In-situ Synthesis of Ammonia by Hydrolysis of Urea for Safe Feedstock in Power Plants in Use of Flue Gas Conditioning and NOx Reduction

摘要

Ammonia has long been known to be useful in the treatment of flue/tail/stack gases from industrial furnaces, incinerators and the electric power generation industry and also for conditioning of the flue gas by which an improved collection and removal of particulate matter (fly ash) is obtained. Earlier day aqueous or anhydrous ammonia was supplied as feedstock for SCR and SNCR. Unfortunately, anhydrous ammonia, as well as aqueous ammonia in strengths above 20%, present significant danger to human health and are classified by OSHA as hazardous chemicals. Their transportation, storage and handling triggers serious safety and environmental regulatory requirements for risk management plans, accident prevention programs, emergency response plans and release analysis. Aqueous ammonia solutions with low concentration present lower health and safety risks but their usage results in a substantial increase in operating costs of SCR and SNCR systems. An alternative approach to ammonia supply suggested in late eighties includes using benign urea feedstock to generate, ammonia on site. It has been determined that use of urea hydrolysis is the preferred process for converting urea/water solution into a gaseous mixture containing ammonia, carbon dioxide and water vapor.