Patent Application
20090307974
The invention relates to the use of pyrolytic reactor technology in reducing carbon dioxide along with conversion of biomass material to more useful fuel.
Increasing amounts of greenhouse gases, particularly carbon dioxide, in the atmosphere, have raised concerns about climate change (or global warming). To reduce these concerns, there have been many proposals for energy conservation and for greater use of energy sources other than carbon based fuels. These can make some contributions to lessening the rate of increase of greenhouse gas. Still, it is recognized carbon based fuels will continue to be widely used, such as for electric power production and as transportation fuels. Substantial amounts of greenhouse gas are likely to be generated long into the future. Other strategies, such as burying carbon dioxide, may not be sufficient to provide an adequate desired limit on the release of greenhouse gas.
One other aspect of the current world energy picture is there may be less access to, and higher cost of, crude oil for fuel and fewer new discoveries of crude oil than in the past. This has led to increasing activity in converting agricultural products to fuel, such as by the conversion of grain or sugar to ethanol. When such biofuel is combusted, carbon dioxide still results. Also, the diversion of agricultural products to such a use impacts the availability and cost of food.
Natural processes, as well as human activities, such as the above-mentioned production of ethanol, result in making massive amounts of biomass material. Biomass includes solid material, (plants or vegetation of any type), produced by solar energy (the sun being Earth's primary energy source) along with carbon dioxide and water by photosynthesis. Such matter comprises various hydrocarbons and oxygen based compounds. When biomass ceases to live, naturally or by man, it will eventually decay to other compounds of the same elements. Over a long period of time, eons, it may revert to forms such as coal, oil, and natural gas such as are currently common fuel sources. Prior to that, accessible biomass, e.g., wood and other cellulosic material, can, of course, be burned as a form of fuel but without producing a significant percentage of the world's energy requirements.
This summary briefly characterizes some aspects of the invention. Statements made are intended to be informative about the invention but not as definitive as the appended claims.
The present invention provides systems and processes that permit reducing carbon dioxide in the atmosphere, or at least minimizing its release to the atmosphere, by use of a reactor apparatus, such as a plasma gasification reactor or PGR, with a carbonaceous bed, that is operated to chemically reduce the carbon dioxide. In addition, some embodiments include the provision of water (generally as steam) to the reactor along with the carbon dioxide. The bed and input materials are heated, such as by plasma torches, to generate carbon monoxide and hydrogen that rises from the bed.
Above the bed, the reactor can have a feed port for the supply of additional material, particularly solid or mostly solid material including biomass. Such material reacts with the gases rising from the bed to form other chemical compounds. In the case of the biomass, the result can include hydrocarbon compounds of lighter molecular weight (compared to that of the biomass fed into the reactor) as well as quantities of hydrogen and carbon monoxide which together form a gas mixture that exits the reactor. The conditions maintained in the reactor may allow an incidental amount of carbon dioxide to exit but only far less than was introduced to the bed.
The exiting gases from the reactor are available for use, for example, as a gas fuel itself or as feed material to another reactor for conversion of the gas mixture into various fuel materials in liquid form, such as ethanol, suitable for use in transportation fuel (e.g., mixed with gasoline).
The following description presents more aspects and information about example embodiments of the invention.
Referring to
The example power plant 10 is a conventional one burning a fuel such as coal 11 (produced long before from biomass by natural processes) with oxygen 12 (e.g., from air). The power plant 10 produces electricity 13 and also produces combustion exhaust, including a substantial amount of carbon dioxide (or CO2) 14 which can be separated (sequestered) from other components of combustion exhaust, e.g., nitrogen and/or water vapor. (The reader will understand that reference numerals such as 11, 12, 13, 14, etc. refer generally to the material or medium mentioned as well as to its inflow or outflow path.)
The electricity 13 from the power plant 10 is supplied to an electrical transmission and distribution system (not shown). The CO2 14 is supplied as one of the inputs at 21 that also supplies plasma energy 22 to the PGR 20. (All of which will be described considerably more in connection with
It can be noted that the inputs 21 to the PGR 20 in
The PGR 20, with its various inputs 21, produces an output of synthesized gas 24 (referred to sometimes herein as “syngas”). The syngas 24 is supplied (in parts 24a and 24b) optionally to either one or both of the syngas to liquid fuel reactor 30 and the gas fuel combustion apparatus 50. (More typically, a single PGR 20 would be used to supply syngas 24 to just one of the units 30 and 50.) The latter apparatus (50) is possibly like or similar to the power plant 10 (and also another possible source of energy introduced as plasma energy 22 to the PGR 20).
In the case in which syngas 24a is supplied to the additional reactor 30, whose character and manner of operation will be generally characterized below, it is converted at least in part to liquid fuel 31, e.g., including ethanol or other liquid hydrocarbons, or a mixture, useful in powering transportation equipment 40, such as conventional motor vehicles. (This discussion is not to exclude use of the syngas 24 for fuel in a gas-powered or hybrid motor vehicle.)
In the alternative case in which syngas 24b is supplied to the gas fuel combustion equipment 50, use of a reactor such as reactor 30 is not necessary. It is to be recognized, however, all the example descriptions herein are open to modification, unless clearly indicated otherwise, to include other or additional treatment processes and apparatus. For example, treatment of syngas 24 from the PGR 24 prior to use of it as syngas 24a to the reactor 30 or as syngas 24b to the apparatus 50, or treatment of liquid fuel 31 between units 30 and 40 of
Each of the illustrative units 40 and 50 consuming, directly or indirectly, syngas 24 from the PGR 20 do so in reactions that produce new carbon dioxide. The transportation equipment 40 produces CO2 41. The gas fuel combustion equipment 50 produces CO2 51. The CO2 quantities, as a general matter, are absorbed by the live vegetation of the biomass fields 60. Biomass 60 also, naturally, receives water 61 (typically as rain) and with solar energy 71 from the sun 70 proceeds by photosynthesis to grow the vegetation in the biomass 60 (producing more quantities of compounds of carbon and hydrogen) and to release oxygen 62 to the atmosphere.
The general system of
Practice of the invention does not depend on necessarily reducing overall energy consumption or even reducing carbon (or hydrocarbon) based energy consumption. The invention allows continued use of present carbon and hydrocarbon type fuels while limiting additions to atmospheric greenhouse gas.
PGR 20 is an example of a prolytic (high temperature) reactor useful in practicing some forms of the invention. PGRs are a known type of apparatus used in a variety of pyrolytic processes. Among such uses are to apply plasma energy to change the composition or character of some feed material, that might otherwise be waste, into more useful materials. Examples of practical application of this technology are described in the literature such as in an article by Dighe entitled “Westinghouse Plasma-Fired Processes for Treatment of Industrial Wastes” in Iron and Steel Engineer, January 1992, pp. 44-48; a publication of Westinghouse Plasma Corporation, Descriptive Bulletin 27-501, published in or by 2005; also in a paper by Dighe in Proceedings of NAWTEC16, May 19-21, 2008, (Extended Abstract # NAWTEC16-1938) entitled “Plasma Gasification: A Proven Technology”; and, a paper of Willerton, Proceedings of 27th Annual International Conference on Thermal Treatment Technologies, May 12-16, 2008, sponsored by Air & Waste Management Assoc. entitled “Plasma Gasification—Proven and Environmentally Responsible” (2008). The contents of such documents are incorporated by reference herein to provide further information of the general structure, nature and processes performed by PGRs which can be adapted for the uses presented herein.
The carbonaceous bed (or carbon bed or coke bed) 112 can be of known constituents (e.g., including fragmented foundry coke, petroleum coke, or mixed coke and coal). Just for example, the vessel 120 can be about 10-12 meters high and the section with the bed 112 can have an inner diameter of about 34 meters; the bed 112 itself having a depth of about 14 meters. By way of further example, the bed 112 can be of particles or fragments with an average diameter of about 5 cm. to 10 cm. to provide ample reactive surface area while allowing flow of supplied materials and reaction products.
Other known types of pyrolytic reactors that may be adapted to the present purposes include, for example, some using a plasma plume that works on material as the plume is transferred between electrodes. Others include, for example, some in which a plasma torch is submerged within the principal reaction site. The example reactor here, PGR 20 with vessel 120, is a type in which a plasma plume (of ionized hot gases) is not required to be transferred to another electrode; rather, a plasma plume is used within the bed 112. Also, here the PGR is such that it does not require a plasma torch submerged within the principal reaction site, the bed 112.
In the example presented here, the carbon bed 112 is substantially stationary and the reactor arrangement may be referred to as a stationary bed reactor or a “plug flow reactor” as such terms have been sometimes used in plasma reactor technology.
The carbonaceous bed 112 may be either (or both) of carbon material (such as described above) placed within the reactor vessel 120 or of carbon material formed within the reactor vessel. For example, the vessel 120 can have material containing hydrocarbon compounds, e.g., biomass, placed in it that is subject to pyrolysis leaving carbon for the bed 112. Reference to a carbonaceous bed (or carbon bed, or C bed) herein is to be understood as either one placed in the reactor, formed in the reactor from other material placed in it, or some combination of these practices.
The illustrated inlets or nozzles 114 to the vessel 120 are two (in this example) plasma torch nozzles located at or near a lower portion of the bed 112. There may be additional material supply nozzles (not shown) to an upper portion of the bed, or, as in
The reactor vessel 120 also has one or more (here two) additional inlets 118 that are feed chutes for material including biomass which enters the vessel 120 through the chutes 118 and descends to form a biomass layer 123 on top of the carbon bed 112. The feed chutes 118 can also be used to supply additional carbonaceous material to replace some consumed by reactions in the bed 112. New carbon material can be added, either or both, in a mixture with the supplied biomass or as a substantially separate layer.
Former practices with PGRs have included treatment of such things as municipal waste and landfill materials. Such materials, which may include incidental amounts of wood scraps, vegetation waste, and the like which are nominally “biomass” (amounting to less than 10% of such materials) may be processed in the reactor vessel 120 along with the supplied biomass which is to comprise at least about 50% of the process material through the feed chutes 118 to form what is referred to as the biomass layer 123 on the bed 112.
Above both the carbon bed 112 and the biomass 123, the vessel 120 has a freeboard region 124 and (at least one) exit port 126 at or near the top of the vessel 120 and the freeboard region 126. Another outlet, optional depending on the composition of the bed 112 and the supplied materials, e.g., including sulfur or various metals, is an appropriately sized molten liquid outlet 122 at or near the bottom of vessel 120, in accordance with known PGR practice. In some instances, material obtained from the outlet 122 may be metal and/or slag that can be marketed for economic benefit from the operation of the reactor 20.
For this example, the nozzles 114 of
In the present embodiment, constituents supplied to the bed 112 through an inlet means, including a torch 126, a material conduit 116, or any unillustrated conduits through the wall of the vessel 120 or the nozzle 114 into the bed 112, would usually collectively include a substantial amount of carbon dioxide, such as CO2 14 from the power plant 10 in
Further in this example, in a lower portion of the bed 112, with the high temperature plasma gas and (at least) CO2 and O2, conditions are established to promote reactions of the gases with the bed chemically reducing CO2 and producing CO. The Boudard reaction is one suitable reaction. Also, with a supply of steam (H2O) to the bed 112, the carbon-steam gasification reaction can occur to form hydrogen and more carbon monoxide.
In an upper portion of the bed 112, or at least near to or above sites at which CO is produced, conditions are such as to produce and promote reaction of carbon monoxide and steam to form hydrogen and some other CO2.
The products formed in a lower part of the bed 112 rise due to the high heat and can react further with other constituents supplied into or rising into an upper part of the bed 112 and the biomass 123. A resulting gas mixture of (or principally including) hydrocarbon compounds, carbon monoxide, hydrogen, and incidental carbon dioxide (usually at least an order of magnitude less in quantity than that the CO2 supplied to the bed 112) rises into the freeboard region 124 and exits the vessel 120 through the exit port 126 for subsequent use, with or without further treatment, as fuel.
In
The nozzle 114 of
a plasma torch 126;
a supply of torch gas 128;
an electrical power supply 130 to electrodes 131 and 132 that develop an electric arc forming plasma in the torch 126 from the torch gas; and,
a plasma mixing chamber 134 in front of the plasma torch 126 into which a plume of plasma 136 from the torch 126 is injected (prior to injection of plasma into the bed 112).
The torch gas of supply 128 can be selected as was previously discussed, e.g., it may, or may not, contain significant amounts of carbon dioxide for treatment in the PGR. The power supply 130 can be in accordance with past plasma torch practice, e.g., including a rectification bridge that develops and supplies DC voltage to the electrodes 131 and 132. The supply 130 may receive AC power from an electrical power system, e.g., a power plant as shown in
Working feed material other than torch gas from its supply 128 can be injected into the vessel 120 at various locations, some of which are discussed above. The example arrangement of
Here the process material of the supply 138 is shown as including carbon dioxide and water (typically as steam). Various other materials could be included as well, such as fluid hydrocarbons or forms of biomass such as solid hydrocarbon particles (e.g., wood chips). The various process materials may be intermixed and supplied together, as suggested by
Among potential arrangements for purposes of promoting the reactions described, air (e.g., compressed) may be supplied as the torch gas and carbon dioxide and steam supplied as shown, or as described above, and quantities consistent with the example molar ranges previously mentioned can be provided.
As mentioned above, biomass, e.g., wood chips or other solid hydrocarbon matter, may be applied at or near a plasma torch. Typically, for the general purposes intended here, there will still be more major amounts of solid hydrocarbon material introduced above the bed 112 as shown as biomass material 123 in
As taught by examples in the above mentioned patent:
chamber 134 can be lined with refractory material (not shown);
the plasma plume 136 can be primarily in a central portion of the chamber 134; and,
an additional supply (not shown) of a shroud gas can be provided in such a way as to swirl as it moves through the mixing chamber 134 from a region near the torch 126 to a region of the chamber 134 near the opening into the vessel 120.
By way of further example, an arrangement can include the supply conduit 140 introducing material or materials into a central portion of the plasma plume 136 and the shroud gas is introduced to swirl around, and at least particularly enclose, that central portion of the plume. For the shroud gas, any of a wide variety of gases may be used including those mentioned as examples for the torch gas as well as additional steam or a mixture of any such fluids. One example arrangement is to supply air as a torch gas and a mixture of carbon dioxide and steam as a shroud gas.
Use of a shroud gas can contribute to maintaining a temperature profile in the nozzle 114 that allows the nozzle structure around the plasma to remain cooler and have longer life.
One example of a plasma torch 126 that may be applied as described is that commercially available as a Marc 11 plasma torch of Westinghouse Plasma Corporation.
Examples of principal reactions promoted by conditions in a reactor such as the PGR 20 of
At the bottom of
The next block 210 represents, in this example, the plasma heated lower part of the C bed that receives the constituents from the block 200, e.g., from a nozzle 114. As a result, reactions performed include (whether or not steam is also present)
C+CO2→2CO,
2C+O2→2CO.
Reaction products from the lower C bed, including those referred to in block 210, along with any unreacted supplied gases, rise to within the upper part of the C bed. Block 220 identifies that among the reactions there is
CO+H2O→CO2+H2.
The H2O can be previously unreacted steam from the lower bed or newly admitted steam to the upper bed, or both. The reaction shown in block 220 can also take place to some degree wherever the CO and steam meet and are sufficiently heated, including the lower part of the C bed if steam is supplied there.
As mentioned, a reaction (called a shift reaction as shown in block 220) produces some CO2 but it would be much less (possibly by orders of magnitude) than that originally supplied at block 200.
Block 230 represents all the reaction products from previous blocks and the unreacted supplied gases that together have been heated in the C bed and rise out of it to reach the biomass above the C bed 112, such as biomass 123 of
Then, as shown in block 240, reactions are performed with the biomass including
CmHnOp+x.H2O+y.CO2→Cm1Hn1+x1.CO+x2.H2+y1.CO2
Where m1 and n1 respectively include integers smaller than m and n, x1 and x2 are each larger than x, y1 is smaller than y (usually quite a bit smaller, such as at least a few orders of magnitude), and m, n, and p are representative characteristics of the biomass feed material. There may be a variety of hydrocarbons in or with the biomass. The oxygen indicated in CmHnOp is whatever occurs as an inherent component of the biomass. (In addition, incidental free air enters the reactor with the biomass and its oxygen can also be reacted.)
The quantities of chemical constituents reacted in the reactor apparatus is variable over a considerable range. Just for example, in terms of approximate weight percentages out of 100% total, the relative amounts of some elements may include 10 to 20% carbon, 5 to 10% hydrogen, and 20 to 60% oxygen (with additional H2O to reach the total). The oxygen indicated in CmHnOp is whatever occurs as an inherent component of the biomass. (In addition, incidental free air enters the reactor with the biomass and its oxygen can also be reacted.)
The products of reactions performed, including those mentioned as well as possible others and unreacted supplied constituents, rise from the biomass represented in block 240 as a synthesized gas in block 250. The syngas of block 250 is a mixture in which a significant amount (typically over 50%) is of, combined, CH compounds, CO and H2. A relatively small amount of CO2 naturally occurs as well. Other extraneous gases in, or with, the syngas may result depending, e.g., on the composition of material in or with the supplied biomass.
Returning to
The reactor 30 for conversion of the syngas from the PGR 20 into liquid fuel can take various forms. One type of reactor that can be readily adapted for the present purposes as the reactor 30 is a Krieg fermentation reactor. Such a reactor is described, for example, in U.S. patent application Ser. No. 11/809,640, filed Jun. 2, 2007, by Krieg. The described fermentation reactor uses apparatus and processes for producing ethanol from waste gas (syngas) including, at least, carbon monoxide and hydrogen by biochemical reaction of the syngas with fermentation microbes in a liquid directed by pumps and spray misters into tunnels of the reactor. The contents of said patent application are incorporated to reference herein for description of such reactors.
Another type of equipment suitable for use as the reactor 30 is that known in the art as a Fischer-Trobsch reactor. Such a reactor, for example, has means for catalytic conversion of syngas to ethanol. The above-mentioned are merely examples of types of suitable reactors for the reactor 30.
Alternatively, rather than conversion by reactor 30 to liquid fuel, the syngas of
New carbon dioxide resulting from the combustion of fuels from the syngas may be returned as an input to a reactor such as PGR 20 but the principal cycle shown in
Consequently, it can be seen how innovative systems and processes are arranged and practiced for purposes such as greenhouse gas reduction (or lessening increases to greenhouse gas), with a corresponding lessening of concerns about global warming, while, also, converting biomass material to more useful fuel (e.g., biofuel).
Additional potential benefits can include lessening, or off setting, demands for agricultural products to be converted to fuel and making more tolerable, economically and environmentally, continued use of natural fuels such as coal, petroleum, and natural gas.
In this description, some mention is made of prior art apparatus and practices that are adapted for use in or with the innovations herein disclosed, such as about plasma gasification reactors and syngas to liquid fuel reactors. Whether, or not, formally incorporated by reference, it will be understood any public knowledge of prior art apparatus and practices is knowledge that can be drawn upon as needed in order to practice the innovations presented.
In the course of the description various embodiments are presented, along with some variations and modifications, all of which are to be taken as examples of practices, but not the sole or exclusive practices, practitioners may employ that are within the scope of the claims.
