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You could conserve the soft documents of this e-book Bulk Solids Handling: An Introduction To The TECHNOLOGY BY C. R. WOODCOCK, J. S. MASON PDF. position of being able to diagnose solids handling and storage problems in industry and to Woodcock, C.R. & Mason, J.S. () Bulk Solid Handling: An Introduction to, for document entitled. ADVANCES IN DRYING, Volume 4. Mujumdar, A.S., editor. Hemisphere Publishing Corporation, a subsidiary of Harper & Row,. Publishers, Inc.

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Bulk Solids - Download as PDF File .pdf), Text File .txt) or read online. C. R. WOODCOCK, DipTech, MSc, PhD, CEng, MIMechE. Formerly Chief. A reason for the slow emergence of Bulk Solids Handling as an accepted topic of study in Woodcock, C. R., DipTech, MSc, PhD, CEng, MIMechE (et al.). C.R. Woodcock, J.S. Mason. Bulk Solids Handling. An Introduction to the Practice and Technology. An understanding ofthe properties and the handling.

Table 2: Broad classification of the material flow function and definition of flowability for each material. Figure 3: Material flow function for each material. Coarse materials can generally be considered to be easy-flowing when dry. This is due to inertial and gravitational forces being the dominant forces in the bulk material. In the case of all of the coarse materials, the material flow function indicates that a low stress is required to generate incipient flow and deformation of the material even after a significant consolidation load has been applied. In the case of both the milled wood pellets and pulverised coal, a strong linear relationship between consolidation stress and unconfined yield stress is observed. Both materials are indicated to be cohesive with the milled wood pellets being observed to be more cohesive than the pulverised coal.

Plotting the inverse of the hopper flow factor on the plots for the material flow function and taking the point of intersection generates a critical stress for flow. From both of these parameters the minimum outlet diameter of a hopper can be determined. Pulverised coal is observed to require the steepest hopper slope in all wall material cases, and the ground anthracite is broadly shown to require the same hopper half angle regardless of wall material type.

Bulk Solids Handling.pdf

All bulk solids highlight that where the mild steel wall material sample is wetted, a steeper hopper slope is required. In the case of the wood pellets, torrefied pellets, ground anthracite, and torrefied wood chips, an intersection of the material flow function with the hopper flow factor does not occur in the stress range measured.

This is due to the easy-flowing nature of the coarse bulk solids. As a consequence, a critical stress for flow cannot be determined and in turn neither can a minimum outlet diameter for a conical hopper.

Where this is found, the general rule of sizing the outlet diameter to a value of 10 to 12 times the average particle diameter can be applied. This general rule is usually sufficient to prompt flow unaided [ 22 , 23 ]. In the case of coarse bulk solid materials, sizing the outlet as such primarily seeks to counter flow problems caused by the formation of mechanical bridges.

Table 4 provides an overview of the minimum outlet diameter required for a conical hopper for both the milled wood pellets and the pulverised bituminous coal. The outlet diameter is expressed as a multiple of the average particle diameter for each fuel and as such the values can be directly compared to the general rule stated to determine the outlet diameter when feeding coarse fuels i.

Table 4: Minimum outlet diameter as a multiple of average particle diameter for a conical hopper containing milled wood pellets and pulverised bituminous coal using TIVAR 88, stainless steel, and mild steel as wall materials. Energy Requirement of the HLH Each of the hoppers used in the experimental setup of the HLH has an outlet diameter of 76 mm and a hopper half angle of While this diameter is smaller than any of those stated in Table 4 , it was found that the limiting factor in the construction of the HLH was the valve diameter due to the operating pressures required for use.

Experimental tests with all fuels highlighted that only the wood pellets, torrefied wood pellets, and ground anthracite grains were able to flow unaided.

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As indicated by Table 4 , the torrefied wood chips, milled wood pellets, and pulverised coal were found to be incompatible with the valve diameter used in the HLH and were not found to flow unaided. Therefore, experimental tests in conjunction with the HLH were only taken further with the wood pellets, torrefied wood pellets, and ground anthracite grains.

Feeding took place against a back pressure of 25 barg in both Mode 1 and Mode 2.

A mass per batch of 4 kg, 4. In addition to the HLH being operated in Mode 1 and Mode 2, the HLH was operated as a conventional single and dual lock hopper to provide a to-scale comparison to a widely deployed high pressure feed system.

Both systems single and dual lock hopper were operated using a three-stage compressor in the compression stage, and thus the energy requirements for all systems HLH, single and dual lock hopper were determined experimentally. Referencing Table 1 and assessing the particle density of each of the materials alongside the mass per batch of fuel fed, it is observed that the void space present in the top hopper varies from fuel to fuel.

An approximate void space of mL, mL, and mL is present for the wood pellets, torrefied pellets, and ground anthracite grains, respectively. Figure 6 shows a trend of decreasing energy use with decreasing void space. Although the results shown in Figure 6 assess the energy use on a mass basis and in turn are inclusive of each respective mass per batch, a decreasing trend of volume of water pumped in the compression stage of Mode 1 is also observed with decreasing void space.

This translates to a trend of decreasing raw energy use with decreasing void space. The volume of water pumped in Mode 2 is maintained constant, and the decreasing trend shown in Figure 6 is solely accounted for by the difference in mass per batch between fuels.

Mode 1 is seen to generate a higher energy saving compared to Mode 2 in all cases and the greatest energy saving comes when feeding the ground anthracite coal in Mode 1 compared to a conventional single lock hopper. This is followed by the torrefied pellets and then the standard wood pellets.


This trend is observed due to the smaller void space present in the top hopper prior to feeding when operating with the ground anthracite compared to the two pelletised fuels and in turn the lower energy requirement by the high pressure water pump operating in Mode 1. Although this also affects both types of conventional lock hopper as this means a smaller volume of gas has to be compressed; energy saving is relative and so this benefit does not translate to a decrease in energy saving.

Bulk Solids Handling

Comparatively, this benefit is not felt when both the conventional and dual lock hopper are compared to Mode 2. As the energy required by the high pressure water pump remains constant for all fuels in Mode 2, it is only the mass per batch that affects the energy required per unit mass fed.

The reduction in void space presented by the torrefied pellets over the standard wood pellets and in turn the ground anthracite over the torrefied pellets does not constitute an advantage for Mode 2, whereas it does for both a conventional and a dual lock hopper.

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Figure 7 shows energy savings to drop for both the torrefied pellets and the ground anthracite coal compared to the standard wood pellets due to the reduction in void space. It can be concluded from Figure 7 that the greatest energy savings are generated in Mode 1 where the void space present between the fuels is minimised, and where the void space between the fuels is maximised in the case of Mode 2.

Figure 7: Energy saving generated by the HLH operating in Mode 1 and Mode 2 compared to a conventional single lock hopper a and a dual lock hopper b.

The effect of wet conditions can be very significant due to the formation of interparticle liquid bridges. Therefore, analysing the effect the HLH has on the moisture content of a fuel being fed allows an assessment to be made regarding the compatibility of a feedstock with the system.

Bulk Solids | Fluidization | Fluid Dynamics

Moisture content variations were analysed using wood pellets as the primary feedstock as wood pellets present an absorbent fuel able to most accurately monitor moisture uptake brought about during feeding. Moisture content was assessed assuming that any mass increase across the pressure boundary was due to the uptake of water by the pellets and so the mass of each batch of wood pellets was assessed before and after feeding was completed.

Table 5 provides an overview of the changes in moisture content recorded while operating the HLH at a range of operating pressures. Table 5: Effect of the HLH on the moisture content of wood pellets. No direct relationship between operating pressure and moisture content increase is observed, and it is proposed that any moisture taken up by the fuel is due to residual moisture present on the hopper walls.

Therefore, it is anticipated that as the HLH is scaled up, increases in the overall moisture content will be reduced. Some difficulty was experienced in presenting the layout and symbols in a first attempt, so please excuse the extended presentation Mass Flow, Circular opening D, Dia.

The Density of material must be related to a loose poured condition. The settled density of many products can be indicated by inserting the name of the product in the appropriate box on the Ajax web site, www.

Bulk Solids Handling

Tables are no use for this value, as the combination of wall surface conditions and product condition involves too many combinations. There is no substitute for proper measured values based on solids testing.

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Mass Flow, Circular opening D, Dia. This will make a small difference to any results that may have been assessed. Dust control Woodcock, C. Explosion hazards Woodcock, C.

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