Vacuum deaerator

VACUUM DEAERATION OF CLAY, PORCELAIN, a OTHER PRODUCTS... 

Pilot compaction trials were conducted to investigate the vacuum deaeration effect when compacting an antibiotic powder with 0.2g/cm density. The... 

Study determined the compact throughput, compact density, and fines (not compacted during vacuum deaeration) when using a new equipment feed system design. The parameters controlled and monitored during the compaction process were vacuum deaeration pressure, roll pressure, roll and screw speeds, room temperature, and humidity. 

The equipment feed design consisted of a funnel-shaped powder hopper (with no vacuum deaeration system) that was located directly above the rolls. The powder hopper was retrofitted with vacuum deaeration capability. A high compression feed screw, fitted inside the funnel hopper, fed the powder directly into knurled rolls. The compaction trials were conducted with and without vacuum deaeration. The compact was carefully collected directly on a 10-mesh screen. Powder particles, that were not compacted (i.e., those particles which were not attached to the compact, for example, fines bypassing roll compaction and the non-adhering compacted powder particles) were weighed and separated. The compact was not milled. The parameters are noted in Table 4. 

The conclusions drawn from this trial indicated vacuum deaeration, employed in the described equipment design, increased the compaction rate, reduced the fines (non-compacted powder), and increased the compact density (R.W. Miller, unpublished notes, June 1996). 

Trial no. Vacuum deaeration (15 in. Hg) Roll pressure (kN) Roll speed (rpm) Screw speed (rpm) Compact density (g/cm ) Compact rate (g/min) Fines not compacted (%)... 

Roll speed and vacuum deaeration were kept constant at 8 rpm and 0.2 atmospheres, respectively. Roller compactor was equipped with 5 mm primary screen. Final sizing was conducted using an oscillator equipped with 20 mesh screen. 

An additional general method to reduce bypass is through vacuum deaeration. Miller9 performed experiments on a low-density active blend with and without vacuum deaeration, while holding all other parameters constant, and quantified the bypass for each trial. With the vacuum deaeration engaged, the bypass rate was 2% as compared to the control rate of over 20%. He also observed that the powder feed was uneven and the compact quality was not uniform. Most units are equipped with this capability and it should be considered to minimize bypass for low-dose products. However, vacuum deaeration can cause potency loss, unless the collected material is recirculated to the feed system. 

The overall recommendation for the roller compaction system design that minimizes bypass is to employ a higher surface roughness or textured surface on the rolls, rolls oriented similar to vi or vii, and to conduct an assessment of vacuum deaeration. 

All mixers are usually enclosed and fitted with a vacuum deaeration facility, particularly necessary for transparent top coat and foam formulations. 

Vacuum deaeration of clay, porcelain, a ofher products... 

Mechanical and Chemical Deaeration. The corrosive quahties of water can he reduced by deaeration. Vacuum deaeration has been used successftdly in once-through cooling systems. When all oxygen is not removed, catalyzed sodium sulfite can be used to remove the remaining oxygen. The sulfite reaction with dissolved oxygen is... 

Certainly, a key enhancement that highlights today s pharmaceutical industry s state-of-the-art roller compactors, is programmable logic controllers (PLCs). They are used to control and monitor mechanical parts that regulate screw feed rate, roll speed, roll pressure, roll gap, vacuum deaeration, and mill speed. This section will not discuss PLC designs as it relates to compactor design features and advancements. 

Fig. 6 Twin horizontal feed screw system with vacuum deaeration. (Courtesy of Alexanderwerk Inc.)...

Compact color pattern twin feed screw with without vacuum deaeration... 

Guigon and Simon, in 2001, showed a similar phenomenon using a horizontal single feed screw without vacuum deaeration when compacting sodium chloride. ... 

Fig. 16 Side view of feed screw system and vacuum deaeration with sintered plate segments. (From Ref courtesy of the Handbook of Pharmaceutical Granulation Technology f...

In several experiments, Miller studied the effects of using horizontal twin auger feed screws under partial vacuum (Alexanderwerk Inc., Horsham, Pennsylvania, model 50/75 compactor). The feed powder was vacuum deaerated just before roller compaction. The experimental design showed that the compactor s deaeration feed system significantly increased compaction output and minimized powder leakage when compacting very low density blends (<0.35 gcm ). ... 

Both experiments clearly demonstrated the importance of vacuum deaerating the bulk powder just prior to compaction. In addition, the second formulation provided increased compaction throughput (with or without the vacuum deaeration) compared to the first... 

Table 3 Compactor operating conditions and throughput yields for poor flowing low density active drug blend, formulation 1, vacuum deaeration and non-vacuum deaeration trials...

In several other trials, Miller also studied the effects of using two different compactors vacuum deaeration systems. The tests, similar to the ones previously described in this section, were carried out using differently designed compactors (employing and not employing vacuum deaeration). The objective of these trials was to increase the active bulk density of the feedstock from 0.22gcm to 0.61 gcm. ... 

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