A method for reducing heat bumps following regeneration of adsorbers in an air separation unit, wherein the air separation unit comprises a front-end purification unit, a direct contact water tower, a chilled water tower, a main air compressor, a main heat exchanger, a distillation column system and a regeneration gas heater, wherein the front-end purification unit comprises two adsorbers, the method comprising the steps of: compressing an air stream in the main air compressor to form a compressed main air stream; cooling the compressed main air stream by chilled water from the chilled water tower in the direct contact water tower to form a wet compressed main air stream; sending warmed water from the direct contact water tower to the chilled water tower to be cooled by low pressure nitrogen from the distillation column system, after the low pressure nitrogen has been warmed against incoming air in the main heat exchanger purifying the wet compressed main air stream in the front-end purification unit to remove water and carbon dioxide to form a dry main air stream; cooling the dry main air stream (32, 34, 36) in the main heat exchanger by indirect heat exchange to form a cooled air stream; introducing the cooled air stream in the distillation column system under conditions effective for rectification of air into nitrogen and oxygen; withdrawing a waste nitrogen gas from the distillation column system and warming said waste nitrogen gas in the main heat exchanger; wherein each of the adsorbers of the front-end purification unit undergoes a processing cycle comprising a regeneration cycle and an adsorption cycle, wherein the regeneration cycle comprises a warming period and a cooling period, wherein during the warming period, the regeneration gas from the main heat exchanger is further warmed in the regeneration gas heater prior to being introduced to the adsorber that is undergoing regeneration, characterized in that the apparatus comprises a regeneration gas cooler and during the cooling period, the regeneration gas from the main heat exchanger is cooled in the regeneration gas cooler using water (72,74) prior to being introduced to the adsorber that is undergoing regeneration until the adsorber undergoing regeneration reaches a targeted temperature, wherein the targeted temperature is at or above a temperature of the wet compressed main air stream and below a temperature of the regeneration gas exiting a warm end of the main heat exchanger, the regeneration gas is cooled by indirect heat exchange against a portion of the chilled cooling water from the chilled water tower, and after cooling the regeneration gas, the portion of the chilled water together with the warmed water from the direct contact water tower is returned to the chilled water tower to be cooled therein. compressing an air stream in the main air compressor to form a compressed main air stream; cooling the compressed main air stream by chilled water from the chilled water tower in the direct contact water tower to form a wet compressed main air stream; sending warmed water from the direct contact water tower to the chilled water tower to be cooled by low pressure nitrogen from the distillation column system, after the low pressure nitrogen has been warmed against incoming air in the main heat exchanger purifying the wet compressed main air stream in the front-end purification unit to remove water and carbon dioxide to form a dry main air stream; cooling the dry main air stream (32, 34, 36) in the main heat exchanger by indirect heat exchange to form a cooled air stream; introducing the cooled air stream in the distillation column system under conditions effective for rectification of air into nitrogen and oxygen; withdrawing a waste nitrogen gas from the distillation column system and warming said waste nitrogen gas in the main heat exchanger; wherein each of the adsorbers of the front-end purification unit undergoes a processing cycle comprising a regeneration cycle and an adsorption cycle, wherein the regeneration cycle comprises a warming period and a cooling period, wherein during the warming period, the regeneration gas from the main heat exchanger is further warmed in the regeneration gas heater prior to being introduced to the adsorber that is undergoing regeneration,