Ikelic - Alliance Digital Repository

COAL
Some similar solvents are already available
(Purisol, Rectisol. Sepasolv, etc.). However, use
of a physical solvent does require that the syngas
be shifted. For IGCC powerplants in the medium
term, membrane separation technology may be
able to replace Selexol separation technology (in
conventional packed absorber columns). The
biggest energy savings would be realized
through reduced compression requirements.
While membrane technology looks promising,
and in particular gas absorption membranes, it is
Impossible to say
whether their potential can be
fully achieved. Also in the longer term, high per
formance fuel cells may replace gas turbines.
IEA says research is needed on how best to take
advantage of this development.
####
MANUFACTURED GAS PLANT SITE
REMEDIATION DRAWS VARIETY OF
SOLUTIONS
Prior to the widespread use of natural gas, com
bustible gas manufactured from coke, coal, and
oil served as the major gaseous fuel for urban
heating, cooking, and lighting in the United
States for nearly 100 years. This manufactured
gas, or town gas, was produced at some 1 ,000 to
2,000 plants. Pipeline distribution of natural gas
following World War II replaced manufactured
gas as the major gaseous fuel, and as a result
manufactured gas production came to an end in
the 1950s.
Today, soil and groundwater contamination
problems exist at many
Gas Plant (MGP)
former Manufactured
sites because of prior process
operations and management practices.
Residuals that were produced in MGP processes
are summarized in Table 1 for the three primary
gas production methods:
- Coal
- Oil
carbonization
Carbureted water gas production
gas production
442
These process residuals are dominated by six
primary
Aromatic Hydrocarbons (PAHs),
classes of chemicals: Polycyclic
volatile aromatic
compounds, phenolics, inorganic compounds of
sulfur and nitrogen, and metals. Tar residuals
were produced from the volatile component of
bituminous coals in coal carbonization, from the
residue of gasifying oils in oil gas processes, and
from the cracking of enriching
oils used to in
crease gas BTU content in carbureted water gas
production.
MGP tars are organic liquids that typically are
denser than water,
with a range of physical and
chemical properties dependent on the feedstock
and operating
conditions of the production
process. Although some MGP tar was used on
site or sold, during certain periods there was in
sufficient demand for all the tar that was
produced. Further, because of changes in tar
composition owing to changes in feedstock,
problems with tar-water emulsions, and other fac
tors, the intrinsic value of MGP tars was often
considered marginal. Consequently, MGP tars
were sometimes managed off-site or were
deposited on-site in tar wells, sewers, nearby
pits, or streams. Nuisances associated with the
disposal of tarry gas-plant wastes to streams and
sewers were recognized early in this century.
Total remediation costs for individual MGP sites
are in the range of tens of millions of dollars, and
the Gas Research Institute has estimated that
nearly 70 percent of such costs may be at
tributed to the management of tar-contaminated
soils and sediments.
Techniques for remediation are discussed in a
number of recent sources, including
R. Luthy et al., Environmental Science & Technol-
Qgy, Volume 28, Number 4, 1994; A. Hatfield,
American Gas Association Operations
Conference 1994; EPRI Journal. December 1994;
IGT Technology Spotlight. 1994.
Recovering Tar
Today, the tar from manufactured gas plants is
being recovered. Even ff the tar is buried in the
THE SYNTHETIC FUELS REPORT, JANUARY 1995