Treatment process for preventing color change and hardening of sodium hyposulfite

Abstract

A treatment process for preventing high soda discoloration and hardening comprises the following steps: two-stage centrifugal treatment: performing first-stage centrifugation (600-800rpm, 5-8min) on a crystallized wet material to remove mother liquor, and synchronously spraying deionized water accounting for 2% of the mass of the wet material through second-stage centrifugation (1200-1500rpm, 3-5min) to elute surface impurities and metal ions, so that the water content of the wet material is reduced to 3%; low-temperature drying: combining countercurrent hot air with a vibrated fluidized bed, and drying at 40-60 DEG C until the water content is less than or equal to 0.5%; packaging with inert gas: filling nitrogen or argon for sealing after sub-packaging. Wherein in the second-stage centrifugation, deionized water is uniformly sprayed through an atomizing nozzle of an annular spraying pipe. According to the process, by optimizing centrifugal cleaning, low-temperature drying and inert packaging, surface impurities are thoroughly removed, oxidation and intergranular water enrichment are blocked, the product stability can be remarkably improved without adding an anti-blocking agent, and the phenomena of discoloration and hardening are avoided after the product is stored for 2 years.

Description

Technical Field

[0001] The invention relates to a treatment process for preventing baking soda from discoloring and hardening. Background Art

[0002] Baking soda is an important chemical product widely used in water treatment, photographic fixing, textile printing and dyeing, and other fields. Currently, the production of baking soda mostly uses sodium sulfide to reduce sulfate-containing wastewater, and then produces the finished product through a concentration and crystallization process. For details, see Chinese patent CN202211621144.X. However, the existing process has the following problems:

[0003] 1. Discoloration problem: During the crystallization process of baking soda, impurities (such as sulfides, heavy metal ions, etc.) can easily migrate to the crystal surface along with moisture during the drying or storage stage. After contact with air, oxidation or moisture absorption reaction occurs, causing the surface to turn yellow or discolor.

[0004] 2. Hardening problem: During the storage of finished products, residual moisture or impurities between the crystals form crystal bridges, causing the particles to stick together and harden, affecting the fluidity and use effect of the product.

[0005] Existing methods typically address this issue by extending the drying time or adding anti-caking agents. However, the former is energy-intensive and inefficient, while the latter can introduce new impurities, affecting product purity. Furthermore, conventional centrifugal equipment is inefficient in separating impurities, and impurities in the residual mother liquor can accumulate on the crystal surface. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a treatment process for preventing baking soda from discoloring and hardening, and significantly extend the shelf life of baking soda by optimizing the centrifugal process, controlling the drying conditions and storage environment.

[0007] In order to solve the above technical problems, the present invention provides a treatment process for preventing baking soda from discoloring and hardening, comprising the following steps:

[0008] (1) The crystallized sodium bicarbonate wet material is subjected to two-stage centrifugation in sequence, using a variable frequency centrifuge. The first stage centrifugal speed is 600-800 rpm, the centrifugal time is 5-8 minutes, and the mother liquor is initially removed; the second stage centrifugal speed is 1200-1500 rpm, and the centrifugal time is 3-5 minutes. During the second centrifugation, deionized water is sprayed into the centrifuge synchronously to elute impurities and other metal ions remaining on the surface of the sodium bicarbonate crystals. The amount of deionized water sprayed is 2% of the mass of the sodium bicarbonate wet material. After the second centrifugation, the water content of the final sodium bicarbonate wet material is 3%;

[0009] (2) drying the wet baking soda crystals obtained after centrifugation by combining countercurrent hot air with a vibrating fluidized bed at a drying temperature of 40 to 60° C. to obtain a dried baking soda product having a moisture content of ≤0.5%;

[0010] (3) The dried baking soda product is divided into packages and filled with nitrogen or argon and then sealed.

[0011] Preferably, in the step (1), an annular spray pipe is provided in the centrifuge, and atomizing nozzles are evenly distributed circumferentially on the annular spray pipe, and external deionized water is sprayed into the centrifuge through the atomizing nozzles on the annular spray pipe.

[0012] For the purpose of simplifying the description, the treatment process for preventing baking soda from discoloring and hardening described in the present invention is referred to as this process.

[0013] Advantages of this process: This process uses variable frequency centrifugation to initially remove the mother liquor through low-speed centrifugation. Then, high-speed centrifugation combined with deionized water spraying removes impurities and other metal ions remaining on the surface of the baking soda crystals. A combination of countercurrent hot air and a vibrating fluidized bed thoroughly removes surface impurities and inhibits intercrystalline moisture accumulation. Finally, the product is sealed with an inert gas, eliminating the need for additional anti-caking agents. Experimental results show that the finished product exhibits no discoloration or caking after two years of storage. This process significantly improves the storage stability of baking soda products and is suitable for use in the chemical industry, environmental wastewater treatment, and other fields. It offers low energy consumption, high compatibility, and ease of implementation. DETAILED DESCRIPTION

[0014] Example 1:

[0015] A treatment process for preventing baking soda from discoloring and hardening comprises the following steps:

[0016] (1) The crystallized sodium bicarbonate wet material (water content 15%) was subjected to two-stage centrifugation in sequence, using a variable frequency centrifuge. The first stage centrifugal speed was 600 rpm and the centrifugal time was 5 min to preliminarily remove the mother liquor; the second stage centrifugal speed was 1200 rpm and the centrifugal time was 3 min. During the second centrifugation, deionized water was sprayed into the centrifuge synchronously to elute the impurities and other metal ions remaining on the surface of the sodium bicarbonate crystals. The amount of deionized water sprayed was 2% of the mass of the sodium bicarbonate wet material. After the second centrifugation, the water content of the final sodium bicarbonate wet material was 3%;

[0017] (2) drying the wet baking soda crystals obtained after centrifugation by combining countercurrent hot air with a vibrating fluidized bed at a drying temperature of 40° C. to obtain a dried baking soda product having a moisture content of ≤0.5%;

[0018] (3) The dried baking soda product is divided into packages and filled with nitrogen or argon and then sealed.

[0019] In the step (1), an annular spray pipe is provided in the centrifuge, and atomizing nozzles are evenly distributed on the annular spray pipe in the circumferential direction. External deionized water is sprayed into the centrifuge through the atomizing nozzles on the annular spray pipe.

[0020] Example 2:

[0021] A treatment process for preventing baking soda from discoloring and hardening comprises the following steps:

[0022] (1) The crystallized sodium bicarbonate wet material (water content 15%) was subjected to two-stage centrifugation in sequence, using a variable frequency centrifuge. The first stage centrifugal speed was 750 rpm and the centrifugal time was 6 min to preliminarily remove the mother liquor; the second stage centrifugal speed was 1300 rpm and the centrifugal time was 4 min. During the second centrifugation, deionized water was sprayed into the centrifuge synchronously to elute the impurities and other metal ions remaining on the surface of the sodium bicarbonate crystals. The amount of deionized water sprayed was 2% of the mass of the sodium bicarbonate wet material. After the second centrifugation, the water content of the final sodium bicarbonate wet material was 3%;

[0023] (2) drying the wet baking soda crystals obtained after centrifugation by combining countercurrent hot air with a vibrating fluidized bed at a drying temperature of 50° C. to obtain a dried baking soda product having a moisture content of ≤0.5%;

[0024] (3) The dried baking soda product is divided into packages and filled with nitrogen or argon and then sealed.

[0025] In the step (1), an annular spray pipe is provided in the centrifuge, and atomizing nozzles are evenly distributed on the annular spray pipe in the circumferential direction. External deionized water is sprayed into the centrifuge through the atomizing nozzles on the annular spray pipe.

[0026] Example 3:

[0027] A treatment process for preventing baking soda from discoloring and hardening comprises the following steps:

[0028] (1) The crystallized sodium bicarbonate wet material (water content 15%) was subjected to two-stage centrifugation in sequence, using a variable frequency centrifuge. The first stage centrifugal speed was 800 rpm and the centrifugal time was 8 minutes to preliminarily remove the mother liquor; the second stage centrifugal speed was 1500 rpm and the centrifugal time was 5 minutes. During the second centrifugation, deionized water was sprayed into the centrifuge synchronously to elute the impurities and other metal ions remaining on the surface of the sodium bicarbonate crystals. The amount of deionized water sprayed was 2% of the mass of the sodium bicarbonate wet material. After the second centrifugation, the water content of the final sodium bicarbonate wet material was 3%;

[0029] (2) drying the wet baking soda crystals obtained after centrifugation by combining countercurrent hot air with a vibrating fluidized bed at a drying temperature of 60° C. to obtain a dried baking soda product having a moisture content of ≤0.5%;

[0030] (3) The dried baking soda product is divided into packages and filled with nitrogen or argon and then sealed.

[0031] In the step (1), an annular spray pipe is provided in the centrifuge, and atomizing nozzles are evenly distributed on the annular spray pipe in the circumferential direction. External deionized water is sprayed into the centrifuge through the atomizing nozzles on the annular spray pipe.

[0032] In the above embodiment, the countercurrent hot air is combined with the vibrating fluidized bed in such a way that horizontal countercurrent hot air is introduced into the fluidized bed simultaneously, and the hot air inlet and outlet are diagonally distributed to ensure that the airflow is fully in contact with the material.

Claims

1. A treatment process for preventing discoloration and hardening of baking soda, characterized in that: The following steps are involved: (1) The crystallized sodium bicarbonate wet material is subjected to two-stage centrifugation in sequence, using a variable frequency centrifuge. The first stage centrifugal speed is 600-800 rpm, the centrifugal time is 5-8 minutes, and the mother liquor is initially removed; the second stage centrifugal speed is 1200-1500 rpm, and the centrifugal time is 3-5 minutes. During the second centrifugation, deionized water is sprayed into the centrifuge synchronously to elute the impurities and other metal ions remaining on the surface of the sodium bicarbonate crystals. The amount of deionized water sprayed is 2% of the mass of the sodium bicarbonate wet material. After the second centrifugation, the water content of the final sodium bicarbonate wet material is 3%; (2) drying the wet baking soda crystals obtained after centrifugation by combining countercurrent hot air with a vibrating fluidized bed at a drying temperature of 40 to 60° C. to obtain a dried baking soda product having a moisture content of ≤0.5%; (3) The dried baking soda product is divided into packages and filled with nitrogen or argon and then sealed.

2. A process for preventing discoloration and hardening of baking soda according to claim 1, characterized in that: In the step (1), an annular spray pipe is provided in the centrifuge, and atomizing nozzles are evenly distributed on the annular spray pipe in the circumferential direction. External deionized water is sprayed into the centrifuge through the atomizing nozzles on the annular spray pipe.