Results for the A6G example simulation

The following figure shows the process conditions for the feed (S1), letdown gas (S15), ammonia product (S16), and purge (S18) streams for the base case (Pro 1 snapshot).

When we switch the process specifications to calculate the flowrate of the purge stream (Purge.F) and set the concentration of the inerts in the reactor feed (Rx_Feed_Inerts) to 0.12, we get the following results. You can revert the simulation to the Pro 2 snapshot to see these results in the simulation.

This change represents a slight increase in the concentration of inerts in the reactor feed. We see an almost negligible decrease in the purity of the overall ammonia product, but an increase in the flowrate of the ammonia product.

If we increase Rx_Feed_Inerts to 0.16, we get the following results. You can revert the simulation to the Pro 3 snapshot to see these results in the simulation.

The ammonia product purity decreases from 99.76% to 99.74%, but the flowrate of ammonia product increases by 1.2%. A greater concentration of inerts in the reactor feed increases the reactor conversion. However, the increased recycle flowrate due to the additional inerts also produces corresponding increases in the recycle compressor work and in the separator (flash drum) duties.

We must compare the value of the increased ammonia product to the increased operating costs to determine if the greater inert concentration in the reactor is the best operating strategy. Economic analysis is outside the scope of this example, but you can extend this example simulation to include the economic data and then identify the optimum operating conditions.