Chemical Engineering July 2010 - 13

Novel gasifier uses liquid copper as the heat source
L
iquid copper is employed to gasify
wastes in a process being developed by
Ze-gen (Boston, Mass.; www.ze-gen.com)
and will be tested in a small commercial
plant in an industrial park in Attleboro,
Mass. Scheduled for completion late next
year, the plant will convert 150 ton/d of
ground wood waste into synthesis gas
(syngas). The gas will generate 7 MWth
of energy for use by the park, either as
electricity or steam.
Ze-gen's gasifier is a refractory-lined
vessel that contains a bath of liquid copper.
Waste material is fed into the top
of the vessel and falls onto the copper,
where it is instantaneously gasified at
2,000-2,500°F. Air or oxygen is also injected
into the gasifier. The resultant
syngas is 1:1 H2:CO, plus some carbon
dioxide, says David Robertson, vicepresident
of technology. Impurities in
the gas are removed by conventional
fluegas treatment, while solid residue
from the waste accumulates as slag,
which is removed periodically. The process
is exothermic, so external heating
(by natural gas or electricity) is needed
only for startup.
Liquid copper is used for the bath because
it maintains a steady temperature
and a constant concentration of O2, says
Robertson. Another advantage of the
process is its flexibility - the feed may
be biomass, construction demolition debris,
and railroad ties or telephone poles,
which now have to be landfilled because
of their creosote content. Ze-Gen has
tested the process in a 5-ton/d pilot plant,
and 90% of the feed was railroad ties.
The Attleboro facility will use air or
enriched air, but future plants may use
O2 to obtain a higher-grade syngas for
liquid fuels. Robertson says the economics
of the process will be demonstrated at
the Attleboro plant, which is expected at
least to break even financially, and that
future, larger plants will be profitable.
Lignite drying-and-refining system formally dedicated
ast month, Great River Energy
(Maple Grove, Minn.; www.greatriverenergy.com)
dedicated its patented
DryFining coal enhancement system at
its power-generating plant, Coal Creek
Station, N.D. The system, developed by
Great River Energy, uses waste heat to
L
reduce the moisture level of low-rank
coal, such as lignite, from 38.5% to 29%,
which boosts heating value of the coal
from 6,250 Btu/lb to 7,100 Btu/lb. As a
result, the overall efficiency of the plant
increases by 2-4%, says the company.
(Continues on p. 16)
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Chemical Engineering July 2010

Table of Contents for the Digital Edition of Chemical Engineering July 2010
