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    Problem No. 68: Chloride stress corrosion cracking risks in urea plants

    Avoiding chloride contamination is critical in urea plants, not only from the process and utility side but also from the atmospheric side. The applied stainless steels in urea plants are susceptible to detrimental failure modes when chlorides and moisture are present. This UreaKnowHow.com Round Table discussion provides several examples of failures and important prevention measures relating to chloride stress corrosion cracking risks in urea plants.

    Problem No. 66: Urea storage for bagged urea

    Storing urea under hot and humid ambient conditions can be a chall enge. Several quality parameters of the urea product itself like moisture, temperature and particle size distribution are critical. Fluctuations of these parameters over time are also important and can lead to caking issues and complaints by clients. Off-spec product means big losses in revenue and results in a troublesome stream that has to be handled separately. Learning from each other’s experiences is vital to minimise and avoid these problems. n

    Problem No. 65: High urea concentration in carbamate recycle

    This UreaKnowHow.com round table discusses the process upset condition of a high urea concentration in the ammonium carbamate recycle. It is commonly known that the urea formation reaction from ammonia and carbon dioxide via ammonium carbamate is an equilibrium reaction and that the urea conversion in any urea plant is limited. That is why downstream of the urea synthesis section the urea is separated from the ammonium carbamate in a recirculation section. Ammonium carbamate is dissociated into ammonia and carbon dioxide gases by means of low pressure and the addition of heat. The ammonia and carbon dioxide gases are dissolved in water and recycled back to the urea synthesis section. The urea content should be minimal as urea in the ammonium carbamate recycle leads to lower efficiencies. What are the causes and remedies for a high urea concentration in the ammonium carbamate recycle? n