Is there a particular order regarding the position of the soda separator and the fan?
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As the title suggests, in process design, is it better to place the gas-liquid separator before or after the fan? What is the basis for this?
The vapor separator is better placed before the fan
If it is placed in front of the fan, the fan’s load will be lower, allowing for a smaller fan to be used； If it is placed after the fan, the load on the fan becomes relatively higher, so a larger fan needs to be used ； A vapor separator is generally used in conjunction with a condenser.
The vapor separator is generally placed before the fan to remove water vapor from the gas, thereby reducing liquid impact on the fan blades
The responses from the brothers above basically all suggest placing a gas-liquid separator before the fan, but in my view it is installed after the fan at the site (as per the design of Jilin Ninth Hospital)
This post was last edited by zpg on 2010-12-14 at 14:32. The gas separator should be placed after the fan; if the incoming gas contains mechanical water, then one is also needed at the fan inlet. Since it is a fan, the medium being transported is mostly air. Whenever air is involved, it is necessary to consider the issue of saturated water forming as a result of pressurization and cooling of the air; this is especially true during summer when the air humidity is high, as water will definitely form in such conditions. Take a very simple example: at 1 standard atmosphere, with a summer temperature of 30°C and a relative humidity of 90%, the water content in the air is 31.5 g of water per Nm3 of dry air. When the pressure is increased to 20 kPa using a fan and the air is cooled back to 30°C, with cooling water taken from the bottom layer of a reservoir at 16°C, the pressure of the air becomes 121.325 kPa (absolute), and its saturated moisture content is 29.15 g of water per Nm3 of dry air. In this case, water will definitely condense. If the fan’s flow rate is 10,000 Nm3/h, then the amount of condensed water will be (31.5 – 29.15) × 10,000/1000 = 23.5 kg/h. The higher the pressure increase by the fan, the lower the temperature to which the compressed air is cooled; consequently, the more water will condense. In this example, if circulating water at 32°C–37°C is used and the air temperature after cooling is 40°C, then the saturated moisture content of the air is 52.1 g of water per Nm3 of dry air. Clearly, in this case the air is not saturated, so no condensation occurs. However, if the compressed air is cooled to 30°C, condensation will definitely take place. If subsequent processes do not allow air to contain water, then a separator must be installed after the fan, within the condenser. The design of Jihua Institute is standard and there are no issues. The conditions described above are quite common in factories; an atmospheric humidity of 90% is also common in summer. In other words, it involves the variation between the saturation dew point at normal pressure and the dew point under certain pressures. It becomes easier to understand if you replace the fan with an air compressor.
Reply 6# zpg: That makes sense, I’ll learn it*. Thank you!