| Popis: |
Ammonium chloride precipitation is a widely-known problem in various units of many oil refineries. Precipitation can cause severe problems by clogging and fouling process equipment, heat exchangers, column trays, etc. One of the widely-used solutions to this problem is to add some water into the process stream in order to dissolve the precipitates. However, the addition of water into the process stream may cause some new problems. Process design and materials selection are normally carried out assuming that the process stream contains no water. The addition of water into the stream can drastically change the corrosivity of the process solution, resulting in heavy corrosion. In some unit processes, it is impossible to remove the chlorides and nitrogen compounds which cause this problem. Thus, in most cases, the only effective and economical way to combat corrosion is by materials selection. In this study, the corrosion behaviour of various materials in ammonium chloride-containing environments has been investigated. Practice has shown that the addition of water can increase the corrosion rate of mild steel about 100 times. Laboratory tests were made in order to screen potential highly-alloyed materials. |
