174
FREEZE—DRYING
"
”
__
chamber needs a little more care at high operating pressures but the results are reliable
reproductible as shown in an example given in Figure 17.
,
“
f
r
.
_
UNLOADING
.
,
,
‘
In most cases the unloading of a freeze—dryier Will be done after the vacuum chamber or the
exit looks have been lled with at least dry air or With an inert gas as
example nitrogen.
‘
For the drying systems mentioned under 1 and 2 (tray—systems) mechanized and automatèd
.
unloading systems for these trays have been developed and are in use as described in 6. As
’
requestedby many products 14the water and oxygen content of the atmosphere surround—'
ing the product should be keptlow or well dened. In such cases the whole unloading and
handling could be done in an controlled or inert atmosphere by remote operation as shown
in Figure 18. For such requirements a continuous system (Figure 11) in which only a small
proportion of the whole system is brought to atmospheric pressure has substantiel economical advantages, including the fact that the inert gas could be re—used after it has been
stored (While the lock—systeris under vacuum). This principle can of course also be applied
for systems mentioned under paragraph 4 (transported particles). The oxygen content of
the inert gas in a
be measured continuously by conventional equipment
Figures 19 a and 13 Show h0w a gas sample is taken from a pilot plant and later on from a
can lled in the pilot plant. The measurement is done by a gas chromatograph (Figure 20).
The additional problems during unloading in such systems as mentioned under para—
graph 3 (product frozen in heating elements) have already
mentioned. The removal
of the product from those heating elements in a production size freeze-drying unit needs
either a certain amount of mechanical devices or the help of gasblows
6 to remove the dried
product from the heating surfaces. After the removal it is possible to grind such products to
a ne powder (as can be done With products dried by any other method) but the necessity
to have this grinding stage only after the product has been
limits the grain size and
grain size distributio‘whichcan be
especially since it Will be diicult to control
the amount of
dust—particles produced while the product is scraped or
blown o‘.
"
:
_
“
‘
'
"SUMMARY"
“
”
'
‘
,
,
Since the commercial
given
'
K. Bird 15 on a very broad basis it Will not be tried to publish—additional cost'guresheré. But
_
it can be noted‘that cost‘gùres published many
the
investment? costs :Ïdue ro. , higher labour a&gamæem
,fare_g,,g't‘akens:winto
account;
‘ -
«=
-v
î
».
has tried to show the: teChnical
'
as they“
be“: seenwtoday;
,
liquids andïä,pulps nd *a”grow1ngmterestbes1desp1ecesofvegetahles,
,
fruits Automatic
,
_
.
desigmœæymg of: the product ÿgfro‘z@m ontheheatmgelementsandthedrymgoffrozen
FREEZE—DRYING
"
”
__
chamber needs a little more care at high operating pressures but the results are reliable
reproductible as shown in an example given in Figure 17.
,
“
f
r
.
_
UNLOADING
.
,
,
‘
In most cases the unloading of a freeze—dryier Will be done after the vacuum chamber or the
exit looks have been lled with at least dry air or With an inert gas as
example nitrogen.
‘
For the drying systems mentioned under 1 and 2 (tray—systems) mechanized and automatèd
.
unloading systems for these trays have been developed and are in use as described in 6. As
’
requestedby many products 14the water and oxygen content of the atmosphere surround—'
ing the product should be keptlow or well dened. In such cases the whole unloading and
handling could be done in an controlled or inert atmosphere by remote operation as shown
in Figure 18. For such requirements a continuous system (Figure 11) in which only a small
proportion of the whole system is brought to atmospheric pressure has substantiel economical advantages, including the fact that the inert gas could be re—used after it has been
stored (While the lock—systeris under vacuum). This principle can of course also be applied
for systems mentioned under paragraph 4 (transported particles). The oxygen content of
the inert gas in a
be measured continuously by conventional equipment
Figures 19 a and 13 Show h0w a gas sample is taken from a pilot plant and later on from a
can lled in the pilot plant. The measurement is done by a gas chromatograph (Figure 20).
The additional problems during unloading in such systems as mentioned under para—
graph 3 (product frozen in heating elements) have already
mentioned. The removal
of the product from those heating elements in a production size freeze-drying unit needs
either a certain amount of mechanical devices or the help of gasblows
6 to remove the dried
product from the heating surfaces. After the removal it is possible to grind such products to
a ne powder (as can be done With products dried by any other method) but the necessity
to have this grinding stage only after the product has been
limits the grain size and
grain size distributio‘whichcan be
especially since it Will be diicult to control
the amount of
dust—particles produced while the product is scraped or
blown o‘.
"
:
_
“
‘
'
"SUMMARY"
“
”
'
‘
,
,
Since the commercial
given
'
K. Bird 15 on a very broad basis it Will not be tried to publish—additional cost'guresheré. But
_
it can be noted‘that cost‘gùres published many
the
investment? costs :Ïdue ro. , higher labour a&gamæem
,fare_g,,g't‘akens:winto
account;
‘ -
«=
-v
î
».
has tried to show the: teChnical
'
as they“
be“: seenwtoday;
,
liquids andïä,pulps nd *a”grow1ngmterestbes1desp1ecesofvegetahles,
,
fruits Automatic
,
_
.
desigmœæymg of: the product ÿgfro‘z@m ontheheatmgelementsandthedrymgoffrozen