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 percent
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 CO2 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 percent 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.”
Oshman Engineering Design Kitchen
Source: Rice University
