FI111751B - Steam boiler using solid biomass fuel - Google Patents

Abstract

The steam boiler has a maximum capacity of 100 tons per hour. It consists of a furnace (1) and a back pass (2) each having a constant rectangular cross-section. Steam superheaters are provided within the back pass but not within the furnace. The furnace and the back pass are separated by a common wall. The ratio of the cross-sectional area of the furnace to the back pass should be in the range of 2:1 - 6:1. The furnace has one wall which is free from traversing tubes and the like so that the design can be enlarged by expanding that side.

Description

111751

STEAM BOILER

FIELD OF THE INVENTION 5

The invention relates to steam boilers with a maximum capacity of 100 tonnes per hour or more, and in particular to boilers capable of burning solid fuel. Such boilers 10 comprise a fire chamber and a rear duct, said fire chamber and said rear duct being closely connected to one another. Such boilers are used as large power plants to produce superheated steam to operate steam turbines.

15 GB-A-1418456 discloses a small-scale conventional steam boiler comprising a furnace having a substantially constant rectangular cross-section and a rear duct having a substantially constant rectangular cross-section and having the furnace and the rear duct being spaced close to one another. · When steam superheaters are located in the rear duct • | so that the furnace is free of steam superheating members.

A: A boiler is a small capacity boiler that uses either oil or gas that is burned as fuel; at several points around the boiler, either on the floor or in the roof area i *.

• · * ... BACKGROUND OF THE INVENTION The fuel burned in these boilers mainly consists of biomass, bark, de-sludge and primary sludge, and possibly auxiliary fuels such as oil and gas.

v \ 35

In particular, bark and sludge incineration processes have progressively evolved over the last few decades, and 2 111751 bark boilers are now expected to not only handle wet bark and sludge with a moisture content of 40-65% or more, but also to cope with load variations (so-called duty cycle). all this without the need for auxiliary fuels.

An efficient technique for burning such fuels without using auxiliary fuels has been achieved by using a sloping grate in combination with a downstream final finishing grate 10 immediately thereafter (e.g., a reciprocating type, such as manufactured by Kablitz in Germany). But these known boilers, having a steam capacity of at least 100 tons / hour, are very large and require hanging on a support structure, with the price of said structure rising sharply with a slight increase in height or width of the structure.

Nowadays, there are many different types of boilers, whose combinations of features vary depending on e.g. materials and the required output power. However, the steam generating boilers, which may be considered prior art for the purposes of the present invention, are generally constructed with a central furnace and one or more bottom grates, to which fuel is fed for combustion. The walls of the furnace may comprise pipes of water. for steam / steam, which in the first step is to be transported to the water / steam * * * separator drum at the top of the furnace before entering the superheat step.

• ♦ «• >> # · '30 The tubes themselves are interconnected so that they are' '···' fixed to flat sheet metal fittings called membranes. This arrangement allows a continuous tube wall to be formed.

35 Prior art boilers are expensive to build due to the total number of pipes, the type of pipe used, and the way the pipes are secured to the various 3,111751 structural support members. In addition, steam extraction and superheat systems are complex, difficult to design, difficult to manufacture, difficult to install and difficult to maintain.

5

For example, a vapor separation system comprising a separating drum (e.g., cyclone separator) usually requires a plurality of tubes each extending from the vapor side of the top of the drum to the si-10 inlet of the superheater or superchargers, the superheaters themselves being positioned vertically or Installing such a large number of tubes is difficult and expensive, but has previously been considered necessary if the mind is to achieve a uniform distribution of steam on the drum. However, such uniform distribution is important in order not to disturb the operation of the defrosting element, as this would result in adverse effects on the turbine, such as deposits causing unbalance in the rotor.

OBJECT OF THE INVENTION Accordingly, it is an object of the invention to improve the overall structure and efficiency of the boiler: ···. with a new structure and / or combination. Thus, a boiler system can be provided which is e.g. very com. covenant and flexible in size and manufacturing ;;; assembly, installation and maintenance costs are * · * low.

In the following description of a preferred embodiment, other objects of the invention will be apparent to one skilled in the art and. benefits.

Summary of the Invention 35

The boiler of the invention is described in claim 1.

4, 111751

Preferred aspects of the invention will become apparent to one skilled in the art upon reading the following description, with reference to the accompanying drawings.

5 Description of Drawings

Fig. 1a shows - for ease of explanation only - a purely schematic view of a part of the power plant to which the invention relates, with the rear duct 10 aligned with the fuel supply (which is a conventional way to construct such units) and thus connected to a different wall than the present invention; Figure Ib shows a side view of a boiler of the invention, partially cut away, with several parts removed for simplification of the presentation; Figure le shows an elongated section of the boiler of the invention, partially cut away, with several parts removed for simplification of the presentation; Figure 2 shows a part of the wall panel of a boiler according to the invention; Fig. 3 shows a schematic view (not to scale) of the superheater connections; ... Fig. 4 shows an enlarged view (not to scale) of »t» 30 of the top of the superheater of Fig. 3, with the middle section excluded; Figure 5 is a sectional view taken along line V-V of Figure 4; Fig. 6 is a sectional view taken along the line VI-VI in Fig. 4; Fig. 7 shows a steam drum according to one aspect of the invention and Fig. 8 shows a section through the drum of Fig. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENT The boiler of the present invention is of a large type, i.e. having a capacity such that it is capable of producing steam of 100 tons per hour or more. As shown in Figures 1a-1c, the boiler consists of two main parts: a fire housing member 1 and one or more rear duct or rear draft members 2, 20. In the example illustrated (see also Figures Ib and le 15), the first rear duct 2 and furnace 1 are separated However, instead of the common wall 3, the furnace and rear duct could be separated by a certain distance, so that separate opposing walls would be needed in sections 1 and 2.

20

At the bottom of the furnace is a combined grate 4,5,6, to which fuel is fed for combustion. Input Unit 7,:. which usually consists of a set of screw feeders 7 '(see fig.

1e), feeds fuel to a first, inclined 25 grate period 4 constructed as a bare tube membrane floor in which the individual tubes are joined together by ribs made of flat sheet metal.

* The rows have a series of holes to allow air from below, and the rails are provided with 30 downward (* not *) individual baffles known as "eyelids" that cover the holes to prevent material from entering the grate and also to minimize bed flutter. .

: * .j 35 Second grate period 5, eg of reciprocating type ·; ··; such as the Kablitz grate is located downstream of the first grate period 4. This grating period could, for example, comprise fixed and alternately interposed movable parts. The parts are typically knurled and staggered, and the reciprocating motion is performed at low speed automatically, e.g. for a few minutes 5. In this way, fuel is fed down the grate toward the final or tipping grate 6, which discharges to the ash conveyor 8 below the ash.

The tilt grate 6 may simply be a manually operated grate which is used when the user feels that this is necessary due to the accumulation of ash, or an automatic device operating e.g. on a time basis, for example twice daily.

When the schematic representation of Fig. 1a shows that the separating wall 3 is above the tilt grate, it is clearly evident from Figures Ib and le that the wall 3 is arranged on the side of the fire housing parallel to the direction of feed to the grate portion 3, 5, 6. In other words, the furnace 20 is at an angle of 90 ° to the longitudinal section of the boiler. As a result of this arrangement, the feed direction of the supply means 7 is parallel to the wall (s) separating the furnace from the rear duct. Thus, ···, thanks to this, and the selected angle of grate periods 4 and 5 and '*. With 25 positions it has been possible to place the tilt grate • ·. 6 on the other side of the boiler (when normally the location is • t · between the boiler body and the rear duct), allowing * 'ash outlet feeder 6' to be positioned on the side of the boiler.

Such an arrangement means that the structure of this high-capacity 30 boiler is very compact, which feature \ t>. * Makes the boiler a stationary boiler, which, until now, has not been possible. If desired, the boiler can also be made partially or completely suspended. For example, for boiler retrofitting, which can reduce retrofitting costs. Even with the hanging option, the compact arrangement of the boiler means that much shorter roof support beams, 7,117,551, would be needed than would otherwise be the case.

In the case of a more preferred standing structure, it is necessary to provide a movable support, such as sliding legs, for the bottom of the boiler 5 in order to allow expansion.

Thanks to this compact design and arrangement, which allows for a size as small as 60% of the size of previous boilers of the same capacity, the billing system 10 as well as the distribution system can be greatly simplified since the number of pipes required is much smaller. For example, the supply to the first rear channel 2, which contains the convection heating surfaces of the generation fields, can now only be effected by two distribution tubes.

Arrows A, B, and C in Fig. 1a indicate primary, secondary, and tertiary air flows supplied by suitable ducts from an air source (e.g., compressed air from a fan).

/ * '. A narrow throat or venturi portion 12 is formed between the drying curve 10 and the finishing arc 11 so as to allow a small amount of excess air to be used while still maintaining a low proportion of unburned material. The combustible gases and air are thus forced to mix by means of the throat member 12. In addition, combustion can be enhanced V 'by providing turbulence to this zone with tertiary air C, which is fed at high speed.

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Above the throat, firebox 1 has a substantially rectangular cross-section. Similarly, the rear duct 2 has a cross section which is substantially rectangular and unchanged. The ratio of the furnace cross section: 3 to 5 sections to the rear channel cross section is preferably ri in the range 2: 1 to 6: 1. This fact is a significant factor affecting the overall cost efficiency of the boiler, as it, combined with the reduction in floor space required and the features of this high capacity boiler, minimizes the need for pipes, chimneys and supports.

5 The constant cross-sections of both the furnace and the rear duct allow for great flexibility in the choice of overall boiler size, since the rear duct and the fire chamber can be built into modules that are easily adaptable to obtain the desired size. In addition, the size of both the rear duct and the furnace can be individually modified by modular addition if necessary. The overall design of the boiler, which is partly based on the location of the air inlets (where most of the air inlets can be arranged on one side, see fig.

15), makes such modular structure and modification even easier to implement.

Due to the compact design and arrangement of the boiler (which in turn is largely due to the fact that the furnace and the boiler are, as mentioned above, arranged at an angle of 90 ° to each other), the air inlets supplying air to the furnace can be positioned so that the air source ( e.g., the fan air flue) may be positioned at one corner of the housing so that only 25 drying air supply lines 74 and secondary and tertiary air supply lines or supply lines 75 pass from one vertical side of the boiler to the other. As a result, the number of air supply lines to the different parts of the furnace is much smaller than the previous '*' 30 boilers of this capacity. In this way, it has now been achieved, '. · ** that more than 50% of the air, preferably more than 80% of the air, can be: fed into the furnace from one side of the boiler, which is not.' ·. so far it could have been carried out without very complicated and expensive pipe installations.

35 i 1 'This minimum number of ducts and flues needed for air ducting also allows for easier modular expansion of the furnace and / or rear duct.

Further, when the boiler is constructed such that at least one of its sides / walls 70 (see Fig. 1c) is free of pipes or the like which break through it, extension of the boiler from this side is much simpler.

The secondary and tertiary air supply lines may, if desired, be combined into a single supply line 75 which is divided into two channels by 10 partitions 76. In addition, an air flow measuring device for said common duct may be provided, comprising a single unit passing through wall 76 in said common duct.

One or more oil and / or gas inlets 9 are provided in the furnace for supplying the oil and / or gas in the event that either is required to assist in ignition and / or to handle extremely high loads or severe load fluctuations.

20

Hot flowing gas from the furnace passes through the furnace wall ** ·. 3 through one or more openings in the upper part and guide <i ·: ·. down to rear duct 2.

The water / steam separator drum 13 (including, for example, a cyclone separator) with a single steam outlet 14 is located on the boiler. This steam drum 13 will be described later in more detail in V *. Depending on the size of the boiler, several drums 13 can also be installed. A mixture of water and steam, ·; * '! 30 which, after separation, has accumulated on the water side of the drum 13, is transferred back to the boiler walls by tubes known as "downpipes", which are usually numerous in prior art devices. But with the * * ♦ 4 »boiler of this invention, it is now possible to limit the number of downpipes 35 to less than four. Besides, there are also ·; ··; thus, it has been achieved that only two metal downpipes with a relatively large shark and thickness, e.g. 450 mm and 60 mm respectively, can be suitably used. Such downpipes are strong enough to provide structural support for the drum 13 from below (bottom support). The downpipes can also be used to support other parts of the boiler. Two downpipes of such dimensions cost more than the smaller, larger number of prior art tubes. But their use directly results in a significant number of significant benefits, which significantly reduce overall costs.

10

In the event that the downpipes support the drum, they must also be installed, directly or indirectly, on a slider for boiler extension.

The tubes, which are part of the side walls of the grate portion, may also function as part of the drainage system, contributing to feeding the boiler tubes through a few sparse, large-diameter distribution tubes 67 ', 67 "(see, e.g., Figure Ib).

20

When moving downstream in the back channel, a secondary superheat step 15 is provided above the primary superheat step • · * l 16, whereby the primary superheater ···. at the inlet there is a vapor size from the outlet 14 of the drum 13 '. 25, 49, 50 (see, e.g., Figure 3). Construction of superheaters. will be explained in more detail below.

The efficiency of the superheat step may be increased by using a heat regulator 21 known per se to inject water 30 into the steam between the two superheating steps 15 and 16.

Reference number 17 refers to a steam generating field portion that uses heat from the flowing gas to provide additional steam. for drum 13. Although only two fields are shown, · · · 35, it is clear that any suitable number can be used. Preferably, the generation field 17 is comprised of convection boiler tubes which form a drip heating surface (i.e., are flag-shaped). Said boiler tubes may also be part of a wall which separates the boiler from the rear draft 2 and thus supports this.

Upon reaching the lower portion of the rear duct 2, the hot flowing gas is directed back upward until it enters the second rear duct 20, where both the air heater 18 and one or more heat recovery fields 19 are located.

The air heater 18 is used to further heat the primary air A, which is supplied from the fan to the inclined bare tube set 4, where it is intended to act as a drying air for a wet beak, which may thus be able to heat the air to 350 ° C or hotter.

In addition, other means may be provided for heating the primary air, such as a steam coil air heater (not shown).

The heat recovery fields 19 are used to recover residual heat in the flowing gas 20 for the initial heating of the feed water used, for example, in the walls of the furnace.

• · ·; The walls of the boiler comprise a series of panels; Figure 2 shows a ".V part of one such panel. The panel consists of tubes 30, 30 ', etc., which carry a mixture of water and steam in a boiler, said tubes being interconnected by metal sheet ribs, V ·' double welded (i.e. welded on each side) to the sides of two corresponding tubes *: ··: 30 along diametrically opposed portions of the tubes as shown.

The structure of such panels and the widths of the ribs 31 are particularly important for attaching the superheaters to the walls of the 35 rear ducts, which, as will be described below, are done in an entirely new way.

12 111751

The superheaters are positioned substantially horizontal in the rear duct. In prior art large boilers, superheaters are hung at the top of the furnace so that the superheater tubes extend vertically downwardly into the fire-housing. In addition, prior art devices require a complicated arrangement of difficult-to-mount connecting brackets between the individual tubes of the superheaters and the walls of the furnace to provide a sufficiently rigid structure to withstand thermal loads that would otherwise cause the tubes to bend or deform.

Figure 3 is a partially schematic view of one panel of the printer 15 or 16 of Figure 1a located inside the back channel. Placed in the back channel, the firebox or superheaters are protected from flames, which not only ensures a longer service life but also reduces the buildup of deposits on the printers and thus maintains efficiency. The temperature in the rear duct is also lower than in the furnace.

The back channel walls alternately consist of tubes 45, 46 and ribs 47, 48. This structure is clearly visible: FIGS. 5 and 6. As shown, printer tubes 40, 41, • 42, 43 are disposed between the steam collector 50 and the steam collector 49.

25

As shown in Figures 3 and 4, the tubes 40-43 are disposed horizontally and extend substantially across the entire width of the duct 2 between the vertical walls. The free length of the tubes (i.e., the self-supporting length of the tubes) is usually more than 2 m, preferably 2.5 m, and even more preferably 3 m or more. Thus, in the embodiment shown in Fig. 4, ···. At 6 m, pipes 40-43 might need only one centrally located support

• I

. a vertical spacer (not shown) that would give '. ·: For 35 pipes approximately 3 m free length. On the other wall of the rear duct (left wall in Fig. 4), the tubes rotate downward in substantially vertical sections 40'-43 'and then back to horizontal to the superheater steam collector 50.

Due to the relatively long length 5 of the superheater tubes 40-43, only a small number of panels and ribs are required, which means that a shorter superheater conduit 49, 50 is possible. This in turn means that there is no need for the superheater stage to have the two outlets required so far in prior art boilers of this capacity to avoid the problems of overheating caused by flow irregularity. Thus, since there is only one connecting cable between the primary and secondary superheaters, only one heat control part is required. This results in significant cost savings and it is obvious to one skilled in the art that this superheater arrangement can also be applied to other types of boilers.

As can be seen in Figures 4 and 5, between the tubes 40-43 there are in each case provided double-seam welded ribs 51 which serve as supporting means to resist this point. **: deformation forces at high thermal load. Thus, the prior art method, which required expensive and time consuming fitting and installation of many brackets, etc., between the individual pipes and the boiler, is no longer required.

The heat load applied to the ribs 51 results from the temperature of the flue gas at this point, which may be, for example, about 800 ° C. However, the steam in pipes 40-43 is at a lower temperature and due to the ribs 51 being connected. to pipes by continuous double seam welding, which, covering a large portion of the pipes, effectively cools the steam * ·. ribs 51.

: Λ! 35

As shown in Figure 5, the distance between the tubes 45 and 45 'in the rear duct wall defining the width of the ribs 47 covering this distance 14 111751 is such that the tubes 40-43 have a diameter smaller than the distance between two adjacent tubes 45, 45'. In this way, the horizontal tubes 40-43 are able to pass through the rib 47 47 of the wall panel without the hassle of bending the various tubes required by the vertical superheaters. This greater dimensioning of the rib width between the tubes 45 and 45 ', which is intended to accommodate the tubes 40-43, is made possible by the fact that the superheater 10 is located in the rear duct where temperatures are lower.

Additional lateral support for pipes 40-43 is provided by the rear duct wall closest to or in common with the furnace. As best shown in Figure 6, the wall of the rear duct 15 is formed by alternating tubes 46, 46 'and ribs 48, 48'and 48 ", as in the case of the second wall shown in Figure 5. The superheater section 40' (see also Figure 4) is supported against lateral movement due to being located between the tubes 46 and 20 46 ', and using the pin joint 90 and the associated sealing cap 91 (see Fig. 6) Thus, no type of clamp is needed to secure the part 40': to the rib 48 , which results in significantly easier installation and * · · · maintenance compared to prior art installations 25.

«« • · ·

The soot blowing means 80, 81, such as steam blowing tubes, are located in the rear passage 2 and are intended to clean the surfaces of various elements, such as superheaters.

'' 30 The arrangement of the boiler allows the steam blowing pipes, including (where necessary) soot blasting means for generating fields, etc., to be located in the rear duct sections, thus eliminating the need to use any more space in the building where the boiler is located. 35 is in use.

Figures 7 and 8 show a steam drum 60 with a steam outlet 61, which in Figures 1a to 1a correspond to a drum 13 and a tube 14. The steam drum may have a diameter of about 2 m, a wall thickness of about 80 mm and an end thickness of about 100 mm. At each end of the drum are hatches 63 and 5 with instrument connections 64, and two down tubes 67 support the drum from below. Within the upper part of the drum is provided a defroster 65 of a known type, which is the last point at which water is separated from the steam in the drum which has entered the steam / water inlets 66. According to one particular aspect of the invention which can be used in other boilers, the drum has only one saturated steam outlet tube 61 fed by saturated steam outlet ports 62a-62f each having substantially the same inside diameter. This is made possible by the particular choice of the respective pipe distances L1 to L5, which results in a steady flow over the length of the defrost. To achieve this uniform flow, the distance L1 between the first tube 62a and the second tube 62b is proportional to the distance L2 between the tube 62b and the tube 62c by the following approximately quadratic ratio: Ln = a + knb where "k" and "a" are constants selected depending on the circumstances (e.g., drum diameter, drum length, no interference,. ·. other operation of other devices), "b" is essential!. '! 2, but may vary slightly (e.g. to 1.8) and "n" 'is the nth distance between the tubes.

30 The same ratio applies to the remaining tubes (that is, ... 'to determine distances L2, L3, L4, etc.). Although six tubes 62a-62f are shown herein, it will be appreciated that there may be any suitable number.

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'·' · 35 An example of the distances L1-L5 for one particular arrangement is': approximately: L1 = 900 mm, L2 = 100 mm, L3 = 1100 mm, L4 = 1200 mm and L5 = 1400 mm.

111751 By using only one saturated steam outlet tube 61 and a plurality of tubes of the same diameter 62a-62f from the drum 60, a simple and cost effective design is achieved.

Another way to achieve the effect described above is to have a plurality of tubes of the same diameter 62a-62f feeding a single saturated vapor tube 61.

In order to achieve a steady flow, the steam outlet connection pipes 62a-62f are provided with chokes which, being either preset or adjustable, are arranged such that a substantially quadratic pressure reduction ratio is achieved between the outlet connections 62a-62f. Thus, in addition to having the same inner diameter of the tubes, the distance between the tubes may be the same.

Function Description 20 After the boiler has been started, fuel, such as a wet bark, is fed from the feed unit 7. The amount of fuel fed into the furnace depends on the prevailing load:. mitusolosuhteista. First, the fuel is dried on a sloping ··. * Bare tube grate 4 with primary, hot (e.g. above 25,100 ° C or even above 350 ° C) drying air A coming from under the grate 4. Mainly due to gravity, the fuel * · '· * goes down and back through the grate 4 to the reciprocating • · · V * grate 5 (e.g. the Kablitz grate), with this grate being transported in a reciprocating motion while being burned. until it becomes ash, which is removed by the tipping grate 6. Boiler heat output can be increased by supplying • «· more air and more fuel and assisting by supplying auxiliary fuel through inlets 9 which are. connected to fuel and air sources. Produced thermal: / · | The energy heats, in a manner known per se, a mixture of water and: *: the vapor contained in the walls of the furnace, so that the vapor enters the drum 13 for further separation. After passing through the separating wall 3 17 111751, the hot gas stream continues into the rear duct 2, heating the various surfaces along the way.

The steam that has entered the drum 13, 60 of the inlets 66 (see FIG.

5 through Fig. 8), passes through the cyclone separator unit or units to separate the water from the steam. This separated water is returned to the boiler walls via downpipes 67 which partially feed the water into distribution taps such as 67 'and 67 ". The vapor passes through a defroster 65 and through various outlets 10 62a-62f to a tube 61 which feeds to a primary superheater 16. at the elevated temperature, the steam passes through a heat regulator 21 which e.g. injects and cools the water, and then the steam 15 enters the secondary superheater 15. The steam then heats as it passes through the superheater 15, after which the steam is used to rotate a turbine.

The heat of the flowing gas remaining in the back passage 20 after the gas has passed through the superheaters is transferred to units 17, 18 and 19 having the functions described above.

* t <• * · * * * ♦. Although certain embodiments of the invention have been described above, it will be apparent to one skilled in the art that many other embodiments of the invention are contemplated. . ·. these are possible within the scope of the following claims.

* · I

Claims (23)

A meadow production boiler comprising a fireplace (1) having a substantially constant rectangular cross-section and a rear channel (2, 20) having a substantially constant rectangular cross-section and the fireplace (1) and the rear channel (2, 20) are arranged in close contact with each other, and means (15, 16) for overheating the meadow, the steam overheating means (15, 16) are arranged in the rear duct (2) in such a way that no steam overheating means (15, 16) are generally provided in the fireplace (1), characterized in that said boiler has a maximum capacity of at least 100 tonnes / hour, and that the fireplace is provided with a sloping grate whose direction of entry is parallel to at least one wall. which separates the fireplace 15 from the rear channel. Boiler according to claim 1, characterized in that the fireplace (1) and the rear duct (2) are separated ... by a common wall (3). '··' · 3. Boiler according to claim 1, characterized by · ... · 2 0 that the boiler is operated with solid fuel, in particular biofuel. Boiler according to claim 1, characterized in that certain parts of the boiler are designed as modules in such a way that the size of the fireplace (1) and the rear duct (2) ....: size can be determined independently of one another. • · • · · • Ί * 25 5. Boiler according to claim 1, characterized in that the fireplace (1) and the rear channel (2) each have a cross-sectional area, the relationship between: the fireplace (1) and the rear channel (1). (2) cross-sectional area is in the range 2: 1-6: 1. Boiler according to Claim 1, characterized in that the fireplace (1) has sides forming walls, and at least one of the sides of the boiler is free from splitting tubes and other such in such a way that when the boiler is constructed it can be easily enlarged by expansion. at said side. Boiler according to claim 1, characterized in that it is further provided with a dispenser (6 ', 8 for ash) and the inclined grate (4, 5) is placed in the boiler in such a way that the dispenser (6', 8) is arranged near one of the outer side walls of the boiler. Boiler according to claim 1, characterized in that it further comprises a meadow drum (13) and several ejector tubes for supporting the meadow drum (13) from below, the number of ejector tubes being less than four. Boiler according to claim 8, characterized in that the number of outlet tubes is only two. The boiler according to claim 1, characterized by a rust with side walls, the side walls serving as part of the outlet system for partially supplying boiler pipes in * in the fireplace. « 11. Boiler according to claim 1, characterized by: a soot-blowing device (80, 81) with soot-blower arranged in the rear channel (2) in such a way that no extra space is needed to place the soot-blowers in a building surrounding .... : the boiler. 12. Boiler according to claim 1, characterized by 25 convection boilers arranged in the rear channel (2), ·: · *! the tubes having a flag shape. * · Tl · '* ·'; Boiler according to claim 12, characterized in that the convection boiler tubes are arranged adjacent one of the boiler outer s in dough walls. 111751 24 The boiler according to claim 1, characterized by at least one overheating step (15, 16), each overheating step comprising panels formed by horizontal pipes (40 - 43) which extend substantially over the entire width of the rear channel and between the metal channels. plate flanges (51) are welded. Boiler according to claim 1, characterized in that the rear channel (2) has cradles, these walls comprising panels of tubes (45, 45 ') / which are connected by flanges (47), the flanges (47) exhibits such a width that the superheat tubes (40 - 43) can be passed through the flanges (47) without bending the tubes (45, 45 ') located in said wall, i.e. that the diameter of the superheater tube (40, 43) is less or equal to the width of a flange (47) of one of the panels. Boiler according to claim 1, characterized in that a single connecting pipe is arranged between a primary ... and a secondary overheater (15, 16) and between the primary and in the secondary overheater (15, 16) is only a thermostat (21). * · I '<··' 20. * · Ti * » 17. Boiler according to claim 1, characterized by _; that only one feed tube is disposed between angles; the drum (13) series of meadow exits and a primary overheater »(16). , ···, 25 18. Boiler according to claim 1 or 17, characterized in that a first and a second adjacent meadow exit connection (62a, 62b) from a meadow separation drum (13) are separated by a first distance »: LI, and a second and a third adjacent meadow exit 30 (62c, 62d) is separated by a distance L2, the distance L being determined as follows: Ln = a + knb * in 111751 where Ma '' and 'kM are constants, 11bM is essentially 2 and MnM is the n: th distance L. 19. Boiler according to claim 1 or 18, characterized in that a plurality of meadow output connections 5 (62a, 62f) from a meadow drum (13) are connected to an input tube (61) which provides a primary superheater (16), the meadow outputs (62a). , 62f) may be throttled one by one to create a substantially square pressure reduction ratio between adjacent meadow outlets (62a, 62f) in order to achieve even flow conditions along the length of the meadow drum (13). The boiler according to claim 1, characterized in that 60% of the air needed in the fireplace (1) is fed into the fireplace (1) from one side of the boiler. 21. Boiler according to claim 1, characterized in that the fireplace is supplied with air via primary air, secondary air and tertiary air inlets (74, 75) and a portion of the primary air is supplied as drying air, whereby the inlet ···. the pipes (74, 75) are arranged in such a way that only the inlet pipes for drying air (74) and the inlet pipes for secondary and tertiary air (75) run from one of the boilers to the vertical side of the boiler. another. The boiler according to claim 21, characterized in that the inlet pipes for the secondary and tertiary air (75) 25 are connected to a common pipe which is divided into two ducts. A boiler according to claim 22, characterized by a means for measuring the air flow arranged in one common pipe (75), the means being a single unit: penetrating a partition (76) in one joint. - •:> * same tube.