The permanent magnet drum magnetic separator is a key equipment for iron
removal and purification in large-scale quartz sand production lines (daily
processing capacity ≥ 3000t), responsible for removing magnetic impurities such
as Fe ∝ O ₄ and Fe ₂ O ∝ from quartz sand (requiring iron removal efficiency ≥
95% and finished sand iron content ≤ 50ppm), directly determining the
applicability of quartz sand in high-end fields such as electronics and
photovoltaics. If the iron removal efficiency is low (less than 85%) and the
magnetic field strength decays quickly (decays by more than 20% after 6 months
of use), it will lead to substandard quality of the finished sand and hinder
access to the high-end market. Based on the particle size distribution and
magnetic impurity characteristics of quartz sand, summarize a three-step
optimization plan to quickly restore the iron removal performance of the
magnetic separator.
Step 1: Optimize the magnetic field configuration and magnetic system design
to enhance the power of the iron removal core
Poor magnetic material, insufficient magnetic field strength, or unreasonable
magnetic arrangement are the core reasons for low iron removal efficiency, and
targeted optimization and adaptation are needed.
Magnetic material and magnetic field strength adaptation: ordinary ferrite
magnetic steel is selected, with an initial magnetic field strength below
12000Gs, which cannot effectively adsorb fine magnetic impurities; Magnetic
steel has poor high temperature resistance, and the magnetic field attenuation
accelerates when the ambient temperature exceeds 60 ℃. Replace rare earth
neodymium iron boron magnetic steel (initial magnetic field strength
15000-18000Gs), which has a magnetic field strength 1.5-2 times that of ordinary
ferrite and strong temperature stability (can withstand environments below 80
℃); Adjust the number of magnetic layers according to the quartz sand particle
size, and use three layers of magnetic stacking when processing fine sand (40-70
mesh) to enhance the adsorption capacity for fine particle impurities.
Optimization of magnetic system layout and drum protection: The magnetic
system is unevenly arranged along the axial direction of the drum, resulting in
"magnetic field blind spots" and incomplete iron removal in some areas; The
wear-resistant layer on the surface of the drum is worn by more than 2mm, the
magnetic field penetration decreases, and the adsorbed magnetic impurities are
prone to detachment. Adopting a "spiral staggered arrangement" magnetic system
to eliminate magnetic field blind spots and ensure that the axial magnetic field
uniformity deviation of the drum is ≤ 5%; Use polyurethane wear-resistant lining
plate (thickness 5-8mm) to cover the surface of the drum, which not only reduces
quartz sand wear but also ensures magnetic field penetration. Replace the lining
plate in a timely manner when the wear exceeds 1mm.
Step 2: Calibrate the drum speed and separation gap to improve the efficiency
of iron removal and separation
Improper rotation speed of the drum and deviation in the gap between the drum
and the groove can lead to weak adsorption or incomplete separation of magnetic
impurities, requiring precise parameter control.
Optimization of drum speed: When the speed is below 25r/min, magnetic
impurities stay on the drum surface for too long and are easily washed off by
subsequent quartz sand; When the centrifugal force is higher than 40r/min, the
magnetic impurities cannot be firmly adsorbed and are discharged with the sand
flow due to excessive centrifugal force. Stabilize the speed at 30-35r/min
through a frequency converter; According to the dynamic adjustment of quartz
sand feed rate, when the feed rate exceeds 90% of the rated value, the speed is
set at 33-35r/min, and when the feed rate is below 70% of the rated value, it is
set at 30-32r/min to balance adsorption and separation efficiency.
Separation gap and drum balance control: The gap between the drum and the
tank exceeds 15mm, and some fine quartz sand particles carrying magnetic
impurities directly pass through and cannot be adsorbed; Gap less than 5mm, high
flow resistance of quartz sand, easy to accumulate and block; The deviation of
the drum's dynamic balance exceeds 0.5mm, and the vibration intensifies during
operation, affecting the stability of the magnetic field. Use a feeler gauge to
calibrate the gap and control it within 8-12mm; use a dynamic balancing
instrument to calibrate the drum and control the deviation within 0.3mm;
Regularly check the wear of the drum bearings, replace aging bearings, and avoid
magnetic field attenuation caused by operational vibration.
Step 3: Optimize feed control and pretreatment to ensure iron removal
stability
Overloading of feed volume, uneven thickness of material layer, or
insufficient pre-treatment of raw materials can exacerbate fluctuations in iron
removal efficiency, and front-end regulation is necessary.
Control of feed rate and layer thickness: If the feed rate exceeds the rated
value (e.g. rated 300t/h, actual 360t/h), the layer thickness inside the tank
exceeds 80mm, and the magnetic impurities in the bottom quartz sand cannot fully
contact the magnetic field; The feed rate fluctuates by more than 10%, the
thickness of the material layer is uneven, and the iron removal efficiency
fluctuates greatly. Strictly control the amount with an electronic belt scale to
maintain the feed rate at 85% -95% of the rated value; Install a material layer
adjustment plate to stabilize the thickness of the material layer at 40-60mm,
ensuring sufficient interaction between quartz sand and magnetic field.
Raw material pretreatment and optimization of feed uniformity: Large
impurities with a particle size exceeding 5mm are mixed into quartz sand raw
materials, which can easily impact the drum and cause magnetic displacement; The
feeding port is not equipped with a fabric feeder, and the material is
concentrated and impacts the drum locally, resulting in incomplete iron removal
in the area. Install a grid and grading screen in front of the magnetic
separator to remove large impurities; Install a spiral feeder to evenly
distribute materials along the axial direction of the drum, avoiding local
overload; Pre wet the quartz sand before feeding (with a moisture content
controlled at 8% -12%) to reduce the interference of dust flying on the magnetic
field.
Daily maintenance should pay attention to: checking the magnetic field
strength, iron removal efficiency, and finished sand iron content every day;
Clean the non-magnetic impurities adsorbed on the surface of the drum every week
and check the stability of the rotation speed; Monthly calibration of separation
gap and inspection of magnetic system fixation status; Conduct comprehensive
inspections of magnetic steel every quarter, and supplement or replace magnetic
systems in areas where magnetic field attenuation exceeds 10%. By implementing
the above measures, the iron removal efficiency can be increased to over 96%,
and the magnetic field strength attenuation rate can be controlled within 8% per
year, ensuring stable iron removal and purification effects in large-scale
quartz sand production lines. If there are still problems, it is recommended to
contact the manufacturer to optimize the magnetic system design and equipment
parameters based on the characteristics of quartz sand.