Methods of converting urea to ammonia for SCR, SNCR and flue gas conditioning
OwnerDavid Lee Wojichowskiinventor
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Abstract
This invention relates to pollution control requirements for fossil fuel burning facilities, such as power plants, incinerators and cement kilns, and more particularity, to improved methods of generating ammonia from urea. Ammonia is the critical chemical additive used to reduce the emissions of nitrogen oxides from the combustion effluent by both selective non-catalytic reduction and selective catalytic reduction techniques.
Claims18
A process for converting an aqueous solution of urea, possibly including urea hydrolysis polymerization byproducts such as biuret, triuret, monomethylolurea, dimethylolurea, ammonium carbamate, cyanuric acid, isocyanic acid, ammelide, ammeline, and melamine, to ammonia. The process comprising:
- a. Heating the incoming fluid to a temperature greater than 300 degrees F.;
- b. The heating medium is steam or hot air, in direct contact with the urea solution by blending together in a mixing apparatus;
- c. The mixing apparatus is a once-through device, with no liquid phase retention, and no liquid phase recirculation.
A process for converting an aqueous solution of urea, possibly including urea hydrolysis polymerization byproducts such as biuret, triuret, monomethylolurea, dimethylolurea, ammonium carbamate, cyanuric acid, isocyanic acid, ammelide, ammeline, and melamine, to ammonia. The process comprising:
- a. An indirect heat exchange chamber for hydrating a liquid urea solution, which includes heated internal and/or external surfaces, which generates gases from the hydrolysis of urea and vaporization of water, said gaseous discharge leading to an SCR catalyst or to the treatment zone of the SNCR process.
- b. Spray means capable of spraying the urea solution into the hydrolysis chamber, comprising of a spray nozzle and it's associated feed line and pumps.
- c. The pump and feed line is located close enough to the injection nozzle to eliminate the need of recirculating urea solution from the injection nozzle back to a prior point in the process.
A process and apparatus for converting commercially available solid urea into ammonia in a fluid bed combustor, comprising:
- a. a furnace section having a turbulent combustion zone;
- b. a bulk storage device for holding said additive;
- c. a motorized metering feeder for controlling the flow rate of solid urea additive out of said bulk storage device;
- d. a mechanical or pneumatic conveying system attached to said bulk storage device whereby the solid urea additives are conveyed to the turbulent combustion zone.
- e. The solid urea additive, once admitted to the turbulent combustion zone decomposes to form ammonia which reduces nitrogen oxides by the SNCR method.
A process for reducing nitrogen oxide emissions present in a rotary incinerator or rotary cement kiln containing combustion gases by the SNCR method, comprising:
- Injecting granular urea at a velocity of at least 75 feet per second into an open end of the rotary drum to propel said granules through the kiln to a zone within the kiln which has a temperature in the range of 1600 to 2000 degrees F. Said granules then decomposing into ammonia which reduces nitrogen oxides in the combustion gasses by the SNCR process.
A process for reducing nitrogen oxide emissions present in a rotary cement kiln containing combustion gases by the SNCR method, comprising:
- Injecting solid urea into a mid-kiln feeder at a point which has a temperature in the range of 1600 to 2000 degrees F. Said granules or prills then decomposing into ammonia which reduces nitrogen oxides in the combustion gasses by the SNCR process.
Dependencies are inferred from the claim text.