The chain-type leaching unit consists of a storage tank, a feeding section, an upper leaching section, a turning section, a lower leaching section, a draining section, and a head section. After entering the chain-type leaching unit, the material is driven forward on the upper grid by the pusher box (the red arrow in the diagram indicates the direction of material movement), and is leached by a gradually diluted mixture. Because the pusher box is a closed area, a liquid layer of a certain height can be formed inside, achieving both penetration and soaking, resulting in better leaching effects. The wet meal, from which some extract has been extracted in the pusher box, falls onto the second grid through a hopper at the break in the upper grid. After rearranging, it is again driven forward by the pusher box, where it is leached again by a diluted mixture and fresh solvent. After thorough draining, it is discharged from the leaching unit and sent to the DTDC (Diluted Thick Discharge Center).
Precautions for operating a chain-type leaching extractor:
1. The higher the material layer in the leaching tank, the slower the extractor rotates, the longer the contact time between the material and the solvent, and the better the leaching effect. However, the material layer height should not be too high, otherwise the material is easily washed into the oil hopper by the mixed oil, then pumped up by the circulating pump and sprayed onto the surface of the material layer. Large particles of material are prone to accumulate in the spray pipes and block them, especially when leaching pre-pressed cake. In actual production, the material layer height is generally controlled at around 80%, and adjusted according to the permeation rate of the material layer.
2. When the permeation rate of the material layer is fast, the material layer height can be appropriately increased, but should not exceed 90%. If the permeation rate is too fast, there is no liquid layer on the surface of the material layer, the material cannot be soaked in the solvent, and the contact time between the material and the solvent is too short, which is not conducive to the extraction of oil from the material. In this case, the operation can appropriately increase the material layer height and increase the spray volume. At the same time, notify the operators of the previous process to adjust the process and reduce the permeation rate of the material layer.
3. When the permeation rate of the material layer is slow, the material layer height can be appropriately reduced. The slow penetration rate results in a thick liquid layer accumulating on the surface of the material. Although the material is continuously immersed in the solvent/mixed oil, the slow penetration speed of the solvent/mixed oil through the material layer means that the mixed oil from the previous spraying section is carried to the next spraying section before it has fully drained. This reduces the concentration difference between the mixed oils in different spraying sections, significantly diminishing the leaching effect. To prevent the mixed oil from overflowing the tank, the material layer height needs to be lowered and the spray volume reduced. Simultaneously, the operators in the preceding process should be notified to make appropriate process adjustments to increase the penetration rate of the material layer.
4. When the permeation rate of the leaching layer is very poor, the mixed oil sprayed onto the surface cannot penetrate and will mix together, eliminating the concentration difference between different spray sections. In this case, it is necessary to contact the operators of the upstream process to adjust the process as soon as possible and restore the permeation rate of the leaching layer. This operator needs to reduce the spray volume above the poorly permeated leaching layer and simultaneously shut down the last one or two sprays in the corresponding spray section to increase the draining time of the leaching layer. Special attention should be paid to the permeation in the draining section. If necessary, the spraying of fresh solvent can be reduced or even shut off to strictly prevent mixed oil from being carried into the DTDC (Distillation-Derived Chemical Distillation), otherwise it will affect the normal operation of the entire leaching system.
5. The industrial solvents used for oil extraction are mainly No. 6 solvent and industrial hexane. No. 6 solvent has a wider boiling point range, increasing the difficulty of desolventizing the mixed oil and wet meal, increasing steam consumption, and resulting in higher solvent consumption. It also affects the quality indicators of the oil and meal. Therefore, many factories are now starting to use industrial hexane, which has a narrower distillation range, to replace No. 6 solvent. Industrial hexane's main component is hexane, with a boiling point of 66℃-69℃, a narrow range, making it easy to recover and requiring minimal solvent consumption. In actual production, the leaching temperature is generally 5℃-10℃ lower than the initial boiling point of the solvent. That is, when using industrial hexane as the leaching solvent, the leaching temperature is typically controlled at 56℃-60℃, and the internal pressure of the leaching tank is maintained at a slight negative pressure to prevent solvent gas leakage.
6. When the fresh solvent sprayed onto the surface of the material layer has a high water content, the cause needs to be identified and addressed promptly. A large amount of water entering the material layer will severely reduce its permeability. If the problem cannot be resolved quickly, the machine must be shut down immediately until the issue is resolved and the water content in the fresh solvent returns to normal. A large amount of water entering the leaching tank is itself a very serious production accident; improper handling can have severe consequences, even leading to more serious safety incidents.
Our Vic Machinery can provide a variety of models and capacity of the solvent extractor, welcome to consult and purchase!
