Hopper feeding systems

Changing the initial melt temperature in either direction may solve the problem. With a barrel and screw, it is important to study the effects of temperature changes. Another approach is to increase the pressure in processes that use process controls. Particle size, melt shape, and the melt delivery system may have to be changed or better controlled. A vacuum hopper feed system may be useful. With screw plasticators, changes in screw design may be helpful. Usually, a vented barrel will solve the problem. 

The simulated FBAC consists of an acrylic main reactor (0.5m-H x 0.5m-W x l.Om-L), an air distributor system, particles feeding system including a feed hopper, a discharging sampler, a bag filter for capture of the elutriated fine particles and, pressure and flow rate measurement systems (Fig. 1). The air distributor system has ten air headers. An individual air header is connected with 5 air nozzles and can regulate the airflow rate. The opening ratio of the distributor is 2.1% and each nozzle has four holes for uniform air supply. To measure the pressure fluctuation at an individual air header, high frequency pressure transmitters were mounted at the approach and the exit headers of the FBAC. 

Figure 12.2 Schematic diagram of a feed system incorporating a hopper and a conveyor belt... 

After an exhaustive investigation, it was determined that the cause of the nonuniform tablets was segregation in the tote/overhead feeding system used in the manufacturing operation. The laboratory- and intermediate-size batches were hand-scooped into the hopper of the tablet press. The overhead-feed duct acted as a classifier. The differences in cohesion and adhesion of the two actives, coupled with the length and angle of the ductwork, fostered segregation. 

Tires acquired from the "flow" are stored in a specially designated area near the existing tire pile. The tires are fed into a hopper located adjacent to the tire pile. An automated tire feed system singulates tires (spaces them individually) up to 800 tires per hour, to a conveyor belt traveling 420 feet up a hill to the power plant. Tire feed rate averages 350 to 400 tires per hour to each boiler.1... 

Figure 6.1 Schematic diagrams depicting different dry granulation designs (four typical feed systems with intermediate hoppers three typical roller compaction systems and two typical granulator systems).

In the case of low-dose formulations, it is important that the feed system convey material without allowing the material to segregate. All of the feed system arrangements shown in Fig. 6.1 rely on gravity feed for the powder to reach the force feeding screws. Feed systems i, ii, and iii can be outfitted with an agitator in the intermediate hopper which will aid in powder flow and delumping. 

The feed section takes the product from the feeding system and conveys it to the plastification section. At the same time, there must be sufficient free volume to allow gas reflux, e. g., air or nitrogen, to escape from the process section upstream. If the throughput rate of the extruder is less than the input product flow, the product will back up in the feed hopper, indicating that the intake limit has been reached. Along with the known extruder data, such as the screw speed, the screw pitch, and the available volume in the screw channel, other influencing factors, such as the fill rate of the screw channel, the conveying efficiency, the bulk density, and other bulk characteristics of the product sometimes affect the... 

As a dry granulation technique, roller compaction has to be considered as a simple continuous process able to convert powder into granules (Fig. 6). The system comprises powder hoppers, feeding screws, a roller press, a mill, and, optionally, a recycling unit. 

A history of hopper and feed screw designs showed that each design evolved to facilitate and improve powder flow to the compactor feed screw conveyance system. Feed hopper designs depicted in Fig. 4 show designs incorporated in older compactor models [examples (A)-(C)]. Dehont et al. described the powder compaction feeding systems that were in use up to 1989. ... 

The test rig is equipped with a feedstock hopper suitable to low-bulk-density biofuels and the biomass is fed continuously into the sand bed of the reactor via an injector screw which can feed fuel either into the bottom of the bed or to about 1 meter above the air distributor. The maximum fuel mass flow rate is 90 kg/h. The feeding system consists of two screw feeders in series separated by a rotary valve. The second screw has a higher feeding rate thus it will remain almost empty and therefore is not likely to be blocked by pyrolysis products. Steam can be added to the primary air as a gasification agent. 

The VUB pilot plant consists of a feeding system (a hopper equipped with a rotary valve and a conveyor screw), the fluidized bed reactor, preheating burner, cyclone and a control system. The bubbling fluidized bed gasifier has a capacity of 400 kg/h and consists of a bed (0.8 m diameter/0.6 m height) with an extended freeboard section (1.2 m diameter/2 m height). More technical details about the gasifier can be found in [16]. 

Fig I shows the dependency of specific investment cost of wood chip boilers (top) and pellet boiler (bottom) on the thermal power. Investment cost for fuel feeding system fiom the main storage to the hopper is not included, if used additional cost of 1.800 to 2.200 EUR per boiler have to be considered. 

---