CS281591A3 - Fluidized bed furnace with a stationary fluidized bed - Google Patents

Description

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Fluid furnace with stationary fluid

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluidized bed furnace with a stationary fluidized bed for hot water or steam generators and to a process for producing hot water or steam using a stationary fluidized bed furnace according to the preamble of claim 1 and 2.

BACKGROUND OF THE INVENTION [0003] In known fluid heaters, e.g. from Technical Communications1984, pages 296-501, combustion air, which serves as a fluidizing gas, penetrates a fluidized bed with a comparatively low flow rate of 1 to 2.0 m.sup.2. Because of the good fluid-bed transfer properties, the recessed heating surfaces transfer a large proportion of the combustion heat released in the boiler to the water or steam circulation, this being the case and the inflated arrangement of the heating surfaces that is possible on the basis of the fluidized bed. The low load of the flue gas results in a compact boiler design, while the embedded heating surfaces offer both steam generation and con- struction advantages, but also cause the disadvantage of being subject to mechanical attack due to corrosion as they capture constantly In another fluidized bed furnace with a stationary fluidized bed and increased solids circulation, see, e.g., VGB Kraftwerkstechnik69, 1989, pages> 84 to &gt; 91, no recessed heating surfaces are available in the fluidized bed. Above the free space above the fluidized bed, convection heating surfaces are formed to cool the flue gas and the solids co-located therein to about 515 ° C. The solid at this temperature separated in the cyclone is returned to the fluidized bed to cool it. This system operates with a fluid velocity of about 4.5 m.s. ^. and a graded air supply, so low NO, ie nitrogen oxides, emissions are possible without secondary measures. In addition, all partial costs can simply be stopped. On the other hand, the construction height of this boiler and the built-up space is quite large. Finally, in the case of the combustion of brown coal containing salts in a stationary fluid layer without recessed heating surfaces, German Patent No. 57 12 801 is known to influence the temperature of the bed and the temperature-free space by returning the cold flue gas to the fluidized bed and above the fluidized bed. A multi-stroke boiler is used. The object of the invention is to provide a fluidized bed furnace of this kind in a way that is suitable for small boilers of less than 50 W, with a good proportion of partial costs and low pollutant emissions.

SUMMARY OF THE INVENTION

This object is achieved according to the invention in a fluidized-bed furnace of the type indicated by the characteristic features of claim 1a in the process of this type by the characteristics of patent-pending operation 2.

The boiler according to the invention, as well as the boiler with recessed heating surfaces in the fluidized bed, is characterized by a compact design which allows for the widest possible pre-treatment in the workshop without high installation costs. In this case, the boiler can be self-supporting, so that the steel supporting structure for the boiler can be dispensed with. By releasing the recessed heating surfaces in the fluidized bed and by recirculating the cold flue gas as a heat carrier, there is a good control of the partial load and avoid erosion problems. and ash recirculation, which is separated in a cold cyclone, results in improved emission and combustion values. List of drawings in the drawing

One embodiment of the invention is shown in the drawing below. The drawing schematically shows the development of steam or hot water. An embodiment of the invention

The boiler 1 used to produce steam or hot water is formed as a single-stroke boiler whose circumferential walls consist of gaps which are welded to each other gas-tight over the webs. An air box 2 is formed at the bottom of the boiler 1, which is closed by a nozzle bottom, on which a stationary fluidized bed 4 is based. There is a free space above the fluidized bed 4. There is a separating wall 6 arranged above this free space. the cross-sections 8 and whose lower edge is closely connected to one of the side walls. In this way, the upstream flow section 8 and downward flow section is formed which connects the flue gas duct 10. This flue gas duct 10 passes through the cyclone 11, the filter 12, and the exhaust fan 10 to a chimney (not shown).

Section 3 has j? The convection heating surfaces 14, 15 are supplied to the convection heating surface 14, then flows through the tubes of the peripheral walls of the boiler 1 and then into the convection heating surface 15 in the upward flowing section 8. In the event that steam is produced, the latter convection heating surface 18 serves as a superheater.

The fuel used is lump lignite with a particle size of less than 25 or lump coal with a grain size of less than 10 mm. The coal is deposited in a coal depot 16. Under the coal storage 16 there is provided a discharge organ 17, e.g. a tub chain conveyor, which is connected to the binding organ 18, e.g. This charging body 18 is arranged in the front wall of the boiler 1 at a height of free space and introduces the fuel of the dofluid layer 4. The lime used for desulphurisation of the flue gas is stored in the lime warehouse 19. The discharge end of the storage vessel 19 is provided with a turnstile closure 20 and is connected to the discharge member 17 of the coal storage 16.

The discharging site of the solids of cyclone 11 and filter 12 is a cross conveyor 21, a vertical conveyor 22, and a further transverse conveyor 25 connected to the ash reservoir 24. The outlet of the ash hopper 24 is provided with a turnstile dispenser 25 and is connected by a blowing device 17 to a coal storage 16. The solid material separated from the cold flue gas is thus introduced together with the carbon by lime into the fluidized bed 4.

The nozzle bottom is provided with a drain pipe 26, through which it can remove the ash from the bed from the fluidized bed 4. This bed ash is also fed through the transverse conveyors 21, 25 and the vertical conveyor 22 also into the ash reservoir 24. Excess solid material is discharged from the system through the second outlet 27 of the ash container 24.

A fresh air fan 28 is connected to the air box 29 with the air box 2. From the air duct 29 ' side pipe 30, which is directed to the air nozzles 1 &apos;, is disposed in the side wall of the boiler 1 in the free space 2 above the fluidized bed 4. In the air duct 29 and the secondary duct 30 is one throttle 38 is always arranged. The fresh air fan 28 sucks in the combustion air and does not overheat it as the primary or fluidizing air through the air box 2 into the fluidized bed 4 and as the secondary air of the allowance space 5. a recirculating duct 4 provided with a recirculating blower 3 through the filter 12 to the air box 2? and throttle 32. Through recirculation of conduit 34, cold flue gas is fed as a heat carrier to control the bed temperature in a controlled amount to fluid bed 4. The gaseous medium flowing through the nozzle bottom is adjusted in such a way that the fluid velocity is maximum 3.5 ms ”\ t

Claims (2)

LZA 34- 34 - 6 - 2 * p 'Ό XJ> O O <c · cd y xxc_ - >> m> o CO x | Fluid furnace with a stationary fluidized bed for hot water or steam, which is designed as a boiler with a one-stroke and above the fluidized bed has one upwardly flowing and one fluidized bed. a downwardly flowing section which is separated by a partition wall through the cross-sections and has convection heating surfaces, wherein an air box connected to the air conduit is formed beneath the fluidized bed, and a mechanical charging organ extends into the boiler above the fluidized bed, and The flue gas conduit is connected to the boiler, in which the arranged dust separator, which is provided with an ash recirculation, is characterized in that the fluidized bed (4) is released from the recessed heating surfaces while the flue gas conduit (10) is behind a dust separator (11, 12) directed to the air housing (2) of the recirculation line (54) while out of the vent pipe (29) is fed to the boiler (1) through the fluidized bed (4) by a secondary pipe (50) and the swirl velocity of the fluid bed (4) maximally 5.5 ms -1 is maintained by the air inlet and flue gas inlet (4) and that the ash return conduit (21, 22, 25) is connected to the charging member (18). 2. A process for producing water or steam in a stationary fluidized bed boiler into which lump coal is fed and combusted with the aid of the combustion air blown into the fluidized bed, the resulting and cooled flue gas being stripped of entrained solids and these separate The solids are partly fed to the back, characterized in that one portion of the cooled flue gas is fed back into the fluidized bed without recessed heating surfaces and the fluidized bed has a set speed of 5.5 ms-1 and one part of the combustion air is blown as the secondary air overfluid layer, and that the backward solids are introduced together with the coal.