The spiral classifier is a key grading equipment for feldspar beneficiation,
responsible for separating fine mud and qualified sand particles in feldspar ore
(with a requirement of -200 mesh fine particle content ≤ 8% in settling sand),
providing high-quality raw materials for subsequent flotation purification. If
the grading efficiency is low (processing capacity below 60% of the rated value)
and the sand is severely mixed with fine particles (fine particle content
exceeding 15%), it will lead to increased consumption of flotation reagents and
substandard whiteness of the finished product. Based on the characteristics of
medium hardness and high mud content of feldspar, a three-step investigation
method is summarized to quickly restore the grading performance.
Step 1: Optimize the spiral structure and grading groove - the core
components determine the separation effect
Improper design of spiral blades and grading grooves is the main cause of
poor grading.
Inappropriate blade pitch or rotation speed: If the pitch is too large (over
300mm), the pushing sand settling speed will be fast, and fine particles will be
carried out before they have fully settled; When the speed exceeds 25r/min, the
water flow in the tank becomes turbulent and the fine mud cannot effectively
overflow. Adjust according to the grain size of feldspar: process 1-5mm
feldspar, select 200-250mm pitch blades, control the speed at 18-20r/min, and
ensure that the settling time is ≥ 15 minutes; Replace wear-resistant rubber
blades (thickness 15mm) to reduce wear on feldspar particles.
Abnormal inclination angle or overflow weir height: inclination angle
exceeding 18 °, fast water flow velocity, insufficient settling of fine
particles; The overflow weir is too low, and the sediment is easily lost with
the overflow; If it is too high, fine mud will remain in the groove. Adjust the
inclination angle of the grading groove to 12 ° -15 ° and calibrate it with a
protractor; Adjust the height of the overflow weir to 2/3 of the depth of the
tank, install an overflow baffle, and control the overflow flow rate to be
stable at 30% -40% of the processing capacity.
Step 2: Calibrate hydraulic parameters and feed control - parameter matching
improves efficiency
Improper slurry concentration and feeding amount can exacerbate grading
problems.
High or low slurry concentration: when the concentration exceeds 35%, the
slurry viscosity is high and the settling of fine mud is hindered; Below 20%,
the processing capacity decreases and energy consumption increases. By adjusting
the water valve, the slurry concentration is controlled at 25% -30%, and an
online concentration detector is installed to provide real-time feedback data;
Install a stirring device (with a speed of 100r/min) at the feed inlet to
prevent feldspar particles from settling and clumping.
Overloading or uneven feeding amount: exceeding the rated processing capacity
(such as rated 50t/h, actual 60t/h), material accumulation in the grading tank;
The feeding varies greatly, and the overflow concentration fluctuates greatly.
Use an electronic belt scale to control the measurement and maintain it at 80%
-90% of the rated value; Install a stabilizing box to evenly distribute the
slurry into the grading tank, avoiding grading imbalance caused by local
overload.
Step 3: Adapting to the characteristics of feldspar and pre-processing -
avoiding faults at the source
The mud content, particle morphology, and insufficient pretreatment of
feldspar can affect the stability of classification.
High mud content or more angular particles: with mud content exceeding 12%,
fine mud adheres to the surface of feldspar and is difficult to separate;
Angular feldspar is prone to mutual obstruction and uneven settling speed.
Before grading, a pre washing process is added to rinse the feldspar with a
high-pressure water gun to reduce the mud content to below 8%; If the mud
content is severe, install an ultrasonic cleaning device (with a power of 800W)
to remove the mud film wrapping.
Inappropriate pH value of slurry: Before feldspar flotation, the pH value
needs to be adjusted to 8-10. If it directly enters the classifier, alkaline
slurry is prone to cause fine mud to agglomerate. Add dispersant (0.05% sodium
hexametaphosphate) into the grading tank to disrupt the coagulation of fine mud;
Adjust the pH value after grading to avoid the influence of chemicals on the
grading effect.
Daily maintenance should pay attention to cleaning the coarse particles that
settle at the bottom of the grading tank and checking the wear of the blades;
Calibrate the spiral speed and slurry concentration weekly, and tighten the
bolts of the spiral shaft coupling; Clean up the debris in the overflow weir
every month and inspect the grading groove lining plate (replace it when the
wear exceeds 10mm). By implementing the above measures, the classification
efficiency can be improved by more than 25%, and the fine sand content can be
reduced to less than 6%, providing high-quality raw materials for the feldspar
flotation process. If there are still problems, it is recommended to contact the
manufacturer to optimize the compatibility between the spiral and the grading
groove, matching the specific characteristics of feldspar ore.