EP0403708A1

EP0403708A1 - Method and apparatus for processing solid waste by pyrolysis

Info

Publication number: EP0403708A1
Application number: EP89311138A
Authority: EP
Inventors: Richard J. Taeger
Original assignee: Frontier Ind Inc; FRONTIER INDUSTRIES Inc
Current assignee: Frontier Ind Inc; FRONTIER INDUSTRIES Inc
Priority date: 1989-06-19
Filing date: 1989-10-27
Publication date: 1990-12-27
Also published as: PT92044A

Abstract

Carbonaceous solid waste such as garbage and other refuse, with recyclable material such as metal, aluminum and glass substantially removed, is ground to small bits and pieces of relatively uniform size for processing by pyrolysis in a vertical retort. Material for processing is moved from a source of supply via a gas stream into the top of the retort in a cyclone fashion or swirling motion where it falls by gravity through countercurrent hot gases to exit for collection at the bottom of the retort as char. The hot gases are initially generated in the startup operation by igniting the first falling particles to reach the bottom with a fuel burning ignitor that is turned off when the material is sufficiently ignited and ambient air is blown into the bottom of the retort in a swirling or cyclone motion to maintain combustion of the swirling ignited material whereby the continual flow of falling material becomes the fuel to sustain the process of generating the hot gases without any outside source of fuel. The material is in constant motion from the time it enters the retort until it exits at the bottom and at no time is there a bed of material or a packed column being processed. The gases exit at the top of the retort where part of the gas stream is reduced in temperature and directed through the source of supply to serve as the vehicle for moving colds materials from such source to the top of the retort and the remaining gas stream is directed to a point of deposit which can be a secondary combustor for incinerating all impurities therein. The flow of the gas stream from the retort to the source of supply is through a closed conduit to provide a closed loop in which material is moved into and out of the system in an air free environment. The quantity of material processed per hour can be varied by varying the speed of delivery of material to the gas stream moving through the source of supply to the retort and the flow of ambient air can be increased or decreased correspondingly with an increase or decrease in the flow of material from the source of supply to maintain combustion. A storage bin may be provided for replenishing the source of supply and the speed of delivery of material from such bin to the source of supply can be varied to correspond with the amount of material being taken therefrom.

Description

Background of the Invention

This invention relates to improvements in an apparatus and method for converting carbonaceous solids in municipal waste such as garbage and other refuse to products that serve a useful purpose and can produce a financial return. Presently, to a limited extent, recyclable materials such as newsprint, glass, metals and plastic are processed for reuse but the vast majority of municipal waste is collected and hauled to landfill areas for burial or to facilities for incineration where residue of burned glass, metal and other organic matter is also buried. Neither method has been wholly satisfactory and the subject of disposition of such waste is a matter of continuing concern. Landfills are becoming full and expansion of present ones or the creation of new ones have created opposition and controversy particularly by those whose property is close by or who would be directly affected. Incinerators create environmental problems and are also a source of controversy.
It is well known that carbonaceous solids in waste materials such as garbage and other refuse can be changed by pyrolysis in the absence of air into valuable products such as carbon, ash, phosphates, for example, that produce char which is useful as a soil conditioner or as a fuel and for which there is a ready market for producing a financial return to thereby reduce the overall costs of disposing of the waste. Present methods of handling municipal waste do not take full advantage of the economic aspects of the waste materials. Also, although not a part of this invention, certain oils are recoverable from the gas streams generated by pyrolysis that can be further processed into useful products by available procedures.
With the above observations in mind, one of the important objects of this invention is to provide an improved apparatus and method for processing carbon based solid waste by pyrolysis to recover char material in a form that has an economic value for commercial sale.
Another object is to provide an apparatus and method of the above class which is highly efficient and extremely economical in operation.
More particularly, it is an object herein to provide an apparatus and method as characterized wherein the solid waste, previously ground to small bits and pieces and with recyclable material such as metals and glass substantially removed, are delivered to the top of a retort to fall by gravity therein through counter current hot gases which are generated at the bottom of the retort initially by temporary ignition of such material from a natural gas fuel source that is turned off when the material is ignited whereby the continual falling material serves as the fuel to sustain the system of generating gases and burns in a stream of ambient air, which consumes the oxygen therein, without any further outside source of fuel.
Still another object is to provide an apparatus and method of the above class wherein the material for processing in the retort is delivered from a hopper in an air free environment provided by channelling hot gases escaping from the top of the retort through closed conduits to the hopper to serve as the vehicle for conveying material to the retort and assisted by a suction fan associated with the hopper.

SUMMARY

In accordance with the present invention, solid waste such as garbage and other refuse material, with recyclable material such as metal, aluminum and glass substantially removed, is ground to small bits and pieces of relatively uniform size for processing by pyrolysis in a vertical retort. Material for processing is conveyed from a storage bin to a locking feed hopper from which it is pneumatically moved by a blower sucking such material via a gas stream from the hopper and directing it into the top of the retort in a cyclone fashion or swirling motion where it falls by gravity through countercurrent hot gases to exit at the bottom of the retort as char that has an economic value for soil conditioners, fertilizer and fuel for power plants. The hot gases are generated in the startup operation by igniting the falling particles with a pilot gas ignitor that is turned off when the material is sufficiently ignited and ambient air is blown into the bottom of the retort in a swirling or cyclone motion to maintain combustion of the swirling ignited material whereby the continual flow of falling material becomes the fuel to sustain the process of generating the hot gases. The material is in constant motion from the time it enters the retort until it exits at the bottom and at no time is there a bed of material or a packed column. The gases exit at the top of the retort to preferably two cyclones and then into two arms of a Y duct. In one duct, the gas stream passes through a cooler to reduce the gas temperature where it moves through a closed conduit to the locking feed hopper to serve as the vehicle for moving cold materials from the hopper to the top of the retort. In the other duct, the remaining gas stream is directed to a secondary combustor where all impurities are incinerated to prevent contamination of the atmosphere and this generates heat that can be utilized to produce steam and electricity. The flow of the gas stream from the retort to the cyclones and through a closed conduit to and through the locking feed hopper provides a closed loop in which material is moved into and out of the system without allowing air to enter or escape from the system. The quantity of material processed per hour can be varied by varying the speed of delivery of material in the locking feed hopper to the gas stream carrying it to the retort. The speed of delivery of material by the conveyor from the bin to the locking feed hopper is constant but the speed of delivery of material from the storage bin to the conveyor can be varied to correspond with the material being taken from the locking feed hopper and the flow of ambient air can be increased with an increased flow of materials from the locking feed hopper.
The foregoing objects and such further objects as may appear herein, or be hereinafter pointed out, together with the advantages of this invention will be more fully discussed and developed in the more detailed description of the accompanying drawings.

Brief Description of the Drawings

Fig. 1 is a top schematic view of an apparatus or plant embodying the features of this invention,
Fig. 2 is a side schematic view of the apparatus shown in Fig. 1,
Fig. 3 is a fragmentary schematic view of a portion of the air free closed loop material feed system of this invention taken from the line 3-3 of Fig. 1,
Fig. 4 is an enlarge fragmentary perspective, partially broken away, showing the locking feed hopper which is a part of the closed loop system of this invention in which waste material is moved to a retort for processing in an air free environment, and
Fig. 5 is an enlarged elevational view of the lower portion of the locking feed hopper taken from the line 5-5 of Fig. 1 with the side of the hopper removed to show the interior thereof when in operation.

Description of the Preferred Embodiments

Referring to the drawings, this apparatus for processing solid waste by pyrolysis is designated generally by the numeral 10 as best seen in Fig. 1 and since many of the components used such as bins, conveyors, blowers and the like are old and well known, they are shown and will be identified in diagrammatic form except where further details are required for a full understanding of their arrangement and function.
Apparatus 10 includes a storage bin 12, preferably in an elevated position, from which material for processing is delivered by a conveyor 14 to the open top of a vertical housing which I have designated as a locking feed hopper 16 that is one of the important and novel features of this invention which will later be described in more detail.
A conduit 18 communicates at one end with the bottom of hopper 16 (Fig. 5) and at the other end with a suction blower 20 for moving waste material through conduit 22 to the open top of a vertical retort 24. In the bottom of retort 24 (Fig. 2) is a gas ignitor 26 adapted for connection through line 28 to a source of natural gas fuel, and a blower 30 with a damper control 31 for ambient air is disposed for discharge into the bottom of retort 24. The bottom of retort 24 communicates with a conduit 32 that communicates with one end of an ash auger 34 for depositing material at its other end in an ash hopper 36 for removal by any suitable means.
At the top of retort 24, a housing 38 in communication therewith includes ducts 40, 42 for communicating respectively with cyclones 44, 46 that in turn communicate with chamber 48 connected to the Y ducts 50, 52. The bottom of each cyclone 44, 46 is provided with an ash receptacle 54. Duct 50 connects with a secondary combustor 56 provided with the exhaust stack 58 and a duct 52 connects to a condensor 60 and continues to communicate with the bottom of the locking feed hopper 16 as seen in Fig. 5. The bottom of hopper 16 is fitted with the rotating rollers 62 operated by a variable speed motor 64 for dispensing material 66 in a well known manner. With the apparatus or plant 10 constructed and arranged as described, the processing of solid waste is accomplished as follows.

Operation

Initially, solid waste such as garbage, refuse and the like, with recyclable material such as metal, aluminum and glass substantially removed although, as will later appear, any such recyclable material remaining does not affect the process to be described, is ground by any conventional means into small bits and pieces of relative uniform size on the order more or less of approximately one fourth inches indicated at 66 as seen in Fig. 5.
Material 66 is conveyed by any suitable means to a storage bin 12 having a live rotating bottom for regulating the amount of material dispensed therefrom all in a well known manner. A conveyor 14, designed to run at a constant speed, delivers material 66 from bin 12 to the top of the locking feed hopper 16 where it is accumulated as shown in Fig. 5. In the initial start up of this process, hopper 16 is filled to approximately eight feet with material 66 as a barrier to air entering the bottom thereof and the depth of such material 66 in hopper 16 should be maintained at at least two feet for such purpose.
Material 66 is dispensed into a gas stream as will become apparent and is sucked in such stream from hopper 16 by blower 20 via conduits 18, 20 into the top of retort 24 in a cyclone fashion or swirling motion where it falls by gravity to the bottom. Initially, the falling particles are ignited by a gas fuel ignitor 26 to create hot gases that move toward the top of retort 24 in a countercurrent flow to the descending particles 66. The swirling flow of the downwardly falling particles 66 keeps the cool incoming material near the walls of the retort 24 and the reduction in size to small bits and pieces provides sufficient air spaces between the particles that they absorb heat by radiation and convection from the hot gases which is preferable than from a packed column of material where heat must be transferred from one particle to another. Material 66 is in constant motion from the time it enters the retort 24 until it exits as char at the bottom to auger 34. THe combustion of the ignited material 66 is maintained in the bottom of the retort 24 by the introduction of ambient air from blower 30 at the bottom of retort 24 to create and maintain a continuous hot bed of swirling particles that flash off the condensable and non-condensable gases and water vapors travelling up and out of the retort to cyclones 44, 46. The ignitor 26 is turned off when the temperature at the bottom of retort 24 reaches approximately 1000 degrees F and this can be done manually or by any suitable automatic control. Once ignitor 26 is turned off, material 66 maintained in combustion by blower 30 becomes the fuel to maintain the system free from any outside source of fuel. The oxygen in the ambient air is consumed in the combustion of material 66 so that the countercurrent upwardly flow of hot gases maintains retort 24 oxygen free.
The temperature at the top of retort 24 will be approximately 780 degrees F to 900 degrees F and this temperature will increase as the falling particles 66 approach the swirling area at the bottom where the temperature ranges from 1125 degrees F to 1225 degrees F. The swirling action of the hot gases at the bottom of the retort 24 produced by the flow of ambient air cerate a cyclone effect so that when they strike the flat bottom of the retort they make a 180 degree turn and start to exit upwardly out of the system. As this occurs, the heavy particles 66 fall through conduit 32 to auger 34 as char for deposit in hopper 36 for removal to a point of deposit or use.
The hot gases travel from retort 24 to cyclones 44, 46 where light weight or fine particles that may be in the gas stream are collected in receptacles 54 and from there continue to chamber 48 where they separate into the respective Y ducts 50, 52. The gas stream in duct 52 passes through a condensor 60 where its temperature is reduced to approximately 250 degrees F to 280 degrees F and enters the bottom of hopper 16 where it serves as the vehicle to carry cold material 66 from such hopper to the top of the retort 24. Such gas stream has little or no oxygen and because of this negative pressure, it is important to maintain a head of at least two feet of material 66 in the hopper 16 (Fig. 5) to prevent the entrance of air. The movement of material into the retort 24 with the hot gases therein and through the cyclones 44, 46 and closed conduit 52 is what I have termed a closed loop system where the cold material 66 for processing is delivered to the retort 24 in an air free environment. The remaining gases from chamber 48 pass through duct 50 to a secondary combustor 56 of any suitable type where all impurities are incinerated to prevent contamination of the atmosphere when they are exhausted through stack 58. The heat from this phase is useful to produce steam and electricity.
In the event that some recyclable material such as aluminum, glass and metals remain in material 66, they would, because of the short time and temperature required by this process, just pass through to come out with the carbon and be separated. The char that is collected in hopper 36 has valuable commercial aspects and can provide substantial financial returns that materially reduce the overall costs of operation which is further reduced by the lack of need for outside fuel to maintain the system described herein.
It may be noted that while two cyclones 44, 46 are described, one such cyclone can be used, if desired. However, it has been determined that one cyclone would have to be of a substantial size to handle the volume of material processed and would be difficult to install and require considerable space so that two smaller cyclones are preferred.
The amount of material processed per hour is regulated by the variable speed motor 64 to increase or decrease the flow of material 66 in hopper 16 to the gas stream that carries it to the retort 24 and the flow of material 66 from bin 12 to conveyor 14 is adjusted accordingly since the speed of conveyor 14 is constant. Likewise, with an increase or decrease of material delivered to retort 24, the amount of ambient air from blower 30 required to maintain combustion is correspondingly adjusted by damper 31. Accordingly, in view of the foregoing, it is thought a full understanding of the construction and operation of this invention will be had and the advantages of the same will be appreciated.

Claims

1. A method for processing carbon based solid waste by pyrolysis to recover char that has a useful purpose and a commercial value, comprising the steps of:
moving carbonaceous solids reduced to small particles of relative uniform size from an air free source of supply to the top of a vertical retort so they will fall by gravity to the bottom thereof in a swirling motion to exit at the bottom,
igniting the first falling particles to reach said bottom from a source of fuel to generate hot gases for countercurrent flow upwardly through said falling particles to exit at the top,
introducing ambient air at the bottom of said retort to maintain combustion of said particles in a swirling motion and discontinuing use of the fuel source when said particles are ignited so that said particles serve as fuel to sustain the system of generating hot gases,
collecting the char resulting from combustion,
cooling part of the gas stream exiting from the top of the retort and directing it to the source of supply to serve as the vehicle for moving particles therefrom to the top of the retort,
directing the remaining parts of the gas stream to a point of disposal, and
maintaining the system of generating hot gases to heat the falling particles to create char and keep the retort air free by continual delivery of said particles to said retort and a continual supply of ambient air to support combustion of the ignited particles at the bottom of said retort.

2. A method as defined in claim 1, including:
provide for selectively increasing and decreasing the speed of delivery f said particles to said retort, and
provide for correspondingly increase and decreasing the flow of ambient air to said ignited particles.

3. A method as defined in claim 1 including removing light weight and fine particles in the gas stream exiting from said retort.

4. A method for processing carbon based solid waste by pyrolysis to recover char that has a useful purpose and a commercial value, comprising the steps of:
maintaining an accumulation of carbonaceous solids reduced to small particles in a vertical hopper that provides an air free environment for dispensing said particles,
to start operation, moving said particles by pneumatic means from the bottom of said hopper to the top of a vertical retort so they will fall by gravity to the bottom thereof,
igniting the first falling particles to reach said bottom by a fuel burning ignitor to generate hot gases for counter-current flow upwardly through said falling particles to exit at the top of said retort and to provide heat to said particles to create char and to maintain said retort air free,
introducing a flow of ambient air at the bottom of said retort into said ignited particles to support combustion thereof,
shutting off said ignitor once said particles are ignited,
maintaining the flow of ambient air to support combustion of said ignited particles at the bottom of said retort whereby said ignited falling particles serve as the fuel to maintain the system of generating hot gases to heat the falling particles to create char and to keep said retort air free without any outside source of fuel,
removing the char resulting from combustion of said particles out of the bottom of said retort for further processing or use,
collecting the gases exiting from the top of the retort,
directing part of said collected gases into an air free environment through a heat exchanger for reduction in temperature and through the bottom of said hopper to communicate with said pneumatic means to serve as the vehicle for moving said particles from said hopper to the top of said retort in the continuing operation of the system,
directing the balance of said collect gas stream to a point of disposal, and
maintaining the system of generating hot gases by continual delivery of said particles from said hopper to said retort and the continual supply of ambient air to support combustion of the ignited particles at the bottom of said retort.

5. A method as defined in claim 4, including directing the balance of said collected gas stream to a secondary combustor for incineration of any impurities therein and then to the atmosphere.

6. A method as defined in claim 4, including:
removing substantially all recyclable material such as metals, aluminum and glass from said solid waste, and
reducing said waste to small particles of relative uniform size of approximately one fourth inches.

7. A method as defined in claim 4, including maintaining the accumulation of solid waste in said hopper to a depth of at least two feet to prevent the entrance of air to the bottom thereof.

8. A method as defined in claim 7, including:
providing for selectively increasing and decreasing the speed of delivery of said particles from the bottom of said hopper to said gas stream, and
provide for correspondingly increasing and decreasing the flow of ambient air to said ignited particles.

9. A method as defined in claim 8, including:
maintaining a supply of reduced size particles in a storage bin, and
providing for increasing and decreasing the amount of particles delivered from said storage bin to said hopper to correspond to the amount of material delivered from said hopper to said retort.

10. A method as defined in claim 4, including:
directing the flow of particles from said hopper into the top of said retort in a cyclone fashion or swirling motion so that said particles are in constant motion in falling downwardly to exit at the bottom of said retort, and
directing the flow of ambient air against the ignited particles to effect a swirling motion of the same and the hot gases being produced.

11. A method as defined in claim 4, including directing said gases exiting at the top of said retort first through a cyclone for removing and collecting light weight or fine particles in said gas stream.

12. A method as defined in claim 10 including providing a temperature gradient in said retort in the range of 780 degrees F to 900 degrees F at the top and 1125 degrees F to 1225 degrees F at the bottom.

13. A method as defined in claim 4, including reducing the temperature of the gas stream directed to the bottom of said hopper to a range of 250 degrees F to 280 degrees F.

14. A method as defined in claim 4, including shutting off said fuel ignitor when the temperature of the ignited particles reaches approximately 1999 degrees F.

15. Apparatus for processing carbon based solid waste material by pyrolysis to recover char that has a useful purpose and a commercial value, comprising:
a vertical hopper for accumulating material to be processed,
a vertical retort defining a reaction chamber for material to be processed,
means for delivering material from the bottom of said hopper to the top of said retort so it falls by gravity to the bottom thereof,
a fuel burning ignitor in the bottom of said retort and adapted for connection to a source of fuel,
said ignitor used only to ignite the first falling material to reach the bottom of said retort and turned off when such material is ignited and generating hot gases that move in a countercurrent flow upwardly through the falling material to exit at the top of the retort,
a source of ambient air directed into the bottom of said retort into said ignited material to maintain combustion thereof,
a first conduit at the top of said retort in communication therewith to receive hot gases exiting therefrom,
a second conduit in communication with said first conduit to receive part of said gas stream,
means associated with said second conduit to reduce the temperature in said gas stream,
said second conduit communicating with the bottom of said hopper whereby the gas stream therein serves as the vehicle for moving material from said hopper to the top of said retort,
a third conduit communicating with said first conduit to receive the balance of said gas stream from said retort and direct it to a point of disposal, and
a receptacle at the bottom of said retort for receiving char produced by combustion of said material in said retort and falling therefrom by gravity.

16. Apparatus as defined in claim 15, including means in said first conduit for collecting light weight and fine particles of material in said gas stream.

17. Apparatus as defined in claim 15, including:
variable speed rollers at the bottom of said hopper for selectively increasing and decreasing the dispensing of material therefrom, and
a damper on said source of ambient air to correspondingly increase and decrease the flow of air relative to the amount of material dispensed from said hopper.

18. Apparatus as defined in claim 17, including:
a supply bin for material to be processed,
conveyor means for moving material from said supply bin to said hopper, and
means to regulate the movement of material from said supply bin to said hopper to correspond with the amount of material dispensed from said hopper.

19. Apparatus as defined in claim 15, including:
pneumatic means for directing said gas stream with material therein from the bottom of said hopper to the top of said retort to effect a cyclone or swirling motion of said material and maintain it in constant motion in falling downwardly in said retort to exit at the bottom, and,
said ambient air directed to effect a swirling motion of the ignited material and hot gases at the bottom of said retort.

20. Apparatus as defined in claim 15, including:
a secondary combustor in communication with said third conduit for removing impurities in said gas stream, and
a stick on said secondary combustor in communication with the atmosphere.