Calcium looping

Calcium looping (CaL), or the regenerative calcium cycle (RCC), is a second-generation carbon capture technology. The captured carbon dioxide can then be transported to a storage site, used in enhanced oil recovery or used as a chemical feedstock.

A variant of chemical looping is calcium looping, which uses the alternating carbonation and then calcination of a calcium oxide based carrier as a means of capturing.

In the calcium looping process, the two species are calcium carbonate (CaCO 3 ) and calcium oxide (CaO).

In the calcium looping process, the two species are calcium carbonate (CaCO 3 ) and calcium oxide (CaO).

The captured carbon dioxide can then be transported to a storage site, used in enhanced oil recovery or used as a chemical feedstock.

The captured carbon dioxide can then be transported to a storage site, used in enhanced oil recovery or used as a chemical feedstock.

The captured carbon dioxide can then be transported to a storage site, used in enhanced oil recovery or used as a chemical feedstock.

Calcium looping is being developed as it is a more efficient, less toxic alternative to current post-combustion capture processes such as amine scrubbing.

It also has interesting potential for integration with the cement industry.

The forward, endothermic step is called calcination while the backward, exothermic step is carbonation.

The forward, endothermic step is called calcination while the backward, exothermic step is carbonation.

The forward, endothermic step is called calcination while the backward, exothermic step is carbonation.

The forward, endothermic step is called calcination while the backward, exothermic step is carbonation.

The calciner and carbonator are fluidised beds with associated process equipment for separating the gases and solids attached (such as cyclones).

Direct provision of heat involves the combustion of fuel in the calciner itself (fluidised bed combustion).

The heat necessary for calcination can be provided by oxy-combustion of coal below.

The provision of oxygen for the combustion uses lots of electricity; other air separation processes are being developed.

Although the heat from the carbonator is not at a high enough temperature to be used in the calciner, the high temperatures involved (>600 °C) mean that a relatively efficient Rankine cycle for generating electricity can be operated.

The low temperature of this heat means that it contains much less exergy and can generate much less electricity through a Rankine or organic Rankine cycle.

The low temperature of this heat means that it contains much less exergy and can generate much less electricity through a Rankine or organic Rankine cycle.

Because calcium sulfate has a greater molar volume than either CaO or CaCO 3 a sulfated layer will form on the outside of the particle, which can prevent the uptake of CO 2 by the CaO further inside the particle.

Firstly, both carbonator and calciner can use fluidized bed technology, due to the good gas-solid contacting and uniform bed temperature.

This product layer grows over the pores and seals them off, forcing carbonation to follow a slower, diffusion dependent mechanism.

CaO is also prone to sintering, or change in pore shape, shrinkage and grain growth during heating.

Ionic compounds such as CaO mostly sinter because of volume diffusion or lattice diffusion mechanics.

Ocean disposal was found to be the best, but current laws relating to dumping waste at sea prevent this.