Methods and systems for producing urea

Methods and systems for producing urea are provided. Ammonia, carbon dioxide, and a carbamate solution can be combined in a pressurized mixer to produce a carbamate reaction mixture. The carbamate reaction mixture can be transferred from the pressurized mixer to a reactor. The carbamate reaction mixture can be heated in the reactor to produce a urea reaction mixture that can include urea, water, ammonia, carbon dioxide, and ammonium carbamate. The urea reaction mixture can be contacted to a membrane to separate an aqueous filtrate and a urea concentrate that can include urea, ammonia, carbon dioxide, and ammonium carbamate. The urea concentrate can be transferred from the reactor to a urea purification system that can include one or more separators and one or more decomposers. The urea concentrate can flow through the urea purification system to produce one or more urea products and one or more carbamate solutions.