out while maintaining the precipitation rate of anhydrous soda carbonate crystals and the slurry concentration in the precipitation tank within region X in Figure 1. A method for producing anhydrous soda crystals.