GB2128724A - Heat regenerator - Google Patents

Abstract

The heat regenerator 51 is detachable at one end from a burner B and at its other end from a reversing valve 58, and comprises two axially engaging portions 56 and 57, portion 56 comprising a cylindrical heat storage bed 59 and a surrounding annular layer 60 of ceramic fibre insulation, while portion 57 comprises a cylindrical body of refractory having a bore 61 forming a passage tapering towards valve 58. Heat storage bed 59 is a monolithic refractory block with multiple gas- carrying channels 65. Channels 65 convey combustion products from burner portion 52 to regenerator portion 56 when the bed is extracting heat from the products for storage. Alternatively channels 65 may convey air from portion 56 to portion 52 so that the air can be heated by the stored heat now released from the bed. <IMAGE>

Description

SPECIFICATION Heat regenerator The present invention relates to a heat regenerator for use in a heat recovery system with a burner particularlythough not exclusively of the type described in the present application.

According to the present invention a heat regenerator is provided for use in a heat recovery system, the regenerator comprising a heat storage bed housed in afluid-impermeable casing, the regenerator being detechable at one end from a burner and atthe other end from a reversing valve.

Embodiments ofthe present invention will now be particularly described with reference to the following drawings in which: Figure lisa sectional side view of one form of a burnersuitablefor usewith the regenerator.

Figure 2 is a side view in section ofthe heat regenerator and another form ofthe burner, Figure 3 is a front view ofthe burner airinletduct shown in Figure 2, Figure 4 is a side view in perspective ofthe inlet duct of Figure 3 shown partly broken away, Figure 5 is a schematicview in section of a heat recovery system incorporating two regenerators and burners shown in Figure 2 and Figures 6 to 8 are schematic views of various alternative arrangements of heat recovery systems incorporating the heat regenerator and burner.

Referring to Figure 1 the burnerAcomprises a body 1 with a through-going bore 2 defining a first end 3 to receive air, a second end 4to discharge the combustion products offuel combusted in the bore 2 and fuel inlet means 5for delivering fuel to a point in the bore 2.

The body 1 comprisesthreeadjoining portions 6,7 and 8 in which the bore 2 is defined.

The first portion 6 comprises a refractory block which defines the first end 3 of the bore 2.

The second portion 7 comprises a refractory ring whose purpose will be described subsequently.

The third portion 8comprises a refractoryquari blockwhich is externally cylindrical and defines the second end 4 ofthe bore 2.

The bore 2 is provided with a conical portion 9 tapering inwardlyfrom the first end 3through both portions 6 and7 to a point where the fuel enters the bore.

The bore 2then has a substantially constant cross-section in a mixing chamber region 10 where thefuel and airmix.Thischamber 10 isactually formed in the portion 8.

The third portion 8 is also formed with a wider cylindrical bore section 11 adjoining a conical bore section l2whichtapersinwardlytowardsthesecond end 4 of the bore 2.

The cylindrical section 11 is separated from the region 10 byan annularstep 12andformsa combustion chamberforfuel and air previously mixed in the mixing chamber 10.

The second end 4 of the bore 2 is formed with a radiussed portion 13forming an inwardly tapering bore section 14 adjoining the conical section 12.

The ring 7 is externally cylindrical and circumventing the ring is an annular manifold 15 for supplying fuel, in this case natural gas, to the chamber 10 for mixing with incoming air. The manifold 15 is provided with an angled inlet tube 16which extends outwardly from the ring 7. Fuel gas enters the manifold 15 by way of an inlet passage 17 formed in one portion of the manifold. Both the manifold 15 and the tube 16 are made of steel.

The manifold 15 communicates with the bore 2 by way offuel inlet means 5 comprising several in this case, five, circumferentially spaced and radially directed ducts 17. These ducts 17 are formed between the ring 7 and the third portion 6 when these components lie adjacent each other. To this end the end face ofthe ring 7 is substantiallyflat while the end face ofthe portion 6 is provided with recesses or slots corresponding to the ducts 17.

The ducts 17 form inlet passagesforthe supply of fuel gas to the bore 2.

Only one duct 17 is shown in detail although the outlet ends 18 of two othersuch ducts 1 7 are shown in Figure 1.

The manifold 15 is provided with outlet apertures 19 circumferentially spaced on the inner surface 20 ofthe manifold 15 and corresponding in numberto the ducts 17.

The manifold outlet apertures 19 and the ducts 17 communicate with each other by way of further passages 21 formed between the ring 7, the duct 17 and the manifold 15. Forthis purpose the ring 7 is formed with a series of circumferentially spaced recesses 22 at one end ofthe ring 8 and angled to the axisthereof.The blind endsofthe radial ducts 17 are closed by a ceramic fibre packing 23 so that gas is prevented from being trapped in the blind ends.

Several, in this case, five, circumferentially spaced semi-conical vanes 24 are formed on the internal surface of the ring 7to promote turbulence in the air entering the mixing region 10 byway of the first bore end 3.

A pilot burnertube and igniter (not shown) extend radially between the ring 7 and the block 8 through a slot 25 formed therebetween to provide ignition of the gas entering the mixing region 10 from the ducts 17.

The ring 7 and the block8 are joined to each other by way of a gasket 26to seal off the gas inlet ducts 17 from the pilot tube, the gasket 26 being provided with suitable apertures 27 to enable the passages 21 to communicate with the ducts 17.

In operation of the device as a burner, fuel gas is supplied through the inlettube 16to the manifold 15 and is then distributed by way of the ducts 17 into the mixing chamber 10 which in this mode serves as a fuel gas/air mixing chamber.

Combustion air which preferably is preheated before entering the burner is supplied to the chamber 10 by way of the bore end 3 which in this mode serves as an air inlet. The air is forced to mixwith the gas and the gas/air mixture is ignited initially bythe pilot burner/igniterwhich is itself supplied with a premix of fuel gas and cold combustion air. Combustion is substantially completed within the cylindrical section 11 which in this mode serves as a combustion chamber, the mixture entering the chamber 11 past the step 12 which provides means forflame front stabilisation. The product of combustion then leave the burner byway ofthe second end 4 and can then be, supplied to a suitable enclosure such as a furnace.

The burner is constructed so asto produce a high intensity and stable flame by burning fuel gas with an appropriate volume ofairwhich may be preheated to very high temperatures.

The various innovative features in the construction ofthe burner namely, the body 1 made of a refractory material, the quarl block bore design (the open bore of the cylindrical mixing chamber 10, the conical bore 9, the radiussed outlet 13 and step 12 between the combustion chamber 11 and the mixing chamber 10) provide means for the same burnerto operate as a low pressure drop flue forthetransfer of hot waste gases from a furnace to a heat recovery system such as a regenerator.

The bore 2 is so designed as to provide a substantially uninterrupted flow path for gas both from the second end 4tofirst end 3 as well as in the opposite direction. The factthat the inlet ducts 17 terminate at, ratherthan in, the bore 2 enhances this effect.

Therefore the burner can also serve as a flue for waste gas leaving an enclosure and enteringthe second end 4when operated in this mode as well as in a burner mode. When operating as a flue the waste gas then flowsthroughthe bore 2 to leave the burner by way of the first end 3 for discharge into a heat regenerator.

In Figure 2the burner B is shown attached to a heat regenerator 51. Burner B is similarto burnerAand identical parts bearthe same reference numbers.

The burners B comprise a cylindrical block portion 8 similarto that in Figure 1. The burner also comprises cylindrical refractory block 52 adjoining portion 8 which replaces and performs the samefunction as the portions 6 and 7 in Figure 1.

Extending through the portions 8 and 52 is a through-going bore 2 which in the portion 8 has identical parts to those shown in the burnerof Figure 1.

The burner portion 52 defines a first end 3 to the bore 2 and a conical portion 54 which tapers to a front end 55 ofthe block 52.

Formed between the portions 8 and 52 is means 5 for delivering fuel to a point in the bore 2.

The heat regenerator 51 comprises two axially engaging portions 56 and 57, the regenerator 51 communicating with the burner bore 2 at a forward end and a reversing valve 58 at the rearward end.

The front portion 56 comprises a cylindrical heat storage bed 59 and a surrounding annular layer 60 of a ceramic fibre insulation material. The rear portion 57 comprises a cylindrical body of refractory having a bore 61 forming a bottle-necktype passage tapering towardsthevalve 58.

The regenerator portions 56 and 57 are housed in a cylindrical steel shell 62 which is provided at its ends with annular connectorflanges 63 and 64. The steel shell provides a gas impermeable lining to preventthe escape of gasthrough thewall ofthe regenerator 51.

The heat storage bed 59 comprises a monolithic refractory blockthrough which a multiplicity of axially aligned gas-carrying channels 65 extend. These chan nels 65 convey combustion products from the burner portion 52 to the regenerator portion 56 in one mode of operation where the bed is extracting heat from the products for storage. In another mode of operation the channels 65 convey airfrom the portion56tothe portion 52 so thatthe air can be heated by the stored heat now released from the bed.

Alternativelythe bed 59 cam comprise several adjoining slabs each of which incorporates the gas-carrying channels.

As with the burner shown in Figure 1, the bore 2 of the burner B forms a substantially uninterrupted flow path for gas in either direction through the bore 2. The burner B can therefore eitheroperate as a burner per so for supplying combustion products to an enclosure such as a furnace or, when operating in another mode, as a flue for receiving waste products from thefurnace for discharge to the heat regenerator 51.

To this endthefront portion 8 ofthe burner B is adapted to be fitted into a suitable aperture in the furnace such as the annular portion 66 forming part of the furnace (not shown). The front portion 8 has a recess 67 formed at the end adjacent to the burner portion 52. The front portion 8 has a cylindrical main body portion 69, the neck 68, in use, being received with clearance within the recess.

The main body 69 ofthe burner portion 52 is housed in a cylindrical steel shell 70 which is provided with connecting flanges 71 and 72 at either end thereof.

Referring to Figures 2 to 4, the neck 68 ofthe burner portion 52 is formed on its end surface 55 with six radially directed and equi-spaced grooves 73. The flange 71 has a section 74 which extends radially outwardlyfrom the shell 70 and asection 75which extends radially inwardly therefrom. Extending into the body of the portion 52 at an acute angle to the axis thereof and in the direction ofthe burner B is a fuel supply duct 76 which terminates at a corresponding aperture in theflange 71.

The outer section 74 of the flange 71 is provided with an inner ring 77 of bolt-holes and with an outer ring 78 of fewer bolt-holes. The holes 77 are used to clamp the burner portion 52 to the burner portion 8 by way of bolts 79whilethe holes 78 are used to clamp the burner portion 52 to the furnace portion 66 by way of bolts 80.

An annular gasket 81 is provided between the flange 71 and both the burner portion 8 and the furnace portion 66 to form a seal,the gasket 81 being suitably apertured to receivethe bolts 79 and 80.

Anannulargasket82 is also mounted betweenthe end face ofthe burner portion neck 68 and theinner' face ofthe recess 67 in the burner portion 8.

When the burner portion 52 is secured toTheburner portion 8 as shown in Figure 2,the annular-cJearance 67 forms an annular manifold for receiving fuel gas from the duct 76 and supplying the gastottle grooves 73 which together with the gasket 82 form the fuel inlets 5tithe bore 2.

Extending through the body ofthe burner portion 52 at an angle to the burner axis is a bo-re83which terminates at one end atthe bore 54 and atthe other end a tube 84 extends outwardlyfrom the bore 83 and is provided with a sight glass.

As shown in Figure 2, the burner B is clamped to the heat regenerator 51. In this case the burner flange 72 is clamped to the regenerator flange 63 by means of bolts 85. Similarly the regenerator 51 is clamped to the reversing valve 58 by means offlange 64.

The burner B shown in Figures 2 to 4 operates in a similar manner to burner A described with reference to Figure 1.

In one mode of operation when the burner B serves as a burner per se, preheated air is supplied from the regenerator 51 and enters the burner bore 54 where it meets and mixes with fuel gas entering the inlet ducts 5. The fuel gas is combusted in the chamber 11 and entersthefurnace in the direction of arrow C.

In the alternate mode of operation when the burner serves as a flue, exhaust combustion products leaving the furnace enterthe burner B in the direction of the arrow D. The exhaust gas flows thorugh the burner bore 2 and enters the regenerator 51 which extracts heat from the waste gas for release to the air in the next cycle of operation.

The heat storage bed 65 in the regenerator 51 serves alternately to extract heat from the waste gas passing through it in one direction in one cycle of operation. In the other cycle of operation the bed 65 releases its stored heatto cold air passing through the regenerator 51 in the opposite direction.

The burner B and heat regenerator 51 may form part of a conventional heat recovery system such as that shown in Figure 5.

In this case the heat recovery system comprises a pairof burners B1 and B2anda pairof heat regenerators 51 a and Sib, togetherwith a conventional rotating reversing valve 58.

The burners B1 and B2 are mounted side by side on a furnace 90 so that their bores 2 communicate with the interior ofthe furnace 90.

The regenerator 51 a is connected at one end to the burner B1 bytheflange connections shown in Figure 2. Similarlythe regenerator Sib is connected atone end to the burner B2 by similarflange connections.

Each ofthe regenerators 51 a and 51b are connected at their other ends to right angled ducts 91 a and 91 b by means ofthe flange connections shown in Figure 2.

The rotary valve 58 comprises a cylindrical housing 92 (the axis of the cylinder extending into the plane of the paper) in which is located a vane 93 which extends axiallythrough the cylinder and dividesthe housing 92 into two always separate but movable compartments 94 and 95 which are of semi-circular section.

The vane 93 is mounted for rotation on a spindle 96 which extendsthrough the housing 92.Thevane93is rotatable between two positions at 90" to each other as shown in Figure 5, one position being shown in full line and the other in broken line. The limits to rotation arefixed by two pairs of elongate seals 97a and 97b and 98a and 98b which are secured tothe internal surface of the housing 92 with adjacent seals 90" apart.

Thevane 93 and the seals 97 and 98 are such that when the vane 93 is engaging one pair of seals the two compartments so formed are sealed from each other.

The ducts 91 a and 91 b lead respectivelyto the compartments 94 and 95 and are welded to the valve housing 92.

The housing 92 is also provided with an inlet duct 99 for receiving cold airforcombustion and opposite to the duct99 a hot waste gas outlet duct 1 00.

The valve 58 is so arranged that when the vane 93 is in one sealing position one duct 91 is connected to the air inlet duct99 and the other duct91 is connected to the waste gas outlet duct 100. In the other position when the vane 93 has rotated through an arc of 900 the connections are reversed.

In operation of the system, one ofthe burners is selected to provide hot gas forthe furnace while the other burnerserves simultaneously as afluefor discharging the hotwaste gas to the regenerator system.

Thus if the burner B1 connected to the regenerator 51 a is serving as a flue and the burner B2 connected to the regenerator 51 b is providing combusted gas, valve 58 is positioned to connect the regenerator Sib to air inlet duct 99 and to connect the regenerator 51 a to the hot waste gas outlet duct 100, the vane 93 being in the full line position of Figure 5. In this mode cold combustion air enters the duct 99 and the regenerator 51 b bywayofthevalve58and theduct91 b. The air then travels up through the regenerator Sib by way of the heat storage bed which will already be heated from previous heat recovery cycles.The now hot air then leaves the regenerator 51 b and enters the burner B2 so asto mix with fuel gas entering the burner B2 to provide combusted hot gas for the furnace 90. (see arrows E).

Simultaneously hot waste gas leaves the furnace 90 after use byway ofthe other burner B1 which in this mode acts asa flue. Thewaste gas enters the regenerator51a and travels downwardlythrough the regenerator 51a by way of the heat storage bed. This bed is thereby heated by the waste gas and serves to store this heat for heating cold combustion air during the next heating cycle. The waste gas then leaves the regenerator ski a and enters the duct 91 a before issuing from the outlet duct 100 by way of the valve 58 (see arrows F).

After sometime, the heatstored in the regenerator 51b will be exhausted and/orthe bed in regenerator 51 a will have been heated up as much as is possible or desirable. Atthis stage therefore the heat cycle is reversed by rotating the valve vane 93 by 900 to the position shown in broken line in Figure 2.

Cold combustion air now enters the burner B1 by way ofthe inlet duct 99, the valve 58, the duct 91 a and the regenerator ski a (see arrows G) and is preheated for the combustion of fuel gas in the burner1.

Waste gas meanwhile leaves the burner B2 and enters the regenerator 51 b to heatthe storage bed therein. The waste gas then leaves the regenerator 51b and passes through the duct 91 band the valve 58 before dischargeto atmosphere via the outlet duct 100 (see arrows H).

Because the heat regenerato r 51 is demountable both from the burner 3 and from the valve means 58 the system is moreflexiblethan a conventional heat recovery system where the regenerator is integral with the burner and the valve means. This flexibility is further improved if the burner is also demountable from the furnace.

The construction of conventional regenerators limitstheirspacial arrangement to the conventional arrangement where one end (the furnace end) is alwaysvertically above the other end (the valve end).

Theconstruction ofthis regenerator permits any desired arrangmentto be achieved. For instance the furnace end could be vertically belowthevalve end if desired or both ends could be in the same horizontal plane.

As shown in Figures 6 to 8, with this flexible system it is possible to design and instal a system to satisfy a whole range ofconfigurational requirements dictated perhaps by space or by heat input or output parameters. It is also possible to vary the configuration and size ofthe system once installed should any ofthese parameters be changed for any reason.

Claims (9)

1. A heat regenerator for use in a heat recovery system comprises a heat storage bed housed in a fluid impermeable casing, the regenerator being detachable at one end from a burner and at the other end from a reversing valve.

2. A regenerator as claimed in Claim 1 in which the casing is made of metal.

3. A regeneratorasclaimed in Claim 1 or Claim 2 in which the heat storage bed comprises a body of heat resistant material provided with axially aligned chan nels extending therethrough forthe passageoffluid between the ends of the regenerator.

4. A regenerator as claimed in Claim 3 in which an annular layer ofceramicfibre is located between the body and the casing.

5. A regenerator as claimed in Claim 3 or Claim 4 in which the body comprises a monolithic block.

6. A regenerator as claimed in Claim 3 or Claim 4 in which the body comprises several adjoining portions, each channel extending through each of the portions.

7. A regenerator as claimed in Claim 6 in which the portions comprise at least two different materials.

8. A regenerator as claimed in any of Claims 3to 7 in which the body is made of refractory.

9. A heat regenerator substantially as hereinbefore described with reference to Figures 2 to 8.