Solids Storage Bin

Frederick F. House2 has suggested the following guidelines for designing solid storage bins ... 

A powder s strength increases significantly with increasing previous compaction. The relationship between the unconfined yield stress/, or a powder s strength, and compaction pressure is described by the powder s flow function FE The flow function is the paramount characterization of powder strength and flow properties, and it is calculated from the yield loci determined from shear cell measurements. [Jenike, Storage and Flow of Solids, Univ. of Utah, Eng. Exp. Station Bulletin, no. 123, November (1964). See also Sec. 21 on storage bins, silos, and hoppers.]... 

Estimate the power required for a conveyor belt system transporting 2.5 tons per hour of radioactive contaminated solids from a location in a utility to a storage bin. The process unit end of the conveyor is at ground level while the top of the storage bin is 25 ft high. The total length of the belt system is 75 ft. Typical power requirements for flat conveyors of this capacity may be assumed to be 2.13 hp per 100 ft. Assume a safety factor of 10%. 

Sometimes neutralized liquid streams are recycled to the system without further unit operations however, insoluble solids such as silica, etc., are to be separated via filtration and removed as solids. Occasionally these waste solids are also to be discarded and discharged in storage bins if they are not suitable for land filling purpose. In any case, minimization of waste materials has to be carried out for GMP and total quality management (TQM) practices. 

A feeder usually consists of a vertical part called the bin and a converging part called the hopper. In the storage bin, the bulk solids normal stress increases linearly with depth due to the weight of individual particles while they transmit static shear forces. Stress at the wall quickly reaches a... 

After assembly of the press, slurry is admitted from a pump or pressurized tank under a pressure of 3 to 10 atm. Filtration is continued until liquor no longer flows out the discharge or the filtration pressure suddenly rises. These occur when the frames are full of solid and no more slurry can enter. The press is then said to be Jammed. Wash liquid may then be admitted to remove soluble impurities from the solids, after which the cake may be blown with steam or air to displace as much residual liquid as possible. The press is then opened, and the cake of solids removed from the filter medium and dropped to a conveyor or storage bin. In many filter presses these operations are carried out automatically, as in the press illustrated in Fig. 30.5. 

It is important to ensure that the maximum feed rate from the storage bin is always greater than the maximum expected operating rate of the feeder. Otherwise, the feeder will become starved and flow-rate control will be lost. This problem is particularly pronounced when handling fine powders because their maximum flow rate through an opening is significantly less than that of coarser-particle bulk solids whenever a mass-flow pattern is used [1]. 

For the flowability, use the Johanson indices to characterize dry particles (see also related topics conveying solids. Section 2.6, storage bins. Section 10.3, mixing. Section 7.4) These indices are ... 

A pneumatic system is used to transport powdered solids from a storage bin to a shipping container, as on the following page. 

To avoid confusion in this chapter, I will use the term bin as a general descriptor of a bulk solids storage vessel of any size. 

G. E. Blight, Temperature changes affect pressures in steel bins, International Journal Bulk Solids Storage in Silos 1 No. 3 1985, pp. 1 to 7. 

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