Patent ID: 8298305

Claim:
An offgas flow controlling method for a hydrogen manufacturing system, wherein the hydrogen manufacturing system includes: a vaporizer that heats and vaporizes a raw material mixture containing a hydrocarbon raw material; a reforming reactor that generates reformed gas from the vaporized raw material mixture by reforming reactions of the hydrocarbon raw material, the reformed gas containing hydrogen; a pressure swing adsorption gas separator having an adsorption tower loaded with an adsorbent that separates gas by pressure swing adsorption, the pressure swing adsorption gas separator causing a cycle including at least an adsorption process and a desorption process to be repeated in the adsorption tower, the adsorption process including introducing the reformed gas into the adsorption tower so as to allow unnecessary components in the reformed gas to be adsorbed by the adsorbent and then extracting hydrogen-enriched gas from the adsorption tower, the desorption process including desorbing the unnecessary components from the adsorbent and discharging offgas containing hydrogen remaining in the adsorption tower and the unnecessary components from the adsorption tower; an offgas supply pipe that supplies the offgas discharged from the adsorption tower to the vaporizer as a fuel that heats the raw material mixture; a buffer tank provided at the offgas supply pipe that temporarily holds the offgas discharged from the adsorption tower; and a flow control unit that controls a flow of the offgas supplied via the buffer tank to the vaporizer; and the method comprises a step of using the flow control unit to change the flow of the offgas supplied from the buffer tank to the vaporizer in accordance with a load change in the pressure swing adsorption gas separator, wherein the change in the flow of the offgas takes place when a cycle time of the cycle including the at least an adsorption process and a desorption process is changed, the flow of the offgas is changed continuously with time during at least part of a time of the change of the cycle time from a preceding cycle to a following cycle, and the pressure swing absorption gas separator is operating continuously in the preceding cycle and the following cycle.