Method for preparation of ammonia gas and CO2 for a urea synthesis process

A process for preparing ammonia gas and carbon dioxide for a urea synthesis, comprising:

• producing a process gas containing nitrogen, hydrogen, and carbon dioxide as main components from a metallurgical gas comprising a mixed gas composed of blast furnace gas and converter gas;
• fractionating the process gas by means of pressure swing adsorption to give a first gas stream containing the carbon dioxide and a second gas mixture consisting essentially of N2 and H2,
• producing an ammonia gas suitable for the urea synthesis directly from the second gas mixture by means of ammonia synthesis;
• branching off carbon dioxide from the first gas stream in a purity and amount suitable for the urea synthesis;
• and
• synthesizing the urea via an intermediate ammonium carbamate from the ammonia gas and carbon dioxide suitable for the urea synthesis,
• wherein:
• the branching step comprises:
• a first separation stage, wherein a carbon dioxide-enriched gas stream is separated from the first gas stream;
• and
• a second separation stage, wherein the carbon dioxide-enriched gas stream from the first separation stage is separated into a third gas stream comprising carbon dioxide suitable for urea synthesis, and a tailgas;
• wherein:
• the blast furnace gas has 35-60% by volume nitrogen and 20-30% by volume of each of carbon dioxide and carbon monoxide.

A process for preparing ammonia gas and carbon dioxide for a urea synthesis, comprising:

• producing a process gas containing nitrogen, hydrogen, and carbon dioxide as main components from a metallurgical gas comprising a mixed gas composed of blast furnace gas and converter gas;
• fractionating the process gas by means of pressure swing adsorption to give a first gas stream containing the carbon dioxide and a second gas mixture consisting essentially of nitrogen and hydrogen;
• producing an ammonia gas suitable for the urea synthesis directly from the second gas mixture by means of ammonia synthesis;
• branching off the carbon dioxide from the first gas stream in a purity and amount suitable for the urea synthesis;
• the branching step comprising:
• a first separation stage, wherein a CO2-enriched gas stream is separated from the first gas stream;
• and
• a second separation stage, wherein the CO2-enriched gas stream from the first separation stage is separated into a third gas stream comprising carbon dioxide suitable for urea synthesis, and a tailgas;
• and
• carbamate from the ammonia gas and carbon dioxide suitable for the urea synthesis,
• wherein:
• the blast furnace gas has 50% by volume nitrogen, 24% by volume carbon dioxide, and 21% by volume carbon monoxide.