In this simulation, a trayed absorption column is used to remove an impurity from a gas feed by absorbing the impurity in a liquid solvent. The number of trays/stages needed to obtain an outlet concentration of y₁ ppm in the gas stream (set with a slider) is calculated. Use a slider to set the inlet concentration x₀ in the liquid stream. A stage is a plate that makes contact with the liquid solvent and the gas to promote mass transfer. When a partial stage is calculated, the number of stages is rounded down to the nearest full stage. Use sliders to change the pressure and temperature in the column, the solvent feed flow rate L and the inlet gas mole ratio y_N+1. The operating line (black), the equilibrium line (orange) and the stages are shown on the x-y diagram. The slope of the operating line L/V is shown on the column on the right. Checking the (L/V)_min box shows the minimum slope for the operating line; the desired separation would require an infinite number of stages at a lower slope.