A pneumatic rice polisher system has been developed to minimize broken content (BP) and maximize the degree of polishing (DP). This polisher consists of a metallic cyclone coated with hard abrasive material, a blower, a collection system. Brown rice is feed vertically at the rate of 1.5 kg/min that flows towards the abrasive cyclone through horizontal air flow at 72.2 m/s.

In modern method of processing, the term milling encompasses cleaning, drying, dehusking, aspirating of husk, separating paddy and brown rice, polishing to remove bran and grading rice and broken. A modern rice mill consists of a paddy pre-cleaning system which sieves and aspirators, efficient paddy separators, improved rice whiteners, graders and auxiliary equipment such as elevators, conveyors, automatic weighing machine. Parboiling is a pre-milling most-heat treatment given to raw paddy in order to improve its milling quality, nutritive value, cooking quality and storability. Equipments for parboiling and drying have been installed in some modern rice mills. If parboiling operation is used then, there is an overall increase in total rice recovery of about 6 % over huller mills and 10–20 % reduced percentage of broken If different sets of machines are used then all the by-products viz.; husk, bran and broken are obtained in a useable form and this rice milling system may be energy intensive.

The outer layers of a grain of rice contain proteins, fats and lipids which although good for eating, are bad for brewing because they produce off flavours in the end product. So as to create as refined and clean a flavour as possible, the outer layers are removed in a process called polishing. In the case of the more premium brews, the rice may be milled to leave just little more than the centre of the grain remaining: a nucleus packed with starch called the 'White Heart' or Shinpaku in Japanese. The ratio always refers to the bit that remains after polishing. For example, rice that has had 30% of the grain removed will have a ratio of 70%.

Grain dust has also long history diseases and its adverse effects on various organs such as eyes, nose, skin, lung and the airways. Asthma has been well documented as being a result of dust exposure. However, few studies have been reported on the effect of dust exposure in rice mill. The major dust hazards for workers in rice mills are the dust emissions from different sections i.e. dumping of rice at a place for subsequent collection in gunny bags, feed of paddy from gunny bags to the dumping pit, cleaning of paddy grains, removal of husk from the paddy and polishing of rice. In addition, a dusty mill increases the risk of workers’ injury and fire hazard, which results in less production, higher insurance rates, and lawsuits. The increasing global attention on control of air pollution has made the containment of nuisance dust from rice milling operations within enclosures more imperative.

Separation of paddy and rice on an oscillating type separator takes place due to difference in specific gravity and surface characteristics of paddy and rice. When a mixture of paddy and rice falls on paddy separator having a serrated surface and is oscillated at the appropriate frequency, rice settles down under the layer of paddy. If the inclination of deck exceeds the angle of friction between the rice and paddy, the paddy moves down the deck on top of the layer of rice. This angle of inclination exceeds the angle of rolling friction between the paddy and the material of the deck and the paddy after having been separated from the layer of rice rolls down on the deck surface. Serrations provided on the deck surface are so shaped that they prevent the rice from sliding down. The values of amplitude of frequency of deck oscillation are such that rice can slide up the deck surface in successive steps per cycle of deck motion and finally reach the rice outlet where the grains escape. The equations of motion of rice on a deck surface have been analysed and the conveying velocity computed. The observed and computed velocities have been found to be in reasonable agreement with each other.

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