Method for unblocking or cleaning of screens in continuous kraft cooking towers

Abstract

This invention relates to a method for unclogging or cleaning screens in a continuous kraft paper digester process, wherein the continuous kraft paper digester includes a plurality of screens, each screen having a side facing the digester zone and a side facing the digester wall, the plurality of screens being arranged in a screen ring, the screen ring having at least one screen outlet exiting the digester and at least one screen inlet entering the screen ring; the at least one screen inlet entering the screen ring provides cleaning fluid to the screens for: unclogging, alkalization, or both without stopping the system.

Description

Technical Field

[0001] This invention relates to a method for unclogging or cleaning the screen in a continuous kraft paper digester process. Background Technology

[0002] Operational instability (overheating) or the presence of calcium carbonate buildup can cause screen clogging. The main sign of this clogging is an increase in screen pressure differential (SPD), followed by a decrease in extract flow. When the SPD reaches a critical value, an alkalization process is employed using hot or cold liquid. These alkalizations tend to become more frequent as the digester's lifespan increases.

[0003] Clogging occurs when cellulose material is retained at the sieve openings (SS), where there are receptacles that can permanently retain it. Individual fragments of wood chips can locally clog the sieve openings, and in a screen with vertical openings, the upper and lower openings bear the responsibility for extraction from point blockages. Continuous cooking liquor flow and the arrival of more cellulose material accumulate more debris at the sieve openings, thus promoting a concentration point of blockage for any further debris passage. The cooking liquor no longer drains through the sieve openings (SS) into the sieve chamber 9.

[0004] Calcium carbonate buildup can also occur at the screen, potentially causing clogging of the screen openings and reducing the amount of cooking liquid that can displace the screen. Both situations lead to an increase in screen pressure differential (SPD), followed by a decrease in the extract flow.

[0005] The lower the extraction flow, the greater the amount carried over in subsequent steps, thus requiring a smaller whitening inlet. Decreased whitening leads to increased chemical consumption to meet quality requirements.

[0006] It is practically impossible to perform alkalization in the upper screen of the digester without stopping the system. Cold alkalization can be performed during operation in the lower screen, but hot alkalization (which is more efficient) can only be performed when the system is stopped.

[0007] Hot alkalization is more efficient than cold alkalization, resulting in a significant increase in the lower extraction flow rate and a significant reduction in the pressure differential. However, it is currently not feasible to perform this type of alkalization frequently, as it requires interrupting the digester effluent. For example, each alkalization process can take up to 7 hours. Summary of the Invention

[0008] This invention relates to a continuous kraft paper digester, comprising a plurality of screens, each screen having a side facing the digester zone and a side facing the digester wall, the plurality of screens being arranged in a screen ring, the screen ring having at least one screen outlet exiting the digester and at least one screen inlet entering the screen ring; the at least one screen inlet entering the screen ring supplies cleaning fluid to the screens for: unclogging, alkalization, or both without stopping the system.

[0009] Furthermore, the present invention relates to an alkalization method for a screen in a continuous process kraft paper digester, the method comprising applying an inflow of cleaning liquid to the screen in a screen ring through an inlet, the cleaning liquid flowing into the screen and into the digester zone, thereby providing at least one of the following: clogging, alkalization, or both without stopping the system; and a declogging or prevention method for preventing screen clogging or fouling in a continuous process kraft paper digester, or a screen cleaning method in a continuous kraft paper digester having multiple screens disposed in a screen ring, and a method for supplying cleaning liquid to the screen, comprising supplying cleaning liquid to the screen ring, the cleaning liquid rinsing towards the screen, the cleaning liquid flowing into the digester zone, providing at least one of the following: clogging, alkalization, or both without stopping the system. Attached Figure Description

[0010] Figure 1 It is a continuous kraft paper digester.

[0011] Figure 2 This is a diagram of a screen ring located in a cooking tower.

[0012] Figure 3 This is a side view of the inside of the screen ring as the waste liquid leaves the digester through the outlet.

[0013] Figure 4 This is a side view of the inside of the screen ring when the cleaning fluid enters the screen ring through the inlet.

[0014] Figure 5 This is a side view of the inside of the screen ring when the cleaning fluid enters the screen ring through the waste liquid outlet.

[0015] Figure 6 This is a view of the screen rings in the upper screen section that receives the incoming flow into the dedicated pipeline.

[0016] Figure 7 It is a diagram of all screen rings, with only two screen rings, that receive the inflow into the dedicated pipe at the upper screen section and the dedicated pipe at the lower screen section of the cooking tower.

[0017] Figure 8 It is a view of all and each screen ring of the screen section receiving the flow into the dedicated pipe. Detailed Implementation

[0018] The term "cooking liquor" refers to a treatment liquid intended to be added to cellulosic material flowing in a cooking vessel (i.e., a cooking tower). Cooking liquor can be a kraft paper cooking liquor containing sodium hydroxide and sodium sulfide, but it can also contain steam, hot waste cooking liquor (i.e., black liquor from previously cooked black liquor), and a mixture of two or more of the following liquids: black liquor, white liquor, dilution liquid from subsequent washing stages (i.e., washing filtrate from these washing stages), steam (added directly to heat the treatment liquid), or its condensate. For example, black liquor is an aqueous solution made from organic materials such as lignin, resinous compounds, polysaccharides, or alcohols. Black liquor also contains inorganic materials from the pulping or cooking system. White liquor is understood as an aqueous mixture of sodium hydroxide and sodium sulfide.

[0019] The term "cleaning fluid" refers to a hot cleaning fluid including dilute black liquor, concentrated black liquor, white liquor, or mixtures thereof.

[0020] The term “cellulose material” refers to fragments of wood, such as wood chips, sawdust, and preferably wood chips, as well as any other material derived from wood in pulverized form, such as sawdust or wood chips, all of which are derived from hardwood or softwood or annual plants.

[0021] The continuous kraft paper digester 1 is in the form of a pressurized, essentially cylindrical container. Figure 1 The digester 1 comprises a top (2), a bottom (3), and walls (5). Cellulose material, such as wood chips, and cooking liquor are continuously fed into the digester 1 through an inlet at the top. For example, the cellulose material is fed through... Figure 1 The pulp is fed through inlet 4. In the digester, wood chips form a column, while the cooking liquor descends from the digester. The cooked pulp is continuously removed or blown out from the bottom of the digester through outlet 3.

[0022] The wood chips undergo gradual dissolution, and in the kraft paper process, most (typically around 50%) of the virgin wood dissolves in the cooking fluid in the form of metallic and organic materials such as turpentine, flaking oil, and hemicellulose, and enters the evaporation process as the black liquor disappears. This means that the packing density in the digester increases during the cooking process, making it more difficult to extract a sufficient volume of fluid to regulate the cooking fluid and simultaneously extract the dissolved organic materials.

[0023] Two or more horizontally arranged screens 10 form a screen structure 6. One or more screen structures 6 may be arranged in the upper, middle or lower part of the container wall 5, through which the cooking liquid can be removed from the cooking tower for reprocessing. One or more vertically adjacent screen structures 6 form a screen segment 7. Accordingly, one or more screen segments 7 may be arranged in the upper, middle or lower part of the container wall 5.

[0024] Typically, the screen structure 6 is positioned on the wall of the digester in the form of square screen surfaces, either as a continuous row of screens, or alternately positioned with square and blunt screens around the entire circumference of the digester wall, the wall of which is composed of multiple square screen surfaces forming screen rings. When two screen rings are positioned one on top of the other, the screens and blunt surfaces alternate, resembling a checkerboard pattern in the screen segments of the digester. Figure 2 ).

[0025] The first and second screen sections can be arranged in the upper ("hot") and lower ("cold") sections of the cooking tower, respectively. Figure 1 In the process, the first screen segment (6) is arranged at the top of the cooking tower, and the second screen segment (7) is arranged at the bottom of the cooking tower. The vertical distance between the bottom of the first screen segment (6) and the top of the second screen segment (7) can be, for example, 5-12m.

[0026] Typically, a screen structure is used to discharge the processing liquid from a suspension of pulverized cellulose material and processing liquid in a substantially cylindrical digester container, wherein a screen adjacent to the inner side of the digester wall 8 of the digester 1 forms a screen chamber 9 between the wall 8 and the screen 10. A typical screen structure is a slotted plate equipped with sieve openings SS, which are formed by mechanical grinding or water jetting, and the perforated or slotted plate faces the suspension of cellulose material in the digester zone. Another configuration has rods facing the suspension of cellulose material, preferably arranged vertically parallel to each other and forming sieve openings SS between adjacent rods, and the screen is positioned at a distance from the digester wall 8 so that the extracted cooking liquid can flow freely and unimpeded between the digester wall and the screen. The combination of the screen structure 6 and the screen chamber 9 forms a screen ring 13. The extracted cooking liquid is discharged through an outlet 11.

[0027] Screen openings (SS) typically have a size between 2 and 10 mm, which is suitable for the quality of wood chips used in the cooking process. Wood chips with a lower content of fine material and better-defined, well-chopped wood chips are cooked in cooking towers with larger screen openings, while wood chips with a higher content of fine material require smaller screen openings.

[0028] The digester wall 8 is the wall of the pressure vessel, and the screen 10 is positioned inside the digester wall, facing the suspension of pulverized cellulose material as it descends through the digester as a pulp column. The screen can be arranged to have a digestion residence time between 15 and 20 minutes.

[0029] Cellulose material and liquid are pressurized within the digester, and the cellulose material is retained on the screen as the liquid exits through the sieve openings SS into the sieve chamber 9. The extracted liquid is collected in the sieve chambers 9 within the digester wall 8. The sieve chambers 9 are typically in fluid communication with each other, and the liquid is then extracted from the sieve chambers 9 through the outlet 11. The digestate is extracted from the screen rings 13 and is typically further processed in a flash evaporator (not shown). A portion of the liquid may be recycled back to the digester to enhance distribution and mixing within the digester.

[0030] In one embodiment of the invention, a continuous kraft paper digester is provided, comprising a plurality of screens 10, each screen having a side facing the digester zone I and a side facing the digester wall 8. The plurality of screens 10 are disposed in a screen ring 13, the screen ring 13 having at least one screen outlet 11 exiting the digester and at least one screen inlet 12 entering the screen ring 13. The screen inlet 12 entering the screen ring 13 provides a cleaning fluid to the screens for: unclogging, alkalization, or both, without stopping the system. Unclogging should be understood as removing blockages from the screens, while alkalization should be understood as washing away deposits on the screens 10, i.e., on the screen bars 13. Preferably, alkalization is thermal alkalization.

[0031] On one hand, the present invention provides an alkalization method for a screen 10 in a continuous process kraft paper digester, the method comprising applying an inflow 100 of cleaning liquid to the screen 10 in a screen ring 13 through an inlet 12, the cleaning liquid flowing into the screen 10 into the digester zone, thereby providing at least one of the following: clogging, alkalization treatment or both without stopping the system.

[0032] For example, in Figure 3 In this process, the cooking liquor is extracted from the screen chamber 9. If the screen ring is located in the lower extraction zone, the extracted cooking liquor can be sent to a heat exchanger for heating. During extraction, outlet 11 allows waste liquid to leave the screen chamber 9. At the same time, inlet 12 is closed.

[0033] exist Figure 4 In this process, the cleaning fluid can be supplied to the screen chamber 9 through inlet 12. During the supply of the cleaning fluid to inlet 12, the cleaning fluid reaches the screen chamber 9, and at the same time, outlet 11 is closed.

[0034] For example, if the screen ring of the screen chamber is located at the top of the digester, the extracted cooking liquor, i.e., white liquor, can be sent to the pipe for transporting black liquor and delivered to the inlet 12 of any screen ring 13. The outlet 11 is closed when the cleaning fluid is supplied to the inlet 12. In another embodiment of the invention, the cleaning fluid is delivered from the heat exchanger 200 to the outlet 11 of the screen in the screen ring 13, reversing the flow of the cooking liquor and reaching the screen chamber 9, the screen 10, and the screen gaps SS. In any case, when the cleaning fluid reaches the screen 10, it creates a countercurrent that flushes out debris located at the screen gaps SS, causing erosion of scale buildup on the surface of the screen 10, or both.

[0035] according to Figure 4 The cleaning solution can be flushed into the screen chamber 9 through a single dedicated inlet 12. Therefore, if the screen chambers in the same screen ring are not in fluid communication with each other, several dedicated inlets 12 can be used for each screen chamber 9 in the screen ring. Alternatively, if the screen chambers 9 in the same screen ring are in fluid communication with each other, several dedicated inlets 12 can be used for a single screen ring 13. In either case, the inward-flowing cleaning solution moves the cooking liquid toward the screen 10 and into the interior I of the cooking tower. Figure 4 As shown, the cleaning fluid removes debris trapped between the bars as it passes through the sieve slots SS formed between adjacent bars. The cleaning fluid is then discharged back into the digester I to remove any remaining residue. Furthermore, the alkaline cleaning fluid removes or corrodes deposits such as calcium carbonate.

[0036] Or, according to Figure 5 The cleaning fluid inflow to the screen is provided by a dedicated inflow pipe connected to outlet 11. In this case, the outlet becomes inlet 12 when the outflowing waste liquid is reversed by displacing the inflowing cleaning fluid towards the interior of the screen chamber 9 and the digester.

[0037] This can be achieved, for example, when each inlet 12 is provided with a dedicated conduit for supplying the cleaning fluid. For instance, one inlet 12 may be connected to a conduit leading away from a heat exchanger containing the heated cleaning fluid, which may be black liquor. If necessary, a pump can be installed at the conduit to increase the pressure. Alternatively, the cleaning fluid may originate from heated and purified dilute black liquor or pumped heated white liquor. Preferably, both are used depending on the desired level of alkalization, for example, when it is necessary to adjust the required residue and eliminate the effects of increased residual alkali evaporation due to alkalization.

[0038] When strong alkalization is deemed necessary, a higher proportion of white liquor and a lower proportion of dilute black liquor can be used. For example, a mixture of 10% white liquor and 90% black liquor can be used. Conversely, during the operation of the digester, when declogging is required, a larger fraction of heated black liquor can be used.

[0039] In this sense, the pipe connected to inlet 12 is connected to a storage tank for white liquor and / or black liquor, or optionally to a heat exchanger also connected to one of such storage tanks. Preferably, virtually all white liquor and black liquor used are locally produced.

[0040] In another embodiment of the invention, a method for cleaning screens during operation in a continuous kraft paper digester is also provided. This method includes applying an inflow 100 of cleaning liquid onto the screen 10, the inflow flowing toward the interior I of the digester to the screen, thereby providing at least one of the following: clogging, alkalization, or both, without stopping the system. Therefore, the inflow 100 is provided by a conduit connected to the screen ring 13 via an inlet 12. Preferably, the inflow conduit is a dedicated conduit, meaning that the conduit is used only for one screen ring 13.

[0041] For example, the cleaning fluid can be introduced into the screen chamber 9. The introduction of the cleaning fluid can be achieved through any delivery device, such as a pump. Piping can be connected to a heat exchanger, for example, allowing heated cleaning fluid to enter inlet 12.

[0042] Furthermore, any configuration of the inlet in the screen ring 13 can be achieved. For example, in Figure 6 In the middle, only the screen ring of the upper screen section can receive the incoming cleaning fluid through a dedicated pipe.

[0043] Or, refer to Figure 7 All the screen rings in the upper part of the cooking tower can receive the pipes, while only two screen rings in the lower part of the cooking tower can receive the dedicated pipes that guide the inflow of the cleaning liquid.

[0044] Or, refer to Figure 8 Each screen segment and each screen ring 13 can receive at least one dedicated conduit.

[0045] Furthermore, a first cleaning fluid 100 can be supplied to one screen, a second cleaning fluid to another screen, and a third cleaning fluid to a third screen, in a consistent manner. Preferably, all screens are capable of receiving cleaning fluid, i.e., all screens can receive cleaning fluid simultaneously or sequentially, following a predetermined sequence determined by a program or feeding logic. The sequence of screen rinsing typically depends on the required degree of fouling and / or the severity of clogging or cleaning at a particular screen, screen assembly, or screen ring. However, preferably, this sequence is determined by a preventative procedure depending on operational needs.

[0046] When the cleaning fluid enters the screen ring 13 once its pressure exceeds the pressure inside the screen chamber 9, the pressure difference between the screen chamber 9 and the inflow dedicated pipeline should be significant. For example, for a digester operating at a maximum pressure of 4.5 bar, the inflow cleaning fluid should be pumped with a pressure difference of at least 10%. For example, the cleaning fluid may be at a pressure of approximately 4.95 bar. Typically, pressures can reach values ​​as high as 10 bar.

[0047] For a specific digester configuration, the cleaning liquid flow rate can be 150-450 m. 3 The flow rate varies between 0.5 and 3.5 m / h. Ideally, the cleaning fluid flow rate can be 0.5-3.5 m / h. 3 / ADt (air dry tonnes), preferably 1.5-3m 3 / ADt. If a larger volume of cleaning fluid is required, i.e., to remove scale buildup, the flow rate can be 400m. 3 / h. If a longer screen cleaning time is required, the flow rate at specific loops can be extended. For example, if preventative operation is intended to prevent clogging or fouling of the screens in a continuous process kraft paper digester, a lower pressure or flow rate can be used, such as a 150m³ flow rate with 5 bar pressure. 3 The flow. Or, 0.5m 3 The flow rate of / ADt may be of interest. On the other hand, for severe clogging of the screen, a larger amount of cleaning fluid may be required. In this sense, the desired pressure for the unclogging process could be 7 bar. If it is desired to remove scale from the screen in a continuous kraft paper digester, 2m³ can be used. 3 The intermediate flow of / ADt. Nevertheless, higher pressures can be used as a preventative measure, while lower pressures can be used for unclogging processes. Additionally, the amount of cleaning fluid can be varied, including diluted black liquor, concentrated black liquor, or white liquor, or mixtures thereof. For example, a cleaning fluid could be 90% diluted black liquor and 10% white liquor for preventative operation, or on the other hand, it could include 60% white liquor for severe clogging at the cooking screen.

[0048] This method can be used with specific screen rings ranging from 5 to 200m. 3 The cleaning solution volume for / ADt ranges from 10 to 300 minutes. For example, a digester with a configuration of 5 screen rings at the top and 6 screen rings at the bottom can operate in one alkalization, declogging, or both phases at a time, i.e., only one screen ring receives the cleaning solution. The alkalization or declogging operation can be performed in descending or ascending order among the screen rings. In one configuration, the uppermost screen ring (i.e., the one closer to the top of the digester) can be 150m... 3The cleaning solution is received for 10 minutes per hour, followed by the next ring. Preferably, after the flow of cleaning solution into the first ring is interrupted, the cleaning solution begins to flow into the second screen ring and continues for, for example, another 10 minutes. The third screen ring receives the cleaning solution after the second ring has finished cleaning, and so on until the fifth screen ring is alkalized, at which point the alkalization of the upper screen segment is complete. The alkalization of another screen segment can begin while each of its screen rings is subjected to thermal alkalization, for example, sequentially, one after the other, for example at 450m. 3 The process is performed for 10 minutes at a time. For a given screen ring, this process may take longer. For example, one of the screen rings in a six-screen-ring segment may undergo a longer cycle or volume. For example, the screen ring could be subjected to thermal alkalization for 4 hours instead of 10 minutes. The completion of the screen segment can be satisfied by stopping the thermal alkalization over a period of time (e.g., 4 hours) before the cycle restarts at the screen ring of the next screen segment, or it can start immediately after all the screen rings of another screen segment are completed. The process can be automated, and instructions for opening and closing valves at dedicated pipes connected to the inlet can be executed manually or via a programmed system without stopping the system. Alternatively, the process can be stochastic, for example, the operator can decide on a more appropriate sequence based on the needs of the immediate process.

[0049] Preferably, the pressure of the cleaning fluid 100 at the inlet 12 of each screen segment 13 is 10% higher than the pressure of the extractant at the screen chamber 9. In this way, once the cleaning fluid moves from the inlet 12 toward the screen chamber 9 and into the digester I, effective replacement of the chips is achieved, and stable movement of the wood chip column can be maintained.

[0050] Another embodiment of the present invention provides a method for supplying cleaning liquid to screens 10 in a continuous kraft paper digester 1 having a plurality of screens 10 disposed in a screen ring 13. The method includes supplying cleaning liquid to the screen ring 13, the cleaning liquid rinsing toward the screens 10, wherein the cleaning liquid flows into the screens 13 into the digestion zone I, thereby providing at least one of the following: clogging, alkalization, or both without stopping the system.

[0051] The method of the present invention can also be implemented through the following steps:

[0052] a) Supply cleaning fluid to the first screen ring 13 through the first inlet 12. The first inlet is connected to a first dedicated pipeline with a first cleaning fluid control valve. Open the first cleaning fluid control valve and supply cleaning fluid to the first screen ring 13. Supply cleaning fluid to the first screen ring for 5-300 minutes. Close the first cleaning fluid control valve. Repeat the above steps for subsequent screen rings, that is, supply cleaning fluid to subsequent screen rings through subsequent inlets 12. Subsequent inlets 12 are connected to subsequent dedicated pipelines with subsequent cleaning fluid control valves. Open the subsequent cleaning fluid control valves and supply cleaning fluid to subsequent screen rings 13 for 5-300 minutes. Close the subsequent cleaning fluid control valves.

[0053] b) Repeat the above steps for subsequent screen rings.

[0054] The first ring should be understood as the first ring receiving the cleaning liquid, not necessarily the first ring in the screen section. In such an instance, the first screen ring can be any ring in the digester, and subsequent rings can be any other screen ring in the digester. Furthermore, the method can be fully automated, i.e., following a previously established sequence pattern without stopping the system.

[0055] Therefore, as discussed, the present invention can reduce losses caused by the cessation of thermal alkalization operations in the digester; thus, it provides greater operational flexibility due to the feasibility of thermal alkalization when necessary or even preventively, without causing the screen to become clogged to a critical level that would impair the stability of the digester.

Claims

1. A continuous kraft paper digester comprising a plurality of screens (10), each screen (10) having a side facing a digester zone (I) and a side facing a digester wall (8), the plurality of screens (10) being disposed in a screen ring (13), the screen ring (13) having at least one screen outlet (11) exiting the digester and at least one screen inlet (12) entering the screen ring (13); the at least one screen inlet (12) entering the screen ring (13) providing a cleaning fluid flowing into the screens (10) for: unclogging, alkalizing, or both without stopping the digester system, wherein the cleaning fluid enters the screen ring (13) once its pressure exceeds the pressure within the screen chamber (9), and wherein when the cleaning fluid reaches the screens (10), the cleaning fluid generates a countercurrent that flushes out debris located at the screen gaps (SS), generates erosion of deposits on the surface of the screens (10), or both.

2. A method for alkalizing a screen in a continuous process kraft paper digester, the method comprising applying an inflow (100) of a cleaning liquid through a screen inlet (12) to a screen (10) in a screen ring (13), the cleaning liquid flowing into the screen into a digester zone (I), thereby providing at least one of the following: unclogging, alkalizing, or both, without stopping the digester system, wherein the cleaning liquid enters the screen ring (13) once its pressure exceeds the pressure within the screen chamber (9), and wherein when the cleaning liquid reaches the screen (10), the cleaning liquid generates a countercurrent that flushes out debris located at the screen gaps (SS), generates erosion of deposits formed on the surface of the screen (10), or both.

3. A method for unclogging a screen (10) in a continuous process kraft paper digester, comprising applying an inflow (100) of cleaning fluid through a screen inlet (12) to a screen in a screen ring, wherein the cleaning fluid flows into the screen into a digester zone (I), thereby providing at least one of the following: unclogging without stopping the system, alkalization, or both, wherein the cleaning fluid enters the screen ring (13) once its pressure exceeds the pressure within the screen chamber (9), and wherein when the cleaning fluid reaches the screen (10), the cleaning fluid generates a counterflow that flushes out debris located at the screen gaps (SS), generates erosion of deposits formed on the surface of the screen (10), or both.

4. A method for preventing screen (10) clogging or fouling in a continuous process kraft paper digester, comprising applying an inflow (100) of cleaning fluid through a screen inlet (12) to the screen (10) in a screen ring (13), wherein the cleaning fluid flows into the screen into a digester zone (I), thereby providing at least one of the following: unclogging, alkalization, or both without stopping the system, wherein the cleaning fluid enters the screen ring (13) once its pressure exceeds the pressure within the screen chamber (9), and wherein when the cleaning fluid reaches the screen (10), the cleaning fluid generates a counterflow that flushes out debris located at the screen gaps (SS), generates erosion against fouling on the surface of the screen (10), or both.

5. A method for cleaning a screen during operation in a continuous kraft paper digester, comprising applying an inflow (100) of cleaning fluid to a screen (10), the inflow (100) flowing toward the interior of the digester to the screen, thereby providing at least one of the following: clogging, alkalization, or both without stopping the system, wherein the cleaning fluid enters the screen ring (13) once its pressure exceeds the pressure inside the screen chamber (9), and wherein when the cleaning fluid reaches the screen (10), the cleaning fluid generates a counterflow that flushes out debris located at the screen gaps (SS), generates erosion of deposits on the surface of the screen (10), or both.

6. The screen cleaning method according to claim 5, wherein the screen (10) is part of the screen ring (13).

7. The method according to any one of claims 2 to 5, wherein the screen inlet (12) is a dedicated screen inlet.

8. The cooking tower according to claim 1, wherein the inflow of the cleaning liquid comprises: white liquor, black liquor, or a mixture thereof.

9. The method according to any one of claims 2 to 5, wherein the inflow of the cleaning fluid comprises: white liquid, black liquid, or a mixture thereof.

10. A method for supplying a cleaning solution to screens (10) in a continuous kraft paper digester having a plurality of screens (10) disposed in a screen ring (13), the method comprising supplying a cleaning solution to the screen ring (13), the cleaning solution being flushed toward the screens (10) and flowing into the screens (10) into the digestion zone (I), thereby providing at least one of the following: clogging, alkalization, or both without stopping the system, wherein the cleaning solution enters the screen ring (13) once its pressure exceeds the pressure within the screen chamber (9), and wherein when the cleaning solution reaches the screens (10), the cleaning solution generates a countercurrent that flushes out debris located at the screen gaps (SS), generates erosion of deposits on the surface of the screens (10), or both.

11. The method for supplying cleaning fluid to a screen (10) according to claim 10, comprising the following steps: a) Supply cleaning fluid to the first screen ring through the first screen inlet, the first screen inlet being connected to a first dedicated pipeline having a first cleaning fluid control valve; open the first cleaning fluid control valve and supply the cleaning fluid to the first screen ring for 5-300 minutes; close the first cleaning fluid control valve. b) Repeat the above steps for subsequent screen rings.

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