System and Method for Obtaining Clean Coal Tars from Pyrolized Coal and Biomass
A system and method for collecting hot coal tar gases emanating from a coal containing pyrolytic kiln are described. The hot coal tar gases, comprising a variety of different hydrocarbons as well as inorganic gases arising from the kiln thermal processing are transferred by diffusion and forced convection to a thermal duct in which the temperature is controlled to be maintained at a temperature below that of the kiln. The gaseous hydrocarbon with the highest condensation temperature is the first to liquefy. Additional useful hydrocarbons liquefy as the temperature of the gas continues to cool from the kiln temperature of ˜5000 C to one approaching the minimum duct temperature, ˜175° C. After a number of desirable hydrocarbons present in the coal tar gas have liquefied, the liquid contents are collected, either separately or as a combination of liquid hydrocarbons. The several remaining inorganic and some hydrocarbons gases with condensation temperatures below the minimum duct temperature are separately collected in gaseous form for further processing and/or safe disposal.
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FIELD OF INVENTIONRecently, there has been an increasing effort to obtain ‘clean’ coal by processing the coal, as mined, at moderate temperatures in a pyrolytic kiln to drive off harmful, polluting gases. The need for clean coal has been mandated and incorporated in numerous National and International pollution standards in order to prevent health hazards as well as crop hazards such as acid rain. The present invention describes methods for pyrolyzing coal both to drive off harmful gases that can be sequestered, and also to recapture condensed gases that can be further used for clean oxidation, providing useful non-polluting or minimally polluting thermal energy. These gases are recovered in liquid form in a special temperature controlled duct.
BACKGROUNDCoal pyrolysis, in which a portion of coal is converted into a series of gases, was first developed as early as the eighteenth century. However, commercial pyrolysis became more widespread in the early 1900's. Intense renewed interest in pyrolysis of a variety of raw coals was spurred by the tensions between the West and the oil rich nations of the Middle Eastern countries in the 1970's. In general, depending on the nature of the raw coal and the exact nature of the pyrolysis process, the gas from coal pyrolysis may contain water vapor, compounds of chlorine, mercury, other heavy metals, hydrogen sulfide, and a range of hydrocarbon volatiles. The solid, non-volatized coal char will contain carbon, a range of hydrocarbon compounds, and traces of other minerals and elemental compounds. The volatized gases can be separated and the individual gaseous products can be further processed for useful chemical applications. At the same time, burning coals that have been properly pyrolyzed reduce air pollutions and hence human health hazards such as emphysema, asthma, and lung cancer. The large number of issued patents involving pyrolysis gives a broad picture of the utility and profitability of gasification of coal by pyrolysis to achieve a cleaner coal.
The history and detailed time-line of coal pyrolysis are well documented and found on a variety of websites. Details of a pyrolysis process can be found, for example, in “Kinetic Studies of Gas Evolution During Pyrolysis of Subbituminous Coal,” by J. H. Campbell et al., a paper published May 11, 1976 at the Lawrence Livermore Laboratory, Livermore, Calif. Numerous issued U.S. patents describe methods for the reduction of sulfur in coal, for example, U.S. Pat. No. 7,056,359 by Somerville et al. Their process involves grinding coal to a small particle size, then blending the ground coal with hydrated lime and water, followed by drying the blend at 300-400 degrees F. U.S. Pat. No. 5,037,450 by Keener et al. utilizes a unique pyrolysis process for denitrifying and desulfurizing coal. Here the sulfur and nitrogen content of coal is again driven off in gaseous form and sequestered for possible further use.
SUMMARY OF THE INVENTIONA system and method for collecting hot coal tar gases emanating from a coal containing pyrolytic kiln are described. First, water vapor and small quantities of oxygen are removed while operating the kiln at moderate temperatures in the range of ˜275 to 500° C. At the upper end of this range, hot coal tar gases are driven from the coal consisting of a variety of useful hydrocarbons as well as inorganic gases. The hot gases are then transferred by way of diffusion and forced convection to a thermal duct in which the temperature is computer controlled to remain at a temperature below that of the kiln, causing certain hydrocarbons to liquefy. The gaseous hydrocarbon with the highest condensation temperature is the first to liquefy as it enters the proximal end of the duct which is kept at the lowest temperature of the duct. Additional useful hydrocarbons liquefy as the temperature of the gas continues to cool from the moderate kiln temperature of ˜5000 C to one approaching the duct temperature, in the range ˜175 C-350 C at the proximal end of the duct. The hydrocarbons with a lower condensation temperature liquefy further down the duct from their original entry point from the kiln. Cooling of the gases occur as the gases flow from the kiln distal end (temperature of ˜500 C) towards the distal end of the duct. After a number of desirable hydrocarbons present in the coal tar gas have liquefied, the liquid contents are collected while several remaining inorganic gases and almost all the water vapor and some gaseous hydrocarbons with lower condensation temperatures remain as gases and are separately sequestered in gaseous form for further processing and/or safe disposal.
The present invention describes a system and a process for obtaining reusable hydrocarbons from coal that undergo a pyrolysis process. The process is particularly advantageous since it requires no wasteful oxidation of the coal but rather utilizes heat in a near oxygen free atmosphere to drive off gases from the coal, especially numerous hydrocarbon gases, many of which can be oxidized at a later time to obtain useful thermal energy. The present invention describes an alternative to conventional methods for eliminating pollutants from coal by using a unique pyrolysis system and process for driving off and capturing many of the gases which are considered to be pollutants, i.e. mercury, sulfur, hydrogen sulfide and the like. At the same time, the invention provides means for capturing and retaining the valuable hydrocarbons that are desired for future use as fuel.
The invention uses a pyrolysis process whereby the coal is not burned, but heated to a moderate temperature in a near oxygen free atmosphere in a pyrolytic kiln. The gases driven off in this manner can be separated from the coal and drawn off for future combustible use, safe disposal or re-processing for future use. Certain other gases that are driven off in the pyrolysis kiln are non-condensable in the present invention such as H2, CO, CO2, C2H6, C3H8 and C2H4 (J. H. Campbell, Fuel, 57, 217 (1978). Even though not condensable in the present invention, this invention collects these gases for re-processing by other means since many such gases continue to have other intrinsic value.
The uniqueness of the present invention lies in part to a method for liquefying the useful hydrocarbons emanating from a hot pyrolysis kiln for pyrolyzing coal without a coal combustion process, then mixing the useful liquefied coal tars (that is, those that can be oxidized at a future time) to the remaining char in the kiln so that both the char and the recovered hydrocarbons can be used for useful clean energy upon oxidation (burning).
The system of the present invention is designed for reclaiming and collecting/capturing hot coal tar gases and coal gas components in a condensed state from a vapor state by utilizing a near oxygen free pyrolytic kiln to heat the coal causing gaseous volatiles to be driven off from the coal and or coal/biomass.
A computerized temperature control unit receives controlling signals from at least one thermal sensor mounted within the duct, the thermal sensor also connected to the computer control unit for regulating the duct temperature. The condensed products are released from the duct by way of at least one drain spout coupled or attached to the duct with the duct draining the condensate into a collection chamber through the drain spout. The condensate, in liquid form, is drained from the duct when a slidable shutter, mounted on the drain spout or over the openings on the undersides of the duct, is in the open position. At other times, the slidable spout shutter is in a closed position. The gases cool in the duct and condense along different portions of the duct as they traverse the length of the duct from the kiln. The position along the duct at which they condense will depend on their individual thermodynamic property, that is, the gas with the highest condensation temperature will cool closest to the flange, the one with the lowest, further from the flange as determined by the thermodynamic property of the individual gas.
Depending on the duct configuration, more than one drain spout can be attached to the duct and for each drain spout and its corresponding slidable shutter; there is a collection chamber in close proximity to the sprout. A fan for the vapor/gas extractor is mounted within the duct at the far or distal end of the duct, opposite to the proximal end connected to the kiln by way the flange. The fan drives uncondensed coal gases from the duct into a collection drum which serves as the vapor/gas extractor which also has a slidable shutter. The contents of the drum can be further processed at a different processing station.
The duct has a near end, a far end, a top side and an underside, a length in the range from of 1-500 feet. Since the duct need not be linear in length and can be made from sections so that the effective length is non-linear in shape/contour, the total length is measured along the perimeter of the underside of the duct. For a non-linear shaped duct, there is one region of the duct that is lower with respect to ground level than any other portion of the duct to allow for efficient drainage. The drain spouts are rigidly attached and mounted on the underside of the duct. Typical cross-sections of the duct are of arbitrary geometry but have an area in the range 1-100 square feet. The temperature of the duct is maintained at a temperature in the range 175-350 C but can also be set to a uniform temperature, desirable under certain conditions. A uniform temperature along the duct length is useful when condensates are being separately collected in separate or individual collection chambers.
There are numerous components of coal gas, many of which are useable hydrocarbons when condensed and re-captured in liquid form. The most useful ones include the carbon-hydrogen chemical form CxHy where x is greater than 9 and y greater than 10. The hydrocarbons that condense and are recoverable will have condensation temperatures in the range from approximately ˜175 to 500 C, more specifically, between the minimum temperature set for the condensation duct, and the exit temperature of the gases set at the distal end of the kiln.
Generally, in the pyrolysis of coal and/or biomass, it is useful to eliminate as much water as possible during the pyrolytic process.
Thermal sensors 16 in
In duct 102, duct temperature control elements 120 are rigidly affixed to the exterior surface of duct 102 and are also set to any desired temperature via the same master control unit 3000 of
During the heating process of coal/biomass 15, kiln core 11 is rotated by details shown in
In one preferred embodiment, duct 102 is shaped so that one portion of duct 102 is lower in height than any other portion of duct 102. At this lower position along duct 102 is spout shutter 1005, rigidly attached to the top of drain spout 105. In the open position of spout shutter 1005, gravity causes the liquefied gas components 102a in duct 102 to flow into spout 105 into collection chamber 106 where drain spout 105 empties into collection chamber 106, positioned with drain spout 105 placed in the interior of collection chamber 106. After the desired components of gas mixture 100d have condensed, slidable shutter 1005, having been in a closed position, opens to cause liquified gases 102a to flow into spout 105 and become collected as liquefied gas 107 in collection chamber 106.
A second duct configuration is shown in
While the embodiment shown in
The control unit 3000
Fan 109 mounted within close proximity of the far/distal end of duct 202 drives the remaining uncondensed components of gas 100d into collection drum 111 when slideable shutter 110 is in an open position. The shutter 110 closes when the drum 111 is to be removed for the re-processing of the uncondensed gases captured within drum 111.
Having described our invention,
Claims
1. A system for reclaiming hot coal tar gases and hydrocarbon coal gas components in a condensed state comprising: a pyrolytic kiln containing hot coal gases, said kiln having at least one open end, an outer shell and an inner core, further comprising means for temperature regulation of said kiln; a duct with a proximal open end, said one open end of said duct and said distal open end of said kiln fixedly connected by a rotatable flange; heating coils in intimate thermal contact with said duct for regulating temperature of said duct, a master control unit; at least one thermal sensor mounted respectively within said kiln and said duct; at least one drain spout coupled to at least one opening on the underside of said duct; at least one collection chamber in close proximity to said drain spout; a fan positioned within said duct; uncondensed hot coal and biomass gases in said kiln core, wherein said gases are driven into said duct by said fan, said condensed gases in said duct collected by at least one collection chamber; a collection drum for collecting uncondensed gases.
2. A system as in claim 1, wherein said duct has a proximal end, a distal end, a top side and an underside.
3. A system as in claim 1 wherein said kiln core is mounted concentrically within said outer shell.
4. A system as in claim 1 where in said distal open end of said kiln core and open end of said duct provide means for hot coal gases to enter said duct from said kiln core.
5. A system as in claim 1 wherein said duct coils control the temperature of said duct by thermal conduction, convection and radiation between said coils and said duct.
6. A system as in claim 1 wherein said fan is positioned near the distal end of said duct.
7. A system as in claim 1 where in said collection chamber is attached to the underside of said duct.
8. A system as in claim 1, wherein said duct has a length as measured along its outer perimeter along said underside of said duct, said length in the range 1-500 feet.
9. A system as in claim 1 wherein said duct has an interior cross sectional area of arbitrary geometry in the range of 1 to 100 square feet.
10. A system as in claim 1 wherein said duct is maintained in the temperature range 175-350 C.
11. A system as in claim 1 wherein said duct temperature can be a uniform temperature along its entire length.
12. A system as in claim 1, wherein said length dimension of said duct is selected from the group consisting of a linear length and a non-linear length, wherein said duct with said non-linear length dimension has one section lower in height with respect to ground level compared to other lengthwise portions of said non-linear duct.
13. A system as in claim 1, wherein said hot gases flow from said kiln core into said duct.
14. A system as in claim 1, wherein the temperature of said heating coils are determined by said master control unit and at least one thermal sensor.
15. A system as in claim 1, wherein the components of said gases are hydrocarbons with the chemical formula CxHy where x is greater than 9 and y greater than 10.
16. A system as in claim 1, wherein components of said hot hydrocarbon gases in said kiln enter said duct from the distal end of said kiln core at a temperature up to ˜500 C and condense in said duct at a temperature determined by the individual thermodynamic properties of said gas component.
17. A system as in claim 1 wherein recoverable hydrocarbon gases condense in said duct in the temperature range ˜175-350 C.
18. A system as in claim 1, wherein at least one opening on underside of said duct further comprises a shutter, said shutter comprising means for controlling the opening and closing of said underside openings.
19. A system as in claim 1, wherein said drain spout is rigidly attached to each of said openings on said underside of said duct.
20. A system as in claim 1 wherein said drain spout empties condensed gas components into a collection chamber with said shutter in said open position.
21. A system as in claim 1 wherein said fan drives said uncondensed gas components in said duct into said drum.
22. A method for retrieving condensed fractions of hydrocarbon coal gases emanating from a heated kiln, the steps comprising:
- heating coal and biomass in a pyrolytic oxygen free kiln to a temperature at which coal emits a mixture of gaseous hydrocarbons; capturing said set of gaseous hydrocarbons in a duct, said duct having a top and bottom surface; a flange intimately connecting said duct to one end of said kiln; fastening at least one drain spout near the center of said duct, said drain spout opening controlled by a shutter mounted on said drain spout; positioning a collection chamber under said set of spouts; wrapping heating coils along length of said duct thereby providing a fixed temperatures along length of said duct; controlling said temperature of heating coils and duct by way of a master control unit, positioning at least one thermal sensor in the interior of said duct, said thermal sensor sending temperature information to said computer control system, liquefying individual fractions of gaseous hydrocarbons by cooling at temperatures corresponding to the condensation temperature of said hydrocarbon; positioning a fan mounted within far end of said duct; attaching a collection drum to far end of said duct in close proximity to said fan for sequestering uncondensed gas.
23. The method of claim 21 further including collecting said liquefied hydrocarbons from said duct through said drain spouts.
24. The method of claim 22 comprising directing said liquefied gases from each said drain spout into an individual collection chamber, further comprising the method of driving uncondensed said gaseous hydrocarbons at the distal end of said duct into said collection drum.
Type: Application
Filed: Jul 27, 2010
Publication Date: Feb 2, 2012
Inventors: Peter Rugg (New York, NY), Robert J. von Gutfeld (New York, NY), Ann Engelkemeir (East Lyme, CT)
Application Number: 12/844,117
International Classification: F23J 15/00 (20060101);