Novel Off-Gas System for Coal and Biomass Pyrolysis

Abstract

The invention describes a unique and novel pyrolysis kiln for separating water vapor from a carbonaceous feedstock early in the pyrolysis process. The kiln structure includes two fans, one located near the proximal end of the kiln, the other near the kiln's distal end. Both fans create a local decrease in pressure at the respective ends with a dead zone in the intermediate region between the two ends of the kiln. At the proximal end, low temperature volatiles are removed, especially water vapor, and directed to a waste water cleanup station. Early removal of the water vapor makes the remaining pyrolysis process substantially more efficient. At the distal end, the high temperature hydrocarbons and other impurities are removed in a conventional manner and directed to a hot gas cleanup unit.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

Not Applicable

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

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REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING COMPACT DISK APPENDIX

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FIELD OF THE INVENTION

The present invention relates to methods and apparati such as a pyrolytic kiln for treating coal and biomass by pyrolysis or similar thermal methods that remove much of the water content at the front end of the kiln where the coal and/or biomass is loaded into the kiln while reclaiming useful hydrocarbons and char at the far end of the kiln. The system described increases the capture of the useful caloric components of the coal and biomass that result from the pyrolysis process.

BACKGROUND OF THE INVENTION

As fossil fuels become increasingly depleted and there is an ever increasing worldwide concern to minimize air pollution, methods to provide clean coal and biomas are receiving rising emphasis. Global warming has become a major issue which relates to find ways to decrease gases that absorb reradiated energy (infrared) from the earth's surface. These gases are principally carbon dioxide, methane and water vapor. More importantly there is a continuing drive to improve the air quality of the earth's atmosphere. To achieve this from the burning of fossil fuels such as coal, biomas, fuel oil and natural gas requires means for removing pollutants such as mercury, selenium, sulfur and sulfur dioxide. One of the chief ways of achieving these goals is to use pyrolytic methods to remove these pollutants while attempting to recapture them and bring them to a stage where they can be utilized in a variety of useful applications. The re-capturing of potential pollutants and reprocessing them makes it possible to use what is initially a pollutant into a saleable item that, in many cases can be utilized in a non-polluting or less polluting manner. This form of waste management is becoming recognized world wide as a necessary and achievable goal. Waste management, as opposed to mere recycling, has become increasingly important since standard recycling methods for the waste products found in coal and biomass are no longer adequate to contain the massive volume produced nor economically prudent.

While some of the waste products from the burning of fossil fuels and biomass can be recovered or recycled, most are disposed of in landfill. This type of disposal is wasteful and in itself potentially polluting, clearly not an environmentally friendly or economical way to proceed. Various government agencies have now put laws into effect that make certain forms of this type of disposal illegal which can result in substantial fines.

There are a large number of patents that that make use of pyrolysis and depolymerization techniques to utilize waste products that are emitted from the treatment of coal and biomasses. As an example, U.S. Pat. No. 5,269,947 describes depolymerization means for converting organic materials such as coal, biomass and inorganic materials into reusable combustible oils and gases. U.S. Pat. No. 5,711,769 consists of a continuous pyrolyzing process for treating coal to form stable coal char by passivating the coal, rehydrating and cooling the product thereby preventing spontaneous ignition. The process pyrolyzes the coal which vaporizes and has means to remove low temperature volatiles. The process also includes capturing the high temperature volatiles and the resulting coal char for useful purposes.

SUMMARY OF THE INVENTION

The invention is one relating to pyrolysis of carbonaceous matter such as coal and biomass. The unique feature of this invention is that it incorporates two airlocks, one at each end of the pyrolytic kiln. In addition there are two fans to draw off volatiles. The low temperature volatiles are drawn off by the first fan located at or near the proximal end of the kiln where the temperature is on the order of 100 C. These gases contain mostly water vapor and other low temperature volatiles. The importance of this fan, and a major novel feature of the present invention, is to withdraw from the pyrolysis kiln the water vapor at an early stage of the pyrolysis process. A second fan, located at or near the proximal end of the kiln, draws off the useful hydrocarbons together with additional contaminant gases to be processed. The remaining solid char is removed from the kiln at the proximal end of the kiln and serves as useful combustible material together with the hydrocarbon volatiles that are separated from the high temperature contaminant volatiles. In some greater detail, we describe a system for pyrolyzing carbonaceuous material to capture and isolate selected gases upon the pyrolyzing the material in a kiln consisting of an inner core and an outer shell each with an inner and outer surface. Both kiln and core have a proximal and distal end. Also, there is a first airlock affixed to the proximal end of the inner core by a first rotating seal and a second airlock attached to the distal end of the inner core with this airlock also attached to the inner core and a second rotating seal. Each end of the core has respectively a first fan connected to tubulation emanating from the proximal end of the inner core and a second fan connected to tubulation emanating from the distal end of the inner core. A helical steel rail is rigidly affixed along the inner surface the inner core while, heating coils fixedly attached to the inner surface of the kiln shell. There is also a first condenser/separator connected to a water cleanup station positioned near the proximal end of said inner core and a second condenser/separator station, positioned near the distal end of said inner core. A gear wheel surrounds the proximal circumferential end of the inner core. There also exists a means for rotation of the core along with a first tabulation connected between said first fan and first condense/separator unit; as well as a second tubulation connected between said the second fan and second condenser separator unit. The entire kiln is supported on mounts to elevate the system above ground level.

The inner core is mounted concentrically on slip rings within said outer shell, while the annular space between the shell and core contains one or more thermal sensors. Rotations of the two aforementioned fans rotate in a manner that provides airflow in opposite directions. The core, prior to loading with coal and or biomass (carbonaceous material) has an internal volume that is open, that is, similar to a hollow tube or duct except for the presence of the aforementioned helical rail. However, it is also possible to run the pyrolyzation with the installation of one or more circular baffles internally mounted within the core volume which enhances the efficiency of the oppositely directed airflows, however such baffles are optional. With the use of a baffle, at least one steel baffle stem, minimum length of 4 inches and a diameter 2-4 inches, has one end of the stem affixed to the baffle, the opposite end affixed to the steel rail of the kiln. Additional steel baffle stems can be used with one end of a stem affixed to the baffle, the opposite end affixed to the inner surface of the inner kiln core. The baffle has a thickness in the range of 0.25-5 inches.

The carbonaceous material external to the kiln is loaded into the inner core through the first airlock by means of a belt, one end of the belt positioned near the bottom of an external carbonaceous material mound and the other end positioned by or near the first airlock. The heating coils positioned on the inner surface of the outer shell provide means for transferring heat to said carbonaceous material in the kiln core, the heat being crucial for operating the pyrolysis. The carbonaceous material to be pyrolyzed can consist of coal, biomass or a combination of the two.

During the pyrolysis process, a motor with a second gear is engaged with the first gear attached to the circumference of the proximal end of the kiln core to cause rotation of the kiln core. Due to rotation of the inner kiln core, lateral movement of carbonaceous material from proximal to distal end of the inner core occurs in combination with the action of the helical rail within the inner kiln core.

Typically, the length of the kiln is in the range of 10 feet to 200 feet, while the diameter of the kiln shell is less than 18 feet but more than 1 foot. The radius of the core is at least 10% less than that of the kiln shell. The heating coils are programmed to provide a temperature of approximately 100 C at the proximal end of the kiln core and approximately 500 C at its distal end. The heating of the carbonaceous material, coal and/or biomass near the proximal end of the core partially gasifies and those gases are drawn off by the first fan through the first tubulation and first rotating seal into a first condenser/separator. Heating of said carbonaceous material (coal and or/biomass near the distal end of the core gasifies the carbonaceous material at the much higher temperature, i.e. ˜500 C, and these gases are drawn off by the second fan through tubulation and a second rotating seal into second said condenser separator. These gases are rich in useful hydrocarbons and therefore have high caloric value. These desirable caloric rich gases also contain some water vapor and hydrogen and other impurities which has not been drawn off at the proximal end, but contain mostly hydrocarbons and some traces of high temperature volatiles contaminants which are separated at the second separator and clean up station.

A control unit is part of the pyrolysis system and has means for controlling and regulating the temperature of the a pyrolyzing system by way of signals transmitted to the unit from the thermal sensors mounted within said pyrolyzing system, that is in the space between the kiln shell and the kiln core. This unit also regulates the rotational speed of the first and second fans mounted respectively at the proximal and distal ends of the kiln core. In addition, the control unit also has the means to regulate the rotation speed of the kiln core.

Since not all of the carbonaceous material is gasified in the pyrolysis process, there remains some solid material, i.e. char which can be released at the distal end of the kiln through the second airlock at the distal end and collected in a char receptacle from the core by way of the second airlock.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the pyrolyzing unit consisting of a kiln with an outer shell and an inner core, the inner core free to rotate within the outer shell, two airlocks and two fans, one airlock and one fan at each end of the kiln. The first fan positioned at the proximal end of the kiln, draws off most of the low temperature volatiles, principally water vapor, while the second fan positioned at the distal end of the kiln, draws off the high temperature volatiles, consisting of useful hydrocarbons with caloric value and a few additional contaminants which can be separated from the useful caloric hydrocarbons.

FIG. 1a is a detail of a motor and gear structure to implement rotation of the inner core carrying the material to be processed by way of heat from the heating coils mounted on the inner surface of the kiln shell. Rotation of the inner core occurs when the gear surrounding the inner core is engaged with the gear driven by the motor which in turn causes the carbonaceous material to move from the proximal to the distal end.

FIG. 2 is a cross sectional view of the inner kiln core illustrating two types of baffles that are optional but are useful in the operation of the overall pyrolyzing system.

FIG. 3 is a sketch of the master control unit that regulates and monitors the speed of the fans, the temperature of the kiln core, the rotation speed of the inner core, monitors the temperature of the thermocouples mounted in the space between the core and the outer shell of the kiln and thereby regulates the temperature of the heater coils. This unit also provides feedback to these sensors and allows them to operate predetermined values set by an operator.

FIG. 4 is a side view sketch of a kiln mounted at an angle to aid in moving the carbonaceous coal/biomass material from the proximal to the distal end.

DETAILED DESCRIPTION OF THE INVENTION

Generally in the pyrolysis of coal and/or biomass, it is useful to eliminate as much water as possible during the pyrolytic process. FIG. 1 is a drawing depicting a kiln for obtaining combustible fuels relatively free of a variety of contaminants by means of several processing steps initiated near the front (proximal) and back (distal) ends of the kiln. The kiln consists of an outer shell 103 and an inner core 104. The inner core 104 is mounted concentrically on slip rings 1022 within the outer shell 103.

As shown in the figure, a portion of carbonaceous coal and/or biomass 1000 from coal or biomass heap 100 is fed through an airlock 102 located at the proximal end of the inner kiln core 104 and dropped into inner kiln core 104 by means of the moving belt 101. Airlock 102 consists of an outer casing containing a finned wheel 1021 that rotates when a fin is loaded with coal or biomass 100. The fins 1021 of airlock 102 act to allow only a minimum of air to enter inner kiln core 104 during the loading of coal or biomass 1000 from coal pile 100 by way of belt 101. Heater coils 1020 bring the coal or biomass 100 inside kiln 104 to an increasing temperature as kiln 104 rotates within the outer shell 103, thereby moving coal 1000 from the proximal to the distal end of kiln core 104 by means of a helical steel rail 105 rigidly attached to the inner wall of kiln core 104. Kiln 104 can be heated to a uniform temperature along its entire length or to a specified temperature gradient, starting with a lower temperature ˜100-225 C at the proximal end and ˜500 C at the distal end. Typically the coal 1000 will be heated from the lower temperature ˜100-225 C as it enters kiln core 104 to a temperature ˜500 C as it travels through kiln 104 where the heat is supplied by the heat coils 1020. Thermocouples 118 spaced along the length of outer kiln shell 103 and located in the space between kiln shell 103 and kiln core 104 relay temperatures within the outer kiln shell 103 to control unit 124, FIG. 3. The heat coils 1020 can be set to desired temperatures via control unit 124, FIG. 3. The gases that volatilize at the lowest temperature are released near the proximal end of kiln core 104. The major gas will be water vapor. To capture the water vapor and other low temperature volatiles, fan 108 containing fan blades 1081 causes the water vapor and gases of similar vaporizing temperature to be drawn by fan 108 through tubulation 1008 into condenser separator 109. The contents of 109 are then routed to the waste water cleanup tank 110. Coal or biomass 1000 continues to be transported inside the core 104, and gases other than the initial low temperature vaporizing gases are released in the vicinity of the distal end of core 104. The movement of coal or biomass 1000 from proximal to distal end occurs due to rotation of core 104 by way of motor 17, FIG. 1a, where a gear 170 engages gear 11, which is mounted near the proximal end of core 104, shown in cross-section as 1040 in FIG. 1a. The movement of biomass 1000 is also aided by the helical rail 105 as core 104 rotates. Core 104 can be made to rotate so that coal and biomass 1000 is mixed as it travels toward the distal end of core 104 while useful gases in the form of hydrocarbons are volatilized and collected for use as combustible fuel. These gases are released at higher temperatures as coal and/or biomass 1000 increases in temperature from its initial temperature to a temperature near the set temperature of outer shell 103, e.g. 500 C. Heat from the shell 103 is transferred by thermal conduction to the interior of core 104, thereby heating coal/biomass 1000. Optional baffles 18, 19, each with at least one baffle stem 20, are shown in cross-sectional detail in FIG. 2. The baffle and baffle stems are mounted in a region within core 104 at a position from the proximal end in the range of 0.1 to 0.5 times the length of core 104. The baffle stem 20 is at least 4 inches in length and at least one stem 20 is fixedly attached to steel rail 105.

Near the distal end of kiln core 104, the hydrocarbon gases are driven by a second fan 111 with fan blades 1111 through tubulation 1011, which directs the hydrocarbon gases to a second condenser separator 112. From there fan 111 directs the gases from separator 112 to the hot gas clean up system 113.

A second airlock 114 mounted near the distal end of kiln core 104 receives heated coal or biomass 1000 which remains in the solid state while traversing the length of kiln core 104 from the proximal to the distal end. At the distal end of 104 airlock 114 directs coal or biomass 1000 by way of fin 1141 into chute 1115 and into vessel 115. This discharged coal 116 is in the form of char, useful as a caloric fuel. Kiln shell 103 is mounted on legs 106.

The temperature of coils 1020 is controlled by the master control unit 124 shown in FIG. 3. Temperature of coils 1020 is monitored by thermal sensors 118 mounted on the inner surface of kiln shell 103 and relayed to the master control unit 124. The master control unit 124 as shown in FIG. 3 controls the speed of motor 17 and hence the rotation speed of kiln core 104, the temperature of heat coils 1020, hence the temperature of kiln core 104 by way of the information of heat sensors 118 and the rotation speeds of fans 108 and 111.

FIG. 4 shows a variation in mounting of the kiln shell 103 and kiln core 104 using a set of supports 117 of unequal length resulting in a tilted mount for kiln shell 103 and kiln core 104. In this position coal 1000 can move by the force of gravity from the proximal to the distal ends of kiln core 104 making helical rail 105 an optional feature.

Claims

1. A system for pyrolyzing carbonaceuous material to capture and isolate selected gases from said carbonaceous material, the pyrolyzing system comprising: a kiln, said kiln comprising an inner core and an outer shell, said shell and core each comprising a proximal and distal end and an inner and outer surface; a first airlock affixed to said proximal end of said inner core by means of a first rotating seal; a second airlock affixed to said distal end of said inner core by means of a second rotating seal; a first fan connected to tubulation emanating from said proximal end of said inner core; a second fan connected to tubulation emanating from said distal end of said inner core; a helical steel rail rigidly affixed along said inner surface of said inner core; heating coils fixedly attached to said inner surface of said kiln shell; a first condenser/separator connected to a water cleanup station positioned near the proximal end of said inner core; a second condenser/separator station, positioned near the distal end of said inner core, a first gear wheel surrounding said proximal circumferential end of said inner core; means for rotation of said core; a first tubulation connected between said first fan and first condense/separator unit; a second tubulation connected between said second fan and second condenser separator unit; a circular baffle and baffle stem, supporting mounts for elevating said system above ground level.

2. A system as in claim 1 wherein said inner core is mounted concentrically on slip rings within said outer shell, further comprising one or more thermal sensors positioned in the annular space between said concentrically mounted kiln shell and core.

3. A system as in claim 1 wherein first and second fans rotate further comprising the airflow produced by first and second fan to occur opposite directions.

4. A system as in claim 1 wherein said interior of said inner kiln core comprises at least one of a circular baffle and helical steel rail and any combination thereof.

5. A system as in claim 4 further comprising at least one steel baffle stem, with one end of said stem rigidly affixed to the periphery of said circular baffle, and with opposite end of said stem rigidly affixed to said helical steel rail, said steel rail affixed to inner surface of kiln core.

6. A system as in claim 4 and 5 with said baffle thickness in the range 0.25-5 inches, said baffle stem at least 4 inches in length, 2-4 inches in diameter, said baffle mounted from said proximal end of said core at a distance in the range 0.1 to 0.5 times the length of the said inner core.

7. A system as in claim 1 wherein said carbonaceous material external to said kiln is loaded into said inner core through said first airlock, said loading means further comprising a moving belt positioned between said first airlock and said external carbonaceous material.

8. A system as in claim 1 wherein said heating coils provide means for transferring heat to said carbonaceous material in said kiln core.

9. A system as in claim 1 wherein the carbonaceous material is selected from the group of materials consisting of coal, biomass and a combination of both.

10. A system as in claim 1 further comprising a motor and second gear, said second gear engaged with said first gear attached to the outer circumference of proximal end of said kiln core whereby said motor enables rotation of said kiln core by way of said second gear.

11. A system as in claim 1 and 10 wherein said rotation of said inner core comprises lateral movement of carbonaceous material from proximal to distal end of said inner core.

12. A system as in claim 1 wherein length of said kiln is in the range of 10 feet to 200 feet.

13. A system as in claim 1 wherein the diameter of said outer shell of said kiln is less than 18 feet but more than 1 foot.

14. A system as in claim 1 wherein the radius of said kiln core is at least 10% less than that of said shell of said kiln.

15. A system as in claim 1 wherein said heating coils are programmed to provide a temperature of approximately 100 C at the proximal end and approximately 500 C at the distal end of said kiln core.

16. A system as in claim 1 wherein heating of said carbonaceous material near the proximal end of said core gasifies said carbonaceous material, said gases drawn off by said first fan through said first tubulation and first rotating seal into said first condenser separator.

17. A system as in claim 1 wherein heating of said carbonaceous material near distal end of said core gasifies said carbonaceous material, said gases drawn off by said second fan through said tubulation and second rotating seal into second said condenser separator.

18. A system as in claim 16 and 17 wherein said gases are selected from the group of gases consisting of water vapor, hydrogen, hydrocarbons and any combination thereof.

19. A control unit comprising means for controlling the temperature of a pyrolyzing system by way of signals transmitted to said unit from said thermal sensors mounted within said pyrolyzing system.

20. A control unit as in claim 19, further comprising means for said unit to regulate the rotational speed of first and second fans mounted respectively at said proximal and distal end of said kiln core.

21. A control unit as in claim 19, further comprising means for said unit to regulate the rotation speed of said core of said kiln core.

22. A pyrolyzing system as in claim 1 further comprising means for releasing solid carbonaceous material residing at the distal end of said kiln through said second airlock, further comprising a char receptacle to receive said carbonaceous material released through said second airlock.