Vacuum drying – how to choose a vacuum pump
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In the vacuum drying process of pharmaceutical manufacturing, how should one choose a vacuum pump? Given the amount of solvent to be dried, G (kg), the drying time required, t (hours), and the evaporation temperature, T (°C), how can I determine the pumping capacity of the vacuum pump that I need to use? Please give me some advice!
It depends on the type of dryer you choose; select one that matches the size of the dryer. I usually opt for a water-ring vacuum pump with two stages
This post was last edited by citywolf on 2011-1-24 at 15:26. The vapor pressure of the solvent at the evaporation temperature T can be determined using the formula pv=nRT and n=G/M. By calculating v and then dividing it by the drying time, the theoretical average pumping speed can be obtained. The vacuum pump should be selected with a pumping speed that is 2 to 3 times this average value; moreover, the ultimate vacuum level of the vacuum pump should be set at 1/10 to 1/15 of the partial pressure at the evaporation temperature T.
First, determine the vacuum level at which you will operate; then calculate the amount of water drained per hour under that pressure. This is a requirement specific to your product’s manufacturing process, and only you know it. After that, use the vacuum level and the amount of water drained to determine the cubic volume, and then multiply it by an appropriate coefficient.