JPH0367901A - Small type low pressure steam boiler - Google Patents

Abstract

PURPOSE:To obtain saturated steam of low pressure for use in steaming and also good boiler efficiencies by providing a guide for combustion gas between adjacent water tubes disposed in a ring-shaped arrangement in a flue, leaving thereby a small gap with arcuate cross section between the guide and the outer periphery of the water tube. CONSTITUTION:When water is fed and a burner is ignited, combustion is carried out in a combustion space defined on the inner side of water tubes 4 and combustion gas guides 5 and combustion gas flows into a flue located outside through small gaps (c), while the combustion gas heats the outer surfaces of outer pipes 4a of the water tubes 4 to raise the temperature of water in the tubes 4. As a result, water within rising water passages 19 goes up, whereby water in a relatively lower region of an upper room 2 returns to the upper side of a partition plate 12 in a lower room 1 through down passages 20 inside inner water tubes 4b. Since water is continuously vaporized from the water level 29, saturated steam required for steaming can be directly obtained, resulting in good boiler efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a small-sized low-pressure steam boiler for obtaining low-pressure steam such as is used for steaming food products.

[Conventional technology]

This type of steam boiler does not produce superheated steam like prime mover boilers or heat exchange boilers, but instead produces saturated steam. This saturated steam can be used to manufacture foods such as American and English rice cakes, mochi, Japanese sweets, kamahoko, noodles, and tea. The boilers used for conventional steaming belong to the small boilers or simple boilers stipulated in the Boiler and Pressure Vessel Safety Regulations, and are structurally divided into multi-tube once-through boilers, entire combustion furnaces, or boilers. In addition to the low-pressure boiler, which was enclosed by a wall, there was also a special steamer, which was a combination of a steamer and a bamboo steamer.

[Invention or problem to be solved] The purpose of steaming is to gelatinize (gelatinize) starch, which is a product of food. Sufficient hydration and heating are required to pregelatinize starch (starch hydrolysis).

When the low-pressure saturated steam touches the product, it immediately condenses and cures on the product surface, forming a condensate film and emitting latent heat. The product becomes pregelatinized by absorbing moisture and latent heat from condensation. Due to its characteristics, superheated steam does not condense when it comes into contact with the product, but instead evaporates the moisture on the surface of the product, which is the opposite of adding water, as a result of removing moisture.
This may cause burns, burnt spots, spots, uneven steaming, etc. on the product.

The multi-tubular once-through boiler is classified as a small boiler and has a maximum pressure of 10 kg/cm2, but when used for steaming, the pressure must be reduced to about 0.5 kg/cUa2. When a pressure reducing valve is used to reduce the pressure, superheated steam is mixed in the saturated steam after the pressure is reduced, and if this superheated steam comes into contact with the product, it may cause burns, burnt spots, uneven steaming, etc., or whether the product is raw or in good condition. It cannot be obtained.

To obtain saturated steam without using a pressure reducing valve, either use a cooling device to cool the superheated steam to a temperature equivalent to 0.5 kg/cm2, or recycle the water in the reboiler (secondary boiler) with superheated steam. Is there a way to evaporate it and extract 0.5 kg/cm2 of saturated steam? Both methods are problematic in that they require high equipment costs. In addition, in the case of the low-pressure boiler and steamer-dedicated oven, whether the steam at the inlet is directly drained or the boiler efficiency is 60%
The limit is about 70%, which is significantly inferior to the 85% of the multi-tubular once-through boiler (provided that superheated steam is obtained).

In addition, the above-mentioned small boilers and simple boilers are subject to restrictions on working pressure, heat transfer area, and others according to the Boiler and Pressure Vessel Safety Regulations (Ministry of Labor Ordinance No. 33 of September 31, 1972), or do not meet the restrictions. By doing so, you can obtain something that is safe and easy to manage.

The object of the present invention is to provide a boiler that can obtain low-pressure saturated steam for use in steaming, has good boiler efficiency, and belongs to the above-mentioned small boilers.

To achieve the above objective, we decided to adopt a water tube system in which the combustion chamber is surrounded by water tubes, which is advantageous in terms of boiler efficiency, or we decided to reduce the number of water tubes due to the heat transfer area limitations in small boilers. It has been found that there is a conflict between creating a large combustion chamber volume necessary to ensure good combustion performance of the burner, and that increasing the interval between water tubes also causes a problem in that thermal efficiency deteriorates.

The technical problem of this invention is to solve the above problem.

[Means to solve the problem]

The means of the present invention includes a lower chamber, an upper chamber which is provided at a distance above the lower chamber and in which the boiler water surface is located, and which is provided to connect the lower chamber and the upper chamber. A furnace cylinder, and a furnace cylinder arranged in an annular manner along the inner periphery of the furnace cylinder at intervals spaced apart from each other on the inner side of the furnace cylinder and communicating with the lower chamber and the upper chamber. In a small low pressure steam boiler, the boiler is equipped with a plurality of water pipes provided in the furnace cylinder, and a burner attachment port provided vertically through the upper chamber and reaching inside the annular arrangement of the water pipes. A combustion gas guide is disposed between adjacent water tubes arranged in an annular arrangement, and a small gap having an arcuate cross section remains between the combustion gas kite and the outer peripheral surface of the water tube.

[Effect]

According to this means, the interior of the furnace-colored cylinder between the upper chamber and the lower chamber is divided into an inner combustion chamber surrounded by water pipes and hegaskite, and an outer cylindrical space. Combustion of fuel by a burner takes place in the space, and the combustion gas passes through a small gap between the water tube and the combustion gas guy 1 to reach the cylindrical space, and is then discharged into a normally provided chimney. During this time, the hot combustion scum heats the water pipes and combustion gas guide within the combustion space, and also heats the water pipes and combustion gas guide while passing through the small gap at high speed. Combustion gas passing through the small gap mainly loses heat to the water pipe side. The combustion transfer efficiency from the combustion gas to the water pipe at this time is that the combustion gas flows at high velocity on the water pipe surface, so the gas that becomes low temperature by giving heat to the water pipe side forms a layer of low temperature gas on the water pipe surface. This is a very good condition as it is pushed out by the subsequent combustion gas without forming. A portion of the heated water in the water pipe rises into the chamber and partially evaporates, and is taken out from above the upper chamber as saturated steam and used. Note that water will be supplied to the lower chamber. Since the combustion space is formed by the water pipe, the combustion gas guide, the lower surface of the upper chamber, and the upper surface of the lower chamber, the combustion space, that is, the volume of the combustion chamber, is It is possible to form the boiler to the required size without making the heat transfer area larger than the limit of a small boiler.

In addition, since the combustion gas guide does not constitute a heat transfer surface, it is made of refractory material, and during boiler operation, the combustion chamber side becomes red hot, preventing carbon from adhering to the water tube surface. To prevent.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. In the figure, l is the lower chamber, 2 is the upper chamber, 3 is the furnace tube, 4 is the water pipe,
5 is a combustion scum guide.

As shown in FIG. 1, the lower chamber 1 has a short cylindrical container shape, has a water supply and drainage port 10 at the center of the lower surface, and has a disk shape inside, leaving a gap between it and the inner peripheral surface of the lower chamber 1. 4 wooden support rods】1
A partition plate 12 supported by the partition plate 12 is provided.

As shown in FIG. 1, the upper chamber 2 is disposed apart above the lower chamber l, and is provided with a burner attachment port 13 vertically penetrating the center thereof, as shown in FIGS. 1 and 2. It has an annular interior with a safety valve mounting seat 14 and a steam outlet 15 on the top surface.
In addition, a pressure gauge mounting seat 16, a water level gauge mounting seat 17.17a, etc. are also provided.

As shown in FIG. 1, the furnace tube 3 is a cylindrical body that connects the outer circumferential surfaces of the lower chamber l and the upper chamber 2, and has a chimney 18 at the top of the circumferential surface.
have been combined.

As shown in FIGS. 1 and 3, in this embodiment, the water pipes 4 include eight outer pipes 4a or a lower chamber l arranged in parallel in the vertical direction to communicate the lower chamber l and the upper chamber 2. The outer tubes 4a are provided on the upper wall 1a and the lower wall 2a of the upper chamber 2, and the outer tubes 4a are arranged in an annular arrangement along a cylindrical surface coaxial with the furnace cylinder 3, separated by 1t recesses. An internal water pipe 4b is arranged coaxially inside each of the outer pipes 4a, and an ascending water pipe 19 is formed between the outer pipe 4a and a descending water pipe 20 inside the inner water pipe 4b.
It is said that The upper end of the inner water pipe 4b extends above the upper end of the outer pipe 4a and is bent to the inside of the annular arrangement, and the lower end extends below the lower end of the outer pipe 4a and opens. There is.

As shown in FIG. 3, the combustion gas guide 5 is an elongated refractory made of a refractory material having a cross-sectional shape or a roughly trapezoidal shape, such as caster full refractory material, so as to fill the spaces between the water pipes 4, and a guide presser 21. They are positioned and supported so as to be tied together with .22. Then, the outer surface of the water pipe 4 and the combustion gas guide 5
A small gap C is formed between the shells, and the width of that C can be determined in relation to the capacity of the burner and the total length of the small gap C. It is said to be about 2 mm. Note that a part of the refractory may be replaced with metal.

In the figure, 23 is a heat insulating material, 24 is a frame, 25 is an outer panel,
26 is a top plate, 27 is an inspection port, 28 is a fine ceramic joint material, 29 is a water surface for regular use, and 30 is a cutting board.

When water is supplied to this boiler and the burner is ignited, combustion occurs in the combustion space inside the water pipe 4 and the combustion gas guide 5, and the combustion gas passes through the small gap C and exits into the flue outside.

During this time, the combustion gas heats the outer tube 4a of the water tube 4 from the outside surface side, raising the temperature of the water inside. As a result, the rising channel 19
The water inside rises, and in response to this rise, the water relatively lower in the upper chamber 2 returns to the upper side of the partition plate 12 of the lower chamber 1 through the descending water channel 20 in the internal water pipe 4b. Evaporation continues from the water surface 29.

This boiler has a heat transfer area of 1 m2 or less and a maximum pressure of 1.0 kg/kg to satisfy the above-mentioned restrictions for small boilers.
It was manufactured with a boiler efficiency of 80% under the conditions of less than cm2 and evaporation rate of 80 kg/h. It was confirmed that the boiler efficiency was 80% in actual operation.

The outer diameter dimensions are 1:100 mm in height and 540 mm in diameter of the outer plate.

The above embodiments have been shown as configurations that satisfy the limitations of small boilers, but they can also be manufactured to meet the limitations of simple boilers.

〔Effect of the invention〕

According to this invention, in an annular arrangement of water tubes that substantially form a combustion chamber, a combustion gas guide is provided between adjacent water tubes, and a combustion gas guide is provided between the combustion gas guide and the outer peripheral surface of the water tube. 4 with a small gap remaining in the arcuate cross section! With the a structure, the volume of the combustion chamber can be increased to the required size even if the number of water tubes is reduced, and water tube boilers have been manufactured with a heat transfer area that satisfies the limitations of small boilers. In addition, the combustion gas flowing at high speed through small gaps has a good heat transfer efficiency to the water pipes, so even though it has a configuration that directly obtains saturated steam, conventional low-pressure boilers and steaming-only boilers that can directly obtain saturated steam are The boiler efficiency will be much better. Its efficiency is comparable to that of conventional small boilers that obtain superheated steam. Therefore, a small low-pressure boiler that is extremely excellent as a steaming wheel is obtained.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of one embodiment of the present invention, FIG. 2 is a plan view of the same embodiment, and FIG. 3 is a sectional view taken along the line A-A in FIG. 1. l...Lower chamber, 2...Upper chamber, 3...Furnace tube, 4...Water pipe, 5...Combustion gas guy 1~. 13
...Burner intake port, C...Small gap.

Claims (2)

[Claims] (1) A lower chamber, an upper chamber provided at a distance above the lower chamber and in which the surface of the boiler water is located, and a furnace tube provided to connect the lower chamber and the upper chamber. , a plurality of tubes arranged in an annular manner along the inner circumferential surface of the furnace tube at intervals at an inner position away from the inner circumferential surface of the furnace tube, and provided so as to communicate the lower chamber and the upper chamber. In a small-sized low-pressure steam boiler, the boiler is equipped with a main water pipe and a burner attachment port that vertically penetrates the upper chamber and reaches inside the annular arrangement of the water pipes, the water pipes being arranged in an annular arrangement within the furnace cylinder. A small-sized low-pressure steam boiler characterized in that a combustion gas guide is disposed between adjacent ones, and a small gap with an arcuate cross section remains between the combustion gas guide and the outer peripheral surface of the water tube. (2) The small-sized low-pressure steam boiler according to claim (1), wherein the combustion gas guide is made of a refractory material.