Hydrothermal preparation of low-rank coal/water fuel slurries

Technical Report · Fri Mar 01 04:00:00 EST 1985

OSTI ID:5830326

Baker, G G; Sears, R E; Maas, D J; Potas, T A; Willson, W G; Farnum, S A

Lignite and subbituminous coals are by nature high in inherent moisture and oxygen content and low in calorific heating value. As-mined low-rank coals when mixed with water generally produce slurries with low solids content and with heating values generally less than 5000 Btu/lb. These same slurries are usually unstable and form hard-pack sediments quickly, unless chemical additives or constant agitation are added. The low heating value and poor storage and flow characteristics of these coal/water mixtures discourage the use of raw lignite and subbituminous coals for preparation of slurries for fuel purposes. Hydrothermal conditioning, in a water slurry at temperatures above 240/sup 0/C and pressures above 800 psig, is one method that can significantly aid in the preparation of low-rank coal-water fuel slurries. High pressure hot-water thermal conditioning of lignites and subbituminous coals has been found not only to change both the chemical and physical characteristics of the coal but also to alter the coal's slurry rheological properties. These changes are controlled by process variables (i.e., temperature, residence time, particle size and mode of processing) and result because of decarboxylation, mild pyrolysis, extraction, dehydration, and surface modification; all of which occur during hydrothermal treatment. Using the hydrothermal process, concentrated low-rank coal/water slurries with heating values approaching or exceeding the heating value of the as-mined coal have been achieved with pseudoplastic flow behavior and stability towards settling, without the use of additives. Pilot scale studies using a 200 lb/hr Process Development Unit (PDU) are currently underway to produce hydrothermally-treated low-rank coal fuel slurries for combustion tests in a pilot-scale, slurry-fed test furnace. 22 references, 7 tables, 10 figures.

• Research Organization: North Dakota Univ., Grand Forks (USA). Energy Research Center
• DOE Contract Number: FC21-83FE60181
• OSTI ID: 5830326
• Report Number(s): DOE/FE/60181-133; CONF-850444-1; ON: DE85009785
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
013000 -- Coal
Lignite
& Peat-- Transport
Handling
& Storage
014000* -- Coal
Lignite
& Peat-- Combustion
AUTOCLAVES
BROWN COAL
CALORIFIC VALUE
CARBONACEOUS MATERIALS
CHEMICAL PREPARATION
CHEMICAL REACTIONS
COAL
COMBUSTION PROPERTIES
DATA
DECARBOXYLATION
DECOMPOSITION
DISPERSIONS
DRYING
ENERGY SOURCES
EXPERIMENTAL DATA
EXTRACTION
FOSSIL FUELS
FUEL SLURRIES
FUELS
FUNCTIONAL MODELS
HYDROGEN COMPOUNDS
INFORMATION
LIGNITE
MATERIALS
MIXTURES
NUMERICAL DATA
OXYGEN COMPOUNDS
PARTICLES
PRESSURE EFFECTS
PROCESS DEVELOPMENT UNITS
PYROLYSIS
REMOVAL
SEPARATION PROCESSES
SLURRIES
SOLVENT EXTRACTION
SUBBITUMINOUS COAL
SUSPENSIONS
SYNTHESIS
TEMPERATURE EFFECTS
THERMOCHEMICAL PROCESSES
TIME DEPENDENCE
WATER
WATER REMOVAL