PRESSURE SWING ADSORPTION APPARATUS

PURPOSE:To raise purity of a gas to be obtained by connecting by-pass pipes to the pipings which are situated adjacent to adsorption towers, near the opening and closing valves and are connected to an adsorption tower to subsequently carry out adsorption and desorption except the main route for washing gas. CONSTITUTION:In the washing process of the adsorption tower to subsequently carry out adsorption and desorption, the washing gas is streamed from a washing gas pipe 8 to a valve V13, the adsorption tower 3a, a pressure equalizing pipe 10a, an adsorption tower 3b, a valve V5, and to a waste gas discharge pipe 4a, in this order, and impurities in the adsorption tower 3a and the pressure equalizing pipe 10a are washed out. On the other hand, the washing gas is also streamed from the valve V13 through a side pipe 12 to a piping A as well as from the valve V13 through a side pipe 13 to a piping B, and the gas in the pipes 12, 13 is replaced with the washing gas. And, by opening a valve F1, the insides of side pipes 14, 15 is also washed. Thus, as all the pipings are washed and replaced with the washing gas, the gas to be obtained is recovered in high purity.