JP2009179927A - Method and system for measuring and controlling digester or impregnation vessel chip level by means of measuring chip pressure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a system for determining chip pressure in a vessel containing a slurry of lignocellulosic material. <P>SOLUTION: The system is for determining chip pressure, in a vessel containing a slurry of a lignocellulosic material. A pressure sensing element is for a vessel containing a slurry of a lignocellulosic chip material and includes: a first pressure sensing surface in contact with the slurry and generating a signal representative of a pressure of the slurry, which is sum of a hydrostatic pressure of liquid and chip pressure; a second pressure sensing surface generating a signal representative of the hydrostatic pressure of the liquid; and a pressure difference transmitter receiving the signals generated by the first and the second pressure sensing surfaces and outputting a signal indicative of the chip pressure. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates generally to chemical processing of lignocellulosic fiber materials in pulp production, and more particularly to an automatic detection and control system in a chemical digestion vessel or impregnation vessel that processes the fiber material.

  Lignocellulosic materials such as wood chips are generally introduced into the head of the cooking or impregnation vessel. Heat, pressure, and liquid are also introduced into the container to process the material. The processing of wood chips may be continuous, with chips being introduced into the top of the container and processed chips being discharged from the bottom of the container. The level of wood chips in the container is monitored so that the appropriate amount of chips is in the container and that chips are maintained in the container for the appropriate time. Accurate information about the chip level is necessary to properly adjust the flow of chips to the container head, the discharge of chips from the container bottom, and the pressure of the chips in the container.

  The tip level is conventionally measured by a strain gauge sensor on a paddle that extends into the digester or impregnation vessel. Generally, three or four paddles are placed in the digester. Each paddle includes a strain gauge sensor that measures the force applied to the paddle by the tip column moving through the container. The strain gauge sensor generates a voltage signal indicating the force applied by the tip column to the paddle. The signal generated by the strain gauge sensor is used to calculate the chip level in the container and to control the chip processing in the container.

  The strain gauge requires a paddle that extends into the chip flow and thus partially blocks the flow. Strain gauges provide legitimate data when there is a tip flow, but do not tend to give legitimate data when the tip is stationary in the container. Similarly, the strain gage generated data is sensitive to a non-constant tip flow through the container. Because of these problems with strain gauges, alternative or additional sensors and methods are needed to detect tip level and other conditions within the container. Furthermore, a method and system for assisting in controlling the chip pressure in the container is also required.

  In accordance with the present invention, a novel system and method is provided for determining the chip level in a vessel such as a digester vessel or an impregnation vessel based on the tip pressure in the vessel. The new system includes determining the tip pressure based on the difference between the total slurry pressure in the vessel and the hydrostatic pressure due to the liquid component of the slurry.

  According to the present invention, there is provided a pressure sensing element for a container containing a slurry of lignocellulose chip material. The element is in contact with the slurry and generates a signal indicating a total static pressure of the slurry, a second pressure detection surface generating a signal indicating the hydrostatic pressure of the liquid in the slurry, A signal generator for receiving respective signals generated by the first and second pressure sensing surfaces and transmitting a signal indicating the chip pressure. A filter such as a screen, perforated plate, mesh, or other element may be in front of the second pressure sensing surface to block the chip and send liquid to the second pressure sensing surface.

  According to the present invention, a method is provided for determining chip pressure in a container containing a slurry of lignocellulosic material. The method detects the total pressure of the slurry in the container, detects the hydrostatic pressure of the liquid in the container, and based on the difference between the detected total pressure of the slurry and the detected hydrostatic pressure of the liquid. Consists of determining the pressure.

  In accordance with the present invention, a method is provided for calibrating an algorithm for determining chip level. The method measures the liquid level in the container; measures the chip pressure in the container; determines the calculated chip level using an algorithm that calculates the chip level based on the chip pressure; Detecting the transition between steady state and changing tip pressure while changing the level; determining the difference present in the transition between the liquid level and the calculated tip level; It consists of adjusting and correcting the difference.

  According to the present invention, a method for treating lignocellulose chip material in a continuous flow container is provided. The method determines the tip pressure of the tip material based on the difference between the detected total pressure of the slurry and the detected hydraulic pressure; and compares the determined tip pressure of the tip material with a predetermined desired tip pressure. Adjusting the flow rate of the tip material passing through the container based on a comparison between the determined tip pressure and a predetermined desired tip pressure.

It is the schematic of the processing container of a lignocellulose fiber material. It is a schematic front view of a pressure detection element. It is a schematic sectional drawing of a pressure detection element. It is a graph which shows the chip | tip pressure in the process which calibrates the algorithm which determines the chip | tip level and liquid level in a container, and a chip | tip level.

  FIG. 1 is a schematic view of a processing vessel 10 for lignocellulosic fiber material (hereinafter referred to as “wood chips” or simply “chips”). The vessel 10 may be, for example, a cooking vessel in a pulping system, one being a cooking vessel and the other being one of two or more vessels, such as an impregnation vessel. Also good. Chemical cooking vessels and impregnation vessels are commonly used to convert wood chips into cellulose pulp for papermaking. In these containers, pressure, heat and cooking liquor are applied to the chips. The cooking vessel or impregnation vessel is generally a vertical column, and the column is often over 100 feet (about 30 meters) high. The container may be utilized in a continuous flow process in which wood chips and liquid slurry are continuously introduced into and discharged from the container. Alternatively, the container may be used in a batch process in which the slurry is sequentially introduced into the container, processed and discharged.

  The conventional chip supply system 12 supplies a continuous flow of wood chips to the top separator 14 at the top of the container 10. The supply system mixes the chips with the white liquor and forms a slurry that flows to the top separator 14. The chip is discharged from the top (or bottom) of the separator as indicated by arrow 13, and a part of the liquid is extracted from the line 15 from the separator and the container.

The vessel may be a gas phase digester or a full liquid digester. Full liquor digesters are typically completely filled to the top of the container 14 with cooking liquor. Vapor digesters typically have an upper gas region 16 filled with gas above the top level chips and liquid in the vessel. In full and gas phase cooking vessels, the tip forms an upper surface 17 commonly referred to as the tip level of the vessel. The tip level may be at, above or below the liquid level 18 in the vapor phase vessel. In a full container, the chip level is generally below the liquid level that fills the container during normal chip processing operations. The chip level 17 may be generally horizontal and may have a convex surface upward. Let L ₁ be the average height of the chip level. Below the chip level 17 and the liquid level 18 (referred to as L ₂ ), the chip is compressed under the hydrostatic pressure of the liquid and the weight of the chip column in the container. In a continuous flow vessel, the tip descends from tip level 17 toward the bottom of the vessel.

  As the wood chip sinks into the chip column of the container (see arrow 20), liquid, heat and pressure act on the chip to dissolve the fiber of the chip from the network of fibers that form the raw wood chip. If not, separate them. The liquid extraction screen 22 may be placed on the side wall of the container at one or more height positions in the container. The liquid portion 25 in the container is extracted via the screen 22 and is at least temporarily removed from the container. The treated wood chips are discharged from the bottom of the container 10 for further processing.

In order to monitor the chip pressure, a pressure sensing element 26 is placed inside the container or on the side wall 24 of the container. The pressure sensing element is preferably located above the highest extraction screen 22 and below the lowest level of the tip during normal continuous flow operation of the vessel. The pressure sensing element 26 provides data on various pressures in the container, particularly the total pressure of the slurry in the container, the hydrostatic pressure of the liquid in the container, and indirectly, the pressure due to the chip in the container. The measured tip pressure is used to determine the calculated tip level 17 in the container. Here, the calculated chip level L ₁ is an average level of the upper chip surface 17.

  In general, the total static pressure in a container is the hydrostatic pressure of the liquid and the weight of the tip column above the position of that height (hereinafter “static pressure”) at any given height of the container. Chip pressure ”or simply“ chip pressure ”). Tip pressure indicates the amount of tip compression in the container at the height in the container that determines the pressure. The total static pressure of the slurry may be determined as the static pressure applied by the slurry to a unit area at a given depth within the container. In a full liquid or gas phase container, the total static pressure varies in direct proportion to the depth of the slurry. Similarly, the static tip pressure varies in direct proportion to the distance between the tip level and the height at which the static pressure is measured. In view of the relationship between the static pressure and the depth, the upper level of the chip in the container can be determined from the pressure measurement and the height at which the pressure in the container is measured. Furthermore, the determination of the chip level is affected by the liquid level in the container, and the measurement of the liquid level is useful for determining the chip level.

  The total static pressure of the slurry is a combination of the hydrostatic pressure of the liquid and the static tip pressure. In general, the hydrostatic pressure of the liquid is much greater than the static tip pressure, so the hydrostatic pressure of the liquid is only slightly less than the total static pressure of the slurry. Due to the difficulty of direct measurement of low static tip pressure, the pressure sensing element 26 directly measures large values of the hydrostatic pressure of the liquid and the static pressure of the slurry. The difference between the total static pressure of the slurry and the hydrostatic pressure of the liquid is used to determine the static tip pressure.

  2 and 3 are a schematic front view and a cross-sectional view of the pressure detection element 26. FIG. The pressure sensing element 26 includes a first pressure sensing surface 28 that is in direct contact with the wood chip and the liquid slurry, and a second sensing surface 30 that is in direct contact with the liquid only and not the chip. Each of the pressure detection surfaces 28 and 30 may be a diaphragm. A filter 32 such as a screen, perforated plate, mesh or perforated disk used for the extraction screen may block the second pressure sensing surface 30 from the chip flow and allow the liquid to flow to the surface 30. Good. The first and second pressure sensing surfaces may be attached to the inner surface of the container sidewall 24 or to the portal on the container sidewall. The pressure sensing element 26 may include a substrate or housing that is fitted or attached to the container wall, which holds the first and second pressure sensing surfaces 28,30. Alternatively, the pressure sensing surfaces 28, 30 may each be fitted into the opening 34 in the side wall 24 of the container. A cylinder 36 fitted into the container wall or the substrate of the pressure sensing element holds the filter 32 and provides a cavity for the liquid to apply pressure to the second pressure sensing surface 30.

  The first and second pressure sensing surfaces 28, 30 are preferably close to each other and are part of the same sensing element 26. The pressure sensing element may be one of many types of sensors that are commonly used to measure the liquid level in tanks and containers. Depending on its function, the pressure sensing element does not require a filter that blocks the flow of the chip. The chip filter 32 may be a screen, a porous plate, a mesh, a honeycomb structure plate, or other members that block the flow of the chip and allow the liquid to pass through the pressure detection surface 30. Openings in the filter, such as openings, slots or passages, are narrow enough to block the chip. The liquid passes through the filter and applies pressure to the second pressure sensing surface 30.

  The two pressure sensing surfaces 28, 30 are preferably at the same height of the container, for example, at an altitude, so that the hydrostatic pressure of the liquid on both sensing surfaces is the same. As an example, both pressure sensing surfaces may be 5 to 10 meters below the normal tip level in the container. Both sensing element surfaces are also preferably placed above the uppermost extraction screen 22 in the container. The exact installation position in the vessel, the distance between the sensors, the detection surfaces 28, 30 and the installation method of the pressure sensing element 26 associated therewith are a matter of design choice, such as a cooking vessel or impregnation vessel, or a cooking vessel. May be defined by the type of design and configuration. For example, if one of the pressure sensing surfaces is installed in the opening on the side wall of the container, the horizontal distance between the sensing surface 30 of the opening and the sensing surface 28 on the side wall is such that the two sensing surfaces 28, 30 are on the side wall. It may be larger than the case of installation.

  Multiple sensing elements 26 may be placed on the inner wall 24 of the vessel, on the digester vessel wall, or on the outer wall of the central pipe in the vessel or on a post extending from the outer wall 24 into the vessel. You may install in a container like. Further, the plurality of sensing elements 26 should be installed so that the influence of the speed and momentum of the chip on the measured pressure signal is minimized. The sensing surfaces 28, 30 are preferably tilted by 10 degrees with respect to a direction parallel to the chip flow direction, for example a chip velocity vector (see arrow 20 for slurry flow direction) and a chip velocity vector (see arrow 20). Arranged at an angle between the direction. If a slight angle, for example up to 20 degrees, and preferably an inclination of about 5 degrees is applied to the sensing surface 28 so that the lower edge of the surface extends more into the slurry than its upper edge, the sensing Surface 28 is more sensitive to static tip pressure. However, if an excessive angle of inclination is applied to the detection surface 28, the speed of the chip affecting the detection surface will distort the response of the detection surface 28.

Each surface area of the pressure sensing surfaces 28, 30 and, in particular, the surface area of the sensing surface 28 in contact with the wood chip is relatively larger, such as within 20 percent of 0.1 meter squared (m ² ). Yes. The large surface area of the pressure sensing surface 28 provides sufficient contact area and tends to contact the surface at various angles, has different chip shapes and sizes, and is somewhat higher in the slurry in the container. It makes it possible to detect a chip that is a concentration. The surface areas of the pressure sensing surfaces 28, 30 may be different. For example, the surface of the detection surface 30 that does not contact the chip may have a smaller area than the surface of the detection surface 28 that contacts the chip. If the surface areas of the pressure sensing surfaces 28, 30 are different, then the pressure sensor electronics are configured to take into account the surface area of the sensing element and determine the pressure applied to that surface.

The relatively large surface area of the sensing surfaces 28, 30, for example 0.1 m ² , minimizes the effects of the following parameter variations. Thus, a sensing surface with a large surface area minimizes undesirable effects on the signal generated by the sensing surface that can reduce the accuracy of pressure measurements. Parameters such as contact angle, chip shape and chip density will vary over time during processing in the container.

  The first pressure sensing surface 28 that is in direct contact with the wood chip measures the total static pressure of the wood chip and liquid slurry. On the other hand, the second pressure detection surface 30 measures the hydrostatic pressure of the liquid. The second pressure sensing surface 30 does not measure the pressure at the tip because the sensing surface 30 is behind the tip filter 32 and is shielded from the tip. The static pressure by the chip is determined from the difference between the measured value of the hydrostatic pressure of the liquid detected by the pressure detection surface 30 and the measured value of the total static pressure detected by the pressure detection surface 28.

  Since the static tip pressure related to the hydrostatic pressure of the liquid is small, it is preferable to use a differential pressure transmitter such as a differential pressure (DP) sensor 35. The pressure sensing element 26 may include a DP sensor 35 having capillary pressure tubes 36, 38 in liquid connection with pressure sensing surfaces 28, 30 as inputs. The DP sensor measures the static pressure in both tubes 36 and 38 and outputs a signal representing the pressure difference in both capillary tubes. Both tubes are each connected to a small liquid cavity 40 behind each of the pressure sensing surfaces. The liquid-filled cavity 40 acts as a pressure relay that transmits the pressure on the sensing surfaces 28, 30 to the capillary tube. As the slurry pushes the first pressure sensing surface 28, the sensing surface deflects and applies a pressure to the cavity 40 and capillary tube 36 that corresponds to the total static pressure of the slurry. Similarly, as liquid pushes the diaphragm of the second pressure sensing surface 30, the pressure in the cavity 40 and capillary tube 38 indicates the hydrostatic pressure of the liquid on the opposite side of the diaphragm.

  The liquid may be highly alkaline and hot. The pressure sensing surfaces 28, 30 act as pressure relays while transmitting the slurry and liquid pressure to the hydraulic liquid in the capillary tube. The diaphragm surfaces 28, 30 allow the pressure of the slurry and liquid to be applied to the DP sensor 35 without exposing the DP sensor 35 to the alkalinity or temperature of the liquid.

  In order to measure the liquid density (R2), it is preferable to include a liquid density 44 (FIG. 1) sensor. Alternatively, the liquid density may be measured using a differential pressure based sensor 45. If the liquid density is known, if the liquid density changes during the chip processing in the container, it can be corrected in the chip pressure determination. In addition, a liquid level sensor 38 may be used to determine the liquid level 18 in the container. The liquid level may be used in calculations that determine the chip level from the chip pressure.

  The tip pressure affects the tip compression in the container. The tip pressure at each height in the container is indicative of the compression of the tip in the container at a height below it and in the container at a lower height. The distribution of chip compression over the entire length of the digester can be created based on the chip pressure measured at various heights within the container. The compression distribution can be used, for example, to determine the chip residence time in the container and the chip residence time in various zones within the container. For example, the compression distribution may be used to determine the residence time of the chips in the cooking zone of the cooking vessel.

  The tip pressure can be used to control the container, for example to control the inflow of the chip into and out of the container, to better stabilize the chip compression distribution in the container and thereby from the container. Variations in the quality of the discharged processed chips can be minimized. Chip pressure measurement provides data that helps stabilize the impregnation or cooking process in the vessel. The tip pressure data is used by the controller for the container to adjust the parameters for the container, such as the amount of tip flow into and out of the container, at a selected height within the container. Maintain a constant tip pressure.

  Knowing and controlling the tip level in the container is generally necessary for reliable control of the tip pressure in the container. For example, the computer controller 42 monitors the chip pressure signal output from the pressure sensing element and compares the measured chip pressure with the desired chip pressure. If the difference between the measured tip pressure and the desired tip pressure exceeds a predetermined range, for example, within 10 percent of the desired tip pressure, the controller will reduce the slurry to the top separator to reduce the difference. Adjust the flow rate or tip flow rate from the bottom of the container.

  The pressure sensing element 26 may be used to monitor the chip level in the container and control the chip pressure in the container. Using the data from the pressure sensing element, the driver or automatic control system 46 may choose to control the in-container tip level or to control the in-container tip pressure. The control system may adjust the amount of slurry flowing into the container or the amount of processed chips flowing out of the container. If the controller 42 is in a mode that maintains the tip level within a predetermined range of height in the container, the controller calculates the tip level based on the tip pressure, and the calculated tip level is within the height tolerance. If so, the controller increases or decreases the slurry inflow to the top separator or the chip outflow from the bottom of the container to raise or lower the chip level to an acceptable range. In addition, the controller 42 compares the measured tip pressure with the permissible limit range of the tip pressure in the container and keeps the tip pressure in and out of the container so as to maintain the tip pressure within these limits. Adjust. Or you may make it maintain a fixed chip | tip pressure within a container on the conditions that a chip | tip level does not exceed the range of the predetermined height in a container by a control system. By maintaining a constant tip pressure, tip density variation can be minimized in the tip compression distribution of the container. Furthermore, controlling the chip pressure in the container (rather than directly controlling the chip level) helps to reduce kappa number fluctuations by correcting for chip density effects and air content fluctuations and sway.

  The chip pressure is a function of the height of the chip column above the sensing element 26, the height of the liquid column in the container above the sensing element, the liquid density in the container, and the chip density. The algorithm for determining the chip pressure (PC) for the range of chip level (L1) and liquid level (L2) above the sensing element 26 is as follows.

  PC = (R1-R2) * G * min {L1; L2} + R1 * G * max {L1-L2; 0}

Where PC is the tip pressure (Pa-atmospheric pressure); L1 is the average tip level in the container (meter (m)); L2 is the liquid level in the container (m); R1 is entrained by the liquid in the container Chip density (kg / m ³ ); R2 is the density of the free liquid (kg / m ³ ); and G is the gravitational constant (kg / (ms ² )). The term min {L1; L2} indicates the selection of the smaller value of L1 and L2. Similarly, the term max {L1-L2; 0} indicates the selection of a positive value for the difference between L1 and L2, or a selection of zero if the difference is a negative value.

  The following algorithm is applied to determine the chip level L1 from the above equation.

  Solution 1: If L1 <L2, then L1 = k1 * PC / [(R1-R2) * G], where k1 is a calibration constant.

  Solution 2: If L1> L2, then L1 = [k1 * PC + k2 * (R2 * G * L2)] / (R1 * G), where k1 and k2 are calibration constants.

  The solution 1 equation is selected when the liquid level is above the chip level, and the solution 2 equation is selected when the chip level is above the liquid level. The solutions 1 and 2 may be used together to determine if the preconditions for the relationship between L1 and L2 are valid. The result obtained by the valid formula (Solution 1 or 2) is selected as the correct chip level estimate L1.

  The measured liquid density R2 from sensor 44 or 45 may be utilized to estimate the density (R2) of the liquid-impregnated wood chip using the following equation:

  R1 = Eps * RW + (1-Eps) * R2

EPS and RW are parameters specific to the wood type, Eps is the volume content of solid wood material in porous wood chips; (1-Eps) is the volume content of liquid in porous wood chips And RW is the solid wood density. For example, Eps is in the range of 0.6 to 0.75, and RW is in the range of 1300 kg / m ³ to 1650 kg / m ³ . It is assumed that the wood chips are completely penetrated by the liquid and that there is no air residue on the wood chips.

FIG. 4 is a chart showing a chip level calibration technique. The horizontal axis represents the time during operation of the container (numbers 1 to 39). The vertical axis 52 on the left side of the chart indicates the height of the container, which is about 12 meters high. The vertical axis 54 on the right side of the chart represents the static pressure of the chip in the container in kilopascals kPa (Newton / m ² ).

  The chip level calculated based on the data from the pressure sensing device 26 is calibrated using the liquid level data collected by the liquid level sensor 38 (see FIG. 1). Liquid level data is directly measured by the liquid level sensor and treated as accurate and appropriate as a reference value for the purpose of calibrating the chip level determination.

  The calibration process varies the amount of liquid in the container so that the liquid level (line 58 in FIG. 4) rises above the actual chip level and then falls below it. The actual chip level is preferably kept constant during the calibration process. During this process, the chip level is determined based on the chip pressure (line 60) using the above algorithm (line 56).

  The solution 2 algorithm shows that the chip level (L1) is a function of the liquid level (L2) when the liquid level is below the chip level. The solution 1 algorithm shows that the tip pressure does not vary with the fluid level while the fluid level is above the tip level. When the liquid level rises or falls through the chip level, the chip pressure undergoes a transition from a constant number to a variable number or vice versa. Assuming a constant tip level, the tip pressure 60 begins to change as the descending liquid level 58 passes the tip level. If the liquid level is below the chip level, the chip pressure will continue to change as the liquid level rises towards the chip level, after which the chip pressure will remain constant as the liquid level rises above the chip level Stay on.

  During the calibration process, the pressure sensing element senses changes 62, 68 in the static chip pressure while the liquid level rises and falls above and below a certain chip level. While the liquid level is above the chip level, the chip pressure 60 remains constant (see times 1 to t1 in FIG. 4). At t1, the tip pressure begins to change (62) by transitioning from a constant pressure to a rising pressure. At that time (t1), the liquid level is equal to the actual chip level. Since at t1, the determined chip level 56 should be equal to the measured chip level 56, the associated chip pressure change 62 is utilized to identify a calibration event for chip level determination. Any difference 64 at t1 between the determined chip level 56 and the measured liquid level 58 indicates an error in the algorithm used to determine the chip level 56. For calibration purposes, the liquid level 58 measured at t1 is treated as representing the actual chip level, and the difference 64 is considered an error in the chip level algorithm. In the example shown in FIG. 4, there is a difference 64 of approximately half a meter (0.5) meter between the determined chip level and the measured liquid level.

  During the period from t1 to t2, the liquid level 58 is further lowered below the chip level, for example approximately 1 meter below. Further, the algorithm for determining the chip level (solutions 1 and 2) is adjusted, for example, by adjusting one or both of the calibration constants k1 and k2 in solutions 1 and 2. In this example, adjustments to solutions 1 and 2 increase (66) the determined chip level by 0.5 meters at time t2. The actual chip level is not changed and only the determined chip level changes at the transition point 66. During the period from t2 to t3, the actual determined chip level remains constant, and the liquid level transitions from a constant low level to a rising level. As the liquid level increases (58), the static chip pressure 60 decreases because the liquid level is below the chip level. The falling tip pressure is modeled by the solution 2 algorithm. Stopping the descending tip pressure at t3 is considered as an indication that the liquid level is equal to the tip level and as a calibration event. In this second calibration event (t3), there is no error between the determined chip level 70 and the measured liquid level. The absence of error indicates that the determined chip level provides an accurate indication of the actual chip level and the calibration process is complete. If, at the second calibration event (t3), a significant difference, such as greater than 0.1 meters, remains between the determined chip level and the liquid level, further adjustments to the algorithms of solutions 1 and 2 In addition, the liquid level drop and rise through the tip level described above may be repeated until the difference in a calibration event falls below the tolerance level.

  Potential benefits and improvements to determining tip pressure using tip pressure to estimate tip level include: That is, continuous and reliable chip level measurement signals that do not require strain gauges or calculations related to strain gauges; pressure sensing elements that provide data across a large vessel operating area; for example, during vessel shutdown Reliable chip level signal even if flow through the container is stagnant; chip level signal independent of chip speed and chip processing output in the container; uniform common pressure for various types of containers Sensing element configuration (in other words, the pressure sensing element may be used in various types of vessels); accurate tip pressure signal for stabilization of digester vessel; accurate tip for determining tip compression distribution Pressure measurement; To detect the chip pressure signal when the level is the same, slowly adjust the chip level or liquid level to a predetermined point It is like and start-up start-up cost is low; that the components and cost of instrumentation is low; online calibration by the.

  While the present invention has been described with respect to the presently most practical and preferred embodiment, the present invention is not limited to the disclosed embodiment, and the present invention is not limited to the various modifications or variations encompassed by the claims. It should be understood that it is intended to include equivalent configurations.

Claims (20)

A pressure sensing element for a container containing a slurry of lignocellulose chip material,
A first pressure sensing surface that contacts the slurry and generates a signal indicative of the slurry pressure, which is the sum of the hydrostatic pressure and tip pressure of the liquid;
A second pressure sensing surface that generates a signal indicative of the hydrostatic pressure of the liquid;
A pressure sensing element comprising: a differential pressure transmitter for receiving respective signals generated by the first and second pressure sensing surfaces and transmitting a signal indicating a chip pressure. The pressure sensing element according to claim 1, wherein an output signal from the signal generator represents a difference between signals generated by the first and second pressure sensing surfaces. 2. A filter is included between the slurry and the second pressure sensing surface, the filter passes liquid through the second pressure sensing surface and prevents the tip material from reaching the second pressure sensing surface. The pressure sensing element according to 1. The pressure sensing element according to claim 1, wherein at least the first pressure sensing surface has orientation in a range of a direction parallel to the slurry flow direction and a direction inclined by 20 degrees with respect to the flow direction. The pressure sensing element according to claim 1, wherein the pressure sensing element is located within the container, above the uppermost extraction screen of the container and below the container inlet separator. The pressure sensing element according to claim 1, wherein the pressure sensing element is mounted on an inner surface of the outer wall of the container. The pressure sensing element of claim 1, wherein at least the first pressure sensing surface has a surface area of about 0.1 square meters. A method for determining the pressure of lignocellulose in a container containing a lignocellulose chip material and a slurry of liquid,
Detect the pressure of the slurry in the container,
Sensing the pressure of the liquid in the container and determining the pressure by the chip based on the difference between the sensed slurry pressure and the sensed liquid pressure. 9. The method of claim 8, wherein the slurry pressure is a static pressure detected by a first pressure sensing surface that contacts the slurry and generates a signal representative of the static pressure of the slurry. 9. The method of claim 8, wherein the pressure of the liquid in the slurry is sensed by a second pressure sensing surface that generates a signal representative of the hydrostatic pressure of the liquid in the slurry. 9. The method of claim 8, wherein a filter is disposed between the slurry and the second pressure sensing surface, the tip is blocked by the filter, and the filter passes the liquid to contact the second pressure sensing surface. 9. The method of claim 8, comprising determining a tip level in the container based on the determined tip pressure. 9. The method of claim 8, wherein the slurry pressure and liquid pressure are sensed above the top extraction screen of the vessel. The method according to claim 8, wherein the chip level (L1) in the container is determined by applying at least one of the following algorithms:
L1 = k1 * PC / [(R1-R2) * G] (when L1 is greater than L2), and
L1 = [k1 * PC + k2 * (R2 * G * L2)] / (R1 * G) (when L2 is greater than L1),
Where PC is the pressure of the chip to be determined, k1 and k2 are calibration constants, L1 is the average chip level in the container, L2 is the liquid level in the container, R1 is the density of the entrained chips in the slurry, and R2 is in the slurry Liquid density, and G is the gravitational constant. A method of calibrating an algorithm for determining chip level,
Measure the liquid level in the container,
Measure the tip pressure in the container,
Determine the calculated chip level using an algorithm that calculates the chip level based on the chip pressure,
While changing the liquid level in the container, the transition between the steady state tip pressure and the changing tip pressure is detected,
Determine the difference present in the transition between the liquid level and the calculated chip level, and
Adjusting the algorithm to correct for the difference. The method of claim 15, wherein the tip level in the container is maintained substantially constant during the calibration method. 16. The method of claim 15, wherein the liquid level is raised or lowered above or below the chip level during the calibration method. 16. The method of claim 15, wherein the tip pressure is measured at a height in the container below the tip and liquid levels and above the first extraction screen. A method of processing lignocell roll material in a continuous flow vessel, the method comprising:
Based on the difference between the detected total pressure of the slurry and the detected hydraulic pressure, the chip pressure of the chip material is determined,
Comparing the determined tip pressure of the tip material with a predetermined desired tip pressure;
Adjusting the flow rate of the tip material passing through the container based on a comparison between the determined tip pressure and a predetermined desired tip pressure. The method of claim 19, wherein the predetermined desired tip pressure is a constant tip pressure.

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