Powder Feeding

Powder Feeding Bulk density control of feed materials and reproducible powder feeding are crucial to the smooth operation of... 

FIG. 20-87 Fliiid-hed granulator for hatch processing of powder feeds. [Ghehre-Selassie (ed.). Pharmaceutical Pelletization Technology, Marcel Dekker (1989)]... 

In processes where new powder feed has a much smaller particle size than the smallest granular product, the feed powder can be considered as a continuous phase which can nucleate to form new granules [Sastry Fuerstenau, Powder Tech., 7, 97 (1975)]. The size of the nuclei is then related to nucleation mechanism. In the case of nucleation by spray, the size of the nuclei is of the order of the droplet size and proportional to cos0, where 0 is binder fluid-particle contact angle (see Fig. 20-67 of Wetting section). 

Fluidity is important for powder feed from the reservoir to the dipping bed and also to permit efficient closing in of the hole left by the dosator. 

It is generally agreed that one of the more important parameters of interest to formulators is the flowability of their powdered solids [57,58], The process-ability of these materials is greatly affected by flowability concerns, since the materials invariably need to be moved from place to place. For example when tablets are to be compressed at high speeds, the efficiency of the machine will only be suitable if the powder feed can be delivered at a sufficiently high rate. 

Different spectral preprocessing and transformations available in SIMCA P-p (version 10.0, Umetrics, Sweden) were evaluated and the best approach for data handling and manipulation was determined. Data collected on the surrogate tablets were divided into a training set to generate the PLS models, and prediction set to test the PLS models. MCC powder, equilibrated at different RH, was also roller compacted at different roll speeds on a Fitzpatrick IR220 roller compactor fitted with smooth rolls. Powder feed rate and roll pressure were kept constant for all experiments. The key sample attributes measured on the surrogate tablets were also measured for the samples prepared by roller compaction. 

The 10% w/w APAP powder blend was roller compacted. Different moisture contents were achieved by equilibrating and roller compacting the above powder blend under 24, 45, and 65% RH conditions, representing 3.3, 5.0, and 6.3% w/w moisture content, respectively. Compacts were prepared at 5.0, 6.0, and 7.2 rpm roll speeds with the powder feed rate and roll pressure kept constant. Compaction run time was four minutes at each roll speed. Samples were also collected for off-line measurements of... 

Fig. 44. Steady-state NO and NH3 concentrations vs. temperature in runs over a small monolith catalyst with 300 cpsi and over the same catalyst crushed to powder. Feed 1,000 ppm NH3, 1,000 ppm NO, 1% HzO, 2% Oz in N2 SV = 45,000 cm3/g/h (STP).

The specifications of the granulator are as follows output (as referred to souece Mounted on the cover of the enclosure are a source powder feed connection, a ventilating connection, several injectors for feeding agglomerating liquid and an Inspection hole cover. Provision is also made for a mechanism adapted to change the angle of inclination of the plate within 45-60°. 

What kind of powder feeding capabilities does the equipment have... 

Typical plasma parameters of the reduction tests with hydrogen can be seen in Table 2. Feed rate of the starting powder was changed by the flow rate of the carrier gas. The specific energy was calculated as the ratio of plate power related to the powder feed rate. Hence, this parameter considers two process variables simultaneously. In each run three samples were collected from different regions of the plasma system (i) from the reactor wall, (ii) from the bottom of the reactor, and (iii) from the cyclone. Particles deposited to different places of the plasma reactor and the cyclone were subjected to different thermal effects, so they probably have different physical and chemical characteristics, as well. 

Air classifiers may also be distinguished by method of powder feed. Particles may be fed either within air stream, or separately by freely pouring them within the device. Other systematizing may be done with respect to the air stream form, classifier design features and operation mode (continuous or batch). 

For hydroxypropyl methylcellulose acetate succinate, a novel enteric dry coating method has been developed [31]. The unique feature of this method is that the enteric polymer is added in powder form (e.g., mixed with talcum directly to tablets or pellets) whereas a plasticizer diluted with paraffin is sprayed separately. The tablet core temperature is around 40°C, and the film is cured for a short time. To achieve a homogenous film, the rates of powder feeding and plasticizer spray have to be adjusted such that the two processes start and end simultaneously. 

Indeed, over the last decade, the area of melting of active compacted particulate assemblies in twin-rotor equipment has received a good deal of experimental attention. This body of experimental work utilizes both glass windows on sections of the barrel for on-line observations f39—43) and, more often, extracted solidified carcasses of the processed stream, which are sectioned along the downstream direction in the melting region (3,44-50). This body of work has confirmed the existence, and elucidated the natures of PED, FED, and DMM and, most importantly, has confirmed the evolution of melting in twin-rotor devices mentioned earlier. Such evolution, based on extensive carcass analyses for both polypropylene (PP) pellets and powder feeds in Co-TSEs, is shown in Fig. 5.14 (3,51). 

However, experimental studies (50), using either powder feed or pelletized feed with some recycled melt over the channel block into the feed port, have not exhibited drag removal melting but a dissipative mix-melting mechanism, discussed in Chapter 5. As... 

---