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US 5,372,706 AGranted
FCC regeneration process with low NO.sub.x CO boiler
AssigneeMobil Oil Corporation
InventorsJ. Scott Buchanan, David L. Johnson
Life of this patent
Estimating the term…
Abstract
Oxides of nitrogen (NO.sub.x) emissions from an FCC regenerator are reduced by operating the regenerator in partial CO burn mode and adding substoichiometric, or just stoichiometric air to the flue gas. Much CO and most NO.sub.x and NO.sub.x precursors are thermally converted at 2000.degree.-2900.degree. F., then the gas is cooled below about 1800.degree. F. and burning of CO completed.
Claims19
A process for the catalytic cracking of a nitrogen containing hydrocarbon feed to lighter products comprising:
- a. cracking said feed by contact a with supply of regenerated cracking catalyst in a fluidized catalytic cracking (FCC) reactor means operating at catalytic cracking conditions to produce a mixture of cracked products and spent cracking catalyst containing coke and nitrogen compounds;
- b. separating cracked products from said spent cracking catalyst to produce a cracked product vapor phase which is charged to a fractionation means and a spent catalyst phase;
- c. stripping spent catalyst in a stripping means to produce stripped, spent catalyst containing coke and nitrogen compounds;
- d. regenerating stripped, spent catalyst in a catalyst regeneration means by contact with oxygen or an oxygen-containing regeneration gas at catalyst regeneration conditions to produce regenerated catalyst and flue gas containing:
- less than 1.0 mole % oxygen;
- at least 7 mole % CO;
- and
- NO.sub.x and NO.sub.x precursors;
- e. recovering from said catalyst regeneration means regenerated catalyst and recycling it to said crack reactor;
- f. adding oxygen or an oxygen containing gas to said regenerator flue gas in an amount sufficient to produce a temperature rise of at least 750.degree. F. and convert from about 50 to 100% of the CO in said flue gas to CO.sub.2 and form a flue gas and oxygen mixture;
- g. converting said NO.sub.x and NO.sub.x precursors in NO.sub.x conversion zone operating at a NO.sub.x and NO.sub.x precursor conversion conditions including a temperature above 2200.degree. F. and a residence time sufficient to convert at least a majority of said NO.sub.x and NO.sub.x precursors to nitrogen in said NO.sub.x conversion zone and convert at least a majority but not all of said CO to CO.sub.2 in said zone to produce a NO.sub.x and NO.sub.x precursor depleted gas mixture having a temperature above 2200.degree. F. and containing CO;
- h. cooling said depleted mixture below 1800.degree. F. to produce a cooled flue gas stream containing CO;
- i. adding oxygen or an oxygen containing gas to said cooled flue gas stream in an amount sufficient to convert all of the CO contained in said cooled flue gas stream to CO.sub.2 and converting CO to CO.sub.2 in a CO conversion zone operating at temperature below 1800.degree. F. to produce a flue gas stream which may be discharged to the atmosphere.
10 more elements
A process for the catalytic cracking of a nitrogen containing hydrocarbon feed to lighter products comprising:
- a. cracking said feed by contact with a supply of regenerated cracking catalyst in a fluidized catalytic cracking (FCC) reactor means operating at catalytic cracking conditions to produce a mixture of cracked products and spent cracking catalyst containing coke and nitrogen compounds;
- b. separating cracked products from said spent cracking catalyst to produce a cracked product vapor phase which is charged to a fractionation means and a spent catalyst phase;
- c. stripping spent catalyst in a stripping means to produce stripped spent catalyst containing coke and nitrogen compounds;
- d. regenerating stripped, spent catalyst in a catalyst regeneration means by contact with oxygen or oxygen-containing gas at catalyst regeneration conditions to produce regenerated catalyst and an FCC regenerator flue gas stream containing:
- less than 0.1 mole % oxygen;
- at least 3.0 mole % CO;
- and
- NO.sub.x and NO.sub.x precursor including HCN in an amount so that if said regenerator flue gas were burned in a conventional CO boiler at 1400.degree.-2000.degree. F. in an oxidizing atmosphere it would produce a CO boiler flue gas containing more than 100 ppmv NO.sub.x ;
- e. recovering from said catalyst regeneration means regenerated catalyst and recycling same to said cracking reactor;
- f. adding oxygen or an oxygen containing gas to said regenerator flue gas in an amount sufficient to produce a temperature rise of at least 750.degree. F. and convert from 60 to 100% of the CO in said flue gas to CO.sub.2 and form a flue gas and oxygen mixture;
- g. converting said NO.sub.x and NO.sub.x precursors in a NO.sub.x conversion zone operating at a NO.sub.x and NO.sub.x precursor conversion conditions including a temperature above 2400.degree. F. and a residence time sufficient to convert at least a majority of said NO.sub.x and NO.sub.x precursors to nitrogen in said NO.sub.x conversion zone and convert at least a majority but not all of said CO to CO.sub.2 in said zone to produce a NO.sub.x and NO.sub.x precursor depleted gas mixture having a temperature above 2400.degree. F. and containing CO;
- h. cooling said depleted mixture to a temperature below 1800.degree. F. to produce a cooled flue gas stream containing CO;
- i. adding oxygen or an oxygen containing gas to said cooled flue gas stream in an amount sufficient to convert all of the CO contained in said cooled flue gas stream to CO.sub.2 and converting CO to CO.sub.2 in a CO conversion zone operating at a temperature below 1800.degree. F. to produce a flue gas stream containing less than 50 ppmv No.sub.x and less than 100 ppmv CO which may be discharged to the atmosphere.
10 more elements
Dependencies are inferred from the claim text.