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Energy-saving retrofit solution for Roller Mill

In 2011, a power plant replaced the steel ball and liner of some Roller Mills of two boilers, using new materials such as ultra-high chromium rare earth grinding balls and new alloy rare earth wear-resistant linings.

Steel ball transformation

The hardness of the ultra-high chromium rare earth grinding ball is consistent, its Rockwell hardness & ge; 58HRC, the hardness difference is less than 2 units, the breaking rate &l; 0.1%. Thereby, the wear resistance of the steel ball can be greatly improved, thereby reducing the generation of the waste steel ball and reducing the screening frequency of the steel ball. At the same time, using the new technology of Roller Mill steel ball ratio, that is, increasing the ratio of medium and small diameter steel balls, the weight of the Roller Mill can be greatly reduced, the running power of the Roller Mill can be reduced, and a certain energy saving effect can be obtained. . Through the sampling analysis of the original Roller Mill steel ball, the following new technology of steel ball ratio is proposed:

1. Perform a screening of the medium-chromium grinding balls thrown out in the Roller Mill, and filter out the round-shaped deformed grinding balls, and no longer use them.

2, in the normal loading ratio, do not use the proportion of the diameter span is too large, such as φ 80, & phi; 90 grinding ball and diameter & phi; 20, & phi; 25 grinding ball at the same time, so for small diameter Grinding balls can have a certain impact, and damage can also be caused to the Roller Mill liner.

3. Perform a screening work on the medium-chromium grinding ball that is pulled out in the Roller Mill, and load the grinding ball of diameter & phi; 30 or more into the ton bag according to the same specifications and continue to use.

4. According to the current condition of the Roller Mill, when the current is lower than 80A, add about 3 tons, and the current of the Roller Mill is controlled at 82A~83A.

5, the proportion of supplemental ball: diameter & phi; 50, & phi; 60 specifications range of about 80%, diameter & phi; 30 ~ & phi; 40 specifications range of about 20%.

Lining replacement

The new alloy rare earth wear-resistant lining is based on the carbon material and supplemented by micro-alloying such as heavy rare earth elements. Combined with a specific heat treatment process, carbide granulation and matrix graining are realized to form hard spots with granular carbides. The main fine and uniform diffuse multiphase structure improves the toughness and wear resistance of the material, and exhibits the characteristics of steel with the composition of the carbon material. Its impact toughness & ge; 49J / cm2, hardness can reach 48 ~ 55HRC. By checking the inner liner of the Roller Mill, the drive end lining plate, the non-drive end slant lining plate, and the cylinder lining plate were replaced, and the movable crusher winch blades and the spokes were replaced.

Separator modification

The Roller Mill separator adopts double-inlet and double-out axial baffle separators. The specific transformation plan is as follows:

1. Change the separator to a diameter & phi; 3300 mm axial baffle separator.

2. The upper part of the separator and the middle part of the separator are made of <12mm 16Mn steel plate, and the lower part of the separator is made of δ 10mm 16Mn steel plate.

3. The separator adjustment baffle is made of δ 10mm 16Mn steel plate, the upper and lower regulating baffles of the separator are δ 10mm 16Mn, and the face-faced surface is 100mm wide wear-resistant ceramic piece.

4. Change the powder return tube from a square tube to a diameter of φ 426 & times; 10mm round tube, made of 16Mn steel tube, and install a positive pressure direct blow external embossed weight locker on each powder return tube.

Problem

Ordinary low- and medium-chromium steel balls have poor wear resistance due to the backward casting process and materials. The diameter of the grinding balls is not balanced during the wear process, which causes the gradation of the grinding balls to deviate greatly, meeting the grading requirements. The proportion of grinding balls is reduced, and the proportion of dead balls is increased, resulting in poor fineness of coal powder or reduced production of coal powder.

Diameter & phi; 30 or more grinding balls account for more than 70% of the total weight, resulting in the same weight of the grinding ball, the action point or the area of ​​action is reduced, the grinding efficiency is not high.

The function of the corrugated wire of the Roller Mill cylinder is to better bring the steel ball up, but after long-term operation, the ribs of the lining plate are seriously worn, and the steel ball can not be taken up, which can not effectively move the inside of the Roller Mill. The coal-fired mill is made into qualified coal powder. At the same time, the head of the lining countersunk head bolt is seriously worn, and the powder of the tank lining bolt often leaks during operation. The factors affecting the powder output of the Roller Mill are: the slamming of the steel ball, the grinding between the steel ball and the steel ball and the Roller Mill lining, the drying of the hot air and the carrying of the dry wind. Therefore, in order to improve the powder output of the Roller Mill, it is necessary to improve the wear resistance and hardness of the grinding ball, increase the grinding area per unit weight of the steel ball, optimize the fineness of the coal powder, reduce the loading of the steel ball, and reduce the power consumption of the milling powder. Ball consumption; improve the lifting ability and wear resistance of the lining, and extend the service life of the equipment.

The Roller Mill separator adopts Raymond gravity radial separator, symmetrically arranged at both ends, and equipped with adjustable blades, which can adjust the fineness of coal powder according to requirements. However, there is a disadvantage that the volume is small, the strength is large, and the separator has a large resistance. At the same time, because the raw coal is mixed with straw, cloth strips, iron wire and other sundries, it is wound on the baffle blades when the closely arranged separator is folded toward the baffle plate, and is often blocked on the separator returning powder locker, resulting in separation. The separation effect of the separator is deteriorated or even the separation ability is lost, resulting in poor uniformity of fineness of coal powder, high combustibles of fly ash and high carbon content of large slag.

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