Understanding aerosol growth and emissions: CO2 capture in the RWE Niederaussem pilot plant using CESAR1

This work presents a new class-based aerosol model using the CESAR1 solvent system, giving improved understanding and predictability of droplet growth and aerosol emissions. The model is validated against two cases from the RWE Niederaussem pilot plant, one with low and one with high particle number count (PNC), 2·10¹⁰ droplets/m³ and 1.4·10¹² droplets/m³, respectively. The model is shown to predict well water wash steady-state amine concentrations, the compositions of droplets falling from and hitting the outlet demister, and outlet emissions.

Aerosol carryover from the absorber accounted for 18 and 30 % of the AMP and 78 and 92 % of the PZ water wash liquid amine content for low and high PNC, respectively. Thus, any simulation model not considering aerosols will overestimate the effect of the water wash if aerosols are present.

For low PNC, all droplets grew to approximately the same size regardless of inlet size. High PNC resulted in outlet droplet sizes strongly dependent on inlet size. Droplet amine concentration was also found to depend on droplet size, and large droplets showed both higher amine concentration and PZ/AMP ratio than small ones. This is important as droplets are selectively removed in a demister, and using classes is a clear improvement over the distribution-based model.

Even low PNC is shown to have a significant effect on the gas phase amine depletion, with PZ much more affected than AMP. High PNC accentuates this effect.