Water Tunnel Facilities
Researchers are using NETL's low-pressure and high-pressure Water Tunnel Facilities
to study technical feasibility and environmental effects of CO2 storage in
freshwater and saltwater environments. Understanding the physical, chemical,
and thermodynamic characteristics of CO2 in such environments is necessary
in order to develop successful storage or sequestration strategies – a major
step toward the national goal of reducing the volume of greenhouse gases released
into the atmosphere.
Researchers have been collecting data on the effects of temperature, pressure,
salinity, and dissolved CO2 concentration in cold, liquid environments. NETL's
onsite Water Tunnel Facilities also are being used to test new concepts and
perform fundamental research. For example, a recent study examined the size,
stability, and settling velocities of CO2 drops coated with calcium carbonate
(limestone) powder. The coated CO2 drops replicate mineral carbonation, which
holds promise for long-term, unmonitored CO2 storage since mineral carbonates
are benign, stable, and long-lived in water environments.
The Water Tunnel Facilities also are frequently used in conjunction with NETL's
Hydrate Laboratory to investigate how CO2 /hydrate compounds – carbon dioxide
trapped in ice – form and dissolve. Research has shown that such compounds
form naturally in deep saltwater environments, as discrete particles or as “shells” on
CO2 drops. Understanding the process that forms a stable, dense, ice-like
CO2 /hydrate is critical to successful introduction of CO2 into deep-water
environments. To achieve long-term sequestration in CO2 /hydrate compounds,
the CO2 must be injected in high enough concentrations and in a manner that
prevents the compound from dissolving. NETL has performed these studies in
collaboration with researchers from the University of Pittsburgh , Oak Ridge
National Laboratory, and the University of Massachusetts, Lowell .
The High-Pressure Water Tunnel Facility (HWTF) permits an accurate simulation
of what occurs when CO2 is injected into an open-water environment. A fluid
particle, such as a CO2 droplet, is suspended in the HWTF. It can then be
observed in a section of the water column, where it is held stationary by a
countercurrent flow of water or seawater. Screens or other restraining devices
are not used to hold the droplet, since such devices could change the structure
of the droplet, and also introduce unnatural heat transfer characteristics
relative to the water environment. The HWTF has specialized internal mechanisms
that permit the operator to modify and control the water flow for extended
periods, providing a unique opportunity to assess what would happen to the
stability of the a fluid particle under various flow conditions. System flow
can be reversed to stabilize both positively buoyant (floating) and negatively
buoyant (sinking) particles.
In addition to the HWTF, other laboratory equipment includes:
- A low-pressure water tunnel and static water tank
- Two environmental chambers with a temperature range of 40–200 °C
- Two variable-volume view cells with pressure ratings up to 135 MPa
- A stirred autoclave with capacities of 50 mL and 100 mL
- Precision syringe pumps
- National Instruments hardware and software
- Analog and digital cameras
- Video recording and analysis equipment
- Professional DVD creation and editing equipment
Ron Lynn, Chief Engineer for the HWTF, performs real-time measurement of objects stabilized in the HWTF.
The HWTF is seen behind a 2.5-cm thick Lexan window.
NETL’s HWTF, with inset image showing a hydrate-covered CO2 drop
stabilized for observation by a countercurrent flow of seawater.
Eilis Rosenbaum and Yi Zhang perform experiments in the Hydrate Laboratory.
The blue and white structures are the environmental chambers in which various reactors
are contained for both CO2 sequestration and methane hydrate research.
For more information contact: Robert