Information Bridge: DOE Scientific and Technical Information - Sponsored by OSTI
We've earlier reported on the Coal Liquefaction research and achievements of Consol, including some documentation of their own "Zinc Chloride" or "Zinc Halide" Coal conversion technology.
Herein, via the enclosed link and following excerpts, it is revealed that they were continuing their efforts in CTL technology at least until 1995. Moreover, as in the "Disclaimer" statement, in the copy below, this report evolved from: "work sponsored by an agency of the United States Government".
Although we downloaded and reviewed the full report ourselves, it is too large for us to efficiently transfer via email. As with so much of what we send you, we feel it begs reading and review by truly knowledgeable people who could translate and summarize it's import for the rest of us.
Comment follows excerpts from:
THE ROLE OF RECYCLE OIL IN DIRECT COAL LIQUEFACTION PROCESS DEVELOPMENT
F. P. Burke; CONSOL Inc., Research and Development; Library, PA
April, 1995
DISCLAIMER
This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process. or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.
(Ho-hum. If they didn't want to claim responsibility for any part of it, then why did the United States Government use our tax money to pay for it? - JtM)
ABSTRACT
It has long been recognized that use of a recycle oil is a convenient and perhaps necessary feature of a practical direct coal liquefaction process. The recycle oil performs a number of important functions. It serves as a vehicle to convey coal into the liquefaction reactor and products from the reactor. It is a medium for mass and heat transfer among the solid, liquid, and gaseous components of the reactor inventory. It can act as a reactant or intermediate in the liquefaction process. Therefore, the nature of the recycle oil can have a determining effect on process configuration and performance, and the characterization of recycle oil composition and chemistry has been the subject of considerable interest. This paper discusses recycle oil characterization and its influence on the industrial development of coal liquefaction technology.
(First of all, did any regular US citizen in US Coal Country, have any idea that it has "long been recognized that" there might even be such a thing as a "practical direct coal liquefaction process"? - JtM)
EARLY GERMAN TECHNOLOGY
In the early 1900's, Bergius used a petroleum "heavy oil" as the vehicle to slurry coal in batch and continuous unit liquefaction experiments. The German technology utilized in the 1940s was based on further development of the Bergius-Pier process, and utilized high temperature and pressure ... and an inexpensive ... iron oxide catalyst (red mud) in a liquid (sump) phase reactor. The recycle solvent was a distillate from gas phase hydrogenation of the sump-phase reactor overheads. Although this technology anticipated the dispersed catalysts under development today, the process employed a high reaction severity, rather than seeking to minimize reaction severity by improved catalyst or solvent activity.
(The Coal liquefaction "catalysts under development today" were "under development" when "today" was sometime in 1995. Where are they now, when "today" is a decade and half later? - JtM)
CONSOL SYNTHETIC FUELS PROCESS
In the 1960s, Consolidation Coal Company sought to improve on the performance of the German liquefaction technology by util izing more active supported-metal hydrogenation catalysts in fixed bed reactors. To overcome catalyst deactivation problems, the coal dissolution and catalytic conversion steps of the two-stage CONSOL Synthetic Fuels (CSF) process' were separated by an interstage deashing step. The coal dissolution step was non-catalytic, and carried out at a relatively low temperature to produce an "extract"
suitable for catalytic upgrading. The process was designed to produce a distillate hydrogen donor solvent in the second stage. The role of recycle solvent was explored in bench-scale tests ... . This work showed that, although the recycle oil increased in molecular weight upon recycle, it became less aromatic. Recycle oil characterization was used to indicate the approach of the process operation to steady state, and revealed the important effect of solvent characteristics on other process operations, particularly solids separation.
(As in earlier of our reports, about the "CONSOL Synthetic Fuels" development, and others; and, as in the "process was designed to produce a distillate hydrogen donor solvent in the second stage", above, processes can be designed wherein liquids initially derived from Coal can be treated to serve as hydrogen donors for further hydrogenation of coal and raw liquid coal product. - JtM)
SOLVENT REFINED COAL PROCESS
In the mid-1970s, interest grew in the development of a process to convert coal into a fuel-oil substitute for use in oil-fired electric utility boilers. TheSolvent Refined Coal (SRC) process was piloted by Gulf at Ft. Lewis, WA, and by Southern Company Services (and later EPRI) at Wilsonville, AL. The objective of the process was to solubilize coal under hydrogen, but in a non- catalytic reaction, so that the ash-forming minerals, including pyrite, could be removed by physical means. Some organic sulfur removal also was expected. The deashed products were distilled to yield the SRC product and a distillate recycle solvent. One objective was to produce only enough distillate to remain in solvent balance. This would ensure the maximum yield of the desired SRC product, while minimizing hydrogen consumption.
(We have earlier reported on the Ft. Lewis and Wilsonville Coal liquefaction pilot plants, and refer you to the WV Coal Association's R&D archives for more information concerning them. - JtM)
Because the SRC process was designed as a thermal distillate-recycle process (perhaps aided by the catalytic effect of the coal ash), the operating conditions had to be chosen to achieve satisfactory coal conversion, SRC yield, and desul- furization, while maintaining an adequate yield of recycle solvent. In practice, this proved to be a difficult balance to achieve. Higher reaction temperature tended to improve coal conversion and reduce SRC ;ulfur, but increased gas make at the expense of recycle solvent and SRC yield.
(Note mention of "the catalytic effect of coal ash". As we have documented, and as we will document further, zeolite minerals are at the heart of some coal conversion processes, most notably ExxonMobil's "MTG"(r), methanol-to-gasoline, Process, wherein the methanol is posited to be made from Coal; and, "synthetic" zeolites can be found in abundance in Coal power plant fly ash. - JtM)
Because it was run at relatively constant conditions for long periods of time, and because of its size, the 6 TPD Wilsonville pilot plant became an excellent source of coal liquefaction data and samples for assessing the longer term effects of coal liquefaction on recycle oil quality. In 1977 and 1978, we obtained three relatively large and representative samples of the recycle distillate from Wilsonville for use in bench-scale liquefaction research.
The research on the evolution of the SRC distillate solvent clearly indicated the importance of higher molecular weight hydroaromatics as hydrogen donor solvent components. However, the low distillate yield in the SRC process provided few options for improving the situation, leading to the conclusion that recycle of vacuum bottoms, or a vacuum-bottoms component, would be necessary to maintain solvent quality. This concept was tested by separating the SRC into "light" and "heavy" components ... . ... results clearly indicated that this non-distillate oil was capable of facilitating gas phase hydrogen utilization for coal conversion in the absence of an added catalyst.
SINGLE STAGE CATALYTIC LIQUEFACTION
The H-Coal process employs a single ebullated-bed reactor to convert coal to distillate products. In PDU and pilot plant development, a relatively high reaction temperature (825-840 F) and resid recycle were used to achieve high conversion while minimizing reactor residence size. Compared to the SRC process,H-Coal approached a steady state recycle composition quickly because of the higher turnover rate of the recycle oil components. ... Characterization of the recycle oil during the PDU ... indicated that the residual recycle components ... reached a consistent composition relatively early in the run ... .
INTEGRATED TWO-STAGE LIQUEFACTION
The idea of separating the coal dissolution and catalytic upgrading functions was further evaluated in the development of the Lummus Integrated Two-Stage Liquefaction Process. The Lummus ITSL process used a short-residence-time (SRT), high temperature (850 'F) coal conversion stage, followed by anti-solvent deashing. The deashed oil was converted to liquid products in an expanded-bed catalytic reactor (LC-Finer), which was operated at a lower temperature ... than the H-Coal reactor. The recycle oil from the second stage contained distillate and unconverted resid. ... Comparison of the process oil characteristics in the Lummus ITSL process to those from single-stage H-Coal process were particularly instructive.The results showed that hydrogen donor solvent quality was a key to coal conversion in the SRT first stage, and promoted thermal resid conversion in both stages. The lower temperature of the LC-Finer, compared to that of the H-Coal reactor, produced a more highly hydrogenated resid that underwent considerable thermal conversion in the short-residence-time, high temperature first stage. ... The Lummus work also demonstrated that interstage deashing was not necessary to maintain catalyst activity, because catalyst activity loss was primarily a function of carbon deposition, which occurred regardless of the presence of solids.
Extensive further development work was done on the two-stage rocess at the Wilsonville pilot plant, in a wide variety of configurations. The Wilsonville operators concluded that it was necessary to use a dispersed iron oxide catalyst to achieve satisfactory conversions with subbituminous coal.
Subsequent work has shown that the insoluble organic matter (IOM) in the recycle resid from Wilsonville is reactive for further conversion, and methods to improve solvent quality by dewaxing and hydrogenation are being evaluated. This work will provide the opportunity to better define the role of recycle solvent quality in the current generation of two stage catalytic liquefaction processes.
CONCLUSIONS
This paper was not intended as a comprehensive review of the subject of recycle oil chemistry, but rather as a perspective on the changing perception of the role of recycle or solvent-mediated phenomena in direct liquefaction process development. In the earlier US work on direct liquefaction, the goal of separating the thermal coal dissolution and catalytic distillate production steps led to process configurations that re1 ied on hydrogen donor solvents for coal conversion. Research showed that the distillate recycle solvents which evolved under mostly thermal conditions were poor hydrogen donors, but that selective recycle of higher molecular weight components improved both donor content and activity. When it was realized that interstage deashing had little practical benefit, conversion of the coal in a catalytic first stage diminished the perceived need for an active hydrogen donor solvent. For subbituminous coals, donor solvent hydrogen alone did not appear to be adequate to achieve satisfactory conversions, leading to the use of dispersed catalysts, greater reaction severity, and solids recycle. However, the improvements of two-stage liquefaction came at the expense of reduced space velocity and increased catalyst usage.
Current research is looking to replace the supported-catalyst systems with dispersed catalysts that offer higher selectivity and activity, while avoiding the capital cost of a supported-catalyst system. As this research and development continues, it will be important to understand and evaluate the role of vehicle solvents, and to look for opportunities to utilize solvent-mediated reactions as part of a overall strategy for reducing the cost of producing liquids from coal."