http://www.osti.gov/scitech/biblio/1164581
We've known how to convert - through one process of gasification or another - our abundant Coal into substitute natural gas for a very long time, actually since before the end of the nineteenth century, when "town gas", or "manufactured gas", plants - - factories that converted Coal into a flammable gas distributed through pipelines for lighting and heating purposes in homes and businesses - - started to become fairly commonplace in larger cities and towns in some parts of the United States and Europe.
More about the Coal-to-Gas industry that once flourished basically around the world can be learned via
History of manufactured gas - Wikipedia, the free encyclopedia; wherein we're told, in part: "The history of manufactured gas, important for lighting, heating, and cooking purposes throughout most of the nineteenth century and the first half of the 20th century, began with the development of analytical and pneumatic chemistry in the eighteenth century. The manufacturing process for "synthetic fuel gases" (also known as "manufactured fuel gas", "manufactured gas" or simply "gas") typically consisted of the gasification of combustible materials, almost always coal ... . The coal was gasified by heating the coal in enclosed ovens with an oxygen-poor atmosphere. The fuel gases generated were mixtures ... including hydrogen, methane, carbon monoxide and ethylene, and could be burnt for heating and lighting purposes. ... The first attempts to manufacture fuel gas in a commercial way were made in the period 1795–1805 in France ... and England. Frederick Winsor was the key player behind the creation of the first gas utility, the London-based Gas Light and Coke Company, incorporated by royal charter in April 1812. Many other manufactured fuel gas utilities were founded first in England, and then in the rest of Europe and North America in the 1820s. The technology increased in scale. ... In the second half of the 19th century, the manufactured fuel gas industry diversified out of lighting and into heat and cooking. In the 1890s, pipelines from natural gas fields in Texas and Oklahoma were built to Chicago and other cities, and natural gas was used to supplement manufactured fuel gas supplies, eventually completely displacing it. Gas ceased to be manufactured in North America by 1966 (with the exception of Indianapolis and Honolulu), while it continued in Europe until the 1980s. "Manufactured gas" is again being evaluated as a fuel source, as energy utilities look towards coal gasification once again as a potentially cleaner way of generating power from coal, although nowadays such gases are likely to be called "synthetic natural gas".
By the 1970's, as seen for just a few examples in:
Texaco Clean Methane from High-Sulfur Coal | Research & Development | News; concerning: "United States Patent 3,928,000 - Clean Methane ... from High-Sulfur Containing Hydrocarbonaceous Materials; 1975; Assignee: Texaco Incorporated, NYC, NY; Abstract: This is an improved process for converting low-cost high-sulfur containing hydrocarbonaceous materials into a clean methane-rich gas stream which may be burned as a fuel without contaminating the atmosphere"; and:
Exxon Converts 99% of Coal to Methane | Research & Development | News; concerning: "United States Patent 4,077,778 - Process for the Catalytic Gasification of Coal; 1978; Assignee: Exxon Research and Engineering Company; Abstract: A process for the production of synthetic natural gas from a carbon-alkali metal catalyst or alkali-metal impregnated carbonaceous feed, particularly coal ... . Claims: (A) process for the production of synthetic natural gas by the conversion of a solid carbonaceous feed, in the presence of a carbon-alkali catalyst, by contact of said feed in a gasification zone containing a fluidized bed of char, with steam and a mixture of hydrogen and carbon monoxide gases added to said zone. Background: Fuel oil and natural gas shortages have sparked renewed world-wide interest in the development of processes that can produce clean synthetic natural gas, or gas or pipeline quality, from carbonaceous solids, particularly coal. It is a specific object of this invention to provide a staged catalytic coal gasification process, particularly a two-stage gasification process, for the more effective gasification and utilization of the carbon content of a carbonaceous feed. In accordance with this invention, it has been found feasible to effectively utilize as high as about 95 to 99%, and higher, of the feed carbon fed to the main gasification zone, or gasifier";
the US petroleum industry itself had gotten pretty good at converting even lower-grade "high-sulfur" Coal into substitute, or synthetic, natural gas of "pipeline quality", often referred to as "SNG", the primary component of which was often specified to be Methane, as in Texaco's above-cited "US Patent 3,928,000 - Clean Methane ... from High-Sulfur Containing Hydrocarbonaceous Materials".
So encouraging were those developments that the United States Government helped to establish a commercial-scale Coal-to-SNG Methane factory in North Dakota, as discussed for one example in:
North Dakota Commercial Coal to Methane | Research & Development | News; concerning: "Practical Experience Gained During the First Twenty Years of Operation of the Great Plains Gasification Plant and Implications for Future Projects; United States Department of Energy; Office of Fossil Energy; April, 2006.Executive Summary: The Dakota Gasification Company’s (DGC) Great Plains Synfuels Plant (GPSP) in Beulah, North Dakota has operated successfully for 20 years as the only commercial coal-to-natural gas facility in the United States. ... The plant’s success has not been achieved without some changes and alterations over its lifetime. The sources for this report, which include past technical reports and interviews with plant operators and managers, revealed that most parts of the original plant design worked well, but a few did not. Many processes in the plant have undergone redesign, repair, or improvement. These changes have made the plant much more productive, efficient, and environmentally sound than even its designers envisioned. Over the years, the plant has diversified to produce a broader slate of secondary products. In the late 1990s, an ammonia synthesis unit was added to the plant to produce anhydrous ammonia for fertilizer. In addition, the ammonia scrubbers on the boiler emissions are used to produce ammonium sulfate, which is also marketed as agricultural fertilizer. ... The plant has operated successfully and efficiently for over 20 years. Remarkably, the plant ran nearly continuously from its commissioning until a planned shutdown in June 2004. During that time, modifications were undertaken that have resulted in the plant producing a greater output of products and achieving greater efficiency than had been expected by the plants designers. Over the period culminating in the planned shutdown in 2004, these modifications have increased productivity by about 41 percent over designed specifications. Designed to produce 125 million standard cubic feet per day (mmscfd) of natural gas, by 1992 the plant was routinely delivering nearly 160 mmscfd, and in recent years has delivered as much as 165 to 170 mmscfd. Initial results from changes made during the June 2004 plant shutdown suggest production has significantly improved, with some days exceeding 170 mmscfd. The clean, sulfur-free raw synthesis gas ... enters the methanation unit where it is converted to methane-rich, high-Btu gas. The main reaction of CO and hydrogen to methane and water takes place in down-flow methanation reactors, which use a pelleted,reduced nickel-type catalyst. CO2 is also reacted with hydrogen to form methane, but this reaction is not as complete. The chemical equations for the two reactions are as follows: CO2 + 4H2 = CH4 + 2H2O (+ Heat) and CO + 3H2 = CH4 + H2O (+ Heat). These reactions are highly exothermic and are used to produce 1,250 psig-saturated steam".
We should emphasize here, that, as in the immediately-above "CO2 + 4H2 = CH4", as has been known since award of the 1912 Nobel Prize in Chemistry to Paul Sabatier, of France, and, as can be learned for an additional interesting example via:
http://pubs.acs.org/doi/abs/10.1021/ie50228a018; "Synthesis of Methane from Carbon Dioxide and Hydrogen; M. Randall and F. Gerard, University of California, Berkely; Industrial And Engineering Chemistry; December, 1928";
the fact that Carbon Dioxide could be made to react catalytically and spontaneously with Hydrogen to synthesize substitute natural gas Methane, CH4, was more fully examined and expounded upon during the early twentieth century.
And, as confirmed much more recently by the National Aeronautics and Space Administration in, for one example:
NASA 2014 CO2 to Methane | Research & Development | News; concerning: "United States Patent 8,710,106 - Sabatier Process and Apparatus for Controlling Exothermic Reaction; April 29, 2014; Inventors: Christian Junaedi, et. al., CT; Assignee: Precision Combustion, Inc., CT; Abstract: A Sabatier process involving contacting carbon dioxide and hydrogen ... so as to produce a product stream comprising water and methane. The first and second catalyst beds each individually comprise an ultra-short-channel-length metal substrate. An apparatus for controlling temperature in an exothermic reaction, such as the Sabatier reaction, is disclosed. Government Support: This invention was made with support from the U.S. government under U.S. Contract No. NNX10CF25P sponsored by the National Aeronautics and Space Administration. The U.S. Government holds certain rights in this invention";
the fact that the CO2-to-Methane Sabatier reaction is "exothermic", as in the USDOE's above equation:
"CO2 + 4H2 = CH4 + 2H2O (+ Heat)", can be capitalized upon by capturing the exothermic heat of the Methane synthesis reaction, both to enable use of that heat energy in other supporting processes and to control the Sabatier reaction itself, so that more Methane is formed and so that the catalyst is protected against thermal damage and inactivation.
And, herein we learn that the USDOE have very recently themselves conducted in-house research and development on the processes of Coal gasification, and, the concurrent and subsequent conversion of the Coal gasification products into a substitute natural gas consisting of nearly pure Methane.
Such efforts might seem unnecessary and even wastefully superfluous in light of the uncritical public press mania trumpeting the dubious "shale gas miracle" in recent years. But, even in addition to the plain fact that the United States is, even with shale gas, and is expected by the USDOE to remain, a net importer of natural gas, as can be learned from various sources, such as FORBES Magazine in an expert analysis piece published in September of 2014:
The Popping of the Shale Gas Bubble; "America’s shale gas resources and reserves have been grossly exaggerated and today’s level of shale gas production is unsustainable. In fact, due the distortions of zero interest rates and other factors, an enormous shale gas bubble has developed. Like all bubbles, this one will pop sooner than expected and when it does, the aftermath will be very unpleasant";
we don't even have all that much shale gas to begin with, irregardless of all the vaporous editorial raptures that have been published about it. So, the conversion of our abundant Coal into a substitute for dwindling natural gas Methane could soon become an issue of great importance, especially if any power producers allow themselves in the meantime to be seduced into switching to shale natural gas as a fuel.
In any case, since Coal isn't pure carbon, there are impurities in the synthesis gas derived from Coal, such as, for instance, a greater or lesser amount of sulfur oxides, as are treated in our above-cited report concerning the Texaco technology disclosed in: "United States Patent 3,928,000 - Clean Methane ... from High-Sulfur Containing Hydrocarbonaceous Materials", which must be removed from the raw product gas generated by the Coal gasification.
As explained in excerpts from the initial link in this dispatch to:
"Coal-Derived Warm Syngas Purification and CO2 Capture-Assisted Methane Production
http://www.pnnl.gov/main/publications/external/technical_reports/PNNL-23777.pdf
Final Report; October, 2014; RA Dagle, et. al.; PNNL-23777
Pacific Northwest National Laboratory, United States Department of Energy
Executive Summary: Gasifier-derived synthesis gas (syngas) from coal has many applications in the area of catalytic transformation to fuels and chemicals.
Raw syngas must be treated to remove a number of impurities that would otherwise poison the synthesis catalysts. Inorganic impurities include alkali salts, chloride, sulfur compounds, heavy metals, ammonia, and various phosphorus-, arsenic-, antimony-, and selenium containing compounds. Systems comprising multiple sorbent and catalytic beds have been developed for the removal of impurities from gasified coal using a warm cleanup approach. This approach has the potential to be more economic than the currently available acid gas removal approaches and improves upon currently available processes that do not provide the level of impurity removal that is required for catalytic synthesis application. Gasification also lends itself much more readily to the capture of carbon dioxide (CO2), which is important in the regulation and control of greenhouse gas emissions.
Carbon dioxide capture material was developed for the warm temperature range (250 to 400C) and in this study was demonstrated to assist in methane production from the purified syngas. Simultaneous CO2 sorption enhances the carbon monoxide methanation reaction through relaxation of thermodynamic constraint, thus providing economic benefit rather than simply consisting of an add-on cost for carbon capture and release.
Molten and pre-molten LiNaKCO3 can promote magnesium oxide (MgO) and MgO-based double salts to capture CO2 with high cycling capacity. A stable cycling CO2 capacity ... was demonstrated. This capture material was specifically developed in this study to operate in the same temperature range and therefore integrate effectively with warm gas cleanup and methane synthesis.
By combining syngas methanation, water-gas-shift, and CO2 sorption in a single reactor, single pass yield to methane of 99% was demonstrated at 10 bar and 330C when using a ... (Nickel/Magnesium Aluminum Oxide catalyst and a molten-phase promoted Magnesium Oxide-based sorbent. Under model feed conditions both the sorbent and catalyst exhibited favorable stability after multiple test cycles.
(We're going to interrupt here with some points we'll emphasize again in closing. First, note mention above of the "water-gas shift" reaction. We've discussed that in previous reports, and, it's done to increase the amount of Hydrogen in the finished synthesis gas, as explained by the USDOE itself via:
water gas shift | netl.doe.gov; "In applications where ... syngas hydrogen/carbon monoxide (H2/CO) ratio must be increased/adjusted ... , the syngas is passed through a multi-stage, fixed-bed reactor containing shift catalysts to convert CO and water into additional H2 and carbon dioxide (CO2) according to the following reaction known as the water-gas shift (WGS) reaction: CO + H2O = H2 + CO2".
And, as per the chemical equation, the WGS reaction, while increasing Hydrogen, increases as well the amount of Carbon Dioxide which will, one way or the other, have to be dealt with. An alternative would be to add Hydrogen from an external source, perhaps one developed by the USDOE at their National Renewable Energy Laboratory, as reported in:
USDOE 2014 Sunshine Extracts Hydrogen from Water | Research & Development | News; concerning: "United States Patent 8,729,798 - Anti-reflective Nanoporous Silicon for Efficient Hydrogen Production; 2014; Inventors: Jihun Oh and Howard Branz, CO; Assignee: Alliance for Sustainable Energy, LLC, Golden, CO(Under the current U.S. Department of Energy contract, in place October 1, 2008, Alliance for Sustainable Energy, LLC (Alliance) manages and operates NREL (National Renewable Energy Laboratory). Abstract: Exemplary embodiments are disclosed of anti-reflective nanoporous silicon for efficient hydrogen production by photoelectrolysis of water. A nanoporous black Si is disclosed as an efficient photocathode for H2 production from water splitting half-reaction. Government Interests: The United States Government has rights in this invention under Contract No. DE-AC36-08GO28308 between the United States Department of Energy and the Alliance for Sustainable Energy, LLC, the manager and operator of the National Renewable Energy Laboratory. Claims: A photocathode comprising: a nanoporous black Si (silicon) photocathode configured for H2 (hydrogen) production from water splitting, The photocathode ... wherein the nanoporous black Si is configured to produce Hydrogen ... in 1 sun illumination. ... The described subject matter relates to anti-reflective nanoporous silicon for photoelectrodes for efficient production of solar fuels, such as hydrogen production by photoelectrolysis of water";
wherein "1 sun illumination" can effect "hydrogen production" through the "photoelectrolysis of water". There would still be some Carbon Dioxide in the Coal-derived synthesis gas itself, and, if we were adding Hydrogen from an external source, so that sufficient Hydrogen was made available for reaction, that Carbon Dioxide, too, could be converted into Methane via the Sabatier reaction, as has been refined by NASA in their process of "United States Patent 8,710,106 - Sabatier Process and Apparatus for Controlling Exothermic Reaction".)
Warm gas cleanup of inorganics was broken down into three major steps: removal of chloride, removal of sulfur, and removal for a multitude of trace metal contaminants. Sodium carbonate was found to optimally remove chlorides at an operating temperature of 450C. For sulfur removal, two regenerable Zinc Oxide beds are used for bulk hydrogen sulfide removal at 450C (<5 ppm sulfur) and a non-regenerable ZnO bed for H2S polishing at 300C (<40 ppb sulfur). We also found that sulfur from carbonyl sulfide could be adsorbed (to levels below our detection limit of 40 ppb) in the presence of water that leads to no detectable slip of H2S. Finally, a sorbent material composed of copper and nickel was found to be effective in removing trace metal impurities such as AsH3 and PH3 when operating at 300C.
Proof-of-concept of the integrated cleanup process was demonstrated with gasifier-generated syngas
produced at the Western Research Institute using Wyoming Decker Coal. When operating with ... multiple inorganic contaminant removal sorbents and a tar-reforming bed was able to remove the vast majority of contaminants from the raw syngas. Employing a tar-reforming catalyst was necessary due to the tars generated from the coal gasifier used in this particular study. It is envisioned that, in a real application, a commercial scale coal gasifier operating at a higher temperature would produce a smaller or negligible amount of tar. Continuous operation of a poison-sensitive copper-based water-gas-shift catalyst located downstream from the cleanup steps resulted in successful demonstration.
Preliminary technoeconomic analysis confirmed that the warm syngas cleanup process offers potential for significant thermal efficiency compared to the significant heat loss associated with water quenching and scrubbing in the cold syngas cleanup process. However, areas of improvement are needed for this technology; specifically, the CO2 sorbent kinetics need to be improved before commercial implementation becomes practical. Relatively high equipment cost required for the integrated synthesis and sorption bed(s) would be alleviated for systems with lower CO2 capture requirements, such as to produce syngas instead of natural gas or hydrogen.
Overall, given future material improvements, there is clear potential for economic benefit.
Introduction: The production and use of synthesis gas (syngas) from gasified coal, biomass, or heavy hydrocarbons has been the subject of many studies. Because the raw syngas produced includes several impurity species, the end use of the syngas dictates the level of treatment of the syngas that is required. Notable among the impurity species are the sulfur-based gases hydrogen sulfide (H2S) and carbonyl sulfide (COS), and to a much lesser extent carbon disulfide. For more sulfur-tolerant industrial processes, such as integrated gasification combined cycle (IGCC) operation, sulfur is removed using a warm gas cleanup (350 to 500C), zinc oxide (ZnO)-based regenerable moving sorbent bed that reduces the sulfur content down to a few parts per million by volume (ppmv).
(Keep in mind that sulfur, which is such a concern, is a valuable industrial product that has a number of uses in various chemical and other manufacturing processes. And, as seen for one example in:
FMC Corporation Recovers Sulfur from Coal Syngas | Research & Development | News; concerning: "United States Patent 4,302,218 - Process for Controlling Sulfur Oxides in Coal Gasification; Date: November, 1981; Inventor: Louis Friedman, NJ; Assignee: FMC Corporation, Philadelphia; Abstract: In a fluidized coal gasification process in which heat for the gasifier is provided by recycle combustor residue from a slagging combustor, SO2 in the combustor's flue gas is removed by contacting the flue gas with the incoming coal feed whereby the SO2 is adsorbed on the coal and converted to H2S in the gasifier. Sulfur is recovered from the H2S in a Claus Plant"
the technology exists to extract it from Coal-derived synthesis gas in such a way that it can be treated as a valuable byproduct of Coal gasification and conversion processes. More about what a "Claus Plant" for sulfur recovery is can be learned via:.
http://en.wikipedia.org/wiki/Claus_process; in which article you'll discover that natural petroleum and what it's boosters like to call "America's Clean Energy Alternative", natural gas, can have their own sulfur issues, as well, which are handled pretty much as the USDOE report which is the subject of this dispatch and the above FMC Corporation "US Patent 4,302,218 - Process for Controlling Sulfur Oxides in Coal Gasification" suggest they be handled. Sulfur contamination of hydrocarbon product streams is an old issue, and it can be profitably dealt with, even though the USDOE herein doesn't exactly spell that out.)
However, industrial processes intolerant to sulfur include processes that use syngas to produce chemical or fuel products (e.g., methanol, synthetic natural gas [SNG], Fischer-Tropsch liquids, mixed alcohols, etc.) and for power generation with fuel cells (e.g., proton exchange membrane fuel cell or solid oxide fuel cell).
(Concerning the above, as we've seen in many past reports, as for only one, sort of random, example in:
Mobil Converts Coal to High Quality Gasoline | Research & Development | News; concerning: "United States Patent 4,076,761 - Process for the Manufacture of Gasoline; 1978; Inventors: Clarence Chang and Anthony Silvestri; Assignee: Mobil Oil Corporation; Abstract: Synthesis gas comprising a mixture of carbon monoxide and hydrogen is derived from fossil fuels and catalytically converted in a first reaction zone to a mixture of methanol and dimethyl ether which in turn is converted in a separate reaction zone ... into a high octane gasoline fraction, a light hydrocarbon gas fraction which may be liquefied and a hydrogen-rich gaseous by-product which is recycled to the conversion of fossil fuels to synthesis gas or may be otherwise used. Claims: (The) process for manufacture of liquid hydrocarbon fuels boiling in the gasoline boiling range from coal which comprises converting the coal to a gaseous mixture of hydrogen and carbon oxides and converting said gaseous mixture to normally liquid hydrocarbons and oxygen-substituted hydrocarbons comprising methanol (with the) additional step of contacting ... said methanol with a catalytically active aluminosilicate zeolite ... (and recovering) liquid hydrocarbons";
it is quite feasible to make a full range of hydrocarbon fuel products from Coal via an initial gasification, including "alcohols", such as Methanol, and, in this specific example, through the alcohol, Gasoline.)
Because these processes require maximum sulfur gas concentrations below 100 parts per billion by volume (ppbv), the standard commercial unit operation is chilled methanol solvent to remove sulfur species to the required low levels (Rectisol process). While effective in removing sulfur, low-temperature desulfurization processes incur economic penalties in that the syngas is substantially cooled for purification and then reheated to synthesis temperatures for use. With end uses for the syngas such as fuel or chemical synthesis, where catalytic conversions occur in the range of 200 to 350C, warm gas cleanup methods (300 to 450C) may be employed. For warm gas cleanup, ZnO-based sorbents have become the leading material because of its high sulfur affinity and high sulfur capacity, and its ability to be regenerated. For control of greenhouse gas emissions, carbon dioxide (CO2) should be captured. Capture of CO2 at warm temperatures is advantageous in terms of thermal efficiency compared to cooling the gas to liquid absorbent temperatures and then reheating to the temperature of use. The subsequent water-gas-shift (WGS) reaction can be used to adjust the hydrogen/carbon monoxide (H2/CO) ratio or for hydrogen production. By capturing CO2 during the shift reaction, the equilibrium conversion of CO can be increased and, in addition, capturing CO2 at this point allows more total CO2 to be captured. Especially attractive is a combined bed that contains both CO2 capture material and WGS catalyst. Alternatively, if SNG is the desired end product, combining CO2 capture with CO methanation offers a similar advantage. The objective of this study is to develop the materials for and demonstrate the successful removal of inorganic impurities and CO2 present in gasified Wyoming‐derived sub‐bituminous coal.
The end product for this particular study is a clean syngas feed that is converted to high purity methane.
However, this approach could be applied to the cleanup of syngas useful for the synthesis of other fuels and chemicals.
(The above, again, as in our citation for just one example of Mobil's "US Patent 4,076,761 - Process for the Manufacture of Gasoline.)
Our general cleanup strategy is to be able to remove the impurities in the raw syngas irrespective of whether a syngas cooling-water quench is employed. The water quench step typically removes some of the impurities in the syngas, depending on the temperature, at some loss in efficiency. We designed our cleanup system to include the possibility that no syngas cooler water quench will be employed.
In this report, we describe the materials that were developed for CO2 and sulfur sorption, and for the removal of other impurities such as chloride, alkali, ammonia, and heavy metals (e.g., arsenic, phosphorus, antimony, selenium, mercury, etc.). Also discussed is development of the CO2 sorption enhanced CO methanation process, a techno-economic analysis, and demonstration results from an entire integrated process train using actual Wyoming coal-derived syngas.
It should be noted that the approach described in this study also can be generally applied to the cleanup of biomass-derived syngas. While the concentrations of impurities differ, similar processing steps could be applied. One difference pertains to the tar impurities (i.e., polycyclic aromatic hydrocarbons) typically contained in biomass-derived syngas. Several tar-removal strategies have been reported including physical (e.g., scrubbing) and catalytic (e.g., cracking, reforming) approaches. A tar-reforming catalyst was employed in this study for coal-derived cleanup application. A tar-reforming unit was justified because of the low operating temperature employed by the gasifier used in this study, which resulted in the production of tars. It is envisioned that a real application for coal gasification would be at a significantly higher temperature, thus resulting in minimal tar production.
The major findings of this technoeconomic study are summarized below:
1. The warm syngas cleanup process reduced heat loss by dry and hot temperature operation compared to the significant heat loss associated with water quenching and scrubbing in the cold syngas cleanup process.
2. The dry and high-temperature operation of the warm syngas cleanup process leads to higher heatrecovery and thus higher power generation compared to the cold syngas cleanup process.
3. The aggregate cost of warm syngas cleanup using the transport-bed design for the mixed WGS and CO2 removal unit is lower than that of the fixed-bed design. Both of these designs cost more than of the cold syngas cleanup process because of the higher capital cost for the transport-bed reactors and higher catalyst cost for the fixed-bed reactors.
4. The warm syngas cleanup process using the transport-bed design uses less mixed WGS catalyst andCO2 adsorbent than the fixed-bed design because the fixed-bed design needs more absorbent for longer online operating times. However, although transport-bed reactors have a short online operating time and therefore use less catalyst, the short online time and high CO2 capture requirement lead to high absorbent circulating rate between the reactor and the regenerator, which imposes challenges on operation and maintenance of the transport-bed unit.
5. Increasing catalyst life would be an important approach to reducing the mixed WGS and CO2 absorbent cost. Based on this work, when the catalyst life increases to more than 6 years, the fixed bed design has a cost advantage than the transport-bed design.
6. The primary reason for the high equipment cost for the transport-bed design and high catalyst cost forthe fixed-bed design is the high CO2 capture requirement for H2 generation. Therefore, for a system with a lower CO2 capture requirement, such as to produce syngas for methanol synthesis, the cost disadvantages for using the CO2 absorbent should be less than that shown in this study. The cost difference between the warm and cold syngas cleanup processes would be smaller, or the cost of warm syngas cleanup process could be lower than that of the cold syngas cleanup process.
Conclusions: In this study, we focused on developing a CO2 capture material suitable for operating in a warmtemperature range. Our primary goal was to minimize or replace the NaNO3 molten salt with other melting salts that are less corrosive and, therefore, would be more amenable to integration with catalysts required for synthesis (e.g., methanation catalysts). We have found that a mixture of carbonate salts, including lithium, sodium, and potassium carbonates, are able to function analogously to NaNO3 in removing CO2 at temperatures at 380C or lower, and they lack the corrosiveness of the nitrate salt. Thus, we have been able to capture CO2 at temperatures below the measured melting point of this mixture of carbonates and under conditions and temperatures that we define as “pre-melting.” Although CO2 capture capacity is not quite as high as with the nitrate salt, we moved forward with these carbonate materials in fixed-bed tests. This type of sorbent was utilized in a process demonstration.
This sorbent material was integrated with methanation catalyst to drive the equilibrium-driven methanation reaction while simultaneously providing CO2 capture. Process conditions were optimized to match sorption-enhanced CO methanation reaction kinetics with CO2 sorption-desorption.
A single unit operation that could yield 99% conversion to CH4 when operating at pressurized conditions (10 bar) and simultaneously capturing CO2 was demonstrated.
Na2CO3 was shown to be effective for removing HCl in the presence of syngas and optimal when operated at approximately 450 C. A sorbent comprising of Cu and Ni active components was shown to be effective for the removal of a multitude of contaminants, including as AsH3 and PH3. Trace amount of sulfur can also be removed using this material.
Proof-of-concept of the integrated cleanup process was demonstrated with gasifier-generated syngas produced at the Western Research Institute using Wyoming Decker coal. When operating with a 1 SLPM feed, multiple inorganic contaminant removal sorbents and a tar-reforming bed were able to remove the vast majority of contaminants from the raw syngas. A proof-of-concept cleanup demonstration was verified through the continuous operation of a poison-sensitive copper-based WGS catalyst located downstream from the cleanup steps. Only very minimal deactivation in the WGS catalytic activity was observed, likely because of the part-per-million levels of sulfur observed on the front end of the catalyst bed. However, the vast majority of contaminates from the raw syngas were removed, thus providing proof-of-concept and viability of this warm cleanup system".
-------------------------
So, it is perfectly feasible to generate a product gas from Coal that consists, in essence, of nearly pure substitute natural gas Methane. Keep in mind, that, as seen in:
USDOE and Arizona Coal to Methane + Electricity | Research & Development | News; concerning: "United States Patent 8,236,072 - System and Method for Producing Substitute Natural Gas from Coal; 2012; Inventor: Raymond Hobbs, AZ; Assignee: Arizona Public Service Company; The present invention provides a system and method for producing substitute natural gas and electricity, while mitigating production of any greenhouse gasses. The system includes a hydrogasification reactor, to form a gas stream including natural gas and a char stream, and an oxygen burner to combust the char material to form carbon oxides. The system also includes an algae farm to convert the carbon oxides to hydrocarbon material and oxygen. Government Interests: This invention was made with Government support under DOE Contract No. DE-FC26-06NT42759 awarded by the Department of Energy. The Government has certain rights in this invention";
contractors employed by the USDOE have also demonstrated that a commercial amount of electricity can be co-produced in such a Coal-to-substitute natural gas Methane facility. And, as indicated in:
USDOE Coal to Gasoline, Diesel and Electricity Profitable | Research & Development | News; concerning: "'Baseline Technical and Economic Assessment of a Commercial Scale Fischer-Tropsch Liquids Facility'; DOE/NETL-2007/1260; Final Report for Subtask 41817.401.01.08.001; April 9, 2007; Economic and national security concerns related to liquid fuels have revived national interest in alternative liquid fuel sources. Coal to Fischer-Tropsch fuels production has emerged as a major technology option for many states and the Department of Energy. This report summarizes the preliminary results of an NETL study to assess the feasibility of commercial scale, coal-to-liquids production using a high Btu Midwestern Coal. Conclusions: The conceptual design uses high sulfur bituminous coal to produce distillate and naphtha liquid pools via indirect coal liquefaction (F-T process). With the addition of additives, the distillate can be converted to a saleable diesel fuel. The naphtha liquids can be shipped to a refinery for upgrading into gasoline ... . This plant produces 22,173 bbls/day of liquid naphtha that is shipped to a refinery for further upgrading to commercial grade products or for use as a chemical feedstock. The plant also produces 27,819 bbls/day of diesel product. The total coal input requirements are 24,533 tons/day of Illinois #6 coal. All production figures are calculated at 100% of design capacity. The plant produces a net power output of 124 MWe which can be exported to the grid";
a similar and related co-generation facility, one producing both liquid hydrocarbon fuels and electricity from Coal, would, as the USDOE itself has determined, be profitable.
Far past time all of this good news published about Coal by our United States Government started making its way to all of the United States citizens, and policy makers, in United States Coal Country, ain't it?