Roll compactor

Hydraulic piston-type compactors for collection vehicles, on-site compactors, and transfer-station compactors roll crushers used to fracture brittle materials and to crush tin and aluminum cans and other ductile materials... 

Figure 3 Plot of d90 and d50 values for the 10% tolmetin granules versus the slope of best-fit line showing good agreement between the values from the compacts prepared under two different sets of roller compactor roll/HFS/VFS speed settings.

Dehont et al. provided a simplified approach to roller compaction theory. They described that powder granules move through stages in the feed area. The material is drawn into the gap by rubbing against the roll surfaces. The densification that occurs in this area is particle rearrangement. At this stage, the speed of the powder is slower than the peripheral speed of the rollers. Fig. 1 represents compactor rolls in the horizontal plane powder is pushed vertically downward into the compaction area. 

Fig. 1 Front view of compactor rolls in horizontal plane. (From courtesy of Ellis Horwood.)...

Typical compactor roll configurations are shown in Fig. 8. Most compactors now have one floating roll and one fixed roll each on separate bearing blocks. An illustration of this is shown in Fig. 9. 

Fig. 9 Compactor roll blocks. (From Ref. courtesy of the Handbook of Pharmaceutical Granulation Technology.)...

The simplest approach during scale-up would be to maintain the applied roller compaction force as the roller compactor roll diameter and width increases on scale-up. This technique assumes that the applied force is linear at the point where the powder sees the maximum force. Dehont s team defined this as the neutral angle, gamma. This approach although simple to understand and theoretically correct has been shown to be successful only in a limited number of cases in the author s experience and is very much dependent on the formulation s composition. 

Figure 3 Front view of compactor rolls, depicting nip angle. (From Ref. 18.)...

A novel stainless steel encasing that leads to the compactor rolls encloses the variable-speed auger screws. Just before the nip area, a pair of sintered stainless steel segments are assembled within the horizontal auger feed system, which can operate under partial vacuum. A small, self-contained vacuum pump draws negative pressure through a dry filter and a stainless steel line connected to the sintered assembly plates. The partial vacuum is adjustable from —0.1 to 0.8 bars. The compaction rolls... 

FIG. 25-60 Small compactor used in conjunction with a dctachal)lc roll-off contiiincr. Note the w hcclcd contiiincr used to collect wastes within the warehouse. 

The roller compactor s full axial rolls produced compacts in the form of sticks. The unmilled compacts from both machines had the same density, 1.3g/cm. The milled roller compacts produced comparative granules except for bulk density and correspondingly the Carr index values ... 

Note Compactor parameters roll pressure = 62-65 bar, roll speed = 8rpm, horizontal screw feed = 52 rpm, de-aeration = —0.2 bar, sized by double rotary granulators 4 mm and 1.2 mm screens. 

The TF-Mini and TF-156 compactors (Vector Corporation, Marion, Iowa, U.S.A.) were equipped with concavo-convex rolls and single flight screws. The roll speed of the TF-156 was scaled to achieve the same linear velocity 74.2 in./min as the TF-Mini model. This setting maintained a comparable dwell time for material in the compaction zone. The TF-156 roll force was scaled to 5.6 ton, which equaled a force per linear-inch approximately equal to the TF-Mini 3.1 ton/in. roll width. The authors established a feed screw speed to roll speed ratio of 1.3 1 for the trials. Table 7 gives the compactor equipment settings. 

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. 

The corresponding AW 200 force/cm roll length of 4.10-7.40 kN translated to 50-85 bar. Therefore, the optimized roller compactor... 

Figure 4 Comparison of the offline slope values (filled circles) with the real-time slope values (open triangles) for the 10% tolmetin compacts prepared at different roller compactor settings. Values on top are the roll, HFS, and VFS speeds, respectively.

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. 

Johanson identified, through very comprehensive mathematical models and relationships, material properties, press dimensions, and operating conditions for roll compactors. For more information, the interested person should read the entire reference. In part, he described that roller compaction involves a continuous shear deformation of the granules into a solid mass. 

Johanson pointed out that no roller compactor theories at that time determined the angle of the nip and the bulk density at 0 = a, except by actually rolling the granular solid in a roll press. He also provided a method to calculate the nip angle and the pressure distribution between the rolls. His calculations... 

Pietsch described a compaction capacity throughput equation for a roller compactor using flat rolls. The equipment capacity equation is theoretical in nature it assumes that all compacts are 100% useable for downstream processing needs. Compact capacity throughput, Cc, for a roller compactor can be determined by Eq. (4). ... 

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