Process to produce a high methane content gas mixture from coal - Patent EP0259927
Enclosed is a European Patent that we're sending along just to further document that the technologies exist, and are known world-wide, that would allow us to convert some of our abundant Coal into Methane.
The significance of such technology is that, once obtained, Methane, aside from being a substitute natural gas fuel, can, as we recently documented in a report from New Zealand, be directly converted into liquid fuel; and, perhaps more importantly, it can be reacted, in the "tri-reforming" process, as described by both Penn State University and WVU, and others, with Carbon Dioxide, in a process that would consume CO2 and recycle it back into liquid fuels and plastics manufacturing raw materials.
Some excerpts:
"Process to produce a high methane content gas mixture from coal
European Patent EP0259927
A process is disclosed, to produce a high methane content gas mixture from coal, comprising the following steps: a) coal grinding to a granulometry not larger than 5 mm, preferably not larger than 2 mm; b) addition of one or more alkali and/or alkali-earth compounds to the ground coal, wherein the alkali or alkali-earth ions are in an amount comprised within the range of from 4 to 20% by weight relatively to dry, ash-free coal, and possible subsequent drying of the additive-containing coal; c) possible pelletizing of the additive-containing coal, so to obtain tablets whose maximum dimension is comprised within the range of from 3 mm to 5 cm, preferably of from 3 mm to 2 cm; d) gasification of the additive-containing coal and methanation of the produced gas, in one single step with a fixed bed of countercurrently descending coal with steam, and in the presence of an amount of air not larger than 35% by weight, relatively to the ash-free dry coal and/or of an amount of essentially pure oxygen amount comprised within the range of from 1 to 25% by weight relatively to the ash-free dry coal, by operating under a pressure higher than 25 abs.atm and at a temperature comprised within the range of from 400 to 850 DEG C, preferably of from 450 to 750 DEG C; e) removal from the gas produced in the (d) step of unreacted steam, and of the condensible compounds formed; f) removal of the acidic gases from the high methane content gas mixture obtained.
Inventors:
Bruno, Giacomo (Via Dogali 30, Santa Margherita Ligure, Genova, I-16038, IT)
Carvani, Luigi (Via 4 Novembre 110, Piacenza, I-29100, IT)
Passoni, Giovanni (Via Bordolano 2B, San Donato Milanese, Milan, I-20097, IT)
Date: 05/06/1992
Claims:
Process for preparing a high-methane-content gas from coal by conversion with steam and oxygen or an oxygen-containing gas, in the presence of an alkali metal- or an alkaline earth metal compound as the catalyst, characterized by comprising the steps of: grinding the coal to a particle size not greater than 5 mm; impregnating the ground coal with an aqueous solution of the catalyst, in which the alkali metal- or the alkaline earth metal ions are present in an amount of from 4% to 20% by weight relative to the dry, ash-free coal, optionally drying the impregnated coal, optionally pelletizing the catalyst-impregnated coal, to a pellet size of from 3 mm to 5 cm; methanizing the catalyst-impregnated coal by gassifying a catalyst-impregnated coal bed descending in a reactor in countercurrent relationship with the steam and oxygen or air stream, the air content being not greater than 35% by weight of the dry, ash-free coal, or the oxygen content being from 1% to 25% by weight of the dry, ash-free coal, under a pressure higher than 24,5165 bar (25 abs.atm.) and at a temperature of from 400°C to 850°C; stripping the unreacted steam and the condensibles from the as-produced gas, and deacidifying the gas so produced.
The present invention relates to a process to obtain from coal a gas mixture with a high methane content.
More particularly, the present invention relates to a process to obtain from coal a high methane content gas mixture, wherein the gasification and methanation reactions take place in one single, descending fixed-bed reactor.
The high methane content gas mixtures which are produced by means of said process are normally denominated "SNG" (substitute natural gas) and can either replace the natural gas, or be mixed with it.
Process have been long known, which start from coal, to produce the above-mentioned mixtures.
At Great Plains (U.S.A.), e.g., a process has been accomplished, which essentially comprises the following steps:
grinding of coal down to a size comprised within the range of from 6 mm to 5 cm;
fixed-bed gasification by means of oxygen and steam under high pressures (of approximately 89,4 bar (30 abs.atm) and at temperatures comprised within the range of from 500°C to 1200°C;
condensation of tars, unreacted water and condensible compounds formed;
shift of a portion of the produced gas, to adjust to a value of approximately 3 the H 2 /CO volume ratio;
removal of the acidic gases;
methanation of the product at a temperature of approximately 400°C
EP-A-0 067 580 on the contrary, designed a process wherein the reactions of gasification and methanation take place in one single step, which essentially comprises the following steps:
grinding of coal to a particle size not larger than 3 mm;
impregnation of the ground coal with water and a catalyst;
gasification and methanation by means of steam on a catalytic fluidized bed at a temperature of approximately 700°C;
removal of the acidic gases from the gas mixture formed;
cryogenic separation, to decrease in the gas mixture the contents of H 2 and CO, which are recycled to the gasification and methanation step;
lixiviation with water of the gasification residue, to partially recover the catalyst (from 70% to 90% per each cycle).
US-A-3 689 240 generally discloses the use of alkali metal catalysts in methanizing a carbonaceous material and, in addition to using steam only, without any added air or oxygen, considers the fixed bed technique, the moving bed technique and the fluidized bed technique as virtually equivalent.
Applicants have surprisingly found a simplified process in which methanization and gassification are a single step, so that the installation first costs are drastically reduced.
The invention, therefore, provides a process for preparing a high-methane-content gas from coal by conversion with steam and oxygen or an oxygen-containing gas, in the presence of an alkali metal- or an alkaline earth metal compound as the catalyst... ."
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The complete document is lengthy and contains many details beyond our scope. Note, however, the mention above of multiple other technologies, some reduced to practice, as in the Great Plains lignite gasification plant, which we have previously documented for you, that would allow us to convert Coal into Methane.
This patent seems to be a refinement of Coal gasification technology through which "costs are drastically reduced".
And, remember: Methane can enable us to recycle Carbon Dioxide; Coal-derived Methane can serve as Substitute Natural Gas; and, Methane can be directly catalyzed into liquid fuels - such as Methanol, as we will further document in yet another dispatch from Penn State University to follow.