Discharge of Non-Reactive Fluids from Vessels

Abstract

-This paper presents simulations of discharges from pressure vessels that consistently account for non-ideal fluid behavior in all the required thermodynamic properties and individually considers all the chemical components present. The underlying assumption is that phase equilibrium occurs instantaneously inside the vessel and, thus, the dynamics of the fluid in the vessel comprises a sequence of equilibrium states. The formulation leads to a system of differential-algebraic equations in which the component mass balances and the energy balance are ordinary differential equations. The algebraic equations account for the phase equilibrium conditions inside the vessel and at the discharge point, and for sound speed calculations. The simulator allows detailed predictions of the condition inside the vessel and at the discharge point as a function of time, including the flow rate and composition of the discharge. The paper presents conceptual applications of the simulator to predict the effect of leaks from vessels containing mixtures of light gases and/or hydrocarbons and comparisons to experimental data.

Pressure relief of nonideal mixtures: Composition trajectories and residue curve maps

“…17 Stene 18 studied consequences of multicomponent two-phase releases to atmosphere, with an emphasis on the dispersion of the vented material. Kanes 19 and Castier 20 4. Rigorously simulate the dynamic pressure relief process over time using specialized computer routines such as SAFIRE 7 or Super-CHEMS.…”

“…The composition trajectories x i (ξ), which result are residue curves, and ξ can be considered a dimensionless time. In practice, the residue curves can be found by integrating Equation (21) forward and/or backward from a given initial composition in the dimensionless time variable ξ until a fixed point (pure component or azeotrope) is reached.Alternatively, to solve equation both(21) and(20) for composition and liquid hold-up over time, the differential terms (dH/dt) and (dH L /dt) in Equation (20) can be expanded in a Taylor expansion andrearranged in terms of differential time δt 28 :…”