WO2009003906A1 - Method and associated bed grinding mill for the continuous comminution of brittle ground stock - Google Patents

Abstract

The invention relates to a method for the continuous comminution of brittle ground stock, in particular ore, in which the ground stock being comminuted is fed through the gap between two counterrotating rollers, wherein the roll sleeves have mounted hard elements forming an autogenous anti-wear protection. The invention further relates to a corresponding grinding mill for carrying out the method.

Description

 Method and associated good bed roller mill for the continuous comminution of brittle material to be ground

The invention relates to a method for the continuous comminution of brittle material to be crushed, in particular ore, in which the ground material to be comminuted is guided through the gap of two counter-rotating rollers, wherein the roller casings have embedded hard bodies for forming an autogenous wear protection. In addition, the invention relates to a corresponding for performing the method Gutbettwalzenmühle.

In roll mills, brittle material to be ground is fed into the nip, by which the two rotatably mounted, counterrotatable rolls are separated from one another, where they are subjected to pressure comminution in the material bed. Depending on the hardness of the material to be comminuted, the roll mantle, like the roll main body, is subjected to a very considerable load due to wear and continuous flexing movements of the entire roll. In order to minimize the wear of the roll shell through the ground material to be comminuted, it is known from DE 40 36 040 A1 to provide the roll shell with embedded hard bodies, wherein the hard bodies protrude from the surface of the roll shell. In the space between adjacent hard bodies the surface of the roll mantle is stored in the use of the roll mill, the grinding material to be crushed, wherein a layer is formed which is fixed on the roll shell by the hard body and thus serves as an actual surface of the roll shells. Training and strength of these autogenous wear protection layers are dependent on various material properties, such as the fracture characteristics and the moisture of the ground material to be crushed. The individual particles of the ground material drawn into the nip are then comminuted in a bed of material, ie in a compressed between two armored roll surfaces bulk material when using a high pressure, which is referred to the Gutbettzerkleinerung.

If moisture is an essential parameter for the formation of a good bed, because the moisture holds these together by adhesion forces between the individual particles of the ground material to be comminuted, it is necessary for the ground material to be comminuted to have a certain minimum moisture content. This is usually not a problem. However, if particularly dry materials are to be comminuted by a good bed roller mill, it has been found that the layer of material to be crushed on the surface of the roll shell is not formed and thus it does not come to the benefits of an autogenous wear protection layer on the surface of the Roller mill offers.

For particularly dry materials, ie those which have moisture of less than two percent, it has been observed that the desired good bed or the autogenous wear protection layer actually does not form or only inadequately. Such materials are found, for example, in the overburden mining of iron or other ores that originate from very dry areas.

Since humidification of the material to be grounded is prohibited in desert areas due to the ever-present lack of water there, it is an object of the invention to provide a method and an associated roller mill for the continuous comminution of particularly dry and brittle material available.

The object according to the invention is achieved by the use of a moistened good bed on the roll surface. Further advantageous embodiments of the invention will become apparent from the corresponding to method claim 1 dependent claims.

Another object of the invention is to provide a roller mill for carrying out the method according to the invention.

This object is achieved in that in addition to a first material for the material to be ground at least a second material loading is arranged, which liquid and / or, a moistened Mahlgutfraktion and / or a Mahlgutfraktion with respect to the millbase changed composition applies to the rollers.

According to the invention, it is proposed to use a moistened good bed on the roll surface. In contrast to the known use of a good bed on the roll surface, which consists of the millbase to be comminuted itself, the invention proposes to use a moist bed of good quality on the surface of the roll to be comminuted. If the ground material to be comminuted is itself moist, it is not necessary to use a special moistened product bed on the roll surface. However, if the comminuted material to be comminuted has a particular dryness or in its state has only a slight tendency to form a Gutbettts or an autogenous wear protection layer, it has proved to be advantageous if a moist or moistened Gutbett is used on the roll surface.

A moist or moistened good bed can be obtained by applying different fractions of material to the rolls. In this case, the larger fraction is the ground material to be comminuted and the smaller fraction is, for example, water, a moisture-displaced fraction of the ground material to be comminuted or a fraction of the ground material mixed with other substances or substance mixtures.

Advantageously, the invention is applied to the roll with moist or moistened ground material, wherein the wet ground material is applied further away from the nip on the rollers and the ground material to be crushed is added directly into the nip. In this case, the moist millbase is added in only a small concentration to the roll mill, so that an autogenous wear protection is formed and this is used for crushing the dry millbase. This method has the advantage that the roll mill can be operated with a substantially smaller amount of moisture in the total amount of ground material to be comminuted, without having to forego the advantages of autogenous wear protection. In this case it is possible to mix the smaller and moist millbase fraction with the drier millbase fraction, but it is also possible to choose different application sites on the roller for the different fractions, so that the moist millbase comes to rest on the drum surface under the drier millbase and thus serves as a wear protection layer for the dry regrind.

In an advantageous embodiment of the invention, the fraction, which is intended for the formation of the wear protection layer, clay, clay, fine sand or other materials that have a tendency to lump, be attached so that the smaller fraction tends even more to form a permanent wear protection layer.

In a particularly advantageous embodiment of the invention, liquid is sprayed onto the roll surface and the entire grinding stock fraction to be comminuted is beaten onto the roll mill in a known manner. The advantage of this is a particularly simple modification of existing roll mills, since they only need to be sprayed with water at a small distance from the nip, so that the liquid present on the roll surface forms a good bed together with the millbase to be comminuted.

It has proven to be advantageous when water, seawater, sewage, agricultural waste, industrial wastewater and / or liquid industrial waste are used as a liquid. Moreover, it is also advantageous if viscosity-influencing substances or substance mixtures are used in the liquid. This allows the necessary ge total amount of liquid based on the amount of ground material to be crushed even further reduced. The viscosity-influencing substances, which advantageously increase the viscosity of the liquid, generally lead to the individual particles of the ground material to be comminuted being formed by stronger adhesion forces forming a more stable layer of good bed while at the same time reducing the necessary amount of liquid. The viscosity-influencing substances may be binders, pulps, cellulose, vegetable flours, organic and / or inorganic salts or clay or clay minerals which are added to the liquid.

Preferably, 0.1% to 2%, preferably from 0.2% to 1% and particularly preferably from 0.3% to 0.5% of liquid per ton of millbase is sprayed onto the roll. The quantitative ratio is given in liters per ton of grinding stock to be comminuted.

In order to reduce the amount of liquid further, it has proved to be advantageous if an arrangement for controlling the amount of liquid application is used, this arrangement spraying more liquid at the same roller rotation speed with increasing freestanding of the roll shell. As a result, a control loop is created which sprays more liquid onto the roll upon collapse of the bedding or wear protection layer formation, and if the bed of the bed is sufficiently formed, the amount of liquid is correspondingly reduced. As a result, liquid is only applied to the roll if a collapse of the good bed or the wear-resistant layer requires this, so that an excess of the water absorption is required. gens can be dispensed with the roller, which means a saving of liquid.

In addition to the arrangement for controlling the liquid application amount, it is also possible to use a model for real-time calculation of the order quantity, wherein the model has the Mahlguteintragsleistung and Mahlgutfeuchte as input parameters and with the help of this model, a liquid application performance is determined and set automatically. The use of a model for the real-time calculation of the application amount has the advantage that the free roll of the roll shell does not have to be determined, but it can be the Mahlguteintragsleistungen and Mahlgutbefuchte be determined that are analytically easier to determine than the release of the roll shell, by complex computerized control loops must be determined.

To implement the abovementioned method, a roll mill is proposed, the roll shells of which have a hard material applied to form an autogenous wear protection, wherein at least a second material application is provided in addition to a first material application for the material to be ground, which liquid and / or a wetted regrind fraction and / or a millbase fraction Apply with respect to the millbase modified composition on the rollers. In the simplest case, water is sprayed onto the roller mill so as to keep the autogenous wear protection layer moist.

The second application of material may be a simple spray head which sprays liquid onto the rollers, so that an autogenous wear protection fluid from the liquid and the dry grinding stock to be comminuted is produced. layer is formed or it is possible that the second material application hangs a previously moistened fraction to be comminuted millbase on the rollers, wherein the second material loading is further away from the nip than the material loading for the millbase to be comminuted.

Advantageously, a spray head for applying liquid to the rolls is arranged at an angle of 35 ° to 55 °, preferably about 45 ° to the vertical of the roll, this angle being measured from the vertical outwards with respect to the position of the nip ,

Here by an optimal application of the liquid is achieved on the roller, so that the roller mill can be operated with the least possible amount to form an autogenous wear protection layer.

If it is provided to regulate the second material loading, it has proved to be advantageous if the roll mill has an arrangement for regulating the power of the second material application, this arrangement for controlling the performance of the free release of the roll surface and determine the optimal liquid application amount or It is possible to determine from the grinding stock performance of the roller mill and the measured moisture of the grinding stock to be comminuted an order quantity of liquid or already wetted material to be ground.

The invention will be explained in more detail with reference to the following figures: Show it

Table 1: The particle size distribution of the test mate neck

Table 2: Summary of experimental conditions and results

FIG. 1: experimental setup,

Figure 2: a sketch of the present invention Gutbettwalzenmühle mit- spraying

FIG. 3: Roll surface after test E1 FIG. 4: Roll surface after test E2 FIG. 5: roll surface after test E3

Table 1 shows the particle size distribution of an iron ore from Mauritania originating from the El Aouj Mine. Here, the "material feed" column represents the cumulative material size distribution of the input material into the commodity bed mill in mass percent, the column "roll center" represents the cumulative material size distribution in the roll center, and the column "roll end" represents the cumulative material size distribution at the lateral ends of the roll. This illustrated ore was subjected to three experiments in accordance with the experimental conditions in Table 2 to determine the influence of the amount of moisture on the formation of an autogenous

Wear protection layer when spraying water on a roller mill üfateöθdhen.

8.00 54.25 88.74 56.65 83.13

8.00 54.25 88.74 56.65 83.13

5.60 43.49 83.10 44.63 76.37

2.80 26.46 69.40 29.12 62.36

1 .00 1 1 .32 49.32 14.51 43.23

0.500 8.24 38.23 9.65 33.23

0.315 6.23 30.96 6.87 26.75

0.200 4.38 23.38 4.50 20.07

0.125 2.85 16.60 2.72 14.17

From Table 2 it can be seen that in the first attempt, the dry ore was milled without spraying the roller. In Experiment E2, the dry ore was milled with a water feed rate of 0.75 liters per minute, which corresponds to a humidification of 0.13 liters of water per square meter of roll surface in the above-described roll mill, and the E3 attempt was with a spray rate of 2.0 liters per minute, which corresponds to an output of 0.36 liters of water per square meter roll surface under the conditions specified. Table 2:

Test condition E1 E2 E3

Moistening capacity per roller, l / min 0 0.75 2.00 Rotational frequency of the rollers, RPM 9.1 9.1 9.1 Water coating, l / m ² 0 0.13 0.36 Nitrogen pressure, bar 66 66 67 Specific pressure, N / mm ² 4.25 4.25 4.29 Flow rate, t / h 28.4 28.6 27.2 Specific flow rate, Ts / hm ³ 376 378 366 Energy requirement, net, kW 33.4 33.3 34, 1 specific energy kWh / t 1, 18 1, 16 1, 25 roll cover,% ^<1) 36 65 90 good bed, visual and haptic test soft, brittle, relatively firm, a tight, slightly too

(2) a lot of empty floor area brittle wet medium good bed layer thickness ⁽³⁾ 1 _2 2.5 4.0

(1) Estimation based on photographs

(2) visual-haptic examination

(3) max. Layer thickness: 5mnn, limited by height of the hard body

In Figure 1 is therefore shown how water was sprayed onto the experimental roller mill 2.3. For this purpose, a simple nozzle body 4 was used, which has sprayed water at an angle of about 40 to 45 degrees to the axis vertical on the roller 2, 3. The roller itself has a diameter of 0.8 meters and a width of 0.25 meters. The operating capacity of this roller mill is about 75 tons per hour. For the spraying experiments, an arrangement of two spray heads was arranged on both rollers at an angle of about 40 degrees with the vertical axis, said spray heads could give a maximum of about 2.5 liters per minute of water to the roller. For example, water was sprayed on every roller up to a maximum of 5 liters per minute during operation. To carry out the experiment, a relatively coarse nozzle was used so that the water was not finely dispersed. The finer the water is dispersed, the more efficient the effect of moistening, however, it is considered that a fine nozzle clogs more easily under the harsh conditions prevailing in the high bed roller mill than a coarse nozzle. Optimal atomization must be stopped by experimentation.

In Figure 2, the experimental arrangement of Figure 1 is shown in a perspective view. It can be clearly seen how a nozzle body 4, spray nozzles arranged next to one another spray liquid onto the roller 2.

The result of experiment E1 is shown in FIG. It adheres only a little to comminuted regrind on the roll surface. The material is brittle and breaks out very easily. On most of the surface no or only a very thin wear protection layer has built up, which is removable with a soft brush from the surface of the roller.

Under the conditions of experiment E2, a significantly better adhesion of the wear protection layer to the roll surface is achieved. It can be seen from FIG. 4 that more material is deposited on the roll surface and that the wear protection layer becomes thicker. Especially at the edge of the rollers more material has embedded. Nevertheless, the moistening performance is not sufficient, because on some parts of the roller surface no wear protection layer has yet built up. Under these conditions, the wear protection layer had already solidified and the stored material could be removed only with the aid of a steel brush from the surface of the roller.

The result of experiment E3 is a clearly complete adhesion of the wear protection layer on the surface of the rolls. FIG. 5 shows that the rollers are almost completely covered with the autogenous coating, and that the layer thickness has reached a maximum height, so that the embedded hard bodies have the same height as the wear protection layer located therebetween. The embedded between the hard bodies material was difficult to remove under the experimental conditions E3, with a steel brush or a screwdriver had to be used to remove the anti-wear layer.

Claims

Method and associated good bed roller mill for the continuous comminution of brittle regrind P ATENTANSPR Ü CHE 1. A method for the continuous comminution of brittle material to be crushed, in particular ore, in which the grinding stock to be comminuted is guided through the gap of two counter-rotating rollers, the rollers having embedded hard bodies for forming an autogenous wear protection, marked by the use of a wetted good bed on the roll surface. 2. The method according to claim 1, marked by The loading of the rolls with moistened regrind, wherein the millbase to be comminuted into a larger and a smaller fraction. the smaller fraction is moistened and the larger fraction is left unburned. 3. The method according to claim 2, marked by a different place of application of the wetter and the drier fraction. 4. The method according to any one of claims 1 to 3, marked by the use of a roller wear protection layer of a different composition than the material to be ground, wherein the bed of soil is enriched with clay, clay, fine sand or other materials having a tendency to lump. 5. The method according to claim 1, marked by the spraying of liquid onto the roll surface of the rolls. 6. The method according to claim 5, marked by the use of water, seawater, sewage, agricultural waste, industrial wastewater and / or industrial liquid waste as a liquid. 7. The method according to any one of claims 5 to 6, marked by the use of viscosity-influencing substances or mixtures of substances in the liquid. 8. The method according to claim 7, marked by the use of binders, pulps, cellulose, vegetable meal, organic and / or inorganic salts as viscosity-enhancing substance or viscosity-influencing substance mixture. 9. The method according to any one of claims 5 to 8, marked by the spraying of 0.1% to 2%, preferably from 0.2% to 1%, particularly preferably from 0.3% to 0.5% liquid per ton of millbase, wherein the quantitative ratio in liters per ton is given. 10. The method according to any one of claims 5 to 9, marked by the use of an arrangement for controlling the amount of liquid application, wherein more liquid is sprayed with increasing free rotation of the roll shell at the same roller rotation speed of the roller. 11. The method according to any one of claims 5 to 10, marked by the use of a model for the real-time calculation of the order quantity of the liquid, wherein the millbase input power and the millbase moisture are received as input parameters, and a liquid application performance is determined and set automatically with the aid of the model. 12. roll mill whose roller shells have embedded hard bodies for the formation of an autogenous wear protection, characterized in that in addition to a first material for the material to be ground at least a second material loading is arranged, which liquid and / or a moistened Mahlgutfraktion and / or a Mahlgutfraktion with respect to the millbase modified composition on the rollers. 13. Roll mill according to claim 12, characterized, that at least one spray head sprays liquid onto one roller each. 14. Roll mill according to claim 13, characterized the at least one spray head at an angle (α) is arranged from 35 ° to 55 ^e, which is opposite from the current drawn by the roll axis vertical plane to the rolling direction of rotation measured. 15. Roll mill according to claim 12, that an arrangement is provided in addition to the Mahlguteintragsort that applies a different Mahlgutfraktion on the roller. 16. Roll mill according to one of claims 12 to 15, characterized, that an arrangement for the performance of the second Materialbeaufschlagung control is provided.