RU2091165C1 - Peripherally dischargeable wet mill for milling ore on self-grinding principle - Google Patents

Abstract

FIELD: mining industry; beneficiation of economic minerals; gold extracting industry; pre-treatment of any ores for beneficiation. SUBSTANCE: proposed mill comprises drum shell made in form of horizontally arranged truncated cone, generatrix of which forms inclination angle up to 6 deg. in relation to horizon. Shell further comprises grate-protected ports equidistantly spaced all over side surface of shell near truncated cone base, and axial- end cover made conical with conicity angle 150-170 deg. Mill is charged through axial-end cover. For this purpose, latter is provided with charging pipe having inner diameter equal to (0.3-0.4) D of mill diameter, and with hollow trunnion resting on 6-8 supporting rollers used as bearings. Finally, mill shell comprises another axial-end cover arranged at discharging end and made conical with conicity angle 160-180 deg. This discharging-end cover is provided with inner, central deflecting ring and blind cantilevered trunnion resting on 6-8 supporting rollers acting as bearings. Proposed peripherally dischargeable wet mill offers number of advantages, viz.: fuller disintegration of clay, more effective breaking of rock, greater selectivity of grinding, increased discharge rate of milled product, reduced slime formation, greater adaptability to mass production during mass-scale fabrication. EFFECT: increased yield; lower electric energy consumption; savings on metal during manufacture. 3 cl, 7 dwg, 3 tbl

Description

 The invention relates to mineral processing, in particular to the design of wet ore self-grinding mills, in which grinding is carried out by large and medium pieces of the original ore, and can be used in the gold mining industry and in the preparation of any ore for processing.

Known mill wet ore self-grinding ores of ferrous and non-ferrous metals, including a drum with loading and unloading devices and a collection of the finished product. The unloading device is a grill mounted vertically on the front side of the drum rotating around the horizontal axis [1]
The disadvantage of this mill is that when the ore is ground in it, the valuable component and ore material are regrind due to the excessive length of stay of the ground material in the drum mill. Therefore, there is an excessive overspending of electricity. At the same time, there are difficulties in adjusting the water regime and ensuring optimal ore treatment conditions.

 All this causes a decrease in the efficiency, productivity of equipment and the quality of the finished product when grinding ore raw materials and excessive energy consumption for regrinding of the finished product by size.

Known ore self-grinding mill, including a drum with loading m unloading devices and a collection of finished by size of the crushed product. Here, the unloading device is a three-tier grate installed on the front side of the drum, the inner tier of which with a diameter of (0.4 0.8) D from the diameter of the drum is made “deaf”, and the middle tier is made with a coefficient of “live” section within (0, 1 0.4) D from the diameter of the mill drum, while the height of the peripheral tier of the lattice is 0.05 from the diameter of the mill, and the coefficient of its "live" section is determined from the ratio KK _e • L, where K is the coefficient of the "live" section of the peripheral tier of the lattice; K _{e the} coefficient of the "live" section of the peripheral tier of the lattice of the reference mill with a diameter D and a drum length L equal to DL 1 m (K _e 0.02 m ^-1 ).

 The disadvantage of this mill is that, although it provides a slight decrease due to maintaining a certain level of material with grain sizes smaller than the openings of the discharge grill, it is impossible to avoid over-grinding of valuable components, while there is a decrease in productivity due to shock damping by an increased level of pulp and equipment performance.

The drum mill consisting of a cylindrical drum with end caps and trunnions, which is equipped with a replaceable annular transverse baffle installed on the discharge side at the end cap, the drainage pipes being made around the perimeter [3], which is closest to the invention in terms of technical essence and the achieved result.
With all the positive aspects of this device, the operation of a drum mill [3] is characterized by the following disadvantages.

 The crushed material entering the mill, due to the large length of the loading pin, requires additional devices in the form of powerful spirals inside the pin or other forced force for its promotion. The presence of an annular transverse baffle in the unloading zone exerts unnecessarily large drag on the movement of ore loading along the mill working zone, resulting in increased regrinding, grinding and increased sludging of both gangue material and grains of heavy valuable minerals, in particular gold, diamonds, platinum, etc. .d. Large and medium-sized grains of a valuable component are forced to accumulate and, until they become sludge, can not enter the discharge chamber of the discharge part, since the presence of a transverse baffle provides the effect of the size classification effect in the mill drum.

 The indicated causes an increased energy consumption for regrinding and a decrease in mill productivity, and in view of the re-slurry of grains of valuable components and waste rock, it reduces the degree of extraction of valuable minerals in subsequent enrichment operations.

 As our practice of using similar technical solutions has shown, a quick clogging with metal scrap alternating with a piece of ore of an annular pocket called a drain chamber (the effect of freezing and clogging by arching of outlet openings) is added to all of the above.

 The objective of the invention is the creation of a mill, the work of which would be characterized by a sufficiently high productivity for a larger number of particle size classes, a minimum degree of sludging of valuable minerals with a sufficiently low value of specific energy consumption.

где S суммарная площадь "живого" сечения отверстий разгрузочных решеток, м²; К коэффициент динамического подобия, учитывающий изменение свойств руды при изменении ее крупности, К 0,6 1,2; Q объемная производительность мельницы, м^3 oCч. D диаметр мельницы при установленной футеровке (в свету) на выходе руды из барабана, м.The objective is achieved in that in a wet ore self-grinding mill, including loading and unloading end caps, a drum and a discharging device made in the form of windows with gratings, a collection of crushed product, according to the invention, the drum shell is made in the form of a horizontally arranged truncated cone with an inclined cone angle surface 0 6 ^o to the horizon, and the discharge grills of the windows are located evenly on the side surface of the shell at the base of the truncated cone with a total area of "living" section, which is determined from the relation

where S is the total area of the "living" section of the openings of the discharge grills, m ² ; To the coefficient of dynamic similarity, taking into account the change in the properties of the ore when changing its size, K 0.6 1.2; Q volumetric productivity of the mill, m ^{3 o} Cch. D mill diameter when the lining is installed (in the light) at the ore outlet from the drum, m

The loading end cap is made with a taper angle of 150 170 ^o and is equipped with a loading nozzle with an inner diameter of (0.3 0.4) D from the diameter of the mill, the loading nozzle at the same time serves as a hollow pin resting on 6 8 support rollers as bearings.

The unloading end cover is conical with a taper angle of 160 180 ^o , equipped with an inner central cone that acts as a deflector ring, and a support blind cantilever pin resting on 6 8 support rollers as bearings.

 The number of unloading windows and the total area of their "live" section are experimentally selected such that the formation of "dead" zones in the drum is excluded and the rigidity of the mill structure is not reduced.

 A comparative analysis of the proposed mill and prototype allows us to conclude that the proposed technical solution meets the criterion of "novelty."

 Comparison with other technical solutions included in the "prior art" showed that there is a device for grinding lumpy and coarse ore material, in which the unloading of the crushed material occurs on a cylindrical surface [4 and 5] In this device, podkolosniki beams are located along the entire cylindrical surface of the drum and divided into fixed distance rods and grate elements.

 This design is unreliable in operation, especially with a significant volume of the drum. In addition, when used for ore self-grinding, the circulating load increases significantly, which necessitates an increase in the classification and screening front.

In the proposed mill, the execution of the shell in the form of a truncated cone with an angle of the generatrix of the conical surface 0 6 ^o to the horizon provides a sufficiently high speed of withdrawal of the crushed product from the zones of intensive destruction without unnecessary regrinding and sludge of waste rock and valuable minerals. This creates optimal conditions for the destruction of pieces and grains of ore to the required size, provides the required impact of a hydroabrasive medium for disintegrating clays and grinding ore particles by friction.

 The above effect is further enhanced by the fact that the discharge grills are located evenly on the side surface of the shell at the base of a horizontally located truncated cone.

 This eliminates the formation of "dead" zones in the drum and the crushed product is unloaded evenly. All this helps to reduce the circulating load, increases the productivity and efficiency of the equipment.

 The proposed design of the mill is characterized by manufacturability, high mechanical strength, reliability and rigidity.

 Reducing the residence time of the product of the calculated size in the mill in the absence of "dead" zones provides a decrease in the specific energy consumption for grinding ore.

The taper angle range of the inner surface of the boot end cap 150 170 ^o is quite sufficient for:
discarding pieces of ore into the working space of the mill during its operation;
ensuring the required spatial shape of the working area and drum volume with sufficient manufacturability of equipment;
ensuring the optimal combination of destructive forces in ore self-grinding.

With a decrease in the taper angle, the speed of the longitudinal movement of the ore load unnecessarily increases. With an increase in the taper angle above 170 ^{o, the} conical cover becomes flat, which will require the installation of an additional deflector ring (as in the Aerofol type dry ore grinding mill).

 When the mill feed size is smaller than 0.1 D from the mill diameter, fulfilling the experimentally verified requirement for the minimum diameter of the through hole, the minimum diameter of the feed pipe is taken to be 0.1 x 3 0.3 of the mill diameter. If this diameter is increased to more than 0.4 D from the mill diameter, the feed opening will require a sharp decrease in the ore filling of the mill drum, which will reduce the productivity of the equipment.

The taper angle range of the inner surface of the drum shell is sufficient for:
ensuring the required speed of the longitudinal movement of ore in the process of self-grinding;
approximation of the shape of the working space to the optimal, in which the required combination of destructive forces is observed during ore preparation;
increasing the efficiency of the mill as an ore-grinding unit.

With an increase in the angle of inclination of the generatrix of the conical surface of more than 6 ^{o, the} mill passes into the role of a feeder rather than a grinder. If the indicated angle becomes 0 ^° , the mill drum becomes standardly cylindrical.

The taper angle range of the discharge end cap is sufficient for:
ensuring the efficient operation of the mill, the discharge cover itself acts as a baffle plate, directing the crushed ore to the discharge windows, and under-crushed ore pieces inside the mill working space, which is additionally facilitated by the central cone installed on the discharge end cover;
providing the required optimal spatial shape of the working space of the mill drum;
ensuring the optimal combination of forces that destroy ore pieces, and improving the efficiency of the mill.

 With a decrease in the taper angle, all the optimal parameters of the kinematic and mechanical operating conditions of the ore load are violated and, as a result, the equipment productivity, the quality of the crushed product decreases, the size of the grinding increases, and the volume of the circulating load increases sharply.

With a taper of the unloading end cap 180 ^{o the} cover goes flat, which will require the installation of an additional deflector ring, as in the Aerofol mill.

 The above allows us to conclude that the proposed technical solution meets the criterion of "inventive step".

In FIG. 1 shows a general view and section of a mill; in FIG. 2 section of the boot end cap; in FIG. 3 is a general view of the boot end cap, view A in FIG. 2; in FIG. 4 section of a mill drum; in FIG. 5 is a general view of the drum from its end; in FIG. 6 section of the discharge end cap; Fig.7 General view of the discharge end cap
The wet ore self-grinding mill (Fig. 1) includes a receiving funnel 1, a loading nozzle 2, which, for technical reasons, relies on 6 8 roller bearings 3 as bearings (instead of plain bearings), which reduces the length of the loading nozzle 2, and the latter is part of the loading end cover 4, which is bolted rigidly connected to a conical drum 5, at the larger base of which discharge windows 6 are provided.

 The 5 drum bolts are rigidly connected to the unloading blind end cap 7. Both end caps are equipped with stiffening ribs 8. The drum 5 itself with the end caps is placed in the bunker box 9 into which the ore material crushed in the mill is unloaded. The unloading end cap 7 is rigidly bolted to the cantilever pin 10, based on the roller bearings 3; a pulley-flywheel 11 is mounted on the cantilever pin 10, to which rotation is transmitted by means of a wedge-belt transmission from a drive (not shown).

Boot end cap 4 (Fig. 2 and 3) is made with a taper angle of 150-170 ^o and lined with conical sectors of armored plates 12, which are attached to the cover by vertical wedge-shaped lifters 13 and bolted joints. In the central part of the loading end cover 4, a loading pipe 2 is fixed on the outside, inside the drum 5 is equipped with a diffuser ring 14 around the loading hole for additional reflection to the center of the drum 5 from the cover 4 of the pieces of ore loading grains during mill operation.

Drum 5 (Fig. 4 and 5) is a geometrically truncated cone with a slope forming up to 6 ^o to the horizon. The ratio of the larger diameter D to its length L is taken to be equal to D: L 1: 1 to 2: 1 Inside the drum 5 is lined with armor plates 15 and lifters 16 that provide protection for the drum body 5 and the recommended optimal shape of the working space.

The unloading end cover 7 (Figs. 6 and 7) is solid (blind) conical with a taper angle of 160 180 ^o , lined with armored plates 17 with vertical wedge-shaped elevators 18 in the image of the loading end cover 4, equipped with a central cone of a welded or cast structure 19 and a cantilever support pin 10.

 The mill drive includes an electric motor, gearbox, V-belt or gear transmission of rotation from the gearbox to the mill drum. The drive pulley or ring gear can be mounted either on the trunnion of the unloading end cap (which is preferable) or on the outside of the drum closer to the loading or unloading covers.

 The mill operates as follows.

 By means of a hopper with a grate, a feeder and a loading funnel 1, feed ore is fed through a loading nozzle (trunnion) 2 into the mill rotating on roller bearings 3, finer (0.1 0.15) D from the diameter of the mill drum 5 and process water. The original ore by the lining 12 and 13 and the deflector ring 14 of the loading end cover 4 is discarded into the working area of the drum 5, where the lifters are lifted by elevators and the liner of the drum 15 and 16 (lifters 16 with a height of 0.04 D from the mill diameter) due to the rotation of the mill and ore cohesion with the lining until the radial component of gravity exceeds the centrifugal force, after which the pieces of ore fall down, slide and slide over the rising upward ore, hit and rub against each other with constant mixing of the crushed material . During this movement, the ore material is crushed by cracking, crushing and abrasion.

 The crushed material penetrates the lower part of the load, where, with the help of water, rotation of the mill and the conical surface of the lining 15, the drum 5 moves to the discharge windows 6. Grains of the crushed ore, the size of which is finer than the size of the slots of the discharge grates (windows) 6, together with water, pass through the cracks, unloaded from the mill into the collection 9 and go to subsequent processing. The direction of movement of the crushed material to the discharge grills coincides with the longitudinal somewhat pressure-free movement of the entire ore load, which increases the speed of its output. In the case of the presence of difficultly eroded clay in the initial ore, the latter is disintegrated in the zone of intensive hydroabrasive wear of the inclined conical surface of the lining.

 To carry out the experiments, an ore sample was taken from the Tasseevsky gold ore deposit. The ore is represented by fissured silicified fine- and medium-grained sandstones, and techno-pebble conglomerate. Ore is characterized by a high degree of silicification and silicification of rocks. Vein and rock-forming minerals are represented by quartz, carbonam, feldspars, mica, amphiboles, pyroxenes, and accessory species are present. The ore of the sample is a poor sulfide quartz-gold-bearing rock. The strength of the rocks is 104.4 MPa (breccias and conglomerates) and 166.4 MPa (metasomatic silicified rocks). The fortress on the Protodyakonov scale is 9.4 and 13.0, respectively.

 In the process of self-grinding, the most durable non-fractured metasomatites are a grinding medium. Breccia rocks during grinding in the aquatic environment are rapidly destroyed with the formation of classes of critical size, which negatively affects the process of ore self-grinding.

 Comparative tests of models of ore self-grinding mills were carried out in order to determine their main technological indicators when grinding a specific gold ore.

 The operating and technological parameters (the rotation frequency of the mill drum 0.75 of the critical speed, the degree of filling of the drum with ore 0.4 of the capacity and the water regime) were kept constant for both mills.

Ore grinding was carried out in a closed cycle with a vibrating screen. The size of the holes of the screen mesh 0.5 mm. Ore in the process of grinding into the mill was supplied continuously. The upper limit of the ore size of the feed was constant and equal to 0.1 D of the mill diameter, i.e. ore size was taken equal to minus 70 mm (table. 1). The size of the slots of the discharge grill was taken from mechanical considerations to be 6 mm, which, when the mill was operating, provided a yield of product smaller than 5 mm. The mass fraction of fineness minus 0.074 mm in the discharge of the mill averaged 16.6%
Studies were carried out at optimal values of productivity, the value of which for each mill was determined experimentally during preliminary experiments.

 Two types of mill design were compared: a wet ore self-grinding mill of known design with a discharge through a grate (MMR) and a wet ore self-grinding mill with peripheral discharge of a MPR (proposed).

 In comparative tests, the water regime for unloading the mill was maintained within 67–70% solid and the fill factor was 35–40% of capacity.

As tests have shown, the efficiency of ore grinding in the proposed mill was higher due to:
increase unloading speed;
exclusion of “dead” zones and harmful circulation of ore loading in the working area of the mill;
the lack of intra-drum circulation of pulp of crushed ore (in the MMR, intra-drum circulation occurs due to the presence of a forced unloading unit (discharge grill, pulleys-discharge trunnion, with most of the pulp circulating as follows: drum-discharge grill-pulper, discharge grill-drum) due to the absence of vertical internal discharge grill, slurry lifters and hollow discharge trunnion, i.e. a standard discharge unit, and the presence of discharge windows, while increasing the manufacturability of the mill is reduced and its metal consumption is reduced;
optimal and efficient dehydration of the grinding process and the absence of the damping effect of water in the pulp, while there was a rapid stabilization of the ore self-grinding process when the mill was put into operation.

 The average optimal sieve characteristics of the products of grinding and classification are given in table. 2.

 When grinding ore in the proposed mill with peripheral discharge (MPR), the productivity of the original ore increases by 40 50% (Table 3), the specific productivity in the class minus 0.074 mm increases by 40 46%. Of course, the yield of this class in the discharge of the mill decreased by 1 , 2 1.4 times, but in the finished (under-sieve) product of the screen there was no decrease in the output of the class 0.074 mm. This indirectly indicates a decrease in sludge formation.

The work of the proposed mill is characterized by a decrease in energy consumption by 7.1% and an increase in grinding efficiency by 50-60%
When grinding ore in the proposed mill with peripheral unloading in the sublattice product, a rumble of free gold grains was observed by 3% more with a decrease in the yield of finely dispersed and pulverized, i.e. a decrease in the deception of the valuable component was observed (Table 4). The enrichment of the obtained crushed product at the same time made it possible to record an increase in the extraction of valuable concentrate by 2-2.5% compared with grinding the ore in a conventional wet ore self-grinding mill with discharge through a vertical grate (MMR). Grinding of gold and other ores in the proposed mill with peripheral discharge is technically possible, technologically and efficiently.

 The tests carried out confirmed the compliance of the proposed criterion with "industrial applicability".

Using the proposed mill will provide:
more complete disintegration of clay contained in the ore;
more effective destruction of crushed rock with increased selectivity of grinding;
an increase in the rate of withdrawal of the crushed product of the calculated size from the zones of intensive destruction, and therefore, a decrease in the sludge of waste rock and valuable mineral;
increase productivity and equipment efficiency.

 Currently, the issue of developing a working draft and manufacturing a batch of the proposed mill at the MZTM plant named after Kuibyshev, Irkutsk for processing gold-bearing ores of primary deposits of Eastern Siberia and Primorsky Territory.

Claims (3)

1. A wet ore self-grinding mill, including a drum with loading and unloading end caps, an unloading device in the form of windows and a collection of crushed product, characterized in that the shell of the drum is made in the form of a horizontally arranged truncated cone with an angle of inclination of the forming conical surface to the horizon of up to 6 ^o , and the windows are made with gratings evenly along the side surface of the shell at the base of the truncated cone with a total living area determined from the ratio

where S is the total liquid cross-sectional area of the gratings, m ² ;
K is the coefficient of dynamic similarity;
Q volumetric productivity of the mill, m ³ / h;
D the diameter of the mill with a lining in the light at the exit of the ore from the drum, m 2. The mill according to claim 1, characterized in that the loading end cap is made conical with a taper angle of 150 170 ^o , is equipped with a loading nozzle with an inner diameter of (0.3 0.4) D from the diameter of the mill and has a hollow trunnion resting on 6 8 support rollers as bearings. 3. The mill according to claim 1, characterized in that the discharge end cap is conical with a taper angle of 160 180 ^o , is equipped with an inner central conical deflector ring and has a support blind console bracket, supported by 6 8 support rollers as bearings.

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