Dense phase transport lines

Dense phase transport lines should have gradual curvatures to prevent rough operation. Aeration should be provided to ease the flow of solids in dense phase transport lines and in risers. Blast connections should be available to clear them in case of plugging. Technique should be developed to weld patches on eroded lines during operation. 

In this chapter the choking and saltation velocities will be used to mark the boundaries between dilute phase transport and dense phase transport in vertical and horizontal pipelines, respectively. These terms are defined below in considering the relationships between gas velocity, solids mass flow rate and pressure drop per unit length of transport line in both horizontal and vertical transport. 

Viscosity. Dense phase solid-gas mixtures may be required to flow in transfer line catalytic crackers, between reactors and regenerators and to circulate in dryers such as Figures 9.13(e), (f). In dilute phase pneumatic transport the effective viscosity is nearly that of the fluid, but that of dense phase mixtures is very much... 

Mass transport across isodensity lines should become particularly important when the lubrication approximation breaks down. This should happen near the contact line in the case when two alternative fluid densities near the solid wall are possible. If. say. the boundary densities are Psv 1 and / 5/ = 1 - a, a 1, the three-phase contact line can be viewed as a sharp transition between 0(1) positive and negative values of the nominal thickness h, such that < 1 on either side. This can be treated as a shock of Eq. (91) or (93). The Hugoniot condition, which should ensure zero net flux through the shock, is the equality of chemical potentials on both sides. Unfortunately, this condition cannot be formulated precisely, since the sharp-interface limit of the surface tension term is inapplicable in the shock region. Moreover, our test computations of the profile of the dense layer using Eq. (94) with different boundary conditions imposed on the shock at h = ho showed that the spreading velocity is very sensitive to the conditions on the shock. 

Captured CO2 will most likely be transported to an appropriate sink by pipelines, a state of the art technology. Today s commercial CO2 pipelines are operated in the dense phase, i.e. at subcritical temperature and supercritical pressure." However, several literature sources indicate that pipeline operating conditions are very case specific." Since it is beyond the scope of this work to design a specific CO2 pipeline, the authors assume a pipeline injection pressure of 130 bar. This assumption is in line with the majority of engineering studies regarding CO2 sequestration, de Visser et alJ and Svensson et al recommend that the injection temperature should not exceed 30 °C. 

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