DK166694B1 - PROCEDURE FOR MANAGING A FLUID BED BOILER AND FLUID BED BOILER FOR USE IN EXERCISING THE PROCEDURE - 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

in DK 166694 B1

BACKGROUND OF THE INVENTION The invention relates to a method for controlling a fluidized bed boiler comprising a combustion chamber containing a primary fluidized bed of fluidizing medium and a spreading plate, a heat energy recovery chamber containing a heat recovery layer of fluidized medium and a gas or air diffuser, and wherein an inclined partition separates the primary fluidized layer from the heat recovery layer, and where the primary fluidized layer and the heat recovery layer communicate with each other top and bottom, and a heat exchanger located in the heat recovery layer for a heat receiving fluid.

These may include coal, anthracite, coke, bark, sugar cane, industrial waste, 15 municipal waste and other fuels.

The invention also relates to a fluidized bed kettle for use in the practice of the invention and of the nature comprising a combustion chamber having a primary fluidized bed and a spreading plate for supplying the fluidized bed with varying amounts of fluidizing gas, a heat energy recovery chamber, containing a heat recovery layer and a gas or air diffuser for supplying the heat recovery layer with gas, an inclined partition separating the primary fluidized layer from the heat recovery layer in such a way that the primary fluidized layer and the heat recovery layer communicate with each other above and below and a heat exchanger located in the heat recovery layer for a heat absorbing fluid.

A boiler of this kind is known from US-A-4 419 330.

JP disclosures 46988/76 and 5242/68 disclose combustion plants with such a fluid bed boiler.

An example of such a boiler is explained in greater detail hereinafter with reference to FIG. 1. An air diffuser plate 2 at the bottom of a combustion chamber 1 serves to fluidize a medium. This plate 2 slopes downward from the side wall where there is a feed assembly 3 for material, such as waste, to the opposite edge, where there is an outlet for non-combustible material. A blower 8 blows air upwards through air chambers 5, 6, 7 and the plate 2 to form the fluidized bed.

The air mass flow through each air chamber must be sufficient to form the fluidized bed, and 10 is blown most from chamber 7 and at least from chamber 5.

For example, the following values may be present: from chamber 7: 4-20 Gmf, preferably 6-12 Gmf; from chamber 6: 3-10 Gmf, preferably 4-6 Gmf, and from chamber 5: 1-4 Gmf, preferably 1-2.5 Gmf.

15 µmf is the value of the mass flow at which fluidization begins.

The state of the fluidized medium changes from static state - static fluid bed - to dynamic state - active fluid bed - at the above 20 values as threshold values between the two states.

The FIG. 1 has three air chambers, but another number may be selected, e.g. 2 or more than 4 and the air mass flow is regulated so that it is greatest for the chamber near the outlet 4 and at least for 25 the chamber most remote from the outlet.

Above the chambers 7 and 6 there is an inclined wall 9 which acts as a deflector for the upward air flow, which is therefore deflected in the direction of the feed unit 3.

In the case where there is non-combustible material in the fuel supplied, the spreading plate 2 preferably has a slope of between 5 and 15 °, but if there is only a little non-combustible material, the plate may lie horizontally, since the fuel can be circulated at setting the exhaust airflow from the respective chambers.

The wall 9 may be flat, convex or concave.

In the top 11 of the combustion chamber there is an outlet 12 for exhaust gas, an inlet 13 for liquid waste generated during operation of the plant and an inlet 14 5 for cooling water, etc.

The combustion chamber 1 operates as follows. Air is blown in with the blower 8 and the blown air volume is regulated with decreasing values from chamber 7 to chamber 5.

10 In the conventional fluidized bed boiler, the fluidizing medium moves violently up and down, like boiling water.

However, near the side wall where the fuel feed assembly 3 is located, the fluidizing medium 15 does not move violently up and down, forming a weakly fluidized layer 15.

This layer has a narrower width at the top and it spreads down due to the difference in mass flow from the respective air chambers. The rear end of the fluidized vortex layer extends over the air chambers 6 and 7 and, due to the stronger air exhaust from these two chambers, the fluidized bed is forced upward and gravity then forces a portion of the fluidized bed 15 downwardly over the air chamber 5. During this downward bending 25 When the layer 15 is wetted, the fluidizing medium is brought into an upward flow 16 up to the upper part of the layer 15, thereby forming the fluidized bed, while this process repeats itself.

The fluidizing medium above the air chambers 30 6 and 7 is blown upwardly against the inclined wall 9, deflected by it and sent in the direction of the sidewall where the feeder is located, the medium having gradually gradually flowing downwards to the upper part of the layer 15, and then circulate again.

The downward vortex layer 15 carries with it the fuel which is fed into the chamber 1 with the feeder unit 3.

In a conventional fluidized-bed boiler, combustible materials, such as paper that weighs slightly and emit a great deal of heat energy, are simply incinerated on the surface of the fluidized bed, without contributing much to heating the fluid medium.

In a circulation boiler, this loss of energy will be avoided, and combustible materials of the kind mentioned will certainly be incinerated in the downward vortex layer 15 and the circulating layer 16 so that they 10 effectively contribute to heating the fluidizing medium.

The fuel-loaded non-combustible materials move downward in the fluidized bed 15, transversely, and during this movement, the combustible materials associated with or integral with the non-combustible materials occur, e.g. insulation on power lines. Due to the transverse movement of the medium and the slope of the air diffuser plate 2, the non-combustible materials will be fed to the outlet 4, from which via 20 a vertical duct 17 and a conveyor 18 are fed to a vibration screen 19 which separates them from the fluidizing medium.

This separated medium or fresh fluidizing medium is returned to the chamber 1 via a transport arrangement 20.

Another example of known combustion plant with circulating vortex layers is explained below with reference to FIG. 2nd

At the bottom of the combustion chamber, as shown in FIG. 2, there is an air diffuser plate 22 for fluidizing air. The two opposite edge zones of the plate 22 are lower than the center of the plate, thus having Δ-shape, in the main axis symmetrical with respect to the center line 42 of the chamber, and there is a drain 24 for non-combustible material next to both of these edge zones.

5 DK 166694 B1

A fan 28 introduces fluidizing air through the plate 22 via air chambers 25, 26, 27 with stronger airflow from the two outer chambers 25 and 27 at the opposing edge zones to create the fluidized bed and 5 with weaker airflow from the central air chamber 26.

For example, the following values may be present: from the air chambers 25 and 27: 4-20 Gmf, preferably 6-12 Gmf, and from the air chamber 26: 0.5-3 Gmf, preferably 1-2.5 Gmf.

10 The number of air chambers is freely selectable at three or more. If there are more than three chambers, the fluidization air flow must be regulated so that it is lowest for the central chambers and more powerful for the chambers at the opposite edge zones.

Above the chambers 25 and 27 at the opposite edge zones there are inclined deflector walls 29 which deflect the air currents towards the center of the combustion chamber.

Above the oblique walls 29, the walls 30 incline in the opposite direction to prevent the collection of fluidizing medium.

In the case where the combustible materials are accompanied by non-combustible materials, the air diffuser plate 22 should have a slope of 5-15 °. If not, no slope is needed.

The oblique walls 29 may be planar, convex or concave.

At the top 31 of the combustion chamber there is an opening 34 for fuel with inlet 33 from a feed unit 23 located above the air chamber 26, and an outlet 32 for exhaust gas.

The inclined walls 29 may be formed with built-in channels for fluidizing air, whereby it can be preheated.

35 This incinerator works as follows. Fluidization air is blown in with the fan 28, 6 DK 166694 B1 with large mass flow from the air chambers 25 and 27 and less mass flow from the air chamber 26.

In this conventional fluidized-bed boiler, the fluidizing medium moves violently up and down, like boiling water. As for the one shown in FIG. 2, however, the fluidizing medium above the air chamber 26 will not induce this violent upward and downward movement, and a weakly fluidized, moving layer is formed. This layer has a narrow 10 width at the top and spreads in the lateral directions, in opposite directions to the fluidized fluidized layers, and the portion of the moving layer reaching above the air chambers 25 and 27 is blown upward while the fluidizing air from the strongest mass flow is introduced into the fluidizing medium. Thus, a portion of the fluidizing medium at the rear of the flow will be pushed upward, so that the layer above the air chamber 26 is forced downward by gravity. Above this moving layer, the fluidizing medium, as will be explained in greater detail later, will be supplemented by the fluidized bed accompanied by a circulating flow 36. When repeated, a certain portion of the fluidizing medium above the air chamber 26 will be to a mass forming a moving layer 35 which gradually moves downward and dilutes.

The fluidizing medium moving above the air chambers 25 and 27 is blown upwardly towards the inclined walls 29, and bends therefrom and further swirls upward toward the center line of the combustion chamber. However, due to the sudden increase of the cross-sectional area of the combustion chamber, this eddy current will lose its upward movement velocity, so that it moves over the top of the downward layer 35, gradually decreases and is brought back into circulation as it reaches forward to the rear of the moving vertebral layer. Part of the fluidizing medium circulates as the currents 36 in the fluidized bed.

When through the inlet 34, fuel is supplied to the combustion chamber in which there is the fluidized state as explained above, this fuel falls on top of the downward layer 35. As the fluid medium near the top behaves. so that it circulates from the sides to the center line, the combustible material will be carried and trapped at the top of the downward layer 35. Consequently, lightweight materials such as paper will certainly be brought into the downward layer 35 instead of merely being fired on the surface of the conventional fluidized bed, without making any contribution to heating the fluidization medium. They will certainly be combusted within the downstream layer 35 and the circulating flows 36 15 and effectively heat the fluidization medium.

Within the moving layer, the combustion of the combustible materials takes place partly to produce a combustible gas. In that case, since the combustible gas spreads in the horizontal direction as the fluidizing medium moves downward and burns in the fluidized bed, the energy released by burning the gas will effectively heat the fluidizing medium.

Heavy and large foreign bodies, such as bottles or pieces of metal that reach down to the surface of the downstream vortex layer 35, will not immediately fall to the top of the air chamber 26, but will instead be suspended in the moving layer. 35, and they gradually descend to the non-combustible material outlets 24, along with the flow of fluidizing medium.

Therefore, relatively large size combustible materials will be dried, gasified or incinerated within the downward layer 35 during the downward progressive movement, and therefore will be nearly two to 35 incinerated and of smaller size as they reach the rear end of the the moving layer so that they do not affect the formation of the vertebral layer.

DK 166694 B1 δ

Therefore, you do not need to treat the combustible materials with a crusher, and you can simply break the packaging containing these materials in the feed unit 23. This avoids the need for pre-crushing and the associated equipment, which makes the system more compact.

The combustible materials introduced into the downstream layer 35 spread rapidly in the fluidizing medium, thereby increasing the efficiency of the combustion process.

Medium-sized non-combustible materials supplied from the feed assembly 23 first move downward and laterally within the downward layer 35, and during this movement, the combustible material 15 such as e.g. insulation on electrical wiring that may be present on or in the non-combustible materials is incinerated. The non-combustible materials which reach the rear end of the fluidized bed are fed to the outlets 24 due to the lateral movement of the fluidizing medium and 20 due to the inclination of the air diffuser plate 22 and these materials are passed through the ducts 37.

From there, these non-combustible materials are fed to a conveyor 38 and to a screen not shown, while the fluidization medium is filtered off.

In the FIG. 1 and 2, circulating flow fluidized boilers, the fluid medium fluidization medium is usually 1 mm in size, and the combustion chamber operates at a temperature of the fluidization medium of 600-800 ° C, while the temperature 30 of the exhaust gas is 750-950 ° C.

The exhaust gas is cooled to approx. 300 ° C in a chamber or air preheater and fed to a chimney after removal of small particles or after heat energy recovery by means of a heat exchanger located downstream of the exhaust gas outlet, or after passage through U-shaped hot water pipes installed in DK 166694 Bl 9 areas 21 or 41 so that additional heat energy is extracted while the exhaust gas is cooled and the dust particles removed.

In the case of combustible materials with high combustion value, and if the fluidizing medium is heated above a given temperature of e.g. more than 800 ° C, there is a risk of sintering fluidization medium, so the fluidized bed cannot function if there are alkaline metal compounds in the combustible materials. If so, it is normal practice to lower the temperature of the fluidizing medium down to a given temperature by spraying water into the medium.

Therefore, it has been necessary to take into account the recovery of heat energy in the fluidizing medium by inserting heat transfer lines therein. However, several problems arise when many heat transfer lines are inserted into the fluidized bed, the non-combustible materials forming obstruction in the fluidized bed, the heat transfer lines being worn by the fluidizing medium, and heat energy extraction always required to protect the lines even if heat energy is not needed. Thus, operation is not free from these disadvantages.

Regarding the conventional fluidized bed boiler 25, as indicated below, there are two types that can be distinguished from one another in terms of the design of the heat-conducting part and the combustion of small, non-burned materials scattered in the fluidized bed.

1) a non-recirculating type fluidized bed boiler (hereinafter referred to as a conventional fluidized bed or bubbling kettle), and 2) circulating type fluidized bed boiler.

In the non-recirculating type, heat transfer lines are arranged in the vortex layer and heat transfer takes place with high efficiency due to the physical contact between the lines and the high temperature burning fuel and the fluidizing medium. In the recirculating type, a portion of the small particles of combustible material which have not yet been burned, as well as the axis or fluidization medium (recirculating solid material) will be combined in a stream of combustion gas and fed to a heat transfer part which is independent of the area where the combustion of unburned materials continues, the solid material returning after this heat transfer to this area together with a portion of the combustion gas. That is why the above has been talked about boiler with recirculation.

Various types of fuel with different properties can be burned in the fluidized boiler, depending on the combustion process in question, but several drawbacks have recently been found. Regarding the bubble type boiler, drawbacks have been recognized in terms of filling capacity, complexity of fuel feed assembly, requirement for a large amount of lime for denitrification, wear of the heat transfer lines, etc., and that a recycle-type boiler is capable of alleviating these drawbacks.

However, further technical development is needed to maintain the correct temperature values in the recirculation system, including a 25 burner and a cyclone, sizing the plant and solving the problem of the need for a long period of cold start.

The invention provides a method of the kind described in the preamble, characterized in that a fluidizing gas having a higher mass flow is introduced from the spreading plate into a region below the inclined partition than to a region opposite to the partition thus: forming an upwardly fluidized layer 35 along the partition and a downwardly fluidized layer on the opposite side of the partition, whereby said two circulating fluidized layers form control of the mass flow of fluidizing gas from said dispersion plate to said region of the partition wall so that a portion of the fluidizing medium in the circulating fluidized bed flows upwardly and reaches the energy recovery chamber, and controlling the mass flow of gas from the air diffuser to the heat recovery layer, thereby controlling the total heat transfer coefficient and thus the heat energy amount that 1 0 is recovered by the fluid in the heat exchanger.

Furthermore, a fluidized bed boiler of the kind initially described in the invention is characterized in that the air diffuser is located in the lower part of the heat energy recovery chamber, that the heat energy recovery chamber near its lower part has an access port for the material from the heat recovery layer. this material is capable of flowing down through this port from the heat energy recovery chamber to the combustion chamber, and that a portion of the spreading plate is located below said inclined partition and is arranged to cause a higher fluidization gas stream to be formed at the partition wall. mass flow than the mass flow induced by other parts of the spreading plate.

The invention is based on the finding that it is hereby possible to easily control the temperature of the primary vortex combustion chamber while efficiently extracting heat energy with the heat exchanger in the fluidized zone, where the extent of wear on this heat exchanger is reduced.

The amount of fluidizing medium in the heat energy recovery chamber can be easily controlled by controlling the amount of air from the air diffuser, especially because it is located at the bottom of the chamber and behind the partition wall.

In addition, this medium will rapidly heat.

The invention will be explained in more detail below with reference to the schematic drawing, in which FIG. 1 and 2 are sectional views of conventional internal circulation fluidized-type boilers; FIG. 3 is a schematic view for explaining the principle of the invention; FIG. Fig. 4 is a sectional view through an internal circulating fluidized-type boiler, to explain the construction according to the invention; 5 is a graph showing the relationship between the amount of air for fluidization (Gmf) at the portion 10 below the inclined partition of the primary combustion chamber and the amount of recycled fluidization medium; FIG. 6 is a graph showing the relationship between the amount of blown air (Gmf) in the heat energy recovery chamber and the rate or rate of downward layer in the recovery chamber; FIG. 7 is a graph showing the relationship between the fluid mass flow (Gmf) and the global heat conduction coefficient in the conventional bubble-type boiler; FIG. Fig. 8 is a graph showing the relationship between the scattering mass flow rate (Gmf) in the recovery chamber and the global heat conduction coefficient in the recycle boiler according to the invention; 9 is a graph showing the relationship between the fluid mass flow and the amount of wear on the heat transfer line; FIG. Figs. 10 and 11 show variations in the amount of fuel, vapor pressure and fluidized bed temperature in relation to time and with control of the fluid mass flow of the recovery chamber in response to a stepwise change in the vapor flow; Fig. 12 shows similar variations over time, in stepwise change of vapor flow; 13 and 14 are sectional views showing further embodiments of the boiler according to the invention; FIG. 15 is a sectional view through yet another embodiment of the invention, particularly suitable for use on a small boiler; FIG. 16 is a sectional view along section line A-A of FIG. 15 for a boiler in circular design, and FIG. 17-19 fluidization patterns in a primary vertebral combustion chamber, indicating the relationship between the horizontal extent L of the combustion chamber and the horizontally projected length 1 of 10 of the inclined partition.

Referring now to FIG. 3. At the bottom of a combustion chamber 51 there is a spreading plate 52 for introducing fluidizing air from a blower 57 through a conduit 53. The spreading plate 52 is shaped like a roof, approximately symmetrical with respect to the center line of the combustion chamber, so that the two opposite edge regions of the plate is lower than the central portion thereof. The fluidization air from the fan 57 is introduced upwardly from the air diffusion plate 20 52 through air chambers 54, 55 and 56, and the mass flow of fluidizing air from the outer chambers 54 and 56 is sufficient to form a fluidized bed in the chamber 51, while the mass flow of fluidizing air from central air chamber 55 is somewhat smaller, in the same manner as explained above in the prior art.

Above the two opposing air chambers 54 and 56, inclined walls 58 are provided which act on the upward flow of fluidizing air and deflect this flow towards the center line of the combustion chamber and the arrows indicate the flow loss that occurs due to the presence of these walls 58 and of the difference in mass flow of blown fluidized air. Between the backside of these inclined walls 58 and the side walls of the combustion chamber, heat energy recovery chambers 59 are formed so that a portion of the fluidizing medium during operation can be introduced into these chambers 59 behind the inclined walls 58.

According to the invention, the inclined walls have a slope of between 10 and 60 °, preferably 25 - 45 ° in relation to the horizontal, and the length projected L to the horizontal is between 1/6 and 1/2, preferably between 1 / 4 and 1/2 of the horizontal length L of the bottom of the combustion chamber.

The angle of inclination with respect to the horizontal and the length projected horizontally of the inclined walls are both factors influencing the fluidization state of the fluidization medium in the primary chamber and the amount of grain introduced into the recovery chambers. With regard to parameters "L" and "1" and 15 for the fluid flow conditions, reference is made to FIG. 17th

If the angle of inclination of the inclined wall is less than 10 ° or greater than 60 ° relative to the horizontal, a satisfactory circulation cannot be obtained and the conditions for combustion of the fuel deteriorate. The angle is preferably in the range between 25 ° and 45 °, and an angle of approx. 356.

If projected on the horizontal: length 1 of the 25 oblique wall is greater than - that. half. of · length: L.-. of the bottom of the combustion chamber, cf. FIG. 18, the amount of fluidization medium deflected by the inclined walls decreases along the center line of the chamber, which adversely affects the formation of the moving member. layers at center., of ·.-combustion chamber · and on. the downward movement and the spread of fuel supplied centrally in the chamber.

If, on the other hand, the length projected 1 of the inclined wall relative to the extension of the bottom of the combustion chamber is less than 1/6 of the bottom length L, cf. FIG. 19, the formation of the circulation flow in the primary chamber, and in particular the formation of the moving layer at the center of the combustion chamber, will be impaired, adversely affecting the supply and spread of the fuel and the deflected flow of the fluidization medium in the recovery chamber becomes insufficient.

At the bottom of the recovery chamber 59 and at the rear of the inclined wall 58 there is a diffuser 62 associated with the recovery chamber for introducing gas, e.g. air from a blower 60 through a conduit 61. X the portion of the recovery chamber 59 located near the location where the spreader 62 is located, there is an access port 63 and the fluidization medium introduced into the recovery chamber 59 is brought to 15 continuous or intermittent, depending on the mode of operation, to move downward with a layer of formation and it is recirculated into the combustion area through the gate 63.

FIG. 4 shows an embodiment based on the embodiment shown in FIG. 3 illustrated principle.

The amount of downstream fluidization medium entering the recovery chamber and to be recirculated is regulated by the amount of the air diffuser and discharged into the recovery chamber, as well as by the amount of fluidizing air 25 in the combustion area. The amount of G 1 fluidization medium introduced into the recovery chamber will, as shown in FIG. 5 is increased if there is correspondingly an increase in the amount of fluidizing air introduced from the spreading plate 52, in particular from the two outer air chambers 30 54 and 56 which are to effect fluidization in the combustion region. Furthermore, cf. FIG. 6, the amount of fluidizing fluid which descends into the recovery chamber will change approximately proportionally to the change in the amount of air blown into the recovery chamber 35 when the change is in the range of 0-1 Gmf, and then be kept approximately constant when the amount of 16 DK 166694 B1 introduced air into the recovery chamber grows above 1 Gmf. This constant amount of fluidizing medium is almost equivalent to the amount of G1 of fluidizing medium introduced into the recovery chamber, so the amount of fluidizing medium flowing down the recovery chamber has a value similar to G 2 in controlling air flow, both for the combustion area and for the recovery chamber. the amount of downstream fluidization medium in the recovery chamber 59 is controlled.

The downward movement of the fluidization medium in the static layer for the area from ol Gmf is due to the difference in weight of the fluidization medium (difference in height of the fluidised layers) between the recovery chamber and the combustion chamber and in the case where the mass flow wet is more than 1 Gmf the height of the moving layer becomes slightly greater or approximately equal to the height of the second layer. A deflected flow with sufficient amount of fluidization medium produced by the inclined wall will contribute to circulation of the fluidization medium.

The relationship between the height of the fluidized bed and the amount of recirculating fluid medium (that of bent current) must now be explained in more detail.

In the case where the surface of the vortex layer 25 is lower than the upper end of the inclined wall, the upward flow along the inclined wall will have its direction determined by the wall and it, together with the accompanying fluidizing medium, will bend from this wall.

The blown air stream thereby becomes a different state than in the fluidized bed, and it will be released from the fluidizing medium with which the fluidized bed is filled, and the airflow suddenly gets a larger flow area, which is why it spreads and its velocity is reduced to a few very high temperatures. . second, with the airflow being weakened in the upward direction. Therefore, the kinetic energy of the fluidizing medium accompanying the blown air flow will decrease due to gravity and friction with the exhaust gas since the particles in the fluidizing medium are too large (about 1 mm) to be supported by the air flow.

In the case where the surface of the fluidized bed is higher than the upper end of the oblique wall, a portion of the fluidization medium collected by the oblique walls is guided along these walls in the given direction in the same manner as with a fluidized-bed combustion chamber with circulating current, while another portion thereof, due to a boiling phenomenon of exploding bubbles, sprays upward over the upper end of the oblique walls and descends along the perimeter. As a result, a greater amount of fluidizing medium will be transferred to the back of the partitions, i.e. inside the recycling chamber.

This means that the introduced fluidization medium will gradually move more and more vertically, the higher the surface of the vertebral layer relative to the upper edge of the inclined wall. Thus, the amount of fluidizing medium introduced into the recovery chamber will increase if the surface is slightly above the upper end of the inclined wall.

FIG. 5 shows the relationship between the amount of fluidizing air in the combustion chamber below the inclined wall and the amount of fluidizing medium which is recycled through the recovery chamber.

For example, if the height of the fluidized bed during operation according to state L1 is reduced due to the dispersion of "abraded" fluidizing medium, the amount of recirculating fluidizing medium will suddenly be reduced to e.g. less than 1/10 of the previous men, and no heat energy can be recovered. The most important factor is thus the amount of fluidizing air, and if it is ensured that it is greater than 4 Gmf, preferably more than 6 Gmf, the value of Gj / Gq can be kept above 1, and the necessary and sufficient amount of recirculating fluidizing medium can be obtained even if the height of the fluidized bed changes.

In addition, ensuring that the mass flow of blown air from the air diffuser at the bottom of the recovery chamber is maintained at between 0 and 3 Gmf, preferably between 0 and 2 Gmf, and that the mass flow of fluidization air from the air diffuser plate below the inclined wall is maintained at between 4 and 20 Gmf, preferably between 6 10 and 12 Gmf, ie. by always ensuring that the mass flow is greater in the combustion chamber than in the recovery chamber, one can regulate the amount of fluidizing medium to be returned from the recovery chamber to the combustion chamber.

With regard to the moving layer in the recovery chamber, it has previously been mentioned, for convenience, about static layer when the mass flow is between 0 and 1 Gmf, and about fluidized layer or vertebral layer when the mass flow exceeds 1 Gmf. and it is well known that to form a stable fluid bed a mass flow of at least 2 Gmf is required. On the other hand, in the case of the moving layer according to the invention, which layer always moves downwards, this layer can be satisfactorily formed until the mass flow is increased to approx. 1.5 - 2 Gmf without risk of bubbling in the layer. It is believed that the grains in the fluidization medium gradually move downwardly in a vibrational pattern where the fluidization air forms small air bubbles that move uniformly upwardly in the direction of the upper portion of the moving layer.

Inside the heat energy recovery chamber 59, heat transfer lines 65 are arranged in which a heat-receiving fluid such as steam or water can be circulated so that heat energy can be recovered from the fluidization medium as it moves downwardly into the recovery chamber. The heat conduction coefficient in the heat recovery region varies greatly as shown in FIG.

8 when the amount of diffused air in the recovery chamber varies in the range from 0-2 Gmf.

we shall now look more closely at such characteristics, 5 as the load response forming the moving layer in the recovery chamber.

Pig. Figure 7 shows the general relation between the global heat conduction coefficient and the mass flow for fluidization. Within the value range of 0-1 Gmf for the 10 mass flow, there is little increase in the heat conduction coefficient, which then grows suddenly when the mass flow exceeds 1 Gmf. In DOE report 6021 (2), 655-633 (1985), "Wing Panel Type" was indicated as a method for disconnecting an eddy layer boiler utilizing the above phenomenon, and heat conduction coefficient as a function of the variation in fluid mass flow is indicated as insensitive (static bed ) or overly sensitive (fluidized bed).

It should also be noted here that, while reviewing some foreign patent disclosures, several instances have been found where there may appear to be some resemblance to the present technique in that the combustion chamber is separate from the heat energy recovery chamber. However, all of the partitions mentioned therein are constructed as vertical walls, and the fluidizing medium in the recovery chamber is capable of switching from static layer to fluidized layer, being a static layer when the recovered heat energy is small and a fluidized layer wherein the medium blows down from and up after, 30 when the recovered heat energy is large. This is because it is more difficult to provide a deflection of a current with a vertical wall than with a sloped wall. Therefore, in the case of a vertical partition, it cannot be avoided that the fluidizing medium, both in the combustion chamber and in the recovery chamber, is in the fluidized state (in the same way as water), so that the fluidizing medium is caused to flows between the two chambers.

FIG. Figure 8 shows the relationship between the global heat conduction coefficient and the fluid mass flow. As can be seen from FIG. 8, the coefficient varies almost linearly, so that the recovered amount of heat energy and the temperature of the primary combustion chamber can be optionally controlled. Furthermore, such control can be easily performed simply by regulating the amount of diffused air in the recovery chamber.

It should be noted that the extent of wear on the heat transfer lines in the fluidized bed is proportional to the third power of the fluid mass flow, cf. FIG. 9. Therefore, the problem of wear of the heat transfer wires can be solved by making sure that the amount of diffused air blown into the moving layer in the recovery chamber is set to be between 0 and 3 Gmf, preferably at between 0 and 2 Gmf.

In order to regulate the amount of recovered heat energy, as explained above, the amount of recirculating fluidizing medium is regulated at the same time as the heat conduction coefficient is adjusted. If the amount of fluidization gas in the air chambers 54 and 56 of the primary combustion chamber is kept constant and the amount of air blown into the recovery chamber is increased, the amount of recirculating fluid medium and the heat conduction coefficient are simultaneously increased to greatly increase the amount of recovered heat energy. because of the combined effect of these two factors. As to the temperature of the fluidized fluid in the fluidized bed, this corresponds to the effect of preventing the temperature of the fluidizing fluid from being raised above the predetermined temperature.

There are various possibilities for introducing scattering gas into the recovery chamber 59, but generally the means for this will be placed along the back of the inclined wall, ie. along the side facing the recovery chamber so that there is effective utilization of the recovery chamber.

With regard to the air diffuser, the access ports for introducing diffusion air are made smaller the closer up to the tip of the air diffuser they are (the thickness of the layer also becomes smaller upwards), thus avoiding the supply of larger quantities of air at said upper end.

Preferably, the respective sizes of the ports are selected such that with the delivered airflow of 2 Gmf there is approximately uniform air delivery over the entire length of the air diffuser 62. When this condition is met, it is possible to obtain maximum heat energy recovery from all heat conducting surfaces in the air. the recovery chamber and the extent of wear on these heat conduit surfaces can be kept at low values over all these surfaces.

Referring now to FIG. 4. at 66, a fuel inlet is shown in the upper part of chamber 51 20 and at 67 is shown a steam chamber having a not shown connection with heat transfer lines 65 in the recovery chambers 59. At 69, outlets for non-combustible materials are shown at the opposite edges of air diffuser plate 52 at the bottom of chamber 51 and at 25 70 a conveyor with two opposing screws 71 is shown.

It should also be noted that the inlet for fuel need not be located in the upper part of the boiler, since it can also be placed adjacent to the boiler, e.g. as a coal spreader 66 '.

The combustible materials F introduced through the inlet 66 or 66 'circulate and incinerate in the fluidization medium which is circulated under the influence of the circulation flow caused by the fluidizing air. At this point, the fluidization medium in the upper central portion of the air chamber 55 is not accompanied by a violent movement up and down, forming a weakly fluidized downward layer. This layer has a narrow width at the top and the trailing edges of the layer extend in mutually opposite directions until they reach above the chambers 54 and 56 at the 5 opposite edge regions, where they are influenced by the fluidizing air which is blown in from the two associated air chambers with a larger mass flow. . As a result, a portion of each trailing edge will shift, which is why the layer above the air chamber 55 flows downward due to the gravitational 10 force. Above this layer, fluidization medium stacks up with supplementation from the fluidized bed, this is explained in more detail later, and the fluidization medium above air chamber 55 forms a gradual and continuous downward layer as the above process continues. The fluidizing medium above the air chambers 54 and 56 is blown upwardly and deflected and swirled by the oblique walls 58 towards the center line of the combustion chamber 51, and it again drops down over the central portion of the moving layer, thus circulating while a portion of the fluidizing medium is transferred to the recovery chambers 59 behind the inclined walls. In the case where the fluidizing medium flows slowly downwardly in the recovery chamber 59, the angle of inclination of the fluidizing medium will form in the upper portion of the recovery chamber and the excess fluidizing medium will fall from the upper portion of the oblique wall to the primary combustion chamber.

With the gas introduced by the spreader 62, the fluidizing medium introduced into the recovery chamber 59 will gradually move downward and return to the combustion chamber through the port 63 after heat transfer to the conduits.

The mass flow for blowing air with the spreader 62 into the recovery chamber 59 is preferably selected in the value range from 0-3 Gmf, preferably from 0-2 Gmf.

The reason for this, cf. FIG. 8, the heat conduction coefficient varies from the minimum to the maximum below the value of 2 Gmf and that, as can be seen from FIG. 9, can control the extent of wear within a narrow range.

The heat energy recovery chamber is also located outside the highly corrosive zone of the combustion chamber where there is a reducing atmosphere, therefore the heat transfer lines 65 are less subject to corrosion than in the conventional constructions and the extent of wear on these lines 65 10 is greatly reduced because there is low fluidization in this area. For a mass flow of fluidizing air of between 0 and 2 Gmf, the air flow velocity is quite small, for example between 0 and 0.4 m / s (surface velocity) at 800 ° C and in practice it depends on the temperature and only the size of the fluidizing medium.

In the case where the combustible materials are mixed with non-combustible particles of particle size greater than just the size of the fluidizing medium, the conveyor 70 at the bottom of the combustion chamber 20 will discharge the combustion waste along with a portion of the fluidization medium.

With regard to the heat transfer in the recovery chamber 59, it should be noted that, in addition to that which occurs through direct contact between the fluidizing medium and the pipelines 65, there is also one which utilizes the upward gas moving upward in an irregular vibration pattern as it progresses. as the fluidization medium moves. In that case, in contrast to the usual heat transfer by contact between gas and solids, there is essentially no boundary layer between the solids which can prevent heat conduction and the fluid medium is subjected to good stirring, so that the heat conduit in the fluidization medium. the grains of the diet may be negligible, a fact which cannot be ignored, in the case where the medium is stationary.

Therefore, a particularly good heat conduction characteristic can be obtained. This makes it possible in the recovery chamber in accordance with the invention to achieve a high heat conduction coefficient of almost 10 times the coefficient obtainable in a conventional gas boiler.

5 As explained above, the heat transfer between the fluidizing medium and the heat-conducting surfaces depends greatly on the extent of fluidization and the amount of recirculating fluidizing medium can be controlled by controlling the amount of gas introduced from the spreader 62. the recovery chamber 59, with its moving layer, separate from the primary combustion chamber in the plant, it is possible to build a compact heat recovery apparatus with good down-regulation ability and where the fluidized layer can be easily controlled.

In a boiler using slow-burning fuel, e.g. coal or coke, in most cases it is possible to quickly change the rate of evaporation, except when it varies only according to the rate of combustion. In a bubble type boiler, the situation is even worse than in the above boiler because the heat energy recovery is carried out on the basis of the temperature of the vortex.

However, in the boiler according to the invention, the amount of heat conduction can be - at one instant - varied from fractions to several times by changing the amount of air blown into the heat recovery chamber. The variation in heat energy introduced into the fluidized bed, based on the variation in the amount of fuel supplied, therefore depends on the rate of combustion and causes there to be a time delay. However, the amount of heat energy extracted from the recovery chamber in the construction of the invention can be rapidly varied by changing the amount of air blown into the recovery chamber and the difference in response between heat input and recovered heat energy can be taken up as a temporary end. increase in the temperature of the fluidizing medium due to the ability of the fluidizing medium forming the fluidized bed to absorb heat. As a result, the heat energy can be utilized without loss and a good response characteristic can be obtained for controlling the amount of evaporation, which cannot be achieved in a conventional boiler, e.g. for example, burning coal.

It should also be noted here that the outlets 69 for non-combustible materials, as shown in the drawing, 10 are preferably located near the openings 63 at the opposite edges of the air diffuser plate in chamber 51, but the location is not limited to this particular design.

In FIG. 4, the air diffuser plate 52 is shown as a roof. However, if the amount of fluidizing air introduced from the air chambers 54 and 56 is chosen to be greater than 4 Gmf, the circulating current generated in the primary combustion chamber due to the effect of the inclined walls, and therefore also the air diffuser plate 52, may be brought. to be horizontal in the case of combustion materials such as coal with few non-combustible materials.

In this case, the exit openings for non-combustible materials may also be omitted.

It is apparent from the foregoing that with the well-layered boiler according to the invention a much greater heat recovery can be achieved. The method of controlling the boiler according to the invention will now be explained in more detail.

The amount of heat energy extracted from the recovery chamber is controlled, depending on the user's need to utilize this energy, by regulating the amount of gas introduced from the spreader into the recycling chamber according to the invention. The control of the temperature in the primary combustion chamber is effected by controlling the amount of fuel supplied, based on the temperature of the combustion chamber or on the vapor pressure and in the boiler according to the invention, the heat conduction coefficient can be adjusted optionally and the variation in the amount of recovered heat energy is taken up as a variation in the heat content of the fluidization medium, and therefore the boiler can be adjusted immediately to meet the needs of the user, and can operate in a stable state.

The explanation is given with reference to FIG. 4th

If the temperature of steam taken out via the pipelines 10 65, e.g. is not sufficient, a regulator 92 provides for an air regulating valve 93, depending on the temperature, which is measured by a sensor 91 in a steam exit line 90 so as to supply more air, thereby increasing the amount of recovered heat energy 15 and the steam temperature. increases to the value the user wants.

The temperature of the vortex combustion chamber is controlled within a given range of values by controlling the amount of fuel supplied to the chamber and / or by regulating the amount of air supplied to the air chambers 54, 55 and 56 based on the temperature of the vortex measured by a sensor 94 .

There is another method in which the amount of fuel supplied to the combustion chamber is controlled by a pressure signal, for example, in the case where the required amount of steam varies due to load variations on the consumer side since the vapor pressure is the most rapidly changing factor in response to a change in need.

FIG. Figures 10 and 11 show response characteristics where the amount of steam varies stepwise by 30% from 70% to 100%.

FIG. 10 shows test results obtained when the airflow from the spreader in the recovery chamber is kept constant while the vapor flow rate is varied incrementally by + 30%, and FIG. 11 shows test results obtained, when the amount of diffused air is regulated depending on the variation of + 30% in the vapor flow rate. Comparing these two figures, one can see that the temperature of the vortex and vapor flow rate in a short time 5 is reduced to given values, and that the range of variation is also narrow in the case (Fig. 11) where the amount of diffused air is controlled in according to the invention in response to the variation in the vapor flow rate, compared to the results of the conventional method illustrated in FIG. 10th

The range for variation of the temperature in the vertebral layer was approx. ± 12 ° C while less than approx. ± 0.3kg / cm2 (0.029 MPa) in the case where the control was carried out as shown in FIG. 11th

15 Pig. Figure 12 shows the response characteristic when the vapor flow rate is varied by a step of -60% and where the amount of air delivered in the recovery chamber according to the invention is controlled in dependence on this variation. In this case, too, it turns out that the temperature in the fluidized bed remains almost constant and there is a small range of variation of the vapor pressure.

Another embodiment of the invention is explained with reference to FIG. 13, wherein the embodiment corresponds to the application of the invention to a plant of the embodiment shown in FIG. 1 in which there is a single circulating vertebral layer and where, in terms of meaning and function, the same reference numerals as in FIG. Third

FIG. 14 shows an embodiment for use in the 30 case where a large boiler is needed. The FIG. 14 is constructed by combining two internal circulation fluidized boilers as shown in FIG. 4th

As shown in FIG. 4 and 14, operation 35 takes place without difficulty in supplying fuel through the inlet at the top of the chamber. In the case where solid fuel is used, such as coal with pieces of coal up to a few centimeters, it is appropriate to introduce this fuel at a somewhat lower height in the combustion chamber, rather than from the top, but above the surface of the vortex layer, using an appropriate equipment with e.g. a spreader which, with rotating blades, ensures the spread of the fuel.

If the plant is used only for solid fuel combustion, such as coal, a diffuser of the above type can be satisfied, without the need for inlet at the top.

Combustible materials with larger bodies from the top and solid fuel can also be introduced with the spreader in the manner described above, so that they both burn in the mix.

Swirl boilers of the type with internal circulation of the type mentioned above are preferably medium or large boilers. For small boilers it is desirable to make them more compact, and fig. 15 shows such an embodiment. In the embodiment shown in FIG. 15, the heat transfer lines 65, which are inserted into the vortex layer of FIG. 4 are oriented in a nearly vertical direction and extend to an exhaust gas heat transfer portion above the recovery chamber such that the group of heat transfer lines also serves to connect a water chamber 91 at the top with a water chamber 92 at the bottom.

By setting up the substantially vertical vaporization channels in a large number in a free zone in the upper part of the combustion chamber and around the heat energy recovery chamber, it is possible to use them as means for reinforcing the boiler construction and alleviating the need for auxiliary equipment, eg. forced circulation pump and associated piping since the fluid in these heat-transferring pipelines and in the invertebrate ducts is automatically circulated.

29 DK 166694 B1

Further, a fluidized bed boiler and an exhaust gas boiler can be combined as a composite unit so that it is economically possible to create a small fluidized bed boiler of the internal circulation type.

5 The construction and function of the invention are further described hereinafter. The exhaust gas produced by combustion in the primary combustion chamber is passed upwardly through the upper part of the chamber and within the group of heat transfer lines arranged along the circumference. The gas then forms a downward flow in a direction substantially perpendicular to the heat transfer lines while heat exchange is taking place. Part of the unburned ash, which gravitates down, is collected on collector plates 93, and caused to fall towards the vortex layer in the recovery chamber, in which the ash is further incinerated due to its prolonged stay in the vortex, improving combustion efficiency.

20 This situation is particularly appropriate when coal is incinerated, since the unburned carbon of the coal requires longer combustion. In other cases where fuel other than coal is used and where unburned ash is not dispersed quite widely, no recirculation of unburned ash is needed.

Regarding the inlet of fuel, if such an inlet is present, for example, in such a construction where fuel is supplied from the top, it is appropriate to inject the secondary combustion air in the direction towards the fluidized combustion chamber. In such an arrangement, the secondary air will form a blanket which prevents the fine fuel particles, such as coal powder, from being spread out with the exhaust gas from the combustion, while at the top of the free zone at the top there is an effective stirring and mixing which can contribute to achieving

Claims (14)

30 DK 166694 B1 extensible contact between oxygen in the secondary air and unburned ash in the exhaust gas, thereby improving combustion efficiency while reducing the amount of NOx and CO, etc. A method for controlling a fluidized bed boiler comprising a combustion chamber (51), wherein there is a primary fluidized bed of fluidizing medium and a spreading plate (52), a heat energy recovery chamber (59) containing a heat recovery layer of fluidized medium and a gas or air diffuser (62), and wherein an inclined partition (58) separates the primary fluidized layer from the heat recovery layer and wherein the primary fluidized layer and the heat recovery layer communicate with each other above and below, and one located in the heat recovery layer heat exchanger (65) for a heat absorbing fluid, characterized in that a fluidizing gas of higher mass flow is introduced from the spreading plate (52) to a region 35 below the inclined partition (58) than to a region on the opposite side of the partition so as to form a 31 DK 166694 B1 upwardly fluidized layer along the partition wall and a downwardly fluidized layer on the opposite side of the partition the said two layers forming a circulating fluidized layer, controlling the mass flow of fluidizing gas from the spreading plate (52) to said region of the partition so that a portion of the fluidizing medium in the circulating fluidized layer flows upwardly and advances. and 10. controlling the mass flow of gas from the air diffuser (62) to the heat recovery layer, thereby controlling the total heat transfer coefficient and thus the amount of heat recovered by the fluid in the heat exchanger (65). A method according to claim 1, characterized in that the supply of gas from the air diffuser (62) at the bottom of the heat energy recovery chamber (59) is carried out with a fluidization mass flow (Gmf) in the value range 0-3 Gmf, preferably in the value range 20-2-2 Gmf. and that the supply of fluidizing gas from the spreading plate (52) below said inclined partition (58) takes place with a fluidization mass flow 1 in the value range 4-20 Gmf, preferably in the value range 6-12 Gmf. Method according to claim 1, characterized in that the amount of fuel is controlled to the combustion chamber (51). Method according to claim 3, characterized in that the temperature of the primary fluidized layer is controlled by controlling the amount of fuel supplied to this layer as a function of this temperature or the vapor pressure. 5. A method according to claim 3, characterized in that the temperature of the primary fluidized layer is controlled within a given range of values by controlling the amount of fuel supplied to said layer and / or by controlling the amount of gas supplied to the spreading plate. 32 DK 166694 B1 FIG. 16 is a sectional view in the horizontal plane along section line A-A of FIG. 15. It shows an example of a circular chain. In the case of a narrow, compact boiler there is no special need to build the boiler in a circular shape as shown in fig. 16, but it is easier 10 to build arrangements of heat transfer wires when using this circular shape. It should also be noted that, with respect to those in FIG. 4, 13 and 14, it is convenient for the structure to use a rectangular configuration. 6. A method according to claim 5, characterized in that the temperature of the primary fluidized layer is measured by means of a thermocouple and that the control is dependent on the measured value of the thermocouple. 7, A method according to claim 3, characterized by controlling the amount of fuel to the primary fluidized layer in response to a pressure indicating signal. A fluidized bed kettle for use in the method of the preceding claims, and of the type comprising a combustion chamber (51) having a primary fluidized bed and with a spreading plate (52) for supplying the fluidized bed of varying amounts Fluidizing gas, a heat energy recovery chamber (59) comprising a heat recovery layer and a gas or air diffuser (62) for supplying the heat recovery layer with gas, an inclined partition (58) separating the primary fluidized layer from the heat recovery layer in such a way that the primary fluidized layer and the heat recovery layer communicate with each other above and below, and a heat exchanger (65) located in the heat recovery layer for a heat absorbing fluid, characterized in that the air diffuser (52) is located in the lower part of the the heat energy recovery chamber (59), the heat energy recovery chamber (59) having in the vicinity of its lower part an access port (63) for the material from the heat source the recovery layer such that this material is able to flow down this gate from the heat energy recovery chamber to the combustion chamber, and 35. that part of the spreading plate (52) is located under said inclined partition (58) and is adapted to DK 336694 B1 33 cause a fluid flow gas having a higher mass flow rate than the mass flow produced by other parts of the spreading plate (52) at the partition. Boiler according to claim 8, characterized in that the spreading plate (52) is located at the bottom of the combustion chamber. Boiler according to claim 8, characterized in that the heat energy recovery chamber (59) is provided between said inclined partition (58) and a side wall 10 of the combustion chamber or between the rear sides of two inclined partitions. Boiler according to claim 8, characterized in that the air diffuser (62) in the lower part of the heat energy recovery chamber (59) is located near the rear of said inclined partition (58). Boiler according to claim 8, characterized in that the inclination of the inclined partition (58) relative to the 0 0 horizontal is between 10 and 60, preferably 0 0 between 25 and 45. Boiler according to claim 8, characterized in that the inclined partition (58) is designed such that its length projected on the horizontal is 1/6 - 1/2, preferably 1/4 - 1/2 of the horizontal extent. of the bottom of the combustion chamber. Boiler according to claim 8, characterized in that the gas or air diffuser (62) is arranged so that the supply of gas or air at the bottom of the heat energy recovery chamber (59) is effected with a fluid mass flow (Gmf) in the range 0-3 Gmf, preferably in the value range 0-2 Gmf, and the spreading plate (52) below said inclined partition (58) is arranged so that the supply of fluidizing gas takes place with a fluidization mass flow in the value range 4-20 Gmf, preferably in the value range 6-12 Gmf.