APPLICATION OF A THREE DIMENSIONAL NETWORK MODEL TO COAL DEWATERING (EQUILIBRIUM DESATURATION, PORE SIZE DISTRIBUTION, PERMEABILITY, POROUS MEDIA, TWO PHASE FLOW)

A three dimensional bond-flow correlated network model has been successfully used to calculate equilibrium desaturation curves, single phase permeabilities and two phase flow properties (dewatering curves) for coal filter cakes. A simple cubic lattice with straight cylindrical bonds is used and the pores are correlated in the direction of macroscopic flow. A new method of pore volume assignment is presented in which the pore volume occupied by the large pores (which give a capillary pressure less than 0.5 psia) is assigned to the nodes and the rest is distributed to the bonds according to the pore size distribution. The micrographic pore size distribution, used as an input, is determined experimentally.; Equilibrium desaturation curves for -32 mesh, -200 mesh and -100+200 mesh coal cakes (Pittsburgh Seam Coal), formed with distilled water, have been calculated. It is determined that a single value of 0.4 for the bond-flow correlation is required for -32 mesh and -200 mesh coals. However, for -100+200 mesh coal, where all small as well as large particles have been removed, a value of 0.0 is recommended. The results for six -32 mesh coal cakes formed with surfactants show that the effect of surfactants can be accounted for by modifying one of the model parameters--the entry diameter constant. A correlation is presented to estimate the modified entry diameter constant using experimentally determined surface tension and contact angle values. Further, the predicted equilibrium final saturations (both for distilled water and surfactant cakes) agree with the experimental values with an average absolute error of 5 percent.; The size distribution of particles in dispersed state has been correlated with that in the cake which in turn has been correlated with the pore size distribution. An equilibrium desaturation curve has been successfully calculated for -32 mesh Pittsburgh Seam coal using the pore size distribution estimated from the dispersed particle size distribution.; Calculated single phase permeabilites, using a bond-flow correlated network and a simple cubic lattice, agree with the experimental values better than a bond-correlated network using a face-centered cubic lattice. Also a comparison of the calculated and the experimental dewatering curves show promising results.; It is concluded that a single set of model parameters can be used to calculate equilibrium and flow properties of coal filter cakes.