1. The name of the design product: oil free screw vacuum pump.
2. Purpose of the appearance design product: the appearance design product is used for the suction and exhaust equipment produced by synchronous high-speed reverse rotation in the pump shell, which belongs to mechanical products.
3. Design key points of the design product: product shape.
Selection of oil-free dry screw vacuum pump
The oil-free dry screw vacuum pump developed and produced by EVP has the following characteristics: the dry screw vacuum pump has advanced temperature control system, low maintenance requirements and a maintenance service interval of up to five years, and is a durable and economical screw vacuum pump in industrial application. It has the characteristics of smaller volume and faster running speed.
At present, the dry oil-free screw vacuum pump is mainly used in the following refining fields: vacuum distillation; vacuum drying; vacuum suction.
It is compared with other types of vortex vacuum pump, roots vacuum pump and water ring vacuum pump as follows:
1. The limit vacuum of dry screw vacuum pump is high, and single pump can be indirectly pumped to 1pA (absolute pressure) vacuum by atmospheric pressure. The device is simple and convenient, with less connecting pipes and less leakage points; However, the limiting vacuum degree of water radiation pump and water ring pump can only reach 2000Pa. It is necessary to obtain a higher vacuum. It must be completed in series with multi-stage Roots vacuum pump or multi-stage steam radiation pump. The layout is complex, and there are many connection and disclosure points, so it is easy to cause problems.
2. The dry screw vacuum pump runs stably for a long time, and is not affected by the water temperature and solvent extraction; while the water jet pump and water ring pump run stably for a long time, because the water temperature rises, the vacuum degree will drop. In order to maintain the vacuum stability of the water jet pump and water ring pump, it is necessary to use chilled salt water to cool the water tank of the water jet pump or water ring pump, resulting in the increase of energy consumption. In addition, the vacuum degree of the water jet pump or water ring pump will decrease when the low boiling solvent extracted from the system but not condensed enters the water body of the water jet pump or water ring pump.
3. Because there is no medium in the working chamber of the dry screw vacuum pump, a clean vacuum can be obtained. Therefore, a condenser under normal pressure can be set at the exhaust end of the screw pump to further condense and recover the uncondensed solvent under vacuum condition, which greatly improves the solvent recovery rate. In the case of toluene, the condensation temperature of toluene is 0 ℃ in the vacuum of 1mmhg. If we want to condense toluene in the vacuum end, we must use a refrigerant below – 15 ℃. Because of the small temperature difference of heat exchange, a large condensation heat exchange area is needed to effectively condense and recover toluene. In the case of toluene, the condensation temperature is 110 ℃ under normal pressure C, we only need to use circulating water and a small condensation heat exchange area to effectively condense and recover toluene, and the solvent recovery can generally be increased to more than 96%. But for the water jet pump and water ring pump, because the uncondensated solvent is directly mixed into the water, it is impossible to carry out the condensation recovery under normal pressure, so the solvent recovery rate is low, and a large number of wastewater is produced. For low boiling solvents, such as methanol, dichloromethane, etc., under vacuum conditions, the condensation temperature is very low, it is difficult to use – 15 ℃ cold brine to condense, and the recovery rate will be lower, so most of the low boiling solvents can only enter the water to generate waste water.
4. Dry screw pump only needs a small amount of circulating cooling water, so the operation cost is low. As for water jet pump and water ring pump, because of the continuous solvent entering into the water tank, it is necessary to change water in the water tank regularly or continuously to maintain the vacuum degree of pump operation and consume a lot of water. Under the condition of rising water cost, the operation cost of water jet pump or water ring pump is relatively large. Although the equipment price of dry screw pump is higher than that of water jet pump or water ring pump, it is long In terms of operation, the cost is lower and more economical and environmental friendly.
5. For the safety of chemical production and product quality, dry screw vacuum pump also has its advantages. In the vacuum system we use, there are many materials that need to react with water, or even produce the danger of decomposition and explosion. When the water ring pump and water jet pump stop suddenly, the water will be sucked back to the vacuum system, which is easy to cause safety risk or product quality pollution. The dry screw pump has no water or oil, even if it is sucked back, it will not cause danger or pollution, which is safe and safe Quality assurance is more advantageous.
6. Corrosion resistance. The flow passage parts of the dry screw vacuum pump can be treated by nickel plating, which can withstand the corrosion of most organic acid gas and inorganic acid gas. It has been successfully used in the distillation system of extracting toluene containing hydrochloric acid gas. However, the water ring pump cannot be used in the acid system because it is inconvenient to carry out anti-corrosion treatment; the water jet pump is generally made of polypropylene or glass fiber reinforced plastic materials for anti-corrosion, but these materials are not resistant to the long-term solution corrosion of toluene and other organic solvents, and the organic solution circulates in the jet pump at high speed, which is prone to the risk of electrostatic ignition.