PURPOSE: To remarkably reduce blowing steam expense to steaming tower, by recovering and removing holding heat of vapor from the top of steaming tower with an indirect heat exchanger and generating blowing steam utilizing the heat in removal of impurity in phenolate.

CONSTITUTION: Vapor from the top of a steaming tower containing an impurity 2 in phenolate extracted by cleaning tar light oil, carbolic oil, naphthalene oil, absorbing oil, etc., with a dilute solution of sodium hydroxide is introduced into an indirect heat exchanger 4 to thermally exchange the vapor with hot water circulating flash tank 5 and indirect heat exchanger 4 and hot water raised in temperature is flashed and the generated flash steam is raised in pressure to raise the temperature and blown into a steaming tower 1. As a result, impurity in phenolate is purified and removed in remarkably reduced blowing steam expense. Further more, operation cost can be reduced as a whole.