Causes and countermeasures of positive pressure in extractor
For the sake of safety, cost and environmental protection, and the other reasons, the extraction workshops are all under negative pressure production, but sometimes due to improper production operation control or equipment failures, the workshop will be under positive pressure for a short time or even for a long time, and more often occur in the workshop to increase production significantly. If the evaporation rate is not adjusted in time, it will cause positive pressure in the extractor, which exposes the workshop to an unsafe state.
The reason for the positive pressure of the extractor mainly comes from the positive pressure of DT. The reason for the positive pressure of DT is that the secondary steam of DT cannot be fully utilized by the evaporation system, and the amount of secondary steam used by DT mainly depends on the flow rate of the mixed oil and the mixed oil.
The situation that the DT secondary steam cannot be fully utilized by the evaporation system mainly occurs when the speed of the extractor increases. After the speed of the extractor is increased, the flow rate of soybean meal entering DT increases. In order to control the gas phase temperature in DT and the residual dissolution of soybean meal, the amount of direct steam will be increased. At this time, if the evaporation in the evaporation system has not risen, the mixed gas discharged by DT cannot be completely absorbed by the evaporation system, which will cause a positive pressure of DT, and even reduce the desolvation time of soybean meal in DT, resulting in residual soybean meal. Exceeding the standard brings serious safety risks. Sometimes factory operators often increase the exhaust gas discharge by increasing the speed of the exhaust fan in order to alleviate this situation. However, due to the limited cooling capacity of the condensing system and the limited absorption capacity of the exhaust system, the solvent gas in the exhaust is not condensed and absorbed and is discharged into the atmosphere, which will cause the solvent in the exhaust gas to exceed the standard seriously and increase the solvent loss, so it is not the fundamental method to solve the problem.
The increase in the speed of the extractor mainly occurs when the squeezing volume changes, especially when the output is increased by the pretreatment. Due to the increase of the leaching material entering the extractor, the material level of the extractor increases, and the speed of the extractor will increase. Therefore, the solvent turnover should be increased first, and then the material flow should be increased when the production is increased substantially. Generally, the production increase should be about 20 minutes ahead of time. The extraction workshop will increase the amount of fresh solvent according to the increase of pretreated soybeans with reference to the solvent ratio, because the time required for the fresh solvent from the solvent working tank (SWS) to the mixing oil hopper of the extractor is longer than that of the material. The time from the rolling mill to the extractor is long. During this period of time, the mixed oil concentration will be relatively low, which can be adjusted by reducing the evaporation of the evaporation system. When the puffed material enters the extractor, the speed will increase, and the direct steam consumption of DT will increase accordingly, and then increase the evaporation of the mixed oil correspondingly to ensure the effective use of the secondary steam generated by DT and prevent positive pressure in the leaching system. When increasing the output, it must not be increased too much at one time, and should be increased slowly after the leaching is stable. After the leaching is stable, adjust the rolling mill, and the leaching material will increase soon. Therefore, do not rush to increase too much. If you increase too much at once, the speed of the extractor is too fast, so that the DT is cut too fast and the desolvation time is short, which will cause the soybean meal to exceed the standard, and the positive pressure of DT and the extractor will be generated, and may bring serious hidden danger.