Burner apparatus

Abstract

The invention provides a burner configured for use with a dryer for drying aggregates, the burner comprising: a burner chamber (3) is which is mounted a fuel-atomizing burner nozzle (3.32) and means for conveying fuel to the burner nozzle; means providing a flow of air through the burner chamber and into the combustion chamber; a combustion chamber (4) in which the fuel is burnt; the combustion chamber (4) having an opening at an upstream end thereof communicating with the burner chamber (3) and an opening at a downstream end thereof for passing combustion gases and heated air into a drying chamber of the dryer; the burner nozzle (3.32) being arranged to direct a flow of atomized fuel into the combustion chamber; a first airflow modifier device (3.11) mounted in or across the opening at the upstream end of the combustion chamber such that there is a gap constituting an air escape channel around a periphery of the first airflow modifier device, the first airflow modifier device (4.3) having one or more windows therein through which a flow of air provided by the fan is directed into the combustion chamber to mix with atomized fuel from the burner nozzle, the one or more windows being configured to impart turbulence to the airflow; and a second airflow modifier device (4.3) comprising one or more air deflector elements (4.31) mounted peripherally about the opening at the upstream end of the combustion chamber, the second airflow modifier device (4.3) being arranged to impart turbulence to excess air passing through the said air escape channel.

Claims

1. A burner configured for use with a dryer for drying aggregates, the burner comprising: a burner chamber is which is mounted a fuel-atomising burner nozzle and a fuel conveyor which conveys fuel to the burner nozzle; a combustion chamber in which the fuel is burnt; the combustion chamber having an opening at an upstream end communicating with the burner chamber and an opening at a downstream end thereof for passing combustion gases and heated air into a drying chamber of the dryer; the burner nozzle being arranged to direct a flow of atomised fuel into the combustion chamber; a fan for providing a flow of air through the burner chamber and into the combustion chamber; a first airflow modifier device mounted in or across the opening at the upstream end of the combustion chamber such that there is a gap constituting an air escape channel around a periphery of the first airflow modifier device, the first airflow modifier device having one or more windows therein through which the flow of air provided by the fan is directed into the combustion chamber to mix with atomised fuel from the burner nozzle, the one or more windows being configured to impart turbulence to the airflow; and a second airflow modifier device comprising one or more air deflector elements mounted peripherally about the opening at the upstream end of the combustion chamber, the second airflow modifier device being arranged to impart turbulence to excess air passing through the said air escape channel.

2. A burner according to claim 1 wherein the size of the air escape channel around the periphery of the first airflow modifier device is variable so as to vary the flow of excess air into the combustion chamber.

3. A burner according to claim 2 wherein the first airflow modifier device is configured to impart twist to a stream of air passing through it.

4. A burner according to claim 3 wherein the first airflow modifier device takes the form of a swirl plate comprising a plurality of radially extending vanes arranged so as to twist the flow of air into a vortex.

5. A burner according to claim 1 wherein the second airflow modifier device is fixed relative to the opening at the upstream end of the combustion chamber.

6. A burner according to claim 5 wherein the second airflow modifier device is mounted in the combustion chamber on a wall separating the combustion chamber from the burner chamber so that it surrounds the said opening.

7. A burner according to claim 1 wherein the second airflow modifier device comprises a plurality of air twist blades mounted on an inner wall of the combustion chamber in close proximity to the air escape channel around the periphery of the first airflow modifier device.

8. A burner according to claim 7 wherein the air twist blades are angled so as to direct the air into a vortex.

9. A burner according to claim 8 wherein the direction of twist imparted by the second airflow modifier device is opposite to a direction of twist imparted by the first airflow modifier device.

10. A burner according to claim 1 wherein the first airflow modifier device has peripheral surface which is inclined at an angle of from 20 to 70 with respect to the plane of the first airflow modifier device so as to direct excess air outwardly and around the first airflow modifier device and into the combustion chamber.

11. A burner according to claim 10 wherein the gap around the periphery of the first airflow modifier device is defined by the distance between an outer edge of the first airflow modifier device and an inner rim of the upstream opening of the combustion chamber, and the size of the gap is controlled by moving the first airflow modifier device with respect to the inner rim of the said opening.

12. A burner according to claim 11 which is configured such that movement of the first airflow modifier device backwards or forwards in an axial direction results in the size of the gap changing.

13. A burner according to claim 1 wherein the first airflow modifier device is immovable so that the distance between an outer edge of the first airflow modifier device and an inner rim of the upstream opening of the combustion chamber is fixed, and a movable baffle element is provided which can be moved into or out of the gap to vary the size of the gap.

14. A burner according to claim 12 wherein the first airflow modifier device, is mounted on a support frame or support rods which are movable by virtue of being mounted on or linked to an actuator.

15. A burner according to claim 1 wherein the combustion chamber is constructed so as to be adjustable in length.

16. A burner according to claim 15 wherein the combustion chamber is formed from two or more telescopic components which can be moved together to reduce the length of the combustion chamber or moved apart to increase the length of the combustion chamber.

17. A burner according to claim 1 which further comprises an air intake, a fan chamber and a motor for driving the fan which together constitute a blower module.

18. A burner according to claim 17 wherein the blower module is constructed so that it can be separated from the burner chamber to allow access to the burner chamber for maintenance purposes, said blower module being movably mounted on a support structure so that it can be moved away from the burner chamber to give access to the burner chamber.

19. A dryer apparatus comprising a burner as defined in claim 1.

20. A burner configured for use with a dryer for drying aggregates, the burner comprising: a burner chamber in which is mounted a fuel-atomising burner nozzle and a fuel conveyor which conveys fuel to the burner nozzle; a fan for providing a flow of air for the burner; a combustion chamber in which the fuel is burnt; the combustion chamber having an opening at an upstream end communicating with the burner chamber and an opening at a downstream end thereof for passing combustion gases and heated air into a drying chamber of the dryer; the burner nozzle being arranged to direct a flow of atomised fuel into the combustion chamber; a first airflow modifier device mounted in or across the opening at the upstream end of the combustion chamber such that there is a gap constituting an air escape channel around a periphery of the first airflow modifier device, the first airflow modifier device having one or more windows therein through which a flow of air provided by the fan is directed into the combustion chamber to mix with atomised fuel from the burner nozzle, the one or more windows being configured to impart turbulence to the airflow; and wherein the combustion chamber is constructed so as to be adjustable in length; and optionally wherein: (i) a second airflow modifier device comprising one or more air deflector elements mounted peripherally about the opening at the upstream end of the combustion chamber, the second airflow modifier device being arranged to impart turbulence to excess air passing through the said air escape channel; and/or (ii) the size of the air escape channel is variable so as to vary the flow of excess air into the combustion chamber.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1A is a side view of a burner apparatus according to one embodiment of the present invention.

(2) FIG. 1B is a view from above of the burner apparatus of FIG. 1A.

(3) FIG. 10 is a view from direction Y of the burner apparatus of FIGS. 1A and 1B.

(4) FIG. 1D is a view from direction X-X in FIG. 1A.

(5) FIG. 2A is a schematic side elevation showing the burner apparatus of FIGS. 1A to 1D mounted in an end wall of a rotary dryer.

(6) FIG. 2B is a schematic side view corresponding to FIG. 2A but showing the blower module rolled back from the burner chamber and the combustion chamber of the burner apparatus.

(7) FIG. 3A is a side view of the support structure for the burner apparatus of FIGS. 1A to 1D.

(8) FIG. 3B is an end view of the support structure of FIG. 3A.

(9) FIG. 4A is a partial sectional elevation of the lower section showing the interior of the fan chamber of the blower module.

(10) FIG. 4B is a view from direction X of FIG. 4A but with some features omitted for clarity.

(11) FIG. 5 is an external side view of the burner chamber of the burner apparatus of FIGS. 1A to 1D.

(12) FIG. 6 is a sectional view showing the interior of the burner chamber of FIG. 5.

(13) FIG. 7 is a view from direction X of the burner chamber shown in FIG. 6, but with some features omitted for clarity.

(14) FIG. 8 is a view from direction X of the burner chamber shown in FIG. 6 but with the interior workings of the burner chamber omitted.

(15) FIG. 9 is a side elevation showing the interior of the burner chamber together with part of the combustion chamber.

(16) FIG. 10 is partial sectional side elevation showing an alternative layout for the burner chamber and combustion chamber but with a number of features omitted for clarity.

(17) FIG. 11 is a side sectional elevation showing the interior of the combustion chamber of the burner apparatus of FIGS. 1A to 1D.

(18) FIG. 12 is a view from one side of the dual fuel valve for use in the burner apparatus of FIGS. 1A to 1D.

(19) FIGS. 13A to 13F show the component parts of the dual fuel valve of FIG. 12.

(20) FIG. 14 is a sectional elevation through the fuel valve of FIG. 12.

(21) FIG. 15 is a side elevation along line XXX-XXX in FIG. 14.

(22) FIG. 16 is schematic view of the fuel pipe work including the dual fuel valve and the burner.

(23) FIG. 17A is sectional view showing the interior of the burner chamber and part of the combustion chamber with a swirl plate in a closed position.

(24) FIG. 17B corresponds to FIG. 17A except that that the swirl plate is shown in an open position.

DETAILED DESCRIPTION OF THE INVENTION

(25) Referring to the drawings, FIGS. 1A to 1D show a burner apparatus according to one embodiment of the invention.

(26) The burner apparatus comprises a support structure 1, a blower module 2, a burner chamber 3 and a combustion chamber 4.

(27) The burner apparatus in use is mounted at one end of a rotary dryer 5 (see FIGS. 2A and 2B) by means of bolts 3.2 passing through holes 3.4 in a flange 3.6 located at the junction between the burner chamber 3 and combustion chamber 4. The blower module 2 is mounted on a support structure 1 which is provided with a plurality (in this case four) of pairs of rollers 1.3 which run in channels 2.12 on the underside of the blower module 2. The inner wall 2.11 of the channel 2.12 is turned inwardly and engages retaining rollers 1.4 on the support structure 1.

(28) The support structure 1 serves not only to take the weight of the blower module 2 but also serves as an air intake for the blower module. Typically, in use, the support structure 1 is mounted on a platform at one end of the rotary dryer. The platform may have ventilation openings so that air may pass through the platform and up through the support structure and into the fan chamber. Preferably, however, the support structure 1 is provided with feet (not shown) at each corner which elevate the support structure so that there is a gap of about 10 centimeters between the underlying surface and the support structure through which air can pass en route to the fan chamber. The support structure is configured such that at least 50% of the air required by the burner passes up through the support structure. An advantage of this arrangement is that the overall length of the burner can be reduced.

(29) In order to reduce the noise associated with the burner, the support structure 1 contains acoustic foam to give noise reduction insulation so that the structure functions as a silencer as well as a support for the blower module.

(30) FIG. 4A shows the interior workings of the blower module. Thus, the blower module comprises a motor 2.4 which is connected via a short shaft to a drive coupling 2.5. The drive coupling 2.5 in turn is connected to the impeller shaft 2.7 which rotates the impeller or fan 2.8. The impeller is attached to the shaft 2.7 by means of a collar 2.21 which is secured to the shaft by means of one or more grub screws 2.22. At one end, the shaft 2.7 is mounted in a bearing 2.20, the construction of which is entirely conventional and need not be described in detail here. The impeller shaft 2.7 is also supported within bearing housing 2.6 which, again, is of conventional construction.

(31) On its upper surface, the blower module is provided with a hinged inlet 2.2 which is fitted with acoustic foam to assist noise reduction. The inlet 2.2 can be lifted up on its hinges to allow access to the interior workings of the blower section.

(32) The blower module is provided with locating pins 2.10 which locate in the pin locators 3.14 on the combustion chamber module 3 to provide correct alignment between the blower module and the combustion chamber module.

(33) FIG. 5 shows the external features of the burner chamber 3. As shown, the burner chamber has an end wall 3.19, the radially outermost part of which forms a flange 3.22 fitted with support studs 3.4 for attaching the combustion chamber 4. Mounted on the external surface of the burner chamber 3 are three pneumatic rams 3.1, one at the top of the burner chamber and the other two being mounted either side of the lower part of the burner chamber.

(34) Also mounted on the outer surface of the burner chamber is a dual fuel valve 3.2, the construction of which is illustrated in more detail in FIGS. 12, 13A to 13F, 14 and 15.

(35) A photocell holder 3.3 containing a photocell device for flame diagnostics purposes is also attached to the outer surface of the burner chamber.

(36) The interior workings of the burner chamber are shown in FIG. 6. Thus, mounted in the wall of the burner chamber 3 are pneumatic ram brackets 3.6 which are attached to the external pneumatic rams 3.1. Each pneumatic ram bracket 3.6 is attached to a swirl plate support rod 3.7 and also to an arm of the lance support spider 3.8. The three arms of the lance support spider are linked by means of a collar 3.40 which holds the burner lance 3.16. Mounted on one of the arms of the spider 3.8 is an ignition lance 3.32. The upper swirl plate support rod 3.7 is attached to a suspending arm 3.42, which has a wheel or roller 3.9 on its upper end. The wheel or roller rests on a support or guide rail 3.10.

(37) A swirl plate 3.11 (which constitutes a first airflow modifier device) is secured to the lance 3.16 and also to the swirl plate support rods 3.7. At the periphery of the swirl plate 3.11 is an air is an inclined surface 3.12 which is inclined at an angle of about 45 with respect to the plane of the swirl plate 3.11.

(38) The end wall 3.19 of the burner chamber has a circular hole in which the swirl plate 3.11 sits. In the rest position, there is a relatively small annular gap 3.13 between the outer surface 3.12 and the rim of the hole in the end wall 3.19. The size of the air gap 3.13 can be increased by actuating the pneumatic rams 3.1 so that the swirl plate 3.11 is moved in a forward direction.

(39) The configuration of the swirl plate 3.11 can be seen more clearly in FIG. 7. As shown, the swirl plate comprises a plurality, in this embodiment thirty two, of radial vanes which are inclined at an angle of about 45 relative to the plane of the swirl plate. In the embodiment shown, the vanes are inclined so as to impart an anticlockwise twist to air passing therethrough.

(40) The support spider 3.8, lance 3.16, ignition lance 3.32 and swirl plate 3.11 can all be removed from the burner chamber 3 by removing the two bolts on the ram bracing bar 3.61 and the bolt on the pneumatic ram top support 3.6. As shown in FIG. 8, removal of the support spider 3.8 and its attached components gives access through the round outlet hole 3.17 into the combustion chamber 4.

(41) FIG. 9 illustrates the interior of the burner chamber and a part of the interior of the combustion chamber immediately downstream of the burner chamber. Mounted on the end wall 3.19 of the burner chamber 3 and encircling the first airflow modifier device is a fixed second airflow modifier device 4.3 which is fitted with air twist blades 4.31. The air twist blades 4.31 are inclined at an angle of about 45 with respect to the central axis of the burner and impart a twist to the airstream which is in the opposite direction to the twist imparted to the airstream by the swirl plate 3.11. By arranging the swirl plate 3.11 and the a second airflow modifier device such that they twist the airstream in opposed directions, the turbulence of the airstream is increased and therefore the efficiency of mixing of the combustion air with atomised fuel oil is greatly improved.

(42) The combustion chamber 4 can be of fixed length or it can be of adjustable length as shown in FIG. 11. The combustion chamber of FIG. 11 comprises a fixed combustion chamber section 4.1 and an adjustable combustion chamber section 4.2. The adjustable combustion chamber section 4.2 has attached thereto a plurality (e.g. three) of combustion chamber support rods 4.21 which are mounted in the combustion chamber support studs 3.4. The combustion chamber can therefore be extended in length by means of telescopic movement between the fixed combustion chamber section 4.1 and the adjustable combustion chamber section 4.2. By enabling the length of the combustion chamber to be varied, it is possible to vary the shape of the flame from a short and wide flame to a long and narrow flame.

(43) The fuel feed to the lance 3.16 is shown in more detail in FIG. 16. The supply of fuel oil is controlled by the dual fuel valve 3.2. The fuel valve 3.2 is fed by a pair of fuel inlet pipes 3.27A and 3.27B which in turn are linked to solenoid valves 3.30A and 3.30B respectively. Each of the solenoid valves 3.30A and 3.30B is connected to a fuel reservoir or supply. The fuel supplies may be identical or different fuels. A choice of fuel for use in the burner can be made by activating the appropriate solenoid valve 3.30A or 3.30B.

(44) Referring to FIGS. 12 to 15, the dual fuel valve 3.2 comprises a machined metal block having a main throughbore 3.40 extending across its width. The main throughbore 3.40 is divided into a narrow bore region 3.40A at the midpoint of the channel, a pair of intermediate bore regions 4.40B and two enlarged bore regions 3.40C at either end of the channel 3.40. Disposed within the main throughbore is a rotatable valve member 3.23 which has two transverse passages 3.42 extending from one side to the other. In this embodiment, the transverse passages 3.42 are square in shape and are approximately 10 millimeters square. However, the size of the transverse channels could be varied as desired. Disposed within the intermediate bore regions 3.40B of the block are a pair of cylindrical obturator elements 3.24 which are slidable in an axial direction along the main throughbore 3.40. Each obturator element has a central passageway 3.44 which is sized so that it can accommodate the valve member 2.3. Each obturator element also has a pair of square cross-section transverse passages (windows) 3.46 of the same cross-sectional area as the transverse passages 3.42 in the rotatable valve member 3.23.

(45) The obturator elements 3.24 each have threaded ends 3.48. A threaded end of one obturator element is attached by means of a thread on the radially inner surface 3.50 of span adjuster 3.21 whereas the threaded end 3.48 of the other obturator element 3.24 is attached by means of a thread on the radially inner surface 3.52 to the other span adjuster 3.22. The span adjuster 3.22 is configured to fit over the end 3.23a of the fuel adjustment stem 3.23 whereas the span adjuster 3.21 has a reduced diameter opening 3.21B through which the end 3.23B of the rotatable valve member adjustment stem 3.23 can be inserted.

(46) The span adjusters 3.21 and 3.22 are each provided with external threads 3.21C and 3.22C respectively which engage threads in the surface of the enlarged bore portions 3.40C of the main throughbore 3.40.

(47) In order to open the valve to fuel to flow through it to the burner, the valve member 3.23 is rotated until the transverse channels 3.42 in the valve member come into alignment with the windows 3.46 in the obturator elements and the inlet 3.27 and outlet 3.28 of the fuel valve thereby creating a free flow path through the valve. In order to turn off the flow of fuel to the burner, the valve member 3.23 is rotated so that the transverse channels 3.42 are moved out of alignment with the windows 3.46 and the fuel inlet 3.27 and fuel outlet 3.28.

(48) The rate of flow of fuel through the passages 3.42 and 3.46 can be varied by rotating the span adjuster 3.21 so that it rides along the threaded region 3.48 of the valve insert 3.24 thereby causing the obturator element 3.24 to move along the main throughbore towards the midpoint. As the valve insert 3.24 moves, the area of overlap of the channels 3.42 and windows 3.46 is progressively reduced thereby reducing the amount of fuel that can pass through the transverse channels. In general, the area of overlap of the channels 3.42 and windows 3.46, and hence the fuel flow rate through the valve, is set prior to use of the burner according to the size and nature of the burner and the type of fuel that is to be used. Thus, for example, more viscous waste oils may require a larger aperture (i.e. larger area of overlap) whereas lighter gas oils may typically require a smaller aperture. It will be appreciated also that a larger burner will require more fuel and hence the valve will be set so as to give a larger area of overlap between the channels 3.42 and windows 3.46.

(49) The inlet 3.27 and outlet 3.28 passages are linked by a bypass passage 3.26 which forms a secondary flow path through the block. A fuel pressure gauge 3.29 is mounted in a threaded aperture in the wall of the fuel valve block so that the inner end of the fuel gauge is in fluid communication with the bypass channel 3.26. Also disposed in the bypass channel is a bypass needle valve 3.25 which has a passageway 3.25C of reduced diameter extending through part of its length.

(50) A stop bolt 3.30 is mounted in a threaded passageway and this can be tightened to prevent rotational movement of the obturator element 3.24.

(51) The rotatable valve member 3.23 is connected to an electronic actuator device 3.31 which can rotate the valve member to allow the passage of fuel through the valve.

(52) When setting up the burner, the fuel to be used is selected by actuating the appropriate solenoid valve 3.30A or 3.30B with the rotatable valve member 3.23 in the closed position, i.e. wherein the transverse channel 3.42 is not aligned with the transverse channel or window 3.46 through the obturator element 3.24. The fuel is therefore diverted along the bypass channel 3.26 past the fuel pressure gauge 3.29 which senses the fuel pressure being delivered. The bypass needle valve 3.25 is set to the minimum aperture required to produce a flame and fuel passes through the valve 3.25 and on towards the lance where it is atomised and ejected into the turbulent air stream. The gas ignition lance 3.32 is used initially to initiate combustion of the atomised fuel. Once the fuel has been ignited, the rotatable valve member 3.23 can be rotated into an open position to allow fuel to pass directly from inlet 3.27 to the outlet 3.28 and on to the lance 3.16.

(53) In use, atomised fuel ejected from the lance 3.16 is mixed with turbulent air passing through the swirl plate 3.11 and the air twist plate 4.31. Excess air is directed through the gap 3.13.

(54) In order to increase the temperature of the burner, more fuel is delivered to the lance 3.16 through the fuel valve 3.2. At the same time, the airflow rate is increased proportionately in order to keep the fuel to air ratio at the correct level. However, increasing airflow through the combustion chamber would lead to the build-up of back pressure behind the swirl plate as only a proportion of the excess air would be able to escape through the gap 3.13. Therefore, in order to avoid the back pressure build-up, the swirl plate is moved forwardly (i.e. towards the combustion chamber 4) thereby increasing the gap 3.13 and allowing more excess air to pass through the gap. By enabling more air to be delivered to the combustion chamber, the fuel is burnt more efficiently and concentrations of carbon monoxide are substantially reduced.

(55) The efficiency of combustion is further enhanced by the presence of the fixed air twist plate 4.3 which rotates the air in the opposite direction to the swirl plate 3.11, thereby increasing turbulence in the air and ensuring mixing of the air and atomised fuel.

(56) In the burner apparatus of FIGS. 1 to 16, the swirl plate 3.11 is mounted on support rods 3.7 and can be moved backwards and forwards in an axial direction in order to vary the size of the air gap 3.13.

(57) FIGS. 17A and 17B illustrate an embodiment of the invention which is provided with alternative means of varying the size of the air gap 3.13. Thus, in FIGS. 17A and 17B, a baffle 3.33 is mounted on support rods attached to the pneumatic rams 3.1. In this embodiment, it is the axial movement of the baffle 3.33 along the line X-XX which results in variation of the gap 3.13. The arrangement shown in FIGS. 17A and 17B is particularly suitable for use with natural gas and LPG fuelled burners but can also be used for oil-fired burners.

(58) The burners of the invention have greatly improved efficiency of combustion compared to known fuel oil burners typically used in asphalt manufacturing plants.

(59) The improved combustion efficiency is demonstrated by the greatly reduced carbon monoxide concentrations produced by burners of the present invention compared with known commercially available fuel oil burners used in asphalt plants. For example, when burning 100% recycled fuel oil, carbon monoxide emissions were comparable to those produced by natural gas burners and were less than a third (and in three out of four cases less than a quarter) of the carbon monoxide emissions produced by commercially available fuel oil burners.

EQUIVALENTS

(60) It will readily be apparent that numerous modifications and alterations may be made to the specific embodiments of the invention described above without departing from the principles underlying the invention. All such modifications and alterations are intended to be embraced by this application.