Method for producing methionine

A method for producing methionine comprising:

• a hydantoin step of reacting 3-methylmercaptopropionaldehyde and hydrocyanic acid, or a compound obtained by reacting 3-methylmercaptopropionaldehyde and hydrocyanic acid, with carbon dioxide and ammonia to obtain a liquid containing 5-(2-methylmercaptoethyl)hydantoin;
• a hydrolysis step of hydrolyzing the 5-(2-methylmercaptoethyl)hydantoin;
• a crystallization step of introducing carbon dioxide into a liquid containing a methionine salt obtained at the hydrolysis step to precipitate methionine;
• a separation step of separating a methionine slurry obtained in the crystallization step into solid and liquid;
• and
• a concentration step of concentrating a mother liquor obtained in the separation step,
• the method further comprising
• a recovery step of introducing a gas generated in the concentration step into a gas washing tower in which water is recycled and bringing the gas into contact with the water to recover ammonia contained in the gas, wherein
• a ratio of flow of the water to flow of the gas introduced into the gas washing tower is 2 or more in terms of mass ratio.