Patent Application
20160033127
Certain features disclosed in this application are disclosed and claimed in U.S. Pat. No. 3,577,940 issued on May 11, 1971 to Robert J. Hasselbring and Robert L. Shields, and U.S. Pat. No. 3,727,563 issued on Apr. 17, 1973 to Robert J. Hasselbring and Robert L. Shields, and U.S. Pat No. 3,568,017 issued on Apr. 25, 1972 to Norman R. Dibelius and William L. Zabriskie. Additional reference is made to application Ser. No. 12/806,807 filed on Aug. 20, 2010, by Robert J. Hasselbring and Ralph W. VanNatta, which claims the benefit of Provisional Application No. 61/235,521, filed Aug. 20, 2009.
1. Field of the Invention
This invention relates to combustors and has particular relation to industrial and municipal-type combustors for burning waste material, mobile combustors for first response disaster cleanup, and combustors using agricultural waste, coal, and tires as alternative fuels.
2. Description of the Prior Art
Conventional industrial and municipal type combustors ordinarily include one or more combustion chambers having drying grates with a flue for discharging to atmosphere the gaseous products of combustion of waste material in the chambers. Depending upon the efficiency of a particular combustor design varying amounts of noxious gases and ash are discharged through the flue to atmosphere. Prior combustor designs in general have been incapable of effecting good combustion of waste material such that the products of the resulting incomplete combustion consist of a large quantity of noxious gases and ash which are discharged to the surrounding atmosphere in the form of dense acrid smoke.
In an effort to comply with regulatory air pollution codes, more recent combustor designs have provided for cleaning the gaseous products of combustion prior to their discharge to atmosphere. Such flue gas cleaning apparatus is usually of costly and bulky construction and in some cases has not operated to clean the flue gases sufficiently to comply with the regulatory codes. One known flue gas cleaning apparatus includes means for conducting the gaseous products of combustion through water sprays so that the suspended ashes and other particulate matter are entrained in the water which is then collected and conveyed to a suitable clarification system.
This type of flue gas cleaning apparatus is expensive and complex and contributes not only to the high cost and massive structure of prior art combustors, but also to water pollution. Further, the very high temperatures within the chambers necessary to effect good combustion result in very hot flue gases which may result in inefficient operation of the flue gas cleaning apparatus and resulting undesirable pollution of the surrounding atmosphere. The provision of flue gas cleaning apparatus thus imposes a limitation upon the temperature within the combustion chambers which contributes to the poor combustion realized by certain prior art designs. It is necessary of course that provision be made for collecting and disposing of any non-combustible material. One known apparatus for accomplishing this function comprises a conveyor disposed beneath the combustion chambers for receiving such material and for conveying the same from the combustion chambers to a suitable disposition area. Such conveying apparatus is also very costly and in addition, occupies considerable space which further contributes to the high cost and massive structure of prior art combustors.
It is therefore a primary object of the invention to provide a novel and improved combustor capable of effecting substantially complete combustion of waste material and wherein essentially solid-free flue gases are discharged to the atmosphere to minimize air and water pollution.
It is another object of the invention to provide a novel and improved combustor of such character which avoids the use of costly and complex flue gas cleaning apparatus.
It is a further object of the invention to provide a novel and improved vortex combustor of the foregoing character wherein non-combustible material is discharged from the combustion chamber during the burning process by action of the vortex without the use of costly and bulky material handling and conveying apparatus.
It is a still further object of the invention to provide a novel and improved vortex combustor of the foregoing character wherein the burning process is more efficiently carried on and the removal of fly ash, as well as the discharge of non-combustible material are facilitated.
In carrying out the invention in one preferred form, a combustor is provided which includes a combustion chamber having spaced end walls and a side wall with its central longitudinal axis extending between the end walls. The chamber is preferably disposed in operative position with its central longitudinal axis extending horizontally or substantially horizontally. Means are provided for introducing a mixture of waste material and primary air into the chamber tangentially to the sidewall for establishing a vortical movement of the waste material toward one of the end walls and provision is made for igniting the waste material during its vortical movement.
Secondary air is introduced into the chamber substantially tangentially to the side wall at a plurality of regions which are spaced substantially throughout the entire length of the chamber and which are aligned along a horizontal axis. These regions are located adjacent the bottom of the chamber at one side thereof such that secondary air is introduced in directions to maintain the vortical movement of waste material. The secondary air entering the chamber at each of the mentioned spaced regions is controlled by an independently controllable damper which can be adjusted automatically and manually to control the amount of air entering the chamber and contributing to the vortex energy at each region. The secondary air is supplied through a blower-feed manifold and automatically controllable dampers control generally the secondary air distributed through the manifold. The automatic dampers are controlled adjustably and operate automatically in response to temperature variations in the chamber.
A discharge flue port has an open end opening in the chamber near the one end wall and substantially concentric with the central longitudinal axis of the chamber. Means are provided external to the chamber and this discharge flue, in which a recuperator is attached in such a way as to return air flow heated with the superheated exhaust gases for use in the secondary air manifold and for the intake means that provides the mixture of waste material and primary air. This recuperator provides necessary heated air flows to those portions of the process that benefit from the heated air, such as drying the shredded waste material prior to entering the chamber and creating a more efficient primary air flow. Additionally, the heated air is added to the secondary air manifold for injection into the chamber, again increasing the efficiency of the burning process.
A second discharge port includes an open end opening in the chamber adjacent to the inner surface of the side wall for discharging from the chamber during the burning process non-combustible material entrained in the outer region of the vortex. The open end of the second discharge port is located adjacent the bottom of the chamber at the side thereof substantially opposite one of the regions of introduction of the secondary air. The material discharged by the second port is conveyed through a conduit to a separator which separates the gases and the solid material and means are provide to introduce the separated gases and any solid particles suspended therein back into the combustion chamber.
The burning waste material moves in the vortical path from the entry point substantially near the front end wall, towards the back end wall, in a free vortex with means provided by use of an adjustable baffle that increase the residence time and allow for the waste material to be entrained back into the outer region of the vortex for continuous burning until complete combustion has been achieved. This baffle enhances the deflection of these residual combustible materials, with adjustments allowed for various fuel sources and conditions.
Means are further provided to integrate the various components of the invention, to ensure proper and efficient control and management of the entire operational process. These means include a combination of a computer and programmable controls, with applicable software and preset conditions, and with the capability of being connected to popular network interface protocols. This network interfacing will allow for real-time data transmission, as well as remote access of the various operational controls.
Referring now to the drawings, there is illustrated in
More specifically, the combustor as schematically shown in
Continuous injection of a mixture of size-reduced waste material and air into the chamber 22 from the pipe 20 tangentially to the side wall 28 establishes a vortical flow of the waste material which travels from adjacent the end wall 26 toward the end wall 24 in a clockwise direction as viewed from the end wall 26 in
The total pressure of the air exiting from the pipe 20 can be as high as 20 inches H2O and is preferably about 12 inches H2O. However, such pressure can be as low as 4 inches H2O when burning finely divided, highly combustible material at a lower heat release rate. Therefore, pressures of air exiting from the pipe 20 are generally within the range of 4 inches H2O to 20 inches H2O.
In order to ignite the waste material entering the chamber 22, a suitable commercially available burner 38 is disposed near the end wall 26 of the chamber 22 to fire tangentially into the chamber adjacent the top and at the right side thereof as viewed in
In order to enhance combustion of the waste material and to maintain the energy of its vortical flow in a predetermined and controlled manner through the entire length of the combustion chamber, provision is made for introducing controlled quantities of high velocity secondary air into the chamber 22 during the burning process and at spaced regions throughout the length of the chamber. To this end, a commercially available, motor-driven fan or blower 40 is disposed to introduce secondary air into an elongated manifold 42 suitably supported externally of the chamber and extending along an axis substantially parallel to the longitudinal axis of the chamber. Also the manifold 42 is located preferably near the bottom and at the right side of the chamber as viewed in
Additionally, in the described arrangement, the tangential injection of the secondary air through the openings 44 and at spaced points along the length of the chamber has the beneficial effect of periodically contributing to the vortex energy in the chamber. Thus, compensation is provided for losses in vortex energy or for effectively sustaining the vortex as the waste material progresses vertically along the length of the chamber.
The periodic or spaced tangential injection of secondary air and the resultant sustenance of the vortex along the entire length of the chamber enhance the efficiency of the waste burning process. Also, it reduces any tendency of combustion material particles, such as fly ash, to drop out of the vortex and settle on the bottom of the chamber which, if permitted to occur, can present substantial difficulties in effecting removal of such particles from the chamber and can require longer shut down times for chamber cleaning purposes. Also, it can adversely affect exhaust emissions.
For the purpose of predeterminedly controlling the secondary air generally and individually at each of the particular regions of injection into the chamber, adjustable control means are provided between the blower 40 and the manifold 42 and in each of the conduits 46 extending between the manifold and the chamber. More specifically, a damper comprising, for example a butterfly valve 48 is provided in the manifold 42 between the fan and the main portion of the manifold to which the several conduits 46 are connected. The operation of the butterfly valve 48 is determined by the operation of a suitable proportional motor 50 adapted for positioning the valve between open and closed positions in accordance with the degree of energization of the motor. The motor energization is, in turn, determined by a suitable control means generally indicated and designated 52 in
The secondary air entering the chamber 22 through the openings 44 is further and individually controllable by means of separate and independently adjustable dampers 56 interposed one in each of the conduits 46. Each damper 56 is adapted for further controlling the secondary air as it enters the chamber at its respective region along the vortical path of the waste material. Thus, the dampers 56 are effective for enabling the operator to control separately and individually the energy added to the vortex at each of the regions, permitting more or less energy to be introduced as required to maintain a desired vortical profile and in accordance with experience as to regions where more or less energy is needed to compensate for energy losses in the vortex.
The total pressure of the air entering the chamber 22 through the openings 44 can be as high as 20 inches H2O and is preferably about 12 inches H2O. However, such pressure can be as low as 4 inches H2O when burning finely divided, highly combustible material at a lower heat release rate. Therefore, pressures of air entering the chamber 22 through the openings 44 are generally within the range of 4 inches H2O to 20 inches H2O.
The construction of the dampers 56 is best seen in
In order to discharge gaseous products of combustion from the chamber 22 to atmosphere first discharge means is provided including a first discharge port or flue 74 having an open end opening in the chamber in the region of the end wall 24 and substantially concentric with the central longitudinal axis of the chamber 22. As best shown in
Second discharge means is provided for discharging from the chamber 22 during the burning process of non-combustible material. For this purpose, the preferred embodiment provides a second discharge port 84 having an open end 85 opening in the chamber 22 at a region downstream from the point of introduction of the waste material in the region adjacent the inner surface of the end wall 24 and adjacent the inner surface of the layer 34 for receiving and discharging from the chamber non-combustible material which is entrained in the outer region of the vortex. In the illustrated embodiment the port 84 comprises a conduit 86 extending through the side wall 28 substantially tangentially thereto and substantially horizontally at the bottom of the chamber as viewed in
The present invention further provides a separator 96 which is effective for separating the non-combustible materials discharged through the conduit 86 and for dropping this solid material into a suitable container 98. Gases and some combustible material in the form of ash will be introduced into the separator 96 as byproducts of the separation process. The separator 96 is preferably a commercially available cyclone or vortex type separator wherein material discharged through the conduit 86 is introduced tangentially into the separator 96 with the result that the solid material drops out the open end of the separator into the container 98. Such solid material constitutes ashes and other particulate matter formed in the combustion process and also non-combustible material which can be disposed of in any suitable manner.
In accord with the invention, the hot gases separated out by the separator 96 are introduced back into the chamber 22. This is very advantageous in that it maintains the vortex within the chamber 22, further cleans such gases by removing residual fly ash, and dries out wet waste material within the chamber 22. For this purpose a conduit 99 extends coaxially into the separator 96 at the top thereof so that the hot gases separated by the action of the separator 96 are drawn into the conduit 99 through the central low-pressure area and are conveyed through the conduit 99 to a fan 95 to withdraw the separated hot gases from the conduit 99 and to introduce such into the chamber 22. These gases are preferably introduced into the chamber 22 at an area downstream from the area of introduction of the secondary air. However, under certain conditions the secondary air fan 40 and the manifold 42 may be employed instead of the fan 95 to introduce the separated gases back into the chamber 22.
The total pressure available from the primary and secondary air entering the chamber is utilized to introduce energy into the vortex for obtaining high combustion rates and also to accelerate material out through the conduit 86 and the flue pipe 76. It has been observed that if the area of the orifice 71, which constitutes the open end of the discharge flue port, is too small relative to an optimum area, then the combustion rates will be lower than optimum because too much of the available pressure will be used to accelerate the flow of material out of the combustion chamber. On the other hand, if the area of the open end of the discharge flue port is too large relative to the optimum area, it is impossible to establish the vortex flow field required for effecting centrifugal separation of the fly ash and for obtaining substantially complete combustion of larger particles. Tests have demonstrated that the optimum area of the open end of the discharge flue port bears a specific relationship to the area of the cross-section of the combustion chamber 22 taken perpendicular to its longitudinal axis.
Most if not all of any non-combustible material will enter the conduit 86 as it initially reaches the end wall 24. However, in the event that such material does not enter the conduit 86 when it initially reaches the end wall 24, this material becomes entrained in the stream of hot gases which normally flows in the direction of the arrows 88 along the inner surface of the end wall 24 toward the open end 90 of the flue pipe 76 where a low pressure area exists. If the open end of the flue pipe 76 were flush with the end wall, a considerable portion of this material would enter the flue pipe 76 thus necessitating provision of flue gas cleaning apparatus to avoid pollution of the surrounding atmosphere. In order to reduce the amount of such solid material which exits from the chamber 22 through the flue pipe 76, the flue pipe 76 is extended into the chamber 22 so that the inner open end of the flue pipe 76 is spaced axially inwardly from the end wall 24 as shown in
In order to still further reduce the amount of solid material entering the flue pipe 76, a baffle 92 is positioned adjacent the open inner end of the flue pipe 76 to divert outwardly toward the inner layer 34 of the chamber 22 any residual solid combustible particulates and non-combustible material which moves from adjacent the end wall 24 toward the open end of the flue pipe 76. The arrangement is such that solid material moving in the direction of the arrows 88 engages the baffle 92 and is thereby deflected in the direction of the arrow 94 so that the material so diverted once again becomes entrained in the vortex for further burning and movement toward the end wall 24 for discharge through the conduit 86. As shown in
The detachable mounting of the flue 74 to the end wall 26 as previously described permits detachment of the flue pipe 76 and the baffle 92 from the chamber 22 so as to permit replacement or repair of pipe 76 and baffle 92 as desired. Additionally, this arrangement disposes the inner end of the flue pipe 76 and the baffle 92 adjacent the region of the vortex which can be influenced by the secondary air injected through the opening disposed for cooperation with the discharge port 85. This arrangement together with the adjustability of the secondary air provided by the respective damper 56 affords the operator the opportunity to adjust the secondary air injected at this region in a manner to predeterminedly influence the energy condition of the vortex in the region of the flue pipe opening. Thus, one can adjust to a degree the pressure conditions in the region of the baffle 92 for thereby influencing the flow paths indicated by the arrows 88 and 94.
In accord with the present invention, the ratio of the area of the open end of the discharge flue port to the area of a cross-section of the combustion chamber taken perpendicular to its longitudinal axis is selected to be within the range of 1/16 to 4/25 and is preferably about 1/9. In the illustrated embodiment of the invention these area ratios can be translated to corresponding diameter ratios with the result that the ratio of the diameter d of the open end of the circular discharge flue port to the diameter D of the cylindrical chamber 22 is selected to be within the range of 1/4 to 2/5. This range of diameter ratios has been found to be effective over a range of diameters of the chamber from 1½ feet to 15 feet. In the preferred embodiment of the invention the ratio of the diameter d and the diameter D is selected to be approximately 1/3 or in other words, the inner diameter D of the chamber 22 is selected to be about three times as great as the diameter d of the open end of the discharge flue port. It is understood of course that the invention is not limited to the particular cylindrical chamber configuration and circular discharge flue configuration illustrated and is applicable in its broader aspects to other configurations of the chamber and discharge flue which are non-cylindrical and non-circular.
The nature of the free vortex flow field is influenced strongly by the ratio of the diameter d to the diameter D. With proper dimensions of these diameters selected in accord with the invention, the strong free vortex flow field provides an increasing tangential velocity with decreasing radius. Thus the tendency of the particles to be drawn to the center of the chamber 22 by the drag forces imparted from the radially inward flow is counterbalanced by a stronger centrifugal force field. Therefore, the particles are maintained in suspension until complete combustion has occurred or until they are withdrawn from the chamber 22 through the conduit 86.
The present invention further provides a means of recycling the heat produced by the combustion process inside of the chamber 22, by use of a recuperator 105 (
The present invention further provides for a control means to integrate the various components for purposes of operational control, such as the size-reduction unit 10 and primary air blower 16, the burner 38, secondary air control 52 and motor 50, a number of chamber atmospheric sensors 100, and flue emissions sensors 102. The control means 101 consists of any combination of commercially available devices, such as a computer, programmable automation controller, programmable logic controller, or similar industrial control system, along with the necessary wired and/or wireless interface materials and equipment. Readings from one or any combination of the atmospheric sensors can be used to cause adjustments with the burner and/or secondary air, using predetermined values. The recuperator 105 is similarly integrated into the control panel 101 to allow control and management of the air flow back to the secondary air manifold 42 and the feed and primary air intake 20.
The chamber atmospheric sensors 100 measure, record, and transmit data related to conditions such as chamber temperature, vortex air speed, moisture content, BTU heat value of material being consumed, pressure, and capacity. The sensors 100 are connected to a control panel 101 that operates in combination with other network equipment as indicated previously, or separately to transmit data and signals to the various components to adjust the operation or functionality of each. For example, the size reduction unit 10 and primary air blower 16 can be connected to control panel 101 to automatically control each, in accordance with the overall system operation, including automatic safety shut-off capability.
The burner 38 is additionally controlled by the control panel 101 by use of a chamber atmospheric temperature sensor 100 transmitting temperature readings within the chamber, and allowing the burner 38 to be turned off following proper ignition of the shredded waste material, or to be turned on to increase the temperature of the mixture of the waste material and primary air, by energizing the burner 38 as with the initial ignition of waste entering the chamber 22.
Control means are further provided for the secondary air process, with the use of an atmospheric sensor 100, through the interfacing of the control panel 101 and the secondary air control 52 and motor 50. Using predetermined criteria, the control panel 101 is capable of adjusting the flow of secondary air into the chamber 22, by operationally controlling the secondary air blower 40, manifold 42, butterfly valves 48, and dampers 56. It has been observed that the control of the burner 38 together with the secondary air blower 40, manifold 42, butterfly valves 48, and dampers 56, can be adjusted in combination to more efficiently control the chamber temperature, moisture content, and vortex speed.
The flue emissions sensor 102 provides for monitoring and data retrieval of all flue emissions and conditions. Although not related to the operations of the combustion system and process, the flue emissions sensor 102 is connected to the control panel 101, and to a computer system with commercially available software for collection, reporting, and transmitting of environmental data in accordance with current United States Environmental Protection Agency's air quality and emissions standards, as well as those for state and local agencies. The control panel 101 and/or any interconnected computer equipment is/are capable of being connected directly or indirectly and can communicate over popular network interface protocols such as TCP/IP, OLE for process control (OPC), and SMTP. This network interfacing will allow for real-time data transmission, as well as remote access of the various operational controls.
By means of the invention a very efficient combustor is provided characterized by the exhaust of gases to the atmosphere which are substantially free of particulate matter so as to minimize air and water pollution. In addition, non-combustible material is discharged from the combustion chamber during the burning process by action of the vortex so as to avoid the provision of costly and complex material handling apparatus for conveying such material away from the combustion chamber. Further, the provision of costly and complex flue gas cleaning apparatus is avoided by the invention which allows operation of the combustor at temperatures which are higher than that which would be allowable in the event flue gas cleaning apparatus were utilized. Moreover, the combustor effects substantially complete combustion of combustible waste material resulting in an extremely high percentage reduction in the original volume of waste material.
A typical design of the combustor of the present invention includes a combustion chamber having an internal length of 11 feet and an inner diameter D of 8 feet. The flue pipe 76 has an inner diameter of 2 feet and extends into the chamber a distance of about 16 inches from the inner surface of the end wall 24. The baffle plate 92 has a diameter of approximately 37 inches and its orifice 71 has a diameter d of about 21 inches. Also, the conduit 86 has an inner diameter of between 4 and 6 inches.
A combustor of such design presently appears capable of disposing of solid waste having up to 25% moisture content and normally 10% ash content and a sufficient BTU rating based on the waste material introduced, to effect more than 99 percent destruction of combustible material. It presently appears that such a combustor deign emits particulate matter to the atmosphere of not more than 0.2 grains per standard dry cubic foot of flue gas. The forgoing results seem to be obtainable with chamber temperatures between 1,800° F. and 2,200° F.
Although the invention has been described with reference to certain specific embodiments thereof, numerous modifications are possible and it is desired to cover all modifications falling within the spirit and scope of the invention.
