The ball mill is the core equipment for ultrafine grinding of quartz sand. If
the grinding efficiency is low (the output per unit time is less than 60% of the
rated value) and the particle size of the finished product does not meet the
standard (such as requiring a 200 mesh pass rate of 95%, but only 80% in
reality), it will drag down the subsequent purification process and increase
production costs. Based on years of operation and maintenance experience,
summarize a three-step troubleshooting method to quickly restore device
performance.
Step 1: Check the grinding medium and liner - the core components determine
the grinding effect
The compatibility and wear state between the grinding steel ball and the
lining plate are key.
Improper steel ball ratio or wear: If the proportion of large balls is too
high (over 60%), the grinding impact force is strong but the fine grinding is
insufficient; The proportion of small balls is too high (over 50%), the impact
force is weak, and coarse particles are difficult to grind. The recommended
ratio for grinding quartz sand is "30% for large balls (Φ 100mm), 40% for medium
balls (Φ 80mm), and 30% for small balls (Φ 60mm)". When the wear of the steel
ball exceeds 15% of its original diameter, it is necessary to promptly replenish
new balls to maintain a stable total amount and ratio.
Lining wear or material error: Lining wear exceeding 1/3 of the original
thickness will reduce the grinding impact force; Using ordinary manganese steel
lining plate with grinding stone and quartz sand (Mohs 7 grade) is prone to
rapid wear. It is necessary to replace the high chromium alloy lining plate
(with wear resistance three times higher than manganese steel). During
installation, ensure that the lining plate is in contact with the cylinder wall,
and tighten the bolts with a torque of 250-300N · m to avoid shaking during
operation.
Step 2: Calibrate operating parameters - parameter deviation slows down
efficiency
Improper settings of ball loading rate, rotation speed, and feed rate
directly affect the grinding effect.
Excessive or insufficient ball loading rate: over 45%, small space for steel
ball movement, low collision efficiency; Less than 30%, insufficient grinding
impact force. The recommended ball loading rate for quartz sand grinding is 35%
-40%, which should be calibrated regularly through weighing method to ensure a
deviation of ≤ 2%.
The speed is too fast or too slow: the supercritical speed is 80% (such as
the critical speed of a Φ 2.2m ball mill of 22r/min, exceeding 17.6r/min), and
the steel ball slides against the cylinder wall without impact grinding; Below
60% (13.2r/min), the steel ball has a low drop height and weak impact force.
Adjust to the critical speed of 65% -75%, and use a frequency converter for
precise control, balancing impact and grinding efficiency.
Overloading or uneven feeding rate: exceeding the rated processing capacity
(such as 20t/h, actual 25t/h), material accumulation in the cylinder, and
insufficient collision of steel balls; The feed fluctuates, the grinding load
fluctuates, and the particle size is uneven. Use an electronic belt scale to
control the quantity and maintain it at 80% -90% of the rated value. Install a
steady flow feeder to ensure that the material enters evenly.
Step 3: Adaptation of materials and daily maintenance - raw material
issues+maintenance deficiencies exacerbate malfunctions
Inadequate material characteristics and maintenance can accelerate equipment
wear and tear.
The initial particle size of the material is large or the moisture content is
high: when the feed particle size exceeds 2mm, the grinding load suddenly
increases; If the moisture content exceeds 8%, the material is prone to adhere
to the cylinder wall, forming "clumps" and insufficient grinding. A fine
crushing process should be added before feeding to reduce the particle size to
below 1mm; When the moisture content is high, add a drying process and control
it to below 5% to avoid adhesion.
Maintenance deficiency: The lack of oil in the main bearing causes operation
to stall, and the wear of the transmission gear leads to unstable speed. Check
the bearing temperature daily (≤ 70 ℃) and add 3 # lithium based grease every
week; Check the gear mesh clearance monthly (maintain 0.2-0.3mm), and replace it
when the wear exceeds 0.5mm; Clean the residual materials in the cylinder every
quarter and check the wear of the lining plate and steel ball.
By following the above three steps, the grinding efficiency of the ball mill
can be improved by more than 25%, and the final particle size pass rate can be
stabilized at over 95%. If there are still problems, it is recommended to
contact the manufacturer to test the compatibility of the equipment and ensure
that it matches the requirements for ultrafine grinding of quartz sand.