BR102015021252A2 - ore roller press and method for obtaining maximum efficiency from a roller press - Google Patents

Abstract

Summary "ore roller press and method for obtaining maximum efficiency of a roller press" describes an ore roller press (1) comprising: two motors (6,6 '), one movable roller (3) , a fixed roller (2), hydraulic cylinders (4) and a feed column (5). The roller press (1) is provided with an efficiency control means configured to perform constant measurements and adjustments on its components to achieve maximum machine efficiency. Also described is a method for obtaining maximum efficiency of a roller press (1), which follows the following steps: (i) determination of a zero gap; (ii) determination of a set point equal to the optimal working point of the press; (iii) automatic manipulation of pressure until set point is reached. 1/1

Description

Field of the Invention The present invention consists of an iron ore roller press and a method for maximizing the efficiency of a roller press. The present invention consists of an ore roller press and a method for maximizing the efficiency of a roller press. .

Background of the Invention The invention relates to an iron ore roller press provided with an efficiency control means and a method configured to maximize the efficiency of a roller press.

[003] The roller press is extremely important equipment in the ore pelletizing process. The pelletizing process contains the steps of comminution, agglomeration and pellet burning. The comminution step is responsible for ore fragmentation, while the agglomeration step is responsible for pellet formation. The roller press in question is used in the first step, ie the ore comminution step.

The roller press is a relatively simple equipment comprising: two rollers supported by bearing housings, one of the rollers being fixed and the other movable; two electric motors are responsible for transmitting torque to the rollers; Hydraulic cylinders are responsible for forcing the movable roller against the fixed roller; and a feed column, configured to evenly distribute the ore between the rollers.

[005] The roller press works as follows: ore is directed into the feed column, which has the function of evenly distributing the material between the rollers. The rollers rotate in opposite directions to force the material through the defined gap between the two structures (GAP) until the ore reaches the compression zone. The compression zone is the region where ore is repressed or compressed. It begins at the top between the two rollers and as it approaches the center, the pressure increases to the maximum point on the centerline of both rollers. Hydraulic cylinders are responsible for forcing the movable roller against the fixed roller in order to comminute the material in the compression zone (see figures 1 and 2 of the drawings).

[006] In the state of the art, in order to make better use of the roller press, adjustments are made to its components to achieve the best machine performance for the given working condition.

[007] A physical stop is installed on the machine to delimit the degree of freedom of movement of the moving roller. The stop prevents one roll from impacting the other, preventing abrasion or fracture of these components, the "GAP Zero", which is the shortest set distance between the rolls, is set by manually adjusting it.

In a first form of adjustment tests are performed and, having the various variables and results, a Zero GAP and an initial working pressure are defined.

[009] Under normal conditions, the press operator does not change the working pressure or the GAP, only special causes such as low power supply, poor performance or any operational restriction of the equipment may intervene.

[010] The level of the ore column, ie the height control that the ore presents over the press rollers, is set by the area engineer and should be the highest possible value with the lowest standard deviation. Once the value is set, it remains permanently during its operation.

[011] The pressure during the process is kept constant and as high as possible so that the torque of the rollers is the highest attainable. However, if the pressure is too high, the moving roller will be driven to the stop and will not contribute to the energy transfer of the rollers to the ore comminution work. In other words, there is optimum hydraulic working pressure, an excess will cause the roll to remain stationary at the stop and, depending on the conditions, the material will be extruded rather than pressed. Too little pressure causes the material to pass through the rollers without being pressed.

[012] The rotation of the rollers varies according to the level of the ore column. All PLC logic that drives the drive is programmed to keep the speaker level constant. However, as the rotation of the rollers is influenced by other factors present in the process, it becomes unstable, requiring constant adjustments in the equipment.

[013] The operator has pressure control in his hands. In addition to knowledge of press operation, it is necessary for the press to know the morphological conditions of the ore, moisture content, grain size, roll wear, air spring pressure, column level, roll rotation and zero GAP. With all the information, the operator can correctly adjust the hydraulic pressure for that specific condition. Minutes later, if any of the variables change, the adjustment will no longer be optimal and a new adjustment will be required. That is, the control is also susceptible to human failure, since adjustments to the machine are made through an operator.

The state of the art comprises roller presses provided with automatic roll opening control means, however, none of the state of the art presses are capable of analyzing all variables, equating them and taking adequate action to render them. her to the great point again.

[015] US5154364 filed September 28, 1990 cites a technique configured for comminution of food grains such as soybeans, wheat, corn, etc. This technique allows an adjustment of the distance between rollers for protection and better efficiency according to the work to be performed. This adjustment is made by means of an electric motor coupled to the press and a sensor responsible for measuring the distance between the rollers. The motor coupled to the roller press is configured to increase and decrease the distance between rolls to achieve the working mode required for the type of grain to be comminuted. Grains that need a larger particle break require a shorter roll distance, while grains that need a smaller particle break require a longer roll distance.

[016] In the technique disclosed in US5154364 it is also possible to make manual adjustments to the roller distance. Such adjustments are made by a crank that performs a male and female thread movement, pushing the movable roller against the fixed roller.

[017] With the technique disclosed in US5154364 it is possible to prevent accidents that damage the press, since the distance between rollers is adjusted by an electric motor whenever there is a need. The distance between rollers is also adjusted to make it as suitable as possible for the process, thus achieving improved safety and efficiency of the roll press.

[018] However, the above technique is not applicable to ore roll press because it does not consider the variables involved in ore comminution, such as: feed column level, ore morphological characteristics, roll rotation, among other factors. inherent to the ore comminution process by roller press.

[019] It can be concluded, therefore, that there is no prior art automatic control technology, configured to maximize the efficiency of a roller press by controlling all the variables present in the ore comminution operation. Nor is there a method configured to obtain maximum efficiency in an ore roller press.

Objectives of the Invention The present invention is directed to an iron ore roller press having a means of control that maintains it at its maximum efficiency during the entire operating time.

[021] The present invention also relates to an iron ore roller press which is more economical, more efficient and less susceptible to human failure than conventional presses.

[022] The invention also aims to maximize the delivery of the end product, which is of higher quality than that delivered by conventionally controlled roll presses.

Finally, the invention also aims at a method of obtaining maximum energy efficiency in a roller press.

Brief Description of the Invention The objects of the present invention are achieved by an ore roller press comprising: two motors; a fixed roller coupled to a reducer and the motor via a cardan shaft; a movable roller arranged in the same manner, but with a degree of freedom for radial movement; hydraulic cylinders supported on bearing housings, arranged perpendicular to the radial face of the movable roller so as to force it against the fixed roller; and a feed column disposed perpendicular to the two rollers just above the defined space between both frames; and the ore roller press is provided with a means for efficiency control.

[025] The objectives of the present invention are also achieved by a method for obtaining maximum efficiency for a roller press. This method comprises the following steps: (i) determination of a zero GAP; (ii) determination of a set point equal to the optimal working point of the press; (iii) pressure manipulation until the set point is reached.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is further described based on the respective figures: Figure 1 is a perspective view of an ore roller press; Figure 2 is a front view of the rollers in operation; Figure 3 illustrates a graph relating the pressure exerted on the rollers with the opening between the rollers; Figure 4 illustrates a graph relating the torque exerted by the motor and the pressure exerted on the rollers; Figure 5 illustrates a graph relating the rotation of the rollers and the torque exerted by the motor; Figure 6 illustrates a graph relating the torque exerted by the motor and the gap between rollers;

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an iron ore roller press 1 provided with an efficiency control means. The present invention also relates to a method for controlling the efficiency of an ore roller press 1.

[027] The ore roller press 1 consists of a machine used in the process of comminution of various ores (see figure 1). The roller press 1 comprises: two rollers 2,3 supported by bearing housings, one fixed 2 and the other movable 3; two 6.6 'electric motors responsible for transmitting torque to the rollers 2,3; hydraulic cylinders 4 forcing the movable roller 3 against the fixed roller 2 by grinding ore passing between the two; and a feed column 5 which evenly distributes the ore between the rollers 2,3 (see figures 1 and 2).

[028] The elements cited are responsible for the efficiency of the machine and the result of the final product. For this reason, automated monitoring and tuning of these components is required.

[029] In the state of the art, two types of control are performed. A first form of control is performed in relation to the pressure setting and a second form of control is performed in relation to the distance between rollers 2,3. However, both forms of control do not involve all components that influence machine efficiency, and, moreover, the first form of control cited is performed through an operator and is therefore susceptible to human failure.

The roller press 1 of the invention comprises an efficiency control means which is responsible for automatically adjusting and controlling all components influencing the efficiency of roller press 1 and which are involved in the comminution process. The efficiency control medium is configured to control - directly or indirectly - virtually all variables involved in the comminution process.

[031] The first controlled variable is the shortest allowable distance between the rollers 2,3. This distance is called zero GAP and consists of a safety spacing established by a physical stop arranged inside the machine. Said stop has the sole function of preventing the movable roller 3 from impacting against the fixed roller 2, causing damage to the roller surface 2,3, or even more serious damage to the roller press 1.

[032] The second controlled variable is the operating distance between rollers 2,3, ie the distance between rollers 2,3 during machine operation. This distance is called the operating GAP and is regulated by the pressure exerted by the hydraulic cylinders 4, so that high pressures tend to close the operating GAP and reduced pressures tend to open it, see figure 3. Because it is controlled by manipulating a third variable (hydraulic pressure), the operating GAP is a variable indirectly controlled by press 1.

[033] The third controlled variable is the torque exerted by the 6,6 'motors. Torque, by definition, is the component of a force that is disposed perpendicular to the axis of rotation of a given object; it is that part of the force that effectively enables the object to rotate about its own axis. The torque of the rollers 2,3 can be measured by the energy required to perform work by the 6,6 'motors in an attempt to fragment the ore.

[034] Torque can be measured through the electric current consumed by the 6.6 'motors, ie the more electric power the 6.6' motors consume, the greater the transfer of ore comminution energy (the electric power is mechanical work, the higher the energy, the more work done). In other words, higher energy consumption implies a higher comminution rate. Torque control is given by two other variables, namely: the pressure exerted by the hydraulic cylinders 4 and the rotation of the rollers 2,3. Because it depends on the control of two other variables to be changed, torque is a variable indirectly controlled by the press.

[035] The fourth controlled variable is the pressure exerted by the hydraulic cylinders 4. The hydraulic pressure applied to an area is reversed by the force that the movable roller 3 exerts on the fixed roller 2. The pressure is adjusted as a function of the operating GAP that is applied. want to work, that is, a smaller operating GAP requires higher pressures, while a larger operating GAP requires reduced pressures.

[036] The fifth controlled variable is the rotation of rollers 2,3, which has the function of regulating the flow of material passing through rollers 2,3. The rotation of the rollers 2,3 is controlled by the 6,6 'motors, and is adjusted according to the amount of material present in the feed column 5 at a given time.

[037] The sixth controlled variable is level 8 of feed column 5, ie the volume of ore found in feed column 5 at a given time. Level 8 rises or falls based on the difference between the ore mass flow at the top of the feed column 5 and the ore flow through press 1. Its level is intended to remain stable as System balance remains the same and there is no variation in the optimal working point. In addition, the risk of column 5 overflowing, press 1 being overloaded, or temporarily inoperative in the event of material missing inside the feed column 5 is avoided.

[038] The only variable that cannot be controlled by press 1 is the moisture of the ore, which is characteristic of the raw material and previous processes, and is defined as a percentage by weight of the material. When the moisture content of the ore is too high, the friction between the surface of the rollers 2,3 and the processed material is reduced, causing the rollers 2,3 to stop compressing the material and to extrude it, ie. , the material "slips" through the GAP rather than being pressed. In other words, when the ore is damp, rollers 2,3 cannot drag material into the compression zone 9. This causes the rotation of rollers 2,3 to be increased to maintain the column level and in addition. , also causes the operating GAP to decrease under the extrusive effect of material in the compression zone and the comminution force to decrease, causing the engine power to fall substantially. In addition to all the aforementioned drawbacks, material extrusion causes premature roll wear, as there is a relative movement between the stud surface and the material, which is undesirable. Serrated marks on the surface of "shark's tooth" pins attest to this movement of the ore.

[039] These are the controlled and uncontrolled variables found in the roll press comminution process 1. It is known that these variables interact with each other, ie the modification of one variable causes changes in the other variables. For a better understanding of this interaction between variables, the following table shows the effect that each change on a given variable has on the other process variables.

Table 1 - Effect and Cause of Process Variables [040] * Increasing pressure causes torque to increase to a certain limit. After the "optimum" point, the increase in pressure causes the torque to fall, and then, when the roller is fixed to the stop, the torque remains constant even as the pressure and excess force (which is not used to process the torque) increase. material) is transferred to the press chassis; * once at the stop, the increase in pressure has no influence on rotation or GAP; ** There is also an ideal point in rotation. Lower speed will not necessarily make the torque higher; *** The same thing applies for operational GAP. An equilibrium point is desired and above or below that point the torque will be reduced; Note: Increasing the column will cause torque to increase and operating GAP to increase as well.

[041] The rotation of rollers 2,3 controls the amount of ore that is pressed, ie the mass of material passing between rollers 2,3.

[042] The speed of rollers 2,3 is increased as level 8 of feed column 5 increases, ie a level higher than the set point of feed column 5 requires higher rotation of rollers 2,3, in order to increase the flow of material that is worked by press 1 at a given time. On the other hand, a level 8 lower than the set point in the feed column 5 requires a lesser rotation of the rollers 2,3 in order to decrease the mass flow of material processed by press 1 at a given time.

[043] Efficiency control reduces conventional system losses to a minimum by continuously regulating process parameters in order to turn maximum electrical energy into comminution work.

[044] As discussed earlier, operating GAP is established through the pressure exerted by hydraulic cylinders 4. In normal work, high pressure tends to decrease operating GAP, while a reduction in pressure tends to increase operating GAP. The pressure exerted by the hydraulic cylinders 4 also influences the torque, the value of the latter being, to some extent, directly proportional to the value of the pressure exerted by the hydraulic cylinders 4, see figure 4.

However, when the operating GAP is reduced, the flow of material passing through the rollers 2,3 is also decreased, and when this happens, the rotation of rollers 2,3 is automatically increased so that level 8 in the column power supply 5 remains stable. It turns out that increasing the rotation of the rollers 2,3 from a certain point has a negative influence on torque (see table 1 and figure 5).

[046] In summary, within determined values, the higher the pressure exerted by the hydraulic cylinders 4, the lower the operating GAP, and the greater the torque of the press. Paradoxically, when operating GAP is reduced, the flow of material worked by press 1 is restricted by causing level 8 in feed column 5 to rise, and when this occurs, press 1 reacts automatically, ordering an increase in rotation. of the rollers 2,3, which in turn decreases the torque of press 1 from a certain point.

[047] This complex relationship between variables is depicted in Figure 6, which displays a second degree equation that relates torque and operating GAP (for the same feed rate). The parable vertex shown in figure 6 is the point where press 1 works with the highest possible torque. This point is called the "optimal working point 15" and is found between regions A and B of the chart.

[048] In region A the torque is impacted by the high rotation of the rollers 2,3, while in region B the torque is impacted by the low pressure exerted by the hydraulic cylinders 4. At the optimum working point 15, the torque is maximum , which implies a high comminution rate. The optimum working point 15 varies according to the properties of the material worked, being influenced, for example, by the moisture and natural qualities of the ore worked at a given time.

[049] Based on the variable relationship described above, an operating GAP set point equal to the optimal working point 15 shown in figure 6 is objectified. In other words, the operating GAP is set so that the torque is maximum. Each feed rate, humidity, roll surface configuration, column level, hydropneumatic spring pressure requires an efficiency curve, hence the difficulty and complexity of balancing the system.

[050] The optimum working point 15 is determined as follows: firstly an Operational GAP control should be implemented as a function of pressure, ie an operational GAP setpoint is defined (the difference between minimum and maximum is recommended). maximum in lmm (eg Min.5mm and Max: 6mm)), so the pressure is modulated to achieve the goal. Subsequently, the operating GAP should be varied, starting from a larger opening to the minimum opening, remembering that the power supply must be constant, thus plotting the curve 6.

[051] When the working GAP is lower than the set point, it may mean that the material has increased its humidity, causing the operational GAP to close by decreasing the coefficient of friction between the material and the rollers 2, 3 and also the extrusion of the material into the compression zone, thus occurring the behavior cited above. In this way, increasing the speed decreases the torque.

[052] On the other hand, when the reverse occurs, the working GAP tends to be higher than the set point, so the rotation decreases and the rollers open, so a pressure increase is necessary for the torque to set. he sees.

[053] After the optimum working point 15 is determined, the efficiency control means changes the system pressure to keep the GAP set point operational according to the set regulation.

[054] Within the same supply range, to reach the set point set, press 1 automatically makes adjustments to the pressure provided by the hydraulic cylinders 4.

[055] When the set point is found, the pressure is kept constant.

[056] Thus, roll press 1 achieves an efficient control system which aims to maximize energy transfer to the comminution process and increased volume of material processed over time.

[057] Note that in order for the operating GAP to operate at different set points within the defined freedom limit, the zero GAP must have the lowest possible value, otherwise the press stops could limit the rollers 2 , 3, operating at an optimal working point 15 defined at a very small operational GAP.

[058] In its preferred configuration, the ore roll press 1 works with the following values: a zero GAP very close to zero, an operating GAP between 3 and 12 mm and a torque between 75 and 98% of its maximum power.

In view of the above considerations, in addition to the roll press 1, the invention also consists of a method for obtaining maximum efficiency of a roll press 1. This method comprises the following steps: i) establishing a distance between the movable roller 3 and the fixed roller 2 through a physical stop; ii) determine a set point for the operational GAP, this set point coinciding with the optimal working point 15; iii) control the pressure exerted by the hydraulic cylinders 4 until the operational GAP set point is reached;

Alternatively, this method may comprise a fourth step, which is to increase the pressure exerted by the hydraulic cylinders 4 until the operational GAP is about to become lower than the set point determined in step ii.

[061] In this case, the method may be defined as follows: (i) determine a minimum distance between moving roll 3 and fixed roll 2 by a physical stop; ii) determine a set point for the operational GAP, this set point coinciding with the optimal working point 15; iii) control the pressure exerted by the hydraulic cylinders 4 until the operational GAP set point is reached; iv) Once the operational GAP reaches the set point, the pressure is no longer changed.

[062] Thus, it is concluded that the invention achieves the objectives it proposes to achieve, being more economical, efficient and less susceptible to human failures than conventional presses and providing a higher quality end product.

[063] Greater savings are achieved through lower specific energy consumption by the machine as well as system automation, which does not require a full-time operator to make press 1 rotation and torque adjustments. Higher efficiency is achieved through an automated control, which ensures the highest possible comminution at any given time.

The higher end product quality of the press of the invention, in turn, comes from the fact that the roll press 1 of the present invention is capable of delivering a final product with a finer particle size than the particle size required for pelletizing. ore.

Having described some preferred embodiments of the invention, it is noteworthy that the scope of protection conferred by this document encompasses all other alternative forms applicable to the execution of the invention, which is defined and limited only by the content of the claim frame. attached.

Claims (11)

1. Ore roller press (1), comprising: two motors (6,6 '); a fixed roller (2) coupled to a reducer and the motor (6) via a first cardan shaft; a movable roller (3) coupled to a gear unit and the motor (6 ') via a second cardan shaft and provided with a degree of freedom for radial movement; hydraulic cylinders (4) supported on bearing housings, arranged perpendicular to the radial face of the movable roller (3), configured to force it against the fixed roller (2); and a feed column (5) arranged perpendicular to the two rollers (2,3) just above the defined space between both structures; characterized in that the roller press (1) is provided with a means for efficiency control. Ore roller press (1) according to claim 1, characterized in that the efficiency control means is configured to perform constant measurements on the distance between rollers (2,3) and to make automatic adjustments capable of correcting the distance between rolls (2,3), keeping it at a preset metric value. Ore roller press (1) according to claim 1, characterized in that the efficiency control means is configured to maximize the torque exerted by the motors (6,6 '). Ore roller press (1) according to claim 1, characterized in that the efficiency control means is configured to keep the ore level (8) in the feed column (5) constant; This control is performed by manipulating the rotation of the rollers (2,3). Ore roller press (1) according to Claim 2, characterized in that the automatic adjustments in the distance between rollers (2,3) are performed by adjusting the pressure exerted by the hydraulic cylinders (4). Ore roller press (1) according to Claim 2, characterized in that the metric value of the distance between the rolls (2,3) ranges from 3 to 12 mm. Ore roller press (1) according to Claim 3, characterized in that the power exerted by the motors (6,6 ') ranges from 75% to 98% of their maximum power. Ore roller press (1) according to Claim 3, characterized in that the automatic adjustments reflect the torque exerted by the motors (6,6 ') and are performed by adjusting the pressure exerted by the hydraulic cylinders (4). Ore roller press (1) according to Claim 3, characterized in that the automatic adjustments reflect the torque exerted by the motors (6,6 ') and are performed by adjusting the roller rotation (2,3). Ore roller press (1) according to Claim 3, characterized in that the automatic adjustments reflect the torque exerted by the motors (6,6 ') and are performed by simultaneous adjustments to the roller rotation (2,3). and the pressure exerted by the hydraulic cylinders (4). Method for obtaining maximum efficiency for a roller press (1) characterized by performing the following steps: (i) establishing a minimum distance between the movable roller (3) and the fixed roller (2) through a physical stop; ii) determine a set point for the operational GAP, this set point coinciding with the optimum working point (15) of the press (1); and iii) automatically control the pressure exerted by the hydraulic cylinders (4) until the operating GAP set point is reached; iv) Once the operational GAP reaches the set point, the pressure is no longer changed.