| 摘要 |
Heat recovery and conversion of reactants to urea are improved in adiabatic and in isothermal urea synthesis systems. Ammonia and carbon dioxide reactor feed streams are charged to a first heat exchanger external to a urea synthesis reactor and are contacted at a NH3/CO2 molar ratio of 2.5/1 to 3.5/1 in the exchanger to form ammonium carbamate. Heat of reaction is removed simultaneously. The resulting reaction mixture is charged to the lower portion of said reactor having an indirect heating coil positioned therein extending from the lower portion to the upper portion thereof. The coil contains a heat exchange medium and has an inlet and an outlet located at the upper portion of the reactor. Heated heat exchange medium passes from the coil inlet to the coil outlet, with heat being transferred to the resulting reaction mixture as said mixture passes upwardly in the reactor. Heat exchange medium removed through the outlet is substantially cooler than that at the inlet. Additional NH3 reactor feed stream is charged to the lower portion of the reactor and is mixed with the resulting reaction mixture so charged thereto to form a total urea synthesis mixture therein.
|
