Selection of water ring vacuum pump

Q=6.7+375* 0.05=25.45kg/hs=QRT/PM=25.45 * 8.314 * 288.15/10 * 32=190m3/h

You'd better calculate it based on the pumping capacity of 1800 m3/h. But this design is wrong. If you choose a liquid ring vacuum pump, the amount of methanol being pumped out will be large, condensation will occur in the pump, and the heat will be unbearable to the pump. So you should design the condenser in front of the vacuum pump, which requires chilled water below 7 degrees.

Selection of vacuum pump The working pressure of the vacuum pump should meet the ultimate vacuum and working pressure requirements of the vacuum equipment. like: Vacuum coating requires a vacuum degree of 1×10-5mmHg, and the vacuum degree of the selected vacuum pump must be at least 5×10-6mmHg. Usually the vacuum degree of the pump is selected to be half to an order of magnitude higher than the vacuum degree of the vacuum equipment. When choosing a vacuum pump, you need to pay attention to the following matters:: 1. The working pressure of the vacuum pump should meet the ultimate vacuum and working pressure requirements of the vacuum equipment. like: Vacuum coating requires a vacuum degree of 1×10-5mmHg, and the vacuum degree of the selected vacuum pump must be at least 5×10-6mmHg. Usually the vacuum degree of the pump is selected to be half to an order of magnitude higher than the vacuum degree of the vacuum equipment. 2. Correctly select the working point of the vacuum pump. Each pump has a certain working pressure range, such as: The diffusion pump is 10-3~10-7mmHg. In such a wide pressure range, the pumping speed of the pump changes with the pressure, and its stable working pressure range is 5×10-4~5×10-6mmHg. Therefore, the working point of the pump should be selected within this range and cannot be allowed to work under 10-8mmHg for a long time. Another example is that the titanium sublimation pump can work at 10-2mmHg, but its working pressure should be less than 1×10-5mmHg. 3. The vacuum pump should be able to discharge all the gas generated during the vacuum equipment process under its working pressure. 4. Correctly combine the vacuum pump. Since vacuum pumps have selective pumping capabilities, sometimes one type of pump cannot meet the pumping requirements, and several pumps need to be combined to complement each other to meet the pumping requirements. For example, the titanium sublimation pump has a high pumping speed for hydrogen, but cannot pump helium, and the tripole sputtering ion pump (or the diode asymmetric cathode sputtering ion pump) has a certain pumping speed for argon. The combination of the two will allow the vacuum device to obtain a better vacuum degree. In addition, some vacuum pumps cannot work under atmospheric pressure and require pre-vacuum. ； The outlet pressure of some vacuum pumps is lower than atmospheric pressure and requires a backing pump, so the pumps need to be used in combination. p 5. Requirements for oil pollution in vacuum equipment. If the equipment strictly requires oil-free, various oil-free pumps should be selected, such as: Water ring pump, molecular sieve adsorption pump, sputter ion pump, cryogenic pump, etc. If the requirements are not strict, you can choose to have an oil pump and add some anti-oil pollution measures, such as adding cold traps, baffles, oil traps, etc., to achieve clean vacuum requirements. 6. Understand the composition of the pumped gas, whether it contains condensable vapor, whether there is particulate dust, whether it is corrosive, etc. When selecting a vacuum pump, you need to know the gas composition and select the corresponding pump for the gas to be pumped. If the gas contains vapor, particles, and corrosive gases, you should consider installing auxiliary equipment, such as condensers, dust collectors, etc., on the air inlet pipeline of the pump. 7. What is the impact of the oil vapor discharged from the vacuum pump on the environment? If the environment does not allow pollution, you can choose an oil-free vacuum pump or discharge the oil vapor outdoors. 8. Does the vibration generated by the vacuum pump during operation have any impact on the process and the environment? If the process does not allow it, a vibration-free pump should be selected or anti-vibration measures should be taken. 9. The price, operation and maintenance costs of vacuum pumps. Selection of water ring vacuum pump 1. Determination of pump type The type of pump is mainly determined by the air volume, vacuum degree or exhaust pressure required for work. When the pump is working, you need to pay attention to the following two aspects:: 1. It is required to operate in the high efficiency zone as much as possible, that is, in the area of ​​critical vacuum or critical exhaust pressure. 2. Avoid operating near the maximum vacuum or maximum exhaust pressure. Operating in this area is not only extremely inefficient, but also unstable and prone to vibration and noise. For vacuum pumps with a high degree of vacuum, cavitation often occurs when operating in this area. The obvious sign of this phenomenon is noise and vibration in the pump. Cavitation will cause damage to the pump body, impeller and other parts, making the pump unable to work. Based on the above principles, when the vacuum degree or gas pressure required by the pump is not high, single-stage pumps can be selected first. If the vacuum degree or exhaust pressure is high, a single-stage pump often cannot meet the requirements, or if the pump is required to still have a large air volume at a higher vacuum degree, that is, the performance curve is required to be flatter at a higher vacuum degree, a two-stage pump can be used. If the vacuum degree is required to be above -710mmHg, a water ring-atmospheric pump or a water ring-Roots vacuum unit can be used as the vacuuming device. If it is only used as a vacuum pump, it is better to choose a single-acting pump. Because the single-acting pump has a simple structure, is easy to manufacture and maintain, and has good cavitation resistance under high vacuum conditions. If it is only used as a compressor with a larger air volume, a double-acting pump is more appropriate. Because the double-acting pump has a large air volume, small volume, and light weight, the radial force can be automatically balanced, the shaft is not prone to fatigue fracture, and the pump has a long service life. 2. Select a vacuum pump based on the air volume required by the system. After initially selecting the type of pump, the vacuum pump model must be selected based on the air volume required by the system.

A condenser is added in front of the vacuum pump, so that the actual pumping of the vacuum pump is only leakage air and saturated methanol vapor at 10kpa. This way you need to pay more attention to the design of the condenser rather than the vacuum pump. The selection of vacuum pumps will also be much smaller.

Repost: Reprinted from the Fine Chemicals Edition. We use vertical oil-free piston vacuum pumps for vacuuming solvents such as methanol. We have been using several of them for 12 years. Reference URL http://www.jlve.com/wlw-b.htm You can consider using dry vacuum pumps, such as claw vacuum pumps and screw vacuum pumps. Dry vacuum pumps do not use water when vacuuming and will not produce water pollution. The organic solvents in the extracted gas can be recovered after low-temperature condensation or adsorption.

The volume of 375kg methanol at 10kpa and 15C° is 2800m3. Then it will be 1866m3/h after 1.5 hours of pumping. The leakage air of 6.7Kg/h is 55m3 at 10Kpa and 15C°. Then the total pumping speed should be 1910m3/h. This is only the theoretical pumping speed, the efficiency of the pump must also be considered.

Don't want to say too much: 1. The design of adding a condenser in front of the pump is not advisable. If you think it is okay, it means that you have not considered the steam partial pressure. 2. The best vacuum equipment selection for methanol recovery is to use a liquid ring vacuum pump. However, the selection of the liquid ring pump cannot be based on the sample data provided by the manufacturer. When a water ring pump is used to pump methanol, since it is soluble in water, the volumetric efficiency of the water ring pump will be further reduced. 3. For the gas volume calculation method, please refer to the vacuum design manual.