CA2376460C

CA2376460C - Waste gasification system with gas conditioning

Info

Publication number: CA2376460C
Application number: CA002376460A
Authority: CA
Inventors: Steve Poulos; Ian Hood
Original assignee: Individual
Current assignee: Poulos Steven
Priority date: 2002-03-06
Filing date: 2002-03-06
Publication date: 2006-03-21
Anticipated expiration: 2022-03-06
Also published as: CA2376460A1

Abstract

A Municipal Waste Gasification System whereby Municipal Solid Waste (MSW) and other forms of waste are converted to useful energy via a close coupled gasification process in an artfully designed Waste Conversion and Recycling Vessel (WCRV) that allows for precise control of the temperature and oxygen content of the batch waste charge while providing for the automatic sorting of all post-gasification residuals. Embodied in the present invention is a Key Accelerant Balancing System (KABS) that precisely controls the temperature in the range of 800-1100°F and oxygen concentration in the 5-7% range within the WCRV continuously for 12-14 hours yielding overall better efficiency of the conversion of the waste to gas and minimizes pollutants in the present invention. The concrete structure that supports the WCRV doubles as a thermal envelope from which hot air is drawn from to dry the incoming waste. The residual glass, aluminum and other metallic components of the waste are automatically sized and separated from the ash for recycling by a logic control system of gravity doors, vibrating super-magnetized grates, vacuuming, screening and eddy currents advantageously increasing the speed, safety and efficiency of the gasification and automatic recycling of unsorted MSW into energy and marketable raw materials. The gas produced in the waste conversion vessel is conditioned in a unique fuel preparation cell by mixing with ambient air or oxygen and can be used to fire the waste conversion vessel's heating elements with the excess gas or used to run a gas fired turbine or boiler to produce electricity with the residual heat used for district heating, or industrial processes.

Description

2,376,460 WASTE GASIFICATION SYSTEM
WITH GAS CONDITIONING
Specification Gasification has been with us for more than a century, and was actually used in antiquity for various purposes including the production of charcoal. Coal gasi~cation was used for the lighting of streets at night in the early 20t" century and utilized in Britain as an energy source for hundreds of years. We are not inventing gasification. We are inventing the use of an energy source and creating a catalyst to use gasification in the most efficient and environmentally friendly application. The emphasis in invention of the Natural State Reduction System or NSRS is to secure a methodology to dispose of various waste types in the most environmentally friendly application possible.
Natural State Reduction System is not an incineration or combustion process.
Incineration and combustion processes seek to destroy waste by burning it, usually at high temperatures with some amount of excess air; the ultimate purpose of which is to burn (for the purposes of waste reduction) as much waste per unit of time as possible.
Various "starved air" combusters have been designed in recent years with the primary focus of improving air emission quality beyond that achievable with conventional incineration methods, but these devices still have the ultimate view of solid waste as a non usable resource.
This past view however, misses a critical element in the environmental benefit of this process. The NSRS approach to converting solids into a gas described herein that municipal and industrial solid wastes (which are routinely buried at landfills) represent a significant economic resource in the form of a high Btu value non-fossil fuel product. The Btu value from this waste can approach the Btu value of natural gas when the waste gas is properly prepared in the NSRS with the residuals economically and safely retrieved .

2,3 76,460 The Environmentally responsible conversion of waste materials, virtual 100%
recycling of the waste stream, and recovery for remanufacturing of all metals, glass, and minerals which compose the waste solids, liquids and sludge exemplifies a safe solution without unnecessary, and dangerous sorting machines, or exposure to airborne or other residual contaminates.
Other gasification processes that are screw fed, and/or sized for specific biomasses cannot accept the variety and sizes of Municipal Solid Waste (MSW) that the NSRS can, and require expensive upfront sorting and shredding processes, and they have no simple controls over the various resulting compounds and recyclables that allow for a safe and continuous mixed waste process.
Typical gasification processes have a high temperature requirement and much higher oxygen requirements that lead to all the problems affecting the environment.
The NSRS
system that GWPT has invented with all of the following modifications and built-in environmental protections operates within 800 to 1100 degrees F and is oxygen balanced in order to eliminate combustion where excess oxygen is required.
Our process in varying degrees is the opposite of incineration and eliminates all of the environmental problems that incineration represents, because at no point does combustion of the waste occur. The terms of reference of our technology is Natural State Reduction whereby we speed up natures' composting process at an accelerated rate.
We are deeply concerned about what landfill represents and the emissions that are affecting the global environment. Methane off-gassing from landfill is 26 times the density of C02 as a greenhouse gas agent. Our technology will help eliminate this threat. This technology has been refined with the ultimatum of protecting the environment while creating client interest and profit incentive for all parties involved. This is by far the most cost effective waste gasification process, and will compete with and better landfill tipping fees. This will make a very attractive investment for government and the corporate community at well below landfill costs for safe disposal methodology second to none with an additional energy profit and recyclable sales incentive. Global warming is a concern of

3 2,376,460 government and corporations alike, and our technology will provide the solution that landfill global warming emissions represent.
The technology illustrated allows for unsorted municipal, industrial and medical wastes, and hazardous wastes to be co-mingled in any given incoming waste load. Waste is dumped directly onto a Waste Chute Collector from the waste carrying vehicle. The chute provides multiple advantages over direct dumping or conveyor dumping into vessels: The chute allows for complete surveillance of waste via camera, overhead crane removal of large steel items or suspect items, PCBs detection, radioactive detection via Geiger counter and tilting of waste mass to tumble and reveal previously undetectable items;
waste is dried in the chute through perforated floor and walls using previously un-captured system waste heat; screening options for the chute allow for waste variations such as municipal solid waste, tires or dewatered biosolids.
The analysis of the waste batch prior to vessel conversion is essential in today's volatile dumping activities that do not normally protect the public from hazardous or uncontrolled dumping. The quick detection and removal of unwanted items also preserves the integrity of the system and removes the possibility of contamination. A hydraulic pump supports both ash doors and the grate doors via a steel vertical tube welded to the top of the ash doors. All doors and collection bins are fully automated, and are camera and electric eye monitored. This unique design allows for a direct and complete transfer of ash without exposing any human operators while employing only a handful of moving parts as compared to other conveyor type transfers that often seize up due to wear and tear. The use of gravity as well to move the incoming waste through to the ash collection bin minimizes total energy outputs. The ash and recyclables bin is computer controlled to move via electric eyes to its destinations. Its upper resting position will be at grade level where the entire bin excluding its wheel mechanisms is loaded directly onto a transport for subsequent cement batching of ash and glass and bailing of metals, or stored in an ash silo for subsequent retrieval. Depending on the site the raising of the bins to grade is accomplished by way of ramp or hydraulic lift.

4 2,376,460 BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1, Shown is the process flow diagram for a NSRS scalable municipal solid waste gasification system that can have one or many waste conversion cells as embodied in the present invention Figure 2, Shown is the plan view of a 120 tonne per day NSRS municipal solid waste gasification system with 4 waste chutes 39, 2 Waste Conversion and Recycling Vessels (WCRVs) and four waste chutes and four Silo-vacs 35&37.
Figure 3, Shown is a side view section of a single waste conversion and recycling cell (WCRV) showing the relationship of the tipping chute to the WCRV, the concrete envelope and the Silo-vacs.
Figure 4 Shows details inside the WCRV with the relationships of the grates shown in open and closed position 65 and the key accelerant tubes 27 defined in relation to the gas jet flows c&b, and extraction of the raw waste gas flow by arrows e.
Figure 5 Shows details inside the WCRV with the relationships of the grates shown in open and closed position 65 and the key accelerant tubes 27 defined in relation to the ash flow by arrows d, and material extraction flow by arrow c.
Figure 6 shows an example site elevation transverse to figure 3 indicating the general relationships of plant components including the fuel preparation cell, the fuel consumption device and boiler.
Figure 7 shows the continuation of the exhaust stream from the boiler through to the heat exchangers 68 emissions control 70 and final vent 83.
s 2,376,460 WASTE GASIFICATION SYSTEM
WITH GAS CONDITIONING
DETAILED DESCRIPTION OF THE INVENTION
Figure 1 is The System Flow Diagram depicting the general arrangement of the several embodiments of the invention, and the direction of solids and gases including their temperatures as they are processed through the system. First MSW (Flow Path f) is loaded into the waste chute 39 where it is screened for radioactive waste and bulky items that are removed via overhead crane 47. The perforated walls14 of the chute allow the MSW to be exposed to the hot air (Flow Path a) exiting from the concrete jacket 2 and optional water jacket around the hot WCRV while waiting over the 12-14 hours for the preceding batch to gasify to reduce the moisture content of the receiving waste from approx. 25%
to 10%.
When the WCRV is ready to receive a charge of waste the chute 39 is tipped hydraulically into the open top doors 44 of the WCRV. The combination of vibrating the angle iron protectors 42 of the Key Accelerant Tubes 27(KATs) and vibrating the grates 65 in the bottom of the WCRV ensure there is a uniform distribution of the waste to allow for even heating and escape of the raw waste gas (e). When the WCRV 1 is full the load doors 44 are closed and the ambient air in the vessel is vacuumed out to reduce the oxygen content in the vessel to between 5-7%. The main burners 22 and the KATs 27 are then ignited with conditioned fuel gas from the previous cycle of the NSRS and/or by supplemental propane or methane to raise the temperature to between 800-1100°F. The Key Accelerant Balancing System (KABS) achieves precise control of the gasification process with oxygen and temperature sensors 59 on the key accelerant balancing tubes 27 reporting to a process logic controller (not shown, commonly known) that decides location, timing and volume of heat (no direct flame) distribution within the waste charge to ensure even conversion of the waste to gas. The raw waste gas is continuously drawn off via gas extraction ducts 24 containing gas sensors (not shown, commonly known). The NSRS will convert combustible solids, liquids and sludges to a raw waste gas comprised chiefly of a heavy, BTU-rich gas vapor of carbon dioxide , carbon monoxide and methane. The raw waste gas vapor is pulled through the remainder of the processing system by the force of 2,376,460 and induced draft fan, downstream at the far end of the system. It takes roughly 12 hours for 60 tonnes of waste to convert to a gas. Within the WCRV the array of tubes that make up the KABS deliver air and/or conditioned fuel converted from the waste and/or natural gas and/or propane and/or any combination of the preceding as specified by the computerized process logic controller balancing the substoichiometric oxygen and supplemental fuel to monitor and regulate the thermal composition of the waste batch. A
balanced mass reduction throughout the vessel is achieved by way of injecting key accelerants located in low temperature anomalies within the batch or by completely starving (0%oxygen) in high temperature anomalies. Precise information on these anomalies from the thermocouples and gas sensors of the Key Accelerant Balancing System mounted on the Key Accelerant Tubes (KATS) allows both starving and accelerating different parts of any waste batch in real time greatly increasing efficiency and safety and greatly reducing tendencies to stalling and/or smoking, or conversely unnecessary ignition. The KATs located strategically amongst the waste batch insure maximum reduction and conversion in the shortest amount of time avoiding cool spots or hot spots without the need of expensive manual waste mixing, sorting ,sizing or pelletization.
When the gas sensors in the extraction ducts 24 sense the reduction of raw waste gas from the WCRV (after approx 12-14 hours) the waste charge has had all or most of its volatile fractions converted to gas. The Key Accelerant Tubes (KATS) 27 and the Gas Jets 61 now start injecting cooled, clean, oxygen free exhaust gas into the WCRV to start cooling the vessel.
The bottom doors 64 and grates 65 are now super-magnetized by built-in electro magnets (not shown, commonly known) trapping the magnetic metal fraction of the debris and ash, then the grate vibrators (not shown, commonly known) are activated to separate the ash fraction (b) by gravity to fall through the grates 65 with the assistance of the cooled exhaust gas at 100 deg.F entering both from the key accelerant tubes 27 and high pressure jets 61 a, fig. 4 opposite from the lower set of vacuum outlets 61 c, fig. 5.
This combination of agitation, gas jets and vacuuming removes the ash to the dedicated Silo-vacs 37 via vacuum pipes 36. Once all of the ash (b) is removed the upper set of gas jets 61, fig. 4 and vacuum outlets 61b, fig. 5 are activated and the vibrating grates 65 2,376,460 remove the aluminum and other non-magnetic metals and glass (c) from the WCRV
1 to Silo-vacs 35 that have beneath them four bins with a movable chute 11 . While the mixed aluminum and glass is falling from the silo-vac 35 an eddy current separator 33 (not shown, commonly known) mounted on the outlet chute forces the aluminum into the first bin while the glass falls into the second bin.
The electric current magnetizing the grates 65 is now turned off and the magnetic metals on flow path (c) are removed by gas jets 61 and vacuum outlets 61 b to the dedicated Silo-vacs 33 and into the third bin via dampers and logic controls. Small ferrous fractions still remaining on the bottom ash doors are then vacuumed and jetted (61a) onto flow path b for a final evacuation of the WCRV and directed by a duct transfer point 81 to silovac 35. The cooled exhaust gas introduced during the removal and vacuuming process has cooled the WCRV enough to allow the bottom doors 64 and grates 65 to open and allow the larger debris, if any, to fall out into movable bins 52 positioned below. Then the bottom doors and all jet and vacuum dampers are shut and the next waste charge (f) is tipped in to repeat the cycle.
Raw waste gas (e) produced in the WCRV during the heating phase is continuously drawn off via ducts 24 during the 12 to 14 hour cycle of the WCRV. The raw fuel gas is mixed with oxygen for conditioning in the secondary fuel preparation cell where a cyclonic action separates any particulates entrained in the gas stream. The now oxygenated conditioned fuel gas (d) is then combusted either in a boiler or a turbine to produce electricity. .
Operating multiple WCRVs in parallel with staggered batch times with allow balancing of the conditioned fuel gas for delivery to the boiler or turbine. A portion of the exhaust gas from the turbine or boiler is then directed to either a heat exchanger (hot water tank , and radiant heat ) or through the ground to cool the exhaust then introduced as make up air volume during the vacuuming process for the removal of the ash and recyclable components of the residue in the WCRV. If desired in specific applications the exhaust gas can be diverted to greenhouses for both its carbon dioxide fraction (if sufficiently purified ) and heat value. Optional further processing via membrane filtering and/or lime filtering cleans the exhaust stream for further industrial uses or district heating.
s 2,376,460 In the configuration of the WCRV illustrated the waste chute tilt 39 includes a hinged support beam at the exit side while the opposite waste-loading end is free to travel 55 degrees off the horizontal to rapidly chute a 30 tonne waste load into the WCRV. The hydraulic piston 13 that lifts the free end of the chute box up once the two end doors are shut into a 20 degree off-vertical position allows the waste to fall into the vessel. A
significant attribute of the chute design is the perforated stainless steel metal floor and walls that allows both drainage to a drying tank of many types of waste and direct drying of the waste mass by way of introducing preheated air from the pump room 54 and collection bin chambers 52, and the vessel perimeter plenums 48,10 and/or downstream preheated air as desired in specific applications.
This de-saturating of the waste while waiting on the chute for the 12 hour preceding batch speeds up the conversion process and gains back valuable BTU energy for subsequent use. The 2 induction forced air fans 71 located below the chute's central axis draws the hot air from the vessel plenum 73 through the chute sides.
The WCRV, the collection bin chamber, and vertical pump rooms share a 1 m wide plenum (not shown) that allows for the recapture of escaping radiant heat from the system and allows for a maintenance space for the various exposed exterior elements of the system.
The outside wall of the envelope is insulated acting as both the structural containment of the system and a heat sink that absorbs overflow heat at maximum temperature times.
This thermal mass provides a balanced supply of hot air for the use of vessel air and chute waste drying air using the structure itself to store temperatures that may or may not be called for either at times of dry waste in the chute or when no or little jacket hot air is available at batch start-up times.
The Waste Conversion and Recycling Vessels 1 can be of any shape and dimension, depending on site conditions and the waste volume to be processed. The WCRV
version illustrated is a rectangular, 12mm thick cold rolled steel box approximately 6m x 6m x 20m.
The inside of this vessel is lined with 250mm of mineral wool, or other insulating, non-combustible material. Over this insulation blanket, lining the WCRV interior is a layer of 304 stainless steel approximately 4 mm thick. The Waste chutes 14 dump directly into the 2,376,460 waste conversion vessels each holding from 40 to 60tonnes of waste. For a double vessel (240 tonne per day system) as shown in Fig.2, 120 tonnes are processed in parallel, but the batch start-up times are staggered between the two vessels to improve waste gas balancing. Bulky items, if any, are dropped storage bins below the vessel, at the end of the process via large bottom opening doors.
The illustrated version of the WCRV contains Key Accelerant Tubes (KATs) that are mounted transversely within the vessel spaced to accept MSW that does not contain bulky items ie: stoves, dryers etc. Depending on the size and shape and constituent waste to be gasified, other versions of the WCRV can have the KATs mounted on the longitudinal walls and/or on a longitudinal spine and /or on a plurality of longitudinal spines and/or on a transverse spine or plurality of transverse spines. The optional central longitudinal spine 84 is configured for a version of the WCRV that has KATs that are mounted on the longitudinal walls and the central longitudinal spine and can accept entire uncrushed cars for the gasification of their volatile fractions before being crushed and smelted thereby greatly reducing the pollutants the smelter discharges.
The Vertical Hydraulic Pump room 54 houses the hydraulic lift pumps that are fully remotely controllable. The collection bins are moved forward of the lift to provide clearance just prior to activating the pump.
The Waste Fuel Preparation Cell 49 is a sphere, 4m in diameter and made from hot rolled steel 6mm thick. It is lined with gunnite applied insulative clay, sufficient in thickness to keep the exterior surface temperature of the cell below 200 ° F. The raw waste gas is vented from the vessel into this sphere shaped processor, which spins the raw gas with compressed air. This process elevates the percentage of oxygen in the finished gas product to ambient (~20%). Further, the turbulence in the sphere acts as a cyclone separator that causes any fine particulate or heavy metals to fall from suspension in the gas. This finished fuel gas is combusted in the primary energy system of the facility (steam boiler, hot water heater, refrigeration unit, or other such industrial processor).
The Waste Fuel Consumption Device embodiment 50 flares the combustible processed fuel gas to produce heat for the subject industrial process (hot water heater, boiler, steam io 2,376,460 turbine, refrigeration unit, etc.) A gas turbine may be used in lieu of hot water or steam requirements where only electrical production is desired. The conditioned fuel gas entering the Waste Fuel Consumption Device passes though a plenum and is flared in burners with little or no supplemental fuel depending on the constituents of the waste batch that generated it. The resulting fireball causes a superheated exhaust stream of +/-1600 ° F
which exits this chamber through a restriction in the opposite end of the unit where the heat is exposed to the hot water element of a steam boiler which can send the super heated steam to a steam turbine for electrical generation, or in the case of the illustrated version to the hot water tank 68 whose heat can be sent to local industrial or residential users via radiators 69 further cooling the exhaust to approximately 200 ° F where it enters the lime screening device 70.
The Lime Screening Device 70 comprises six lime screens 97 removes the hydrogen chloride and sulphur dioxides from the exhaust gas. This proprietary three tiered flow dampened device is coupled to a final emission regulator on the vent stack detecting any emissions over 25 ppm of hydrogen chloride or sulphur dioxide at which time one of the three manifolds 96 open putting into flow an appropriate volume of gas through the screens and a screen by-pass. This system preserves the lime applied to the screens for times of need only when emission guidelines are encroached upon. In most waste batches this should not be necessary. The detectors on the stack can be constructed by those with ordinary skill in the art Optionally (not shown) exhaust now can be used to provide heat and carbon dioxide to the plants of a greenhouse operation or piped to a industrial workspace through radiant heat tubing Optionally (not shown) a portion of the exhaust can be redirected to a heat exchanger or passed through pipes in the ground to be returned by duct to the WCRV
vessel plenum. The temperature of the exhaust column reaching the induced draft fan surge tank 74 is approximately 100° F.
The final exhaust 83 can be vented to the atmosphere or sequestered as desired .
n

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A solid waste gasification system consisting of:
a) integral waste chute or chutes that dry the waste in using scavenged process heat before introduction into a primary waste conversion and recycling vessel scanning the incoming waste for radioactive , hazardous or oversized waste both in the chute and the waste conversion and recycling vessel (WCRV) with cameras and probes;
b) said primary WCRV that heats the waste in an oxygen deprived atmosphere to convert the bulk of the waste to gas, ash and metal debris;
c) a secondary fuel preparation cell for receiving and conditioning the gas produced in the primary WCRV by mixing it with either pure oxygen or ambient air;
d) a means of combusting the conditioned gas either in a gas turbine to run electrical generators and/or in a fuel consumption device to fire a boiler to produce hot water or steam for use selected from the group of electrical generation, greenhouse heating, district heating and hot process water for industrial uses.

2. A system of claim 1 whose said primary WCRV has attached a hydraulically operated waste chute that pre-dries multiple truck loads of waste then tips the batch into the top loading doors in the primary WCRV to allow for rapid charging of waste before each cycle.

3. A municipal solid waste gasification system as defined in claims 1 &2 and oxygen/ambient air to start the gasification process then once the WCRV is in its optimal temperature and oxygen concentration range will precisely meter the gas and/or oxygen/ambient air within the WCRV, mounting configuration of the said tubes dependant on the waste to be processed and the shape of the WCRV.

4. A solid waste gasification system as defined in claim 3 whose said key accelerant balancing tubes to have a plurality of integral temperature sensors, preferably in the form of thermocouples, to measure temperature variations within the waste charge.

5. A solid waste gasification system as defined in claim 3 whose said key accelerant balancing tubes to have a plurality of integral oxygen sensors to measure oxygen levels throughout the waste charge.

6. A solid waste gasification system as defined in claim 4 whose said temperature sensors to be connected to process logic controls that can be programmed to independently control each individual key accelerant balancing tube to allow for maintaining an even heating of the waste charge keep it in the range of between 800 &1100 degrees Fahrenheit and holding in this range for up to 12 - 14 hours to therefore more tightly control the quality of the product gas.

7. A solid waste gasification system as defined in claim 3 whose said key accelerant balancing tubes having a dual function as oxygen and gas controllers so as to tightly control oxygen levels within the waste charge and therefore more evenly convert the waste charge to gas without actually igniting the waste .

8. A solid waste gasification system as defined in claim 1 whose primary waste conversion vessel has a plurality of doors and grates in its bottom that allow for the automatic separation of the ash from the recyclable material by vibrating the grates and then vacuuming out the ash.

9. A solid waste gasification system as defined in claim 1 whose primary waste conversion vessel has a plurality of doors and grates in its bottom that allow for the automatic separation of the magnetic metallic recyclables from the non-magnetic recyclables by super magnetizing the grates in the bottom of the waste conversion vessel, after the ash has been vibrated and vacuumed out, by vibrating the grates while they are super magnetized to bind the magnetic metallic debris to the grates and then vacuuming out the non-magnetic metallic debris, thus achieving automatic separation of the recyclable components of the waste.

10. A solid waste gasification system as defined in claim 8 whose primary waste conversion vessel is cooled by the vacuuming procedures so that there is little or no cool down time needed between waste conversion cycles.

11. A solid waste gasification system as defined in claim 1 that includes a lime screening device with multiple damped manifolds passing the final exhaust stream through as many times as required to completely detoxify the final exhaust, and controlled by sensor devices on the final exhaust vent reporting to a logic control computer data base for the dampers in the lime screen manifolds.