Process for the production of carbon monoxide from a solid fuel
Herein, we submit yet another example of technology, developed more than half a century ago, by the former, and formerly-famous, Texaco, wherein Coal can be indirectly converted, through an initial gasification, into conventional types of liquid hydrocarbon fuels, with no, or very, very little, co-production, or emission, of Carbon Dioxide.
As we've documented in numerous reports, including:
Texaco 1950 Coal + Steam = Hydrocarbon Syngas | Research & Development; concerning: "United States Patent 2,516,974 - Gasifying Carbonaceous Material; 1950; Assignee: Texaco Development Corporation;
Abstract: The present invention relates to gasification of solid fuels and is more particularly concerned with the conversion of carbonaceous materials into a gaseous product of high heating value composed primarily of carbon monoxide and hydrogen ... . In accordance with the present invention a stream of combustible gases, predominantly hydrogen and carbon monoxide, is produced by the reaction of water vapor with carbon"; and:
Texaco 1951 Coal + CO2 + H2O + O2 = Syngas | Research & Development; concerning: "United States Patent 2,558,746 - Carbon Monoxide and Other Gases from Carbonaceous Materials; 1951; Assignee: The Texas Company, NYC; Abstract: This invention relates to a process and apparatus for the generation of gases comprising carbon monoxide from carbonaceous materials. In one of its more specific aspects it relates to a process and apparatus for the generation of a mixture of carbon monoxide and hydrogen, suitable as a feed for the synthesis of hydrocarbons, from powdered coal"; and:
Texaco 1953 CO2-Free Coal Syngas | Research & Development; concerning: "United States Patent 2,655,443 - Synthesis Gas Generation; 1953; Assignee: The Texas Company (Texaco), NY; Abstract: This invention relates to a process and apparatus for the generation of gases comprising carbon monoxide from carbonaceous materials. In one of its more specific aspects it relates to a process and apparatus for the generation of a mixture of carbon monoxide and hydrogen, suitable as a feed for the synthesis of hydrocarbons, from powdered coal";
Texaco began to develop, soon after World War II, and it's revelations about the extensive and extraordinary industry founded by Germany and Japan, wherein Coal was converted into the liquid hydrocarbon fuels that kept their economies and militaries functioning during a time of international conflict and embargo, an extensive suite of technologies that enabled the efficient, and essentially complete, conversion of the Carbon content in Coal into hydrocarbons.
A close read of those earlier Texaco Coal conversion disclosures reveals that much of the Hydrogen needed to, in combination with the co-produced Carbon Monoxide, formulate synthesis gases suitable for catalytic chemical condensation into a full range of liquid hydrocarbons, is generated within the Coal gasification process itself, primarily through the reaction of Steam, H2O, with hot Carbon, according to the simple equation: H2O + C = CO + H2.
However, since relatively more Hydrogen than Carbon Monoxide is needed to formulate synthetic hydrocarbons, those Texaco technologies also included provision for the "water gas shift reaction" to be included in the synthesis gas generation process; which reaction is illustrated as "CO + H2O = CO2 + H2"; and, which thereby, as specifically stipulated by the above-cited "US Patent 2,655,443 - Synthesis Gas Generation", enables control of the "quantity of hydrogen in the product gas".
The Carbon Dioxide co-produced by the Hydrogen-forming water gas shift is often left unaccounted for, although in some disclosures it, or a portion of it, is specified to be reclaimed and recycled to the initial Coal gasification, where, according to the equation: "CO2 + C = 2CO", it reacts with hot Coal to form more of the desired Carbon Monoxide.
That reaction is more clearly explained in our report of a later Texaco innovation, as accessible via:
Texaco CO2 + Coal = Hydrocarbon Synthesis Gas | Research & Development; concerning: "United States Patent 3,976,442 - Synthesis Gas from Gaseous CO2-Solid Carbonaceous Fuel Feeds; 1976; Assignee: Texaco, Incorporated, NY; Abstract: This is an improved continuous partial oxidation process for producing synthesis gas or fuel gas from gaseous CO2 (and) solid carbonaceous fuel feeds".
In any case, we see herein that Texaco had, more than half a century ago, brought all of those separate concepts, and some others, together, in a consolidated Coal gasification system that used multi-stage, sequential and integrated, gasification steps to effect the essentially complete conversion of the Carbon in a feed of raw Coal into Carbon Monoxide, with very little or no co-produced Carbon Dioxide; along with the generation, from Steam, of sufficient, or nearly-sufficient, Hydrogen to effect hydrocarbon synthesis.
Comment follows, and is inserted within, excerpts from the initial link to:
"United States Patent 2,803,530 - Production of Carbon Monoxide from a Solid Fuel
Date: August, 1957
Inventor: Clifford Ludeman, NY
Assignee: Texaco Development Corporation, NYC
Abstract: This invention relates to a process for the generation of carbon monoxide and hydrogen from a solid carbonaceous fuel. In one of its more specific aspects, this invention relates to an improved method for the reaction of powdered coal with oxygen and steam to produce carbon monoxide and hydrogen.
(We are compelled to, with apologies, interrupt at some length here. Note in the above that pure "oxygen" is specified as one of the co-reactants; and, "hydrogen" is specified as one of the desired products. We remind you, that, as seen in:
General Electric Hydrogen from Geothermal Energy | Research & Development; concerning: "United States Patent 7,331,179 - System and Method for Production of Hydrogen; 2008; Assignee: General Electric Company; Abstract: A technique is disclosed for a system and method for combined production of power and hydrogen utilizing the heat from a first working fluid heated by a geothermal energy source using a steam generator and an electrolyzer designed to receive the steam produced by the steam generator for the production of hydrogen and oxygen using electrolysis"; and:
NASA Hydrogen from Water and Sunlight | Research & Development; concerning: "United States Patent 4,045,315 - Solar Photolysis of Water; 1977; NASA; Abstract: Hydrogen is produced by the solar photolysis of water (and, simultaneously) oxygen is produced in a second photo-reduction reactor"; and:
Hydrogen from Wind Power | Research & Development; concerning: "United States Patent 7,329,099 - Wind Turbine and Energy Distribution System; 2008; Abstract: A new design of vertical axis wind turbine is disclosed ... . An apparatus for conversion of a wind energy resource into rotational power ... coupled to electrical generating means, and said electrical generating means is connected to an electrical load (which)comprises at least one electrolysis cell, said at least one electrolysis cell connected to an output stream of hydrogen gas and further connected to an input stream of water"; and:
West Virginia Coal Association | Germany & Pennsylvania Hydrogen from Hydropower | Research & Development; concerning, in part: "United States Patent 6,864,596 - Hydrogen Production from Hydro Power; 2005; Assignees: Voith Siemens Hydropower Generation GmbH and Incorporated, Germany and York, PA; Abstract: A turbine installation configured for large scale hydrogen production includes a foundation structure separating an upper elevation headwater from a lower elevation tailwater. The foundation structure defines a water passageway extending therethrough between an inlet adjacent the headwater and an outlet adjacent the tailwater. A runner is supported for rotation by the foundation and disposed in the water passageway intermediate the inlet and the outlet so that water flowing through the passageway as a result of head differential causes rotation of the runner. A generator is supported by the foundation and connected to the runner by a rotary shaft for generating electrical power as the runner rotates. An electrolyzer is electrically coupled to the generator for receiving the electrical power and producing hydrogen. A control system is capable of sensing the remaining hydrogen storage capacity and performing an economic comparison analysis to determine whether operating the turbine to produce additional hydrogen or to supply a utility grid with power provides the highest economic return";
we have a smorgasbord of options available to us for utilizing freely-available environmental energies to generate all the Oxygen we might need for this CO2-free Coal conversion process; and, concurrently, all of the Hydrogen we might need to then supplement the product gases for better hydrocarbon synthesis, from plain old Water, that is, H2O.)
Gasification of coal to carbon monoxide and hydrogen is an industrially important operation.
Coal ... may be reacted with a restricted quantity of free oxygen at temperatures above about 1,800F to produce carbon monoxide and hydrogen relatively free from carbon dioxide.
Carbon monoxide, hydrogen and mixtures thereof are useful in a number of industrial processes. For example, liquid hydrocarbons suitable for use as motor fuels may be produced by reaction of hydrogen with carbon monoxide in the Fischer-Tropsch type synthesis reaction.
One of the objects of this invention is to provide an improved process for the generation of carbon monoxide and hydrogen from a solid carbonaceous fuel by reaction with oxygen and steam. Another object is to provide a process for generation of carbon monoxide and hydrogen wherein the efficiency of gasification is substantially increased.
In accordance with this invention, ... coal, in the form of small particles, is subjected to gasification.
The particles are smaller than about 3/8 inch in diameter, and may range downward to extremely fine particle sizes.
(As is made clear in the full Disclosure, but which won't be well-reflected in our excerpts, the energy expended in sizing the Coal is well-invested. The small particle sizes improve conversion efficiencies.)
The coal is introduced into a fluidized bed gasification reaction zone wherein a dense phase fluidized bed of coal is maintained. A stream of gaseous reactants, comprising steam, carbon dioxide and ... oxygen ... are passed upwardly through the reaction zone at a rate sufficient to violently agitate the particles ... .
Fine particles entrained in the resulting gaseous reaction products ... are separated therefrom and subsequently reacted with an oxygen-containing gas in such proportions that they are substantially completely burned to carbon dioxide.
The carbon dioxide so produced is supplied to the fluid bed gasifier as gaseous reactant therefor.
(Not only is the "carbon dioxide" a "gaseous reactant" for and with the Coal and Steam; but, as the full Disclosure makes clear, it also carries heat, from the finer particles of Coal being "completely burned"; which heat energy drives the reactions between the Coal, Steam and Carbon Dioxide to form Hydrogen and Carbon Monoxide. It is similar in that respect to a similar technology originating in the same era, about which we reported in:
Esso 1956 Self-powered Coal + Steam = Hydrogenated Syngas | Research & Development; concerning: "United States Patent 2,741,549 - Conversion of Carbonaceous Solids into Volatile Products; 1956; Assignee: Esso Research and Engineering Company; Abstract: The present invention relates to the conversion of carbonaceous materials including solids such as all types of coal ... into volatile products such as light oils (and) gasses containing CO and H2".)
Claims: In a process for the production of carbon monoxide and hydrogen by reacting a solid carbonaceous fuel containing an incombustible residue and consisting of particles within the size range of from about 3/8 inch to about 150 to 200 mesh and particles smaller than 150 to 200 mesh with an oxygen-containing gas in a fluidized bed maintained in a gasification reaction zone at a temperature above about 1800F wherein fresh fuel particles are charged directly into said fluidized bed; the improvement which comprises passing reactant gases comprising steam, carbon dioxide and oxygen-containing gas upwardly through said fluidized bed at a rate effecting fluidization of said bed and entrainment of fuel particles smaller than 150 to 200 mesh therefrom in resulting product gases without substantial entrainment of larger particles; separating said entrained smaller fuel particles from said product gases; subjecting said smaller fuel particles to substantially complete combustion with free oxygen and steam in a separate reaction zone at a temperature of 2200F effecting substantially complete consumption of carbon contained therein and producing hot products of combustion resulting from consumption of said smaller fuel particles at said combustion temperature and substantially free from solid residue into said gasification reaction zone into contact with said fluidized bed as reactant gas."
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It's a bit more complicated, but, in essence, what they're doing is completely burning fine particles of Coal, perhaps we could think of it as "soot", that remain un-reacted from a gasification process, wherein Coal is being reacted with Steam, and with the Carbon Dioxide arising from the combustion of the soot, to form a blend of Hydrogen and Carbon Monoxide synthesis gas.
The Carbon Dioxide arising from the combustion of that soot is hot, and conveys heat into the Coal gasification process to help drive it forward. However, it won't, due to straightforward laws of chemistry and physics, have enough heat energy to completely drive the process, especially since Steam is being reacted therein as well, and, some combustion of the Coal in the gasifier will have to take place just as it does in the "separate reaction zone", wherein the soot is combusted.
To completely eliminate the Carbon Dioxide, some external heat energy, derived from other than oxidative processes, would have to be added.
That fact is acknowledged by the somewhat related, but more contemporary, technology developed by our United States Department of Energy, as seen in:
USDOE Hydrogasifies Coal with Solar Power | Research & Development; concerning: "United States Patent 4,415,339 - Solar Coal Gasification Reactor; 1983; Assignee: The USA, as represented by the Department of Energy; Abstract: Coal (or other carbonaceous matter, such as biomass) is converted into a duct gas that is substantially free from hydrocarbons. Claims: A method of producing a substantially hydrocarbon-free product gas with a solar reactor from a carbonaceous-material feed ... (and) wherein the feed is coal and includes water, thereby generating steam from said water (and) injecting at least one reactive gas selected from the group consisting of steam, CO2, H2 and CH4 into said solar reactor between said solar energy reactor entry and said gasification zone";
wherein solar heat is used to drive the reactions between Coal, CO2 and Steam, and other intermediate product gases.
Herein, though, Texaco seems to call for the addition of some extra Oxygen to the Coal gasification, so that oxidative reactions can provide the additional heat energy.
That will result in the amount of Carbon Dioxide ultimately produced being minimized, but not eliminated; and, we're cautioned, as we have been about similar technologies, that there might ultimately build an imbalance between materials and available energy, so that some energy, from whatever source outside the system, as in the above-cited "United States Patent 4,415,339 - Solar Coal Gasification Reactor", would have to be added; or, some Carbon Dioxide discharged.
That would be especially true if the water gas shift reaction, as described above, were employed as an essential facet of the system for generating needed amounts of extra Hydrogen. But, that, as well, could be minimized if supplemental Hydrogen, as we also suggested above, were added from an external, and Carbon-free, source, such as that disclosed in the above-cited "United States Patent 6,864,596 - Hydrogen Production from Hydro Power".
Nonetheless, it is an efficient process for converting Coal and Steam into a hydrocarbon synthesis gas suitable for conversion into "motor fuels (by the) Fischer-Tropsch type synthesis reaction"; an efficient process, that, as it stands, minimizes the generation of waste Carbon Dioxide and requires, aside from the energy invested for any needed or wanted supply of purified Oxygen, little or no input of energy from outside the gasification system itself; that is, energy that can't be derived from the basic raw material being utilized:
Coal.