JPH08152101A - Small-sized, low-pressure steam boiler - Google Patents

Abstract

PURPOSE: To obtain saturated steam of low pressure for use in steaming and boiler efficiency substantially equal to the boiler efficiency of a once-through boiler. CONSTITUTION: A small-sized, low-pressure steam boiler comprises an outer wall 8, a combustion chamber 9, a flue 10 provided in a boiler water 23 between the outer wall 8 and the combustion chamber 9 to communicate with the combustion chamber 9 and to be opened to outside the outer wall 8, and a high load burner 11 for causing a combustion gas 31 to pass through the flue 10 at a relatively high speed. The flue 10 comprises a jacket 24 composed of a jacket inner cylinder 26 having a short cylindrical-shape to surround the combustion chamber 9 with the boiler water 23 therebetween and a jacket outer cylinder 27 having a short cylindrical-shape to surround the jacket inner cylinder 26 with a spacing therebetween, and guides 25, 25a-25f provided in the jacket 24 in non-contact with the boiler water 23 for permitting the combustion gas 31 passing through the jacket 24 to be discharged from a funnel 29 after being moved in a peripheral direction of the jacket 24 while being reciprocatingly moved vertically.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small-sized low-pressure steam boiler for obtaining low-pressure steam such as used in steam processing of food.

[0002]

2. Description of the Related Art A steam boiler of this type does not produce superheated steam like a boiler for a prime mover or a boiler for heat exchange but a saturated steam. Applications of this saturated steam include the production of foods such as rice crackers, rice cakes, Japanese sweets, kamaboko, noodles, tea, and brewed products (liquor, soy sauce, miso). Conventional boilers used for steaming belong to boilers and small boilers stipulated in the safety regulations for pressure vessels or simple boilers, and are structurally multi-tube once-through boilers and the entire combustion furnace has a can wall. There is also a low-pressure boiler surrounded by, and in addition to this, there is a steamer dedicated to steaming, which combines a feather cooker and a steamer. The purpose of the steaming process as described above is to gelatinize (gelatinize) the starch component which is the main component. Sufficient water addition and heating are required for the gelatinization of starch (hydrolysis of starch).

The low-pressure saturated vapor immediately condenses on contact with the product, forming a condensed liquid film along the product surface and radiating latent heat. Products become alpha by absorbing moisture and latent heat from condensation. Due to its characteristics, superheated steam evaporates the water on the surface of the product without condensing even when it comes into contact with the product, and removes water as opposed to water, resulting in burning, scorching, spots, or uneven steaming of the product.

Most of the multi-tube type once-through boilers have a maximum pressure of 10 kg / cm ² so that they belong to small boilers, and when used for steaming, the pressure is reduced to about 0.5 kg / cm ^2. . When using a pressure reducing valve for decompression, superheated steam is mixed in the saturated steam after depressurization, and burns, scorching, spots, uneven steaming, etc. occur due to contact of this superheated steam with the product. Cannot be obtained.

To obtain saturated steam without using a pressure reducing valve, the superheated steam is cooled to a temperature corresponding to 0.5 kg / cm ² by using a cooling device, or the water in the reboiler (secondary boiler) is superheated steam. Although there is a method of re-evaporating to obtain saturated steam of 0.5 kg / cm ² , there is a problem in that the facility cost increases. Further, in the low-pressure boiler or a steamer dedicated to the steamer, saturated steam can be directly obtained, but the boiler efficiency is around 60% and the limit is about 70%, and that of the once-through boiler is 85% (however, overheated steam is required). Is significantly inferior when compared to

The small boiler and the simple boiler are subject to restrictions on operating pressure, heat transfer area, etc. in accordance with the boiler and pressure vessel safety regulations (Ministry of Labor Ordinance No. 33 of September 30, 1972). By satisfying the requirements, a safe and easy-to-manage product can be obtained. Table 1 shows the maximum working pressure and heat transfer area limits of the low pressure boiler and once-through boiler. Table 2 shows the actual efficiency of the conventional low-pressure boiler, the once-through boiler, and the low-pressure boiler of the embodiment according to the present invention, which will be described later. However,
The actual efficiency is the efficiency obtained by subtracting 15% of steam loss due to the pressure reducing valve from the boiler efficiency when the pressure reducing valve is used. That is, in the once-through boiler, since the pressure reducing valve is used, the actual efficiency is 85% −15% = 70%, and in the low pressure boiler, since the pressure reducing valve is not used, the boiler efficiency and the actual efficiency are equal.

[0007]

[Table 1]

[0008]

[Table 2]

FIG. 4 is a sectional view showing an example of a conventional low-pressure boiler used for steaming. 1 shown in FIG.
Is a burner port and is provided in the furnace tube (combustion chamber) 2. A burner (not shown) is attached to the burner port 1 to burn fuel in the furnace tube 2. Then, the high-temperature combustion gas generated by this combustion flows into the flue 3 provided on the upper side of the furnace tube 2, heats a plurality of water pipes 4 provided on the flue 3, and is discharged from the chimney 5. It

[0010]

However, the boiler efficiency of the conventional low-pressure boiler shown in FIG. 4 is 70% as shown in Table 2.
%, Which is lower than 85% of once-through boilers. In this way, the boiler efficiency of the low-pressure boiler is lower than that of the once-through boiler because the heat transfer area of the former is 3.
The heat transfer area of the former cannot be wider than that of the latter because it is 45 m ² and is narrower than 4.00 m ² of the once-through boiler. Because there is. Therefore, the water pipe 4 shown in FIG.
Boiler efficiency cannot be improved by increasing the number of.

As described above, since the heat transfer area cannot be widened in the low pressure boiler, as shown in FIG. 4, the high temperature combustion gas 6 flowing in from the furnace tube 2 is heated by the combustion gas 6 held by the combustion gas 6. Can not be efficiently transmitted to the boiler water 7 and is discharged from the chimney 5 in a relatively high temperature state, which reduces the boiler efficiency.

An object of the present invention is to provide a small-sized low-pressure steam boiler which can obtain a low-pressure saturated steam used for steaming and can obtain a boiler efficiency substantially equal to that of a once-through boiler.

[0013]

A first invention is to provide an outer wall,
A combustion chamber provided inside the outer wall, a flue provided in the boiler water supplied between the outer wall and the combustion chamber and communicating with the combustion chamber and opening to the outside of the outer wall,
In a small low-pressure steam boiler comprising a high-load burner that allows combustion gas to pass through the flue at a relatively high speed, the flue is a box provided in the boiler water, and the boiler water is not in contact with the boiler water. A guide provided to the inside of the box body in a state and moving the combustion gas passing through the box body along the inner surface of the peripheral wall of the box body in a meandering direction and then discharging the gas from the opening. It is characterized by.

A second aspect of the present invention is provided with an outer wall, a combustion chamber provided inside the outer wall, and in the boiler water supplied between the outer wall and the combustion chamber so as to communicate with the combustion chamber. A small low-pressure steam boiler comprising a flue opening to the outside of an outer wall and a high-load burner that allows combustion gas to pass through the flue at a relatively high speed, wherein the flue separates the boiler water. A jacket formed by a short cylindrical jacket inner cylinder surrounding the combustion chamber, and a short cylindrical jacket outer cylinder surrounding the inner jacket cylinder at a distance from the inner jacket cylinder, and a jacket not in contact with the boiler water. The combustion gas that is provided inside the jacket in the state and moves in the circumferential direction of the jacket while reciprocating the combustion gas passing through the jacket in the cylindrical direction of the jacket and then opening the opening. It is characterized in that it has a guide for al discharged, the arrangement comprising a.

[0015]

According to the first aspect of the invention, the fuel is burned in the combustion chamber, and the high-temperature combustion gas generated by this combustion passes through the flue at a relatively high speed and is discharged from the opening. Then, when the combustion gas passes through the flue, the guide guides the combustion gas to meander along the inner surface of the peripheral wall of the box,
The contact distance between the combustion gas and the peripheral wall of the box can be substantially lengthened. Moreover, the combustion gas meanders at a relatively high speed in the box, causing the combustion gas to become a turbulent flow, which gives heat to the peripheral wall side of the box and the temperature of the gas becomes low. Without forming
Since the high temperature combustion gas sequentially contacts the peripheral wall of the box body, the heat of the combustion gas can be efficiently applied to the peripheral wall. The fact that the combustion gas passes through the flue at a relatively high speed is due to the draft force of the draft fan provided in the high load burner.

Since the guide is provided inside the box without contacting the boiler water, the heat transferred to the guide is transferred to the boiler water through the peripheral wall of the box. In other words, not all the surface area of this guide is the heat transfer area.

Therefore, even if the heat transfer area is formed within the limits of the low-pressure boiler shown in Table 1, the heat held by the combustion gas can be efficiently transferred to the boiler water by the above-mentioned action of the guide. As a result, the boiler efficiency can be improved as compared with the conventional low pressure boiler shown in FIG. In this way, part of the boiler water heated by contacting the outer surface of the peripheral wall of the combustion chamber and the outer casing evaporates and is taken out as saturated steam for use.

According to the second aspect of the invention, it operates in the same manner as the first aspect of the invention. Moreover, since the jacket surrounds the combustion chamber, the heat escaping from the peripheral wall of the combustion chamber, which has become hot, to escape to the outside through the outer wall,
This jacket allows for shielding, which reduces the heat escaping to the outside.

[0019]

An embodiment of the present invention will be described with reference to the drawings. In each figure, 8 is an outer wall, 9 is a combustion chamber, 10 is a flue, and 11 is a high load burner.

As shown in FIG. 1, the outer wall 8 is in the form of a short cylinder, and has a drain port 12 in the center of the lower surface and a water supply port 1 in the side surface.
3, an inspection hole 14 and a water gauge mounting seat (for lower limit) 15 are provided, and a water gauge mounting seat (for upper limit) 16 and a steam outlet 17 are provided on the upper surface. In addition, 18 is a regular surface of boiler water, 19 is a baffle plate, and 20 and 21 are inspection holes. Then, as shown in FIG. 3, an inspection hole 22 is provided on the upper surface. The outer wall 8 shown in FIG. 1 has, for example, a diameter of about 7
The height is 00 mm and the height is about 1500 mm.

The combustion chamber 9 (furnace tube) is, as shown in FIG.
It is provided inside the outer wall 8 and has a short cylindrical container shape.

The flue 10 is, as shown in FIGS. 1 and 2,
A jacket 24 provided in the boiler water 23 and a guide 25 provided inside the jacket 24 are provided. The jacket 24 has a short cylindrical inner jacket 26 that surrounds the combustion chamber 9 with the boiler water 23 in between, and a jacket inner jacket 2
6 and a jacket outer cylinder 27 in the form of a short cylinder that surrounds the jacket inner cylinder 26 at a distance, and the upper edges of the jacket inner cylinder 26 and the jacket outer cylinder 27 are coupled to each other. The lower edges are also joined together. Then, as shown in FIG. 1, the inside of the lower right portion of the jacket 24 and the lower right portion of the peripheral wall of the combustion chamber 9 communicate with each other via a communication pipe 28. Further, a chimney 29 is provided outside the upper left side of the jacket 24, and the chimney 29 is open to the outside of the outer wall 8. That is, the flue 10 through which the combustion gas 30 flowing from the combustion chamber 9 passes is formed between the inner jacket body 26 and the outer jacket body 27.

As shown in FIGS. 1 and 2, the guide 25 is a plate-like fin elongated in the vertical direction, and is composed of five upper guides 25 and five lower guides 25. The total of 10 upper and lower guides 25 are used for the combustion chamber 9
Combustion gas 3 generated by combustion of fuel inside
0 indicates the communication pipe 2 as indicated by an arrow 31 in FIGS. 1 and 2.
2 and flows into the jacket 24 through 8 to the left side along the circumferential direction of the jacket 24 (upper side in FIG. 2).
And the right side (lower side of Fig. 2), and jacket 2
After moving in the circumferential direction of the jacket 24 while reciprocating up and down along the cylinder direction of 4 (vertical direction in FIG. 1), the chimney 2
It is provided in the jacket 24 so as to go out from 9.
That is, a first upper guide 25a extending from the inner surface of the upper portion of the jacket 24 to a position slightly lower than the central portion is provided at a position extending from the communication pipe 28.
2 pieces of 2nd in total on both sides with a space in between
A lower guide 25b is provided. Each of these second lower guides 25b has a shape extending from the inner surface of the lower portion of the jacket 24 to a slightly upper position in the central portion. Then, the first upper guides 25a are spaced apart from the respective second lower guides 25b.
A total of two third upper guides 25c equivalent to the above are provided, and similarly, four fourth lower guides 25d and two fifth upper guides 25e are sequentially provided.
A single sixth lower guide 25f is provided at a location communicating with 9.

As shown in FIG. 1, the high load burner 11 is attached to a burner attachment port 33 formed at the upper end of a cylindrical burner attachment tube 32. The lower opening of the burner mounting cylinder 32 is connected to the upper portion of the combustion chamber 9 and communicates with the inside of the combustion chamber 9. This high load burner 11
Has a flame jet speed of, for example, about 20 m / sec, and has a burner provided with a ventilator, for example, a sirocco fan. Combustion gas 3 by the wind force of this sirocco fan
0, 31 can be passed through the flue 10 at high speed.

In the small-sized low-pressure steam boiler having the above structure, when water is supplied and the burner 11 is ignited, combustion is performed in the combustion chamber 9, and high temperature combustion gas 30 (3) generated by this combustion is generated.
1) passes through the flue 10 at a relatively high speed and is discharged from the chimney 29. When the combustion gas 30 passes through the flue 10, the guide 25 follows the inner surfaces of the inner body 26 and the outer body 27 (hereinafter, simply referred to as the peripheral wall) of the jacket 24, as indicated by the arrow 31 of the combustion gas 30. Since it guides so as to meander vertically, the contact distance between the combustion gas 30 and the peripheral wall of the jacket 24 can be made substantially longer. That is,
In the conventional boiler shown in FIG. 4, a part of the combustion gas 6 that has flowed into the flue 3 from the furnace tube 2 (combustion chamber) is part of the inlet 3 of the flue 3.
Since it may go out of the chimney 5 through the shortest path connecting a and the chimney 5 with a straight line, the heat of the combustion gas 6 cannot be efficiently transmitted to the water pipe 4 and the flue 3. In this embodiment, the combustion gas 30 is forcibly meandered along the inner surface of the jacket 24 so that the combustion gas 30 moves.
The heat of the combustion gas 30 (31) can be efficiently transferred to the jacket 24 side. Of course, the heat transmitted to each guide 25 is also transmitted to the jacket 24 side.

Further, the combustion gas 31 meanders and moves in the jacket 24 at a relatively high speed, so that the combustion gas 31 becomes a turbulent flow. As a result, heat is applied to the peripheral wall side of the jacket 24 to lower the temperature of the combustion gas 31. Does not form a low temperature gas layer on the inner surface of the peripheral wall, and the high temperature combustion gas sequentially contacts the peripheral wall of the jacket 24, so that the heat retained by the combustion gas 31 can be efficiently transferred to the peripheral wall (jacket inner case 26 and outer case 27). Can be told.

Further, since the guide 25 is provided in the jacket 24 in a state of not contacting the boiler water 23,
The heat transmitted to the guide 25 is transmitted to the boiler water 23 via the peripheral wall of the jacket 24. That is, not all the surface area of the guide 25 is the heat transfer area. By the way, the heat transfer area S (m ² ) of the 10 guides 25 shown in FIG.
0.044 (width of one guide 25) x 0.37 (length of guide 25) x 10 (number of guides 25) x 0.4
(Heat transfer coefficient) ≈0.065 (m ² ). That is, the heat of the combustion gas 31 can be efficiently transferred to the boiler water 23 by only slightly increasing the heat transfer area.

Further, since the jacket 24 surrounds the combustion chamber 9, the heat radiated from the peripheral wall of the combustion chamber 9 (the peripheral wall forming the combustion chamber 9) having a high temperature is radiated via the outer wall 8. The heat that escapes to the outside
It can be reduced by shielding with. As a result, the boiler efficiency can be further improved. In this way, the boiler water 23 that is heated by contacting the peripheral wall surfaces of the combustion chamber 9 and the jacket 24 is partially evaporated and is taken out from the steam outlet 17 as saturated steam for use.

The heat transfer area of this boiler is 3.46 m ² (see Table 2) that satisfies the heat transfer area limit value of less than 3.5 m ² shown in Table 1, and the maximum working pressure is 0.5.
It was manufactured with a boiler efficiency of 85% planned at less than kg / cm ² . It was confirmed that the boiler efficiency (= actual efficiency) was 85% in the actual operation. Moreover, as shown in Table 2, the actual efficiency is 85%, which exceeds 70% of the once-through boiler, which is extremely economical.

However, in the above embodiment, the flue 10 is formed as the cylindrical jacket 24, and the jacket 2
Although the combustion chamber 9 is surrounded by 4, the flue is formed as, for example, a hollow disc-shaped container, and the disc-shaped flue is located above the combustion chamber 9 although not shown in the drawing. It may be provided so that the flue does not surround the combustion chamber 9. The guide is provided inside the flue without contacting the boiler water 23, and the combustion gas is directed in the direction of the chimney 29 while meandering along the horizontal direction between the upper wall and the lower wall of the flue. It is formed so as to be discharged from the chimney 29 after being moved.

[0031]

According to the first aspect of the present invention, the combustion gas is made to meander along the inner surface of the peripheral wall of the box forming the heat transfer surface, and is then discharged from the opening. The contact distance between the box and the peripheral wall of the box can be made substantially longer. Moreover, since the combustion gas is configured to meander and move at a relatively high speed in the box body, the combustion gas becomes a turbulent flow, whereby the high temperature combustion gas sequentially contacts the peripheral wall of the box body. The retained heat can be efficiently given to the peripheral wall. As a result, the efficiency of heat transfer to the peripheral wall of the box body by the combustion gas flowing through the flue can be improved, so that the boiler efficiency can be improved as compared with the conventional low-pressure boiler shown in FIG. is there.

Since the guide is provided inside the box without contacting the boiler water, not all the surface area of the guide is the heat transfer area, so that the heat transfer area is relatively narrow. The effect is that it can be increased.

As a result, the heat transfer area can be manufactured so as to satisfy the restrictions of the low pressure boiler shown in Table 1, and
Boiler efficiency is 85% similar to once-through boiler that obtains superheated steam
There is an effect that it can be improved to. Therefore, it is possible to obtain a very low-pressure boiler as a steam boiler.

According to the second invention, it has the same effect as that of the first invention. Moreover, the heat escaping to the outside through the outer wall of the heat radiated from the peripheral wall of the combustion chamber, which has become high temperature, can be shielded by this jacket.
As a result, the heat escaping to the outside can be reduced, which has the effect of significantly improving the boiler efficiency.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a compact low-pressure steam boiler according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the small low-pressure steam boiler of the same embodiment.

FIG. 3 is a plan view of the small low-pressure steam boiler of the same embodiment.

FIG. 4 is a vertical cross-sectional view of a conventional small-sized low-pressure steam boiler.

[Explanation of symbols]

 8 Outer Wall 9 Combustion Chamber 10 Flue 11 High Load Burner 23 Boiler Water 24 Jacket 25 (25a-25f) Guide 26 Inner Jacket Body 27 Outer Jacket Body 28 Communication Pipe 29 Chimney 30, 31 Combustion Gas

Claims (2)

[Claims] 1. An outer wall, a combustion chamber provided inside the outer wall, and a boiler water provided between the outer wall and the combustion chamber. The outer wall is communicated with the combustion chamber and is outside the outer wall. In a small low-pressure steam boiler having an open flue and a high-load burner that allows combustion gas to pass through the flue at a relatively high speed, the flue is a box provided in the boiler water, and A guide which is provided inside the box body in a state of not contacting boiler water, and which causes the combustion gas passing through the box body to meander along the inner surface of the peripheral wall of the box body and then to discharge it from the opening, A small-sized low-pressure steam boiler, which is configured to include. 2. An outer wall, a combustion chamber provided inside the outer wall, and a boiler water that is provided between the outer wall and the combustion chamber and is in communication with the combustion chamber and outside the outer wall. In a small low-pressure steam boiler comprising an open flue and a high-load burner that allows combustion gas to pass through the flue at a relatively high speed, the flue encloses the combustion chamber with the boiler water in between. And a jacket formed by a short cylindrical inner jacket body and a short cylindrical outer jacket body that surrounds the inner jacket jacket at a distance from the inner jacket jacket, and the jacket in a non-contact state with the boiler water. Of the combustion gas that is provided inside the jacket and moves in the circumferential direction of the jacket while reciprocating along the cylinder direction of the jacket and then exhausted from the opening. A small low-pressure steam boiler, characterized in that it is provided with a guide.