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Your Location: Home >> News >> Technical support >> How to choose the degree of vacuum in the drying process of the freeze dryer?

How to choose the degree of vacuum in the drying process of the freeze dryer?

Release Date: 2019/10/29 17:09:05 .
Browse: 139

How to choose the degree of vacuum in the drying process of the freeze dryer? It is a scientific method to determine the appropriate pressure for freeze drying by the vapor pressure of ice. A basic criterion for selecting system pressure: ice is in the range of 20% to 30% of the vapor pressure at the target product temperature. Sublimation occurs when the vacuum level set point is lower than the vapor pressure at which the ice is at the current product temperature.

Normally, the freeze-drying vacuum level is controlled between 50 and 300 mTorr (0.06 to 0.40 mbar), and 100 to 200 mTorr (0.13 to 0.26 mbar) is the most common range.

As can be seen from the table below, there is a direct relationship between temperature and pressure. The lower the temperature of ice, the lower the saturated vapor pressure. If the lyophilizer is not continuously controlled to very low vacuum levels, it will not be possible to have the system pressure set point at 20% to 30% of the ice vapor pressure at very low product temperatures (below -40oC). between. Therefore, freeze drying will proceed very slowly at very low product temperatures.

Temp Vapor Pressure
[Deg C] [milliTorr] [milliBar] [pascals]
0 4,584.000 6.1115 611.148
-2 3,883.000 5.1769 517.689
-4 3,281.000 4.3743 437.429
-6 2,765.000 3.6864 368.635
-8 2,325.000 3.0997 309.974
-10 1,949.000 2.5984 259.845
-12 1,630.000 2.1731 217.315
-14 1,359.000 1.8118 181.185
-16 1,130.000 1.5065 150.654
-18 936.800 1.2490 124.896
-20 774.400 1.0324 103.245
-22 638.200 0.8509 85.086
-24 524.300 0.6990 69.901
-26 429.400 0.5725 57.248
-28 350.500 0.4673 46.729
-30 285.100 0.3801 38.010
-32 231.200 0.3082 30.824
-34 186.800 0.2490 24.905
-36 150.300 0.2004 20.038
-38 120.600 0.1608 16.079
-40 96.300 0.1284 12.839
-42 76.700 0.1023 10.226
-44 60.800 0.0811 8.106
-46 48.000 0.0640 6.399
-48 37.700 0.0503 5.026
-50 29.500 0.0393 3.933
-52 23.000 0.0307 3.066
-54 17.900 0.0239 2.386
-56 13.800 0.0184 1.840
-58 10.600 0.0141 1.413
-60 8.100 0.0108 1.080
-62 6.160 0.0082 0.821
-64 4.660 0.0062 0.621
-66 3.510 0.0047 0.468
-68 2.630 0.0035 0.351
-70 1.960 0.0026 0.261
-72 1.450 0.0019 0.193
-74 1.060 0.0014 0.141
-76 0.780 0.0010 0.104
-78 0.570 0.0008 0.076
-80 0.410 0.0005 0.055
-82 0.290 0.0004 0.039
-84 0.210 0.0003 0.028
-86 0.150 0.0002 0.020
-88 0.100 0.0001 0.013
-90 0.072 0.0001 0.010
-92 0.049 0.0001 0.007
-94 0.034 0.0000 0.005
-96 0.023 0.0000 0.003
-98 0.015 0.0000 0.002
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