JPS6317765B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for producing soda bicarbonate that can obtain sodium bicarbonate crystals with a large particle size, has high carbon dioxide gas absorption efficiency, is easy to operate, and can be operated continuously for a long period of time. It is.

Until now, a reaction column generally called a Solvay column has been used as a device for producing sodium bicarbonate by bringing ammonia brine or ammonium chloride separated mother liquor into countercurrent contact with a carbon dioxide gas-containing gas in the ammonia process or the ammonium chloride/soda process. ing. A similar reaction tower is also used to produce bicarbonate of soda from caustic soda.

These reaction towers have a plurality of cast iron rings stacked one on top of the other, and a number of open partition shelves each having a pair of bells (also called jinkasa) and collars (also called passets) are inserted between each ring.

Ammonia brine, etc. is supplied to the upper part of the reaction tower, and as it descends in the tower, it reacts with the carbon dioxide-containing gas introduced from the lower part of the reaction tower to precipitate sodium bicarbonate crystals. A suspension of sodium bicarbonate crystals in ammonia brine or ammonium salt separated mother liquor is hereinafter referred to as slurry).
Furthermore, due to the reaction heat generated at this time, the temperature gradually increases as it moves toward the lower part of the column. This increase in temperature of the slurry is a good condition for the growth of sodium bicarbonate crystals, but it is not favorable in terms of carbon dioxide absorption efficiency. Cooling the slurry.

However, in a reaction tower having such a structure, sodium bicarbonate crystals scale severely on the bell and collar installed in the reaction tower, on the inner wall surface of the tower, and on the outer surface of the cooling pipe, eventually clogging the inside of the tower. Therefore, long-term continuous operation becomes impossible. For this reason, the current situation is that several of these reaction towers, for example, five reactors, are set up in a set and are operated while being alternately switched such that four reactors are operated and one reactor is washed. The open partition racks used in these towers do not have a sufficient partitioning effect, and the liquid and gas present in the upper and lower reaction stages move vertically through the openings, resulting in a back-mixing phenomenon, and the solids are It is difficult to retain solids as they settle and fall to the next stage one after another. Therefore, approximately 30 pairs of partition shelves have been installed to maintain gas absorption efficiency and slurry concentration, but this is not sufficient. Another disadvantage is that the average diameter of the sodium bicarbonate crystals obtained in these reaction towers is extremely small, about 100 μm. Therefore, when over-separating sodium bicarbonate crystals, a large amount of liquid adheres to the overcake, and a large amount of washing water is required to remove impurities such as salt contained in the overcake. rate decreases. Furthermore, there are drawbacks such as the consumption of a large amount of energy in the subsequent firing process. In addition, special public service 51-
No. 31239 proposes an apparatus for producing soda bicarbonate, which has a plurality of stages of reaction sections, and in each reaction section, the liquid is circulated and reacted by the gas lift action of carbon dioxide gas. In the apparatus shown in the proposal, an open partition shelf called a dowel is used between each reaction stage, but this partition shelf is also different from the bell and collar pair partition shelves in the conventional Solvay tower. Similarly, through the openings, liquid back-mixing and crystal short-circuiting occur, and the slurry concentration in each reaction stage is inevitably reduced considerably.

Therefore, the proposed method does not necessarily provide satisfactory results in terms of crystal particle size and gas absorption efficiency. Furthermore, the liquid level in each reaction stage must be controlled by the pressure balance between the gas section at the upper part of each reaction stage and the upper reaction liquid, which may complicate the operation.

In order to improve these drawbacks, the inventor of the present invention conducted intensive research and obtained bicarbonate of soda crystals with large particle size, high carbon dioxide absorption efficiency, easy operation, and long-term continuous operation. This is a completed device for producing bicarbonate of soda.

That is, in the present invention, the cells are divided into closed partition shelves having a conical protrusion in the center, and a guide tube is installed at the center of the cross section inside each shelf to form a reaction section. Slurry consisting of multiple reaction stages and for transferring ammonia brine or ammonium chloride separated mother liquor containing produced sodium bicarbonate from the upper part of each stage reaction part to each lower reaction part (however, the lowest stage reaction part is in a slurry receiving tank). Outflow pipe,
Then, gas inflow pipes are installed to transfer carbon dioxide-containing gas from the gas phase section at the top of each reaction stage except for the top reaction stage to the bottom of each upper reaction section and the bottom reaction section. The present invention is an apparatus for producing soda bicarbonate in which ammonia brine or ammonium chloride separated mother liquor and carbon dioxide gas are contacted and reacted countercurrently in a stage reaction section.

Hereinafter, the present invention will be explained based on the drawings.

FIG. 1 shows a multistage reaction tower showing an example of the present invention. In FIG. 1, 1a, 1b, and 1c are reaction stages of the reaction column main body 1, where 1a corresponds to the uppermost reaction stage and 1c corresponds to the lowermost reaction stage. In this example, there are three stages, but the number of stages is not limited to three, and any suitable number of stages can be used.

Each reaction stage 1a, 1b, 1c is completely divided by a closed type partition shelf 4a, 4b, 4c having a conical protrusion 3a, 3b, 3c in the center, and the center of each internal cross-section A guide cylinder 2a is provided in the part,
2b, 2c are attached to each partition shelf 4a, 4b, 4c with appropriate spacing, and each reaction section 5a, 5
b, 5c.

Slurry outflow pipes 6a, 6b are connected between the upper parts of the reaction stages 1a, 1b and the reaction stages 1b, 1c corresponding to the lower stages, respectively, for transferring the slurry from the upper parts of the upper reaction parts to the lower reaction parts. Reaction stage 1
A slurry outflow pipe 6c for transferring slurry to the slurry receiving tank 12 is connected to the upper part c.
Further, from the upper gas phase portions 7b, 7c of the reaction portions 5b, 5c of the reaction stages 1b, 1c, each upper reaction portion 5
Gas inflow pipe 8 for transferring carbon dioxide-containing gas to the outside of the guide tubes 2a, 2b at the bottom of a, 5b
a and 8b are installed.

9 is a supply port for ammonia brine or ammonium salt separation mother liquor provided in the uppermost stage reaction 1a;
1 is a bicarbonate soda slurry receiving tank, and 13 is a slurry discharge port. 10 is a supply port for carbon dioxide-containing gas provided at the bottom of the lowest reaction stage 1c, and 8c is a gas inflow pipe for supplying carbon dioxide-containing gas to the outside of the guide tube 2c at the bottom of the reaction section 5c. . Reference numeral 11 denotes an outlet for exhaust gas containing unreacted carbon dioxide, which is provided at the top of the reaction stage 1a.

In the reaction tower configured in this way, ammonia brine or ammonium chloride separated mother liquor is continuously introduced from the supply port 9 in the reaction section 5a of the reaction stage 1a, separated in the reaction section 5b of the next stage, and then transferred to the gas phase section 7b. The sodium bicarbonate crystals are precipitated by reacting with the carbon dioxide gas introduced through the gas inlet pipe 8a.

This bicarbonate of soda crystal slurry is transferred to the reaction section 5a.
More preferably, the slurry is introduced into the reaction section 5b of the next stage 1b via the slurry outflow pipe 6a by an overflow method.

The slurry reacts in the middle reaction section 5b with carbon dioxide gas introduced from the gas phase section 7c of the next stage via the gas inflow pipe 8b, and further reacts with the carbon dioxide gas introduced into the reaction stage 1c, that is, the reaction section 5c of the final reaction stage. After completing the reaction with the carbon dioxide introduced from the carbon dioxide-containing gas supply port 10 through the gas inflow pipe 8b, the slurry is led to the bicarbonate soda slurry receiving tank 12 through the slurry outflow pipe 6c, and is taken out from the slurry discharge port 13. .

In each reaction section 5a, 5b, 5c, the guide tubes 2a, 2b, 2c are
A difference in specific gravity occurs between the inner and outer fluids, and due to the gas lift action, an upward flow of the slurry is generated on the outside of the guide tube, and a downward flow is generated on the inside of the guide tube, forming a circulating flow of the slurry.

Note that for this circulation of the slurry, for example, a forced circulation method may be employed in which a part of the slurry is extracted from the upper part of the guide cylinder to the outside by a pump and then introduced again to the lower part of the same guide cylinder.

A characteristic feature of the present invention is that the slurry flowing down inside the guide tubes 2a, 2b, 2c provided in the reaction section of each reaction stage is
a, 4b, 4c conical projections 3a, 3b,
3c and the reverse upward flow that occurs by being dispersed radially from the center of the protrusion, and the guide cylinder 2a,
An extremely good circulation flow of the slurry is formed by the upward flow occurring outside of 2b and 2c.

Therefore, the precipitated slurry of sodium bicarbonate crystals is circulated vigorously throughout each reaction zone, and can sufficiently absorb the supersaturation generated by the carbon dioxide gas absorption reaction, and the supersaturation is effectively used for crystal growth. . Furthermore, since the slurry flows extremely smoothly at the bottom of each reaction section, there is no dead space and no crystal particles or crystal lumps are deposited at the bottom of the reaction section. Therefore, the scaling phenomenon that occurs on the walls and partition shelves in each reaction stage is prevented, and continuous operation for a long period of time becomes possible.

Furthermore, in the present invention, since the closed type partition shelf is used instead of the previously used open partition shelf in which the crystals are short-circuited from the bottom of each reaction stage, the sodium bicarbonate crystals remain in each reaction section. The time could be made sufficiently long, and it became possible to obtain sodium bicarbonate crystals with an extremely large particle size, which had not been possible before.

The guide cylinder in the present invention is not particularly limited in shape, and can be of any shape as long as it can perform circulation, and is usually a cylinder, an inverted conical cylinder, or the like. Of these, the upper end is wider in terms of circulation efficiency.
It is preferable to use an inverted conical guide tube with a narrow lower end.

Furthermore, any shape of the partition shelf having conical protrusions can be adopted as long as the slurry can be dispersed radially and a reverse upward flow can be formed.

When the reaction column is divided into reaction stages using open partition shelves as in conventional Solvay columns, back-mixing of the reaction liquid occurs between each reaction section through the partition shelves. On the other hand, in the present invention, since the slurry is transferred from the upper part of each reaction stage to the next reaction stage through the slurry outflow pipe, back mixing of the liquids does not occur. In particular, in the method of overflowing the slurry from the gas-liquid interface of the reaction section, which is a more preferred embodiment of the present invention, the liquid in the reaction section and the liquid in the slurry outflow pipe are discontinuous, so back mixing of the liquids is difficult. It never happens.

Therefore, the present invention has the advantage that the same partitioning effect as the conventional Solvay tower can be achieved with a very small number of closed partition shelves, and that the carbon dioxide gas absorption efficiency is extremely high.

Furthermore, in the present invention, a cooler can be used to control temperature rise due to reaction heat. In that case, it is effective to take a portion of the liquid out of the reaction section, cool it, and then return it to the reaction section.

[Brief explanation of the drawing]

FIG. 1 shows an example of an apparatus for producing soda bicarbonate according to the present invention. Explanation of numbering, 1...Reaction tower main body, 1a, 1b,
1c...Reaction stage, 2a, 2b, 2c...Guide tube, 3a, 3b, 3c...Protrusion, 4a, 4b,
4c... Partition shelf, 5a, 5b, 5c... Reaction section,
6a, 6b, 6c... Slurry outflow pipe, 7a, 7
b, 7c... Gas phase part, 8a, 8b, 8c... Gas inflow pipe, 9... Supply port for ammonia can, etc., 10
... Carbon dioxide-containing gas supply port, 11 ... Exhaust gas outlet, 12 ... Slurry receiving tank, 13 ... Slurry discharge port.

Claims (1)

[Claims] 1 Consisting of multiple reaction stages divided by a closed partition shelf with a conical protrusion in the center, each with a guide tube installed at the center of the internal cross section to form a reaction section. , and a slurry outflow pipe for transferring ammonia brine or ammonium chloride separated mother liquor containing produced sodium bicarbonate from the upper part of each stage reaction part to each lower stage reaction part, provided that the lowest stage reaction part is a slurry receiving tank, and Gas inflow pipes are installed to transfer carbon dioxide-containing gas from the gas phase section at the top of each reaction stage, except for the top reaction stage, to the lower part of the upper reaction part and the lower part of the bottom reaction part. A bicarbonate of soda production device in which ammonia brine or ammonium chloride separated mother liquor and carbon dioxide gas are brought into contact and reacted in a countercurrent manner in a reaction section.