oil-free dry screw vacuum pump selection

Oil free dry screw vacuum pump, with the following characteristics: dry screw vacuum pump with advanced temperature control system, low maintenance requirements and up to five years of maintenance service interval, is a durable and economic screw vacuum pump in industrial applications. 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:

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 limit vacuum degree of water radiation pump and water ring vacuum pump can only reach 2000Pa. It is necessary to obtain higher vacuum. It is necessary to complete the capacity of serial connection with multi-stage Roots vacuum pump or multi-stage steam radiation pump. The layout is complex, and there are many connection points, which easily causes problems.

The dry screw vacuum pump operates stably for a long time, and is not affected by the water temperature and the solvent extracted; while the water jet pump and the water ring vacuum pump operate 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 the water ring vacuum pump, it is necessary to cool the water tank of the water jet pump or the water ring pump with the frozen brine, resulting in the increase of energy consumption. In addition, the vacuum degree of water jet pump or water ring vacuum pump will decrease when the low boiling solvent extracted from the system but not condensed is fed into the water body of water jet pump or water ring vacuum pump.

Because there is no medium in the working chamber of the dry screw vacuum pump, a clean vacuum can be obtained. Therefore, a condenser can be set at the exhaust end of the screw vacuum pump under normal pressure to further condense and recover the uncondensed solvent under vacuum conditions, which greatly improves the solvent recovery rate. Taking toluene as an example, under the vacuum condition of 1mmhg, the condensation temperature of toluene is 0 ℃, if we want to condense toluene at the vacuum end, we must use a refrigerant below – 15 ℃, because the temperature difference of heat exchange is small, it needs a large condensation heat exchange area to effectively condense and recover toluene, and the condensation temperature of toluene at atmospheric pressure is 110 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%. However, for water jet pump and water ring vacuum pump, the uncondensed solvent is directly mixed into the water, which can not be condensed 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.

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.

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.

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.