RU2245490C2 - Gas-tube boiler - Google Patents

Abstract

FIELD: thermal engineering; coolant heating.

SUBSTANCE: proposed boiler has horizontal cylindrical shell and furnace, front and rear fireboxes, front and rear vertical bottoms, fire-tube banks secured with the latter, and smoke bonnet disposed on front bottom end. Front firebox is joined through its casing to front bottom of boiler and elevated so that casing center is at boiler-furnace center level. Rear firebox is joined through its casing to rear bottom of boiler and elevated so that casing center is above center line of furnace and communicates with fire-tube bank first along gas flow. Gas bypass chamber installed above rear firebox communicates through fire-tube bank with front firebox and smoke bonnet. Fire-tube banks inserted between front and rear fireboxes and between front firebox and gas bypass chamber are inclined to horizon and those disposed between gas bypass chamber and smoke bonnet are mounted horizontally. Rear firebox has double-wall casing; space formed between walls is filled with coolant and communicates with inner space of boiler by means of through holes in its rear bottom. Fire-tube banks are installed so that tube number in each bank sequentially increases along gas flow.

EFFECT: improved performance characteristics and operating reliability of boiler.

1 cl, 2 dwg

Description

The invention relates to the field of power engineering, and specifically to boiler building, and can be used in gas-tube (fire-tube) boilers.

A gas-tube (fire-tube) boiler is known, comprising a horizontal cylindrical shell and vertical front and rear bottoms bonded to each other, which together form the internal cavity of the boiler with a heat carrier, a cylindrical horizontal firebox (flame tube) and a fire chamber, located in the internal cavity of the boiler, a smoke chamber ( a smoke box) and horizontal smoke tubes connected with a fire chamber and a smoke chamber (see in the book. Enin V.I. et al. Ship boiler installations. M: Transport, 1993, p. - 111-112).

The disadvantages of the known gas tube boiler are:

- the complexity of the layout of the flame tube and the fire chamber in the internal cavity of the boiler;

- the use of short smoke tubes communicated with the fire chamber, i.e. with a length less than the distance between the front and rear bottoms, it reduces the surface of convective heat transfer and the thermal efficiency of the boiler as a whole;

- low thermal efficiency of the boiler due to the limited ability to reduce the temperature of the gases when the gas stream passes through only one bundle of smoke tubes.

These shortcomings limit the construction and use of well-known boilers in ship and stationary conditions.

A gas-tube boiler is known comprising a horizontal cylindrical shell and vertical front and rear bottoms bonded to each other, which together form the internal cavity of the boiler with a coolant, a horizontal horizontal firebox (flame tube), front and rear fire chambers, fastened with their casings respectively to the front and rear the bottoms of the boiler at such a level that the center of each of them is located at the level of the central axis of the furnace, two bundles of smoke tubes, bonded to the front and rear bottoms and forming together with fire chambers, there are sections of gas ducts with sequential passage of a gas stream, and a chimney, moreover, the rear fire chamber is in communication with the first bundle of smoke pipes along the gas stream, and the pipe bundles themselves have the ratio of the number of pipes in the beam with decreasing to each other along the gas (see in the book. A. Khryapchenkov. Ship auxiliary and recycling boilers. L .: Sudostroenie, 1988, p. - 170-172). This boiler, as the closest one, is selected as a prototype of the claimed solution for most of the features.

The disadvantages of the known gas tube boiler are:

- a small amount of radiant (radiation) heat transfer of the rear fire chamber, since it corresponds only to the area of the rear bottom within the casing of the fire chamber;

- unfavorable conditions for the afterburning of products of incomplete combustion of fuel at the exit of the furnace, which is due to the low location of the casing of the rear fire chamber (at the level of the axis of the boiler furnace);

- the presence of excessive thermal stresses at the joints of the casing of the rear fire chamber with the rear bottom of the boiler, i.e. in the high temperature zone of the gas stream;

- insufficient decrease in the temperature of the exhaust gases behind the boiler during their passage through the bundles of smoke tubes successively arranged along the gas flow while reducing the ratio of the number of pipes in the bundles;

- accumulation of deposits on the lower generatrix of the smoke tubes, which reduces the efficiency of heat transfer during operation of the boiler.

Thus, the prototype gas boiler has significant operational and design flaws that reduce the technical and economic performance and increase the cost of repairs.

The task to be solved by the claimed invention is directed is the elimination of these operational and structural disadvantages, namely:

- increase the area of radiation heat exchange of the rear fire chamber to reduce the temperature of the gases in front of the convective heat exchange surface;

- creating favorable conditions for the afterburning of products of incomplete combustion of gases at the outlet of the furnace;

- removal of thermal stresses in the area of contact of the rear firing chamber with the rear bottom of the boiler, as a region of high temperature gas flow;

- a decrease in the amount of deposits on the gas side and, as a result, an increase in heat transfer efficiency;

- an increase in the heat exchange surface of consecutively arranged bundles of smoke tubes along the gas flow with a simultaneous increase in the ratio of the number of pipes in bundles and, as a result, the thermal efficiency of the boiler as a whole.

The task is achieved in that in a known gas-tube boiler containing horizontal cylindrical shells fastened to each other and vertical front and rear bottoms, which together form the internal cavity of the boiler with a coolant, a horizontal cylindrical firebox (flame tube), front and rear fire chambers, front of which it is fastened with its casing to the front bottom of the boiler at such a level that the center of the casing is located at the level of the central axis of the boiler furnace, several bundles of smoke tubes are fastened x with front and rear bottoms and forming, in conjunction with the fire chambers, sections of gas ducts with sequential passage of the gas stream, and a smoke chamber, the rear fire chamber communicating with the first along the gas flow bundle of smoke tubes, in contrast to the inventive one, the rear fire chamber is fastened by a casing with the rear bottom of the boiler at such a level that the center of the casing is located above the central axis of the furnace, a gas transfer chamber is additionally installed above the rear fire chamber, the cavity of which is inside the side and bottom its perimeters are limited respectively to the upper part of the rear bottom of the boiler and the upper part of the casing of the rear fire chamber, the smoke chamber is located on the side of the front bottom of the boiler, the gas transfer chamber communicates via bundles of smoke tubes with the front fire chamber and the smoke chamber, bundles of smoke pipes located between the front and rear fire chambers and between the front fire chamber and the gas transfer chamber, are installed with an inclination to the horizon, and located between the gas transfer chamber and the smoke chamber - horizontally, with the rear fire chamber made with a double-walled casing, between the inner and outer walls of which a cavity is formed, filled with coolant and communicated with the internal cavity of the boiler through the through holes of its rear bottom, and the bundles of smoke tubes are installed with a sequential increase in the number of pipes in each of the beams along the gas stream.

The claimed combination of restrictive and distinctive features improves the technical, economic and operational characteristics of the boiler.

The increase in the area of the radiation surface of the heat exchange of the cooled rear fire chamber due to the introduction of a double-walled casing into it makes it possible to increase the total heat exchange surface of the furnace space, as well as the degree of shielding of the furnace, which, all other things being equal (constant fuel and air consumption and convective heat exchange surface) lowering the temperature of the gas stream at the outlet of the furnace (fire chamber) in front of the convective surface of the heat exchange of smoke tubes and temperature flue gas. As a result, the thermal power of the boiler and its efficiency increase. In this case, thermal stresses are removed at the points of contact of the inner casing of the rear fire chamber with the rear bottom of the boiler, since the temperatures of the mentioned casing and bottom are the same and correspond to the temperature of the coolant in the internal cavity of the boiler. This increases the reliability and efficiency of the radiation surface of the heat exchange of the boiler, which achieves an additional effect.

An increase in the location of the rear fire chamber above the central axis of the furnace facilitates the afterburning of products of incomplete combustion of fuel in the form of heavy hydrocarbons and carbon (soot) in the chamber and prevents their sedimentation from being deposited in the lower part of the fire chamber due to the aerodynamic removal of heavy fractions by the torch flow to the upper part of the fire space chambers with their oxidation with atmospheric oxygen until the products of incomplete combustion are oxidized to the level of products of complete combustion of fuel. This increases the completeness of burnout of the fuel in the furnace and increases the efficiency of the boiler.

The installation of smoke tube bundles between the fire chambers and between the front fire and gas transfer chambers with an inclination with respect to the horizon allows to increase the length of the pipes between the front and rear bottoms, which also allows to increase the gas flow path with a decrease in their temperature between the boiler bottoms. This increases the efficiency of heat transfer of the tube bundle.

The installation of up to three numbers of consecutive bundles of smoke tubes along the gas flow with a simultaneous increase in the ratio of the number of pipes in bundles allows to reduce the cost of obtaining thermal energy in the boiler due to more efficient heat transfer and lowering the temperature of the flue gases.

The implementation of the heat-exchange surface inclined with respect to the horizon in the internal cavity of the boiler provides additional benefits associated with the occurrence of an additional longitudinal circulation of the coolant. Due to the asymmetry of the location of the heat transfer surface and the supply of heat to it with respect to the front and rear bottoms of the boiler in the internal cavity of the boiler, there is a movement of the coolant from the back to the front bottom along the lower generatrix of the shell and the movement of the coolant from the front to the rear bottom along the upper generatrix of the cylindrical shell which, in addition to the traditional symmetric transverse circulation of the coolant in the boiler, ensures the existence of an additional asymmetric longitudinal circulation. The longitudinal circulation of the coolant in the boiler prevents the formation of stagnant coolant zones with an elevated temperature on the inclined surface of the heat transfer and thereby prevents local overheating of the wall metal and the appearance of thermal stresses, which ultimately increases the reliability of the convective heat transfer surface in the form of smoke pipes and brings an additional effect.

Thus, the improvement of the technical, economic and operational characteristics of the boiler is achieved when a number of additional effects appear.

The claimed technical solution is illustrated by the following illustrations. Figure 1 presents a diagram of a longitudinal section (section aa according to the view of figure 2), and figure 2 is a diagram of a cross section (section bb according to a view of figure 1) of a gas tube boiler.

Gas pipe boiler has the following device. The gas-tube boiler contains a cylindrical shell 1, fastened with its front bottom 2 and rear bottom 3. The latter are made in the form of front and rear tube plates with coaxial holes of large diameter 4, in communication with the cylindrical furnace 5, with smoke tubes 6 and with misaligned 7 and 8 vertically, the holes of the tube plates and coaxial 9 holes of small diameter in communication with the smoke pipes 6. The space bounded on the inside by the shell 1, the bottoms 2 and 3, the cylindrical firebox 5 and the pipes 6 forms an internal cavity l boiler 10 with a coolant. On the outside, the rear bottom 3 is bonded to the inner 11 and outer 12 walls of the casing of the rear fire chamber 13, the center of which is above the axis of the furnace 5. The space between the walls 11 and 12 is formed by a cavity 14 filled with a coolant and communicated with the cavity 10, through two horizontal rows through holes 15 and 16, made in the bottom 3, respectively, at levels higher and lower than the axis of the furnace 5. Above the outer wall 12 of the casing of the chamber 13 is installed a gas transfer chamber 17, the cavity of which is inside the side perimeter limited by the rear bottom 3, and along the lower perimeter it is bounded by the upper part of the wall 12. From the bottom 2 side, a front fire chamber 18 is mounted, which is fastened by its casing 19 to the bottom 2 at such a level that the center of the casing 19 is at the level of the central axis of the furnace 5. The smoke chamber 20 is placed from the front the bottom, and its cavity along the lateral perimeter is limited by the front bottom 2, and along the lower perimeter is limited by the upper part of the casing 19. The cavities of the smoke chamber 20 and the chamber 18 are interconnected by means of a gas control valve 21 with manual control of its position ("open" - " closed"). The gas cavity of the rear fire chamber 13 is in communication with the front fire chamber 18 by means of the first along the gas stream bundle 22 of smoke tubes installed inclined to the horizontal and into the misaligned openings of small diameter 7. The gas cavity of the chamber 18 is also connected to the gas transfer chamber 17 by means of a second the gas stream of the beam 23 of smoke tubes installed parallel to the beam 22 and into the misaligned holes of small diameter 8. The chamber 17 is in communication with the smoke chamber 20 through a third along the gas stream of the beam 24 of the smoke tubes, installed horizontally in coaxial holes of small diameter 9. Moreover, all the bundles of smoke tubes are installed with a sequential increase in the number of pipes in each of them along the gas. The cavity of the smoke chamber 20 through the chimney 25 is in communication with the atmosphere. Traditional details of accessories, headsets and fittings, depending on the type of fuel and the purpose of the boiler, are not shown in the diagram.

Gas tube boiler operates as follows. When burning fuel in the furnace of boiler 5, high-temperature products of fuel combustion enter the rear fire chamber 13 and are cooled by the radiation heat exchange surface in the form of the inner wall 11 of the fire chamber. Next, the gases pass through the inclined smoke tubes 6 of the first beam 22 along the gas stream with some cooling in this beam to the front fire chamber 18. The casing 19 of the chamber 18 is isolated (not shown) from heat exchange with the environment of the boiler room (not shown). From chamber 18, the gases then pass, further cooled, through the inclined smoke tubes of the second beam 23 in the course of the gas stream, to the gas transfer chamber 17. From the chamber 17, gases are supplied, finally cooled, through the horizontal smoke pipes of the third beam 24 in the direction of the gas stream, to the smoke chamber 20 and then at a reduced temperature they go into the atmosphere through a chimney 25.

The use of a fully cooled rear fire chamber 13 allows you to increase the radiation surface of the heat exchange of the combustion space and reduce the temperature of the gases at the entrance to the bundle 22 of smoke tubes 6, which reduces the heat load of the smoke tubes. The location of the rear fire chamber 13 above the level of the axis of the furnace 5 allows to achieve more complete combustion of products of incomplete combustion of fuel due to their additional circulation in the fire chamber, which increases the completeness of fuel burn in the furnace 5. Communication cavity 14 in the space between the walls 11 and 12 of the fire chamber 13 with the internal cavity of the boiler 10 with a coolant by means of two horizontal rows of through holes 15 and 16 allows for reliable cooling of the heated walls of the chamber.

Using a sequential passage of gases through three bundles of smoke tubes 22, 23 and 24 can significantly reduce the temperature of the exhaust gases from the boiler and thereby increase its efficiency.

When the combustion products move along the heat exchange surface, heat exchange occurs with a decrease in the temperature of the gas stream, and heat is transferred to the internal cavity 10 of the boiler with the coolant with the formation of different densities of media in the coolant due to different temperatures or steam bubbles.

Moreover, as shown by arrows 26 in FIG. 2, a medium with a reduced density heated at the heat exchange surface of the furnace 5 and smoke tubes 6 moves upward of the inner cavity symmetrically to the vertical axis of the boiler. The coolant with a reduced density first moves to the side unheated walls of the cylindrical shell 1, goes down and then moves on both sides towards the vertical axis of the boiler. Thus, a natural coolant circulation loop is formed in the transverse direction relative to the longitudinal axis of the boiler.

Due to the different heights of the smoke tubes 6 inclined to the horizon relative to the front 2 and rear 3 bottoms, the height of the different-density heat carrier flows is not the same. In this regard, in the internal cavity 10 of the boiler there will be a natural circuit for the circulation of the coolant and in the longitudinal direction relative to the longitudinal axis of the boiler, as shown by arrows 27 in figure 1. The coolant in the region of the side cavities, limited by the space between the side surfaces of the furnace 5 and the side surfaces of the shell 1, the beam of smoke tubes 22 and the rear bottom 3 will go down, and then after turning 90 degrees it will move in two opposite directions along the longitudinal axis of the boiler: the furnace to the front front and into the cavity 14 between the housings 11 and 12 through the holes 16 and then 15.

Organized in this way, the natural circulation of the coolant in the internal cavity 10 of the boiler eliminates the formation of stagnant zones on the heat exchange surface with local wall overheating and thereby increases the reliability of operation of the boiler.

Using the gas control shutter 21 with setting it to the “open” position ensures a sure start of the boiler to work from a cold state when the boiler is operating on solid fuels due to the self-pulling of the chimney 25 without smoke in the boiler room. In this case, the aerodynamic resistance of the smoke tubes decreases due to the shutdown of the tube bundles 23 and 24 from the heat exchange and aerodynamic drag processes, since the gases immediately pass into the smoke chamber 20 after the passage of the tube bundle 22.

This ensures the improvement of the technical, economic and operational characteristics of the boiler, the reliability of the boiler increases, the efficiency increases and the cost of obtaining thermal energy decreases.

A specific example of the use of a gas-tube boiler shows that for the same fixed values of the parameters (heat transfer surface, pipe diameter and degree of contamination, weight and size characteristics and heat output, fuel characteristics and its complete combustion, excess air ratio, capex and depreciation, fuel cost, electric energy and water, maintenance costs, operating time during the year) of two compared boilers in the form of a prototype boiler and the proposed boiler, naib Leah important relative characteristics change as follows. In a gas tube boiler, according to the proposed solution, the gas temperatures decrease by 40 by the furnace and by 137 ° C behind the boiler, the boiler efficiency is increased by 4.8%, and the reduced costs of generating heat energy are reduced by 5.5%. At the same time, technical, economic and operational characteristics are improved and the reliability of the gas tube boiler is increased.

Claims (1)

A gas-tube boiler containing a horizontal cylindrical shell and vertical front and rear bottoms, which together form the internal cavity of the boiler with a coolant, a horizontal horizontal fire chamber, front and rear fire chambers, the front of which is fastened with its casing to the front bottom of the boiler at such a level that the center of the casing is located at the level of the central axis of the boiler furnace, several bundles of smoke tubes, bonded to the front and rear bottoms and forming in conjunction with the fire the chambers of the gas ducts with sequential passage of the gas flow, and a smoke chamber, the rear fire chamber communicating with the first along the gas flow bundle of smoke tubes, characterized in that the rear fire chamber is fastened with its casing to the rear bottom of the boiler at such a level that the center of the casing is located higher the central axis of the furnace, an overflow chamber is additionally installed above the rear fire chamber, the cavity of which from the inside along its lateral and lower perimeters is bounded by the upper part of the rear bottom, respectively la and the upper part of the casing of the rear fire chamber, the smoke chamber is located on the side of the front bottom of the boiler, the gas transfer chamber communicates via bundles of smoke tubes with the front fire chamber and smoke chamber, bundles of smoke pipes located between the front and rear fire chambers and between the front fire chamber and gas transfer chamber, installed with an inclination to the horizontal, and located between the gas transfer chamber and the smoke - horizontally, and the rear fire chamber is made with double-walled ying casing between the inner and outer walls is formed by a cavity filled with coolant and communicated with the interior of the boiler via through holes its back plate, and the beams themselves are installed flue pipes sequentially increasing the number of tubes in each of the beams along the gas flow.

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