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Feature
Modernisation of rice milling – A necessity in future
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Saturday, 03 July, 2010, 08 : 00 AM [IST]
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Sujit Pande
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Rice is the staple food of one-third of the world's population, and is gaining more popularity in the west, for it is a light healthy food with most of the vital nutrients. Rice is grown in the wet regions of the tropics, derived from wild grasses probably native to India and Southeast Asia. Rice is unique among cereal crops in that it grows standing in water. The yields are very large per crop. Rice takes 150–200 days to mature in warm, wet conditions. During its growing period, it needs to be flooded either by the heavy monsoon rains or by irrigation. This restricts the cultivation of swamp rice, the usual kind, to level land and terraces. The major rice producing countries are China, India, Indonesia, Thailand, and Vietnam. China (193 million metric tonnes) and India (130 million tonnes) alone account for half of the total global crop of 630 million tonnes of paddy per annum.
Outside Asia, centres of rice production include the Po Valley in Italy, Louisiana, the Carolinas, and California in the USA.
The worldwide acceptance of rice has increased the demand for it but the climatic and geographic requirement to cultivate rice does not allow all the countries to produce rice. This clubbed with the population increase drives us to look at means to increase the production of rice. One way would be to look at newer agricultural fields to produce rice and another way would be to optimise the yield from the existing produce. Better machines and automation bring in higher efficiency and yield to the rice milling process.
Conventional Rice milling Process
Rice processing (drying, cleaning, hulling, whitening) is predominantly an agricultural activity. The rice miller’s motto is - “Remove as little as possible and as much as necessary from the rice grains”. Before the rice grains are fit for consumption, they pass through numerous processes. Paddy rice is cleaned, husked, and graded. Then the clean but still brown rice grains are milled until they are white (“whitening process”). These white grains are further polished either superficially or until they are glossy, as per the customer preference. Rice loses around 30 per cent of its weight after undergoing these processes.
Prior to packing brokens (broken rice grains) are eliminated by an optical sorting operation; in this process the discoloured grains too are removed. This further reduces the yield.
The yield is primarily determined in the whitening and polishing process operations. Hence the whiteners and polishers form the heart of a rice processing facility. The quality of these operations depends on the technical quality and the stability of the machines, and the fine tuning of the process. Customers using modern processes from highly reputed companies like Buhler get a handsome return on their investment vis-a-vis the customers who invested in local machine (for the initial cost benefit).
Many varieties, many preferences – customised rice mills
Though the love of rice is common to all Asian countries, preferences do differ widely. Long grain rice is preferred in India and Thailand whereas the main varieties consumed in China are round, medium, and long grain rice, depending on the region. The Japanese all but exclusively use round grain rice.
The difference in preferences requires corresponding differences in the design of rice processing plants. Depending on the varieties consumed and exported from the region the rice processing plants require customization. Till date there is no such thing as an efficient and well-designed ‘off-the-shelf’ rice processing system. This precisely is the reason why established machinery providers like Buhler believe in customization in design and construction of plants. More so established large scale mills believe in turn key projects entrusted to reputed manufacturers than buying part machines, to have a plant which is efficient and trouble free from the day it is commissioned.
Non-automated machines - Higher production costs
Non-automated mills have various limitations in reaching optimum capacity. The per tonne operating cost is high due to higher power consumption per tonne of production. Usage of centrifugal fans increases the power consumption. The total connected motor rating for the centrifugal fans in a mill is almost equal to the connected motor rating of main processing machines. Frequency drives instead of normal starters for centrifugal fans, can provide considerable power saving. Use of soft starters for main processing machines (like whiteners & polishers) can further help in saving power.
Generally, a non-automated mill requires approx. 35-40 units of electric power per tonne of paddy processed whereas an automated mill with frequency drives & soft starters would only require approx. 25-30 units.(depending upon the configuration of the machines).
Automation – Success mantra for Rice millers
A number of factors need to be observed for building a new rice mill. Any new facility should be built in the proximity of rice growing areas. Workforce should be available locally. The tax structure, infrastructure (power supply, communication, transportation) and the stability of the local government and its policies too are vital in deciding the location.
Still the success of a plant depends on the machinery and processes deployed.
Automation is the very logical step to address the higher demand of good quality rice. State-of-the-art rice processing systems are typically fully automated and optimally adapted to the customer’s needs right from start-up.
Automation leads to better utilization of manpower
An automated rice mill of 5 tonnes per hour (TPH) to 10 TPH capacity paddy input, would require only two persons (an operator & helper) to run the mill excluding the manpower required for paddy intake and bagging the finished products. Automated plant takes care of bin filling, avoids overload of machines/conveying elements by controlling the product flow through level switches in bins/hoppers and sensors in conveying elements. The control system can take care of automatic start & stop of sections depending upon the product levels, so that all sections are optimally utilised - no section is idle for want of product. This enhances the plant utilisation to optimum capacity. The operator can concentrate on the machine setting and monitoring & controlling the quality of the product at different stages.
But a non-automated mill requires more manpower to monitor the product flow in to the bins. The operators manually check the bin filling, to avoid material overflow as well as to avoid sections being run empty. It is impossible to reach the optimum capacity of the mill, even with more number of mill operators due to human limitations.
Latest developments in Automation
Buhler, a global leader in food processing Industry, has set a higher standard in the design and construction of rice mills. Buhler technology team is working to improve rice processing by increasing the level of automation and energy balance. Energy balance is attained by increasing the efficiency of the individual pieces of equipment.
Automation specialists from Buhler have taken new approaches; in addition to equipment automation they have made considerable advancement in the making of ‘smart machines and systems’. The goal is to develop “self-regulating systems” that will make the appropriate corrections on the basis of continuous yield measurements. The system called – WinCoS. The basic system already includes all the
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