JPS58113700A - Electric heating method of pipe line - Google Patents

Abstract

PURPOSE:To make it possible to prevent uneven temperature distribution caused by a voltage drop in the electric heating method of a pipe line by dividing the power supply section of the line pipe into a plural number of divisions, and supply, in time shearing, power to the respective divisions. CONSTITUTION:Power is supplied to a pipe line until a fluid inside the pipe line reaches the prescribed temperature, and further in order to maintain said temperature, the power is intermittently supplied. Since a power supply section has been divided, electrical switchgears 6, 7 and 8 are ignited and controlled in order, and the power is successively supplied to respective divisions 41, 42 and 43. And, when the fluid temperature inside a pipe line reaches a prescribed value, uneven temperature distribution caused by a voltage drop in the electric heating method of the pipe line can be prevented, since the ignition intervals of respective electrical swithgears 6, 7 and 8 have been made wider compared with those at rise of the operation.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power supply heating method for a pipeline that transports a high viscosity fluid such as high viscosity crude oil.

High viscosity crude oil has the property of solidifying at room temperature, so in order to transport it efficiently by pipeline, the tube body must be heated.
There is a need to maintain the fluid temperature at a predetermined temperature. There are two methods of heating the tube: one using steam (hot water) and the other using electric heating.1. As an electric heating method, there is a double pipe electric linear heating system as shown in FIG. 111, for example.

This O system is a steel pipe 1 (inner pipe) that transports fluid.
A heat insulating material 2 is placed that also serves as sK insulation, and a steel pipe 5 is placed on the outside of the heat insulating material 2.
If the inner pipe 1 and the outer pipe 5 are short-circuited at one end of the pipeline 4, which has a double-pipe structure protected by Heat is generated due to the electrical resistance of the tube.This heat generation occurs uniformly throughout the steel pipe, and due to the efficiency of heat transfer to the fluid, there is no local temperature rise, making it possible to achieve reasonable heating.

However, even in such a system, the range laI/'i is limited primarily by the voltage drop. The following method is adopted to prevent this.

(1) Increase the power supply voltage.

(The feeding point is provided in the center of the heating circuit.)

(ii) Power is supplied through multiple systems.

However, each of the above methods (1) to (txt) has the following problems.

(i) If the voltage is set to high, insulation becomes difficult.

(11) The practical distance is slightly extended, but there is a limit.

(i　i　l) The cost of the power supply line becomes large.

The present invention was invented in view of this situation, and is a good idea because it divides the power supply section of the pipeline into multiple sections and supplies power to each section by time sharing, thereby suppressing the voltage drop and improving the practicality of the ship. This invention provides a method for electrically heating a pipeline that makes it possible to extend the length of the pipeline.

Since the present invention is aimed at reducing the voltage drop in electric heating methods, it includes all electric heating methods regardless of the heating method. In other words, not only the above-mentioned double-pipe electric direct heating system, but also
(a) Direct electric heating method where electricity is applied directly to the pipeline and the pipe body generates heat, (b) 5ECT method (product name) where a 1liliL heat-generating steel pipe with a built-in heat-resistant cable is connected to the pipeline and electricity is applied to this circuit to generate heat. C) Fill insulation between the inner and outer pipes of the double pipe and insert the MI cable,
This includes any method such as the MI cable method in which heat is generated by the electrical resistance of the cable.

Embodiments of the present invention will be described below based on the drawings. FIG. is based on, therefore,
Although not shown in detail, the details are the same as those of the kite in Figure 1.

In this embodiment, the power supply section of the pipeline 4 is divided into three sections, each extending from the power supply line 5 to the switchgear 6, 7.
Power is supplied to each section via 8.

Here, each switching device 6.7.8 is assumed to be composed of a semiconductor switch and its ignition control device, although not shown.

Focusing on the voltage drop in the feeder line, in the conventional method, the feeder section is not divided, so the heating element also serves as the feeder line, which inevitably results in a large voltage drop, resulting in the characteristics shown in Figure 6. - As shown in @A, the practical ship 11iLe is extremely short.

On the other hand, since the method according to the present invention has a power supply system as described above, the power supply voltage to the heating element is reduced by the voltage drop E of the power supply line 5, as shown in characteristic-11AB of FIG.
By -, the practical distance is extended to the distance node where the allowable minimum supply voltage 'E;

Next, the power supply method in this embodiment will be explained while comparing it with that of a conventional method.

The conventional method of power supply is shown in Figure 164 (A).
Power is supplied until the fluid in the pipeline reaches a predetermined temperature (temperature maintenance), and then power is supplied in stages to maintain that temperature (temperature maintenance).

The power supply method according to this embodiment is also similar to the above case and the basic KtiF
J, but since the power supply section is separated, the 4th E
As shown in CB), by sequentially controlling the opening and closing devices 6, 7, 8, power was supplied to each section 41, 42, and 43 in sequence, and the fluid in the pipeline reached a predetermined temperature of 11 degrees. If so, the firing interval of each opening/closing control device 6, 7.8 is set to be wider than that at the time of startup. In this way, the fluid temperature is kept constant.゛Also, since power is supplied through time sharing, the temperature distribution along the length of the pipeline is also uniform.

As is clear from the above explanation, the method according to the present invention divides the power supply section of the pipeline into a plurality of sections and supplies power to each section by time sharing, which suppresses voltage drop. Excellent effects have been achieved in that the practical distance is extended and the temperature distribution along the length of the pipeline is also uniform.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of a double pipe electric direct heating system for pipelines, Fig. 2 is an explanatory diagram of an example of a heating system for carrying out the method according to the present invention, and Fig. 3 is an explanatory diagram of a distance-voltage drop characteristic. Fig. 4 (A). (B) is an explanatory diagram of a conventional power supply method and a power supply method according to the present invention, respectively. 4...Pipeline, 5...Power line, 6,7.8・
...Semiconductor switch. Daishioiri Patent Attorney Masatoshi Sato

Claims (1)

[Claims] 4111. A method for electrically heating a pipeline, in which the power supply section of the pipeline is divided into a plurality of sections, and power is supplied to each section by time sharing.