Apparatus and methods for urea production

An apparatus for producing urea, comprising:

• a first zone comprising at least three flow channels at least partially disposed about a set of trays having a first end and second end, wherein:
• a first flow channel is at least partially disposed about the first end of the trays,
• a second flow channel is at least partially disposed about the first and second ends of the trays, and
• a third flow channel is at least partially disposed about the first and second ends of the trays, wherein the flow channels are not in fluid communication with one another,
• a second zone comprising a fixed bed comprising one or more inert packing materials disposed therein to provide additional surface area;
• and
• a third zone comprising a plurality of tubes disposed therein, the tubes defining a first flow path therethrough and a second flow path therearound, wherein the first and second flowpaths are not in fluid communication with one another but are situated to be in indirect heat exchange with one another, wherein the second zone is disposed between the first and third zones, and wherein a fourth flow channel is at least partially disposed within the first zone at a first end thereof and at least partially disposed within the second zone at a second end thereof, and wherein at least a portion of the fourth flow channel is external to the first zone.

A method for producing urea, comprising:

• introducing ammonia, ammonium carbamate, and carbon dioxide to an apparatus for producing urea, the apparatus comprising:
• a first zone comprising a first flow channel in fluid communication with a first tube disposed about a first end of a plurality of trays, a second flow channel in fluid communication with a second tube disposed about the first end of the trays and a second end of the trays, and a third flow channel in fluid communication with a third tube disposed about the first and second ends of the trays;
• a second zone comprising a fixed bed comprising one or more inert packing materials disposed therein to provide additional surface area;
• and
• a third zone comprising a plurality of tubes disposed therein, the tubes defining a first flow path therethrough and a second flow path therearound, wherein the first and second flowpaths are not in fluid communication with one another but are situated to be in indirect heat exchange with one another, wherein the second zone is disposed between the first and third zones,
• contacting the ammonia, ammonium carbamate, and carbon dioxide within the first zone at conditions sufficient to provide a solution comprising urea, ammonium carbamate, carbon dioxide, ammonia, and water;
• flowing the solution to the second zone, wherein the solution is distributed about the fixed bed;
• and
• flowing the distributed solution through the third zone, wherein the solution flows through the tubes counter-currently to a gas mixture comprising ammonia and carbon dioxide, thereby providing a second gas mixture and a second solution comprising urea, ammonia, ammonium carbamate, and water;
• wherein the second gas mixture flows counter-currently through the second zone, contacting the distributed solution and continues flowing to the first zone contacting the ammonia and ammonium carbamate therein.