Analysis and treatment of water-steam quality deterioration of generating units caused by urea leakage

Abstract

After the implementation of the liquid ammonia to urea conversion project in a coal-fired power plant， urea leakage into the steam-water system of unit may lead to deteriorated steam-water quality. With an unscheduled shutdown of a 1，000 MW unit due to urea leakage into water-steam system as an example， the accident phenomenon， treatment process， investigation and analysis process， formulation of precautionary measures， and diagnostic means are discussed. Abnormal increase of feedwater hydrogen conductivity is the main accident phenomenon. Through analysis the laws of correlation between feedwater hydrogen conductivity， ammonium ions and TOCi contents of demineralized water and condensate， it is determined that the accident is caused by leakage of urea into the water-steam system. The systematic investigation shows that the accident results fundamentally from the contamination of raw water in the power plant by wastewater from the urea station. Meanwhile， measures to prevent urea leakage into the water-steam system and means to diagnose urea leakage into the system are proposed.

Keywords

• ammonia production from urea
• water-steam quality
• hydrogen conductivity
• accident analysis