NO168912B - BOILING WITH FLUIDIZED DISEASES AND PROCEDURE FOR MANAGING THESE - Google Patents

Abstract

An internal circulation type fluidized bed boiler in which a fluidized bed primary combustion chamber is formed by providing above the portion of an air distributing plate from which the air having a higher mass velocity is ejected an inclined partition wall which is adapted to intercept an upward flow of the fluidization air ejected from this air ejection portion, and turn this upward flow of the air toward the position above the portion of the air distributing plate from which a gas having a low mass velocity is ejected, with a heat recovery chamber formed between the inclined partition wall and a furnace wall. The inclined partition wall is formed so as to have an angle of inclination of 10 DEG -60 DEG with respect to a horizontal plane, and a horizontal projection length of 1/6-1/2 of the horizontal length of the furnace bottom. The method of controlling this fluidized bed boiler consists of the steps of controlling the quantity of heat recovered from the heat recovery chamber in compliance with the request by the users of recovered heat by suitably regulating the flow rate of the air ejected from a diffuser for the heat recovery chamber, and controlling the feed rate of the fuel supplied to the fluidized bed primary combustion chamber, on the basis of the temperature of the fluidized bed primary combustion chamber.

Description

The present invention relates to a boiler with a fluidized bed, of the recirculation type, comprising a primary combustion chamber with a fluidized bed, formed by an air diffusion plate arranged at the bottom of a combustion device and arranged to introduce fluidizing air upwards with a mass flow that is at least greater on one side than on the other side, an inclined partition wall arranged over the part of the diffusion plate where the mass flow is greatest, to influence the upward flow of the fluidizing air and thereby deflect the air towards the part over the other side of the diffusion plate where the mass flow is least, the inclined partition wall is inclined by 10° - 60° in relation to the horizontal direction and the projected length thereof in the horizontal direction is 1/6 - 1/2 of the horizontal length to the bottom of the combustion device, and a movable layer is formed over that part of the diffusion plate where the introduced mass flow is the smallest, so that a medium to be fluidized sinks and spreads in nne in the moving layer, and a circulating fluidized layer is formed over the part of the diffusion plate where the mass flow of the fluidizing air is greatest, so that the medium is actively fluidized and swirled towards a place above the moving layer, as the formation of the moving layer and the circulating fluidized beds occurs by regulating the amount of air that is introduced upwards from the diffusion plate.

The invention also relates to a method for controlling a boiler with an internal fluidized bed, of the recirculation type, which boiler comprises a primary combustion chamber with a fluidized bed, formed by an air diffusion plate arranged at the bottom of a combustion device and arranged to introduce fluidizing air upwards into a mass flow which is at least larger on one side than on the other side, an inclined partition wall arranged over the part of the diffusion plate where the mass flow is greatest, to influence the upward flow of the fluidizing air and thereby deflect the air towards the part above the other side of the diffusion plate where the mass flow is the least, as the amount of air introduced from the diffusion plate is regulated so that a moving layer is formed over the part of the diffusion plate where the introduced mass flow is the least, as a medium to be fluidized sinks and spreads inside the moving layer, and a circulating fluidized bed is formed over the portion of diffusion the plate where the mass flow of the fluidizing air is greatest, so that the medium is actively fluidized and circulated towards a place above the moving bed.

Such a boiler is known from US patent 4419330. Reference is also made to the Japanese patent publications 46988/76 and 5242/68. An example of a known boiler of this type will be explained in more detail below, with reference to the following fig. 1.

A diffusion plate 2 is arranged at a furnace bottom in a combustion device 1 for the purpose of effecting fluidization of a fluidizing medium. Diffusion

the plate 2 is inclined so that the wall side which is equipped with a device 3 for supplying waste is higher than the opposite side, and the lower part of the opposite side is connected to an outlet opening 4 for non-combustible materials.

Fluidizing air supplied from a fan 8 is blown

upwards from the diffusion plate 2 through air chambers: 5, 6

and 7, to fluidize the fluidizing medium.

The mass flow of the fluidizing air that is inflated

from each of the air chambers is arranged so that it is sufficient to cause a fluidized layer, the flow that is blown up from chamber 7 being the largest and that coming from chamber 5 the smallest.

The mass flow is e.g. selected in the following areas,

so that the one inflated from the air chamber 7 is in the range 4-20 Gmf, or preferably 6-12 Gmf, the one coming from the air chamber 6 is in the range 3-10 Gmf,

or preferably 4-6 Gmf, and the one coming from the chamber 5 is in the range 1-4 Gmf, preferably 1 - 2.5 Gmf. 1 Gmf is the value for the mass flow at which fluidization starts.

The state of the fluidizing medium changes from a static state, which is called a static layer, to a dynamic state, which is called a fluidized layer, with the value indicated above as a threshold between the two states.

While the example shown in fig. 1 shows three air chambers, the number can be chosen, and can e.g. be two or more than four chambers, and the mass flow for the fluidizing air is arranged so that it is large for chambers close to the outlet opening 4 and small for chambers that are distant from the outlet opening.

Just above the air chambers 7 and 6, an inclined wall 9 is arranged to serve as a deflecting wall to interrupt the passage of the upwardly flowing, fluidizing air, to deflect the air towards the supply device 3 for combustible material.

On the upper end of the inclined wall 9 is arranged an inclined surface 10 with an inclined direction which is opposite to the direction of the wall 9, in order to prevent the fluidizing medium from collecting on it.

The slope of the diffusion plate 2 is, in the case that the non-combustible materials are contained in the combustible materials to be supplied, preferably in the range 5 - 15°. However, in the case that the amount of non-combustible materials is small, the angle of inclination can be 0 and the plate can be horizontal, since the fluidizing medium can be circulated by regulating the flow rate per minute. time unit of the air blown from the respective air chambers.

The surface of the wall 9 can be either flat, convex or concave. An outlet 12 for combustion gas, a supply line 13 for the supply of liquid waste that is formed during operation of the combustion device, and a supply line 14 for cooling water, etc., are arranged in a roof 11 of the combustion device.

Regarding the operation of the combustor 1, the fluidizing air is fed into it by the fan 8, and the fluidizing air flows in regulated amounts with respect to mass flow, decreasing in the order of the chambers 7, 6 and 5.

In the conventional fluidized bed, the fluidizing medium moves violently up and down, much like boiling water, to produce a fluidized state. However, the fluidizing medium moves in the area

close to the side wall which is equipped with the supply device

3 for combustible material does not violently up and down, and forms a movable layer 15 which performs a weak fluidization. The width of the moving bed is small in the upper part, and widens in the lower part due to the difference in the mass flow of the air flowing in from the respective air chambers. That is that the rear end of the moving layer projects above the air chambers 6 and 7, and thus the fluidizing medium is blown upwards by the large mass flow from these chambers, in order to

is displaced from these, so that part of the movable layer 15 above the air chamber 5 sinks due to gravity. With such a downward movement of the layer 15, the fluidizing medium is supplemented from the fluidized layer and follows a circulating flow 16 towards the upper part of the layer 15, and with repetition of the above described as a whole, the circulating fluidized layer is formed.

The fluidizing medium which has moved over the air chambers 6 and 7 is blown upwards towards the inclined wall 9, where it is deflected and swirled towards the side wall which has the supply device for combustible material, and gradually sinks after it reaches the upper part of the moving layer 15, and is then blown upward again to circulate after it reaches the rear end.

The combustible materials supplied from the supply device 3 to the top of the moving layer 15 in the combustion device 1 in the state just described are contained within the descending, moving layer 15 and move downwards.

In the conventional fluidized bed, such combustible materials as paper, which are light in weight and have high exothermic energy, burn on the surface of the fluidized bed without making any major contribution to heating the fluidizing medium. However, such loss is prevented in the circulating type of fluidized bed, and such combustible materials are safely burned inside the descending, moving bed 15 and the circulating, fluidized bed 16, thereby enabling such combustible materials to effectively heat the fluidizing medium.

The non-combustible materials which are supplied together with the combustible materials first sink inside the descending, moving layer 15, and then move in the lateral direction, and during this movement the combustible materials which are attached to or uniformly included in the non-combustible materials are burned materials (e.g. coating on electrical wires). The non-combustible materials arriving at the rear end are discharged to the non-combustible material discharge port 4 due to the lateral movement of the fluidizing medium and the inclined direction of the air diffusion plate 2, passing through a vertical channel 17 and a conveyor 18 for discharge of non-combustible materials , and is fed out after the fluidizing medium has been sorted using a vibrating screen 19.

The sorted fluidizing medium or new fluidizing medium is supplied to the combustion device 1 by means of a transport device 20, such as an elevator. 1 the following will explain another example of the conventional type of combustion device with a circulating fluidized bed, with reference to fig. 2.

As shown in fig. 2, a diffusion plate 22 for fluidizing air is arranged at the inner bottom part of the combustion device. The opposite edge parts of the air diffusion plate 22 are arranged so that they are lower than the middle part, and the diffusion plate is shaped so that it has the shape of a ridge (angular shape) in section, approximately symmetrical about the center line 42 of the combustion device, and an outlet opening 24 for not combustible materials are connected to each of the opposite edge parts.

The fluidizing air supplied from a fan 28 flows upwards from the air diffusion plate 22 and through air chambers 25, 26 and 27. The mass flow of the fluidizing air flowing in from each of the air chambers 25 and 27 at the opposite edge portions is large enough to form the fluidized bed, but the mass flow flowing in from the middle air chamber 26 is made smaller than from the former.

E.g. the mass flow of the fluidizing air flowing in from the air chambers 25 and 27 is chosen so that it is in the range 4-20 Gmf, preferably in the range 6-12 Gmf, while the mass flow of the fluidizing air flowing in from the air chamber 26 is chosen so that it is in the range 0.5-3 Gmf, preferably in the range 1-2.5 Gmf.

The number of air chambers is determined by choice, such as three or more. In a case where the number is more than three, the mass flow of the fluidizing air is arranged so that it is small at the chambers near the middle part and large at the chambers near the opposite edge parts.

Just above the air chambers 25 and 27 at the opposite edge portions, inclined walls 29 are arranged as deflecting walls, to influence and deflect the fluidizing air towards the center of the combustion device.

Above the inclined walls 29 are arranged inclined surfaces 30, each of which has an inclined direction which is opposite to the walls 29, in order to prevent the fluidizing medium from accumulating.

The slope of the diffusion plate 22 is preferably

in the range 5 - 15° in the event that the combustible materials are added together with non-combustible materials.

It does not need to have any slanting direction in the event that no non-combustible materials are contained in the combustible materials.

The surface of the inclined walls 29 can be either flat, convex or concave.

In a roof section 31 inside the combustion device, a supply opening 34 for combustible materials is arranged in communication with an outlet 33 from a supply device 23 for combustible materials, situated opposite the central air chamber 26, and an outlet section 32 for combustion gas is also arranged.

The inclined wall 29 can be constructed as a wall element formed by metallic conduits, through which the fluidizing air passes to be preheated.

When it comes to the operation of this combustion device, the fluidizing air is fed into it by a fan 28, and it flows in with a large mass flow per time unit from the air chambers 25 and 27 and with a small mass flow per time unit from the air chamber 26.

In the conventional fluidized bed, the fluidizing medium moves violently up and down in a manner similar to boiling water to form the fluidizing state. In the case in fig. 2, however, the fluidizing medium above the air chamber 26 does not cause this violent movement up and down, and forms a moving layer in a state of weak fluidization. The width of this moving layer is small in the upper part, and expands laterally at the rear ends in opposite directions to the parts of the fluidized layers, and a part of the moving layer that comes over the air chambers 25 and 27 is blown upwards, where the fluidizing medium is subjected to inflow of the fluidizing air with the large mass flow per unit of time. Thus, part of the fluidizing medium at the rear end will be displaced from this upwards, so that the layer just above the air chamber 26 sinks downwards due to the force of gravity. Above this moving layer, the fluidizing medium is supplemented, as explained below, from the fluidized layer which is followed by a circulating current 36. With repetition of the above, a certain part of the fluidizing medium above the air chamber 26 constitutes a mass which forms a moving layer 35 which gradually sinks and spreads.

The fluidizing medium which is moved over the air chambers 25 and 27 is blown upwards towards the inclined walls 29, where it is deflected and swirled towards the center of the combustion device in an upward direction. However, due to the sudden increase in the cross-sectional area of the combustor, it loses its upward velocity so that it moves to the top of the descending moving bed 35, and gradually descends, and is again blown upward for circulation after reaching the rear end of the moving layer. A part of the fluidizing medium circulates as circulating currents 36 inside the fluidized layer.

When combustible materials are supplied through the combustible material supply opening 34 in the combustion device in the fluidized state as explained above, the combustible materials fall onto the top of the descending, moving bed 35. As the fluidizing medium near the top behaves in such a way that it flows in the direction to gather toward the center and away from the sides, the combustible materials are held in the streams and included in the top of the descending moving bed 35. Accordingly, light substances such as paper will be safely contained within the descending moving bed 35 , and are prevented from burning only on the surface of the conventional fluidized bed without contributing to the heating of the fluidizing medium, and they are safely burned inside the descending moving bed 35

and the circulating currents 36, for efficient heating of the fluidizing medium.

inside the moving layer 35, a partial thermal decomposition of the combustible materials takes place to form a combustible gas. In this case, as the generated combustible gas spreads in the horizontal directions as the fluidizing medium sinks and spreads and burns within the fluidized bed, the exothermic energy generated by combustion of the gas will cause heating of the fluidizing medium.

Although heavy and large materials such as bottles and pieces of metal etc. supplied to the surface of the descending, moving layer 35, these do not immediately fall down on top of the air chamber 26, but are kept suspended by the moving layer 35 and gradually sink towards the outlet opening 24 for non-combustible materials, together with the flows of the fluidizing medium.

Therefore, combustible materials having relatively large dimensions are dried, gasified, or burned inside the descending moving bed 35 during the gradual downward movement, and they are burned almost to small dimensions by the time they reach the rear end of the moving bed. layer, so that they do not interfere with the formation of the fluidized layer.

It is therefore not necessary to divide the combustible materials in advance with a dividing device, and it is sufficient to tear open the sacks containing the combustible materials with the aid of the supply device 23 for combustible materials. The ripping device or the ripping step can thus be omitted, in order to make the plant compact.

The combustible materials which are supplied to the descending, moving bed 35 are quickly dispersed in the fluidizing medium, and thus the combustion efficiency increases.

Medium-sized non-combustible materials supplied through the combustible material supply device 23 first move downwards and laterally within the descending, moving bed 35, and during this movement any combustible materials (e.g. the coating on electrical wires) that are uniform are burned attached to or included in the non-combustible materials.

The non-combustible materials arriving at the rear end are discharged to the outlet openings 24 for non-combustible materials, due to the lateral movement of the fluidizing medium and the inclined direction of the diffusion plate 22, and are discharged through vertical channels 37.

The non-combustible materials are then delivered by a conveyor 38 to a screen (not shown), and the fluidizing medium is sorted.

In the combustion device with circulating type fluidized bed shown in fig. 1 and 2 mentioned above, the fluidizing medium consists of solid particles which usually have a size of approximately 1 mm, and the combustion device is operated with a temperature in the fluidizing medium of 600 - 800°C, and the exhaust gas temperature is 750 - 950°C.

The exhaust gas is cooled to approximately 300°C in a gas cooling chamber or an air preheater, and flows out through a chimney after removal of small particles, or after recovery of heat energy by means of a boiler located downstream of the outlet opening of the exhaust gas, with the intention of utilizing the waste heat energy, or after passing through U-shaped pipes in a water heater mounted in the free wall part 21 or 41, etc., and more of the heat energy is recovered, or it is cooled when the dust is removed.

In cases where the exothermic energy in the combustible materials is large and the fluidizing medium is heated above a predetermined temperature, e.g. to more than 800°C, it is possible that the fluidizing medium will be sintered, so that the fluidized bed cannot be kept in operation if alkaline metal compositions are included in the combustible materials. In such cases, it has been common to lower the temperature in the fluidizing medium to a predetermined temperature by injecting water into the medium.

In such cases, it has therefore been considered to recover heat energy contained in the fluidizing medium by installing thermally conductive lines in the fluidizing medium, but this has led to several problems, because if many thermally conductive lines are installed in the fluidized layer, not only is the fluidization prevented of non-combustible materials as well as abrasion of the conductive lines due to the fluidizing medium, but the operation with recovery of heat energy must be in order to protect the thermally conductive lines even if recovery of heat energy is unnecessary. Therefore, the operation has not been free of these disadvantages.

On the other hand, when it comes to the conventional

type of fluidized bed boiler, there are two types, as explained below, which can be distinguished from each other by considering the arrangement in the thermally conductive part and the combustion of small, unburnt, combustible materials that are spread from the fluidized bed. (1) a fluidized bed boiler of the non-recirculation type (called a conventional fluidized bed boiler or bubble type boiler), and (2) a fluidized bed boiler of the recirculation type.

In the type without recirculation, the thermally conductive lines are arranged inside the fluidized bed, and the heat transfer occurs with high heat transfer efficiency due to the physical contact between the lines and the burning fuels at the high temperature and the fluidizing medium. In the type with recirculation, part of the small, combustible materials that have not yet been burned, as well as ash or fluidizing medium (recirculating solid material), enters a stream of combustion gas and is led to a heat-transferring part arranged independently

of the combustion device, where combustion of the

unburned substances continue, as the solids after this heat transfer are returned to the combustion device together with part of the combustion gas, and the name of this type of boiler is given because of the type of recirculation mentioned above.

In the type of boiler that has a fluidized bed, many different fuels with different properties can be burned according to the particular combustion process, but several disadvantages have recently been demonstrated. When

what concerns the bubble type is the complicated system for fuel supply, the need for a large amount of lime

for denitrification as well as the abrasion of the thermally conductive wires etc. have been considered inherent disadvantages, and the

it has been established that the type with recirculation is able to solve these inherent disadvantages. However, it remains to arrive at further technical development with regard to maintaining suitable temperatures in the recirculation system comprising a combustion device and a cyclone, removing the frost in the device and solving the problem that a long time is required for cold starting.

With the present invention, a boiler of the type indicated at the outset has been arrived at, and which is characterized by the fact that a recovery chamber for heat energy is formed between the inclined partition and a side wall in the combustion device or between the backs of two inclined partitions,

that a device with a heat exchanger surface is arranged inside the recycling chamber for the flow of a cooling fluid, that an air diffuser is arranged at the lower part of the recycling chamber and the back of the inclined partition wall, and that the recycling chamber in the upper and lower parts communicates with the primary combustion chamber with fluidized layer, with a part of the medium to be fluidized being introduced into the recovery chamber outside the upper part of the partition wall, and regulation of the fluidizing air which

introduced from the diffuser into the recovery chamber causes the medium inside the recovery chamber to sink into a state as a moving layer for circulation.

The method according to the invention is characterized by the fact that a boiler is used with a heat energy recovery chamber formed between the inclined partition wall and a side wall of the combustion device or between the rear sides of two inclined partition walls, and with a device with a heat exchanger surface arranged inside the recovery chamber, for the flow of a cooling fluid, and an air diffuser arranged at the lower part of the recovery chamber and the rear of the inclined partition wall, with the recovery chamber at the upper and lower parts communicating with the primary combustion chamber with a fluidized bed, and part of the medium is introduced into the recovery chamber outside the upper part of the inclined partition wall, and the fluidizing air is introduced from the diffuser into the recovery chamber, for to cause the medium inside the recovery chamber to sink and recirculate in a condition as a moving bed, the amount of heat energy recovered in the recovery chamber being controlled by regulating the amount of gas introduced from the diffuser into the recovery chamber, based on the needs of users utilizing steam and hot water that is formed, and the amount of fuel that is supplied to the primary combustion chamber with a fluidized bed is controlled, based on the energy needs of the users or the temperature in the primary combustion chamber.

With the above-mentioned arrangement, it is possible to easily control the temperature in the primary combustion chamber with a fluidized bed in the combustion device described above, while the heat energy is efficiently recovered by means of the thermally conductive lines in the fluidized zone where the degree of abrasion on the thermally conductive wiring is small.

The amount of fluidizing medium in the heat recovery chamber can be easily regulated by regulating the amount of air from the diffuser, particularly because the diffuser is located at the lower part of the heat recovery chamber and the back of the inclined partition wall. There is also rapid heating of the medium to be fluidized.

The invention will be explained in more detail below, with reference to the attached drawings. Fig. 3 is a schematic illustration explaining the principle of the present invention. Fig. 4 is a section through a boiler with an internal fluidized layer of recirculating type, and explains the entire construction according to the present invention. Fig. 5 is a diagram showing the relationship between the amount of air for fluidization (Gmf) in the section below the inclined partition wall in the primary combustion

fluidized bed chamber and the amount of recycled fluidizing medium. Fig. 6 is a diagram showing the relationship between the amount of diffusion air (Gmf) in the heat energy recovery chamber and the sink rate of the downwardly moving bed in the heat energy recovery chamber. Fig. 7 is a diagram showing the relationship between the mass flow per fluidization time unit (Gmf)

and the overall heat conduction coefficient in a conventional bubble-type boiler. Fig. 8 is a diagram showing the relationship between the diffusion mass flow per time unit (Gmf) in the recovery chamber for heat energy and the overall heat conduction coefficient in the boiler with internal fluidized bed of recirculating type according to the present invention. Fig. 9 is a diagram showing the relationship between the mass flow per unit of time for fluidization and the abrasion rate of the thermally conductive wire. Fig. 10 and 11 show variations in the supplied amount of fuel, the vapor pressure and the temperature in the fluidized bed in relation to the elapsed time, without and with regulation of the fluidizing mass flow per unit of time for the thermal energy recovery chamber depending on stepwise change of steam

the current per unit of time. Fig. 12 shows similar

variations in relation to the elapsed time depending on a gradual change in the steam flow per unit of time. Fig. 13 and 14 are sectional drawings explaining other embodiments of the boiler with an internal fluidized bed of the recirculation type according to the present invention. Fig. 15 is a section seen from the side, through a boiler with an internal fluidized bed of the recirculation type, and explains a further embodiment of the present invention which is particularly suitable for use as a small boiler. Fig. 16 is a section horizontally along a line shown by arrows A - A on the drawing of the embodiment shown in Fig. 15, and which partially shows a horizontal section through a boiler with an internal fluidized bed of the recirculation type intended for use in a circular boiler, and fig. 17 - 19 show fluidization progress in a primary combustion chamber with a fluidized bed, with the ratio between the horizontal length L to the bottom of the combustion device and the projected length 1 to the inclined partition in the horizontal direction.

In fig. 3, a diffusion plate 52 is arranged at the bottom of a combustion device 51, for the supply of fluidizing air which is supplied with a fan 57 through a supply line 53 for fluidizing air, and the diffusion plate 52 is designed with the shape of a ridge (angle shape) which is approximately symmetrical about the center line of the combustion device, so that the opposite end parts are lower than the middle part. The fluidizing air supplied from the fan 57 is arranged so that it is supplied upwards from the air diffusion plate 52 through the air chambers 54, 55 and 56, and the mass flow of fluidising air supplied from the air chambers 54 and 56 at the opposite ends is arranged to be sufficient to form the fluidized layer of the fluidizing medium inside the combustion device 51, while the mass flow of the fluidizing air supplied from the middle air chamber 55 is chosen so that it is smaller than from the others, as mentioned above in connection with the examples of known technology.

Inclined partitions 58 are provided above the air chambers 54 and 56 at the opposite ends, as a deflecting wall device adapted to affect the upwardly directed flow of fluidizing air and to deflect the air toward the center of the combustion device, and the circulating currents in the direction of the arrows shown are formed due to the presence of the inclined partitions 58 and the difference in mass flow of the supplied fluidizing air. On the other hand, the heat energy recovery chamber 59 is formed between the rear side surfaces of the inclined partitions 59 and the side walls of the combustion device, so that part of the fluidizing medium can be introduced during operation into the heat energy recovery chambers 59 outside the upper ends of the inclined partitions 58 .

In the present invention, the slanted part of

the inclined partition arranged so that it inclines 10 - 60°, or preferably 25 - 45° in relation to the horizon, and the projected length 1 of this in the horizontal direction in relation to the bottom of the combustion device is arranged so that it is 1/6 - 1 /2, or preferably 1/4 - 1/2 of the horizontal length L to the bottom of the combustion device.

The angle of inclination relative to the horizon and the projected length in the horizontal direction of the inclined partition are both factors that affect the fluidizing state of the fluidizing medium in the primary fluidized bed combustion chamber and the amount of particles that are fed into the heat energy recovery chambers. Otherwise, the meaning of L and 1 and the flow paths of the fluidizing medium are shown in fig. 17.

If the angle of inclination of the inclined part is either less than 10° or greater than 60° in relation to the horizon, no satisfactory circulating current occurs, and the condition under which the fuel is burned becomes worse. This angle is preferably in the range between 25° and 45°, and it is particularly advantageous if it amounts to approximately 35°.

In the event that the projected length 1 of the inclined partition wall in the horizontal direction in relation to the bottom of the combustion device is greater than 1/2 of the bottom length L of the combustion device, as shown in fig. 18,

the amount of fluidizing medium that is deflected from the inclined partitions and is caused to fall towards the center of the combustion device becomes smaller, and this negatively affects the formation of the moving layer at the center of the combustion device and the sinking and spreading of the fuel supplied in the center of the combustion device.

On the other hand, in a case as shown in fig. 19, where the projected length 1 of the inclined partition relative to the bottom of the combustion device is less than 1/&

of the bottom length L of the combustion device, the formation of the circulating flow in the primary combustion chamber with a fluidized bed, and in particular the formation of the moving layer at the center of the combustion device, becomes worse, so that the effect with regard to containing and spreading fuel is also negatively affected , and the deflected flow of fluidizing medium into the recovery chamber becomes insufficient.

In the lower part of the recovery chamber 59 for heat energy and the back of the inclined partition 58, a diffuser 62 for recovery chambers for heat energy is arranged,

for the introduction of gas, such as air, from a fan 60 through a supply line 61. In the part of the recovery chamber 59 for heat energy closest to the place where the diffuser

a 62 is placed, an opening 63 is arranged, and the fluidizing medium which is introduced into the heat energy recovery chamber 59 is made to sink continuously or intermittently while a moving layer is formed, depending on the operating condition, and is recirculated in the combustion section through the opening 63.

Fig. 4 shows an embodiment based on the principle in fig. 3.

The degree of lowering of the fluidizing medium in the heat energy recovery chamber for recirculation is regulated by the amount of diffusion air for the heat energy recovery chamber and the amount of fluidizing air for the combustion section. That is that the amount of fluidizing medium (G^) which is introduced into the heat energy recovery chamber is increased as shown in fig. 5 if the amount of fluidizing air that is introduced from the diffusion plate 52, in particular that from the end air chambers 54 and 56, which is

calculated to cause fluidization in the combustion section, is increased. Moreover, as shown in fig. 6, the amount of fluidizing medium that sinks into the heat energy recovery chamber changes approximately proportionally to the change in the amount of diffusion air blown into the heat energy recovery chamber, when the change is in the range 0-1 Gmf, and it becomes approximately constant if the amount of diffusion air for the heat energy recovery chamber increases beyond 1 Gmf. This constant quantity

of fluidizing medium is almost equal to the amount of fluidizing medium (G^) that is introduced into the heat energy recovery chamber, and thus the amount of fluidizing medium that sinks into the heat energy recovery chamber is equal to a value corresponding to G1. By controlling the amount of air for both the combustion part and the recovery chamber, the decreasing amount of fluidizing medium in the heat energy recovery chamber 59 can be regulated.

The sinking of the fluidizing medium in the static layer when this is in the range 0 - 1 Gmf is due to the weight difference of the fluidizing medium (the difference in height of the fluidized layers) between the recovery chamber for heat energy and the primary combustion chamber with fluidized layer, and in the in the event that the mass flow is more than 1 Gmf, the height of the moving layer becomes slightly greater or approximately equal to the other.

The recirculation of the fluidizing medium is assisted by

a deflected flow with a sufficient amount of fluidizing medium provided by the inclined partition.

Now the relationship between the height of the fluidized layer and the recirculating amount of the fluidizing medium (the deflected flow) will be explained in more detail.

In the event that the surface of the fluidized bed

is lower than the upper end of the inclined partition, the direction of the airflow moving upwards along the inclined partition is determined by this wall, and the airflow is introduced along the inclined partition from the fluidized bed, and the fluidizing medium is included. The introduced airflow is brought to a state different from that of the fluidized bed and is without the fluidizing medium filling the fluidized bed, and the cross-sectional area of the airflow channel suddenly increases, so that the introduced airflow is dispersed and its velocity decreases to a few meters per second. sec., so that it becomes a calm stream, and it flows out upwards. Therefore, the fluidizing medium that comes with it loses

the introduced airflow's kinetic energy, and falls due to gravity and friction against the exhaust gas when the grain size in the fluidizing medium is too large (approximately 1 mm) to be carried with the airflow.

In the event that the surface of the fluidized bed is higher than the upper end of the inclined partition wall, a part of the fluidizing medium collected by the partitions along the deflecting partition wall is introduced and given a similar direction as in the circulating type fluidized bed combustion device , while the other part, due to a sudden boiling phenomenon caused by the explosion of bubbles, boils upwards like a firework just above the upper end of the inclined partition, and falls along the entire circumference. Consequently, part of the fluidizing medium is introduced in a large amount towards the rear of the partition wall, i.e. into the heat energy recovery chamber.

This means that the direction of movement of the introduced fluidizing medium approaches vertical when the surface gets higher above the upper end of the inclined partition wall. Therefore, the amount of fluidizing medium that is introduced becomes

in the recovery chamber for heat energy greater in the case that the surface is slightly above the upper end of the inclined partition.

In fig. 5 shows the relationship between the amount of fluidizing air in the section below the inclined partition wall in the primary combustion chamber with a fluidized bed and the amount of fluidizing medium that is recycled through the heat energy recovery chamber.

E.g. during operation in the condition L^, if the height of

the fluidized bed decreases due to dispersion of the removed fluidizing medium, the recirculating amount of the fluidizing medium suddenly decreases, to e.g. below 1/10 of the previous amount, and heat energy recovery cannot be carried out. What is thus essential is the quantity of the fluidizing air, and if it is arranged to be more than 4 Gmf and preferably more than 6 Gmf, the value of G^/Gq greater than 1 is maintained, and the necessary and sufficient quantity of the recirculating fluidizing medium can be obtained even if the height of the fluidized bed is changed.

Also, by arranging the mass flow of air introduced from the diffuser at the bottom of the heat energy recovery chamber to be 0-3 Gmf, or preferably 0 - 2Gmf, and the mass flow of fluidizing air introduced from the diffusion plate arranged below the inclined partition is 4 - 20 Gmf or preferably 6-12 Gmf, i.e. by constantly keeping the mass flow greater on the combustion chamber side than in the heat energy recovery chamber, the amount of fluidizing medium that is fed back to the primary combustion chamber with fluidized bed from the heat energy recovery chamber can be regulated.

As for the moving bed in the heat energy recovery chamber, in academic terms this is called a static bed in the case that the mass flow is 0 - 1 Gmf and a fluidized bed in the case that the mass flow is more than 1 Gmf, and it is common known that a minimum mass flow of 2 Gmf is required for the formation of a stable fluidized bed. On the other hand, in the case that the moving bed according to the present invention is constantly sinking and moving, the sinking moving bed is formed satisfactorily until the mass flow increases to a magnitude of about 1.5 - 2 Gmf, without causing destruction of the moving bed due to the bubble phenomenon. It is assumed that the grains in the fluidizing medium gradually sink and move in a vibrating manner, so that the fluidizing air is converted into small air bubbles which uniformly flow upwards towards the upper part of the moving layer.

Inside the recovery chamber 59 for heat energy, thermally conductive lines 65 are led, through which a cooling fluid such as steam or water etc. is led, so that the heat energy is recovered from the fluidizing medium by heat transfer occurring while the fluidizing medium moves downwards in the recovery chamber for heat energy. The heat conduction coefficient in the heat energy recovery section varies greatly, as shown in fig. 8, in a case where the amount of diffusion air in the heat energy recovery chamber changes in the range 0-2 Gmf.

Now it will be explained such properties as load-dependent properties caused by the formation of the moving layer in the heat energy recovery chamber.

The general relationship between the total heat conduction coefficient and the mass flow for fluidization is shown in fig. 7. Between the values for the mass flow in the range 0 - 1 Gmf, the increase in the heat conduction coefficient is small,

and it increases suddenly when the mass flow becomes greater than

1 Gmf. As a method of stopping the fluidized bed boiler by utilizing the aforementioned phenomenon, the "Wing Panel Type" was introduced in DOE Report, 6021 (2), 655 - 633 (1985), and the heat conduction coefficient depending on the variation of the fluidizing mass flow is indicated to be insensitive (static bed) or too sensitive (fluidized bed).

When reviewing certain foreign patent descriptions, several cases have been found that appear to be similar to the present technology in that the combustion chamber and the heat energy recovery chamber are separated. However, all the described partitions are constructed with vertical orientation, and the fluidizing medium in the heat energy recovery chamber is in a state to transition to the static bed and to the fluidized bed, and it is static bed when the heat energy recovery is small and fluidizing layer, in which the medium is blown upwards from the lower part, when the recovery of heat energy is great. This is because it is difficult to produce a deflected flow with a vertically oriented partition wall, compared to the case where the partition wall is inclined. It is therefore inevitable in the case that the partition wall is vertically oriented that the fluidizing medium is arranged both in the combustion chamber and in the heat energy recovery chamber so that it is in a fluidized state (similar to water), so that the fluidizing medium is made to flow between the two chambers.

The relationship between the overall heat conduction coefficient and the mass flow for fluidization is shown in fig. 8. As shown in fig. 8, this changes almost linearly, and thus the amount of recovered heat energy and the temperature in the primary combustion chamber with fluidized bed can be controlled as desired. Moreover, such control can be easily carried out by regulating the amount of diffusion air in the heat energy recovery chamber.

It is also mentioned that the rate of wear of the thermally conductive lines in the fluidized bed is proportional to the third power of the mass flow for fluidization, and the relationship is shown in fig. 9. Accordingly, the problem of wear with respect to the thermally conductive wires can be solved by ensuring that the amount of diffusion air blown into the moving bed in the heat energy recovery chamber is 0-3 Gmf or preferably 0-2 Gmf.

In order to regulate the amount of heat energy that is recovered, regulation of the amount of recirculating fluidizing medium is performed, as explained earlier, while at the same time regulation of the heat conduction coefficient is performed, i.e., if the amount of fluidizing gas in the air chambers 54 and 56 for the primary fluidized bed combustion chamber is kept constant and the amount of diffusion air in the heat energy recovery chamber increases, the amount of recirculating fluidizing medium increases, and at the same time the heat conduction coefficient increases, so as to greatly increase the amount of heat energy recovered, as an effect of a combination of the two factors .

Seen from a temperature point of view with regard to the fluidizing medium in the fluidized layer, this corresponds to the effect that the temperature in the fluidizing medium is prevented from rising above the predetermined temperature.

As a means of introducing the diffusion gas into the heat energy recovery chamber 59, several means can be considered, but they are generally arranged so as to be inclined along the back of the inclined partition wall (the side facing the heat energy recovery chamber),

for efficient utilization of the heat energy recovery chamber.

In the diffuser, the open openings for the introduction of diffusion air are also made smaller as their location gets closer to the pointed end of the diffuser (as the height of the layer becomes smaller), so that the diffusion air is prevented from being introduced in large quantities at the pointed end part .

The respective dimensions of the open openings are preferably determined in such a way that an approximately uniform diffusion quantity is introduced throughout the entire length of the diffuser 62 when the diffusion air quantity is 2 Gmf. That is, when this is fulfilled it is possible to achieve the maximum amount of recovered heat energy from all the thermally conductive surfaces in the heat energy recovery chamber, and the rate of wear of the thermally conductive surfaces can be kept small on all surfaces.

In fig. 4, the reference number 66 is an inlet for the supply of combustible material arranged at the upper part of the combustion device 51, and 67 is a steam container for forming a circulation channel (not shown) together with the thermally conductive lines 65 in the recovery chambers

59 for heat energy. The reference number 69 indicates expiry

for non-combustible materials, connected to the opposite ends of the air diffusion plate 52 at the bottom of

the combustion device 51, and 70 is a screw conveyor equipped with screws 71 which have mutually opposite screw directions.

Otherwise, the location of the inlet for the supply of combustible material is not limited to the upper part of the boiler, and it can be arranged on the side of the boiler,

as a spreader 66' for the supply of coal, etc.

The combustible materials F supplied through the combustible material inlet 66 or 66' are circulated and burned in the fluidizing medium which circulates under the influence of the circulating current caused by the fluidizing air. At this time, no violent up and down movement of the fluidizing medium occurs at the upper center point above the air chamber 55, and the medium forms a descending, moving layer which is in a state of weak fluidization. The width of this movable bed is small at the upper portion, and the rear ends are extended in opposite directions to reach the portions above the air chambers 54 and 56 at the opposite ends, so as to be exposed to the fluidizing air which is introduced with greater mass flow. from both air chambers and blown upwards. Consequently, a portion of each rear end is displaced, and thus the layer just above the air chamber 55 sinks due to gravity. Above this layer, the fluidizing medium which is supplemented from the fluidizing layer collects, as will be explained in the following, and the fluidizing medium above the air chamber 55 forms a gradually and continuously descending moving layer during repetition of the conditions stated above.

The fluidizing medium which has moved over the air chambers 54 and 56 is blown upwards and deflected and swirled by the inclined partitions 58 towards the center of the combustion device 51, and falls down on top of the middle, moving layer and is recirculated as explained earlier, a part of the fluidizing medium is introduced into the recovery chambers 59 for heat energy outside the upper parts of the inclined partitions. In the event that the sinking speed of the fluidizing medium in the heat energy recovery chamber 59 is small, the slope angle of the fluidizing medium is formed at the upper part of the heat energy recovery chamber, and the excess fluidizing medium falls from the upper part of the inclined partition to the primary combustion chamber with fluidized bed.

The fluidizing medium introduced into the heat energy recovery chamber 59 forms a gradually descending moving layer due to the gas introduced from the diffuser 62,

and is fed back to the primary combustion chamber with a fluidized bed from the opening portion 63 after the heat transfer has been carried out with the thermally conductive lines.

Mass flow of diffusion air introduced from the diffuser

62 in the recovery chamber 59 for heat energy is selected from values in the range 0-3 Gmf or preferably 0-2 Gmf.

The reason for the above mentioned is, as shown in fig. 8,

that the heat conduction coefficient varies from minimum to maximum below the value of 2 Gmf, and the wear rate can be controlled, as shown in fig. 9, within a small area.

Moreover, the thermal energy recovery chamber is outside the highly corrosive zone of the primary fluidized bed combustion chamber under the reducing atmosphere, and thus the thermally conductive lines 65 are exposed to less corrosion, compared to conventional lines, and the degree of wear of the thermally conductive lines 65 is very small due to the fact that the fluidization rate in this part, as mentioned earlier, is small. As regards the speed of the air flow in the mass flow range 0-2 Gmf for the fluidizing air, this is very small, e.g.

0-0.4 m/sec. (surface velocity), at 800°C, and in practice depends on the temperature and grain size in the fluidizing medium.

In a case where the combustible materials are mixed with non-combustible materials with a dimension larger than the grain size in the fluidizing medium, the combustion residues are carried out together with a part of the fluidizing medium, by the screw conveyor 70 arranged at the bottom of the combustion device.

Regarding the heat conduction in the heat energy recovery chamber 59, in addition to the heat conduction that takes place due to the direct contact between the fluidizing medium and the thermally conductive lines 65, another form of heat conduction takes place that utilizes the rising gas that moves upward as the conducting medium, the gas moving upward with irregular vibration as the fluidizing medium moves. In the latter case, there is mainly no boundary layer between the solid objects that prevents heat conduction, in contrast to normal thermal contact between gas and solid objects, and the fluidizing medium is stirred so that the heat conduction inside the grains in the fluidizing medium can be disregarded i from, which fact cannot be disregarded i from in the case that the medium is stationary. Very significant heat conduction properties can thus be achieved.

Consequently, it is in the heat energy recovery chamber

according to the present invention it is possible to obtain a large heat conduction coefficient which is almost ten times as large as that which can be obtained in the conventional boiler with gas combustion.

As explained above, the heat conduction phenomenon that occurs between the fluidizing medium and the heat conducting surfaces depends to a large extent on whether the fluidization is strong or weak, and the amount of recirculating fluidizing medium can be controlled by regulating the amount of gas introduced from the diffuser 62. Also by arrange the recovery chamber 59 for heat energy and its moving bed independently of the primary combustion chamber inside the combustion device, it is possible to construct a compact recovery device for heat energy, in which the reduction ratio is large and the fluidized bed can be easily controlled.

In a boiler that uses combustible materials that have a low burning rate, such as coal or petrocoke as fuel, it is impossible in most cases to quickly vary the amount of evaporation, except when it comes to varying the amount of evaporation only in connection with the burning rate. In a bubble-type boiler, the situation is even worse compared to the above-mentioned boiler due to the fact that the recovery of heat energy is carried out on the basis of the temperature in the fluidized bed.

In the present invention, however, the amount of heat conduction is varied momentarily in the range between several times and several fractions by changing the amount of diffusion air in the heat energy recovery chamber. Therefore, the variation in the supply of heat energy in the fluidized bed based on the variation in the supply amount of combustible materials depends on the combustion rate and causes a time delay. However, the amount of recovered heat energy that takes place in the heat energy recovery chamber according to the present invention can be rapidly varied by varying the amount of diffusion air in the heat energy recovery chamber and the corresponding difference between heat input and heat recovery can be absorbed as a temporary change in temperature in the fluidizing medium due to the heat-sensitive cooling capacity of the fluidizing medium forming the fluidized bed. Consequently, the heat energy can be utilized without waste, and the regulation of the evaporation amount with good response characteristics can be achieved, which cannot be achieved with a conventional boiler such as for coal combustion.

Optionally, the location of the discharge openings 69 is determined for non-combustible materials, such as e.g. shown in the drawing, preferably at locations near the openings 63 and the opposite ends of the air diffusion plate in the combustion device 51. However, the location is not limited to what is explained above.

In fig. 4, the air diffusion plate 52 is shown in the form of a ridge. However, if the amount of fluidizing air introduced from the air chambers 54 and 56 is set to be more than 4 Gmf, the circulating current is formed in the primary fluidized bed combustion chamber due to the action of the inclined partitions, and therefore the air diffusion plate 52 can be horizontal in the event that combustible materials such as coal containing some non-combustible materials are burned. In addition, the discharge openings for the non-combustible materials can be omitted.

As explained above, the fluidized bed boiler according to the present invention has a superior ability to recover heat energy. Now the method for controlling the boiler according to the present invention will be explained in the following.

In the present invention, the amount of heat energy that is recovered from the heat energy recovery chamber is controlled, depending on the needs of the users who utilize the heat energy that is recovered, by regulating the amount of gas supplied from the diffuser into the heat energy recovery chamber. Also, the regulation of the temperature in the primary combustion chamber with fluidized bed is carried out by controlling the amount of supplied fuel, based on the temperature in the primary combustion chamber with fluidized bed or the steam pressure, and in the boiler according to the present invention the heat conduction coefficient can be regulated as desired,

and the variation of the amount of heat energy recovered with the present invention is absorbed as variation of the sensible heat in the fluidizing medium, so that the boiler can be controlled momentarily to meet the needs of the user, and it can work under stable conditions.

The explanation must be made in connection with fig. 4.

E.g. in a case where the temperature of the steam removed from the thermally conductive lines 65 is insufficient, a diffusion air control valve 93 is regulated in its opening direction by means of a regulator 92 for the valve 93, based on the temperature sensed by a thermosensor 91 on a line 90 for removal of steam. To increase the amount of diffusion air supplied, so that the amount of heat energy recovered is increased and the steam temperature is raised according to the user's needs.

The temperature in the primary combustion chamber with a fluidized bed is controlled within a certain range by regulating the amount of fuel supplied to the primary combustion chamber with a fluidized bed and/or by regulating the amount of air supplied to the air chambers 54, 55 and 56, based on the temperature in the fluidized bed layer sensed by a thermosensor 94.

There is another method by which the amount of fuel supplied to the primary combustion chamber with a fluidized bed can be controlled by means of a pressure signal, e.g. in the event that the amount of steam needed varies due to load variation on the user side, as steam pressure is the factor that changes most rapidly depending on changes in demand. The response characteristics are shown in fig. 10 and 11, where the flow amount of steam per time unit changes with a step of 30%, from 70% to 100%.

Fig. 10 shows experimental results obtained when the amount of air from the diffuser in the heat energy recovery chamber was kept constant while the flow amount of steam per time unit was varied step by step by 30%, and fig. 11 shows experimental results obtained in a case where the diffusion air quantity was regulated in dependence on the 30% stepwise variation in the flow quantity of steam per unit of time. By comparing the two experiments, it has been found that the temperature in the fluidized bed and the flow rate of steam per time unit is limited to predetermined values within a short period of time, and the range of variation is also small in the case (fig. 11) that the amount of diffusion air is regulated according to the present invention, depending on the variation in the flow amount of steam per time unit, compared to the results for the conventional method shown in fig. 10.

E.g. the range of variation for the temperature in the fluidized bed was approximately +12°C, and for the vapor pressure it was approximately below +0.3 kg/cm 2 (0.029 MPa) in the case that the regulation was carried out according to the present invention, as shown in fig. 11.

The response characteristics are also shown in fig. 12, when the flow amount of steam per time unit is varied in a step of -60%, the amount of diffusion air in the heat energy recovery chamber being regulated in dependence on the above-mentioned variation according to the present invention. In this case, it has also been found that the temperature in the fluidized bed is almost constant and that the variation range of the vapor pressure is small.

In the following, another embodiment according to the present invention will be explained with reference to fig. 13. The embodiment shown in fig. 13 corresponds to the case where the present invention is used in the combustion device shown in fig. 1, in which there is a single circulating, fluidized bed, and the reference numerals are the same as used in fig. 3 with regard to meaning and function.

Fig. 14 shows a design that can be used when a boiler with large dimensions is required. The embodiment shown in fig. 14 is constructed by combining the two boilers with an internal fluidized bed, of the recirculation type, shown in fig. 4.

As shown in fig. 4 and 14 the operation takes place without problems at

to supply fuels from the supply inlet arranged in the roof. In the event that solid fuels such as coal with a grain size below several cm are burned, it is preferred to supply the fuel in the combustion section from a relatively low place instead of from the ceiling, but still higher than the surface of the fluidized bed, using a suitable type equipment such as a spreader adapted to distribute the fuel by means of a rotating blade.

Consequently, in a case when the device is used only for burning solid fuels such as coal, it is possible to arrange a spreader of the above-mentioned type without arranging an inlet in the roof. It is also possible to supply combustible materials containing objects with large dimensions from the roof and to supply solid fuels from the spreader as just explained, to burn both of these mixed together.

The boilers with internal fluidized bed of the recirculation type explained above are of the type that are preferably used for boilers of medium or large size.

In the case of small size boilers it is

it is desirable that these are made more compact, and an embodiment designed for this purpose is shown in fig. 15. In execution

shown in fig. 15, the thermally conductive lines 65 are shown inside the layer in fig. 4 oriented in an almost vertical direction, and leading to a thermally conductive part for exhaust gas arranged above the heat energy recovery chamber, so that this group of thermally conductive lines is arranged to also serve as means for connecting an upper water chamber 91 and a lower water chamber 92.

By arranging the approximately vertical evaporation lines as several lines in a free area at the upper part of the primary fluidized bed combustion chamber and around the thermal energy recovery chamber, it is possible to use these as elements for strengthening the boiler house and to eliminate the need for auxiliary -devices such as a circulation pump and associated lines, etc., because the fluid in the thermally conductive lines and what is in the lines inside the layer is automatically circulated.

In addition, a fluidized bed boiler and a boiler can

for exhaust gas are combined as a unified construction, so that a boiler with an internal fluidized bed of the recirculation type can be made economically available in a small size.

The construction and operation of the present invention shall be further described in more detail below. The exhaust gas formed after the combustion in the primary fluidized bed combustion chamber flows upwards through the free part in the area above the combustion chamber, and is then supplied to the group of thermally conductive lines formed around the circumference from the upper part of the group. It then moves downward in a stream moving in a direction almost perpendicular to the thermally conductive wires, as heat transfer occurs. While this is happening, a part of the unburnt ash which is collected by means of guide plates 93 is caused by gravity to fall towards the moving bed in the heat energy recovery chamber, so that the unburnt ash is thereby completely burnt due to its long residence time in the moving bed, thereby improving combustion efficiency.

The situation described above is particularly effective when coal is used, as the unburnt carbon in this takes a long time to burn. However, in other cases when a fuel other than coal is used, and the unburnt ash cannot be spread around, means for recycling the unburnt ash may be unnecessary.

As regards the inlet for the supply of fuel, if this is arranged, e.g. as a top feed type, as shown, it is preferred to blow the secondary combustion air towards the primary fluidized bed combustion chamber. With the above-mentioned arrangement, an air curtain effect caused by the secondary air is assumed to prevent fine fuel particles such as coal in powder form from being dispersed together with the combustion exhaust gas and to carry out an effective stirring and mixing operation in the free part, so that it can also contribute to creating sufficient contact between oxygen in the secondary air and the unburnt ash in the exhaust gas, thereby improving the combustion efficiency and reducing the density of N0x and CO, etc.

Fig. 16 is a horizontal section along the line shown by the arrow A - A in fig. 15, and it particularly shows an example of

a boiler of the circular type. In a case where it is a small boiler, it is not particularly necessary to shape it as a circular type as shown in fig. 16, but the production of the arrangement of the thermally conductive wires is simplified if it is circular.

Optionally, it is preferred in the designs shown in fig. 4,

13 and 14 etc. to arrange these in a square shape, from an assembly point of view.

Claims (7)

1. Fluidized bed boiler, of the recirculation type, comprising a primary fluidized bed combustion chamber formed by an air diffusion plate (52) arranged at the bottom of a combustor and arranged to introduce fluidizing air upwards with a mass flow rate at least greater than one side than on the other side, an inclined partition wall (58) arranged over the part of the diffusion plate where the mass flow is greatest, to influence the upward flow of the fluidizing air and thereby deflect the air towards the part over the other side of the diffusion plate where the mass flow is least, the inclined partition wall is inclined by 10° - 60° in relation to the horizontal direction and the projected length of this in the horizontal direction is 1/6 - 1/2 of the horizontal length to the bottom of the combustion device, and a movable layer is formed over that part of the diffusion plate (52) where the introduced mass flow is the smallest, so that a medium to be fluidized sinks and spreads inside the moving layer, and a circulating fluidized layer is formed over the part of the diffusion plate (52) where the mass flow of the fluidizing air is greatest, as that the medium is actively fluidized and swirled towards a place above the moving layer, as the formation of the moving layer and the circulating fluidized layer takes place by regulation of the amount of air introduced upwards from the diffusion plate (52), characterized in that a recovery chamber (59) for heat energy is formed between the inclined partition wall (58) and a side wall in the combustion device or between the backs of two inclined partition walls, that a device (65) with a heat exchanger surface is arranged inside the recovery chamber (59) for the flow of a cooling fluid, that an air diffuser (62) is arranged at the lower part of the recycling chamber (59) and the back of the inclined partition wall (58), and that the recovery chamber (59) in the upper and lower parts communicates with the primary combustion chamber with a fluidized bed, with a part of the medium to be fluidized being introduced into the recovery chamber (59) outside the upper part of the partition wall (58), and regulation of the fluidizing air introduced from the diffuser (62) into the recovery chamber (59) causes the medium inside the recovery chamber (59) to sink into a condition as a moving bed for circulation. 2. Boiler as stated in claim 1, characterized in that the mass flow of air introduced from the diffuser (62) at the bottom of the recovery chamber (59) is in the range of 0-3 times the smallest mass flow that causes fluidization, or preferably 0-2 times this mass flow (Gmf), and the mass flow of fluidizing air that is introduced from the diffusion plate (52) under the inclined partition (58) is in the range 4-20, and preferably 6-12 times this mass flow. 3. Boiler as stated in claim 1 or 2, characterized in that the inclined partition (58) is inclined at 25° - 45° in relation to the horizontal direction. 4. Boiler as specified in claim 1 or 2, characterized in that the inclined partition (58) is inclined at 35° in relation to the horizontal direction. 5. Boiler as specified in claim 1, 2, 3 or 4, characterized in that the inclined partition (58) is designed such that the length of its projection in the horizontal direction is 1/4 - 1/2 of the horizontal length to the bottom of the combustion device . 6. Method for controlling a boiler with an internal fluidized bed, of the recirculation type, which boiler comprises a primary combustion chamber with a fluidized bed, formed by an air diffusion plate (52) arranged at the bottom of a combustion device and arranged to introduce fluidization flowing air upwards in a mass flow which is at least greater on one side than on the other side, an inclined partition wall (58) arranged over the part of the diffusion plate (52) where the mass flow is greatest, to affect the upward flow of the fluidizing air and thereby deflecting the air towards the part over the other side of the diffusion plate where the mass flow is least, the amount of air introduced from the diffusion plate (52) being regulated so that a moving layer is formed over the part of the diffusion plate where the introduced mass flow is least , as a medium to be fluidized sinks and spreads inside the moving layer, and a circulating fluidized layer is formed over the part of the diffusion plate (52) where the mass flow of the fluidizing air is greatest, so that the medium is actively fluidized and circulated towards a place above the moving layer, characterized in that a boiler is used with a recovery chamber (59) for heat energy formed between the inclined partition wall (58) and a side wall in f the combustion device or between the backs of two inclined partitions (58), and with a device (65) with a heat exchanger surface arranged inside the recovery chamber (59), for the flow of a cooling fluid, and an air diffuser (62) arranged at the lower part of the recovery chamber (59) ) and the back of the inclined partition wall (58), with the recovery chamber (59) at the upper and lower part communicating with the primary fluidized bed combustion chamber, and part of the medium is introduced into the recovery chamber (59) outside the upper part of the inclined partition wall (58) , and the fluidizing air is introduced from the diffuser (62) into the recovery chamber (59), to cause the medium inside the recovery chamber to sink and recirculate in a state as a moving bed, the amount of heat energy recovered in the recovery chamber (59) is controlled by regulating the amount of gas introduced from the diffuser (62) into the recovery chamber (59), based on the needs of users who utilize steam and hot water nn that is formed, and the amount of fuel supplied to the primary combustion chamber with a fluidized bed is controlled, based on the users' energy needs or the temperature in the primary combustion chamber. 7. Method as stated in claim 6, characterized in that the mass flow of air that is introduced from the diffuser (62) at the bottom of the recovery chamber (59) is in the range of 0-3 times the smallest mass flow that causes fluidization, preferably 0-2 times this mass flow (Gmf), and the mass flow of fluidizing air which is introduced from the diffusion plate (52) under the inclined partition (58) is in the range 4-20, preferably 6-12 times this mass flow.