In chemical factories and the like, gases which contain harmful organic solvents are generated and therefore they must be purified by removing such organic solvents therefrom. For this purification of gases, they are subjected to adsorption treatment and there has been employed a gas treating apparatus having an adsorption means which contains activated carbon as an adsorbent. The adsorption means of the gas treating apparatus is, for example, a paper sheet containing activated carbon which is formed into a honeycomb structure, and adsorption treatment of a harmful organic solvent is carried out by passing a gas containing the organic solvent through the adsorption means of the gas treating apparatus to adsorb the harmful organic solvent with activated carbon to obtain a purified gas, while passing a regenerating gas at a high temperature such as at about 120.degree. C. through the adsorption means onto which the organic solvent has been adsorbed to desorb the adsorbed organic solvent from the adsorbent. In such a gas treating apparatus, since adsorbability of activated carbon can be recovered by desorbing an organic solvent from it, a gas containing such an organic solvent is continuously treated by alternately repeating the adsorption step for adsorbing the organic solvent and the regenerating step for desorbing the organic solvent from the adsorbent to regenerate activated carbon.
In the gas treating apparatus using a honeycomb-structured paper sheet as the adsorption means, the means is provided rotatably, and the zone in which the adsorption means rotates is divided into two parts, that is, one part through which a gas containing an organic solvent to be treated is passed and the other part through which a high temperature regenerating gas is passed. By rotating the adsorption means, the means travels by turns through one part wherein the organic solvent containing gas is passed and the other part wherein the regenerating gas is passed during the rotation and, thereby, the organic solvent is adsorbed onto the adsorption means and then desorbed from it.
In the regenerating step of the adsorption means, a regenerating gas such as air, nitrogen gas or the like at about 120.degree. C. is passed through the adsorption means which has adsorbed an organic solvent thereon to desorb the solvent from the adsorbent. For example, in the case where the desorbed solvent is recovered, the organic solvent is transferred together with the regenerating gas to a condenser to recover it by condensation. Upon condensing and recovering the solvent by using the condenser, it is necessary to lower the temperature of the regenerating gas. However, when the amount of the regenerating gas is large, for example, a high load must be applied to a refrigeration machine of the condenser in order to lower the temperature of the regenerating gas. Further, when the concentration of the organic solvent in the regenerating gas which is fed to the condenser is low, the load to be applied to the refrigeration machine of the condenser is large, whereas the amount of the organic solvent recovered is small, which impairs workability, economy and the like.
In addition, in the case where the desorbed organic solvent in the regenerating step is not recovered, it is treated, for example, with a catalytic incinerator. However, in this case, since the concentration of the organic solvent is low, a larger-sized incinerator is required and it is uneconomic. Further, in the case of an oxygen enriching apparatus wherein air is treated by adsorption as described above using an adsorption means of a honeycomb-structured sheet containing molecular-sieving-carbon as an adsorbent and then concentrated oxygen is taken out in the regenerating step, there is a problem that the concentration of oxygen can not be sufficiently increased in a conventional method.