CN111058329B - Air recirculation system and method for a dryer section of a board or paper machine - Google Patents
Air recirculation system and method for a dryer section of a board or paper machine Download PDFInfo
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- CN111058329B CN111058329B CN201811239440.7A CN201811239440A CN111058329B CN 111058329 B CN111058329 B CN 111058329B CN 201811239440 A CN201811239440 A CN 201811239440A CN 111058329 B CN111058329 B CN 111058329B
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- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
- D21F5/00—Dryer section of machines for making continuous webs of paper
- D21F5/20—Waste heat recovery
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/10—Greenhouse gas [GHG] capture, material saving, heat recovery or other energy efficient measures, e.g. motor control, characterised by manufacturing processes, e.g. for rolling metal or metal working
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Abstract
Air recirculation system and method for a dryer section of a board or paper machine. The system comprises at least three air recirculation sections, which are connected to the dryer section hood one by one in the travelling direction of the web-like material. Each of which includes a heat recovery unit comprising a circulating air fan and an air-to-fluid heat exchanger to draw moist exhaust air from the dryer section hood through the heat recovery unit and supply at least a portion of the conditioned moist exhaust air to the dryer section hood, and to condition by cooling and reducing the moisture content of the moist exhaust air. The air-to-fluid heat exchanger comprises a fluid circuit connected to a fluid cooling unit and a spraying unit connected to clean humid exhaust air. The first, second and third air recirculation components are connected to the beginning, middle and end of the dryer section hood, respectively. The system and method of the present invention is effective and energy efficient, reducing the amount of exhaust gas flow to the atmosphere.
Description
Technical Field
The present invention relates to an air recirculation system and method for a dryer section of a board or paper machine, and more particularly to a dryer section, in which water from a moving web-like material is evaporated to the air during operation of the board or paper machine to produce humid exhaust air.
Background
Drying of web-like material in the dryer section or sections of a board or paper machine is an energy intensive operation due to the high latent heat of evaporation. Water from the moving web-like material evaporates into the surrounding hot air to produce moisture-laden exhaust air.
It is known to recover heat from moisture laden exhaust gases. For example, fresh supply air may be preheated or heated by moisture laden exhaust gas. The cooled moisture laden exhaust gas is then discharged to the atmosphere. The cooled, moisture laden exhaust stream produces emissions when it is discharged to the atmosphere. Even a clean water vapor exhaust plume is unacceptable, even in some areas. Visible water vapor plumes may be of interest to people living near the plant. In addition, plume-induced fogging and icing cause accident risks and may harm crops and equipment.
Therefore, there is a need for an efficient and energy-efficient system and method for recirculating air in the dryer section of a board or paper machine, and which also reduces the amount of exhaust air flow discharged to the atmosphere.
Disclosure of Invention
It is an object of the present invention to provide an air recirculation system and a method for a dryer section of a board or paper machine that solves or at least alleviates the drawbacks of the prior art. The object of the invention is achieved by the following air recirculation system for a dryer section of a board or paper machine. The object of the invention is also achieved by the following method for air recirculation for a dryer section of a board or paper machine.
Preferred embodiments of the invention are disclosed below.
The invention is based on the concept of an air recirculation system for the dryer section of a board or paper machine. During operation of a board or paper machine, in the dryer section, water from the moving web-like material evaporates to the air to produce moist exhaust air. The system comprises at least three air recirculation components which are connected to the dryer section hood one after the other in the travelling direction of the web-like material. Each air recirculation component includes one or more heat recovery units. Each heat recovery unit comprises a circulating air fan for drawing the humid exhaust gas from the dryer section hood through the heat recovery unit and for supplying at least a portion of the conditioned humid exhaust gas to the dryer section hood, an air-to-fluid heat exchanger for conditioning the humid exhaust gas by cooling and reducing the moisture content of the humid exhaust gas, and a spraying unit connected with the air-to-fluid heat exchanger for cleaning the humid exhaust gas. The air-to-fluid heat exchanger includes a fluid circuit connected to a fluid cooling unit. The first air recirculation part is connected to the beginning of the dryer section hood, the second air recirculation part is connected to the middle of the dryer section hood, and the third air recirculation part is connected to the end of the dryer section hood.
During operation of a board or paper machine, the dryer section hood comprises several zones in the travelling direction of the web-like material, in which zones the moisture content of the exhaust gases is at different levels. In the system and method, the dryer section hood includes at least three zones. In the beginning of the dryer section hood is a zone where the moisture content of the exhaust gases is low, since the web-like material is heating up. In the beginning of the hood of the dryer section, the evaporation rate is generally 0 to 20kg/m2h. In the middle of the dryer section hood is a zone where the moisture content of the exhaust gases is high due to the high evaporation rate of the web-like material. In the middle of the dryer section hood, the evaporation rate is generally 20-40 kg/m2h. In the end of the dryer section hood is a zone where the moisture content of the exhaust gases is again lower due to the reduced drying rate of the web-like material. In the end of the hood of the dryer section, the evaporation rate is generally 20-0 kg/m2h. The beginning and the end of the dryer section hood therefore comprise regions in which the moisture content of the exhaust gases is lower than in the region in the middle of the dryer section hood. These areas are preferably defined by the evaporation rate and may be separated by lightweight walls such as flaps. However, the zones need not be separated from each other by a dividing wall configured to restrict movement of humid exhaust air from one zone to another.
In the system and method, moist exhaust air is conditioned by cooling and drying and cleaning, which moist exhaust air removes water vapour evaporated from the web-like material from a dryer section hood in the dryer section, and at least a part of the conditioned moist exhaust air is recirculated to the dryer section hood as supply air.
With the system and method, regions having different moisture content levels inside the dryer section hood can be individually manipulated to produce humid exhaust air at different moisture content levels. Each zone may be provided with supply air, i.e. conditioned humid exhaust air, to have a temperature and moisture content independent of the other zone. In the middle of the dryer section hood, the temperature and humidity of the supplied air, i.e. the conditioned humid exhaust gas, are preferably higher than in the other areas.
While the air recirculation in the heat recovery unit also makes it possible to completely or largely shut down the air recirculation system, it is only necessary to provide one circulating air fan for each heat recovery unit.
The dryer section hood is an enclosure surrounding the dryer in the drying section. The positions of the dryer section hood, for example in the beginning, in the middle and in the end of the dryer section hood, are defined in the direction of travel of the web-like material in the length direction of the dryer section hood. Web-like materials include, for example, paper webs, cardboard webs or fiber webs. The cooling fluid flowing in the fluid circuits of the air-to-fluid heat exchanger and the second air-to-fluid heat exchanger comprises for example a water-glycol mixture or a liquid having a low freezing point, for example below-15 ℃.
The fluid cooling unit may comprise a cooling tower and/or a heat driven heat pump. The heat driven heat pump uses humid exhaust gas having a higher temperature as a heat source, and in addition, the heat driven heat pump may provide cooling to the humid exhaust gas to have a lower temperature.
The fluid cooling unit may comprise an absorption chiller. The fluid loop of the air-to-fluid heat exchanger of the second air recirculation component connected to the middle of the dryer section hood is connected to the one or more generators of the absorption chiller for driving the absorption chiller. The fluid loop of the air-to-fluid heat exchanger of the first air recirculation component and/or the third air recirculation component is connected to the one or more evaporators of the absorption chillers.
The absorption chiller utilizes the humid exhaust gas having a higher temperature as a heat source and provides cooling to the humid exhaust gas to have a lower temperature. The moisture content of the exhaust gases is lower in the beginning and end of the dryer section hood than in the region in the middle of the dryer section hood, and the moist exhaust gases are conditioned by providing cooling, so that the moisture content of the conditioned moist exhaust gases is further reduced. Since the dryer section hood requires an amount of 55% to 80% of the humid exhaust gas flow to be supplied as dry heated supply air, a portion of the conditioned humid exhaust gas is discharged to the atmosphere. The main part of the exiting conditioned humid exhaust gas is preferably discharged from the beginning and end of the dryer section hood. Thus, the reduced moisture content of the conditioned humid exhaust gas reduces the risk of visible water vapour plumes.
The fluid cooling unit may comprise a heat driven heat pump and the fluid circuit of the air-to-fluid heat exchanger of the second air recirculating part is connected to one or more generators of the heat driven heat pump for driving the heat driven heat pump. During operation of the heat-driven heat pump, one or more evaporators of the heat-driven heat pump generate cooling power. Furthermore, the fluid circuit of the air-to-fluid heat exchanger of the first air recirculation part and/or the third air recirculation part may be connected to one or more evaporators of the heat driven heat pump. In this case, the heat driven heat pump generates cooling power to the air recirculation system. Furthermore, the evaporator or evaporators of the heat driven heat pump may comprise an inlet connection and an outlet connection to the cooling water network of the paper or pulp production plant for providing cooling water for treatment and building cooling purposes. In this case, the heat driven heat pump generates cooling power to a paper or pulp production plant comprising an air recirculation system.
The fluid cooling unit may include a heat driven heat pump and a cooling tower. The fluid circuit of the air-to-fluid heat exchanger of the heat recovery unit of the second air recirculation part is connected to the heat driven heat pump for driving the heat driven heat pump. The heat driven heat pump is connected to the cooling fluid circuit of the cooling tower for releasing heat from the heat driven heat pump to the cooling fluid. The heat collected from the hot humid exhaust gas drawn from the middle of the dryer section hood, where the web-like material has a high evaporation rate, is used to drive a heat driven heat pump.
The heat recovery unit may further comprise an air-to-air heat exchanger for heating the conditioned humid exhaust gas flowing out of the air-to-air heat exchanger with the humid exhaust gas, a spraying unit connected to the air-to-air heat exchanger for cleaning the humid exhaust gas, and a heater for heating the conditioned humid exhaust gas flowing out of the air-to-air heat exchanger before at least a portion of the conditioned humid exhaust gas is supplied to the dryer section hood.
The heat recovery unit may further comprise a heater for heating the conditioned humid exhaust gas before it is supplied to the dryer section hood, and a second air-to-fluid heat exchanger comprising a second fluid circuit connected to the cooling fluid circuit of the heat driven heat pump, wherein the cooling fluid enters the heat driven heat pump at a lower temperature than the second air-to-fluid heat exchanger.
The second air recirculation component connected to the middle of the dryer section hood may include two heat recovery units. The heat recovery unit further comprises an air-to-air heat exchanger for heating conditioned humid exhaust gas flowing from the air-to-air heat exchanger with humid exhaust gas, a spraying unit connected to the air-to-air heat exchanger for cleaning the humid exhaust gas, and a heater for heating the conditioned humid exhaust gas flowing from the air-to-air heat exchanger before at least a portion of the conditioned humid exhaust gas is supplied to the dryer section hood. The fluid cooling unit may comprise a heat driven heat pump and the fluid circuits of the air-to-fluid heat exchangers of both heat recovery units are connected to one or more generators of the heat driven heat pump for driving the heat driven heat pump. Furthermore, the fluid circuits of the air-to-fluid heat exchangers of the two heat recovery units may be connected in parallel to the fluid cooling unit.
During operation of a board or paper machine, the dryer section hood may comprise at least three zones inside the dryer section hood in the travelling direction of the web-like material, one after the other, which zones comprise exhaust gases at different moisture content levels.
The at least three zones are located to the beginning, middle and end of the dryer section hood. In the system, a first air recirculation part is arranged to recirculate humid exhaust air from a zone located at the beginning, a second air recirculation part is arranged to recirculate humid exhaust air from a zone located in the middle, and a third air recirculation part is arranged to recirculate humid exhaust air from a zone located at the end.
The invention is based on the concept of an air recirculation method for a dryer section of a board or paper machine and in which, during operation of the board or paper machine, water from a moving web-like material evaporates to the air to produce humid exhaust air. The method comprises at least three air recirculation components which are connected to the dryer section hood one after the other in the travelling direction of the web-like material. Each air recirculation component includes one or more heat recovery units. Each heat recovery unit includes a circulating air fan and an air-to-fluid heat exchanger. The circulating air fan draws moist exhaust air from the dryer section hood through the heat recovery unit and supplies at least a portion of the conditioned moist exhaust air to the dryer section hood. The air-to-fluid heat exchanger conditions the humid exhaust gas by cooling and reducing the moisture content of the humid exhaust gas. The fluid circuit of the air-to-fluid heat exchanger is connected to the fluid cooling unit, and the fluid in the fluid circuit of the air-to-fluid heat exchanger is cooled in the fluid cooling unit. A spray unit connected to the air-to-fluid heat exchanger cleans the humid exhaust gas. The first air recirculation part is connected to the beginning of the dryer section hood, and the first circulation air fan draws in humid exhaust air and supplies at least a portion of the conditioned humid exhaust air to the beginning of the dryer section hood. The second air recirculation component is connected to a middle portion of the dryer section hood, and the second recirculation air fan draws in the humid exhaust air and supplies at least a portion of the conditioned humid exhaust air to the middle portion of the dryer section hood. A third air recirculation component is connected to an end of the dryer section hood, and a third recirculation air fan draws moist exhaust air and supplies at least a portion of the conditioned moist exhaust air to the end of the dryer section hood.
During operation of a board or paper machine, the amount of water from the web-like material evaporating to the air may vary in the dryer section hood in the direction of travel of the web-like material. At least three zones generating exhaust gases at different moisture content levels are arranged inside the dryer section hood one after the other in the travelling direction of the web-like material. The at least three zones are located at a beginning of the dryer section hood, a middle of the dryer section hood, and an end of the dryer section hood. In the method, a first air recirculation part recirculates humid exhaust gas from a zone located at the beginning, a second air recirculation part recirculates humid exhaust gas from a zone located in the middle, and a third air recirculation part recirculates humid exhaust gas from a zone located at the end of the dryer section hood.
The fluid cooling unit may comprise a cooling tower. A fluid circuit of the air-to-fluid heat exchanger is connected to the cooling tower, and fluid in the fluid circuit is cooled in the cooling tower.
The fluid cooling unit may comprise a heat driven heat pump. The fluid circuit of the air-to-fluid heat exchanger of the second air recirculating component is connected to one or more generators of the heat driven heat pump, and the fluid in the fluid circuit of the air-to-fluid heat exchanger of the second air recirculating component is cooled in the heat driven heat pump by driving the heat driven heat pump.
The fluid cooling unit may include a heat driven heat pump and a cooling tower. The fluid in the fluid circuit of the air-to-fluid heat exchanger of the heat recovery unit of the second air recirculation section flows to the heat driven heat pump for driving the heat driven heat pump. The cooling fluid in the cooling fluid circuit of the cooling tower flows to the heat driven heat pump, and the heat driven heat pump releases heat to the cooling fluid.
Furthermore, the heat recovery unit may further comprise a heater and a second air-to-fluid heat exchanger comprising a second fluid circuit connected to the cooling fluid circuit of the heat driven heat pump. The heater heats the conditioned humid exhaust gas before supplying at least a portion of the conditioned humid exhaust gas to the dryer section hood. The fluid in the second fluid circuit of the second air-to-fluid heat exchanger cools the conditioned humid exhaust gas flowing out of the air-to-fluid heat exchanger in the second air-to-fluid heat exchanger, and the fluid in the second fluid circuit of the second air-to-fluid heat exchanger enters the heat driven heat pump at a lower temperature than the temperature of the fluid entering the second air-to-fluid heat exchanger.
The fluid cooling unit may comprise an absorption chiller. The fluid loop of the air-to-fluid heat exchanger of the second air recirculation component is connected to one or more generators of the absorption chiller. The fluid in the fluid circuit of the air-to-fluid heat exchanger of the second air recirculation component is cooled in one or more generators of the absorption chiller by driving the absorption chiller. The fluid loop of the air-to-fluid heat exchanger of the first air recirculation component and/or the third air recirculation component is connected to the one or more evaporators of the absorption chillers. The fluid in the fluid circuit of the air-to-fluid heat exchanger of the first air recirculation component and/or the third air recirculation component is cooled in one or more evaporators of the absorption chiller.
The heat recovery unit may further include an air-to-air heat exchanger, a spray unit connected to the air-to-air heat exchanger, and a heater. The conditioned humid exhaust gas flowing out of the air-to-air heat exchanger is heated in the air-to-air heat exchanger by the humid exhaust gas drawn from the dryer section hood, the spray unit cleans the humid exhaust gas by spraying a cleaning liquid, and the heater heats the conditioned humid exhaust gas flowing out of the air-to-air heat exchanger before at least a portion of the conditioned humid exhaust gas is supplied to the dryer section hood.
The fluid cooling unit may comprise a heat driven heat pump and the fluid circuit of the air-to-fluid heat exchanger of the second air recirculation section is connected to one or more generators of the heat driven heat pump. The fluid in the fluid circuit of the air-to-fluid heat exchanger of the second air recirculation part is cooled in one or more generators of the heat driven heat pump by driving the heat driven heat pump. The fluid circuit of the air-to-fluid heat exchanger of the first air recirculation section and/or the third air recirculation section is connected to one or more evaporators of the heat driven heat pump. The air of the first air recirculation part and/or the third air recirculation part cools the fluid in the fluid circuit of the fluid-to-fluid heat exchanger in one or more evaporators of the thermally driven heat pump.
The second air recirculation component connected to the middle of the dryer section hood may include two heat recovery units. The heat recovery unit further comprises an air-to-air heat exchanger, a spraying unit connected with the air-to-air heat exchanger, and a heater, and the humid exhaust gas drawn from the dryer section hood heats the conditioned humid exhaust gas flowing out of the air-to-air heat exchanger in the air-to-air heat exchanger, and the spraying unit cleans the humid exhaust gas by spraying a cleaning liquid, the heater heats the conditioned humid exhaust gas flowing out of the air-to-air heat exchanger before at least a portion of the conditioned humid exhaust gas is supplied to the dryer section hood.
Furthermore, the fluid cooling unit may comprise a heat driven heat pump, and the air of the two heat recovery units flows to the fluid in the fluid circuit of the heat-to-fluid heat exchanger to one or more generators of the heat driven heat pump for driving the heat driven heat pump.
The air recirculation system and method for a dryer section of a board or paper machine of the present invention provides an efficient and energy efficient system and method and reduces the amount of exhaust air flow emitted to the atmosphere.
Drawings
The invention is described in detail by means of specific embodiments with reference to the accompanying drawings, in which:
figure 1 shows an air recirculation system for a dryer section of a board or paper machine;
figure 2 shows an air recirculation system for a dryer section of a board or paper machine;
fig. 3 shows an air recirculation system for a dryer section of a board or paper machine.
Detailed Description
Fig. 1-3 show an air recirculation system 1 for a dryer section of a board or paper machine 2. During operation of the board or paper machine, water from the moving web-like material 3 evaporates to the air to produce moist exhaust air 4 a-c in the dryer section. The shown system comprises at least three air recirculation sections 5 a-c, which air recirculation sections 5 a-c are connected to the dryer section hood 6 one after the other in the travelling direction r of the web-like material 3. The system may comprise four or more air recirculation sections 5 a-c. The illustrated air recirculation components 5 a-c comprise heat recovery units 7 a-c. The air recirculating member 5 a-c may also comprise two or more heat recovery units 7 a-c, which heat recovery units 7 a-c are arranged one after the other in the direction of travel r of the web-like material 3.
The heat recovery unit 7 a-c comprises circulating air fans 8 a-c, which circulating air fans 8 a-c are used to draw moist exhaust air 4 a-c from the dryer section hood 6 into the heat recovery unit 7 a-c. The circulating air fans 8 a-c circulate the humid exhaust air 4 a-c through the heat recovery units 7 a-c and supply at least a part of the conditioned humid exhaust air 9 a-c as supply air to the dryer section hood 6.
The heat recovery units 7 a-c further comprise air-to-air heat exchangers 10 a-c and air-to-fluid heat exchangers 11 a-c. The circulating air fans 8 a-c move the humid exhaust air 4 a-c through the air-to-air heat exchangers 10 a-c where the humid exhaust air 4 a-c is cooled as it transfers heat to the conditioned humid exhaust air flowing from the air-to-air heat exchangers 11 a-c. The heat recovery unit 7 a-c further comprises a heater 12 a-c for heating the conditioned humid exhaust gas 9 a-c flowing from the air-to-air heat exchanger 10 a-c before it is supplied as supply air to the dryer section hood 6.
In fig. 1-3, the circulating air fan 8 a-c is positioned before the air-to-air heat exchanger 10 a-c in the flow direction of the humid exhaust air 4 a-c in the heat recovery unit 7 a-c. The circulating air fans 8 a-c may also be positioned after the air-to-air heat exchangers 10 a-c in the flow direction of the humid exhaust air 4 a-c in the heat recovery units 7 a-c. Furthermore, the circulating air fans 8 a-c may also be positioned after the heaters 10 a-c in the flow direction of the moist exhaust air 4 a-c in the heat recovery units 7 a-c.
The humid exhaust gas 4 a-c is conditioned in the air-to-fluid heat exchanger 11 a-c by cooling and reducing the moisture content of the humid exhaust gas 4 a-c. The air-to-fluid heat exchanger 11 a-c comprises a fluid circuit 13 a-c, which fluid circuit 13 a-c is connected to a fluid cooling unit 14. The fluid in the fluid circuits 13 a-c of the air-to-fluid heat exchanger is cooled in the fluid cooling unit 14.
In the embodiment of fig. 1, the fluid cooling unit 14 comprises a cooling tower or an air-cooled air-to-fluid heat exchanger, such as a plate and shell heat exchanger. The cooling tower may, for example, be a closed loop evaporative cooling tower. The closed loop, in which the fluid in the fluid circuits 13 a-c circulates within the flow channels inside the cooling tower, allows the fluid to maintain its chemical and physical properties and prevents contamination of the fluid by external particles. The flow channel is constantly wetted by the spraying system, in which a portion of the sprayed water evaporates.
During operation of the board or paper machine, the dryer section hood 6 comprises several zones 15 a-c one after the other in the travelling direction r of the web-like material 3, in which zones the moisture content of the exhaust air 4 a-c is at different levels. In fig. 1-3, the dryer section hood includes three zones 15 a-c. In the beginning of the dryer section hood 6 is a zone 15a in which the moisture content of the exhaust gases is lower as the web-like material is heating up. In the middle of the dryer section hood 6 is a zone 15b in which the moisture content of the exhaust gases is high due to the high evaporation rate of the web-like material. In the end of the dryer section hood 6 is a zone 15c in which the moisture content of the exhaust gases is again lower due to the reduced evaporation rate of the web-like material. The beginning and the end of the dryer section hood therefore comprise regions 15a, c in which the moisture content of the exhaust gases is lower than in the region 15b in the middle of the dryer section hood.
The moisture content of the humid exhaust gases 4 a-c is not constant in the areas 15 a-c inside the dryer section hood 6. In the beginning of the dryer section hood 6 the moisture content increases in the direction of travel r of the web-like material, whereas in the end of the dryer section hood 6 the moisture content decreases in the direction of travel r of the web-like material. In the figure the areas 15 a-c are indicated by dashed lines.
Each air recirculation part 5 a-c is positioned in connection with one zone 15 a-c. A first air recirculation part 5a is connected to the beginning of the dryer section hood 6, a second air recirculation part 5b is connected to the middle of the dryer section hood 6, and a third air recirculation part 5c is connected to the end of the dryer section hood 6.
The first air recirculation part 5a recirculates moist exhaust air 4a from a zone 15a located at the beginning, the second air recirculation part 5b recirculates moist exhaust air 4b from a zone 15b located in the middle, and the third air recirculation part 5c recirculates moist exhaust air 4c from a zone 15c located at the end of the dryer section hood 6.
In the embodiment shown in fig. 2 and 3, the fluid cooling unit 14 comprises a cooling tower and a heat driven heat pump 16. The heat driven heat pump 16 operates at several temperature levels. The driving heat is supplied at high temperature levels to one or more generators of the heat-powered heat pump 16. Useful cold (cold) in cooling operation is supplied at low temperature levels from the evaporator or evaporators of the heat-driven heat pump 16. The supplied heat is released to the flow of cooling fluid 17 of the heat driven heat pump 16 at an intermediate temperature level. The thermally driven heat pump 16 enables the use of low grade heat. Examples of thermally driven heat pumps 16 are absorption chillers and adsorption chillers. In the embodiment shown in fig. 2 and 3, the heat collected from the hot humid exhaust gas 4b sucked from the middle of the dryer section hood 6 where the web-like material 3 has a high evaporation rate is used to drive the heat driven heat pump 16.
In the embodiment shown in fig. 2 and 3 comprising a heat driven heat pump 16, the air to air heat exchanger 10b in the heat recovery unit 7b of the second air recirculation section 5b may be omitted. In this case, the humid exhaust gas 4b may release more heat in the air-to-fluid heat exchanger 11b for driving the heat pump 16.
In the embodiment shown in fig. 2 and 3, the heat driven heat pump 16 comprises, for example, an absorption chiller. The air-to-fluid heat exchanger 11b of the second air recirculation section 5b is then connected to the one or more generators of the absorption chiller in the fluid circuit 13 b. The fluid in the fluid circuit 13b of the air-to-fluid heat exchanger 11b of the second air recirculation section 5b is cooled in one or more generators of the absorption chiller by heating the working medium of the absorption chiller. As an example, the temperature of the air of the second air recirculation part 5b to the fluid entering the heat driven heat pump in the fluid circuit 13b of the fluid to fluid heat exchanger 11b comprises 55-75 ℃.
The air of the first air recirculating part 5a and/or the third air recirculating part 5c is connected to the fluid circuit 13a of the fluid-to-fluid heat exchanger 11a to one or more evaporators of the heat-driven heat pump 16. The air of the first and third air recirculation part 5a, 5c cools the fluid in the fluid circuit 13a, c of the fluid heat exchanger 11a, c in one or more evaporators of the heat driven heat pump 16. Since the evaporator or evaporators of the absorption chiller operate at a lower temperature than the generator or generators of the absorption chiller, the temperature of the fluid entering the air-to-fluid heat exchanger 11a, c in the beginning and end of the dryer section hood 6 is lower than the temperature of the fluid entering the air-to-fluid heat exchanger 11b in the middle of the dryer section hood 6. This allows the moisture content of the conditioned moist exhaust gases 9 a-c to be reduced to a lower level in the beginning and end of the dryer section hood 6 than in the middle of the dryer section hood 6. As an example, the temperature of the fluid entering the air-to-fluid heat exchanger 11a, c in the fluid circuit 13a, c of the air-to-fluid heat exchanger 11a, c of the first and third air recirculating parts 5a, 5c comprises 13-18 ℃.
In the embodiment shown in fig. 2, the cooling fluid 17 of the thermally driven heat pump 16 is cooled by means of a cooling tower. The flow of cooling fluid 17 from the cooling tower enters a heat driven heat pump 16, such as an absorption chiller, and the heat supplied to the heat driven heat pump 16 is released into the flow of cooling fluid 17. In the heat driven heat pump 16, the heated cooling fluid flow is returned to the cooling tower. By way of example, the temperature of the cooling fluid 17 entering the heat driven heat pump 16 comprises 27-33 ℃.
In the embodiment shown in fig. 3, the heat recovery units 7 a-c in the recirculation sections 5 a-c further comprise second air-to-fluid heat exchangers 18 a-c for conditioning the humid exhaust gases 4 a-c. The humid exhaust gas 4 a-c is conditioned in a second air-to-fluid heat exchanger 18 a-c, which second air-to-fluid heat exchanger 18 a-c comprises a second fluid circuit 19 a-c, which second fluid circuit 19 a-c is connected to a circuit of cooling fluid 17 of the heat driven heat pump 16. The cooling fluid 17 of the heat driven heat pump 16 is cooled by means of a cooling tower. The flow of cooling fluid 17 from the cooling tower enters a heat driven heat pump 16, such as an absorption chiller, and the heat supplied to the heat driven heat pump 16 is released into the flow of cooling fluid 17.
In the thermally driven heat pump 16, the flow of heated cooling fluid 17 is further split into a plurality of split portions that flow to second air-to-fluid heat exchangers 18a, c connected to the beginning and end of the dryer section hood 6. The humid exhaust gas 4a, c releases heat to the split of the cooling fluid 17 in the second air-to-fluid heat exchanger 18a, c. The split portion of the cooling fluid 17, which is heated in the second air-to-fluid heat exchanger 18a, c, flows to a second air-to-fluid heat exchanger 18b connected to the middle of the dryer section hood 6. Cooling fluid 17 exiting from a second air-to-fluid heat exchanger 18b connected to a middle portion of dryer section hood 6 enters the cooling tower.
In the embodiment shown in fig. 3, the cooling fluid 17 exiting the cooling tower enters the heat driven heat pump 16 at a lower temperature than it enters the second air-to-fluid heat exchanger 18 a-c. The second air-to-fluid heat exchangers positioned at the beginning and end of the drying section hood 6 precede the second air-to-fluid heat exchanger positioned in the middle of the drying section hood in the flow direction of the cooling fluid 17. Thus, the temperature of the cooling fluid 17 as it enters the second air-to-fluid heat exchanger 18b located in the middle of the drying section hood 6 comprises a higher temperature than when the cooling fluid enters the second air-to-fluid heat exchangers 18a, c located at the beginning and end of the drying section hood 6. By way of example, the temperature of the cooling fluid 17 entering the heat driven heat pump 16 comprises 27-33 deg.C, while the temperature of the cooling fluid 17 entering the second air-to-fluid heat exchanger 18a, c connected to the beginning and end of the dryer section hood 6 comprises 33-39 deg.C.
In the recirculation part 5b connected to the middle of the dryer section hood 6, the air-to-fluid heat exchanger 11b and the second air-to-fluid heat exchanger 18b are arranged such that the air-to-fluid heat exchanger 11b precedes the second air-to-fluid heat exchanger 18b in the flow direction of the humid exhaust gas in the heat recovery unit 7 b.
In the recirculation parts 5a, c connected to the beginning and end of the dryer section hood 6, the air-to-fluid heat exchanger 11a, c and the second air-to-fluid heat exchanger 18a, c are arranged such that the second air-to-fluid heat exchanger 18a, c precedes the air-to-fluid heat exchanger 11a, c in the flow direction of the humid exhaust gas 4a, c in the heat recovery unit 7a, c.
In the embodiment shown in FIG. 3, the fluid cooling unit 14, which is arranged to provide fluid cooling to the air-to-fluid heat exchangers 11 a-c and the second air-to-fluid heat exchangers 18 a-c, includes a heat-driven heat pump 16 and a cooling tower. The heat driven heat pump 16 provides cooling to the air-to-fluid heat exchangers 11 a-c and the cooling tower provides cooling to the second air-to-fluid heat exchangers 18 a-c. The cooling tower also provides cooling to the heat-driven heat pump 16.
At some point in the year, the outdoor air temperature may be high enough to allow the conditioned humid exhaust air 9 a-c from the beginning and end of the dryer section hood 6 to be discharged to the atmosphere without risk of visible plume. The system 1 shown in fig. 3 then comprises one or more valves to close the fluid circuits 13a, c of the air-to-fluid heat exchangers 11a, c of the first and third air recirculating parts 5a, 5 c. The system 1 further comprises a bypass channel to bypass the air-to-fluid heat exchangers 11a, c of the first and third air recirculation components 5a, 5 c. Additionally, the system 1 comprises an inlet connection to a heat driven heat pump, which can be used to provide cooling water to a cooling water network of a paper or pulp production plant for cooling purposes, and an outlet connection from the heat driven heat pump.
In all embodiments, each air recirculation section 5 a-c comprises at least one washing system 20, which washing system 20 is a continuous washing system comprising a washing liquid storage tank and a washing liquid pump. The air-to-air heat exchangers 10 a-c, the air-to-fluid heat exchangers 11 a-c and the second air-to-fluid heat exchangers 18 a-c are each connected with a spraying unit 21 a-c for cleaning the humid exhaust air 4 a-c. In the figures, the washing liquid inlets to the spraying units 21 a-c and the washing liquid outlets leaving the heat exchangers 10 a-c, 11 a-c, 18 a-c are shown by arrows, and the connections to the washing system 20 are shown only for one heat exchanger 10b in one heat recovery unit 5 b. For the sake of clarity, only the reference numerals of the spraying units 21 a-c are indicated with respect to fig. 1. The continuous washing of the humid off-gas 4 a-c is preferably performed in one of the heat exchangers 10 a-c, 11 a-c, 18 a-c in each recovery unit 7 a-c, while the periodical washing of the humid off-gas 4 a-c is performed in the other heat exchangers 10 a-c, 11 a-c, 18 a-c. The cleaning of the humid exhaust gases 4 a-c in the recirculation sections 5 a-c is necessary to meet the quality requirements set for the supply air.
The embodiment shown in fig. 1-3 may comprise in the second air recirculation section 5b two heat recovery units 7 a-c connected to the middle of the dryer section hood 6 and arranged one after the other in the travelling direction r of the web-like material 3. The fluid circuits of the air-to-fluid heat exchangers of the two heat recovery units are then connected in parallel to the fluid cooling unit.
Typically, modern dryer section hoods 6 require a flow of humid exhaust air 4 a-c in an amount of 55% to 80% to be supplied as dry, heated replacement air. The remainder is supplied by infiltration around the hood seal and door to prevent hot moist air from escaping into the machine room. In one embodiment, a first circulating air fan 8a connected to the beginning of the dryer section hood 6 provides at least 60% by volume of the conditioned humid exhaust air 9a as supply air to the dryer section hood 6, while a second circulating air fan 8b connected to the middle of the dryer section hood 6 provides at least 90% by volume of the conditioned humid exhaust air 9b as supply air to the dryer section hood 6, and a third circulating air fan 8c connected to the end of the dryer section hood 6 provides at least 60% by volume of the conditioned humid exhaust air 9c as supply air to the dryer section hood 6.
The invention has been described above with reference to the examples shown in the drawings. However, the invention is by no means limited to the examples described above, but may vary within the scope of the invention.
List of parts: 1 an air recirculation system; 2 dryer section of a board or paper machine; 3a web-like material; 4 a-c moist exhaust gases; 5 a-c air recirculation components; 6 dryer section hood; 7 a-c heat recovery units; 8 a-c circulating air fans; 9 a-c conditioned humid exhaust gas; 10 a-c air to air heat exchanger; 11 a-c air-to-fluid heat exchangers; 12 a-c heaters; 13 a-c fluid circuit; 14 a fluid cooling unit; 15 a-c region; 16 a heat pump; 17 cooling the fluid; 18 a-c a second air-to-fluid heat exchanger; 19 a-c a second fluid circuit; 20, cleaning the system; 21 a-c spraying unit; r direction of travel.
Claims (19)
1. An air recirculation system (1) for a dryer section (2) of a board or paper machine, in which dryer section (2) water from a moving web-like material (3) is evaporated to air during operation of the board or paper machine to produce humid exhaust air (4 a-c), characterized in that the system (1) comprises at least three air recirculation parts (5 a-c) which are connected to a dryer section hood (6) one after the other in the travelling direction (r) of the web-like material (3), each air recirculation part (5 a-c) comprising one or more heat recovery units (7 a-c), each heat recovery unit (7 a-c) comprising a circulating air fan (8 a-c), a first air-to-fluid heat exchanger (11 a-c) and a spray connected to the first air-to-fluid heat exchanger (11 a-c) A sprinkling unit (21 a-c), the circulating air fan (8 a-c) for drawing moist exhaust air (4 a-c) from the dryer section hood (6) through the heat recovery unit (7 a-c) and for supplying at least a portion of the conditioned moist exhaust air (9 a-c) to the dryer section hood (6), the first air-to-fluid heat exchanger (11 a-c) for conditioning the moist exhaust air (4 a-c) by cooling and reducing the moisture content of the moist exhaust air (4 a-c), the first air-to-fluid heat exchanger (11 a-c) comprising a first fluid circuit (13 a-c) connected to a fluid cooling unit (14), the sprinkling unit (21 a-c) for cleaning the moist exhaust air (4 a-c), and a first air recirculation component (5 a) connected to the beginning of the dryer section hood (6), a second air recirculation part (5 b) is connected to the middle of the dryer section hood (6) and a third air recirculation part (5 c) is connected to the end of the dryer section hood (6), the fluid cooling unit (14) comprising a heat driven heat pump (16), the first fluid circuit (13 b) of the first air-to-fluid heat exchanger (11 b) of the second air recirculation part (5 b) being connected to one or more generators of the heat driven heat pump (16) for driving the heat driven heat pump (16).
2. An air recirculation system according to claim 1, characterized in that the heat driven heat pump (16) comprises an absorption chiller and the first fluid circuit (13 b) of the first air-to-fluid heat exchanger (11 b) of the second air recirculation part (5 b) connected to the middle of the dryer section hood (6) is connected to one or more generators of the absorption chiller for driving the absorption chiller, the first fluid circuit (13 a, c) of the first air-to-fluid heat exchanger (11 a, c) of the first air recirculation part (5 a) and/or of the third air recirculation part (5 c) being connected to one or more evaporators of the absorption chiller.
3. An air recirculation system according to claim 1, characterized in that the first fluid circuit (13 a, c) of the first air-to-fluid heat exchanger (11 a, c) of the first air recirculation part (5 a) and/or the third air recirculation part (5 c) is connected to one or more evaporators of the heat driven heat pump (16).
4. An air recirculation system according to claim 1 or 3, characterized in that the fluid cooling unit (14) further comprises a cooling tower, the heat driven heat pump (16) being connected to a circuit of cooling fluid (17) of the cooling tower for releasing heat from the heat driven heat pump (16) to the cooling fluid (17).
5. An air recirculation system according to any of claims 1-3, characterized in that the heat recovery unit (7 a-c) further comprises an air-to-air heat exchanger (10 a-c) for heating conditioned humid exhaust air (9 a-c) flowing from the first air-to-fluid heat exchanger (11 a-c) with the humid exhaust air (4 a-c), a spraying unit (21 a-c) connected with the air-to-air heat exchanger (10 a-c) for cleaning the humid exhaust air (4 a-c), and a heater (12 a-c) for heating the conditioned humid exhaust air (9 a-c) flowing from the air-to-air heat exchanger (10 a-c) before at least a part of the conditioned humid exhaust air (9 a-c) is supplied to the dryer section hood (6) -c).
6. An air recirculation system according to any of claims 1-3, the heat recovery unit (7 a-c) further comprising a heater (12 a-c) and a second air-to-fluid heat exchanger (18 a-c), for heating the conditioned humid exhaust gas (9 a-c) before at least a portion of the conditioned humid exhaust gas (9 a-c) is supplied to the dryer section hood (6), the second air-to-fluid heat exchanger comprising a second fluid circuit (19 a-c) connected to a circuit of cooling fluid (17) of the heat driven heat pump (16), wherein the cooling fluid (17) enters the thermally driven heat pump (16) at a lower temperature than entering the second air-to-fluid heat exchanger (18 a-c).
7. An air recirculation system according to any of claims 1-3, characterized in that the second air recirculation part (5 b) connected to the middle part of the dryer section hood (6) comprises two heat recovery units (7 a-c), which heat recovery units (7 a-c) further comprise an air-to-air heat exchanger (10 a-c) for heating conditioned humid exhaust air (9 a-c) flowing from the first air-to-air heat exchanger (11 a-c) with the humid exhaust air (4 a-c), a spraying unit (21 a-c) connected to the air-to-air heat exchanger (10 a-c) for cleaning the humid exhaust air (4 a-c), and a heater (12 a-c), the heater is used for heating the conditioned humid exhaust air (9 a-c) flowing out of the air-to-air heat exchanger (10 a-c) before at least a portion of the conditioned humid exhaust air (9 a-c) is supplied to the dryer section hood (6).
8. An air recirculation system according to claim 7, characterized in that the first fluid circuit (13 a-c) of the first air-to-fluid heat exchanger (11 a-c) of the two heat recovery units (7 a-c) is connected to one or more generators of the heat driven heat pump (16) for driving the heat driven heat pump (16).
9. An air recirculation system according to any of claims 1-3, characterized in that the dryer section hood (6) comprises, during operation of the board or paper machine, at least three zones (15 a-c) inside the dryer section hood (6) one after the other in the travelling direction (r) of the web-like material (3), which comprise humid exhaust air (4 a-c) at different moisture content levels, and which at least three zones (15 a-c) are located to the beginning, middle and end of the dryer section hood (6), and in that in the system (1) the first air recirculation part (5 a) is arranged to recirculate humid exhaust air (4 a) from the zone (15 a) located to the beginning of the dryer section hood (6), the second air recirculation part (5 b) is arranged to recirculate humid exhaust air (4 b) from a region (15 b) located in the middle of the dryer section hood (6), and the third air recirculation part (5 c) is arranged to recirculate humid exhaust air (4 c) from a region (15 c) located at the end of the dryer section hood (6).
10. An air recirculation method for a dryer section (2) of a board or paper machine, in which dryer section (2) water from a moving web-like material (3) is evaporated to air during operation of the board or paper machine to produce humid exhaust air (4 a-c), characterized in that the method comprises at least three air recirculation parts (5 a-c) which are connected to a dryer section hood (6) one after the other in the travelling direction (r) of the web-like material (3), and that each air recirculation part (5 a-c) comprises one or more heat recovery units (7 a-c), each heat recovery unit (7 a-c) comprising a circulating air fan (8 a-c) and a first air-to-fluid heat exchanger (11 a-c), the circulating air fan (8 a-c) draws moist exhaust gases (4 a-c) from the dryer section hood (6) through the heat recovery unit (7 a-c) and supplies at least a portion of the conditioned moist exhaust gases (9 a-c) to the dryer section hood (6), the first air-to-fluid heat exchanger (11 a-c) for conditioning the moist exhaust gases (4 a-c) by cooling and reducing the moisture content of the moist exhaust gases (4 a-c), the first fluid circuit (13 a-c) of the first air-to-fluid heat exchanger (11 a-c) being connected to a fluid cooling unit (14) and the fluid in the first fluid circuit (13 a-c) of the first air-to-fluid heat exchanger (11 a-c) being cooled in the fluid cooling unit (14), a spraying unit (21 a-c) connected to the first air-to-fluid heat exchanger (11 a-c) -cleaning the moist exhaust gases (4 a-c), and a first air recirculation part (5 a) is connected to the beginning of the dryer section hood (6) and a first circulating air fan (8 a) sucks moist exhaust gases (4 a) and supplies at least a part of the conditioned moist exhaust gases (9 a) to the beginning of the dryer section hood (6), -a second air recirculation part (5 b) is connected to the middle of the dryer section hood (6) and a second circulating air fan (8 b) sucks the moist exhaust gases (4 b) and supplies at least a part of the conditioned moist exhaust gases (9 b) to the middle of the dryer section hood (6), -a third air recirculation part (5 c) is connected to the end of the dryer section hood (6) and a third circulating air fan (8 c) sucks the moist exhaust gases (4 c) and supplies at least a part of the conditioned moist exhaust gases (9 c) to the dryer section hood (6) -the end of the section hood (6), -the fluid cooling unit (14) comprises a heat driven heat pump (16), -the first fluid circuit (13 b) of the second air-to-fluid heat exchanger (11 b) of the second air recirculation part (5 b) is connected to one or more generators of the heat driven heat pump (16) for driving the heat driven heat pump (16).
11. The air recirculation method according to claim 10, characterized in that the fluid cooling unit (14) further comprises a cooling tower to which the first fluid circuit (13 a-c) of the first air-to-fluid heat exchanger (11 a-c) is connected and in which the fluid in the first fluid circuit (13 a-c) is cooled.
12. The air recirculation method according to claim 10, characterized in that the heat driven heat pump comprises an absorption chiller and the first fluid circuit (13 b) of the first air-to-fluid heat exchanger (11 b) of the second air recirculation component (5 b) is connected to one or more generators of the absorption chiller and the fluid in the first fluid circuit (13 b) of the first air-to-fluid heat exchanger (11 b) of the second air recirculation component (5 b) is cooled in one or more generators of the absorption chiller by driving the absorption chiller, the first fluid circuit (13 a, c) of the first air-to-fluid heat exchanger (11 a, c) of the first air recirculation component (5 a) and/or the third air recirculation component (5 c) being connected to one or more evaporators of the absorption chiller, and the fluid in the first fluid circuit (13 a, c) of the first air-to-fluid heat exchanger (11 a, c) of the first air recirculation component (5 a) and/or the third air recirculation component (5 c) is cooled in one or more evaporators of the absorption coolers.
13. An air recirculation method according to claim 10, characterized in that the fluid in the first fluid circuit (13 b) of the first air-to-fluid heat exchanger (11 b) of the second air recirculation part (5 b) is cooled in one or more generators of the heat driven heat pump (16) by driving the heat driven heat pump (16), the first fluid circuit (13 a, c) of the first air-to-fluid heat exchanger (11 a, c) of the first air recirculation part (5 a) and/or the third air recirculation part (5 c) is connected to one or more evaporators of the heat driven heat pump (16), and the first fluid circuit (13 a, c) of the first air-to-fluid heat exchanger (11 a, c) of the first air recirculation part (5 a) and/or the third air recirculation part (5 c), c) Is cooled in one or more evaporators of the thermally driven heat pump (16).
14. The air recirculation method according to claim 10, characterized in that the fluid cooling unit (14) further comprises a cooling tower, the cooling fluid (17) in the circuit of the cooling fluid (17) of the cooling tower flows to the heat driven heat pump (16), and the heat driven heat pump (16) releases heat to the cooling fluid (17).
15. The air recirculation method according to any of the claims 10-14, characterized in that the heat recovery unit (7 a-c) further comprises an air-to-air heat exchanger (10 a-c), a spraying unit (21 a-c) connected with the air-to-air heat exchanger (10 a-c), in which the humid exhaust air (4 a-c) sucked from the dryer section hood (6) heats conditioned humid exhaust air (9 a-c) flowing from the first air-to-air heat exchanger (11 a-c), and a heater (12 a-c), the spraying unit (21 a) cleans the humid exhaust air (4 a-c) by spraying a washing liquid, the heater (12 a-c) supplies at least a part of the conditioned humid exhaust air (9 a-c) flowing from the air-to-air heat exchanger (10 a-c) to the air-to The conditioned humid exhaust gas is heated before the dryer section hood (6).
16. The air recirculation method according to any of the claims 10-14, characterized in that the heat recovery unit (7 a-c) further comprises a heater (12 a-c) and a second air-to-fluid heat exchanger (18 a-c) comprising a second fluid circuit (19 a-c) connected to the circuit of cooling fluid (17) of the heat driven heat pump (16), the heater (12 a-c) heating the conditioned humid exhaust gas (9 a-c) before at least a part of the conditioned humid exhaust gas is fed to the dryer section hood (6), the fluid in the second fluid circuit (19 a-c) of the second air-to-fluid heat exchanger (18 a-c) cooling in the second air-to-fluid heat exchanger (18 a-c) the conditioned humid exhaust gas flowing out of the first air heat exchanger (11 a-c) of the fluid -throttling humid exhaust gas (9 a-c), the fluid in the second fluid circuit (19 a-c) of the second air-to-fluid heat exchanger (18 a-c) entering the heat driven heat pump (16) at a lower temperature than entering the second air-to-fluid heat exchanger (18 a-c).
17. The air recirculation method according to any of the claims 10-14, characterized in that the second air recirculation part (5 b) connected to the middle of the dryer section hood (6) comprises two heat recovery units (7 a-c), the heat recovery units (7 a-c) further comprising an air-to-air heat exchanger (10 a-c), a spraying unit (21 a-c) connected with the air-to-air heat exchanger (10 a-c) and a heater (12 a-c), the humid exhaust gas (4 a-c) sucked from the dryer section hood (6) heating the conditioned humid exhaust gas (9 a-c) flowing out from the first air-to-air heat exchanger (11 a-c) in the air-to-air heat exchanger (10 a-c), the spraying unit (21 a-c) cleaning the humid exhaust gas (4 a-c) by spraying a cleaning liquid, the heater (12 a-c) heats conditioned humid exhaust air (9 a-c) flowing out of the air-to-air heat exchanger (10 a-c) before at least a portion of the conditioned humid exhaust air is supplied to the dryer section hood (6).
18. An air recirculation method according to claim 17, characterized in that the fluid in the first fluid circuit (13 a-c) of the two heat recovery units (7 a-c) to the fluid-to-fluid heat exchanger (11 a-c) flows to one or more generators of the heat driven heat pump (16) for driving the heat driven heat pump (16).
19. An air recirculation method according to any of the claims 10-14, characterized in that during operation of the board or paper machine the amount of water from the web-like material (3) evaporating to the air is changed in the direction of travel (r) of the web-like material (3) in the dryer section hood (6), at least three zones (15 a-c) generating moist exhaust air (4 a-c) at different moisture content levels are provided inside the dryer section hood (6) one after the other in the direction of travel (r) of the web-like material (3), the at least three zones (15 a-c) being positioned to the beginning of the dryer section hood (6), the middle of the dryer section hood (6) and the end of the dryer section hood (6), and in the method, the first air recirculation part (5 a) recirculates moist exhaust air (4 a) from a region (15 a) located at the beginning of the dryer section hood (6), the second air recirculation part (5 b) recirculates moist exhaust air (4 b) from a region (15 b) located at the middle of the dryer section hood (6), and the third air recirculation part (5 c) recirculates moist exhaust air (4 c) from a region (15 c) located at the end of the dryer section hood (6).
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FI20185875A FI128325B (en) | 2018-10-17 | 2018-10-17 | An air re-circulation system and a method for a dryer section of a board or paper machine |
| FI20185875 | 2018-10-17 |
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| CN111058329A CN111058329A (en) | 2020-04-24 |
| CN111058329B true CN111058329B (en) | 2021-09-17 |
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| CN201811239440.7A Active CN111058329B (en) | 2018-10-17 | 2018-10-23 | Air recirculation system and method for a dryer section of a board or paper machine |
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| Country | Link |
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| CN (1) | CN111058329B (en) |
| FI (1) | FI128325B (en) |
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| AT525741B1 (en) * | 2022-04-20 | 2023-07-15 | Iaf Process Eng Gmbh | PROCESS AND SYSTEM FOR WASTE HEAT RECOVERY |
| DE102022119307A1 (en) | 2022-08-02 | 2024-02-08 | Voith Patent Gmbh | Paper mill and process for controlling high-temperature media for the production or treatment of a fibrous web |
| DE102022124572A1 (en) | 2022-09-23 | 2024-03-28 | Voith Patent Gmbh | Machine and method for its operation for the production or treatment of a fibrous web with a heat pump |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SU956678A1 (en) * | 1981-02-18 | 1982-09-07 | Ивановский Ордена "Знак Почета" Энергетический Институт Им.В.И.Ленина | Heat recuperation unit |
| DE3106567A1 (en) * | 1981-02-21 | 1982-09-09 | Battelle-Institut E.V., 6000 Frankfurt | "METHOD FOR REDUCING HEAT LOSS IN FACILITIES FOR DRYING SOLIDS" |
| SU1585418A1 (en) * | 1988-09-23 | 1990-08-15 | Центральный Научно-Исследовательский И Проектно-Конструкторский Институт По Проектированию Оборудования Для Целлюлозно-Бумажной Промышленности | Arrangement for utilizing heat of steam-air mixture of paper-making machine |
| FI20000387A0 (en) * | 2000-02-21 | 2000-02-21 | Valmet Corp | Method and apparatus for arranging the discharge and supply of air in the dryer section |
| RU2229546C1 (en) * | 2003-02-10 | 2004-05-27 | Климов Андрей Александрович | Apparatus for closed-circuit heat recuperation in papermaking machine ventilation system |
| CN101760980B (en) * | 2010-01-22 | 2012-07-18 | 华南理工大学 | Monitoring control system of paper-making machine drying part energy system and working method thereof |
| EP2609983A1 (en) * | 2011-12-29 | 2013-07-03 | Brunnschweiler S.A. | Method and system for processing hot humid air resulting from an industrial process,prior to expelling it into the outside air, to recover water and remove the plume |
| FI20140051A (en) * | 2014-02-21 | 2015-08-22 | Tm System Finland Oy | The heat recovery cell |
| FI128437B (en) * | 2016-08-18 | 2020-05-15 | Tm System Finland Oy | A method and an arrangement for recirculating air in a drying process |
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2018
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- 2018-10-23 CN CN201811239440.7A patent/CN111058329B/en active Active
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| WO2020079326A1 (en) | 2020-04-23 |
| FI128325B (en) | 2020-03-31 |
| CN111058329A (en) | 2020-04-24 |
| FI20185875A1 (en) | 2020-03-31 |
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