WO1988005887A1 - Fluidized bed combustion plant with recycling of solids - Google Patents

Abstract

Fluidized bed combustion plants with recycling of solids have a combustion chamber (1), at least one solid matter separator (7, 13) arranged downstream of the combustion chamber, connected in the flue gas discharge line, a flue gas chimney flue (3) arranged downstream of the solid matter separator and at least two terminal heating surfaces. In such plants, the flue gas chimney flue is usually arranged next to the combustion chamber, with the result that the required erecting space is unnecessarily large, without the known compactness of other combustion plants. The new fluidized bed combustion plant should require less space and be more compact. At least one section (2) of the flue gas chimney flue (3) forms a single piece with at least one terminal heating surface (5, 11, 12) above the combustion chamber. The invention mainly concerns heat-generating fluidized bed combustion plants.

Description

 Description

Fluidized bed combustion system with solids recirculation

The invention relates to a fluidized bed combustion system with solids recirculation, with a combustion chamber, at least one solids separator connected downstream of the combustion chamber on the flue gas side, one flue gas duct downstream of the solids separator and at least two secondary heating surfaces in the flue gas duct.

From the message No. 156 of the Deutsche Babcock Werke AG "The different methods of fluidized bed combustion", (1984), pages 1-7, such furnaces with external cyclones as solids separators are known from Figs. 7 and 8, in which the cyclones have a falling flue gas flue is connected downstream, in which a large number of Nachschalthei surfaces are arranged. The solid-laden flue gas is removed from the upper end of the combustion chamber, fed to the cyclone and leaves it with two deflections by 90 ° and enters the falling flue gas draft.

A fluidized bed combustion system is known from WO 83/03294, in which a labyrinth separator is arranged at the upper end of the combustion chamber in such a way that the separated solids fall into a separate storage room and the flue gas enters a falling flue gas flue. With the application P 36 40 377 dated November 26, 1986, the applicant of the present invention proposed an arrangement in which the labyrinth separator is arranged directly in the upper region of the combustion chamber, and this leads the separated solids onto at least one wall surface on which the solids are covered or not covered - drain down.

In all known fluidized bed combustion systems, the installation space occupied by the combustion chamber in the system is insufficiently used and the compactness known from other combustion systems is therefore not achieved.

It is therefore the object of the present invention to provide a fluidized bed combustion system of the type mentioned in the preamble of claim 1, which leads to a much more compact structure of the system.

This object is achieved in that at least a portion of the flue gas flue with at least one secondary heating surface, preferably superheater, is arranged above the combustion chamber to form a structural unit with the latter.

With this arrangement, not only is a compact structural unit achieved, but also the construction of this structural unit is simplified, since the piping of the combustion chamber can pass into the piping of the partial section of the flue gas flue, as in a tower boiler.

If the solids separation is to take place in a manner known per se in an external cyclone, it is expedient that a partition is arranged between the partial section of the flue gas flue and the combustion chamber, below which the flue gas laden with solids can be removed from the combustion chamber and above which the flue gas is at least an outside cyclone cleaned flue gas can be introduced into the section. The partition is preferably arranged at an incline in order to be able to remove the flying dust which is still settling out of the flue gas and which is not also separated in the solids separator.

When using an internal labyrinth separator according to patent application P 36 40 377, it is expedient that it extends between the combustion chamber and the section of the flue gas flue.

A structure comparable to the tower boilers of other types of firing can be achieved if a large number or all of the secondary heating surfaces are arranged in the flue gas duct above the firing chamber.

However, it is also possible for the partial section above the combustion chamber to be followed by a falling partial section in which further secondary heating surfaces are arranged.

The invention will now be explained in more detail with reference to the accompanying figures. Show it

1 shows a combustion system with an external one

Solids separator and a flue gas flue, which also has a falling section,

2 shows an embodiment of the furnace, in which all secondary heating surfaces are arranged in a section of the flue gas flue, which forms a structural unit with the furnace,

3 shows an embodiment comparable to FIG. 1, but with an internal labyrinth separator and

4 shows an embodiment comparable to FIG. 2 with an internal labyrinth separator. In the fluidized bed combustion system according to FIG. 1, a combustion chamber (1) and a first section (2) of a flue gas flue (3) connected downstream of the combustion chamber are combined to form an assembly. The pipe (4) of the combustion chamber

(1) and section (2) is switched on as an evaporator in the water-steam circuit of the combustion system. The dashed circles indicate, however, that the upper part of the wall pipe can also be switched as an overheat.

In the subsection (2) of the flue gas flue (3), a secondary heating surface (5), preferably connected as a superheater heating surface, is arranged.

The combustion chamber (1) is separated from the section (2) by an inclined partition. Flue gas laden with solids is drawn off below the partition (6) and fed to a solids separator, preferably a cyclone (7). The separated solid is fed into the combustion chamber above the fluidized bed (8). The cyclone (7) shown in FIG. 1 is tubular; however, it is also possible to use a brick cyclone.

The flue gas cleaned from the solid enters the section (2) above the partition (6) and is deflected towards the secondary heating surface (5). In order to be able to remove the airborne dust which is separated during the deflection and at the secondary heating surface, the floor is inclined to one side and the solid is drawn off via appropriate devices, as is shown schematically by the arrow (9). From the subsection

(2) of the flue gas flue (3), the flue gas enters a falling section (10) of the flue gas flue, in which further secondary heating surfaces (11) and (12) are arranged. The post-heating surface (11) can be connected, for example, as a feed water preheater and the post-heating surface (12) as an air preheater. The present The invention is not limited to the division and assignment of the secondary heating surfaces described above.

In the embodiment shown in FIG. 2, in which a plurality, preferably all, of the secondary heating surfaces are arranged in the section (2) of the flue gas flue, a tower-like structure of the combustion system is realized. For the sake of simplicity, the upper secondary heating surface is provided with the double reference symbol (11, 12).

In the embodiment shown in FIG. 3, solids are separated on a labyrith separator (13) that separates the combustion chamber (1) from the flue gas section (2). The separated solids are discharged to the left in FIG. 3 from the individual gutters (14) and in the shafts (15) derived down into the firebox. With regard to the description and the disclosure, reference is expressly made here to the disclosure of DE-OS 36 40 377 and this is also made the subject of the disclosure of the present application.

From the description of FIGS. 1 to 4 it can be seen that by arranging at least one secondary scarf in a flue gas duct section which represents a structural extension of the combustion chamber, an extremely compact construction of the combustion system is achieved, the combustion chamber pipe and the pipe section of the section also being a functional unit form, such as form the usual screw winding of a BENSON boiler.

Fuel and air supply are not shown in the figures for the sake of simplicity. For this, e.g. reference is made to the prior art mentioned in the introduction to the description.

(2 sheets of drawings)

Claims

Claims 1.Fluid bed combustion with solids recirculation, with a combustion chamber, at least one solids separator downstream of the combustion chamber on the flue gas side, one flue gas duct downstream of the solids separator and at least two secondary heating surfaces in the flue gas duct, characterized in that at least one section (2) of the flue gas train (3) with at least one secondary heating surface (5 ; 11; 12), preferably superheater, is arranged above the combustion chamber (1) to form a structural unit with the latter. 2. Fluidized bed combustion system according to claim 1, characterized in that between the section (2) of the flue gas train (3) and the combustion chamber (1) a partition (6) is arranged below which the solid-laden flue gas from the combustion chamber (1) is removable and above which the Flue gas cleaned in at least one external cyclone (7) can be introduced into the subsection (2). 3. Fluidized bed combustion system according to claim 2, d a d u r c h g e k e n n z e i c h n e t that the partition (6) is inclined. Fluidized bed combustion system according to claim 1, characterized in that an internal labyrinth separator (13) extends between the combustion chamber (1) and the section (2) of the flue gas flue (3). 5. Fluidized bed combustion system according to one of claims 1 to 4, d a d u r c h g e k e n z e i c h n e t that a plurality or all Nachschaltheizflächen (5, 11, 12) in the flue gas flue (3) above the combustion chamber (1) are arranged. 6. Fluidized bed combustion system according to one of claims 1 to 4, d a d u r c h g e k e n z e i c h n e t that the subsection (2) above the combustion chamber (1) is followed by a falling subsection (10) in which further Nachschalthei surfaces (11, 12) are arranged. 7. Fluidized bed combustion system according to one of claims 1 to 4, d a d u r c h g e k e n n e e c h n e t that the tubing of the combustion chamber (1) and the piping of the section located above the combustion chamber (2) form a functional unit.