Cooking system and method

Abstract

The invention discloses a cooking system and method.The cooking system comprises a wood chip bin, a presoaking tower and a cooking tower which are sequentially connected in series. According to the cooking system, the independent pre-soaking tower is arranged on the upstream of the cooking tower, the pre-soaking tower can independently work relative to the cooking tower, the pre-soaking process of the pre-soaking tower on wood chips and the cooking process of the cooking tower do not interfere with each other, the pre-soaking tower can continuously convey the wood chips which are fully permeated with cooking liquid to the cooking tower, and the productivity of the cooking system is guaranteed; meanwhile, according to the scheme, the wood chips are independently subjected to the pre-impregnation procedure through the pre-impregnation tower, the pre-impregnation time of the wood chips in the cooking tower can be correspondingly shortened, the cooking time of the wood chips in the cooking tower can be correspondingly prolonged, and therefore the cooking steam temperature is reduced, the cooking reaction of the wood chips is milder, steam consumption is reduced, meanwhile, fiber loss is reduced, and the whiteness of discharged pulp is improved; the wood chip consumption and the subsequent chemical consumption of the oxygen removal section and the bleaching section are reduced, and the operation cost and the sewage COD generated in the bleaching section are reduced.

Description

Technical Field

[0001] This application relates to the technical field of pulp production, and particularly relates to a cooking system and method. Background Art

[0002] As Figure 1 shown, it is a schematic structural diagram of a related cooking system. The related cooking system mainly includes a chip bin 01, a chip pump 02, and a cooking tower 03. Among them, the chip bin 01 is an atmospheric vessel used for pre-steaming chips, discharging the air inside the chips, and providing conditions for pre-impregnating the chips; the cooking tower 03 is a pressure vessel used for the equipment where chips react with lye under high temperature conditions to form brown pulp and generate delignification. The delignified matter dissolves into the black liquor and is extracted from the sieve plate area of the washing and extraction, flashed through a flash tank, filtered through a fiber filter, and then sent to the evaporation workshop.

[0003] The cooking of chips into pulp is determined by two parameters: cooking temperature and cooking time. In the cooking process, the integral of temperature with respect to time can be used to quantify the cumulative heat load. The integral value can be approximated as the total heat actually transferred to the chips and the cooking liquor. When the cooking time is shortened, the cooking temperature will increase; when the cooking time is extended, the cooking temperature will decrease. With the increase in production capacity and the increase in the chip throughput, the residence time of chips in the cooking tower is shortened. Only by increasing the temperature can the delignification reaction be improved. However, the increase in cooking temperature requires more steam consumption. At the same time, the final reaction temperature of delignification in the cooking tower increases, resulting in increased fiber loss, decreased pulp brightness, increased chip consumption, increased consumption of chemicals in the subsequent oxygen delignification and bleaching sections, increased operating costs, and high COD (chemical oxygen demand) of the sewage generated in the bleaching section.

[0004] Therefore, how to solve the above problems has become an urgent technical problem for those skilled in the art. Summary of the Invention

[0005] This application proposes a cooking system to reduce the floor area, operating costs, and investment costs of the new cooking system. At the same time, it reduces the problems of increased fiber loss, decreased pulp brightness, increased chip consumption, increased consumption of chemicals in the subsequent oxygen delignification and bleaching sections, increased operating costs, and high COD (chemical oxygen demand) of the sewage generated in the bleaching section due to too high steam temperature. This application also proposes a cooking method.

[0006] To achieve the above object, this application provides a cooking system. Based on the flow direction of chips in the cooking system, it includes a chip bin and a cooking tower located downstream of the chip bin, and also includes a pre-impregnation tower located downstream of the chip bin and upstream of the cooking tower, used for pre-impregnating chips.

[0007] The chip bin is used for pre-steaming chips, and the chip bin is communicated with the impregnation tower through a first pipeline to transport the chips to the impregnation tower;

[0008] The impregnation tower is communicated with the cooking tower through a second pipeline to transport the chips to the cooking tower.

[0009] Preferably, in the above cooking system, a third pipeline is further included, and a transfer circulation pump is arranged on the third pipeline for pumping the cooking liquor from the top of the cooking tower to the bottom of the impregnation tower, and the cooking liquor pumped to the bottom of the impregnation tower carries the chips and is transferred to the top of the cooking tower through the second pipeline.

[0010] Preferably, in the above cooking system, a heater is arranged on the third pipeline, and the heater is used to increase the temperature of the cooking liquor.

[0011] Preferably, in the above cooking system, a level gauge is arranged in the impregnation tower for controlling the impregnation time of the chips in the impregnation tower.

[0012] Preferably, in the above cooking system, the cooking tower is arranged to only include a cooking zone and a washing zone located downstream thereof, so that the chips start the cooking reaction when entering the cooking tower.

[0013] Preferably, in the above cooking system, the cooking zone includes a first co-current cooking zone, a counter-current cooking zone and a second co-current cooking zone.

[0014] Preferably, in the above cooking system, the washing zone is a counter-current washing zone.

[0015] Preferably, in the above cooking system, a stirring and discharging device is arranged at the bottom of the impregnation tower.

[0016] A cooking method applicable to the cooking system described in any of the above solutions includes:

[0017] S1. Pre-steam the chips to discharge the air in the chips to obtain the chips to be impregnated;

[0018] S2. Transport the chips to be impregnated to the impregnation tower, and the cooking liquor in the impregnation tower penetrates into the chips to be impregnated to obtain impregnated chips;

[0019] S3. Transport the impregnated chips to the cooking zone of the cooking tower, the impregnated chips are largely delignified in the cooking zone, and the delignified chips are washed in the washing zone of the cooking tower.

[0020] Preferably, in the above cooking method, the impregnated chips are largely delignified in the cooking zone specifically as follows,

[0021] The pre-impregnated wood chips are subjected to the first forward cooking, countercurrent cooking, and the second forward cooking in sequence in the cooking zone to carry out a large amount of delignification.

[0022] The cooking system provided by the embodiment of the present application sets an independent pre-impregnation tower upstream of the cooking tower, separates the pre-impregnation function at the top of the original cooking tower from the cooking tower. The pre-impregnation tower is used to realize the wood chip pre-impregnation function. The pre-impregnation process of the wood chips by the pre-impregnation tower does not interfere with the cooking tower. The pre-impregnation tower can continuously transport the fully penetrated wood chips to the cooking tower, ensuring the production capacity of the cooking system, and reducing the number of equipment of the entire cooking system that needs to be increased due to increasing production capacity, reducing the floor area of the cooking system, and also reducing the configuration of auxiliary facilities, reducing the subsequent maintenance and operation costs and the total investment cost; at the same time, the cooking tower includes a cooking zone and a washing zone. After the pre-impregnated wood chips enter the cooking tower, the cooking reaction directly starts, prolonging the cooking time of the wood chips, thereby reducing the steam temperature of cooking, making the cooking reaction of the wood chips more gentle, reducing steam consumption, reducing fiber loss at the same time, improving the pulp brightness, reducing wood chip consumption and the consumption of chemicals in the subsequent oxygen delignification and bleaching sections, reducing the operation cost and the sewage COD generated in the bleaching section.

[0023] The present application also discloses a cooking method applicable to the cooking system described in any of the above solutions. Since the cooking system has the above technical effects, the cooking method applicable to this cooking system also has the same technical effects, which will not be elaborated here. Description of the Drawings

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required to be used in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some examples or embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the provided drawings, and the present application can also be applied to other similar scenarios according to the provided drawings. Unless obvious from the language context or otherwise stated, the same reference numerals in the drawings represent the same structure or operation.

[0025] Figure 1 is a schematic structural diagram of a prior art cooking system;

[0026] Figure 2 is a schematic structural diagram of the cooking system disclosed in the embodiment of the present application.

[0027] Wherein:

[0028] 01 - wood chip bin; 02 - wood chip pump; 03 - cooking tower;

[0029] 1 - Chip bin; 2 - Pre - impregnation tower; 3 - Cooking tower; 31 - First co - current cooking zone; 32 - Counter - current cooking zone; 33 - Second co - current cooking zone; 34 - Washing zone; 4 - Heater; 5 - Chip pump; 6 - Transfer circulation pump; 7 - First pipeline; 8 - Second pipeline; 9 - Third pipeline; 10 - Stirring discharging device. Detailed implementation manners

[0030] The present application will be further described in detail below with reference to the drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the relevant application, rather than limiting the application. The described embodiments are only a part of the embodiments of the present application, not all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative work fall within the scope of protection of the present application.

[0031] It should be noted that for the convenience of description, only the parts related to the relevant application are shown in the drawings. Without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other.

[0032] It should be understood that the "system", "device", "unit" and / or "module" used in the present application are a way to distinguish different components, elements, parts, portions or assemblies at different levels. However, if other words can achieve the same purpose, the word can be replaced by other expressions.

[0033] As shown in the present application and the claims, unless the context clearly indicates an exception, words such as "a", "an", "one" and / or "the" are not specifically singular and may also include plural. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of the steps and elements that have been clearly identified, and these steps and elements do not constitute an exclusive list. The method or device may also include other steps or elements. An element defined by the statement "comprising one..." does not exclude the existence of another identical element in the process, method, commodity or device including the element.

[0034] Among them, in the description of the embodiments of the present application, unless otherwise specified, " / " means "or". For example, A / B can mean A or B; the "and / or" herein is only a description of the association relationship of the associated objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, and B exists alone. In addition, in the description of the embodiments of the present application, "a plurality of" means two or more than two.

[0035] Hereinafter, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features.

[0036] Please refer to Figure 2 , which is a schematic structural diagram of the cooking system.

[0037] The present application discloses a cooking system, including a chip bin 1, a pre-impregnation tower 2, and a cooking tower 3. Figure 2 As a schematic structural diagram of the cooking system, based on the flow direction of the chips in the cooking system, the cooking system includes a chip bin 1 and a cooking tower 3 located downstream of the chip bin 1. The cooking system further includes a pre-impregnation tower 2, which is located downstream of the chip bin 1 and upstream of the cooking tower 3. Specifically, the chips sequentially pass through the chip bin 1, the pre-impregnation tower 2, and the cooking tower 3.

[0038] The chip bin 1 is connected to the pre-impregnation tower 2 through a first pipeline 7 to convey the chips to the pre-impregnation tower 2. Optionally, a chip pump 5 is provided on the first pipeline 7, and the chips provide power for the conveyance of the chips from the chip bin 1 to the pre-impregnation tower 2.

[0039] The pre-impregnation tower 2 is connected to the cooking tower 3 through a second pipeline 8 to convey the pre-impregnated chips to the cooking tower.

[0040] The chip bin 1 is an atmospheric pressure vessel, which is used for pre-steaming the chips. The flash steam and low-pressure steam generated by the flash tank are added from the bottom of the chip bin 1 to steam the chips, discharge the air in the chips, and heat the chips to about 100 °C in the chip bin 1, providing conditions for the pre-impregnation of the chips.

[0041] The upper part of the chip bin 1 is a cylinder, and the lower part of the chip bin 1 is formed by connecting three semi-conical structures with different sizes at a 90° angle. There is a corner on only one symmetry plane in each semi-cone, and the other symmetry plane is a vertical plane with an inclination angle of zero degrees to avoid the problem of chip bridging in the chip bin 1.

[0042] The advantage of the cooking system having the chip bin 1 is that it enables the chips to be degassed thoroughly, the chips to be preheated evenly, which helps to enhance the pre-impregnation effect of the pre-impregnation tower 2, the moisture content and specific gravity of the chips to be uniform, ensuring the precise control of the liquor ratio and alkali consumption, thereby enhancing the cooking uniformity, reducing the coarse slag rate, and improving the pulp strength.

[0043] Optionally, in some embodiments, a chip metering screw, a heavy impurity separator, and a chip chute are provided at the bottom of the chip bin 1. The pre-steamed chips in the chip bin 1 sequentially pass through the chip metering screw and the heavy impurity separator and enter the chip chute, and after being mixed with the reflux liquid of the pre-impregnation tower 2 or the cooking tower 3 in the chip chute, they are sent to the pre-impregnation tower 2 through the chip pump 5.

[0044] The impregnation tower 2 is used for impregnating wood chips. Inside the impregnation tower 2, the wood chips absorb the cooking liquor, enabling the cooking liquor to fully penetrate into the interior of the wood chips, preparing for subsequent cooking and making the subsequent cooking more uniform. At the same time, a small amount of lignin in the wood chips will react preliminarily with the cooking liquor to form alkali lignin, and a small amount of the limiting substance will also dissolve. However, the above chemical reactions in the impregnation tower 2 are relatively weak, mainly laying the foundation for the intense chemical reactions in the subsequent cooking area and making the cooking more uniform.

[0045] The cooking tower 3 is used for cooking wood chips. The cooking area of the cooking tower 3 is the area where a large amount of lignin is removed from the wood chips. The dissolved lignin enters the black liquor and is extracted from the sieve plate area of the washing and extraction section. The sieve plate of the washing and extraction section is close to the bottom of the cooking tower 3. The extracted black liquor is flashed in a flash tank, filtered by a fiber filter, and then sent to the evaporation workshop for evaporation. The washing area 34 of the cooking tower 3 is the area in the pulp process for removing impurities from the pulp. It is located downstream of the cooking tower 3. By means of physical separation (such as filtration or pressing) or chemical assistance (such as bleach or enzyme), etc., the residual cooking liquor, lignin fragments, hemicellulose, and ash in the cooked pulp are removed to ensure that the pulp purity meets the requirements of subsequent processes.

[0046] In the cooking system disclosed in this solution, an independent impregnation tower 2 is provided upstream of the cooking tower 3. The cooking tower 3 can have an impregnation area. Since the wood chips enter the cooking tower 3 only after being impregnated in the impregnation tower 2, the time for impregnating the wood chips in the cooking tower 3 can be correspondingly shortened, and the cooking time of the wood chips can be extended. Preferably, the cooking tower 3 does not have an impregnation area, and the wood chips are only impregnated in the impregnation tower 2. After the wood chips enter the cooking tower 3, cooking of the wood chips begins.

[0047] The impregnation tower 2 works independently relative to the cooking tower 3. The impregnation process of the wood chips in the impregnation tower 2 does not interfere with the cooking process of the cooking tower 3, enabling the impregnation tower 2 to continuously convey the wood chips fully penetrated with the cooking liquor to the cooking tower 3, ensuring the production capacity of the cooking system. Compared with the method of setting two stock preparation lines, two wood chip bins 1, and two cooking towers 3 in the related art, the number of equipment in the cooking system is reduced, the floor area of the cooking system is reduced, the configuration of auxiliary facilities is also reduced, the subsequent maintenance and operation costs and the total investment cost are reduced, more economic benefits can be created, providing a practical operation reference case for the construction of future large pulp mills, significantly reducing the investment of the pulp mill, and providing a new solution idea for the high-yield design of the cooking tower 3.

[0048] The cooking tower 3 includes a cooking zone and a washing zone 34 located downstream of the cooking zone, and does not include a pre-impregnation zone. After the pre-impregnated wood chips enter the cooking tower 3, the cooking reaction starts directly, which prolongs the cooking time of the wood chips, thereby reducing the steam temperature of cooking, making the cooking reaction of the wood chips milder, reducing steam consumption, while reducing fiber loss, increasing the brightness of the pulp, reducing wood chip consumption and the consumption of chemicals in the subsequent oxygen delignification and bleaching sections, reducing the operating cost and the COD of the wastewater generated in the bleaching section.

[0049] In some embodiments, the cooking zone includes a first cocurrent cooking zone 31, a countercurrent cooking zone 32, and a second cocurrent cooking zone 33. The first cocurrent cooking zone 31, the countercurrent cooking zone 32, and the second cocurrent cooking zone 33 are arranged in sequence along the flow direction of the wood chips. When the cooking tower 3 cooks the wood chips, the wood chips first pass through the first cocurrent cooking zone 31 in the cooking tower 3, then pass through the countercurrent cooking zone 32, and finally pass through the second cocurrent cooking zone 33 and enter the washing zone 34. In this solution, the first cocurrent cooking zone 31 is larger, which can prolong the cooking time and reduce the cooking temperature.

[0050] Cocurrent cooking means that the flow direction of the cooking liquor is the same as that of the wood chips. Cocurrent cooking can reduce the temperature difference loss during the heat exchange process. Cocurrent cooking can perform multi-stage heating and stepwise temperature increase to avoid fiber loss caused by local overheating and improve the pulp strength. The waste liquor impurities concentration generated by cocurrent cooking is lower, reducing the pressure of subsequent wastewater treatment; Countercurrent cooking means that the flow direction of the cooking liquor is opposite to that of the wood chips. Countercurrent cooking can obtain a larger temperature difference, and has good heat transfer effect. Countercurrent cooking can perform multi-stage heating and stepwise temperature increase to accurately control the degree of lignin decomposition and improve the pulp strength. The content of impurities in the waste liquor of countercurrent cooking is lower, and the load of the alkali recovery system is lighter.

[0051] The cooking tower 3 of the cooking system disclosed in this solution changes the pre-impregnation zone to the first cocurrent cooking zone 31. The wood chips are cooked in the first cocurrent cooking zone 31. The cooking time of the cooking zone of the cooking tower 3 for the wood chips is the sum of the cooking times in the first cocurrent cooking zone 31, the countercurrent cooking zone 32, and the second cocurrent cooking zone 33. Compared with the related technology, the residence time of the wood chips in the cooking tower 3 is prolonged, thereby prolonging the cooking time and reducing the temperature of the cooking liquor in the cooking tower 3.

[0052] Taking the production capacity of the cooking tower as 1100 adt / d as a comparison and explanation,

[0053] In the traditional cooking system, after the wood chips are steamed in the wood chip bin 01, they pass through the wood chip metering spiral, heavy impurity separator and wood chip chute, and then are sent to the cooking tower 03 by the wood chip pump 02. The actual operating production capacity is 1100 adt / d. The residence time of the wood chips in the pre-impregnation zone of the cooking tower 03 is 0.18H, the residence time of the wood chips in the countercurrent cooking zone of the cooking tower 03 is 0.27H, the residence time of the wood chips in the co-current cooking zone of the cooking tower 03 is 2.08H, and the residence time of the wood chips in the countercurrent washing zone of the cooking tower 03 is 0.33H;

[0054] In the cooking system disclosed in this solution, the pre-impregnation tower 2 and the cooking tower 3 are operated in series. After the wood chips are steamed in the wood chip bin 1, they pass through the wood chip metering spiral, heavy impurity separator and wood chip chute, and then are sent to the pre-impregnation tower 2 by the wood chip pump 5. After the wood chips are fully pre-impregnated in the pre-impregnation tower 2, they are sent into the cooking tower 3. The actual operating production capacity is 1100 adt / d. The residence time of the wood chips in the pre-impregnation tower 2 is 0.33H, the residence time of the wood chips in the co-current cooking zone of the cooking tower 3 is 0.18H, the residence time of the wood chips in the countercurrent cooking zone 32 of the cooking tower 3 is 0.27H, the residence time of the wood chips in the co-current cooking zone of the cooking tower 3 is 2.08H, and the residence time of the wood chips in the countercurrent washing zone of the cooking tower 3 is 0.33H.

[0055] The effects brought:

[0056] The unit consumption of wood chips per ton of pulp is reduced by 0.012 bdt / adt;

[0057] The steam consumption per ton of pulp is reduced by 10 - 20 kg / adt;

[0058] 3 The effective chlorine consumption in the bleaching section is reduced by 1.1 kg / adt.

[0059] As can be seen from the above content, in the cooking system disclosed in this solution, the wood chips are pre-impregnated alone in the pre-impregnation tower 2 for 0.33H, the cooking time of the wood chips in the cooking tower 3 is extended. On the basis of the full penetration of the wood chips and the chemicals, the cooking time is extended, which can reduce the steam temperature of cooking, make the cooking reaction of the wood chips more gentle, reduce the steam consumption, reduce the fiber loss at the same time, improve the pulp brightness, reduce the wood chip consumption and the chemical consumption in the subsequent oxygen delignification section and bleaching section, and reduce the operating cost and the sewage COD generated in the bleaching section.

[0060] In some embodiments, the washing zone 34 is a countercurrent washing zone. The function of the countercurrent washing zone is to remove the un-dissociated wood chips in the softening unit. The setting of the countercurrent washing zone helps to improve the quality and mechanical properties of the pulp, and also helps to improve the stability and reliability of the cooking process.

[0061] In the countercurrent washing area, countercurrent washing can extend the contact time between the washing liquid and the wood chips, enabling the detergent to come into full contact with the wood chips and improving the washing effect. Countercurrent washing can also reduce the consumption of detergent to a certain extent, and helps to reduce the emission of harmful substances and protect the environment.

[0062] The washing method in the washing area 34 can also be co-current washing or a combination of co-current washing and countercurrent washing.

[0063] Optionally, a level gauge is provided on the pre-impregnation tower 2 to control the pre-impregnation time of the wood chips in the pre-impregnation tower, ensuring that the cooking liquor can fully penetrate into the wood chips.

[0064] The level gauge is used to detect the height change of the wood chips in the pre-impregnation tower 2 in real time. As the pre-impregnation process progresses, the height of the wood chips in the pre-impregnation tower 2 will change. The staff can judge the pre-impregnation degree of the wood chips by observing the level gauge, realizing the visual observation of the pre-impregnation degree of the wood chips.

[0065] As Figure 2 shown, a second pipeline 8 and a third pipeline 9 are provided between the top of the cooking tower 3 and the bottom of the pre-impregnation tower 2. The second pipeline 8 is used to convey the wood chips in the pre-impregnation tower 2 to the cooking tower 3, and the third pipeline 9 is used to convey the cooking liquor at the top of the cooking tower 3 to the bottom of the pre-impregnation tower 2. The second pipeline 8 and the third pipeline 9 form a cycle between the bottom of the pre-impregnation tower 2 and the top of the cooking tower 3. A transfer circulation pump 6 is provided on the third pipeline 9 to provide power for the cycle between the pre-impregnation tower 2 and the cooking tower 3. The transfer circulation pump 6 pumps the cooking liquor from the top of the cooking tower 3 to the bottom of the pre-impregnation tower 2, allowing the wood chips to be transferred from the bottom of the pre-impregnation tower to the top of the cooking tower 3 along with the circulating cooking liquor.

[0066] As Figure 2 shown, the liquid inlet end of the third pipeline 9 is connected to the top of the cooking tower 3, the liquid outlet end of the third pipeline 9 is connected to the bottom of the pre-impregnation tower 2, and a transfer circulation pump 6 is provided on the third pipeline 9. The transfer circulation pump 6 is used to pump the cooking liquor from the top of the cooking tower 3 to the bottom of the pre-impregnation tower 2;

[0067] The liquid inlet end of the second pipeline 8 is connected to the bottom of the pre-impregnation tower 2, and the liquid outlet end of the second pipeline 8 is connected to the top of the cooking tower 3. The cooking liquor pumped to the bottom of the pre-impregnation tower 2 carries the wood chips and is transferred to the top of the cooking tower 3 through the second pipeline 8.

[0068] The transfer circulation pump 6 provides power for the conveyance of the wood chips from the pre-impregnation tower 2 to the cooking tower 3.

[0069] A stirring and discharging device 10 is provided at the bottom of the pre-impregnation tower 2 to stir the mixture of the wood chips and the cooking liquor, ensuring the smooth conveyance of the wood chips.

[0070] As Figure 2As described above, a heater is provided on the third pipeline 9, and the heater is used to heat the cooking liquid in the third pipeline 9 to increase the temperature of the cooking liquid entering the bottom of the impregnation tower 2 from the cooking tower 3.

[0071] This application also discloses a cooking method applicable to the cooking system described in any of the above solutions. Specifically, the cooking method includes:

[0072] S1. Pre-steam the wood chips to discharge the air in the wood chips and obtain the wood chips to be impregnated.

[0073] S2. Transport the wood chips to be impregnated to the impregnation tower 2, and the cooking liquid in the impregnation tower 2 penetrates into the wood chips to be impregnated to obtain the impregnated wood chips.

[0074] S3. Transport the impregnated wood chips to the cooking area of the cooking tower 3. A large amount of delignification occurs to the impregnated wood chips in the cooking area, and the delignified wood chips are washed in the washing area 34 of the cooking tower 3.

[0075] Since the cooking system has the above technical effects, the cooking method applicable to this cooking system also has the same technical effects, which will not be elaborated here.

[0076] Specifically, in S2, a large amount of delignification of the impregnated wood chips in the cooking area means that the impregnated wood chips are subjected to the first forward cooking, reverse cooking, and the second forward cooking in sequence in the cooking area for a large amount of delignification.

[0077] The above description is only for the preferred embodiments of this application and the description of the applied technical principles, and is not used to limit this application. For those skilled in the art, this application can have various changes and modifications. The scope of the application involved in this application is not limited to the technical solutions formed by the specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the above application concept. For example, the technical solutions formed by mutually replacing the above features with the technical features (but not limited to) having similar functions disclosed in this application.

Claims

1. A cooking system, based on the flow direction of wood chips in the cooking system, comprising a wood chip bin (1) and a cooking tower (3) located downstream of the wood chip bin (1), characterized in that: It also includes a prepreg tower (2) located downstream of the wood chip bin (1) and upstream of the cooking tower (3), which is used for prepregging wood chips. The wood chip bin (1) is used for pre-steaming wood chips, and the wood chip bin (1) is connected to the prepreg tower (2) via a first pipeline (7) to transport the wood chips to the prepreg tower (2); The prepreg tower (2) is connected to the cooking tower (3) via a second pipeline (8) so as to transport wood chips to the cooking tower (3).

2. The cooking system according to claim 1, characterized in that: The invention also comprises a third pipeline (9), on which a transfer circulation pump (6) is arranged, which is used to pump the cooking liquid from the top of the cooking tower (3) to the bottom of the prepreg tower (2), and the cooking liquid pumped to the bottom of the prepreg tower (2) carries the wood chips and is transferred to the top of the cooking tower through the second pipeline (8).

3. The cooking system according to claim 2, characterized in that: The third pipeline (9) is provided with a heater (4), and the heater (4) is used to increase the temperature of the cooking liquid.

4. The cooking system according to claim 1, characterized in that: A material level meter is arranged in the prepreg tower to control the prepreg time of the wood chips in the prepreg tower.

5. The cooking system according to claim 1, characterized in that: The cooking tower is configured to include only a cooking zone and a washing zone located downstream thereof, so that the cooking reaction begins when the wood chips enter the cooking tower.

6. The cooking system according to claim 5, characterized in that: The cooking zone comprises a first co-current cooking zone (31), a counter-current cooking zone (32) and a second co-current cooking zone (33).

7. The cooking system according to claim 5, characterized in that: The washing zone (34) is a countercurrent washing zone.

8. The cooking system according to claim 1, characterized in that: A stirring and discharging device (10) is provided at the bottom of the prepreg tower (2).

9. A cooking method, characterized in that: The cooking system according to any one of claims 1 to 8 comprises: S1. Pre-steaming wood chips to exhaust the air in the wood chips to obtain pre-impregnated wood chips; S2. conveying the wood chips to be prepreg to the prepreg tower (2), wherein the cooking liquid in the prepreg tower (2) penetrates into the wood chips to be prepreg, thereby obtaining prepreg wood chips; S3. The prepreg chips are transported to the cooking zone of the cooking tower (3), the prepreg chips are largely delignified in the cooking zone, and the delignified chips are washed in the washing zone (34) of the cooking tower (3).

10. The cooking method according to claim 9, characterized in that: The prepreg wood chips are largely delignified in the cooking zone, specifically, The prepreg wood chips are sequentially subjected to a first co-current cooking, a counter-current cooking and a second co-current cooking in the cooking zone for a large amount of delignification.

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