CROSS-REFERENCE TO RELATED APPLICATIONS
- TECHNICAL FIELD
This application claims priority to Canadian Patent Application No. ______, filed on Dec. 15, 2005, and entitled “High Efficiency Cyclone Gasifying Combustion Burner to Produce Thermal Energy and Devices and Method of Operation”, and hereby incorporated by reference.
- BACKGROUND ART
The present invention relates in general to fuel burners, and in particular to a high-efficiency cyclone gasifying combustion burner and methods of operation.
In U.S. Pat. No. 6,336,449, a solid fuel burner is disclosed of cylindrical shape with holes disposed in an inner cylindrical wall to create a swirling motion to burn the combustion gases. Further experimental work and testing of this concept has led to important improvements beneficial to human health.
There has been a considerable increase in the use of wood-burning devices to heat residential buildings. This increase has been precipitated by the high cost of oil and gas. However, these wood-burning devices pollute the atmosphere and are harmful to human health.
According to Environment Canada, a woodstove that is not certified emits as many fine particles into the air in nine hours as does a certified woodstove in 60 hours or a mid-size automobile traveling 18,000 km in one year. Heating with wood represents a major source of contaminant discharge into the air: carbon monoxide (CO), volatile organic compounds (VOC), fine particles (PM2.5), nitrogen oxides (NOx) and polycyclic aromatic hydrocarbons (PAH, among others). Smoke from the combustion of wood is present in both inside and outside the home.
In residential neighbourhoods where wood heating is common, exposure to contaminants from chimney smoke can have a significant impact on health.
In the Province of Quebec, Canada, wood-fire home heating is responsible for half of the fine particle emissions associated with human activities. At the local level, wood combustion may contribute far more severely to pollution. For example, a report by the Montreal Urban Community has shown that, in winter, the concentrations of fine particles, VOC's and PAH's were often higher in residential neighbourhoods than in the downtown sector. Under certain weather conditions, the concentration of contaminants in the ambient air can reach high levels in certain neighbourhoods. This type of situation can occur in many places.
The number of wood-heating systems is increasing in Canada and many other countries in the world. Statistics Canada data indicates that the number of dwellings using wood heating increased by about 60% from 1987 to 2000. During the same period, the number of dwellings increased by less than 20%. This is true also for many cities of the world employing wood heating-systems.
The particles emitted when heating with wood are very small, less than 2.5 microns, allowing them to penetrate deep into the respiratory tract, affecting breathing. The following Table illustrates the potential health impacts of certain contaminants from high concentration of wood smoke in the air.
| || |
| || |
| ||Contaminants || ||Effects |
| || |
| ||Carbon monoxide ||CO ||Headaches, nausea, dizziness, |
| || || ||aggravation of angina in |
| || || ||people with cardiac problems |
| ||Volatile organic ||VOC ||Respiratory, irritation and |
| ||compounds || ||difficulties, certain VOC are |
| || || ||carcinogenic (ex: Benzene) |
| ||Acrolein and ||— ||Irritation of the eyes and |
| ||formaldehyde || ||respiratory system |
| ||Fine particles ||PM2.5 ||Irritation of the respiratory |
| || || ||system, aggravation of |
| || || ||cardiorespiratory diseases, |
| || || ||hastened mortalities |
| ||Nitrogen oxides ||NOx ||Irritation of the respiratory |
| || || ||system, painful inhalation, |
| || || ||coughing, pulmonary oedema |
| ||Polycyclic aromatic ||PAH ||Certain PAH are considered or |
| ||hydrocarbons || ||suspected of being mutagenic |
| || || ||or carcinogenic |
| ||Dioxins and furans ||— ||Potentially carcinogenic |
| || |
The magnitude of these effects depend upon people's sensitivity. Very young children, the elderly and individuals who suffer from asthma, emphysema or heart problems are among the most sensitive to air pollution.
In addition to emitting contaminants outdoors, wood combustion units may alter the quality of the air inside the home as portions of the combustion gases and fine particles make their way back indoors. These leaks inside the home will vary in importance according to the type of unit used, the quality of its installation and the way in which the homeowner operates the wood-burning unit. A study carried out by the Direction de la santé publique de Montréal-Centre showed that people using a woodstove had higher concentrations of contaminants in their urine than people without woodstoves. The combustion of wood thus represents an additional source of exposure to toxic substances in the home. Unlike most solid fuel burning devices, the burner of this invention can utilize solid fuels like wood and other types of non wood based solid fuels and substantially reduce emissions of toxic components during combustion.
Each type of mineral that may be present in the solid fuel has a known melting point, and some of these minerals are further transformed by temperature into a gas vapor state, a term known as alkali metal species migration. Some of these minerals occurring substantially as potassium and chlorides, which may have lower melting points than for example silicates, pose many difficulties during and after combustion of the fuel, as they promote the agglomeration (by melting and or cooling into masses) of minerals on adjacent metal surfaces. The deposition of inorganic elements such as alkali metals can have a significant impact on an operating system's overall performance, which further impacts on the efficacy of the operating system over time. Agriculture based fibers usually contain higher levels of chlorides and potassium salts.
- SUMMARY OF INVENTION
The high cost of natural gas and fuel oil and our dependency thereon and the effects of burning fossil fuels on climate change is another reason why alternate clean sources of energy are required today. According to the United Nations and the scientific community, the combustion of solid Biomass fuel, is considered to be green house gas neutral, that is, absorbing the equivalent CO2 (carbon dioxide) during growth as is emitted during combustion.
In accordance with various aspects of the present invention, a cyclone gasifying combustion burner is configured for use in or coupled to a solid fuel biomass device that substantially eliminates various disadvantages of wood-stoves or other solid fuel combustion devices. For example, an exemplary burner and method of operation can substantially reduce the emission levels of volatile organic compounds (VOC), particulates and fly ash as well as the level of nitrogen oxide (NOx) and/or all other carbon and volatile gases released during combustion of a solid fuel.
In accordance with an exemplary embodiment, a cyclone gasifying combustion burner can be incorporated into or coupled to a device having a thermal energy source and that can be automatically controlled in a modulated manner to achieve optimum efficiency. Such a cyclone gasifying combustion burner can comprise a fuel bed support system, such as a pyrolytic fuel bed, that automatically removes ashes from the fuel bed and thereby substantially reduces emission of volatile organic compounds, particulates, fly-ash, nitrogen oxides and other pollutants into the atmosphere. In accordance with another aspect, a cyclone gasifying combustion burner can also be configured such that the fuel bed temperature is starved of combustion air whereby to reduce the temperature of the fuel bed to prevent the fusion of inorganic elements within the solid fuel. An exemplary cyclone gasifying combustion burner may also be coupled to heating devices for residential, commercial and industrial applications, whereby to replace fossil fuel dependent heating devices. Such heating devices incorporating the cyclone gasifying combustion burner can also be configured to achieve significant reduction of greenhouse causing gases.
In accordance with an exemplary embodiment, a cyclone gasifying combustion burner comprises a combustion housing defined by an inner cylindrical wall surrounded by a manifold chamber having combustion air inlet devices and mechanisms. The inner cylindrical wall has air jet holes therein of substantially predetermined diameter and disposed at a substantially predetermined angle to create an air cyclone flow in a reaction zone in the inner cylindrical wall and spaced above a lower air-starved gasifying fuel bed thereof. The cyclone flow in the reaction zone can increase the residency time, turbulence, and mixing of oxygen and volatile gases to substantially complete combustion of the gases drawn into the reaction zone and causes suspended particles to gravitate into the fuel bed and thereby substantially reduce the emission of pollutants into the atmosphere.
In accordance with an exemplary embodiment, a device having a combustion chamber and requiring a thermal energy source can be configured in combination with the cyclone combustion burner. A heat exchanger can be provided in the combustion chamber. An air displacement system or device can create a negative pressure in the combustion chamber to displace hot air against the heat exchanger and to draw air through the air jet holes in the inner cylindrical wall of the combustion chamber. Mechanisms are provided to control the air displacement systems. In accordance with an exemplary embodiment, the combustion burner comprises a low pressure burner having an air/fuel ratio of about 6:1 to 10:1.
In accordance with an exemplary embodiment, there is provided a controller for automatically controlling the operation of the heating device. A user interface pad, having a memory and switch means, is also provided to set parameters into the controller relating to a desired mode of operation. The pad is also equipped with visual display device.
In accordance with another aspect of the present invention, there is provided a method of substantially reducing the emission levels of volatile organic compounds (VOC), particulates entrained fly ash, and the level of nitrogen oxides (NOX) during combustion of a solid fuel. In accordance with an exemplary embodiment, an exemplary method comprises the steps of feeding the solid or gas fuel in particle-form into an open end of a cyclone gasifying combustion burner and onto a flaming pyrolysis fuel bed thereof. The fuel bed is disposed below a reaction zone of the burner. The burner has a burner chamber defined by an inner cylindrical wall having a predetermined number of inclined air jet holes of predetermined diameter and height disposed at substantially predetermined locations to create a cyclone air flow within the reaction zone when combustion air is drawn therethrough. Air is drawn into the burner chamber through the inclined air jet holes whereby to draw combustion gases from the fuel bed into the reaction zone to mix with the cyclone air flow thereby substantially increasing the residency time of the combustion gases in a turbulent, mixing of oxygen and volatile gases for substantially complete combustion of gases and tars in the reaction zone and to simultaneously precipitate suspended particles against an inner surface of the inner cylindrical wall to cause at least some of the particles to agglomerate with other particles to increase their molecular weight and gravitate to the fuel bed.
In accordance with an exemplary embodiment, the vertical combustion housing has an open top end. A mechanism is provided to feed a solid biomass fuel in a particle, granular, pellet or whole or partial grain form to the fuel bed. A further combustion housing having an inner cylindrical wall surrounded by a manifold chamber is also provided. The inner cylindrical wall of the further combustion housing has air jet holes therein to create a reaction zone for the combustion of gases. The further combustion housing has a closed end wall and an opposed open end wall and is secured adjacent to the closed end wall to an open top end of the combustion housing and extends substantially transversely thereto. The inner cylindrical wall of both the vertical combustion housing and the further combustion housing communicate with one another to form a continuous internal combustion chamber.
In accordance with an exemplary embodiment, the further combustion housing has an open rear end and an open front end. The open rear end is connected to the open top end of the vertical combustion housing by conduit means for the supply of hot combustible gases released from the open top end for mixing with an air cyclone of the further combustion housing.
In accordance with an exemplary embodiment, there is provided a cyclone gasifying combustion burner having a combustion housing defined by an inner cylindrical wall surrounded by a manifold chamber having a combustion air inlet mechanism or system. The inner cylindrical wall has air jet holes therein of predetermined diameter and disposed at a predetermined angle to create an air cyclone flow in a reaction zone in the inner cylindrical wall spaced above a lower combustion gas supply. The cyclone flow in the reaction zone increases the residency time, turbulence, mixing of oxygen with volatile gases for substantially complete combustion of gases drawn in the reaction zone thereby substantially reducing the emission of pollutants into the atmosphere.
BRIEF DESCRIPTION OF DRAWINGS
In accordance with an exemplary embodiment, a method of substantially reducing the emission levels of any one of volatile organic compounds (VOC), particulates, entrained fly ash, and/or the level of oxygen oxides (NOx) during combustion of a gas can comprise supplying a combustion gas from below a reaction zone of a cyclone gasifying combustion burner. For example, the burner can comprise a burner chamber defined by an inner cylindrical wall having a substantially predetermined number of inclined air jet holes of substantially predetermined diameter disposed at substantially predetermined locations to create a cyclone air flow within the reaction zone when combustion air is drawn therethrough. The method further comprises drawing air into the burner chamber through the inclined air jet holes whereby to draw the combustion gases into the reaction zone to mix with the cyclone air flow thereby increasing the residency time of the combustion gases, turbulence, and mixing of oxygen with volatile gases for substantially complete combustion of gases in the reaction zone to substantially reduce the emission of pollutants into the atmosphere.
The exemplary embodiments of the present invention will be described in connection with the appended drawing figures in which like numerals denote like elements, and wherein:
FIG. 1 is a simplified side view, partly sectioned, of an exemplary pellet stove heating device and showing the airflow path through the cyclone combustion burner and through a heat exchanger chamber of the device and out through a flue conduit in accordance with an exemplary embodiment of the present invention;
FIG. 2 is a view similar to FIG. 1 but showing an airflow path of ambient air for heating the air around the pellet stove in accordance with an exemplary embodiment of the present invention;
FIG. 3 is a fragmented perspective view showing the construction of an inner cylindrical wall of a cyclone combustion burner and the disposition of exemplary air jet holes therein in accordance with an exemplary embodiment of the present invention;
FIG. 4 is a side view of an inner cylindrical wall illustrating a transverse angle of air jet holes with respect to the transverse axis of the inner cylindrical wall in accordance with an exemplary embodiment of the present invention;
FIG. 5 is a top view of an exemplary inner cylindrical wall illustrating a tangential angle of the air jet holes with respect to the curvature of the inner cylindrical wall in accordance with an exemplary embodiment of the present invention;
FIG. 6 is a schematic sectional view of a cyclone combustion burner illustrating a cyclone effect of the combustion zone and the separation of suspended particles therein and its precipitation into the fuel bed in accordance with an exemplary embodiment of the present invention;
FIG. 7 is a perspective view showing the construction of an exemplary support tray and ash discharge augers in accordance with an exemplary embodiment of the present invention;
FIG. 8 is an end view of an exemplary support tray showing the drive of the augers and its connection to a motor drive shaft in accordance with an exemplary embodiment of the present invention;
FIG. 9 is a plan view illustrating the construction of a user interface pad in accordance with an exemplary embodiment of the present invention;
FIG. 10 is a block diagram illustrating the construction of an exemplary controller and its associated component parts within a pellet burning stove constructed in accordance with an exemplary embodiment of the present invention;
FIG. 11 is a simplified schematic view wherein an exemplary cyclone combustion burner modified for coupling to other heating devices and wherein a cyclone chamber is mounted horizontally for coupling to existing air-to-air or liquid heat exchange systems, or to absorbtive chilling devices, thermoelectric, thermophoto-voltaic generators, and heat engines to provide thermal energy for their specific application in accordance with other exemplary embodiments of the present invention;
FIG. 12 is another exemplary embodiment of the application as shown in FIG. 11 but wherein the two cyclone gasifying combustion burners are separated from one another;
FIG. 13 is a schematic illustration, partly in section, illustrating a further application wherein the fuel bed is replaced by a gas burner which is supplied gas from another source in accordance with an exemplary embodiment of the present invention; and
DESCRIPTION OF EXEMPLARY EMBODIMENTS
FIG. 14 is a schematic illustration wherein an exemplary burner is incorporated in a hot air or hydronic hot water producing furnace, herein provided with a solid fuel supply system, in accordance with an exemplary embodiment of the present invention.
The present invention may be described herein in terms of various systems, devices, components and processing steps. It should be appreciated that such systems, devices, components and steps may be realized by any number of structural components configured to perform the specified functions. For example, the present invention may employ various electronic control devices, venting systems, flow controls and the like, which may carry out a variety of functions under the control of one or more control systems, microprocessors or other control devices. In addition, the present invention may be practiced in any number of burner contexts and the exemplary embodiments relating to a system and method for a high-efficiency cyclone gasifying combustion burner as described herein are merely a few of the exemplary applications for the invention. For example, the principles, features and methods discussed may be applied to any fuel burning application or process.
Referring now to FIGS. 1 and 2, in accordance with an exemplary embodiment, a solid fuel heating device 10 having a combustion chamber 12 in which an exemplary cyclone gasifying combustion burner 11 is configured to produce thermal energy is illustrated. The cyclone combustion burner 11 is disposed proximate to the bottom of a combustion chamber 12 and/or otherwise proximate to a fuel bed 25. In an exemplary embodiment, combustion air indicated by arrows 13 is drawn through a manifold chamber 14 defined between an outer steel cylindrical wall 15 and an inner steel cylindrical wall 16. The inner steel cylindrical wall 16 can be provided with angularly oriented or otherwise inclined air jet holes in various manners and configurations as will be described later. In the exemplary embodiment, air entering the manifold chamber is heated and drawn into a reaction zone of the burner 11 through the air jet holes and is convected in the direction of arrows 17 towards an exhaust flue 18, such as by a combusion fan 68, which can be located internally to heating device 10 or proximate the exterior of device 10. While drawing of air can provide improved operation, such air can also be suitably blown or otherwise forced into the reaction zone in other exemplary embodiments.
As shown in FIG. 2, an exemplary heat exchange arrangement in the form of hollow pipes 19 can be disposed towards the top end of the combustion chamber 12 and heated by the flow of hot air as indicated by arrow 17. Ambient air, as indicated by arrows 20, is circulated through the hollow pipes 19 by a fan 21 mounted in a side wall of the heating device, or any other convenient location such as proximate the hot air exhaust area, to exhaust heated air from the pipes 19 into the ambient air, as indicated by arrow 22, whereby to heat the surrounding area of the solid fuel heating device 10. Fan 21 can be configured in various locations for circulating ambient air through pipes 19, with such pipes 19 being arranged in various manners for discharging heat to the surrounding area.
The solid fuel heating device 10, as herein illustrated in the exemplary embodiment, comprises a biomass pellet, fuel and/or grain-fed space heating stove and can include a hopper 23 configured for storage of fuel sources, such as solid fuel pellets 24, for example. Hopper 23 can comprise various sizes, shapes and configurations for storage of fuel. In accordance with an exemplary embodiment, the feed pellets are fed into a fuel bed 25 of the cyclone burner 11 by an auger 26 feeding a chute 27. In the exemplary embodiment, the solid fuel, pellets 24 entering the cyclone burner 11 are projected into the fuel bed 25 by gravity and supported by a support mechanism in the form of a support tray 28 fixedly secured under the bottom open end of the inner cylindrical wall 16. An ash collecting tray 29 is removably secured under this support tray 28 and accessible through a door 30. It is pointed out that the solid fuel pellets and grains 24 could also be fed from the bottom or the side of the unit or any other configuration for providing fuel pellets and the like onto fuel bed 25. For example, rather than hopper 23 and/or auger 26, any other mechanisms or systems for conveying materials can be suitably implemented.
Referring now to FIGS. 3 to 6, in accordance with exemplary embodiments, an inner cylindrical wall 16 of the cyclone combustion burner 11 is illustrated. As hereinshown, an exemplary inner cylindrical wall 16 is provided with a series of angulated air jet holes 31 of substantially predetermined diameter and disposed at substantially predetermined locations therein to create a uni-directional cyclone to create a reaction zone 33 within the combustion chamber. For example, an exemplary cyclone-like effect is illustrated by reference numeral 32 in FIG. 6. This cyclone 32 is oriented in the reaction zone 33 in an area above the fuel bed 25 and extending close to the top open end 34 of the inner cylindrical wall 16. By angulating the air jet holes, the cyclone path can be oriented to achieve optimum separation of suspended particles to facilitate sufficient retention time to burn the combustion gases. This reaction zone 33, defined by the inner cylindrical wall 16, can be of a substantially predetermined length depending on the size of the cyclone combustion burner 11, among other parameters and criteria.
As shown in FIG. 3, in accordance with an exemplary embodiment, the air jet holes 31 are disposed in groups on at least two inclined axes 35, such as, for example, the three groups of these holes shown in FIG. 3; however, this disposing of groups may vary depending on the diameter of the inner cylindrical wall. Moreover, while at least two inclined axes 35 are desirable, using a single inclined axis 35 can also be provided in other exemplary embodiments.
In accordance with the exemplary embodiment of FIG. 3, each group of the air jet holes 31 comprise four holes, but again this may vary depending on the size of the cyclone burner for applications at the commercial and industrial scale. Also, the holes can be offset from one another and not necessarily be equidistantly spaced apart provided that they create a uni-directional cyclone which achieves the desired result of increasing at least one of the residency time, turbulence, and/or the mixing of oxygen and volatile gases to substantially combust the gases drawn into the reaction zone 33. In addition, the configuration of air jet holes 31 can also cause suspended particles to gravitate to the fuel bed. It should be noted that the relative sizes, number, spacing and linearity of the holes 31 within an axis 35 can suitably configured in various manners to facilitate the cyclone effect. Therefore, although FIG. 3 shows an exemplary pattern for the angulated air jet holes, it is conceivable that other suitable patterns may produce a similarly satisfactory result.
As shown in FIGS. 4 and 5, in accordance with an exemplary embodiment, each of air jet holes 31 can be disposed at a tangential angle 36 (e.g., see FIG. 5) with respect to the curvature of the inner cylindrical wall 16. Holes 31 can also be oriented at a transverse angle 37 (e.g., see FIG. 4) extending in the direction of the open top end 34. While in accordance with the exemplary embodiments each of holes 31 may be configured with substantially the same tangential angle 36 and/or transverse angle 37, in accordance with other exemplary embodiments, one or more of holes 31 can also be configured with different tangential angles 36 and/or transverse angles 37. In accordance with an exemplary embodiment, the negative pressure within the combustion chamber 12 of the solid fuel heating device 10 draws the combustion air through the manifold 14 and through the one or more angled air jet holes 31 at a low pressure wherein the air/fuel ratio is from about 6:1 to 10:1, or other like air/fuel ratio sufficient to create a high velocity cyclone within the reaction zone 33 to provide one or more of the intended functions.
In accordance with an exemplary embodiment, the tangential angle 36 is in the range of between approximately 15° to 89° with respect to the curvature of the inner cylindrical wall 16. This angle is calculated from a tangent 38 of the curved outer surface 39 at the point of entry of the air jet hole 31′ into the inner cylindrical wall 16, as illustrated in FIG. 5. For example, for a 4 inch diameter inner cylindrical housing, this angle can be between approximately 55° and 65°, e.g, approximately 61°. The transverse angle 37 is in the range of approximately 1° to 15° or more with respect to the transverse axis 40 as illustrated in FIG. 4, such as at an angle of approximately 13°. However, holes 31 can be configured at any tangential and/or transverse angle configured to generate air flow configured to create a cyclone-like effect and/or suspend particles.
The angular orientation of these air jet holes 31 creates the cyclone combustion air flow within the reaction zone 33 inside the inner cylindrical wall and causes the combustion gases released from the fuel bed to follow a cyclone path with the combustion air whereby the residency time of these combustion gases is increased to achieve substantially total combustion thereof. This increase in residency time within the combustion zone 33 can also cause the suspended particles, herein designated by reference numeral 41, to be projected against the inner surface 42 of the inner cylindrical wall 16 by the centrifugal force of the cyclone and agglomerate with other particles 41 to increase their molecular weight and thereby gravitate to the fuel bed 25. For example, particles at the center of the cyclone 32, herein illustrated by reference numeral 41′, can also precipitate towards the fuel bed since the center of the cyclone can comprise an area of entrapment. These particles can collect at the bottom of the fuel bed in the support tray 28 below the combustion zone 251 of the fuel bed 25. Accordingly, this cyclone action in the reaction zone results in a substantial total reduction of the emission of pollutants into the atmosphere.
As shown in FIGS. 3 and 4, one or more other air jet holes, such as holes 45, can be provided in the inner cylindrical housing whereby to admit combustion air into the fuel bed 25. Such holes 45 may have minimal to no inclination as they feed combustion air to the bed. The number of these holes will depend on the desired air fuel ratio and as above-indicated, this fuel ratio is about 6:1 to 10:1, such as approximately 8:1, whereas with conventional pellet stoves, the fuel is burned at a fairly high ratio of 35:1 or more.
A problem with burning pellet fuel, such as corn, wood pellets, etc., at high temperature is that the mineral elements in these pellets fuse, deform to a semi-liquid state and crystallize to form a slag like clinker deposit within or adjacent to the fuel bed combustion area. Usually, these conventional wood pellet stoves operate at an air to fuel ratio of at least 35:1 or more, thus the air blowers need to operate at a high rate of speed. This high rate of speed causes ash to fly out of the burner, thereby affecting the operation of the fans and motors and entraining in the atmosphere fly ash, volatiles, particulates and substantially increased levels of NOX from excess combustion air. With burner 11, it can be said that the system is an air-starved system and accordingly, burner 11 burns the solid fuel at a lower temperature, substantially below the fusion point of the inorganic elements which may be present and which make up the ash which is also metered out of the fuel bed area and into an ash holding area. Solid fuels have different mineral contents and when properly controlled and subjected to a balanced air to fuel ratio and ash management system, which substantially influence the fuel bed characteristics and reaction zone cyclone, and it has been found that substantially no clinkers are formed.
It is pointed out that the inner diameter of the inner cylindrical wall 16 may vary within a minimum of approximately 1 inch to 48 inches or more depending on the application of the burner be it residential, commercial or industrial. The height of the inner and outer cylindrical walls can also vary between a minimum of approximately 2 inches to 48 inches or more. The air jet hole diameter may also vary from approximately 1/16 of an inch to 6 inches or more. The air jet holes 31 can also spaced apart at a predetermined distance from one another, depending on various design criteria.
As the solid particles and ash collect within the bottom end of the fuel bed 25 below the combustion zone 25′ and into the support tray 28, such particles and ash can be automatically removed from the bottom of the fuel bed as will now be described with reference to exemplary embodiments illustrated in FIGS. 6 to 8. For example, in accordance with an exemplary embodiment, a support tray 28 can comprise an elongated shallow rectangular housing 50 in which there is disposed one or more auger screws 51, such as the three screws 51 illustrated in FIG. 7, that are coupled to a drive shaft 52 through inter-engaging gears 53. A drive device, herein an electric motor 54, connects to the drive shaft 52 and rotates the one or more auger screws at a controlled speed rate. The rate of speed of the motor 54 is determined by a controller 60. The housing 50 has a top wall 54 with an opening 55 which is disposed under the inner cylindrical wall 16 and this open area 55 defines the fuel bed. The combustion zone 25′ of the fuel bed 25 is an area above this fuel bed once the fuel bed has been lit and the combustible material has established the combustion zone 25′. By rotating the auger screws 51 at a predetermined speed, it creates a “bubbling effect” in the fuel bed improving combustion of the solid fuel particles and causing the ashes produced to percolate, to the bottom of the fuel bed area, wherein the auger screws displace the ashes towards an open bottom end section of the housing which constitutes an ash discharge section 56 where ashes are discharged within an ash collecting tray 29 positioned thereunder, as illustrated by reference numeral 57. Although housing 50 can comprise auger screws 51 configured to induce a “bubbling effect”, any other mechanism or devices, such as vibrating screens or conveyors, can also be suitably incorporated. Moreover, rather than a housing 50 and screw 51 configuration, support tray can also include a grating configuration for holding fuel within fuel bed 25.
Referring now to FIGS. 9 and 10 in accordance with exemplary embodiments, there will be described the operation of an exemplary controller 60. This controller 60 is connected to a user interface pad 61 that is provided with an internal memory 62 (see FIG. 10), and which keypad permits a user to control the operation of the solid fuel biomass pellet heating device 10, such as illustrated in FIGS. 1 and 2. The main controller 60 controls the motor 54 and the fans and inputs operating parameters by sensors, as will be described later. To start the operation of a biomass pellet device 10, as illustrated in FIGS. 1 and 2, a measured quantity of pellets 24 are placed in the fuel bed 28 along with a starter fluid, and this is ignited by the user and the door of the biomass burner device is closed, or the pellets are automatically fed to the burner and ignited by an ignition device, to create an initial fuel bed. The user then selects a desired mode of operation of the device 10 by inputting desired parameters into the controller by the use of the interface pad 61. The interface pad 61 can also be provided with pressure sensitive switches 62 whereby to set the fuel feed and speed of the exhaust fan and consequently the quantity of air admitted into the combustion zone of the cyclone burner, whereby to increase or decrease the temperature in the combustion chamber 12 and consequently the temperature of the heated air released by the biomass pellet device through the heat exchanger located above the flame which is also regulated by a separate fan. All of the operating parameters step up or down, to maintain optimum performance levels, according to the desired heat performance required of the device. Additionally the entire system can operate from a remote thermostat to regulate all of these operating parameters according to what the thermostat is set to. Ash control switches 63 can also be provided to fine-tune the ash evacuation rate and this is inputted into the controller which regulates the speed of the motor which drives the auger screws. Output temperature control switches 64 are also provided to set a desired BTU output of the pellet stove. Through the software of the controller, the type of fuel and substantially ideal operating conditions of the device are regulated and maintained.
As shown in FIG. 10, an exemplary controller 60 is provided with input signals from a low temperature sensor 65 that senses the temperature of the heating device 10 and it is conveniently located on a wall of the heating device. The controller 60 also monitors input signals from an operational thermo sensor 66 which indicates that a flame is present in the burner chamber. A high temperature sensor 67 can also be conveniently located on the outside, back wall of the combustion chamber 12 to sense the temperature thereof. For example, if the sensor 67 detects a predetermined high temperature signal, the controller 60 shuts off the fuel feed auger that delivers the biomass fuel pellets to the fuel burner fuel bed, thus commencing an orderly automatic shutdown of the device 10. Accordingly, the controller modulates the operation of the system to maintain a desired temperature output.
As also shown in FIG. 10, the controller controls the speed of the combustion fan 68, which can be located within heating device 10 as illustrated in FIG. 1, or otherwise outside or otherwise in flow communication to facilitate intake and exhaust air. Controller 60 can also control the speed of the convection fan 21 that is used to force the air through the heat exchangers 19. As mentioned hereinabove, controller 60 can also control the ash auger motor 54 that evacuates the ashes depending on the operating parameters of the system and high or low ash fuel type. A power supply 69 provides the 12 VDC power for the controller and interface.
In accordance with an exemplary embodiment, the user interface pad 61 is also provided with switches 70 to condition the controller to operate within a stored programmed mode of operation depending on the type of fuel being fed to the burner. A red stop switch 71 is provided to shut down the operation of the heating device. A manual feed switch 72 is also provided to feed fuel to the combustion bed during the priming cycle at start-up. Additionally this can be regulated automatically from a thermostat prior to automatic ignition of the fuel present in the burner.
Digital numeric display windows display a number indicative of the set parameters inputted by the user person by the switches 62, 63 and 64. These display windows will display numbers such as 1 to 5 with the highest number indicating the highest feed rate or fan speed. When the operator selects a desired operation of the stove, normally a setting from 1 to 5, each of these settings is associated with a program fuel feed rate with corresponding air feed rates for optimum efficiency in the operation of the unit. As the unit operates the controller senses the operating parameters thereof and automatically adjusts the elements that it controls such as fan speed and ash evacuation rates, and the convection fan 21 is adjusted so that the output air temperature of the stove is substantially the one selected by the user. The sensors also provide a safety system for the heating device by monitoring the temperature of the combustion chamber and the exhaust temperature. The controller and/or sensors can also be configured to detect if there is no longer a fire in the burner and will turn the heating device off once the unit has cooled down to a pre-set temperature.
Although the application of the cyclone burner 11 is herein described with respect to an application of a wood and biomass pellet and whole grain burning stove, it is pointed out that this burner can be coupled to existing air-to-air and liquid heat exchange systems to provide thermal energy for their respective applications and heat exchanger surfaces or their combustion chambers. As example of applications, the cyclone burner can be coupled to boilers or hot air furnaces and can be mounted at any suitable angle as is required, examples include vertically or horizontally, as will be described later. As previously described, the size of the cyclone burner can vary greatly and its dimensions can be substantially increased for residential, commercial, and industrial thermal heat transfer applications. It is envisaged that such a burner can replace existing fuel burners such as oil or gas burners, and this technology can be scaled up from current levels, for biomass pellet and whole grain applications, to over 60 million BTUs or more depending on the required application. In such larger applications, and as previously described, more air jets can be provided to allow oxygen to catalyze with the volatile gases which are entering the burner from the gasification chamber.
It is also pointed out that in the pellet stove application because the system is operating at a low air-to-fuel ratio, most ash particles that leave the cyclone burner will not be drawn out or up into the exhaust or flue but will precipitate within the lower part of the device where the ash collecting compartment is located. Accordingly, there are virtually no volatized organic compounds emitted into the atmosphere with the exhaust and complete combustion of the gases therefore takes place in the cyclone burner and complete containment of the particulate is substantially accomplished.
As shown in FIG. 6, a deflector bracket 80 may be secured to the cyclone burner and project within the reaction zone 33. This deflector 80 can be formed by a strip of stainless steel or other suitable steel material and provided with a hook end 81 to hook onto the top edge 82 of the burner, or any other configuration for connecting a deflector to a burner wall. The deflector projects inside the inner wall 42 a predetermined distance and is sloped in a bottom end section to form a deflecting end 83, whereby fuel pellets or grains, such as shelled corn, when projected into the burner by the chute 27, will be deflected into the fuel bed to prevent such fuel from forming an uneven fuel bed. The deflector is secured in alignment with the chute 27. This deflection is derived and positioned to cause minimum interference with the cyclone 32. It is also conceivable that a deflector could also be coupled to the feeding chute, or any other like manners for deflecting fuel into the bed; deflector 80 as shown herein is simple to construct and effective, but can certainly be configured in various other sizes, shapes, angles and configurations.
- TEST RESULTS
The following is a summary of test results obtained on a pellet stove equipped with the “close coupled gasification” cyclone burner of the present invention and tested by the McGill University Energy and Environmental Research Laboratory.
- MAIN OBSERVATIONS
Three different biomass fuels were used for testing: corn, bark, and wood pellets. Each biofuel was tested four times in order to verify data repeatability at two feed rates of 2.5 lbs/hr and 3.0 lbs/hr. Tests were performed according to ASTM and Environment Canada/Quebec testing protocols (e.g., standards concerning the following articles were applied: B.315, articles 8, 10, 11, 12, 24, 27, 45, 65, 67). Collection of data was conducted after achieving a steady-state. Gas concentration measurements (VOC, CO, CO2, NOx) were taken at a rate of 1 ft3/min. In addition, samples of solid particulates in the exhaust gas and residual ashes were collected to determine mass concentration, chemical composition and morphology.
- Negligible amount of solid particulates were found in the exhaust gas.
- Less than detectable amount of VOCs were found.
- NOx concentrations were below acceptable emission standards.
- In most cases CO concentration was within a range of 11-25 ppm/hr.
- Exhaust temperature changed between 130 and 150° C.
- Corn yielded lowest CO emissions
- The following hierarchy of the biomass fuel was established at lower feeding rate of 2.5 lbs/hr: bark>wood>corn.
- The following hierarchy of the biomass fuel was established at a higher feeding rate of 3.0 lbs/hr: corn>bark>wood.
It can therefore be concluded that with the construction of a cyclone burner having air jet holes oriented to create a particle suspension, reaction zone in the burner chamber to increase the residency time of combustion gases and particulate material, substantially all of the combustion gases are burned and substantially all the particulate material precipitates into an ash collecting tray. The burner is also operated at low pressure (air tight sealed) with low excess combustion air which lowers the fuel bed temperature (air starved) which substantially prevents the fusion of inorganic elements within the fuel bed and the formation of slag deposits. Independent testing has shown that the emission levels of volatile organic compounds (VOC), particulates and fly ash, and the level of nitrogen oxides (Nox), is substantially reduced below acceptable regulated levels.
Referring now to FIG. 11, in accordance with other exemplary embodiments, there is shown a modification of the cyclone gasifying combustion burner for different applications whereby the burner can be coupled to boilers or hot air furnaces and can be mounted either vertically or horizontally or angularly. As shown in FIG. 11, the burner 11 can be constructed as previously described with the exception that the fuel bed 25 is not fed from above but from a supply conduit 80 also provided with an auger screw 81 to transfer the solid biomass fuel pellets 24 from a hopper 82. Various other conventional configurations and methods for feeding fuel bed 25 can also be implemented in various other exemplary embodiments. The supply conduit 80 has an open end 83 formed in the inner cylindrical wall 16 of the combustion burner housing 11, herein mounted vertically. The opening 83 is positioned above the fuel bed 25 and below the series of air jets 31.
The open top end 84 of the vertical combustion burner housing 11 is coupled to a further combustion burner housing 11′ mounted horizontally. The further combustion housing also has an inner cylindrical wall 16′ provided with air jet holes 31′ therein and its manifold 14′ is connected to a fan 85 to provide air pressure to create the cyclone within the combustion burner housing 11′. As hereinshown each of the manifold chambers 14 and 14′ are connected and coupled together whereby the fan 85 is sufficient to draw air through the air jet holes 31 of the vertical combustion burner housing 11. However, a further fan may be connected to the manifold chamber 14 which may be independent from the manifold chamber 14′ and this further fan is illustrated schematically by reference numeral 86. Although not shown, the ash collector as described hereinabove with reference to FIGS. 7 and 8 would be connected to the bottom end of the vertical combustion burner 15.
As hereinshown, the further combustion burner 11′ has a closed end wall 87 and an opposed open end 88 for the flame 89 to exit and provide a source of thermal energy. The further combustion burner housing 11′ is mounted substantially transversely to the vertical burner and the inner cylindrical walls about these burners are connected together in communication to form a continuous internal combustion chamber. An igniter device 90 may also be provided to start a flame within the horizontal combustion burner housing 11′. Of course, although not shown, the fuel bed 25 can be ignited as previously described. Because the hopper 82 is located exteriorly of a boiler or furnace, to which this burner is coupled, the hopper can be continuously supplied with biomass fuel pellets to provide continuous operation, if necessary to do so.
FIG. 12 shows another exemplary embodiment similar to that illustrated in FIG. 11 but wherein the combustion burner housing 11′ is not directly coupled to the vertical combustion burner housing 11. As hereinshown, the horizontal combustion burner housing 11′ has an open rear end 91 which is coupled by conduit 92 to a gas collecting chamber 93 and into which are fed combustion gases from the fuel bed 25 flowing out of inner cylindrical wall 16 through a further conduit 94 and from the top end 95 thereof through a feed auger screw 96 which connects to the bottom of the collecting chamber 93. Pellets are fed from a hopper 97 and a feed auger 98 into the bottom of the gas collecting housing 93 onto the auger screw 96 where they are transported and released into the fuel bed 25 is hereinshown. This hot combustible gas in the collecting chamber maintains a flame extending into the conduit 92 and into the inner cylindrical chamber of the combustion housing 11′ where it is mixed with additional air within the cyclone therein. A blower 99 is provided to create a cyclonic combustion air flow within the horizontal combustion burner housing 11′. A further burner 100 is also connected to the manifold chamber 14 of the vertical combustion burner housing 11. The ash collecting tray 50 is also connected to the bottom of the vertical chamber if deemed necessary but the blower 99 may be sufficient to create a negative pressure within the vertical combustion burner housing 11 to create the cyclonic air flow path within its inner cylindrical wall.
As previously described, the disposition of the air jet holes within the inner cylindrical wall can suitably create a cyclone-like flow in a reaction zone in the inner cylindrical wall and it is also conceivable that combustion gases may be applied directly within the inner cylindrical wall below the cyclone path to mix therewith, whereby to increase the residency time of the gas for substantially complete combustion thereof. Accordingly, FIG. 13 shows another exemplary embodiment where the fuel bed is replaced by a combustion gas supply 101 connected to an injector 102 secured to the burner housing 11 adjacent a bottom end thereof. The bottom end of the burner is hereinshown having a bottom end 103 but if the gas being burned is one that contains suspended particles which would collect at the bottom end of the burner 11 then a collecting tray such as the tray 50 could be mounted at this bottom end.
In this exemplary embodiment, a regulator device 104 is mounted in the supply line 105 and may be controlled by a controller such as the one described hereinabove. An igniter 106 provides for the ignition of the injector 107. A fan 108 provides air under pressure to the manifold 14 to create the cyclone 32.
Referring now to FIG. 14, there is shown a further embodiment wherein an exemplary high efficiency cyclone gasifying combustion burner is incorporated into a hot air furnace 120. For example, a large hopper structure 121 is mounted next to the furnace 120 and supplies solid biomass fuel pellets or other granular particles 122 to the combustion burner 11 by means of a chute, not shown herein but similar to chute 27 as illustrated in FIG. 2. The supply of pellets to the chute is provided via a screw conveyor 123, the speed of which is controlled by a controller modulating the speed of the motor 124 which drives the auger screw, not shown, within the screw conveyor 123. The controller is coupled to a thermostat whereby to control the burner 11 within the furnace 120 in a manner as previously described. It is also pointed out that the furnace 120 may be an industrial furnace of large dimension. Also, the solid combustion fuel may be coal which is fed to the burner 11 from the hopper 121.
As described above, an exemplary high efficiency cyclone gasifying combustion burner can be incorporated with several devices requiring a thermal energy source to heat an area as in space and central heating, such devices may have applications for processing materials, for cooling by an absorptive chilling device to reduce the temperature of an area, for processing materials, to produce electricity through the thermal expansion of gases which produce mechanical force, as in steam turbines, and as a source of thermal energy in thermoelectric and thermo photovoltaic devices for the generation of electricity, and/or as a thermal heat source for a heat engine.
The present invention has been described above with reference to various exemplary embodiments. However, those skilled in the art will recognize that changes and modifications may be made to the exemplary embodiments without departing from the scope of the present invention. For example, the various operational steps, as well as the components for carrying out the operational steps, may be implemented in alternate ways depending upon the particular application or in consideration of any number of cost functions associated with the operation of the system, e.g., various of the component and methodologies and/or steps may be deleted, modified, or combined with other components, methodologies and/or steps. For example, various of the systems and devices within controller 60, can suitably be modified, removed or replaced. These and other changes or modifications are intended to be included within the scope of the present invention, as set forth in the following claims.