Ammonia synthesis converter and method for small production units

An ammonia synthesis method comprising:

• providing an ammonia synthesis converter comprising a shell with a removable top head;
• removably mounting an annular basket in the shell, the annular basket comprising inner and outer walls and defining an annular zone between the inner and outer walls, an inner basket zone located centrally within the inner wall and an outer basket zone between the outer wall and the shell;
• passing gas axially in down-flow through first and second catalyst beds disposed in the annular zone in series, the first and second catalyst beds comprising catalyst to convert a mixture of hydrogen and nitrogen to ammonia;
• wherein:
• the first catalyst bed is disposed in one or more first catalyst pods and wherein the second catalyst bed is disposed in one or more second catalyst pods, wherein the first and second catalyst pods are located side-by-side in the annular zone and extend substantially a height of the basket;
• or
• the first and second catalyst beds are vertically stacked in the annular zone, wherein the first catalyst bed is disposed in an insert removably received in the annular zone above the second catalyst bed;
• supplying quench gas to a direct-quench system in the first catalyst pod(s) to introduce the quench gas into a first effluent from a bottom of the first catalyst bed, and passing the resulting mixture of the quench gas and the first effluent through the annular zone and into a top of the second catalyst bed;
• receiving a second effluent from the second catalyst bed in a feed-effluent interchanger in the inner basket zone to indirectly heat a gas feed to the first catalyst bed;
• recovering the second effluent from the feed-effluent interchanger;
• introducing exchanger bypass gas from a bypass gas distributor into the heated gas feed and introducing the resulting bypass-feed mixture into a top of the first catalyst bed;
• and
• supplying the gas feed through the outer basket zone to the interchanger.

An ammonia synthesis converter having dimensions for a design capacity of 100 metric tons per day (MTPD) or less and comprising:

• a shell having a removable top head;
• an annular basket mounted in the shell, the annular basket comprising inner and outer walls and defining an annular zone between the inner and outer walls, an inner basket zone located centrally within the inner wall and an outer basket zone between the outer wall and the shell;
• wherein the annular basket further comprises inner and outer removable top cover plates;
• an expansion joint to seal the outer top cover plate to a top of the inner wall of the basket;
• first and second catalyst beds disposed in the annular zone of the basket for axial down-flow in series, the first and second catalyst beds comprising catalyst to convert a mixture of hydrogen and nitrogen to ammonia, wherein the first catalyst bed is disposed in one or more first catalyst pods, wherein the second catalyst bed is disposed in one or more second catalyst pods, wherein the first and second catalyst pods are located side-by-side in the annular zone and extend substantially a height of the basket;
• wherein the first and second catalyst pods are supported from the inner wall of the basket, wherein the first catalyst pod(s) is supported from a top inlet duct contiguous with the inner wall of the basket, and the second catalyst pod(s) is supported from a bottom outlet duct contiguous with the inner wall of the basket, the inlet and outlet ducts providing fluid communication between the inner basket zone and the respective first and second catalyst pods;
• a quench gas supply to a direct-quench system in a bottom of the first catalyst pod(s) to introduce quench gas into a first effluent from the first catalyst bed;
• a flow path through the annular zone to introduce the resulting quench gas-first effluent mixture into a top of the second catalyst pod(s);
• a feed-effluent interchanger in the inner basket zone to receive a second effluent from the second catalyst bed and indirectly heat a gas feed to the first catalyst bed, wherein the feed-effluent interchanger is removably mounted on a closed inverted conical support, connected to the inner wall of the basket;
• a bypass gas distributor to introduce exchanger bypass gas into the heated gas feed and a flow path to introduce the resulting bypass-feed mixture into a top of the first catalyst pod;
• a gas feed flow path to supply the gas feed through the outer basket zone to the interchanger;
• and
• a converter outlet pipe to recover the second effluent from the feed-effluent interchanger.