Sodium bicarbonate concentration and crystallization process

Abstract

The invention belongs to the technical field of chemical production, and particularly relates to a sodium bicarbonate concentration and crystallization process which comprises the following steps: S1, feeding a sodium bicarbonate-containing solution into a stirring kettle, and then adding sodium hydroxide; s2, feeding the mixed solution into an evaporator for evaporation, concentration and crystallization; s3, feeding evaporated distilled water into a heating jacket of the reaction kettle, and feeding evaporated mother liquor containing crystals obtained by evaporation into a first filter for filtering; s4, preheating the sodium bicarbonate saturated solution fed into the reaction kettle by using distilled water; s5, feeding the filtered solid into a reaction kettle, and heating and dissolving; s6, cooling water enters the heating jacket to cool the solution in the reaction kettle, so that the solution in the reaction kettle is crystallized; and step S7, feeding the mixed solution in which crystals are generated into a second filter for filtering to obtain a solid sodium bicarbonate product, so as to solve the problems of more equipment used for producing sodium bicarbonate and high operation cost in the prior art.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical production, in particular to a sodium bicarbonate concentration and crystallization process. Background Art

[0002] Sodium bicarbonate, commonly known as baking soda, is widely used in food, medicine, chemical industry and other fields.

[0003] In the prior art, the sodium bicarbonate production process utilizes a saturated sodium carbonate solution to absorb carbon dioxide to generate sodium bicarbonate crystals. The required equipment includes an evaporator and a carbonization tower, etc. There are many pieces of equipment and the operating cost is high. Therefore, the present invention provides a sodium bicarbonate concentration crystallization process. Summary of the invention

[0004] In order to make up for the shortcomings of the prior art, the problem of multiple equipments and high operating costs in the prior art for producing sodium bicarbonate is solved.

[0005] The technical solution adopted by the present invention to solve the technical problem is: a sodium bicarbonate concentration and crystallization process of the present invention comprises the following steps:

[0006] Step S1: After feeding a solution containing sodium bicarbonate into a stirring tank, sodium hydroxide is added into the stirring tank to increase the alkalinity of the solution;

[0007] Step S2: the alkaline enhanced mixed solution is sent to an evaporator for evaporation, concentration and crystallization;

[0008] Step S3: the distilled water obtained by evaporation is sent into the heating jacket of the reactor, and the evaporation mother liquor containing crystals obtained by evaporation is sent into the first filter for solid-liquid separation;

[0009] Step S4: preheating the saturated sodium bicarbonate solution fed into the reactor with distilled water;

[0010] Step S5: sending the separated solid crystals into a reaction kettle for heating and dissolution;

[0011] Step S6: cooling water is used to enter the heating jacket through the three-way valve to cool the solution inside the reactor to crystallize the solution inside;

[0012] Step S7: The mixed solution containing crystals is sent to a second filter for filtration, and the solid crystals obtained by filtration are sodium bicarbonate products.

[0013] Preferably, the low-temperature evaporation temperature in step S2 is 50°C.

[0014] Preferably, the crystals obtained by solid-liquid separation in the first filter in step S3 are natural alkali crystals.

[0015] Preferably, the first mother liquor obtained by solid-liquid separation in the first filter in step S3 is refluxed to the evaporator for reuse.

[0016] Preferably, the second mother liquor obtained by filtering in the second filter in step S7 is refluxed into the stirring tank for reuse.

[0017] Preferably, the reactor in step S4 comprises a reactor body, a heating jacket is fixedly connected to the outside of the reactor body; a water inlet and a liquid discharge port are fixedly connected to the bottom of the heating jacket; a water outlet is fixedly connected to the outer cylindrical wall of the heating jacket; a spiral plate is fixedly connected between the heating jacket and the reactor body; a mixed material outlet is fixedly connected to the bottom of the reactor body; a liquid inlet and a solid inlet are fixedly connected to the top of the reactor body; and a mixing mechanism and a scraping mechanism are provided inside the reactor body.

[0018] Preferably, the mixing mechanism includes a rotating shaft, one end of which passes through the top of the kettle body and is connected to the output end of the motor; a pair of first scraping arms are fixedly connected to the rotating shaft; a group of second scraping arms are fixedly connected to the rotating shaft; the second scraping arms are adapted to the curvature radius of the bottom of the kettle body.

[0019] Preferably, the mixing mechanism includes a group of axial mixing blades, which are fixed to the rotating shaft and located above the first scraper arm; a pair of radial mixing blades are fixed to the rotating shaft and located inside the first scraper arm.

[0020] Preferably, a group of positioning rods are fixedly connected inside the second scraping arm; an auxiliary crystallization rod is fixedly connected to the positioning rod; and a group of nucleation bumps are fixedly connected to the auxiliary crystallization rod.

[0021] The beneficial effects of the present invention are as follows:

[0022] 1. The sodium bicarbonate concentration and crystallization process of the present invention improves the alkalinity of the sodium bicarbonate solution by adding sodium hydroxide, creates a natural alkali crystallization environment, and improves the crystallization rate of natural alkali during evaporation and concentration, thereby improving the sodium bicarbonate output rate.

[0023] 2. The sodium bicarbonate concentration and crystallization process of the present invention utilizes the distilled water obtained by evaporation to heat the reactor, thereby increasing the dissolution rate of natural alkali crystals and improving the heat utilization rate. Meanwhile, the coordination of the axial mixing blades and the radial mixing blades in the reactor shortens the time for natural alkali dissolution and improves production efficiency.

[0024] 3. The sodium bicarbonate concentration and crystallization process of the present invention requires less equipment, and the first mother liquor is refluxed to the evaporator for reuse and the second mother liquor is refluxed to the stirring tank for reuse, thereby improving the solute utilization rate and saving costs and resources.

[0025] 4. The sodium bicarbonate concentration and crystallization process of the present invention utilizes cooling water to cool the reaction kettle along the spiral plate, and the inner wall of the kettle body is cooled from bottom to top to form a temperature gradient, thereby increasing the non-spontaneous nucleation and crystallization speed of sodium bicarbonate in the solution on the inner wall of the kettle body. At the same time, an auxiliary crystallization rod is arranged in the first scraping arm, and the nucleation protrusion on the auxiliary crystallization rod provides a starting point for the formation of crystal nuclei, thereby increasing the non-spontaneous nucleation and crystallization speed of sodium bicarbonate in the solution on the nucleation protrusion, shortening the crystallization time of sodium bicarbonate, and improving the production efficiency of sodium bicarbonate products. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present invention will be further described below in conjunction with the accompanying drawings.

[0027] Figure 1 It is a process flow chart of the present invention;

[0028] Figure 2 is a three-dimensional diagram of a crystallization reactor;

[0029] Figure 3 is a side sectional view of a crystallization reactor;

[0030] Figure 4 It is the internal structure diagram of the crystallization reactor;

[0031] Figure 5 yes Figure 4 Enlarged view of point A in the middle.

[0032] In the figure: 1, stirring kettle; 2, evaporator; 3, first filter; 4, reactor; 41, kettle body; 411, mixture outlet; 412, solid inlet; 413, liquid inlet; 42, heating jacket; 421, water inlet; 422, drain outlet; 423, water outlet; 424, spiral plate; 43, motor; 44, rotating shaft; 45, first scraper arm; 451, positioning rod; 452, auxiliary crystallization rod; 453, nucleation bump; 46, second scraper arm; 47, axial mixing blade; 48, radial mixing blade; 5, second filter; 6, three-way valve. DETAILED DESCRIPTION

[0033] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below in conjunction with specific implementation methods.

[0034] Embodiment 1

[0035] like Figure 1 As shown, a sodium bicarbonate concentration and crystallization process according to an embodiment of the present invention comprises the following steps:

[0036] Step S1: After feeding a solution containing sodium bicarbonate into the stirring tank 1, sodium hydroxide is added into the stirring tank 1 to increase the alkalinity of the solution;

[0037] Step S2: the alkaline enhanced mixed solution is sent to the evaporator 2 for evaporation, concentration and crystallization;

[0038] Step S3: the distilled water obtained by evaporation is sent into the heating jacket 42 of the reactor 4, and the evaporation mother liquor containing crystals obtained by evaporation is sent into the first filter 3 for solid-liquid separation;

[0039] Step S4: preheating the saturated sodium bicarbonate solution fed into the reaction kettle 4 with distilled water;

[0040] Step S5: sending the separated solid crystals into the reaction kettle 4 to be heated and dissolved;

[0041] Step S6: cooling water is used to enter the heating jacket 42 through the three-way valve 6 to cool the solution inside the reactor 4 to crystallize the solution inside;

[0042] Step S7: The mixed solution containing crystals is sent to the second filter 5 for filtration, and the solid crystals obtained by filtration are sodium bicarbonate products.

[0043] Furthermore, the low-temperature evaporation temperature in step S2 is 50°C.

[0044] Furthermore, the crystals obtained by solid-liquid separation in the first filter 3 in step S3 are natural alkali crystals.

[0045] Furthermore, the first mother liquor obtained by solid-liquid separation in the first filter 3 in step S3 is refluxed to the evaporator 2 for reuse.

[0046] Furthermore, in step S7, the second mother liquor obtained by filtering by the second filter 5 is refluxed into the stirred tank 1 for reuse. During operation, increasing the alkalinity of the solution can provide a natural soda crystallization environment, improve the natural soda crystallization rate, and thus improve the sodium bicarbonate output rate. By utilizing the distilled water obtained by evaporation to heat the reactor 4, both the dissolution rate of the natural soda crystals in the saturated sodium bicarbonate solution and the heat utilization rate are improved. By cooling the reactor 4 with cooling water, a temperature gradient is formed on the inner wall of the reactor body, which increases the non-spontaneous nucleation crystallization rate of the solution in the reactor 4 and shortens the sodium bicarbonate crystallization time. By reflux of the first mother liquor to the evaporator 2 for reuse and reflux of the second mother liquor to the stirred tank 1 for reuse, the solute utilization rate is improved, and costs and resources are saved.

[0047] Embodiment 2

[0048] like Figures 2 to 5As shown, on the basis of Example 1, the reactor 4 in the step S4 includes a reactor body 41, and a heating jacket 42 is fixedly connected to the outside of the reactor body 41; a water inlet 421 and a liquid discharge port 422 are fixedly connected to the bottom of the heating jacket 42; a water outlet 423 is fixedly connected to the outer cylindrical wall of the heating jacket 42; a spiral plate 424 is fixedly connected between the heating jacket 42 and the reactor body 41; a mixed material outlet 411 is fixedly connected to the bottom of the reactor body 41; a liquid inlet 413 and a solid inlet 412 are fixedly connected to the top of the reactor body 41; and a mixing mechanism and a scraping mechanism are provided inside the reactor body 41.

[0049] The mixing mechanism includes a rotating shaft 44, one end of which passes through the top of the kettle body 41 and is connected to the output end of the motor 43; a pair of first scraping arms 45 are fixedly connected to the rotating shaft 44; a group of second scraping arms 46 are fixedly connected to the rotating shaft 44; the second scraping arms 46 are adapted to the curvature radius of the bottom of the kettle body 41.

[0050] The mixing mechanism includes a group of axial mixing blades 47 , which are fixed to the rotating shaft 44 and located above the first scraper arm 45 ; a pair of radial mixing blades 48 are fixed to the rotating shaft 44 and located inside the first scraper arm 45 .

[0051] A group of positioning rods 451 are fixedly connected in the second scraping arm 46; an auxiliary crystallization rod 452 is fixedly connected to the positioning rod 451; and a group of nucleation protrusions 453 are fixedly connected to the auxiliary crystallization rod 452. During operation, when the distilled water is heated, the motor 43 drives the rotating shaft 44 to work, and the axial mixing blades 47 on the rotating shaft 44 generate a downward axial force on the mixed material in the reactor 4, and at the same time, the radial mixing blades 48 generate a radial force on the mixed material, which not only accelerates the heat transfer between the mixed materials, but also accelerates the dissolution rate of the natural alkali crystals in the mixed materials, shortening the time of natural alkali dissolution. When the cooling water is cooled along the spiral plate 424, the inner wall of the kettle body 41 is cooled from bottom to top, and a temperature gradient is formed on the inner wall. At the same time, through the action of the auxiliary crystallization rod 452, the non-spontaneous nucleation crystallization rate of sodium bicarbonate in the solution is increased, shortening the crystallization time of sodium bicarbonate. At the same time, the first scraping arm 45 and the second scraping arm 46 scrape the crystals generated on the inner wall of the kettle body 41 to prevent the crystals from agglomerating with the inner wall of the kettle body 41.

[0052] Working principle: sodium hydroxide is added into the stirring tank 1 to increase the alkalinity of the raw material solution, providing a natural soda crystallization environment. After low-temperature evaporation and concentration, the natural soda crystals obtained by filtration are sent to the reactor 4. The solubility of the natural soda is increased by heating the reactor 4, so that it is dissolved in the saturated sodium bicarbonate solution, in which the solubility of sodium bicarbonate is relatively small, and the solubility of sodium bicarbonate changes little with temperature. Then, the sodium bicarbonate crystals with relatively small solubility in the solution are precipitated by cooling, and the sodium bicarbonate solid crystal product can be obtained after filtration.

[0053] The above-mentioned front, back, left, right, top and bottom are all based on the figures in the specification. Figure 1 As a benchmark, according to the person's observation perspective, the side of the device facing the observer is defined as the front, the left side of the observer is defined as the left, and so on.

[0054] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the scope of protection of the present invention.

[0055] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A sodium bicarbonate concentration and crystallization process, characterized in that: The following steps are involved: Step S1: After feeding a solution containing sodium bicarbonate into the stirring tank (1), sodium hydroxide is added into the stirring tank (1) to increase the alkalinity of the solution; Step S2: the alkaline-enhanced mixed solution is sent to an evaporator (2) for evaporation, concentration and crystallization; Step S3: the distilled water obtained by evaporation is sent into the heating jacket (42) of the reaction kettle (4), and the evaporation mother liquor containing crystals obtained by evaporation is sent into the first filter (3) for solid-liquid separation; Step S4: preheating the saturated sodium bicarbonate solution fed into the reaction kettle (4) with distilled water; Step S5: sending the separated solid crystals into the reaction kettle (4) to be heated and dissolved; Step S6: cooling water is fed into the heating jacket (42) through the three-way valve (6) to cool the solution inside the reactor (4) to crystallize the solution inside; Step S7: The mixed solution containing the crystals is sent to a second filter (5) for filtration, and the solid crystals obtained by filtration are sodium bicarbonate products.

2. A sodium bicarbonate concentration and crystallization process according to claim 1, characterized in that: The low-temperature evaporation temperature in step S2 is 50°C.

3. A sodium bicarbonate concentration and crystallization process according to claim 2, characterized in that: The crystals obtained by solid-liquid separation in the first filter (3) in step S3 are natural alkali crystals.

4. A sodium bicarbonate concentration and crystallization process according to claim 3, characterized in that: In the step S3, the first mother liquid obtained by solid-liquid separation in the first filter (3) is refluxed to the evaporator (2) for reuse.

5. A sodium bicarbonate concentration and crystallization process according to claim 4, characterized in that: In the step S7, the second mother liquor obtained by filtering in the second filter (5) is refluxed into the stirring tank (1) for reuse.

6. A sodium bicarbonate concentration and crystallization process according to claim 1, characterized in that: The reaction kettle (4) in step S4 comprises a kettle body (41), the kettle body (41) is fixedly connected to a heating jacket (42) on the outside; the bottom of the heating jacket (42) is fixedly connected to a water inlet (421) and a liquid discharge port (422); the outer cylindrical wall of the heating jacket (42) is fixedly connected to a water outlet (423); a spiral plate (424) is fixedly connected between the heating jacket (42) and the kettle body (41); the bottom of the kettle body (41) is fixedly connected to a mixed material outlet (411); the top of the kettle body (41) is fixedly connected to a liquid inlet (413) and a solid inlet (412); and a mixing mechanism and a scraping mechanism are provided inside the kettle body (41).

7. A sodium bicarbonate concentration and crystallization process according to claim 6, characterized in that: The mixing mechanism comprises a rotating shaft (44), one end of which passes through the top of the kettle body (41) and is connected to the output end of the motor (43); a pair of first scraping arms (45) are fixedly connected to the rotating shaft (44); a group of second scraping arms (46) are fixedly connected to the rotating shaft (44); the second scraping arms (46) are adapted to the curvature radius of the bottom of the kettle body (41).

8. A sodium bicarbonate concentration and crystallization process according to claim 7, characterized in that: The mixing mechanism comprises a group of axial mixing blades (47), the axial mixing blades (47) are fixedly connected to the rotating shaft (44), and the axial mixing blades (47) are located above the first scraping arm (45); a pair of radial mixing blades (48) are fixedly connected to the rotating shaft (44), and the radial mixing blades (48) are located inside the first scraping arm (45).

9. A sodium bicarbonate concentration and crystallization process according to claim 8, characterized in that, A group of positioning rods (451) are fixedly connected inside the second scraping arm (46); an auxiliary crystallization rod (452) is fixedly connected to the positioning rod (451); and a group of nucleation bumps (453) are fixedly connected to the auxiliary crystallization rod (452).

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