Corrosion Cause Of The Accident And Its Prevention In Large Fertilizer Plant

In the 1970s. SiNOPEC Baling Petrochemical Company introduced a set of large production device of nitrogenous fertilizer. After operation for twenty years, some equipment of the device has nearly reached the design life. In addition, the variation of raw material of production has greatly changed the circumstances of operation. Because of these two factors, many accidents of corrosion destroy have happened, which have also brought about serious economic losses. To effectively solve this problem, we conducted a thorough investigation into the causes of the accidents and made a careful analysis of the material quality and operation circumstances. Then, we put forward our measures. The practice have proved that our measures have greatly lowered the accident rate of the device and gained notable economic benefit.1. Since 1992, blast accidents of heat exchange pipes of the first waste heat boiler of synthetic ammonia have taken place eight times. Among these accidents, a blast accident happened only 59 days after it was changed on 20th June, 1994, which led to stop production. Through test determination for chemical composition, mechanical performance and metallurgical tissue of the heat exchange pipe of 101-C and analysis of quality of supply water from the boiler, the main reason why the accident happened was that the quality of the water from the boiler and the supply water did not accord with the stipulations. Management enhancement, technological operation optimization and serious control of all indexes of water quality were measures to solve this problem. Resin applicators were installed on both the outlet of the main pipe for desalting water and that for urea reclaimed condensate to guarantee no impurity in the reclaimed condensate, such as resin. After these measures were taken, the device has been in smooth operation without blast accidents for 5 years, which has reduced losses of morn than RMB ten million annually.2. Ash and coke on the boiler and heat exchanger raised the temperature of theflue gas in the boiler, which led to the results that the heat exchange rate was decreased and the temperature of process medium did not meet the requirements.. Therefore, high temperature corrosion took place on heat surface. In particular, after substituting heavy oil for naphtha as lite! for the converter in the synthetic ammonia device, ashing in the heat exchange pipes of the converter was more serious because of the large quantity of ash content of heavy oil. Through analysis of the principles of vapor blow, sound wave blow and gas-fired blow of high energy pulse, and through comparing their effects and expenses, we finally decided to combine the last method and dry ice cleaning, which provided theoretical basis to solve the problem for Baling petrochemical company and Hubei petrochemical company. In 2002 and 2003, the two companies solved the problem of ashing and coking on the heat exchange pipe of the boiler better than before after they adopted the method in succession. In the meantime, they saved RMB eight million annually.3. Since 1993, puncture leakages have happened many times in the pipe duct on the cha-gang section, which resulted in delivery suspension, environment pollution and large economic losses. Through spot investigation and soil analysis, the main reason why puncture leakages happened was that the abnormal operation caused the industrial waste water to permeate into the external surface of underground pipe and thus led to corrosion destroy of the oil pipe. The local government adopted the above-mentioned analysis results and ordered the factory to stop operation and carry on rectification. So hidden danger of corrosion destroy of the oil pipe was basically resolved.