US 20080040975 A1
A method for pyrolyzing coal to produce a raw hydrogen-rich gas and a hot char composed of carbon that is divided into two streams, one gasified to make a second gas and one reacted with steam to produce hot activated carbon that is divided into a first sub-stream and a second sub-stream.
The hydrogen rich gas, after cleanup, is converted to methanol which, in turn, is synthesized into gasoline or synthetic natural gas. The second gas, after clean-up, fuels a turbine to generate electricity while exhausting a flue gas (N2+CO2) that is reacted with the first sub-stream of hot activated carbon and with hydrogen for synthesis into urea (CO(NH2)2).
The urea is mixed with the second sub-stream of activated carbon to produce a fertilizer which is introduced into soil to store plant nutrients.
This process produces fuel, electricity, and enhancement of plant growth.
1. A method for maximizing the value of carbonaceous material in an environmentally acceptable manner comprising the following steps:
pyrolyzing the carbonaceous material in an atmosphere which is deficient of oxygen to produce a first gas and a hot char which possesses a cellular structure that is essentially made up of carbon;
dividing said char into two streams comprising a first stream of char and a second stream of char;
gasifying said first stream of char to produce a second gas;
utilizing said first stream of gas and said second stream of gas as fuels for the formation of one or more than one subsequent form of energy while emitting a flue gas containing carbon dioxide (CO2) into the atmosphere, said CO2 being a greenhouse gas and being suspected of causing global warming; and
sequestering said second stream of char in soil in order to compensate for at least a portion of the CO2 emitted into the atmosphere while increasing the capability of the soil to retain nutrients in the cellular structure of the sequestered char to result in an increase in the yield of plant growth from said soil, said increase of plant growth being a greater consumer of CO2 than if said second stream of char were not sequestered in the soil.
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This invention relates to a clean and efficient poly-generation of various valuable products from carbonaceous materials such as bituminous coal, sub-bituminous coal, lignite, peat, coke, biomass, etc. This invention which is a continuation-in-part of the Applicant's pending patent application bearing Ser. No. 11/506,939 filed on Aug. 21, 2006, relates to the co-production of enhanced fuels and efficient electric power while mitigating the ill-effects caused to the environment by utilizing said carbonaceous materials as combustible fuels, particularly with respect to emitting carbon dioxide (CO2) into the atmosphere. CO2 is commonly referred to as a “greenhouse gas” and is suspected of contributing to global warming. Specifically, this invention is an improvement of the Applicant's issued patent bearing No. 6,911,058 B2 issued on Jun. 28, 2005; this patent fails to address the ever-increasing ill effects to the environment caused by the emission of greenhouse gases, in particular by carbon dioxide (CO2).
Attempts are being made to capture CO2 where it is generated and to sequester it by introducing it under pressure into such places as deep wells and underground reservoirs for permanent storage—a costly, inefficient and questionable solution, except in cases wherein it is injected into oil or gas wells in order to recover residual oil or gas from such wells; however, the infrastructure related to the piping necessary to transport the CO2 to such wells is a major disadvantage; there is no assurance that CO2 will not leak out via fissures in such wells.
The Applicant has discovered a method herein disclosed that reduces the formation of CO2 by being efficient while still using said carbonaceous fuels, and especially coal, and at the same time converting CO2 into a useful by-product such as urea, a valuable fertilizer that enhances the growth of biomass, a renewable energy resource in the agriculture sector.
Before listing the objectives of the instant invention and proceeding with its description, coal will be used as the energy resource as an example, since more than four billion tons of coal are combusted yearly worldwide, but the instant invention is applicable to the use of carbonaceous materials in general.
The main object of the instant invention is to maximize the value of said carbonaceous materials by making their efficient use possible and yet mitigating the ill-effects that they cause to the environment.
Another object of the instant invention is to extract from the coal via pyrolysis a raw hydrogen rich gas which, after cleanup, is used as a resource to make valuable and sorely needed products such as gasoline or synthetic natural gas (SNG) while at the same time producing a hot char.
Still another object of the present invention is to gasify a first stream of the hot char with air preferably, to produce a raw lean gas which, after cleanup, becomes an excellent fuel for combustion turbines which, when configured in a combined cycle mode, generate electric power most efficiently by virtue of mass and low NOX formation while emitting a flue gas composed mainly of nitrogen and carbon dioxide (N2+CO2).
Yet another object of the instant invention is to pass steam through a second stream of said hot char in order to transform it to activated carbon.
Therefore another object of the instant invention is to divide said activated carbon into two sub-streams wherein a “first” sub-stream is set aside for export to the agriculture sector for introduction into soils to stimulate more vigorous growth of crops by providing a cellular structure to store plant nutrients while at the same time sequestering carbon in Mother Earth whence it originated.
Therefore another object of the instant invention is to elevate the temperature of the “second” sub-stream of said activated carbon to enable it to react with nitrogen (N2) to thus activate the N2.
Further another object of the instant invention is to use off-peak power to electrolyze water to co-produce hydrogen (H2) and oxygen (O2).
Further still another object of the instant invention is to react hot activated carbon (C) with flue gas (N2+CO2) and with hydrogen (H2) to make urea (CO(NH2)2) while at the same time sequestering CO2 via the formation of urea, such as CO2 being produced in the generation of electric power.
Further yet another object of the instant invention is to mix activated carbon with urea to make a super-fertilizer.
Therefore yet another object of the instant invention is to utilize the O2 derived from electrolysis to serve as the oxidant in the pyrolysis of the coal.
It is yet another object of the present invention to mix said hydrogen rich gas and said lean gas to create a fuel suitable to co-produce electric power and urea while sequestering carbon in the soil.
It is still another object of the present invention to mix said hydrogen rich gas and said lean gas to create a fuel suitable to generate electric power while activated carbon is sequestered in soil.
These and other objects of the present invention will become more apparent to those skilled in the art to which this invention pertains from the following description and appended claims. Reference is now being made to the accompanying drawings forming a part of this specification. It is to be noted that the embodiments shown herein are for the purpose of description and not limitation.
Before proceeding with the detailed description of the invention by making use of the drawings, it is to be noted that for the sake of clarity reference will be made to the numerals and to the words to represent the various components and process streams.
Before describing the operation of the instant invention, it is to be noted that the various streams incorporated in the method would include pressure boosting and pressure let-down equipment, such as compressors, expanders, and miscellaneous valves as required, depending upon the prevailing conditions to enable the navigation of the flow of each stream. Since the use of such equipment is common practice in the field of chemical engineering and is known in the art to which this invention pertains, the Applicant has obviated the inclusion of such equipment in the drawings, even though such equipment will be used in the application of the instant invention.
Assuming that the process is already at steady state and referring to both
Hot char stream 31, the second part of the char from stream 24, is directed to the activator denoted by numeral 63 for converting the hot char into activated carbon by means of steam-stream 33; stream 66 denotes the off-gas from activator 63; stream 55 represents the activated carbon discharged from activator 63. During the activation of the hot char with steam, it loses temperature by virtue of the water-gas reaction that takes place.
Activated carbon stream 55 is, in turn, further divided into sub-stream 58 and sub-steam 61, with sub-stream 58 being fed into reheater 64 where the temperature of the activated carbon is raised by making use of the elevated temperature of the hot, raw lean gas-stream 67, by directly contacting the activated carbon contained in reheater 64. The partially cooled raw lean gas leaves reheater 64 as stream 25 and is directed to lean gas cleanup 18. In both cleanup systems 12 and cleanup 18, the sulfur in the gases is removed, and it leaves cleanup 12 via stream 28 and cleanup 18 via stream 29; these two sulfur streams join to form stream 44.
The cleaned rich gas which essentially is CO+2H2 leaves cleanup 12 via stream 46 and is directed to methanol plant 13 where the rich gas is converted to methanol which, in turn, is directed as stream 47, to gasoline plant 14 where the methanol is converted to gasoline via Exxon Mobil's process known as “MTG” for short. The clean lean gas which essentially is N2+CO leaves cleanup 18 via stream 30 to which CO—stream 48, is added to form stream 32 which fuels gas turbine 15; air to combust stream 32 is furnished by stream 52 which is compressed prior to entering the combustion chamber (not shown) of gas turbine 15. The flue gas exhausting from the gas turbine is passed through heat recovery steam generator 16 to raise steam which is directed to steam turbine 17 via stream 50. Both gas turbine 15 and steam turbine 17 are each followed by a generator (not shown) to generate electric power most efficiently via the combined cycle mode which power leaves as streams 37 and 38, respectively, to form stream 39. The flue gas leaving heat-recovery steam generator 16, which is made up of nitrogen and carbon dioxide (N2+CO2) is denoted by stream 34. A portion of the steam generated in heat-recovery steam generator 16 is withdrawn as a side stream which is denoted by numeral 36; this side stream of steam together with H2 stream 49 form stream 53 which is directed to high-temperature electrolysis system 19 in order to increase the efficiency of H2 generation. It is to be noted that side stream 36 may also be withdrawn from steam turbine 17.
An alternating electric current stream denoted by numeral 40 is directed to rectifier 21 where it is converted to direct electric current to form streams 42 and 43 which are introduced into electrolysis system 19 in order to electrolyze the steam contained in stream 53 to yield a larger output of H2-stream 56 and also producing O2 as stream 22; this larger output of H2 is directed to synthesis system 20, while the O2, after being compressed (not shown), is directed to pyrolysis chamber 10 as stream 22.
Referring now to the flue gas, stream 34 (N2+CO2) is split to create a bleed of flue gas to maintain system balance denoted by numeral 35, to result in stream 57 which joins H2 stream 45 (the net H2 produced in electrolysis system 19) to form stream 65. The activated carbon (C)—stream 68 and the flue gas (N2+CO2) together with the H2—stream 65 are respectively introduced into urea plant 20 to produce urea (CONH2)2)+CO as stream 69. The CO, as stream 48, is separated from stream 69 to result in the formation of urea as stream 59 whence this stream joins activated carbon sub-stream 61 to form a super-fertilizer for export denoted by stream 62.
It is to be noted that the hot activated carbon may be reacted with the flue gas by itself in a reactor to form CO and cyanogen (C2N2), and the H2 may then be added in a subsequent reaction to form the urea. Further, the formation of urea may also occur via the ammonia (NH3) route by reacting N2 with 3H2 to make 2NH3 and subsequently reacting the 2NH3 with CO2 to form CO(NH2)2+H2O, the conventional method of making urea.
The step of making urea may be obviated by making use of the method to make activated carbon from a portion of the char, activating such portion, and sequestering it in the soil to enhance it by introducing cellular structure to store plant nutrients and to provide time release of such nutrients to result in causing the vigorous growth of plant life.
In summation, it is submitted that the method described herein for maximizing the benefits derived from a carbonaceous material such as coal which contains sulfur in an environmentally acceptable manner while co-producing liquid fuel, electric power and urea is comprised of pyrolyzing the coal with oxygen to produce a raw hydrogen (H2) rich gas and a hot char which is cellular in structure and substantially composed of carbon (C). The hot char so produced is divided into two streams, with the first stream being directed to a gasifier that is air blown to make a raw lean gas which is made up of nitrogen and carbon monoxide (N2+CO) and a second stream being activated with steam to produce activated carbon that is further divided into a “first” sub-stream of activated carbon and a “second” sub-stream of activated carbon whose use will be described hereinafter.
Subsequent to the cleaning of the H2 rich gas and the lean gas, including the removal of mercury from these gases, the cleaned H2 rich gas (syngas) may be converted to one or more chemicals, but preferably to methanol which, in turn, is converted to a transportation fuel such as gasoline, a most valuable liquid fuel. The cleaned lean gas fuels a gas turbine that is part of a combined-cycle system to generate electric power most efficiently by virtue of its large N2 content which contributes a large mass flow of gases through the gas turbine while exhausting an off-gas (flue gas) made up of N2+CO2. This flue gas which is reacted with activated carbon and H2, is synthesized with 2H2 to produce urea which is characterized chemically as NH2.NH2.CO or CO(NH2)2 plus CO. Alternatively, the formation of the urea may be the conventional route of making urea by first forming ammonia (NH3) and, in turn, reacting two molecules of NH3 with CO2 to form CO(NH2)2, and H2O as by-product; in this case, the N2 in the flue gas is separated from the CO2 prior to reacting with the NH3.
Preferably during off-peak periods, the excess of the electric power that can be generated for which there is no demand, such power is utilized to electrolyze steam in a high-temperature electrolysis system to generate H2 and O2, with the H2 produced being the source for the H2 needed in synthesizing the N2+CO2 (with the aid of hot activated carbon) into urea. Preferably, some of the H2 produced via electrolysis is recycled with the steam fed to the electrolysis system to enhance the production of H2. The O2 which is co-produced via electrolysis is used in the pyrolysis of the coal mentioned above.
The “first” sub-stream of activated carbon serves to activate N2 in the flue gas (N2+CO2) to make possible the formation of urea according to the following chemical reaction: (N2+CO2)+C+2H2→CO+CO(NH2)2, wherein the CO is separated from the urea and is added to the lean gas to become part of the fuel for the gas turbine mentioned above.
The urea so formed is mixed with the “second” sub-stream of activated carbon, mentioned above, to produce a super-fertilizer which is put into the soil, not only for the sequestration of carbon (C) directly and carbon dioxide (CO2) indirectly via the urea, but also to provide storage for plant nutrients in the abundant cellular structure of the activated carbon, thus: