• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    The invention relates to a method of slurry circulation, in which a aqueous slurry for a sizing agent, is located in a slurry tank (10), the aqueous slurry is pumped from the slurry tank (10) by a pump (11) to a circulation line (12) and to an outlet line (14), via which the slurry is guided to further processing of the sizing agent before it will be applied onto the fiber web. The aqueous slurry is alternatively guided along the circulation line (12) back to the slurry tank (10). The route of the slurry flow is selected by the position of a valve (13) of the circulation line (12) such, that selection the flow of the aqueous slurry is selected to the outlet line (14) or to continue in the circulation line (12) back to the slurry tank (10). The invention also relates to a system of slurry circulation comprising a slurry tank (10), a pump (11), a circulation line (12), an outlet line (14), via which the slurry is guided to further processing of the sizing agent. The system further comprises a valve (13) of the circulation line (12) for selection the flow of the aqueous slurry to the outlet line (14) or to continue in the circulation line (12) back to the slurry tank (10).
    公开号:FI20195515A1
    申请号:FI20195515
    申请日:2019-06-14
    公开日:2020-12-15
    发明作者:Janne Heinilä；Christian Prinz；Tuomas Pesonen；Teemu J Nieminen
    申请人:Valmet Technologies Oy；
    IPC主号:
    专利说明:

    Method and system of slurry circulation Technical field In general, present invention relates to producing of fiber webs. More especially the present invention relates to a method according to preamble part of independent method claim and to an arrangement according to preamble part of independent system claim.
    Background As known from the prior art in fiber web producing processes typically comprise an assembly formed by a number of apparatuses arranged consecutively in the process line. A typical production and treatment line comprise a head box, a wire section and a press section as well as a subsequent drying section and a reel-up. The production and treatment line can further comprise other devices and sections for finishing the fiber web, for example, a sizer, a calender, a coating section. The production and treatment line typically also comprise at least one winder for forming customer rolls as well as a roll packaging apparatus. In this description and the following claims by fiber webs are meant for example paper and board webs. In production of fiber webs, for example of paper or board webs, sizing is used to alter the properties of a fiber web by adding sizing agents, for example starch or other glue chemicals. Sizing can be divided to internal sizing and = surface sizing. In internal sizing the sizing agent is added to pulp in the wet N end of the fiber web production line before forming. In surface sizing the sizing S agent is added onto the surface of the fiber web, typically at the dry end of the 3 30 fiber web production line. Internal sizing is done in the beginning of the wet I end of the fiber web machine by using different kinds of chemical treatments so in order to influence the penetration of a liquid, for example of water into the o fiber web. The sizing agent is typically applied as an agueous slurry containing O starch and/or other sizing chemicals for example pigments, retention agents N 35 etc.
    The aqueous slurry for the sizing agent is typically prepared in a separate system connected to the sizer and located in connection with the fiber web production line.
    A known system of preparing a slurry for a sizing agent is known typically as so called enzymatic starch preparation in the following described by reference to preparing a starch based slurry but it is applicable in main parts to other sizing agents, as well, as such known by one skilled in the art. Starch is provided to the preparing system in powdered form, typically from a storage container a required amount of starch powder is fed by a conveyor, for example a screw conveyor, via a weighing station to a elutriation container, in which liquid, typically water, is added to the starch powder for elutriating the slurry such, that desired dry solids content is achieved, typically the solids content is around 30 %. There after the aqueous slurry is guided to slurry cooking process, typically via coarse screening, in which coarse impurities are removed from the slurry. The slurry cooking begins in a first stage cooking in a first cooker, in which typically enzymes and/or biocatalysts are added to the slurry and the slurry is heated to the required reaction temperature in order to the enzymes and/or the biocatalysts to react. After the first stage cooking the slurry is fed to a converting container, in which the slurry stays for time required for the enzymes and/or the biocatalysts to convert the starch to required form.
    After converting the slurry is fed to a second stage cooking in a second cooker, in which the slurry is heated to required temperature in order to stop the converting reaction caused by the enzymes and/or the biocatalysts and additionally a delay time in the required temperature needed to finalize and to fully stop any reactions caused by the enzymes and/or the biocatalysts by = guiding the slurry via a delay pipe. Afterwards, any excessive steam is N removed in steam removal stage. Finally, the slurry is diluted to the desired S solids content and guided to a storage container, from which, when needed in 3 30 the sizing process, the sizing agent is guided to sizing agent / starch I application at the sizer. As the process stops pipes and other process related so equipment like filters and jet cookers must be washed in order to prevent 0 plugging due to sedimentation or other process effects like extreme viscosity 3 after pipes and other process equipment were cooking down. Special cleaning is required during longer process stops because of bacterial activity and the bacterial related build-up on pipe and tank walls. Also, the waste may need to be cleaned due to the possible harmful substances, for example biocatalysts before it enters the wastewater system. In case the process stop takes a long time, for example due to a web break, the temperature of the slurry container decreases and viscosity of the slurry changes and needs to be corrected, when the process is started again.
    Another known system of preparing a slurry for a sizing agent known typically as so-called modified starch preparation process where starch has already been modified before it enters the system of preparing a slurry for a sizing agent at the fiber web production line. Modified starch is commonly used for wet end sizing, but it is also used in many surface sizing applications.
    Further known processes of preparing a slurry for a sizing agent are cationic starch and bentonite preparation processes.
    Typically, all known continuous slurry preparation processes have problems with sedimentation, which can only be avoided if flow speed inside piping is high enough for turbulent flow (usually > 1m/s). This is the main reason why the known slurry preparation processes have usually a rather narrow capacity range. The low flow speed is for example also a reason for accelerated bacterial build-up inside the piping systems.
    An object of the invention is to create a method and a system of slurry circulation, in which the problems and disadvantages of prior art are eliminated or at least minimized.
    Another object of the invention is to provide a method and a system of slurry = circulation, in which the problems and disadvantages relating to waste N formation of the slurry circulation due to stops in the process are eliminated or S at least minimized. > 30 I A particular object of the invention is also to create a method and a system of so slurry circulation with the possibility of continuously running slurry circulation 0 and thus, with the possibility of continuous production of the sizing agent for 3 the sizing agent application. & 35 Summary
    In order to achieve the above objects and those that become apparent later, the method according to the invention is mainly characterized by the features of the characterizing part of the independent method claim. The system, in turn, is mainly characterized by the features of the characterizing part of the independent system claim. Advantageous embodiments and features are disclosed in the dependent claims. According to the invention in the method of a slurry circulation a agueous slurry for a sizing agent is located in a slurry tank, the agueous slurry is pumped from the slurry tank by a pump to a circulation line and to an outlet line, via which the slurry is guided to further processing of the sizing agent before it will be applied onto the fiber web, and the agueous slurry is alternatively guided along the circulation line back to the slurry tank and the route of the slurry flow is selected by the position of a valve of the circulation line such, that selection the flow of the agueous slurry is selected to the outlet line or to continue in the circulation line back to the slurry tank. According to one advantageous feature of the invention in case the agueous slurry is guided to the outlet line, the slurry flow is controlled by a control valve of the outlet line and the control valve is controlled based on information from a flow indicator controller of the control valve of the outlet line. According to one advantageous feature of the invention new liguid is injected in calculated relation depending on the slurry flow guided from the circulation line through the outlet line to the circulation line via a feed line, and the new liquid flow is controlled by a valve of the feed line controlled by a flow indicator = controller of the feed line flow.
    N S According to the invention the system of slurry circulation comprises a slurry 3 30 tank, a pump, a circulation line, an outlet line, via which the slurry is guided to I further processing of the sizing agent, and a valve of the circulation line for so selection the flow of the aqueous slurry to the outlet line or to continue in the o circulation line back to the slurry tank. > N 35 According to one advantageous feature of the invention the system further comprises a control valve of the outlet line and a flow indicator controller of the control valve of the outlet line.
    According to one advantageous feature of the invention the system further comprises a feed line for new liquid flow, a valve of the feed line and a flow indicator controller of the feed line flow.
    5 According to one advantageous feature of the invention the system comprises a mass flow meter measuring starting solids and thus accurate controlled using starting solids mass is achieved.
    According to advantageous aspect of the invention in the method and in the system of the slurry circulation, a circulation line is provided for returning the slurry, not needed in the sizing process, back to the slurry tank. Thus, designing the method and the system of the slurry circulation is possible in a wide capacity range.
    By the invention many advantages are achieved: Designing the method and the system of the slurry circulation is possible in a wide capacity range due to the circulation line giving the possibility of circulation of the slurry not needed in the sizing process. The capacity range of the method and the system of the slurry circulation in accordance with the invention is advantageously around 20 — 100 t/d (D.S.). Additionally, the waste slurry is eliminated or at least minimized and thus no waste lines and equipment for handling the waste slurry is needed. Same mechanical equipment and pipes of the system can be used with all capacities, because production capacity has only minor effect to the flow speed inside circulation line. The circulation line of the system can be used with optimum flow speed (to avoid sedimentation) at the entire capacity = range, because new liguid is injected into circulation line and it replaces most N of the liguid, which was guided through outlet connection out of the circulation S line for further processing. Due to the circulation of the slurry there is no need 3 30 for washing of lines of the system during production breaks. By the invention it I is possible to optimize the piping system i.e. the circulation line based on the so highest expected capacity and then to utilize this piping system with any 0 capacity starting from zero capacity until the maximum dimensioned capacity 3 without risk of sedimentation or other capacity related problems.
    & 35 Brief description of the drawings
    In the following the invention is describe in more detail with reference to the accompanying drawing in which Figure 1 shows schematically an advantageous example of a slurry circulation system in accordance with the invention.
    During the course of the following description relating to figure 1 like numbers and signs will be used to identify like elements according to the different views which illustrate the invention and its advantageous example.
    In the figure some repetitive reference signs have been omitted for clarity reasons.
    Detailed description In the figure 1 is schematically shown an example of a slurry circulation system, in which the aqueous slurry for sizing agent, for example starch and water with possible other chemical substances, is located in a slurry tank 10. The aqueous slurry is pumped from the slurry tank 10 by a pump 11 to a circulation line 12. The circulation line 12 has an outlet line 14, via which the slurry is guided to further processing of the sizing agent before it will be applied onto the fiber web, as known as such by one skilled in the art.
    The circulation line 12 comprises a valve 13 of the circulation — outlet selection.
    The aqueous slurry is guided along the circulation line 12 back to the slurry tank 10, when in the further process is no need of the slurry, for example during times there is a break in the applying process in the sizing or for example during time when there is no capacity to process the slurry in the further processing.
    Thus, by = the position of the valve 13 of the circulation line — outlet line selection the flow N of the agueous slurry is selected to the outlet line 14 or to continue in the S circulation line 12 back to the slurry tank 10. In case the agueous slurry is 3 30 guided to the outlet line 14, the slurry flow is controlled by a control valve 16 of I the outlet line 14. The control valve 16 is advantageously a by-pass valve.
    The so control valve 16 is controlled based on information from a flow indicator Oo controller 17 of the control valve 16 of the outlet line 14. To the circulation line 3 12 is connected a feed line 15, via which new liquid, for example water, is injected in calculated relation depending on the slurry flow guided from the circulation line 12 through the outlet line 14. The slurry is mainly a mixture of water and powder of the sizing agent (for example starch) and it may contain certain additives, e.g. enzymes. Slurry solids are used to define the mass relation between water and dry content, mainly in powder form. The dry content of other additives like enzymes is usually insignificant in comparison to the dry content of powder. Thus, the solid percentage is determined based on the weight percentage of the bone-dry powder in the slurry. In case the slurry is prepared according a specific solid target, which may be changed during production, but which is always known for the ongoing production. According the known slurry solids and the measured flow (the flow measurement form the flow indicator controller 17), it is possible to calculate exactly how much water was guided towards the outlet connection 14 and how much water needs to be injected from line 15 in order to replace the water losses, which were guided towards the outlet connection. The volume flow inside circulation line is after the water injection almost at the same level as at the starting point of the circulation line. The percentage of the volume flow reduction after water injection from line 15 is smaller than the weight percentage of powder which is defined by dry solids as the true density of powder (density without air and water) is in most cases significantly higher than water density. True density of starch powder can be for example around 1,64 * water density. True density of other additives agents (e.g. bentonite) could be more than double of water density. The feed line 15 comprises a valve 18 of the feed line 15 and is controlled by a flow indicator controller 19 of the feed line flow. The system may comprise a mass flow meter 17 for measuring starting solids mass. Starting solids can be measured by the density output of the mass flow meter 17. The flow meter 17 could also be a magnetic flow meter, but in case a magnetic flow meter it is not possible to measure the slurry density and = calculated the starting solids. Slurry density can be calculated for any given N dry solid percentage based on the true density of the powder of the sizing S agent. Vice versa the dry solids can be calculated from any measured slurry 3 30 — density. = a
    LO o The valves 13, 16 are advantageously on-off valves. > & 35 In the description in the foregoing, although some functions have been described with reference to certain features, those functions may be performable by other features whether described or not. Although features have been described with reference to the certain example, those features may also be present in other examples whether described or not.
    Above only an advantageous example of the invention has been described to which example the invention is not to be narrowly limited and many modifications and alterations are possible within the invention.
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    Reference signs used in the drawing: 10 tank 11 pump 12 circulation line 13 valve of the circulation line — outlet line selection 14 outlet line 15 feed line 16 control valve of the outlet line 17 flow indicator controller of the control valve of the outlet line flow 18 valve of the feed line 19 flow indicator controller of the feed line flow oO
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    权利要求:
    Claims (7)
    [1] 1. Method of slurry circulation, in which a aqueous slurry for a sizing agent, is located in a slurry tank (10), the aqueous slurry is pumped from the slurry tank (10) by a pump (11) to a circulation line (12) and to an outlet line (14), via which the slurry is guided to further processing of the sizing agent before it will be applied onto the fiber web, characterized in that the aqueous slurry is alternatively guided along the circulation line (12) back to the slurry tank (10), that the route of the slurry flow is selected by the position of a valve (13) of the circulation line (12) such, that selection the flow of the aqueous slurry is selected to the outlet line (14) or to continue in the circulation line (12) back to the slurry tank (10).
    [2] 2. Method according to claim 1, characterized in that in case the aqueous slurry is guided to the outlet line (14), the slurry flow is controlled by a control valve (16) of the outlet line (14) and the control valve (16) is controlled based on information from a flow indicator controller (17) of the control valve (16) of the outlet line (14).
    [3] 3. Method according to claim 1 or 2, characterized in that new liquid is injected in calculated relation depending on the slurry flow guided from the circulation line (12) through the outlet line (14) to the circulation line (12) via a feed line (15), and the new liquid flow is controlled by a valve (18) of the feed line (15) controlled by a flow indicator controller (19) of the feed line flow.
    [4] 4. System of slurry circulation comprising a slurry tank (10), a pump (11), = 25 a circulation line (12), an outlet line (14), via which the slurry is guided N to further processing of the sizing agent, characterized in that the S system further comprises a valve (13) of the circulation line (12) for 3 selection the flow of the aqueous slurry to the outlet line (14) or to E continue in the circulation line (12) back to the slurry tank (10). = 30
    [5] 5. System according to claim 4, characterized in that the system further S comprises a control valve (16) of the outlet line (14) and a flow indicator > controller (17) of the control valve (16) of the outlet line (14).
    [6] 6. System according to claim 4 or 5, characterized in that the system further comprises a feed line (15) for new liquid flow, a valve (18) of the feed line (15) and a flow indicator controller (19) of the feed line flow.
    [7] 7. System according to any of claims 4 - 6, characterized in that the system comprises a mass flow meter measuring starting solids and thus accurate controlled using starting solids mass is achieved.
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    ATA50477/2020A| AT522850A2|2019-06-14|2020-06-02|PROCESS AND SYSTEM FOR MANAGING A SUSPENSION IN A CIRCUIT|
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