Patent ID: 7732635

Claim:
A production method of an organic acid comprising the steps of; carrying out a gas-phase catalytic oxidation reaction of raw material gas with molecular oxygen at a temperature from 250° C. to 450° C.; collecting gas of an organic acid, a product of the gas-phase catalytic oxidation reaction with a liquid medium to produce an organic acid solution; cooling the organic acid solution by using cold water obtained in an absorption refrigerator to crystallize the organic acid; recovering at least a part of reaction heat generated in the gas-phase catalytic oxidation reaction and/or heat generated in combustion of a waste from the production of the organic acid as high pressure steam at a pressure of 1 MPaG or higher; supplying at least a part of the high pressure steam to a back pressure steam turbine connected with a blower which supplies the molecular oxygen to drive the blower; and supplying at least a part of discharged gas from the back pressure steam turbine, low pressure steam A at a pressure lower than 1 MPaG, to the absorption refrigerator to utilize the low pressure steam A as a heat source of the absorption refrigerator.