http://www.anl.gov/PCS/acsfuel/preprint%20archive/Files/42_1_SAN%20FRANCISCO_04-97_0125.pdf
This submission is a companion to our report of yesterday, and actually predates the paper recorded in that earlier submission, "Kinetics of Coal Liquefaction Distillation Resid Conversion", delivered, by the same authors, at a conference in Australia.
There is some redundancy; but, some differences and additional information, which might suggest some error in our interpretation of the original report, as well, to be found in:
"Kinetics of Hydroprocessing of Coal Derived Vacuum Resids
Shaojie Wang, He Huang, Keyu Wang, M.T.Klein and W.H. Calkins
Department of Chemical Engineering; University of Delaware
Introduction
The direct liquefaction of coal produces a substantial amount of high boiling, non-distillable residuum, whose amount depends upon a number of factors such as the coal type, the hydrogen donor strength of the solvent, activity of the catalyst, and the conditions under which the direct liquefaction was run. Because of its high boiling point and potential thermal instability, this material is not suitable for processing in a conventional petroleum refinery. In a commercial liquefaction process as visualized today, therefore, this material would be recycled to the process to recover its energy value and to provide some of the solvent needed for the coal liquefaction process itself. Furthermore, this recycle oil has been shown to have a beneficial effect; it increased oil yield in the liquefaction process. Thus, it became important to determine the rates of conversion of these residual materials to products boiling in the fuel range ... and to know whether these high boilers will build up or be rapidly broken down in the recycling process. It was to follow the rates of resid breakdown (resid reactivity) under conditions approximating the conditions in the liquefaction process that this program was undertaken. Knowing the rates of resid condensation as well as breakdown are also important as retrograde processes reduce product yields and foul catalysts and equipment. This required the use of a reactor system capable of measuring hydroprocessing rates at very short contact times and the development of analytical methods for measuring the conversion and boiling ranges of the products. Resid conversion rates (both condensation and breakdown) would be correlated with composition data obtained by other analytical methods ... .
Materials Studied. Thirteen resid samples (boiling above 850 F) from coal liquefaction runs made at the Wilsonville pilot plant and two resid samples from Hydrocarbon Research Institute bench scale unit were prepared and supplied by CONSOL Inc. The feed coals for the resids produced at the Wilsonville pilot plant were Wyodak-Anderson, Illinois 6 and Pittsburgh coals.
All reactions were run as mixtures of tetralin ... and resid ... over a range of ... temperatures ... .
Molybdenum naphthenate was used as the catalyst and was sulfided in-situ using methyldisulfide.
Results and Discussion: As discussed in a previous section of this paper, conversion has been determined in part by an ash balance. Efforts to carry out hydroprocessing of resids using the Ni/Mo on alumina catalyst used in Wilsonville, however, resulted in unreliable conversions data because of the large amount of ash in the catalyst.
Summary and Conclusions: With the appropriate catalyst and conditions approximating coal liquefaction, high boiling coal-derived resids do break down to lower boiling products as they are recycled to the coal liquefaction process.
The support of various portions of this work by the Department of Energy and CONSOL Inc. under subcontract DE-AC22-94PC93054 is acknowledged.
-----------
There appear, to us, to be some discrepancies, or perhaps carelessness, in the use of some terminology.
For instance, they speak of using residues from direct Coal liquefaction processes; but, the Coal conversion process used at the Wilsonville, Alabama, CoalTL pilot plant, they specified as an example, which we have documented for the West Virginia Coal Association, was, we believe, a variety of indirect Coal conversion technology.
Nonetheless, a very interesting fact is revealed in Delaware's use of the Hydrogen donor solvent, Tetralin, to effect secondary recovery of additional hydrocarbon values from the residue of primary Coal conversion processes. Tetralin is the Hydrogen donor solvent now specified by West Virginia University in their "West Virginia Process" for direct, primary Coal liquefaction.
However, this Delaware research mirrors similar activities and findings from the earlier operation of the FMC company's "COED" Coal liquefaction facility in New Jersey, wherein solid carbonaceous residues from that indirect Coal conversion process were shipped to Spain for the extraction of additional hydrocarbons, via a direct liquefaction process utilizing Tetralin; all as we have documented in the West Virginia Coal Association's R&D archives.
It has, in fact, been elsewhere suggested that the best economies in the conversion of Coal into hydrocarbon liquids might be achieved by a first, indirect, processing of raw coal, as in a typical Fischer-Tropsch, or similar, process; followed by secondary direct liquefaction of the still-carbonaceous residues via use of a Hydrogen donor solvent, such as Tetralin.
In any case, herein is yet more evidence that our understanding of Coal liquefaction technology, and the levels to which we've refined that technology, are far more advanced than general, public knowledge of the subject would make it seem.
That is one situation, among many, relative to the realities of Coal liquefaction's potential to help us resolve our liquid transportation fuel shortage, which needs to be changed.