July and August 2011 have been very exciting months here at CE! For the past year, one of our principal efforts as a team has been the design, engineering, and fabrication of our “Outdoor Contactor” (OC) prototype. The OC has been designed to test critical aspects of our full-scale air contactor design, and to gain us the operational experience in running our device outdoors in the harsh spectrum of weather we will see over several seasons here in Alberta. On July 27, the OC was delivered to our test site, and at 20+ tons, the delivery required a flat-bed truck, flag cars, and two large cranes. With the OC in place, we are now working on start-up procedures and water-testing, and we are aiming to capture “first CO2” from the air by end of month. The primary component of interest on our OC is the air contactor, which forces air through a “structured packing” material full of numerous air-flow channels that distribute our CO2-absorbing liquid (sodium hydroxide plus additives) into a large surface area of liquid film. This absorbent sodium hydroxide film reacts with atmospheric CO2 passing through the channels to form sodium carbonate, which is flushed off the packing and collects in the OC basin. The OC also has the ability to chemically react this sodium carbonate and filter out our captured CO2 which by this point is fixed in the form of a wet limestone powder that we can safely and cheaply dispose of. In the "calcium cycle" variant of our full-scale air capture design, this limestone powder will instead be processed to liberate pure pipe-line quality CO2 and regenerate the original capture solution. Carbon Engineering’s air contactor technology has been based on designs used in both the cooling tower and gas scrubber industries, and also embodies many of our own proprietary innovations. Since nobody has yet used this combination of technologies to scrub CO2 from atmospheric air for long durations of time, our OC has been built to test and explore the key technical risks in our design. Our OC device has been built with dimensions and components selected to replicate the “smallest representative unit” of our full-scale modular air contactor design, so that we can gain the most relevant operational experience and performance estimates. The key technical risks that we are examining with our OC are:
- Successful control of “drift” with best-in-class “Drift Eliminators” supplied by our partner in the cooling tower supply industry. “Drift” refers to the small liquid droplets that can be present in the air flow from a gas-liquid contactor, and which would contain sodium hydroxide in our design. Successful drift elimination is the key to operating our contactor in a way that does not pose health and safety risks to people nearby.
- Long term performance trends, in the absorption performance of our liquid solution, in the frictional air resistance (or “pressure drop”) of our structured packing, and in the fraction of packing surface that stays wetted under long-duration low-flow operation.
- Effects on operability and on absorption performance by ingested atmospheric particulates - such as fine particulate matter, soot, dust and silica, and biological debris such as leaves or insects.
We are enjoying these weeks of real field engineering and look forward to updating our site further as we work towards "first CO2". -GH