Grinding Comminution Equipment

The main factors to be considered when selecting equipment for crushing and grinding are 

The properties of the material hardness, abrasiveness, stickiness, density, toxicity, flammability  

The selection guides given by Lowrison (1974) and Marshall (1974), which are reproduced in Tables 10.13 and 10.14, can be used to make a preliminary selection based on particle size and material hardness. Descriptions of most of the equipment can be found in the literature see Perry et al. (1997), Hiorns (1970), and Lowrison (1974). The most commonly used equipment for coarse size reduction are jaw crushers and rotary crushers and for grinding, ball mills or their variants—pebble, roll, and tube mills. 

The preparation of mixtures of solids, liquids, and gases is an essential part of most production processes in the chemical and allied industries, covering all processing 

Diamond Sapphire Topaz Quartz Feldspar Apatite Fluorspar Calcite Gypsum Talc 

---

To use natural minerals it is necessary to grind them down to a desired particle size distribution. Grinding can be performed with the minerals dry or slurried in liquid. In most laboratories, this process is performed in a batch jar mill while on an industrial scale, continuous comminution equipment is used in conjunction with size classification equipment to recycle the coarse material. Figure 4.1 shows a typical comminution circuit with classification and recycle steps, as well as separation of the mineral from the conve3ring fluid. 

Breaking is the term applied to size operations on large material (say +75 mm) and crushing to particle size reduction below 75 mm the term grinding covers the size reduction of material to below about 6 mm. However, these terms are loosely employed. A general term for all equipment is size reduction equipment, and because the term comminution means size reduction, another general term for the equipment is comminution equipment. 

The final stage in dye manufacture is grinding or milling. Dry grinding is usually carried out in impact mills equipped to control dust. More modern methods such as continuous drying allow the production of materials that do not require a final comminution stage [7]. 

Comminution is one of the most inefficient unit operations from the viewpoint of energy consumption. Continuous crushing and grinding equipment can... 

Ore beneficiation consists of two main steps comminution and concentration. Comminution is first performed by crushing. Equipment in use comprises jaw, cone, or impact crushers working mostly in closed circuits with vibratory screens. The second step in comminution is grinding, which is undertaken in rod or ball mills working in closed circuits with classifiers. 

The size distribution of products from various types of size-reduction equipment can be predicted by a computer simulation of the comminution process. This makes use of two basic concepts, that of a grinding-rate function S and a breakage function A5 a. The material in a mill or crusher at any time is made up of partides of many different sizes, and they all interact with one another during the size-reduction process, but for purposes of computer simulation the material is imagined to be divided into a number of discrete fractions (such as the ones retained on the various standard screens) and that particle breakage occurs in each fraction more or less independently of the other fractions. 

Grinding equipment used for comminution operations in chemical analysis varies in design and layout with application requirements, i.e., sample make-up, desired degree of particle size decrease, etc. The selection of the grinding kit to be used depends on... 

Dispersion methods. In this case one starts with preformed particles of the bulk chemical, which are then subdivided into smaller partides by a suitable dis-persion/comminution process. An example of this method is the production of suspensions by wet milling (using grinding equipments). Emulsification of oils (using high speed stirrers or homogenisers) is also a kind of dispersion method. 

---