JPH06241376A - Heating method by electroheating pipe - Google Patents

Abstract

PURPOSE:To suppress unevenness of the temperature of an electroheating pipe by a simple method. CONSTITUTION:Electrodes 4 and 5 are installed on both ends of a conductive pipe 1, a current is supplied from connecting leads 6 and 7, and the electrodes are heated by joule's heat. Accordingly, a fluid passing through the inside of the pipe 1 is heated. In the pipe 1, a metallic plate of the same material as that of the piping is installed as a bypass pipe 2. Based on the temperature of each part measured without mounting the bypass pipe 2, the bypass pipe 2 is installed in an area where the temperature is high while taking the area where the temperature is lowest as a reference. Then, since the amount of heating value in the area can be adjusted according to the resistance value of the bypass pipe 2, unevenness of the temperature of the pipe 1 can be suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating method using an electric heating pipe, for example, in a raw material carrying pipe that requires temperature control, a metal pipe is used as a carrying pipe, and a direct current is applied to the metal pipe. The present invention relates to a heating method using an electric heating pipe for flowing a raw material to heat a fluid raw material flowing in the metal pipe.

[0002]

2. Description of the Related Art For example, S which is a raw material used in the VAD method.
When a raw material that is liquid at room temperature, such as iCl ₄ , is to be transported in a vaporized state, it is necessary to maintain the temperature of the transport pipe at a certain temperature. In such a case, a metal pipe is used as a pipe for transportation, an electric current is directly applied to the metal pipe, the metal pipe is heated by Joule heat, and a raw material flowing in the pipe is heated. .

FIG. 5 is a schematic view of a conventional example of a heating method using an electric heating pipe. In the figure, 1 is a pipe, 3 is a temperature sensor, 4 and 5 are electrodes, 6 and 7 are connection conductors, 9 is a control unit, 1
0 is a heating current source. The pipe 1 is a long pipe,
Electrodes 4 and 5 are attached to both ends of the heating current source 10
The piping itself is electrically heated by the energizing current from. A temperature sensor 3 is attached to one point of the pipe 1. As the temperature sensor 3, a suitable temperature sensor such as a thermocouple or a thermistor is used. In accordance with the output signal of the temperature sensor 3, the control unit 9 controls the heating current source 10 to control the current flowing through the pipe and adjust the temperature of the pipe.

When the pipe is heated, if there is no temperature unevenness in the longitudinal direction of the pipe, the temperature sensor 3 always keeps the entire pipe at a predetermined heating temperature. However, in the case of a long pipe, temperature unevenness occurs in the longitudinal direction of the pipe due to the difference in heat insulating efficiency of each part. Then, the portion where the temperature is detected by the temperature sensor 3 is controlled to a constant temperature,
The temperature of the portion without the temperature sensor becomes different.

By the way, the temperature of the piping must not rise above the heat resistant temperature of each component. Also,
For example, the temperature should not drop below the temperature at which the source gas does not liquefy. Therefore, the temperature of each part of the pipe must be kept at the maximum between the upper and lower temperature limits. However, if temperature unevenness occurs in the longitudinal direction of the pipe,
When adjusting the temperature with the temperature sensor,
It becomes difficult to adjust the temperature so that each part is between the upper limit temperature and the lower limit temperature.

Therefore, conventionally, in order to keep the heat insulating effect constant, a method of suppressing a decrease in temperature by adding a heat insulating material to the low temperature portion of the pipe is adopted, but the amount of the heat insulating material added is After adding the heat insulating material, there is only a method of determining the temperature distribution again by a trial-and-error method such as re-adjusting the temperature distribution, and there is a problem that it takes a lot of work. Also, depending on the location of the piping, there may not be enough space to install the required amount of insulation.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and provides a heating method capable of suppressing the temperature unevenness of an electric heating pipe in a completely different method from the conventional one. It is intended.

[0008]

DISCLOSURE OF THE INVENTION The present invention is a heating method using an electric heating pipe in which an electric current is directly applied to a metal pipe to heat a fluid flowing in the metal pipe, and the resistance distribution in the longitudinal direction of the metal pipe is changed. It is characterized by adjusting the temperature distribution in the longitudinal direction of the metal pipe by making the resistance of the metal pipe in the longitudinal direction by joining a metal of the same kind as the metal pipe around the metal pipe. It is also characterized by changing the distribution.

[0009]

By changing the resistance distribution in the longitudinal direction of the metal pipe, it is possible to adjust the partial heat generation amount of the pipe, thereby adjusting the temperature distribution in the longitudinal direction of the metal pipe. Further, by partially joining the same kind of metal as the metal pipe around the metal pipe, the substantial cross-sectional area is increased and the resistance distribution in the longitudinal direction of the metal pipe can be changed.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic diagram of an electric heating pipe according to an embodiment of the present invention. In the figure, the same parts as those in FIG. 2 is a bypass. Each of the electrodes 4 and 5 is configured so that it can be divided into two, and is clamped from both sides with the pipe 1 sandwiched between them. A current for heating is supplied by the connecting conductors 6 and 7 to energize the pipe 1. . The bypass 2 is a metal plate having a predetermined length and different widths are prepared. Of course, the thickness, or
Both width and thickness may be different. If the bypass is made of a different metal, it becomes a local battery due to the difference in ionization tendency, which may corrode the pipe. Considering this point, it is desirable to use the same material as the piping. For example, SUS can be used for the pipe 1 and SUS for the bypass 2.

The bypass 2 is attached to a portion having a large amount of heat generation, as will be described later. The attachment may be performed by welding, but a fixing means such as a tightening band may be used. The tightening band is bypass 2 or pipe 1.
Although the same material as described above may be used, an insulating material or a material having a large resistance value may be used when the influence of the tightening material is a problem. The portion to which the bypass 2 is attached has a low resistance value and the amount of heat generation is reduced.

An example of a bypass setting method will be described with reference to FIGS. FIG. 3 is a schematic diagram for explaining the temperature distribution state of the pipe. In this figure, the piping is divided into n equal lengths of 1, 2, 3, ..., N for convenience. The temperature at the midpoint in each divided range θ ₁ , θ ₂ ,
θ _3, to measure ..., the θ _n as a representative temperature.

Here, the jth (j is 1, 2, 3, ..., In the equilibrium state in which the temperature at a temperature control point to which a temperature sensor (not shown) is attached reaches a set temperature (target temperature).
The representative temperature θ _j of n) can be considered as θ _j = I ² R / k _j (1), ignoring the heat conduction in the pipe and the change in resistance value due to temperature. Here, I is the current [A] R flowing through the pipe in the equilibrium state, the resistance Q [Ω] k _j of the pipe is the heat transfer coefficient [W / K] to the outside in the j-th divided range. From equation (1), the equivalent heat transfer coefficient k _{j at} each division point can be estimated from the representative temperature of each division range.

Therefore, in order to match the resistance value of each divided range with the heat transfer coefficient, when the resistance value of each divided range is R _j , R ₁ : R ₂ : R ₃ : ...: R _n = It is sufficient to set k ₁ : k ₂ : k ₃ : ...: k _n = 1 / θ ₁ : 1 / θ ₂ : 1 / θ ₃ : ...: 1 / θ _n .

FIG. 4 is an explanatory diagram showing a state in which a bypass resistor is attached to each divided range in order to satisfy the above-mentioned relationship. Now, assuming that the m-th divided range has the lowest temperature, the divided range is left as R without bypass, and the j-th divided range except the m-th divided region has the following resistance value _RAj. It will be good if the bypasses with are attached in parallel. R _Aj = Rθ _m / θ _j −θ _m (2)

In the description of FIGS. 1 to 3, the divided ranges have the same length, but this is for convenience of description, and it is not necessary that the divided ranges have the same length. The bypass resistance may be determined in consideration of the length of each divided range and the resistance value.

FIG. 2 is a schematic diagram of an electric heating pipe according to another embodiment of the present invention. In the figure, the same parts as those in FIG. 8 is an adhesive tape. In this embodiment, the bypass 2 is a linear body having a constant thickness. SUS was used as the material of the pipe 1, and the temperature of each part was kept within a constant temperature range over the entire length of the pipe 1. As described above, the temperature unevenness is suppressed by attaching the bypass. The bypass 2 uses the same SUS wire as the pipe.

After measuring the temperature distribution, the resistance value can be adjusted by the number of bypasses 2. Bypass 2 is
The number is determined so as to be close to the resistance value calculated by the above formula (2), and the resistance value is fixed with a heat-resistant adhesive tape 8 such as a glass tape. At this time, care must be taken not to insulate the bypass 2 and the pipe 1 with the adhesive tape 8.

The cross-sectional area a of the wire used as the bypass 2
When the temperature difference between the temperature to be adjusted and the outside air temperature is T ₁ , the allowable temperature range is T ₂ , and the cross-sectional area of the pipe is a _p , a <(T ₂ / T ₁ ) _ap (3) And it is sufficient. If a wire having a small cross-sectional area a is used, finer adjustment can be made. Also, several kinds of wires having different cross-sectional areas may be prepared.

If the adhesive tape or the adhesive cannot be used due to high temperature, the bypass 2 may be attached by welding.

[0021]

As is apparent from the above description, according to the present invention, it is possible to suppress the temperature unevenness in the longitudinal direction of the pipe with a simple structure in which the electric current bypass is attached to the electric heating pipe. There is.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an electric heating pipe according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of an electric heating pipe according to another embodiment of the present invention.

[Figure 3]

FIG. 4 is an explanatory diagram of a bypass setting method.

FIG. 5 is a schematic diagram of a conventional example of a heating method using an electric heating pipe.

[Explanation of symbols]

 1 Piping 2 Bypass 3 Temperature Sensor 4,5 Electrode 6,7 Connection Conductor 8 Adhesive Tape 9 Controller 10 Heating Current Source

Claims (2)

[Claims] 1. A heating method using an electric heating pipe, in which an electric current is directly applied to a metal pipe to heat a fluid flowing in the metal pipe, wherein a longitudinal resistance of the metal pipe is changed by changing a resistance distribution in the longitudinal direction of the metal pipe. A heating method using an electric heating pipe, characterized in that the temperature distribution in the direction is adjusted. 2. The heating according to claim 1, wherein the resistance distribution in the longitudinal direction of the metal pipe is changed by joining the same kind of metal as the metal pipe around the metal pipe. Method.