CHEE2695 – Lecture 8
Climate change:
- We cannot rely on simply running out of fossil fuels, as we have enough to
irreversibly make Earth uninhabitable.
- Current modelling predicts that we must reach net zero CO 2 emissions by
2050.
Clean coal:
- There is a very controversial ‘clean coal’ concept, that captures and stores the
CO2 produced by coal combustion
- There are a few main ways to make coal cleaner:
o Post combustion separates and stores the produced CO 2.
o Pre-combustion aims to make the burning of the coal more efficient,
e.g., through gasification.
- Flue gas separation is also referred to as ‘post-combustion capture’ (PCC).
When combined with CO2 storage, it is known as carbon capture and storage
(CCS).
- CCS has a large impact on plant efficiency and costs.
- Oxy-fuel combustion is the combustion of coal in either enriched or pure
oxygen. This allows the avoidance of the purification of the flue gas.
- To purify air, cryogenic methods that rely on the different boiling points of O 2
and N2 are often used. Other times, the gas is pressurised, so that it adsorbs
into a surface.
- Via gasification, hydrogen can be obtained from coal by first forming CO 2,
then CO, then H2 by the water-gas shift.
- CO2 cannot be stored as a gas. It must first be converted to a liquid, or a
carbonate. 75% of CCS costs are related to CO2 capture.
- The stability of CO2 storage is often questionable. The CO2 must be stored in
a place where it will not be released due to geological events or rising
temperatures.
CO2 utilisation:
- CO2 could be used for mineral carbonation, which could be used in
construction.
- It could also be used for microalgae growth.
- It could be transformed into oxygen and carbon, and the solid carbon is a very
useful substance.
Climate change:
- We cannot rely on simply running out of fossil fuels, as we have enough to
irreversibly make Earth uninhabitable.
- Current modelling predicts that we must reach net zero CO 2 emissions by
2050.
Clean coal:
- There is a very controversial ‘clean coal’ concept, that captures and stores the
CO2 produced by coal combustion
- There are a few main ways to make coal cleaner:
o Post combustion separates and stores the produced CO 2.
o Pre-combustion aims to make the burning of the coal more efficient,
e.g., through gasification.
- Flue gas separation is also referred to as ‘post-combustion capture’ (PCC).
When combined with CO2 storage, it is known as carbon capture and storage
(CCS).
- CCS has a large impact on plant efficiency and costs.
- Oxy-fuel combustion is the combustion of coal in either enriched or pure
oxygen. This allows the avoidance of the purification of the flue gas.
- To purify air, cryogenic methods that rely on the different boiling points of O 2
and N2 are often used. Other times, the gas is pressurised, so that it adsorbs
into a surface.
- Via gasification, hydrogen can be obtained from coal by first forming CO 2,
then CO, then H2 by the water-gas shift.
- CO2 cannot be stored as a gas. It must first be converted to a liquid, or a
carbonate. 75% of CCS costs are related to CO2 capture.
- The stability of CO2 storage is often questionable. The CO2 must be stored in
a place where it will not be released due to geological events or rising
temperatures.
CO2 utilisation:
- CO2 could be used for mineral carbonation, which could be used in
construction.
- It could also be used for microalgae growth.
- It could be transformed into oxygen and carbon, and the solid carbon is a very
useful substance.
