Hopper discharge

Wood chips are reclaimed from the storage pile by chip dozers and deposited in reclaim hoppers adjacent to the wood pile. Steel grates above the hoppers prevent frozen chips or oversized objects from jamming conveyors or otherwise fouling handling equipment. Draft conveyors installed beneath the hoppers discharge chips to inclined belt conveyors which elevate the wood fuel to storage bunkers situated above the power plant boilers. Chips are continuously fed to the boiler feeders to provide adequate fuel supply. 

When a hopper discharges, there is a pronounced velocity gradient across any horizontal section. If the outflow from the hopper is recycled then there will be considerable axial mixing. If a suitable distributor can provide radial mixing at some point in the cycle then, in principle, mixing can be carried out within a storage area. The recycle can be effected by either pneumatic or mechanical means. 

Bates, L. (1969) Entraimnent pattern of screw hopper discharges. Trans. ASME, J. Engng for Industry, 91 (2), 295-302. 

Screw conveyor feeder from bottom of hopper capacity is very sensitive to screw flight clearances for moderately incompressible solids (whose FDI and BDI differ by < 5 %). Hopper discharge active flowrate of solids limited to about one screw diameter (if hopper discharge is > 1 screw diameter there is a potential for cohesive solids to bridge and free-flowing solids to cause overload of drive). 

Rotary dryer, (continuous, indirect convection) atmospheric, steam tube, c/s including shell and flights, motor, drive, intake hopper, discharge. FOB 155000 at heat transfer area = 100 m with n = 0.75 for the range 40-700. L-rM = 2.2-3. L/M = 0.4. Alloy cost factors c/s X 1.00 s/s shell and flights X 1.25. 

On the other hand, the system illustrated in Fig.42 is much simpler, involving merely a weighing unit and a controlled feeder completely separate from it. Any of the familiar types of bin or hopper discharge devices can be used in conjunction with this equipment. 

Poor dewatering Hopper discharge - Wall deposits - Conveyor buildup... 

Flowability based on hopper discharge The prediction of the rate of discharge of granular materials from conical mass hoppers should take into account the friction of the materials and the effect of container wall friction. 

Two related gravity-driven flows are chute flow [3,33,146-155] and vertical tube flow [156-159]. Chute flow generally differs from hopper discharge in that the chute is opened so that the flow experiences a free surface. Vertical tube flow is similar to hopper flow, but there is no narrowing of the flow chamber at the outlet. A similar flow-rate scaling holds for vertical tubes [156] but the velocity profile tends to be plug like [157] for slow flows. For faster flows, density waves have been observed [159]. 

Commercial sensors are used to measure pressure, strain, acceleration, and sound propagation. These sensors are usually mounted on walls of granular experiments, for example, on hoppers [142] and shear cells [183]. However, there are sensors developed in the late 1950s, which can be placed into a granular material and report measurements wirelessly. The "rf-pill" was developed for medical applications [353-357] to measure the pressure in the digestive tract. The rf-pill is a small transmitter and sensor, which has been used to measure stress in vertical tube flow [158] and pressure in hopper discharge [128,133]. 

---