JPH0221285B

PURPOSE:To obtain high purity product carbon monoxide at a high recovery ratio, by first introducing the outflow gas at the time of a process for purging other tower and subsequently introducing the outflow gas at the time of a pressure reducing process to the direction opposite to a stock gas flow direction to perform a pressure raising process. CONSTITUTION:An A-tower is raised in pressure by supplying stock gas by opening a valve 1 and the desorption of product gas is performed in a B-tower with a vacuum pump 11 by opening a valve 5. After the pressure of the A-tower is raised, valves 7, 10 are opened to perform an adsorbing process by the flow of the stock gas and outflow gas is discharged. After adsorption up to a breakthrough point, valves 1, 10 are closed and a valve 9 is opened to reduce the pressure of the A-tower and the outflow gas discharged from said A-tower is taken in a buffer tank 13. Next, valves 9, 5 are closed to finish the desorption of the B-tower. Subsequently, valves 3, 8 are opened to purge the A-tower with the product gas from a product gas intermediate tank 12 and the outflow gas from the A-tower is introduced into the B-tower. Next, valves 3, 7 are closed and the valve 9 is opened to introduce the pressure reduced discharge gas of the A-tower and, after the leveling of pressure, valves 9, 8 are closed.