The energy-saving ball mill is the core equipment for ultrafine grinding in
large-scale quartz sand production lines (daily processing capacity ≥ 3000t),
responsible for grinding the crushed quartz sand raw materials (particle size ≤
5mm) to a fine powder of 0.074-0.4mm (required 200 mesh pass rate ≥ 95%,
photovoltaic grade product iron pollution ≤ 50ppm), directly determining the
purity and grading quality of the finished sand. If the grinding efficiency is
low (below 60% of the rated output) and the particle size of the finished
product is uneven (with a pass rate deviation of more than 10%), it will drag
down the subsequent purification process, increase production costs, and even
affect high-end market access. Based on the high hardness characteristics of
quartz sand, summarize a three-step optimization plan to improve grinding
efficiency and accuracy.
Step 1: Optimize the ratio of grinding media and strengthen the core grinding
power
Improper ratio, severe wear or material mismatch of grinding steel balls are
the core reasons for low grinding efficiency, and it is necessary to adapt to
the specific needs of quartz sand grinding.
Optimization of steel ball grading and ball loading rate: A single
specification of steel ball cannot balance coarse and fine grinding. If the
proportion of large balls is too high (over 60%), there will be insufficient
fine grinding, and if the proportion of small balls is too high (over 50%),
coarse particles will be difficult to break. It is recommended to use a
scientific ratio of 30% for large balls (Φ 100mm), 40% for medium balls (Φ
80mm), and 30% for small balls (Φ 60mm); The ball loading rate should be
controlled at 35% -40%. If it is too high, it will limit the movement space of
the steel ball, and if it is too low, the grinding impact force will be
insufficient. Regular calibration should be carried out through weighing method
to ensure that the deviation is ≤ 2%. When the wear of the steel ball exceeds
15% of the original diameter, timely supplement with new balls of corresponding
specifications to maintain a stable ratio.
Adaptation of grinding medium and lining material: Ordinary manganese steel
lining has poor wear resistance and is prone to rapid wear when facing Mohs
grade 7 quartz sand; Traditional steel balls are prone to iron pollution, which
affects the quality of high-purity quartz sand. Replace the high chromium alloy
lining plate (with wear resistance three times that of manganese steel), and use
silica ceramic lining plate for high-purity quartz sand production to reduce
iron pollution; The grinding medium uses high chromium steel balls, which can be
replaced with silicon nitride composite balls for high-end demand. The annual
wear rate is ≤ 8%, and the iron pollution is extremely low.
Step 2: Calibrate the structural parameters of the cylinder to improve the
uniformity of grinding
Improper rotation speed of the cylinder, wear of the lining plate structure,
or failure of the compartment plate can cause fluctuations in the grinding
effect, requiring precise control and maintenance.
Optimization of cylinder speed and lining plate: When the speed exceeds the
critical speed of 80%, the steel ball slides against the wall without impact
grinding; When the drop height of the steel ball is below 60%, the impact force
is weak. Stabilize the speed at 65% -75% of the critical speed through a
frequency conversion system, balancing impact and grinding efficiency; When the
wear of the lining plate exceeds 1/3 of the original thickness, the grinding
force drops sharply and needs to be replaced in a timely manner. During
installation, ensure a tight fit with the cylinder wall and tighten the bolts
with a torque of 250-300N · m to avoid shaking during operation.
Optimization of partition plate and ventilation system: If the grate holes of
the partition plate are blocked by more than 30%, it will cause poor material
circulation and prolonged grinding cycle; Poor ventilation leads to the
retention of humid and hot gases, and materials are prone to adhere to the
cylinder wall and form clumps. Regularly clean the grate holes of the
compartment board to ensure unobstructed aperture; Install high-efficiency
ventilation devices, paired with pulse dust collectors, to accelerate the
discharge of humid and hot gases, while reducing dust pollution and improving
grinding efficiency.
Step 3: Optimize feed control and intelligent adaptation to ensure grinding
stability
Overloading of feed volume, insufficient pretreatment, or lagging regulation
can exacerbate fluctuations in grinding efficiency, requiring effective
front-end control and intelligent regulation.
Optimization of feed quantity and pretreatment: If the feed quantity exceeds
the rated value by more than 10%, the accumulation of materials in the cylinder
will prevent the steel balls from fully colliding; If the feed particle size
exceeds 5mm or the moisture content exceeds 8%, it will significantly increase
the grinding load. Use an electronic belt scale and a steady flow feeder to
accurately control the amount of material, maintaining the feed rate at 80% -90%
of the rated value; Before feeding, the particle size is reduced to below 1mm
through a fine crushing process. When the moisture content is high, a pre drying
process is added to control the moisture content to ≤ 5% and avoid material
bonding.
Intelligent regulation and impurity control: Traditional manual regulation
lags behind and cannot adapt to material characteristic fluctuations. Install
online particle size monitoring and grinding sound sensors to provide real-time
feedback on grinding status, dynamically adjust speed and feed rate; Install
magnetic separation equipment at the feeding end to remove iron impurities and
avoid abnormal wear of the grinding medium; The production of high-purity quartz
sand requires anti iron pollution treatment inside the cylinder to ensure that
the iron content of the finished product meets the standard.
Daily maintenance should pay attention to: checking the bearing temperature
(≤ 70 ℃), grinding efficiency, and finished product particle size every day;
Clean the residual materials in the compartment board and cylinder every week,
and add 3 # lithium based grease; Calibrate the steel ball ratio and loading
rate monthly, and check the wear of the lining plate; Conduct comprehensive
maintenance on transmission gears and motors every quarter. By taking the above
measures, the grinding efficiency can be improved by more than 25%, and the 200
mesh pass rate can be stabilized at over 95%, which is suitable for the fine
grinding needs of large-scale quartz sand production lines.