Turbine exhaust system and method of ventilation for a closed hood

Abstract

The application provides a turbine air supply and exhaust system and a closed gas cover ventilation method. The turbine air supply and exhaust system comprises a first exhaust passage, a first air supply passage, a second exhaust passage, a second air supply passage, a fresh air passage and a preheating passage; an axial flow fan is arranged in the first exhaust passage; a first centrifugal fan is arranged in the second exhaust passage; a first heat exchanger, a second heat exchanger and a third heat exchanger are sequentially arranged in the second air supply passage, and a second centrifugal fan is arranged in the second air supply passage; the closed gas cover ventilation method has two exhaust parts and two air supply parts. The air supply and exhaust system and the ventilation method matched with the air supply and exhaust system can save energy and improve the comprehensive effect of the closed gas cover ventilation process in energy saving, power consumption and environmental protection.

Description

TECHNICAL FIELD

[0001] The present application relates to the papermaking technical field, and particularly relates to a turbine air supply and exhaust system and a closed hood ventilation method. BACKGROUND

[0002] The main function of the closed hood on the drying section of the high-speed paper machine is to collect the water vapor generated by the evaporation of the drying section, to save the heat energy evaporated by the drying section, and to isolate the outside environment to form a heat preservation effect. In order to ensure that the water vapor evaporated by the drying section is discharged in time and to avoid air condensation and water droplets on the paper web to form paper defects, the hood needs to be ventilated while the paper machine is running normally, so as to reduce the humidity in the hood and ensure the balance of the air volume in the hood.

[0003] The conventional exhaust system discharges the hot and humid air outside the hood, and then uses the air supply system to send hot air with lower humidity into the hood. The hot air is obtained by three-stage heating of room temperature air through the hood exhaust heat recovery device + turbine heat recovery device / condensate heat exchanger + steam heater, and the temperature of the hot air sent into the hood needs to reach 100 DEG C or above to meet the normal operation requirements of the paper machine evaporation.

[0004] In the conventional exhaust system, a steam heater needs to be separately configured, the steam consumption of the steam heater is high, that is, the operation cost is high, the number of heat recovery devices is large, the investment cost is high, the exhaust system layout is complex, and the maintenance is relatively troublesome. In addition, due to the wind resistance between the pipe wall of the heat recovery device and the gas in the pipe, when the number of heat recovery devices increases, the power consumption will increase significantly.

[0005] Therefore, the comprehensive effect of the current air supply and exhaust system in energy saving, power consumption and environmental protection needs to be improved. SUMMARY

[0006] In view of the deficiencies in the prior art, the present application provides a turbine air supply and exhaust system and a closed hood ventilation method, which does not consume new steam, the exhaust system is simple in layout, convenient in maintenance and low in energy consumption. The technical scheme adopted by the present application is as follows:

[0007] On the one hand, the present application provides a turbine air supply and exhaust system for air supply and exhaust of a closed hood, which comprises a first exhaust passage, a first air supply passage, a second exhaust passage, a second air supply passage, a fresh air passage and a preheating passage.

[0008] One end of the first exhaust passage is directly connected to the hood, and an axial flow fan is arranged in the first exhaust passage.

[0009] One end of the first air supply passage is directly connected to the hood, and the other end is connected to the exhaust port of the multi-stage turbine, and the exhaust of the multi-stage turbine enters the hood through the first air supply passage.

[0010] The second air supply channel is sequentially arranged with a first heat exchanger, a second heat exchanger, and a third heat exchanger. One end of the second air exhaust channel is directly connected to the air hood, and the other end is connected to the inlet of the first heat exchange channel of the first heat exchanger. A first centrifugal fan is provided in the second air exhaust channel. One end of the fresh air channel is connected to the inlet of the second heat exchange channel of the first heat exchanger. One end of the preheating channel is connected to the first heat exchange channel of the first heat exchanger, and the other end is connected to the exhaust port of the single-stage turbine. The exhaust air of the single-stage turbine enters the first heat exchange channel of the first heat exchanger through the preheating channel.

[0011] The second air supply channel includes an air supply section 1, an air supply section 2, and an air supply section 3; one end of the air supply section 1 is connected to the outlet of the second heat exchange channel of the first heat exchanger, and the other end is connected to the inlet of the second heat exchange channel of the second heat exchanger; one end of the air supply section 2 is connected to the outlet of the second heat exchange channel of the second heat exchanger, and the other end is connected to the inlet of the second heat exchange channel of the third heat exchanger; one end of the air supply section 3 is directly connected to the air hood, and the other end is connected to the outlet of the second heat exchange channel of the third heat exchanger;

[0012] A second centrifugal fan is arranged in the second air supply channel.

[0013] Furthermore, the second heat exchanger is a condensed water heat exchanger.

[0014] Furthermore, the third heat exchanger is a flash steam heat exchanger.

[0015] On the other hand, the present invention also proposes a high-speed papermaking confidential closed air hood ventilation method, which is achieved through the turbine air supply and exhaust system. The air hood is exhausted in two aspects.

[0016] In the first aspect, the hood exhaust is carried out by an axial flow fan, which extracts the air with high humidity in the hood through the first exhaust channel;

[0017] On the other hand, the air hood exhaust uses the first centrifugal fan to extract the air with high moisture content in the air hood through the second exhaust channel, send it into the first heat exchange channel of the first heat exchanger, and finally discharge it from the outlet of the first heat exchange channel of the first heat exchanger;

[0018] The hood supplies air in two directions.

[0019] In the first aspect, the air hood air supply sends the exhaust air of the multi-stage turbine into the air hood through the first air supply channel;

[0020] On the second aspect, the air supply from the hood uses the second centrifugal fan to draw fresh air at room temperature into the hood through the fresh air channel and the second air supply channel. The fresh air undergoes three stages of heat exchange and temperature increase between the first heat exchanger, the second heat exchanger, and the third heat exchanger. In the hood, it is mixed with the air supply from the first aspect to form mixed air with a temperature of 110°C-115°C and a humidity of 40g-60g H2O / kg dryair, which is then blown to the drying section in the hood.

[0021] Further, the exhaust air temperature of the multi-stage turbine is not lower than 125 DEG C, and the humidity is not higher than 100 g H2O / kg dry air, the exhaust air temperature of the single-stage turbine is lower than 125 DEG C, and the humidity is higher than 100 g H2O / kg dry air.

[0022] Further, in the second air supply channel, the temperature of the fresh air in the first air supply section is 55 DEG C-65 DEG C.

[0023] Further, in the second air supply channel, the temperature of the fresh air in the second air supply section is 70 DEG C-80 DEG C.

[0024] Further, in the second air supply channel, the temperature of the fresh air in the third air supply section is 88 DEG C-95 DEG C.

[0025] Further, the temperature of the mixed air is 112 DEG C-114 DEG C, and the humidity is 44 g-54 g H2O / kg dry air.

[0026] The present application has the following advantages: the exhaust air of the multi-stage turbine with low humidity and high temperature is directly supplied into the air hood without heat exchange, and is directly used, the exhaust air has no heat loss, the exhaust air with high humidity and high temperature is used to preheat the exhaust air of the air hood, and energy utilization is realized;

[0027] The axial flow fan and the centrifugal fan are used as two independent exhaust air channels to complete the exhaust air of the air hood, a part of the exhaust air is mixed with the exhaust air of the turbine to increase the temperature of the mixed air, the temperature of the mixed air is higher after the preliminary heat exchange with the room temperature air, energy utilization is improved, and the working pressure of the heat exchanger is reduced, and the exhaust air can continue to work when one of the fans is damaged;

[0028] The room temperature fresh air is heat exchanged for three times to form dry hot air with low humidity and high temperature, and the exhaust air of the turbine with low humidity and high temperature is mixed in the air hood, the air humidity of the mixed area is neutralized, and the temperature and humidity requirements of the air supply are met;

[0029] The whole ventilation process does not participate in the air heat exchange of the new steam, the steam required for heat exchange is not needed, investment cost, operation cost and maintenance cost are reduced;

[0030] The use number of the heat recovery device is saved, the air resistance is reduced, the ventilation system is more simple, and the power consumption of the air supply and exhaust is reduced by more than 25%. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 The ventilation system diagram of the closed air hood of the high-speed paper machine.

[0032] In the figure: 1-first exhaust duct, 11-axial fan, 2-first air supply duct, 3-second exhaust duct, 31-first centrifugal fan, 4-second air supply duct, 41-first heat exchanger, 42-second heat exchanger, 43-third heat exchanger, 44-second centrifugal fan, 4a-first air supply section, 4b-second air supply section, 4c-third air supply section, 5-fresh air duct, 6-preheating duct. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0034] First of all, it should be noted that the turbine used for turbine exhaust is used to extract air when dehydrating papermaking pulp, playing the role of extracting air and dehydrating the pulp. Due to the high speed of the turbine, the exhaust temperature of the turbine is relatively high. Generally, the temperature of the turbine exhaust is above 110°C, and the exhaust temperature of the turbine in different working areas is also different. According to the requirements of the water suction box, the turbine can be divided into single-stage turbine and multi-stage turbine; single-stage turbine generally has lower temperature and higher humidity, while multi-stage turbine is just the opposite. Therefore, the exhaust of single-stage turbine and multi-stage turbine is separately collected and sent to the corresponding channel to achieve the secondary utilization of the turbine exhaust.

[0035] Please see the attached Figure 1 The present invention first proposes a turbine air supply and exhaust system, including a first exhaust channel 1, a first air supply channel 2, a second exhaust channel 3, a second air supply channel 4, a fresh air channel 5 and a preheating channel 6.

[0036] In the first exhaust channel 1, one end of the first exhaust channel 1 is directly connected to the air hood, and an axial flow fan 11 is arranged in the first exhaust channel 1 so that the air in the first part of the air hood with a temperature of 80℃-85℃ is directly drawn out of the air hood by the axial flow fan 11 and discharged through the first exhaust channel 1.

[0037] In the first air supply channel 2, one end of the first air supply channel 2 is directly connected to the air hood, and the other end is connected to the exhaust port of the multi-stage turbine. The exhaust air of the multi-stage turbine (the exhaust air temperature is not lower than 125°C and the humidity is not higher than 100g H2O / kg dry air) enters the air hood through the first air supply channel 2.

[0038] The second exhaust duct 3, the second air supply duct 4, the fresh air duct 5 and the preheating duct 6 work in coordination. The second air supply duct 4 is sequentially arranged with a first heat exchanger 41, a second heat exchanger 42 and a third heat exchanger 43. The second air supply duct 4 includes a first air supply section 4a, a second air supply section 4b and a third air supply section 4c.

[0039] One end of the second exhaust air passage 3 is directly connected to the air hood, the other end is connected to the inlet of the first heat exchange passage of the first heat exchanger 41, and the first centrifugal fan 31 is arranged in the second exhaust air passage 3. The first centrifugal fan 31 makes the second part of the air in the air hood at 80-85℃ enter the first heat exchange passage of the first heat exchanger 41 through the second exhaust air passage 3, and finally is discharged from the outlet of the first heat exchange passage of the first heat exchanger 41;

[0040] One end of the new air passage 5 is connected to the inlet of the second heat exchange passage of the first heat exchanger 41, so that the air at room temperature is sucked into the second heat exchange passage of the first heat exchanger 41;

[0041] One end of the preheating passage 6 is connected to the first heat exchange passage of the first heat exchanger 41, and the other end is connected to the exhaust port of the single-stage turbine. The exhaust air (air temperature is lower than 125℃, humidity is higher than 100g H2O / kg dry air) of the single-stage turbine enters the first heat exchange passage of the first heat exchanger 41 through the preheating passage 6. The air in the new air passage 5 exchanges heat with the air in the second exhaust air passage 3 and the air in the preheating passage 6 respectively, and the preliminary heating is completed;

[0042] One end of the supply air first section 4a is connected to the outlet of the second heat exchange passage of the first heat exchanger 41, and the other end is connected to the inlet of the second heat exchange passage of the second heat exchanger 42. The air (air temperature is 55-65℃) preliminarily heated after heat exchange enters the second heat exchange passage of the second heat exchanger 42 through the supply air first section 4a, exchanges heat with the medium in the first heat exchange passage of the second heat exchanger 42, and the air heated again after heat exchange is discharged from the outlet of the second heat exchange passage of the second heat exchanger 42;

[0043] One end of the supply air second section 4b is connected to the outlet of the second heat exchange passage of the second heat exchanger 42, and the other end is connected to the inlet of the second heat exchange passage of the third heat exchanger 43. The air (air temperature is 70-80℃) heated again after heat exchange enters the second heat exchange passage of the third heat exchanger 43 through the supply air second section 4b, exchanges heat with the medium in the first heat exchange passage of the third heat exchanger 43, and the air heated three times after heat exchange is discharged from the outlet of the second heat exchange passage of the third heat exchanger 43;

[0044] The centrifugal fan 44 is arranged on the air supply third section 4c, one end of the air supply third section 4c is directly connected with the air hood, the other end is connected with the outlet of the second heat exchange channel of the third heat exchanger 43, and the second centrifugal fan 44 is arranged in the air supply third section 4c, the second centrifugal fan 44 sends the air after the third heat exchange (i.e. the air with a temperature of 88-95℃) into the air hood through the air supply third section 4c, and the position of the air supply third section 4c connected with the air hood is on the same side of the mixing area in the air hood as the position of the first air supply channel 2 connected with the air hood, so that the two parts of the air supply are preliminarily mixed and evenly before the air supply in the air hood generates the ventilation effect, and the temperature and humidity of the two parts of the air are neutralized.

[0045] In some embodiments, the centrifugal fan 44 can be arranged on the air supply first section 4a and the air supply second section 4b, as long as the fresh air can be smoothly pumped.

[0046] From the arrangement of the turbine exhaust air supply system, it can be seen that the exhaust air of the air hood is divided into two parts: the axial flow fan 11 directly extracts a part of the wet air in the air hood, and the first centrifugal fan 31 extracts another part of the wet air in the air hood; originally, the centrifugal fan is used for the exhaust air of the air hood, but due to the high power consumption and large air pressure of the centrifugal fan, the air pressure of the axial flow fan 11 is low and the running air resistance is small, so the axial flow fan 11 and the first centrifugal fan 31 are combined to reduce part of the power consumption; the first centrifugal fan 31 pumps another part of the wet air in the air hood to the first heat exchange channel of the first heat exchanger 41 to make it as the heat source for the first heat exchange of the room temperature air, so that the exhaust air of the air hood is completed and the heat recovery of the part of the exhaust air is realized. Another part of the exhaust air of the air hood still uses the centrifugal fan to ensure the balance of the temperature and the air volume in the air hood; during the system design, the axial flow fan and the centrifugal fan are both controlled by frequency conversion, and in addition, the axial flow fan and the centrifugal fan have a certain design margin in the air volume design, so the frequency of the fan can be adjusted according to the production needs to realize the switching of the air volume.

[0047] From the arrangement of the turbine exhaust air supply system, it can be seen that the exhaust air of the air hood is divided into two parts: the axial flow fan 11 directly extracts a part of the wet air in the air hood, and the first centrifugal fan 31 extracts another part of the wet air in the air hood; originally, the centrifugal fan is used for the exhaust air of the air hood, but due to the high power consumption and large air pressure of the centrifugal fan, the air pressure of the axial flow fan 11 is low and the running air resistance is small, so the axial flow fan 11 and the first centrifugal fan 31 are combined to reduce part of the power consumption; the first centrifugal fan 31 pumps another part of the wet air in the air hood to the first heat exchange channel of the first heat exchanger 41 to make it as the heat source for the first heat exchange of the room temperature air, so that the exhaust air of the air hood is completed and the heat recovery of the part of the exhaust air is realized. Another part of the exhaust air of the air hood still uses the centrifugal fan to ensure the balance of the temperature and the air volume in the air hood; during the system design, the axial flow fan and the centrifugal fan are both controlled by frequency conversion, and in addition, the axial flow fan and the centrifugal fan have a certain design margin in the air volume design, so the frequency of the fan can be adjusted according to the production needs to realize the switching of the air volume.

[0048] From the arrangement of the turbine exhaust system, the single-stage turbine exhaust is sent to the first heat exchange channel of the first heat exchanger 41 to preheat the fresh air, achieving the effect of temperature compensation. Generally, the hood exhaust temperature is between 80-85℃, and the single-stage turbine exhaust temperature is between 110-125℃. The turbine exhaust temperature sent to the first heat exchanger 41 is higher than the hood exhaust temperature. The temperature of the fresh air after heat exchange with the hood exhaust increases, and the temperature after heat exchange with the hood exhaust increases more stably, achieving the reuse of waste energy and reducing the temperature difference between the first heated air and the second heat exchanger 42 and the third heat exchanger 43, thereby improving the energy-saving effect.

[0049] In an embodiment, the first heat exchange channel of the first heat exchanger 41 is divided into a first heat exchange part and a second heat exchange part, and the second exhaust channel 3 is connected to the first heat exchange part, and the preheating channel is connected to the second heat exchange part. The second heat exchange channel of the first heat exchanger 41 passes through the first heat exchange part and the second heat exchange part in sequence, so that the fresh air is gradually heated.

[0050] In a specific embodiment, the first heat exchange part and the second heat exchange part are connected in parallel, and the outlet of the first heat exchange part and the outlet of the second heat exchange part are independent of each other. The air passing through the first heat exchange part and the air passing through the second heat exchange part are respectively discharged independently, and are independent of each other, thereby reducing the safety hidden danger caused by gas cross.

[0051] In another specific embodiment, the first heat exchange part and the second heat exchange part are connected in parallel, and the outlet of the second heat exchange part is combined with the outlet of the second heat exchange part. The air passing through the first heat exchange part and the air passing through the second heat exchange part are respectively combined and discharged after heat exchange with the fresh air, thereby reducing the number of pipeline arrangements and the space occupancy rate.

[0052] In still another specific embodiment, the first heat exchange part and the second heat exchange part are connected in series. The exhaust gas in the first heat exchange part is mixed with the exhaust gas in the second heat exchange part while being heat-exchanged with the fresh air, and then discharged from the outlet of the second heat exchange part. This design also has the effect of heating the fresh air, but since the mixed gas temperature is unstable when the two exhaust gases are mixed, it is easy to affect the heating effect of the fresh air.

[0053] In the second air supply channel 4, the condensate water in the first heat exchange channel of the second heat exchanger 42 is heat-exchanged with the fresh air in the second channel thereof, so that the fresh air is heated for the second time. Generally, the condensate water is mainly derived from the drying cylinder for heating the paper web, and we use this part of the condensate water for the second heat exchange, thereby saving part of the energy consumption.

[0054] In the second air supply channel 4, the flash steam in the first heat exchange channel of the third heat exchanger 43 is heat-exchanged with the fresh air in the second channel thereof, so that the fresh air is heated for the third time. The fresh air heated for the third time is dry air with a temperature of 88-95℃.

[0055] The third temperature rising process is different from the prior art, and the flash steam in the first heat exchange channel during the third temperature rising is derived from the condensed water formed after the drying cylinder heats the paper, and the flash steam is formed due to the pressure reduction of the condensed water when the condensed water enters the condensed water pipe. The flash steam cannot be used at other positions, and is generally directly discharged, causing energy waste. Therefore, the flash steam is used in the third temperature rising of the fresh air, replacing the original steam heating step, so that the waste energy is reused, and the fresh air is not heated by steam in the whole temperature rising stage, so that the energy is greatly saved and the cost is reduced.

[0056] In an embodiment, the air hood air supply outlets and the air hood air exhaust inlets are respectively located on two sides of the drying part in the air hood.

[0057] In a specific embodiment, the first air supply channel 2 and the second air supply channel 4 correspond to two air hood air supply outlets respectively, one air hood air supply outlet is uniformly distributed with a plurality of air outlet pipes along the length direction of the air hood, and the multi-stage turbine exhaust enters the air hood from the plurality of air outlet pipes, and the other air hood air supply outlet is uniformly distributed with a plurality of air outlet nozzles along the length direction of the air hood, and the fresh air after the third temperature rising enters the air hood from the air outlet nozzles; wherein the air outlet nozzles are located downstream of the air supply outlet, so that the multi-stage turbine exhaust does temperature compensation for the dry air after the third temperature rising.

[0058] In a specific embodiment, the first air exhaust channel 1 and the second air exhaust channel 3 correspond to two air hood air exhausts respectively, and a louver is arranged at each air hood air exhaust for filtering impurities in the exhaust air.

[0059] In a specific embodiment, the air hood ventilation process is as follows: during exhaust, the axial flow fan 11 and the first centrifugal fan 31 cooperate to extract the air in the air hood at 80-85°C and 150-170 g H2O / kg dry air, respectively, and the air in the air hood extracted by the first centrifugal fan 31 is sent to the first heat exchange channel of the first heat exchanger 41; during air supply, the exhaust of the multi-stage turbine is sent to the air hood for direct use, the exhaust of the single-stage turbine at 110°C and higher than 110 g H2O / kg dry air is sent to the first heat exchange channel of the first heat exchanger 41, and the new air is extracted by the second centrifugal fan 44 for three-stage heat exchange; during the heat exchange process, the temperature and humidity of the new air after the first heat exchange are 65°C and 25 g H2O / kg dry air, respectively, the temperature and humidity of the new air after the second heat exchange are 82°C and 25 g H2O / kg dry air, respectively, and the temperature and humidity of the new air after the third heat exchange are 90°C and 25 g H2O / kg dry air, respectively, and the new air after the three heat exchanges has high temperature and low humidity, which meets the air supply requirements, and the 90°C air after the three heat exchanges enters the air hood and mixes with the multi-stage turbine exhaust at 125°C and 100 g H2O / kg dry air in the mixing area on one side of the air hood, so as to adjust the temperature and humidity of the air entering the drying part in the air hood and balance the exhaust air volume and the supply air volume of the air hood.

[0060] On the other hand, the application also proposes a high-speed paper machine closed air hood ventilation method, which is realized by a turbine exhaust and supply system and is divided into two aspects of air hood exhaust and two aspects of air hood air supply; the first aspect of air hood exhaust is to extract the air with high moisture content in the air hood through the first exhaust channel 1 by the axial flow fan 11; the second aspect of air hood exhaust is to extract the air with high moisture content in the air hood through the second exhaust channel 3 by the first centrifugal fan 31, send it to the first heat exchange channel of the first heat exchanger 41, and finally exhaust it from the outlet of the first heat exchange channel of the first heat exchanger 41; the first aspect of air hood air supply is to send the exhaust of the multi-stage turbine from the first air supply channel 2 to the air hood; the second aspect of air hood air supply is to extract the new air at room temperature through the new air channel 5 and the second air supply channel 4 by the second centrifugal fan 44 to the air hood, and the new air is heated through three-stage heat exchange between the first heat exchanger 41, the second heat exchanger 42, and the third heat exchanger 43, mixed with the first aspect of air hood air supply in the air hood to form mixed air with a temperature of 110-115°C and a humidity of 40-60 g H2O / kg dry air, and then blown to the drying part in the air hood.

[0061] Specifically, the exhaust air temperature of the multi-stage turbine is not lower than 125℃, and the humidity is not higher than 100g H2O / kg dry air, the exhaust air temperature of the single-stage turbine is lower than 125℃, and the humidity is higher than 100g H2O / kg dry air.

[0062] Specifically, in the second air supply channel 4, the temperature of the fresh air in the first air supply section 4a is 55℃-65℃.

[0063] Specifically, in the second air supply channel 4, the temperature of the fresh air in the second air supply section 4b is 70℃-80℃.

[0064] Specifically, in the second air supply channel 4, the temperature of the fresh air in the third air supply section 4c is 88℃-95℃.

[0065] Specifically, the temperature of the mixed air is 112℃-114℃, and the humidity is 44g-54g H2O / kg dry air.

[0066] Since the source of the final mixed air is room temperature air + exhaust air of the multi-stage turbine, the comprehensive humidity of the mixed air has a certain floating interval, but as long as the humidity of the mixed air is within a reasonable range, it does not affect the air supply and exhaust process of the closed hood.

[0067] This ventilation method not only saves the operation of steam heating, but also reduces the number of heat recovery devices, saves energy and energy consumption, and part of the exhaust air and part of the supply air are independent channels, making the layout of the heat recovery system more simple and convenient to maintain; the originally prepared energy is reused, the energy utilization rate is improved, it is more energy-saving and environmentally friendly, and the comprehensive effect of the closed hood ventilation in energy saving, power consumption and environmental protection is improved.

[0068] Finally, it should be explained that the above specific embodiments are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail with reference to examples, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the present application, and they should be covered in the scope of the claims of the present application.

Claims

1. A turbine air supply and exhaust system for supplying and exhausting air in a closed air hood, characterized by: It comprises a first exhaust passage (1), a first air supply passage (2), a second exhaust passage (3), a second air supply passage (4), a fresh air passage (5) and a preheating passage (6); One end of the first exhaust channel (1) is directly connected to the air hood, and an axial flow fan (11) is provided in the first exhaust channel (1); One end of the first air supply channel (2) is directly connected to the air hood, and the other end is connected to the exhaust port of the multi-stage turbine. The exhaust air of the multi-stage turbine enters the air hood through the first air supply channel (2). The second air supply channel (4) is sequentially arranged with a first heat exchanger (41), a second heat exchanger (42) and a third heat exchanger (43); one end of the second air exhaust channel (3) is directly connected to the air hood, and the other end is connected to the inlet of the first heat exchange channel of the first heat exchanger (41); a first centrifugal fan (31) is provided in the second air exhaust channel (3); one end of the fresh air channel (5) is connected to the inlet of the second heat exchange channel of the first heat exchanger (41); one end of the preheating channel (6) is connected to the first heat exchange channel of the first heat exchanger (41), and the other end is connected to the exhaust port of the single-stage turbine; the exhaust air of the single-stage turbine enters the first heat exchange channel of the first heat exchanger (41) through the preheating channel (6); Wherein, the second air supply channel (4) includes an air supply section (4a), an air supply section (4b) and an air supply section (4c); one end of the air supply section (4a) is connected to the outlet of the second heat exchange channel of the first heat exchanger (41), and the other end is connected to the inlet of the second heat exchange channel of the second heat exchanger (42); one end of the air supply section (4b) is connected to the outlet of the second heat exchange channel of the second heat exchanger (42), and the other end is connected to the inlet of the second heat exchange channel of the third heat exchanger (43); one end of the air supply section (4c) is directly connected to the air hood, and the other end is connected to the outlet of the second heat exchange channel of the third heat exchanger (43); A second centrifugal fan (44) is arranged in the second air supply channel (4).

2. The turbine air supply and exhaust system according to claim 1, characterized in that: The second heat exchanger (42) is a condensate heat exchanger.

3. The turbine air supply and exhaust system according to claim 1, characterized in that: The third heat exchanger (43) is a flash steam heat exchanger.

4. A method for ventilating a high-speed papermaking confidential airtight hood, implemented by the turbine air supply and exhaust system according to any one of claims 1 to 3, characterized in that: The hood exhausts air in two ways. In the first aspect, the hood exhaust is performed by an axial flow fan (11) to extract the air with high humidity in the hood through the first exhaust channel (1); On the other hand, the air hood exhaust uses the first centrifugal fan (31) to extract the air with high humidity in the air hood through the second exhaust channel (3), sends it into the first heat exchange channel of the first heat exchanger (41), and finally discharges it from the outlet of the first heat exchange channel of the first heat exchanger (41); The hood supplies air in two directions. In the first aspect, the air hood air supply sends the exhaust air of the multi-stage turbine into the air hood through the first air supply channel (2); The second air hood air supply is supplied by the second centrifugal fan (44) to draw fresh air at room temperature into the air hood through the fresh air channel (5) and the second air supply channel (4). The fresh air is heated by three stages of heat exchange between the first heat exchanger (41), the second heat exchanger (42), and the third heat exchanger (43). The fresh air is mixed with the first air hood air supply in the air hood to form mixed air with a temperature of 110°C-115°C and a humidity of 40g-60g H2O / kg dry air, and then blown to the drying part in the air hood.

5. The high-speed papermaking confidential airtight hood ventilation method according to claim 4, characterized in that: The exhaust temperature of the multi-stage turbine is not lower than 125°C and the humidity is not higher than 100g H2O / kg dry air. The exhaust temperature of the single-stage turbine is lower than 125°C and the humidity is higher than 100gH2O / kg dry air.

6. The high-speed papermaking confidential airtight hood ventilation method according to claim 4 is characterized in that: In the second air supply channel (4), the temperature of the fresh air in the air supply section (4a) is 55°C-65°C.

7. The high-speed papermaking confidential airtight hood ventilation method according to claim 4, characterized in that: In the second air supply channel (4), the temperature of the fresh air in the second air supply section (4b) is 70°C-80°C.

8. The high-speed papermaking confidential airtight hood ventilation method according to claim 4 is characterized in that: In the second air supply channel (4), the temperature of the fresh air in the third air supply section (4c) is 88°C-95°C.

9. The high-speed papermaking confidential airtight hood ventilation method according to claim 4, characterized in that: The temperature of the mixed air is 112°C-114°C, and the humidity is 44g-54g H2O / kg dry air.

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