| 主权项 |
1. A method for increasing the capacity of an ammonia plant fed with natural gas, wherein:
said plant comprises a front-end section for converting natural gas into a make-up gas for ammonia synthesis, and said front-end section comprises a primary reformer and a secondary reformer, the overall supply of natural gas fed to the plant comprises a process quote which is used for the catalytic conversion of methane into hydrogen and is fed to said primary reformer, and a fuel quote, said primary reformer comprises a radiant section and a convective section, said radiant section performs a catalytic conversion of said process gas and transfers to said process gas a thermal power also called duty of the reformer, said secondary reformer is fed with comburent process air and with partially reformed process gas coming from the primary reformer, the method comprises at least the following interventions: decreasing said duty of the primary reformer relative to the amount of ammonia produced, and consequently decreasing the exit temperature of the partially reformed gas effluent from said primary reformer; addition of a feeding line of substantially pure oxygen directed to said secondary reformer (12), at least partially replacing said comburent process air; addition of a nitrogen injection line in a quantity necessary to obtain said make-up gas suitable for ammonia synthesis; reducing said fuel quote and consequently increasing said process quote, for a given supply of natural gas. |
