Clean Coal Technology

Dr. Lee’s group has long been actively involved with various aspects of clean coal technology development and has accumulated a great deal of expertise and technological ideas. Even Dr. Lee’s own doctoral dissertation was in the field of coal gasification and his graduate study project was sponsored by the U.S. DOE’s Synthane Gasifier Program.

Some of the highlights of the group’s research accomplishments and on-going efforts in the field of clean coal technology are described below.

  1. Precombustion Coal Desulphurization Technology based on binary and ternary supercritical fluid extraction processes. The original work was sponsored by the Ohio Coal Development Office (OCDO) and the Electric Power Research Institute (EPRI). The process study tested many supercritical fluid combinations and developed a number of treatment processes that are effective in extracting and reactively removing sulfurous species, all three forms (organic, inorganic, and sulfatic), from Eastern U.S. high-sulfur coals, more specifically various seams of Illinois and Ohio coals. This process study was one of the most extensive and pioneering studies using various combinations of binary and ternary mixtures of supercritical fluids in chemical and fuel processing, and provided a technological foundation for advanced utilization of supercritical fluid mixtures in a wide variety of process applications. Further, extracted sulfurous species from coal helped elucidate the molecular forms and structures of organic sulfur compounds present in coal and their potential reactivities and transformational routes in treatment conditions. The original study resulted in a U.S. patent (U.S. Patent No. 5,080,692), which also provided a successful example of finding beneficial and synergistic combinations of supercritical fluid mixtures for targeted chemical process operations based on the structure-property relations.

  2. Perchloroethylene (PCE) Coal Cleaning and Refining Process originally invented by Mr. Henry H. Leehe, Midwest Ore Processing Company (MOPC), Indiana. Dr. Lee’s research team worked very closely with Mr. Leehe and the MOPC with the sponsorship of the Electric Power Research Institute (EPRI) to develop this technology for full-scale commercial exploitation.
    • S. Lee (PI), P. Vishnubhatt, and K. L. Fullerton, "Perchloroethylene Coal Cleaning Process", (Licensable Material), EPRI TR-103200, pp. 1-151, EPRI, Palo Alto, January, 1994.
    • S. Lee (PI), "Conceptual Design of 36-TPD Pilot Plant for Perchloroethylene Coal Cleaning Process", pp. 1-107, EPRI, Palo Alto, CA, 1993.

    The process has outstanding merits of high removal efficiency of organic sulfur via highly selective solubilization and subsequent isolation of simplistic sulfurous fragments and elemental sulfur precursors such as intermediate sulfur polyhydrides (-SxHy-) using near-boiling perchloroethylene (PCE). Perchlorethylene, also known as tetrachloroetheylene, boils at 121°C under atmospheric pressure, and

    Perchloroethylene Coal Clean EPU

    its solubility toward elemental sulfur (S8) exponentially increases as the temperature nears the boiling point to 68-69 grams of sulfur per 100 grams of perchloroethylene. Further, perchloroethylene at room temperature has specific gravity of about 1.6, which makes it ideal as a heavy medium for coal deashing, demineralization, and removal of pyritic sulfur. With an ingenious combination of both chemical and physical cleaning of high-sulfur coal, the technology can produce highly refined low-sulfur clean coal using a single train of chemical process treatments. The process fully (99.987+%) recycles perchloroethylene within the process and thus, require very little replenishment of perchloroethylene. MOPC operated its pilot plant (of 100 tons/day capacity) at Plainville, IN and Lee’s group collaborated very closely with the MOPC and the original inventor, Mr. Leehe, on process engineering for large-scale commercialization of the process. While this process showed great promise in many aspects and related areas as well, the national trend in 1990’s was going with the post-combustion coal cleaning technology represented by scrubber technology, and the MOPC ceased its plant operation in mid 1990’s. However, the R&D studies conducted have generated many valuable scientific and technological insights as well as peripheral coal and ore processing technologies, besides a viable pre-combustion coal cleaning technology. To list a few, they include:

    • (a) wet grinding process in which coal particles can be ground to fine powders without going through heat generation, premature partial oxidation and potential crosslinking
      (b) ultra-clean coal that has exceptionally low ash and sulfur contents
      (c) permanently or near-permanently nonsettling coal-water mixture (CWM) slurry for substitute aviation fuel
      (d) organic sulfur chemistry during the process treatment involving formation of sulfurous fragments, isolation and removal of organic sulfur, and detrimental recombination of these fragments leading to crosslinking and inter-penetrating polymer network (IPN)
      (e) co-beneficiation of different types and ranks of coals
      (f) efficient sulfur ore processing that was perfected by Mr. Henry H. Leehe

    Coal-Water (CWM) and Coal-Oil (COM) Slurry Maker

  3. Coal and Biomass Gasification. As a follow-up to his earlier research in coal char gasification, Dr. Lee’s life-long interest in green processing of coal and clean utilization of natural resources, the group has been involved in gasification of coal and biomass for synthesis gas generation. While coal has a higher fixed carbon contents than biomass, biomass contains valuable hydrogen and higher moisture contents than coal with very low sulfur contents. Further, serious handicaps using biomass as process raw materials stemming mostly from associated logistical burdens, such as collection, gathering, transportation, and sustainable low-cost supply to the processing plants, can be offset by using biomass together with low-rank coals. The mixed gasification has more realistic merits of synergistic feed material compositions and co-beneficiation potentials, besides ultimately increasing the use of renewable resources. Dr. Lee’s group has special interests in the areas of steam gasification, advanced oxidation, plasma gasification, molten salt gasification, and beneficial use of CO2-rich syngas.Dr. Lee's group has expertise and experience in fast pyrolysis of biomass for liquid bio-oil production.

  4. Reactive Utilization of Carbon Dioxide and Carbon Dioxide Rich Synthesis Gas. Dr.Lee and his graduate researchers have long been studying the roles of carbon dioxide in many reactive chemical processes involving synthesis gas. These processes include, but not limited to: (1) methanol synthesis, (2) single-stage dimethylether synthesis, (3) formic acid synthesis, and (4) hydrocarbon synthesis from synthesis gas. For example, his research elucidated the roles of carbon dioxide and water in methanol synthesis and also found that, to some extent, the two have interchangeable roles in the synthesis. Further, this research firmly established the beneficial roles of carbon dioxide in both stabilization of Cu/ZnO/Al2O3 catalyst and potential beneficial transition of the catalyst ingredient of ZnO to ZnCO3 in a CO2-rich environment. Also, it was found that the liquid-phase synthesis of methanol demands a substantially higher concentration of carbon dioxide as an optimal syngas composition than the vapor-phase synthesis of methanol. The latter fact serves as a good starting point for further exploitation of carbon dioxide reaction chemistry. If properly managed, carbon dioxide can be very effectively and beneficially utilized in this reaction chemistry, thus claiming that carbon dioxide is not hopeless in its reactive conversion, rather is full of promise.

  5. Conversion of Carbon Dioxide and CO2-rich syngas into Hydrocarbons . As briefly mentioned above, Dr. Lee’s group and collaborators are investigating various chemical routes and associated catalysis that will lead to a major breakthrough of utilizing carbon dioxide as a reacting raw material for production of target hydrocarbons, thus establishing or helping establish the renewablility of carbon dioxide and CO2-rich gas. Major collaborative efforts in this global research agenda are currently under way.

  6. Methanol Synthesis . Dr. Lee’s team has done extensive R&D work with the financial sponsorship from the Electric Power Research Institute (EPRI) and his team’s research has contributed to the commercialization of the Liquid-Phase Methanol process.
      • S. Lee (PI), "Research to Support Liquid Phase Methanol Process Development", Electric Power Research Institute, EPRI AP-4429, pp. 1-312, Palo Alto, CA, February 1986.
      • S. Lee (PI), "Mass Transfer Characteristics of the Liquid Phase Methanol Synthesis Process", Electric Power Research Institute, EPRI AP-5758, pp. 1-214, Palo Alto, CA, April, 1988.
      • S. Lee (PI) and V. Parameswaran, "Reaction Mechanism in Liquid-Phase Methanol Synthesis", Electric Power Research Institute, pp. 1-206, EPRI ER/GS-6715, Palo Alto, CA, February 1990.

    Methanol is one of the most promising chemicals that can be synthesized using synthesis gas derived from coal and biomass feedstocks. Methanol is also an outstanding building block chemical, which can be further converted into a long list of other petrochemicals including premium gasoline, olefins, higher alcohols, carboxylic acids, formaldehyde, etc. Further, Dr. Lee’s team has acquired technological expertise in designing small scale methanol plants utilizing coal, biomass, or/and waste oil as starting materials. Please refer to methanol synthesis section of the Alternative Fuels Research.

  7. Dimethylether Synthesis. Dr. Lee’s research team developed an efficient single-stage synthesis process of dimethylether (DME) from syngas, in which methanol is in-situ converted into dimethylether via a novel dual catalysis technology. By doing the concurrent conversion of methanol into dimethylether, the equilibrium limitation of the methanol synthesis reaction is not only overcome, but also exploited in a more beneficial way. The original R&D was supported by the Electric Power Research Institute (S. Lee (PI) and M. R. Gogate, "Development of a Single Stage, Liquid Phase Synthesis Process of Dimethyl Ether from Syngas", EPRI TR-100246 (Licensable Material), pp. 1-179, EPRI, Palo Alto, CA, February, 1992). Further advances have been made by his team, with regard to (1) process optimization, (b) CO2 tolerance, (c) catalyst life management, and (d) gas separation. Some more details can be found in Dimethylether section of the Alternative Fuels R&D.

  8. Green Manufacturing Process of Synthetic Gasoline. Dr.Lee’s research group invented a novel process technology that converts dimethylether into premium gasoline and received a U.S. patent ( U.S. Patent 5,459,166). The process is quite versatile and can also be used for target olefins and higher hydrocarbons. When this process is coupled with the single-stage dimethylether synthesis, its resultant benefits are quite significant with substantial cost savings in comparison to MTG (methanol-to-gasoline) synthesis.

  9. Hydrogen Production from Coal. Steam gasification of coal, especially low rank coal like lignite, can be very eminently employed for hydrogen production. This area of research is in close connection with the team’s efforts in hydrogen production from a variety of other feedstocks.
  10. Dimethyl Ether to Synthetic Fuels EPU

  11. Coal Characterization. The Sustainable Energy and Advanced Materials (SEAM) Laboratory, Ohio University, Athens, OH is equipped with the state-of-the-art and most extensive coal characterization and processing equipment. They include LECO CHN Analyzer, LECO Sulfur Analyzer, LECO Chlorine Analyzer, LECO Ash Fusion Analyzer, Fisher Proximate Analyzer, Parr Oxygen Bomb Calorimeter, Coulter Counter, Total Organic Carbon Analyzer, Gas Chromatograph/Mass Spectrometer (GC/MS), FTIR, HPLC, TGA, Coal-Water and Coal-Oil Slurry Maker, Coal Wet Grinder, Ball Mill, Roll Mill, Steam Stripper, Heavy Medium Separator, Organic Sulfur Removal System, and more.

LECO Fuel and Coal Characterization Laboratory at the SEAM Lab