The Finnish physicist Matti Nurmia has patented a different type of CO2 sequestration with real commercial potential, using very little energy in the conversion process and creating byproducts with high commercial value. His firm, Cuyha Innovation Oy (Oy means company) converts acidic CO2 into harmless bicarbonates.
Nurmia’s process differs from carbonization, where CO2 is neutralized with carbonate minerals such as limestone, the way that companies like California’s Calera are making cement with sequestered CO2. But Cuyha is sequestering CO2 in Feldspars, a group of rock-forming minerals, by washing the flue emissions with water at a very high pressure.
The process creates salable byproducts (depending on which feldspar is employed) of lithium carbonate ($10 a kg) or alumina (worth about $300 a ton) or quartz sand.
Neutralizing 1 ton of carbon dioxide with anorthite produces about 1 ton of alumina plus 1.3 tons of quartz which sells at about $70,000 a ton. (But of course, it costs money to mine and move the feldspar too, so it’s not pure profit.)
One ton of coal produces 2.9 tons of CO2 (this sounds nonsensical, but in combining with oxygen, carbon adds weight to become CO2; see how at Coal Combustion and Carbon Emissions at EIA), which will require 9 tons of anorthite to catalyze it and should yield about 3 tons of alumina. If albite feldspar is used, it takes more: 17.3 tons of feldspar to get the same 3 tons of alumina from 1 ton of coal.
Cuyha’s patented process captures CO2 from flue gas by cooling the flue gas and pressurizing it in a turbo compressor with water injection, essentially washing it with water.
“If the flue gas contains 16% CO2 , the CO2 partial pressure at a total pressure of 5 bar is 0,8 bar. A ton of water at +50 will dissolve 2.4 kg of CO2 from the gas. The dissolution takes place in column 23 into which cold water is sprayed from connection 12. The flue gas exiting from column 23 is warmed in heat exchanger 21 and expanded in turbine 26 to recover part of the compression energy.
The CO2 solution exiting from column 23 is passed into neutralization tank 24 filled with crushed feldspar. From there the neutralized solution passes into settling tank 25, where the insoluble aluminum compounds settle. The solution can then exit the process or it can be recycled into the CO2 dissolution process.
In order to keep the amount of water needed for the dissolution within reasonable limits, the partial pressure of CO2 should be sufficiently high, in practice at or above 0.4 bar”.
To reduce the water used, the bicarbonate solution can be recycled, and the two processes can be combined to take place simultaneously in a container filled with crushed rock.
The amount of water required in the process can be reduced by recycling a part of the bicarbonate solution formed back to the neutralization process. The dissolution and neutralization processes can also be combined to take place in one container filled with crushed rock.
The feldspar itself would have to be mined and shipped, so it would preferable to site new coal power plants or cement factories (that produce the most CO2) near feldspar formations, or to use pipelines to ship the CO2 to the feldspar mine for neutralization after the high pressure washing process that separates out the CO2 at the source. (Even though coal is about $100 a ton, it is frequently shipped hundreds of miles by rail to where it is burned, and about 15,000 tons is burned every day in an average sized coal plant.)
With Durban’s new (and first ever) international agreement on carbon reduction that is set to take effect within 8 years internationally, carbon capture will be key for those nations, China, South Africa and the US, that are big coal burners and had formerly resisted emissions reduction agreements for this reason. Carbon capture has for the first time been included as a permissible offset under the Clean Development Mechanism, under which polluters in Kyoto Protocol nations can invest in emissions reductions in developing nations to meet targets.