Chemical Engineering July 2013 - 13

A gas turbine with low NOx emissions
N
EDO (see story on p. 14) and Hitachi Ltd. (Tokyo, www.
hitachi.com) have developed a new combustion technology
that could reduce the emissions of oxides of nitrogen
(NOx) to below 10 ppm without the addition of diluents.
As part of the CCS-IGCC project (carbon capture and storage
- integrated coal gasification, combined cycle), the
researchers have developed a " multi-hole, coaxial jet-flow
burner " for use in a gas turbine combustor. The burner
enables stable combustion of the H2-rich fuel and NOx
emissions are suppressed below the 70 ppm required by
environmental regulations without having to add diluents,
which normally reduce the power-generation efficiency.
Tests have been performed at the facility's " Eagle " pilot
plant using actual gas from a coal gasifier. The pilot unit
has six cans of multi-hole jet flow burners. The researchers
also confirmed stable operation of the system, all the way
from turbine startup to maximum power generation, and
during the fuel change from liquid fuel (at startup) to coalgasified
gas. This is claimed to be first real application of a
CCS-IGCC plant that enables both reduction of NOx emissions
and also high-efficiency power generation.
Nanowires improve the properties
of metal composites
F
reestanding nanowires exhibit ultrahigh elastic-strain
limits (of up to 7%) and yield strengths. However, it has
been difficult to exploit their properties in bulk composites,
due to the mismatch between the elasticity of the
nanowires and the elasticity of the metals that form the
matrix. The nanowires will experience an elastic deformation
of several percent, but normally the metals that form
the matrix can stretch elastically to no more than 1%. Beyond
that, the matrix deforms plastically.
Now, a team from Australia, China, Japan and the U.S.
has produced a metal nanocomposite - a combination of
Nb nanowires with a NiTi shape-memory alloy - that allows
the mechanical properties of nanowires to be exploited
in bulk materials. " The trick is with the NiTi matrix - a
shape-memory alloy with a special property in its martensitic
transformation, " says a team member, professor Yinong
Liu, head of Mechanical and Chemical Engineering
at the University of Western Australia (www.uwa.edu.au).
" The transformation can produce a deformation compatible
with the elastic deformation of the nanowires without plastic
damage to the composite structure. This allows the nanowires
to bear the high load and be super strong, " he says.
The team developed a composite with a quasi-linear
elastic strain of over 6%, a low Young's modulus of about
28 GPa and a high yield strength of about 1.65 GPa. The
team says this breakthrough opens the door for many
new applications. The low Young's modulus matches that
of human bone, making the composites suitable for medical
implants. The composites could also lead to improvements
in properties of solid materials, such as electronic,
optoelectronic, piezoelectric, piezomagnetic, photocatalytic
and chemical-sensing properties
Rule the Liquids
Extreme forces must be
safely under control.
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ws.info@gea.com, www.gea.com
engineering for a better world
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CP-214-1-012
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Chemical Engineering July 2013

Table of Contents for the Digital Edition of Chemical Engineering July 2013
