Miller Magazine Issue: 132 December 2020

56 COVER STORY MILLER / december 2020 matic, drag force, terminal (supercritical) velocity, min- imum fluidization velocity, particle density, air density etc. Any air system in the mill can be divided into three distinct parts, each of which contributes to the effi- ciency of the system. These are the fan or blower that generates the pressure and moves the air, the ducts or lines that convey clean air or a mixture of air and material and the dust disposal system that separates the dust from the air before returning the later to the tile atmosphere. vi) Cleaning by Surface Friction, Elasticity, Texture and Hardness Friction on grain kernels separates impurities adher- ing to the kernel’s surface. It has a polishing effect and cleans grain surface. In paddy separation or cleaning these principles are widely used. Additionally, ergot are mud balls, due to their hardness, they are separated from grains by the impact of the paddy table channel walls together with screening. vii) Cleaning by Friability w/ Impact In the cleaning operation, friability of a particle when subjected to impact, crushing or attrition forces are also characteristics used in separation. Some impurities and insect-damaged and–infested kernels can be broken by impact and the small particles later removed by aspira- tion or sieving. viii) Cleaning by Electrostatic Characteristics Electrostatically charged particles can be separated from another particle, which depend on their charge load. The electrostatic forces between the electronic field and the electrically charged particles cause movement, which is used for the separation. ix) Cleaning by Color Differences Color sorting of seeds is a commonly started to use in grain industry especially in cleaning section. It is used to different colored foreign materials. Today, these machines have high capacity and perfect accuracy due to advance camera and ejector system with microcomputers. 1.1.7. Design of cleaning building Multi-floor (multilevel) building is used to use potential energy (flow from up to down); i) to decrease convey- ing investment, ii) for easy process control and flow and iii) to decrease energy consumption due to conveyors. The cleaning building (or house) can be construct from concrete and steel depend on plant-design requirement, price and construction time. Depends on floors and plant-layout, each equipment can be put on floor/level and the next machine should be installed down-floor. 1.1.8. Cleaning layout and flow diagram As shown in Figures 1 and 2, there is a logic for se- quencing of machines in cleaning section. Firstly, magnet or metal detector should be used to separate ferrous ma- terials and/or the others. Magnets to separate ferrous materials are followed by sieves to separate foreign ma- terials that is used to separate foreign materials that are smaller or larger materials that are of the same size as the table is used to separate foreign materials that are of the same size as the grain but differ in specific gravity. At this stage, aspirator are used to light foreign materials. The next equipment should be destoner to separate stones. Then, intendent cylinder is used to separate foreign seed. Then, if required, gravity table can be used to sepa- rate empty kernels. Depend on the grain, a gravitational ro- tating separator, paddy separator and color sorter are used. 1.2. Tempering process Tempering is a process to add water i) to separate bran, ii) to give flexibility to bran for easy separation, iii) for debranning iv) for whitening and polishing. In general, in