Properties of feed materials

Knowledge of the compression properties of feed materials can indicate the type of force most likely needed in size reduction. A friable or crystalline structure can be reduced through fracture along cleavage planes using compressive forces. However, if new crack tips must be formed, impact and shear forces may be more effective. For food materials of fibrous structures, shredding or cutting should be considered for the desired size reduction. 

The important parameters of composting are temperature, pH, moisture content, and oxygen transfer, which is regulated by aeration, free airspace, and agitation. The main properties of feed materials include C/N ratio, ratio size, rigidity, and nutrient and lignin compost. 

PROPERTIES OF FEED MATERIALS AFFECTING THE SIZING PROCESS... 

The milling or sizing process is affected by a variety of factors and has a direct effect on the quality of the final product. The properties of feed material and the finished product specifications determine the choice of equipment to be used for the process of comminution. The properties of feed material include melting point, brittleness,... 

Properties of feed material Size, shape, moisture content, physical and chemical properties, temperature sensitivity, grindability, and material compatibility... 

Physical Properties of Feeding Material - Flowability, Packing and Friction... 

The type of evaporator to be used and the materials of construc tion are generally selected on the basis of past experience with the material to be concentrated. The method of feeding can usually be decided on the basis of known feed temperature and the properties of feed and produc t. However, few of the listed variables are completely independent. For instance, if a large number of effects is to be used, with a consequent low temperature drop per effect, it is impractical to use a natural-circiilation evaporator. It expensive materials of construction are desirable, it may be found that the forced-circulation evaporator is the cheapest and that only a few effec ts are justifiable. 

Typical Operating Conditions Table 19-26 presents some typical values oF important operating conditions For the separation oF several diFFerent types oF Feed materials. In considering candidate processes For a given separation job, the table can sometimes be help-Fiil in showing that materials oF similar properties and/or economic v ahie can be treated bv electrostatic separation. 

The combined group Ua has been shown 25 26-1 to be influenced by the feed rate of solids, the air rate and the properties of the material, and a useful approximation is given by ... 

Measurement of the physieal properties of feed and produet phases (e.g., mass densities, viseosities, surfaee tensions, and wettability) and their dependenee on temperature on typieal equipment materials Qualitative examination of the mass transfer intensity of a single droplet (kicking drop)... 

Fig. 5.6. Flow and compression properties of feed solids for theoretical roll press design [15]. (a) Shear cell to measure internal friction of granular solid, (b) Cell to measure angle of friction between roll face and granular solid, (c) Pressure-density relationship of feed material.

These equipment items are used to store feed and, in some cases, process bulk solids. The design of economical hopper systems is dependent on the physical, chemical, and flow properties of the materials being stored. It is essential to provide bin, hopper, and feeder designs to enhance the flow of the material from the hopper and to minimize potential problems. 

It has been noted that proportionately more work is done in the precompaction stage of a single-row press. This extra work may result in a general degradation of feed material, a change of the position at which compaction begins, an increase of the bulk density at the start of compaction, and even a difference in the adhesive properties of the material s surface. 

Agglomeration by heat or sintering is also very common in the metallurgical industry. However it is mostly applied for the size enlargement of feed materials (minerals. Section 6.8.3), for the preparation of secondary raw materials from metal bearing by-and waste-products (Section 8.2) and for the development of final properties of powder metallurgical parts (Chapter 7). These chapters should be consulted for further information. 

---