WO2016112203A1

WO2016112203A1 - System and method for monitoring and control of multiple processing zones within pressurized vessels

Info

Publication number: WO2016112203A1
Application number: PCT/US2016/012508
Authority: WO
Inventors: Tyson Hunt; Jarmo KAHALA; Pasi NIEMELAINEN; Jay Sheerer
Original assignee: Andritz Inc.
Priority date: 2015-01-07
Filing date: 2016-01-07
Publication date: 2016-07-14

Abstract

A system and method to monitoring and control of solid chips and liquids within pressurized vessels, typically having a vertical orientation, used in the production of pulp from lignocellulosic material. The monitoring equipment comprises multiple electrochemical probes configured to perform continuous analysis on the operating conditions of a pressurized vessel at the periphery of the pressurized vessel. The monitoring equipment is preferably disposed in one or more annuluses around the pressurized vessel

Description

SYSTEM AND METHOD FOR MONITORING AND CONTROL OF MULTIPLE PROCESSING ZONES WITHIN PRESSURIZED VESSELS

CROSS-RELATED APPLICATION

[0001] This application is a Non-Provisional Application claiming the benefits of U. S. Provisional Patent Application Serial No. 62/100,720 filed January 7, 2015, the entirety of which is incorporated herein by reference and U. S. Provisional Patent Application Serial No. 62/139,286, filed March 27, 2015, the entirety of which is also incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. TECHNICAL FIELD

[0002] This disclosure relates to monitoring and control of solid and liquid within pressurized vessels, such as digesters. These pressurized vessels are typically vertically oriented, and can be used to produce pulp from lignocellulosic material. In particular, this disclosure relates to monitoring and control of lignocellulosic material and reaction liquid (cooking liquor) within pressurized vessels such as, but not limited to impregnation vessels, digesters, reactors, diffusers, and bleach towers. Further embodiments of this disclosure relate more specifically to the monitoring and control of extracted liquid and wash liquid (wash liquor, cold blow, weak black liquor or any suitable liquid) as well as cooking liquor (for example white liquor or other suitable liquid used in the cooking or other treatment of lignocellulosic material) within a digester vessel wash and cooling zones.

2. RELATED ART

[0003] The pulp and paper industry, and other process industries, employ chemical reactions in processes that are often performed in vessels under pressures greater than atmospheric pressure. Typically, these processes are performed within vessels that maintain the product at predetermined super-atmospheric pressures and at elevated temperatures to promote the desired chemical reaction. These pressurized vessels may be 100 meters tall and have a bottom diameter of about 8 meters to more than 12 meters. These pressurized vessels typically operate at a pressure of 3 to 6 bar gauge or even 8 to 10 bar gauge at the top of the pressurized vessel. [0004] Processing lignocellulosic material in this manner is known as "cooking". Such vessels include continuous or batch impregnation and digester vessels. For simplicity, lignocellulosic material shall be referred to as "chips" throughout this disclosure, but it will be understood that "lignocellulosic material" may refer to wood chips, plant material, bagasse, wheat straw, mixed corn stover, mixed municipal waste and other cellulose- containing material.

[0005] Cooking is often sensitive to temperature, chip level, chip density throughout the vessel, concentration of alkaline chemicals, and liquid level. The liquid may be alkaline, acidic, or other process liquids useful in the conversion of lignocellulosic material into various constituents.

[0006] In a batch cooking system, chips and the desired carrier medium fill the pressurized vessel (batch digester) to a desired level. When the desired level of chips is obtained, the flow of chips to the batch digester is stopped and cooking liquor(s) cook the chips. Once the cooking is completed, operators empty the batch digester before refilling the batch digester with chips and restarting the cooking process.

[0007] In a continuous cooking system, there is continuous flow of chips into the pressure vessels (for example, impregnation vessels and digester vessels) and a continuous flow of processed chips out of the pressure vessels. Typically, when using a pressure vessel to produce pulp from chips, the chips are fed to a pressure vessel along with cooking liquor or a mix of cooking liquor and water.

[0008] In an impregnation vessel, chips entering the vessel may have previously undergone heating and denaturing. Fresh or used cooking liquor or other suitable chemicals may be introduced to the vessel for a predetermined contact time with the chips, thereby forming impregnated chips. Impregnated chips from the impregnation vessel can be transferred, along with cooking liquor, to a pressurized vessel, digester, for cooking. Both the impregnation vessel and the digester may be pressurized vessels and may operate at different pressures. Any requirement for pressurization of the material leaving the impregnation vessel transferred to the digester is accomplished using known means. In certain configurations, a single pressurized vessel may be used for both impregnation and cooking. A single pressurized vessel for impregnation and cooking is typically referred to as a "digester" or a "reactor" or a "treatment vessel". If multiple vessels are used for impregnation and cooking, the cooking vessel is typically referred to as a "digester". [0009] The pressurized vessel, or vessels, in the cooking system may be either a hydraulic phase vessel or a vapor phase vessel. In a hydraulic phase vessel, the vessel contains liquid up to and above the level of the chips. In a vapor phase vessel, the liquid level is established below the top of the vessel, usually below the chip level, which thereby leaves a vapor space above the liquid level. This vapor space typically receives steam or other suitable vapor phase compounds. The steam or other vapor phase compounds can heat the chips.

[0010] The pressurized vessel of a continuous cooking system may have multiple process zones. The process zones may include an impregnation zone, heating zone, cooking zone, washing zone, and cooling zone. Operators generally inject fluids to pretreat and cook the chips in the impregnation, heating, and cooking zones. Additionally, operators generally inject washing and cooling fluids in the wash and cooling zones. Wash liquid can decrease the concentration of dissolved organics in a wash zone and can facilitate chip cooling before the chips are discharged from the pressurized vessel.

[0011] The measuring, and thereby monitoring, of the chip level and liquor level by one known means involves the use of paddles and differential pressure (dp) cells to measure chip and liquid level in the pressurized vessel. Such a system is described in US patent 5,882,477. A second known method to measure and monitor chip level and liquor level in a pressurized vessel is to use a device (for example, a vertical tube) mounted with pairs of electrodes at varying heights within the pressurized vessel, where pairs of electrodes are connected to electric circuits. The electric circuits can supply current between two electrodes to measure voltage potential and calculate impedance and thus the height of material within the pressurized vessel. These probes were only capable of measuring the voltage potential of the material within the pressurized vessel on material in the center of the pressurized vessel, without attributing a reading to a particular processing zone within the pressurized vessel. Moreover, these probes generally occupy the top 20 percent of the pressurized vessel.

[0012] While known methods and equipment exist to monitor chip and liquor levels in pressurized vessels, these methods and equipment are limited to monitoring chip and liquor levels in the pressurized vessel, other parameters including for example chip column density and residual alkali concentration cannot be measured using the devices available for monitoring chip and liquor levels. In conventional pressurized vessels, operators generally use a probe to measure chips levels and another probe to measure liquor levels, and further probe to measure extracted liquid temperature and residual alkali concentration. Using a probe configured to measure a single operating condition tends to minimize manufacturing costs. A probe configured to measure a single operating condition may be simpler to design and manufacture. Moreover, using a single probe per operating condition instead of multiple probes for the same operating condition optimizes costs per probe. Chip levels are measured by inserting a strain gauge into the pressurized vessels, extending about one foot into the interior of the vessel. Because the strain gauge extends into the vessel by a distance of approximately one foot, the strain gauge is vulnerable to breaking as chips move past the strain gauge.

[0013] A second device, a differential pressure transmitter, is required to establish the liquor level in the pressurized vessel. The differential pressure transmitter is positioned in the pressurized vessel and can calculate the static pressure of the liquor to establish the liquor level. A nozzle holds the differential pressure transmitter within the pressurized vessel. Solids, pieces of chips, or even debris such as dirt may plug the transmitters and prevent the transmitters from operating, as the solids move past the nozzles.

[0014] To measure extracted liquor temperature and residual alkali concentrations, operators generally take samples from a point source. A point source may be a sample port in the vessel wall. In some vessels, an operator may physically insert a sampling rod through the sample port to collect the sample. In other digesters, the point source may be a sampling apparatus that automatically isolates a sample of the wash liquid. Operators use such point source information to control the application rate of cooking liquor in certain zones.

[0015] The measuring of liquid temperature and alkali level in current systems requires samples to be taken and processed outside the vessel. Such processing requires time, and conditions may change while operators process the samples. Processing time further delays changes to vessel operating conditions; this can result in suboptimal product production. For the wash zone and cooling zones in particular, a delay in receiving new temperature and alkali level desired set points causes periods of less desirable operations. The periods of less desirable operations of a digester can result in poor pulp quality.

[0016] Delays in receiving information on operating parameters, especially temperature and residual alkali concentration, from the wash zone can cause delays in adjusting flows, particularly of wash liquid and cooking liquor. It is important to have sufficient residual alkali in the liquid obtained via the wash extraction screen to provide the desired product quality. That is, the alkali is an active ingredient in the cooking liquor that breaks down the lignin in the lignocellulosic material. Breaking down the lignin liberates the cellulose and hemicellulose fibers that are the desired fibers to comprise paper pulp. If operators detect insufficient residual alkali in the liquid from the wash extraction screen, this can indicate that the digester did not sufficiently treat the lignocellulosic material to cause the lignin to be broken down. The breaking down of lignin is also known as delignification. As a result, the treated chips, pulp-like product, exiting the digester may contain knots, clumps of partially digested chips, or other solid aggregates that may clog downstream equipment and degrade the quality of any paper manufactured from this pulp.

[0017] It is also important to not have an abundance of residual alkali in the liquid from the wash extraction screen to prevent wasting of cooking chemicals. An abundance of residual alkali may cause continued treatment of the lignocellulosic material beyond the desired point of reactions where the reactions begin to cause damage to the cellulose and hemicellulose portions of the lignocellulosic material. In addition to adverse chemical reactions caused by an abundance of residual alkali, having an abundance of residual alkali results in the costly inefficient use of cooking chemicals.

[0018] In addition to residual alkali level, it is important the wash extraction return liquid be of a temperature to begin cooling of the column of chips by the wash extraction return liquid to enhance the efficiency of the cooling zone. Beginning the cooling in the wash zone helps to stop reactions of the alkali and the lignocellulosic material and thereby prevents additional damage to the cellulose and hemicellulose.

[0019] For the cooling zone, delays in information on operating parameters, particularly temperature, can result in a warmer than desired product leaving the digester. Warmer than desired product leaving the digester may be more easily damaged by the mechanical action imparted by the discharge equipment to the material being discharged from the digester. Additionally, warmer than desired product from the digester requires equipment downstream of the digester to remove the heat not removed in the cooling zone. If the material discharged from the digester is damaged as a result of mechanical action, pulp quality is reduced. If the material discharged from the digester must be cooled in downstream equipment, downstream equipment operations can become compromised.

[0020] Operators use other probes or methods to monitor temperature of the material within the pressurized vessels, chip column density and scale buildup on the probe using the same monitoring equipment as used for chip and liquor level monitoring. Once the information is available for chip level, liquor level, material temperature, chip column density, and scale buildup on the probe, operators can use the gathered information from the monitoring equipment to provide input for control of the pressurized vessel operating parameters.

BRIEF DESCRIPTION OF THE INVENTION

[0021] The systems, methods and equipment disclosed herewith allow for the monitoring and controlling of chip level, liquor level, liquor composition, material temperature, chip column density, chip compaction, residual alkali concentration in the wash zone and cooling zone and scale buildup on the probe within the pressurized vessel simultaneously for a pressurized vessel such as an impregnation vessel or a digester vessel, which permits operators to obtain a more comprehensive understanding of internal digester conditions than previously possible.

[0022] Applicant has recognized that placing electrochemical probes in an annular formation at multiple heights along the wall of the pressurized vessel wall allows operators to collect comprehensive, real-time data on the process occurring within the pressurized vessel. Whereas separate probes configured to measure separate operating conditions may be most cost effective to a plant manager, Applicant has found that arranging electrochemical probes in the manner described herein allows operators to record operating conditions in real time and to gain a more comprehensive understanding of the operating conditions within a pressurized vessel and the impact of these operating condition's effect on product quality. If the pressurized vessel is a digester, product qualities may include pulp tensile strength, receptiveness to bleaching agents, durability, average pulp fiber length, etc.

[0023] Accordingly, it is an object of the present disclosure to reduce the time between signal detection and response. It is a further object of the present disclosure to obtain data about the processes occurring in a pressurized vessel at multiple points at or near the periphery of the pressurized vessel, such as at or near the circumference of a pressurized vessel. Applicant has discovered that chips do not flow down the length of a pressurized vessel at a uniform rate. Placing multiple electrochemical probes through the wall of the pressurized vessel at multiple elevations along the pressurized vessel height such that the sensor end of the electrochemical probe extends not substantially greater than two inches into the pressurized vessel may allow operators to identify areas of chip compaction, areas of non- plug flow, and other operating conditions while reducing the probability that solids within the pressurized vessel will damage the sensors on the probes. If a probe malfunctions during pressurized vessel operation, increasing the number of the probes in the pressurized vessel further reduces the probability that a single damaged probe will substantially affect process condition measurements.

[0024] Applicant has discovered the periphery of the pressurized vessel can be a dynamic region within a vertically oriented pressurized vessel. It is an object of the present disclosure to obtain additional sources of data at the periphery of the pressurized vessel to create an accurate model of the operating conditions within a pressurized vessel. It is a further object of the present disclosure to obtain data on pressurized vessel internal temperature, chip level, liquor level, residual alkali concentration, chip compaction, and other operating conditions from a single probe, wherein the probe is disposed in a nozzle communicating with the interior of the pressurized vessel and wherein multiple nozzles may be disposed on the wall of a pressurized vessel and wherein each nozzle is configured to house a probe.

[0025] In other exemplary embodiments, the probe may monitor a subset of the group comprised of the chip level, liquor level, liquor composition, temperature of the material, chip column density, residual alkali concentration in the washing zone and cooling zone, compaction, and scale buildup on the probe within the pressurized vessel. The monitoring system may be comprised of multiple probes located at various vertical points of the pressurized vessel. Each probe probes and electrodes may be a probe or electrode described in US patent 5, 167,769, the entirety of which is incorporated herein by reference or in US published patent application 2013/0248127, the entirety of which is also incorporated herein by reference. At each vertical point, a series of probes are positioned around the circumference of the pressurized vessel to form rings of probes at various heights in the vertical direction. In an exemplary embodiment, between four and twelve probes may be used to form a ring of probes at each of the vertical points. The exact number of probes forming a ring of probes can be dependent on the diameter of the pressurized vessel as well as the function (heating, impregnating, cooking, washing, cooling) of the pressurized vessel at the location of any specific ring of probes. In other exemplary embodiments, the number of rings of probes may vary between pressurized vessels, with the exact number of rings being a function of pressurized vessel size as well as the vessel's purpose.

[0026] Each probe can be positioned within a holder, such as a nozzle, and each probe may protrude from the exterior of the pressurized vessel through the pressurized vessel interior wall a minimal distance. For example, the probe may be flush with the pressurized vessel interior wall or protrude into the pressurized vessel interior space a distance of up to a few inches, for example from half an inch to two inches. In other embodiments, the probe may extend greater than zero inches up to two inches into the interior space of the pressurized vessel. These probes generally use electrochemistry to monitor the parameters of chip level, liquor level, liquor composition, material temperature, chip column density, and scale buildup on the probe.

[0027] The probes are desirably electrochemical probes. A probe feeds a signal input to an algorithm where values from the algorithm are compared to desired parameters and adjust operations via an analyzer such as an "AIC" (analyzing indicating controller). The AIC may then send a signal to the various valve controllers to control the chip flow rate, liquor flow rate, liquor strength, and temperature of the liquor as well as extraction and addition rates of various liquors in addition to adjusting circumferential flow to the pressurized vessel.

[0028] The use of such electrochemical probes to gather the necessary process information allows for a short time between measurement and reaction to the measurements. Electrochemical probes, such as those provided by Savcor Forest Oy of Mikkeli, Finland, use a combination of electric current, electric voltage, resistance and temperature measurements to obtain the process information needed.

[0029] Because rings of probes may be located at multiple vertical points of the pressurized vessel, monitoring information is available at each location of the multiple rings of probes and allows for localized control. As an example, within a specific region of the pressurized vessel, one parameter such as liquor temperature may be adjusted, while within another specific region liquor flow rate could be adjusted or other operating parameters of the pressurized vessel. By adjusting operating parameters based on the conditions at the various individual points, both vertically and horizontally situated about the pressure vessel, improved overall pressurized vessel operations, product quality and product yield is achieved.

[0030] Arranging multiple rings of probes around the circumference of a pressurized vessel increases the demand for external access to each probe. This may require mill owners to retrofit existing pressurized vessels with walkways and platforms proximate to the pressurized vessel's exterior. Adding these platforms may disincentives a mill owner to retrofit an existing pressurized vessel, and the presence of the multiple, specialized probes and access platforms may increase the cost of manufacturing new pressurized vessels. Adding additional holes to the pressurized vessel configured to receive a nozzle and probe can create areas of structural weakness in the wall of the pressurized vessel. The increased presence of external holes in the pressurized vessel can also increase the probability that hot, caustic cooking liquors, acidic cooking byproducts, and steam may leak from the pressurized vessel. This can jeopardize the safety of nearby operating personnel.

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] FIG. 1 shows a pressurized vessel with multiple rings of probes along the vertical height of the pressurized vessel.

[0032] FIG. 2 shows a ring of probes to be attached at various vertical heights of the pressurized vessel.

[0033] FIG. 3 is a flow diagram of a cooking system according to one embodiment.

[0034] FIG. 4 shows a digester wash zone and a cooling zone, exemplary application zones for this invention.

DETAILED DESCRIPTION OF THE INVENTION

[0035] Although this disclosure describes in context a single continuous digester as the pressurized vessel, it is understood this disclosure is applicable to other pressurized vessels where monitoring and control of the chemical composition in the cooking liquor, level of solids, level of treatment liquor (chemicals), temperature of the material within the pressurized vessel, density of the solids column formed within the pressurized vessel, or circumferential differences are desired.

[0036] FIG. 1 shows a diagram of a single vessel digester 100. The digester 100, a pressurized vessel, has a feed material inlet 101 at the top of the vessel and a processed material outlet 102 at the bottom of the vessel. Feed material 119, which may be chips, enters the feed material inlet 101 and moves through the digester 100 and is discharged from the digester 100 through the processed material outlet 102. Processed material 121 may be discharged from the digester 100 through the processed material outlet 102. While in the digester 100, the feed material 119 passes through various process zones A, B, C, D, and E within the digester 100. As shown in FIG. 1, the pressurized vessel is a single vessel digester 100 having multiple process zones A, B, C, D and E. The process zones are: impregnation zone A, heating zone B, cooking zone C, washing zone D, and cooling zone E.

[0037] As feed material 119 enters the digester 100, feed material 119 is in the form of a slurry of solids particles (chips) and liquid (liquor such as cooking liquor or alkali). The liquid content of the slurry tends to be substantially higher than the necessary or desired liquid content in the digester 100. As the feed material 119 enters the top separator 127, some excess liquid is removed from the feed material 119. The excess liquid may be removed from the digester 100 via liquid return line 108. Excess liquid in liquid return line 108 may be reintroduced to chips as transport liquid upstream of the digester 100 or may be removed from the process for further treatment or use in other locations within the mill. After removal of the excess liquid, chips along with the remaining liquid or entrained liquor, are discharged from the top separator 127 and move down through the digester 100.

[0038] Chips with entrained liquor fill the digester 100 forming a column of chips 228 having a chip column top 114 within the digester 100. The column of chips 228 moves through the digester 100 in a vertical direction from top to bottom. As the column of chips 228 moves through the digester 100 the column of chips 228 passes screens 109. Liquid can be extracted from the screens 109 and recirculated to the digester 100 through center pipe inlets 110 and center pipes 150, or can be removed from the digester system 200 (FIG. 3) and sent for further processing elsewhere in the mill.

[0039] Additionally, fresh treatment chemicals such as alkali, acid, white liquor, other chemical or wash liquid or cooling liquid may be added to the digester 100 via the center pipes 150 having center pipes inlets 110. Extracted liquor 116 may be extracted through screens 109 and may be supplemented with fresh liquor or extracted liquor 116 from a different screen 109 in a different process zone A, B, C, D, or E to become circulation loops. At least a portion of extracted liquor 116 may be removed from the digester 100 as removed liquor 116A and may be processed in other parts of the mill such a chemical recovery unit. As an example, extracted liquor 116, black liquor, from cooking zone C may be used as impregnation liquor by retuming the extracted liquor 116 to the appropriate center pipe inlet 110 to enter the impregnation zone A. Liquid in the various circulation loops 115 may require temperature adjustment; such temperature adjustment may be via any known equipment to allow for the desired heat exchange. One or more probes 113 (FIG. 2) are positioned along the digester 100. Each probe 113 may be a probe as described more fully in US published patent application 2013/0248127. The probe 113 uses electrochemistry, to gather information regarding the column of chips 228 in the digester 100 as the column of chips 228 in the digester 100 moves past the probes 113 at the various locations where the rings 105 of probes 113 are positioned. Electrochemical probes 113 may measure the electric conductivity of the chips, gas, and liquor between electrodes in the probe. That is, the material within the digester 100 may have sufficient conductivity to complete an electric circuit between electrodes in a probe 113. For example, steam is generally an insulator. Steam's conductivity is insufficient to complete an electric circuit, so operators may deduce that the level of chips and liquor is below electrochemical sensors that detect little to no current. In the impregnation zone A, heating zone B, and cooking zone C, the amount of liquor in the chips can complete the electric circuit and provide a profile of the chips in these zones at normal operating conditions. In the cooking zone C, the chips are generally fully immersed in cooking liquor. This cooking liquor can complete the electric circuit between the electrodes with less resistance because the liquor is a better conductor than liquor- impregnated chips. Probes 113 in zone C can measure the conductivity of the liquor at normal operating conditions.

[0040] The electrical conductivity of the chips, gas, and liquor within the digester 100 can change during normal operation. The probes 113 can detect these changes by comparing the differences between the measurements obtained at normal operating conditions with the measurements obtained at abnormal operating conditions. The probes 113 may further comprise a thermometer for reading the temperature of the materials within the digester 100. The electrodes within the probes 113 may have polarized surfaces in the anodic and cathodic direction at intervals to prevent scaling. Multiple rings 105 of probes 113 may be positioned along the height h of the digester 100. The information from the probes 113 is useful to determine chip level in digester 100. By knowing the chip level within the digester 100 the flow rate of feed material 119 to the digester 100, can be controlled, thereby providing improved process conditions within the digester 100.

[0041] Likewise, information from the probes 113 regarding liquor level and liquor composition in the digester 100 allows adjustments to many of the liquid stream flows. Examples of liquid stream flows which can be adjusted include: the volume of liquor added with the feed material 119; the volume of liquid extracted from the feed material 119 as the feed material 119 enters the digester 100; the volume of liquid circulated back to the digester 100 through center pipe inlets 110; or the volume of fresh liquor added at various points to the digester 100. Using the information from the probes 113 allows adjustments to be made to the liquid streams. Liquid stream adjustments allow for improved liquor level control, reaction conditions and overall digester 100 operations.

[0042] Additionally, the probes 113 may provide information to allow monitoring of the temperature of the column of chips within the digester 100. With circumferential temperature information at various heights h along the digester 100, a temperature profile of the column of chips 228 within the digester 100 may be developed. The temperature profile information may be used to adjust the temperature of circulated or fresh liquid being added to digester 100 between the various process zones A, B, C, D, and E, or even within a process zone A, B, C, D, or E, thereby allowing for improved temperature control between and in the various process zones A, B, C, D, or E. Improved temperature control between and in the various process zones A, B, C, D, and E results in improved temperature control within the digester 100 and therefore improved digester 100 operations.

[0043] Additionally, the probes 113 may provide information to allow monitoring of the liquor composition within the digester 100. With circumferential liquor composition information at various heights h along the digester 100, a profile of the reaction characteristics within the digester 100 may be developed. Once developed, the profile of the reaction characteristics may be used to adjust the concentration and rate of circulated or fresh liquid being added to digester 100 between the various process zones A, B, C, D, E, or even within a process zone A, B, C, D, E thereby allowing for improved reaction characteristics within the digester 100. Improved control of reaction characteristics within the digester 100 results in improved digester 100 operations.

[0044] In certain exemplary embodiments, the probes 113 may provide information regarding the density of the column of chips 228. Probe information relating to the density of the column of chips 228 can be monitored to develop a profile along the height h and width w of the digester 100. Inconsistencies, variations or fluctuations in the profile of the density of the column of chips 228 may indicate channeling (i.e. areas within the column of chips 228 with varying densities where streams of liquor may form and result in inconsistent reaction characteristics) or other process upset condition within the column of chips 228. By monitoring the density of the column of chips 228 directly and in real-time, undesirable operations of the digester 100 are quickly recognized and addressed to minimize or eliminate digester 100 unfavorable operating conditions.

[0045] FIG. 2 shows an exemplary ring 105 of probes 113. Each holder 112 has a probe 113 contained in and protruding through the holder 112 from the outside of the digester 100 into the inside of the digester 100. The ring 105 of probes 113 is mounted to the digester exterior wall surface 106 at various locations along the vertical height h of the digester 100. The probes 113 extend through the holders 112 through the digester's exterior wall surface 106 and penetrate the digester's interior wall surface 107. The probes 113 may be essentially flush with the interior wall surface 107 surface or extend minimally, such as up to two inches, beyond the digester interior wall surface 107 surface into the digester 100 interior.

[0046] Probes 113 may be contained within a holder 112. A holder 112 may be a nozzle, receptacle, or other housing configured extending through the wall of the digester 100 configured to hold the probe 113. A control valve 155 may be attached to each holder 112. A valve controller 160 connects to each control valve 115. Information gathered by each probe 113 is sent to an analyzer (AIC) 170 where the information gathered is analyzed using an algorithm. Based on the results of the analyzed information, the analyzer 170 sends a signal to individual valve controllers 160. In turn the signal received by the individual valve controllers 160 changes the control valve 155 position to adjust operations of the digester 100

[0047] Probes 113 use electrochemistry technologies to obtain information about the column of chips 228 flowing past the probe 113, but cannot extend so far into the digester 100 interior as to obstruct the column of chips 228 flowing past the probe 113. Information gathered by the probes 113 is used in an algorithm allowing analyzer 170 to send signals to various valve controllers 160 to make adjustments as needed to feed material 119 flow rate, liquor addition rate, extraction and return flow rates, fresh liquor feed rates, temperature and circumferential flows of feed material 119 as well as liquid flow stream and thereby positively impact digester 100 operations.

[0048] As the column of chips 228 passes the probes 113 inside the digester 100, scale (a by-product of the cooking reactions, a solid precipitate) may be deposited on the probes 113. As the scale deposits are detected on the probes 113, an electrochemical device can be used to clean the scaled probe 113, cleaning of the probe 113 is initiated from outside the digester 100 and does not require the probe 113 to be removed from the digester 100.

[0049] Information gathered from probes 113 allows improved overall digester 100 operations resulting in improved product quality for example tear strength, tensile, etc., improved cooking liquor utilization, and improved product yield.

[0050] FIG. 3 shows a simplified flow diagram of a cooking system 200. Lignocellulosic material 204 is fed to a holding and receiving vessel 201 through the lignocellulosic material inlet 219. Steam 205 is added to the holding and receiving vessel 201 through a steam inlet 220. While within the receiving and holding vessel 201, the lignocellulosic material 204 is contacted by steam 205 to form a steamed lignocellulosic material 225. The steamed lignocellulosic material 225 leaves the receiving and holding vessel 201 through the steamed lignocellulosic outlet 208. The receiving and holding vessel 201 may be any suitable device, such as a vibratory chip bin, or an Andritz brand DIAMONDBACK® chip bin, or a combined steaming and impregnation vessel, or a steaming vessel. Typically the receiving and holding device (in this case the receiving and holding vessel 201) operates at or near atmospheric pressure, but could also operate at below atmospheric pressure (operate under a vacuum) or even may operate at elevated pressure (pressure above atmospheric pressure). The operating pressure of the receiving and holding vessel 201 is generally lower than the operating pressure of downstream equipment.

[0051] The steamed lignocellulosic material 225 is fed to a pressurizing and transporting device 217. The pressurizing and transporting device 217 may be any suitable device which increases the pressure of the steamed lignocellulosic material 225 from operating pressure of the receiving and holding vessel 201 to the operating pressure of downstream equipment as well as to provide pressure to transport the steamed lignocellulosic material 225 from the receiving and holding vessel 201 to downstream equipment. Such as device may be a high pressure feeder, or pumps positioned in series or in parallel, or a combination of high pressure feeder and pumps, or any other suitable device.

[0052] The steamed lignocellulosic material 225 enters the pressurizing and transporting device 217 through the low pressure inlet 223. A pressurized steamed lignocellulosic material 209 leaves the pressurizing and transporting device 217 through a high pressure outlet 224. The steamed lignocellulosic material 225 may be increased in pressure from atmospheric pressure (0 bar gauge) to 25 bar gauge, or 15 bar gauge, or 10 bar gauge, or 5 bar gauge by the pressurizing and transporting device 217 such that the pressure of the pressurized and steamed lignocellulosic material 209 enters a treatment vessel 203 at the operating pressure of the treatment vessel 203. There may exist multiple treatment vessels 203 in parallel or series.

[0053] The pressurized steamed lignocellulosic material 209 may be fed to the treatment vessel 203 through an upper pressurized material inlet 212. Upon entering the treatment vessel 203 through the upper pressurized material inlet 212, the pressurized steamed lignocellulosic material 209 may flow into a treatment vessel top separator 227 where excess liquor 211 is separated and removed from the treatment vessel 203. Should a treatment vessel top separator 227 not be used, another device to remove excess liquor 211 from the treatment vessel 203 may be used.

[0054] Once the excess liquor 211 is removed from the pressurized steamed lignocellulosic material 209 entering the treatment vessel 203, a mass of chips with entrained liquor remains in the treatment vessel 203. The chips with entrained liquor pass from the treatment vessel top separator 227 and fall into the treatment vessel 203 interior where the chips form a column of chips 228 (as shown in FIG. 1). A chip column top 214 (as shown in FIG. 1) may be located just below the treatment vessel top separator 227. The treatment vessel 203 may be hydraulically full or may have a vapor space 229 (as shown in FIG. 1) above the chip column top 214. If a vapor space 229 exists, steam or other hot gas may be added to the treatment vessel 203 in the vapor space 229 to heat the column of chips 228 as necessary for treatment.

[0055] As discussed in relation to the pressurized vessel of FIG. 1 (digester 100), the treatment vessel 203 may have multiple process zones A, B, C, D, and E. Process zones A, B, C, D, and E, as shown in FIG. 1, are typical for a single vessel treatment vessel. Other treatment vessels may have all or some of the process zones A, B, C, D, and E shown in FIG. 1. Process zones A, B, C, D, and E may be: impregnation zone A, heating zone B, cooking zone C, washing zone D, and cooling zone E.

[0056] The pressurized steamed lignocellulosic material 209 fed to treatment vessel 203 may be a slurry of solids particles (chips) and liquid (liquor such as cooking liquor or alkali). As previously stated, the liquid content of the pressurized steamed lignocellulosic material 209 tends to be substantially higher than the necessary or desired liquid content in the treatment vessel 203. As the pressurized steamed lignocellulosic material 209 enters the treatment vessel top separator 227, some excess liquor 211 is removed from the pressurized steam lignocellulosic material 209. The excess liquor 211 may be removed from the treatment vessel 203 and may be reintroduced to steamed lignocellulosic material 225 as transport liquid at the pressurizing and transporting device 217 or another location upstream of the treatment vessel 203 or may be removed from the cooking system 200 for further treatment or use in other locations within the mill.

[0057] The column of chips 228 moves through the treatment vessel 203 in a vertical direction from top to bottom. As the column of chips 228 moves through the treatment vessel 203 it passes extraction screens 213. Extracted liquor 230 can be removed, extracted, from the extraction screens 213 and recirculated to the treatment vessel 203 through a center pipe inlet 210 and center pipe 250, or can be removed from the cooking system 200 and sent for further processing elsewhere in the mill.

[0058] Additionally, fresh treatment chemicals such as alkali, acid, white liquor, other chemical or wash liquid or cooling liquid may be added to the treatment vessel 203 via the center pipes 250. Extracted liquor 230 extracted through extraction screens 213 may be supplemented with treatment liquor 216 or extracted liquor 230 from a different extraction screen 213 in one of the process zones A, B, C, D, and E to form liquor circulation loop 215. Treatment liquor 216 may include one or more of fresh cooking liquor (alkali or other suitable chemical), acid, black liquor, green liquor, wash water (from downstream processes units), cooling liquid, dilution liquid. There may be more than one liquor circulation loops 215 communicating with the treatment vessel 203. Liquor circulation loops 215 may be at more than one vertical location of the treatment vessel 203. Liquids in the various liquor circulation 215 loops may require temperature adjustment; such temperature adjustment may be via any known equipment to allow for the desired heat exchange.

[0059] Once the column of chips 228 has moved through the treatment vessel 203 it may be removed from the treatment vessel 203 as treated material 226 through the processed material discharge port 202.

[0060] One or more probes 113 (probes 113 shown in FIG. 1 and FIG. 2 and discussed previously) may be positioned along the receiving and holding vessel 201 and the treatment vessel 203. Probes 113 may be formed into rings 105 of probes 113 (as shown in FIG. 2). Each probe 113, using electrochemistry, gathers information regarding the material (the lignocellulosic material 204 and the column of chips 228, respectively) in the receiving and holding vessel 201 or the treatment vessel 203 as the respective material moves past the probes 113 at various locations.

[0061] Multiple rings 105 of probes 113 may be positioned along the vertical height h of the receiving and holding vessel 201 and the treatment vessel 203 (vertical height h of the treatment vessel 213 of FIG. 3 is as shown for digester 100 shown in FIG. 1). The information gathered by the probes 113 may be useful to determine operating parameters within the receiving and holding vessel 201 and the treatment vessel 203. Operating parameters may include, but not be limited to, level of the lignocellulosic material, level of the column of chips 228, liquor level, liquor composition, temperature, chemical composition of the liquor, etc.

[0062] As explained for FIG. 1, the information gathered by the probes 113 will provide information useful in making changes to the operating parameters of the digester 100. The same information may be useful when making changes to the operating parameters of the receiving and holding vessel 201 and the treatment vessel 203. Probes 113 gather the same information without regard for the type of vessel on which the probes are mounted.

[0063] Probes 113, whether used and placed individually or as rings 105 of probesll3, may be positioned within and protrude through the holder 112. Similarly to the probes 113 shown and discussed in FIG. 1 and FIG. 2, the probes 113 shown in FIG. 3 may extend through the receiving and holding vessel exterior wall surface 206 penetrating the receiving and holding vessel interior wall surface 207 or may extend through the treatment vessel exterior surface 221 penetrating the treatment vessel interior wall surface 222. The probes may be essentially flush with the receiving and holding vessel interior wall surface 207 or the treatment vessel interior wall surface 222. In some embodiments, the probes 113 may extend minimally, such as up to two inches, beyond the receiving and holding vessel interior wall surface 207 or the treatment vessel interior wall surface 222.

[0064] The information gathered by the probes 113 is used in an algorithm allowing analyzer 170 to send signals to the valve controllers 160 to make adjustments as needed to feed material flow rate, liquor addition rate, extraction and return flow rates, fresh liquor feed rates, temperature and circumferential flows of feed material as well as liquid flow stream and thereby positively impact cooking system 200 operations.

[0065] As the material passes the probes 113 inside the receiving and holding vessel 201 and the treatment vessel 203, scale may be deposited on the probes 113. As the scale deposits are detected on the probes 113, an electrochemical device can be used to clean the scaled probe 113, cleaning of the probe 113 is initiated from outside the receiving and holding vessel 201 and the treatment vessel 203 and does not require the probe 113 to be removed from the receiving and holding vessel 201 or the treatment vessel 203. Other probes may be polarized to prevent scaling.

[0066] Information gathered from probes 113 allows improved overall cooking system 200 operations resulting in improved product quality for example tear strength, tensile, etc., improved cooking liquor utilization, and improved product yield.

[0067] FIG. 4 is a cross sectional side view of a wash zone D and a cooling zone E of a digester 400. The digester 400, typically a vertical pressurized vessel, has a wash zone D in the lower portion of the pressurized vessel. The wash zone D extends from the top of a cooking extraction screen 491 to the top of wash extraction screen 490. In addition to the wash zone D, the digester 400 has a cooling zone E. The cooling zone E typically is located vertically below the wash zone D. The cooling zone E extends from the top of wash extraction screen 490 to a digester bottom 495.

[0068] As feed material enters the digester 400, the feed material is a slurry of solids particle (chips) and liquid (liquor such as cooking liquor or alkali). Some excess liquor is removed from the digester 400 via cooking extraction screen 491 and wash extraction screen 490 positioned along the vertical height of the digester 400. Chips with entrained liquor (alkali) fill the digester 400 forming a column of chips within the digester 400 where the chips exit the digester 400 through the digester discharge device 496, specifically through digester outlet 497.

[0069] The column of chips (chips and entrained liquor) moves through the digester 400. As the column of chips moves through the digester 400 in the direction of arrow 499, the column of chips may pass at least one cooking extraction screen 491. Liquid can be removed from the column of chips through the cooking extraction screens 491 and recirculated to the digester 400 or can be removed from the digester system and sent for further processing elsewhere in the mill. Additionally, fresh treatment chemicals such as alkali or white liquor or wash liquid or cooling liquid may be added to the digester 400 at desired points along the vertical height of digester 400. Liquid extracted through cooking extraction screens 491 may be supplemented with fresh alkali or extracted liquor from a different cooking extraction screen 491 to become circulation loops. [0070] One circulation loop involves the wash zone D including a wash extraction screen 490. Wash zone D includes the wash extraction screen 490, wash extraction conduit 420, wash extraction return conduit 421, wash extraction flash conduit 422, and cooking liquor conduit 425.

[0071] The wash extraction conduit 420 is connected to wash extraction screen 490 and encircles the outer diameter of the digester 400. The wash extraction conduit 420 may be located within the digester shell 471 or preferably encircles the exterior of digester 400 at or near the position of the wash extraction screen 490. Around the circumference of the digester 400 are multiple wash extraction pipes 423.

[0072] The number of wash extraction pipes 423 usually varies between six (6) and twelve (12), but may have more than 12, depending on the diameter of the digester 400. Each wash extraction pipe 423 contains a wash extraction nozzle 410a and a probe nozzle 410b. The individual wash extraction pipes 423 connect at header 410 to form wash extraction conduit 420. Each wash extraction pipe 423 fluidly communicates with one header 410 used to connect each wash extraction pipe 423 to wash extraction conduit 420.

[0073] A probe nozzle 410 further fluidly communicates each wash extraction pipe 423 is a probe nozzle 410b. Each probe nozzle 410b contains a probe. Each probe, using electrochemistry, gathers a sample of the material in the wash extraction pipe 423 as the material in the wash extraction pipe 423 moves past the probe nozzles 410b in the wash extraction pipe 423 upstream of the header 410. At headers 410 each wash extraction pipe 423 is joined to wash extraction conduit 420.

[0074] The samples from the probes contained in probe nozzles 410b are processed by analyzer 470. Analyzer 470 may be an Analyzing Indicator Controller ("AIC") or other suitable device. The analyzer 470 provides information regarding the material in the wash extraction conduit 420 relating to the alkali (black liquor) composition, temperature, and flow rate contained within the wash extraction conduit 420.

[0075] Specifically, analyzer 470 provides information relating to the residual alkali in the wash extraction conduit 420. Residual alkali information includes, but is not limited to, concentration of dissolved solids in the alkali in the wash extraction conduit 420, temperature of the material in the wash extraction conduit 420, alkali concentration (or other desired chemical level) of the alkali in the wash extraction conduit 420, and other physical properties of the material in the wash extraction conduit 420. [0076] Once the physical properties of the material in the wash extraction conduit 420 have been determined, multiple flows to and from the wash zone D as well as cooling liquid, dilution liquid, white liquor charge to various locations in the digester 400 can be controlled, for example flows to the cooling zone E.

[0077] Cooling zone E is physically positioned vertically below the wash zone D of digester 400. The purpose of cooling zone E, as the name suggests, is to cool the column of chips prior to leaving the digester through digester outlet 497. This cooling is accomplished by the addition of liquid, such as wash liquid, dilution liquid or other suitable liquid at a temperature lower than the temperature of the material in wash extraction conduit 420. In addition to cooling the column of chips, the liquid added to the cooling zone may also be suitable to as liquid to adjust the consistency of the column of chips thereby allowing the treated column of chips to be discharged from digester 400 through digester outlet 497.

[0078] Within the cooling zone E there may be multiple locations where wash liquid or dilution liquid can be introduced to the digester 400. A side dilution line 430 may be located below the wash extraction screen 490 and enters the digester shell 471 to introduce dilution liquid to the cooling zone E. Side dilution line 430 may have a valve 405 and a wash extraction return conduit valve 402 and a side dilution line nozzle 431. Valve 405 does not receive action-causing signals from analyzer 470. Analyzer 470 does provide action-causing signals for the wash extraction return conduit valve 402.

[0079] Also available to introduce liquid into the cooling zone E may be one or more vertical lines (typically one vertical line), counter wash bottom flow line 440. The counter wash bottom flow line 440 may be located on the bottom of digester 400 and provide wash liquid to the digester bottom 495. A counter wash bottom flow line valve 403 and a counter wash bottom flow line nozzle 441 may both communicate with the counter wash bottom flow line 440

[0080] Digester 400 may have another liquid addition capability, that liquid addition capability being through a scraper 480. A scraper 480 may be located in the bottom of digester 400. The scraper 480 is moved by a motor (not shown) attached to the digester discharge device 496 and rotates to enhance the movement of material (pulp) out of the digester 400 through digester outlet 497. To also enhance material movement out of digester 400, a diverter cone 488 may exist and may be positioned within the digester 400 at the point where the scraper 480 attaches to the digester discharge device 496. A counter wash scraper flow line 450 may be attached to the digester discharge device 496 to allow liquid to enter the digester 400 through openings in the scraper 480.

[0081] The counter wash scraper flow line 450 may fluidly communicate with a counter wash scraper flow line valve 404 and a nozzle 451. Liquid in the counter wash scraper flow line 450 may have the same source as the liquid in the side dilution line 430 or the counter wash bottom flow line 440. In some cases, multiple liquid sources may be suitable for introduction into the cooling zone E via the side dilution line 430, the counter wash scraper flow line 450 and the counter wash bottom flow line 440.

[0082] Based on the information from analyzer 470, using an valve controller 461, 462, 463, 464 configured to send action-causing information to the wash extraction return conduit valves 401, the wash extraction return conduit valve 402, counter wash bottom flow line valve 403, counter wash scraper flow line valve 404, flows to digester 400 via wash extraction return conduit 421, side dilution line 430, counter wash bottom flow line 440, and counter wash scraper flow line 450 can be regulated to the wash zone D and cooling zone E as well the white liquor charge to the wash zone D via cooking liquor conduit 425. Wash extraction return conduit valve 401 is positioned in a wash extraction retum conduit 421 and regulates the flow in the wash extraction return conduit 421 to digester 400. Wash extraction retum conduit 421 provides liquid to the vicinity of wash extraction screen 490 based on information from analyzer 470.

[0083] Analyzer 470 receives information the samples taken by the probes within probe nozzles 410b. Using the information available from analyzer 470, a signal is sent to various valve controllers 461, 462, 463, 464, which in turn send action-causing signals to wash extraction retum conduit valve 401, wash extraction return conduit valve 402, counter wash bottom flow line valve 403, counter wash scraper flow line valve 404 (respectively) to allow the flows through wash extraction return conduit valve 401, wash extraction return conduit valve 402, counter wash bottom flow line valve 403, counter wash scraper flow line valve 404 to be adjusted. Valve controllers 461, 462, 463, 464 may modulate power acting on the wash extraction return conduit valve 401, wash extraction retum conduit valve 402, counter wash bottom flow line valve 403, counter wash scraper flow line valve 404 (respectively) to allow the position of the wash extraction return conduit valve 401, wash extraction return conduit valve 402, counter wash bottom flow line valve 403, counter wash scraper flow line valve 404 to be changed resulting in more or less flow through wash extraction retum conduit valve 401, wash extraction return conduit valve 402, counter wash bottom flow line valve 403, counter wash scraper flow line valve 404 based on the information from analyzer 470.

[0084] In one embodiment the wash extraction conduit 420 contains the wash extraction flow from wash extraction screen 490. At least a portion of the wash extraction flow may be returned via wash extraction return conduit 421 to the digester 400 at or near the location of the wash extraction screen 490 or elsewhere in the digester if so desired.

[0085] In another exemplary embodiment, at least a portion of the wash extraction flow removed via wash extraction conduit 420 to be sent via wash extraction flash conduit 422 to other locations within the mill or other locations within the digester.

[0086] Wash extraction return conduit valve 402 and valve 405 are positioned in the side dilution line 430. Wash extraction return conduit valve 402 is used to regulate flow of dilution liquid through the side dilution line 430 to the cooling zone E. The side dilution line 430 is located below wash extraction screen 490 and transports dilution liquid to the cooling zone E. Dilution liquid from the side dilution line 430 enters the cooling zone E via side dilution line nozzle 431. Valve 405 may be used to eliminate flow of dilution liquid to the cooling zone E and may not be impacted by information from analyzer 470.

[0087] Counter wash bottom flow line valve 403 is located in the counter wash bottom flow line 440 and is used to control the flow rate of liquid through the counter wash bottom flow line nozzle 441 into the cooling zone E. The liquid in the counter wash bottom flow line 440 enters digester bottom 495 through counter wash bottom flow line nozzle 441 and provides liquid to digester 400 in a region between the scraper 480 and the lower most area of digester 400, digester bottom 495. Liquid entering the digester bottom 495 may be wash liquid or may include cooking liquor or white liquor as suggested previously. The flow rate, temperature, chemical composition of the liquid in the counter wash bottom flow line 440 may be regulated using information from analyzer 470.

[0088] Counter wash scraper flow line valve 404 is positioned in the counter wash scraper flow line 450. The counter wash scraper flow line 450 provides liquid into a passage in the digester discharge device 496 and into the scraper 480 through which liquid can flow into cooling zone E. The liquid in the counter wash scraper flow line 450 enters the digester discharge device 496 through counter wash scraper flow line nozzle 451. The flow rate, temperature, chemical composition of the liquid in the counter wash scraper flow line 450 may be regulated using information from analyzer 470. [0089] In addition to controlling the flow of liquid into and out of the wash zone D and cooling zone E of the digester 400, the analyzer 470 may use the samples extracted by probes in the probe nozzles 410b to control white liquor charge to the white liquor addition points of the digester system, specifically through cooking liquor conduit 425. The probe nozzle 410b is a holder configured to hold the probe. Cooking liquor conduit 425 allows white liquor to be added to the circulation loop engaged to wash extraction screen 490.

[0090] In a typical digester system, multiple locations may be used to introduce white liquor into the digester system. Using information from analyzer 470 operators can control the flow of white liquor to at least one of the white liquor introduction or addition points.

[0091] A conceived embodiment comprises a pressurized vessel monitoring and control system. The system has a pressurized vessel having a top and a bottom, an exterior wall surface, and an interior wall surface, the top of the pressurized vessel having a feed material inlet and the bottom of the pressurized vessel having a processed material outlet. The feed material inlet being configured to accept a feed material, and the feed material is comprised of chips and liquid. The chips in the feed material form a column of chips in the pressurized vessel. The pressurized vessel has a process zone within the pressurized vessel, and wherein column of chips moves through the process zone. The pressurized vessel has an extraction screen configured to remove liquor in the process zone; multiple probes engaged to the exterior wall surface of the pressurized vessel, where a probe of the multiple probes extends into the pressurized vessel and wherein each probe of the multiple probes engages the exterior of the pressurized vessel at a height, wherein a probe in the multiple probes measures chip level, liquor level, and temperature within the pressurized vessel.

[0092] In at least some embodiments, a first set of multiple probes extend through the exterior wall surface of the pressurized vessel in a ring. There may be multiple rings, wherein each ring is engages the pressurized vessel at a height. A probe in the multiple probes may be positioned within a holder and protrudes through the exterior wall surface and through the interior wall surface.

[0093] In at least some embodiments the probe extends into the pressurized vessel beyond the interior wall surface no more than two inches, but in other embodiments the probe may be positioned to be flush with the pressurized vessel interior wall surface.

[0094] In at least some embodiment, the information gathered consists of information selected from the group consisting of: chip flow rate, liquor flow rate, liquor chemical strength, temperature of the liquor flow, temperature of the chip flow, liquor extraction rate, liquor addition rate, chip level, chip column density, and residual alkali concentration in the wash zone and cooling zone, chip compaction.

[0095] In some embodiments the pressurized vessel is a digester and has a process zone, the process zone consists of a processing zone selected from the group consisting of: an impregnation zone, a heating zone, a cooking zone, a washing zone, and a cooling zone.

[0096] In some embodiments the pressurized vessel has more than one process zones and the at least of the more than one process zones has a concurrent flow of the column of chips and liquid through the process zone. In some embodiments the process zone has countercurrent flow of the column of chips and liquid through the process zone.

In at least some embodiments, a probe of the multiple probes uses electrochemistry to gather information.

[0097] An exemplary method has been conceived for monitoring and controlling a pressure vessel. The method comprises: feeding a feed material of solid particles and liquid through a feed material inlet of a pressurized vessel, wherein the feed material is separated into at least solids particles with entrained liquor and excess liquor. After separating the solids particles with entrained liquor is retained in the pressurized vessel and forms a column of chips. The column of chips is treated with at least one liquor while within the pressurized vessel to produce a processed material. Once formed, the processed material is removed from the pressurized vessel through a processed material outlet. Passing the column of chips by at least one probe, the probe positioned at at least one vertical location along the pressurized vessel. While passing the column of chips by the probe, information is gathered. The gathered information includes: chip flow rate, liquor flow rate, temperature of the column of chips, temperature of the liquor flow, liquor chemical strength, liquor extraction rate, liquor addition rate, chips level, chip column density, scale buildup on the probe. The gathered information is sent to a control device where the gathered information becomes feed inputs to an algorithm. Values are calculated using the algorithm; the values from the algorithm are compared to at least one desired parameter. The pressurized vessel operations are adjusted and controlled based on the comparison of the at least one value from the algorithm and the at least one desired parameter.

[0098] In at least some embodiments, the feeding of feed material to the feed material inlet is continuous and the processed material is continuously discharged through the process material outlet. Some embodiments provide for the calculation of multiple values by the algorithm using the gathered information from at least one probe.

[0099] In some embodiments, multiple values are compared to multiple desired parameters and adjusting and controlling the pressurized vessel operations is based on the comparison of multiple values and multiple desired parameters.

[00100] A lignocellulosic material cooking system monitoring and control system, the system comprising: a cooking system including a receiving and holding vessel, a pressurizing and transporting device, and at least one treatment vessel; the receiving and holding vessel including a lignocellulosic material inlet, a steam inlet, a steamed lignocellulosic material outlet, a receiving and holding vessel exterior wall surface, and a receiving and holding vessel interior wall surface; the treatment vessel including an upper pressurized material inlet, a center pipe, a extraction screen, a processed material outlet, a treatment vessel exterior wall surface, and a treatment vessel interior wall surface; the pressurizing and transfer device having a low pressure inlet and a high pressure outlet, wherein the low pressure inlet is operatively connected to the receiving and holding vessel steamed lignocellulosic material outlet and the high pressure outlet is operatively connected to the upper pressurized material inlet of the treatment vessel; multiple probes engaged to the exterior wall surface of at least one of the receiving and holding vessel and the treatment vessel, where a probe of the multiple probes extends into at least one of the receiving and holding vessel and the treatment vessel, and wherein each probe of the multiple probes engages the exterior of at least one of the receiving and holding vessel and the treatment vessel, at a height, wherein a probe in the multiple probes measures chip level, liquor level, and temperature within at least one of the receiving and holding vessel and the treatment vessel.

[00101] In some embodiments the first set of multiple probes is extend through the exterior wall surface of at least one of the holding and receiving vessel and the treatment vessel in a ring. The multiple rings may each engage at least one of the receiving and holding vessel and the treatment vessel at a height of the receiving and holding vessel. In at least some embodiments, there exists a holder and the holder may protrude through the exterior wall surface and through the interior wall surface of at least one of the receiving and holding vessel and the treatment vessel. The probe extends into at least one of the receiving and holding vessel and treatment vessel beyond the interior wall surface by no more than two inches. In some instances, the probe is positioned to be flush with at least one of the receiving and holding vessel interior and the treatment vessel interior wall surface.

[00102] In some exemplary embodiments, the information gathered consists of information selected from the group consisting of: a chip flow rate, a liquor flow rate, a liquor chemical strength, temperature of the liquor flow, a temperature of the chip flow, a liquor extraction rate, a liquor addition rate, a chip level, a chip column density, and residual alkali concentration in the wash zone and cooling zone, chip compaction. In at least some embodiments a probe of the multiple probes uses electrochemistry to gather information.

[00103] A method for monitoring and controlling of a cooking system, where the cooking system includes a receiving and holding vessel, a pressuring and transporting device and a treatment vessel has been conceived. The method comprising: feeding lignocellulosic material to a receiving and holding vessel; steaming the lignocellulosic material to remove air from the lignocellulosic material to form a steamed lignocellulosic material; transferring the steamed lignocellulosic material to a pressurizing and transporting device; pressurizing the steamed lignocellulosic material using the pressurizing and transporting device to form a steamed pressurized lignocellulosic material; transferring steamed pressurized lignocellulosic material from the pressurizing and transporting device to a treatment vessel wherein the treatment vessel includes an upper pressurized material inlet and a processed material outlet; removing excess liquor from the steamed pressurized lignocellulosic material to form a column of chips, wherein the column of chips includes entrained liquor; treating the column of chips with at least one treating liquor while within the treatment vessel to produce a processed material; removing the processed material from the treatment vessel through a processed material outlet; passing the column of chips by at least one probe positioned at at least one vertical location along the treatment vessel; allowing the at least one probe to gather information as the column of chips flows past it, wherein the gathered information includes at least one of the following: chip flow rate, liquor flow rate, temperature of the column of chips, temperature of the liquor flow, liquor chemical strength, liquor extraction rate, liquor addition rate, chip level, chip column density, scale buildup on the probe; sending the gathered information to at least one control device where the gathered information becomes feed inputs to an algorithm; using the algorithm to calculate at least one value; comparing the at least one value from the algorithm with at least one desired parameter; adjusting and controlling the pressurized vessel operations based on the comparison of the at least one value from the algorithm and the at least one desired parameter.

[00104] In some embodiments, while in the receiving and holding vessel passing the lignocellulosic material past at least one probe positioned at at least one vertical location along an interior wall surface of the receiving and holding vessel. Some embodiments, the pressurized steamed lignocellulosic material transferred to the treatment vessel upper pressurized material inlet is continuous and the processed material is continuously discharged through the processed material outlet of the treatment vessel.

[00105] In some embodiments wherein multiple values are calculated by the algorithm using the information gathered by the at least one probe. Some embodiments may have multiple values compared to multiple desired parameters and adjusting and controlling the pressurized vessel based on the comparison of multiple values and multiple desired parameters.

[00106] Some embodiments may select a treating liquor from the list of: water, white liquor, green liquor, dilution liquid, black liquor, or any combination thereof.

[00107] An exemplary embodiment of a system in accordance with this disclosure allows for monitoring and control of an extraction flow out of the digester in the wash extraction conduit; flow of fresh dilution liquid (wash liquid) to the digester in the same or nearby zone; flow of cooling liquid to the digester via external nozzles such as dilution or counter wash nozzles; flow of counter wash liquid to the digester through the scraper arms in the bottom of the digester; and flow of white liquor, or cooking liquor, to the digester. External nozzles, such as dilution or counter wash nozzles, may be located either above or below the zone where the extracted liquor is removed and monitored.

[00108] An exemplary embodiment has digester wash zone and cooling zone monitoring and control system comprising: a wash zone within a digester; a cooling zone within the digester; a wash extraction screen within the digester; a wash extraction pipe configured to remove liquid from the wash extraction screen, the wash extraction pipes each having a probe nozzle containing a probe, the probe nozzle extending into each of the wash extraction pipes; a wash extraction return conduit configured to add liquid to the digester, the wash extraction return conduit positioned in a processing zone of the digester, the wash extraction return conduit having a wash extraction return conduit valve configured to control the flow of liquid to the processing zone; a side dilution liquid conduit configured to add fresh dilution liquid to the cooling zone of the digester, the side dilution liquid conduit having a side dilution conduit valve configured to control the flow of dilution liquid to the cooling zone, and wherein a probe contacts the liquid removed from the wash extraction screen and measures the temperature of the liquid removed from the wash extraction screen and the residual alkaline concentration in the liquid removed from the as extraction screen.

[00109] In some embodiments the cooking liquor may be added to the wash extraction return conduit prior to the wash extraction return conduit valve, and the addition of the cooking liquor is prior to the wash extraction return conduit valve. A side dilution liquid conduit is positioned along a horizontal axis of the digester, along an axis parallel to a vertical axis of the digester or both.

[00110] In some embodiments a counter wash bottom flow line is configured to add fresh dilution liquid to the cooling zone of the digester, the counter wash bottom flow line having a counter wash bottom flow line valve configured to control the flow of dilution liquid to the cooling zone. A counter wash scraper flow line is configured to add fresh dilution liquid to the cooling zone of the digester, the counter wash scraper flow line having a counter wash scraper flow line valve configured to control the flow of dilution liquid to the cooling zone.

[00111] A method of monitoring and controlling a wash zone and a cooling zone within a digester for comminuted cellulosic material has been conceived. The method comprising: washing the comminuted cellulosic material in a wash zone of a digester; cooling the washing comminuted cellulosic material in a cooling zone of a digester; extracting liquid from the digester through a wash extraction screen; locating a probe in a liquid extraction conduit engaged to the wash extraction screen; contacting the liquid extracted from the wash extraction screen with the probe to gather process information; sending information gathered by the probe to an analyzer; sending a signal from the analyzer to one or more valves in conduits to the wash zone and the cooling zone of the digester to modulate the flow rate of liquid through the one or more valves, wherein one valve is within a conduit between a source of cooking liquor and a conduit to the wash zone, the cooling zone or both the wash zone and the cooling zone.

[00112] While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

CLAIMS:

1. A pressurized vessel monitoring and control system, the system comprising:

a pressurized vessel having a top and a bottom, an exterior wall surface, and an interior wall surface, the top of the pressurized vessel having a feed material inlet and the bottom of the pressurized vessel having a processed material outlet, the feed material inlet being configured to accept a feed material, wherein the feed material is comprised of chips and liquid;

wherein the chips in the feed material form a column of chips in the pressurized vessel, wherein the pressurized vessel has a process zone within the pressurized vessel, and wherein column of chips moves through the process zone;

an extraction screen configured to remove liquor in the process zone; multiple probes engaged to the exterior wall surface of the pressurized vessel, wherein a probe of the multiple probes extends into the pressurized vessel and wherein each probe of the multiple probes engages the exterior of the pressurized vessel at a height, wherein a probe in the multiple probes measures chip level, liquor level, and temperature within the pressurized vessel.

2. The system of claim 1 , wherein a first set of multiple probes extends through the exterior wall surface of the pressurized vessel, and wherein the first set of multiple probes are arranged in a ring around the exterior wall surface of the pressurized vessel.

3. The system of claim 2 further comprising multiple rings, wherein each ring engages the pressurized vessel at a height of the pressurized vessel.

4. The system of claim 1, wherein a probe in the multiple probes is positioned within a holder and protrudes through the exterior wall surface and through the interior wall surface.

5. The system of claim 4, wherein the probe extends into the pressurized vessel beyond the interior wall surface no more than two inches.

6. The system of claim 4, wherein the probe is positioned to be flush with the pressurized vessel interior wall surface.

7. The system of claim 1, wherein the probe measures pressurized vessel operating conditions and wherein the pressurized vessel operating conditions consists of operating conditions selected from the group consisting of: chip flow rate, liquor flow rate, liquor chemical strength, temperature of the liquor flow, temperature of the chip flow, liquor extraction rate, liquor addition rate, chip level, chip column density, and residual alkali concentration in the wash zone and cooling zone, chip compaction.

8. The system of claim 1, wherein the process zone consists of a processing zone selected from the group consisting of: an impregnation zone, a heating zone, a cooking zone, a washing zone, and a cooling zone.

9. The system of claim 8, wherein the process zone has concurrent flow of the column of chips and liquid through the process zone.

10. The system of claim 8, wherein the process zone has countercurrent flow of the column of chips and liquid through the process zone.

11. The system of claim 8, wherein the pressurized vessel has more than one process zone.

12. The system of claim 11, wherein a process zone of the more than one process zones has column of chips and a liquid flowing concurrently through the process zone.

13. The system of claim 1, wherein a probe of the multiple probes uses electrochemistry to measure pressurized vessel operating conditions.

14. The system of claim 1, wherein the pressurized vessel is a digester.

15. A lignocellulosic material cooking system monitoring and control system, the system comprising:

a cooking system including a receiving and holding vessel, a pressurizing and transporting device, and a treatment vessel;

the receiving and holding vessel including a lignocellulosic material inlet, a steam inlet, a steamed lignocellulosic material outlet, a receiving and holding vessel exterior wall surface, and a receiving and holding vessel interior wall surface;

the treatment vessel including an upper pressurized material inlet, an extraction screen, a processed material outlet, a treatment vessel exterior wall surface, and a treatment vessel interior wall surface;

the pressurizing and transfer device having a low pressure inlet and a high pressure outlet, wherein the low pressure inlet is operatively connected to the receiving and holding vessel steamed lignocellulosic material outlet and the high pressure outlet is operatively connected to the upper pressurized material inlet of the treatment vessel; multiple probes engaged to the exterior wall surface of at least one of the receiving and holding vessel and the treatment vessel, wherein a probe of the multiple probes extends into at least one of the receiving and holding vessel and the treatment vessel, and wherein each probe of the multiple probes engages the exterior of at least one of the receiving and holding vessel and the treatment vessel, at a height of at least one of the holding vessel and the treatment vessel, wherein a probe of the multiple probes measures chip level, liquor level, and temperature within a receiving and holding vessel and the treatment vessel.

16. The system of claim 15, wherein a first set of multiple probes extends through the exterior wall surface of at least one of the holding and receiving vessel and the treatment vessel and wherein the first set of multiple probes are arranged in a ring around the exterior wall surface of the pressurized vessel.

17. The system of claim 16 further comprising multiple rings wherein each ring engages at least one of the receiving and holding vessel and the treatment vessel at a height of at least one of the holding vessel and the treatment vessel.

18. The system of claim 15, wherein a probe in the multiple probes is positioned within a holder and protrudes through the exterior wall surface and through the interior wall surface of at least one of the receiving and holding vessel and the treatment vessel.

19. The system of claim 18, wherein the probe extends into at least one of the receiving and holding vessel and treatment vessel beyond the interior wall surface by no more than two inches.

20. The system of claim 18, wherein the probe is positioned to be flush with at least one of the receiving and holding vessel interior and the treatment vessel interior wall surface.

21. The system of claim 15, wherein the pressurized vessel operating conditions gathered consists of operating conditions selected from the group consisting of: a chip flow rate, a liquor flow rate, a liquor chemical strength, temperature of the liquor flow, a temperature of the chip flow, a liquor extraction rate, a liquor addition rate, a chip level, a chip column density, and residual alkali concentration in the wash zone and cooling zone, chip compaction.

22. The system of claim 15, wherein a probe of the multiple probes uses electrochemistry to measure pressurized vessel operating conditions.

23. A digester wash zone and cooling zone monitoring and control system comprising: a wash zone within a digester;

a cooling zone within the digester;

a wash extraction screen within the digester;

a wash extraction pipe configured to remove liquid from the wash extraction screen, the wash extraction pipes each having a probe nozzle containing a probe, the probe nozzle extending into each of the wash extraction pipes;

a wash extraction return conduit configured to add liquid to the digester, the wash extraction return conduit positioned in a processing zone of the digester, the wash extraction return conduit having a wash extraction return conduit valve configured to control the flow of liquid to the processing zone;

a side dilution liquid conduit configured to add fresh dilution liquid to the cooling zone of the digester, the side dilution liquid conduit having a side dilution conduit valve configured to control the flow of dilution liquid to the cooling zone, and wherein a probe contacts the liquid removed from the wash extraction screen and measures the temperature of the liquid removed from the wash extraction screen and the residual alkaline concentration in the liquid removed from the as extraction screen.

24. The monitoring and control system of claim 23, wherein cooking liquor may be added to the wash extraction return conduit prior to the wash extraction return conduit valve, and the addition of the cooking liquor is prior to the wash extraction return conduit valve.

25. The monitoring and control system of claim 23, wherein the dilution liquid conduit is positioned along a horizontal axis of the digester, along an axis parallel to a vertical axis of the digester or both the horizontal axis of the digester and the axis parallel to a vertical axis of the digester.

26. The monitoring and control system of claim 23, wherein a counter wash bottom flow line is configured to add fresh dilution liquid to the cooling zone of the digester, the counter wash bottom flow line having a counter wash bottom flow line valve configured to control the flow of dilution liquid to the cooling zone.

27. The monitoring and control system of claim 23, wherein a counter wash scraper flow line is configured to add fresh dilution liquid to the cooling zone of the digester, the counter wash scraper flow line having a counter wash scraper flow line valve configured to control the flow of dilution liquid to the cooling zone.

28. A method of monitoring and controlling a wash zone and a cooling zone within a digester for comminuted cellulosic material, the method comprising:

washing the comminuted cellulosic material in a wash zone of a digester; cooling the washing comminuted cellulosic material in a cooling zone of a digester;

extracting liquid from the digester through a wash extraction screen; locating a probe in a liquid extraction conduit engaged to the wash extraction screen;

contacting the liquid extracted from the wash extraction screen with the probe to measure digester operating conditions;

sending digester operating conditions gathered by the probe to an analyzer; sending a signal from the analyzer to one or more valves in conduits to the wash zone and the cooling zone of the digester to modulate the flow rate of liquid through the one or more valves, wherein one valve is within a conduit between a source of cooking liquor and a conduit to the wash zone, the cooling zone or both the wash zone and the cooling zone.