Control over wood-pulp production in chip refiner. RU patent 2519891.

FIELD: process engineering.

SUBSTANCE: developed is the method for estimation of fibre mass proportion in chip refiner relative to that in completely filled grinding zone by timely measurements of accessible process parameters.

EFFECT: adequate estimate of filling factor is used got refiner loading reserve and control to prevent worst case operation.

23 cl, 11 dwg

THE TECHNICAL FIELD

The present invention relates to a method of controlling the quality of wood pulp produced in the refiner chips, in particular to a method of rapid assessment capabilities download refiner and prevent operation of the device in an undesirable operating modes. The load on the refiner is closely connected with the mass of fibers in the area of refining. Insufficient or excessive weight of the fiber to that which can normally be placed in the volume zone refining, leads to difficulties when downloading refiner and lower quality wood pulp obtained. The fill factor is estimated in online mode and is used to evaluate working conditions and the adoption if necessary of control measures.

PRIOR ART

Download refiners chips

Mechanical quality of wood pulp in a very large extent a function of the energy applied to the ton of the product, i.e. the specific energy. Therefore it is very important to be able to adjust the load on the motor refiner to develop the required energy density for pulping the required quality. Most refiners is the hydraulic load, and the usual way of increasing the load on the motor refiner is the increase of the axial force due to increase hydraulic pressure. There increased the cutting force acting on the fibers, which lead to higher torque and the load on the motor. Reduced clearance plate.

It is well known that it is impossible to reach the maximum load of the motor is determined by the power of the motor. In SA, Allison et al., a method is proposed for determining the maximum load of the motor and the load slightly smaller this maximum load. In the publication "A practical approach to operator acceptance of advanced control with dual functionality", Preprints of Control Systems'98 Conference, Porvoo, Finland, September 1-3, 1998, Owen et al. the developed technology controls to ensure operation of the refiner with motor load is lower to prevent sudden fall and to avoid abrupt decrease of quality of wood pulp. It also conducted experiments showing that work when motor load is over the maximum breaks fibers and loss of durability of wood pulp. Although these two developments represent a significant step to determining the proper operating range refiner, the fundamental causes difficulties when downloading refiner not been studied. As a result, corrective measures are empirical and limited gap adjustment plate, which, in essence, does not eliminate the source of the problem. Such developments applicable to refiners types that react quickly to changing the settings hydraulic pressure and sensor position plate or gap plate.

In the work "Theoretical estimates of expected refining zone pressure in a mill scale TMP refiner", Nordic Pulp & Paper Research Journal (2006), 21(1), 82-89, Eriksen et al. it was estimated mechanical pressure from wood pulp in the double-disc refiner as a function of the number of fibers, covering rods plates. However, it was not considered a problem loading refiner and the download is associated with a number of fibers in the area of refining.

Nowhere in the literature does not mention the possibility that the difficulties with loading refiners may be associated with the mass of fibers in the zone refining, filling zone refining or lack pulp fibers. However, it is important for process monitoring and corrective action.

Duration of processing of wood pulp

The estimated time for processing wood pulp in the area of the grinding is a key element in estimating the mass of fibers in the area of refining. Pioneering work in this area "A Simplified Method for Calculating the Residence Time and Refining Intensity in a Chip Refiner", Paperi-ja Puu, Vol. 73/No.9 (1991), Miles led to the emergence of the concept of intensity grinding, but no effort was made to use it to estimate the mass of fibers refiner and its maximum value.

DISCLOSURE OF THE INVENTION

The present invention is directed to the creation of a way of management of quality wood pulp produced by the refiner chips.

According to the present invention is offered the method of controlling the quality of wood pulp obtained refiner chips, including the stages at which:

grind wood chips in the area of refining refiner chips with the formation of a wood-fiber pulp,

define the fill factor fibers of this zone refining,

if necessary, adjust at least one worker parameter refiner chips in response to found the fill factor to obtain the required quality wood pulp.

A key element of the present invention is a method that allows online to assess the degree of filling zone refining refiner and use this assessment to boot properly refiner, and avoid some of the harmful impact on the quality of wood pulp work with a lack or excess weight fibers. And the real mass of fibers in the area of refining and mass, when the refiner completed, evaluated and compared to calculate the filling factor, which is used to adjust refiner, if necessary. The present invention comprises:

the method of estimating the mass of fibers in the zone refining,

the method of estimating the mass of fibers, when the refiner is full,

evaluation fill factor

how to use the fill factor to prevent work in unwanted areas in which the quality of wood pulp is declining.

BRIEF DESCRIPTION OF DRAWINGS

Figure 1 is a graphic illustration of the relationship between the load on the motor primary refiner and a mass of fibers in the zone refining, and the relationship is linear. Indeed, to load the motor refiner in the area of refining should be sufficient weight fibers.

Figure 2 - graphic illustration of the relationship between the load on the motor primary, secondary refiner and refiner waste and weight fibers in the area of refining. Despite very different operating bands, these three refiner located on the same linear characteristic.

Figure 3 - a concrete example, graphically illustrating the lack of mass fibers for maintaining download refiner.

4 is a graphic illustration of the relationship between the load on the motor and the gap plate refiner, showing that soon after the 0.2 closing the gap plate leads to a rapid drop the load on the motor. The mass of the fiber is insufficient to create the desired cutting efforts with acceptable shear stress.

5 is a graphic illustration of the relationship between the load on the motor and hydraulic pressure (pressure). As it is filled zone refining, the load on the motor reaches the maximum value and does not increase with the increase hydraulic pressure.

6 is a graphic illustration of the relationship between the mass of fibers in the area of refining and power or hydraulic pressure.

Fig.7 - graphic illustration of a linear ratio of the mass of fibers in the area of refining and value of the inverse of the pressure or reverse hydraulic pressure. A lot of fibers when the refiner is full, can be estimated by the value of this characteristic in the starting point.

Fig - graphic illustration of the relationship between the fill factor and performance refiner waste. The area of the grinding is populated when performance reaches 400 tons per day.

Fig.9 - graphic illustration of the relationship between the load on the motor and performance. When the zone refining is full, you cannot increase the load on the motor, despite the increase in productivity.

Figure 10 - the sequence diagram method of the present invention.

11 is a block diagram of the device for realization of the method of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Download refiner

Mechanical wood pulp is produced from wood chips using disk refiners. For separation and processing of wood chips spent a lot of electricity, from 2000 to 3000 kWh per tonne of product. The quality of the resulting pulp is largely a function of the energy applied to the tonne of product, and, to some extent, the conditions in which this energy is supplied, i.e. the intensity of grinding or consistency of grinding.

Changing the load on the motor and the accompanying energy can be accomplished by modifying the consistency of grind (threads solution), performance, but, first of all, changing the hydraulic pressure exerted on the boards of a refiner.

High blood pressure leads to increased pressure load and increase the mechanical forces acting on wood pulp. Pressure load is balanced by the amount of the mechanical forces acting on wood pulp, and power, created by the steam pressure plate.

The increase of mechanical forces acting on wood pulp, increases the cutting force and, hence, to increased torque and the load on the motor. Eventually, this can lead to excessive shear stress in wood mass.

The mass of fibers and the load on the motor

The weight of the fiber in the area of the grinding is a work performance and duration of treatment. Performance is usually judged by the speed of the feeder and calibration coefficient is proportional to the volumetric density of the feed material. Duration of processing of wood mass can be estimated using a model developed in the work of "A Simplified Method for Calculating the Residence Time and Refining Intensity in a Chip Refiner", Paperi-ja Puu, Vol. 73/No.9 (1991), Miles, and based on the balance of forces acting on wood pulp. This duration of treatment depends mainly on the specific energy and consistency of grind, increasing together with both of these variables.

The mass of fibers in the area of refining plays an important role when loading refiner. There is a limit to shear stress, which may take the fiber before it will break. The mass of fibers in the area of refining should be sufficient to ensure that the surface area required for the emergence of the cutting force and torque required for the desired load on the motor. This is well illustrated in figure 1, where the data on the primary refiner show that the load on the motor is proportional to the mass of fibers in the area of refining.

This is further illustrated by the comparison of operational data for single-threaded BCTMP mill, as shown in figure 2. Three refiner - primary, secondary and refiner of waste - are identical. Schedule of load on the motor relative mass of fibers for these three refiners lies on the same linear characteristic, but the ranges of work are totally different.

Although secondary refiner has the same performance as the primary refiner, it works with other weight fibers in the area of refining and therefore in a different range of loads on the motor. Crushing smaller and more spread out fiber than primary refiner, secondary refiner works with a lower specific energy, which reduces the duration of processing of wood mass and mass of the fiber in the area of refining.

The refiner waste handles only 30-40% of the performance of the main line with a high share of long fibers. In comparison with secondary refiner here you can attach a greater number of specific energy than in the secondary refiner, and get increased duration of treatment and therefore a lot of fibres greater than one would expect at reduced performance.

Knowing the mass of fibers in the area of the grinding can help to avoid the situation when the download refiner impossible.

Download insufficient weight fibers

Inadequate weight in the zone of grinding can prevent the need to download refiner. Typical of such conditions is to work at too low consistency grinding. The duration of treatment decreases as the consistency grinding reduces weight fibers in the area of grinding with a constant performance. Attempts to support the load on the motor by means of closing the gap plate increasing shear stress and lead to rupture of fibers and to drop the load on the motor and the specific energy. The fall of specific energy reduces time of processing of wood mass and weight fibers. An additional gap fibers and additional drop the load on the motor and weight fibers.

This is shown in figure 3, which shows the rapid decline of the mass of fibers and the load on the motor, despite the closure of the gap plate (see figure 4).

The band filling grinding

At constant performance duration of processing of wood mass and, consequently, the mass of fibers in the area of refining increase if to put more energy density (the higher the load on the motor). At a constant energy density and consistency of the crushing weight fibers increases. In both cases reached the point at which it becomes impossible to increase the load on the refiner and in which the quality of wood pulp begins to decline. In all these situations, when the zone refining becomes filled fibers, there is less and less space for the increasing volume of the steam generated when increasing the load on the motor. Steam pressure is growing almost exponentially. Hydraulic pressure is required to balance the forces generated by steam pressure plate, exceeds the capacity of the hydraulic system, and the load on the motor to increase impossible. Maximum load on the motor. Shown in figure 5, where refiner waste is reached, the load on the motor as a function of hydraulic pressure. With the increase hydraulic pressure load on the motor remains constant. When it reaches the limit of the hydraulic system, the load on the motor max.

Another important phenomenon is the reduction of the strength properties of wood pulp. When the increase in the mass of fibers, resulting from increased productivity or duration of treatment, will fill the entire area of zone refining, any attempt to increase the load on the motor will lead to a proportional increase in the shear stresses in wood mass. This leads to the shortening of the fibres.

Rapid assessment fill factor

As noted above, the mass of fibers in the area of refining assessed directly on work performance for the duration of processing of wood pulp.

There are different ways of estimating the mass of fibers in the zone refining, when the refiner is full.

The first method is the product of the volume of the zone of grinding on the density of wood pulp. Volume zone refining depends on the physical characteristics of the plates. It changes with gap plate, which essentially measure quickly, and with wear plate, which is more difficult to assess. The density of wood pulp promptly do not measure. This method is time.

The other, the preferred approach is based on the relationship between axial pressure and weight fibers in the area of refining. Axial pressure required to maintain the load on the motor increases very rapidly as the filling area refining. This is illustrated by the operative data from the refiner waste installation. When the hydraulic pressure increases, the load on the motor (figure 5) and the mass of fibers (6) remain constant. The refiner is full. The mass of the fiber is linearly connected with the reciprocal of the axial pressure, or the reciprocal of the value of hydraulic pressure, as shown in Fig.7. Such a linear characteristic, the inverse of axial pressure relative to the mass of the fiber is evaluated promptly by direct measurements axial pressure and to estimate the mass of fibers. This linear dependence has the form

m=a-b/T,

where m is the mass of fibers in the area of refining and - assessment of the mass of fibers when the refiner filled, b is the slope of the linear dependence, and the T - head.

The coefficient and the coefficient b is easily determined using one of the methods of operative calculation, for example recursive least square method. The ratio determines the mass corresponding filled the refiner. This linear relation is used only to determine the ratio . The actual mass m in the area of refining determine performance multiplied by the duration of treatment, as indicated above. Estimated fill factor is determined by the formula

The fill factor (%)=100 m / a,

what is the ratio of the current mass of fibres by weight of filaments, when the refiner is full.

Maximum mass of fibers in the area of refining or mass of fibers, in which the refiner is full, can vary depending on the wear plate, gap, consistency grinding and properties of the crushed material.

The specific conditions for cone-disk refiners

Refiners with flat disks are loaded only with axial pressure, and evaluation fill factor may be available in all working conditions. Conical refiners contain flat area, but have also conical zone, which forms the main part of the zone refining.

In conical area, because of the geometric configuration, the main contribution into the development of torque and the load on the motor makes the centrifugal force. There are conditions when the pressure of the input stream is not enough to maintain the required load on the motor used negative axial pressure. The refiner in this case is loaded only by centrifugal force. Although in such conditions it is possible to work for a long time, from the point of view of stability and controllability refiner this mode is not desirable.

The method used to estimate the fill factor is applicable for cone refiners only when the hydraulic pressure remains positive. When the hydraulic pressure becomes negative, rapid assessment is delayed.

Monitoring and management

Means of estimating the mass of fibers in the area of the grinding and fill factor can be considered software sensors, output signals which can be displayed on the operator console and use it to monitor a refiner and control actions.

In particular, the fill factor indicates the presence of some provision for performance or increasing the specific energy. He can turn on the alarm, indicating that the refiner has reached its capacity limit, and the quality of wood pulp can be reduced. It can be used for recommendations or initiation of control actions, such as productivity or reducing specific energy.

An example of using the fill factor is shown on Fig, where for a certain length of time shows performance and the estimated coefficient of filling. It is clear that from 10:30 to 13:30 fill factor rises to 100%, the performance is too high to ensure adequate refining, and, as shown in figure 9, the load on the motor remains to the highest attainable value. During this period, the performance had to be reduced to less than 400 tons per day.

At about 12:00 at Fig observed the sudden fall fill factor and constant performance. This was the result of an increase in the flow dilution water. Duration of processing of wood mass and mass of the fiber in the area of the grinding decreased. This example illustrates the application of dilution water to adjust the mass of fibers in the area of refining and fill factor.

The method of the present invention, thus, can be based on the following steps:

1. The method of rapid assessment mass of fibers in the area of refining;

2. The method of rapid assessment mass of fibers with a full refiner;

3. The method of rapid assessment fill factor refiner;

4. Use the fill factor to maintain refiner in the proper operating range, when the refiner can be properly loaded.

In particular, the method involves defining a fill factor on actual weight fibers in the area of refining and mass of the fiber in the zone refining, when the refiner is full.

This is further illustrated in chart sequence shown in figure 10, beginning on update current data of technological parameters, such as the load of power, energy density, performance, consistency in the discharge line, the consistency of the output, you need to calculate the filling factor. Then calculate the mass of fibers in the zone refining, a lot of fibers when the refiner is full, and the fill factor, as described above, and remove the fill factor in the display. If the fill factor is in a reasonable range, the procedure is repeated data updating of technological parameters. If the fill factor is too low or too high, provide alarm and apply appropriate control actions, such as a reduction or increase in productivity or reducing the supplied energy. After corrective actions procedure is resumed, beginning with the current data of the technological parameters.

Description of the preferred option

Figure 11 shows the distributed control system (DCS), the typical hardware tool used for pulp and paper plants for process monitoring and perform management functions. In particular, on 11 shows the node 8 refiner 10 chips with input 15 for wood chips or wood pulp, subject to grind, and exit 17 for ground wood pulp distributed system 11 control, located in operational communications with the refiner 10; console 12 operator, under operative communication with the distributed system 11 management; and optional computer 13, under operative communication with the distributed management system 11. The refiner 10 defines the area of refining (not shown). Distributed system 11 control can be programmed to determine the fill factor, and in this case, the computer 13 does not require that either the computer 13 can be programmed to determine the fill factor and transfer information in a distributed system 11 management.

Technological parameters, such as the load of power, energy density, performance, consistency in the discharge line and consistency at the entrance, are readily available in DCS 11 most plants either by direct measurements in the process prior to the refiner 10, or by calculations. In most modern plants such parameters regulated, and their setpoints are adjustable. With the DCS 11 are connected console 12 of the operator and, in many cases, a computer system 13.

In a preferred embodiment, in the DCS 11 there are software tools that perform calculations mass of fibers in the area of refining refiner 10 and calculations fill factor to print to console 12 operator's emergency indication.

In older installations that DCS has limited computing power, software, evaluating the fill factor will be installed in your computer 13, United with the DCS 11.

As shown in figure 11, the results of measurements of process parameters refiner 10 chips, such as the load on the motor, the load pressure, rotation frequency of the screw, going DCS 11, which initiates and carries out the regulation or management of these parameters refiner 10 chips. Information and data for the calculation of the coefficient of filling, control actions, etc. are part of the communications exchanged between the DCS 11 and computer 13. The console 12 operator displays information and data on the technological parameters and operation modes refiner 10 chips and specified values of technological parameters and limits, such as energy density, the stress on the motor and consistency that are transmitted to the DCS 11 for control and adjustment of process parameters and operating modes refiner 10.

Determination of the coefficient of filling can be carried out continuously or periodically, or intermittently. However, in the latter case, such a definition is switched off for short periods of time.

1. A method of controlling the quality of wood pulp obtained refiner chips, including the stages at which: ground into wood chips in the area of refining refiner chips with the formation of a wood-fiber pulp, define the fill factor fibers of this zone grinding on actual weight fibers in the area of refining and mass of the fiber in the area of the grinding when fully populated area of refining and, if necessary, adjust at least one worker parameter refiner in response to certain fill factor to obtain the required quality wood pulp.

2. The method according to claim 1, comprising the step where determine the actual mass of fibers in the area of the grinding on measured performance refiner chips and duration of processing of wood pulp in the area of refining.

3. The method according to claim 1, comprising the step on which determine the mass of fibers in the zone refining, when this area is completely filled, the center-to the pressure generated by the hydraulic pressure in the area of refining.

5. The method according to claim 1, wherein monitor fill factor in refining in the area of refining and, if necessary, adjust the specified at least one working option in response to certain fill factor.

6. The method according to claim 4, wherein monitor fill factor in refining in the area of refining and, if necessary, adjust the specified at least one working option in response to certain fill factor.

7. The method according to any one of claims 1 to 6, carried out in a linear process of pulping of wood chips.

8. The method according to claim 1, wherein, in response to the definition of the fact of the fill factor within the acceptable range regulate specified at least one worker parameter to return the fill factor in the valid range.

9. The method according to claim 4, which in the determination of the fact of the fill factor within the acceptable range regulate specified at least one worker parameter to return the fill factor in the valid range.

10. The method according to claim 5, which in the determination of the fact of the fill factor within the acceptable range regulate specified at least one worker parameter to return the fill factor in the valid range.

11. The method of claim 6, wherein in response to the definition of the fact of the fill factor within the acceptable range regulate specified at least one worker parameter to return the fill factor in the valid range.

12. The method of claim 10, wherein when determining the fact of the fill factor within the acceptable range include alarms and in response to activate the alarm regulate specified at least one worker parameter.

13. The method according to claim 11, wherein when determining the fact of the fill factor within the acceptable range include alarms and in response to activate the alarm regulate specified at least one worker parameter.

14. The method according to claim 1, wherein, in response to the definition of the fact of being the filling factor in the valid range is specified, at least one business setting is not regulate.

15. The method according to claim 1, wherein the specified at least one worker parameter choose from degraded performance, increase productivity and reduce energy consumption.

16. The method according to claim 4, wherein the specified at least one worker parameter choose from degraded performance, increase productivity and reduce energy consumption.

17. The method of claim 10, wherein the specified at least one worker parameter choose from degraded performance, increase productivity and reduce energy consumption.

18. The method according to 14, where specified, at least one business setting is selected from a decrease productivity, increase productivity and reduce energy consumption.

19. The device for realization of the method according to claim 1, containing the tool to determine the fill factor fibers zone refining.

20. The device according to claim 19, containing refiner chips that defines the area of refining and having an inlet for wood chips and outlet for wood pulp; distributed control system, promptly connected to the refiner chips for performance of the functions of process monitoring and process control, with the indicated tool to determine contained in the specified distributed control system.

21. The device according to claim 19, containing refiner chips that defines the area of refining and having an inlet for wood chips and outlet for wood pulp; distributed control system, promptly connected to the refiner chips for performance of the functions of process monitoring and process control, computer, quickly connected to a distributed control system, with the indicated tool to determine contained in the specified computer.

22. The device according to claim 20, next containing the alarm system, which is managed by distributed control system, while the alarm is activated when the output is determined fill factor within the acceptable range, with distributed control system regulates at least one working option in response to activate the alarm.

23. The device according to item 21, next containing the alarm system, which is managed by distributed control system, while the alarm is activated when the output is determined fill factor within the acceptable range, with distributed control system regulates at least one technological option in response to activate the alarm.