The oil solvent extraction workshop of the oil production plant is under negative pressure for safety, cost, environmental protection and other reasons. However, sometimes due to improper production operation control or equipment failure, the workshop may be in a positive pressure state for a short time or even for a long time. It happens more often that when the workshop increases production significantly, the evaporation volume is not adjusted in time, which will cause the extractor to have positive pressure, thus exposing the workshop to an unsafe state.
The reason for the positive pressure of the oil extractor machine is mainly due to 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 of DT mainly depends on the flow rate and concentration of the mixed oil.
The situation that the secondary steam of DT cannot be fully utilized by the evaporation system mainly occurs when the speed of the extractor is increased. 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 and residual solubility of soybean meal in DT, the direct steam consumption will be increased. At this time, if the evaporation volume in the evaporation system has not risen, the mixed gas discharged by DT cannot be completely absorbed by the evaporation system, which will cause positive pressure in DT. Even due to the reduction of the desolventizing time of soybean meal in DT, the residual solvent of soybean meal exceeds the standard, which brings serious safety hazards. Sometimes, in order to alleviate this situation, factory operators often increase the exhaust gas discharge by increasing the speed of the exhaust fan. However, due to the limited cooling capacity of the condensation system and the limited absorption capacity of the exhaust system, the solvent gas in the exhaust gas is not condensed and absorbed and is discharged into the atmosphere, which will cause the solvent in the exhaust gas to seriously exceed the standard and increase the solvent loss. Therefore, it is not a fundamental solution to the problem.
The increase in the speed of the extractor mainly occurs when the pressing volume changes, especially when the pretreatment increases the output. Because the amount of material entering the extractor increases, the material level of the extractor increases, and the speed of the extractor will increase. Therefore, when the production is greatly increased, the solvent turnover should be increased first, and then the flow rate of the material should be increased. Generally, the production should be increased about 20 minutes in advance. The leaching workshop increases the amount of fresh solvent according to the incremental reference solvent ratio of the pretreated soybeans, because the time required for the fresh solvent from the solvent working tank to the extractor mixed oil bucket is longer than the time for the material from the rolling mill to the extractor. During this period, the concentration of the mixed oil will be relatively low, and the evaporation of the evaporation system can be reduced to make adjustments. When the expanded material enters the extractor, the speed increases, the corresponding DT direct steam consumption increases, and then the mixed oil evaporation volume is increased accordingly to ensure the effective use of the secondary steam generated by DT and prevent positive pressure in the leaching system. When increasing production, do not increase too much at one time, and increase it slowly after the leaching runs steadily. After the leaching is stable, adjust the rolling mill, and the amount of material entering the leaching machine will increase soon. Therefore, do not rush to increase too much at once. If you increase too much at once, the extractor speed will be too fast, causing the DT to discharge too quickly and the desolventizing time to be short, which will cause the residual solvent in the soybean meal to exceed the standard, and the DT and extractor will have positive pressure, resulting in serious safety hazards.
