Description

The invention relates to so-cai!ed Circulating Fluidized Bed Apparatus (CFBA). which main components are:

- A so-cailed Circulating Fluidized Bed Furnace (Reactor) - CFBF designed as a cornbustor, incineration reactor, boiler, gasifier, steam generator etc. as disclosed - i.a. - in US 8,802,890 B2. In a typical CFBF gas (air) is passed through a permeable grate-like bottom area of the furnace (so-caiied air plenum), which grate (grid) supports a circulating fluidized bed of particulate material, the so-cai!ed incineration charge, mostly including a fuel-!ike material such as coal, sand etc. In typical applications aeration is achieved by corresponding nozzles, feeding air and/or gas into the particulate materia! present with in the furnace space. The aerated particulate materia!/fuei mixture (air plen um) ai!ows to promote the incineration process and effectivity .

The outer walls of the furnace, which define the combustion chamber (reaction chamber) , are usually so-ca!!ed tube walls , comprising welded tubes with or without fins in between , I n operation a heat transferring fluid like water and/or steam is fed through said tubes/pipes of said furnace walls in order to cool the same and to transfer heat therefrom for further purposes.

The CFBF typically has at least one outlet port at its upper end , via which a mixture of gas and solid particles, exhausted from the reactor, may flow into at least one associated separator.

- The separator, for example a cyclone separator, serves to

separate solid particles (the particulate material , including ash) from said gas. A typicai design of such a separator is disclosed in US 4,61 5, 71 5. Again the outer walls of the separator can be designed with hollow spaces to allow water flowing through ,

- While the gas is extracted from the separator and fed into

subsequent installations of the plant, there are means for the transfer of said separated solid particles out of the separator and into at least one heat exchange chamber, often designed as a Fluid ized Bed Heat Exchanger (FBHE) , via a corresponding inlet port of said heat exchange chamber. These means may be d ucts/pipes/channels or the like. As far as reference is made in the following to an FBH E th is refers to a preferred heat exchange chamber, but includes all types of heat exchangers suitable for that purpose, independently of whether constructed as a

superheater etc . - A syphon along the way from the separator to the CFBF and/or heat exchanger to aliow decoupling of pressure (fields) between separator and CFBF,

- The at least one heat exchange chamber allows to use the heat, provided by the particulate material, for generating power, for example to heat up and increase the pressure of a steam transported as a heat transfer medium via tubes or the like, through said heat exchanger and further to turbines or the like,

- Typically the heat exchange chamber is equipped with at least one outlet port, being part of return means, in order to transport at least part of the solid particles out of the heat exchanger and back into the Circulating Fiuidized Bed Furnace CFBF.

US 5,840, 258A discloses a design of such CFBA, wherein the CFBF and the- FBHE have been integrated closely together; in other words: FBHE and CFBF have a common wall (tube wail). In operation, i.e. under temperature load , this design provides the advantage of close (similar) temperatures in both units and thus, minimizes any thermal stresses between both units.

Indeed these temperature expansions and temperature stresses are a major problem in such installations. The thermal expansion of a CFBF of a height of ca, 35 to 50m may range ^' from 0.1 m to 0,3m and may cause serious stresses within the furnace walls, independently of whether the furnace is bottom supported (according to US 5,840,258A) or top-supported (suspended), as shown in US 6, 305, 330B 1 .

It is an object of the invention to provide a compact design for a circulating fiuidized bed apparatus and in particular for its combustor (furnace) in combination with at least one associated unit, in particular a heat exchange unit. The invention is based on the following findings:

A compact design may be realized by bringing associated units of the CFBA as close as possible or even better to fix one unit to another (as known from US 5,840,258) , but any such friction-locked atTangement of adjacent/associated units causes serious structural problems in view of the extreme weights/loads of such units.

A generic heat exchanger of a CFBA has a size of for example 5x5x5m and a corresponding weight of 100.000kg in an empty state (hereinafter referred to as basic load). Additional loads (hereinafter called variable load) by the solid . material transported through said heat exchanger vary strongly and may be in a range of up to 100.000kg or more.

The (outer) furnace wall, to which the heat exchanger may be friction- locked, typically a so-called tube wall, cannot withstand/compensate such high and variable loads unless constructed as a "castle-wall", being unacceptable in view of costs and the thermal conditions of a CFBA. The thermal expansions/constrictions mentioned above cause further structural problems.

In other words: The extreme forces and moments, caused by a heat exchange unit which Is friction-locked (for example welded) to a conventional furnace wall (like a tube wail) cannot be compensated yet in an economically and mechanically acceptable way.

The invention discloses a technical solution for this problem and furthermore a technically relatively simple construction, by further providing at least one structural element, by which the heat exchanger is mechanically linked to the furnace wall, which structural element allows to compensate any such loads, caused by the heat exchanger and/or the material passing therethrough, at least partially. I n its most genera! embodiment the invention relates to a circulating fsuidized bed apparatus, comprising a circulating f!uid izecl bed furnace with an outer furnace wall and at least one heat exchange chamber, which is friction-locked to a section of the outer furnace wall, as weil as a piatform , which extends horizonta lly and at a d istance to an upper ceiling of said heat exchange chamber, wherein the heat exchange chamber is further supported by at least one leverage, which is arranged onto said platform and extends from a first end , pivotaiiy mounted to the outer furnace wall, away from said furnace wal l to a second end , and a fastener, extending downwardly from said second end of said leverage to a part of the heat exchange chamber offset the outer fu rnace wall .

I n other words: The structura l element between furnace wall and heat exchanger (and/or similarly to any other unit which is fixed ly secured to the outer furnace wall and thus follows any expansions/contractions of the furnace wall under temperature load during operation , for example a syphon system) comprises a leverage (a system of cooperating levers/arms), which serves to compensate such tolerances, and a fastener, which is fixed (coupled) to said leverage and thus follows any movements of the leverage, in particu lar movements of the second end of the leverage to which said fastener is hingedly secured . The platform serves to provide a basis for mounting said levers and is mostly structurally independent of the other units of the C FBA.

The leverage allows to provide a system wh ich transmits vertical movements, caused by the furnace wall , for example a vertical downwa rd movement of the furnace wall, and thus a downward

movement of the first end of the leverage (or its first lever respectively) into a downward movement of the second end of the leverage by tilting (turn ing) the correspond ing levers, which are h inged to each other, in different directions by their corresponding bearings. Obviously the system works analogously in the other vertical direction (vice versa).

This transmission may be 1 : 1 , for example in case of levers of identical design and the a rrangement of a pivot bearing (swivel) for each lever in the middle of its axial length. The transmission rate may also be set to another ratio, if requested, for example by providing levers (arms, bars) of different length or displacements of the lever bearings onto said static platform.

Therefore the platform should be constructed as an independent item and in a way to provide a defined and rigid support for the leverage and the fastener respectively.

The structural element "absorbs" all (additional) forces and moments, which have not been absorbed by the furnace wall, to which the heat exchanger is fixedly secured for example by welding.

Insofar the first end of the structural element (leverage) is fixed to the furnace wall at a vertical distance above the heat exchanger, while it is important for the fastener being affixed to the heat exchanger at a horizontal distance to the furnace wall. The fastener may be connected to a vertica lly extending wall of the heat exchanger, for example its outer wall, being the wall opposite to the furnace wall, to which the heat exchanger is mounted.

Further embodiments of the CFBA are characterized by one or more of the following features, wh ich can be realized individually or in arbitrary combinations if not explicitly excluded or technically absurd: .

A favorable construction of the leverage comprises - a first lever, a first end of which is pivotaily mounted to the outer furnace wall, a second end of which is hinged to a second lever and an intermediate section of which is pivotaily mou nted in a pivot bearing , arranged onto said platform .

- a second iever, a first end of which is hinged to the second end of first lever, a second end of which is hinged to the fastener, and an

intermediate section of which is pivot-mounted in a pivot-bearing arranged onto said platform.

The arrangement of Severs (leverage), which are interconnected by hinges, may comprise more than two !evers (bars, arms), for example four or six in a row.

The first end of the leverage, being the end connected to the furnace, may be pivotaily mounted in pivot bearing (swivel) , wh ich is fixed to the outer furnace wall . This pivot bearing follows any movements of the furnace wall. Therefore: in a d ownwa rd movement the corresponding Iever is then tilted by the pivot bearing , arranged onto the platform, and the second end of the first lever moves upwardly.

As a consequence: The first end of the second lever, which is hinged to the second end of the first lever, moves up as well, thus causing the second end of the second Iever to move downwardly, while the second lever as such is tilted by its correspond ing pivot bearing , fitted onto the platform .

Finally: The fastener, fixed to the second end of the second Iever, transmits said downward movement of the fastener to the heat

exchanger, to which the fastener is fastened by its lower end , while keeping the stress-relief (germa n : Zugentlastung) for the heat

exchanger. Accord ing to one embod iment the second end of the leverage comprises a pivot joint (hinge, joint) , coupled to the fastener.

The fastener itself may be a bar, a rod , a strut or a hinge, allowing to compensate the tensile forces as well as compressive forces, caused for example by the heat exchanger and its load and/or any constant hangers.

Another embod iment is characterized by at least one of the pivot bearings of the first and second levers being a floating bearing , wh ich allows movement of the pivot bearing in a horizonta! direction (thus the movement is substantially perpendicu lar to the section of the furnace wall to wh ich the heat exchange chamber is friction-locked). This avoids any stresses in sa id bearing d uring tilting of the corresponding lever. I nsofar all said lever bearings should be floating bearings (a!so called friction bearings or journal beatings) in an optimized embodiment.

The platform can be realized- as one or more bars, as a scaffold ing or the like. The main task of the platform is to provide a defined and rigid structure for the leverage and the bearings, mounted onto the platform .

The platform may be autarc, i .e. part of a structure which is

independent from the CFBA. !t may be a scaffold of corresponding structural integrity.

The lower end of the fastener may be hinged to any part of the heat exchanger, offset the furnace wail , for example to the ceiling of the heat exchange chamber or to a section of the heat exchanger chamber adjacent to said ceiling .

The lower end of the fastener and/or the second end of the leverage should be arranged at an offset to the furnace wa!i being larger tha n 50% , for example > 70% or >30% or >90% of a correspond ing length of the heat exchange cham ber, seen in a d irection perpend icular to the adjacent section of the outer furnace wal i to achieve best results in compensating the extensive loads of the heat exchanger.

One or more suspensions means between the p!atform and the heat exchange chamber define another embodiment, wherein the

suspensions means may be constant !oad hangers (german :

Konstant!ast Hanger) , for example constant ioad springs as disclosed by www. liseqa.de. defining these hangers as "transferring the working · load over the who le travel area while maintaining constancy, i .e.

without any considerable deviation".

These constant hangers allow compensate the basic load , but may also be used to compensate at least part of the varying load , caused e.g . by the solids passing through the heat exchanger, by a corresponding dimensioning . .

The leverage/fastener arrangement primarily serves to compensate the basic load of the heat exchanger and more precisely: the

leverage/fastener combination red uces the transmission of moments, caused by the weig ht of the heat exchanger and its position at the furnace wall, into the furnace wall .

Further suspension means- may be provided , wherein at least one of the following is suspended to a rigid support structure: platform , circulating fluid ized bed furnace. The support structure can be a separate

structure, for example a (rigid) frame, to which the furnace and/or other units of the CFBA are suspended .

The inner wall of the heat exchange chamber can be the same (a common wall) as the section of the furnace wail to which the heat exchanger is mounted , which reduces the costs and increases the thermal efficiency of the CFBA. The heat exchanger further features at least one inlet port and at least one outlet port {the fatter to allow a re-transport of solid particles from said heat exchange chamber into said circulating fluid ized bed furnace), which design arid. placement are not crucial here and may be realized according to known embodiments.

The invention will now be described by way of an example and

reference to the attached

Figure, which displays a schematic side view on the new CFBA.

The CFBA comprises a circulating fluidized bed furnace 10, only part of which is shown, with an inlet port 10i for solid materials (fuel) and a. fluidized bed FB at its lower part, as well; as an outlet port 10o for a corresponding gas/solids mixture at its -upper end. The furnace 10 and its furnace chamber are defined by an outer furnace wall 10r, to which a heat exchange chamber 20 is friction-locked at a lower section 10s of the outer furnace wall 10r. Section 10s of furnace wall 10r and inner wall 20w of heat exchanger 20 are represented by one common wall and made of tubes, through which water flows, with fins extending between said tubes.

The heat exchange chamber 20 features a solids (ash etc) inlet port 20i at its upper end and a solids outlet port 20o at its lower end, allowing to re-transport the solids after having passed the heat exchanger, into the fluidized bed FB of the furnace 10.

A separator and a syphon arranged between the furnace outlet port 10o and the heat exchanger inlet port 20 i are not displayed as known to the skilled person. S he heat exchanger 20 may be of any type and constructed according to prior art.

An independent platform PL, which extends horizontally and at a distance to an upper ceiling 20c of said heat exchange chamber 20, is fixed by ropes PR to a frame like support structure SS, being the same- support structure SS, to which the furnace 10 is suspended by rows RO. The platform PL is arranged in a defined position between heat exchanger and leverage and provides a rigid support for a leverage.

This platform PL serves to integrate the leverage 50, which is arranged onto said platform PL and extends from a first end 50f , pivotally mounted (pivot bearing 10p) to the outer furnace wall 10r away from said furnace wail 10r to a second end 50s, constructed as a pivot joint 50j, to allow a rod-like fastener 60 extending downwardly from said pivot joint 50j to a part of the heat exchange chamber 20 offset to the outer furnace wall 10r, namely to the very right and upper corner of said heat exchanger 20, i.e. to the ceiling 20c of the heat exchanger 20 offset with respect to furnace wall 10r. In this embodiment the fixation of the fastener 60 to the heat exchanger 20 corresponds to 100% of the length of the heat exchange chamber, seen in a direction perpendicular to the adjacent section 10s of the furnace wall 10r.

The leverage comprises a first lever 52, a first end 52f of which is pivotally mounted (pivot bearing 10p) to the outer furnace wall 10r, a second end 52s of which is hinged to a second lever 54 and an intermediate section 52 i of which is pivotally mounted in a pivot bearing 51 , arranged onto said platform PL.

The leverage 50 further comprises this second lever 54, a first end 54f of which is hinged to the second end 52s of first lever 52, a second end 54s of which is hinged to the fastener 60, and an intermediate section 541 of which is pivot-mounted in a pivot-bearing 53, arranged onto said platform PL at a horizontal distance to pivot bearing 51 ,

The fastener 60 connects the leverage 50 and the heat exchanger 20,

Each of said pivof bearings 51 , 53 is a floating bearing, which allows to move on said platform PL in a horizontal direction as will be described hereinafter. ^"

A number (here: six) .constant hangers C H are arranged - at a distance to each other - between platform PL and cei!ing 20c of heat exchanger chamber 20, being responsible for basic and varying loads of the heat exchanger chamber 20.

Sn a position as displayed in the Figure, the following may happen under thermal load of the apparatus:

The suspended furnace 10 (its outer wa!I 10r respectively) expands and thus outer wail 10r moves downwardly (arrow 10d). Simultaneously:

- pivot bearing 10p moves downwardly, urging lever 52 to tilt (around pivot bearing 51 ,

- the second end 52s of lever 52 moves upwardly and the same does the first end 54f of second lever 54, as both ends (52s, 54f) are coupled by a hinge,

-in view of the arrangement of pivot bearing 53, lever 52 tilts such that its second end 54s moves downwardly and the same does fastener 60.

As the two levers 52, 54 are of identical length and shape and both pivot bearings 51 ,53 are arranged just in the middle of the axial length of both levers 52, 54, the lower end (hinge) of said fastener 60 lowers by the same distance as pivot bearing 10p does and insofar no

additional stresses are initiated. At the same time the system reduces or even avoids excessive moments being transmitted into the furnace wail 1 0r/1 0s. in view of the turning/tilting movement of both levers 52, 54, causing a movement perpendicular to the outer furnace wall 1 0r. both bearings 51 ,53 are floating bearings, which a!low such horizontal dispiacement.