Institute of Paper Science
and Technology
500 10th Street, NW
Atlanta, Georgia 30318-5794
404 894-9592
FOR
IMMEDIATE RELEASE
For more information contact:
David Bell, Director of Institute Development and Assessment (404)
894-9592
Black Liquor Gasification Offers Increased
Yield, Power Generation, and Profit
ATLANTA, GEORGIA, April 30, 2003,
-- The pulp and paper industry consumes large amounts
of energy, leaving it extremely vulnerable during this
time of surging energy costs and fuel shortages.
At IPST, a group of scientists are working to hone a technology that
may one day slash—or even eliminate—the industry’s
reliance on fossil fuel. Black liquor gasification, or BLG, is an
efficient alternative to conventional technology for recovering process
chemicals and energy from spent pulping liquor. When implemented
fully, the technology is expected to save the industry millions of
dollars in energy costs.
“The timing could not be better,” explains Dr. Scott Sinquefield,
a senior associate engineer leading the gasification research program at IPST.
He points to the industry’s urgent need to increase its use of renewable
energy, a goal that is very much in sync with the goals of the U.S. Department
of Energy. In its Agenda 2020 vision, the agency articulated the industry’s
need for increased energy and resource efficiency and formed a partnership with
the wood, paper, and forest industries. The Department of Energy is providing
government funds to leverage industry funds in support of the development and
commercialization of the new gasification technologies.
Although BLG has been in existence for almost 20 years, the technology
is still evolving. Dr. Chris Verrill, an IPST senior associate engineer
working on the BLG research team, refers to the many aspects of the
technology that are still not widely understood.
“There remain some gaps in our understanding,” he explains. “For
example, there is almost no published data to describe the fate of carbon, sodium,
and sulfur (the three principal components of kraft black liquor) as a function
of operating pressure.”
One major area of research at IPST is an approach known as black
liquor gasification combined-cycle (BLGCC). Here, the black liquor
is partially oxidized to produce a gaseous fuel for firing in a gas
turbine, resulting in the production of electricity from a coupled
generator and steam from a waste-heat boiler installed in the gas
turbine exhaust duct. This steam is subsequently used in a steam
turbine. Together the gas and steam turbines produce electric power
in greater quantities than the conventional process of burning black
liquor in a chemical recovery boiler. The result is not just increased
energy production for the mill but also the possibility that these
facilities may one day be exporters of energy. Scientists are excited
about such a possibility, seeing an opportunity for paper companies,
even the smaller ones, to become more self-reliant.
At the center of IPST’s research efforts is a pressurized entrained-flow
reactor (PEFR) acquired from the Danish government in 1998 and modified
for black liquor research. Capable of reaching 2730°F at 1200
psi (1500°C, 80 bar) this 38-foot-tall reactor is the flagship
of the pressurized gasification research efforts.
“IPST already had this facility up and running in 1999,” says Verrill, “way
ahead of the rest of the research community.”
Verrill, whose work centers on the fundamental chemistry of BLG,
explains that the PEFR is a fully functioning test facility that
is being used to study BLG under a wide range of conditions. The
PEFR is an ideal tool for helping scientists to answer questions
about such topics of interest as the effects of temperature, pressure,
and gas composition on the rates of carbon conversion, distribution
of sulfur products, and vaporization of other chemicals in black
liquor.
Although questions remain about the feasibility of BLG on a commercial
scale, scientists believe the momentum and the interest in the industry
are such that implementation may occur within the next several years. “One
reason is that the infrastructure required for the wide-scale implementation
of BLG largely exists,” says Sinquefield.
“There are more than180 recovery boilers operating at mills throughout
the U.S.,” he says, explaining that several of them will require major
refits or replacement within the next 10 years. “If we in the research
community can overcome the remaining hurdles, these inefficient machines could
be replaced with gasifiers, dramatically improving the energy efficiency of the
mill.”
But increased generation capacity is only one of the benefits that
come from black liquor gasification. Scientists also believe that
BLGCC will result in higher pulp yields for the mills. In other words,
more material for papermaking can be extracted from the same amount
of wood. Because the gasification process naturally results in the
separation of sodium and sulfur, this facilitates the introduction
of certain variants into the pulping process that have shown promise
for increased pulp yield in the laboratory.
“This allows for a great deal of flexibility,” says Verrill of the
gasification process. “It makes lots of things possible in the pulp mill.”
“Alternate chemistries for pulping wood are typically prohibitively expensive,
but gasification makes them more attractive,” explains Sinquefield. It
is hoped that the promise of increased yield, once fine-tuned, will heighten
the interest in BLG as mills consider which route to take as they replace equipment
in the future.
“Another exciting development that will one day become possible with BLG
is in-situ causticization,” explains Dr. Ingrid Nohlgren, an assistant
professor at IPST. This process is accomplished by adding a chemical agent such
as sodium titanate to the black liquor, thus allowing causticization to occur
in the gasifier. This would eliminate the conventional lime cycle, translating
to energy and capital savings.
“It also makes the causticization much more efficient,” Nohlgren
explains, adding that some equipment may ultimately be eliminated with the in-situ
causticization process.
Implementation of in-situ causticization is the next evolution of
BLG and would probably come after gasification technologies are commercialized.
Scientists and many in the industry hope that they will soon be reaping
the benefits that BLG can offer. “The need for new technology
is tremendous,” notes Verrill. “My long-held belief is
that the pulp and paper industry needs this to remain globally competitive.”
