Material recirculating

Low material potency at least 10/h High material potency between 10 and 20/h Recirculation of air is only allowed when working with low potency materials when working with high potency materials, recirculation is not recommended. In case of built-in HEPAs, recirculation is possible while working with low potency materials Local extraction at dust generating points by a separate system leading into a cyclone is recommended To be monitored To be monitored... 

Material Recirculation. Material is recirculated from the center of the turret into the feed frame. Some press designs include recessed recirculation channels to minimize particle attrition and prevent excess material loss to the vacuum system. It is critical not to recirculate too much material because this can result in low product yields and can have a detrimental effect on the powder s physical properties, which could result in poor compressibility, uniformity, and final properties (e.g., reduced dissolution rate). 

A minimum amount of material recirculation is necessary to provide steady flow and fill. Too much recirculation can result in material back-up and reduction in the granulation particle size. The recirculation channel must be free of obstructions (i.e., broken tablets). 

The fill cam size should be reduced to minimize overfilling and material recirculation. 

Material in the material recirculation channel should be maintained at a minimal level. As more material is recirculated, the likelihood for loss is greater. The piece guiding the material from the recirculation channel to the feeder must be properly positioned. 

Excessive feeder speeds cause excess material recirculation and increase material loss. 

The most economical pressure agglomeration method, which is also applicable for a wide range of capacities, uses roller presses (see Section 4.2.2.4). Depending on the surface configuration of the rollers, either compacted sheets are produced which are subsequently crushed and screened into a granular product or, if the rollers are pocketed, briquettes are formed. For waste treatment and the production of secondary raw materials (recirculation of valuable components) the latter is often preferred. Briquettes are usually pillow shaped and almost monosized, featuring a volume that may typically range between 20 and 100 cm3. 

If a plant is equipped with multiple lines and features separate day bins for fresh material, recirculating fines, and granulated product, each line can process different formulations. 

As the coal-feed jet decreases from its nozzle velocity, it entrains surrounding fluid to conserve its axial momentum and thereby sets up recirculation currents. The mass rate of material recirculated, mr, per mass rate of material fed, ra0, can be estimated from the following equation proposed by Thring (15) ... 

Recirculated systems require that a pool of liquid be held within the equipment. Feed mixes with the pooled liquid and the mixture circulates across the heating element. Only part of the liquid is vaporized in each pass across the heating element unevaporated liquid is returned to the pool. All the liquor in the pool is therefore at the maximum concentration. Recirculated systems are therefore not well suited for evaporating heat sensitive materials. Recirculated evaporators, howevar, can operate over a wide range of concentration and are well adapted to single-effect evaporation. 

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