JPH0658503A - Case structure of multi-pipe type once-through boiler - Google Patents

Abstract

PURPOSE:To provide a case structure facilitating water level control by expanding a proper water level control range to control water level with redundancy. CONSTITUTION:In a multi-pipe type once-through boiler constructed such that a boiler can is constructed by coupling an upper heater 1 and a lower header 2 through a plurality of water pipes 3, and there are connected a steam takeout pipe 4 to the upper header 1 and a water supply pipe 5 to the lower header 2, and further there are provided water supply means 6 for supplying water into the case and heater means 7 for heating water in the case, flow resistance of an outlet portion of the water pipe having a greater heat load is set to be greater than flow resistance of an outlet portion of the water pipe having a smaller heat load.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in the can structure of a multi-tube type once-through boiler.

[0002]

2. Description of the Related Art Generally, a can body structure of a multi-tube type once-through boiler is constructed by connecting an upper header and a lower header with a plurality of water pipes to keep the water level in the can at a predetermined position. For this purpose, a water level control cylinder having a built-in water level detector is provided to detect the water level, and the water supply pump is turned on in response to a signal from the water level detector.
It is designed to operate N-OFF. The water level control cylinder is arranged at a lateral position of the water pipe, and an upper end of the water level control cylinder is connected to an upper header and a lower end of the water level control cylinder is connected to a lower header by a connecting pipe.

[0003]

With the above structure, the water levels in all the water pipes are controlled to be the same, but in reality, the relative position of the water pipes with respect to the burner and the structure of the combustion gas passages. As a result, the heat load on each water pipe is not uniform, and the boiling state varies from pipe to pipe. A water pipe with a high heat load is boiled heavily, and a large amount of water is ejected from the upper end of the water pipe together with steam, which is a factor that reduces the dryness of the steam. On the other hand, a water pipe with a low heat load has a weak boiling point and a small rise in the water surface, so that the chance of water reaching the upper part of the water pipe is reduced, and if it is extremely high, the upper part of the water pipe is overheated. These water level control positions that simultaneously satisfy the contradictory conditions that the dryness of steam is good and the water pipe is not overheated are only in a very narrow range, which makes the water level control difficult. Further, if the water level control width is narrow, there is a problem that the number of times the water supply pump is started and stopped increases and the life of the water supply pump is shortened.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and can expand the appropriate water level control range to facilitate the water level control, and can control the water level with a margin. It provides a body structure.Specifically, a boiler can is constructed by connecting an upper header and a lower header with a plurality of water pipes, and a steam extraction pipe is provided in the upper header and a water supply pipe is provided in the lower header. In a multi-tube once-through boiler configured to have a water supply means for supplying water into the can and a heating means for heating the water in the can, which are connected to each other, reduce the flow resistance at the outlet of the water pipe with a large heat load. It is characterized in that it is set to be larger than the flow resistance at the outlet of the water pipe having a small heat load.

[0005]

According to the above construction, the flow resistance at the outlet of the water pipe is set to be large for a water pipe with a large heat load and small for a water pipe with a small heat load, so that the water level in each water pipe is adjusted according to the heat load. It is possible to adjust and set an appropriate water level for each water pipe.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings. In the figure, (1) is an upper header, (2) is a lower header, and both headers are connected by a plurality of water pipes (3) to form a boiler can. The upper header (1) is connected to the steam extraction pipe (4), and the lower header (2) is connected to the water supply pipe (5).
A water supply means (6) for supplying water into the can is inserted.
(7) is a heating means, which operates according to the amount of steam used and functions to heat the water in the can. (8) is a water level control tube having a built-in water level detector, which is connected to the upper header and the lower header by connecting pipes (9) and (9). In response to a signal from the water level detector in the water level control cylinder, the water supply means (6) is turned on and off to maintain the water level in the can at a predetermined level.

[0007] (10) is a flow resistance adjusting member provided at the outlet of the water pipe (3), which functions to adjust the flow resistance of the water pipe outlet. The flow resistance of the water pipe outlet is adjusted according to the heat load of each water pipe, and the flow resistance of the water pipe having a large heat load is set to be larger than the flow resistance of the water pipe having a small heat load. For example, when the flow resistance of the outlet is adjusted by the flow passage cross-sectional area of the outlet, the flow passage cross-sectional area of the outlet in the water pipe with a large heat load is Set smaller. Such adjustment of the flow resistance at the outlet of the water pipe may be set so as to be gradually increased according to the heat load of each water pipe, or may be set by dividing into three or four stages. it can.

Next, the operation will be described. The heat load of the water pipe differs depending on the relative position of the water pipe to the burner, the structure of the combustion gas passage, and the like. In a water pipe having a large heat load, a large amount of air bubbles are present in the pipe due to intense boiling in the pipe, and the amount of water is small accordingly, so that the weight or pressure of the water applied to the lower end of the pipe becomes small. On the other hand, in a water pipe with a small heat load, the amount of water in the pipe is small and the amount of water is large.
If all water pipes are connected to a common bottom header,
When the external water level by the water level control cylinder is high, the pressure in the lower header becomes high, and in the water pipe with a large heat load, water flows in from the lower end according to the pressure difference and flows out toward the upper header.
Therefore, the dryness of steam is likely to decrease. On the other hand, if the external water level due to the water level control cylinder is low, the pressure in the lower header will be low, and in the water pipe with a small heat load, water cannot reach the upper end of the pipe, the upper pipe surface will dry, and The heating causes the wall temperature to rise above the allowable limit.

That is, each water pipe has an appropriate water level according to its heat load, and a water pipe with a large heat load is provided with the flow resistance adjusting member (10) or the like at the outlet to increase the pressure in the pipe.
The pressure at the bottom of the water pipe is approximately balanced with the relatively high external water level to prevent excessive water inflow. In this way, by providing a greater resistance at the pipe outlet for a water pipe having a larger heat load, an appropriate water level can be set for each water pipe even if the external water level is common to all water pipes.

[0010]

The present invention has the above-mentioned structure.
The following practical effects can be obtained. (1) The appropriate water level control range that simultaneously satisfies the contradictory conditions that the dryness of steam is good and the water pipe is not overheated can be set wide, and the water level control becomes easy. (2) Since the water level control range can be set wide,
The number of times of starting and stopping the water supply pump can be reduced, and the life of the water supply pump is extended. (3) Even with a simple boiler having no separator, high-quality steam with a high degree of dryness can be provided without the problem of water tube overheating. (4) Even in a small boiler equipped with a separator, the degree of dryness of the steam flowing into the separator is high, so a separator with a simpler structure than the conventional one may be used, and the separator mounting position should be lower than the conventional one. Therefore, the height of the entire boiler device can be set low. Therefore, the boiler can be easily transported and carried in.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view showing an enlarged main part of an embodiment of the present invention.

[Explanation of symbols]

 1 Upper Header 2 Lower Header 3 Water Pipe 4 Steam Extraction Pipe 5 Water Supply Pipe 6 Water Supply Means 7 Heating Means 8 Water Level Control Cylinder 9 Communication Pipe 10 Flow Resistance Adjusting Member

Claims (2)

[Claims] 1. A boiler can body is constructed by connecting an upper header (1) and a lower header (2) with a plurality of water pipes (3).
The upper header (1) is connected to the steam extraction pipe (4), and the lower header (2) is connected to the water supply pipe (5). The water supply means (6) for supplying water into the can and the water in the can are heated. In a multi-tube once-through boiler having a heating means (7) for controlling the flow resistance of the outlet portion of the water pipe having a large heat load,
A can body structure for a multi-tube once-through boiler, which is set to be larger than the flow resistance at the outlet of a water pipe with a small heat load. 2. The can structure of the multi-tube once-through boiler according to claim 1, wherein the flow passage cross-sectional area of the outlet portion of the water pipe having a large heat load is equal to the flow passage cross-sectional area of the outlet portion of the water pipe having a small heat load. The can body structure of a multi-tube once-through boiler characterized by being set smaller.