4 ms·

> the bad economics of carbon capture systems Can you expand on this?

bloaf 6y ago
Thermodynamically, the higher concentration of CO2 in industrial flue gas means you can capture CO2 there more efficiently than you can from the ambient air. However, industrial carbon capture typically is a loser because processing the huge volumes of gas produced by industrial equipment is neither cheap nor easy, requiring very large & energy intensive facilities. The products produced by such purification aren't valuable enough to offset those costs, and industry will not shoulder that burden out of the goodness of its cold mechanical heart. Chemical looping can reduce the cost of these processing facilities (or eliminate them completely) by dramatically reducing the number of impurities in the CO2 that is produced from combustion, especially nitrogen. I.e. it makes a more pure CO2 product from the get-go, which means the total volume of gas to process is lower, and purification is even easier.
- PaulHoule 6y ago
  Right, "carbon capture" either from a hydrocarbon stream (carbon neutral) or biomass (carbon negative) competes with many energy sources (solar, wind, nuclear, hydro, conventional fossil fuel combustion) so you'd have to pay operators for the service of stashing CO₂ underground.
PaulHoule 6y ago
Most gas streams from combustion contain a mixture of N₂ and CO₂. CO₂ is disposed of by compressing it 1500 psi and injecting it underground. Even small amounts of N₂ or H₂O will cause the gas to misbehave in the pipeline. The obvious answer to this is https://en.wikipedia.org/wiki/Amine_gas_treating https://en.wikipedia.org/wiki/Amine_gas_treating which is a well-understood process but it is not cheap. The other is to remove the N₂ before combustion. They do this https://en.wikipedia.org/wiki/Rectisol https://en.wikipedia.org/wiki/Rectisol at what used to be the biggest carbon capture plant in the world https://www.dakotagas.com/about-us/gasification/gasification-process https://www.dakotagas.com/about-us/gasification/gasification... but they have a liquid oxygen plant at the head end of the thing and they are separating acid gases from a stream of hydrogen and carbon monoxide about to be built up into methane. There are other methods of combustion with oxygen but they are tricky: temperatures would be high (melt your turbine) if you really used pure oxygen, but if you recycle some of the output gas back into the turbine you might make it work. Of course there is the cost of the oxygen separator so it is hard to be competitive. The hope with CLC is that you might be able to bolt it onto a fluidized bed combustion system and not raise the cost as much as the alternatives.

Thermodynamically, the higher concentration of CO2 in industrial flue gas means you can capture CO2 there more efficiently than you can from the ambient air. However, industrial carbon capture typically is a loser because processing the huge volumes of gas produced by industrial equipment is neither cheap nor easy, requiring very large & energy intensive facilities. The products produced by such purification aren't valuable enough to offset those costs, and industry will not shoulder that burden out of the goodness of its cold mechanical heart. Chemical looping can reduce the cost of these processing facilities (or eliminate them completely) by dramatically reducing the number of impurities in the CO2 that is produced from combustion, especially nitrogen. I.e. it makes a more pure CO2 product from the get-go, which means the total volume of gas to process is lower, and purification is even easier.

PaulHoule 6y ago
Right, "carbon capture" either from a hydrocarbon stream (carbon neutral) or biomass (carbon negative) competes with many energy sources (solar, wind, nuclear, hydro, conventional fossil fuel combustion) so you'd have to pay operators for the service of stashing CO₂ underground.

PaulHoule 6y ago

Most gas streams from combustion contain a mixture of N₂ and CO₂. CO₂ is disposed of by compressing it 1500 psi and injecting it underground. Even small amounts of N₂ or H₂O will cause the gas to misbehave in the pipeline. The obvious answer to this is https://en.wikipedia.org/wiki/Amine_gas_treating https://en.wikipedia.org/wiki/Amine_gas_treating which is a well-understood process but it is not cheap. The other is to remove the N₂ before combustion. They do this https://en.wikipedia.org/wiki/Rectisol https://en.wikipedia.org/wiki/Rectisol at what used to be the biggest carbon capture plant in the world https://www.dakotagas.com/about-us/gasification/gasification-process https://www.dakotagas.com/about-us/gasification/gasification... but they have a liquid oxygen plant at the head end of the thing and they are separating acid gases from a stream of hydrogen and carbon monoxide about to be built up into methane. There are other methods of combustion with oxygen but they are tricky: temperatures would be high (melt your turbine) if you really used pure oxygen, but if you recycle some of the output gas back into the turbine you might make it work. Of course there is the cost of the oxygen separator so it is hard to be competitive. The hope with CLC is that you might be able to bolt it onto a fluidized bed combustion system and not raise the cost as much as the alternatives.