JP2000146714A - Temperature detector for digester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect an optical fiber cable for detecting temperature in a digester with a protection pipe that is strong against simple corrosion and stress corrosion crack. SOLUTION: An optical fiber cable 11 for detecting temperature in a digester is inserted into a protection pipe 12 and is turned in the digester for a specific number of times. Either one material out of inconel 625 and incoloy 825 and SUS 304 is used as the material for the protection pipe. Also, an inactive gas is sealed or circulated into the protection pipe. Further, a lubrication substance is provided outside the protection pipe to achieve a dimension where stress cannot remain easily due to the deformation of the dimension of the protection pipe.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature detector for a digester used in a continuous digester of a paper manufacturing plant.

[0002]

2. Description of the Related Art Generally, in a paper production plant, paper of a desired quality is produced through a digestion step, a washing / selection step, a bleaching step, a pulp preparation step and a paper making step.

[0003] Among these steps, in the digestion step, a pulp is produced by filling an alkaline cooking liquor containing chemical raw materials such as wood chips and caustic soda from the outside and heating the wood chips at a predetermined temperature to produce pulp. A digester is used.

As shown in FIG. 7, this continuous digester has a predetermined gap between the outer cylinder 102 constituting the wall of the digester main body and the cylinder 102 at a portion where the cooking liquor is taken out. Is filled with chips and cooking liquor from the upper part of the kettle, and the chips are heated from the upper part to the lower part of the kettle while heating the chips for about 8 to 10 hours. The wood chips are digested while lowering their own weight.

[0005] At this time, it is necessary to maintain the temperature of each part inside the digester at a predetermined temperature different depending on the user's request and the product as shown on the right side of the drawing, for example. Variations occur and have a major effect on product quality. Incidentally, the user is often required to control the temperature within an allowable range of ± 1 ° C. with respect to a predetermined temperature which is set in advance, and very strict is required for temperature control in the digester. .

[0006] Therefore, the temperature inside the digester is controlled by controlling the liquid during chip digestion that enters the gap through a strainer formed by an inner cylinder 101 having a slit shape or the like into a plurality of digesters in the depth direction of the digester. The heat exchanger 1 is controlled by controlling the amount of supplied steam and controlling the temperature based on the temperature detected by the resistance temperature detectors 103 ₁ , 103 ₂ ,...
04 _1, 104 _2, ... are the heat exchange, the pipes 105 _1, 105 ₂ of the hook center portion be represented by a schematic diagram shown top, by returning ... in a predetermined position in the digester via a internal digester Control is performed so that the temperature of each part becomes a predetermined temperature.
Note that i means an integer of 3 or more excluding 1 and 2.

[0007]

Accordingly, the above-described method for measuring the temperature of the digester is performed by measuring the temperature inside the digester measured by the resistance temperature detectors 103 ₁ , 103 ₂ ,... Installed near the liquid outlet. Using the temperature, the heat exchangers 104 ₁ , 10 ₁
4 _2, controls the ... temperature, the temperature of the digester is in practice a temperature in the vicinity of the liquid outlet, not the temperature of each part of the digester. For this reason, the accuracy of the detected temperature is lacking, and it is difficult to control the temperature of each part in the digester to a predetermined temperature, which is a factor of deteriorating the quality of the product.

As a thermometer other than the resistance thermometer, a conventionally well-known optical fiber temperature detector having an optical fiber cable having a temperature detecting function may be used. Difficult to do. The reason is that the inside of the continuous digester is in a high-temperature, high-pressure and crisp atmosphere.

Therefore, it is conceivable to protect the optical fiber cable by inserting it into the protective tube. However, since the optical fiber cable is in the above-described environment, the protective tube is broken by simple corrosion that gradually melts, Alternatively, there is a problem that crystal grains constituting the structure of the protective tube are dispersed by stress and chemical reaction caused by pressure and other factors, that is, so-called stress corrosion cracking occurs.

[0010] Furthermore, the core of the optical fiber cable is coated with a polymer resin, and the polymer resin is thermally decomposed by the high temperature in the continuous digester to generate hydrogen, and the polymer resin is exposed to air in the protective tube. There is also hydrogen. As a result, when the optical fiber cable is used at a high temperature in the continuous digester, there is a problem that the temperature detection characteristics of the optical fiber cable deteriorate due to the atmosphere of hydrogen generated from the polymer resin and hydrogen in the air.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a temperature detector for a digester suitable for detecting a temperature in a special atmosphere in the digester.

Another object of the present invention is to provide a temperature detector for a digester that prevents deterioration of characteristics of an optical fiber cable even in an atmosphere where hydrogen is present.

Still another object of the present invention is to provide a temperature detector for a digester which is suitable for installation work in a digester and has a structure in which residual stress is hardly left in a protective tube.

[0014]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is to insert an optical fiber cable for detecting the temperature in a digester for digesting wood chips into a protective tube and to rotate the inside of the digester. As this protective tube, Inconel 62
5, a temperature detector for a digester having a structure using any one material of Incoloy 825 and SUS304.

According to the present invention, by taking the above-mentioned means, the protective tube is made of one of Inconel 625, Incoloy 825 and SUS304 based on long-term experimental results, thereby achieving high temperature, high pressure and Even when laid in a digester in an alkaline atmosphere, it has excellent durability against both simple corrosion and stress corrosion cracking, and the protective tube does not break before its useful life, and thus the optical fiber cable It can provide sufficient protection and prevent damage to the optical fiber cable for a long time.

Further, another invention is to insert an optical fiber cable for detecting the temperature in a digester for digesting wood chips into a protective tube, and to fill the protective tube with an inert gas to circulate in the digester. It is a temperature detector for a digester in which an inert gas is allowed to flow through a protective tube.

According to the present invention, by taking the above measures, the air containing hydrogen in the protective tube is replaced by an inert gas which is circulated or sealed in the protective tube, or the hydrogen is removed during the circulating process. This makes it possible to avoid the characteristic deterioration of the optical fiber cable beforehand, and to detect the temperature in the digester with high accuracy over a long period of time.

Still another aspect of the present invention is to insert an optical fiber cable for detecting a temperature in a digester for digesting wood chips and to circulate around a gap formed by an inner cylinder and an outer cylinder of the digester. This is a temperature detector for a digester in which a lubricating substance is applied to the outer circumference of a protective tube.

According to the present invention, a lubricating substance is applied to the outer periphery of the protective tube when the protective tube is inserted through the gap formed by the inner and outer cylinders of the digester by taking the above measures. By applying the protective tube, the friction on the outside of the protective tube can be reduced, the work of inserting the protective tube becomes easy, and the residual stress on the protective tube can be reduced because a large force is not applied when the protective tube is inserted.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 is a diagram showing an example of a configuration of a temperature control system for a digester including a temperature detector for a digester according to the present invention.

This temperature control system for a digester comprises a digester 1 for digesting wood chips while heating a wood chip filled from the top of the kettle and a cooking liquor containing a predetermined chemical raw material for a predetermined time and at a predetermined temperature. A temperature detector 2 for the digester for detecting the temperature inside the digester 1 (2 ₁ , 2 ₂ ,...); And a temperature measuring device 3 for measuring the temperature detected by the temperature detector 2 for the digester. And a temperature control system 4 for controlling the temperature inside the digester 1 based on the temperature measured by the temperature measuring device 3.

In the digester 1, for example, a slit-shaped inner cylinder 1a is disposed inside an outer cylinder 1b which is a kettle body and is overlapped so as to have a predetermined gap to form a strainer having a double cylindrical structure. Then, the liquid being cooked by the wood chips passes through the slit-shaped inner cylinder 1a, fills the gap, and is taken out to the outside. In addition, the slit-shaped inner cylinder 1a does not necessarily have to be slit-shaped, and it is sufficient that holes are scatteredly formed on the cylinder surface. Generally, only the portion from which liquid is taken out is inside the outer cylinder 1b. Is provided with a slit-shaped inner cylindrical body 1a, and liquid is taken into a gap portion thereof. In addition, the inner cylinder 1
a is generally arranged at a portion from which a liquid is taken out.
Further, the outer cylinder 1b is not limited to the external shape shown in the drawing.

Since the temperature measuring device 3 uses the temperature detector 2 for the digester using an optical fiber cable,
An OTDR temperature measuring device is used. This OTDR temperature measuring device applies a high-speed optical pulse to an optical fiber cable, and the intensity ratio of the high frequency component and the low frequency component of the scattered light reflected from each point of the optical fiber cable and the scattered light reception time. The temperature at a specific position is measured from the above.

The temperature control system 4 takes in liquids from a plurality of predetermined portions in the depth direction of the digester 1 and heats the heat exchangers 5 ₁ and 5 ₁ .
5 _2, and heat exchange ..., the pipe 6 _and 62, other liquid circulating arrangement for returning to a predetermined position of the digester 1 via a ..., heat exchanger 5 _1, 5 _2, corresponding to ... shown Temperature controller is provided. The temperature controller controls the circulating liquid outlets of the heat exchangers 5 ₁ , 5 ₂ ,... So that the temperature at a predetermined position in the digester 1 becomes a predetermined target temperature based on the temperature measured by the temperature measuring device 3. It has the function of individually controlling the temperature or the circulating liquid supply flow rate. Specifically, in order to control the temperature of the circulating liquid at the outlet of the heat exchanger, a method of adjusting the flow rate of the heating steam supplied to the heat exchanger is used.

Next, an embodiment of the temperature detector 2 for the digester according to the present invention will be described.

As shown in FIG. 2, the temperature detector 2 for the digester is constructed such that an optical fiber cable 11 is inserted into a protective tube 12, and a plurality of predetermined portions in the depth direction in the digester 1 as shown in FIG. Are continuously laid in the digester 1 so as to pass through the gap between the inner tubular body 1a and the outer tubular body 1b corresponding to the above, and to make one or more rounds for each gap. In this configuration, a plurality of temperatures along the circumferential direction in the digester can be detected in the depth direction. The distal end of the optical fiber cable 11 is connected to the temperature measuring device 3, and the terminal end of the optical fiber cable 11 is taken out of the digester 1.
Is terminated.

Since the inside of the digester has a high-temperature, high-pressure, and alkaline atmosphere as described above, even if the optical fiber cable 11 is inserted through the protective tube 12, the protective tube 12 remains in an alkaline atmosphere. Therefore, simple corrosion gradually occurs, and a problem of stress corrosion cracking occurs due to stress under high pressure and chemical reaction due to high temperature and alkalinity.

Therefore, it is very important what kind of material of the protection tube 12 is used.

The reason why the present inventor chose the material for the protection tube 12 is as follows. SUS31
The fiber optic cable was protected using a protective tube made of the material of No. 6 and laid in the digester. However, since the inside of the digester was exposed to high-pressure, high-temperature alkaline cooking liquor, a primary test was performed after one year. In, we examined how the protective tube including the optical fiber cable is changing. At this time, the protection tube was subjected to stress corrosion cracking, and the cooking liquor solidified while passing through the protection tube, and the outflow into the protection tube stopped at a slight point, but the optical fiber cable was in a broken state. This may lead to human safety and environmental pollution, as well as breakage of the optical fiber cable, and has come to recognize the importance of material selection.

Therefore, the present inventor attached the following four types of test pieces (large and small) which are expected to be relatively strong in the above-mentioned atmosphere from a large number of materials during the periodic inspection of the digester. After standing for one year under normal operation, the analysis of each test piece was conducted. (1) Test sample (4 types) * SUS304 * SUS316 (used for primary test protection tube) * Inconel 625 * Incoloy 825 (2) About test results As an analysis result of each test piece, appearance observation is performed using an optical microscope. As a result, none of the test pieces showed signs of cracking, but were covered with corrosion products. It should be noted that pitting is observed only in SUS316, and stress corrosion cracking may occur when stress concentration occurs at the pitting occurrence part. The results confirm the cause of the breakage of the protective tube in the primary test. became.

Further, weight loss measurement (analytical balance) was performed. The results are as shown in Table 1.

[0032]

[Table 1]

As is clear from this table, Inconel 6
It was found that No. 25 had a large weight loss but was strong against stress corrosion cracking. The corrosion resistance in the atmosphere inside the digester is Incoloy 82.
5 was found to be the best.

Therefore, as the temperature detector 2 for the digester,
As is clear from the above experimental results, Inconel 62
5. If the protective tube 12 is formed using any one of the materials of Incoloy 825 and SUS304, and the optical fiber cable 11 is inserted into the protective tube 12 and used as the temperature detector 2 for the digester, high temperature and high pressure And, even when laid in a digester in an alkaline atmosphere, it becomes excellent in durability against both simple corrosion and stress corrosion cracking, and the protective tube 12 does not break before its useful life, Consequently, the optical fiber cable 11 can be sufficiently protected, and the optical fiber cable 11 can be prevented from being damaged for a long period of time. (Second Embodiment) FIG. 3 is a sectional view showing another embodiment of a temperature detector for a digester according to the present invention.

Since each core of the optical fiber cable 11 is coated with a polymer resin, hydrogen is generated by thermal decomposition at a high temperature in the digester, and hydrogen is present in the air in the protective tube. Hydrogen fiber optic cable 11
It is considered to be a cause of deteriorating the characteristics of.

Therefore, in the temperature detector for the digester according to the present invention, as shown in FIG. 4, the protection jig 14 is attached to the terminal processing section 13 of the protection tube 12 in an airtight manner, and the protection jig 14 is inactivated. The protective tube 12 is connected to a gas cylinder 15 and is filled with an inert gas 16 or is circulated. Reference numeral 17 denotes a stand for the cylinder 15.

According to the above configuration, by filling or flowing the inert gas 16 in the protective tube 12,
Even in a situation where hydrogen is present around the optical fiber cable 11, that is, in a state where hydrogen is present in the protective tube 12, hydrogen present in the protective tube 12 is replaced by the sealed inert gas 16 and hydrogen is removed. The characteristic deterioration of the optical fiber cable 11 can be avoided over a period, and thus the optical fiber cable 11 can be stably used as a temperature detector even at a high temperature.

Further, as the protective tube 12, Inconel 6
25, any one of Incoloy 825 and SUS304
If the two materials are used, the above-described effects can be obtained, and the optical fiber cable 11 can also realize a temperature detector for a digester that can sufficiently withstand a bad environment.

According to the temperature detector for the digester in which the inert gas 16 is allowed to flow through the protective tube 12, not only the hydrogen present in the protective tube 12 can be replaced by the inert gas 16, but also It is also possible to extract hydrogen to the outside in the circulation process by a conventionally known means. As a result, the deterioration of the characteristics of the optical fiber cable 11 due to hydrogen can be prevented as before.

As one type of the inert gas, for example, nitrogen gas can be mentioned.
Needless to say, the same effect can be obtained by enclosing or distributing in the inside 2. (Third Embodiment) FIGS. 5 and 6 are views for explaining another embodiment of the temperature detector for a digester according to the present invention.

The protective tube 12 into which the optical fiber cable 11 has been inserted is inserted into a strainer 21 which is a gap between the two cylindrical bodies 1a and 1b located at predetermined positions in the digester 1 as shown in FIG. The part is laid in the digester so as to make one or more rounds. 22 is a traffic line position,
23 is a mounting flange for the temperature detector for the digester.

The protective tube 12 into which the optical fiber cable 11 is inserted is inserted into a very narrow gap between the two cylindrical bodies 1a and 1b constituting the strainer 21.
At the time of insertion, the friction outside the protection tube becomes large and workability is deteriorated. In addition, a large force needs to be applied to insert the protection tube, which causes a stress to remain in the protection tube 12.

Therefore, in the temperature detector for the digester according to the present invention, the lubricating substance 24 is applied to the outer circumference of the protective tube 12 as shown in FIG. Function reduces friction,
The workability of attaching the temperature detector for the digester to the digester can be smoothly performed. Further, if the friction of the protection tube 12 is reduced, it is possible to eliminate the problem that the stress remains in the protection tube 12.

The lubricating substance 2 applied to the outside of the protective tube 12
As one material of No. 4, for example, a material such as PTFE {polytetrafluoroethylene (tetrafluoroethylene resin)} or PFA (tetrafluoroethylene-perfluoroalkylvinyl ether copolymer) can be used. Effects can be achieved. These PTFE, P
FA stands for molding powder, fine powder,
Used for lining, electric wire coating, film, etc., it has excellent heat resistance, chemical resistance, electrical properties, and self-lubricating properties. (Fourth Embodiment) A protective tube 12 in which an optical fiber cable 11 is inserted is provided in a strainer 21 which is a gap between the two cylindrical bodies 1a and 1b corresponding to a predetermined portion in the depth direction in the digester 1. And circulates once or plural times, and is laid in the digester 1.

Therefore, if the protective tube 12 is not of an appropriate thickness, flexibility and strength are insufficient, workability is poor, it is difficult to mount a temperature detector for a digester, and durability is insufficient. is there. That is, when the protective tube 12 is inserted into the strainer 21 to circulate around the continuous digester, if the thickness of the protective tube 12 is large, the friction on the outside of the protective tube increases, and the workability deteriorates. Therefore, a large force is required to cause the stress to remain in the protective tube 12.

Therefore, the thickness of the protective tube 12 used in the temperature detector for the digester according to the present invention becomes very important.

In consideration of the above points, the present inventor tried experiments such as workability while variously changing the thickness of the protective tube 12, and found that the inner diameter was 1.6 to 1.9 mm and the outer diameter was 1.6 mm. To 2.
2 to 2.5 mm, and the thickness is 0.6 mm ±
When the thickness is in the range of 0.1 mm, it is possible to solve the problem of poor workability such as extreme flexibility or strength, which makes it difficult to insert into the strainer 21 without leaving any stress on the protective tube 12. It could be made to go around the inside of the digester 1, and it was confirmed that it was enough from the viewpoint of durability.

[0048]

As described above, according to the present invention, even if the inside of the digester is in a high-temperature, high-pressure, alkaline atmosphere,
A temperature detector for a digester suitable for temperature detection resistant to simple corrosion and stress corrosion cracking can be provided.

Further, the present invention can provide a temperature detector for a digester capable of preventing the characteristic deterioration of the optical fiber cable even in an atmosphere in which hydrogen exists, and capable of detecting the detected temperature with high accuracy.

Further, the present invention provides a digester which is capable of smoothly circling the inside of a digester without installing stress in the protective tube with a small friction when the protective tube in which the optical fiber cable is inserted is installed in the digester. A kettle temperature detector can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing one configuration example of a digester temperature control system including a digester temperature detector according to the present invention.

FIG. 2 is a sectional view showing an embodiment of a temperature detector for a digester according to the present invention.

FIG. 3 is a sectional view showing an embodiment different from FIG. 2 of the temperature detector for the digester according to the present invention.

FIG. 4 is an explanatory view showing a mechanism for enclosing or flowing an inert gas into a protective tube constituting a temperature detector for a digester according to the present invention.

FIG. 5 is a diagram illustrating a state in which the temperature detector for the digester according to the present invention is inserted into the digester and circulated.

FIG. 6 shows a temperature detector for a digester according to the present invention.
Sectional drawing which shows embodiment different from FIG.

FIG. 7 is a configuration diagram illustrating a conventional temperature control system for a digester.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Distiller 1a: Inner cylinder, 1b: Outer cylinder (side wall of digester main body) 2 ... Temperature detector for digester 3 ... Temperature measuring device 4 ... Temperature control system 11 ... Optical fiber cable 12 ... Protective tube 16 ... Inert gas 24 ... Lubricant

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoji Matsuo 2-1-1, Ojimachi, Tomakomai City, Hokkaido Inside the Tomakomai Mill of Oji Paper Co., Ltd. (72) Inventor Shigeki Yamazu 1-1-1, Shibaura, Minato-ku, Tokyo No. Toshiba Corporation Head Office (72) Inventor Yukio Sai 1-1-1, Shibaura, Minato-ku, Tokyo Inside Toshiba Corporation Head Office (72) Inventor Hiroshi Ota 1-1-1, Shibaura, Minato-ku, Tokyo Stock Company F-term in Toshiba head office (reference) 2F056 CL13 VF02 VF20 4L055 CA23 DA13 DA30 EA15 FA13 FA19 FA22 FA30

Claims (5)

[Claims] In a digester temperature detector for detecting the temperature in a digester for digesting wood chips, an optical fiber cable is inserted into a protective tube to circulate around the digester, and the protective tube is made of Inconel 625. , Incoloy 825 and SUS304. 2. A digester temperature detector for detecting a temperature in a digester for digesting wood chips, wherein an optical fiber cable is inserted into a protective tube and an inert gas is sealed in the protective tube. A temperature detector for a digester characterized by being circulated in the kettle. 3. A temperature detector for a digester for digesting wood chips for detecting the temperature in a digester, wherein an optical fiber cable is inserted into a protective tube to circulate around the digester, and an inert gas is contained in the protective tube. A temperature detector for a digester characterized by flowing gas. 4. A digester temperature detector for detecting a temperature in a digester for digesting wood chips, wherein a lubricating substance is applied to an outer periphery of a protective tube for passing around the inside of the digester by inserting an optical fiber cable. A temperature detector for digesters. 5. The protective tube has an inner diameter of 1.6 to 1.9 m.
m, the outer diameter is 2.2 to 2.5 mm, and the thickness thereof is in the range of 0.6 mm ± 0.1 mm. Temperature detector for digesters.