EP0340464B1 - Material bed roller mill - Google Patents

Description

The invention relates to a material bed roller mill for pressure comminution of brittle regrind, according to the preamble of claim 1.

Gutbett roll mills are generally known from DE-C-27 08 053 and allow considerable energy savings in the pressure reduction of brittle regrind, such as. B. cement clinker, ores, etc. In such material bed roller mills, two horizontally arranged, driven rollers are pressed against one another at high pressure. The material is largely crushed as it passes through the grinding gap formed between the two rollers, agglomerates (so-called slugs) being formed which contain a high proportion of fine or finished goods and which are then broken down in a downstream unit with low energy consumption.

Of the two rollers of such a material bed roller mill, one roller is designed as a stationary fixed roller and the other as a loose roller movably mounted transversely to the grinding gap, the loose roller being pressed with high pressure in the direction of the fixed roller in order to reduce the pressure described above To bring ground material. For the generation of this high pressure it is known in practice to assign a combined hydraulic gas spring system to each side of the idler roller, in which at least one hydraulic working cylinder is provided for each side of the idler roller, ie for each knuckle of the idler roller cooperates with a working gas spring. With the help of these hydraulic gas spring systems, the best possible grinding force in the grinding gap and also a desired gas spring characteristic (spring stiffness) should be set via the loose roller.

In this embodiment, which is known from practice, the optimum setting, in particular of the grinding force, is made above all by several tests, various settings of the gas and hydraulic fluid pre-filling pressures being made, for which purpose the roller mill is then switched off and the pre-filling pressures are reset. The working gas spring in each hydraulic gas spring system is first filled with gas to a predetermined gas pre-pressure during the operating setting, and then hydraulic oil is supplied to a predetermined pre-pressure to adjust the grinding force at a so-called zero gap, i.e. when the force flow between the two rollers is above runs several spacers through which a minimum roller distance is maintained. The gas spring characteristics and the grinding force behavior during the grinding of the material to be ground are determined by the gas and oil pre-filling pressures. In the known good bed roller mills designed in this way, it is not possible to directly adjust the pressure in the hydraulic gas spring systems - for example by supplying and removing hydraulic oil - if the spring characteristics of the gas springs on both sides of the idler roller are identical even after the adjustment should, which is why it is always necessary to switch off the roller mill for each adjustment step of the grinding force and then readjust it.

The known embodiment according to US-A-3 938 732 does not fall under the preamble of claim 1. In this case, several combined gas-hydraulic cylinder arrangements are in each case provided directly between the stationary roller frame and the corresponding sides of the idler roller. In each of these arrangements, the cylinder arranged between the roller frame and the idler roller is divided into three separate chambers by a main piston and a bowl-shaped, floating piston in such a way that the cylinder chamber facing the idler roller is pressurized with gas, while the other two chambers, one behind the other, each apply hydraulic oil are.

A still further embodiment is known from US-A-2 765 731, which describes in particular with the aid of a sugar cane comminution mill how two fixed comminution rolls can be assigned a third roll provided in the gusset above it as an up and down movable loose roll. In this case, the main issue is reliable lubrication and sealing in the area of the hydraulic piston for holding the idler roller, with a pressure accumulator in the form of a bladder accumulator (with a flexible wall) being connected to the upper hydraulic fluid space, while one filled with hydraulic fluid the lower annular space is connected via a tube to a vertical chamber, via which a scale indicator for the nip between the idler roller and an underlying fixed roller is created.

The invention is therefore based on the object of a material bed roller mill in the preamble of claim 1 to further develop the presupposed type in such a way that the grinding force can be adjusted in a simple manner even during operation and can be adapted to changed crushing conditions with relatively simple measures.

This object is achieved by the features specified in the characterizing part of claim 1.

Advantageous further developments and refinements of the invention are the subject of the dependent claims.

In the case of the good bed roller mill designed according to the invention, above all the hydraulic gas spring systems and, in particular, the associated working gas springs have been modified. The spring container of each working gas spring is divided into a central gas filling space (between the two pistons) and two hydraulic fluid spaces assigned to the two container end sections, which are essentially variable according to the operating pressures occurring on the part of the working cylinders. It is of further importance that the second piston of the working gas spring, which delimits the second hydraulic fluid chamber, is assigned a displacement measuring device which responds to the respective reciprocating piston movement and whose measured quantity determines the pre-filling pressure of the hydraulic fluid with the same gas spring characteristic on both sides of the Loose roller (i.e. in both hydraulic gas spring systems) can be adjusted during operation. The hydraulic fluid pre-filling pressure and thus also the grinding force in the grinding gap can thus be controlled via each working gas spring The roller mill during the shredding operation can be adjusted in the desired manner using the path measuring device provided in such a way that the optimum grinding force and thus the optimum comminution of the roller mill are controlled or regulated. This can take place during the commissioning of the roller mill, when changing the regrind, when changing the regrind parameters (eg fine material content, moisture, etc.) or when the idler roller has to be adjusted if there is a large amount of grinding roller wear. Such a readjustment of the grinding force can be carried out, for example, either directly by hand or also electromagnetically from a control station or via a control loop. Due to the design of the working gas springs according to the invention, the previously described control or regulation of the grinding force (via the pre-filling pressure of the hydraulic fluid) can be carried out independently of fluctuations in each hydraulic gas spring system which can be attributed to a horizontal movement of the idler roller, and independently of the position of the idler roller (e.g. inclined position) are, whereby the gas spring characteristic is essentially identical even after a new adjustment of the grinding force via the hydraulic pre-filling pressure in the working gas springs of the loose roller on both sides.

In a particularly advantageous manner, the load occurring via the grinding force can also be limited or set to a maximum permissibility without the roller mill having to be switched off. For this purpose, with the second hydraulic fluid chamber of the working gas spring, there is a pressure relief valve for setting the maximum permissible grinding force in the grinding gap connected. This represents a particularly simple and at the same time effective

Measure with regard to overstressing at least some parts of the roller mill.

• Fig. 1 eine schematische Seitenansicht der Gutbett-Walzenmühle;
• Fig. 2 ein vereinfachtes Fließschema von einem Hydraulik-Gasfedersystem für eine Seite der Loswalze.

The invention is described below with reference to the drawing. Show it

• Figure 1 is a schematic side view of the Gutbett roll mill.
• Fig. 2 is a simplified flow diagram of a hydraulic gas spring system for one side of the idler roller.

The general structure of the material bed roller mill will first be explained with reference to FIG. 1. This material bed roller mill contains, in a stationary mill housing 1, two horizontally arranged rollers 2, 3, which are driven by drive mechanisms (not shown), of which the roller 2 is designed as a fixed roller and the roller 3 as a loose roller. The fixed roller 2 is mounted via its two steering knuckles 2a in two associated bearing blocks 4 in a stationary manner in the mill housing 1, while the two steering knuckles 3a of the floating roller 3 are mounted in two associated floating bearing blocks 5, which can be moved within the mill housing 1 together with the loose roller 3 in accordance with the double arrow 6 are so that the latter is movable or displaceable relative to the fixed roller 2. A grinding gap (roll gap) 7 is formed between the two rolls 2, 3. Since the loose roller 3 is movable in the direction of the double arrow 6, it is also movable transversely to the grinding gap 7, ie the width of this grinding gap 7 can be changed accordingly by the mobility of the loose roller 3.

On the mutually facing end faces 4a and 5a of the bearing blocks 4, 5, a plurality of spacers in the form of spacers 8, 9 are attached, which determine the minimum roller distance of the two rollers 2, 3 when they are in mutual contact; this minimum roller spacing ensures that when the roller mill is idling, that is to say if there is little or no supply of regrind, the two rollers 2, 3 do not abut one another with their roller surfaces, thereby preventing unnecessary wear. This minimum roll distance represents the so-called zero gap.

In order to press the loose roller 3 with the required high pressure in the direction of the fixed roller 2, a hydraulic gas spring system is provided for each side of the loose roller 3, each of which has two hydraulic working cylinders 10, 11, one in the exemplary embodiment illustrated in FIG. 1 Contains hydraulic pump 12 and a working gas spring 13, which is connected by a hydraulic line 14 to the two working cylinders 10, 11.

A first throttle 15, to which a first check valve 16 lies in series, can be arranged in the hydraulic line 14. A second throttle 17, to which a second check valve 18 lies in series, can be arranged parallel to this series connection. This arrangement of the two throttles 15, 17 and the two check valves 16, 18 prevents the occurrence of disturbing resonance vibrations.

It should be emphasized that instead of two working cylinders 10, 11 on each side of the idler roller 3 only one such working cylinder could be provided in each case; However, the arrangement of two working cylinders 10, 11 according to FIG. 1 ensures that the associated floating bearing blocks 5 (the loose roller 3) are not tilted.

The detailed details of one of the associated hydraulic gas spring systems of the material bed roller mill according to FIG. 1 are explained below with reference to the flow diagram of FIG. 2, in which, for the sake of simplicity, only one working cylinder, for example the working cylinder 10 and the loose roller 3 with an associated loose bearing block 5 (on one side or on a steering knuckle 3a of the loose roller 3) is illustrated. The mobility of the loose roller 3 with the aid of its loose bearing blocks 5 is again illustrated by the double arrow 6, while the grinding force required for comminuting the material to be ground is indicated in the grinding gap between the two rollers by an arrow 19 directed against the loose roller.

The hydraulic gas spring system shown on the one side of the idler roller working gas spring 13, which through the line 14 with the working cylinders, for. B. 10, is connected, has an elongated spring container 20 approximately in the manner of a cylinder, which is essentially closed at both end sections by an end wall 20a, 20b - apart from sealed line bushings or the like. Furthermore, this working gas spring 13 has two pistons 21, 22 which are movable relative to one another and which are each assigned to a container end section within the spring container 20. As can be seen in Fig. 2, the opposing limits

Piston sides of these two pistons 21, 22 define a central gas filling space 23 of the gas spring 13, while the respectively opposite piston sides with the associated end walls 20a and 20b of the spring container 20 delimit a first hydraulic fluid space 24 and a second hydraulic fluid space 25. The first hydraulic fluid chamber 24 delimited by the first piston 21 is connected via the hydraulic line 14 to the hydraulic working cylinders, e.g. B. 10, in connection.

The two pistons 21 and 22 can basically be designed essentially in the form of a piston plate or a piston body. However, the second piston 22 is assigned a displacement measuring device which responds to the piston movements in one direction or the other and which is generally designed in any suitable manner and This second piston 22 can be assigned to respond to each of the reciprocating piston movements and measure their sizes. One possibility for the formation of such a path measuring device is indicated at 26 in FIG. 2. For this purpose, the second piston 22 has a piston rod 22a which projects through the associated end wall 20b of the spring container 20 and which cooperates with the displacement measuring device 26 for the precise determination of the respective change in position of the piston 22 in the spring container 20.

A structurally particularly simple design of the displacement measuring device which can be used very favorably in terms of control and regulation technology can consist in the design as an ultrasonic measuring device which responds to any change in position of the second piston 22 in the spring container 20. Here, for. B. a transmitter and receiver can be provided in or on the associated end wall 20b of the spring container 20 in such a way that corresponding signals are reflected by the piston 22, from which the exact relative position of the piston 22 in the spring container 20 can be derived.

Via such a measuring device, the hydraulic fluid pre-filling pressure of the working gas spring 13 can then be measured and during milling operation with approximately the same gas spring characteristic on both sides of the idler roller 3 and thus at the same time the grinding force in the grinding gap 7 can be set, as will be explained in more detail below.

A pressure limiting valve 28 is also connected to the second hydraulic fluid chamber 25 of the spring container 20 via a line 27, via which a maximum permissible grinding force in the grinding gap 7 can be set or controlled. The outflow side of this pressure relief valve 28 is connected to a hydraulic fluid tank 29. It should be emphasized in this connection that any suitable hydraulic fluid can be used; however, this is preferably hydraulic oil.

To the line 27 connected to the second hydraulic fluid chamber 25, a partial line 30 is also connected, which is connected to the oil tank 29 via an oil feed pump 31 and in which a multi-way / multi-position valve which enables hydraulic fluid chamber 25 to be supplied and removed 32 and a manometer 33 are arranged.

A branch line 34 is also connected to the hydraulic line 14 connected to the first hydraulic fluid chamber 24 of the spring container 20, in which a further multi-way / multi-position valve 35 which permits the supply and discharge of hydraulic fluid and a manometer 36 are arranged and which are likewise via the oil feed pump 31 communicates with the oil tank 29.

The supply of gas into the gas filling space 23 of the spring container 22 can be done in any suitable manner. According to the example in FIG. 2, the piston rod 22a can be designed as a hollow rod and connected to a gas supply line 37. However, it is just as possible and structurally often particularly favorable to supply the gas to the gas filling space 23, for example, by means of a spiral or helically wound supply hose, which can be arranged within the second hydraulic fluid space 25 without impeding the relative movements of the second piston 22. In the latter case, a piston rod led out of the spring container can be dispensed with, which is favored, for example, by using an ultrasound measuring device for the distance measurement.

In any case, the gas supply line 37 is provided and is connected, for example, via a pressure gauge 39 and a further multi-way / multi-position valve 40 and a simple shut-off valve 41 to a compressed gas source designed, for example, as a compressed gas bottle 38.

Furthermore, it can be advantageous if to the from the first hydraulic fluid chamber 24 of the spring container 20 to the working cylinder 10 leading hydraulic line 14 an auxiliary gas spring 42 is additionally hydraulically connected, the spring force of which is adapted to the restoring force for the idler roller 3 in the zero gap position determined by the spacers 8, 9; this additional auxiliary gas spring is therefore referred to below as the zero gap gas spring 42.

The zero gap gas spring 42 can be made significantly simpler than the working gas spring 13. It has a substantially closed, preferably cylindrical spring container 43 and a simple piston (e.g. plate or membrane piston) arranged axially movably therein, which divides the container interior into a gas filling chamber 45 and a hydraulic fluid chamber or oil chamber 46. The oil space 46 is connected to the hydraulic line 14 via a connecting line 14a, while the gas filling space 45 is also connected to the compressed gas bottle 38 via a gas line 47. In turn, a multi-way / multi-position valve 48 and a pressure gauge 49 are installed in the gas line 47.

This zero gap gas spring 42 is designed and arranged in a special way for interaction with the working gas spring 13 provided here. For this purpose, it is provided that if the supply of grinding material to the grinding gap 7 is interrupted, the rollers 2, 3 on the part the working gas spring 13 are relieved of pressure. In this pressure-relieved idling state, the two rollers 2, 3 are to be brought together again in their starting position, that is to say in the zero gap position, in that the loose roller 3 is guided against the fixed roller 2 via its loose bearing blocks 5 until the spacers 8, 9 abut one another. In order to accomplish this return in the pressure-relieved state, the zero gap gas spring 42 is effective, the spring force of which only has to be so great that the corresponding frictional forces are overcome and the floating bearing blocks 5 together with the loose roller 3 can be reset. This simple measure entails that the corresponding components of the roller mill can be considerably reduced in terms of both their weight and their processing costs compared to the previously known mills, and that, in the event of interruptions or idling conditions, no undesirable large impacts on the corresponding components of the mill are exercised and that due to these relatively low loads, an increased service life, in particular of the associated bearings (spherical roller bearings) and, if appropriate, of the jewels can be achieved.

The following should be noted regarding the function of the hydraulic gas spring system for the loose roller 3 in particular:
It is initially assumed that the gas and oil priming pressures are set at the zero gap position (spacers 8, 9 abut one another). If one looks at the flow diagram in FIG. 2, the valves 32, 35 are first opened and the gas pre-filling pressure in the gas filling chamber 23 of the working gas spring 13 via the gas supply line 37 and the valve 40 and the pressure gauge 39 and then the gas pressure in the zero gap gas spring 42 via gas line 47, valve 48 and pressure gauge 49 are set to the respectively required pressure. Here, the gas pre-filling pressure of the working gas spring 13 is generally significantly higher than that in the zero-gap gas spring 42 (e.g. the gas pre-filling pressure in the working gas spring 13 can be approximately 40 bar and the gas pressure in the zero-gap gas spring 42 can be approximately 8 bar). After setting these gas pressures, the two oil valves 32, 35 are then temporarily closed. After the oil feed pump 31 is started, the oil prefill pressure in the second hydraulic fluid chamber 25 of the working gas spring 13 is first set via the oil valve 32 and then the oil prefill pressure in the oil chamber 46 of the zero-point gas spring 42 via other oil valve 35, the oil prefill pressure in the second hydraulic fluid chamber 25 being significantly higher than that of the oil space 46 of the zero gap gas spring 42 will lie. Here, the oil pre-filling pressure in the oil space 46 of the zero gap gas spring 42 must be lower than the gas or oil pre-filling pressure in the working gas spring 13. The hydraulic gas spring system is then ready to start.

For setting and controlling or regulating the grinding force in the grinding gap 7, it should again be pointed out that the loose roller 3 is moved over its two loose bearing blocks 5, on which two working cylinders 10, 11 and an associated working gas spring 13 of the corresponding hydraulic gas spring system act ( corresponding to Fig. 2). However, these two hydraulic gas spring systems are decoupled, ie they work with the same zero setting (same gas and oil pre-filling pressures) of the working springs 13 independently of one another, so that depending on the operating conditions that occur, that is to say, for example, with different regrind application over the roll width and thus when the idler roll 3 is inclined, the working gas springs 13 of both pressure systems are loaded differently can. The aforementioned zero setting in both working gas springs is necessary because the load profile of the rollers 2, 3 can differ depending on the size reduction situation, so that the same zero setting offers the greatest possibilities for compensation.

In the configuration and arrangement explained in particular with reference to FIG. 2, the oil pre-filling pressure and thus the grinding force during operation of the roller mill can be adjusted in a defined manner by means of the path measuring device 26 explained with each working gas spring 13, which in turn optimally controls or regulates the grinding force in the grinding gap 7 can. With the help of the path measuring device 26, the mean pressure at the two floating bearing blocks 5 can be optimally set under different loads across the width of the rollers 2, 3, the initially set oil pre-pressures for the working gas springs 13 on both loose roller sides changing identically. Through this distance measurement via the second piston 22 of the working gas springs 13, the grinding force can always be readjusted in each operating phase, for example if the grinding conditions in the roller mill have changed due to changes in the grinding material parameters or when the loose roller 3 is adjusted in the event of excessive grinding roller wear. These new hires or readjustments can be made during operation without having to stop the roller mill; The same naturally also applies to the control or regulation at the start of operation.

In this material bed roller mill, the hydraulic gas spring systems explained on both loose roller sides, and in particular the design and function of the associated working gas springs 13, have an extremely favorable effect. Each working gas spring 13 provides a manipulated variable, namely the respective position of the second piston 22 in the spring container 20 (displacement measurement), with which the oil pre-pressures in the associated hydraulic gas spring system can be adjusted uniformly on the corresponding loose roller side in the grinding operation. This means that the gas spring characteristics after a readjustment in both hydraulic gas spring systems (on both loose roller sides) are the same. If you imagine a corresponding coordinate diagram on which the spring characteristics (for the spring characteristics) are plotted for different grinding gaps and grinding pressures, the spring characteristics are the same even after the two working gas springs have been adjusted in the two hydraulic gas spring systems. With the above-mentioned manipulated variable (displacement measurement of the second piston of each working gas spring), the grinding pressure (grinding force) can be controlled in grinding mode or regulated by comparing the actual and setpoint values of the specific shredding work. This means that with the newly created manipulated variable, the material bed roller mill with always identical spring characteristics of the working gas springs 13 of both hydraulic gas spring systems on the basis of the optimal operating point (specific Shredding) can be regulated.

Furthermore, the pressure-limiting valve 28 explained above, which limits the maximum grinding force and thus prevents overloading of the roller mill, can be installed particularly advantageously in each hydraulic gas spring system. After this pressure limiting valve 28 has responded (when the oil pre-filling pressure changes), the oil pre-filling pressure can be reset to the optimum value by means of the actual and setpoint comparison mentioned above, without the roller mill having to be switched off after the pressure relief valve has responded.

Claims (5)

1. Material bed roller mill for the comminution under pressure of brittle material for grinding, containing

   a) two driven rollers (2, 3) which together form a grinding gap (7) and of which one roller (2) is constructed as a fixed roller which is mounted so as to be stationary and the other roller (3) is constructed as a floating roller which is movable at right angles to the roller gap,

   b) two hydraulic-pneumatic spring systems which are arranged one on each side of the floating roller (3) and'press this floating roller under high pressure in a sprung manner in the direction of the fixed roller (2) and which each contain at least one hydraulic working cylinder (10, 11), a working pneumatic spring (13) connected to this working cylinder and controllable arrangements for delivery and removal of hydraulic fluid and gas, and, with a zero gap determining the minimum roller spacing, the working pneumatic springs of these two systems can be set to predeterminable preliminary filling pressures of the gas and hydraulic fluid for the pneumatic spring characteristic and the grinding force in the grinding gap (7),
      characterised by the following features:

   c) each working pneumatic spring (13) has a substantially closed elongated spring container (20) and two pistons (21, 22) which are each associated with one end section of the container and are movable relative to one another and in which opposing sides of the piston define the gas filling chamber (23) of the working pneumatic spring and in each case opposing sides of the piston with the appertaining end walls (20a, 20b) of the spring container define first and second hydraulic fluid chambers (24, 25), the first hydraulic fluid chamber (24) defined by the first piston (21) being connected to the hydraulic working cylinder (10, 11) by a hydraulic pipe (14);

   d) a stroke-measuring device (26) responding to the movement of the piston to and fro is associated with the second piston (22) of each working pneumatic spring (13) defining the second working fluid chamber (25) and by means of the stroke measurement value detrmined thereby the preliminary hydraulic fluid filling pressures of the working pneumatic springs (13) on both sides of the floating roller can be set with the same pneumatic spring characteristic;

   e) a pressure-limiting valve (28) for setting a maximum permissible grinding force in the grinding gap (7) is connected to the second hydraulic fluid chamber (25) of the spring container (20).
2. Material bed roller mill as claimed in claim 1, characterised in that the second piston (22) of the working pneumatic spring (13) has a piston rod (22a) which projects through the appertaining end wall (20b) of the spring container (20) and with which the stroke measuring device (26) co-operates.
3. Material bed roller mill as claimed in claim 1, characterised in that an ultrasonic measuring device which responds to every alteration in position of the second piston (22) in the spring container (20) is provided as a stroke measuring device.
4. Material bed roller mill as claimed in claim 1, in which a plurality of spacers (8, 9) are associated with the two rollers (2, 3) and by reciprocal abutment determine a zero gap which represents the minimum roller spacing, characterised in that if the delivery of material for grinding to the grinding gap (7) is interrupted the floating roller (3) can be relieved of pressure on the part of the working hydraulic spring (13), and an auxiliary pneumatic spring (42) with a spring force adapted to the restoring force for returning the floating roller (3) to the zero gap position is additionally joined to the hydraulic pipe (14) leading from the first hydraulic fluid chamber (24 ) of the spring container (20) of the working pneumatic spring to the working cylinder (10, 11).
5. Material bed roller mill as claimed in claim 1 and/or claim 4, characterised in that each hydraulic fluid chamber (24, 25) of the working pneumatic spring (13) is connected by a multi-way/multi-position valve (32, 35) and by a common hydraulic fluid pump (31) to a hydraulic fluid source (29) and each gas filling chamber (23, 45) of the pneumatic springs (13, 42) is connected by a multi-way/multi-position valve (40, 48) to a common compressed gas source (38).

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