Liquefaction co-processing of coal shale oil at - Argonne National ...
Liquefaction co-processing of coal shale oil at - Argonne National ...
Liquefaction co-processing of coal shale oil at - Argonne National ...
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ENHANCED COAL LIQUEFACTION WITH STEAM PRETREATMENT<br />
P.R. Bienkowski, R. Narayan, R.A. Greenkorn and K.C. Chm'<br />
School <strong>of</strong> Chemical Engineering<br />
Purdue University<br />
West Lafayette, Indiana 47907<br />
SUMMARY<br />
A two step process for the liquefaction <strong>of</strong> <strong>co</strong>al, in a semi-Eow micro reactor, was investig<strong>at</strong>ed. The<br />
process <strong>co</strong>nsisted <strong>of</strong> pretre<strong>at</strong>ing <strong>co</strong>al with low temper<strong>at</strong>ure steam, followed by tre<strong>at</strong>ment with supercriti-<br />
cal steam. The maximum observed <strong>co</strong>nversion <strong>of</strong> a Wyodak subbituminous <strong>co</strong>al, using this two step pro-<br />
cess, was 40 wt% on a moisture and ash free basis (MAF). The 240 ' c pretre<strong>at</strong>ment step resulted io a<br />
32% increase over the <strong>co</strong>nversion observed with just a 400 c tre<strong>at</strong>ment. The <strong>co</strong>al liquid obtained has<br />
a number average molecular weight <strong>of</strong> 325 and a mass average molecular weight <strong>of</strong> 373, with a narrow<br />
molecular weight distribution. The hydrogen and oxygen <strong>co</strong>ntent <strong>of</strong> the extract is increased, a significant<br />
amount <strong>of</strong> the oxygen is present as dihydroxyl arom<strong>at</strong>ics. A highly <strong>co</strong>ndensed residue <strong>of</strong> lower hydrogen<br />
and oxygen <strong>co</strong>ntent is obtained which can be <strong>of</strong> value as a solid fuel.<br />
INTRODUCTION<br />
Recent investig<strong>at</strong>ions have led to the observ<strong>at</strong>ion (1) th<strong>at</strong> in its n<strong>at</strong>ive unwe<strong>at</strong>hered st<strong>at</strong>e <strong>co</strong>al is a<br />
reactive m<strong>at</strong>erial, far from being the inert solid th<strong>at</strong> it is <strong>co</strong>mmonly regarded. Extensive hydrogen bonds<br />
<strong>co</strong>nnect the poly nuclear arom<strong>at</strong>ic cluster to form a semi-permanent macro molecular structure. The<br />
structure is particularly fragile in subbituminous <strong>co</strong>als, and may le subject to rupture with mild tre<strong>at</strong><br />
ment to dissoci<strong>at</strong>e the hydrogen bonds. GraU and Brandes (2) found th<strong>at</strong> carbon <strong>co</strong>nversion to liquids in<br />
pyroiysls <strong>at</strong> 940 c was raised from 23% to over 50% if the <strong>co</strong>al was exposed to steam for times less<br />
than 30 minutes <strong>at</strong> temper<strong>at</strong>ures between about 320 and 360 O c. Both pretre<strong>at</strong>ment and pyrolysis were<br />
<strong>co</strong>nducted in 50 <strong>at</strong>m <strong>of</strong> steam. This result suggests th<strong>at</strong> <strong>co</strong>al is partially depolymerized by the steam<br />
pretre<strong>at</strong>ment, perhaps by the removal <strong>of</strong> oxygen linkages. If this is indeed the case, improved yields<br />
and/or lighter liquids should result if the pretre<strong>at</strong>ed <strong>co</strong>al is liquefied instead <strong>of</strong> pyrolyzed.<br />
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