DK2525911T3 - Process and apparatus for pre-grinding and finishing of mineral and non-mineral materials - Google Patents

Description

Technical field

The invention relates to a method and a device for coarse grinding and fine grinding of mineral and non-mineral materials, preferably hard and brittle materials such as e.g. limestone, cement clinker, slag sand, old concrete or ashes, wherein the material to be comminuted is fed into the first roller gap which forms between a lower driven roller and an upper roller, wherein in the region of the vertex of the lower driven roller a quantity of the material to be processed is fed as a material layer, the thickness of which can be adjusted, to the lower driven roller and supplied to the first roller gap, and wherein the upper roller is elastically set against the lower driven roller with an adjustable pressing force and dragged by friction fit with the material layer or has a dedicated drive.

State of the art

The coarse grinding and fine grinding of preferably hard and brittle materials, such as e.g. limestone, cement clinker, slag sand, old concrete or ashes, traditionally takes place in ball mills and more recently in vertical roller mills and also in high-pressure roller mills. A high-pressure roller mill called material-bed roll mill is known from DE 27 08 053 B2, in which the comminution of the material takes place by a single compressive-load application between two surfaces at pressures far greater than 50 MPa in the gap of two cylindrical rolls driven in opposite directions.

It is disadvantageous that the high-pressure roller mill operates at very high pressures which are adjustable to only a limited extent and lead to an expensive and very heavy machine design. Moreover, the high-pressure roller mill has an unfavorable throughput-to-speed behavior. The throughput characteristic line of the high-pressure roller mill is non-linear i.e., depending on the material properties and also on the geometry of the surfaces subjected to load stress, the throughput drops markedly as the circumferential speed increases with a simultaneous increase in the specific energy requirement. High throughputs are therefore possible only by widening the grinding rollers with a proportional increase in the pressing forces, which is, however, limited in mechanical engineering terms.

To improve the procedure as well as the energy utilization of vertical roller mills and also high-pressure roller mills, it is known from WO 99/54044 to channel the material to be comminuted, prepared as a defined layer on a circulating plate conveyor, horizontally into the gap formed between a roller hydropneumatically adjusted onto the material layer and a moving plate conveyor, and subjected to load stress by applying specific pressing forces in the range from 6 to 30 MPa or 6000 to 30000 kN/m2, respectively. Extensive investigations have shown that, because of technical limits, this process principle can neither replace the vertical roller mill nor the high-pressure roller mill.

Firstly, the material channeling of a material layer prepared on a circulating plate conveyor requires a large technical outlay, as the plate conveyor must be also be laid out for the high applications of compressive load stress in the loading zone, whereby to control the wear of both the tension member and the plating and also to limit noise pollution, significant speed and throughput reductions must be accepted.

Secondly, material channelling using a plate conveyor pulled over the driven lower roller leads to high losses for reasons associated with mechanical engineering.

Thirdly, the arrangement of a grinding roller hydropneumatically adjusted onto the horizontally guided plate conveyor impairs the material feed, with the result that material can jam and overflow.

Fourthly, efficient fine grinding up to a Blaine value of 5000 and higher by means of a single pressure roller is not unlimitedly realizable because of the high portion of circulating product and its high portion of air supply in view of the speed of the grinding roller of up to 4 m/s and higher. The Blaine value is a standardized measure of the grade of fine grinding of cement and results from its specific surface area (cm2/g). Standard Portland cement CEM I 32.5 has a Blaine value of approximately 3,000 to 3,500. A roll press with a drive roll and two offset smaller idling rolls is known from DE 38 23 929 A1. The ground material drops from the discharge-side end of a conveyor belt into the roll gap formed by the drive roll and the first idling roll. Alternatively, the ground material can also be transported into the roll gap by means of a drop tube. The compressed ground material is subsequently mixed with return product and then conveyed to the second roller gap which is formed from the drive roll and the second idling roll, whereby the product is ground to the desired product fineness. The grinding compression pressures can be set to values of between 50 and 600 MPa. A roll mill with a fixed roll, a vertically offset clearance roll and a product-feed device is known from DE 28 30 864 A1, wherein the straight line defined by the centers of the two rolls forms an angle of between 35 and 75 degrees to the horizontal. The discharge-side end of the product-feed device is located above the topmost region of the circumference of the lower fixed roll. A slider serves to adjust the height of the product layer which is conveyed to the roller gap. The product-feed device can have at least one movable element which imparts a movement component in the direction of the roll movement to the ground material, with the result that the ground material reaches the circumferential speed of the roll more quickly. A multi roll mill for grinding granular material is known from WO 00/56458 A1 which has a driven roll and three non-driven rolls. Each grinding roll is provided with a hydraulic mechanism for applying individual ground pressures. Furthermore, the mill possesses a reservoir that enables adjusting the layer thickness of raw material that is fed into the first roll gap. The non-driven rollers can be mechanically, hydraulically or electrically decelerated, wherein subjection to shear stress in the grinding region can be generated with the help of the breaking device. A multi roll mill for grinding food, animal feed or other pourable materials which has two fixed rollers and two grinding rolls, which are assigned to each fixed roll is known from DE 195 14 955 C2. The ground material is conveyed to the first grinding gap, which is formed between the fixed roll and the upper grinding roll, and then conveyed to a second grinding gap, which is formed between the fixed roll and the lower grinding roll. The fixed rolls and the grinding rolls have a joint drive 18. A roll press for grinding granular material is known from EP 0 399 192 A1, which has two rolls, a product-feed duct and a pre-compressing roll for compressing the feed product prior to conveyance to the roll gap. The rolls have a dedicated drive and a dedicated pressure application mechanism. A roller mill for the coarse and fine grinding of mineral and non-mineral materials, such as e.g. limestone, cement clinker, slag sand, old concrete or ashes is known from WO 2009/037356 A1, wherein the ground material is fed as a defined and laterally limited material layer with predefined thickness from a material feed container belonging to the comminution apparatus, with the help of a roll or star wheel feeder, which is attached to the outlet and the rotational speed of which can be altered continuously, to the vertex of the driven lower roller provided with lateral rims, accelerated to the roller speed, and continually transported into the gap formed with the upper roller, which is provided offset above the driven roller, hydropneumatically subjected to load stress by applying specific pressing forces of 2 to 7.5 kN/mm and subsequently deagglomerated by a preferably fast running impact rotor within the comminution device. In this way, high energy efficiency and also a low outlay on mechanical construction, maintenance and upkeep is achieved. Application in a broad range for comminution of different materials is possible and implementing a linear throughput and speed behavior both in partial-load operation and under the conditions of high mass throughputs is realizable.

The object of the invention is to provide a method and the corresponding device for the coarse and fine grinding of mineral and non-mineral materials, such as e.g. limestone, cement clinker, slag sand, old concrete or ashes, with a fineness of a Blaine value of up to 5000 and higher, characterized by a high energy utilization and also by a low outlay on mechanical construction, maintenance and upkeep, able to be used in a wide range to comminute different materials and implementing a linear throughput-to-speed behavior both in partial-load operation and under the conditions of high mass throughputs.

The object is achieved according to the invention with a method according to claim 1 and a device according to claim 6.

The material to be comminuted is fed from a material feed container by means of a conveyor belt as a laterally limited material web to the first roller gap.

Preferred embodiments of the invention are specified in the dependent claims.

The ground material, normally consisting of fresh and circulating ground material, is fed from a material feed container forming part of the comminution apparatus as a defined and laterally limited material layer with a predefined thickness on a conveyor belt with variable speed, the speed being preferably adjusted to the circumferential speed of the driven lower roller in the region of the vertex of the driven lower roller. Beater rollers, provided in the region of the conveyor belt, hereby already provide a first ventilation of the ground material. The ground material is continually conveyed by the driven lower roller to the first gap, which is formed with the upper pressure roller provided above the lower driven roller and is hydropneumatically subjected to load stress by applying specific pressing forces of 1,000 to 3,500 kN/m2. By subjection to load stress by the upper grinding roller, the ground material is on the one hand repeatedly vented and on the other hand already pre-comminuted. The final comminution then takes place in the second grinding gap, which is formed with the lateral pressure roller and which is also hydropneumatically subjected to load stress by applying specific pressing forces of 1,000 to 5,000 kN/m2. Subsequently, the ground material is deagglomerated by a prefereably fast running impact rotor within the comminution device. The deagglomerator can be dispensed with, if the new comminution device is operated e.g. as a pre-mill in combination with a ball mill.

The device comprises three rollers, namely a lower driven roller, an upper roller and a roller which is provided laterally offset. The upper roller is offset by 70° to 90°, preferably 80° to 90°, to the horizontal counter to the rotational direction of the lower roller and is adjusted with a pressure of up to approximately 3,500 kN/m2 (corresponding to a value of up to approximately 3 to 5.5 kN/mm (force/gap length)) onto the material-covered surface subjected to load stress of the driven lower roller. The lateral roller is offset by 45° to 60°, preferably approximately 45°, to the horizontal counter to the rotational direction of the lower roller and is adjusted with a pressure of up to approximately 5,000 kN/m2 (corresponding to a value of up to approximately 7.5 kN/mm (force/gap length)) onto the material-covered surface subjected to load stress of the driven lower roller. The upper rollers and the laterally offset roller are connected with a hydropneumatic system of levers for the generation of the grinding force. Hereby, they can be provided with a dedicated drive or can be dragged along by the lower roller. The material subjected to load stress, which emerges from the second roller gap more or less agglomerated, is eventually supplied to a directly following deagglomerator.

The material feed container is a vertical duct, which is positioned above the beginning of a revolving conveyor belt. The top side of the conveyor belt is bordered by two lateral, parallelly running plates. The lateral parts of the material feed container overlap slightly with the inner part of these plates, such that the ground material is fed to the region bordered by the plates. The outlet opening of the material feed container can be regulated by means of a height adjustable sluice. The material layer conveyed to the first roll gap is hence laterally limited and has a substantially rectangularly-shaped cross-section, i.e. a uniform thickness. At the lower edge of the plate, elastic lips are provided, which touch the conveyor belt.

Below the upper strand of the conveyor belt, multiple beater rollers are provided. The ground material lying on the conveyor belt is caused to vibrate by the beater rollers, such that the homogeneity and uniformity of the ground material layer is improved and the ground material is vented.

In the first roller gap, which is formed between the upper and lower roller, the ground material is pressed against the lower roller such that it adheringly rests on the lower roller and such that a defined material-bed is obtained for further processing. The pressing force required for this is dependent on the humidity and the fineness of grind of the ground material.

The pressure of the first roller gap is set such that no oscillations occur at the lateral roller. Oscillations do occur, if the pressure in the first roller gap is too high.

Because the homogeneity and the uniformity of the material-bed is also kept when conveyed to the second roller gap, the pressure in the second roller gap can adjusted arbitrarily in the range from 0 to 10 kN/mm and in correspondence to the desired comminution.

Preferably, by observing a maximally possible material layer thickness, the material throughput thorough the roller gap is regulated according to a continuous change in the circumferential speed of the driven roller.

Preferably, during fine grinding, the material portion with excessive grain size is returned to the comminution process, wherein the mass flow of the circulating product is kept constant by adjusting the fresh product conveyed to the grinding process.

Preferably, depending on the material properties and the desired comminution result, the grinding force transmitted with the upper and the lateral roller can be regulated during the grinding process and adjusted independently of each other.

Preferably, a mass flow proportional to the circumferential speed of the roller with an approximately constant layer thickness in the region of the vertex of the lower roller is conveyed in by means of the material feed apparatus.

Preferably, the circulating product is conveyed to the comminution device with admixed fresh product.

Preferably, the thickness of the material layer is continuously measured and displayed during operation before it is subjected to load stress in the roller gap.

Preferably, the ratio of the diameter of the driven lower roller to that of the upper and lateral roller is > 1.5, and particularly preferably 2.0 to 3.0 (This ratio of diameters is not adhered to in Fig. 3).

Preferably, to generate the grinding force, the upper and lateral roller is connected to at least one hydraulic cylinder via a system of levers.

Preferably, replaceable rims are attached to both sides at the ends of the lower roller to laterally restrict the material layer. The rims may be segmented.

Preferably, the surfaces of the rollers subjected to load stress are designed wear-protected and structured by deposit welding or mechanical working.

The beater rollers are n-cornered, e.g. triangular rollers in cross-section, which are provided below the conveyor belt and are in mechanical contact with the conveyor belt of the material feed apparatus. Rotation of the n-cornered beater rollers results in the beating process occurring n-times per rotation, by which the conveyor belt is exposed to permanent vibrations. Due to the vibrations of the conveyor belt, the material layer located on the conveyor belt is compressed and vented, respectively.

The drive of the upper and the lateral roller serves to accelerate the start-up of the roll mill, in particular in the case of large and heavy installations. However, it is thereby also possible to purposefully allow the pressure rolls during the grinding process to run slower than the fixed roll, whereby the ground material also experiences a horizontal shearing pressure component in addition to the vertical roll pressure.

The solution according to the invention which realizes these features has a number of further advantages compared with the known high-pressure roller mill, belt-roller mill and multi-roller mill. The advantages of the multi-roller mill according to the invention in process engineering terms are that specific grinding forces can be set in two grinding stages as desired depending on both the material and the comminution objective to be achieved and the comminution result can be kept constant and defined irrespective of the roller speed by the parameters of the specific grinding force and the material layer thickness. In the first grinding stage, forces of up to 3,500 kN/m2 and in the second grinding stage grinding forces of up to 5,000 kN/m2 may be set. Hereby, it has been proven advantageous, in particular when fine grinding hard and brittle material such as e.g. cement clinkers and slag sands, to Blaine values up to 5,000, to apply the load stress using high specific grinding forces whenever a particularly high-quality finished product with a high portion of entrapped air is to be produced in a loop with a separator profitably with the lowest possible number of rotations.

In mechanical engineering terms, the advantages of the comminution apparatus according to the invention compared to the comminution apparatus known from WO 2009/037356 A1, are that an additional grinding roller makes better fine grinding possible by which a quality of the finished product with Blaine values of up to 5,000 and higher can be achieved.

Brief description of the drawings

The invention is explained in more detail with the help of embodiment examples. In the associated drawings, there are shown in:

Fig. 1: the apparatus according to the invention in a schematic representation;

Fig. 2: a cross-section of the conveyance device and

Fig. 3: details about the conveyance of the ground material from the conveyor belt into the first roll gap.

Way(s) of carrying out the invention

Figure 1 shows, in a schematic representation, the comminution apparatus according to the invention, consisting of one driven lower roller 10, an upper roller 12, a laterally provided roller 14, and also a material feed and discharge device 18. The material feed and discharge device 18 has a material feed container 20, a conveyor belt 22, an apparatus 24 for adjusting the layer thickness of the ground material and also six beater rollers 26. The lower roller 10 is driven in accordance to direction of the arrow illustrated in Figure 1. Above the driven lower roller 10 is the provided the upper roller 12. The lateral roller 14 is provided laterally offset by an angle of approximately 45° to the horizontal counter to the rotational direction of the lower roller 10. The upper and the lateral roller 12, 14 are hydropneumatically adjusted against the lower roller 10 via a system of levers by means of a hydraulic cylinder. The upper and the lateral roller 12 and 14 are dragged by frictional fit with the material-covered surface subjected to load stress of the driven lower roller 10 or can have a dedicated drive. The diameter of the driven lower roller 10 is twice as big as the diameter of the upper and the lateral roller 12, 14. The material feed and discharge apparatus 18 is arranged in the region of the vertex of the driven lower roller 10. The ground material, which is in a filling-level-controlled container 20, reaches the conveyor belt 22 as a defined material layer 32 with a predefined thickness. A first ventilation phase of the ground material is achieved by subjection to load stress by the beater rollers 26 provided at the conveyor belt. The ground material is continually and with a defined speed conveyed to the lower roller 10 and subsequently conveyed to the first load or roller gap, respectively, formed by the rollers 10 and 12. In the first roller gap 34, the ground material is simultaneously vented and pre-comminuted. The final fine grinding then takes place in the second roller gap 36, which is formed by the laterally provided roller 14 and the driven lower roller 10.

As can be seen in Figure 2, the lower end of the material feed container 20 ends between two plates 38, which border, on the upper side of the conveyor belt 22, the region, in which the ground material is transported. For flexible sealing of this region, elastic lips 40 are provided at the lower end of the plates 38, which touch the upper side of the conveyor belt 22.

The conveyor belt 22 is slightly tilted in the direction of transport (Figure 3). At the frontal end of the conveyor belt 22, a sheet plate 42 is provided, which bridges the distance between the conveyor belt 22 and the lower roller 10, such that the homogeneity of the ground material is kept, and the ground material can be inserted into the first roller gap with a strength, which is exceedingly uniform transverse to the transport direction. Hereby, the lateral plates 38 are continued to the frontal end of the sheet plate 42. The surface of the driven lower roller 10 is also laterally borderd by circular plates 44, wherein the upper roller 12 and also the lateral roller 14, which is not shown in Figure 3, extend within these circular plates 44. The material web is hence also within the first and second roller gap 34, 36 laterally limited.

After the lateral roller 14, a scraping roller 46 is further provided, which removes adhering material from the surface of the lower roller 10. The scraping roller 46 rotates in opposite direction to the lower roller 10.

Reference signs list 10 driven lower roller 12 upper roller 14 lateral roller 18 material feed apparatus 20 material feed container 22 conveyor belt 24 apparatus for adjusting the layer thickness of the ground material 26 beater roller 30 system of levers 32 material layer 34 first roller gap 36 second roller gap 38 plates 40 seal 42 sheet plate 44 circular plate 46 scraping roller

Claims (10)

A process for pre-grinding and finishing of mineral and non-mineral materials, preferably hard and brittle materials such as e.g. limestone, cement clinker, granulated slag, old concrete or ash where the material to be comminuted is dispensed from a material feed container (20) via a conveyor belt (22) into the first roller slot (34) forming between a driven lower roller (10) and an upper roller (12) wherein, in the region at the apex of the lower driven roller (10), a quantity of the material to be processed is delivered as a material layer (32) adjustable in its thickness, to the lower driven roller (10) and fed to the first roller slot (34), where the upper roller (12) is resiliently mounted to the lower driven roller (10) with adjustable pressing force and is pulled by friction connection to the material layer (32) or has a drive of its own wherein the speed of the conveyor belt (22) is adapted to the circumferential speed of the driven lower roller (10), after which the grinding material is fed to a second roller slot (36) formed by the first roller slot (34) after passing through the first roller slot (34). n lower driven roller (10) and a laterally displaced roller (14) and wherein the laterally displaced roller (14) is also resiliently pressed against the lower driven roller (10) with adjustable pressing force and by frictional connection with the material layer (32). ) is pulled or has its own drive, characterized in that the conveyor belt (22) is subjected to vibration by means of which the material layer (32) located on the conveyor belt (22) is ventilated so that the material to be comminuted via the conveyor belt (22) is dispensed as a defined and laterally constrained material layer with a predetermined thickness down into the first roller slot (34) that the upper roller (12) is positioned at 70 ° to 90 ° relative to the horizontal towards the lower direction of rotation roller (10) and the laterally displaced roller (14) is positioned at 45 ° to 60 ° relative to the horizontal towards the direction of rotation of the lower roller (10). The method of claim 1, wherein the material to be comminuted is delivered to the first roll slot (34) from a material feed container (20) by means of a conveyor belt (22) as a laterally defined material web. A method according to any one of claims 1 to 2, wherein the upper roller and the side roller (12, 14) are further accelerated in their own operation when the grinding device is started or during the grinding process moving at a different speed than the lower roller (10), thus that by means of the relative movement of the rollers (10, 12, 14) an additional shear force is exerted on the grinding material. A method according to any one of the preceding claims, wherein the material portion is, in a final grinding, fed again to the grain-grinding process, wherein the mass flow rate of the feedstock material is kept constant by controlling the fresh raw material supplied to the grinding process. Process according to one of the preceding claims, wherein the grinding forces transmitted with the upper roller and the side roller (12, 14) are adjusted controlled during the grinding process depending on the material properties and the desired comminution result. 6. Process for pre-grinding and finishing of mineral and non-mineral materials, preferably hard and brittle materials such as e.g. limestone, cement clinker, granulated slag, old concrete or ash, with a comminuting device having a driven lower roller (10) and an upper roller (12), which are mounted horizontally and arranged one above the other, forming a first roller slot (34) , wherein the driven lower roller (10) is operated at a grinding web speed, with a feeding device (18), a material feed container (20) and a conveyor belt (22) which delivers the grinding material to the driven lower roller (10), wherein the conveyor belt (22) speed is adapted to the circumferential speed of the driven lower roller (10) and with a further laterally displaced roller (14) in addition to the upper roller (12), wherein the further laterally displaced roller (14) together with the driven lower roller (10) forms another roller slot (36), which is also elastically pressed against the driven lower roller (10) and is pulled or has its own drive by friction connection with the material layer (32).characterized in that cleaning rollers (26) are arranged below the conveyor belt (22) by means of which the material to be comminuted is ventilated on the conveyor belt (22) by vibrations, the upper roller (12) being arranged at 70 ° to 90 ° with respect to the horizontal towards the direction of rotation of the lower roller (10), and that the laterally displaced roller (14) is arranged at 45 ° to 60 ° relative to the horizontal towards the direction of rotation of the lower roller (10). Device according to claim 6, with a conveyor belt (22) which delivers the material to be comminuted to the first roller slot (34) from a material feed container (20) as a laterally defined material web. Device according to one of claims 6 or 7, wherein the upper and laterally displaced roller (12, 14) each has its own drive. Device according to one of claims 6 to 8, wherein the rollers (12, 14) for generating the grinding force are connected to at least one hydraulic cylinder via a rod system (30). Device according to claim 6, wherein a material feed and export device disposed in the vertex region laterally displaced relative to the driven lower roller (10) has a fill-controlled material feed container (20), a conveyor belt (22) which is disposed at the material outlet, a device (24) for adjusting the layer thickness of the material layer (32) and a plurality of cleaning devices (26) for venting the material layer (32).