The permanent magnet drum magnetic separator is a key equipment for feldspar
beneficiation and purification. Its core function is to remove magnetic
impurities such as Fe ₂ O3 and Fe Ⅲ O ₄ from the raw materials (with a required
Fe ₂ O3 content of ≤ 0.1% in the finished product), which directly affects the
whiteness of feldspar and the quality of subsequent ceramic and glass products.
If the iron removal is not thorough (iron content exceeds 0.2%) and the magnetic
field strength decays quickly (decays by more than 20% after 3 months of use),
it will lead to product degradation and raw material waste. Based on the
characteristics of medium hardness and large fluctuations in mud content of
feldspar, a three-step investigation method is summarized to quickly restore the
iron removal performance of equipment.
Step 1: Optimize the magnetic structure and protection - the core components
determine the iron removal effect
Improper magnetic material, arrangement, and protective measures are the main
causes of iron deficiency and magnetic field attenuation.
Poor adaptability or disordered arrangement of magnetic materials: Ordinary
ferrite magnetic materials have low magnetic field strength (surface magnetic
field ≤ 8000Gs), making it difficult to remove weak magnetic impurities; If the
neodymium iron boron magnetic system is not treated with anti-corrosion, it is
easily corroded by feldspar slurry, leading to rapid decay of the magnetic
field; The magnetic blocks are not arranged tightly in an alternating N-S
pattern, resulting in insufficient magnetic field gradient and weak adsorption
of impurities. Suggest replacing the N38 or higher grade neodymium iron boron
magnetic system (surface magnetic field ≥ 12000Gs), controlling the gap between
magnetic blocks at 2-3mm, and using a stainless steel shell for corrosion
protection; Install magnetic fixing devices to prevent magnetic block
displacement during operation and ensure uniform magnetic field coverage.
Wear or deviation of drum shell: The stainless steel shell of the drum is
worn by more than 2mm, and the magnetic field penetration force decreases by
more than 30%; Deviation exceeding 1mm, insufficient contact between feldspar
and magnetic field, and local iron removal omission. Replace the 304 stainless
steel shell (thickness ≥ 5mm) and calibrate it with a laser leveling instrument
during installation to ensure that the parallelism deviation between the drum
and the hopper is ≤ 0.5mm. Install an anti deviation retaining ring and
regularly check the clearance between the drum bearings to avoid shaking during
operation.
Step 2: Calibrate operating parameters and feed control - parameter matching
for iron removal efficiency
Improper settings of drum speed, feed rate, and slurry parameters can
exacerbate iron removal issues.
The drum speed is too fast or too slow: when the speed exceeds 35r/min,
magnetic impurities stay on the drum surface for less than 2 seconds and are not
completely adsorbed before falling off; Below 20r/min, the material accumulates
on the surface of the drum, and the magnetic field cannot penetrate the bottom
material. Use a tachometer to detect and adjust to 25-30r/min, and achieve
stepless speed regulation through a frequency converter; High speed (28-30r/min)
is selected for fine-grained feldspar (<1mm), and low speed (25-28r/min) is
selected for coarse-grained feldspar (1-3mm), balancing adsorption efficiency
and processing capacity.
Overload of feed volume or abnormal slurry concentration: feed volume exceeds
the rated value (such as rated 40t/h, actual 50t/h), material layer thickness
exceeds 10mm, and the bottom feldspar cannot be magnetized; If the slurry
concentration is below 25%, the material is excessively dispersed, and magnetic
impurities are easily lost with the slurry; Above 40%, the viscosity of the
slurry is high, and the resistance to impurity adsorption increases. Use an
electronic belt scale to control the measurement and maintain it at 80% -90% of
the rated value; Adjust the slurry concentration to 30% -35% by adding a water
valve, and install a stirring device (with a speed of 150r/min) to avoid
material settling.
Step 3: Adapting to the characteristics of feldspar and pre-processing -
avoiding magnetic field attenuation at the source
The mud content, impurity types, and insufficient pretreatment of feldspar
can affect the stability of iron removal and accelerate magnetic field
attenuation.
High mud content or mixed with hard materials: if the mud content exceeds
15%, the mud powder will envelop magnetic impurities, hindering magnetic field
adsorption; Mixing metal blocks, granite and other hard objects (hardness>7
levels) can impact the drum shell and indirectly damage the internal magnetic
system. Before magnetic separation, a pre washing process is added to rinse the
feldspar with a high-pressure water gun to reduce the mud content to below 8%;
Install a grille (aperture ≤ 5mm) and iron removal device to remove hard objects
and large magnetic impurities in advance, reducing equipment impact.
Inappropriate pH value of slurry or insufficient cleaning of magnetic system:
If the pH value of slurry is below 6, acidic environment will corrode the outer
shell of magnetic system; Above 10, it is easy to form hydroxide precipitation,
covering the surface of the magnetic system and shielding the magnetic field;
Excessive dust accumulation or adsorption of iron filings on the surface of the
magnetic system can cause local attenuation of the magnetic field. Add lime milk
to the slurry and adjust the pH value to 7-8; Clean the iron filings and dust on
the surface of the drum with a brush every day, and blow the magnetic protective
shell with a high-pressure air gun (0.4MPa) every week to avoid the accumulation
of impurities.
Daily maintenance should pay attention to: checking the magnetic field
strength every week (using a Gaussian meter to detect, and promptly handling
when the surface magnetic field is below 9000Gs), and tightening the drum drive
bolts; Calibrate the rotational speed and feed rate monthly, and check the
sealing of the magnetic system packaging; Replace worn bearings every quarter
and conduct a comprehensive inspection of the magnetic system. By implementing
the above measures, the iron content of feldspar can be reduced to below 0.08%,
and the monthly attenuation rate of the magnetic field can be controlled within
1%, ensuring stable quality of the finished product. If there are still
problems, it is recommended to contact the manufacturer to optimize the magnetic
system arrangement and match the specific iron removal requirements of
feldspar.