Citric acid waste production citric acid technology
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Citrus residues → pressing (solids after pressing → drying → dried orange peel) → juice → heated concentrated → molasses Step 2: Fermentation.
Orange peel 50 g, molasses more than 500 ml, placed in the flask → 121 °C, 30 minutes sterilization → Inoculation spore inoculant (yeast) → Add 50 times distilled water extraction → Filtration → Add calcium carbonate → Filtered solids → Add Sulfuric acid treatment → Filter to remove calcium sulfate → Concentrate the filtrate → Crystallize → Finished product Second, processing (1) Raw material treatment: The processing residue of the citrus processing plant is used as raw material, and then squeezed, the juice is heated and concentrated to molasses; the solid is dried to orange peel . Tangerine is treated with a 0.25 cm mesh screen.
(2) Fermentation: The obtained tangerine peel and molasses are placed in a container, and yeast is added for fermentation. The spore growth and mycelium development temperature was 35°C, and the post-fermentation acid production temperature was 30°C. The optimum fermentation time was 4 days, the humidity was 50%, and 2% methanol solution was added. At this time, the citric acid yield was the highest.
(3) Adding calcium carbonate: After the fermentation is finished, add 2% activated carbon to adsorb and filter, add calcium carbonate to the filtrate, and add while stirring. Citric acid and calcium carbonate form insoluble calcium citrate, which is separated and precipitated from the fermentation broth, filtered, and the filtrate removed.
(4) Acid hydrolysis: dilute the calcium citrate with water to a paste, heat it to 85°C, and slowly add sulfuric acid (Calculate the amount of sulfuric acid based on the amount of calcium carbonate input, and use 92%-95% of calcium carbonate) After adding 80% of the calculated amount, the end point was measured. The method is as follows.
Take two test tubes A and B. Pipette absorbs 1 ml of 20% sulfuric acid. Pipe B draws 2 ml of calcium chloride 1 ml and adds the filtered acid solution. The water bath is heated to boiling. After cooling, observe the two tubes. If no turbidity occurs, add 1 ml of 95% alcohol. If two tubes, A and B, are still not cloudy, they are considered to have reached the end. There was turbidity in the tube, indicating that the amount of sulfuric acid was insufficient and additional sulfuric acid was needed. If there is turbidity in the B tube, it indicates excessive sulfuric acid and calcium citrate should be added.
(5) Concentration and Crystallization: The resulting clear solution will be filtered and decanted, and then heated to a concentration of 36.5-37 Baume to be canned. After cooling to citric acid crystals, the mother liquor is de-prepared by a centrifuge, and the crystals are washed with cold water, and the moisture is removed from the surface in a cool place.
Third, pay attention to matters (1) wash the calcium citrate should be acid solution in time to prevent moldy deterioration.
(2) Lemon acid is more corrosive when concentrated, so it is more commonly used in pots with enamel linings. If the concentration of the concentrate is too high, it will easily become powder. If it is too low, it will result in less crystal nucleus. The finished product will have large particles. There will be a large amount of citric acid remaining in the mother liquor and affect the yield.
Author: Liaoning Liaozhong County Chemical Factory