Method for producing carbamate, method for producing isocyanate, carbamate production system, and isocyanate production system

A method for producing isocyanate comprising a carbamate production step of producing carbamate by a method for producing carbamate, and

• an isocyanate production step of producing isocyanate by thermally decomposing the obtained carbamate, the method for producing carbamate comprising the steps of:
• a urea production step of producing urea by reaction between ammonia and carbon dioxide gas,
• a carbamate-forming step of producing carbamate by carbamate-forming reaction between amine, the urea, and alcohol, and by-producing a gas containing alcohol, ammonia, and carbon dioxide,
• an ammonia separation step of absorbing the gas with water to produce a gas absorption water, and separating ammonia,
• an aqueous alcohol solution separation step of separating an aqueous alcohol solution from the gas absorption water,
• an ammonia/carbon dioxide separation step of separating carbon dioxide gas from the aqueous ammonia solution in the gas absorption water from which the aqueous alcohol solution is separated, and
• an aqueous ammonia solution reusing step of using the aqueous ammonia solution along with the water for production of the gas absorption water.