A process for the production of anti-caking sodium bicarbonate

Abstract

The present application belongs to the technical field of powder material production, and discloses a process for producing anti-caking baking soda, comprising the following steps: 1) after centrifugal separation of sodium bicarbonate slurry, the slurry is delivered to a screw feeder and sent to a belt filter for washing; 2) the wet material after washing is delivered to an air flow drying tube by a screw conveyor, and is contacted with heated hot air; the dried material is sent to a cyclone separator for separation; the separated finished product is sent to a powder flow cooler, and the finished product is cooled to below 50 DEG C and then packed into a packaging system to form a product. The present application increases a vacuum washing process before drying of the wet baking soda from the crystal structure, and dissolves the fine particles in the baking soda product and the fine particle crystals attached to the large particles by elution principle, so as to wash away the plate crystals, powder crystals and needle crystals, reduce the crystal bridges and capillary absorption effect between the crystals, and thus make the product particle size relatively uniform, and the product particle after drying is uniform and concentrated, so as to fundamentally solve the baking soda caking problem.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of powdery material production, and relates to the production of baking soda, in particular to a process for producing anti-caking baking soda. BACKGROUND

[0002] Baking soda is an important chemical raw material. In addition to being used for food additives, household cleaners, feed additives, etc., it is also an effective flue gas desulfurizer, foaming agent, fire extinguishing agent, etc. Domestic baking soda production devices are basically built in conjunction with soda ash devices, and the production scale is generally determined by the soda ash production scale. The main production process is as follows: the furnace gas after calcination of the light ash calciner in the heavy soda production workshop contains a large amount of alkali dust, CO2 and NH3. If it is directly discharged, it will not only cause a large amount of soda ash loss, but also cause environmental pollution. Therefore, after separation and washing, the hot lye is collected, the hot lye is concentrated and heated, and then impurities are removed, and then it is contacted with carbon dioxide to generate NaHCO3 by carbonization. The slurry is thick, centrifuged, cooled, packaged, and baking soda products are produced.

[0003] In recent years, the problem of baking soda caking has been a difficult problem in industrial production, especially in summer, and serious caking occurs within 3-7 days, causing serious losses to production enterprises and downstream customers. After research, the main reasons for the caking of baking soda are uneven crystal size, too much fine powder, too high temperature during packaging after drying, and too much stacking. The industry often uses methods such as increasing the powder flow cooler, using a pneumatic conveying system, sealing the package after cooling, unloading the package, and reducing the stacking pressure, but none of these methods can completely solve the problem of baking soda caking in the short term. Therefore, the main reason for product caking is still the crystal structure, and the problem of product caking must be solved fundamentally.

[0004] After research, fine powders have capillary adsorption effect between the crystal grains during compaction, which causes water vapor to diffuse between the crystal grains, causing the product to become damp and caking. At the same time, when the product is not completely cooled, the residual heat diffuses outward from the center of the crystal, the pressure increases after stacking, plastic deformation occurs, the contact area between the crystals increases, the intermolecular attraction increases, and the surface re-dissolves to form crystal bridges, resulting in caking. The smaller the particle size, the poorer the compression resistance of the particles, and the easier the caking; the contact surface of the plate crystal, powder crystal and needle crystal structure is large, and has strong cohesiveness, which can easily cause caking.

[0005] Therefore, the particle size of the product should be controlled to be large and uniform, and the occurrence of plate crystals, powder crystals and needle crystals should be avoided to reduce the crystal bridges and capillary adsorption effect between the crystals, which can fundamentally solve the problem of baking soda caking. SUMMARY

[0006] In view of the deficiencies of the prior art, the present application provides a process for producing anti-caking baking soda, which adds a vacuum washing process before the sodium bicarbonate slurry obtained in the original baking soda process is dried, and then is dried, cooled and packaged.

[0007] The present application is realized by the following technical solutions:

[0008] A process for producing anti-caking baking soda, comprising the following steps:

[0009] (1) After the sodium bicarbonate slurry is centrifuged, it is transported to a screw feeder and fed into a belt filter for washing;

[0010] (2) The wet material after washing is sent to an air flow drying pipe by a screw conveyor and contacted with heated hot air, and the dried material is separated by a cyclone separator, the separated finished product is sent to a powder flow cooler, the feed temperature is 50-75 DEG C, the finished product is cooled to below 50 DEG C, and then is packaged into products in a packaging system, and the tail gas from the cyclone separator is vented after being dedusted in a tail gas dedusting tower.

[0011] Further improved schemes of the present application are:

[0012] The water content of the sodium bicarbonate slurry is 40%-50%, and the water content of the sodium bicarbonate after centrifugation is 5%-20%.

[0013] Further, the belt filter is a vacuum filter, and the length-width ratio is 15:1-30:1, 2-5 washing waters are added, and the vacuum degree is-0.05--0.07MPa.

[0014] Further, the washing water of the belt filter in step (1) can be sent to a heavy alkali workshop as filtered washing water through a pipeline.

[0015] Further, the tube pressure of the air flow drying pipe in step (2) is 3-5kPa.

[0016] Compared with the prior art, the present application has the following beneficial effects:

[0017] 1. The present application takes the problem of more dust in the product and uneven baking soda particles leading to caking as a breakthrough, breaks the traditional method of reducing baking soda caking by adding a powder flow cooler and a cooled alkali process in subsequent drying, and instead increases a vacuum washing process before drying the wet baking soda, dissolves the superfine particles in the baking soda product and the fine particle crystals attached to the large particles by elution principle, washes away the plate crystals, powder crystals and needle crystals, reduces the crystal bridges and capillary adsorption effects between the crystals, so that the product particle size is relatively uniform, the product particles after drying are uniform and concentrated, and the problem of baking soda caking is fundamentally solved.

[0018] 2. The baking soda product of the present application is washed and purified, which not only washes away the platelets, powder crystals, needle crystals, reduces the crystal bridges and capillary adsorption effects between the crystals, and increases the uniformity of the product particle size, but also greatly reduces the impurities in the baking soda, meets the product demand of high-end customers, improves the product added value and market competitiveness;

[0019] 3. The product of the present application can greatly reduce the product temperature by adding a washing process, and the high packaging temperature is one of the main reasons for the product caking. The present application can significantly reduce the temperature when packaging by washing and cooling, which is beneficial to increase the anti-caking performance of baking soda.

[0020] 4. The water used for washing the baking soda in the present application is used for washing water in the soda ash production with a filter, the washing water increases the concentration of NaHCO3, and when washing NaHCO3 out of the carbonation tower of soda ash, the solid loss can be reduced, the production energy consumption is reduced, and at the same time, the washing water is balanced by using the soda ash production system, without destroying the system water balance. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The process flow chart of the present application. EMBODIMENT

[0022] The present application will be described in detail below in combination with specific examples. EXAMPLE

[0023] A process for producing anti-caking baking soda: sodium bicarbonate slurry (NaHCO3 slurry, for example, with a moisture content of 40%) is centrifuged (with a moisture content of 10%), transported (for example, by a belt or a wet material auger) to a screw feeder, and sent to a belt filter (the belt filter is preferably vacuum filtered, 2 washing water is added to the belt filter, the length and width ratio is 15:1, and the loss rate of solid material during the washing process is 7%), the amount of washing water is adjusted according to the needs, and the vacuum degree is-0.05MPa. The belt filter washing water is sent to the heavy soda workshop as filtered washing water through a pipeline.

[0024] The washed wet material is sent to an air flow drying pipe (for example, the pipe pressure is 4kPa) by a screw conveyor, and is contacted with heated hot air. The dried material is sent to a cyclone separator, the separated finished product is sent to a powder flow cooler, the feed temperature is 50℃, and the finished product is cooled to below 40℃, then enters a packaging system to be packaged into a product, and the tail gas from the cyclone separator is sent to a tail gas dust removal tower for dust removal and then vented. EXAMPLE

[0025] A process for producing anti-caking sodium bicarbonate: sodium bicarbonate slurry (NaHCO3 slurry, for example, with a moisture content of 45%) is centrifuged (with a moisture content of 15%), transported (for example, by a belt or a wet material auger) to a screw feeder, and fed into a belt filter (preferably a vacuum filter, with 3 washing water added, a length to width ratio of 20:1, and a solid material loss rate of 8% during washing), the amount of washing water is adjusted as needed, and the vacuum degree is -0.06 MPa. The belt filter washing water is sent to the heavy alkali workshop as filtered washing water through a pipeline.

[0026] The washed wet material is sent to an air flow drying pipe (for example, with a pipe pressure of 4 kPa) by a screw conveyor, contacts heated hot air, and the dried material is sent to a cyclone separator, the separated finished product is sent to a powder flow cooler, the feed temperature is 58°C, the finished product is cooled to below 45°C, enters a packaging system to be packaged into a product, and the tail gas from the cyclone separator is sent to a tail gas dust removal tower for dust removal and then vented.

[0027] The test results of the sodium bicarbonate products obtained in Examples 1-2 are as follows:

[0028] Test item Original easy-caking bicarbonate Example 1 Example 2 Average particle size, um 150 161 175 Median particle size, um 126 134 155 80% particle size distribution range, um 40-340 75-300 90-280 Percentage of particles less than 90 um 18 11 9 Percentage of particles greater than 260 um 12 9 6 Packaging temperature, °C 42 37 32 Summer caking time, days 6 No caking after 30 days No caking after 30 days

[0029] As can be seen from the comparison between Examples 1-2, the anti-caking sodium bicarbonate product produced by the process of the present application has a smaller proportion of fine particles and large particles than the sodium bicarbonate produced by the traditional method, the uniformity of the obtained product is better, the packaging temperature is also reduced, and the anti-caking performance of the product is significantly improved.

[0030] The above embodiments are only for illustrating the technical concepts and characteristics of the present application, the purpose is to enable those skilled in the art to understand the content of the present application and implement it, and cannot limit the protection scope of the present application. Any equivalent transformation or modification made according to the spirit and essence of the present application should be covered within the protection scope of the present application.

Claims

1. A process for the production of anti-caking baking soda, characterized in that, It comprises the following steps: (1) The sodium bicarbonate slurry is transported to a screw feeder after centrifugal separation and is sent to a belt filter for washing; the belt filter is a vacuum filter with a length-width ratio of 15:1-30:1, 2-5 washing water is added, and the vacuum degree is -0.05--0.07 MPa; (2) The wet material after washing is sent to an air flow drying pipe by a screw conveyor and is contacted with heated hot air, the dried material is sent to a cyclone separator for separation, the separated finished product is sent to a powder flow cooler, the feeding temperature is 50-75 DEG C, the finished product is cooled to below 50 DEG C, enters a packaging system to be packaged into products, and the tail gas from the cyclone separator is vented after being dedusted in a tail gas dedusting tower; The water content of the sodium bicarbonate slurry is 40%-50%, and the water content of the sodium bicarbonate slurry after centrifugal separation is 5%-15%.

2. A process for the production of anti-caking small soda according to claim 1, characterized in that: The belt filter washing water in step (1) can be sent to a heavy alkali workshop as filtered washing water through a pipeline.

3. A process for the production of anti-caking small soda according to claim 1, characterized in that: The tube pressure of the air flow drying pipe in step (2) is 3-5 kPa.

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