Urea production method

A urea production method, comprising:

• a first concentration step of concentrating an aqueous urea solution sent from a urea synthesis step to generate a concentrated urea solution;
• a granulation step of producing solid urea from the concentrated urea solution generated in the first concentration step and discharging an exhaust gas containing urea dust;
• a urea recovery step of washing the exhaust gas discharged from the granulation step with a circulating aqueous urea solution to recover urea dust in the exhaust gas, generate a recovered aqueous urea solution in which the majority of the urea dust is dissolved or absorbed, and discharge a washed exhaust gas,
• an additive addition step whereby a separate additive, not generated in whole or in part by the urea recovery step, is added to the recovered aqueous urea solution, and
• a second concentration step of concentrating the recovered aqueous urea solution containing the separate additive by removing at least a part of the water in the recovered aqueous urea solution to generate a concentrated recovered urea solution, wherein
• the granulation step is configured to treat a concentrated urea solution containing the additive;
• the separate additive is formalin or a condensation product of formaldehyde with urea and does not contain recovered urea dust, and
• the concentrated recovered urea solution generated in the second concentration step is joined to the concentrated urea solution downstream of the of the first concentration step.