The efficacy and price of stevia sugar are incomparable to other sugars, and the requirements for its delivery process are also much stricter. As an important section of stevia sugar production, the quality requirements of resin directly determine the purity, chromaticity, transmittance and other quality indicators of the product. Therefore, it is crucial to ensure the normal operation of the separation process! Especially, our company has developed DA201-H and SQ-338 specialized resins specifically for the adsorption and decolorization of stevia, which have demonstrated their excellent characteristics in the production and application of stevia. Now, the Suqing brand DA201-H, 001 × Introduction to the pre-treatment and operation methods of 16 and SQ-338 resins used in the steviol separation process is as follows:
1、 Basic main process:
1、 Specific process: Stevia leaf soaking (water to leaf ratio of 10:1, soaking at 60 ℃ for 2 hours per soaking) - Stevia sugar clear solution storage tank - (lime and iron) flocculation - plate and frame pressure filtration - storage tank (5 cubic meters, 2 sets) - precision filter (two sets in series, totaling 4 sets) - to sugar solution storage tank (10 cubic meters) - sugar solution pump - to resin adsorption column - analytical solution storage tank (10 cubic meters) - activated carbon decolorization kettle (3 cubic meters) - plate and frame pressure filtration (filtering activated carbon) - Filtrate storage tank (6 cubic meters) - positive column - negative column - negative column - distillation tower (including alcohol distillation tower and water distillation tower, concentrating the dilute sugar solution to about 40% of the concentrated sugar solution) - to the concentrated sugar solution recovery tank - activated carbon decolorization - spray drying - packaging of finished products.
2. Main steps:
2.1 Stevia Leaf Soaking: Mainly soak the stevia sugar inside the stevia leaves. Simply soak in hot water.
2.2. Flocculation of soaking solution: Due to the high amount of dust and impurities in stevia leaves, most of them can be removed through this step.
2.3. Plate and Frame Filter for Flocculant: Remove the flocculent sediment through a plate and frame filter press;
2.4. Separation adsorption: The filtered sugar solution is completely adsorbed by the adsorption resin DA201-H, while some pigments and impurities are also adsorbed. After the adsorption is completed, the adsorption resin can be cleaned with deionized water to remove some pigments and impurities, but stevia sugar will not be washed away
3. Analysis of Stevia Sugar: Use a 65% edible alcohol solution that is approximately 3 times the volume of the resin to analyze the adsorption resin, and use a flow rate that is approximately 3 times the volume of the resin to analyze the sugar solution (a flow rate that is 6.7 times the volume of the resin in Paraguay is also normal! However, it should be adjusted lower for better results!)
4. Activated carbon decolorization and pressure filtration: The color of the analytical solution is dark brown, and activated carbon is used for decolorization to remove some of the pigments and odors, reducing the pressure on the resin. The amount of carbon added is generally 2Kg/m3 of sugar, (1kg of carbon needs to absorb about 1kg of sugar, so activated carbon cannot be added too much!); Adding more activated carbon syrup does not significantly improve the color.
5. Demineralization and decolorization of inbreeding: core steps! After running in series with one positive and two negative, the dark brown sugar solution has a basic clear and transparent color; Manifested in: the incoming yang is dark brown, and the outgoing yang is light brown; The first yin is basically colorless, with a slight yellowish color in the later stage; The outlet of the second anion is basically clear and transparent;
6. Concentration of sugar solution: After separation, the dilute sugar solution should be concentrated, including an alcohol distillation tower and a water distillation tower. The dilute sugar solution should be concentrated to about 40% of the concentrated sugar solution, and the alcohol should be recycled and reused;
7. Re decolorization of concentrated sugar solution: After concentration, the sugar solution still has a slight yellow color and needs to be further decolorized; (The activated carbon used this time is different from last time!)
8. Spray drying of sugar solution: spray drying and packaging of sugar solution can produce finished products.
2、 Pre treatment of new resin:
Filling the resin according to the design amount should be strictly prevented from mixing. To ensure the clarity and transparency of the treated sugar solution, it is crucial to remove oligomers in the new resin and impurities that may be brought in during the filling process. The following methods must be followed for operation:
1. Backwash the resin and control the appropriate backwash expansion rate. The backwash flow rate for DA201-H and SQ-338 is about 5-8 m/h, 001 × The backwashing flow rate is about 10-15 m/h, and it is important not to flush out normal particles of resin to remove air and suspended debris from the resin inside the column. The time is about 30 minutes, and the water used is raw water or softened water.
2. Inject 5-7% NaCl solution into each column, and soak for at least 8 hours when the salt concentration in the effluent reaches 3-4%.
3. Rinse the NaCl solution in the resin thoroughly with raw water. Rinse DA201-H with deionized water and wait for use (it is best to soak it in alcohol once!).
4. To 001 × Add 3-4% HCl solution to the 16 resin and 2-3% NaOH (prepared with deionized water) to the SQ-338 resin. When the outlet acid and alkali concentration reaches about 2%, stop the injection, soak for about 8 hours, and then clean with deionized water until it is basically neutral;
5. To 001 × Add 2% NaOH to the 16 resin (preferably prepared with deionized water, as shown on site that the cation resin is easy to clean, this step can also be omitted), and add 2-3% HCl solution to the SQ-338 resin. When the outlet alkali and acid concentration reaches 2%, stop the introduction, soak for 8 hours, and then wash with deionized water until it is basically neutral;
6. Backwash all ionized columns with deionized water to further remove oligomers released during pre-treatment until the backwash water is clear and ready for regeneration.
3、 Initial regeneration of resin (using deionized water for acid, alkali, and cleaning):
The initial regeneration dose should be slightly higher than normal, as follows:
1. Yangzhu 001 × Regeneration of 16: Inject approximately 3.5 times the resin volume of 4-5% HCl solution into the cation column, control the flow rate to about 2.5m/h (soaking for 2 hours is better), and then clean with deionized water until it is basically neutral;
2. Regeneration of anion column SQ-338: Inject about 3.5 times the resin volume of 3-4% NaOH solution into the anion column, control the flow rate to about 2.5m/h (soaking for 2 hours is better), and then wash with water until it is neutral;
4、 Preparation of salt, acid, and alkali:
1. Salt: Each column is equipped with 7% saline water, with an agreed amount of 5 tons, requiring approximately 350kg of salt;
2. Hydrochloric acid: 5 tons of 5% acid are added to the cation column each time, requiring 830kg of 30% hydrochloric acid;
3. Alkali: 5 tons of 4% alkali are added to the anion column each time, requiring 200kg of solid alkali (100%);
4. 3 tons of 2% alkali can be added to the adsorption column each time, requiring 60kg of solid alkali (100%);
5、 Regeneration of resin during normal operation:
Some stevia leaves are soaked in tap water, but due to the adsorption resin intercepting sugar and leaking other impurities, and the water used for squeezing sugar is deionized water, the content of inorganic ions in the sugar solution after adsorption resin is very low, which greatly reduces the pressure of positive and negative resin. Here, its desalination ability is surplus, mainly for decolorization!
The steps after the failure of the separation column mainly include sugar squeezing, washing, backwashing, regeneration, and re cleaning.
1. Sugar squeezing: After the failure of the negative and positive columns, in order to avoid wasting the sugar solution, water should be used to replace and recycle the sugar solution inside the column. Generally, when the concentration of the replaced sugar is less than ± 1% When (depending on the situation in each factory, such as 0.3%), it can be directly discharged into the trench, and the sugar squeezing flow rate is the same as the operating flow rate. (The adsorption column is directly analyzed with 65% edible alcohol);
2. Front washing: The purpose is to further clean the sugar solution to prevent it from being too high in concentration and too high in specific gravity during backwashing. When backwashing with resin, it is recommended to rinse out (especially with anion resin), and the cleaning flow rate should be twice the resin volume, with a time of about 30-60 minutes.
3. Backwashing (main step): Clean all impurities intercepted by the resin, with a flow rate of 5m/h for the positive column and 4m/h for the negative column (based on the principle of no resin loss during backwashing), until the backwash water is clear and waiting for regeneration.
4. Regeneration:
4.1. Yangzhu 001 × Regeneration of 16: Inject approximately 2.5 times the resin volume of 4-5% HCl solution into the cation column, control the flow rate to approximately 2.5m/h (soaking for 2 hours is better), and then clean with deionized water until it is basically neutral;
4.2 Regeneration of anion column SQ-338: Inject about 3 times the resin volume of 3-4% NaOH solution into the anion column, control the flow rate to about 2.5m/h (soaking for 2 hours is better), and then clean with water until it is basically neutral; Add about 2.5 times the resin volume of 4-5% HCl solution to the anion column, control the flow rate to about 2.5m/h (soaking for 2 hours is better), and then clean with deionized water until it is basically neutral; Add about 3 times the resin volume of 3-4% NaOH solution to the anion column, control the flow rate to about 2.5m/h (soaking for 2 hours is better), and then wash with water until it is basically neutral; (According to experience, SQ-338 resin has a better decolorization effect when soaked for 1-2 hours with alkali, acid, alkali, and regeneration liquid leakage.)
4.3. After analyzing DA201-H with 60-70% edible alcohol, backwash with water, then scrub with air, and then clean until it is clear. Soak and clean with 3% NaOH for later use; (Due to the deep color of the adsorbent resin after use, it can be revived regularly according to the specific situation, and it is best to wash it with alkali every time!)
6、 Suggestion:
1. Flowmeters should be installed for regeneration and feeding;
2. It is best to have a pressure gauge on the feeding pipeline to monitor the resin or impurities inside the column;
3. The position of the tank mirror should be designed reasonably to facilitate monitoring of the operating conditions inside the column;
4. The height to diameter ratio of resin filling should be appropriate;
5. We should pay attention to the quality of process water, and the formulation of operating parameters varies depending on the water quality.