JP3157135B2 - Drying equipment for papermaking - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drying apparatus for papermaking, which uses low-pressure oil heated by heat exchange with combustion gas such as propane gas or city gas, instead of using steam as a heat medium. The aim is to improve safety and reduce air pollution.

[0002]

2. Description of the Related Art Conventionally, a drying apparatus for papermaking uses high-pressure steam as a heat source. That is, a boiler that uses heavy oil as a heat source for obtaining high-pressure steam is provided, and the high-pressure steam obtained by the boiler is transported to a drying device by piping. A pipe for connecting the boiler to the drum of the drying device is provided, high-pressure steam from the boiler is sent to the drum jacket via the pipe, and the paper is dried during its movement by contacting the hot drum. .

[0003] Boiler equipment for high-pressure steam uses heavy oil as fuel to generate smoke during combustion, which is a major cause of air pollution. In addition, since steam is at high pressure, a high-pressure resistant drum is used. And the production cost of the drum increases. In addition, since the weight of the drum is increased, power consumption during operation is increased, and the running cost is increased. High-pressure boiler equipment is legally required to have periodic inspections and the installation of a dedicated manager. In a paper mill where continuous operation is usually performed day and night, replacement personnel are required, which increases personnel costs.

In view of the above problems, Japanese Patent Application Laid-Open No. 61-75
Japanese Patent Application Laid-Open No. 896 and JP-A-61-75897 propose an electromagnetic induction heating system instead of using steam as a heating source. That is, in this method, the electromagnetic induction heating coil is provided close to the dryer drum, and the drum is heated by Joule heat of the eddy current induced in the drum by passing an alternating current through the electromagnetic induction heating coil. .

[0005]

SUMMARY OF THE INVENTION Japanese Patent Laid-Open No. 61-7589
No. 6, JP-A-61-75897 discloses a technique in which a drum is heated by Joule heat of eddy current induced in a dryer drum by an electromagnetic induction heating coil. Therefore, although this prior art system is a kind of heating system using electric power, burying a normal electric heater in a rotating drum makes it difficult to energize the electric heater. It is understood that an induction heating method is employed to cause the drum to generate heat electrically while being fixedly disposed on the case side.

However, heating by electroheating is not high in terms of fuel efficiency in the first place (it goes without saying that electric power is obtained by fuel and conversion loss is inevitable), and the electromagnetic induction heating method uses a non-contact method for the medium to be heated. Therefore, even if the heat generation method using electric heat is used, the efficiency is not high. Therefore, the power cost is significantly increased. Furthermore, for uniform drying of the paper, it is necessary to arrange the induction heating coil over the entire length of the drum, which increases the equipment cost. On the other hand, in the papermaking industry, fields such as newsprint and dustpaper are typically exposed to strict cost requirements, and the possibility of the above-mentioned conventional patent system being small in terms of widespread adoption in the papermaking industry.

In view of the above-mentioned problems of the prior art, an object of the present invention is to use steam without using steam, and in terms of manufacturing cost and running cost, to compete with the system by using steam or lower in cost. It is an object to provide a feasible heating device.

According to the present invention, a heating device for heating oil as a heating medium, and a drying drum having a jacket for oil as a heating medium, which is in contact with the paper to be dried on the outer periphery thereof A piping system for circulating oil, and a pump for circulating oil in the piping system, wherein the jacket has an inlet and an outlet connected to the piping system, The device is constituted by a gas combustor arranged in close proximity to a heat exchange section as a meandering pipe which is a part of a piping system, and by causing combustion gas formed by the gas combustor to act on the heat exchange section, There is provided a papermaking drying apparatus characterized in that circulating oil passing through a meandering pipe constituting a heat exchange section is directly heated by a combustion gas.

In the operation of the apparatus of the present invention, the oil heated by the heating device is supplied to the jacket by the pump, and the drying drum is heated. As a result, the paper contacting the drying drum is dried. The oil is returned from the oil jacket to the heating device, where it is heated to a predetermined temperature and then supplied to the drum again.

[0010] According to the present invention, since the oil serving as the heat source is circulated and used in the closed system, the amount of the oil can be reduced, and the use of the oil does not increase the cost. Further, it is sufficient that the oil is at a pressure (for example, 0.2 kg / cm ² ) at which the oil can be uniformly supplied to the drying drum, and the pressure in the drum and the piping system is lower than that of a conventional drying system using steam. Can be greatly reduced. For this reason, even a lightweight material can sufficiently withstand use, reducing manufacturing costs,
Since the required power can be reduced, the power cost can also be reduced.

The heating device is constituted by a gas combustor arranged in close proximity to a heat exchange section as a meandering pipe which is a part of a piping system, and directly burns the combustion gas formed by the gas combustor. By acting on the heat exchange section,
The oil passing through the heat exchange section as a meandering pipe is heated. By using gas as fuel, it is possible to reduce smoke damage as compared with a conventional boiler using heavy oil, and to provide an environmentally friendly papermaking facility.

The oil jacket forms a spiral passage in the circumferential direction of the drum, the inlet of the oil jacket is located at one end of the passage, and the outlet of the oil jacket is located at the other end of the passage. The heated oil flows from the inlet to the outlet through the spiral passage, so that the accumulation of oil in the jacket is minimized, and the paper can be uniformly dried from the drum.

The drying drum is made of light metal such as aluminum, and its surface can be coated with a hard material. By coating the surface of the lightweight aluminum with various hard materials (for example, chrome) suitable for the type of paper to be dried by thermal spraying or the like, it is possible to secure necessary strength while maintaining the lightweight of the drum. The power required for driving the drum can be reduced by reducing the weight of the drum.

An oil tank can be installed at a position before the jacket in a piping system for oil circulation. By installing an oil tank, high-temperature oil can always be supplied to the jacket. Also,
The oil tank is kept warm by providing a vacuum chamber around it, and the oil temperature to the jacket can be secured.

[0015] A vacuum chamber can be formed inside the jacket of the drying drum, thereby improving heat retention.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 schematically shows a papermaking drying apparatus, in which reference numeral 10 denotes a drying drum, which is basically formed of a thin aluminum sheet. The rotating shaft 12 of the drum 10 is rotatably supported by a support 14.
16, 18, 20, and 22 are guide rollers, and the canvas 24
Are arranged so as to go between the guide rollers 16, 18, 20, and 22. Reference numeral 26 denotes a sheet to be dried, and the guide roller 1
Between 6 and 18 the canvas 24 presses the paper 26 against the drying drum 10. With the rotation of the drum 10 as indicated by the arrow a, the canvas is rotated by the guide rollers 16,
The paper circulates between 18, 20, and 22, and the paper is conveyed in the direction of arrow c, at which time the paper 26 is dried by the high temperature of the drum 10.

FIG. 2 shows a drum 10 in contact with the paper to be dried.
2 schematically shows the structure on the outer peripheral surface of FIG. The base material 10A of the drum 10 is formed from an aluminum plate as described above. The surface in contact with the paper to be dried is formed by a hard layer 10B such as chrome. The chrome hard layer 10B can be formed by thermal spraying or the like.
Depending on the type of paper to be dried, the hard layer 10B on the surface can be formed of a material other than chrome. Further, depending on the material for forming the hard layer, it is possible to employ a surface forming means other than thermal spraying.

In FIG. 3, the drum 10 includes an outer cylinder 30 and
End plates 32A and 32B welded and fixed to both ends of the outer cylinder 30; an outer inner cylinder 34 disposed inside the outer cylinder 30;
4 and an inner inner cylinder 36 disposed inside. Outer cylinder 3
The annular space between 0 and the outer inner cylinder 34 constitutes a heating oil jacket 38. A partition plate 40 is arranged in the jacket 38. The partition plate 40 extends spirally along the inner circumference of the outer cylinder 30, in other words, along the outer circumference of the outer inner cylinder 34, so that the jacket 38 has a spiral path centered on the central axis of the drum 10. Has formed. The entrance of the jacket 38 which is such a spiral passage is represented by 38A, and the exit is represented by 38B.

An annular space 42 is formed between the outer inner cylinder 34 and the inner inner cylinder 36, and this space 42 is maintained at a vacuum, so that the inner space of the jacket 38 can be efficiently kept warm. It can function as an insulator. Therefore, even if the amount of circulating oil is small, the temperature in the jacket 38 can be maintained, and the thermal efficiency can be increased.

The rotating shaft 12 of the drum 10 is hollow, and both ends are fixed to end plates 32A and 32B of the drum 10, and the ends of the rotating shaft 12 protruding from the end plates 32A and 32B are bearings 44A and 44A.
It is supported on the support 14 by 44B. Rotary shaft 12
Partition plates 46 and 48 are fixed therein, the hollow portion of the rotary shaft 12 outside the partition plate 46 forms an oil supply chamber 50, and the hollow portion of the rotary shaft 12 outside the partition plate 48 forms an oil discharge chamber 52. Has formed. The oil supply chamber 50 is connected by a radial passage 51 to the jacket inlet 38A.
The oil discharge chamber 52 is connected to the jacket outlet 38B by a radial passage 53.

Next, a description will be given of a circulation system of oil as a heat medium to the jacket 38. The oil circulation system is configured as a completely closed type, and an oil supply pipe 54 opening to an oil supply chamber 50 and an oil discharge chamber 52 are provided. , An oil discharge pipe 56 that opens to the inside, a heat exchanger 60 as a heating device for heating the oil, a pipe 62 for taking out the oil heated by the heat exchanger 60, and a pipe 6
Oil tank 64 for storing heated oil from 2
And an oil pump 6 installed in the oil supply pipe 54.
And 6. The position of the oil pump 66 may be before the heating device 60. Further, in addition to the oil pump 66 on the oil supply pipe 54, the oil discharge pipe 5
A second oil pump (not shown) can be additionally installed at 6. The auxiliary pump may be provided in parallel with and switchable with the oil pump 66 so that the oil pump 66 can be immediately switched to the auxiliary pump and used when a failure occurs.

The oil supply pipe 54 is rotatable with respect to the rotary shaft 12 by a pair of bearings 68. During the rotation of the rotary shaft 12, that is, the drum 10, oil is introduced into the oil jacket 38 inside the drum. It is possible. Similarly, the oil discharge pipe 56 is rotatable with respect to the rotary shaft 12 by a pair of bearings 70, so that oil can be discharged from the oil jacket 38 inside the drum 10 while the drum 10 is rotating. Oil seal 7
1 seals the oil supply chamber 50 to the outside, and the oil seal 72 seals the oil discharge chamber 52 to the outside.

FIG. 4 schematically shows the flow of oil in the drum 10. That is, the oil from the supply pipe 54 enters the oil supply chamber 50 from the center axis (arrow a), is guided radially outward through the passage 51 (arrow b), and enters the inlet 38A.
And enters the jacket 38 at the outer periphery of the drum 10 in a spiral manner (arrow c), and the outlet 38
B is guided inward from the radius via the passage 53 (arrow d),
The oil enters the oil discharge chamber 52, then turns in the axial direction (arrow e), and is discharged from the pipe 56. Jacket 3
Due to the spiral flow of the heating medium in 8, the stagnation of oil in the jacket 38 is prevented and the temperature of the oil becomes uniform, so that an ideal drying effect can be realized.

The oil heating device 60 is preferably of a direct fire type having a structure similar to that of an instantaneous water heater used for a bath pot or the like in terms of thermal efficiency. That is, the oil heating device 60 is a meandering pipe-shaped heat exchange unit 60 that receives oil from the oil pump.
A and a combustion part 60B for a combustion gas such as propane gas or city gas. The oil is passed through a direct heat exchange between the oil passing through the heat exchange part 60A and the combustion gas generated by the combustion part 60B. Can be heated. In order to heat the oil in the heat exchange unit 60A by direct combustion by the combustion gas, the pipes constituting the heat exchange unit 60A must not leak oil passing therethrough, but the oil temperature is low and the oil Due to the low pressure, it is technically possible to avoid problems by properly designing the material and thickness of the pipe. Further, when the amount of heat is insufficient with one heat exchanger, a plurality of heat exchangers may be installed in multiple stages in parallel or in series.

In this embodiment, the combustion section 60B is constituted by switching the combustion state between a high combustion state and a low combustion state (including a pilot flame only state). The oil temperature is lowered in the combustion state, and the combustion state is turned on / off in accordance with the detected oil temperature. However, the configuration of the combustion unit 60B may be any configuration that can realize more complicated combustion state control including continuous control.

The oil used as the heating medium has such a characteristic that when the oil is heated to the surface temperature of the drum 10 necessary for drying the paper, the oil can be used stably without being deteriorated by heat for a long period of time. Although there is a demand to select an oil, since the surface temperature of the drum 10 at the time of drying the paper is as low as 200 ° C. at the highest, an oil satisfying such a demand can be obtained by using a commercially available mineral oil or aromatic oil for a heat carrier. It can be selected from those of the system.

Since the required drum surface temperature is not high as described above, the oil heating device 60 can be constituted by an electric heater. However, when an electric heater is used, it is inevitable that the efficiency is lower than oil heating by direct gas fire.

The controller 74 is constituted by a microcomputer or the like, is connected to sensors for detecting the temperature of each part of the system and various setting devices, and controls the oil pump 66 based on the information so as to perform the optimal oil circulation. A signal is formed, and a control signal to the oil heating device 60 is formed so that optimal oil heating is performed. In this embodiment, as the sensors for detecting the temperature, the inlet 80, the outlet 82,
And an outlet 84 of the heating device 60.

FIG. 5 is a block diagram showing the configuration of the controller, which includes a microprocessor unit (MPU) 88, a read only memory (ROM) 90, a random access memory (RAM) 92, a clock pulse generator 94, and an input / output port. The microcomputer includes ordinary components such as a microcomputer 96 and a bus 98 connecting these components.
The input / output port 96 is connected to the jacket inlet temperature sensor 80, the jacket outlet temperature sensor 82, and the oil temperature sensor 84 described above.

Further, a sensor 100 for detecting the rotation speed of the oil pump 66 is connected to the input / output port 96. The temperature setting device 102 is configured as a potentiometer or the like, and operation means such as a knob (not shown) can be provided on the control panel, and the oil temperature can be arbitrarily set by a manual operation of the knob. Set temperature T _SET set by the operation of the temperature setter 102 is taken from the output port 96. Further, the input / output port 96 is connected to a pump rotation speed setting unit 104, and operation means such as a knob (not shown) can be provided on the control panel. Volume) can be set arbitrarily. The set pump rotational speed N _SET set by operating the pump rotational speed setting device 104 is taken in from the input / output port 96. The calculated value of the oil pump rotation speed obtained as a result of the calculation by the microcomputer is sent to the pump rotation speed controller 108 and the oil pump 66
Is controlled so that the rotation speed of the control signal coincides with the calculated value.

The combustion controller 106 is provided in the combustion section 60B of the heat exchanger 60, and sets the temperature of oil as a heat exchange medium by controlling the amount of combustion gas used for combustion in the heat exchange section 60A. Control to a value. In this embodiment, the combustion controller 106 sets the amount of combustion gas to two for high combustion and low combustion.
The oil temperature is increased by increasing the amount of combustion gas during high combustion, and the oil temperature is decreased by decreasing the amount of combustion gas during low combustion. The oil temperature is controlled to a set value by the control. It is of course arbitrary to incorporate more complicated control in order to perform combustion control with higher accuracy.

Next, an example of the basic operation of the controller will be described with reference to the flowcharts of FIGS. 6 to 8 and the timing chart of FIG. It goes without saying that the program for realizing the control of this flowchart is stored in the ROM 90. Further, for simplicity, this control flowchart describes the operation of the controller in the simplest case as an example, and does not intend to limit the present invention. It is possible for a person skilled in the art to incorporate more complex operations depending on the situation within the scope of the present invention. FIG. 6 shows a routine for reading the set value of the rotation speed of the main pump 66. This routine is executed at regular intervals. When the routine is started, in step 110, a set value _NSET of the rotation speed of the main pump 66 set by an operation knob (not shown) of the pump rotation speed setting device 104 provided on the controller panel is read. N _SET corresponds to the flow rate of oil as a heat exchange medium to the jacket 38 (flow rate of circulated oil). The optimal value of the oil flow varies depending on the paper drying conditions (papermaking speed, water content, etc.), but the pump rotation speed setting device 104 is set so as to have a set value suitable for the conditions.

In step 112, the temperature set value _TSET is read. _TSET is appropriately set by operating an operation knob (not shown) of the temperature setting device 102 provided on the controller panel. That is, the optimum temperature of the oil changes according to the drying condition of the paper, but the operation knob of the temperature setting device 102 is set to the oil temperature that matches the drying condition at that time.

FIG. 7 shows the gas combustion section 60B so that the oil temperature Т at the outlet of the heat exchanger 60 matches the temperature set value T _SET set in step 110 of FIG.
2 shows a routine for controlling the combustion state in the above. In step 114, the heat exchanger 6 measured by the temperature sensor 84
A reading of the oil temperature Т at the 0 outlet is taken. In the next step 116, it is determined whether or not the combustion state in the gas combustion section 60B is a high combustion state. In the high combustion state, the oil temperature from the heat exchanger 60 is increasing as shown in FIG. Next, the routine proceeds to step 118, where it is determined whether or not T-T _SET > δ1 is satisfied, in other words, whether or not the measured temperature value Т is equal to or higher than T _SET + δ1. In the determination of step 118,
When T-T _SET > δ1 is not satisfied, in other words, when the measured temperature value Т is lower than T _SET + δ1, the routine is terminated as it is. When T-T _SET > δ1 is satisfied, in other words, the temperature measurement is performed. When the value Т is equal to or higher than T _SET + δ1, the routine proceeds to step 120, where the gas combustion unit 60B
Is switched from the high combustion state (A in FIG. 9B) to the low combustion state (B in FIG. 9B). By switching to low combustion, the heat exchanger 6 is switched as shown in FIG.
The oil temperature from zero goes down.

When the process shifts to the oil temperature decreasing process due to the low combustion operation in the gas combustion section 60B, step 116 is executed.
Is negative, the process proceeds to step 122, and T _SET -T
> Δ2 is satisfied, in other words, the measured temperature value Т is T
_SET- Determined if less than or equal to δ2. In the determination at step 118, T _SET -T> δ2
Does not hold, in other words, the measured temperature value Т is T _SET-
When it is equal to or higher than δ2, the routine is terminated as it is. However, when T _SET −T> δ2 holds, in other words, when the measured temperature value よ り falls below T _SET −δ2, the routine proceeds to step 124. The combustion state in the gas combustion section 60B is switched from the low combustion state to the high combustion state. By switching to high combustion, the oil temperature from the heat exchanger 60 shifts to increase as shown at a 'in FIG.

[0036] Thus repetition of control, such as (low fire and on-off control of the sense of the high combustion), the oil temperature is controlled in the range of at most be + .delta.1 lower -δ2 the set value T _SET Is done.

FIG. 8 shows a rotational speed control routine of the main oil pump 66. This routine is for oil jacket 3
The number of rotations of the oil pump 66 is controlled so that the temperature difference between the inlet 38A and the outlet 38B in FIG. In step 130, the jacket inlet temperature sensor 8
0 and the temperature T _IN at the jacket inlet section 38A by the jacket outlet temperature sensor 82 and the jacket outlet section 38
The measured value of the temperature T _{OUT at} B is input. Step 132
Then, jacket inlet temperature T _IN and jacket outlet temperature T
The difference ΔТ from _OUT is calculated. Step 134 In the temperature difference DerutaT is discriminated whether greater than the set value ΔТ _SET, when the temperature difference DerutaT is larger than the set value DerutaT _SET Step 1
At 36, the calculated value N of the oil pump speed is updated by N = N _SET + G × ΔT. G represents a gain (sensitivity). This equation shows that the rotation speed (oil circulation speed) of the oil pump is proportionally corrected with respect to the set value _NSET according to the temperature difference between the inlet and the outlet of the jacket. When it is determined that the temperature difference DerutaT is not greater than the set value DerutaT _SET at step 134 is step 136 is bypassed, the rotational speed of the oil pump without updating the N is carried out is not controlled.

With this control, the temperature difference between the inlet portion 38A and the outlet portion 38B of the oil jacket becomes the set value ΔТ.
The rotation speed (oil circulation speed) of the oil pump 66 is corrected with respect to the set value _NSET so as not to become larger than _SET . That is, when the temperature difference becomes large, the oil flows from the inlet 38A to the outlet 38B by increasing the flow rate of the oil.
Correct so that the temperature drop during the travel is small. In other words, the amount of oil circulation is controlled so that the temperature drop during passage through the spiral oil jacket 38 does not increase. Thereby, the drying drum 1
Regardless of the configuration in which the oil as the heating medium flows spirally from the inlet to the outlet along the zero axis, the drying effect in the width direction of the paper can be kept substantially unchanged.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing an entire configuration of a dryer.

FIG. 2 is a cross-sectional view schematically illustrating a surface structure of a drying drum.

FIG. 3 is a schematic view showing the entire oil circulation system in a drying drum.

FIG. 4 is a perspective view schematically showing a flow of oil in a drying drum.

FIG. 5 is a diagram showing a schematic configuration of a controller.

FIG. 6 is a flowchart schematically illustrating a setting process of a pump rotation speed and a temperature.

FIG. 7 is a flowchart schematically showing a control method of an oil temperature sent to a drying drum.

FIG. 8 is a flowchart schematically showing a control method of an oil circulation speed.

FIG. 9 is a diagram showing a control state of oil temperature.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Drying drum 12 ... Rotating shaft 14 ... Support body 16, 18, 20, 22 ... Guide roller 24 ... Canvas 26 ... Drying paper 30 ... Outer cylinder 34 ... Outer inner cylinder 36 ... Inner inner cylinder 38 ... Jacket 38A ... Jacket Inlet 38B ... Jacket outlet 40 ... Partition plate 42 ... Vacuum space 50 ... Oil supply chamber 52 ... Oil discharge chamber 54 ... Oil supply pipe 56 ... Oil discharge pipe 64 ... Oil tank 66 ... Oil pump 60 ... Oil heating device 60A ... Heat Replacement unit 60B Combustion unit 74 Controller

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) D21F 5/02 F28F 1/00-27/02

Claims (1)

(57) [Claims] 1. A heating device for heating oil as a heating medium, which comes into contact with the paper to be dried at the outer periphery thereof,
A drying drum having a jacket for oil as a heating medium therein, a piping system for circulating oil, and a pump for circulating oil in the piping system; An inlet and an outlet connected to the system, wherein the heating device is constituted by a gas combustor arranged close to a heat exchange section as a meandering pipe which is a part of a piping system, The circulating oil passing through the meandering pipes constituting the heat exchange section is heated directly by the combustion gas by causing the combustion gas formed by the heat to act on the heat exchange section. .