Predicting aerosol based emissions in a post combustion CO2 capture process using an Aspen Plus model

Industrial scale implementation of post combustion CO2 capture (PCCC) can be hindered by solvent emissions due to its impact on the environment and the operating costs. The issue of aerosol based emissions has only been recently reported for a PCCC process and very little fundamental knowledge is available in the scientific community on this topic. Therefore, it is important to understand the mechanism of aerosol formation and growth so that appropriate countermeasures can be applied in reducing the total emissions. In this study, a simplified methodology is presented for predicting aerosol based emissions from a CO2 capture column of a PCCC process. The basis of this methodology is to split the counter-current gas-liquid interaction from the co-current gas-aerosol interaction. The absorption column is discretised into multiple alternating gas-liquid and gas-aerosol sections in Aspen Plus with an assumption that aerosols behave as a continuous phase rather droplets. The degree of supersaturation, which is important for aerosol formation and growth, is calculated along the column. The effect of the changes in parameters of the PCCC plant, such as the CO2 content of the inlet flue gas, the lean solvent temperature and the lean solvent loading on aerosol based emissions are investigated. The aerosol based emissions follows the trend of the supersaturation ratio in the absorber column

Sheared force-networks: anisotropies, yielding and geometry

A scenario for yielding of granular matter is presented by considering the ensemble of force networks for a given contact network and applied shear stress $\tau$. As $\tau$ is increased, the probability distribution of contact forces becomes highly anisotropic, the difference between average contact forces along minor and major axis grows, and the allowed networks span a shrinking subspace of all force-networks. Eventually, contacts start to break, and at the yielding shear stress, the packing becomes effectively isostatic. The size of the allowed subspace exhibits simple scaling properties, which lead to a prediction of the yield stress for packings of arbitrary contact number.Comment: 4 pages, 4 figure

Force balance in canonical ensembles of static granular packings

We investigate the role of local force balance in the transition from a microcanonical ensemble of static granular packings, characterized by an invariant stress, to a canonical ensemble. Packings in two dimensions admit a reciprocal tiling, and a collective effect of force balance is that the area of this tiling is also invariant in a microcanonical ensemble. We present analytical relations between stress, tiling area and tiling area fluctuations, and show that a canonical ensemble can be characterized by an intensive thermodynamic parameter conjugate to one or the other. We test the equivalence of different ensembles through the first canonical simulations of the force network ensemble, a model system.Comment: 9 pages, 9 figures, submitted to JSTA

The tail of the contact force distribution in static granular materials

We numerically study the distribution P(f) of contact forces in frictionless bead packs, by averaging over the ensemble of all possible force network configurations. We resort to umbrella sampling to resolve the asymptotic decay of P(f) for large f, and determine P(f) down to values of order 10^{-45} for ordered and disordered systems in two and three dimensions. Our findings unambiguously show that, in the ensemble approach, the force distributions decay much faster than exponentially: P(f) ~ exp(-f^{\alpha}), with alpha \approx 2.0 for 2D systems, and alpha \approx 1.7 for 3D systems.Comment: 4 pages, 4 figures, submitted to Phys. Rev.

Force network ensemble: a new approach to static granular matter

An ensemble approach for force distributions in static granular packings is developed. This framework is based on the separation of packing and force scales, together with an a-priori flat measure in the force phase space under the constraints that the contact forces are repulsive and balance on every particle. We show how the formalism yields realistic results, both for disordered and regular ``snooker ball'' configurations, and obtain a shear-induced unjamming transition of the type proposed recently for athermal media.Comment: 4 pages, 4 figures, changed conten