WO2005054748A1

WO2005054748A1 - Combustion device and method

Info

Publication number: WO2005054748A1
Application number: PCT/IB2004/003952
Authority: WO
Inventors: Edward Joseph Shane Mcfadden
Original assignee: Sacranie, Bashir
Priority date: 2003-12-04
Filing date: 2004-12-02
Publication date: 2005-06-16
Also published as: ZA200409826B; BRPI0411271A; EP1743123A1; GB0328089D0

Abstract

A combustion device (10) and a method are provided for combusting ethanol fuel (82). The liquid ethanol (82) is provided from a reservoir (12) to maintain a predetermined level of fuel (82) in an evaporation chamber (30), where it is heated. The heated liquid ethanol (82) seeps into lower ends (38) of tubes (36,42), evaporates and flows upwardly in the tubes (36,42) to a combustion zone (62), where it is combined with air and burnt. The combustible mixture of air and ethanol vapour is dehydrogenated in contact with a copper containing catalyst (60), supported on a burner (52) that is connected to a heating element (32) in the evaporation chamber (30). Heat from the combustion zone is transferred via the burner (52) and heating element (32) to the liquid ethanol (82) in the evaporation chamber (30).

Description

COMBUSTION DEVICE AND METHOD

FIELD OF THE INVENTION

THIS INVENTION relates to a device and a method for the processing and combusting of alcohol based fuel, such as ethanol, for use in combustion devices in appliances such as stoves, boilers, ovens, space heaters, and the like or where such heat may be used to power other devices or to be transformed into other forms of energy. In particular, the invention relates to a device and a method for combusting alcohol based fuel, such as ethanol.

BACKGROUND TO THE INVENTION

In locations where energy sources such as a distribution networks for electricity or liquid petroleum gas are not readily available, appliances that require heat for their operation are often driven by the combustion of fuels such as paraffin. These appliances are generally inefficient in the use of fuel and consequently expensive to run. Further, incomplete combustion of the paraffin often results in the emission of harmful gases. Paraffin is also a petroleum product and is therefore a non-renewable fuel.

Cellulosic material, such as wood, paper and other plant based combustible materials, where available, are often used, being cheaper and locally accessible, but the use of these materials can lead to environmental problems such as deforestation and pollution, as well as health and socio- economic problems.

The use of ethanol has been suggested, as a source of combustible hydrogen that can be stored to be used in fuel cells, to generate forms of electrical energy for use in, for example, internal combustion engines for driving vehicles. However, the cost, complexity and size of equipment for using ethylene as a source of energy in this manner, would not be suitable in many appliances.

There is a need for a combustion device using a renewable source of energy for use in heating appliances, or those in which heat is the primary or driving energy, in a simple, cost effective and energy efficient manner.

SUMMARY OF THE INVENTION

According to a first aspect of the invention there is provided a device for combusting alcohol based fuel, for use in heating and similar appliances, said device including: means defining a combustion zone that is open to the atmosphere; means defining an evaporation chamber, separated at least in part from the combustion zone, that is connectable to a source of the fuel; means defining at least one vapour flow passage enabling flow communication between the evaporation chamber and the combustion zone heating means enabling thermal communication between the combustion zone and the evaporation chamber; and a catalyst in the proximity of the combustion zone.

The device may include means defining a fuel reservoir, connected in flow communication with the evaporation chamber, configured so as to provide for the flow of fuel from the reservoir to the evaporation chamber and back again in such manner as to maintain a prescribed constant level of fuel in the evaporation chamber. The device may include means defining: a filling passage with an inlet opening in the fuel reservoir near its bottom, and an outlet opening in the evaporation chamber, for supplying liquid fuel from the reservoir to the evaporation chamber; and a return passage with an inlet opening in the evaporation chamber at a lower elevation, in use, than the inlet opening of the filling passage, and with an outlet opening in the fuel reservoir at a higher elevation, in use, than the inlet opening of the filling passage, for maintaining the level of liquid fuel in the evaporation chamber at a predetermined level.

The device may include a burner disposed adjacent the combustion zone with the catalyst supported on an outer surface of the burner, configured so that combustible gases can be heated when in contact with the burner for dehydrogenation to produce hydrogen gas which can be combusted in the combustion zone, and with the burner in thermal communication with the combustion zone, the evaporation chamber, and the catalyst in the proximity of the combustion zone. The burner may define a peripheral contact surface adjacent the catalyst, and may define a peripheral recess in the contact surface, in proximity of an outlet of the at least one vapour flow passage.

The word "burner" refers in this specification to a heat conducting body adjacent the combustion zone.

The device may include a heater element, connected for thermal communication, to the burner, and extending into the evaporation chamber.

The burner may define a preheating recess in which liquid fuel is receivable in proximity of the combustion zone, so that fuel in the preheating recess can be burned to preheat the burner to preheat in turn, the fuel in the evaporation chamber and to ignite fuel vapour from the vapour flow passage, in the combustion zone.

The vapour flow passage defining means may include at least one tube extending from close proximity to a bottom of the evaporation chamber, to the proximity of the combustion zone.

According to another aspect of the invention there is provided an appliance that includes a heating device as described hereinabove. The appliance may be in the form of a stove including support means suitable for supporting a cooking vessel in direct thermal communication with the combustion zone. Alternatively, the appliance may be in the form of a unit that is attachable to a boiler with the combustion zone in direct thermal communication with the boiler, an oven including a box in direct thermal communication with the combustion zone, or the appliance may be in the form of a space heater including a radiator in direct thermal communication with the combustion zone, and defining a radiating surface in contact with the atmosphere. The appliance may instead be in the form of a lamp that includes a light emitting mantle in thermal communication with the combustion zone.

According to a further aspect of the invention there is provided a method of combusting alcohol based fuel, said method including: heating the fuel in liquid form, to form fuel vapour; dehydrogenating the fuel vapour to form a hydrogen containing combustible gas; and combusting the combustible gas in a combustion device; wherein the combustion takes place in a combustion zone that is open to the atmosphere.

The fuel may include ethanol, and the step of dehydrogenation may include bringing the heated fuel vapour into contact with a metallic catalyst including copper. The method may include a prior step of preheating part of the device by burning liquid fuel, and may also include superheating the fuel vapour, after the device has been pre-heated.

The liquid fuel may be supplied from a reservoir, under vacuum.

The airflow my be stimulated by means of an air compressor or similar means for supplying compressed air to the combustion zone to improve the combustion rate and to achieve higher temperatures.

The invention will now be described by way of non-limiting example, with reference to the accompanying diagrammatic drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings: Figure 1 shows an exploded view of a combustion device in accordance with the invention; Figure 2 shows sectional side view of the part of the device of Figure

1 ; Figure 3 shows a three-dimensional schematic diagram of a stove, including the device of Figure 1 ; and Figure 4 shows a diagrammatic view of an industrial combustion unit, including the device of Figure 1.

DETAIL DESCRIPTION OF THE DRAWINGS

Referring to the drawings, a combustion device in accordance with the invention is generally indicated by reference numeral 10.

Referring to Figures 1 and 2 of the drawings, the device 10 includes an annular fuel reservoir 12, disposed around an upright cylindrical combustion cup 14 that is divided generally horizontally by a flash lid 16. A regulator housing 18 fits over an open upper end of the combustion cup 14, and is supported on top of the reservoir 12, on the outside of the combustion cup 14.

The reservoir 12 is made from steel and includes a circumferentially protruding seam 20. An angled fuel pipe 22 extends from the inner cavity of the reservoir 12, in close proximity to its bottom with a gap of about 0.25mm, to the outside, and includes a replaceable fuel cap 24 that can seal the fuel pipe in an air tight manner.

The cavity defined inside the combustion cup 14 below the flash lid 16 is the evaporation chamber 30 and includes a central heating element 32 attached to the flash lid at the upper end and to the bottom wall 34 of the combustion cup. Six feed tubes 36 are tightly fitted to the flash lid 16 and extend in an axial direction, with their lower ends 38 resting on the bottom wall 34, and their upper ends 40 protruding upwardly through the flash lid into a combustion zone 62. A pilot tube 42 is provided that is identical to the feed tubes 36, except that it is longer and protrudes higher above the flash lid 16. The resting relationship of the lower ends 38 of the feed tubes 36 and pilot tube 42, on the bottom wall 34 allows liquid fuel to seep into the lower ends, from the evaporation chamber 30.

An inlet tube 26 and return tube 28 extend between the reservoir

12 and the evaporation chamber 30. The inlet tube 26 defines a filling passage with an inlet opening 44 in the reservoir, in close proximity to the bottom wall 34, and with an outlet opening 46 in the evaporation chamber 30 in close proximity to the bottom wall of the evaporation chamber. The return tube 28 defines a return passage with an inlet opening 48 in the evaporation chamber 30 at a lower elevation than the outlet opening 46, and with an outlet opening 50 in the reservoir 12 at a higher elevation than the inlet openings 44, 48 and the outlet opening 46.

The device 10 includes a burner 52 in the form of a solid body that is disposed immediately above the flash lid 16 and that is connected to the heating element 32 by a fastener 54, so that the burner 52 is in good thermal communication with the heating element. In order to ensure good thermal conductivity from the burner 52 to the heating element 32, both these components are made of aluminium, copper or similar conductive materials. The burner 52 has a generally cylindrical shape and defines a preheating recess 56 extending downwardly from the top of the burner, and defines a peripheral annular recess 58, circumferentially around its outside. Around the circumference of the top of the burner 52, a catalyst 60 in the form of a copper ring is fixedly attached to the burner.

The volume enclosed in part by the regulator housing 18, the upper end of the combustion cup 14 and the upper periphery of the burner 52, forms the combustion zone 62 that is situated directly above the catalyst 60. The peripheral surface of the annular recess 58, as well as the outer surface of the burner 52 between the annular recess and the catalyst 60, form a peripheral contact surface 64.

The length by which the upper ends 40 of the feed tubes 36 protrude above the flash lid 16, aligns them generally with the upper periphery of the annular recess 58, so that the contact surface 64 extends from the proximity of the upper ends 40, to the catalyst 60. The upper end of the pilot tube 42 extends above the flash lid 16 to the approximate height of the catalyst 60.

The regulator housing 18 includes a lower cylindrical part 66, a frusto-conical part 68 and an upstanding lip 70, extending around an upper opening 72. A number of intake holes 74 are defined in the frusto-conical part 68, so that the inside of the regulator housing 18, and thus the combustion zone 62, is open to the atmosphere via the upper opening 72 and the intake holes 74. A frusto-conical regulator 76 is complemental in shape to the frusto- conical part 68, and rests directly on top of it, with its upper periphery extending around the lip 70. The regulator 76 also defines intake holes 78 that can be in register with the intake holes 74, depending on the angular position of the regulator 76 on the regulator housing 18. An adjustment handle 80 is attached to the regulator 76, and can be gripped manually to rotate the regulator relative to the regulator housing 18, to adjust the extent by which the intake holes 74,78 are in register, thereby to control the effective joint aperture size of the intake holes 74,78. Further intake holes 86 are defined in the upper part of the wall of the combustion cup 14.

In a preferred embodiment of the invention, a piezoelectric spark ignition device is provided, that can produce a spark in the combustion zone 62. However, the function of the ignition device can be performed manually with a match or the like and consequently, the ignition device is not shown in the drawings. The spark producing means is not an essential feature of the heating device 10.

In use, the reservoir 12 is filled, at least in part, with liquid fuel via the fuel pipe 22 and the fuel cap 24 is replaced. The fuel should be an alcohol based fuel and in a preferred embodiment of the invention, ethanol 82 is used. Liquid ethanol 84 is also poured into the preheating recess 56 and is ignited with a spark, a match, or the like, as described hereinabove. While the liquid ethanol 84 burns, the combustion causes convection in the combustion zone 62, and air is drawn from the evaporation chamber 30 through vent holes 90 defined in the flash lid 16, to cause a vacuum in the evaporation chamber. The vacuum in the evaporation chamber 30 causes liquid ethanol 82 to be drawn from the reservoir 12 to the evaporation chamber via the inlet tube 26, resulting in a vacuum within the reservoir 12. The vacuum in the reservoir 12 causes liquid ethanol 82 to be drawn from the evaporation chamber 30 to the reservoir 12 via the return tube 28, and the level of liquid ethanol in the evaporation chamber is thus maintained at a predetermined level, that helps to speed up the preheating and evaporation of the ethanol, by preventing an excessive volume of ethanol in the evaporation chamber. The formation of these vacuums in the reservoir 12 and evaporation chamber 30 prevents the fuel in these components from igniting and so acts as a safety feature.

The liquid ethanol 82 in the evaporation chamber 30 is heated by heat from the combustion of liquid ethanol 84 that heats the burner 52 and the heating element 32. The heat from the heating element 32 causes the liquid ethanol 82 in the evaporation chamber 30 to heat up and causes ethanol that has seeped into the submerged bottoms 38 of feed tubes 36 and pilot tube 42 to vaporise and flow upwardly in the vapour flow passages 88 defined in the feed tubes and pilot tube. The vapour flowing from the pilot tube 42 is ignited by the flame in the preheating recess 56 and in turn ignites the vapours from the upper ends 40 of the feed tubes 36. Combustion of vapours from the feed tubes 36 takes place in the combustion zone 62.

The combustion of ethanol vapours in the combustion zone 62 continually heats the burner 52 and heat is continually conducted via the heating element 32 to vaporise the liquid ethanol 82 in the evaporation chamber 30, and the combustion, heating and vaporisation keeps escalating until the burner reaches a temperature high enough for the catalyst 60 to be activated. This typically occurs at a temperature above 300°C, at which temperature the ethanol vapours are also superheated. The temperature in the combustion zone 62 will typically be of the order of 400°C.

Once the catalyst 60 has reached its activation temperature, unburnt ethanol vapours that flow from the upper ends 40 of the feed tubes 36 and from the upper end of the pilot tube 42 contact the catalyst 60, in the combustion zone 62. Upon contact with the catalyst 60, the ethanol vapours are dehydrogenated to form a combustible gas including ethanol vapours and hydrogen gas, and the combustible gas mixture is combusted in the combustion zone 62, when the operation of the heating device 10 has reached a stable operating condition. The flame with which the combustible gas burns has a blue colour, as a result of the combustion of hydrogen gas.

The combustion process is enhanced by an upward flow induced by heating air and ethanol vapour immediately adjacent the contact surface 64, that in turn causes a cross flow of air from the intake holes 74,78,86 across the upper ends 40 of the feed tubes 36. The cross flow of air draws ethanol vapours from the feed tubes 36, and thus enhances the feed of ethanol vapours through the feed tubes. The annular recess 58 assist in the induction of the cross flow.

The rate of combustion of ethanol vapours in the combustion zone 62 is controlled by rotating the regulator 76 relative to the regulator housing 18, and thus throttling the airflow through the intake holes 74, 78, as required.

The invention illustrated in Figures 1 and 2 of the drawings holds the advantages that the heating device 10 is simple and safe to operate. The simplicity also allows the heating device 10 to be manufactured at low cost and the vaporisation and dehydrogenation of the ethanol fuel allows it to be combusted very efficiently in the combustion zone 62, so that the energy yield from the heating device 10 is high, thus reducing fuel costs.

Ethanol can also be produced easily from plant material and is renewable, when compared to paraffin, wood, or many other combustible materials. Referring to Figures 3 and 4 of the drawings, the combustion device 10 is designed to be used in a stove, industrial combustion unit, or other similar combustion or heat driven appliances.

Figure 3 of the drawings shows an appliance in the form of a stove 92 including a combustion device 10 as described with reference to Figures 1 and 2. The stove 92 also includes support means in the form of a frame 94 for supporting a pot or pan.

Figure 4 of the drawings shows an appliance in the form of an industrial combustion unit 98 including a combustion device 10 as described with reference to Figures 1 and 2, set in a fuel chamber 100 with a fuel sensor 102, a float 104 connected to the fuel sensor, a fuel inlet 106 and an overflow valve 108. The inlet 106 is connected to control means 110 for the supply of fuel and a pump 112 to pump fuel between an external fuel tank 114 and the fuel chamber 100. The combustion device 10 is also connected to an air compressor 116 which supplies air to the combustion device via tubes 118 with air nozzles at their ends. The unit includes means (not shown) for mounting it underneath an object to be heated, such as a boiler, in thermal communication with the combustion zone 62 of the combustion device 10, to heat the boiler, or the like. In a preferred embodiment of the unit 98, a plurality of combustion devices 10 are used to heat the boiler.

Claims

1. A combustion device 10 for combusting alcohol based fuel 82, said device including: means defining a combustion zone 62 that is open to the atmosphere; means defining an evaporation chamber 30, separated at least in part from the combustion zone 62, that is connectable to a source 12 of the fuel 82; means defining at least one vapour flow passage 88 enabling flow communication between the evaporation chamber 30 and the combustion zone 62; and heating means 52,54,32 enabling thermal communication between the combustion zone 62 and the evaporation chamber 30; characterised in that the device includes a catalyst 60 in the proximity of the combustion zone 62.

2. A device 10 as claimed in Claim 1 , characterised in that it includes means defining a fuel reservoir 12, connected in flow communication with the evaporation chamber 30.

3. A device 10 as claimed in Claim 2, characterised in that it includes means defining: a filling passage 26 with an inlet opening 44 in the fuel reservoir 12 near its bottom, and an outlet opening 46 in the evaporation chamber 30; and a return passage 28 with an inlet opening 48 in the evaporation chamber 30 at a lower elevation, in use, than the outlet opening 46 of the filling passage 26, and with an outlet opening 50 in the fuel reservoir 12 at a higher elevation, in use, than the inlet opening 44 of the filling passage 26.

4. A device 10 as claimed in Claim 1 , characterised in that it includes a burner 52 disposed adjacent the combustion zone 62, with the catalyst 60 supported on an outer surface of the burner 52, and with the burner 52 in thermal communication with the combustion zone 62.

5. A device 10 as claimed in Claim 4, characterised in that the burner 52 defines a peripheral contact surface 64 adjacent the catalyst 60.

6. A device 10 as claimed in Claim 5, characterised in that the burner 52 defines a peripheral recess 58 in the contact surface 64, in proximity of an outlet 40 of the at least one vapour flow passage 88.

7. A device 10 as claimed in Claim 4, characterised in that it includes a heater element 32, connected for thermal communication, to the burner 52, and extending into the evaporation chamber 30.

8. A device 10 as claimed in Claim 4, characterised in that the burner 52 defines a preheating recess 56 in which liquid fuel 84 is receivable in proximity of the combustion zone 62, so that fuel 84 in the preheating recess 56 can be burned to preheat the burner 52 and to ignite fuel vapour from the vapour flow passage 88, in the combustion zone 62.

9. A device 10 as claimed in Claim 1 , characterised in that the vapour flow passage defining means includes at least one tube 36,42 extending from close proximity to a bottom of the evaporation chamber 30, to the proximity of the combustion zone 62.

10. An appliance, characterised in that it includes a combustion device 10 as claimed in any one of Claims 1 to 9.

11. An appliance as claimed in Claim 10, characterised in that it is in the form of a stove 92 and includes support means 94 suitable for supporting a cooking vessel, in direct thermal communication with the combustion zone 62.

12. An appliance as claimed in Claim 10, characterised in that it is in the form of a unit 98 that is attachable to a boiler with the combustion zone 62 in thermal communication with the boiler.

13. A method of combusting alcohol based fuel 82, said method including: heating the fuel in liquid form 82, to form fuel vapour; dehydrogenating the fuel vapour to form a hydrogen containing combustible gas; and combusting the combustible gas in a combustion device 10; characterised in that the combustion takes place in a combustion zone 62 that is open to the atmosphere.

14. A method as claimed in Claim 13, characterised in that the fuel 82 includes ethanol.

15. A method as claimed in Claim 13, characterised in that the dehydrogenation includes bringing the heated fuel vapour into contact with a metallic catalyst 60 including copper.

16. A method as claimed in Claim 13, characterised by a prior step of preheating part of the device 10 by burning liquid fuel 84.

17. A method as claimed in Claim 13, characterised by super heating the fuel vapour.

18. A method as claimed in Claim 13, characterised by supplying the liquid fuel 82 from a reservoir 12, under vacuum.

19. A method as claimed in Claim 13, characterised by supplying compressed air to the combustion zone 62.