Attaining ricemill efficiency in the countryside through the impeller compact ricemill

The type of ricemill being used in the countryside is vital towards achieving and sustaining the government’s food self-sufficiency program, a study shows. In more specific terms, the study also shows the relevance of the type of huller used by the ricemill on particular grains.

Majority of rice varieties produced in the country are “Indica” or long grains. The physical characteristics of long grain are appropriate for impeller type of ricemill. Unlike the rubber roll machine whose husked ratio performance very much depends on the size and shape of rough rice, the impeller type of huller, with almost the same performance, works for both long and short grain samples.

Experts explain that a ricemill is composed of the huller which removes the husk and the polisher which removes the rice bran. 

Hullers may be of three types, stone disk, rubber roll, and impeller. The stone disk huller is a standard component of the conventional “cono” rice mill. It consists of two circular discs laid flat one on top of the other with their grinding surfaces facing each other. The rubber roll huller consists of a pair of rubber rollers mounted on a horizontal shaft and designed so that one roller rotates clockwise and the other counterclockwise. The impeller huller is designed based on centrifugal and Coriolis forces, whereby the paddy is thrown against the liner part of the impeller housing. 

The only available ricemills in the country are the stone disk, commonly known as “kiskisan” and the rubber roll popularly known as “cono.” On the average, the kiskisan has a milling efficiency of 50-55% compared with single pass rubber-roll cono rice mill that provides an average milling recovery of 60-63% or the multi-pass rubber-roll’s milling recovery of 63-65%. As such, a 100-kg dried paddy that passes through a kiskisan could produce only a 50-55 kg of milled rice compared with the 60-67 kg recovery of rubber-roll type rice mills.

While the rubber-roller type “cono” rice mill is very popular in the Philippines because of its good milling efficiency, this type of rice mill requires higher investment and operating cost, higher power requirement, and regular replacement of rubber rolls.

With the study conducted at the Philippine Center for Postharvest Development and Mechanization (PhilMech), researchers conclude that one potential approach in improving the current milling system in the Philippines is the development of impeller type rice mill given its relatively simple hulling mechanism and good performance for long grains. The machine has a milling capacity of 230 kg/hr. Head rice recovery is 64% while for brown rice is 91%.

The first prototype of the fabricated commercial model of impeller-type ricemill is easy to install, requires a small working space, has a lower maintenance and operating cost, and has a higher milling capacity, among other advantages.

The commercial unit will be field and pilot tested in major rice producing areas in the country.

The study on the impeller compact ricemill is one of the Council’s initiatives to improve the state of R&D in the agriculture, aquatic and natural resources sectors. This is in keeping with its commitment under DOST’s Outcome One: to provide science-based know-how and tools that will enable the agricultural sector to raise productivity to world-class standards.