GB2192264A - Thermal regenerators - Google Patents

Abstract

A regenerator for a regenerative heating system, comprises a generally upwardly directed first chamber 2 surmounting a second chamber 4, the first chamber 2 housing a fluid permeable heat storage bed 6 between a port 18 which serves during a heat collecting phase as an inlet for receiving waste gas from an enclosure and a lowermost port which communicates with the second chamber 4, the second chamber 4 having a port 12 serving during a firing phase as an inlet to receive combustion air for supply to the first chamber 2 and during a heat collecting phase as an outlet to discharge waste gas supplied by the first chamber 2, the lowermost port in the first chamber 2 serving as a means for draining under gravity from the heat storage bed 6 to the second chamber 4 any carry-over material which has been reduced to or retained in a molten state by heat released to the bed 6 by waste gas during a heat collecting phase. <IMAGE>

Description

SPECIFICATION A regenerator The Present invention relates to a regenerator for a regenerative heating system, the regenerator being of the type comprising a chamber which houses a fluid permeable heat storage bed.

Regenerators of this type are used in combinations of two or more to form a regenerative heating system for heating a charge held in an enclosure such as a furnace or the like.

Each regenerator is provided with a first port located above the bed which first port may contain a fuel fired burner to provide combustion products for heating the charge during a so-called firing phase of the regenerator.

These combustion products produced by a regenerator provide waste gas after heating the charge. The port also serves as an inlet to receive waste gas during a so-called heat collecting phase of the regenerator whereby the bed recovers the waste heat from the waste gas. The egenerator is also provided with a second port located beneath the bed. This port serves during a firing phase to receive combustion air for passage through the chamber in the opposite direction to the movement of waste gas during the heat-collecting phase.

The combustion air is then preheated by heat released from the bed before providing combustion of fuel. During a heat collecting phase the second port serves as an outlet for waste gas used to preheat the bed.

In use while one regenerator is operating in its firing mode a partner regenerator is operating in its heat collecting mode.

In use of such regenerators in certain industrial processes, particularly but not exclusively those processes which involve the melting of an alloy of several elements, those elements with the lowest melting and vapourisation temperatures will tend to produce vapour which will be carried over with the waste gas to any regenerator which at that time is operating in its heat collecting mode.

In collecting the sensible heat of the vapour and waste gas, the heat storage bed of the regenerator will normally at some point have reduced the temperature of the waste gas to a level at which the vapourised materials will assume a liquid phase, recovery of the latent heat then taking place. Subsequently in even cooler zones of the heat storage bed the materials will solidify-if the temperature of the bed is low enough.

As a result there will in some cases be partial blocking of the gas passages in the heat storage bed by the solidified material.

This will tend to lead over time to a reduction in the efficiency of heat recovery.

It is an object of the present invention to provide a regenerator of the type defined from which the solidified carry-over material can be removed.

According therefore to the present invention we provide a regenerator for a regenerative heating system, the regenerator comprising a generally upwardly directed first chamber surmounting a second chamber, the first chamber housing a fluid permeable heat storage bed between a port which serves during a firing phase as an outlet for supplying combustion products to an enclosure to be heated and during a heat collecting phase as an inlet for receiving waste gas from the enclosure and a lowermost port which communicates with the second chamber, the second chamber having a port serving during a firing phase as an inlet to receive combustion air for supply to the first chamber and during a heat collecting phase as an outlet to discharge waste gas supplied by the first chamber, the lowermost port in the first chamber serving both as a means for transferring combustion air or waste gas between the chambers and as means for draining under gravity from the heat storage bed to the second chamber any carryover material which has been reduced to or retained in a molten state by heat released to the bed by waste gas during a heat collecting phase.

An embodiment of the invention will now be particularly described with reference to the accompanying drawings in which Figure 1 is a vertical section through the regenerator, Figure 2 is a perspective view of a heat storage bed retaining plug, and, Figure 3 is a schematic representation of a regenerative heating system incorporating two of the regenerators shown in Figure 1.

Referring to Figure 1, the regenerator 1 comprises two identical generally cylindrical uppermost chambers 2 and 3 extending vertically upwardly and surmounting a lowermost chamber 4 with which the chambers 2 and 3 communicate.

The chambers 2 and 3 are formed by two cylindrical open ended refractory bodies 5 which house heat storage beds 6. The beds 6 comprise discrete particles 7 in the form of refractory balls.

The chambers 2 and 3 comprise uppermost cylindrical sections 8 in which the beds 6 are located, lowermost cylindrical sections 9 of reduced diameter compared to the uppermost sections 8 and intermediate sections 10 adjoining sections 8 and 9, the intermediate sections 10 being of inverted frusto-conical shape. The chambers 2 and 3 are provided with plugs 11 retained by the walls surrounding the sections 9 and 10 and serving to support the bed particles 7. The plugs 11 which will be described subsequently in more detail with reference to Figure 2 are designed when seated within the sections 9 and 10 to permit transfer of waste gas or combustion air be tween the chambers 2 and 3 by way of the chamber 4 and the lowermost chamber openings or parts 12 formed by the sections 9.In the case of the chamber 2, the plug 11 also permits molten carry-over material to be discharged from this chamber 2 to the lowermost chamber 4 by way of the opening 12.

The lowermost chamber 4 is formed between an uppermost refractory block 13 and a lowermost refractory block 14 upon which the uppermost block 13 rests.

The lowermost extremities 15 of the bodies 5 have a reduced external diameter in comparison to the external diameter of the remainder 16 of the bodies 4. These extremities 15 and lower parts 17 of the remainder of the bodies 4 seat within corresponding apertures in the block 14 so that the bodies 4 are supported on the block 14.

The chamber 2 and 3 have uppermost openings or ports 18 which in the case of chamber 2 communicates with the chamber 19 of a fuel-fired refractory type burner 20 of known type; which burner 20 is supported on the upper end 21 of the body 4.

The uppermost opening 18 in the chamber 3 communicates with a reversing valve (not shown) of known type by way of a vertically extending steel duct 22 secured to the upper end 23 of the body 4.

The lowermost chamber 4 is provided with a drainage port 30 situated immediately beneath the lowermost opening 12 in the chamber 2 for discharging under gravity molten carry-over material 31 directly from the chamber 2 into a water filled tank 32. The port 30 is formed in a lowermost vertical tubular extremity 33 of the block 14. Surrounding the block 14 is a steel shell 34 which forms a sleeve 35 for the extremity 33 and extends downwardly therebeyond to terminate beneath the surface of the water 36 in-the tank 32.

By ensuring that the sleeve 35 is immersed in the water 36 a gas-tight seal is provided between the chambers 2, 3 and 4 and the enclosure which is being heated, it being appreciated that all the connections between the various parts of the regenerator are gas tight.

The refractory bodies 4 and the uppermost block 13 are also housed in a steel shell 37 which is connected by a flange 38 to a similar flange 39 with which the steel shell 34 is provided. Similarly the refractory burner 20 is also housed in a steel shell 40.

Referring to Figures 1 and 2, the plug 11 comprises an uppermost head portion 50 and a lowermost body portion 51. The head portion 50 has an uppermost surface 52 separated from an underneath surface 53 by a circumferential rim 54 providing the radially outermost part of the plug 11.

The uppermost surface 52 is generally convex in shape and is provided with six radially directed and circumferentially equi-spaced channels 55 terminating at the rim 54.

The underneath surface 53 tapers conically inwardly in the downward direction before adjoining the body portion 51. This comprises a cylindrical uppermost portion 56 adjoining the surface 53 and a lowermost portion 57 in the form of an inverted truncated cone.

As is most ciearly shown in Figure 2, the plug is also formed with three (only two shown) circumferentially equi-spaced radially outwardly projecting ribs 58 adjoining the surface 53 and the portion 51.

These ribs 58 have radial outer faces 59 and 60 which are angled respectively to abut, in use, the walls forming the sections 9 and 10 of the chambers 2 and 3 as shown in Figure 1. In this position the rim 54 of the plug 11 is located within the cylindrical section 8 of the chambers 2 and 3, the diameter of the head 50 of the plug 11 being less than that of the internal diameter of the chambers 2 and 3 at this point so that the head 50 is spaced from the surrounding chamber wall.

In use, with the plugs 11 in position, three channels 61 are formed between the ribs 58 and the surrounding walls of the chambers 2 and 3. These channels 61 permit the transfer of waste gas or combustion air between either of the chambers 2 or 3 and the chamber 4.

In the case of chamber 2, the channels 61 also permit the discharge of molten carry-over material 31 directly into the tank 32 after passage through the opening 12 and the port 30.

The channels 55 in the head 50 of the plug 11 serve to collect the molten carry-over material discharging from the heat storage bed 6 for delivery to the channels 61.

In use of the regenerator, the burner 20 supplies combustion products to an enclosure containing a charge to be heated, during a firing phase. To this end, combustion air is supplied to the burner combustion chamber 19 for mixture with fuel e.g. natural gas injected into the burner 20. The combustion air enters the chamber 3 by means of the duct 22 and then passes through the chambers 3, 4 and 2 in turn before entering the combustion chamber 19. The combustion air travels downwardly through the chamber 3 and then upwardly through the chanber 2 and is preheated in two stages by the storage beds 6 in these chambers 2 and 3.

During a heat collecting phase, waste gas enters the combustion chamber 19 of the burner 20 and then passes through the chambers 2, 4 and 3 in turn before leaving the regenerator 1 by way of the duct 22. The waste gas travels downwardly through the chamber 2 and upwardly through the chamber 3 giving up its heat to the storage beds 6 in two stages.

The directions of waste gas flow and subsequent combusiton air flow are such as to produce vertical temperature profiles in the beds 6, the bed temperature decreasing vertically downwards in the bed of chamber 2 (hereinafter called the first stage bed) and decreasing vertically upwards in the bed of chamber 3 (hereinafter called the second stage bed).

By suitable selection of the comparative heat storage capacities of the two beds, one compared to the other, it is possible to produce temperature distributions in the beds ensuring that condensing of volatile materials from the waste gas and subsequent entrapment by solidification will occur exclusively in the first stage bed and further that the vertically delineated temperature profile occurring in this bed in normal operations will position the critical temperature range over which condensing may occur close to the lower extremity of this bed.

By restricting the zone of potential blockage to the first stage bed and to a zone close to the base of that bed, a relatively small change in temperature profile would result in movement of the- blocking material down the first stage bed resulting in this material being converted to a molten state and then being discharged from the bed and dropped through the opening 12 in the chamber 2 and thence into the water tank 32.

By discharging the molten carry-over material into water, the material is rapidly quenched ensuring that the material does not coagulate. The material may then be moved frqm its settlement point in the tank 32 to allow for its removal. The removal may be performed continuously.

With experience it is possible to select the appropriate length of heat collecting period necessary to ensure that any solidified materials carried over by the waste gas are reduced to a molten state for removal from the heat storage bed of the regenerator 1.

Referring to Figure 3, a regenerative heating system incorporating two of the regenerators 1 previously described is shown, the regenerator being denoted 1A and 1B. In this case the ducts 22 of the regenerators 1 A and 1B are connected by lines 70 to a conventional reversing valve 71. This valve 7 1 permits the regenerators 1 A and 1B to be connected on alternate phases of the regenerative cycle to an exhaust gas duct 72 for the removal of waste gas from the regenerator currently operating in its heat collecting mode and to an air supply line 73 for supplying combustion air to that regenerator currently operating in its firing mode.

Claims (6)

1. A regenerator for a regenerative heating system, the regenerator comprising a generally upwardly directed first chamber surmounting a second chamber, the first chamber housing a fluid permeable heat storage bed between a port which serves during a firing phase as an outlet for supplying combustion products to an enclosure to be heated and during a heat collecting phase as an inlet for receiving waste gas from the enclosure and a lowermost port which communicates with the second chamber, the second chamber having a port serving during a firing phase as an inlet to receive combustion air for supply to the first chamber and during a heat collecting phase as an outlet to discharge waste gas supplied by the first chamber, the lowermost port in the first chamber serving both as a means for transferring combustion air or waste gas between the chambers and as means for draining under gravity from the heat storage bed to the second chamber any carry-over material which has been reduced to or retained in a molten state by heat released to the bed by waste gas during a heat collecing phase.

2. A regenerator as claimed in claim 1 in which the second chamber has a further port immediately beneath the lowermost port in the first chamber to discharge from the second chamber any molten carry-over material supplied by the first chamber.

3. A regenerator as claimed in claim 2 in which the further port is formed by a downwardly extending tubular member, the lowermost part of which, in use, is immersed in a fluid bath.

4. A regenerator as claimed in any of claims 1 to 3 in which the lowermost port in the first chamber is provided with means to support the bed above the port while permitting molten carry-over material to be drained from the chamber through the port.

5. A regenerator as claimed in any of claims 1 to 4 in which there is provided a generally upwardly directed third chamber surmounting the second chamber, the third chamber housing a fluid permeable heat storage bed between- a lowermost port common to the port in the second chamber and an uppermost port serving during a firing phase as an inlet for supplying combustion air to the second chamber and during a heat collecting phase as an outlet for discharging waste gas supplied by the second chamber.

6. A regenerator substantially as hereinbefore described with reference to the accompanying drawings.