JPS5825955B2 - Strip drying equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a drying device for a strip material such as paper produced in a paper making machine.

It is generally known that paper produced in papermaking equipment is dried by successively passing through a number of rotating drying drums. (Published by Business Times), etc.

Conventional drying equipment of this type divides the rotary drying drum into multiple groups along the paper feeding direction, and sends steam to each group from a steam pipe through a pressure control valve. The surface is heated by the steam generated.

For example, if the rotating drying drum is divided into three groups along the paper feeding direction, the temperature of the rotating drying drum within each group is the same, but between each group, the first group on the upstream side in the paper feeding direction The temperature was increased in order from the first to the third group.

Temperature control using steam is determined by the pressure of the steam, so the steam pressure is set to be higher sequentially from the first group to the third group, and this is controlled by the pressure control valve mentioned above. .

Further, in this type of drying apparatus, the steam used in the third group still maintains high temperature and high pressure, and it is uneconomical to wastefully dispose of this steam.

Therefore, the steam used in the third group is sent to the second group for reuse, and the steam discharged from the second group is used in the first group, thereby making effective use of heat and improving economic efficiency. It's forcing me.

Therefore, the second group has a lower vapor pressure and a lower temperature than the third group, and the first group has a lower vapor pressure and a lower temperature than the second group.

On the other hand, inside the rotary drying drum, heat is removed from the supplied steam and some of it becomes condensed water.This condensate is rotated by centrifugal force within the drum, which only increases the drum drive load. However, it must be eliminated because it reduces the heat transfer efficiency of steam.

A rotary siphon is usually used as this ejection means.

This rotary siphon uses the steam pressure difference to take out condensate along with the steam discharge.

However, as mentioned above, the condensate tends to stay on the inner wall of the drum due to the centrifugal force, so if you want to overcome the centrifugal force and take out the condensate with it, you will need a considerable pressure difference between the inside and outside of the drum.

Therefore, it is impossible to set the pressure difference between each drum group below the pressure difference required for the operation of the rotary siphon, and this is the reason why it is not possible to ensure a small temperature difference between each drum group. There is.

In other words, in the conventional device, the temperature of the rotary drying drum is determined by the pressure of the steam, so even if you try to reduce the temperature difference between each drum group, it is difficult to ensure the pressure difference required for the operation of the rotary siphon. Therefore, there was a problem in that the temperature difference between each drum group could not be set small.

By the way, depending on the papermaking conditions, drying may be relatively easy. For example, there are papermaking conditions where drying can be performed only with the first and second groups, and there are papermaking conditions that do not require the use of the third group. .

For this reason, in the past, for example, the third group of rotary drying drums was not used and the steam supply was stopped in this area. This resulted in drawbacks such as structural deterioration.

The present invention was developed based on these circumstances, and its purpose is to forcefully feed air and steam to each drum group and mix them together, and to control the temperature difference between each drum group by the partial pressure of the steam. In addition, the pressure difference between each drum group is ensured by the total pressure of air pressure and steam pressure, and the pressure difference between each drum group can be set large, making it easy to discharge condensate etc. In addition, it is an object of the present invention to provide a strip drying device that can set the temperature difference between each drum group to be smaller than the pressure difference and can be applied to paper making under various conditions.

That is, the present invention focuses on the fact that when steam and air are mixed, the temperature is determined by the partial pressure of the steam based on Dalton's law, and the pressure is set by the total pressure of the mixture of steam and air. However, since the temperature difference can be set smaller than the pressure difference, a large number of rotary drying drums are divided into groups according to operating pressure, and each drum group is connected to a steam supply source via a temperature control valve. At the same time, the group of drums with the highest operating pressure is connected to a pressurized air supply source via a pressure control valve, and within this group of drums with the highest operating pressure, the steam sent through the temperature control valve and the pressure are controlled. The air sent in through the valve is mixed, and the temperature of the drum group having the highest pressure is controlled by introducing steam by operating a temperature control valve that responds to the temperature of the mixture, and the temperature of the drum group having the highest pressure is controlled by introducing steam. The pressure of the air-fuel mixture is controlled by mixing air based on the operation of the pressure control valve that responds to the total pressure of the air-fuel mixture, and the air-fuel mixture discharged from the drum group with the highest pressure is transferred to other air-fuel mixtures with lower operating pressures at that total pressure. The temperature of the drum group with the lower operating pressure is controlled by the steam sent through the temperature control valve, and the pressure of the mixture sent from the drum group with the higher operating pressure is controlled by the other pressure control valves. The feature is that the pressure is controlled by controlling.

Hereinafter, one embodiment of the present invention will be described based on the drawings.

1 in the figure is a rotary drying drum, and a large number of rotary drying drums are divided into a plurality of groups along the feeding direction A of paper making (not shown).
A group 1S, a second group 2S, and a third group 3S.

For example, the first group 1S includes four drums, the second group 2S uses eight drums, and the third group 3S uses twenty drums.

In each group 18-3S, steam header 4, 5.6
Both steam and air are supplied from the drums to the respective drums, and these drums are fed to the drums via a known rotary siphon (not shown).
Steam, air and condensate in the drain header 7.8.9 are discharged to the drain header 7.8.9.

Reference numeral 10 denotes a steam supply pipe, which is connected to the steam headers 4.degree. 5.6 of each group 18 to 3S through branch pipes 11, 12.degree. 13.

Each branch pipe 11, 12° 13 has a temperature indication control valve 14, 15.
, 16 are equipped with steam headers 4, 5, and 16, respectively.
6 temperature is detected to automatically control the supply and stop of steam.

In this case, as will be described later, the relationship between the temperature t1 of the first group of steam headers 4, the temperature t2 of the second group of steam headers 5, and the temperature t3 of the third group of steam headers 6 is tl<
The temperature is set so that t2<t3, and the temperatures t11, t21, and t3 are controlled by the temperature instruction control valves 14, 15, and 16, respectively.

Reference numeral 20 denotes an air supply pipe, which sends air pressurized by a jet compressor or a near compressor 21, and is connected to the branch pipe 13 related to the third group.

This air supply pipe 20 is provided with a pressure instruction control valve 22 .

This pressure instruction control valve 22 controls the total pressure in the third group of steam headers 6, and introduces pressurized air from the compressor 21 when the pressure in the steam headers 6 is lower than the set pressure P3S, and When the pressure reaches the set pressure p3s or higher, it will self-operate to stop the supply of air.

Further, the third group of steam headers 6 and the second group of steam headers 5 are communicated via a bypass pipe 23, and this bypass pipe 23 is provided with a pressure indicating control valve 24.

This pressure indication control valve 24 is configured to release the pressure of the steam header 6 to the steam header 5 of the second group when the pressure of the steam header 6 of the third group exceeds P35.

Therefore, the steam header 6 of the third group has a constant pressure P3 due to the action of the pressure instruction control valve 22 and the pressure instruction adjustment valve 24.
．． It is now possible to maintain the

The third group of drain headers 9 is connected to a first steam separator 31 via a drain pipe 30.

The steam/water separator 31 accommodates a mixture of steam and air (hereinafter referred to as a mixture) and condensate discharged from the drums of the third group, and separates the condensate and the mixture here.

A mixture feed pipe 32 is led out from the upper part of the steam/water separator 31, and this mixture feed pipe 32 is connected to the second group of steam headers 5.

Similarly, a mixture gas release pipe 33 is led out from the upper part of the steam/water separator 31, and this mixture gas release pipe 33 is connected to a condenser 34.

This mixture release pipe 33 is provided with a first differential pressure indicating control valve 35 .

This differential pressure indicating control valve 35 is set when the pressure of the second group steam header 5 is set to P2. Close the steam/water separator 3 in the following cases.
The air-fuel mixture in the second steam header 5 is sent to the second steam header 5 to keep the pressure of the steam header 5 constant.

Further, a condensate recovery pipe 36 is led from the lower part of the steam/water separator 31, and this condensate recovery pipe 36 is connected to a second steam/water separator 39.

This condensate recovery pipe 36 is provided with a liquid level control valve 37 .

Further, another drain pipe 38 is led from the second group of drain headers 8, and this drain pipe 38 is connected to a second steam separator 39.

This steam/water separator 39 also leads out a mixture feed pipe 40, which is connected to the first group of steam headers 4.

Further, a mixture gas release pipe 41 is led out from the steam/water separator 39, and this mixture gas release pipe 41 is connected to the condenser 34 via a second differential pressure indicating control valve 42.

The differential pressure indicating control valve 42 operates to keep the pressure P15 of the first group of steam headers 4 constant.

Further, a condensate recovery pipe 43 is led from the second steam separator 39, and a third condensate recovery pipe 43 is connected to the condensate recovery pipe 43 via a liquid level control valve
is connected to a steam/water separator 46.

Furthermore, the first group of drain headers 7 is connected to the third steam separator 46 via a drain pipe 45.

This steam/water separator 46 is connected to the above-mentioned condenser 34, and is also connected to a steam generator, that is, a boiler (not shown) via a condensate pump 47 and a liquid level control valve 48.

Note that 49 is a cooling water pipe of the condenser 34, 50 is a flow rate control valve, and 51 is an air discharge pipe, which is sucked by a vacuum pump 53 or released to the atmosphere via a vacuum control valve 52.

The operation of the embodiment having such a configuration will be explained.

The branch pipe 1 of the steam supply pipe 10 is connected to the steam header 6 of the third group.
3, and pressurized air is sent through the air supply pipe 20.

In this case, the pressure indication control valve 22 stops supplying air when the pressure inside the steam header 6 reaches p3s, and the temperature indication control valve 16 stops supplying steam when the temperature inside the steam header 6 reaches t3s. .

Since steam and air are mixed in the steam header 6, the pressure P38 of the steam header 6 is the partial pressure P3 of steam.
The sum of SS and the partial pressure P3sa of air (P3S = p3s
s + P3Sa).

Furthermore, the temperature t3s of the steam header 6 is the partial pressure P of upper air steam.
It is determined by Dalton's law based on the ratio between 3SS and the partial pressure P3Sa of air.

Note that the pressure inside the steam header 6 is P3. If the temperature is below tas even though the temperature has reached tas, the temperature indication control valve 16
is open and supplies steam, which increases the pressure inside the steam header 6. However, the pressure indication control valve 24 of the bypass pipe 23 opens and releases the air-fuel mixture to the steam header 5 of the second group, so the pressure inside the steam header 6 increases. The pressure inside is always the predetermined pressure P3
It is kept at 5.

Then, the partial pressure of steam P3SS and the partial pressure of air P3. What is a?
The temperature inside the steam header 6 will be maintained at a rate such that it reaches t3S.

In this way, within the steam header 6, the pressure P38. The air-fuel mixture maintained at the temperature t3s is supplied to the third group of rotary drying drums, and the paper is dried by these drums.

A part of the steam is condensed in the drum, and the condensate is discharged to the drain header 9 by a rotary siphon.

In addition to the mixture of steam and air, condensate is also led to the drain header 9, and such a mixture and condensate are passed through a drain pipe 30 to a steam-water separator 31.
be led to.

In the steam/water separator 31, air-fuel mixture accumulates in the upper part, and condensate accumulates in the lower part.

The mixture is sent to the second group of steam headers 5 through the mixture feed pipe 32.

The second group of steam headers 5 is the first group of steam headers 6
The air-fuel mixture sent from the air-fuel mixture via the bypass pipe 23 and the air-fuel mixture sent from the air-fuel mixture feed pipe 32 are mixed.

Furthermore, steam is fed into the steam header 5 through a branch pipe 12 of a steam supply pipe 10.

This steam header 5 is also connected to the air-fuel mixture feed pipe 32.
It is connected to a mixture release pipe 33 via a steam/moisture concentration device 31.

Therefore, the pressure of this steam header 5 is
A constant P2S is maintained by the first differential pressure indicating control valve 35 provided in
The temperature is maintained at a constant value t2s by the temperature indication control valve 15.

In this case as well, the pressure P28 of the steam header 5 is the sum of the steam partial pressure P288 and the air partial pressure p2sa (P2S=P
2S5 + P2sa), and the temperature t2S is determined by the mixing ratio of steam based on Dalton's law.

The air-fuel mixture is sent from the second group of steam headers 5 to the second group of rotary drying drums, and these drums dry the paper.

The air-fuel mixture and condensate are discharged from this drum and sent to the drain header 8.

The drain header 8 sends the air-fuel mixture and condensate to a steam separator 39 via a drain pipe 38.

This steam/water separator 39 also separates the mixture into a mixture and condensate, and the mixture is sent to the first group of steam headers 4 via a mixture feed pipe 40.

The first group of steam headers 4 is a branch pipe 11 of a steam supply pipe 10.
Steam is sent through the

The pressure of the mixture is controlled by the differential pressure indicating control valve 42 of the mixture relief pipe 41.
Constant P1. At the same time, the temperature is maintained at a constant value t1s by the temperature indication control valve 14.

In this case as well, the pressure P18 of the steam header 4 is the sum of the steam partial pressure p1ss and the air partial pressure PISa (PIs-PIS
S+Pxsa), and the temperature t1s is determined by Dalton's law based on the mixing ratio of the steam.

Such a mixture is sent to the first group of rotary drying drums to dry the paper.

The air-fuel mixture and condensate are discharged from each drum and sent to the drain header 7, and then sent to the steam-water separator 46 via the drain pipe 47.

The air-fuel mixture separated from condensate in this steam-water separator 46 is sent to the condenser 34 together with the air-fuel mixture sent from the first and second steam-water separators 31 and 39, and is converted into condensate. In this case, air and water are separated and the air is released into the atmosphere.

Further, the condensate from the steam-water separator 46 is returned to the boiler via the condensate pump 47 together with the condensate sent from the first and second steam-water separators 31 and 39.

A drying device that functions in this way has each rotary drying drum.
・Since air is mixed with steam and sent to the tank, a large pressure difference between each group can be ensured with the help of air pressure.

In other words, it is possible to ensure the pressure difference for drain discharge necessary for using the rotary siphon to a certain value or more.

Moreover, even though the pressure difference is large, the temperature of each group depends on the partial pressure of steam, so the temperature difference between each group can be reduced, and the degree of freedom in operating the drying equipment can be increased depending on the paper drying conditions. This makes it possible to eliminate waste such as stopping some drums.

That is, for example, in the case of a certain type of paper making, the temperature of the first group is 11s2100°C, the temperature of the second group is 102°C, and the temperature of the third group is 11s2100°C.
If you want to dry the group at a temperature of t3s-105℃,
The table below shows the conventional case where only steam is used and the case where steam and air are mixed as in this embodiment.

As can be seen from the above table, in the conventional case, the pressure difference between the first group and the second group is 0.1 kg/cm-G s The pressure difference between the second group and the third group is 0.15 kg/cni- G, and with such a pressure difference, it is practically impossible to use a rotary siphon.

On the other hand, in the case of this embodiment, even though the temperature difference between each group is the same as the conventional one, the pressure difference between each group is 0 and 5 kg/
The condensate can be discharged smoothly since it can be secured to the crtt-G and a rotary siphon can also be used.

In this way, even though the pressure difference between each group is large, the temperature difference between each group can be set small. It is also possible to set the same temperature difference between the two groups. Therefore, in contrast to the conventional usage mode in which, for example, the third group is stopped, in this embodiment, if all the first to third groups are used, this conventional usage mode can be achieved. Paper making can be dried under the same conditions, and since there are no drums to stop, problems such as rust on the outside of the drums and deterioration of the seal structure can be prevented.

Although the above embodiments have been described for drying paper, the present invention is not limited thereto, and can also be applied to drying other belt materials such as films and fabrics.

As detailed above, the present invention divides the rotary drying drums according to each operating pressure, sends a mixture of steam and air to each drum group, and the temperature in each drum group is regulated by a temperature control valve. By controlling φ based on Dalton's law using the partial pressure of steam, the temperature difference between each drum group can be made smaller than in the conventional method in which control is performed only using steam pressure.

In addition, a mixture of steam and air is sent to each drum group, and the total pressure of this mixture is controlled by each pressure control valve, and is sent sequentially from the drum group with the higher operating pressure to the drum group with the lower operating pressure. The pressure difference is ensured by the total pressure of the air-fuel mixture, and therefore the pressure difference between each drum group can be made larger than the temperature difference.

Therefore, when discharging condensate using a rotary siphon, etc., the large pressure difference due to the total pressure mentioned above can be used, so the condensate can be discharged reliably, and the problem caused by condensate accumulation This makes it possible to reduce the drum drive load.

Moreover, as mentioned above, the temperature difference can be made small despite the large pressure difference, so the temperature difference between each drum group can be made smaller than before, and the temperature can be adjusted according to the drying conditions of the strip material such as paper making. It is possible to select the operation mode by setting the , and to avoid waste such as stopping some drums.

Since there is no need for the drum to rest, various effects can be achieved, such as preventing the drum from rusting and seals from deteriorating.

[Brief explanation of the drawing]

The drawing is a schematic piping configuration diagram showing an embodiment of the present invention. 1...Rotary drying drum, 1S...1st
drum group, 2S... Second drum group, 3S...
...Third drum group, 4,5,6...Steam header, 7,8°9...Drain header,
10...Steam supply pipe, 14°15.16...
... Temperature indication control valve, 20 ... Air supply pipe,
22...Pressure instruction control valve, 3L39, 46...
...Steam water separator, 32,40...Mixture feed pipe, 33.41...Mixture release pipe, 35.4
2...Differential pressure indication control valve.

Claims (1)

[Claims] 1 A large number of rotary drying drums are divided into groups according to operating pressure, each drum group is connected to a steam supply source via a temperature control valve, and the drum group with the highest operating pressure is connected via a pressure control valve. The steam fed through the temperature control valve and the air fed through the pressure control valve are mixed in the drum group at the highest pressure, and the air fed through the pressure control valve is mixed. The temperature of the drum group is controlled by introducing steam by the operation of the temperature control valve that responds to the temperature of the mixture, and the pressure control valve that controls the pressure of the drum group at the highest pressure in response to the total pressure of the mixture. The mixture discharged from the drum group with the highest pressure is sequentially sent to other drum groups with lower operating pressure at its total pressure, and the drum group with lower operating pressure is controlled by the temperature control valve. Drying of a strip material characterized in that the temperature is controlled by the steam sent through the drum group, and the pressure is controlled by controlling the pressure of the mixture sent from the drum group having a high operating pressure with another pressure control valve. Device.