Abstract The structure of the whitening chamber of the rice mill is different. The rice mill exhibits different characteristics of rice milling during the whitening process. In this paper, the different process characteristics of horizontal rice milling machine and vertical rice milling machine are discussed and analyzed, and suggestions are put forward.

Key words horizontal rice mill vertical rice mill rice milling process characteristics
CLC number TS 212.3

Relationship between Rice Whitener Types and Rice Whitening Technology Characteristics

ABCTRACT When the whitening chamber design of a rice whitener is different, also the rice whitening technology characteristies are different during whitening. The different technology characteristics of horizontal and vertical rice whiteners were discussed and analysed, and several suggestions were put forward.

KEYWORDS horizontal rice whitener vertical rice whitener characteristics of whitening technology

The rice milling machine used in the rice milling industry has two types: horizontal rice milling machine and vertical rice milling machine. The roller spindle of the horizontal rice milling machine is horizontally designed, and the whitening chamber is horizontal in the space. The roller spindle of the vertical rice milling machine is vertically designed, and the whitening chamber is in a vertical position in the space. The milling principle of these two types of rice milling machines is the same, but due to the different design forms of the whitening chamber, the overall structure of the two types of rice milling machines is different, the feeding and discharging methods of the rice milling machine are different, and the characteristics of the rice milling process are different, especially Two key indicators for the evaluation of the effect of rice milling machine: whitening and crushing rate, and whitening uniformity are also different. The author combines his own experiences in the use, measurement and development of rice milling machines, and puts forward several viewpoints for discussion. Due to the unconditional comparison and analysis of the process effects of the two types of rice milling machines, only the observed phenomena can be discussed and analyzed.

1 horizontal rice mill
The whitening material of the horizontal rice milling machine enters the whitening chamber from one end and flows out from the other end of the whitening chamber. Under the action of a high-speed rotating roller, the rice grains are whitened in a flowing state. The movement of the rice fluid in the whitening chamber can be seen as a horizontal spiral around the roller. The flow direction of the rice flow in the whitening chamber is perpendicular to the gravity direction of the rice flow. This type of rice milling machine has the following technological features:

1.1 Good whiteness uniformity
The whiteness uniformity of the rice grains is related to the structural form of the roller, the roll surface manufacturing material, and the roller motion parameters. It is important to relate to the movement state of the rice grains in the whitening chamber. The rice grains are whitened in the rolling, and the whitening uniformity is the best. In the horizontal rice milling machine, the movement of the rice grains in the whitening chamber is obtained from the roller. Under the action of a high-speed rotating roller, the rice grain rolls sharply, and the rice grain has both rolling along its long axis and flipping along its short axis (see Figure 1). The rice grain is in a random state in the whitening chamber. Sharply tumbling motion. It is this irregular and sharp tumbling that gives the rice grain a chance to be subjected to grinding and rubbing, and achieves a good effect of uniform whitening.

1.2 Broken rice is easy to produce during the whitening process

In the process of whitening, the horizontal rice milling machine is affected by the gravity of the rice grain fluid. The density of the rice grain in the cross section of the whitening chamber is not uniform. The density of the rice grain in the lower part of the whitening chamber is large, and the density of the upper part is small. Therefore, the rice is subjected to a large white pressure in the lower half of the whitening chamber, which is easy to produce broken rice. In the upper part of the whitening chamber, due to the small density of the rice grains, the gap between the rice grains is large, and the roller is rotated at a high speed. Under the rapid collision between the rice grain and the white room components, it is easy to produce broken rice. In particular, the amount of small broken rice and rice bran produced is large. The broken rice bran is mixed into the rice bran, which makes the separation of the clams an indispensable process.

1.3 Out of the rice with more glutinous rice
In the design of the horizontal rice mill, the milled rice is required to be discharged from the row of glutinous rice sieves by a 360° circumference to the whitening chamber. In the production, the sieve hole in the upper part of the glutinous rice sieve is affected by the gradual accumulation of the rice bran discharged during the whitening process, the sieve hole is blocked or the sieve hole size is reduced, and the effective drainage area is smaller than the designed drainage area. In production, it is often impossible to clean the surface of the drainage shovel in time, so that the milled rice can not be discharged into the whitening room in time, and the rice produced contains more glutinous rice. Of course, the above phenomenon does not exist in the drainage of the horizontal spray rice mill. If in the production, after the shift, the operator can strengthen the cleaning of the drainage screen, this problem can be solved.

2 vertical rice mill
According to the different ways of feeding and discharging, the vertical rice milling machine is divided into two types: the vertical rice milling machine under the upper feeding material and the vertical rice milling machine with the lower feeding material. The following are discussed separately.

2.1 Vertical feeding machine under the feeding material
The whitening material enters the whitening chamber of the machine from above the rice milling machine. Under the combined action of the roller and the gravity of the rice liquid, the rice grains are whitened in the flow and discharged from the machine under the whitening chamber. The movement of the rice fluid in the whitening chamber can be seen as a vertical spiral that moves from top to bottom around the roller. The flow of rice in the whitening chamber is in the same direction as its own gravity. The machine exhibits the following process characteristics:

2.1.1 Rice mill has low power consumption
During the whitening process, the rice grain fluid moves from top to bottom. Affected by gravity, the rice has the ability to transport itself from top to bottom, thus reducing the power consumption of the rice machine. The rice mill consumes the power on the roller and is mainly used for the whitening of rice grains. Unlike horizontal rice mills and vertical feed mills, the power consumed on the rice mill rolls is used for both rice milling and axial transport of rice.

2.1.2 Less broken rice produced during the whitening process
During the whitening process, the density of the rice grains in the cross section of the whitening chamber of the machine is uniform, so the whitening pressure is uniform, the generated broken rice is less, the small broken rice and rice bran are produced less, and the discharged rice bran is pure. Compared with the horizontal rice milling machine, there is basically no small broken rice in the rice bran, and the content of the rice bran is also very small. In the production, it is considered that the separation process is not required.

2.1.3 Out of the rice with less glutinous rice
The whitening chamber of the machine is in a vertical state, and the rice bran discharged from the machine does not accumulate on the drainage screen and blocks the sieve hole of the drainage rice sieve. The effective drainage area of ​​the rice machine is equal to the design drainage area. The rice skin milled during the whitening process can be discharged into the whitening room in time, and the rice produced is less than the powder. If there are less powder in the rice, it will help to reduce the load of the rice machine, help the rice machine to reduce the crushing, and help to improve the smoothness of the rice.

2.1.4 The uniformity of whitening is slightly poor, and it is better to use multiple roads.
The self-gravity of the rice-grain fluid in the whitening chamber accelerates the speed at which the rice grains pass through the whitening chamber. When using the same roller structure parameters and motion parameters as the horizontal rice milling machine, gravity causes the rice grain to be milled in the machine shorter than the horizontal rice milling machine, and the rice grain is slightly weaker. When the rice grain is shortened by the milling time, the number of tumbling times during the whitening process is also relatively reduced, and the whitening uniformity is slightly worse than that of the horizontal rice milling machine. In the production, multi-pass whitening can be used to improve the whiteness uniformity, and 4 or 5 lanes of whitening are better, which can ensure good whitening uniformity, and can be multi-machined to reduce the broken rice.

2.2 Lower feed vertical rice mill
The whitening material enters the whitening chamber from below the rice milling machine, and the rice grains are whitened in the flow and discharged from the top of the whitening chamber. The movement of the rice fluid in the whitening chamber can be seen as a vertical spiral moving from bottom to top around the rice milling roller. The flow direction of the rice grain fluid in the whitening chamber is opposite to its own gravity direction. The machine has the following process characteristics.

2.2.1 Reduce lifting equipment and simplify the process
Since the machine feeds under the upper discharge, when multiple lanes of whitening are used, the outlet of the front rice milling machine can be connected with the inlet of the downstream rice milling machine, and two meters can be omitted. The hoist usually used between machines simplifies the production process. The front and rear road rice milling machines are directly connected, and the flow rate in production is stable, which reduces the unstable flow of the rice machine caused by the shovel slippage and blocking materials, and is beneficial to improving the effect of the rice milling process. The hoist's bucket is prone to wear and its maintenance work is a very arduous task. Reducing the hoist can reduce the cost of disposable equipment investment and equipment maintenance management.

2.2.2 Out of the rice with less glutinous rice
The whitening chamber of the machine is in a vertical state, and there is no accumulation phenomenon of rice bran on the drainage screen. The same as the vertical rice milling machine under the feeding, the rice with less rice is less.

2.2.3 Good whitening uniformity, pay attention to avoid over-grinding
In the production, the roller should overcome the gravity of the rice fluid to transport the rice from bottom to top. Affected by gravity, the rice granules run slower from bottom to top. Compared with horizontal rice mills and vertical feed mills, the rice granules are milled in the machine for a long time. The number of times of turning in the process also increases correspondingly, and the whiteness uniformity of the rice grains is good. If it is not handled properly, it will easily cause the rice grains to over-mill and the broken rice to increase. The design of a reasonable roller structure, select the appropriate roller motion parameters, adjust the flow rate, can achieve better whitening uniformity while avoiding over-grinding and crushing.

2.2.4 meter machine power consumption is higher
In the process of whitening, the rice grains must overcome their own gravity to run from bottom to top. The movement of the rice grain is obtained from the roller, and the power consumed by the rice milling machine on the roller is not only used for the whitening of the rice grain, but also the gravity of the rice stream is transmitted from the low end of the whitening chamber to the high end. Compared with the vertical rice machine and the horizontal rice machine under the upper feeding material, the power consumption of the rice machine is higher.

3 recommendations
The process characteristics of horizontal and vertical rice milling machines are both good and bad. It is important to select the rice milling machine according to the production needs and make full use of the good side of the different types of rice milling machine.

(1) Multi-channel whitening small-scale rice milling equipment, it is better to use vertical feeding machine for lower feeding and discharging. The number of equipment can be reduced, the rice mill can be arranged compactly, and a good process effect can be obtained.

(2) When the large and medium-sized rice mills are multi-passed, the first roughing rice mill is better to use the top-loading rice milling machine. When the rice grain is roughened, the power consumption is high. The machine can be used to reduce the dynamic consumption and the broken rice is less. Multi-pass whitening, the first few used the vertical rice mill under the feed, the latter several use the horizontal rice mill. While ensuring better whitening uniformity, the broken rice is reduced and the dynamic consumption is reduced.

Author unit: Wuhan Institute of Food Industry (430022)

references
1 Wuxi Institute of Light Industry, Wuhan Institute of Grain Industry, edited. Rice milling process and equipment. Beijing: China Finance and Economics Publishing House, 1985
2 Liu Ying. Analysis of structural characteristics of vertical rice milling machine. Grain and Feed Industry, 1994(1)