Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
331 words
In a process for producing ammonia which comprises: (a) primary catalytically reforming at super atmospheric pressure in a direct-fired primary reforming zone, a hydrocarbon feedstock with steam to produce a gas containing carbon oxides, hydrogen and methane; (b) secondary catalytically reforming the gas from step (a) by introducing air and bringing the mixture towards equilibrium thereby producing a secondary reformer effluent gas containing nitrogen, carbon oxides, hydrogen and a decreased quantity of methane; (c) converting carbon monoxide catalytically with steam to carbon dioxide and hydrogen; (d) removing carbon oxides to give an ammonia synthesis gas comprising nitrogen and hydrogen and compressing said gas to ammonia synthesis pressure; (e) reacting the synthesis gas in an ammonia synthesis zone to produce ammonia and recovering ammonia from the reacted gas to produce an ammonia-depleted gas stream; (f) recycling at least a portion of said ammonia-depleted gas stream to said ammonia synthesis zone; and (g) treating a sidestream of said ammonia-depleted gas to separate a stream enriched in hydrogen and an inerts-enriched gas stream, and returning the enriched hydrogen stream to the ammonia synthesis zone; the improvement which comprises: (i) operaring step (b) at a temperature in the outlet gas of not greater than about 1735° F. and with an amount of air sufficient to provide from about 3 to 11 molar % excess N 2 , and to form a secondary reformer outlet gas containing at least 0.8 vol. % methane; (ii) operating step (e) under conditions sufficient to provide at least 10 volume percent inert gases in said ammonia-depleted gas stream; and (iii) introducing as synthesis gas feed to the ammonia synthesis zone a mixture comprising the synthesis gas formed in step (d) having a methane content of at least about 1.2 mole % CH 4 , on a dry basis, the recycled gas produced in step (f) plus the hydrogen-enriched gas stream formed in step (g), whereby the H 2 loss from the process with the separated inerts-enriched gas stream is minimized.
Claim 2
Dependent Claim
331 words
In a process for producing ammonia which comprises: (a) primary catalytically reforming at super atmospheric pressure in a direct-fired primary reforming zone, a hydrocarbon feedstock with steam to produce a gas containing carbon oxides, hydrogen and methane; (b) secondary catalytically reforming the gas from step (a) by introducing air and bringing the mixture towards equilibrium thereby producing a secondary reformer effluent gas containing nitrogen, carbon oxides, hydrogen and a decreased quantity of methane; (c) converting carbon monoxide catalytically with steam to carbon dioxide and hydrogen; (d) removing carbon oxides to give an ammonia synthesis gas comprising nitrogen and hydrogen and compressing said gas to ammonia synthesis pressure; (e) reacting the synthesis gas in an ammonia synthesis zone to produce ammonia and recovering ammonia from the reacted gas to produce an ammonia-depleted gas stream; (f) recycling at least a portion of said ammonia-depleted gas stream to said ammonia synthesis zone; and (g) treating a sidestream of said ammonia-depleted gas to separate a stream enriched in hydrogen and an inerts-enriched gas stream, and returning the enriched hydrogen stream to the ammonia synthesis zone; the improvement which comprises: (i) operaring step (b) at a temperature in the outlet gas of not greater than about 1735° F. and with an amount of air sufficient to provide from about 3 to 11 molar % excess N 2 , and to form a secondary reformer outlet gas containing at least 0.8 vol. % methane; (ii) operating step (e) under conditions sufficient to provide at least 10 volume percent inert gases in said ammonia-depleted gas stream; and (iii) introducing as synthesis gas feed to the ammonia synthesis zone a mixture comprising the synthesis gas formed in step (d) having a methane content of at least about 1.2 mole % CH 4 , on a dry basis, the recycled gas produced in step (f) plus the hydrogen-enriched gas stream formed in step (g), whereby the H 2 loss from the process with the separated inerts-enriched gas stream is minimized.
Claim 3
Dependent Claim
25 words
The improved process of claim 1 wherein step (b) is operated at a temperature in the outlet gas of from about 1620° to 1720° F.
Claim 4
Dependent Claim
44 words
The improved process of claim 2 wherein step (b) is operated at an outlet gas pressure of from about 400 to 600 psig and wherein the outlet gas of step (b) contains from about 1 to 2 volume percent methane, on a dry basis.
Claim 5
Dependent Claim
26 words
The improved process of claim 1 wherein from about 2.5 to 6 volume percent of said ammonia-depleted gas is passed as said sidestream to step (g).
Claim 6
Dependent Claim
20 words
The improved process of claim 4 wherein said ammonia-depleted gas stream contains from about 10 to 20 volume percent inerts.
Claim 7
Dependent Claim
25 words
The improved process of claim 5 wherein said synthesis gas feed to the ammonia synthesis zone contains from about 7 to 13 volume percent methane.
Claim 8
Dependent Claim
32 words
The improved process of claim 1 wherein said ammonia-depleted gas stream contains from about 10 to 20 percent inerts and is characterized by a hydrogen:nitrogen mole ratio of from 2.5 to 3.5:1.
Claim 9
Dependent Claim
53 words
The improved process of claim 1 wherein step (a) is operated at an outlet gas temperature of from about 1250° to 1475° F., at a steam to carbon molar ratio of from 2.5 to 5.0:1 and employs an outlet gas methane content of at least about 13 volume percent, on a dry basis.