Abstract:
The present invention provides a burner system which uses waste fuels, especially waste plastic fuels. Burner size is minimized by having multiple combustion chambers concentrically located around a rotating screw conveyor. Heat efficiency is improved by having air passages disposed around the combustion chambers, thus preheating air for the combustion prior to its delivery to the combustion chambers, while simultaneously thermally insulating the combustion chambers against the environment. Waste fuel is transported from a fuel hopper to the combustion chambers by a rotating screw conveyor having the spiraling auger blades. Speed of screw conveyor rotation controls the consumption of waste fuel and, thus, the amount of thermal energy generated in the burner. The burner system includes an intelligent control system for controlling operation of the burner system, so that the burner system performs at optimum efficiency, safely and with minimum operator intervention.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation-in-part of application Ser. No. 12/367,462, filed Feb. 6, 2009, now U.S. Pat. No. 8,240,258. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to fuel burners, especially burners for waste fuel, such as waste plastic. Considerable research effort has been invested toward finding methods of converting waste plastics to usable fuels as a means of plastic recycling. Waste plastics are burned to generate heat, which may be used for water heating, industrial heat, or other purposes. Important considerations related to waste plastics as fuel sources are: maximizing energy by burning the solid fuel completely, minimizing heat losses to the environment, compactness of the burner, and minimizing soot and harmful gases emission. 
     Some existing waste fuel burners have multiple combustion chambers, which improve the completeness of the burning, but the combustion chambers are arranged one after another, therefore resulting in a long burner and significant heat losses due to the exposed outer surfaces. 
     Other existing waste fuel burners accumulate ash, soil, and sand during the burning process. These burners have to be periodically stopped for the removal of accumulated non-combustible material. 
     There is therefore a need for solid waste burners that minimize burner size and heat losses, while maximizing the completeness of fuel burning. The burner should also minimize soot and harmful gases emission, while reducing the accumulation of the non-combustible material inside the burner. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention relates generally to burners that use solid fuels, especially waste plastic fuels. Burner size is minimized by having multiple combustion chambers arranged concentrically around a rotating screw conveyor. Heat efficiency is improved by having an air chamber disposed around the combustion chambers, because the air for the combustion is preheated prior to being delivered to the combustion chambers, while the air chamber at the same time thermally insulates the combustion chambers against the environment. Waste plastic is transported from a fuel hopper to the combustion chambers by a rotating screw conveyor having spiraling auger blades. Speed of the screw conveyor rotation controls the consumption of waste plastic and, hence, the amount of thermal energy generated in the burner. Parts of the combustion chambers can also rotate to auger waste plastic for better oxidation, therefore enhancing the combustion process. 
     In one embodiment, a burner system for waste fuel, comprises 1) a combustion unit having a plurality of combustion chambers arranged concentrically around a single rotatable feed mechanism, wherein the individual ones of said combustion chambers are in fluid communication with one another; 2) an air chamber surrounding the plurality of combustion chambers facilitates preheating combustion air delivered to the plurality of combustion chambers and further facilitates insulting said plurality of combustion chambers against thermal losses to the environment; and 3) a discharge chamber in fluid communication with the plurality of combustion chambers and a boiler for heating water and/or oil to facilitate an energy conversion process. 
     In one aspect of the above described embodiment, the single rotatable feed mechanism is a variable speed conveyor screw for directing the waste fuels along a fuel consumption path through the individual ones of said plurality of combustion chambers; wherein the plurality of combustion chambers include a first combustion chamber, a second combustion chamber, and a third combustion chamber; wherein the plurality of combustion chambers are arranged radially one after another so that the combustion unit has an overall axial length in the direction of said variable speed conveyor screw; and wherein said variable speed conveyor screw has a longitudinal length that is about equal to a longitudinal length of an individual one the combustion chambers in the plurality of combustion chambers. 
     In another embodiment of the present invention, a burner system for waste fuels comprises 1) a rotatable feed mechanism for directing the waste fuel to a combustion unit; the combustion unit having first, second and third combustion chambers in fluid communication with one another and substantially coaxially arranged with respect to the rotatable feed mechanism; wherein the first combustion chamber being arranged to receive the waste fuel from the feed mechanism; an outlet for discharging exhaust materials from the third combustion chamber; wherein the combustion chambers have approximately like axial extents and wherein the first through third combustion chambers are arranged radially one after the other so that the combustion unit has an overall axial length in the direction of the feed conveyor approximately equal to the length of an individual combustion chamber. 
     In one aspect of this another embodiment, the burner system includes a combustion air inlet orifice for each combustion chamber arranged upstream of the respective combustion chambers. 
     In another aspect of the present invention, each combustion chamber is radially spaced apart from the other combustion chambers by inner and outer tubular walls. 
     In still yet another aspect of the present invention each combustion chamber is defined in part by a tubular wall that is common to two combustion chambers. 
     In yet another aspect of the present invention, the burner system includes radially oriented end walls arranged between adjacent combustion chambers and spaced apart from respective ends of the tubular walls for generating an S-shaped flow of combustible materials, combustion air, smoke and particulates from the first through the third combustion chambers. 
     In another aspect of the present invention, at least one of the end walls is rotatably fixed to the feed mechanism for rotation with the feed mechanism. 
     In yet another aspect of the present invention the burner system includes auger blades fixed to the tubular walls for rotation therewith for advancing the combustible materials and products of combustion through the combustion unit. 
     In yet another aspect of the present invention the burner system includes auger blades fixed to the tubular walls for rotation therewith for advancing the combustible materials and products of combustion through the combustion unit. 
     In another aspect of the present invention the burner system includes orifices located in the housing and communicating with the air flow passage of the housing for directing combustion air from the air flow passage in the housing to upstream ends of the combustion chambers. 
     In one aspect of the present invention, the feed mechanism of the burner system includes a screw conveyor having a hollow interior extending axially along the conveyor and into the combustion unit for directing combustion air to the combustion unit, and one or more orifices disposed radially from the hollow interior and axially located on the screw conveyor so that the orifices discharge air to at least one combustion chamber. 
     In yet another aspect of the present invention, the burner system includes discharge blades attached with the feed mechanism for swirling combustion gases and flushing non-combustible material out of the burner system. 
     In still yet another aspect of the present invention, the burner system includes an auxiliary burner configured to start burning of the waste fuel. 
     In yet another aspect of the present invention, the auxiliary burner of the burner system is selected from a group consisting of an oil burner, a gas burner, a solid fuel burner, an electrical burner and combinations thereof. 
     In another aspect of the present invention, the burner system includes a fuel hopper configured to provide waste fuel to the feed mechanism. 
     In one aspect of the present invention, the fuel hopper comprises a rotator configured to rotate substantially inside a rotator housing, the rotator further comprising a plurality of rotator protrusions inclined opposite from the direction of the rotator&#39;s rotation, thus reducing the incidence of waste fuel sticking to a rotator housing as waste fuel approaches the feed mechanism. 
     In yet another aspect of the present invention, the rotator protrusions of the burner system have substantially triangular shape. 
     In still yet another aspect of the present invention, the rotator protrusions of the burner system have substantially semicircular shape. 
     In yet another embodiment of the present invention, a burner system for consumption of waste fuel, comprises 1) a screw conveyor configured to revolve around its longitudinal axis, the screw conveyor having a longitudinal hollow interior for air distribution and a plurality of radially disposed air intake orifices connecting the hollow interior to combustion chambers, thus providing air for combustion process; 2) one or more auger blades disposed substantially spirally around a portion of length of the screw conveyor, the auger blades being configured to move waste fuel along the longitudinal axis as the screw conveyor revolves; 3) a first combustion chamber disposed substantially centrally around the screw conveyor and around at least one orifice connecting the longitudinal hollow interior with the outer surface of the screw conveyor; 4) a second combustion chamber disposed substantially concentrically around the first combustion chamber and configured to receive burning waste fuel from the first combustion chamber, the second combustion chamber being in fluid communication with at least one air intake orifice disposed on a housing and configured to provide air for the waste fuel burning; and 5) a third combustion chamber disposed substantially concentrically around the second combustion chamber and configured to receive waste plastic from the second combustion chamber, the third combustion chamber being in fluid communication with at least one air intake orifice disposed on the housing and configured to provide air for the waste fuel burning. 
     In one aspect of this yet another embodiment of the present invention, the burner system includes discharge blades attached with a feed mechanism for swirling combustion gases and flushing non-combustible material out of the burner system. 
     In another aspect of the present invention, the burner system includes an air blower configured to provide air for waste plastic burning. 
     In yet another aspect of the present invention, the burner system includes an auxiliary burner configured to start burning of waste plastic. 
     In still yet another aspect of the present invention, the burner system includes another auxiliary burner configured to start burning of waste plastic. 
     In yet another aspect of the present invention, the burner system includes a motor coupled to the screw conveyor for revolving the screw conveyor. 
     In another aspect of the present invention, the motor of the burner system is a constant speed motor. 
     In one aspect of the present invention, the constant speed motor of the burner system includes a chain drive engaging the screw conveyor. 
     In another aspect of the present invention, the motor of the burner system is a variable speed motor. 
     In yet another aspect of the present invention, the variable speed motor of the burner system is a direct drive motor. 
     In still yet another aspect of the present invention, the first combustion chamber of the burner system is adapted to increase air flow for combustion of substantially all the burning waste fuel. 
     In yet another aspect of the present invention, the burner system includes an intelligent control system for controlling operation of at least the screw conveyor, the one or more auger blades, the first combustion chamber, the second combustion chamber, and the third combustion chamber. 
     In another aspect of the present invention, the intelligent control system of the burner system includes an emergency stop circuit for stopping operation of the burner system. 
     In one aspect of the present invention, the burner system includes a boiler coupled to the third combustion chamber for heating water and/or oil in the boiler. 
     In still yet another embodiment of the present invention, a burner system for consuming waste fuel, comprises 1) a combustion unit having at least three combustion chambers arranged concentrically around a variable speed conveyor screw for directing the waste fuel along a fuel consumption path through said at least three combustion chambers; 2) an air chamber surrounding said at least three combustion chambers to facilitate preheating combustion air delivered to said at least three combustion chambers and to facilitate insulting said at least three combustion chambers against thermal losses to the environment; a boiler in fluid communication with said at least three combustion chambers for heating water and/or oil to facilitate an energy conversion process; and 3) an intelligent control system for controlling operation of the system, said control system for further helping to control operating parameters of said boiler including pressure, temperature, and water and/or oil level and for activating an emergency stop alarm if any one of the operating parameters of said boiler is outside a predetermined range of operating valves. 
     In another aspect of present invention, the control system includes sensors for helping to control the operation of a variable frequency drive motor coupled to an auger rotatably feeding a waste fuel into said combustion unit, the auger being rotated at a non-operational speed, so that the waste fuel is delivered at a lean rate; and for facilitating the operation of the variable frequency drive motor for feeding the waste fuel into said combustion unit at an operational speed, so that the waste fuel is delivered at a run rate. 
     In yet another aspect of the present invention, control system further includes sensors for facilitating the automatic operation of said combustion unit for a predetermined demonstration time to demonstrate operation of the combustion unit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be more fully understood by reference to the detailed description in conjunction with the following figures, wherein: 
         FIGS. 1A and 1B  show partial sectional plan and right views, respectively, of a first embodiment of the invention; 
         FIG. 2  shows a side sectional view of a second embodiment of the invention; 
         FIG. 3  shows a detail sectional view a fuel supply unit; 
         FIG. 4  shows a side sectional view of a third embodiment of the invention; 
         FIG. 5  shows a plan view of the third embodiment of the invention; 
         FIG. 5A  shows a side sectional view of a fourth embodiment of the invention; 
         FIG. 5B  is a view along section line  5 B- 5 B of  FIG. 5A ; 
         FIG. 6  shows a flow chart of an intelligent control system belonging to the third and fourth embodiments of the invention; 
         FIG. 7  is a continuation of the flow chart of  FIG. 6 ; 
         FIG. 8  is a further continuation of the flow charts of  FIGS. 6-7 ; and 
         FIG. 9  illustrates a burner coupled to a vertical boiler, which burner boiler system is constructed in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIGS. 1A ,  1 B, and  2 , a burner system  1  for burning waste material, particularly waste plastic, has a feed mechanism  2  defined by an elongated transport or conveyor screw  4  provided with a central lumen  6  extending substantially through the entire length of the conveyor screw  4 . The conveyor screw  4  is situated below an intake opening  8  of the feed mechanism and extends forwardly (to the right as seen in  FIGS. 1A and 2 ) to a combustion unit  10 . The combustion unit  10  that is defined by a plurality of concentric combustion chambers, indicated generally at  11 , include, for example, a first combustion chamber  12 , a second combustion chamber  14 , and a third combustion chamber  16 . The plurality of combustion chambers  11  is coaxially disposed about conveyor screw  4  at increasing radial distances from the conveyor screw  4 . The downstream end of the third combustion chamber  16  is in fluid communication with a discharge section  18  of the burner system  1 , which receives smoke and incombustible particulates from the plurality of combustion chambers  11  and discharges these materials from the burner system  1  into the atmosphere, via a nose cone  30 ′. A double walled outer housing  20  defines an air passage  48 , which surrounds a portion of the conveyor screw  4 , the combustion unit  10  and the discharge section  18 . 
     Feed mechanism  2  of burner system  1  includes the earlier mentioned conveyor screw  4  with spiral windings  5  and a generally tubular, double walled conveyer housing  22 , which partially encloses the rotating screw  4 . A motor  24  drives a shaft  28  of the screw  4  via a chain  26 . Other suitable drives such as a gear drive, a belt drive or the like can be employed, so there is no intention of limiting the disclosed invention to only a chain driven shaft. 
     Intake opening  8  is arranged proximate to an upstream end of the screw  4  (on the left as seen in  FIG. 2 ) through which plastic waste or other material is entrained for conveyance in a downstream direction (to the right as seen in  FIG. 2 ) towards combustion unit  10 . The downstream end of shaft  28  of screw  4  is free of spiral windings and extends into the combustion unit  10  where it is suitably journaled. 
     Combustion unit  10 , as already described, is formed by the three concentric combustion chambers  12 ,  14 ,  16 , each of which has inner and outer radial boundaries that are concentric with the axis of shaft  28  and interconnected by radially extending walls. In particular, the inside radial boundary of first combustion chamber  12  is defined by the area bounded by the outer surface circumference area of conveyor shaft  28 . The outside radial boundary of first combustion chamber  12  is defined by an interior surface area of an extension  30  of the tubular housing portion  20  surrounding the conveyor screw  4 . The inside radial boundary of second combustion chamber  14  is defined by the exterior surface area of the extension  30 . The outside boundary of the second chamber  14  is defined by a tubular wall  34  that is coaxial with and spaced apart from extension  30 . An end wall  32  that is connected to and substantially perpendicular to tubular wall  34  is fixed to conveyor shaft  28  and is axially spaced from a downstream end of extension  30 , so as to form a transition space between the first and second combustion chambers  12 ,  14 . Finally, an exterior surface of tubular wall  34  defines the inside radial boundary of third combustion chamber  16 , while the outside radial boundary of the third combustion chamber is formed by a portion of the inside interior surface area of housing  20 , as best seen in  FIGS. 1A and 2 . The transition space between the second combustion chamber  12  and third combustion chamber  16  is provided by radial air passage  47  of housing  20 . The downstream end of the third combustion chamber  16  opens to the discharge section  18  of the burner system  1 . 
     As is illustrated in  FIG. 1A , gaseous material, particulates and the like from first combustion chamber  12  move along an S-shaped line  38 , past the second combustion chamber  14  and the third combustion chamber  16 , and into discharge section  18 . As best seen in  FIG. 1B , to facilitate movement of the materials through the plurality of combustion chambers  11 , a plurality of sets of auger plates  40 , which are preferably inclined relative to the axis of shaft  28  to help advance the materials in a downstream direction, are suitably arranged on the inner radial surfaces of the first through third combustion chambers  12 ,  14 ,  16 . In the embodiment illustrated in  FIG. 2 , the auger plates for the first and third combustion chambers  12 ,  16  rotate with shaft  28 , while the set of auger plates  40  for the second combustion chamber  14  are stationary. Alternatively, the plates for the second combustion chamber  14  can be mounted on the inside of tubular wall  34  so that they, too, rotate with the shaft  28 . Waste fuel, in particular, waste plastic fuel, introduced through intake opening  8 , is moved in a downstream direction (to the right as seen in  FIGS. 1A and 2 ) and it enters first combustion chamber  12 . Auger plates  40  in the first combustion chamber  12  distribute the material relatively evenly where it is liquefied, gasified and ignited by heat generated by flames and friction or heat transfer via tubular wall  34 . The resulting partially combusted waste plastic together with flames, smoke and other particulates generated in the first combustion chamber  12  propagates in a downstream direction through second and third combustion chambers  14 ,  16  where the waste plastic burns so that substantially only smoke, gaseous matter and non-combustible particulates are then discharged into the discharge section  18  of the burner system  1 . Rotational discharge blades  19  swirl the exhaust gas flow, thus improving a flush-out of the incombustible materials from the burner system  1 . The discharge blades  19  which provide a sufficient swirling of the incombustibles may be made in different shapes. One example is a substantially propeller shaped discharge blade. 
     A particular advantage provided by the waste burner system  1  of, the present invention is that fresh combustion air is provided just upstream of each of the combustion chambers  12 ,  14 ,  16 . Complete incineration of all the waste plastic takes time, thus feeding just sufficient air at the upstream end of each chamber helps to sustain optimal combustion therein. Optimal combustion, in turn, helps to maintain maximum temperature in each chamber  12 ,  14 ,  16 , because combustion air that is needed further downstream in the process, namely in the second and third combustion chambers  14 ,  16 , does not travel through the combustion chamber  12  where it is not needed and need not be heated. In addition, the flow of relatively cool combustion air along the outside of the housing  20  enhances energy efficiency because the air flow reduces heat losses from the combustion unit  10  to the atmosphere, while at the same time preheating the air needed for the combustion in the combustion chamber. 
     Referring now to  FIG. 2 , according to a second embodiment, air for incinerating waste plastics is supplied from a suitable source (or sources) at an air inlet  44 , like, for example, a fan or a blower (not shown) used to enhance the air intake. Air next enters inner air passage  46  defined by tubular double-walled housing portion  22 . Some of the air in passage  46  is released into the space for conveyor screw  4  from an orifice  50 , enters shaft lumen  6  via inlets  52 , and continues to flow in the direction of combustion unit  10 , while simultaneously cooling the conveyor screw  4 , thus increasing the reliability of the conveyor screw  4  and its bearings. The remainder of the air in the annular inner air passage  46  continues in a downstream direction and partially encircles first combustion chamber  12 . A radial air passage  47  fluidically connects axially extending inner air passage  46  with axially extending outer air passage  48 , which surrounds combustion unit  10  and discharge section  18  of the burner. 
     As shown in  FIG. 2 , air from the lumen  6  is discharged via first, second and third sets of orifices  54  arranged, respectively, in the transition space between the first and second combustion chambers  12  and  14  and into discharge section  18  of the burner, as is further described below. Additionally, the air needed for burning the waste plastic is separately introduced into each of the three combustion chambers. Air flowing along air passage  46  is discharged into an upstream portion of first combustion chamber  12  via orifices  56 . A further set of housing orifices  58  is arranged upstream of third combustion chamber  16  and extends from air passage  46  into the transition space between the second and third combustion chambers  14 ,  16 . Instead of or in addition to orifices  58 , radial air passage  47  can be provided with additional orifices such as, for example, orifices  60  located just upstream of third combustion chamber  16 , as shown in  FIG. 2 . Air for the second combustion chamber  14  is introduced by the first set of orifices  54  (located on screw  4 ) into the transition space between the first and second combustion chambers  12 ,  14  and therefore also upstream of the second combustion chamber. The air flow through orifices  54 ,  56 ,  58  and  60  is suitably modulated to match the air flow rate to the amount of waste plastics introduced through intake opening  8 . 
     To facilitate the incineration of waste plastic, particularly during startup operations, an auxiliary burner  62  in the transition space between the second and third combustion chambers  14 ,  16  for heating all three chambers, either directly (chamber  16 ) or indirectly (chamber  12  via housing section  30  extending into the combustion unit and chamber  14  via tubular wall  34 ). The auxiliary burner  62  may be oil burner, gas burner, solid fuel burner, or electrical heater. The inventors have found that using the auxiliary burner for about 5 minutes preheats the waste plastic sufficiently to efficiently start the combustion. 
     Referring now to  FIG. 3 , a waste plastic supply unit  150  can be attached to the intake opening  8 . Waste plastic is deposited in a fuel hopper  151 , wherefrom it is gravitationally fed into rotator housing  153 . A granular waste plastic GWP is illustrated in the fuel hopper  151 , but other constitutions of the waste plastic are possible. Rotation of a rotator  154  directs waste plastic towards the intake opening, and further toward the conveyor screw  4 . The inventors have found that the rotator protrusions  155  having a triangle or a semi-circular shape work well, but other rotator protrusion shapes can also be used. The inventors have also found that inclining the rotator protrusions  155  in the direction opposite from the direction of their rotation minimizes sticking of the waste plastic against the rotator housing  153 . 
     Referring to  FIGS. 4 and 5 , there is shown an alternative or third embodiment of another burner system, generally referred to as  160 . The burner system  160  includes another embodiment of a combustion unit, generally referred to as  170 . In this embodiment of combustion unit  170 , nose cone  30  is eliminated. Elimination of nose cone  30  increases air flow within and exiting combustion unit  170 . The increased air flow and exhaust allows combustion of substantially all solid fuels moved into combustion unit  170  by conveyor screw  4 . This ability to obtain substantially complete combustion of solid fuels substantially increases energy output of burner system  160  while reducing energy consumption and therefore improving overall financial performance of burner system  160  by about 50%. 
     Referring again to  FIGS. 4 and 5 , a variable frequency drive (hereinafter, “VFD”) motor, such as variable speed, direct drive motor  180  is coupled to conveyor screw  4  for revolving or rotating conveyor screw  4 . The previously mentioned second embodiment burner  1  includes motor  24  that drives shaft  28  of conveyor screw  4  by means of a chain  26 . However, this alternative or third embodiment burner system  160  includes variable speed, direct drive motor  180 , rather than motor  24  of burner  1 . The direct drive and variable speed capability of motor  180  that belongs to alternative embodiment burner system  160  allows burner system  160  to accommodate variable size and density of solid fuels. Accommodating variable size and density of solid fuels, in turn, increases capacity of burner system  160  and reduces energy consumption of burner system  160 . More specifically, direct drive motor  180  increases overall efficiency by reducing energy consumption and allows for increased variances in fuel types, sizes and feed rates which, in turn, substantially increases overall energy output of burner system  160  by over approximately 50%. In addition, direct drive motor  180  provides more power to auger shaft  28  and therefore aids in releasing fuel that might otherwise stick or adhere to shaft  28 . Also, the increased power of direct drive motor  180  can increase speed of fuel feeding. Moreover, the increased power of direct drive motor  180  increases the capability of burner system  160  to efficiently accept dual fuel compositions, such as waste plastic combined with liquid oil. 
     As best seen in  FIG. 4 , a second igniter or auxiliary burner  190  is provided in addition to the first igniter or auxiliary burner  62 . In a manner similar to location of auxiliary burner  62 , second auxiliary burner  190  is provided in the transition space between the second and third combustion chambers  14 ,  16  for heating all three chambers, either directly or indirectly. A purpose of second auxiliary burner  190  is to decrease time needed to preheat combustion unit  170  and for the introduction of a larger volume of liquid fuel that can be used in conjunction with solid plastic fuels. Decreasing time needed to preheat combustion unit  170  and introducing a larger volume of liquid fuel increases overall efficiency of combustion unit  170  by about 50%. 
     As best seen in  FIG. 4 , a pair of fuel injectors  65  and  165  is also provided in the transition space between the second and third combustion chambers  14 ,  16  for amplifying the burning of the waste fuel to facilitate increasing the energy output of the combustion unit  170 . In this regard, a fuel, such as oil, or gas, is directly injected into the combustion chambers to increase the burn rate of the waste fuel as it passes through the third chamber  16 . The fuel is supplied through fuel lines from a secondary fuel source. 
     Referring to  FIGS. 5A and 5B , there is shown an alternative or fourth embodiment of the burner system, generally referred to as  191 . Burner system  191  is substantially similar to third embodiment burner system  160 , except a boiler  192  is included to heat a fluid, such as water and/or oil, for any process requiring fluid of elevated temperature, such as in the case of district heating. In the case of district heating, fluid (e.g., water) in boiler  192  will be heated by burning waste fuel, such as waste plastic, and then pumped through insulated, underground or above-ground plumbing/pipes (not shown) to homes and businesses for use in space heating, water heating and industrial processes. Once energy from the heated fluid is used by the home or business, the fluid can be returned to boiler  192  by means of underground or above-ground plumbing/pipes. Thus, such a piping system will be a closed-loop piping system (not shown). As an example of another application, boiler  192  may be configured to produce steam for uses such as generating electricity by passing the steam through a suitable turbine-generator (not shown). Alternatively, high pressure oil (e.g., thermal oil) for use in driving single or multiple turbines that generate electricity. In one configuration, boiler  192  is coupled to combustion unit  170  and is an annular cylinder defining a central longitudinal cavity  193  in which combustion unit  170  is disposed. Boiler  192  and combustion unit  170  are coaxially aligned, as shown. An annular fluid chamber  194  is formed in boiler  192  and extends longitudinally substantially the entire length of boiler  192 . A fluid inlet pipe P 1  is coupled to boiler  192  and is in fluid communication with fluid chamber  194  for supplying the fluid to fluid chamber  194 . In addition, a fluid outlet pipe P 2  is coupled to boiler  192  for exit of heated fluid (e.g., water, water and/or oil, steam), as the case may be, from fluid outlet pipe P 2 . It should be appreciated that the boiler  192  configuration that is described herein comprises only one exemplary configuration for boiler  192 , there being many possible configurations for boiler  192 . For example, boiler  192  is shown as horizontally oriented. Alternatively, boiler  192  may be vertically oriented, if desired. Vertical orientation of boiler  192  may be desirable when horizontal space is limited. 
     It will be appreciated by a person of ordinary skill in the art of power generation that it is important to control operation of burner systems  160 ,  191 , so that burner systems  160 ,  191  perform at optimum efficiency, safely and with minimum operator intervention. Therefore, in order to suitably control burner systems  160 ,  191 , a computer apparatus  195  includes an intelligent control system, generally referred as  200 , as described in detail hereinbelow. Intelligent control system  200  includes a plurality of sensors  205  (only one of which is shown) disposed in burner systems  160 ,  191  for sensing or measuring the operational parameters of burner systems  160 ,  191 , such as pressure, temperature, boiler fluid level, power generated, as well as other operational parameters of burner systems  160 ,  191 . With reference to  FIGS. 4 and 5 , burner system  160  does not include boiler  192 , it being understood that burner system  160  may include boiler  192  as an option, if desired. Sensing these operational parameters will allow an operator of burner systems  160 ,  191  to monitor the operational parameters and take appropriate corrective action should any one of the operational parameters fall outside a permissible predetermined range of values. However, it will be appreciated that intelligent control system  200  will be capable of automatically taking any necessary corrective action with minimum operator interaction. In addition, intelligent control system  200 , which will use a computerized software platform with an open architecture, is adapted to integrate therewith off-the-shelf, commercially available boiler vessel management systems. Such a commercially available boiler vessel management system may be of a type such as may be available from Tru-Steam Boilers &amp; Services Pty Ltd, located in Chipping Norton, Australia. 
     In addition, intelligent control system  200  will provide substantially complete control and monitoring of all burner mechanical and electrical components, so that burner systems  160 ,  191  perform at optimum efficiency, safely and with minimum operator intervention. Intelligent control system  200  will provide redundant safety capability for substantially all functional components of burner systems  160 ,  191 . A control panel (not shown) will also substantially enhance performance of burner systems  160 ,  191  by providing operator or automatic control of each function of burner systems  160 ,  191 . Integration and interface design for boiler safety systems will virtually ensure burner systems  160 ,  191  operate within predetermined and safe parameter ranges for a preselected boiler vessel, such as boiler  192 . Also, intelligent control system  200  will assist in enabling use of burner systems across a broad spectrum of applications including the ability to manage energy output and use of various fuel types. It is believed that use of intelligent control system  200  will increase overall performance of burner systems  160 ,  191  by about 75%. The method of operation of intelligent control system  200  is described hereinbelow. 
     Therefore, referring to  FIGS. 6 ,  7  and  8 , there is shown a flow chart illustrating the methods by which intelligent control system  200  controls burner systems  160 ,  191 . For purposes of brevity, the methods by which intelligent control system  200  controls burner systems  160 ,  191  will be described only with reference to burner system  191 , it being understood that the methods may apply to burner system  160 , as well. The method of intelligent control system  200  starts at a step  1200  by the operator of burner system  191  activating a power-on system step  1202 . Activating power-on system step  1202  supplies electrical power to intelligent control system  200  and begins operation of burner system  191 . It should be appreciated by a person of ordinary skill in the art of power generation that power-on system step  1202  may include a “toggle switch” (not shown) that energizes intelligent control system  200  when placed in a first position and de-energizes intelligent control system  200  when placed in a second position. 
     As best seen in  FIG. 6 , power-on system step  1202  generates a signal that is received by a decision step  1204 . The decision step  1204  determines whether an emergency stop (hereinafter “ESTOP”) circuit has been energized. The ESTOP circuit (not shown) must be energized for motion devices to be powered and operational, such as previously mentioned variable frequency drive motor  180  (i.e., VFD  180 ). The ESTOP circuit may be either manually or automatically operated to shut-down burner system  191  in an emergency, such as might occur during boiler overpressure, based on a signal output from previously mentioned sensor  205  (see  FIG. 4 ). Referring to  FIG. 6 , the ESTOP circuit at step  1204  is enabled by a programmable logic circuit (hereinafter “PLC” circuit, not shown) output and preferably by two maintained pushbuttons (not shown). PLC instructions may be loaded into the PLC from a pre-programmed Erasable Programmable Read Only Memory (EPROM, not shown) or an Electrically Erasable Programmable Read Only Memory (EEPROM, also not shown) included in the PLC. Also, one of the maintained pushbuttons turns-on the ESTOP circuit to energize the ESTOP circuit and the other maintained pushbutton turns-off the ESTOP circuit to de-energize the ESTOP circuit. If the ESTOP circuit is not energized, then a “false” output signal (hereinafter a “no” output signal) is generated by decision step  1204 . The “no” output signal activates an ESTOP alarm at a step  1205 . An output signal from the ESTOP alarm activated at step  1205  continuously loops back to decision step  1204 , whereupon decision step  1204  again tests whether the ESTOP circuit has been energized. It should be appreciated by a person of ordinary skill in the art of power generation that if the ESTOP circuit is de-energized (i.e., output from decision step  1204  is “no”), the PLC in the ESTOP circuit will detect the condition and display the appropriate alarm message on a Human Machine Interface panel (i.e., “HMI panel”, not shown) that may be located in an operator control room (also not shown) associated with burner  160 . However, if the ESTOP circuit is energized, then a “true” output signal (hereinafter “yes” output signal) is generated by decision step  1204 . The ESTOP alarm is in an “on” state only upon depressing of the previously mentioned ESTOP push buttons or failure of PLC output. At a step  1206 , the “yes” output signal from the ESTOP circuit (i.e., from step  1204 ) is used to initiate a call subroutine step  1206 , which calls the “boiler ready” subroutine  1400  to verify that the boiler (see  FIG. 5A ) belonging to burner  160  is ready to start operation. After the call step  1206  has been executed, the program advances to an end step  1208 , since the boiler ready subroutine  1400  is now being executed by the program. The boiler ready subroutine  1400  is best seen on  FIG. 6 . 
     Referring again to  FIG. 6 , when power is supplied to intelligent control system  200  by activating the power-on system at step  1202 , a continuous check subroutine  1300  is initiated which begins with a start step  1301 . The system parameters comprise at least auger VFD, blower VFD, fuel feeder VFD, safety controller alarm active, and fluid pump failed, which parameters are detected, sensed or measured by previously mentioned plurality of sensors  205  (see  FIG. 4 ). As shown in  FIG. 6 , when the continuous check of system parameters starts at step  1301 , auger VFD faulted is checked at decision step  1302 . If auger VFD faulted is not active, then a “no” signal is generated at decision step  1302  and the fault condition is checked again. The continuous check method does not proceed further, until a fault condition is detected at decision step  1302  which, in turn, results in a “yes” signal and the method proceeds to a set alarms exist command step  1313 . 
     The program then advances to a stop heat command step  1315  which disables the burner system  191 . Next the system proceeds to a decision step  1317  to determine whether the burner system  191  has been disabled for a predetermined number of minutes, where the predetermined number of minutes is a sufficient number of minutes to allow the burner system  191  to cool down. The program will loop at this decision step  1317  until the predetermined number of minutes has elapsed. Once the predetermined number of minutes has elapsed, a yes condition exists and the program then proceeds to the decision step  1204  and proceeds as previously described relative to that decision step  1204 . 
     In  FIG. 6 , when the call boiler ready subroutine step  1206  is executed, the boiler verification subroutine  1400  begins at a start step  1401  to verify the boiler  192  is ready for operation. In this regard, the system proceeds to a set of boiler ready decision steps  1402 ,  1404 ,  1406 ,  1408 , and  1410  that will be described hereinafter in greater detail. The verification begins at a pressure verification decision step  1402 , and if the pressure of the boiler is not within a correct range, a “no” signal is generated which causes the program to advance to the command step  1313  where the program proceeds as previously described with a set alarms exist. If instead, the pressure is within range, a “yes” signal is generated allowing the program to advance to a boiler over temperature decision step  1404 . If the boiler  192  has an over temperature condition, a “no” signal is generated which causes the program to advance to the command step  1313  where the program proceeds as previously described with a set alarms exist. If instead, the boiler temperature is within range, a “yes” signal is generated to permit the program to jump to the next decision step  1406  to verify that the first boiler water level is sufficient. The terminology “water level” is intended to include “water and/or oil level” because the fluid in the boiler can be water alone or a combination of water and oil. If the first boiler water level is not sufficient, a “no” signal is generated which causes the program to advance to the command step  1313  where the program proceeds as previously described with a set alarms exist. If instead, the first boiler water level is sufficient, a “yes” signal is generated and the program goes to the next decision step  1408  to verify that the second boiler water level is sufficient. If the second boiler water level is not sufficient, a “no” signal is generated which causes the program to advance to the command step  1313  where the program proceeds as previously described with a set alarms exist. If the second boiler water level is sufficient, a “yes” signal is generated and the program advances to a decision step  1410 . 
     Next, at the decision step  1410 , the program detects whether the “disable heat sensor” is active. If it is active, a “yes” signal is generated and the system goes to the command step stop heat at step  1315 , where the system proceeds as described previously. If the disable heat active sensor is not active at decision step  1410 , the program advances to a call command to call the water ready subroutine  1600  that will be described hereinafter in greater detail. After the call command  1412  is executed the program proceeds to an end step  1414  as the water ready subroutine  1600  will not be executed. 
     Turning now to  FIG. 7 , at a step  1601 , the water ready call signal from step  1412  (see  FIG. 6 ) is provided to a decision step  1602  that tests whether a call for heat signal is true or is energized. If the call for heat signal is not energized, then a “no” output signal is generated at decision step  1602  and the decision step  1602  loops to again test whether the call for heat is energized. If the call for heat signal is energized, a “yes” output signal is generated. Similarly, in a logical or other fashion with decision step  1602 , another decision step  1603  tests presence of whether the manual CFH (“Call for Heat”) signal is true. If the manual CFH signal is not true, then a “no” output signal is generated at decision step  1603  and the decision step  1603  loops back and again tests for manual CFH signal. If the manual CFH signal is true, a “yes” output signal is generated at decision step  1603 . The “yes” output signals from both the CFH signal energized at decision step  1602  and manual CFH signal at decision step  1603  are passed to a decision step  1604  that determines whether water flow rate is acceptable. 
     Referring again to  FIG. 7 , if the water flow acceptable decision step  1604  outputs a “no” signal, then a “watchdog” routine at step  1606  generates a water pump failed alarm signal. A “watchdog” routine is a computer software routine combined with sensor instrumentation that performs a timer action wherein multiple conditions are monitored. If the monitored conditions are not valid for more than the timer duration, then the watchdog times-out and an alarm is activated. In this specific case, an output signal from the watchdog routine at step  1606  that generates the water pump failed alarm is passed to a call command  1608  which calls the set alarms exist subroutine  1500  as best seen in  FIG. 6 . The program then proceeds to an end step  1610  since the set alarms exist subroutine  1500  will have been executed via a start set alarms exist step  1501 . The start alarms exist step  1501  advances the program to the set alarms exists command  1313  where the program proceeds as previously described. 
     If the water flow acceptable decision step  1604  outputs a “yes” signal, then a set output to start blower VFD step is started at a step  1607  to facilitate combustion. The process then advances from the command step  1607  to a decision step  1609  to test whether a desired air flow is detected in burner  160 . If desired air flow is not detected, then a “no” signal is output from decision step  1609 . The “no” signal is received by a watchdog routine  1611 . This watchdog routine  1611  generates a blower failed to start alarm signal that is passed to the previously mentioned call command  1608  where the program proceeds as previously described. However, if the output signal from the air flow detected decision step  1609  is “yes”, then the “yes” output signal causes the program to advance to a command step  1615  that sets an output to start a liquid fuel pump. The liquid fuel may be oil or kerosene and is used to aid combustion. The output signal from command step  1615  is received at a command step  1617  that, in turn, causes the output to generate an output signal to enable a safety controller (not shown). The program then advances to a call step  1619  which calls the safety controller subroutine  1800  as best seen in  FIG. 8 . When the safety controller subroutine  1800  has completed its execution, the program will return to this point advancing to a decision step  1621  to determine whether the safety controller output signal is active as will be described hereinafter in greater detail. 
     Considering now the decision step  1621 , when the safety controller subroutine  1800  has been successfully executed and a safety controller active signal is generated, the call safety controller command  1619  advances to the decision step  1621  via the return step  1815  enabling the program to advance. A safety controller active decision step  1621  tests whether the safety controller has started. If the output from safety controller active decision step  1621  is “no”, then a watchdog routine at a step  1623  produces the safety failed to start alarm and the method of the intelligent control system  200  then advances to step  1625  and ends. On the other hand, if the output signal from safety controller active decision step  1621  is “yes”, then an instruction is generated at a step  1627  to go to a step  1631 . From step  1631 , the program advances to a command step  1631  which initiates a burner startup timer (not shown). The system then proceed to a decision step  1633  to determine whether the delayed rotation of previously mentioned auger shaft  28  has elapsed for a predetermined time that is selected by the operator of burner  160 . If output from decision step  1633  is “no”, then decision step  1633  continuously loops and again tests whether the predetermined period of time has elapsed. If the time period has elapsed, then decision step  1633  passes a “yes” signal to a command step  1635  to set the output to “start rotation of auger shaft” routine at a step  1635 . After the auger shaft  28  starts rotating, the start rotation of auger shaft routine step  1635  passes an output signal to a waste plastic fuel start decision step  1637  that determines whether plastic fuel feed has started to feed fuel along auger shaft  28  by means of previously mentioned auger plates  40 . The decision step  1637  will cause the program to loop at this decision step until the waste plastic fuel feed starts. In this regard, when a “yes” signal is generated at decision step  1637 , the system proceeds to a command step  1639  that sets the output to start the plastic feeder VFD modulus or subroutine. 
     Once the command step  1639  has been executed, the program proceeds to a command step  1641  which will set the plastic fuel feeder VHF speed to a “transition speed”. The program then goes to a decision step  1643 . At decision step  1643 , a determination is made by the system as to whether a liquid fuel bypass time delay has ended. The time delay in starting the liquid fuel pump is provided to ensure that auger shaft  28  is in fact rotating before starting the liquid fuel pump. If the liquid fuel bypass time delay has not ended, then a “no” output signal is produced by decision step  1643 . Decision step  1643  loops and then again tests whether liquid fuel bypass time delay has ended. If the liquid fuel bypass time delay has ended, the method of intelligent control system  200  executes a go to command step  1645  that advances the program to step  1647  as best seen in  FIG. 8 . 
     Referring to  FIG. 8 , after the liquid fuel time delay that is tested at decision step  1643  ends with a “yes” signal being generated, the program proceeds to a go to step  1645  that takes the routine to step  1647  as best seen in  FIG. 8 . From step  1647 , the program goes to a command step  1649 , which causes the system to set output to start a liquid fuel pump. However, operation of the liquid fuel pump is stopped at a command step  1651  after the liquid fuel pump is started at step  1649 . Stopping the liquid fuel pump after starting the liquid fuel pump confirms that the liquid fuel pump is operational. An output signal from the stop liquid fuel pump step  1651  is provided to initiate a plastic fuel feeder variable frequency drive (VFD) motor at a command step  1653 . The speed of the VFD motor is set to a predetermined “lean rate” for feeding the plastic fuel at a predetermined, lower non-operational rate. The plastic fuel is fed at the lean rate for a predetermined time selected by the operator of burner  160 . During this time, the normal operating plastic fuel feed rate or “run rate” is delayed. The routine advances to a decision step  1655  that determines whether this time delay has ended before feeding the plastic fuel at the run rate. If the time delay for feeding the plastic fuel at the lean rate has ended, then the plastic fuel VFD motor speed is set to the operational “run” rate at command step  1702  via a go to step  1657  that advances the program to step  1700 , from where the program proceeds to the command step  1702 . 
     Referring again to  FIG. 8 , an output signal from step  1702  is provided to a decision step  1704  to determine whether there is a “call for heat”. The call for heat is a PLC input point that is connected to a temperature switch, such as a thermostat. If the call for heat at decision step  1704  is true, then a “yes” output signal is generated. This “yes” output signal is provided to a decision step  1706  that determines whether an automatic stopping of a plant demonstration has completed. In this regard, operation of burner system  191  occasionally may need to be demonstrated to interested parties, such as government regulators, investors and members of the public. When demonstration of burner system  191  in an operating state is required, burner system  191  is run only for a predetermined time. The predetermined time is set for the time allowed for the demonstration. Therefore, burner system  191  is operated until decision step  1706  determines that the allotted demonstration time has elapsed. At that point, intelligent control system  200  automatically stops operation of burner system  191  if the demonstration time has elapsed by advancing to the stop heat command  1315  as best seen in  FIG. 6 . Alternatively, if the call for heat at decision step  1704  is false, then a “no” output signal is generated. This “no” output signal is not provided to the “demonstration” decision step  1706 . Rather, this “no” output signal is provided to previously mentioned stop heat step  1315 . 
     Referring to  FIGS. 4 ,  7  and  8 , when the safety controller subroutine  1800  is called at the previously mentioned call step  1619  (see  FIG. 6 ), the safety controller subroutine  1800  begins at a start routine step  1801 . From the start step  1801 , the operation of igniters  62 ,  190  (see  FIG. 4 ) are initiated at a command step  1802 , that produces an igniter output signal indicating that igniters  62 ,  190  are operating. It should be appreciated that the disclosure herein recites two igniters  62 ,  190 ; however, any number of suitable igniters may be used to initiate a flame. Next, the igniter output signals are received by an open liquid fuel solenoid (not shown) instruction at a command step  1804 . The igniter output signal of step  1802  in combination with the open liquid fuel solenoid instruction from step  1804  are passed to a decision step  1806  to determine whether a flame is detected by an appropriate sensor  205  (see  FIG. 4 ), such as an ultraviolet photoeye and amplifier board combination (not shown). The ultraviolet photoeye and amplifier board combination may be of a type, such as a “C7027A1023 ULTRAVIOLET MINIPEEPER FLAME SENSOR”, that may be available from Honeywell International, Incorporated, located in Morristown, N.J., U.S.A. In this regard, the “C7027A1023 ULTRAVIOLET MINIPEEPER FLAME SENSOR” is a compact flame detector for use with flame safeguard controls having ultraviolet amplifiers and detects ultraviolet radiation in flames. The “C7027A1023 ULTRAVIOLET MINIPEEPER FLAME SENSOR” is used with Honeywell Flame Safeguard primary safety controls for burners requiring ultraviolet flame detection. Suitable operation of igniters  62 , 190  in combination with the proper operation of the liquid fuel solenoid should produce a flame. However, if the flame is not detected within a “flame proving” time period, then the safety controller turns off its “valve” output signals in order to close the liquid fuel valves and turns on its alarm output. If no flame is detected at decision step  1806 , a “no” output signal is generated by decision step  1806 . The “no” output signal generated by decision step  1806  is passed to decision step  1808  that tests whether the previously mentioned flame proving timing period has elapsed. If the output signal from decision step  1808  is “no”, then the output signal from decision step  1808  is passed back to decision step  1806  and the presence of the flame is again tested. However, if the flame proving timing period has elapsed without presence of a flame, then decision step  1808  outputs a “yes” signal that is provided to a safety controller alarm at a step  1810 . From the set safety controller alarm output step  1810 , the program advances to the return step  1813 , where the program proceeds as previously described. 
     Referring again to  FIG. 8 , if a flame is detected at decision step  1806 , the decision step  1806  outputs a “yes” signal that is provided to a command step  1809  which sets a main valve out to enable solid fuel feed. Output from step  1809  is provided to a command step  1811  that sets a safety controller “active” input value that is supplied to previously mentioned return step  1813  which returns the program to step  1621  via step  1815  as described previously (see  FIG. 7 ). 
     The pollution emission of one embodiment of the invention was tested by the KTL (Korean Testing Laboratory, located in Seoul, Korea) by measuring harmful gas emissions during the waste fuel burning. According to the tests, the dioxin level was 0.119 ng-TEQ/Sm3, the hydrogen chloride level was 0.78 ppm, and the sulfur oxides level was 6.60 ppm. Thus, these harmful gas emission levels were significantly below the Korean emission standard levels (dioxine: 5 ng-TEQ/Sm3, hydrogen chloride: 50 ppm, and sulfur oxides: 6.60 ppm), rendering the invention environmentally friendly. 
     The above description is illustrative and is not restrictive, and, as it will become apparent to those skilled in the art upon review of the disclosure, the present invention may be embodied in other specific forms without departing from the essential characteristics thereof. For example, while the above invention is described in conjunction with plastic waste fuel, the embodiments of the present invention can also be used with other solid fuels, waste or not, like, for example, coal, saw dust, wood chips, or a mixture of solid fuels. Furthermore, while three combustion chambers are described, a different number of combustion chambers may be used. These other embodiments are intended to be included within the spirit and scope of the present invention. The scope of the invention should, therefore, be determined not with reference to the above description, but instead should be determined with reference to the following and pending claims along with their full scope of equivalents.