Chemical Engineering July 2012 - 10

CHEMENTATOR
A treatment process for coal-bed-methane-extraction water
I
n the development process
for coal-bed methane,
water is produced
from wells. It is highsalinity
water, with total
dissolved solids (TDS)
generally at least 1,000
mg/L. The main concern
with coal-bed methane
co-produced water is the
amount of Na+ and its
influence on the environment.
Therefore, the
water must be treated
before discharge and
cost-effective technologies
are needed to allow
the use of the water for
irrigation, livestock watering
and industrial
uses. The technologies
available include evaporation,
ion exchange,
electrodialysis and reverse
osmosis (RO).
The first pilot-scale
demonstration in China for treating
and recycling coal-bed methane extraction
water has been conducted by a team
from the Graduate University of the
Chinese Academy of Sciences (Beijing;
www.gucas.ac.cn), led by professor Zhang
Hongxun. The team focused on coal-bedmethane
co-produced water in Liulin
County of Luliang City, Shanxi Province,
and developed a system with sand filtration,
ultrafiltration (UF) and RO to treat
that water.
In the process (flowsheet), the raw
Raw
water
inlet
M
FI
D
Security
filter
D
Water
tank
PI
CI
CF
PS PI
Cleaning filter
Cleaning tank
Butterfly
valve
Check
valve
Stop
valve
M
D
Ball valve
Electrical
ball valve
Electromagnetic
valve
PS
TI
PI
Pressure
switch
Manometer
Temperature
indicator
H
L
amount of dissolved oxygen. The water
is then passed through a manganese
sand filter, sand filter and bag filter to
remove Fe, Mn and suspended solids.
The water passes the UF system, and
then goes through a security filter in the
RO system. Finally, the output water
from RO enters storage tanks.
The chemical components of coal-bedmethane
co-produced water are mainly
HCO3
-, CO3
water is first aerated to increase the
-2, Cl-, Ca+2, Mg+2, and Na+.
There are also small amounts of K+, F-,
Hg, Cd, and Cr+6. At Liulin, a single well
produced up to 10 m3/d of water in the
Making artificial water channels
A group of scientists from Fudan University
(Shanghai, China; www.fudan.ac.cn) China,
has reported what it claims to be the first
example of artificial single-molecular water
channels that can transport water across
lipid membranes.
Transmembrane water transport -
through water channel proteins called aquaporins
- is of crucial importance in living
organisms because it regulates the osmotic
pressure of cells. The development of synthetic
systems with high water-transport
capability could lead to new devices for
medical use or environmental applications,
such as water purification and desalination.
The creation of synthetic water transport
systems has been difficult to achieve
because of a lack of synthetic architectures
that could form long and narrow channels
for water.
The Fudan University group says it was
inspired to design artificial water channels
by mimicking the single pore feature
of natural channel proteins. It constructed
the water channels from single pillar[5]
arene molecules with hydrazide-containing
side channels.
A member of the group, professor Hou
Jun-Li says the group attached 10 hydraz(Continues
on p. 12)
10 CHEMICAL ENGINEERING WWW.CHE.COM JULY 2012
LS
CI
LS
Conductivity
meter
Level
indicator
Temperature
switch
FI
M
Rotameter
Electrical
butterfly valve
Ditch
early stage and reached 20 m3/d for normal
extraction. The chemical oxygen demand
(COD) of the water was low, in the
range of 0.5 to 3.6 mg/L, indicating a low
level of organic pollution.
In the pretreatment process, the COD
removal rate was 45.7%, TDS removal
was 4.94%, Cl- removal was 42.4% and
NH3-N removal was 46.2%. In the RO
stage the total removal rates for COD,
NH3-N, Cl- and TDS were 81.0, 85.4,
97.7 and 99.7%, respectively. The water
quality met the " Drinking Water Standards "
(GB 5749-2006).
(Continued from p. 9)
ogy, and will have exclusive
worldwide rights to engineer,
procure and construct NET
Power plants. Shaw will invest
up to $50.4 million as milestones
are completed for the
four phases of the project.
Phases 1 and 2 (front end
engineering and combustor
rig testing) are expected to be
completed in 2012. Phase 3 -
construction of a 25-MW plant
- is expected to be completed
in mid-2014. Development of
the fi rst full-scale commercial
natural-gas plant is expected
to begin by early 2015.
Freshwater
tank
PI
FI
PI
Manganese sand filter
PI
Sack filter
Booster pump Aeration
jet
D PI
Ultrafilter
PI
Reducing agent feeding
FI
D
D
D
PI
M
D
D
Inhibitor feeding
PS
Reverse osmosis
CI
CF
Reducing agent feeding
Raw
water
tank
Flocculant feeding
Sand filter
PI
Concentrated
water tank
FI
http://www.gucas.ac.cn http://www.fudan.ac.cn http://WWW.CHE.COM
Chemical Engineering July 2012

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