FIELD OF INVENTION

The present invention relates to a waste to energy combustion system, which involves a proprietary air injection system that is deployed with a conventional rotary kiln incinerator.

BACKGROUND ART

Waste disposal practices differ for developed and developing nations. As a result, issues and problems are different for both developed and developing countries. Developed countries generate larger amount of wastes which corresponds to a larger population with diversified operations in multiple sectors of industrial plants, household waste, clinical waste as well as waste produced by commercial areas and public places. As amount of waste at dumpsite have increased considerably, it is advantageous to approach and make the transition towards better waste management.

Sorting waste upstream by separating between the dry and wet refuse is being practiced in the more developed countries but this is lacking in the less developed countries. One problem with unsorted waste is that it comprises a mixture of both dry and wet substance and therefore contains a higher level of moisture compared to the sorted waste. A result of this wet waste is that more energy is required to ensure complete burning of such unsorted waste if incineration is chosen as the means of disposal.

Waste management involves monitoring, collection, transport, processing and disposal of industrial and household rubbish. There are several different methods of waste management for disposing of waste. The common waste disposal methods are landfilling, composting and incineration.

In a comparison between the common waste disposal methods, the advantages of incineration outweigh the other available methods for waste disposal. Incineration effectively reduces the volume or the actual size of waste by 95-97% by reducing waste to ash. Incineration is also environmentally safer compared to landfilling, which is the most common method of disposing municipal solid waste. Composting allows large amounts of organic waste to break down properly, which is advantageous for bio-waste.

Landfilling seems to be the easy option. However, there are various environmental hazards such as soil and water contamination, emission of excess greenhouse gases that contribute to global warming and the discharge of odour that impacts on human and animals. In addition, capped landfill areas would require maintenance for many years after dumping had stopped. Therefore, incineration would mitigate the extensive use of landfills.

An enhanced incineration process, which deploys a complete combustion system by means of an optimal air supply, is desirable as an alternative to the current systems available.

The subject matter claimed herein is not limited to embodiments that solve any disadvantages or that operate only in environments such as those described above. Rather, this background is only provided to illustrate one exemplary technology area where some embodiments described herein may be practiced in modern day waste management technology.

SUMMARY OF INVENTION

In one embodiment of the present invention is a system for waste to energy combustion comprising a hydraulic ram feeder, a primary chamber that is a rotary kiln incinerator, a bottom ash handling system and a proprietary air injection system. The proprietary air injection system comprises of a duct, which runs the length of the kiln offset from center with a plurality of air injection nozzles directed tangentially and in the opposite direction of kiln rotation supplying combustion air into the rotary kiln incinerator. The duct is located as close to the inner wall of the rotating kiln as possible. The proprietary air injection system induces a vortex air motion, which impinges turbulently against the waste as it rotates and burns. The proprietary air injection system may further comprise of a plurality of water nozzles supplied through a conduit within the air duct having means for quenching the combustion process to reduce the temperature of exhaust gases and to reduce calorific value of waste. Advantageously, the air pattern of this system provides efficient pre-drying of the waste introduced.

In another embodiment of the present invention is a secondary chamber, comprising an air delivery system, a pressure relief valve, a burner and a detection mechanism. The secondary chamber comprises means for receiving flue gas in an effort to lengthen the resident time which exits from the rotary kiln incinerator, provides means for oxidizing residual flue gas by applying additional air and heat as well as means for detecting a need for further combustion through the detection mechanism. The cyclonic separator shape of the secondary chamber allows for separation of fly ash particles by means of a vortex and the flue gas exits from a high point in the chamber through a connecting duct while fly ash settles at the bottom of the combustion chamber. The hot flue gas is then transported to a waste heat boiler to produce superheated steam, which is converted into electrical energy in a steam turbine located on site.

The present invention consists of several novel features and a combination of parts hereinafter fully described and illustrated in the accompanying drawings, it being understood that various changes in the details may be made without departing from the scope of invention or sacrificing any of the advantages of the present invention. BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS

To further clarify various aspects of some embodiments of the present invention, a more particular description of the invention will be rendered by references to specific embodiments thereof, which are illustrated, in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail through the accompanying drawings in which:

FIG.1 illustrates a system arrangement for waste to energy combustion system.

FIG. 2 is an exploded view of the assembly parts of a waste to energy combustion system.

FIG. 2A is an exploded view of an enlarged sub-section of the assembly parts of a waste to energy combustion system.

FIG. 3 is a cross-section of the top view for the waste to energy combustion system's overall assembly.

FIG. 4 is a cross-section of the side view for the waste to energy combustion system's overall assembly.

FIG. 5 is a cross-section of the side view of support thrust rollers for the waste to energy combustion system.

FIG. 6 is a cross-section of the drive assembly of the rotary kiln incinerator.

FIG. 7 is an isometric cross section view for the waste to energy combustion system.

FIG. 8 is a cross-section of the side view of the intake head of the rotary kiln incinerator. DETAILED DESCRIPTION OF THE PREFFERED EMBODIMENTS

Embodiments of the invention relate to a waste to energy combustion system. Hereinafter, this specification will describe the present invention according to the preferred embodiments of the present invention. However, it is to be understood that limiting the description to the preferred embodiments of the invention is merely to facilitate discussion of the present invention and it is envisioned without departing from the scope of the appended claims.

The system for waste to energy combustion according to the embodiments of the present invention describes a system, which employs a proprietary air injection system (106) deployed with a primary chamber (108), which is a conventional rotary kiln incinerator (108). The system provides for waste to energy combustion, which reduces the operating cost of waste to energy as it minimizes and eliminates the use of auxiliary fuel used in most existing incinerators.

Reference is first being made to FIG.1 and FIG. 2 collectively. FIG. 1 illustrates an arrangement for the waste to energy combustion system while FIG. 2 illustrates the assembly parts exploded view, which structures the entire waste to energy combustion system. Table 1.0 provides the detail description of each part. The system according to the embodiments of the present invention comprises a hydraulic ram feeder (104), a proprietary air injection system (106), a primary chamber, which is a rotary kiln incinerator (108), a secondary chamber (112) and a bottom ash handling system (114).

The system according to the embodiments of the present invention employs a proprietary air injection system (106) in a conventional rotary kiln incinerator (108,2). The rotary kiln incinerator (108,2) is installed at an angle of inclination. Fuel media (102) may comprise municipal solid waste, clinical waste, scheduled waste, biomass and other form of waste. Fuel media (102) is fed into the higher end of the rotary kiln incinerator (108, 2) through a hydraulically operated ram feeder (8) through a feeder duct (3) and supplied by a hopper (4). The ram face has its top leading edge heat treated and sharpened to act as a cutter to shear waste as it travels down the hopper (4) to the feeder duct (3). In addition to the edge of the cutter, a taper shaped harpoon is attached to the ram feeder (8) face to provide a void in the remaining undelivered waste when the ram is retracted. This void in the remaining waste waiting to be delivered eliminates clogging of the feeder duct (3).

A gasket is applied between sections of the feeder duct (3) for the ram to seal against. This seal prevents paper, food and liquids from bypassing the hydraulic ram feeder (8) as it travels back and forth. The hopper (4) configuration is such that the top portion has a positive taper to collect the waste and transitions to a negative taper to reduce clogging where the opening starts large and converges to a narrow throat which diverges to a large exit into the feeder duct (3). The portion of the feeder (3), which enters the stationary intake head (14), is a double walled, insulated and water cooled design to withstand the high temperature of the rotary kiln incinerator. In addition, the insulated jacketed feeder (9) is fabricated from high temperature resistant metal type of material such as stainless steel. The stroke of delivery is limited to a length that leaves behind a "charge" of fuel media waiting for the next delivery stroke before it travels into the rotary kiln incinerator. The "charge" of fuel media prohibits unwanted introduction of uncontrolled air into the combustion process while hot combustion gases are restricted from moving through the feeder duct (3).

The rotary kiln incinerator (108,2) is driven through a drive chain (22) coupled to a speed reducing transmission, an electric motor and a series of sprockets (11 ,12) to the main drum sprocket (10). The drive chain (22) is arranged such that the main drum sprocket

(10) links the drive chain (22) and supported by outrigger sprockets (11 , 12). One of the outrigger sprockets (11, 12) is coupled to an inverter driven motorized gearbox (20) through flexible coupling. Further to that, a small tensioning sprocket (21) is employed to adjust a tension of the drive chain (22).

The rotary portion of the rotary kiln incinerator (108,2) between the two stationary heads is supported by a series of two tires (1) of steel type. The steel tires (1) are mounted to the rotary kiln incinerator (108,2) through a series of steel wedge blocks welded together at a predetermined height. The steel tires (1) are fitted over the series of wedge blocks, which floats with a minimal radial gap. Trunnion (18) and thrust rollers (15) are used to support the steel tires (1) and the rotary kiln incinerator. Each tire (1) sits on two trunnion rollers (18), which are mounted to the base of the rotary kiln incinerator. As the rotary kiln incinerator is installed at an angle of inclination, a plurality of thrust rollers (15) provide axial support through the sidewalls of the steel tires (1). Two thrust rollers (15) are used to support both sides of one steel tire (1 ) while a third roller supports the lower end of the second steel tire (1). The plurality of thrust rollers (15) and trunnion rollers (18) are arranged in a manner for free rotation of the rotary kiln incinerator (108, 2) while compensating for expansion of thermal effect.

In FIG. 3, the rotary kiln incinerator (2) is depicted in a cross-sectional view of the overall assembly of the waste to energy combustion system. As the rotary kiln incinerator (2) rotates, combustion is initiated simultaneously. Waste material travels towards the lower end of the rotary kiln incinerator (2) before being discharged as ash through the bottom ash handling system. The ash, or known as "bottom ash" which leaves the discharge head (13) is sealed from the ambient air via a water seal to be then transported wet on a conveyor system. The processed bottom ash represents a reduction in overall volume of the initial waste.

In FIG. 4, the proprietary air injection system is depicted in a cross-sectional view of the overall assembly of the waste to energy combustion system. When started from cold, heat energy for ignition is supplied by a diesel or gas burner (25). When the fuel media ignites, combustion air is supplied from a primary air fan through the proprietary air injection system deployed within the rotary kiln incinerator (2). The proprietary air injection system comprises of stepped chambers, which inject air tangentially and at an opposite direction to rotation of the rotary kiln incinerator (2) to promote self autogenous combustion.

Air enters the rotary kiln incinerator (2) through a plurality of nozzles directed tangentially and in the opposite direction of the rotary kiln incinerator (2). Air swirls in a vortex motion in a direction opposite to the rotation of the rotary kiln incinerator (2) and impinges turbulently against the waste as it ignites and burns. The plurality of nozzles of varying cross-sectional area allows the angular velocity of varying air flow to be constant which provides an ideal combustion environment. The proprietary air injection system allows air flow to be tailored to sections of the rotary kiln incinerator (2) with compartmentaϋzation of the air duct (17). In addition to delivering air for purpose of combustion, the air duct (17) provides a protective conduit to employ a water spray system to reduce the temperature of exhaust gases or reduce the calorific value of the waste if necessary. The conduit may be fabricated from a metal type of material such as stainless steel. The conduit together with water nozzle is inserted into one of the duct chambers at the discharge head (13). The water conduit follows along the length of the air duct (17) prior to exiting at a suitable point. At this exit point, a suitable nozzle is utilized to provide proper dispersement of the water spray. The constant flow of ambient air through the air duct (17) prevents the water conduit from overheating and provides an appropriate height to spray the interior of the rotary kiln incinerator.

In the rotary kiln incinerator (2), ash formed falls from the burning heap as the rotary kiln incinerator (2) rotates and travels to the bottom ash handling system without any insulation layer to impede continuous burning. The bottom ash handling system comprises means for collecting ash, which is sealed off, from the atmosphere through a discharge head (13) of the rotary kiln incinerator (2) and means for transporting the bottom ash in a wet condition through a conveyor.

In FIG. 3, the secondary chamber (7) is depicted in a cross-sectional view of the overall assembly of the waste to energy combustion system. As the bottom ash exits the discharge head (13), flue gas generated exits the rotary kiln incinerator (2) and enters the secondary chamber (7). The secondary chamber (7) comprises an air delivery system, a diesel or a gas burner and a detection mechanism. Flue gases entering the combustion chamber are given more resident time while additional air and heat from a burner is applied to oxidize residual hydrocarbons. The detection mechanism comprises means for detecting a need for further combustion through detection mechanism means such as a sensor. The flue gas eventually exits thru an elevated point thru the cylindrical wall of the secondary chamber (7) while fly ash settles at the bottom of the secondary chamber (7). The hot flue gas is then transported to a waste heat boiler to generate superheated steam, which can be converted into electrical energy in a steam turbine plant located on site.

The combustion process in the rotary kiln incinerator (2) may comprise of either a counter current-flow or a co-current flow process. When the direction of flue gas is in an opposite direction of the flue media, the process is termed counter current-flow whereas when the direction of flue gas and the flue media moves in the same direction, the process is then termed co-current flow. For solid material with high moisture content with low calorific value such as municipal solid waste, counter current-flow process, which comprises of double counter current-flow processes, would be applicable. The first counter current-flow process is that of a rotational movement of the kiln with the fuel media and the combustion air swirling in opposing direction. The second counter current-flow process is the axial counter current-flow resulting from the bulk flow of flue gas opposite to that of the flue media and ash. Incineration of waste in the rotary kiln incinerator (2) is triggered when waste is rotated upward from the bottom. The resulting flame travels backwards and swirls into the unburned waste substance. The swirling counter current-flow process allows heat energy to be distributed evenly across the waste. Thus, heat energy is thoroughly distributed throughout to achieve autogenous and complete combustion.

With this invention, the proprietary air injection system described above when used in a conventional rotary kiln incinerator (2) promotes self autogenous combustion. The turbulence in combustion promotes complete oxidation of all hydrocarbon elements and reduces the possibility of incomplete combustion. The even and thorough distribution of heat also minimizes cold spots within the rotary kiln and therefore reduces dioxin formation and pollutants resulting from incomplete combustion of waste. The waste to energy combustion system can act as an incineration power plant capable of providing its own energy needs by using the energy generated from the combustion process. As such, fuel required to sustain the incineration cycle can be minimized.

The present invention may be embodied in other specific forms without departing from its essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore indicated by the appended claims rather than by the foregoing description. All changes, which come within the meaning and range of equivalency of the claims, are to be embraced within their scope.

TABLE 1.0