Pulp (suspension) parameters
Definitions and formulas for calculation
Pulp is usually called a mixture of mineral particles and water. In which solid particles are in suspension and evenly distributed in the volume of water.
If such a mixture is used as a medium for separation by density, then it is customary to call it not a pulp, but a suspension.
The pulp (or suspension) is characterized by the following parameters: solids content in the pulp by mass or volume, liquefaction by mass or volume, density.
P \u003d Q / (Q + W)
λ \u003d V T / (V T + V g),
where V T \u003d Q / ρ; V f = F /Δ ; ρ and Δ – density respectively solid and liquid, kg/m 3 , if the liquid phase is water Δ=1000 kg/m 3 .
With highly liquefied pulps, the solid content in it is characterized by the mass of solids, ĸᴏᴛᴏᴩᴏᴇ is contained in the unit volume of the pulp, ᴛ.ᴇ. indicate how many grams or milligrams of solid matter per 1 m 3 or 1 liter of such liquefied pulp. This is how they characterize, for example, thickener plums, filtrates and centrates. In this case, the conversion to the usual solids content by weight or volume is carried out in accordance with the formulas () according to the following formulas:
where Q 1 is the mass of solid per unit volume of the pulp (for example, in 1 l), g; V T 1 - volume of solid per unit volume of the pulp, l, V T 1 \u003d Q 1 / ρ.
When calculating the values of P and λ it is extremely important to carefully monitor the units of solid mass, pulp volume, and solid and water densities.
Pulp liquefaction by mass R is the ratio of the mass of liquid F to the mass of solid Q in a certain amount of pulp:
R \u003d W / Q \u003d (1-P) / R.
R = 1 / (R + 1).
Pulp liquefaction by weight can be calculated from its moisture content:
R = M / (100-M),
where M is pulp moisture content, %.
Pulp liquefaction by volume R 0 - the ratio of the volume of liquid to the volume of solid: R 0 \u003d V w / V T \u003d (1-λ) / λ; solid content by volume λ = 1 / (1 + R 0).
Pulp liquefaction by mass and volume are related to each other, as well as the solids content in the pulp by mass and volume:
pulp volume V is determined through liquefaction according to the formulas:
V = Q ( + ) or
In the formulas () and (), the units of volume will be determined by the units of density of the solid and liquid ( and Δ), which, of course, must be the same and correspond to the unit mass of the solid. For example, if the values and Δ are measured in kg/m 3 . then the value of Q should be expressed in kg, then the pulp volume V will be obtained in cubic meters.
The density of the pulp (or suspension) n is the mass per unit volume of the pulp. It is determined by directly weighing a certain volume of pulp (most often 1 liter) or calculated using the formulas below, if the content of solids in the pulp (mass or volume) or its liquefaction is known, as well as the density of solid and liquid:
where p and Δ are defined in kilograms per cubic meter, P and λ - in fractions of a unit.
If the density of the pulp is determined by directly weighing a certain volume of the pulp (usually 1 liter), then it is possible to calculate the density of the solid (knowing its mass and volume content in the pulp) or, on the contrary, knowing the density of the solid, its mass or volume content in the pulp and liquefaction:
Here the pulp density is q·10 3 , kg/m 3 ; q is the mass of 1 l. Pulp, kg, obtained by direct weighing.
By the density of the pulp and the density of the solid, one can determine both the mass and volumetric liquefaction of the pulp:
In the formulas () - () the values \u200b\u200bof ρ p (ρ c), ρ, Δ, are determined in kilograms per cubic meter; P and λ are in fractions of a unit.
According to the parameters of the pulp (or suspension), you can directly calculate the mass of solid and water in 1 m 3 of pulp (suspension) or in 1 ton of pulp (suspension):
where Q is the mass of solid (for a suspension, the weight of the weighting agent) in 1 m 3 of pulp (suspension), kg; Q T - mass of solid (for a suspension of weighting agent) in 1 ton of pulp (suspension), tons;
W is the mass of water in 1 m 3 of pulp (suspension), kg; W T - mass of water in 1 ton of pulp (suspension), t.
5. Control questions on disciplines:
1. Basic concepts and types of screening for technological purposes: independent, preparatory, auxiliary, selective, dehydrating.
2. The screening surface of the screens: grates, sheet sieves with stamped holes, rubber sieves, wire mesh, spalt, jet sieves. Living section of screening surfaces (live section coefficient).
3. Granulometric composition of bulk material, size classes. The average diameter of an individual particle and a mixture of particles. Types of screening according to the size of the material: large, medium, fine, thin.
4. Sieve analysis, standard sieve scales. Apparatus for the production of sieve analysis. Characteristics of bulk material size according to private and total outputs size classes. Forms of the total (cumulative) size characteristic: by ʼʼplusʼʼ and ʼʼminusʼʼ, semi-logarithmic, logarithmic.
5. Equations of material size characteristics (Godin–Andreev, Rozin–Rammler). Distribution curves. Calculation of the surface and the number of grains according to the equation of the total size characteristic. Calculation of the average grain diameter of bulk material.
6. Efficiency of screening - overall and for individual size classes. ʼʼLightʼʼ, ʼʼdifficultʼʼ and ʼʼhinderingʼʼ grains. The probability of grains passing through the sieve holes.
7. Influence on the screening process of various factors: the moisture content of the material, the shape and size of its particles, the shape of the holes and the slope of the screening surface, the speed of the screened material, the amplitude and frequency of vibrations of the box of inertial screens. The sequence of selection of size classes: from large to small, from small to large, combined.
8.. Dependence of screening efficiency on screening duration, screen load and particle size distribution of screened material. Extraction of the fine class into the undersize product. ʼʼCrushingʼʼ oversize product.
9. General classification of screens. Fixed grate screens. Roller screens. Scheme of the device, principle of operation, dimensions, scope, performance, performance indicators. Advantages and disadvantages.
10. Drum screens. Flat oscillating screens. Scheme of the device, principle of operation, dimensions, scope, performance, performance indicators. Advantages and disadvantages.
11. Vibrating (inertial) screens with circular and elliptical vibrations, self-centering screens. Amplitude-frequency characteristic of inertial screens. Scheme of the device, principle of operation, dimensions, scope, performance, performance indicators. Advantages and disadvantages.
12. Vibrating screens with linear vibrations. Types of vibrators. Screens with a self-balancing vibrator, self-synchronizing, self-balancing screens. Scheme of the device, principle of operation, dimensions, scope, performance, performance indicators. Advantages and disadvantages.
13. Resonant horizontal screens. Electrovibrating inclined screens. Scheme of the device, principle of operation, dimensions, scope, performance, performance indicators. Advantages and disadvantages.
14. Conditions affecting the performance and efficiency of vibrating screens. Technological calculation of inclined inertial screens. Hydraulic screens: arc screens, flat screens for fine screening.
15. Operation of screens. Ways of fastening sieves, replacement of sieves. Balancing of vibrating screens. Fight against sticking of the working surface and dust emission. Basic techniques for safe maintenance of screens.
16. Basic concepts and purpose of crushing processes. The degree of crushing and grinding. Stages and schemes of crushing and grinding. Specific surface area of loose material.
17. Modern ideas about the process of destruction of elastic-brittle and brittle solids under mechanical action. Physical and mechanical properties rocks: strength, hardness, viscosity, plasticity, elasticity, their significance in the processes of destruction. The scale of the fortress of rocks according to M.M. Protodyakonov.
18. Structure of rocks, porosity, defects, fracturing. Formation and propagation in a stressed elastic-brittle body of a rupture crack of ʼʼcriticalʼʼ length, as a criterion for the stress of atomic-molecular bonds at the mouth of the crack. The physical essence of stress and its maximum possible value.
19. Laws of crushing rocks (Rittinger, Kirpichev-Kick, Rebinder, Bond), their essence, advantages and disadvantages, scope. The dependence of the specific energy consumption of the destruction of a piece or particle of a solid body on their size, general expression for energy costs for size reduction. Bond crushing work index, the possibility of its practical use. Selectivity of crushing, the physical basis of the process, criteria and indicators characterizing the selectivity. The role of defects and cracks in the separation of intergrowths of various minerals and their relationship with selectivity indicators.
20. Granulometric composition of the rock mass supplied to the crushing and screening plant. crushing methods. Crushing coarse, medium and fine. The degree of crushing, its definition. Schemes of crushing, stages of crushing. Open and closed crushing cycles. The operation of fine crushers in a closed cycle with a screen.
21. Technological efficiency of crushing. Energy indicators of crushing. Circulating load in crushing cycles. Technological features of crushing during the processing of various mineral raw materials: ores of metallic and non-metallic minerals, coal.
22. Operation of crushing departments, requirements for technological regime maps for the final product of crushing. Optimum size of the crushed product ͵ entering the subsequent grinding operations. Pre-concentration operations in crushing cycles: dry magnetic separation, enrichment in heavy suspensions, etc.
23. Classification of crushing machines. Jaw crushers with simple and complex jaw movement. Device diagrams and principle of operation, formulas for determining the grip angle, theoretical performance, swing frequency (for cone and jaw), crushing degree, power and metal consumption for crushing, advantages and disadvantages, applications.
24. Cone crushers for coarse crushing with upper suspension and lower crushing cone support. Cone reduction crushers. Cone crushers of medium and fine crushing. Crushers with hydraulic damping and adjustment of the loading gap. Non-eccentric impact crusher. Device diagrams and principle of operation, formulas for determining the grip angle, theoretical performance, swing frequency (for cone and jaw), crushing degree, power and metal consumption for crushing, advantages and disadvantages, applications.
25. Roll crushers, devices, peripheral speed of rolls, scope. The dependence of the diameter of the rolls on the size of crushed pieces. Crushers with smooth, corrugated and toothed rolls. Device diagrams and principle of operation, formulas for determining the grip angle, theoretical performance, swing frequency (for cone and jaw), crushing degree, power and metal consumption for crushing, advantages and disadvantages, applications.
26. New types of crushing machines. Physical methods of crushing: electro-hydraulic, cavitation, Snyder process, etc.
27. Machines for medium and fine crushing of soft and brittle rocks. Roll crushers for coal. Hammer and impact crushers, disintegrators. Schemes of the device and the principle of operation, degree of crushing, productivity, consumption of electricity and metal, control methods.
28. Selection of the type and size of crushers for medium and fine crushing to work in given conditions. Advantages of impact crushers Methods for automatic control of crushing units.
29. Features of the destruction of mineral particles and grains in grinding processes. The size of the initial and final products. The concept of ʼʼscale factorʼʼ and its influence on the energy intensity of the grinding process based on the fineness of grinding.
30. Opening of ore and non-metallic minerals in the process of grinding, determination of opening parameters, selectivity of grinding, ways to increase it. The relationship between the processes of grinding and enrichment during the processing of ores with different sizes of disseminated minerals.
31. Grindability of minerals. Methods for determining grindability.
32. Kinetics of grinding, equations of kinetics of grinding, the value of the parameters of the equation, their definition. Technological dependencies arising from the equation of grinding kinetics.
33. Types of mills, their classification. Rotary drum mills as the main grinding equipment at processing plants: ball mills with central discharge and through a grate, rod mills, ore-pebble mills. Design features, modes of operation, feeders, drive.
34. Speed modes of grinding in ball mills: waterfall, cascade, mixed, supercritical. Ball break angle. Critical and relative frequency of rotation of mills. Equations of circular and parabolic trajectory of balls in a mill. Coordinates of the characteristics of the points of the parabolic trajectory of the balls in the mill. Turnover of balls in the mill, cycles of movement of the grinding load.
35. The degree of filling the volume of the mill drum with grinding medium. Bulk mass of balls of rods, ore haul in a mill. Determination of the degree of filling the volume of the mill drum with a grinding load.
36. The power consumed by the mill in cascade and waterfall modes of its operation. The dependence of useful power on the frequency of rotation of the mill and the degree of filling of its volume with grinding medium. Useful power formulas.
37. Patterns of wear of balls in a mill, equations for the characteristics of the size of balls in a mill with their regular additional loading. Rational loading of balls. Factors affecting the consumption of balls in the grinding process.
38. Drum mills of dry and wet self-grinding, features of the grinding process, its advantages. Formation of "critical size" classes in self-grinding mills and ways to reduce their accumulation. Semi-self-grinding mills. Ore-pebble mills, size and density of ore pebble, its consumption. design features, operating modes, feeders, drive. Design features, modes of operation, feeders, drive. Mill lining, lining types, service life. Areas of use. Operation of drum mills.
39. Vibrating, planetary, centrifugal, jet mills. The principle of operation, device diagrams. Areas of use.
40. Open and closed grinding cycles. The process of formation and establishment of a circulating load in a closed grinding cycle, the relationship with the productivity of the mill. Determination of the circulating load. throughput of the mill.
41. Technological schemes of grinding, stages of grinding. The number of stages and their connection with enrichment processes. Features of the use of rod, ball and ore-pebble mills in technological schemes of staged grinding. Combination of ore-pebble grinding with primary ore self-grinding. Classifiers and hydrocyclones in grinding schemes. Features of interface nodes ʼʼmill - classifierʼʼ. Effect of classification efficiency on mill performance. Pulp, indicators of its composition, pulp properties.
42. Performance of mills by initial feed and design class, factors affecting performance. Determination of the performance of mills. Calculation of mills by specific productivity.
43. Automation of grinding cycles, features of regulation of these cycles.
44. Technical and economic indicators of grinding. The cost of grinding for individual items of expenditure.
Main literature:
Perov V.A., Andreev E.E., Bilenko L.F. Crushing, grinding and screening of minerals: A textbook for universities. - M.: Nedra, 1990. - 301 p.
1. Handbook of ore dressing. Preparatory processes / Ed. O.S. Bogdanova, V.A. Olevsky. 2nd edition. – M.: Nedra, 1982. – 366 p.
2. Donchenko A.A., Donchenko V.A. Handbook of an ore-dressing plant mechanic. – M.: Nedra, 1986. S. 4-130.
3. Magazines ʼʼEnrichment of oreʼʼ, ʼʼMining magazineʼʼ.
4. M.N. Kell. Enrichment of minerals. Collection of tasks. - L.: LGI, 1986. - 64 p.
Pulp (suspension) parameters - concept and types. Classification and features of the category "Pulp (suspension) parameters" 2017, 2018.
Union of Soviet
Socialist
Reslublhtc
Auto dependent. certificate no.
Applied on 05.!V.1971 (No. 1646714/18-10) with attachment of Application No.
M. Cl. G Olga 17/04
Committee for Inventions and Discoveries under the Council of Ministers
All-Union Scientific Research and Design Institute of Hydraulic Coal Mining and Hydromine
Gramoteinskaya 3-4
Applicants
METHOD FOR DETERMINING THE WEIGHT OF SOLID IN THE PULP where P is the weight of the pulp, P, is the weight of the solid, P" is the weight of the liquid.
P = P,+P, The invention relates to methods for measuring the mass flow rate of pulp.
A known device for measuring the performance of suction dredgers, which measure the consumption of pulp, using for this electromagnetic flowmeter, Venturi tube, calculator and secondary pointing device.
The operation of the known device is based on the processing of data on the specific gravity of the pulp, pressure drops, device constant in a calculating device, as a result of which data on the flow rate are obtained on the pointing device. Determination of weight on a known device does not provide the necessary accuracy, as it requires additional and complex calculations.
The proposed method requires simpler equipment and provides high accuracy in determining the weight of solids in the pulp, due to the fact that the container is filled with pulp to a predetermined weight, the volume occupied by it is measured, and the weight of solids in the pulp is calculated by calculation. Since the pulp is a two-phase medium (a mixture of solid and liquid), then, knowing the weight of the pulp and its volume, it is possible to determine the weight of the solid in the pulp by calculation:
Knowing specific gravity liquid y "and solid y" you can get an expression for determining the weight of the solid in the pulp: p tt (V> ") (2)
10 tt tzh where V is the volume of pulp weighing P.
According to the proposed method, the weight of the solid in the pulp is measured as follows. The pulp is sent to a weighing tank equipped with a device for measuring the volume of the pulp in the tank. After filling the container with pulp to a given weight, which is fixed by any weighing device, the volume occupied at a given weight is determined.
® pulp, after which the weight of the solid is determined by the formula (2).
Subject of invention
A method for determining the weight of a solid in a pulp by weighing it in a container, characterized in that, in order to increase the productivity and accuracy of measuring the weight of the solid in the pulp, the container is filled to a predetermined weight, the volume occupied by it is measured, and the weight of the solid in the pulp is calculated by calculation.
The density of the pulp is usually characterized by either liquefaction or solids content.
The density of the pulp affects the technological parameters of enrichment: the extraction of PC into the concentrate and its content in the concentrate. In very dense pulps, when close to 100%, the continuity of the phase flow disappears, so flotation is not possible, and ε=0. At very low densities, ε of the floated mineral decreases due to a decrease in foam strength. The content of the floated mineral in the foam product continuously decreases with increasing density due to an increase in the mechanical removal of waste rock.
The density of the pulp also affects the technological indicators: the consumption of reagents, the performance of flotation machines, the specific energy consumption of water. With an increase in the density of the pulp, the performance of the flotation machines increases to a certain limit, then begins to decrease.
Thus, in flotation it is disadvantageous to have both too dense and too thin pulps. The optimal dilution of the pulp depends on the size and density of the floating PI, as well as on the purpose of the flotation operation, the required quality of the foam product. With an increase in the size and density of the floated ore, the optimal density of the ore increases, and with a high content of sludge and a low density of the processed material, flotation is carried out in more liquid pulps. In the operations of the main and control flotation, denser pulps are used to reduce losses in the tailings. And in the operations of recleaning the concentrate to improve their quality - in more diluted ones.
REAGENT MODE
This is the nomenclature of reagents, their dosage, the point of supply and distribution of each reagent to individual points, the duration of their contact with the pulp. Of great importance for the result of flotation is the composition of the water.
Reagents are added in the following order:
1. Environmental regulators;
2. Depressants that are loaded together with or later than regulators;
3. Collectors;
4. Foamers are loaded sequentially;
5. Activators are added after the first flotation stage to recover hard-to-float particles of the same mineral or to activate the minerals depressed in the first stage.
The duration of contact of the reagent with the pulp before flotation varies widely. Usually with soluble collectors, 1-3 minutes is sufficient for contact. With poorly soluble collectors, the contact time increases dramatically. The collector can be loaded at a time or in batches. With a one-time load, the flotation rate is higher, and the quality of the froth product is lower.
If the reagent quickly decomposes or is quickly consumed for side reagents, then batch loading is advisable, which is given by higher collectors with different sorption activity of the floated minerals.
The amount of collector affects the extraction and content of the valuable mineral in the concentrate. With an increase in the consumption of the collector, the extraction increases, and the content decreases.
The operating mode of movement of the slurry (pulp) is determined by its speed in the pipeline. The average flow rate of the slurry, corresponding to the beginning of the settling of solid particles in the pipe, is called the critical speed. Depending on the critical speed of the slurry, there are three modes of motion:
- at speeds above critical, at which the soil is transported in suspension;
- closer to critical - the soil stratifies and large particles begin to fall out;
- below critical - the soil falls to the bottom and it is possible to block the slurry pipeline with soil.
For normal operation of soil hydraulic transport, it is necessary that the speed of the slurry be higher than the critical speed by 15 ... 20%, i.e. vr = (1,15…1,2) v kr
At vr < v kr, sedimentation of the transported material is possible and, as a result, clogging, silting of pipes. At vr > 1,2 v kr, the energy consumption for transportation increases and the wear of pipelines accelerates.
The calculation of soil hydrotransportation consists in determining the speeds necessary for its transportation, as well as the diameters of pipelines and pressure losses in them. Several methods have been developed for calculating the hydrotransportation of soil for various conditions and for various purposes. In the production of works on, which are represented mainly by coarse and medium-grained soil particles with a diameter of more than 0.1 mm and a mixture with a limited amount of finer particles, the most suitable calculation of the parameters of pressure hydraulic transport can be adopted using the VNIIG method. B.E. Vedeneeva.
According to this technique, the critical speed is calculated by the formula:
where D n- pulp pipeline diameter, m; C 0 - an indicator of the bulk consistency of the pulp; K m is the weighted average value of the coefficient of transportability of soil particles, depending on the diameter of the particles.
Table 3.1
Soil particle transportability coefficient
where Pi- content i th soil, %.
The indicator of the bulk consistency of the pulp is determined as follows:
where ρ cm, ρ in, ρ s are the densities of the slurry, water and solid soil, respectively, t/m 3 .
The values of critical velocities in slurry pipelines for various soils, depending on the consistency, are given in Table. 3.2.
Table 3.2
Critical pulp speeds vkr, m/s
| Priming | D n, mm | pulp consistency | ||
| S:W= 1:5 | S:W = 1:10 | S:W =1:15 | ||
| Sand-gravel-pebble with a content of gravel and pebbles over 45% | 200 | 3,38 | 3,11 | 2,85 |
| 300 | 3,93 | 3,56 | 3,3 | |
| 400 | 4,5 | 4,03 | 3,74 | |
| 500 | 5,0 | 4,46 | 4,20 | |
| 600 | 5,48 | 4,95 | 4,60 | |
| Sand and gravel with a content of gravel and pebbles 20–45% | 200 | 2,91 | 2,71 | 2,57 |
| 300 | 3,37 | 3,14 | 2,9 | |
| 400 | 3,87 | 3,57 | 3,28 | |
| 500 | 4,34 | 3,90 | 3,64 | |
| 600 | 4,76 | 4,28 | 4,0 | |
| coarse sands | 200 | 2,55 | 2,15 | 2,17 |
| 300 | 2,92 | 2,6 | 2,46 | |
| 400 | 3,32 | 2,94 | 2.76 | |
| 500 | 3,67 | 3,30 | 3,08 | |
| 600 | 4,04 | 3,6 | 3,40 | |
| fine sands | 200 | 2,06 | 1,62 | 1,82 |
| 300 | 3,38 | 2,03 | 2,07 | |
| 400 | 2,77 | 2,48 | 2,32 | |
| 500 | 3,10 | 2,88 | 2,58 | |
| 600 | 3,42 | 3,0 | 2,86 | |
| Loess loams | 200 | 1,41 | 1,07 | 1,21 |
| 300 | 1,65 | 1,37 | 1,38 | |
| 400 | 1,88 | 1,68 | 1,57 | |
| 500 | 2,12 | 1,88 | 1,77 | |
| 600 | 2,32 | 2,07 | 1,94 | |
The diameter of the slurry pipeline is chosen based on the supply of the soil pump through the slurry:
Slurry pipeline diameter
The diameter of the slurry pipeline is checked by the average velocity of the pulp required for the hydraulic transport of the soil, after which the nearest standard diameter is taken.
The calculated diameters of the slurry pipelines are established and adjusted by practice, and the approximate value of the velocities of the pulp during the development of sandy soils in these pipelines is presented in Table. 3.3.
Table 3.3
Approximate value of slurry movement speeds in the development of sand pits on existing dredgers
| Dredger with soil pump | Slurry pipeline diameter D n, mm | |||
| 200 | 300 | 400 | 500 | |
| GRAU 400/20 | 3,53 | – | – | – |
| GRAU 800/40 | – | 3,17 | – | – |
| GRAU 1600/25 | – | 4,93 | 3,55 | 3,33 |
Pulp is a mixture of mineral particles and water. In which solid particles are in suspension and evenly distributed in the volume of water.
If such a mixture is used as a density separation medium, then it is not called a pulp, but a suspension.
The pulp (or suspension) is characterized by the following parameters: solids content in the pulp by mass or volume, liquefaction by mass or volume, density.
P \u003d Q / (Q + W)
λ \u003d V T / (V T + V W),
where V T \u003d Q / ρ; V f = F /Δ ; ρ and Δ - the density of the solid and liquid, respectively, kg/m3, if the liquid phase is water Δ = 1000 kg/m3.
With highly liquefied pulps, the solid content in it is characterized by the mass of solid, which is contained in a unit volume of the pulp, i.e. indicate how many grams or milligrams of solid matter per 1 m 3 or 1 liter of such liquefied pulp. This characterizes, for example, thickener overflows, filtrates and centrates.
In this case, the conversion to the usual solid content by weight or volume is carried out in accordance with the formulas () according to the following formulas:
where Q 1 is the mass of solid per unit volume of the pulp (for example, in 1 l), g; V T 1 - volume of solid per unit volume of pulp, l, V T 1 = Q 1 /ρ.
When calculating the values of P and λ it is necessary to carefully monitor the units of solid mass, pulp volume and solid and water densities.
Pulp liquefaction by mass R is the ratio of the mass of liquid W to the mass of solid Q in a certain amount of pulp:
R \u003d W / Q \u003d (1-P) / R.
R = 1 / (R + 1).
Pulp liquefaction by weight can be calculated from its moisture content:
R = M / (100-M),
where M is pulp moisture content, %.
Liquefaction of the pulp by volume R 0 - the ratio of the volume of liquid to the volume of solid: R 0 \u003d V W / V T \u003d (1-λ) / λ; solid content by volume λ = 1 / (1 + R 0).
Pulp liquefaction by mass and volume are related to each other, as well as solids content in the pulp by mass and volume:
pulp volume V is determined through liquefaction according to the formulas:
V = Q ( + ) or
In the formulas () and (), the units of volume will be determined by the units of density of the solid and liquid ( and Δ), which, of course, must be the same and correspond to the unit mass of the solid. For example, if the values and Δ are measured in kg/m 3 . then the value of Q should be expressed in kg, then the pulp volume V will be obtained in cubic meters.
The density of the pulp (or suspension) n is the mass per unit volume of the pulp. It is determined by directly weighing a certain volume of pulp (usually 1 liter) or calculated using the formulas below, if the solid content (mass or volume) or its liquefaction in the pulp is known, as well as the density of solid and liquid:
where p and Δ are defined in kilograms per cubic meter, P and λ - in fractions of a unit.
If the density of the pulp is determined by directly weighing a certain volume of the pulp (usually 1 liter), then it is possible to calculate the density of the solid (knowing its mass and volume content in the pulp) or, conversely, knowing the density of the solid, its mass or volume content in the pulp and liquefaction:
Here the pulp density is q·10 3 , kg/m 3 ; q - weight of 1 l. Pulp, kg, obtained by direct weighing.
By the density of the pulp and the density of the solid, one can determine both the mass and volumetric liquefaction of the pulp:
In the formulas () - () the values of ρ p (ρ c), ρ, Δ, are determined in kilograms per cubic meter; P and λ - in fractions of a unit.
According to the parameters of the pulp (or suspension), you can directly calculate the mass of solid and water in 1 m 3 of pulp (suspension) or in 1 ton of pulp (suspension):
where Q is the mass of solid (for a suspension, the weight of the weighting agent) in 1 m 3 of pulp (suspension), kg; Q T - mass of solid (for weighting agent suspension) in 1 ton of pulp (suspension), tons;
W is the mass of water in 1 m 3 of pulp (suspension), kg; W T - mass of water in 1 ton of pulp (suspension), t.
Control questions on the discipline:
1. Basic concepts and types of screening for technological purposes: independent, preparatory, auxiliary, selective, dehydrating.
2. Screening surface of screens: grates, sheet sieves with stamped holes, rubber sieves, wire mesh, spalt, jet sieves. Living section of screening surfaces (live section coefficient).
3. Granulometric composition of bulk material, size classes. The average diameter of an individual particle and a mixture of particles. Types of screening according to the size of the material: large, medium, fine, thin.
4. Sieve analysis, standard sieve scales. Apparatus for the production of sieve analysis. Characteristics of bulk material size by private and total yields of size classes. Forms of the total (cumulative) size characteristic: by "plus" and "minus", semi-logarithmic, logarithmic.
5. Equations of material size characteristics (Godin-Andreev, Rozin-Rammler). Distribution curves. Calculation of the surface and the number of grains according to the equation of the total size characteristic. Calculation of the average grain diameter of bulk material.
6. Efficiency of screening - overall and for individual size classes. "Easy", "difficult" and "obstructive" grains. The probability of grains passing through the sieve holes.
7. Influence on the screening process of various factors: material humidity, the shape and size of its particles, the shape of the holes and the inclination of the screening surface, the speed of the screened material, the amplitude and frequency of vibrations of the box of inertial screens. The sequence of separation of size classes: from large to small, from small to large, combined.
Fig. 8. Dependence of the screening efficiency on the duration of screening, the load of the screen and the granulometric composition of the screened material. Extraction of the fine class into the undersize product. "Crushing" of the oversize product.
9. General classification of screens. Fixed grate screens. Roller screens. Scheme of the device, principle of operation, dimensions, scope, performance, performance indicators. Advantages and disadvantages.
10. Drum screens. Flat oscillating screens. Scheme of the device, principle of operation, dimensions, scope, performance, performance indicators. Advantages and disadvantages.
11. Vibrating (inertial) screens with circular and elliptical oscillations, self-centering screens. Amplitude-frequency characteristic of inertial screens. Scheme of the device, principle of operation, dimensions, scope, performance, performance indicators. Advantages and disadvantages.
12. Vibrating screens with linear vibrations. Types of vibrators. Screens with a self-balancing vibrator, self-synchronizing, self-balancing screens. Scheme of the device, principle of operation, dimensions, scope, performance, performance indicators. Advantages and disadvantages.
13. Resonant horizontal screens. Electrovibrating inclined screens. Scheme of the device, principle of operation, dimensions, scope, performance, performance indicators. Advantages and disadvantages.
14. Conditions affecting the performance and efficiency of vibrating screens. Technological calculation of inclined inertial screens. Hydraulic screens: arc screens, flat screens for fine screening.
15. Operation of screens. Ways of fastening sieves, replacement of sieves. Balancing of vibrating screens. Fight against sticking of a working surface and dust emission. Basic techniques for safe maintenance of screens.
16. Basic concepts and purpose of crushing processes. The degree of crushing and grinding. Stages and schemes of crushing and grinding. Specific surface area of loose material.
17. Modern ideas about the process of destruction of elastic-brittle and brittle solids under mechanical action. Physical and mechanical properties of rocks: strength, hardness, viscosity, plasticity, elasticity, their significance in the destruction processes. The scale of the fortress of rocks according to M.M. Protodyakonov.
18. Structure of rocks, porosity, defects, fracturing. Formation and propagation in a stressed elastic-brittle body of a bursting crack of a "critical" length, as a criterion for the stress of atomic-molecular bonds at the mouth of the crack. The physical essence of stress and its maximum possible value.
19. Laws of crushing rocks (Rittinger, Kirpichev-Kik, Rebinder, Bond), their essence, advantages and disadvantages, scope. The dependence of the specific energy consumption of the destruction of a piece or particle of a solid body on their size, a general expression for the energy consumption for reducing the size. Bond crushing work index, the possibility of its practical use. Selectivity of crushing, the physical basis of the process, criteria and indicators characterizing the selectivity. The role of defects and cracks in the separation of intergrowths of various minerals and their relationship with selectivity indicators.
20. Granulometric composition of the rock mass supplied to the crushing and screening plant. crushing methods. Crushing coarse, medium and fine. The degree of crushing, its definition. Schemes of crushing, stages of crushing. Open and closed crushing cycles. The operation of fine crushers in a closed cycle with a screen.
21. Technological efficiency of crushing. Energy indicators of crushing. Circulating load in crushing cycles. Technological features of crushing in the processing of various mineral raw materials: ores of metallic and non-metallic minerals, coal.
22. Operation of crushing departments, requirements of technological mode maps for the final product of crushing. Optimum size of the crushed product entering the subsequent crushing operations. Pre-concentration operations in crushing cycles: dry magnetic separation, enrichment in heavy suspensions, etc.
23. Classification of crushing machines. Jaw crushers with simple and complex jaw movement. Schemes of the device and the principle of operation, formulas for determining the angle of capture, theoretical performance, swing frequency (for cone and jaw), crushing degree, electricity and metal consumption for crushing, advantages and disadvantages, applications.
24. Cone crushers for coarse crushing with upper suspension and lower crushing cone support. Cone reduction crushers. Cone crushers of medium and fine crushing. Crushers with hydraulic damping and adjustment of the loading gap. Non-eccentric inertial crusher. Schemes of the device and the principle of operation, formulas for determining the angle of capture, theoretical performance, swing frequency (for cone and jaw), crushing degree, electricity and metal consumption for crushing, advantages and disadvantages, applications.
25. Roll crushers, devices, peripheral speed of rolls, scope. The dependence of the diameter of the rolls on the size of crushed pieces. Crushers with smooth, corrugated and toothed rolls. Schemes of the device and the principle of operation, formulas for determining the angle of capture, theoretical performance, swing frequency (for cone and jaw), crushing degree, electricity and metal consumption for crushing, advantages and disadvantages, applications.
26. New types of crushing machines. Physical methods of crushing: electro-hydraulic, cavitation, Snyder process, etc.
27. Machines for medium and fine crushing of soft and brittle rocks. Roll crushers for coal. Hammer and impact crushers, disintegrators. Schemes of the device and the principle of operation, degree of crushing, productivity, consumption of electricity and metal, control methods.
28. Selection of the type and size of crushers for medium and fine crushing to work in given conditions. Advantages of impact crushers Methods for automatic control of crushing units.
29. Features of destruction of mineral particles and grains in grinding processes. The size of the initial and final products. The concept of "scale factor" and its influence on the energy intensity of the grinding process, depending on the fineness of grinding.
30. Opening of ore and non-metallic minerals in the process of grinding, determination of opening parameters, grinding selectivity, ways to increase it. The relationship between the processes of grinding and enrichment during the processing of ores with different sizes of disseminated minerals.
31. Grindability of minerals. Methods for determining grindability.
32. Kinetics of grinding, equations of kinetics of grinding, the value of the parameters of the equation, their definition. Technological dependencies arising from the equation of grinding kinetics.
33. Types of mills, their classification. Rotary drum mills as the main grinding equipment at processing plants: ball mills with central discharge and through a grate, rod mills, ore-pebble mills. Design features, modes of operation, feeders, drive.
34. Speed modes of grinding in ball mills: waterfall, cascade, mixed, supercritical. Ball break angle. Critical and relative frequency of rotation of mills. Equations of circular and parabolic trajectory of balls in a mill. Coordinates of the characteristics of the points of the parabolic trajectory of the balls in the mill. Turnover of balls in the mill, cycles of movement of the grinding load.
35. The degree of filling the volume of the mill drum with grinding media. Bulk mass of balls of rods, ore haul in a mill. Determination of the degree of filling the volume of the mill drum with grinding load.
36. The power consumed by the mill in cascade and waterfall modes of its operation. The dependence of useful power on the frequency of rotation of the mill and the degree of filling of its volume with grinding medium. Useful power formulas.
37. Patterns of wear of balls in a mill, equations for the characteristics of the size of balls in a mill with their regular additional loading. Rational loading of balls. Factors affecting the consumption of balls in the grinding process.
38. Drum mills of dry and wet self-grinding, features of the grinding process, its advantages. Formation of "critical size" classes in self-grinding mills and ways to reduce their accumulation. Semi-self-grinding mills. Ore-pebble mills, size and density of ore pebble, its consumption. design features, operating modes, feeders, drive. Design features, modes of operation, feeders, drive. Mill lining, lining types, service life. Areas of use. Operation of drum mills.
39. Vibrating, planetary, centrifugal, jet mills. The principle of operation, device diagrams. Areas of use.
40. Open and closed grinding cycles. The process of formation and establishment of a circulating load in a closed grinding cycle, the relationship with the productivity of the mill. Determination of the circulating load. throughput of the mill.
41. Technological schemes of grinding, stages of grinding. The number of stages and their connection with enrichment processes. Features of the use of rod, ball and ore-pebble mills in technological schemes of staged grinding. Combination of ore-pebble grinding with primary ore self-grinding. Classifiers and hydrocyclones in grinding schemes. Features of interface nodes "mill - classifier". Effect of classification efficiency on mill performance. Pulp, indicators of its composition, pulp properties.
42. Performance of mills by initial feed and design class, factors affecting performance. Determination of the productivity of mills. Calculation of mills by specific productivity.
43. Automation of grinding cycles, features of regulation of these cycles.
44. Technical and economic indicators of grinding. The cost of grinding for individual items of expenditure.
Main literature:
Perov V.A., Andreev E.E., Bilenko L.F. Crushing, grinding and screening of minerals: A textbook for universities. - M.: Nedra, 1990. - 301 p.
Additional literature:
1. Handbook of ore dressing. Preparatory processes / Ed. O.S. Bogdanova, V.A. Olevsky. 2nd edition. - M.: Nedra, 1982. - 366 p.
2. Donchenko A.A., Donchenko V.A. Handbook of an ore-dressing plant mechanic. - M.: Nedra, 1986. S. 4-130.
3. Magazines "Ore enrichment", "Mining magazine".
4. M.N. Kell. Enrichment of minerals. Collection of tasks. - L.: LGI, 1986. - 64 p.