A paper web drying section condensate recovery system

Abstract

The utility model discloses a kind of paper web drying section condensate water recovery system, comprising: heat exchanger, the coolant inlet of heat exchanger is connected with the exhaust port of drying section, the coolant outlet of heat exchanger is connected with the steam inlet of drying section, the heat medium outlet of heat exchanger is connected with water treatment workshop;Total condensate tank, the water outlet of total condensate tank is connected with the heat medium inlet of heat exchanger, to directly provide heat medium medium to heat exchanger;Transfer condensate tank, the water inlet of transfer condensate tank is connected with the drain port of drying section, the water outlet of transfer condensate tank is connected with the water inlet of total condensate tank, to temporarily store and provide condensate water to total condensate tank. All condensate water converges to participate in heat exchange again, avoid temperature difference to produce flash steam damage equipment, the temperature of condensate water convergence is sufficient to participate in heat exchange, heat is fully recovered also sufficient, without adding steam, the utility model has the advantages of pressure stability, heat recovery is sufficient and sufficient.

Description

Technical Field

[0001] This application relates to the field of condensate recovery technology in paper web drying section, and specifically to a condensate recovery system for paper web drying section. Background Technology

[0002] After pressing and before drying, the wet paper width is generally only 30-40%. Even in new paper machines with compound pressing, the dryness only reaches 40-50%. Therefore, it is necessary to evaporate the moisture again in the drying section to achieve the moisture control required for paper production.

[0003] The drying section consists of one or more drying cylinders. Its main function is to heat the wet paper web after pressing. The heat is released by the condensation of the steam entering the drying cylinder and transferred to the wet paper web on the drying cylinder, so that the excess moisture is evaporated, thereby meeting the product quality requirements. At the same time, it improves the strength of the paper web, improves some physical properties of the paper web, and completes processes such as sizing and dyeing.

[0004] Water vapor consumption accounts for 5-15% of production costs. Therefore, the secondary water vapor evaporated from the paper web and the condensate formed by condensation need to be recovered. The secondary water vapor is heated by a heat exchanger and then recycled back into the drying cylinder. The condensate is temporarily stored in a transfer condensate tank and then drawn into the heat exchanger to participate in heat exchange. After the heat exchange is completed, it flows into the main condensate tank.

[0005] The high-temperature condensate from the intermediate condensate tank flows into the main condensate tank after heat exchange. Due to the large temperature difference between the two, the pressure in the main condensate tank drops sharply, generating flash steam and causing equipment vibration and noise, threatening production safety. In addition, only the heat of the high-temperature condensate in the intermediate condensate tank is recovered and utilized. The low-temperature condensate in the main condensate tank cannot fully participate in heat exchange because of its low temperature, resulting in a waste of heat in the condensate in the main condensate tank. When producing low basis weight paper, the amount of condensate in the intermediate condensate tank is relatively small, so a large amount of fresh steam still needs to be added to the drying cylinder, and the consumption of water vapor is still relatively large. Utility Model Content

[0006] Therefore, a paper web drying section condensate recovery system is needed to solve the problems in the existing technology where condensate recovery in the drying section is damaged due to temperature fluctuations, and the heat recovery is incomplete and cannot meet the heat requirements for drying.

[0007] To achieve the above objectives, the inventors provide a condensate recovery system for a paper web drying section, comprising:

[0008] A heat exchanger, wherein the refrigerant inlet of the heat exchanger is connected to the exhaust port of the drying section, the refrigerant outlet of the heat exchanger is connected to the steam inlet of the drying section, and the heat outlet of the heat exchanger is connected to the water treatment workshop.

[0009] A main condensate tank, the outlet of which is connected to the heat medium inlet of the heat exchanger, to directly supply the heat medium to the heat exchanger;

[0010] A transfer condensate tank, the inlet of which is connected to the drain outlet of the drying section, and the outlet of which is connected to the inlet of the main condensate tank, are used to temporarily store and supply condensate to the main condensate tank.

[0011] In some embodiments, it also includes:

[0012] The first water pump connects the inlet of the main condensate tank to the outlet of the intermediate condensate tank to draw water from the intermediate condensate tank into the main condensate tank.

[0013] In some embodiments, it also includes:

[0014] The first valve group is located between the first water pump and the main condensate tank.

[0015] In some embodiments, it also includes:

[0016] The second water pump connects the outlet of the main condensate tank to the heat medium inlet of the heat exchanger to draw water from the main condensate tank into the heat exchanger.

[0017] In some embodiments, it also includes:

[0018] The second valve assembly is located between the second water pump and the heat exchanger.

[0019] In some embodiments, the drying section includes a front drying section and a rear drying section, both of which include a double-row drying cylinder and a single-hanging drying cylinder.

[0020] In some embodiments, the inlet of the intermediate condensate tank is connected to the outlet of the double-row drying cylinder of the front drying section.

[0021] In some embodiments, the inlet of the main condensate tank is also connected to the drain outlet of the single hanging drying cylinder of the rear drying section.

[0022] Unlike existing technologies, the paper web drying section condensate recovery system described in the above technical solution has an intermediate condensate tank inlet connected to the drying section outlet for temporary condensate storage. The intermediate condensate tank outlet is connected to the main condensate tank outlet, allowing condensate to be directly supplied to the main condensate tank. The main condensate tank outlet is connected to the heat medium inlet of the heat exchanger. All condensate first converges in the main condensate tank, and then the main condensate tank directly supplies the heat medium to the heat exchanger. Therefore, the condensate in the intermediate condensate tank does not undergo heat exchange before directly flowing into the main condensate tank. The temperature difference between the condensate flowing into the main condensate tank and the intermediate condensate tank is small, ensuring stable pressure within the main condensate tank and effectively reducing the impact of heat exchange. Flash steam generated by large temperature differences and sudden pressure drops reduces equipment vibration and noise, avoids equipment damage, reduces the frequency of downtime for maintenance, and improves production efficiency. Additionally, the condensate temperature in the transfer condensate tank is higher than that in the main condensate tank. After flowing into the main condensate tank, the condensate temperature in the main condensate tank rises, ensuring that the condensate in the main condensate tank meets the heat exchange temperature requirements. All the heat from the collected condensate in the main condensate tank is recovered and utilized. The collected condensate is abundant and carries sufficient heat. After heat exchange, the condensate in the main condensate tank can heat more secondary steam, significantly reducing the use of fresh steam in the production of high-basis-weight paper. The condensate, after heat exchange, is then transported to the water treatment workshop for other uses. This condensate recovery system in the paper web drying section breaks away from the original independent tank recovery model. By converging through the main condensate tank, it achieves unified utilization of condensate heat throughout the system, filling the gap in waste heat recovery from the main condensate tank. This can increase heat energy recovery by approximately 30%, reduce flash steam emissions and fresh steam consumption, and has the advantages of stable pressure and sufficient heat recovery.

[0023] The above description of the utility model is merely an overview of the technical solution of this application. In order to enable those skilled in the art to better understand the technical solution of this application and to implement it based on the description and drawings, and to make the above-mentioned objectives and other objectives, features and advantages of this application easier to understand, the following description is provided in conjunction with the specific embodiments and drawings of this application. Attached Figure Description

[0024] The accompanying drawings are only used to illustrate the principles, implementation methods, applications, features, and effects of specific embodiments of this application and other related content, and should not be considered as limitations on this application.

[0025] In the accompanying drawings of the instruction manual:

[0026] Figure 1 This is a connection diagram illustrating the condensate recovery and reuse in the drying section according to a specific implementation method.

[0027] Figure 2This is a connection diagram of the condensate recovery system in the paper web drying section according to a specific embodiment;

[0028] Figure 3 This is a connection diagram of the condensate recovery system in the paper web drying section of another specific embodiment;

[0029] The reference numerals used in the above figures are explained as follows:

[0030] 1. Heat exchanger;

[0031] 2. Main condensate tank;

[0032] 3. Transfer condensate tank;

[0033] 4. Water treatment workshop;

[0034] 5. First water pump;

[0035] 6. First valve group;

[0036] 7. Second water pump;

[0037] 8. Second valve group;

[0038] 9. Drying section;

[0039] 900. Double-row drying cylinders in the front drying section;

[0040] 901. Single hanging drying cylinder in the post-drying section. Detailed Implementation

[0041] To illustrate the possible application scenarios, technical principles, implementable specific solutions, and achievable objectives and effects of this application in detail, the following description, in conjunction with the listed specific embodiments and accompanying drawings, provides a detailed explanation. The embodiments described herein are merely illustrative of the technical solutions of this application and are therefore intended to limit the scope of protection of this application.

[0042] In this document, the term "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The term "embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment, nor does it specifically limit its independence or connection with other embodiments. In principle, in this application, as long as there are no technical contradictions or conflicts, the technical features mentioned in each embodiment can be combined in any way to form corresponding implementable technical solutions.

[0043] Unless otherwise defined, the technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the use of related terms herein is merely for the purpose of describing particular embodiments and is not intended to limit this application.

[0044] In the description of this application, the term "and / or" is used to describe the logical relationship between objects, indicating that three relationships can exist. For example, A and / or B means: A exists, B exists, and A and B exist simultaneously. Additionally, the character " / " in this document generally indicates that the preceding and following objects have an "or" logical relationship.

[0045] In this application, terms such as “first” and “second” are used only to distinguish one entity or operation from another, and do not necessarily require or imply any actual quantity, hierarchy or order relationship between these entities or operations.

[0046] Unless otherwise specified, the use of terms such as “comprising,” “including,” “having,” or other similar expressions in this application is intended to cover non-exclusive inclusion, which does not exclude the presence of additional elements in a process, method, or product that includes the stated elements, such that a process, method, or product that includes a list of elements may include not only those defined elements but also other elements not expressly listed, or elements inherent to such a process, method, or product.

[0047] As understood in the Examination Guidelines, in this application, expressions such as "greater than," "less than," and "exceeding" are understood to exclude the stated number; expressions such as "above," "below," and "within" are understood to include the stated number. Furthermore, in the description of the embodiments in this application, "multiple" means two or more (including two), and similar expressions related to "multiple" are also understood in this way, such as "multiple groups" and "multiple times," unless otherwise explicitly specified.

[0048] In the description of the embodiments of this application, the space-related expressions used, such as "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "vertical," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," indicate the orientation or positional relationship based on the orientation or positional relationship shown in the specific embodiments or drawings. They are only for the purpose of describing the specific embodiments of this application or for the reader's understanding, and do not indicate or imply that the device or component referred to must have a specific position, a specific orientation, or be constructed or operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0049] Unless otherwise expressly specified or limited, the terms "installation," "connection," "linking," "fixing," and "setting," as used in the description of the embodiments of this application, should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral setting; it can be a mechanical connection, an electrical connection, or a communication connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal connection of two components or the interaction between two components. For those skilled in the art to which this application pertains, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0050] After pressing and before drying, the wet paper width is generally only 30-40%. Even in new paper machines with compound pressing, the dryness only reaches 40-50%. Therefore, it is necessary to evaporate the moisture again through the drying section 9 to achieve the moisture control required for paper production.

[0051] The drying section 9 consists of one or more drying cylinders. Its main function is to heat the wet paper web after pressing. The heat is released by the condensation of the steam entering the drying cylinder and transferred to the wet paper web on the drying cylinder, so that the excess moisture is evaporated, thereby meeting the product quality requirements. At the same time, it improves the strength of the paper web, improves some physical properties of the paper web, and completes processes such as sizing and dyeing.

[0052] Water vapor consumption accounts for 5-15% of production costs; therefore, please refer to [link / reference needed]. Figure 1 The secondary water vapor evaporated from the paper web (which is the steam recovered after the fresh steam passes through the drying section 9) and the condensate formed by condensation need to be recovered. The secondary water vapor is heated by the heat exchanger 1 and then recycled back to the drying cylinder of the drying section 9. The condensate is temporarily stored in the transfer condensate tank 3 and then drawn into the heat exchanger 1 to participate in heat exchange. After the heat exchange is completed, it flows into the main condensate tank 2.

[0053] Please see Figure 1 The high-temperature condensate from the intermediate condensate tank 3 flows into the main condensate tank 2 after heat exchange. Due to the large temperature difference between the two, the pressure in the main condensate tank 2 drops sharply, generating flash steam and causing equipment vibration and noise, threatening production safety. In addition, only the heat of the high-temperature condensate in the intermediate condensate tank 3 is recovered and utilized. The low-temperature condensate in the main condensate tank 2 cannot fully participate in heat exchange because of its low water temperature, resulting in a waste of heat in the condensate in the main condensate tank 2. When producing low-basis-weight paper, the amount of condensate in the intermediate condensate tank 3 is relatively small. Therefore, a large amount of fresh steam (steam supplied by the thermal power plant that has not been recycled) still needs to be added to the drying cylinder, and the consumption of water vapor is still relatively large.

[0054] To address this, the present invention provides a condensate recovery system for the paper web drying section 9, which is used to recover and utilize the secondary steam and condensate output from the drying section 9. In particular, it breaks the original independent recovery mode of separate tanks and realizes the overall utilization of condensate heat in the whole system through the convergence of the main condensate tank 2, fills the gap in waste heat recovery of the main condensate tank 2, can increase the amount of heat energy recovered, and reduce flash steam emissions and fresh steam consumption.

[0055] Please see Figure 2 In a specific embodiment, the condensate recovery system of the paper web drying section 9 includes a heat exchanger 1, a main condensate tank 2, and a transfer condensate tank 3. The heat exchanger 1 is used to heat secondary steam for recycling and participation in the drying of the paper web. Since the entire system path is very long, in order to avoid large heat loss during transportation, a transfer condensate tank 3 is necessary so that the output high-temperature condensate can be collected midway. The main condensate tank 2 is used to collect all the condensate to neutralize the heat and centrally supply it to the heat exchanger 1.

[0056] The refrigerant inlet of the heat exchanger 1 is connected to the exhaust port of the drying section 9, the refrigerant outlet of the heat exchanger 1 is connected to the steam inlet of the drying section 9, and the heat medium outlet of the heat exchanger 1 is connected to the water treatment workshop 4. The outlet of the main condensate tank 2 is connected to the heat medium inlet of the heat exchanger 1 to directly supply the heat medium to the heat exchanger 1. The heat medium is the condensate discharged from the drying section 9. The condensate in the heat exchanger 1 transfers heat to the secondary steam, thereby heating the secondary steam discharged from the drying section 9. The inlet of the transfer condensate tank 3 is connected to the drain port of the drying section 9, and the outlet of the transfer condensate tank 3 is connected to the inlet of the main condensate tank 2 to temporarily store and supply condensate to the main condensate tank 2.

[0057] The inlet of the intermediate condensate tank 3 in the condensate recovery system of the paper web drying section 9 is connected to the outlet of the drying section 9 to temporarily store condensate. The outlet of the intermediate condensate tank 3 is connected to the inlet of the main condensate tank 2, so that the condensate is directly supplied to the main condensate tank 2. The outlet of the main condensate tank 2 is connected to the heat medium inlet of the heat exchanger 1. All condensate first converges in the main condensate tank 2, and then the main condensate tank 2 directly supplies the heat medium to the heat exchanger 1. Therefore, the condensate in the intermediate condensate tank 3 does not undergo heat exchange first, but directly flows into the main condensate tank 2. The temperature difference between the condensate flowing into the main condensate tank 2 is small, which ensures that the pressure in the main condensate tank 2 is stable. This can effectively reduce flash steam caused by large temperature differences and sudden pressure drops, reduce equipment vibration and noise, avoid equipment damage, reduce the frequency of downtime maintenance, and improve production efficiency.

[0058] In addition, the temperature of the condensate in the transfer condensate tank 3 is higher than that in the main condensate tank 2. After flowing into the main condensate tank 2, the temperature of the condensate in the main condensate tank 2 can be increased, ensuring that the condensate in the main condensate tank 2 meets the heat exchange temperature requirements. All the heat of the condensate collected in the main condensate tank 2 can be recovered and utilized. Moreover, the collected condensate is sufficient and carries enough heat. After participating in the heat exchange, the condensate in the main condensate tank 2 can heat more secondary steam, which can significantly reduce the use of fresh steam when producing high-grammage paper. After the condensate has undergone heat exchange, it is transported to the water treatment workshop 4 for other uses and is not sent back to the main condensate tank to avoid affecting the temperature inside the main condensate tank.

[0059] The condensate recovery system in the paper web drying section 9 boasts advantages such as stable pressure and ample heat recovery. Breaking away from the original independent tank recovery model, it achieves comprehensive utilization of condensate heat across the entire system through the convergence of the main condensate tank 2, filling the gap in waste heat recovery in the main condensate tank 2. This results in approximately 30% more heat energy recovery compared to the original design (increasing the calorific value of the condensate in the main condensate tank 2 to 2000 kJ / t), and is expected to save 20 million yuan in steam costs annually. It also reduces flash steam emissions and fresh steam consumption, lowering the overall energy consumption per unit product by more than 9%, aligning with the national energy conservation and emission reduction guidelines for light industry.

[0060] In some embodiments, a first water pump 5 is also included. The inlet of the main condensate tank 2 is connected to the outlet of the intermediate condensate tank 3 through the first water pump 5. That is, the inlet of the first water pump 5 is connected to the outlet of the intermediate condensate tank 3, and the outlet of the first water pump 5 is connected to the inlet of the main condensate tank 2, so as to draw water from the intermediate condensate tank 3 into the main condensate tank 2.

[0061] In some embodiments, a first valve assembly 6 is also included, which is disposed between the first water pump 5 and the main condensate tank 2. That is, the first valve assembly 6 is connected to the outlet of the first water pump 5 and the inlet of the main condensate tank 2 to open or close the pipeline or regulate the flow rate.

[0062] In some embodiments, the first valve group 6 is a solenoid valve.

[0063] Similarly, in some embodiments, a second water pump 7 is also included. The outlet of the main condensate tank 2 is connected to the heat medium inlet of the heat exchanger 1 through the second water pump 7. That is, the inlet of the second water pump 7 is connected to the outlet of the main condensate tank 2, and the outlet of the second water pump 7 is connected to the heat medium inlet of the heat exchanger 1, so as to draw the main condensate tank 2 into the heat exchanger 1.

[0064] In some embodiments, a second valve assembly 8 is also included, which is disposed between the second water pump 7 and the heat exchanger 1. That is, the second valve assembly 8 is connected to the outlet of the second water pump 7 and the heat medium inlet of the heat exchanger 1 to open or close the pipeline or regulate the flow rate.

[0065] Please see Figure 3 In some embodiments, the drying section 9 includes a front drying section and a rear drying section, both of which include a double-row drying cylinder and a single-hanging drying cylinder.

[0066] In some embodiments, the inlet of the transfer condensate tank 3 is connected to the outlet of the double-row drying cylinder 900 of the front drying section, that is, the condensate entering the transfer condensate tank 3 comes from the condensate discharged from the double-row drying cylinder 900 of the front drying section.

[0067] In some embodiments, the inlet of the main condensate tank 2 is also connected to the outlet of the single hanging drying cylinder 901 of the rear drying section, that is, the condensate flowing into the main condensate tank 2 also includes the condensate discharged from the single hanging drying cylinder 901 of the rear drying section, and the condensate of the single hanging drying cylinder 901 of the rear drying section is directly discharged to the main condensate tank 2.

[0068] In some embodiments, the pre-drying section and the post-drying section are respectively located upstream and downstream of the sizing section to dry the paper web before sizing and the paper web after sizing, respectively.

[0069] Finally, it should be noted that although the above embodiments have been described in the text and drawings of this application, this should not limit the scope of patent protection of this application. Any technical solutions that are based on the essential concept of this application and utilize the content described in the text and drawings of this application, resulting in equivalent structural or procedural substitutions or modifications, as well as the direct or indirect application of the technical solutions of the above embodiments to other related technical fields, are all included within the scope of patent protection of this application.

Claims

1. A condensate recovery system for a paper web drying section, characterized in that, include: A heat exchanger, wherein the refrigerant inlet of the heat exchanger is connected to the exhaust port of the drying section, the refrigerant outlet of the heat exchanger is connected to the steam inlet of the drying section, and the heat outlet of the heat exchanger is connected to the water treatment workshop. A main condensate tank, the outlet of which is connected to the heat medium inlet of the heat exchanger, to directly supply the heat medium to the heat exchanger; A transfer condensate tank, the inlet of which is connected to the drain outlet of the drying section, and the outlet of which is connected to the inlet of the main condensate tank, are used to temporarily store and supply condensate to the main condensate tank.

2. The condensate recovery system for the paper web drying section according to claim 1, characterized in that, Also includes: The first water pump connects the inlet of the main condensate tank to the outlet of the intermediate condensate tank to draw water from the intermediate condensate tank into the main condensate tank.

3. The condensate recovery system for the paper web drying section according to claim 2, characterized in that, Also includes: The first valve group is located between the first water pump and the main condensate tank.

4. The condensate recovery system for the paper web drying section according to claim 1, characterized in that, Also includes: The second water pump connects the outlet of the main condensate tank to the heat medium inlet of the heat exchanger to draw water from the main condensate tank into the heat exchanger.

5. The condensate recovery system for the paper web drying section according to claim 4, characterized in that, Also includes: The second valve assembly is located between the second water pump and the heat exchanger.

6. The condensate recovery system for the paper web drying section according to claim 1, characterized in that, The drying section includes a front drying section and a rear drying section, both of which include a double-row drying cylinder and a single-hanging drying cylinder.

7. The condensate recovery system for the paper web drying section according to claim 6, characterized in that, The inlet of the intermediate condensate tank is connected to the outlet of the double-row drying cylinder of the front drying section.

8. The condensate recovery system for the paper web drying section according to claim 6, characterized in that, The inlet of the main condensate tank is also connected to the drain outlet of the single hanging drying cylinder of the rear drying section.

Images