RU2361675C2 - Method for fine grinding of cement clinker - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention is related to technologies of cement clinker fine grinding in conditions of large-tonnage production and may be used in cement industry. Method for fine grinding of cement clinker includes stage of preliminary grinding in impact grinder and stage of fine crushing in tubular mill. Preliminary grinding is realised in vertical rotor-chain crusher, having linear velocity of impact elements rotation of 20-150 m/s, and producing ground product with specific surface of 300-3100 cm²/g, and tubular mill efficiency is determined on the basis of the following ratio: P_GRIND=P_INIT·K, where P_GRIND is efficiency of double-stage grinding with account of particle size after rotor-chain grinder; P_INIT is efficiency of tubular mill without preliminary grinding in rotor-chain grinder; K is proportionality ratio,

where k₁ is coefficient that accounts effect of specific surface of ground product at efficiency determined according to table; k₂ is coefficient that accounts effect of rotor-chain grinder working elements wear, k₂=1.0÷0.85; a₁ is material size after grinding in rotor-chain grinder; a is size of initial product.

EFFECT: reduced energy intensity of grinding process, simplified used equipment, reduced costs for maintenance and repair.

5 cl, 1 dwg

Description

The present invention relates to technologies for fine grinding of cement clinker in the conditions of large-scale production and can be used in the cement industry.

A known method of fine grinding in a drum mill, carried out by exposing the processed medium to a grinding charge (balls or tsilpeps) (see Perov V.A., Andreev E.B., Bilenko L.F. Crushing, grinding and screening of minerals. - M .: Nedra, 1990, p. 169-170).

This method of grinding is characterized by extremely low energy efficiency and is due to a number of factors: a small number of useful collisions of grinding media, amounting to one in a thousand, the irrationality of the selection of grinding media by size, since particles of polydisperse composition are present in the apparatus, large losses in the drive system, etc. d.

There is also a method of grinding high-strength cement in a drum mill with the introduction of a grinding intensifier in the form of a mineral additive with a strength of 100-200% of the strength of cement and containing 40-80% of a fraction of 1-30 microns (see ed. Certificate. USSR No. 59244, Mcl ² В02С 17/00, BI No. 6, publ. 15.02.78).

This technical solution is also largely characterized by very high energy consumption. This lies both in the inefficiency of ball grinding of a mixture of particles of a polydisperse composition with a large range of particle size dispersion, which was described above, and in the high energy consumption of producing an additive, which is a ready-made cement.

The closest in technical essence and the achieved technical, technological and economic result to the proposed invention is a method of two-stage grinding of materials with the stage of coarse grinding of tube ball mills in a press roller mill (see Pirockiy V.Z. Improving the technique and technology of grinding Portland cement clinker: evaluation of the efficiency of grinding systems // Collected Works of the Research Institute of Cement, 1986, issue 90, pp. 3-23).

Now the main machines in large-tonnage production are tube ball mills. They have an efficiency of less than 1% and are characterized by huge operating costs, especially in terms of electricity. There has been a steady trend in the use of aggregates for pre-grinding of feedstock, which is especially characteristic of the cement industry. The most widespread here is the press roller grind. Such grinding systems generally provide a reduction in specific energy consumption by about 30%.

However, the material crushed in a press-roll grinder has specific properties, has a commodity form of pressed plates with maximum strength in the direction of force, and its constituent particles have a microdefect structure. All this requires the inclusion in the grinding system of either an additional apparatus for the disaggregation of pressed leather, or equipping the tube mills with special devices for their destruction in the mill space. All this together complicates the technological cycle of raw materials processing and hinders the widespread adoption of such complexes. To this it should be added that press roller shredders cannot process the material in a wet way.

Numerous attempts to use impact crushers - hammer and centrifugal, for fine grinding of strong and abrasive materials (see Duda V. Cement M .: Stroyizdat, 1981, - 392 p.) Were unsuccessful, since such a grinding method leads to intensive wear of elements design, requires special balancing, massive and rapidly rotating rotors with working shock elements. Depreciation, in turn, leads to destabilization of the grain composition and makes the aggregate grinding process difficult to manage, especially taking into account machine stops to replace worn parts and elements.

One of the new types of machines for the effective grinding of mineral raw materials is the impact-centrifugal rotor-chain crusher-mill (see Shulyak V.A., Sivachenko L.A., Seleznev N.G. Adaptive rotor-chain crushers // Mineral processing. - 1994, No. 2, pp. 40-44).

These machines are not only simple in design, but also provide a finely dispersed product with a cement or flotation particle size content of 20 to 60% for one processing cycle with an initial particle size of 40-60, 20-40 or 10-20 mm coming into the processing and with an energy consumption of grinding of 1.5-4.0 kW · h / t.

However, such a grinding unit cannot completely grind the product to the required dispersion, which makes it necessary to additionally equip the grinding system with a fine grinding mill, or to equip the rotor-chain crusher-mill with equipment for classifying the processed material with a circulation rate from 2 to 6-7. The latter direction is advisable only for rough processing of low-strength materials, such as chalk, limestone, lime, etc. On durable materials and during fine or ultrafine grinding, grains of especially strong particles will accumulate, which will lead to instability of the grinding complex, since impact destruction is similarly effective when an individual grain with a grain size of more than 2-3 mm is impacted, and the destruction of individual grains with a grain size of 0 , 2-0.3 mm practically stops at a linear impact speed even above 100 m / s, although wear already at a speed of 75-80 m / s can reach 0.2-0.3 kg / t of crushed product.

The aim of the invention is to reduce the energy intensity of the grinding process by improving technology, equipment and optimizing the stages of coarse and fine grinding of cement clinker.

The goal is achieved in that in accordance with the method of fine grinding of cement clinker, including the stage of preliminary grinding in the impact mill and the stage of fine grinding in the tube mill, according to the invention, the preliminary grinding is carried out in a vertical rotor chain mill having a linear speed of rotation of the impact elements 20 -150 m / s and grinding product to a specific surface of 300-3100 cm ² / g, and the performance of the tube mill is determined from the ratio

P _meas = P _out · K,

where P _ISM - the performance of two-stage grinding, taking into account the particle size after the rotor chain crusher;

P _ISM - the performance of the tube mill without preliminary grinding in a rotary chain grinder;

K - coefficient of proportionality

where k ₁ - coefficient taking into account the influence of the specific surface of the crushed product on the performance, determined by table 1.

Table 1 The specific surface of the finished product, S, cm ² / g 6500 6000 5500 5000 4500 4000 3500 3000 k 0.25-0.60 0.30-0.70 0.35-0.75 0.40-0.85 0.45-0.9 0.50-0.95 0.55-1.05 0.6-1.1

k ₂ - coefficient taking into account the influence of wear of the working elements of the rotor - chain crusher; k ₂ = 1.0 ÷ 0.85

a ₁ - the fineness of the material after grinding in a rotary chain grinder;

and - the size of the original product.

In addition, in additional embodiments of the method, it is provided that fine grinding in a tube mill is ensured by ball loading with a diameter of 5-75 mm, cilpeps with a diameter of 8-50 mm or a mixture of balls and cilpeps with a percentage of balls of 0-100%. The method can also be implemented in such a way that after grinding in a rotary chain grinder, the fine fraction is selected, and the grits are fed to the milling mill in the tube mill.

In the process of grinding the feedstock in a rotary chain crusher with a linear impact velocity of 20-150 m / s, the effective destruction of solid particles is ensured. The selected range of linear impact velocities is determined by both the properties of the material being destroyed and the operating conditions of the apparatus itself. The maximum rotation speed is limited by the operating conditions of the bearing assemblies of the chopper and the requirements for balancing the rotor. At an impact speed of 10 m / s, brittle materials, for example, low-strength ore with large inclusions of valuable minerals, should be crushed. The impact speed of less than 10 m / s is ineffective in terms of the destruction of solids. For the vast majority of mineral raw materials, its destruction should be carried out at high-speed loading of 40 ... 90 m / s, which allows to obtain from 20 to 60% of particles with sizes less than 80 microns in one pass for most materials. This occurs when grinding clinker, ores of ferrous and non-ferrous metals, coal, coke, marl, fillers of all kinds, lime and other materials. It should be borne in mind that each type of destructible product has its own speed regime, and the optimization of this process is limited to a negative increase in wear, the proportionality of which grows in the square relative to the rate of destruction. The choice of the desired speed parameter for the operation of the rotor chain crusher is in the triangle: the degree of grinding - wear of the working headset - power consumption.

Obtaining a crushed product after a rotor chain crusher with a specific surface of 300-3100 cm ² / g is necessary for rational loading of the tube mill and is provided by changing the following parameters: the number of rows, the number of branches of the shock elements, the linear velocity of the impacts, the amount of material supplied to the apparatus, etc. d. For different materials, this value will be different.

The performance of the tube mill in the proposed method is functionally related to the operation of the rotor chain crusher. The grinding kinetics inherent in the dependencies that determine the performance of the two stages of grinding allows you to take into account all the features of the unit: the performance of the rotor chain crusher, the degree of grinding in it, estimated by the average particle size before and after processing, the performance of the tube mill in accordance with the dispersion of the crushed product at the final stage.

Signs 2-4, introduced in the claims, allow the user of the invention to have a set of factors with which you can control the dispersion of the granular product. So, these signs make it possible to obtain such a number of strokes to particles of material from grinding media, which will lead to the desired dispersion.

The implementation of the tube mill is preferably single chamber is logically justified, because finely ground product does not require a large difference in the assortment of grinding media. The latter are recommended to be selected in accordance with paragraphs 2-4 of the claims: Technological developments in this area allow this to be done quite accurately. The selection of the crushed and ready-to-use part of the product after the rotor chain crusher allows to reduce the load on the tube mill and significantly reduce the specific energy consumption due to the lower processing volume. The selection of crushed powder can be carried out by means of a pneumatic classifier or screw loaders.

The features included in the characterizing part of the claims are new, neither analogues nor prototypes have, and ensure the achievement of the goal.

An example implementation of the method. The processed material is cement clinker PRUP "Krichevcementoshifer" (Krichev, Mogilev region) with a particle size of 0-50 mm.

Used equipment for grinding:

I. Rotary chain crusher. Its technical characteristics are given in table 2.

table 2
Technical Specifications of Rotor Chain Crusher Parameter Name unit of measurement Value 1. Mineral performance t / h 30-100 2. The maximum size of the processed material mm one hundred 3. The particle size of the crushed product is less than 1 mm % 50-95 4. The diameter of the working chamber mm 1500 5. The height of the working chamber mm 930 6. The linear velocity of the shock elements m 58 7. The number of rows of percussion elements PC. 3-12 8. Power of the drive electric motor kw 200 9. Overall dimensions length mm 4400 width 2900 height 3100 10 mass kg 4650

2. Tube ball mill 3.2 × 15 m. Used without modernization in a two-chamber design with loading balls and cilpeps, respectively, into these chambers. [Construction vehicles. Directory. T.2. Ed. Bauman V.L. and Lanira F.A. - M.: Mechanical Engineering, 1977, p. 59-61].

A diagram of the grinding complex for implementing the method is shown in the drawing, which shows: 1 - supply of gypsum, 2 - supply of clinker, 3 - rotor chain crusher, 4 - tube mill, 5-6, respectively, chambers for grinding with balls and tsilpeps. The tube mill was loaded with 60 tons of balls with a diameter of 50-75 mm into the first chamber and 50 tons of cilpeps with a diameter of 18 and 25 mm in the second. The rotor chain crusher developed and simultaneously fed the required amount of material into the transport line of the tube mill, where it was crushed in the mode corresponding to the passport data.

The results of a sieve analysis of crushed clinker after a rotor chain crusher showed that 30% of the material is less than 0.08 mm, and larger than 0.2 and 1.0 mm, respectively 45 and 8%. The specific surface of the crushed clinker was 1750 cm ² / g.

This is achieved with a specific energy consumption of 3.0-3.2 kW · h / t clinker.

The finely dispersed material thus obtained was then fed into a 3.2 × 15 m tube ball mill. The productivity of the tube mill was determined based on the formula

where P _Izm = 50 t / h - determined by passport data.

k is selected according to table 1 for cement with S = 5000 cm ² / g, and a ₁ are found by sieve analysis of samples of the material of the initial clinker and clinker, crushed in a rotary chain grinder. This is the average particle size of the material, mm.

As a result, we have

P _meas = 50 × 1.08 = 54 t / h.

As a result, cement was obtained, characterized by a specific surface area of 5240 cm ² / g and corresponding to GOST 10178-76.

The power of the main drive consumed by the electric motor reached 1600 kW. The total energy consumption of grinding cement clinker was 32.6 kWh / t.

The combination of impact and impact-abrasion effects on the processed material allows you to get the best product in terms of particle size distribution and grain shape, which is especially important in the production of building materials.

The use of the invention in comparison with the known methods of fine grinding cement clinker reduces the specific energy consumption by 1.3-1.8 times, reduces the cost of the entire material processing cycle, simplifies the hardware design, reduces maintenance and repair costs.

This is due to the increased technological and energy efficiency of the rotor chain crusher, which implements the principle of free impacts with the effect on individual grains, the removal of crushed particles from the apparatus due to gravitational forces and optimal energy input into the environment of the material being destroyed.

The simplicity of the design of the rotor chain crusher, the ability to quickly replace worn working elements, the absence of wear of the machine body due to its self-lining can significantly reduce maintenance costs, the cost of crushed impact elements.

The main advantage of the method is the successful combination of the advantages of various types of grinding - shock and ball grinding.

The present invention can also be used in the implementation of the wet method of grinding the majority of mineral materials used in large-scale industries, where such processing is permissible from the point of view of their further use.

Claims (5)

1. The method of fine grinding of cement clinker, including the stage of preliminary grinding in a impact mill and the stage of fine grinding in a tube mill, characterized in that the preliminary grinding is carried out in a vertical rotary chain mill having a linear speed of rotation of the impact elements 20-150 m / s and grinding the product to a specific surface of 300-3100 cm ² / g, and the performance of the tube mill is determined from the ratio
P _meas = P _out · K,
where P _ISM - the performance of two-stage grinding, taking into account the particle size after the rotor chain crusher;
P _ref is the productivity of a tube mill without preliminary grinding in a rotary chain grinder;
K is the coefficient of proportionality,

where k ₁ - coefficient taking into account the influence of the specific surface of the crushed product on productivity, determined by the table:
The specific surface area of the finished product S,
cm ² / g 6500 6000 5500 5000 4500 4000 3500 3000 TO 0.25-0.60 0.30-0.70 0.35-0.75 0.40-0.85 0.45-0.9 0.50-0.95 0.55-1.05 0.60-1.1
k ₂ - coefficient taking into account the impact of wear of the working elements of the rotor chain crusher, k ₂ = 1,0 ÷ 0,85;
a ₁ - the fineness of the material after grinding in a rotary chain grinder;
and - the size of the original product. 2. The method of fine grinding according to claim 1, characterized in that the fine grinding is carried out, preferably, in a single chamber tube mill with a ball load with a diameter of 5-75 mm 3. The method of fine grinding according to claim 1 or 2, characterized in that the grinding in a tube mill is carried out by cilpeps with a diameter of 8-50 mm. 4. The method of fine grinding according to claim 1, characterized in that the grinding in a tube mill is carried out with a mixture of balls and zilceps with a percentage of balls of 0-100%. 5. The method of fine grinding according to claim 1, characterized in that after grinding in a rotary chain grinder, a fine fraction is selected, and the grits are sent to a milling mill in a tube mill.