JPS61280301A - Boiler - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to one or more large-diameter vertical straight, preferably vertical evaporation tubes, or a long vertical evaporation tube whose lower part is bent into a J shape. This relates to a boiler in which the ratio (L/D) of diameter (C) to diameter (C) is 25 or less.

[Conventional technology]

Conventional multi-tube boilers have a large number of small diameter tubes vertically arranged, the diameter of which is less than a few tens of nTn, the majority of which are less than 50 mm, and they are gathered up and down with a ladder, water is supplied to the lower header, and the upper Does it have a structure that extracts steam from the header?
Alternatively, single-tube boilers in which one small-diameter tube is arranged in a spiral manner are common, and boilers composed of large-diameter tubes have not existed.

[Problem that the invention seeks to solve]

In a boiler with many small-diameter pipes arranged vertically, the flow pattern of the vertical upward flow in the evaporator tube is as shown in Figure 3.The flow pattern is as shown in Figure 3, the amount of bubbles generated increases along the flow direction. In order to do this, the flow changes from bubble flow to slag flow to froth flow to annular flow.

As is clear from Figure 3, the length of the tube (
When L) becomes large, the bubbles in the boiler evaporation tube boil off at the tube wall, and as they move toward the top of the tube, they turn into a slag flow → a cross flow, and finally become an annular flow that covers the circumferential cross section of the water tube. Become.

When this happens, fluctuations in the water level inside the pipe become extremely large, causing problems with control and a reduction in the dryness of the steam.Also, because the thermal conductivity of air bubbles is low, it causes overheating and shortens the life of the pipe. However, there are various problems that can lead to tube failure. These problems are the same whether the evaporation tube is a straight tube or the evaporation tube whose lower end is bent into a J shape.

According to the research results of the present inventors, it has been found that large-diameter tube boilers with an L/D of 25 or more have the same various problems described above as small-diameter tube boilers.

[Means for solving problems]

The present invention is based on the above research results of the present inventors, and in a boiler consisting of one or more vertical evaporation tubes, the diameter of the vertical evaporation tube is preferably several tens of Rml Vis.

In a boiler configured with a large-diameter vertical evaporator tube, especially a vertical evaporator tube, a run-up distance is necessary for the coalescence and growth of bubbles, and according to the above research results of the present inventors, L/D is 25
Hereinafter, even in a vertical evaporation tube with a large diameter of several 10 rrffn, preferably 50 mm or more, a run-up distance is required for the coalescence and growth of bubbles, and in that case, an evaporation tube with an L/D of 25 or less requires a run-up distance. At the point 1 where the bubbles cover the cross section, the bubbles do not coalesce and grow to the so-called annular flow (c) shown in Figure 3, but remain in the small bubble flow state (a), and the small bubbles as shown in Figure 3 Due to the intense flow of the mass, the cooling effect is high and safety is guaranteed.

When L/D exceeds 25 in a large diameter pipe, the flow progresses to slag flow (B), eJ-"yrrtx flow), (E) → annular flow (H) depending on the degree, and the pipe diameter described above is several tens of mm.
Preferably, this method cannot be adopted in the present invention because it causes various troubles in large diameter pipes of 50 mm or more.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

Figures 1 and 2 are longitudinal sectional views of one embodiment of the present invention, and in Figures 1 and 2, (1) large-diameter evaporation pipe (2) fins (3) steam chamber (5) Blow pipe (6) Water supply pipe (7) Water supply pump (8) Burner (9) Air forced fan (1O) Combustion pipe (■) Fuel cutoff valve (1 @ Combustion chamber Exhaust gas duct (I4) Air water separation Internal device (l→ Steam pressure detection device O) Water absorption control device Oη Detection conduit (181 smoke chamber, (I@ Steam pipe.

As shown in Figures 1 and 2, the ratio (L/D) of the length of the heating part in the combustion chamber of a large-diameter evaporator tube to the diameter (2)
is 25 or less.

By setting L/D to 25 or less, the above-mentioned object of the present invention is achieved and the following effects are produced.

〔Effect of the invention〕

The present invention focuses on the length of the heating section of a large-diameter steam pipe and its diameter (6
) By setting the ratio L/D to 25 or less, a bubble flow is formed in the large diameter steam pipe as shown in Figure 3, and the flow does not grow into an annular flow, which prevents overheating of the evaporator pipe. Therefore, the evaporation tube will not be damaged, and the life of the evaporation tube will be long.

Furthermore, there are significant advantages such as small fluctuations in the water level in the pipe, accurate control of water supply, and no loss of steam quality such as a decrease in steam dryness.

[Brief explanation of drawings]

Figures 1 and 2 are longitudinal cross-sectional views of respective embodiments of the present invention in which the ratio L/D between the length of the heating section of the large-diameter evaporation tube of the present invention and its diameter is set to 25 or less. Fig. 1 shows a case where the lower part of a large diameter evaporation tube is J-shaped, and Fig. 2 shows a case where a vertical pipe is used as the large diameter evaporation tube. FIG. 3 shows the flow pattern in the vertical upward flow of vapor bubbles in the evaporation tube in the flow direction. 1. Large diameter evaporation pipe 2, fins 3, evaporation pipe 5, blow pipe 6°, water supply pipe 8, burner 9, air forced fan 12° combustion chamber 1, exhaust gas tact 18° smoke chamber, steam pipe. Length of the heating part in the combustion chamber of the evaporator tube, diameter of the evaporator tube Patent applicant: Hirakawa Iron Works Co., Ltd. Representative: Patent attorney Takashi Mizuta, -:'□, ((,::,':
”, +, ), 1(' Figure 2 Figure 1 Figure 3 Procedural amendment document July λθ, 1985)

Claims (1)

[Claims] 1. In a boiler consisting of one or more vertical evaporation tubes, the vertical evaporation tube is a large-diameter tube with a tube diameter of several tens of mm or more, and the length (L) of the heating part of the large-diameter tube and its diameter ( D) A boiler characterized by having a ratio (L/D) of 25 or less.