JP2010169356A - Electric boiler - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the dryness of steam to be obtained while preventing the overheating of electric heaters even when the watt density of the electric heaters is improved. <P>SOLUTION: This electric boiler includes: an upper header 2 and a lower header 3 arranged to be vertically separated from each other; a plurality of water tubes 4 extended upwardly from the lower header 3; a plurality of riser tubes 5 branched from the peripheral side wall upper parts of the respective water tubes 4, extended upwardly and having upper ends connected to the upper header 2; and the electric heaters 7 inserted downwardly from the upper ends of the respective water tubes 4 and held at the upper ends of the respective water tubes 4. In the electric heater 7, the lower region serves as a heating part X, and a region above the lower region serves as a non-heating part Y. The non-heating part Y is relatively long, and water supply to the lower header 3 is controlled to maintain the water level in a set region within the non-heating part Y. Since the water level is lowered, the overheating of the electric heater 7 can be prevented. A distance from the water level to the upper header 2 is secured, so as to improve the dryness of steam. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an electric boiler.

  An electric boiler as disclosed in Patent Document 1 below is known. In this type of conventional electric boiler, a sheathed heater bent in a U shape is used as an electric heater. However, with such a heater, it is difficult to improve the watt density in order to increase the capacity (evaporation amount) of the electric boiler. On the other hand, if an attempt is made to use a cartridge heater having a high watt density, when the low water level is generated, the temperature rises abruptly because the watt density is high, and the risk of burning the electric heater increases.

  Moreover, in the conventional electric boiler, the non-heating part (the upper part that does not generate heat among the parts inserted into the water pipe) of the electric heater is relatively short, and only about 50 mm from the upper end of the water pipe is the non-heating part. Therefore, the upper end of the heating part (the lower part that generates heat among the parts inserted into the water pipe) is the connection part between the water pipe and the riser pipe (a pipe that branches off from the upper peripheral wall of the water pipe and extends further upward). The position was almost the same as the center.

JP 61-134503 A

  In order to prevent overheating of the electric heater, it is necessary that the heating unit is always buried in water. Therefore, in the conventional configuration in which the non-heating portion is short, the water level maintenance range is set in the upper region outside the non-heating portion. In this case, the vertical separation from the water surface to the upper header becomes relatively short, and it is difficult to improve the dryness of the steam. In order to improve the dryness of the steam, it is desirable to increase the vertical separation from the upper end of the heating portion of the electric heater to the lower end of the upper header.

  The problem to be solved by the present invention is to improve the dryness of steam obtained while preventing overheating of the electric heater even if the watt density of the electric heater is improved.

  The present invention has been made to solve the above-mentioned problems. The invention according to claim 1 is directed to an upper header and a lower header, which are spaced apart from each other vertically, and extend upward from the lower header. A plurality of water pipes to be provided, a plurality of ascending pipes branched from the upper part of the peripheral side wall of each water pipe and extending further upward, and whose upper ends are connected to the upper header, and each of the water pipes A plurality of electric heaters inserted downward from the upper end portion and held at the upper end portion of each water pipe, the lower region being a heating portion, and the upper region being a non-heating portion, and each of the electric heaters An electric boiler comprising: a water supply pump that controls water supply to the lower header so that a water level is maintained in a set region in a non-heating unit.

  According to the first aspect of the present invention, the non-heated portion of the electric heater is long enough to maintain the water level maintenance range within the non-heated portion of the electric heater. By taking a long non-heating part, the risk of overheating of the electric heater can be reduced. Moreover, since the length of the water pipe of the location where the non-heating part is arranged and the length of the riser pipe are relatively long, the dryness of the steam can be improved. Furthermore, by taking a long non-heating part, heat transfer to the upper end part of the electric heater can be suppressed to prevent an increase in the wiring temperature, and the durability and safety of the wiring part of the electric heater can be improved.

  According to a second aspect of the present invention, in the electric heater according to the first aspect, the heating unit is disposed below a lower end portion of a portion where the rising pipe branches from the water pipes. This is an electric boiler.

  According to invention of Claim 2, the non-heating part is set comparatively long so that the heating part of an electric heater may be arrange | positioned below from the lower end part of the location where a riser pipe branches from a water pipe. By taking a long non-heating part, the risk of overheating of the electric heater can be reduced. Moreover, since the length of the water pipe of the location where the non-heating part is arranged and the length of the riser pipe are relatively long, the dryness of the steam can be improved. Furthermore, by taking a long non-heating part, heat transfer to the upper end part of the electric heater can be suppressed to prevent an increase in the wiring temperature, and the durability and safety of the wiring part of the electric heater can be improved.

  The invention according to claim 3 is characterized in that the vertical separation distance from the upper end of the heating portion of the electric heater to the lower end of the upper header is longer than the length of the heating portion of the electric heater. The electric boiler according to claim 1 or claim 2.

  According to the third aspect of the present invention, by increasing the separation distance from the upper end of the heating portion of the electric heater to the upper header, the dryness of the steam can be improved more reliably.

  The invention according to claim 4 is the electric boiler according to any one of claims 1 to 3, wherein a baffle plate for air-water separation is provided in the upper header.

  According to the fourth aspect of the present invention, the dryness of the steam can be further improved by providing the baffle plate in the hollow upper header and separating the air and water.

  Furthermore, the invention described in claim 5 includes an upper baffle plate and a lower baffle plate that are spaced apart from each other as the baffle plate, and the upper baffle plate and the lower baffle plate are alternately arranged. The electric boiler according to claim 4, wherein a gap or an opening through which steam from the riser pipe passes upward is formed at a position.

  According to the invention described in claim 5, the dryness of the steam can be easily improved by the combination of the upper baffle plate and the lower baffle plate.

  According to the electric boiler of the present invention, overheating of the electric heater can be prevented even if the watt density of the electric heater is improved. Moreover, the dryness of the vapor | steam obtained can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic front view which shows one Example of the electric boiler of this invention, and shows a part in cross section. It is a schematic left view of the electric boiler of FIG. 1, and has shown one part in cross section. It is a schematic sectional drawing which shows an example of the heater body of the electric heater of the electric boiler of FIG.

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings.
1 and 2 are schematic views showing an embodiment of an electric boiler according to the present invention, in which FIG. 1 is a front view and FIG. 2 is a left side view, each showing a part thereof in cross section.

  The electric boiler 1 of a present Example is comprised as a steam boiler. The electric boiler 1 of the present embodiment connects the upper header 2 and the lower header 3 with a plurality of (three in the illustrated example) water pipes 4, 4,... And ascending pipes 5, 5,. A can body 6 is provided.

  The upper header 2 and the lower header 3 are each formed in a horizontal hollow cylindrical shape, and both end surfaces thereof are closed. The upper header 2 and the lower header 3 are arranged with their axes extending in the left-right direction and spaced apart from each other in the vertical direction. At this time, the upper header 2 is arranged rearwardly with respect to the lower header 3 by a set distance.

  Each water pipe 4 is formed in a hollow cylindrical shape, and its axis is arranged along the vertical direction. The water pipes 4 are arranged at equal intervals on the left and right, and the lower ends are connected to the lower header 3. At that time, the lower end of each water pipe 4 is connected to the upper part of the peripheral side wall of the lower header 3. In this way, each water pipe 4 is provided to extend upward from the lower header 3. In the present embodiment, each water pipe 4 is provided so as to extend to the central portion between the upper header 2 and the lower header 3.

  Each rising pipe 5 is composed of a pipe whose lower end is curved in an arc shape of approximately a quarter. And as for each riser pipe 5, a lower end part is connected to the peripheral wall upper rear part of each water pipe 4, and an upper end part is connected to the peripheral side wall lower part of the upper header 2. FIG. In this way, each rising pipe 5 extends rearward from the upper peripheral wall of each water pipe 4 and then extends upward to be connected to the upper header 2.

  Each water pipe 4 is detachably provided with an electric heater 7 inserted downward from its upper end. The electric heater 7 includes a plurality (six in this embodiment) of heater bodies 8, 8,. Each heater body 8 has a round bar shape having the same shape and size.

  FIG. 3 is a schematic cross-sectional view showing an example of the heater body 8 of the electric heater 7. The heater body 8 of this embodiment includes a heating coil 11 in which a heating wire 10 such as a nichrome wire is wound around an insulating core material 9 such as ceramic. More specifically, the heating coil 11 is configured by winding a heating wire 10 in a coil shape around the outer peripheral surface of an elongated cylindrical insulating core material 9.

  The heating coil 11 is accommodated in a cylindrical sheath tube 12 such as stainless steel. The sheath tube 12 is formed in a cylindrical shape having one end closed and the other end opened. A gap between the sheath 12 and the heating coil 11 is filled with an insulating powder 13 such as magnesium oxide (MgO). The sheath tube 12 is preferably squeezed and reduced in diameter in a state where the heating coil 11 and the insulating powder 13 are accommodated. Thereby, the filling area | region of the insulating powder 13 can be consolidated, and the improvement of a watt density can be aimed at.

  A pair of electrode wires 14 and 14 are disposed in the opening of the sheath tube 12, and the end portions of the electrode wires 14 are connected to the end portions of the heating wire 10. At this time, the electrode wire 14 can be connected to each end of the coiled heating wire 10 through the hollow hole 15 of the core member 9. The sheath tube 12 is closed with the sealing material 16 in a state where the electrode wires 14 are led out from the opening.

  A plurality of the heater bodies 8 having such a configuration are combined to form an electric heater 7 as shown in FIGS. 1 and 2. Specifically, the electric heater 7 includes a stepped flange 17, and the upper end portion of each sheath tube 12 is passed through and fixed to the flange 17. In this embodiment, six heater bodies 8, 8,... Are arranged on the common flange 17 at equal intervals in the circumferential direction, and each sheath tube 12 is fixed. The flange 17 is attached such that the lower small diameter portion 18 is a mounting portion to the upper opening of the water pipe 4, while the upper large diameter portion 19 is placed on the upper end surface of the water pipe 4.

  In the electric heater 7 having such a configuration, a heating part X in which the heating wire 10 is wound in a coil shape in each heater body 8 is a heating part X that generates heat, and above (the attachment of the electric heater 7 to the water pipe 4) In the state, the distance from the upper end of the heating part X to the upper end of the water pipe 4) is defined as the non-heating part Y (FIG. 2). The electric heater 7 is arranged so that the non-heating portion Y is arranged upward, is inserted downward from the upper opening of each water pipe 4, and is detachably fixed to the upper end portion of the water pipe 4 in an airtight state. In the electric heater 7 of the present invention, the non-heating portion Y is set to be relatively long, and in the present embodiment, it is set to 150 mm to 250 mm. In the case of the illustrated example, the non-heating portion Y is 150 mm, the vertical separation distance between the axes of the upper header 2 and the lower header 3 is 1265 mm, and the combined length of the heating portion X and the non-heating portion Y is The vertical distance from the upper end of the heating section X to the axis of the upper header is 755 mm.

  A drainage port 21 is formed in the lower portion of the peripheral side wall of the lower header 3 by providing a 45 ° elbow-shaped short tube 20 (FIG. 1). A drain pipe (not shown) is connected to the drain port 21. Further, a water supply pipe 22 is connected to the lower header 3 so that water can be supplied via a water supply pump 23 (FIG. 2).

  As shown in FIG. 1, steam can be led out from the upper part of the peripheral side wall of the upper header 2 through a main steam valve 24. Further, a safety valve 25, a control pressure switch 26, and a safety pressure switch 27 are provided on the upper peripheral wall of the upper header 2. The safety valve 25 is a valve that automatically opens when the internal pressure of the can exceeds a predetermined value to release the steam to the outside and prevents the internal pressure of the can from rising excessively. The control pressure switch 26 is a pressure switch that controls whether each electric heater 7 is energized based on the pressure in the can. On the other hand, the safety pressure switch 27 is a pressure switch that cuts off the power supply to the electric heater 7 when the internal pressure of the can rises above a set value.

  It is preferable to provide baffle plates 28 and 29 for air-water separation in the upper header 2. In the present embodiment, an upper baffle plate 28 and a lower baffle plate 29 are provided apart from each other in the vertical direction. The upper baffle plate 28 and the lower baffle plate 29 are appropriately formed with a gap or opening 30 through which the steam from the riser pipe 5 passes upward.

  Specifically, each of the baffle plates 28 and 29 is composed of a plurality of plate members, and is separated in the axial direction of the upper header 2 in the axial direction (left and right direction in FIG. 1) within the upper header 2 to form a gap 30 with each other. Open and install horizontally. Alternatively, each of the baffle plates 28 and 29 is made of a single plate material, but openings 30 are formed at a plurality of locations separated in the longitudinal direction, and the axial direction of the upper header 2 is formed in the upper header 2. Can be installed horizontally. In the latter case, two plate members with appropriate openings 30 are attached in parallel with a vertical separation through a spacer (not shown), and then accommodated in the upper header 2 to receive the upper header. If the two right and left ends are welded, the baffle plates 28 and 29 can be easily attached to the upper header 2.

  In any case, it is preferable that the front and rear end sides of the plate members constituting the baffle plates 28 and 29 are brought into contact with the front and rear of the peripheral side wall of the upper header 2. Further, the gaps or openings 30 are preferably provided at alternate positions between the upper baffle plate 28 and the lower baffle plate 29. In particular, it is preferable that a lower baffle plate 29 is disposed directly above the upper opening of each riser pipe 5, and an upper baffle plate 28 is disposed immediately above the gap between the lower baffle plate 29 and the opening 30. Further, an upper baffle plate 28 may be disposed directly below the steam outlet from the upper header 2 to the main steam valve 24. In this way, it is possible to effectively separate the steam from the ascending pipe 5 and take out steam with improved dryness. The separated water separated from the gas and liquid by the baffle plates 28 and 29 may be returned to the lower header 3 via a downpipe (not shown) different from the ascending pipe 5.

  The electric boiler 1 of the present embodiment further includes an electrode type water level detector 31. The electrode-type water level detector 31 includes a water level detection cylinder 32 provided in communication with the upper header 2 and the lower header 3, and a plurality (three in the illustrated example) of electrode rods 33 to 35 inserted therein. Is provided.

  The water level detection cylinder 32 is a hollow container formed of a conductive material, and is connected to the upper header 2 via the upper communication pipe 36 and connected to the lower header 3 via the lower communication pipe 37. . At that time, the upper communication pipe 36 connects the upper part of the water level detection cylinder 32 and the upper part of the peripheral side wall of the upper header 2. Further, the lower communication pipe 37 connects the lower part of the water level detection cylinder 32 and the peripheral side wall of the lower header 3.

  A plurality of electrode rods 33 to 35 having different lengths are inserted and held in the water level detection cylinder 32 with their lower end portions having different height positions. In this embodiment, the water supply stop electrode bar (S bar) 33, the water supply start electrode bar (M bar) 34, and the low water level detection electrode bar (L bar) 35 are lowered in height in order, The water level detection cylinder 32 is inserted. Each of the electrode rods 33 to 35 is an elongated rod formed of a conductive material, and the upper portion thereof is held on the upper wall of the water level detection cylinder 32 through an insulating material insulator (not shown).

  And each electrode rod 33-35 is connected to a water supply controller (illustration omitted), setting the water level detection cylinder 32 as a common electrode. Each electrode rod 33 to 35 is electrically connected to the water level detection cylinder 32 if its lower end is immersed in water. Therefore, the water supply controller detects whether or not there is a water level at the lower end of each of the electrode rods 33 to 35 based on whether or not there is a current flowing through each of the electrode rods 33 to 35.

  A water supply controller adjusts the water level in the can 6 based on the presence or absence of the water level detection by each electrode rod 33-35. Specifically, the water supply controller operates the water supply pump 23 when the water supply start electrode bar 34 no longer detects the water level, and stops the water supply pump 23 when the water supply stop electrode bar 33 detects the water level. Thereby, the water level in the can 6 is maintained in the range between the lower end portion of the water supply start electrode rod 34 and the lower end portion of the water supply stop electrode rod 33. Further, the water supply controller monitors the water level so that the water level does not become a predetermined level or less by the low water level detection electrode rod 35 during the operation of the electric boiler 1. If the low water level detection electrode bar 35 does not detect the water level for a predetermined time, the water pipe 4 may be overheated, and an alarm to that effect is given and power supply to each electric heater 7 is cut off.

  According to the electric boiler 1 having the above configuration, the non-heating portion Y of the electric heater 7 is set relatively long. Therefore, in the electric heater 7, the non-heating portion Y extends from the lower end portion of the portion where the rising pipe 5 branches from the water pipe 4 to below. And the water supply to the lower header 3 is controlled so that a water level is maintained in the setting area | region in this non-heating part Y. FIG. That is, the lower end of each of the water supply stop electrode bar 33 and the water supply start electrode bar 34 is disposed at a height corresponding to the non-heating part Y of the electric heater 7.

  The risk of overheating of the electric heater 7 can be reduced by making the non-heating part Y longer than the conventional one and performing water supply control in the non-heating part Y. Moreover, the length of the water pipe 4 and the length of the ascending pipe 5 where the non-heated portion Y is arranged are relatively long, and the separation distance from the water surface to the upper header 2 is increased, thereby drying the steam. The degree can be improved. Furthermore, by making the non-heating part Y long, heat transfer to the upper end part of the electric heater 7 is suppressed, the rise of the wiring temperature is prevented, and the durability and safety of the wiring part of the electric heater 7 are improved. Can do.

  Further, the vertical separation distance from the upper end of the heating part X of the electric heater 7 to the lower end of the upper header 2 is longer than the length of the heating part of the electric heater 7, for example, 1.2 times. Also with this configuration, the separation distance from the upper end of the heating portion X of the electric heater 7 to the upper header 2 can be increased, and the dryness of the steam can be improved. Moreover, if appropriate baffle plates 28 and 29 are provided in the upper header 2 and the gas-liquid jets from the ascending pipe 5 collide with each other to achieve gas-liquid separation, the dryness of the steam can be further improved. it can.

  The electric boiler 1 of the present invention is not limited to the configuration of the above embodiment, and can be changed as appropriate. In particular, the configuration of the can 6 is an example and can be changed as appropriate. For example, in the above-described embodiment, the upper header 2 and the lower header 3 are connected by the three water pipes 4 and the rising pipe 5, but the number of the water pipes 4 and the rising pipes 5 can be appropriately increased or decreased.

  Moreover, in the said Example, although the six heater bodies 8 were provided in each electric heater 7, the number of the heater bodies 8 can be increased / decreased suitably. However, in consideration of the connection with the three-phase alternating current, it is preferable to provide the heater body 8 having a multiple of 3 in one electric heater 7.

  Further, the number of installed baffle plates 28, 29, the installation position, the gap, the position and size of the opening 30, and the like can be changed as appropriate.

DESCRIPTION OF SYMBOLS 1 Electric boiler 2 Upper header 3 Lower header 4 Water pipe 5 Rising pipe 7 Electric heater 23 Water supply pump 28 Upper baffle plate 29 Lower baffle plate 30 Crevice or opening 31 Electrode type water level detector 33 Water supply stop electrode rod 34 Water supply start electrode rod X Heating part Y Non-heating part

Claims (5)

An upper header and a lower header that are spaced apart vertically, and
A plurality of water pipes extending upward from the lower header; and
A plurality of ascending pipes that branch off from the upper peripheral wall of each water pipe and extend further upward, and whose upper ends are connected to the upper header;
A plurality of electric heaters inserted downward from the upper end of each water pipe and held at the upper end of each water pipe, the lower region is a heating unit, while the upper region is a non-heating unit,
An electric boiler comprising: a water supply pump that controls water supply to the lower header so that a water level is maintained in a set region in a non-heating portion of each electric heater. 2. The electric boiler according to claim 1, wherein each of the electric heaters has the heating unit disposed below a lower end portion of a portion where each of the rising pipes branches from each of the water pipes. The vertical dimension from the upper end of the heating part of the electric heater to the lower end of the upper header is longer than the length of the heating part of the electric heater. Electric boiler. The electric boiler according to any one of claims 1 to 3, wherein a baffle plate for air-water separation is provided in the upper header. As the baffle plate, comprising an upper baffle plate and a lower baffle plate that are spaced apart in the vertical direction,
The electric boiler according to claim 4, wherein the upper baffle plate and the lower baffle plate are formed with a gap or an opening through which steam from the riser pipe passes upward at alternate positions.

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