The type and specification of the concentrator of the A thickener is generally determined according to the nature of the material being processed, the production and construction conditions, and the relevant technical data provided by the experimental study. In foreign countries, the manufacturer calculates and selects based on the information provided by the user, and then recommends it to the user. In China, it is selected by the user or the design unit. For large scale production beneficiation plant, in the case of conditions should be used a large concentrator. Foreign data shows that the use of large diameter thickener can save about 25% of reinforced concrete, saving construction costs by about 50%.
a Peripheral drive concentrator The peripheral drive concentrator that supports the truss with reinforced truss, the truss and the steel truss support are combined as a whole, with good rigidity and high strength. However, the truss structure is higher than the water surface during the working process, and has a stirring action on the clear layer, which is not conducive to the sedimentation of the fine particle material and affects the water quality of the overflow. The truss is a peripheral drive concentrator with a cantilever structure. The technical requirements for the surrounding track are not strict. The truss operation has less influence on the settlement layer and the overflow water quality is better.
b Center drive concentrator for large central drive concentrator support (using hydrostatic bearings) The central drive concentrator has very low frictional resistance and high effective transmission torque; the central drive concentrator with precision ball bearings can prevent load Damage to the arm and drive when it is too large. Used to process iron, copper ore dressing products.
The large caisson center column concentrator adopts a hollow column foundation structure, which can accommodate discharge materials, electronic control, process pipe network and auxiliary facilities, and provide a space space for equipment operation and maintenance. The underflow of the equipment is piped from the hollow column to the subsequent operation point through the bridge, which can save the construction cost of the underground passage and the pump house. The underflow of this type of concentrating tank is discharged in parallel by a multistage pump. When the peak load occurs, the sand pump can handle it by itself until the concentration of the slurry in the collecting trench around the center is reduced to a normal value. This method of discharging can make the pulp have a higher line speed and prevent the discharge port from being blocked. If a short circuit occurs in the discharge, the underflow concentration becomes lean and the suction head of the pump increases. In production, we should try to prevent short circuit in mine discharge. The pipeline installation cost of this type of thickener is high, the suction pipe of the pump is easy to block, and the maintenance is difficult. However, the structure is simple, the operation is convenient, the transmitted torque is large, and the operation is stable and reliable.
The cable-type center drive concentrator has a diameter of 12 meters to 75 meters. The steel rope can automatically adjust the load of the rafter to measure the load inside the concentrator. Under uniform load conditions, the concentrator can obtain the best working condition by input data processing. The machine is suitable for dewatering operations with volatility and intermittent loads. The automatic compensation of the position of the dice can prevent unbalanced load in the pool, so the ore concentration is uniform, and the torque can be adjusted by itself to ensure the normal operation of the equipment.
The multi-layer central transmission machine has a simple structure, small floor space, low power consumption and low capital construction cost. This type of thickener should be used when the industrial site is tight and sufficient settlement area is required. The device delivers less torque and a smaller diameter and is suitable for use in small and medium sized concentrateries.
The feedstock of the high-efficiency concentrator (the sloping plate can also be installed in the tank) needs to be added with flocculant, and after being stirred, it is sent to the sedimentation part of the concentrator. The machine has a small footprint and high concentration efficiency. It is suitable for processing fine-grained materials and materials that must be dehydrated indoors. It is also suitable for the expansion of production capacity of old factories.
Calculation of B-type concentrator In order to determine the area, structural size and number of concentrators operating under certain conditions, the technical calculation of the concentrator must be performed. Since the precipitation process of the ore particles is very complicated in the continuous operation of the rake concentrator, there is no accurate calculation method. Some foreign companies design concentrators based on experience and different research methods, such as simulation, graphic method, initial settling velocity method, and empirical quota method.
At present, China's concentrator calculation is based on the production capacity of the unit's concentrated area and the sedimentation speed of the slurry in the static sedimentation test to determine the required effective settlement area, the size of the concentrator and the number of units. The production practice of China's concentrator shows that in the current situation, the more realistic calculation method should be determined through the settlement test and referring to the actual production data of similar mines. The overflow water quality requirements should be considered while meeting the underflow concentration requirements. When ferrous metals used in mines by water, the required solids content of less than 0.5% in the overflow, nonferrous metal mines should be a minimum of loss of metal. [next]
The production capacity per unit area of ​​the concentrator is related to the particle size, density, concentration of feed and underflow, slurry composition, foam viscosity, slurry temperature and material value of the treated material particles or flocs. The production capacity per unit area is generally determined according to semi-industrial test or static sedimentation test. In the absence of test conditions, it can be determined by reference to the production index of similar factories and mines.
a Concentrated area calculation The following methods can be used to calculate the concentrated area:
(1) Calculating the concentrator area using semi-industrial tests or production quota indicators can be calculated using the following empirical formula:
Where A———the total effective area of ​​the thickener, m 2 ;
q————The weight of the solid material treated per unit area of ​​the concentrator under the condition of meeting the requirements of overflow water quality,
t / (m 2 · d), this value is determined by experiment.
W—the weight of solids in the feed, t/d;
K———The coefficient of fluctuation of the slurry. Generally, for the industrial test, k=1, for the simulation test, k=1.05～1.20; when the ore sample is representative, the quantity and properties of the ore are stable, and the larger diameter concentrator can be used to take a small value, and vice versa. .
(2) Calculate the concentrator area according to the static settlement test or simulation test data:
A=KQ 0 c 0 a max (2)
Or A=KWa max (3)
Where A - the total area of ​​the required thickener, m 2 ;
K———coefficient, take 1.05～1.2, the principle of value is the same as formula 1;
Q 0 ———The amount of slurry fed into the design, m 3 /d;
C 0 ———The unit volume of the designed ore is solid weight, t/m 3 ;
a max ——— the maximum settlement area required to concentrate each ton of solid material, m 2 (t · d -1 ) is determined by experiment;
W———The weight of solids fed into the thickener, t/d.
(3) In the absence of test data and no actual empirical data, the settlement speed of the solid material can be approximated according to the Stokes formula, and then the area of ​​the concentrator is approximated by the following formula:
In the formula A———the area of ​​the thickener, m 2 ;
W———the weight of solids fed into the thickener, t/d;
R 1 , R 2 ——— the liquid-solid ratio of the slurry before and after concentration;
K 1 ———The effective area coefficient of the thickener is generally 0.85～0.95; the concentrator above ф12m takes a large value;
K———The fluctuation coefficient of the ore, depending on the grade of the ore. When the diameter of the thickener is less than 5m, take 1.5, and when it is larger than 30m, take 1.2;
υ 0 ———The free settling velocity of the largest particle in the overflow in water, mm/s.
The settling velocity can also be approximated by the 4 formula:
υ 0 = 545(δ-1)d 2 (5)
δ———solid material density, g/cm 3 ;
υ 0 ———The free settling velocity of the largest particle in the overflow in water, mm/s;
D --- overflow solids maximum diameter, mm, a maximum particle size of the concentrate overflow generally take 5 m, when the concentrated coal sludge, a maximum should not exceed 30 ~ 50μm. [next]
For flocculation settling, υ 0 can only be determined by experiment. The calculation of A value should be selected within the entire concentration range between feed and underflow, with the maximum value being the cross-sectional area of ​​the settling tank. The area of ​​the concentrator must ensure that the slowest settled particles in the slurry have sufficient residence time to settle to the bottom of the tank. Therefore, the concentrator overflow velocity υ (or rising water flow velocity) must be less than the sedimentation velocity of the largest particle in the overflow. The area of ​​the selected concentrator shall be checked by (6) and shall be maintained at υ<υ 0. The overflow velocity is calculated as follows:
Where υ——— rising water flow velocity, mm/s;
A———the area of ​​the thickener, m 2 ;
V———The overflow of the thickener, m 3 /s.
b Concentrator depth calculation The depth of the 浓缩 concentrator determines the residence time of the slurry in the compression layer. In order to ensure the discharge concentration of the underflow, the slurry must have sufficient residence time in the concentrator. Therefore, the concentrator should have a certain height, namely:
H=h c +h p +h Y (7)
Where H—the total height required for the concentrator, m;
h c ———the height of the clarification zone, 0.5～0.8m;
h p ———the height of the arm movement zone, m; can be calculated by:
D———the bottom diameter of the thickener, m;
A—the bottom horizontal inclination, usually a=12°;
h Y ———The height of the compression zone, m; can be calculated by the following formula:
Where t—the time required for the slurry to concentrate to the specified concentration (measured), h;
δ———mineral density, g/cm 3 ;
a max —- clarify the maximum clarification area required for a ton of thousand ore, m 2 /(t · d -1 );
R c ——— The average liquid to solid ratio of the slurry in the compression zone can be calculated as the average of the liquid to solid ratio and the liquid to solid ratio (both measured) of the slurry at the critical point.
When China's concentrator uses a domestic serial concentrator, its structural size has been fixed. When using this type of standard concentrator, the height h Y of the compression zone should meet the following requirements:
h Y ≤H-(h c +h p ) (10)
When the calculated hY does not meet the requirements of equation (10), the area of ​​the thickener should be increased.
c Concentrator diameter calculation:
Where D———concentrator diameter, m;
A———The cross-sectional area of ​​the thickener, m 2 .
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