AMMONIA GENERATOR CONVERTING LIQUID AMMONIA PRECURSOR SOLUTIONS TO GASEOUS AMMONIA FOR DENOX-APPLICATIONS USING SELECTIVE CATALYTIC REDUCTION OF NITROGEN OXIDES

摘要

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.