Method using on site generated ammonia to reduce particulates in combustion gas streams
AssigneeEC&C Technologies, Inc.
InventorsHal B. H. Cooper, Herbert W. Spencer, III
Life of this patent
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Abstract
This patent describes technology for generating ammonia from urea. The method is based on the hydrolysis of an aqueous solution of urea and/or biuret by heating under pressure to form a mixture of ammonia, carbon dioxide and water. The gas mixtures produced are useful for supplying ammonia at controlled pressure and rate of flow for many industrial applications without the risks and hazards associated with the transportation and on-site storage of ammonia, thereby providing a significant safety advantage over present industrial practice.
Claims28
In a method adapted to provide a pressurized gas stream useful for removing nitrogen oxides from a combustion gas stream by SNCR (Selective Non-Catalytic Reduction), or SCR (Selective Catalytic Reduction), or for particulate conditioning processes, the improvement which comprises:
- a) establishing an aqueous solution of urea or mixtures of urea containing biuret and/or ammonium carbamate, having a concentration of about 1% to about 76% by weight of solids in a reactor and hydrolyzing the urea therein at temperatures of at least 110° C. up to about 300° C. and under pressures of about 20-500 psig, the temperature or pressure of the reaction mixture being controlling by the input of heat to the reactor to produce a gaseous product stream of ammonia, carbon dioxide and water at a rate sufficient for external use in step d), and a residual liquid phase reaction medium containing unreacted urea, biuret and/or ammonium carbamate;
- b) separating the gaseous product stream at a controlled pressure and flow rate;
- c) retaining the liquid phase reaction medium in the reactor for further conversion to gaseous ammonia and carbon dioxide, and/or recycling at least a portion of the reaction medium for further conversion;
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- d) with drawing the gaseous ammonia and carbon dioxide containing product stream and feeding it for external use at a controlled rate which is approximately the amount necessary to the demands of said external use in removing said nitrogen oxides or for particulate conditioning.
In a method adapted to removing nitrogen oxides from a combustion gas stream by SNCR (Selective Non-Catalytic Reduction) or SCR (Selective Calalytic Reduction), the improvement which comprises:
- a) establishing an aqueous solution of urea or mixtures of urea containing biuret and/or ammonium carbamate, having a concentration of about 10% to about 50% by weight of solids in a reactor and hydrolyzing the urea therein at temperatures of about 125°-180° C. and under pressures of about 20-200 psig, the temperature or pressure of the reaction mixture being controlled by the input of heat to the reactor to produce a gaseous product stream of ammonia, carbon dioxide and water at a rate sufficient for reaction of the ammonia in step d) with the nitrogen oxides in the combustion gas stream, and a residual liquid phase reaction medium containing unreacted urea, biuret and/or ammonium carbamate;
- b) separating the a gaseous product stream at a controlled pressure and flow rate while maintaining its temperature above 60° C.;
- c) retaining the liquid phase reaction medium in the reactor for further conversion to gaseous ammonia and carbon dioxide, and/or recycling at least a portion of the reaction medium for further conversion;
- and
- d) withdrawing the gaseous ammonia and carbon dioxide-containing product strema and feeding it, while maintaining its temperature above 60° C., into the conbustion gas stream at a controlled rate which is approximately the amount necessary to react the ammonia therein with the nitrogen oxides in the combustion gas stream.
A method for producing a gaseous ammonia-containing product from urea, or mixtures of urea containing biuret and/or ammonium carbamate, said ammonia-containing product being essentially free of urea, biuret, or ammonium carbamate, the process comprising:
- a) establishing an aqueous solution of urea or mixtures of urea containing biuret and/or ammonium carbamate, having a concentration of about 1% to about 76% by weight of solids in a reactor and hydrolyzing the urea therein at temperatures of at least 110° C. up to about 300° C. and under pressures of about 20-500 psig, the temperature or pressure of the reaction mixture being controlled by the input of heat to the reactor to produce a gaseous product stream of ammonia, carbon dioxide and water at a rate sufficient for external use in step d), and a residual liquid phase reaction medium containing unreacted urea, biuret and/or ammonium carbamate;
- b) separating the gaseous product stream at a controlled pressure and flow rate while maintaining its temperature above 60° C.;
- c) retaining the liquid phase reaction medium in the reactor for further conversion to gaseous ammonia and carbon dioxide, and/or recycling at least a portion of the reaction medium for further conversion;
- and
- d) with drawing the gaseous ammonia containing product stream and feeding it, while maintaining its temperature above its temperature above 60° C., at controlled pressure and rate of flow for said external use.
A method for producing a gaseous ammonia-containing product from urea, or mixtures of urea containing biuret and/or ammonium carbamate, said ammonia-containing product being essentially free of urea, biuret, or ammonium carbamate, the process comprising:
- a) establishing an aqueous solution of urea or mixtures of urea containing biuret and/or ammonium carbamate, having a concentration of about 1% to about 76% by weight of solids in a reactor and hydrolyzing the urea therein at temperatures of at least 110° C. up to about 300° C. and under pressures of about 20-500 psig, the temperature or pressure of the reaction mixture being controlled by the input of heat to the reactor to produce a gaseous product stream of ammonia, carbon dioxide and water at a rate sufficient for external use in step d), and a residual liquid phase reaction medium containing unreacted urea, biuret and/or ammonium carbamate;
- b) separating the gaseous product stream at a controlled pressure and flow rate while maintaining its temperature about 60° C.;
- c) retaining the liquid phase reaction medium in the reactor for further conversion to gaseous ammonia and carbon dioxide, and/or recycling at least a portion of the reaction medium for further conversion;
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- d) withdrawing the gaseous ammonia and carbon dioxide-containing product stream and feeding it, while maintaining its pressure and controlled rate which is approximately the amount necessary to the demands of said external use.
Dependencies are inferred from the claim text.