Method for producing sodium bicarbonate

Abstract

To provide a more efficient method for producing sodium bicarbonate compared to conventional methods, from the perspective of energy conservation and effective use of resources. [Solution] A method for producing sodium bicarbonate, comprising supplying water, carbon dioxide, and a solid sodium carbonate to a first aqueous slurry or a first aqueous solution of sodium bicarbonate containing solid sodium bicarbonate to produce a second aqueous slurry containing solid sodium bicarbonate.

Description

Technical Field

[0001] The present invention relates to a method for producing sodium hydrogen carbonate.

Background Art

[0002] Sodium hydrogen carbonate is used in a wide range of fields such as for food, feed, deodorants, pharmaceuticals, and treatment of incineration exhaust gases. As a method for producing sodium hydrogen carbonate, for example, the so-called ammonia soda method in which ammonia and carbon dioxide are sequentially supplied to an aqueous solution containing sodium ions to obtain sodium hydrogen carbonate crystals has been known for a long time (Patent Document 1).

[0003] In addition, as another method for producing sodium hydrogen carbonate, a method of producing sodium hydrogen carbonate by supplying carbon dioxide to an aqueous solution of sodium hydroxide has also been known for a long time.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The reaction formulas of the method for producing sodium hydrogen carbonate by supplying carbon dioxide to an aqueous solution of sodium hydroxide are represented by the following Formulas 1 and 2. That is, sodium hydroxide and carbon dioxide react to form sodium carbonate and water, and the formed sodium carbonate and water react with carbon dioxide to form sodium hydrogen carbonate. 2NaOH + CO2 → Na2CO3 + H2O Formula 1 Na2CO3 + CO2 + H2O → 2NaHCO3 Formula 2

[0006] Combining equations 1 and 2 above yields equation 3 below. In other words, it appears that sodium hydroxide and carbon dioxide react to produce sodium bicarbonate. NaOH+CO2→NaHCO3 formula 3

[0007] Although water (H2O) is not listed on the left side of equation 1 above, the reaction between solid sodium hydroxide and carbon dioxide is inefficient. Therefore, the reaction in equation 1 is usually carried out by supplying carbon dioxide to an aqueous sodium hydroxide solution. The water contained in the aqueous sodium hydroxide solution is not used in the reaction and is ultimately left as a surplus, which is not efficient from the standpoint of effective resource utilization. Furthermore, the reaction of aqueous sodium hydroxide solution with carbon dioxide yields an aqueous slurry containing solid sodium bicarbonate. Sodium bicarbonate is obtained by separating this aqueous slurry into solid and liquid components and drying the resulting wet solid. Sodium bicarbonate is dissolved in the separated liquid, and by discarding it, not only the water but also this sodium bicarbonate is lost. Although it is possible to evaporate the excess water from the separated liquid, this requires a great deal of energy and is not efficient.

[0008] The present invention aims to provide a more efficient method for producing sodium bicarbonate compared to conventional methods, from the viewpoint of energy conservation and effective use of resources. [Means for solving the problem]

[0009] The present invention is as follows [1] to

[11] . [1] A method for producing sodium bicarbonate, comprising supplying water, carbon dioxide, and a solid sodium carbonate to a first aqueous slurry or a first aqueous solution of sodium bicarbonate containing solid sodium bicarbonate to produce a second aqueous slurry containing solid sodium bicarbonate. [2] The method for producing sodium bicarbonate according to [1], wherein the supply of water, carbon dioxide, and solid sodium carbonate is obtained by supplying water and solid sodium carbonate to obtain a reaction solution, and carbon dioxide is supplied to the obtained reaction solution. [3] The method for producing sodium bicarbonate according to [2], wherein the sodium bicarbonate concentration relative to the total mass of the reaction solution is 7 to 44% by mass. [4] A method for producing sodium bicarbonate according to any one of [1] to [3], wherein the water and the solid sodium carbonate are supplied as a water slurry containing the solid sodium carbonate. [5] A method for producing sodium bicarbonate according to any one of [1] to [4], wherein the water is supplied as an aqueous solution or an aqueous slurry, the aqueous solution comprises at least one aqueous solution selected from the group consisting of an aqueous sodium hydroxide solution, an aqueous sodium carbonate solution, and an aqueous sodium bicarbonate solution, and the aqueous slurry comprises an aqueous slurry containing solid sodium bicarbonate. [6] The method for producing sodium bicarbonate according to [5], wherein the aqueous solution is an aqueous solution of sodium hydroxide. [7] The method for producing sodium bicarbonate according to any one of [1] to [6], wherein the carbon dioxide is supplied by the fine bubble method. [8] The sodium carbonate is sodium carbonate, the method for producing sodium bicarbonate according to any one of [1] to [7]. [9] A method for producing sodium bicarbonate according to any one of [1] to [8], wherein at least a portion of the first aqueous sodium bicarbonate solution is a separated liquid obtained by solid-liquid separation of an aqueous slurry containing solid sodium bicarbonate.

[10] A method for producing sodium bicarbonate according to any one of [1] to [9], wherein a second aqueous slurry containing the solid sodium bicarbonate is subjected to solid-liquid separation to obtain a second aqueous sodium bicarbonate solution as the separated liquid, and the obtained separated liquid is used as the first aqueous sodium bicarbonate solution.

[11] A method for producing sodium bicarbonate according to any one of [1] to

[10] , wherein a second aqueous slurry containing the solid sodium bicarbonate is subjected to solid-liquid separation to obtain a wet solid, and the obtained wet solid is dried to obtain sodium bicarbonate powder. [Effects of the Invention]

[0010] According to the present invention, a more efficient method for producing sodium bicarbonate can be provided compared to conventional methods, from the viewpoint of energy conservation and effective utilization of resources. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic diagram showing an example of a sodium bicarbonate production apparatus according to the present invention. [Figure 2] This is a schematic diagram showing another example of the sodium bicarbonate production apparatus of the present invention. [Figure 3] This is a schematic diagram showing yet another example of the sodium bicarbonate production apparatus of the present invention. [Figure 4] This is a schematic diagram showing yet another example of the sodium bicarbonate production apparatus of the present invention. [Modes for carrying out the invention]

[0012] The meanings and definitions of terms used in this specification are as follows: A numerical range represented by "~" means a range of numbers whose lower and upper limits are the numbers before and after the "~". "Sodium bicarbonate equivalent concentration" refers to the sodium bicarbonate concentration when all sodium bicarbonate, sodium carbonates, and sodium hydroxide in a solution are converted to sodium bicarbonate. If the solution is an aqueous slurry, this also includes solid sodium bicarbonate, sodium carbonates, and sodium hydroxide. Specifically, it can be calculated by measuring the sodium concentration in the solution and converting that sodium concentration to a sodium bicarbonate concentration. The conversion from sodium concentration to sodium bicarbonate concentration can be done by multiplying the sodium concentration by the molecular weight of sodium bicarbonate (84.01) and dividing by the atomic weight of sodium (22.99). The sodium concentration in the solution can be measured by atomic absorption spectroscopy after preparing an acidic aqueous solution by diluting the reaction with nitric acid. The size of gas bubbles containing carbon dioxide can be measured, for example, using a particle size analyzer (product name: Particle Track) manufactured by Mettler Toledo using FBRM (Focused Beam Reflectance Measurement). In this specification, the distribution of bubble size is shown by the 50% diameter (median diameter, hereinafter referred to as "d50") and 90% diameter (hereinafter referred to as "d90") in the cumulative distribution curve of bubble volume relative to bubble size. "Carbon dioxide utilization rate" refers to the ratio, expressed as a percentage, of the actual amount of carbon dioxide consumed, calculated from the amount of sodium bicarbonate produced, to the amount of carbon dioxide supplied for the production of sodium bicarbonate. "Water slurry" refers to a mixture of a saturated aqueous solution of a specific solute and the undissolved solid form of the solute. In this specification, "aqueous solution" and "water slurry" are distinguished.

[0013] The oil absorption capacity of sodium bicarbonate powder is measured according to JIS K5101-13-1:2004. The apparent density of sodium bicarbonate powder is a value measured using an apparent density meter in accordance with the provisions of JIS K5101-12-1:2004. The crystallite sizes of the (210) plane and the (121) plane of sodium hydrogen carbonate powder are obtained by selecting the diffraction peaks of the (210) plane and the (121) plane as peaks that do not overlap with other peaks and have relatively high relative intensities among the peaks derived from NaHCO3 in the X-ray diffraction pattern, and calculating the crystallite sizes for each crystal plane using the following Scherrer's formula. D = Kλ / {(B - B0)cosθ} D is the crystallite size (nm), K is the Scherrer constant, and 0.89 is used. λ is the wavelength of X-ray (nm), and 0.1542 nm of Cu-Kα ray is used. B is the full width at half maximum (rad) of each diffraction peak, B0 is the instrumental function, and the full width at half maximum (rad) of the peak obtained by measuring an α-alumina sintered body with a crystallite size of 1 μm or more is used. θ is the diffraction angle (rad) of each diffraction peak. The full width at half maximum (rad) is preferably 0.2 to 0.3. The d50 of sodium hydrogen carbonate powder is the volume-based cumulative 50% diameter (median diameter) determined by the laser diffraction / scattering method. That is, the particle size distribution is measured by the laser diffraction / scattering method, a cumulative curve is obtained with the total volume of the particle population as 100%, and it is the particle diameter at the point where the cumulative volume becomes 50% on the cumulative curve.

[0014] ≪Manufacturing method of sodium hydrogen carbonate≫ The manufacturing method of sodium hydrogen carbonate of the present embodiment supplies water, carbon dioxide, and solid sodium carbonate to a first water slurry or a first aqueous sodium hydrogen carbonate solution containing solid sodium hydrogen carbonate to produce a second water slurry containing solid sodium hydrogen carbonate. For example, when the reaction is carried out at a high temperature, water, carbon dioxide, and solid sodium carbonate may be supplied to a first water slurry or a first aqueous sodium hydrogen carbonate solution containing solid sodium hydrogen carbonate to obtain an aqueous sodium hydrogen carbonate solution, and the aqueous sodium hydrogen carbonate solution may be cooled to produce a second water slurry containing solid sodium hydrogen carbonate (the same applies in the following description).

[0015] In this specification, ordinal numbers such as "first," "second," etc., are used to distinguish between things that have the same wording (substance) but differ in the timing of their use. "First aqueous slurry containing solid sodium bicarbonate" and "second aqueous slurry containing solid sodium bicarbonate" are both aqueous slurries containing solid sodium bicarbonate. However, the former refers to the aqueous slurry containing solid sodium bicarbonate before supplying water, carbon dioxide, and solid sodium carbonate in the sodium bicarbonate production method of this embodiment, while the latter refers to the aqueous slurry containing solid sodium bicarbonate after supplying water, carbon dioxide, and solid sodium carbonate to the first aqueous slurry containing solid sodium bicarbonate and carrying out the reaction in the sodium bicarbonate production method of this embodiment. Note that "aqueous slurry containing solid sodium bicarbonate" without an ordinal number means that the timing of its use is not limited, and includes both the first aqueous slurry containing solid sodium bicarbonate and the second aqueous slurry containing solid sodium bicarbonate. Both "first sodium bicarbonate aqueous solution" and "second sodium bicarbonate aqueous solution" are sodium bicarbonate aqueous solutions. However, the former refers to the sodium bicarbonate aqueous solution before supplying water, carbon dioxide, and solid sodium carbonate in the sodium bicarbonate production method of this embodiment, while the latter refers to the sodium bicarbonate aqueous solution that is the separated liquid obtained by solid-liquid separation of the second aqueous slurry containing the solid sodium bicarbonate mentioned above in the sodium bicarbonate production method of this embodiment. Note that "sodium bicarbonate aqueous solution" without an ordinal number means that the timing of its use is not limited, and includes both the first sodium bicarbonate aqueous solution and the second sodium bicarbonate aqueous solution.

[0016] Sodium bicarbonate is produced when a sodium carbonate reacts with water and carbon dioxide, yielding a second aqueous slurry containing solid sodium bicarbonate. When the sodium carbonate is sodium carbonate (Na2CO3), this reaction is represented by equation 2 below. Na2CO3+CO2+H2O→2NaHCO3 formula 2

[0017] The supply of water, carbon dioxide, and solid sodium carbonate to the first aqueous slurry or first sodium bicarbonate aqueous solution containing solid sodium bicarbonate may be carried out simultaneously or separately. In particular, the method of supplying water and solid sodium carbonate to the first aqueous slurry or first sodium bicarbonate aqueous solution containing solid sodium bicarbonate to obtain a reaction solution, and then supplying carbon dioxide to the obtained reaction solution is preferred. Hereinafter, "reaction solution" means the solution obtained by supplying water and solid sodium carbonate to the first aqueous slurry or first sodium bicarbonate aqueous solution containing solid sodium bicarbonate, before the supply of carbon dioxide.

[0018] By supplying carbon dioxide to the above reaction solution, the precipitation rate of sodium bicarbonate can be easily controlled, and clogging of the pipes can be easily suppressed. The sodium carbonate in the reaction solution may be completely dissolved, or it may be an aqueous slurry containing solid sodium carbonate. Furthermore, sodium bicarbonate is dissolved in the reaction solution. In addition, sodium hydroxide may be dissolved in the reaction solution, or it may contain solid sodium bicarbonate.

[0019] The sodium bicarbonate equivalent concentration relative to the total mass of the reaction solution (including solids contained in the reaction solution) is preferably 7 to 44% by mass, more preferably 8 to 39% by mass, and even more preferably 9 to 36% by mass. If the sodium bicarbonate equivalent concentration is above the lower limit, it can be determined that the increase in the volume of reaction liquid in the reaction vessel is suppressed. If the sodium bicarbonate equivalent concentration is below the upper limit, the increase in the viscosity of the reaction solution is suppressed, and the reaction solution can be sufficiently stirred and circulated. In addition, the rate of sodium bicarbonate production is less likely to decrease.

[0020] The temperature of the reaction solution when reacting a sodium carbonate with carbon dioxide is preferably 0 to 100°C, more preferably 5 to 80°C, and even more preferably 10 to 60°C. If the temperature is above the lower limit, freezing of the reaction solution can be suppressed. If the temperature is below the upper limit, evaporation of water can be suppressed. Furthermore, the dissolution of carbon dioxide can be promoted.

[0021] <Solid sodium carbonate and water> Solid sodium carbonates are solid salts containing sodium ions and carbonate ions as constituent ions. They may also be hydrates. However, sodium bicarbonate is not included in solid sodium carbonates. Examples of solid sodium-based carbonates include sodium carbonate (Na2CO3), sodium sesquicarbonate (NaHCO3·Na2CO3·2H2O), and Wigscheider salt (Na2CO3·3NaHCO3), with sodium carbonate being preferred.

[0022] The solid sodium carbonate and water may be supplied by adding the solid sodium carbonate and water separately, or by supplying them simultaneously as an aqueous slurry containing the solid sodium carbonate. The aqueous slurry may also contain dissolved sodium hydroxide and sodium bicarbonate, or it may contain solid sodium bicarbonate.

[0023] Water may be supplied as water alone, or as an aqueous solution or aqueous slurry. Examples of aqueous solutions include at least one aqueous solution selected from the group consisting of aqueous sodium hydroxide solution, aqueous sodium carbonate solution, and aqueous sodium bicarbonate solution, with aqueous sodium hydroxide solution and aqueous sodium carbonate solution being preferred, and aqueous sodium hydroxide solution being more preferred. As for the aqueous slurry, an aqueous slurry containing solid sodium bicarbonate is preferred. Note that two or more solutes (two or more of sodium hydroxide, sodium carbonate, and sodium bicarbonate) may be dissolved in the above aqueous solutions and aqueous slurry.

[0024] <Carbon dioxide> Regarding the supply of carbon dioxide, it is preferable to supply gas bubbles containing carbon dioxide. In other words, it is preferable to supply carbon dioxide by the fine bubble method. The gas containing carbon dioxide is not particularly limited as long as the carbon dioxide concentration is 10% by volume or more. It is not limited to mixed gases of carbon dioxide with air or nitrogen gas, such as exhaust gas from combustion furnaces, exhaust gas from glass melting furnaces, or gases generated by the neutralization of carbonates, but can also be used, including high-purity carbon dioxide gas. The carbon dioxide concentration is preferably 30% by volume or more, and more preferably 50% by volume or more. There is no particular upper limit on the carbon dioxide concentration, and it may be 100% by volume.

[0025] Fine bubbles are preferred for gas bubbles containing carbon dioxide. Fine bubbles are a general term for microbubbles with a diameter of 1 to 100 μm and nanobubbles with a diameter of less than 1 μm. When many microbubbles are generated in water, it appears as turbidity. On the other hand, because nanobubbles are extremely small, the water remains clear. By making the bubbles of gas containing carbon dioxide into fine bubbles, the dissolution rate of carbon dioxide into the reaction solution can be increased, and almost all of the supplied carbon dioxide can easily react with the sodium carbonate and sodium hydroxide in the reaction solution, allowing the carbon dioxide to react without loss. This not only eliminates the need for conventional equipment to recover unreacted carbon dioxide, but also allows for a sufficient reaction rate even with gases with low carbon dioxide concentrations. Furthermore, it has the advantage of not requiring pressurized reaction vessels, and allowing the use of simple atmospheric pressure equipment. In addition, because the crystallization of sodium bicarbonate can be performed at a very high speed, microcrystalline sodium bicarbonate precipitates, making it easy to obtain sodium bicarbonate powder with high oil absorption and low apparent density.

[0026] The d50 of the carbon dioxide-containing gas bubbles is preferably 100 μm or less, more preferably 50 to 90 μm, and even more preferably 60 to 80 μm. Furthermore, the d90 of the carbon dioxide-containing gas bubbles is preferably 150 μm or less, more preferably 100 to 150 μm, and even more preferably 100 to 130 μm.

[0027] In this embodiment, so-called nanobubbles with a diameter of less than 1 μm do not necessarily need to be present. The minimum size of the bubbles in the carbon dioxide-containing gas is not particularly limited, but from the viewpoint of ease of adjusting the size of the bubbles in the carbon dioxide-containing gas, it may be greater than 1 μm or even 10 μm or more. According to this embodiment, the utilization rate of carbon dioxide can be sufficiently increased even without the presence of nanobubbles with a size of less than 1 μm or less.

[0028] The carbon dioxide utilization rate is preferably 95% or higher, more preferably 98% or higher, and even more preferably 100%.

[0029] Gas bubbles containing carbon dioxide of the size described above can be obtained by appropriately adjusting the conditions of known fine bubble preparation methods. The apparatus for producing such fine bubbles is not particularly limited, but includes the following: (Example 1) A device that supplies gas to the suction side of a pressure pump and uses mixing blades that rotate at high speed inside the pressure pump to turn the inhaled gas into fine bubbles. A specific example is the "Vortex Turbo Mixer Pump" (product name) manufactured by Nikuni Corporation. (Example 2) A device that creates a low-pressure region in a liquid flow by using the Venturi effect (narrowing the flow path of a pressurized liquid to increase the flow velocity and create a low-pressure region), and then supplies gas to that region to create fine bubbles. Specific examples include the "YJ Nozzle" (product name) from Envirovision and the "Aqua Transfer Nozzle" (product name) from Waternavi. (Example 3) A device that creates a negative pressure zone in the center by ejecting water radially from a high-speed rotating disc, and then draws in gas to create fine bubbles. A specific example is "Spinor" (product name) manufactured by Waternavi. Regarding the time for supplying carbon dioxide-containing gas bubbles to the reaction solution, there are no particular restrictions as long as the desired reaction can proceed sufficiently, but for example, it is 0.2 to 16 hours, and preferably 0.5 to 8 hours.

[0030] <Solid-liquid separation> The second aqueous slurry containing the generated solid sodium bicarbonate is treated in a solid-liquid separator to separate it into a second sodium bicarbonate aqueous solution (separate liquid) and a wet solid. The separated liquid is, for example, the filtrate when the solid-liquid separation method is filtration, and the supernatant when the solid-liquid separation method is centrifugation. The wet solid is, for example, the residue when the solid-liquid separation method is filtration, and the precipitate when the solid-liquid separation method is centrifugation. The wet solid contains solid sodium bicarbonate as well as a sodium bicarbonate aqueous solution. The wet solid is dried to obtain sodium bicarbonate powder. As will be described later, it is preferable to supply the separated liquid, which is the second sodium bicarbonate aqueous solution, back to the reaction vessel (recycle it). That is, it is preferable to use the second sodium bicarbonate aqueous solution from the previous batch as the first sodium bicarbonate aqueous solution from the next batch.

[0031] It is not necessary to use the second sodium bicarbonate aqueous solution as the first sodium bicarbonate aqueous solution. For example, a sodium bicarbonate aqueous solution produced by a method other than the one described above may be used as the first sodium bicarbonate aqueous solution. Alternatively, a separated liquid obtained by solid-liquid separation of an aqueous slurry containing solid sodium bicarbonate produced by a method other than the one described above may be used as the first sodium bicarbonate aqueous solution. Furthermore, when using the second sodium bicarbonate aqueous solution from the previous batch as the first sodium bicarbonate aqueous solution for the next batch, it is sufficient that at least a portion of the first sodium bicarbonate aqueous solution for the next batch is the second sodium bicarbonate aqueous solution from the previous batch. Preferably, 50% by mass or more of the first sodium bicarbonate aqueous solution for the next batch is the second sodium bicarbonate aqueous solution from the previous batch, more preferably 80% by mass or more is the second sodium bicarbonate aqueous solution, and even more preferably all of it is the second sodium bicarbonate aqueous solution.

[0032] <Recycling of the second sodium bicarbonate solution> As described above, the sodium bicarbonate produced in Equation 2 is obtained in the form of an aqueous slurry (i.e., a second aqueous slurry containing solid sodium bicarbonate). Solid-liquid separation is performed on this second aqueous slurry containing solid sodium bicarbonate, and the resulting wet solid is dried to produce sodium bicarbonate powder. The second aqueous sodium bicarbonate solution, which is the separated liquid obtained by solid-liquid separation, is sometimes recycled back into the reaction vessel. In this recycling case, conventionally, an aqueous sodium hydroxide solution with a sodium amount equivalent to the sodium bicarbonate powder produced above was supplied back into the reaction vessel, and the reaction was carried out again (the reaction of the next batch).

[0033] On the other hand, as mentioned above, in the method of producing sodium bicarbonate by reacting an aqueous sodium hydroxide solution shown in Equation 3 with carbon dioxide, no water is consumed. That is, in the reaction of the next batch, the amount of water that needs to be supplied to the reaction vessel is only the amount of water that evaporated in the reaction process of the previous batch and the amount of water contained in the wet solid.

[0034] However, even when using a high-concentration sodium hydroxide aqueous solution, supplying a sodium hydroxide aqueous solution with an amount of sodium equivalent to the sodium bicarbonate powder produced as described above to the reaction vessel will result in a larger amount of water being supplied to the reaction vessel than the amount of water required. As the above reaction and the recycling of the separated liquid are repeated, the amount of water in the reaction vessel will gradually increase, and eventually, the volume of liquid in the reaction vessel will exceed the internal volume of the reaction vessel.

[0035] Two methods are known for controlling the volume of liquid in a reaction vessel to a constant level. The first method involves discarding a portion of the separated liquid and recycling only the remaining separated liquid back into the reaction vessel, thereby controlling the volume of liquid in the reaction vessel to a constant level. The second method involves processing the separated liquid in a concentration device to remove a certain amount of water, and then recycling the concentrated separated liquid back into the reaction vessel, thereby controlling the volume of liquid in the reaction vessel to a constant level.

[0036] However, the first method is inefficient from the standpoint of resource utilization because the sodium bicarbonate dissolved in the discarded separated liquid is lost. While it is conceivable to reduce sodium bicarbonate loss by cooling a second aqueous slurry containing solid sodium bicarbonate to a low temperature before solid-liquid separation to lower the concentration of sodium bicarbonate in the separated liquid, this method also results in loss of sodium bicarbonate in the separated liquid. Furthermore, cooling requires a significant amount of energy, making it inefficient.

[0037] Furthermore, the second method requires a concentration device for concentration. Concentration methods include evaporation of water by heating, gas-liquid contact in a packed column, and fine bubble supply, but these require a great deal of energy. In addition, water is lost during concentration, making it inefficient from the standpoint of effective resource utilization.

[0038] On the other hand, in the method for producing sodium bicarbonate according to this embodiment, a solid sodium-based carbonate is supplied as the sodium source. Therefore, the inventors of this application have found that it is possible to supply only the amount of water equivalent to the water evaporated in the reaction process of the previous batch and the water contained in the above-mentioned wet solid to the reaction vessel, thereby solving the above problem.

[0039] The following describes the method for producing sodium bicarbonate in this embodiment, in which the second aqueous sodium bicarbonate solution, which is the separated liquid, is recycled back into the reaction vessel, with reference to the sodium bicarbonate production apparatus.

[0040] <<Sodium bicarbonate production equipment>> The sodium bicarbonate production apparatus 100A shown in Figure 1 comprises a raw material storage tank 1, a reaction tank 5, a solid-liquid separation device 10, a drying device 12, and a separated liquid recovery tank 14. The raw material storage tank 1 is equipped with a stirring device 2. The reaction tank 5 is equipped with a stirring device 6. The reaction tank 5 is equipped with a circulation pipe 8. The circulation pipe 8 is equipped with a magnetic pump 7 and a YJ nozzle 21. The YJ nozzle 21 is connected to a carbon dioxide supply pipe 20. In the sodium bicarbonate production apparatus 100A shown in Figure 1, the YJ nozzle 21 is equipped as an example of a device for creating fine bubbles, but other devices for creating fine bubbles as described above may be provided instead of the YJ nozzle 21. The raw material storage tank 1 and the reaction tank 5 are connected via a pipe 4. The pipe 4 is equipped with a magnetic pump 3. The reaction tank 5 and the solid-liquid separation device 10 are connected via a pipe 9 (circulation pipe 8 → pipe 9). The solid-liquid separation device 10 and the separated liquid recovery tank 14 are connected via a pipe 13. The solid-liquid separation device 10 and the drying equipment 12 are connected via piping 11. The separated liquid recovery tank 14 and the reaction tank 5 are connected via piping 16. A magnetic pump 15 is installed in piping 16.

[0041] The sodium bicarbonate production apparatuses 100B to 100D shown in Figures 2 to 4 are modified versions of the sodium bicarbonate production apparatus 100A shown in Figure 1. Below, we will omit explanations of configurations similar to those of the sodium bicarbonate production apparatus 100A, and only describe the differences. In the sodium bicarbonate production apparatus 100B shown in Figure 2, the separation liquid recovery tank 14 and the reaction tank 5 are not connected via piping 16, while the separation liquid recovery tank 14 and the raw material storage tank 1 are connected via piping 16. Furthermore, the circulation piping 8 and piping 9 are not connected, and the reaction tank 5 and the solid-liquid separator 10 are connected only via piping 9. This configuration facilitates continuous operation. Note that in the sodium bicarbonate production apparatus 100A shown in Figure 1 and the sodium bicarbonate production apparatus 100C shown in Figure 3, the reaction tank 5 and the solid-liquid separator 10 may also be connected only via piping 9. In the sodium bicarbonate production apparatus 100C shown in Figure 3, the reaction vessel 5 is further equipped with a cooling pipe 22. In the sodium bicarbonate production apparatus 100D shown in Figure 4, the reaction vessel 5 does not have circulation piping 8. The reaction vessel 5 is equipped with a nozzle pipe 23. A carbon dioxide supply pipe 20 is connected to the nozzle pipe 23.

[0042] <First batch of sodium bicarbonate production> Referring to the sodium bicarbonate production apparatus 100A shown in Figure 1, the first batch of sodium bicarbonate production will be described. An aqueous solution or aqueous slurry of the sodium source compound and, if necessary, water are supplied to the raw material storage tank 1 and mixed by the stirring device 2 to produce a sodium source-containing liquid. Either sodium hydroxide or sodium carbonate, or both, can be used as the sodium source compound. That is, at least one selected from the group consisting of aqueous sodium hydroxide solution, aqueous sodium carbonate solution, and aqueous slurry containing solid sodium carbonate is supplied to the raw material storage tank 1. The sodium source compound may be supplied to the raw material storage tank 1 as a solid and then converted into an aqueous solution or aqueous slurry within the raw material storage tank 1. Water is also supplied as necessary to adjust the concentration. When using an aqueous sodium carbonate solution or aqueous slurry containing solid sodium carbonate, it is necessary that there is at least the stoichiometric amount of water relative to the sodium carbonate as shown in Equation 2 above.

[0043] The obtained sodium source-containing liquid is supplied to the reaction vessel 5 via piping 4 using a magnetic pump 3. The sodium source-containing liquid is mixed by a stirrer 6. In the first batch of sodium bicarbonate production, the reaction vessel 5 may or may not contain an aqueous sodium bicarbonate solution (i.e., the first aqueous sodium bicarbonate solution) or a water slurry containing solid sodium bicarbonate (i.e., the first water slurry containing solid sodium bicarbonate). The sodium source-containing liquid is supplied to the YJ nozzle 21 by circulating it through the circulation piping 8 using a magnetic pump 7. Gas containing carbon dioxide is supplied to the center of the YJ nozzle 21 via the carbon dioxide supply piping 20, and is atomized into fine bubbles within the YJ nozzle so that d50 and d90 are within the above range, and the bubbles of carbon dioxide-containing gas are supplied to the sodium source-containing liquid. As gas containing carbon dioxide is introduced, the pH of the sodium source-containing liquid in the reaction vessel decreases, and sodium bicarbonate precipitates, causing it to become cloudy. Finally, when the pH of the sodium source-containing liquid in the reaction vessel falls below 8.5, the supply of gas containing carbon dioxide is stopped. As a result, a water slurry containing solid sodium bicarbonate is obtained. If the sodium bicarbonate production apparatus 100A is equipped with the above-mentioned other fine bubble generating device instead of the YJ nozzle 21, gas bubbles containing carbon dioxide are supplied to the sodium source-containing liquid by the above-mentioned other fine bubble generating device. In the case of the sodium bicarbonate production apparatus 100D shown in Figure 4, gas containing carbon dioxide is supplied to the sodium source-containing liquid by bubbling from the nozzle pipe 23. The sodium bicarbonate production apparatus 100A is preferable to the sodium bicarbonate production apparatus 100D in that carbon dioxide can be supplied by the fine bubble method. In the case of the sodium bicarbonate production apparatus 100C shown in Figure 3, the water slurry containing the obtained solid sodium bicarbonate may be cooled by the cooling pipe 22. By cooling, the amount of solid sodium bicarbonate in the water slurry containing solid sodium bicarbonate can be increased, and the concentration of sodium bicarbonate in the separated liquid obtained by the solid-liquid separation described later can be lowered.On the other hand, according to the sodium bicarbonate production method of this embodiment for the second batch and subsequent batches of sodium bicarbonate production, when the separated liquid is recycled back into the reaction vessel, the volume of liquid in the reaction vessel can be controlled to be constant regardless of the sodium bicarbonate concentration of the separated liquid, so cooling is not required. Energy can be saved by not performing cooling.

[0044] The resulting aqueous slurry containing solid sodium bicarbonate is supplied to the solid-liquid separator 10 via piping 9 using a magnetic pump 7. The solid-liquid separator 10 is, for example, a centrifuge, a filter, etc. The wet solid separated in the solid-liquid separator 10 is supplied to the drying equipment 12 via piping 11, where it is dried to obtain sodium bicarbonate powder. The separated liquid, which is a saturated sodium bicarbonate aqueous solution separated in the solid-liquid separator 10, is recovered in the separated liquid recovery tank 14 via piping 13. The separated liquid is then recycled to the reaction tank 5 via piping 16 using a magnetic pump 15. This separated liquid can be used as the first sodium bicarbonate aqueous solution in this embodiment. In the case of the sodium bicarbonate production apparatus 100B shown in Figure 2, the separated liquid is recycled to the raw material storage tank 1 via piping 16 using a magnetic pump 15. The above process may be performed sequentially or in batches.

[0045] <Second batch of sodium bicarbonate production> The second batch of sodium bicarbonate production will be described with reference to the sodium bicarbonate production apparatus 100A shown in Figure 1 or the sodium bicarbonate production apparatus 100B shown in Figure 2. The raw material storage tank 1 or reaction tank 5 contains the separated liquid (i.e., the first sodium bicarbonate aqueous solution), which is a saturated sodium bicarbonate aqueous solution obtained in the first batch of sodium bicarbonate production. In the second batch of sodium bicarbonate production, water and solid sodium carbonate are supplied to the reaction tank 5 to obtain a reaction solution. The method of supplying water and solid sodium carbonate is as described above. For example, when supplying water and solid sodium carbonate as an aqueous slurry containing solid sodium carbonate, the aqueous slurry containing solid sodium carbonate may be supplied directly to the reaction tank 5. Alternatively, the aqueous slurry containing solid sodium carbonate and the separated liquid may be mixed in the raw material storage tank 1, and then the resulting aqueous slurry or aqueous solution may be supplied to the reaction tank 5 via piping 4 using a magnetic pump 3. Furthermore, when supplying the above-mentioned aqueous solution or aqueous slurry as water, the aqueous solution or aqueous slurry may be prepared in the raw material storage tank 1, and then supplied to the reaction tank 5 via piping 4 using a magnetic pump 3. The amount of water supplied to the reaction tank 5 is preferably an amount equivalent to the water consumed when the sodium carbonate contained in the sodium source liquid of the first batch of sodium bicarbonate production is converted to sodium bicarbonate (Equation 2 above), the water evaporated during the reaction process, and the water contained in the above-mentioned wet solid. As a result, the volume of the liquid after reaction with carbon dioxide in the reaction tank 5 can be controlled to be equivalent to the volume of the liquid after reaction with carbon dioxide in the reaction tank 5 of the first batch of sodium bicarbonate production. The amounts of sodium carbonate, sodium hydroxide, and sodium bicarbonate supplied to the reaction tank 5 are adjusted according to the target yield of sodium bicarbonate powder. For example, if the target yield is the same as that of the first batch of sodium bicarbonate production, the sodium bicarbonate equivalent concentration in the sodium source liquid in the reaction tank 5 of the first batch of sodium bicarbonate production should be the same.The water and solid sodium carbonate may be supplied to the separated liquid in the separated liquid recovery tank 14, and then recycled to the reaction tank 5 via the piping 16 using the magnetic pump 7.

[0046] In the sodium bicarbonate production apparatus 100B shown in Figure 2, the raw material storage tank 1 contains a separated liquid (i.e., the first sodium bicarbonate aqueous solution), which is a saturated sodium bicarbonate aqueous solution obtained in the first batch of sodium bicarbonate production. In the second batch of sodium bicarbonate production, solid sodium carbonate and water may be supplied to the raw material storage tank 1 to obtain a reaction solution. The method and amount of supply of solid sodium carbonate and water are as described above. The reaction solution is supplied to the reaction tank 5 via piping 4 using a magnetic pump 3. As long as the amount of solid sodium carbonate and water supplied to the reaction solution in the reaction tank 5 does not exceed the appropriate supply amount of solid sodium carbonate and water described above, solid sodium carbonate and water may be supplied further to the reaction solution supplied to the reaction tank 5. In this embodiment as well, water and solid sodium carbonate may be supplied directly to the reaction tank 5.

[0047] A gas containing carbon dioxide is supplied to the resulting reaction solution to obtain an aqueous slurry containing solid sodium bicarbonate (i.e., a second aqueous slurry containing solid sodium bicarbonate). The obtained second aqueous slurry containing solid sodium bicarbonate is subjected to solid-liquid separation to obtain a separated liquid consisting of a wet solid and a saturated sodium bicarbonate aqueous solution. The wet solid is dried to obtain sodium bicarbonate powder. These steps can be carried out in the same manner as in the first batch of sodium bicarbonate production. The obtained separated liquid (i.e., the second sodium bicarbonate aqueous solution) is recycled to the reaction tank 5 or raw material storage tank 1 in the same manner as in the first batch of sodium bicarbonate production, and becomes the first sodium bicarbonate aqueous solution in the third batch of sodium bicarbonate production. Thereafter, the same steps as in the second batch of sodium bicarbonate production are repeated.

[0048] When the target yield of sodium bicarbonate powder for the nth batch and the (n+1)th batch are the same (where n is an integer greater than or equal to 1), the ratio of the volume of the water slurry after the reaction of the (n+1)th batch (i.e., the second water slurry containing solid sodium bicarbonate) to the volume of the water slurry after the reaction of the nth batch (i.e., the second water slurry containing solid sodium bicarbonate) is preferably 1.08 or less, more preferably 1.06 or less, even more preferably 1.04 or less, and particularly preferably 1.00. If the ratio is greater than 1 and the batch is repeated multiple times, it leads to an increase in the liquid volume in the reaction apparatus, and it becomes necessary to discard a portion before it exceeds the limit that can be held in the apparatus. On the other hand, if the ratio is less than 1, it is not a major problem in repeating the operation because water and a sodium source can be added, but in that case, it is preferably 0.90 or more, and even more preferably 0.95 or more. According to the method for producing sodium bicarbonate of this embodiment, it is easy to control the above ratio within the above range. Furthermore, by keeping the above ratios within the specified range, resources such as sodium carbonate, sodium hydroxide, sodium bicarbonate, water, and carbon dioxide can be utilized effectively. Additionally, since concentration of the separated liquid and the need for larger reaction vessels are eliminated, energy conservation is achieved.

[0049] <Sodium bicarbonate powder> By supplying carbon dioxide using the fine bubble method, sodium bicarbonate powder with the following physical properties can be easily obtained.

[0050] (Oil absorption amount) The oil absorption capacity of sodium bicarbonate powder is preferably 40 mL / 100g or more, more preferably 60 mL / 100g or more, and even more preferably 100 mL / 100g or more. When the oil absorption capacity is above the lower limit, the sodium bicarbonate powder tends to have excellent moisture resistance and deodorizing properties. There is no upper limit to the oil absorption capacity, but it is usually 200 mL / 100g or less.

[0051] (Apparent density) The apparent density of sodium bicarbonate powder is preferably 0.32 g / mL or less, more preferably 0.25 g / mL or less, and even more preferably 0.10 g / mL or less. When the apparent density is below the above upper limit, the sodium bicarbonate powder tends to have excellent moisture resistance and deodorizing properties. The lower limit of the apparent density is not limited, but is usually 0.04 g / mL or more.

[0052] (crystallite size) The sodium bicarbonate powder preferably has a crystallite size of 75 nm or less for the (210) plane and 70 nm or less for the (121) plane. The crystallite size of the (210) plane is more preferably 60 nm or less, and even more preferably 45 nm or less. When the crystallite size of the (210) plane is below the above upper limit, the moisture resistance and deodorizing properties of the sodium bicarbonate powder can be further improved. There is no particular lower limit to the crystallite size of the (210) plane, but it is usually 20 nm or more. The crystallite size of the (121) plane is more preferably 55 nm or less, and even more preferably 40 nm or less. When the crystallite size of the (121) plane is below the above upper limit, the moisture resistance and deodorizing properties of the sodium bicarbonate powder can be further improved. There is no particular lower limit to the crystallite size of the (121) plane, but it is usually 15 nm or more. Furthermore, the ratio (D210 / D121) of the crystallite size of the (210) plane (D210) to the crystallite size of the (121) plane (D121) is preferably 0.60 to 1.00, and more preferably 0.70 to 0.90. When this ratio (D210 / D121) is within the above range, the moisture resistance and deodorizing properties of the sodium bicarbonate powder can be further improved.

[0053] (d50 sodium bicarbonate powder) The d50 of the sodium bicarbonate powder is preferably 1 to 100 μm, and more preferably 5 to 50 μm. When d50 is within the above range, it becomes easier to improve the moisture resistance and deodorizing properties of the sodium bicarbonate powder. [Examples]

[0054] The present invention will be described in more detail below using examples, but the present invention is not limited to these examples. Examples 1 to 6 are examples, and Examples 7 and 8 are comparative examples.

[0055] <Measurement method> (carbon dioxide utilization rate) The carbon dioxide utilization rate was defined as the ratio, expressed as a percentage, of the theoretical amount of carbon dioxide (L) required to convert all of the sodium hydroxide and sodium carbonates in the reaction solution to sodium bicarbonate, to the amount of carbon dioxide (L) supplied for the production of sodium bicarbonate. This is referred to as "CO2 utilization rate" in Table 1.

[0056] (Concentration equivalent to sodium bicarbonate) The sodium bicarbonate equivalent concentration (hereinafter also simply referred to as "sodium bicarbonate concentration") in an aqueous slurry containing solid sodium bicarbonate was calculated by measuring the sodium concentration in the aqueous slurry containing solid sodium bicarbonate and converting the above sodium concentration to the sodium bicarbonate concentration. The sodium concentration in the aqueous slurry containing solid sodium bicarbonate was measured by atomic absorption spectroscopy after preparing an acidic aqueous solution by diluting the aqueous slurry containing solid sodium bicarbonate with nitric acid.

[0057] [Example 1] (First batch of sodium bicarbonate production) The sodium bicarbonate production apparatus 100A shown in Figure 1 was used. First, 800g of sodium carbonate powder and 4000g of deionized water were placed in a raw material storage tank 1 with an internal volume of 8L and stirred to obtain 4800g of a 16.7% by mass sodium carbonate aqueous solution, which was the sodium source-containing liquid. Next, this sodium source-containing liquid was transferred to a reaction tank 5 with an internal volume of 8L using a magnetic pump 3, and then the magnetic pump 7 was started and the liquid was circulated using the circulation piping 8. The magnetic pump used was the "Stainless Steel Motor Pump MM-254 (product name)" manufactured by Maruhachi Pump Manufacturing Co., Ltd. (the same applies hereafter). The circulation flow rate was 20L / min. Immediately after starting the circulation, carbon dioxide was supplied to the YJ nozzle 21 at a rate of 2.8L / min to supply the carbon dioxide in the form of fine bubbles. The YJ nozzle used was the "YJ-6 inline (product name)" manufactured by Envirovision Co., Ltd. (the same applies hereafter). The liquid temperature of the sodium source-containing liquid in the reaction tank 5 during carbon dioxide supply was 22-50°C. Sixty minutes after the start of carbon dioxide supply, the reaction vessel 5 contained a cloudy aqueous slurry with a pH of 8.4 containing solid sodium bicarbonate. The mass of the aqueous slurry containing solid sodium bicarbonate withdrawn from reaction vessel 5 was 5094 g. The entire amount of this aqueous slurry containing solid sodium bicarbonate was separated using a solid-liquid separator 10 to obtain 1106 g of centrifugal dewatered cake (moist solid) and 3978 g of filtrate (separated liquid). The solid-liquid separator 10 used was the "H-110F model" manufactured by Kokusan Co., Ltd. (the same applies hereafter). The centrifugal dewatered cake was dried under a carbon dioxide atmosphere at 80°C to obtain 883 g of sodium bicarbonate powder. The separated liquid was a saturated aqueous sodium bicarbonate solution (sodium bicarbonate concentration: 9.3 mass%), and this entire amount was recycled back into reaction vessel 5. It was confirmed that the concentration of the aqueous slurry containing solid sodium bicarbonate before solid-liquid separation was 24.6 mass%.

[0058] (Second batch of sodium bicarbonate production) 563g of sodium carbonate powder and 319g of deionized water were added to reaction vessel 5 containing the separated liquid (i.e., the first sodium bicarbonate aqueous solution) to obtain the reaction solution. This reaction solution was circulated using the circulation piping 8 by starting the magnetic pump 7. Immediately after starting the circulation, carbon dioxide was supplied to the YJ nozzle 21 at a rate of 2.0 L / min to supply the carbon dioxide in the form of fine bubbles. The temperature of the reaction solution in reaction vessel 5 at the time of carbon dioxide supply was 30-50°C. 60 minutes after starting the supply of carbon dioxide, the contents of reaction vessel 5 became a cloudy aqueous slurry containing solid sodium bicarbonate with a pH of 8.4 (i.e., a second aqueous slurry containing solid sodium bicarbonate). The mass of the aqueous slurry containing solid sodium bicarbonate withdrawn from reaction vessel 5 was 5086g, which was approximately the same amount as the first batch of sodium bicarbonate production. The entire aqueous slurry containing solid sodium bicarbonate was separated using a solid-liquid separator 10 to obtain 1113 g of centrifugal dewatered cake (moist solid) and 3964 g of filtrate (separated liquid). The masses of each were approximately the same as those of the first batch of sodium bicarbonate production. The centrifugal dewatered cake was then dried in a carbon dioxide atmosphere at 80°C to obtain 888 g of sodium bicarbonate powder, which was confirmed to be approximately the same as the amount of sodium bicarbonate produced in the first batch. The concentration of the aqueous slurry containing solid sodium bicarbonate before solid-liquid separation was confirmed to be 24.7% by mass. Table 1 shows the carbon dioxide utilization rate (referred to as "CO2 utilization rate"), whether or not solid sodium carbonate was used, the type of water added, the operating method, the concentration of sodium bicarbonate in the aqueous slurry containing solid sodium bicarbonate obtained after reaction with carbon dioxide (referred to as "NaHCO3 concentration in NaHCO3 aqueous slurry" in Table 1), the mass of the aqueous slurry containing sodium bicarbonate (referred to as "NaHCO3 aqueous slurry mass" in Table 1), and the yield of sodium bicarbonate powder (referred to as "NaHCO3 powder yield" in Table 1) in the first and second batches of sodium bicarbonate production (the same applies to Examples 2-8 below).

[0059] [Example 2] (First batch of sodium bicarbonate production) The sodium bicarbonate production apparatus 100B shown in Figure 2 was used. The first batch of sodium bicarbonate production was carried out in the same manner as in Example 1. The mass of the aqueous slurry containing solid sodium bicarbonate withdrawn from reaction vessel 5 was 5100 g. Note that the slight difference in the mass of the aqueous slurry containing solid sodium bicarbonate obtained from Example 1 is due to the difference in the amount of loss during recovery. The entire amount of this aqueous slurry containing solid sodium bicarbonate was separated using a solid-liquid separator 10 to obtain 1108 g of centrifugal dewatered cake (moist solid) and 3983 g of filtrate (separated liquid). The centrifugal dewatered cake was dried in a carbon dioxide atmosphere at 80°C to obtain 884 g of sodium bicarbonate powder. The separated liquid was a saturated aqueous sodium bicarbonate solution (sodium bicarbonate concentration: 9.3 mass%), and this entire amount was recycled to the raw material storage tank 1. It was confirmed that the sodium bicarbonate concentration of the aqueous slurry containing solid sodium bicarbonate before solid-liquid separation was 24.6 mass%. Next, following the same procedure as in Example 1, an aqueous slurry containing 5106 g of solid sodium bicarbonate with a sodium bicarbonate concentration of 24.7% by mass was prepared in reaction vessel 5.

[0060] (Second batch of sodium bicarbonate production) 240 g of sodium carbonate powder and 509 g of a 48% by mass sodium hydroxide aqueous solution were added to the raw material storage tank 1 containing the separated liquid to obtain the reaction solution. The aqueous slurry containing solid sodium bicarbonate in reaction tank 5 was circulated using the circulation piping 8 by activating the magnetic pump 7. Immediately after the start of circulation, carbon dioxide was supplied to the YJ nozzle 21 at a rate of 3.1 L / min. Immediately after the start of carbon dioxide supply, the reaction solution was supplied to reaction tank 5 at a rate of 79 g / min via piping 4 using the magnetic pump 3. Immediately after that, the aqueous slurry containing solid sodium bicarbonate in reaction tank 5 was continuously drained by overflow via piping 9. The liquid temperature of the reaction solution in reaction tank 5 during carbon dioxide supply was 30-50°C. Sixty minutes after the start of carbon dioxide supply, all of the reaction solution from raw material storage tank 1 had been supplied to reaction tank 5, and the contents of reaction tank 5 became a cloudy aqueous slurry containing solid sodium bicarbonate with a pH of 8.4 (i.e., a second aqueous slurry containing solid sodium bicarbonate). The mass of the aqueous slurry containing solid sodium bicarbonate that was withdrawn from reaction tank 5 was 5081g, which was approximately the same amount as before the supply of the reaction solution from raw material storage tank 1 began.

[0061] The reaction was carried out continuously as described above. After an arbitrary time had elapsed since the start of the reaction, the total mass of the aqueous slurry containing solid sodium bicarbonate continuously withdrawn for 30 minutes during the reaction was 2551 g, and the sodium bicarbonate concentration was 24.6 mass%. The entire aqueous slurry containing solid sodium bicarbonate was separated using a solid-liquid separator 10 to obtain 554 g of centrifugal dehydrated cake (moist solid) and 1969 g of filtrate (separated liquid). The centrifugal dehydrated cake was then dried in a carbon dioxide atmosphere at 80°C to obtain 442 g of sodium bicarbonate powder. Subsequently, the entire aqueous slurry containing solid sodium bicarbonate withdrawn from the reaction tank 5 after the reaction was separated using a solid-liquid separator 10 to obtain 1111 g of centrifugal dehydrated cake (moist solid) and 3961 g of filtrate (separated liquid). The sodium bicarbonate concentration of the aqueous slurry containing solid sodium bicarbonate was 24.7 mass%. The centrifugal dehydrated cake was then dried under a carbon dioxide atmosphere at 80°C, yielding a mass of 886g of sodium bicarbonate powder. The masses of the centrifugal dehydrated cake, filtrate, and sodium bicarbonate powder were all confirmed to be approximately the same as those obtained by filtering and drying the aqueous slurry containing sodium bicarbonate continuously extracted during the reaction. Note that in Table 1, the values ​​for "NaHCO3 concentration in NaHCO3 aqueous slurry," "mass of NaHCO3 aqueous slurry," and "NaHCO3 powder yield" are based on the aqueous slurry containing solid sodium bicarbonate continuously extracted for 30 minutes, but these values ​​were approximately the same regardless of the reaction stage. Note that in Table 1, "NaHCO3 powder yield" is shown as twice the measured value in order to match the first batch of sodium bicarbonate production.

[0062] [Example 3] (First batch of sodium bicarbonate production) The sodium bicarbonate production apparatus 100A shown in Figure 1 was used. First, 691g of solid sodium carbonate and 2303g of deionized water were placed in a raw material storage tank 1 with an internal volume of 8L and stirred to obtain 2994g of a 23.1% by mass sodium carbonate aqueous solution, which was the sodium source-containing liquid. Next, this sodium source-containing liquid was transferred to a reaction tank 5 with an internal volume of 8L using a magnetic pump 3, and then the magnetic pump 7 was started and the liquid was circulated using the circulation piping 8. The circulation flow rate was 20L / min. Immediately after the start of circulation, carbon dioxide gas was supplied to the YJ nozzle 21 at a rate of 2.4L / min to supply carbon dioxide in the form of fine bubbles. The liquid temperature of the sodium source-containing liquid in the reaction tank 5 during carbon dioxide supply was 22-50°C. 60 minutes after the start of carbon dioxide supply, the contents of the reaction tank 5 became a cloudy aqueous slurry containing solid sodium bicarbonate with a pH of 8.4. The mass of the aqueous slurry containing solid sodium bicarbonate withdrawn from reaction vessel 5 was 3251 g. The entire aqueous slurry containing solid sodium bicarbonate was separated using a solid-liquid separator 10 to obtain 1105 g of centrifugal dewatered cake (moist solid) and 2137 g of filtrate (separated liquid). The centrifugal dewatered cake was dried under a carbon dioxide atmosphere at 80°C to obtain 881 g of sodium bicarbonate powder. The separated liquid was a saturated aqueous sodium bicarbonate solution (sodium bicarbonate concentration: 9.3% by mass), and this entire amount was recycled back into reaction vessel 5. It was also confirmed that the sodium bicarbonate concentration of the aqueous slurry containing solid sodium bicarbonate before solid-liquid separation was 33.2% by mass.

[0063] (Second batch of sodium bicarbonate production) 546 g of sodium carbonate powder and 345 g of sodium bicarbonate aqueous solution (sodium bicarbonate concentration: 8.3% by mass) were added to reaction vessel 5 containing the separated liquid to obtain the reaction solution. This reaction solution was circulated using the circulation piping 8 by starting the magnetic pump 7. Immediately after starting the circulation, carbon dioxide gas was supplied to the YJ nozzle 21 at a rate of 1.9 L / min to supply the carbon dioxide in the form of fine bubbles. The temperature of the reaction solution in reaction vessel 5 during carbon dioxide supply was 30-50°C. 60 minutes after starting the supply of carbon dioxide, the contents of reaction vessel 5 became a cloudy aqueous slurry containing solid sodium bicarbonate with a pH of 8.4 (i.e., a second aqueous slurry containing solid sodium bicarbonate). The mass of the aqueous slurry containing solid sodium bicarbonate withdrawn from reaction vessel 5 was 3249 g, which was approximately the same amount as the first batch of sodium bicarbonate production. The entire aqueous slurry containing solid sodium bicarbonate was separated using a solid-liquid separator 10 to obtain 1113 g of centrifugal dehydrated cake (moist solid) and 2127 g of filtrate (separated liquid). The masses of each were approximately the same as those of the first batch of sodium bicarbonate production. The centrifugal dehydrated cake was then dried in a carbon dioxide atmosphere at 80°C to obtain 888 g of sodium bicarbonate powder, which was confirmed to be approximately the same as the amount of sodium bicarbonate produced in the first batch. The concentration of the aqueous slurry containing solid sodium bicarbonate before solid-liquid separation was confirmed to be 33.4% by mass.

[0064] [Example 4] (First batch of sodium bicarbonate production) The sodium bicarbonate production apparatus 100A shown in Figure 1 was used. First, 633g of sodium carbonate powder and 1407g of deionized water were placed in a raw material storage tank 1 with an internal volume of 8L and stirred to obtain 2040g of a 31.0% by mass sodium carbonate aqueous solution, which was the sodium source-containing liquid. Next, this sodium source-containing liquid was transferred to a reaction tank 5 with an internal volume of 8L using a magnetic pump 3, and then the magnetic pump 7 was started and the liquid was circulated using the circulation piping 8. The circulation flow rate was 20L / min. Immediately after the start of circulation, carbon dioxide gas was supplied to the YJ nozzle 21 at a rate of 2.2L / min to supply carbon dioxide in the form of fine bubbles. The liquid temperature of the sodium source-containing liquid in the reaction tank 5 during carbon dioxide supply was 22-50°C. 75 minutes after the start of carbon dioxide supply, the contents of the reaction tank 5 became a cloudy aqueous slurry containing solid sodium bicarbonate with a pH of 8.4. The mass of the aqueous slurry containing solid sodium bicarbonate withdrawn from reaction vessel 5 was 2281 g. The entire aqueous slurry containing solid sodium bicarbonate was separated using a solid-liquid separator 10 to obtain 1104 g of centrifugal dewatered cake (moist solid) and 1168 g of filtrate (separated liquid). The centrifugal dewatered cake was dried under a carbon dioxide atmosphere at 80°C to obtain 881 g of sodium bicarbonate powder. The separated liquid was a saturated aqueous sodium bicarbonate solution (sodium bicarbonate concentration: 9.3% by mass), and this entire amount was recycled back into reaction vessel 5. It was also confirmed that the sodium bicarbonate concentration of the aqueous slurry containing solid sodium bicarbonate before solid-liquid separation was 43.4% by mass.

[0065] (Second batch of sodium bicarbonate production) 563g of sodium carbonate powder and 319g of deionized water were added to reaction vessel 5 containing the separated liquid to obtain the reaction solution. This reaction solution was circulated using the circulation piping 8 by starting the magnetic pump 7. Immediately after starting the circulation, carbon dioxide was supplied to the YJ nozzle 21 at a rate of 2.0 L / min to supply the carbon dioxide in the form of fine bubbles. The temperature of the reaction solution in reaction vessel 5 during carbon dioxide supply was 30-50°C. 75 minutes after starting the supply of carbon dioxide, the contents of reaction vessel 5 became a cloudy aqueous slurry containing solid sodium bicarbonate with a pH of 8.4 (i.e., a second aqueous slurry containing solid sodium bicarbonate). The mass of the aqueous slurry containing solid sodium bicarbonate withdrawn from reaction vessel 5 was 2277g, which was approximately the same amount as the first batch of sodium bicarbonate production. The entire aqueous slurry containing solid sodium bicarbonate was separated using a solid-liquid separator 10 to obtain 1111 g of centrifugal dehydrated cake (moist solid) and 1157 g of filtrate (separated liquid). The masses of each were approximately the same as those of the first batch of sodium bicarbonate production. The centrifugal dehydrated cake was then dried in a carbon dioxide atmosphere at 80°C to obtain 886 g of sodium bicarbonate powder, which was confirmed to be approximately the same as the amount of sodium bicarbonate produced in the first batch. The concentration of the aqueous slurry containing solid sodium bicarbonate before solid-liquid separation was confirmed to be 43.7% by mass.

[0066] [Example 5] (First batch of sodium bicarbonate production) The sodium bicarbonate production apparatus 100C shown in Figure 3 was used. First, 1371g of sodium carbonate powder and 16207g of deionized water were placed in a 20L raw material storage tank 1 and stirred to obtain 17578g of a 7.8% by mass sodium carbonate aqueous solution, which was the sodium source-containing liquid. Next, this sodium source-containing liquid was transferred to a 20L reaction tank 5, and then the magnetic pump 7 was started and the liquid was circulated using the circulation piping 8. The circulation flow rate was 20L / min. Immediately after the start of circulation, cooling of the reaction tank 5 was started using the cooling pipe 22. Subsequently, carbon dioxide was supplied to the YJ nozzle 21 at a rate of 4.8L / min, and the carbon dioxide was supplied in the form of fine bubbles. The liquid temperature of the sodium source-containing liquid in the reaction tank 5 during carbon dioxide supply was 5~22°C. 60 minutes after the start of carbon dioxide supply, the contents of the reaction tank 5 became a cloudy aqueous slurry containing solid sodium bicarbonate with a pH of 8.4. The mass of the aqueous slurry containing solid sodium bicarbonate withdrawn from reaction vessel 5 was 18067 g. The entire aqueous slurry containing solid sodium bicarbonate was separated using a solid-liquid separator 10 to obtain 1115 g of centrifugal dewatered cake (moist solid) and 16894 g of filtrate (separated liquid). The centrifugal dewatered cake was dried under a carbon dioxide atmosphere at 80°C to obtain 885 g of sodium bicarbonate powder. The separated liquid was a saturated aqueous sodium bicarbonate solution (sodium bicarbonate concentration: 7.5% by mass), and this entire amount was recycled back into reaction vessel 5. It was also confirmed that the sodium bicarbonate concentration of the aqueous slurry containing solid sodium bicarbonate before solid-liquid separation was 11.9% by mass.

[0067] (Second batch of sodium bicarbonate production) 563g of sodium carbonate powder and 325g of deionized water were added to reaction vessel 5 containing the separated liquid to obtain the reaction solution. This reaction solution was circulated using circulation piping 8 by starting the magnetic pump 7. Cooling of reaction vessel 5 was started immediately after the circulation began using the cooling pipe 22. Subsequently, carbon dioxide was supplied to the YJ nozzle 21 at a rate of 2.0 L / min, and the carbon dioxide was supplied in the form of fine bubbles. The temperature of the reaction solution in reaction vessel 5 during carbon dioxide supply was 5-22°C. 60 minutes after the start of carbon dioxide supply, the contents of reaction vessel 5 became a cloudy aqueous slurry containing solid sodium bicarbonate with a pH of 8.4 (i.e., a second aqueous slurry containing solid sodium bicarbonate). The mass of the aqueous slurry containing solid sodium bicarbonate withdrawn from reaction vessel 5 was 17996g, which was approximately the same amount as the first batch of sodium bicarbonate production. The entire aqueous slurry containing solid sodium bicarbonate was separated using a solid-liquid separator 10 to obtain 1119 g of centrifugal dehydrated cake (moist solid) and 16819 g of filtrate (separated liquid). The masses of each were approximately the same as those of the first batch of sodium bicarbonate production. The centrifugal dehydrated cake was then dried in a carbon dioxide atmosphere at 80°C to obtain 888 g of sodium bicarbonate powder, which was confirmed to be approximately the same as the amount of sodium bicarbonate produced in the first batch. The concentration of the aqueous slurry containing solid sodium bicarbonate before solid-liquid separation was confirmed to be 12.0% by mass.

[0068] [Example 6] (First batch of sodium bicarbonate production) The sodium bicarbonate production apparatus 100D shown in Figure 4 was used. First, 800g of sodium carbonate powder and 4071g of deionized water were placed in a raw material storage tank 1 with an internal volume of 8L and stirred to obtain 4871g of a 16.4% by mass sodium carbonate aqueous solution, which was the sodium source-containing liquid. Next, this sodium source-containing liquid was transferred to a reaction tank 5 with an internal volume of 8L using a magnetic pump 3, and then carbon dioxide was supplied to the nozzle pipe 23 at a rate of 2.8L / min. The liquid temperature of the sodium source-containing liquid in the reaction tank 5 during carbon dioxide supply was 22-30°C. 1064 minutes after the start of carbon dioxide supply, the contents of the reaction tank 5 became a cloudy aqueous slurry containing solid sodium bicarbonate with a pH of 8.4. The mass of the aqueous slurry containing solid sodium bicarbonate withdrawn from the reaction tank 5 was 5092g. The entire aqueous slurry containing solid sodium bicarbonate was separated using a solid-liquid separator 10 to obtain 1106 g of centrifugal dehydrated cake (moist solid) and 3977 g of filtrate (separated liquid). The centrifugal dehydrated cake was dried under a carbon dioxide atmosphere at 80°C to obtain 882 g of sodium bicarbonate powder. The separated liquid was a saturated aqueous sodium bicarbonate solution (sodium bicarbonate concentration: 9.3% by mass), and this entire amount was recycled to the reaction vessel 5. It was confirmed that the sodium bicarbonate concentration of the aqueous slurry containing solid sodium bicarbonate before solid-liquid separation was 24.6% by mass.

[0069] (Second batch of sodium bicarbonate production) 563 g of sodium carbonate powder and 369 g of deionized water were added to reaction vessel 5 containing the separated liquid to obtain the reaction solution. Carbon dioxide was supplied to tube 23 at a rate of 2.0 L / min. The temperature of the reaction solution in reaction vessel 5 was 22-30°C when carbon dioxide was supplied. 1064 minutes after the start of carbon dioxide supply, the contents of reaction vessel 5 became a cloudy aqueous slurry containing solid sodium bicarbonate with a pH of 8.4 (i.e., a second aqueous slurry containing solid sodium bicarbonate). The mass of the aqueous slurry containing solid sodium bicarbonate withdrawn from reaction vessel 5 was 5069 g, which was approximately the same amount as the first batch of sodium bicarbonate production. The entire amount of this aqueous slurry containing solid sodium bicarbonate was separated using a solid-liquid separator 10 to obtain 1109 g of centrifugal dewatered cake (moist solid) and 3951 g of filtrate (separated liquid). The masses of each were approximately the same as the first batch of sodium bicarbonate production. The centrifugal dehydrated cake was then dried under a carbon dioxide atmosphere at 80°C, yielding 885 g of sodium bicarbonate powder, which was confirmed to be approximately the same amount as the first batch of sodium bicarbonate produced. Furthermore, the concentration of the aqueous slurry containing solid sodium bicarbonate before solid-liquid separation was confirmed to be 24.6% by mass.

[0070] [Example 7] (First batch of sodium bicarbonate production) The sodium bicarbonate production apparatus 100A shown in Figure 1 was used. 5090 g of aqueous slurry containing solid sodium bicarbonate with a sodium bicarbonate concentration of 24.7% by mass was obtained in the same manner as the first batch of sodium bicarbonate production in Example 1. Also, 1106 g of centrifugal dewatered cake (moist solid) and 3975 g of filtrate (separated liquid) were obtained in the same manner as the first batch of sodium bicarbonate production. The centrifugal dewatered cake was dried under a carbon dioxide atmosphere at 80°C to obtain 882 g of sodium bicarbonate powder. The separated liquid was a saturated sodium bicarbonate aqueous solution (sodium bicarbonate concentration: 9.3% by mass), and this entire amount was recycled to reaction vessel 5.

[0071] (Second batch of sodium bicarbonate production) 2577g of a 20% by mass sodium hydroxide aqueous solution was added to reaction vessel 5 containing the separated liquid to obtain a sodium source-containing solution. This sodium source-containing solution was circulated using circulation piping 8 by starting the magnetic pump 7. Immediately after starting the circulation, carbon dioxide was supplied to the YJ nozzle 21 at a rate of 4.8 L / min to supply the carbon dioxide in the form of fine bubbles. The temperature of the sodium source-containing solution in reaction vessel 5 during carbon dioxide supply was 22-50°C. 60 minutes after starting the supply of carbon dioxide, the contents of reaction vessel 5 became a cloudy aqueous slurry containing solid sodium bicarbonate with a pH of 8.4. The mass of the aqueous slurry containing solid sodium bicarbonate withdrawn from reaction vessel 5 was 7113g, which was a significant increase from the 5090g produced in the first batch of sodium bicarbonate production. The entire aqueous slurry containing solid sodium bicarbonate was separated using a solid-liquid separator 10 to obtain 1114 g of centrifugal dewatered cake (moist solid) and 5990 g of filtrate (separated liquid). The mass of the centrifugal dewatered cake was approximately the same as that of the first batch of sodium bicarbonate production. On the other hand, the mass of the separated liquid was significantly larger than that of the first batch of sodium bicarbonate production (3975 g). The centrifugal dewatered cake was then dried in a carbon dioxide atmosphere at 80°C to obtain 889 g of sodium bicarbonate powder, which was confirmed to be approximately the same amount as that of the first batch of sodium bicarbonate production. The sodium bicarbonate concentration in the aqueous slurry containing solid sodium bicarbonate before solid-liquid separation was 20.4% by mass, which was confirmed to be a decrease from 24.7% by mass in the first batch of sodium bicarbonate production.

[0072] [Example 8] (First batch of sodium bicarbonate production) The sodium bicarbonate production apparatus 100A shown in Figure 1 was used. The reaction vessel 5 had an internal volume of 10 L. 5092 g of aqueous slurry containing solid sodium bicarbonate with a sodium bicarbonate concentration of 24.7% by mass was obtained in the same manner as the first batch of sodium bicarbonate production in Example 1. Also, 1106 g of centrifugal dewatered cake (moist solid) and 3977 g of filtrate (separated liquid) were obtained in the same manner as the first batch of sodium bicarbonate production. The centrifugal dewatered cake was dried under a carbon dioxide atmosphere at 80°C to obtain 882 g of sodium bicarbonate powder. The separated liquid was a saturated sodium bicarbonate aqueous solution (sodium bicarbonate concentration: 9.3% by mass), and this entire amount was recycled to reaction vessel 5.

[0073] (Second batch of sodium bicarbonate production) 4265g of an 18% by mass sodium carbonate aqueous solution was added to reaction vessel 5 containing the separated liquid to obtain a sodium source-containing solution. This sodium source-containing solution was circulated using circulation piping 8 by starting the magnetic pump 7. Immediately after starting the circulation, carbon dioxide was supplied to the YJ nozzle 21 at a rate of 2.7 L / min to supply the carbon dioxide in the form of fine bubbles. The temperature of the sodium source-containing solution in reaction vessel 5 during carbon dioxide supply was 22-50°C. 60 minutes after starting the supply of carbon dioxide, the contents of reaction vessel 5 became a cloudy aqueous slurry containing solid sodium bicarbonate with a pH of 8.4. The mass of the aqueous slurry containing solid sodium bicarbonate withdrawn from reaction vessel 5 was 8562g, a significant increase from the 5092g produced in the first batch of sodium bicarbonate production. The entire aqueous slurry containing solid sodium bicarbonate was separated using a solid-liquid separator 10 to obtain 1115 g of centrifugal dewatered cake (moist solid) and 7438 g of filtrate (separated liquid). The mass of the centrifugal dewatered cake was approximately the same as that of the first batch of sodium bicarbonate production. On the other hand, the mass of the separated liquid was significantly larger than that of the first batch of sodium bicarbonate production (3977 g). The centrifugal dewatered cake was then dried in a carbon dioxide atmosphere at 80°C to obtain 890 g of sodium bicarbonate powder, which was confirmed to be approximately the same amount as that of the first batch of sodium bicarbonate production. The sodium bicarbonate concentration in the aqueous slurry containing solid sodium bicarbonate before solid-liquid separation was 18.5% by mass, which was confirmed to be a decrease from 24.7% by mass in the first batch of sodium bicarbonate production.

[0074] [Table 1]

[0075] As shown in Table 1, in Examples 1-8, in the second batch of sodium bicarbonate production, sodium hydroxide and / or sodium carbonate are added to the recycled separation liquid so that the yield of sodium bicarbonate powder is equivalent to that of the first batch of sodium bicarbonate production. In Examples 1-6, since solid sodium carbonate is added, it is possible to control the volume of the aqueous slurry containing solid sodium bicarbonate after the reaction in the first batch of production and the aqueous slurry containing solid sodium bicarbonate after the reaction in the second batch of production to be equivalent by adjusting the amount of water added. As a result, the sodium bicarbonate concentration in the aqueous slurry containing solid sodium bicarbonate is equivalent in the first and second batches of sodium bicarbonate production. On the other hand, in Examples 7 and 8, since solid sodium carbonate is not added, the amount of water added depends largely on the amount of aqueous sodium hydroxide solution added in Example 7 and the amount of aqueous sodium carbonate solution added in Example 8. As a result, the volume of the aqueous slurry containing solid sodium bicarbonate after the reaction in the second batch of production is larger than the volume of the aqueous slurry containing sodium bicarbonate after the reaction in the first batch of production. As a result, the concentration of sodium bicarbonate in the aqueous slurry containing solid sodium bicarbonate was lower in the second production batch than in the first production batch.

[0076] Furthermore, let's consider the case where no water is added in the second production batch in Examples 1-6. As mentioned above, water is consumed in the reaction of Equation 2. In addition, water that evaporates during the reaction process and water contained in the centrifugal dewatered cake (moist solid) after solid-liquid separation are also lost from the reaction system. Therefore, as batches are repeated, the amount of water in the reaction system decreases steadily, and eventually the reaction of Equation 2 stops proceeding, making it impossible to produce sodium bicarbonate. Furthermore, in Examples 1-6, it is conceivable to use solid sodium hydroxide instead of solid sodium carbonate. However, solid sodium hydroxide is expensive and, moreover, is hygroscopic, making it difficult to handle. Problems due to hygroscopicity include difficulty in managing the raw material, difficulty in getting all the sodium hydroxide into the equipment because it adheres to the walls of the equipment, and the need to consider the amount of water absorbed by the sodium hydroxide when determining the amount of water to add. On the other hand, solid sodium carbonate is less prone to the problems that sodium hydroxide has, offering advantages such as energy saving, efficient use of resources, and the ability to produce sodium bicarbonate more stably. [Explanation of Symbols]

[0077] 1…Raw material storage tank, 2…Agitator, 3…Magnetic pump, 4…Piping, 5…Reaction vessel, 6…Agitator, 7…Magnetic pump, 8…Circulation piping, 9…Piping, 10…Solid-liquid separation device (centrifugal dehydrator), 11…Piping, 12…Drying equipment, 13…Piping, 14…Separated liquid recovery tank, 15…Magnetic pump, 16…Piping, 20…Carbon dioxide supply piping, 21…YJ nozzle, 22…Cooling pipe, 23…Nozzle pipe, 100A, 100B, 100C, 100D…Sodium bicarbonate production equipment

Claims

1. A method for producing sodium bicarbonate, A method for producing sodium bicarbonate, comprising supplying water, carbon dioxide, and a solid sodium carbonate to a first aqueous slurry or a first aqueous solution of sodium bicarbonate containing solid sodium bicarbonate to produce a second aqueous slurry containing solid sodium bicarbonate.

2. The method for producing sodium bicarbonate according to claim 1, wherein the supply of water, carbon dioxide, and solid sodium carbonate is to supply water and solid sodium carbonate to obtain a reaction solution, and then supply carbon dioxide to the obtained reaction solution.

3. The method for producing sodium bicarbonate according to claim 2, wherein the sodium bicarbonate concentration relative to the total mass of the reaction solution is 7 to 44% by mass.

4. A method for producing sodium bicarbonate according to any one of claims 1 to 3, wherein the water and the solid sodium carbonate are supplied as a water slurry containing the solid sodium carbonate.

5. A method for producing sodium bicarbonate according to any one of claims 1 to 3, wherein the water is supplied as an aqueous solution or an aqueous slurry, the aqueous solution comprises at least one aqueous solution selected from the group consisting of an aqueous sodium hydroxide solution, an aqueous sodium carbonate solution, and an aqueous sodium bicarbonate solution, and the aqueous slurry comprises an aqueous slurry containing solid sodium bicarbonate.

6. The method for producing sodium bicarbonate according to claim 5, wherein the aqueous solution is an aqueous solution of sodium hydroxide.

7. The method for producing sodium bicarbonate according to any one of claims 1 to 3, wherein the carbon dioxide is supplied by the fine bubble method.

8. The method for producing sodium bicarbonate according to any one of claims 1 to 3, wherein the sodium carbonate is sodium carbonate.

9. The method for producing sodium bicarbonate according to any one of claims 1 to 3, wherein at least a portion of the first aqueous sodium bicarbonate solution is a separated liquid obtained by solid-liquid separation of an aqueous slurry containing solid sodium bicarbonate.

10. A method for producing sodium bicarbonate according to any one of claims 1 to 3, wherein a second aqueous slurry containing the solid sodium bicarbonate is subjected to solid-liquid separation to obtain a second aqueous sodium bicarbonate solution as the separated liquid, and the obtained separated liquid is used as the first aqueous sodium bicarbonate solution.

11. A method for producing sodium bicarbonate according to any one of claims 1 to 3, comprising separating a second aqueous slurry containing the solid sodium bicarbonate to obtain a wet solid, and drying the obtained wet solid to obtain sodium bicarbonate powder.

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