P. Massarotto

Conditional model for sorption in porous media with fractal properties

In this study, the conditional moment closure approach, which is proven to be very useful for modelling of reactions in turbulent flows, is extended to characterise adsorbing, desorbing or reacting flows in porous media. A complete specification of the porous distance conditioned moment closure model, which is formulated in terms of single-conditioned expectations, is presented. The closure of the model equations is obtained assuming the diffusion approximation for fluxes of the reactive species. The model simulates complex multi-cascade processes of convective and diffusive transport of species between pores in a continuous and consistent manner and is a generalisation of dual (or triple) porosity concept. The model addresses the major difficulty of describing transport, entrapment and sorption processes in porous media with fractal properties, where distant transport occurs in the largest pores or fractures, while the adsorbing or desorbing surface is mainly allocated in small pores. The model is able to simulate various regimes of methane replacement by CO2 in a coal sample, which makes it useful for optimising the design and parameters of enhanced coal bed methane recovery operations. It is demonstrated that the power-low decrease in downstream methane concentration, which has been observed experimentally, can be accurately reproduced by the model.

Effects of Operating Conditions on Pressure Drop in a Pulse-Jet Bagfilter for Coke Dust

A pilot-scale pulse-jet bagfilter was designed, built, and tested for the effects of four operating conditions (filtration velocity, inlet dust concentration, pulse pressure, and pulse interval time) on the total system pressure drop, using coke dust from a steel mill factory. Four models were used to predict the total pressure drop according to the operating conditions. These model parameters were estimated from the 192 experimental data points. The filtration velocity has been determined to be the most relevant variable affecting the pressure drop. An efficient operating condition considering the four variables is proposed from analysis of the dimensionless group model.

A case study on the numerical simulation of enhanced coalbed methane recovery

A hypothetical pilot-scale project was studied to investigate the capabilities of existing coalbed methane (CBM) models in simulating the multicomponent gas sorption and diffusion in coalbeds for CO- sequestration enhanced coalbed methane (ECBM) production. Further, the effects of coal properties, e.g. cleat permeability, porosity, cleat spacing, sorption isotherms of CH and CO, and initial reservoir conditions, on CO breakthrough and methane recovery were investigated as well. The calculated results suggested that the multicomponent sorption equilibria described using IAS/Langmuir isotherm and extended Langmuir isotherm are quite different. The gas diffusion rate can not be accurately modeled using Warren & Root equation based on dual-porosity model (pseudo-steady state approach), which is so far the most popular approach used in CBM models to describe gas diffusion process. This indicates that a rigorous multicomponent gas diffusion model should be incorporated in CBM models to improve numerical simulation and prediction of CBM/ECBM production.