MODEL	OUTSIDE DIAMETER	LENGTH/PCS	INSIDE DIAMETER	SUITABLE RICE WHITENER
JM1A(330)	330	205	212	330
NZ20.5	205	810/3	75	NZ21.5
MNMF20.5	205	600/2	75	MNMF22
PG277×77	270	770/3	60	PG277×77
MS60F	600	22678	305	MS60F
SP40	400	40	210	SP40
SM600	250	445	50	SM600
QMJ60	600	120/2	100(260)	QMJ60

 

(4) effect of sand roller on rice quality

4.1 grain size because of the wide rice planting area and the complex and changeable climate conditions, the quality of rice is different. Therefore, the grain size of the sand roller should be different when processing raw grain of different quality. If the sand roller with too coarse grains is selected, not only the scratch on the surface of rice grains by the sand roller is deep, the surface of rice grains is rough and uneven, but also it is easy to damage rice grains and cause broken rice; If the sand roller with too fine grain size is selected, the surface of rice grain is smooth and flat, but the milling efficiency is low and the power consumption is high. Therefore, the sand roller with suitable grain size should be selected according to the quality of raw grain.

Specifically, when the multi-stage light rolling process is adopted, the grain size of the rice grinding sand roller should be coarse in the front and fine in the rear. Because the brown rice just entering the rice mill has a thick skin and smooth surface, and has a large capacity of compression, bending and shear resistance, in order to improve the rice grinding efficiency, the sand rollers with 24 # and 30 # grain sizes can be used; The rice milling machine in the rear is mainly used to whiten the rice. Because the surface of the rice grain is rough and the resistance to compression, bending and shearing is weakened, if the coarse grain size sand roller is used again, the rice grain will be damaged and broken. Therefore, the grain size of the sand roller should be smaller. Generally, 46 # and 60 # sand rollers can be used.

When the process flow of one machine (roller) whitening is adopted, the grain size of the sand roller from the feed end to the discharge end should be coarse first and then fine. For example, the sand roller with grain size of 30 # can be used at the feed end and the sand roller with grain size of 46 # can be used at the discharge end.

It is worth noting that the relationship between the grain size of the sand roller and its working speed should also be well mastered. Generally, when the grain size of the sand roller is relatively coarse, the grinding grain has a greater effect on the rice grain. In order not to break the rice, the working speed of the rice grinding sand roller can be lower; On the contrary, when the grain size of the sand roller is fine, the impact and rolling of the abrasive particles on the rice particles are relatively soft. In order to improve the rice milling efficiency, the working speed of the sand roller can be higher.

4.2 hardness if the hardness of the sand roller is too high, the abrasive particles are difficult to fall off, and the self sharpening performance is poor, the rice particles are slippery and not easy to peel, the milling efficiency is low, the power consumption is high, and the rice temperature rises quickly, resulting in the weakening of the physical and mechanical strength of the rice particles and the formation of broken rice; On the other hand, if the hardness of the sand roller is too low, the abrasive grains are easy to fall off, and the abrasion of the rice grinding sand roller is too fast, which not only seriously affects the service life of the sand roller, but also affects the quality grade of the rice when the abrasive grains dropped in the rice grains are mixed in the finished products. Therefore, the hardness of the sand roller seriously affects the rice milling efficiency, rice yield, rice quality and power consumption. Obviously, when processing raw grain or powdered plasmid raw grain with poor quality, the hardness of the sand roll can be lower (such as soft 2, code L) because the physical and mechanical strength of the rice grain is lower; When processing raw grain or horny grain with better quality, the hardness of the sand roll can be higher because of the high physical and mechanical strength of the rice grain (such as medium hard 1, code P). In short, in order to ensure the quality of rice and reduce the amount of broken rice, in practice, the hardness of the sand roller is better than soft.

4.3 organization number: if the organization number of the sanding roller is too small, it will have a large grinding effect on the rice grain, which is easy to damage the rice grain and cause broken rice; On the other hand, if the organization number of the sand roller is too large, that is, the content of abrasive grains in the organization structure of the sand roller is too small, the grinding effect on the rice grains is very weak, and the milling efficiency is low. Therefore, the organization number of the sand roller seriously affects the rice milling efficiency, rice yield, rice quality and power consumption. Obviously, when processing raw grain or powdered plasmid raw grain with poor quality, because the physical and mechanical strength of rice grain is low, the number of tissue number of sand roll can be larger; However, when processing raw grain or horny grain with better quality, the number of the tissue number of the rice grinding sand roller can be smaller due to the high physical and mechanical strength of the rice grain.

4.4 strength if the strength of the sand roller is too low, the structure of the sand roller is loose, and the sand roller is easy to fall off in blocks during operation, which is a phenomenon often encountered in practice and production. As a result, not only the service life of the sanding roller is reduced, but also the rice grains are easily damaged and broken; In addition, the falling off of abrasive particles mixed in the finished products also seriously affects the process performance of subsequent processes, the quality grade and price of rice. Therefore, we should strive to improve the strength of the sand roller, which is conducive to extending the service life of the sand roller.

4.5 roll shape

4.5.1 groove width and groove depth: if the groove on the surface of the sand roller is too narrow and shallow, the impact and rolling of the sand roller on the rice grain are particularly large, which is easy to damage the rice grain and cause broken rice; On the contrary, if the groove on the surface of the sand roller is too wide and too deep, the number of abrasive grains that impact and roll the rice grains will be reduced, resulting in the reduction of rice milling accuracy and efficiency. Therefore, in a certain range, appropriately widening and deepening the spiral groove of the sand roller is conducive to reducing broken rice and obtaining high-quality rice. In practical production, the groove width and groove depth of the sand roller are designed to be the maximum at the feeding end of the rice grains, and then gradually decreased, and the spiral groove at the discharging end is designed to be zero or slightly greater than zero according to the characteristics of the gradual discharge of the bran powder and the gradual reduction of the volume of the rice grains during the whitening process, which can ensure that the whitening pressure in the whole whitening chamber tends to be uniform, which is conducive to improving the effect of the rice milling process and obtaining the rice of the predetermined quality level.

4.5.2 thrust angle β Advance angle of sand roller β The impact, tumbling and axial transport of rice grains are seriously affected within a certain range. With the advancing angle of the sand roller β The increase of the can increase the impact and rolling of the rice grains, but the pushing effect on the rice grains (i.e. the axial transport effect) is weakened, which is conducive to obtaining high-precision rice. If the advance angle of the sand roller β If it is too large, the collision and tumbling between rice grains and between rice grains and the components of the whitening chamber will be extremely severe, which is easy to damage rice grains and cause broken rice. Therefore, in order to obtain rice with appropriate accuracy level and small amount of broken rice β Generally, it can be selected between 0 and 50 °.

4.5.3 spiral rise angle λ Spiral rise angle of sanding roller λ In a certain range, it also seriously affects the impact, tumbling and axial transport of rice grains. With the spiral rising angle of the sand roller λ That is, the increase of the lead of the spiral sand roller forces the rice grains to collide with each other and the rice grains and the members of the whitening chamber to produce greater impact and tumbling, but the pushing effect on the rice grains (i.e., the axial conveying effect) is weakened, which is conducive to obtaining high-precision rice. If the spiral rise angle of the sanding roller λ If it is too large, the collision and tumbling between rice grains and between rice grains and the components of the whitening chamber will be extremely severe, which is easy to damage rice grains and cause broken rice; If the spiral rise angle of the sanding roller λ It is too small. Although the sand roller strengthens the pushing effect on the rice grains (i.e., the axial conveying effect is strong), it weakens the milling effect on the rice grains, resulting in uneven milling and reduced milling accuracy. Therefore, in order to obtain rice with appropriate accuracy level and small amount of broken rice, the spiral rise angle of the sand roller λ Generally, it can be selected between 20 and 30 °.

4.6 location and ventilation area of ventilation hole during rice milling production, some or all of the rice grain cortex is removed due to collision and rolling, and some heat is also generated. Part of the heat is radiated to the atmosphere through the whitening chamber members, the other part is lost with the evaporation of the water of the rice grains, and another part of the heat is transferred to the inside of the rice grains to promote the rise of the rice temperature. If these heat can not be released in time, it will cause a sharp rise in rice temperature and a large amount of evaporation of rice water. As a result, not only will the load of the rice mill increase, but also the compressive strength, bending strength and shear strength of the rice grains decrease, resulting in an increase in the amount of broken rice. Therefore, at present, the production technology of rice milling with strong pulling wind is almost adopted in the practice production, that is, injecting a proper amount of room temperature air into the milling room to cool the rice grains, reduce the rice temperature, ensure that the rice temperature does not rise too high, and achieve the purpose of improving and improving the effect of the rice milling process. The room temperature air usually enters the inner cavity of the sand roll through the radial ventilation holes or ventilation grooves of the main shaft through the central holes at both ends of the high-speed rotating main shaft, and then is injected into the whitening chamber through the radial ventilation holes or ventilation grooves of the sand roll, thereby forming a gas vortex rotating around the rice grinding sand roll. This gas vortex promotes the rice grains to produce large collision and tumbling movements, so as to achieve the functions of uniformly whitening the rice grains, cooling and cooling, and forcing the bran powder to be discharged out of the machine. If the number of ventilation holes or ventilation grooves of the sand roll is too small and the ventilation area is too small, the effect of cooling the rice grains and reducing the rice temperature can not be achieved, which will easily lead to the reduction of the compression, bending and shear strength of the rice grains, and generate a large number of broken rice; On the contrary, if the number of ventilation holes or ventilation grooves of the sand roll is too large, and the ventilation area is too large, the amount of gas entering the whitening chamber per unit time will increase, which will cause the rice grains to collide violently and roll, and a large number of broken rice will also be produced. If the radial ventilation hole of the sand roll is located on the spiral groove, the rice grains are easily to enter the inner cavity of the sand roll through the ventilation hole on the spiral groove of the sand roll, which hinders the injection of greenhouse air from the sand roll into the whitening chamber. It can not cool the rice grains and reduce the rice temperature, and it will also form broken rice. Therefore, in practice, the ventilation hole should avoid the spiral groove of the sand roller and have a suitable ventilation area to achieve the purpose of cooling rice grains, reducing rice temperature and reducing broken rice.

4.7 quality of sand roller

4.7.1 raw materials: the quality of raw materials of sand roll includes the quality of abrasive and the quality of resin binder. Obviously, by selecting high-quality black silicon carbide abrasive and resin binding agent with superior bonding performance, high-strength rice grinding sand roll can be obtained, which can ensure that the rice grinding sand roll will not fall off, so as to improve the rice grinding efficiency, rice quality and prolong the service life of the sand roll.

4.7.2 the manufacturing quality of the sand roll refers to the manufacturing error in the organization structure, geometric shape, position and size of the sand roll. Obviously, selecting a sand roller with uniform structure, good self sharpening performance, high mechanical strength, solid combination of iron core and abrasive, high geometric position and dimensional accuracy and no crack can significantly improve the rice milling efficiency, rice milling quality and prolong the service life of the sand roller.

4.8 other factors, such as the structural form of the sand roller rice mill, operation management, parameters of the whitening chamber, rotation speed of the roller, quality of raw grain and rice milling process, also seriously affect the quality of rice. Among them, the structure of the sand roller rice mill has the most significant impact on the quality of rice. According to the number of rollers, the sand roller rice mill can be divided into single sand roller rice mill and double sand roller rice mill; According to the difference of structural form, it can be divided into vertical sand roller rice mill (the rotation axis of the roller part is perpendicular to the installation foundation surface of the rice mill) and horizontal sand roller rice mill (the rotation axis of the roller part is parallel to the installation foundation surface of the rice mill). The vertical sand roller rice mill is driven by the The difference in discharging mode can be subdivided into vertical reverse sand roller rice mill (also known as reverse vertical sand roller rice mill, i.e. the working mode of feeding the lower part of the roller and discharging the upper part of the roller is opposite to the gravity direction of the rice grains) and vertical forward sand roller rice mill (also known as forward vertical sand roller rice mill, i.e. the working mode of feeding the upper part of the roller and discharging the lower part of the roller is consistent with the gravity direction of the rice grains). Although the working principles of the horizontal sand roller rice mill, the vertical forward sand roller rice mill and the vertical reverse sand roller rice mill are the same, there are great differences in the magnitude of the whitening pressure and the uniformity of its distribution, which are specifically shown as follows: when the formula, specification, roll shape, manufacturing process flow, rotation speed of the roller, raw grain quality, milling process flow and parameters of the whitening chamber are the same, due to the gravity of the rice particles:

① In the horizontal sand roller rice mill, most of the rice grains are gathered in the lower part of the whitening chamber, and only a small part of the rice grains are located in the upper part of the whitening chamber. Therefore, the gap between the rice grains in the upper part of the whitening chamber is large. Obviously, the generated whitening pressure is small, the milling efficiency is low, and the milling accuracy is poor; In the vertical rice milling machine, the gravity of the rice grains causes the rice grains to be squeezed more tightly in the whitening chamber, resulting in a large whitening pressure, especially in the reverse sand roller rice milling machine. The gravity of the rice grains also hinders the discharge movement of the rice grains outside the machine. Therefore, the reverse sand roller rice milling machine has a large whitening pressure, a strong milling effect on the rice grains, a high milling efficiency and a high milling accuracy; The efficiency and precision of vertical sand roller rice mill are between the two;

② Due to the influence of the gravity of rice grains, the distribution of the whitening pressure in the horizontal sand roller rice mill is uneven, that is, in the same cross section of the roller, the whitening pressure at the lower part of the roller is too large, the whitening pressure at both sides of the roller is too small, and the whitening pressure at the upper part of the roller is too small, resulting in uneven whitening of rice, poor milling accuracy and more broken rice; However, the whitening pressure in the same cross-section of the vertical reverse sand roller rice mill and the vertical forward sand roller rice mill is uniform everywhere, the rice is whitened evenly, the rice milling accuracy is high and the broken rice is small.

(5) conclusion

When selecting the sand roll of the rice mill, it is necessary to optimize the formula, roll shape design and manufacturing process of the sand roll according to the structural form of the rice mill, the parameters of the whitening chamber, the rice milling process, the quality of raw grain and the quality grade requirements of the rice processing, so as to improve the uniformity of the sand roll's structure, physical and mechanical strength and the accuracy of the geometric position and size, and minimize the defects of the sand roll such as block shedding and dynamic imbalance, High strength and high quality sand roll with suitable grain size, texture number, hardness and roll shape shall be selected. Only by properly storing, storing and assembling the sand roll and paying attention to and strengthening the cooling, ventilation and bran removal in the whitening room can we achieve the goals of cooling rice grains, reducing rice temperature, reducing power consumption, reducing broken rice, improving the effect of rice milling process and extending the service life of the sand roll.

reference

1、 This is the identification of Fangfang brand rice grinding sand roller. Please check carefully before installation.

1. Examples of common sand rollers:

Product name and specification (outer diameter × Length / number × Pore size) abrasive grain size hardness binder

NF15A 150 × 400/2 × 85 C 46# Q B

2. Example of packing sand rollers in boxes: when multi section sand rollers are packed in boxes, the packing box and the sand rollers are marked with sequence numbers, which shall be carefully checked during installation.

Product name and specification (outer diameter × Length / number × Aperture) abrasive grain size hardness binder number

MNMF30 300 × 800/5 × 80 C 46# Q B 1083-1、2…

explain:

1) Abrasive C - black silicon carbide

2) Common particle sizes 24 #, 30 #, 36 # - for roughening 40 #, 46 # - for whitening, 60 #, 80 # - for fine grinding.

3) Common hardness: p-medium hard 1, q-medium hard 2

4) Common binder

B - resin binding agent

V-ceramic binding agent

2、 Selection of sand roller

The use effect and durability of the sanding roller are related to a series of factors such as the state of the rice machine, the characteristics of the sanding roller, the type, variety and water content of the brown rice, the rice milling process and the operation level. When you feel that you can't get what you want during rice milling, you can consider selecting a relatively suitable sand roller according to the following requirements

(only the following single phenomenon is considered from the angle of sand roller):

1. The service life of the sand roller is not ideal

(1) try to select sand roller with higher hardness.

(2) try to select sand roller with finer grain size.

2. The output is not ideal

(1) try to select sand roller with coarse grain size.

⑵ try to select sand roller with loose structure.

(3) try to select the sand roller with fast advancing speed (for example, the spiral groove is deepened and widened or the full thread type roller is selected).

3. Poor accuracy

(1) try to select sand roller with finer grain size.

⑵ try to select sand roller with higher hardness.

(3) try to select the sand roller with a slow advancing speed (such as narrow spiral groove or molding sand roller with straight groove).

3、 Replacement and protection of sand roller

It is normal that the output and accuracy of rice milling will decrease after the sand roller is used for a period of time. As for the decrease in output, if conditions permit, the sand roller can be removed and the spiral groove can be trimmed with a portable grinder, and the output will generally recover. For accuracy: