CZ301745B6 - Method of controlling fluidized bed height of fluidized bed combustion boiler and fluidized bed combustion boiler for making the method - Google Patents

Abstract

The present invention relates to a method of controlling fluidized bed height of fluidized bed combustion boiler with a stationary oxidation fluid layer comprising a layer of an inert material with a height up to 1 meter above the nozzles (2) of the fluidized bed grate and with the inert material granule size up to 3 mm wherein the invented fluidized bed furnace is delimited from sides by an airtight wall and is provided in its lower section with a fluidized bed grate with nozzles (2) connected to a combustion air supplied under a pressure within the range of 300 to 10 000 Pa, as measured at ambient temperature and pressure. The invention is characterized in that the fluidized bed height increases by the supply of the inert material, separated from combustion products inside a turn-over chamber (6) between the second and third boiler droughts (7, 8), into the fluidized bed furnace, and decreases by the withdrawal of the inert material from the fluidized bed outside the fluidized bed furnace. The fluidized bed combustion boiler for making the above-described method has, in the lowest point of the turn-over chamber (6) between the second and third boiler droughts (7, 8), a discharge opening (9) for mineral matter that can be closed by a connection such as turnstile (10) and connected to a mixing chamber (11) connected to a compressed air piping (12) for discharge of the mineral matter outside the boiler. The mixing chamber (11) is provided with a bottom outlet (13) connected to a mineral matter discharge piping (4) with controllable bidirectional drive of the mineral matter, wherein one end of said mineral matter discharge piping (4) enters the combustion chamber (1) while the other end thereof is lead out to a mineral matter dump, outside the boiler.

Description

A method for controlling the height of a fluidized bed boiler by a fluidized bed combustion and a fluidized bed boiler for carrying out the method

Technical field

The invention relates to a method for controlling the fluidized bed height of a fluidized bed boiler with a stationary oxidative fluidized bed having an inert material layer up to 1 m above the fluidized bed nozzles and an inert material granule size of up to 3 mm. is provided at its lower part with a fluid grate with nozzles connected to the combustion air supplied at a pressure of 3000 to 10 000 Pa, measured at normal pressure temperature, and a fluidized bed boiler for carrying out this method, in which the bottom of the reversing chamber is with the second and third draft of the boiler, an ash opening.

BACKGROUND OF THE INVENTION

In fluidized bed boilers with a stationary oxidizing fluidized bed, it is generally necessary to be able to control the height of the fluidized bed. One reason for this is that by varying the height of the fluidized bed, the size of the heat exchange surface changes and the fluidized bed boiler output is controlled. A further reason for this need may be the need to control the height of the fluidized bed when a fuel with a lower calorific value is used instead of a standard fuel, for example a mixture of biomass with sewage treatment plants. Such a fuel has a much lower calorific value and a much higher ash content. The addition of such fuel to an existing boiler entails that the excessive amount of ash, which forms part of the inert component of the fluidized bed, gradually congestes the fluidized bed, and if there is insufficient ash removal, the fluidized bed is gradually inadequately mixed, thereby unevenly distributed. temperature in the fluidized bed, which ultimately leads to the cessation of boiler operation.

The fluid layer may also need to be controlled for another reason. When a low ash fuel such as a biomass blend is used instead of a standard higher ash ash fuel, an insufficient amount of ash is produced during combustion. Since this ash forms part of the inert component of the fluidized bed, the fluidized bed gradually decreases until it reaches such a low level that it ceases to function, and the fluidized bed collapses by overheating, baking or cooling by the fluidized bed, thereby stopping the boiler operation.

The height of the fluidized bed can be varied, for example, by adding or removing inert material to the fluidized bed. For this purpose, a container of inert material is usually connected to the boiler from which the inert material is removed or returned to it.

The problem arises in smaller boilers, such as a 5 MW boiler, where adding a tank means that the boiler will be tens of percent more expensive. This makes a small boiler with an integrated tank of inert material uneconomical and therefore these boilers are not used in practice and other solutions are sought instead.

From the Czech utility model CZ 13483U relating to sulphation processes, more precisely desulphurisation of flue gases, it is clear from Fig. 4 that the material separated from the flue gases after part of the combustion chamber is returned to the ash recycling. However, there is no indication in the text of this utility model that it is possible or expedient to regulate the height of the fluidized bed by the material separated from the flue gas downstream of a portion of the combustion chamber and returning to the ash recycle, and the boiler described in the utility model is likewise unregulated.

- 1 GB 301745 B6

SUMMARY OF THE INVENTION

The above-mentioned drawbacks of the prior art in fluidized bed boilers with a stationary oxidative fluidized bed having an inert material layer up to 1 m above the fluidized bed nozzles and an inert material granule size of up to 3 mm where the fluidized bed is circumscribed by an airtight wall its bottom part by means of a fluid grate with nozzles connected to the combustion air supplied at a pressure of 3000 to 10,000 Pa, measured at normal temperature at pressure, largely eliminates the method of controlling the height of the fluidized bed according to the invention inert material separated from the flue gas in the reversing chamber between the second and third draft of the boiler into the fluidized bed furnace. In a preferred embodiment of the method, the height of the fluidized bed is reduced by removing the inert material from the fluidized bed outside the fluidized bed.

The method of controlling the height of the fluidized bed is preferably implemented by a fluidized bed boiler equipped with a baffle chamber dividing the baffle chamber into second and third thrust, wherein at the lowest point of the bottom of the manhole chamber between the second and third thrust of the boiler According to the invention, the essence of the invention is that the ash-discharge opening is connected to the conveying device for the removal of ash from the fluidized bed boiler or the supply of ash to the boiler's fluidized bed by means of a closed connection.

In a preferred embodiment of the boiler according to the invention, the conveying means for the removal or supply of ash from outside or into the boiler fluidized bed is formed by a mixing chamber connected to a pneumatic ash line outside the boiler, the mixing chamber being provided vin. At the same time, the ash-discharge pipe is connected to the combustion chamber at one end and to the ash dump outside the boiler at the other end.

This controllable bidirectional ash drive is in the preferred embodiment of the invention formed as a worm arranged in the ash removal line and connected to a reversible drive motor. In another preferred embodiment, the controllable bidirectional ash drive is designed as a pneumatic conveyor in the ash removal line.

In a further preferred embodiment of the invention, the closure connection of the ash discharge opening to the mixing chamber is in the form of a turnstile.

Overview of the figure in the drawing

The invention will now be described in more detail with reference to the accompanying drawing, in which an exemplary embodiment of a fluidized bed boiler for carrying out the process according to the invention is shown schematically.

DETAILED DESCRIPTION OF THE INVENTION

The figure shows schematically a fluidized bed boiler. At the bottom of the combustion chamber 1 there is arranged a fluid grate with nozzles 2, under which a screw 3 is arranged, arranged in the ash duct 4 and connected to a reversible drive motor 5. In the bottom of the reversing chamber 6 between the second draft 7 and the third draft 8 of the boiler there is an ash discharge opening 9 which is connected via a turnstile 10 to a mixing chamber 11 connected to a pneumatic duct 12 for ash removal outside the boiler. The mixing chamber JT is connected via its lower outlet 13 to an ash-evacuation duct with controlled bi-directional ash-driving, where the ash-evacuation duct 4 is terminated at one end into the combustion chamber 1 and at the other end to an unrecognized ash dump outside the boiler.

-2EN 301745 Bo

When the fluidized-bed boiler is in equilibrium operation, a fluid level sensor (not shown) monitors the optimum level of the fluidized bed and the ash falling into the mixing chamber 11 from the ash discharge opening 9 in the return chamber 6 is discharged through the pneumatic duct 12. .

If the level exceeds the optimum value, the motor 5 switches on and the screw 3 draws inert material through the ash-removal duct 4 into a non-boiler ash dump (not shown) until the equilibrium state is set with the optimum fluidized bed level.

If the level does not fall below the optimum value, the pneumatic drive for draining ash from the mixing chamber 11 is switched off and the motor 5 is switched on and rotated at reverse speed. The ashes deposited at the bottom of the reversing chamber 6 pass through the discharge opening 9 via the turnstile 10 into the mixing chamber II and through its lower outlet 13 to the auger 3, which transports them to the combustion chamber 1 until the equilibrium state is optimized. height of the fluidized bed.

Industrial applicability

The method and the fluidized bed boiler for carrying out the method can be advantageously used in particular for smaller boilers, such as a 5 MW boiler.

Claims (7)

PATENT CLAIMS 1. A method for controlling the height of a fluidized bed of a fluidized bed boiler with a stationary oxidation 30 with a layer of inert material with a layer of inert material up to 1 m above the fluidized bed nozzles and with an inert material granule size of up to 3 mm, where the fluidized bed is bounded by an airtight wall on its sides and provided with a fluidized bed with nozzles connected to the combustion air under a pressure of 3000 to 10,000 Pa, measured at normal temperature at a pressure, characterized in that the height of the fluidized bed is increased by the introduction of inert material, 35 separated from the flue gas in the reversing chamber between the second and third draft of the boiler, into the fluidized bed furnace. Method for controlling the height of the fluidized bed of a fluidized bed boiler according to claim 1, characterized in that the height of the fluidized bed is reduced by draining the inert material from the fluidized bed. 40 of the fluidized bed outside the fluidized bed. Fluidized bed boiler for carrying out the method according to claim 1 or 2, provided with a baffle chamber (6) with a partition dividing the baffle chamber (6) into second and third thrust (7, 8), in which the bottom of the bed is reversible a chamber (6) between the second and third thrust (7, 8) of the boiler 45 an ash discharge opening (9), characterized in that the ash discharge opening (9) is connected by a closure connection to a ash conveying conveyor (14) outside the fluidized bed boiler or ash feed to the boiler fluidized bed furnace. Fluidized bed boiler according to claim 3, characterized in that it is conveying The apparatus (14) for evacuating or conveying ash outside or into the boiler fluidized bed is formed by a mixing chamber (11) connected to a pneumatic duct (12) for ash removal outside the boiler, the mixing chamber (11) having a bottom outlet (13) connected on the ash removal pipe (4) with controllable bi-directional ash drive where the discharge pipe (4) -3E 301745 B6 The ash ends at one end into the combustion chamber (1) and at the other end at the ash dump outside the boiler. Fluidized bed boiler according to claim 4, characterized in that the controllable bi-directional ash drive is designed as a worm (3), which is arranged in the ash outlet pipe (4) and connected to a reversible drive motor (5). Fluidized bed boiler according to claim 4, characterized in that the controllable bidirectional ash drive is designed as a pneumatic conveyor in the ash outlet pipe (4). A fluidized bed boiler as claimed in any one of claims 4 to 6, characterized in that the closable connection of the ash ash discharge opening (9) to the mixing chamber (11) is designed as a turnstile (10).