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A two-stage process for staged combustion of crushed retorted particles, especially sulfur and nitrogen-bearing shale, provides maximum heat from combustible materials in shale while emissions of carbon monoxide and oxides of sulfur and nitrogen are minimized. In the first stage, combustion is maint

A two-stage process for staged combustion of crushed retorted particles, especially sulfur and nitrogen-bearing shale, provides maximum heat from combustible materials in shale while emissions of carbon monoxide and oxides of sulfur and nitrogen are minimized. In the first stage, combustion is maintained under fluidizing conditions with a substoichiometric amount of oxygen. Off-gases from the first stage are burned in a second-stage combustion zone utilizing an oxygen-containing gas stream controlled to limit emission of carbon monoxide in the flue gas. To minimize production of sulfur oxides, combustion temperature is concurrently maintained below a peak value of 1700° F. by introducing inert gas or recycled decarbonized fines to the first-stage combustion zone to reduce temperature therein.

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1. A process for combusting retorted shale particles of a size suitable for fluidization, said shale particles containing materials, which process comprises: (1) combusting a substantial proportion of the combustible material contained within said shale particles by staged combustion, said staged

1. A process for combusting retorted shale particles of a size suitable for fluidization, said shale particles containing materials, which process comprises: (1) combusting a substantial proportion of the combustible material contained within said shale particles by staged combustion, said staged combustion comprising: (a) combusting said particles in a first-stage combustion zone, the particles being maintained as a fluidized bed by a fluidizing gas stream comprising oxygen introduced into said first-stage combustion zone at a rate sufficient to maintain said particles as a fluidized bed therein while providing a substoichiometric quantity of oxygen for combustion of said combustible material in said first-stage combustion zone; (b) controlling the concentration of gaseous ammonia in said first stage combustion zone in the range between about 5 and 100 ppm by volume of the gases produced in the first stage combustion zone; (c) combusting off-gases from said first-stage combustion zone in said second-stage combustion zone, with combustion being maintained by a gas stream comprising oxygen introduced into said second-stage combustion zone, said combustion being under conditions sufficient to produce a flue gas of relatively low carbon monoxide, nitrogen oxides, and sulfur oxides content; (2) discharging said flue gas from said second-stage combustion zone; and (3) discharging crushed particles in a relatively decarbonized condition from said first-stage combustion zone. 2. A process for combusting shale particles as defined in claim 1 wherein said shale particles are raw shales fines. 3. A process for combusting shale particles as defined in claim 1 wherein the fluidizing gas stream fed to the first-stage combustion zone and the gas stream fed to the second-stage combustion zone comprise in total an oxygen content greater than 100 percent of that required for complete combustion of the coke present on the shale entering said first-stage combustion zone. 4. A process for combusting crushed shale particles as defined in claim 1 wherein said fluidizing gas stream comprises between about 60 and about 100 percent of the oxygen required for complete combustion of the combustible materials in the shale particles and said gas stream comprises between about 10 and about 50 percent of the oxygen required for complete combustion of the combustible materials in the shale particles. 5. A process for combusting crushed shale particles as defined in claim 4 which further comprises: (4) maintaining the concentration of gaseous ammonia in said first-stage fluidized combustion zone between about 50 and about 100 ppm by volume by adjusting the amount of oxygen in said fluidizing gas stream; and (5) maintaining the concentration of gaseous carbon monoxide in said flue gas below about 500 ppm by volume by adjusting the amount of oxygen in said gas stream. 6. A process for combusting crushed shale particles as defined in claim 5 which further comprises: (6) introducing into said dense bed region a mixture in any proportion of decarbonized fines of shale and inert diluent gas sufficient to control the temperature of said staged combustion at or below a peak value of 1700° F. while maintaining said particles as a fluidized bed. 7. A process for combusting crushed shale particles as defined in claim 6 wherein said decarbonized fines of shale comprise between about 1 and about 6 percent by weight of all shale particles introduced into said first-stage combustion zone. 8. A process for combusting crushed particles as defined in claim 7 which further comprises: (7) maintaining the concentration of gaseous ammonia in the dense bed region of said first-stage combustion zone between about 50 and about 100 ppm by volume by adjusting the oxygen content of said fluidizing gas stream; and (8) maintaining the concentration of gaseous carbon monoxide in said flue gas below about 500 ppm by volume by adjusting the oxygen content of said gas stream into said second-stage combustion zone. 9. A process as defined in claim 1 wherein the content of gaseous ammonia is controlled in step (1) (b) in the range between about 50 and 100 ppm by volume of the gases produced in the first-stage combustion zone. 10. A process as defined in claim 9 wherein temperature in the first-stage combustion zone is maintained between about 1400° and 1670° F. 11. A process as defined in claim 1 wherein the retorted shale particles contain components which remove gaseous sulfur compounds during combustion in step (1) (a) in the first-stage combustion zone and in step (1) (c) in the second-stage combustion zone. 12. A process as defined in claim 1 wherein essentially decarbonized fines are introduced into the first-stage combustion zone to aid in controlling temperature therein. 13. A process as defined in claim 1 wherein flue gas diluent is introduced into the first-stage combustion zone to control temperature therein. 14. A process as defined in claim 1 wherein temperature in the first-stage combustion zone is maintained below 1700° F. 15. A process as defined in claim 14 wherein essentially decarbonized fines are introduced into the first-stage combustion zone to aid in controlling temperature therein. 16. A process as defined in claim 14 wherein flue gas diluent is introduced into said first-stage combustion zone to aid in controlling temperature therein. 17. A process for combusting crushed retorted particles containing combustible materials comprising sulfur and nitrogen-containing compounds by staged combustion, said staged combustion comprising: (1) combusting a substantial proportion of the combustible material contained within said particles by staged combustion, said staged combustion comprising: (a) combusting said particles in a first-stage fluidized combustion zone having a dense bed, the particles being maintained as a fluidized bed by a fluidizing gas stream comprising oxygen introduced into said first-stage combustion zone at a rate sufficient to maintain said particles as a fluidized bed while providing a substoichiometric quantity of oxygen for combustion of said combustible material in said first-stage combustion zone; (b) combusting off-gases from said first-stage combustion zone in a second-stage combustion zone, with combustion being maintained by a gas stream comprising oxygen introduced into said second-stage combustion zone, said combustion being under conditions sufficient to produce a flue gas of relatively low carbon monoxide, nitrogen oxides, and sulfur oxides content; (2) controlling the flow of said fluidizing gas stream so as to maintain the concentration of gaseous ammonia in said first-stage fluidized combustion zone below about 100 ppm by volume; (3) discharging said flue gas from said second-stage combustion zone; and (4) discharging crushed particles in a relatively decarbonized condition from said first-stage combustion zone. 18. A process for combusting retorted particles as defined in claim 17 wherein said fluidizing gas stream comprises between about 60 and about 100 percent of the oxygen required for complete combustion of the combustible materials in said retorted particles and said gas stream comprises between about 10 and about 50 percent of the oxygen required for complete combustion of the combustible materials in the retorted particles. 19. A process for combusting retorted particles as defined in claim 18 which further comprises: (5) introducing into the dense bed region of said first stage combustion zone a mixture in any proportion of decarbonized fines of said retorted particles and inert diluent gas sufficient to control the temperature of said staged combustion at or below a peak value of 1700° F. while maintaining said particles as a fluidized bed. 20. A process for combusting crushed retorted particles as defined in claim 19 wherein said decarbonized fines of shale comprises between about 1 and about 6 percent by weight of all particles introduced into said first-stage combustion zone. 21. A process as defined in claim 17 wherein the retorted shale particles contain components which remove gaseous sulfur compounds during combustion in step (1) (a) in the first-stage combustion zone and in step (1) (b) in the second-stage combustion zone. 22. A process as defined in claim 21 wherein essentially decarbonized shale fines are introduced into said first-stage combustion zone to aid in contolling temperature therein. 23. A process as defined in claim 17 wherein temperature in the first-stage combustion zone is maintained between about 1400° and 1670° F. 24. A process as defined in claim 23 wherein essentially decarbonized fines are introduced into the first-stage combustion zone to aid in controlling temperature therein. 25. A process as defined in claim 24 wherein flue gas diluent is introduced into said first-stage combustion zone to aid in controlling temperature therein. 26. A process as defined in claim 23 wherein the content of gaseous ammonia is controlled in step (1) (a) in the range between about 5 and 100 ppm by volume of the gases produced in the first stage combustion zone. 27. A process for combusting crushed retorted particles containing combustible materials comprising sulfur and nitrogen-containing compounds by staged combustion, said staged combustion comprising: (1) combusting a substantial proportion of the combustible material contained within said particles by staged combustion, said staged combustion comprising: (a) combusting said particles in a first-stage fluidized combustion zone, the particles being maintained as a fluidized bed by a fluidizing gas stream comprising oxygen introduced into said first-stage combustion zone at a rate sufficient to maintain said particles as a fluidized bed while providing a substoichiometric quantity of oxygen for combustion of said combustible material in said first-stage combustion zone, said fluidized bed having a dense bed region; (b) combusting off-gases from said first-stage combustion zone in a second-stage combustion zone, with combustion being maintained by a gas stream comprising oxygen introduced into said second-stage combustion zone, said combustion being under conditions sufficient to produce a flue gas of relatively low carbon monoxide, nitrogen oxides, and sulfur oxides content; (2) controlling the flow of said fluidizing gas stream so as to maintain the concentration of gaseous ammonia in the dense bed region of said fluidized bed below about 100 ppm by volume; (3) discharging said flue gas from said second-stage combustion zone; and (4) discharging crushed particles in a relatively decarbonized condition from said first-stage combustion zone. 28. A process for combusting crushed retorted shale particles of a size suitable for fluidization, said shale particles containing combustible materials comprising sulfur and nitrogen-containing components and components capable of reacting with gaseous sulfur components in step 1 (a) hereinafter to produce stable solid sulfur-containing materials, which process comprises: (1) combusting a substantial proportion of the combustible material contained within said shale particles by staged combustion, said staged combustion comprising: (a) combusting said particles in a first-stage fluidized combustion zone, the particles being maintained as a fluidized bed by a fluidizing gas stream comprising oxygen introduced into said first-stage combustion zone at a rate sufficient to maintain said particles as a fluidized bed while providing a substoichiometric quantity of oxygen for combustion of said combustible material in said first-stage combustion zone, said first-stage combustion zone having a dense bed region; (b) combusting off-gases from said first-stage combustion zone in a second-stage combustion zone, combustion being maintained therein by a gas stream comprising oxygen introduced into said second-stage combustion zone, said combustion being sufficient to produce a flue gas of relatively low carbon monoxide, nitrogen oxides, and sulfur oxides content; (2) discharging said flue gas from said staged combustion; (3) discharging crushed particles in a relatively decarbonized condition from said staged combustion; (4) maintaining the concentration of gaseous ammonia in the dense bed region of said first-stage fluidized combustion zone between about 50 and about 100 ppm by volume, said concentration of gaseous ammonia being controlled by adjusting the amount of oxygen in said fluidizing gas stream; (5) maintaining the concentration of gaseous carbon monoxide in said flue gas to less than about 500 ppm by volume by adjusting the amount of oxygen in said gas stream; (6) feeding decarbonized fines of shale particles at a relatively cool temperature into the dense bed region of said first-stage combustion zone to aid in controlling temperature during staged combustion below a peak value between about 1400° and about 1670° F., said decarbonized fines of shale comprising no more than 50 percent by weight of the total shale particles introduced into said first-stage combustion zone; and (7) introducing inert diluent gas into said fluidizing gas stream to aid in controlling temperature during staged combustion below said peak value while maintaining said shale particles as a fluidized bed. 29. A process for combusting retorted shale particles as defined in claim 28, said process further comprising: (8) admixing inert diluent gas into said fluidized bed during periods of reduced feed of retorted particles so as to maintain said concentration of gaseous ammonia as in step (4) hereinabove while maintaining said particles as a fluidized bed. 30. A process for combusting crushed retorted shale particles as defined in claim 29 wherein said fluidizing gas stream comprises between 60 and 100 percent of the air necessary for complete combustion of the combustible materials in said retorted particles, and said air stream comprises between about 10 and about 50 percent of the air necessary for complete combustion of the combustible materials in said retorted particles. 31. A process for combusting crushed retorted shale particles as defined in claim 15 wherein said fluidizing gas stream comprises between about 75 and about 85 percent of the oxygen necessary for complete combustion of the combustible materials in said retorted shale particles, said gas stream comprises between about 25 and about 35 percent of the oxygen necessary for complete combustion of the combustible materials in said retorted shale particles, the concentration of carbon monoxide in said flue gas is less than about 50 ppm by volume, and the size of said crushed particles ranges from about zero to about 1/2 inch means diameter. 32. A process for combusting crushed retorted shale particles as defined in claim 29 wherein said inert diluent gas is recycled flue gas. 33. A process for combusting crushed retorted shale particles as defined in claim 28 wherein said inert diluent gas is flue gas. 34. A process for combusting retorted shale particles as defined in claim 18 wherein the size of said crushed particles ranges from about zero to about 1/4 inch mean diameter, said fluidizing gas stream comprises between about 75 and about 85 percent of the oxygen necessary for complete combustion of combustible materials in said retorted shale particles, said gas stream comprises between about 25 and about 35 percent of the oxygen necessary for complete combustion of the combustible materials in said retorted shale particles, and the concentration of carbon monoxide in said flue gas is less than about 50 ppm by volume.