IE53952B1 - A condenser - Google Patents

Abstract

In a fuel supply bin 8 for accommodating a high-moisture-containing fuel such as peat or woodchips to be fed to a gasifier 1 for combustion, a condenser 9 is provided in the upper part of the bin to collect water vapour liberated by the fuel. The vapour condenses on a finned plate 11 and in order to prevent it from falling back into the fuel, the condensate is collected on an array of collector plates 13, 14, 15, 16 and 17 as it falls from the fins 10, the collector plates 13 to 17 being arranged to intercept the falling droplets and direct them to a drain 18 outside the fuel bin but not to obstruct the free flow of moisture-carrying air from the fuel to the finned plate 11. The condensing surface may alternatively be provided by the exterior wall of a coolant duct, or a duct may be provided in addition to the finned plate 11.

Description

This invention relates to a condenser and in particular to a condenser for the fuel supply bin of a solid fuel gasifier. Such gasifiers are used for the thermal deconposition of a solid fuel which takes place in a combustion space of the gasifier. Secondary air is added to the gas generated, which then passes to a boiler or the like where conplete combustion takes place in substantially smokeless manner. Gasifiers may form part of new installations or they may be used to replace oil burners in existing installations.

Gasifiers are suitable for use with various forms of low-grade fuel io such as wood chips or peat in lunp form, and automatic feed of the fuel to the gasifier is provided by means of a fuel bin or hopper from which the fuel descends under its own weight by gravity into the combustion chamber. The fuel is heated and dried in the lower part of the fuel bin with the result that in the case of fuels such as peat, is which have a high moisture content, water vapour is given off and makes its way up through the peat in the bin to the space above the top surface of the fuel. Due to the vertical tenperature gradient through the fuel, the fuel is progressively cooler at higher levels in the bin and in particular, the space above the fuel is relatively cool ίθ by contrast with conditions at the bottom of the fuel bin, so that the water vapour condenses at the higher levels of the bin and in particular in the cool upper region of the bin, and the condensate falls back into the fuel in the form of droplets, thus raising the -2moisture content of the unburnt fuel. This water is thus evaporated and condensed several times during the consunption of a binload of peat, which reduces the effective heat content of the fuel and thereby also the efficiency of the gasifier. In addition the water droplets s' falling back into the peat cause clunps to form in it, so that bridging of the fuel may occur and the flow of the fuel into the combustion chamber may be inpeded and may even be stopped conpletely.

It is an object of the invention to provide a fuel supply bin for a gasifier in which this disadvantage of known constructions is to substantially eliminated or minimised. It is a further object of the invention to provide a condenser for a gasifier fuel supply bin which will be readily adaptable to existing fuel bins as well as being capable of incorporation in new units. It is also an object of the invention to provide a condenser which will be suitable for fitting to supply bins for both domestic installations and industrial gasifiers.

According to the invention, there is provided a condenser for a gasifier fuel bin conprising a condensing surface disposable in an upper region of the fuel bin for cooling water vapour in the vicinity of the surface so that water vapour may condense thereon as droplets a.o of condensate, and a condensate collector disposed beneath at least part of the condensing surface for receiving condensate falling from the condensing surface and directing it to the exterior of the bin.

The condensate collector preferably conprises at least one tray or plate, which is spaced from the condensing surface and disposed so zr that condensate collected thereon flows to a drain. In a particularly preferred embodiment, the condensate collector conprises a plurality of trays or plates, each of which is spaced from the condensing surface and from the other plate or plates to provide communication at least for gas flow from a lower fuel storage region of the bin to the condensing surface, and at least one of the plates is disposed so that condensate collected thereon flows onto another or the other of the plates. Said at least one plate suitably has an edge region disposed substantially vertically above and spaced from a surface of another or the other of said plates. -3a 3 9 5 The condensing surface may be provided by the inner face of the top wall of the fueT bin, but in the preferred embodiment, the condenser according to the invention conprises at least one plate positionable on the fuel bin to define an i^jper boundary wall portion of the upper £ region of the bin, the plate having a plurality of fins extending from one face thereof in the direction of the upper region of the bin, and the condensing surface being defined at least in part by the faces of the fins and the face of the or each plate from which they extend.

In this embodiment where the condensing surface is defined in part by /o the faces of fins, the plate from which the fins extend may also be provided with further fins, upstanding from the opposite face thereof and optionally in substantial continuation of the condensing surface fins, to provide additional cooling of the condensing surface and increase the condensing capacity of the unit. The plate and fins may 'S’ advantageously conprise at least part of the lid of the bin and are displaceable for filling the bin with fuel.

In another embodiment of the condenser according to the invention, the condensing surface is defined at least in part by the outer surface of at least one duct through which a flow of a cooling medium may be 2.Ή directed and which may be disposed to extend through the upper region of the fuel bin.

In another arrangement the condensing surface is defined by the faces of fins upstanding from one or more plates positionable on the fuel bin to define an upper boundary wall portion thereof and by the face Zs or faces of said plate or plates from which said fins extend and is further defined by the outer surface of at least one cooling duct through which the flow of a cooling medium may be directed and which may be arranged to pass through at least a portion of the upper region of the fuel bin. 3o in a modification of those embodiments of the condenser according to the invention in which the condensing surface is in part defined by the faces of fins, lower edge portions of the fins may be arranged to extend at an angle to the horizontal and at least a part of the -4g J s 5 8 condensate collector may be disposed beneath and spaced from the lower edges of the fins at least 1n their lowermost regions. In this case the cooling duct or ducts where present may be disposed in the vicinity of the lowermost regions of these edges, the plate or plates s' of the condensate collector then being disposed beneath and spaced from both the fins and the cooling duct or ducts.

The cooling medium circulated through the or each cooling duct, where provided, may be water and the water warmed by the heat taken up from the condensate may be drawn off from the or each duct following its io passage through that portion of the duct contained in the upper region of the fuel bin for use for domestic or other purposes.

The condenser may conprise an integral part of the fuel bin, the walls of which should preferably be insulated so that condensation of water vapour in the bin is confined to the region of the condenser. Alter'S natively the condenser may conprise a self-contained unit, mountable on an upper portion of an existing fuel bin.

Some embodiments of the invention will now be described by way of exanple having regard to the drawings, in which: Figure 1 is a schematic sectional view of a boiler and an associated 2-0 gasifier, fuel being fed to the gasifier from a fuel bin fitted with a condens.er according to the invention; Figure 2 is a sectional view on the line 2-2 of Figure 3 of the fuel bin and condenser shown schematically in Figure 1; Figure 3 shows the fuel bin and condenser of Figure 1 in section, on ax the line 3-3 of Figure 2; Figure 4 is a pictorial view of the upper region of the fuel bin with two sides of the bin, and also the tcp of the bin along with the condensing surface, being cut away to show the condensate collecting arrangement; -55 3 9 5 1 Figures 5 and 6 are views similar to those of Figures 2 and 3, showing another embodiment of the condenser; Figures 7 and 8 are views similar to those of Figures 2 and 3, showing a further embodiment of the condenser according to the invention; Figures 9 and 10 are views similar to those of Figures 2 and 3 showing an embodiment of the condenser according to the invention in which the condensing surface is provided on the lid of the fuel bin; Figures 11 and 12 are similar views to those of Figures 2 and 3 showing an embodiment similar to that of Figures 9 and 10 in which the ό condensing surface is provided in part by a cooling duct and in part on the lid; Figures 13 and 14 are views of a first embodiment of a condenser according to the invention mountable as a unit on a fuel bin; Figures 15 and 16 are views of another embodiment of the condenser according to the invention mountable as a unit on a fuel bin.

As shown in Figure 1, a gasifier 1 produces gas for combustion in a boiler 3 by the thermal decomposition of solid fuel in a combustion chamber 4, and the gas flows from the combustion chamber of the gasifier to the boiler along a duct 5. Primary air is supplied to the 2-0 combustion chamber 4 through a danper flap 6, the degree of opening of which can be adjusted depending on the heat demand of the boiler 3, and secondary air is added to the gas through the side air duct 7 during its passage through the duct 5, so that conplete combustion of the gas ensues in the boiler without the generation of smoke. The 2S solid fuel is supplied to the combustion chamber of the gasifier from a fuel supply bin or hopper 8. The fuel may consist of wood chips or lunps of peat of a size such that they will move downwards in the hopper as combustion proceeds in the combustion chamber, resulting in automatic feeding of fuel to the combustion chamber. A suitable size 3o of lunp in the case of peat would be in the range 10 to 20 mm, and the fuel bin may typically be of 350 to 750 litre capacity. -65 .ί 2 When the gasifier is in operation, a tenperature gradient in a vertical direction develops in the fuel bin, the tenperature being typically of the order of 80°c in the region of the fuel outlet, while it may fall to approximately 20°C at the upper surface of the jr fuel stored in the bin. Thus the fuel in the vicinity of the combustion chamber is warmed and dried before entering the chamber, with the consequent evolution of water vapour which travels up through the fuel into the relatively cool space above the fuel in the upper region of the hopper. A condenser 9 according to the invention is <© provided in this region to condense this water vapour, collect it and direct it to a condensate discharge point disposed externally of the fuel storage space.

The condenser 9 is shown in more detail in Figures 2, 3 and 4, of which the first two are sectional views and Figure 4 is a pictorial zs· view. Cooling means in the form of fins 10 are provided on the plate 11 forming the top of the fuel bin 8, and extend downwardly into the upper region of the bin, above the top surface of the fuel 12. The plate 11 itself provides part of the condensing surface of the condenser, but the area of the condensing surface and hence the 2.0 cooling capacity of the condenser are both increased by the presence of the fins, so that condensate forming on the plate 11 and on the fins accumulates into droplets which then run down along the fins and drop off their lower edges. The falling droplets are Intercepted by a plurality of collecting trays or plates 13, 14, 15, 16 and 17, which zs~ collect the droplets and direct the collected condensate to a condensate discharge point or drain 18 disposed externally of the fuel bin. The arrangement of the plates 13 to 17 is such that substantially none of the condensate can fall back into the fuel, but the flow of air and water vapour upwards to the cooling fins is 3o relatively uninpeded, taking place as indicated by the arrows 19 in Figure 2.

As can be seen from Figure 4, rear plate 13 is shaped to bring the collected condensate finally to the discharge point or drain 18, and the majority of the condensate will reach this plate from the central plate 16, which is inclined towards drain 18 and intercepts the -75 a .< 5 2 greater proportion of the falling droplets. It is supported by mounting menbers from the plate 11 (not illustrated in these Figures) so that there is a gap between the edges of the plate and the walls of the fuel bin. The front plate 17 and the side plates 14 and 15 each s' abut and are affixed to a wall of the bin along one edge. Plate 17 is disposed above central plate 16 so that droplets falling onto plate 17 are directed onto plate 16. Side plates 14 and 15 are disposed below plate 16 so that droplets not intercepted by plate 16 or falling off the edges of plate 16 at the sides thereof disposed above plates 14 /° and 15 are retained by these plates and directed onto plate 13, by virtue of the inclination of these plates in their longitudinal direction towards the rear plate 13 and drain 18. Thus condensate collected on the various plates flows to the lowermost point or edge of each respective plate where it falls onto a plate below or passes /£ to the drain (in the case of plate 13).

The side walls of the bin below the upper region of the fuel bin in which the condenser is located are Insulated so that condensation is largely prevented from taking place on these walls and takes place substantially only on the cooling surfaces of the condenser unit. As zo shown in Figure 2, the condensate finally drains into a tank or container 21 on the outside of the bin 8.

The modified enbodiment of the condenser shown 1n Figures 5 and 6 is similar to that of Figures 2, 3 and 4 apart from the provision of external cooling fins 22, which extend upwardly from the outside z.£ surface of the top plate 11, in substantial continuation of the internal cooling fins 10, and Increase the cooling effect of these and hence the condensing capacity of the unit.

In the embodiment shown in Figures 7 and 8, the cooling fins are replaced by a cooling duct 23, through which cooling water is conducted, and which traverses the space of the upper region of the fuel bln in the vicinity of the top plate 11 occupied by the fins 10 In the earlier embodiments. Thus the enhanced condensing effect is now provided by this duct, and the water circulated through it to carry away heat from the condensate may be heated sufficiently for use -85 ο .) 8 2 for domestic or other purposes. The arrangement of the interceptor trays or plates for collecting the condensate is similar to that of the previously described embodiments.

In each of the embodiments previously described, the condenser forms s' part of the fuel bin and is built into it in an upper region above the maximum fuel level. Loading of the bin takes place through a lid 24 disposed on one side of the condenser. The lid 24 is in each case suitably insulated. This arrangement for loading is suited to fuel bins for domestic or small-scale use. ,o Figures 9 and 10 show a fuel bin intended for industrial or large-scale use, and in this case the lid 25 is in the shape of a cone or pyramid and is lifted bodily off the top of the fuel bln in order to load fuel, for example by means of mechanical handling equipment In this case, another embodiment of condenser is used, in which the >5 fins 26 are disposed on the inside of the lid and their lower edges extend parallel to the lid plate or plates, so that they are inclined to the horizontal, and the water droplets forming on them run down along these edges to the lowermost points thereof, where they fall onto collector plates 27 disposed around the periphery of the mouth of ζσ the bin, to be directed to drains 28. The lid 26 msy also have external fins 29, as already described 1n relation to Figures 5 and 6.

In the embodiment of Figures 11 and 12, the condensing fins are again disposed on the inner surface of a removable lid 30, but In this case, the condenser also includes a cooling duct or coil 31, fixed with respect to the bin, for heating water flowing through the duct or coil and for providing additional condensing capacity. As can be seen from the Figures, the lid 30 is smaller for a similar size of fuel bin than that of Figures 9 and 10, on account of the presence of the duct 31 surrounding the mouth of the bln and located outwardly of its periphery.

The embodiments described above relate to condensers to be installed in fuel bins in the construction of the bin. The condenser according to the invention may also be fitted to existing fuel bins, and Figures -913 and 14 show a suitable embodiment for this purpose. It will be seen that it resembles the embodiment of Figures 2 to 4 in general construction but is provided with flanges 33 by which it can be bolted to the top of an existing fuel bin.

Figures 15 and 16 show another embodiment of condenser for mounting on an existing fuel bin, which resembles in principle the embodiment already described in relation to Figures 7 and 8, namely condensation of the water vapour is brought about by means of an array of cooling ducts 34, but which differs therefrom in the provision of flanges 33 io for securing the condenser to a fuel bin.

Figures 13 and 14 and 15 and 16 also show schematically the mounting members 36 by means of which the central condensate collector plate 16 is in each case supported from the plate 11 of the condenser.

The condenser according to the invention permits water vapour given ie off by fuels of high water content such as peat stored in a fuel bin for a gasifier to be condensed, collected and directed to a drain external of the fuel bin. It thus improves the efficiency with which the gasifier operates by eliminating sucessive evaporations and condensations of the same moisture within the bin, and may also serve 2.0 to heat water for domestic or other purposes. It thus renders the use of peat in gasifier installations more practicable.

The condenser according to the invention may suitably be fabricated from metal parts both 1n the case where it 1s fitted to a new fuel bln and also in the case where it is formed as a separate unit to be mounted on an existing fuel bin.

Claims (15)

1. A condenser for a gasifier fuel bin comprising a condensing surface disposable in an upper region of the fuel bin for cooling water vapour in the vicinity of the surface and on which water vapour may condense as droplets of condensate, and a condensate collector s disposed beneath at least part of the condensing surface for receiving condensate falling from the condensing surface and directing it to the exterior of the bin.

2. A condenser according to claim 1, wherein the condensate collector comprises at least one plate, which is spaced from the io condensing surface and disposed so that condensate collected thereon flows to a drain.

3. A condenser according to claim 2, wherein the condensate collector comprises a plurality of plates, each of which is spaced from the condensing surface and from the other plate or plates to ts provide communication at least for gas flow from a lower fuel storage region of the bin to the condensing surface, and at least one of which is disposed so that condensate collected thereon flows onto another or the other of the plates.

4. A condenser according to claim 3, wherein said at least one plate 2.0 has an edge region disposed substantially vertically above and spaced from a surface of another or the other of the plates.

5. A condenser according to any of claims 1 to 4, comprising at least one plate positionable on the fuel bin to define an upper boundary wall portion of the upper region of the bin and having a s-k plurality of fins extending from one face thereof in the direction of the upper region of the bin, wherein the condensing surface is defined at least in part by the faces of the fins and the face of the or each plate from which they extend.

6. A condenser according to claim 5, wherein a plurality of fins extend from the face of the boundary-wall-portion-defining plate or at least one of said plates opposite to that face from which the condensing-surface-defining fins extend. -117. A condenser according to claim 5 or 6, wherein the boundary-wallportion-defining plate or at least one of said plates is a lid portion for the fuel bin.

7. 8. A condenser according to any of claims 1 to 3, comprising at r least one duct through which a flow of a cooling medium may be directed and which may be disposed to extend through the upper region of the fuel bin, wherein the condensing surface is defined at least in part by the outer surface of the or each duct.

8. 9. A condenser according to any of claims 5 to 7, further comprising ° at least one duct through which a flow of a cooling mediisn may be directed and which may be disposed to extend through at least a portion of the upper region of the fuel bin, wherein the condensing surface is further defined by the outer surface of the or each duct.

9. 10. A condenser according to any of claims 5 to 7 or claim 9, wherein the fins have lower edge portions disposed at an angle to the horizontal and at least a part of the condensate collector is disposed beneath said lower edge portions at least in their lowermost regions.

10. 11. A condenser according to claim 10 when dependent on claim 9, wherein at least one cooling duct is disposed in the vicinity of the lowermost regions of the lower edge portions of the fins.

11. 12. A condenser according to any preceding claim mountable on an upper region of a gasifier fuel bin.

12. 13. A gasifier fuel bin comprising a condenser according to any preceding claim.

13.

14. A condenser for a gasifier fuel bin substantially as described herin with reference to and as shown 1n Figures 1 to 4, Figures 5 and 6, Figures 7 and 8, Figures 9 and 10, Figures 11 and 12 or Figures 13 and 14 of the accompanying drawings. -12

15. A gasifier fuel bin comprising a condenser and substantially as described herein with reference to and as shown in Figures 1 to 4, Figures 5 and 6, Figures 7 and 8, Figures 9 and 10 or Figures 11 and 12 of the accompanying drawings.