Ammonia Generator Converting Liquid Ammonia Precursor Solutions to Gaseous Ammonia for Denox-Applications Using Selective Catalytic Reduction of Nitrogen Oxides

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This invention presents a compact ammonia generator designed to convert concentrated liquid ammonia precursor solutions (e.g., urea, ammonium formate) into gaseous ammonia. The conversion occurs in a pressurized and heated reactor using a catalyst, efficiently producing hot ammonia gas, which can then be injected into engine exhaust gas streams upstream of an SCR (Selective Catalytic Reduction) catalyst. This helps to reduce nitrogen oxides (NOx) emissions, especially at low exhaust temperatures, while avoiding common problems like deposit formation and poor mixing found in previous systems.

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• Automotive vehicles (cars, trucks, buses) requiring SCR systems for NOx emission control.
• Industrial or stationary combustion sources (power plants, incinerators, boilers) using SCR to comply with emission standards.
• Retrofit of existing SCR systems to replace spray nozzles with compact ammonia generators for improved performance.
• Supplying ammonia and/or hydrogen for fuel cells or other industrial processes needing dynamic or continuous gas flows.
• Marine engines and off-highway vehicles subject to stringent NOx regulations.

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• Enables efficient NOx reduction (DeNOx) at lower exhaust temperatures, improving compliance with increasingly strict emission standards.
• Improved mixing of gaseous ammonia with exhaust, leading to higher reaction rates and better SCR performance.
• Eliminates formation of problematic deposits due to incomplete decomposition of ammonia precursors.
• Compacter and more adaptable design allows for easy retrofit into existing SCR systems.
• Reduces cooling of exhaust gases during ammonia dosing, maintaining optimal conditions for the SCR catalyst.
• Capable of processing a range of ammonia precursors, increasing system flexibility and potentially reducing costs.
• Can also produce hydrogen as a byproduct, which can further enhance NOx removal or support other applications like fuel cells.

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Patent Abstract

The presented invention is an ammonia generator, constructed to convert liquid ammonia precursor solutions to gaseous ammonia. The precursor compound is decomposed in the liquid reducing agent solution at elevated pressures and temperatures. After conversion of most of the ammonia precursor compound to ammonia and other gases, the evolved gases are released to ambient pressure. Providing heat to the precursor compound solution without allowing it to boil enables good hydrolysis reaction conditions for the ammonia precursor compound. The high pressure in the ammonia generator keeps water mostly in its liquid state and in direct contact with the reactant ammonia precursor compound and the catalyst bed. The heat transfer is accelerated if water is still mostly liquid, as the heat consumed by the decomposition reactions is quickly replenished. Applying the presented principle according to claims 1 to 820 enables the design and production of a highly compact converter unit for continuous hydrolysis of ammonia precursor compounds to hot ammonia gas. The yielded ammonia gas can be introduced into the hot exhaust gas without causing cooling, thus enabling SCR of NOx at unprecedented low exhaust gas temperatures. In the ammonia generator described the formation of deposits due to incomplete precursor compound decomposition can be eliminated. Ammonia mixes much faster with the exhaust gas than the spray of a liquid reducing agent giving the described generator a significant increase in reaction rate and yield for DeNOx compared to previous designs for the SCR process. It may even be possible to replace a spray nozzle in an existing SCR system by a compact converter.