Handling solids

Maintenance costs depend on whether processing fluids are solids on the one hand or gas and liquid on the other. Solids handling tends to increase maintenance costs. Highly corrosive process fluids increase maintenance costs. Average maintenance costs tend to be around 6 percent of the flxed capital investment. ... 

L. Hus, C. Chang, J. Beddow, and A. Vetter, Proc. Tech. Prog. Int. Powder andBulk Solids Handling and Processing, Atlanta, Georgia, May 24—26, 1983, Books Demand UMI, Ann Arbor, Mich., 1983, pp. 52—66. 

C. R. Woodcock and J. S. Mason, Bulk Solids Handling, Chapman and Hah, London, 1987. 

For certain types of stochastic or random-variable problems, the sequence of events may be of particular importance. Statistical information about expected values or moments obtained from plant experimental data alone may not be sufficient to describe the process completely. In these cases, computet simulations with known statistical iaputs may be the only satisfactory way of providing the necessary information. These problems ate more likely to arise with discrete manufactuting systems or solids-handling systems rather than the continuous fluid-flow systems usually encountered ia chemical engineering studies. However, there ate numerous situations for such stochastic events or data ia process iadustries (7—10). 

Eocus Conveying Belt Technology," Bulk Solids Handling (Nov. 1991). 

Year Book and Directoy Powder Bulk Solids Handling and Processing, Trans Tech PubHcations, Clausthal-ZeUerfeld, Germany. 

Bulk Blenders Vlanv of the mixers used for solids blending (Sec, 19) are also suitable for some liquid-solids blending. Ribbon blenders can be used for such tasks as wetting out or coating a powder, When the final paste product is not too fluid, other solids-handling equipment finds frequent use. 

Permeability Bulk sohd permeability is important in the iron and steel industiy where gas-solid reactions occur in the sinter plant and blast furnace. It also strongly influences compac tion processes where entrapped gas can impede compaction, and solids-handling equipment where restricted gas flow can impede product flowabihty. The permeabihty of a granular bed is inferred from measured pressure drop under controlled gas-flow conditions. 

Personnel Hazards The following case history illustrates how vacuum can be harmful and dangerous to personnel. A plant superintendent was checkiug an open nozzle on a glass-lined reactor on which there was a vacuum pump pulling vacuum, when suddenly his arm was sucked into the nozzle, up to his shoulder. He could not remove his arm until help arrived to release the vacuum on the vessel. He was injured painfully, though not seriously. The injury could have been veiy serious if help had not been nearby. Personnel hazards can also result from vacuum conveyor systems for solids handling. 

Due to the nature of batch operations, transferring and charging of process materials is a common activity. This can entail gas, liquids, and/or solids handling via open equipment. This may include pumping of liquids from drums or dumping of solids from other containers into an open vessel, shoveling material into a dryer, or making temporary connections such as at hose stations. 

Fluidized-bed adsorbers have several disadvantages. The continuous handling and transport of solids is expensive from an equipment standpoint fluidized-bed systems must be large to be economical. Solids handling also presents a potential for mechanical problems. Careful control is required to keep the adsorbent fluidized, while minimizing adsorbent loss with the gas-phase attrition of the adsorbent can be high, requiring substantial makeup. 

Ash solubilization and volatile suspended-solids oxidation also decrease the solids loads to downstream solids-handling units. 

Solids handling frequently has the potential for dusting, which can lead to potential health and explosion hazards. Handling solids in the form of larger particle size granules or pellets rather than a fine powder reduces the potential for worker exposure. Worker exposure hazards are reduced by formulating dyes as liquids or wet pastes rather than dry solids or powders (Burch, 1986). 

It may even be possible to eliminate solids handling by processing in a solution. However, this may require an assessment of the hazards of a toxic or flammable solvent in a process compared to the hazards of the solvent-free process. 

Use gravity flow in plant layout where feasible to minimize the need for pumps or solids handling equipment for hazardous materials. Conduct a hazard review to assess the effect of layout on potential spills. 

Neville, I.M. and Seider, W.D., 1980. Coal pre-treatment - extensions of ELOWTRAN to model solids-handling equipment. Computers and Chemical Engineering, 4, 49. 

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