In the pharmaceutical industry, there are vacuum evaporation, vacuum concentration, vacuum transportation, vacuum sterilization, vacuum drying, vacuum packaging and vacuum mixed emulsification and other vacuum equipment. These equipment must be equipped with vacuum pumps. What are the common vacuum pumps in the pharmaceutical industry? What are their advantages and disadvantages?
How to apply the vacuum pump in the process of pharmaceutical production, first of all, the following concepts need to be clarified:
1. The concept of “vacuum”: Vacuum refers to the state of gas that is lower than one atmospheric pressure in a given space, that is, the molecular density of gas in the space is lower than that of the atmospheric pressure in the area. The space state without gas is called absolute vacuum.
2. Vacuum pump: it is a device used to generate, improve and maintain vacuum.
3. Air extraction: the flow rate of the air pumped by the vacuum pump in unit time under the working pressure.
4. Limit pressure (vacuum degree): the absolute pressure that the vacuum pump can reach when the extraction volume is zero.
5. Working pressure (vacuum degree): absolute pressure of jet pump at rated air extraction.
6. Working steam pressure: working steam pressure of steam jet vacuum pump.
7. Working steam consumption: steam consumption per unit time of steam jet vacuum pump.
8. Cooling water temperature: circulating water temperature of water jet pump or condenser of steam jet vacuum pump.
9. Circulating amount of cooling water: circulating water flow through water ejector or steam jet pump condenser per unit time.
Next, let’s get to the main point and understand the advantages and disadvantages of several common vacuum pumps in the pharmaceutical industry.
The common vacuum pumps in pharmaceutical industry can be simply divided into variable volume vacuum pump and jet vacuum pump. Variable volume vacuum pump is a device that uses the periodic change of pump cavity volume to complete suction and exhaust. Reciprocating vacuum pump, rotary vane vacuum pump, slide valve vacuum pump, water ring vacuum pump and roots vacuum pump are variable volume vacuum pumps. Jet vacuum pump is a kind of momentum transfer pump which uses the high-speed jet produced by the pressure drop of Venturi effect to deliver gas to the outlet. Water jet vacuum pump, steam jet vacuum pump, steam water series jet vacuum pump and steam water combination jet vacuum pump belong to jet vacuum pump.
Here, we select several of them for research, such as: reciprocating vacuum pump, water ring vacuum pump and jet vacuum pump.
1. Reciprocating vacuum pump
It draws in, compresses and exhausts the gas by reciprocating or rotating the piston. Their advantage is that the vacuum degree of the new pump is relatively high, but the piston is a running part, so the wear of the piston can not be avoided. With the increase of maintenance times, the working vacuum degree will continue to decline until it can not meet the production requirements. This kind of pump works with high noise, fuel consumption and high failure rate, which is also a fatal disadvantage. Generally, one pump needs to be opened for standby, which increases the equipment investment and operation cost. In addition, if this kind of pump is used to pump water vapor and other condensable gases, the lubricating oil will be emulsified, so it can only be used to pump non condensable (air) gases, and it can not pump medium with particles, which limits its application scope.
It relies on the eccentric rotor with multiple blades installed in the pump casing to rotate, throwing water to the pump casing to form a water ring concentric with the pump casing, and the water ring and the rotor blades form a periodic change of volume, so as to suction, compress and discharge the gas. The advantages of the utility model are that the air volume is large when the vacuum is low, and the condensable gas such as water vapor can be directly pumped. Its disadvantage is that the vacuum degree is low, and it can’t pump the medium with particles.
3. Jet vacuum pump
The jet vacuum pump is widely used in the process of chemical operation because of its wide range of vacuum, direct extraction of condensable gases such as steam and granular media, simple structure, convenient operation, small maintenance amount of non operating parts, energy saving and consumption reduction.