Dimensionless hydrodynamic simulation of high pressure multiphase reactors subject to foaming

Arturo Macchi
2002
Safoniuk (1999) proposed that three-phase fluidized bed hydrodynamics can be scaled based on geometric similarity and matching of five dimensionless groups: the M-group, M = g(p[sub L]-P[sub g])μ[sub L]⁴/(p[sub L]²σ³); a modified Eotvos number, Eo* = g(p[sub L] – p[sub g])d[sub p]²/σ; the liquid Reynolds number, Re[sub L] = P[sub L]d[sub p]U[sub L]/μ[sub L]; a density ratio, P[sub P]/P[sub L] ; and a superficial velocity ratio, Ug/UL- This approach implicitly assumes that the major physical
more » ... major physical properties of the liquid (density, viscosity and surface tension) are sufficient to characterize the bubble coalescence behaviour and that the influence of the gas density is negligible. Since many commercial reactors operate at high pressure with multicomponent liquids that may be subject to foaming, an experimental program was designed to test whether multiphase systems that match Safoniuk's criteria but differ in interfacial properties and gas density produce the same fluid dynamic parameters. The liquid density, viscosity and surface tension were found to be insufficient to characterize bubble coalescence in multicomponent solutions. Multicomponent and contaminated liquids present interfacial effects that reduce the bubble coalescence rate and hinder the bubble rise velocity resulting in greater gas holdups than in pure monocomponent liquids under similar conditions. The extent of interfacial effects depends on the bubble size and is most important for Eo < 40. Additional liquid physical properties such as dynamic surface tension and dilatational surface elasticity were also found insufficient since surface-active components were well-dispersed and in equilibrium with the gas-liquid interface. Gas density was found to be an important parameter in both gas-liquid and gas-liquid-solid systems. The dispersed bubble flow regime is sustained to higher gas velocities and gas holdups for denser gases. This phenomenon can be attributed to enhanced bubble break-up, rather than to the formation of smaller bub [...]
doi:10.14288/1.0058969 fatcat:aubwcupp2raq5oyavvcqjz3lxu