Nitrogen+Syngas 325 Sept-Oct 2013
31 October 2013
Problem No. 20: Unblocking pipelines after a urea plant shutdown (continued)
In several sections of a urea plant pipelines, and sometimes heat exchangers, can easily become blocked below a certain temperature and crystallisation can take place. In the evaporation section, urea melt is present which crystallises at about 133°C when in the pure form.
Urea can also polymerise to form biuret, triuret and polyurea with high crystallisation temperatures when urea is kept for a prolonged period at high temperatures.
