| Depropanizer is propylene recovery unit in the process of chloropropene synthesis. As one of the key devices of production propane, its operation status directly impacts the whole production units. The corrosion of the depropanizer is very serious under the operation condition, and its factors were studied systemtically through on-site investigation and laboratory simulation test. Weight loss test, galvanic corrosion test, SEM&EDS, XRD, electrochemical test and metallographic analysis were used to analyze the corrosion behavior of this tower material in the thesis. Most importantly, seven categories of anti-corrosion coatings were optimized to verify the feasibility, and the corrosion prevention measure was given in the thesis at last.There are four main reasons for the corrosion of depropanizer: First, the raw material propylene and chlorine, cooling during quenching tower spray liquid and the liquid propane into propylene bring a lot of water, causing the formation of very high concentrations of hydrochloric acid; Second, different materials such as the tray, the support frame ,weld and base materials will have different potential in hydrochloric acid, which resulting in galvanic corrosion; Third, tray and downcomer plate special structure determines the presence of fluid area, where flow was turbulent state, prone to erosion corrosion; Fourth, previous methods used in the construction quality is not anti-corrosion guarantee.The different concentrations of hydrochloric acid were used as simulation corrosion solution to study the corrosion behavior of different tower materials. Weight loss test under acid mist condition and damp-heat condition were taken to simulate the environment of depropanizer in operation and maintenance situation, the results incicated the corrosion rate of 16MnR steel was 3.1mm/a. The metallographic structure were observed after immersed the weld region and the base metal into corrosion solution, it was easily got that the weld region was much poorer corrosion resistance than the base metal. The potential between Hastelloy C-276 alloy and 16MnR steel was 200mV, the former was the material of tray and the latter was the material of supporting ring in the depropanizer. Therefore, to ignore the galvanic corrosion between them was impossible. The anode corrosion rate of anode area was increased with the enlargement of the area ratio between the cathode and the anode, and with rise of temperature nonlinearly. The temperature differential corrosion was also researched in the thesis. When 16MnR steel exposed to different temperature, the corrosion current of the steel under high temperature region, was raised with the temperature by electrochemical test.The anti-corrosion coatings were optimized in the simulation corrosion solution content of chlorobutane and hydrochloric acid. Glass flake modified by epoxy obtained from Shanghai Xuan Yang Chemical Material Technology Co., Ltd and Ceramic anti-corrosion coating obtained from Jia Dewei Chemical (Shenzhen) Co., Ltd., had better anti-corrosion performance than the other coatings. Also, these two kinds of coatings showed the upmost solvent resistance, so these coatings can be applied in the inner surface of depropanizer. The failure mechanism of glass flake modified by epoxy was studied by electrochemical impedance spectroscopy, and the Bode plots of coating under different stages were analyzed.It was concluded that process reformation and equipment anticorrosion should consider simultaneously. In the aspect of technology, water elimination device, such as molecular sieve device, should be added between high temperature chlorination reactor and liquid inlet of depropanizer to remove water and Hydrogen chloride generated in the tower. In the aspect of equipment anticorrosion, the effective anti-corrosion coating should be coated. Besides, the processing of the depropanizer should consider the anti-corrosion measurement, such as insulation treatment between the tray and the supporting ring of the depropanizer.
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