The vortex type powder selector is the core equipment for ultrafine powder
classification in large-scale quartz sand production lines (daily processing
capacity ≥ 3000t), especially suitable for the fine classification requirements
of photovoltaic and electronic grade quartz sand (particle size ≤ 45 μ m, i.e.
325 mesh) (requiring powder selection accuracy deviation ≤ 4%, 325 mesh fine
powder recovery rate ≥ 90%), directly determining the purity, gradation
stability, and high-end application adaptability of the finished powder. If
there is poor powder selection accuracy (deviation exceeding 10%) and low fine
powder recovery rate (less than 75%), it will lead to disorder of finished
product grading, waste of raw materials, and significantly increase production
costs. Based on the lightweight and highly dispersed characteristics of
ultrafine quartz sand powder, a three-step optimization plan is summarized to
comprehensively improve the operational performance of the powder selection
machine.
Step 1: Optimize the airflow system configuration and build a solid
foundation for the core power of powder selection
The core reason for poor powder selection accuracy is the imbalance of
airflow velocity, fluctuation of air volume, or uneven distribution of airflow,
which requires targeted adaptation to the requirements of ultrafine powder
classification.
Accurate control of airflow parameters: ordinary centrifugal fans are used,
with air pressure below 8kPa, which cannot effectively classify ultrafine
powder; When the airflow velocity is below 12m/s, fine powder is prone to
settling and accumulating; Above 18m/s, qualified fine powder is prone to
excessive separation. Replace the high-pressure centrifugal fan (with a wind
pressure of 10-12kPa) and equip it with a variable frequency speed control
system to stabilize the airflow velocity at 14-16m/s; Adjust the air volume
according to the standard of "1000-1200m ³ per ton of ultra-fine powder", and
dynamically adjust it based on the target particle size. When grading 325 mesh
fine powder, set the upper limit of air volume, and when grading 200 mesh medium
powder, set the lower limit to ensure air flow stability.
Optimization of airflow distribution and steady flow: A single air inlet
leads to airflow deviation, resulting in a "classification dead angle" in the
powder selection chamber; The deviation of the guide vane angle exceeds 3 °, and
the airflow trajectory is disordered. Install a circular homogenizer to evenly
distribute the airflow along the circumference of the powder selection chamber;
Calibrate the angle of the guide vanes to 18-22 ° and optimize the airflow
rotation trajectory; Install an airflow stabilizer in the inlet duct to reduce
the fluctuation of air volume (controlled within 5%) and ensure a stable powder
selection environment.
Step 2: Calibrate the rotor structure parameters to improve the precision
separation ability of powder selection
Improper rotor speed, blade wear, or poor sealing can cause fluctuations in
the powder selection effect, requiring precise regulation and maintenance.
Optimization of rotor speed and blades: When the speed is below 2500r/min, it
cannot effectively cut fine powder, and coarse powder is mixed into the finished
product; Above 3500r/min, the centrifugal force is too high, and the qualified
fine powder is misjudged as coarse powder and discharged; The blade wear exceeds
2mm, and the efficiency of airflow cutting decreases. Stabilize the speed at
2800-3200r/min through a frequency conversion system, with the upper limit set
for ultrafine powder classification and the lower limit set for medium powder
classification; Replace the high hardness wear-resistant steel blades, and
ensure that the end face runout deviation after blade installation is ≤ 0.2mm to
ensure even airflow cutting.
Sealing and leak prevention optimization: The aging of the powder chamber
seal and the infiltration rate of external air exceeding 8% can disrupt the
stability of the airflow; The rotor shaft seal is poor, and dust enters the
bearing, causing it to jam. Replace the fluororubber seal and install a sealing
pressure ring to control the air infiltration rate within 3%; Adopting a dual
protection structure of "labyrinth seal+oil seal", the sealing performance of
the rotor shaft is improved, and the sealing status is regularly checked to
avoid dust intrusion.
Step 3: Optimize feed control and pretreatment to ensure continuous stability
of powder selection
Overloading of feed volume, powder agglomeration, or insufficient
pretreatment can exacerbate fluctuations in powder selection efficiency,
requiring effective front-end control.
Optimization of feeding quantity and feeding method: The feeding quantity
exceeds the rated value (such as rated 120t/h, actual 150t/h), the powder
concentration in the powder selection chamber is too high, and the airflow
cannot penetrate; The lack of a dispersing device at the feed inlet resulted in
incomplete classification due to powder agglomeration. Use electronic belt
scales and variable frequency feeders to accurately control the amount of
material, maintaining the feed rate at 85% -95% of the rated value; Install an
electromagnetic vibration disperser, combined with high-pressure airflow pre
dispersion, to control the powder agglomeration rate below 5%, ensuring that the
powder enters the powder selection chamber uniformly.
Raw material pretreatment and impurity control: Raw materials with a moisture
content exceeding 0.5% are prone to powder agglomeration; Mixing coarse
particles with a diameter exceeding 1mm can easily impact the rotor blades and
cause damage. Add a low-temperature drying process before feeding to control the
moisture content of the raw materials below 0.3%; Install a high-precision pre
screening machine (with a mesh size of 100) before the powder selection machine
to remove coarse particles and impurities; Equipped with a pulse bag filter to
purify the dust generated during the powder selection process and improve the
safety of the production environment.
Daily maintenance should pay attention to: checking the airflow speed, powder
selection accuracy, and fine powder recovery rate every day; Clean the residual
dust in the powder selection chamber every week and check the integrity of the
sealing components; Monthly calibration of rotor speed and airflow parameters,
and inspection of blade wear; Conduct comprehensive maintenance on fans and dust
collectors every quarter. By implementing the above measures, the accuracy
deviation of powder selection can be stabilized within 3%, and the recovery rate
of 325 mesh fine powder can be increased to over 92%, ensuring that the quality
of photovoltaic/electronic grade quartz sand meets the standards and is suitable
for the ultrafine grading needs of large-scale production lines.