A team of Rice University students accepted a challenge to turn
shale gas produced in China
into a range of useful, profitable, and environmentally friendly products and
did so in a cost-effective manner.
The CHBE Pandas (CHBE stands for chemical and biomolecular
engineering) designed a process by which shale gas extracted in the rich Sichuan Basin could be turned into methanol,
hydrogen, and carbon disulfide, all valuable products in the booming Chinese
economy. The Rice team was one of seven groups of students presented similar
challenges for locations outside of the United States as their capstone
design projects, required of most graduates of Rice’s George R. Brown School of
Engineering.
For their efforts, the Pandas—Apoorv Bhargava, Prachi
Bhawalkar, Valicia Miller, Shelby Reinhardt, Kavita Venkateswar, and Erte Xi—were
grand prize winners at the Engineering Design Showcase, part of Rice’s
UnConvention earlier this month.
“We literally got the last one in the hat,” Bhargava said of
the assignment handed out for their final semester at Rice. “All of the
chemical engineering projects were the same, just in different locations, and
how we approached the solution depended on the location.”
The team had to deal not only with processing what’s known
as “sour gas” straight out of the wellhead, but also had to come up with a
solid budget for the construction and profitable operation of the plant as well
as a strategy to protect the environment.
“We think it’s a viable project because of what we’re
transforming the natural gas into,” Venkateswar said. The process they designed
would take in the raw shale gas produced in the controversial extraction
process known as hydraulic fracturing, or fracking. The primary product would
be methanol, of which China
is the largest user in the world. China blends methanol into gasoline
and is developing cars that would run on pure methanol.
The second product, hydrogen, would be a feedstock for
ammonia in fertilizer production, which has great value in the Sichuan Basin,
the largest agricultural area in China. The third would be carbon
disulfide, widely used in the Sichuan
textile industry. The team said 99% of the recovered fracturing fluid
would be purified into water and fed into methanol production. A small amount
of crystallized sludge from fracturing chemicals would be sent to a landfill.
Team advisers Kenneth Cox and Richard
Strait were inspired to issue the
assignment by a Department of Energy-funded 2011 study on shale gas and U.S. national
security by Rice’s Baker Institute for Public Policy. The report details the
rapid development over the last decade of technology to extract natural gas
from shale, an increasingly rich resource in the United States, and the resulting
shift in the world’s energy economy.
“The world of shale gas presents a real interesting
situation,” said Strait, an adjunct professor of chemical and biomolecular
engineering at Rice and former director of coal monetization and carbon dioxide
management at KBR. “We’re in boom times—if you want to produce gas at what are
now historically low prices. You make no profit.” He said energy producers are
considering ways to turn raw shale gas into products that will better serve the
market’s needs.
“We tried to give the students problems for which there’s no
current solution,” said Cox, a Rice professor in the practice of chemical and
biomolecular engineering. “Major companies are looking at ways to upgrade shale
gas, but no one’s built a plant to do that yet.”
Also, Cox said, “There are a lot of issues associated with
the public perception of fracking, and part of the assignment was to help
change that perception by offering something that was environmentally friendly,
gave benefit to the community, helped clean up the water and was still able to
pull a profit at the end of the day.”
He said the Pandas’ solution was “very imaginative” for
their handling of the high concentration of highly toxic hydrogen sulfide found
in Sichuan
shale gas. “It’s 8.38% of the incoming feed,” said Venkateswar. “Usually
natural gas feeds have it on the order of several hundred parts per million.”
“The ability to make carbon disulfide provides us a solution
to the high hydrogen sulfide content,” Xi said.
Building the Pandas’ plant with the team’s innovative
assembly of known technologies would cost the Chinese government $5 billion,
Bhargava said. “Chemical engineering design in the real world, the way we
understand it, works in three phases,” he said. “You start off with a
preliminary design analysis, as we did. Then we move into another stage where
the chemical engineers meet up with the mechanical engineers and start
designing it in more detail: ‘What pipes do we need to go from here to there?’
“And then we meet with the architects for the final design
stage: ‘OK, what is this going to look like when we build it? Is it going to
look terrible in someone’s backyard?'”
Bhargava said the Pandas designed a process that would
generally take as many as 15 engineers six or seven months to accomplish. The
team spent long hours using simulation software at Rice’s Oshman Engineering
Design Kitchen, where the students aligned components and tested for the
desired chemical reactions. “But a computer can tell you only so much,”
Bhargava said. “A chemical engineer has to make the decisions. Our design is
very, very close to what a real chemical engineer does in his or her job. We
were working in a very realistic setting.”