The moisture content in the heat exchanger fluid is above the acceptable level, resulting in its disposal after short-term use

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This post was last edited by Wang Wei2 on 2024-1-25 at 10:09. Excessive water content in the heat exchanger fluid led to its premature failure after short-term use. Example: In a PVC production plant, the converter used was a tubular heat exchanger; both the shell and the tubes were made of carbon steel, with the tubes joined to the tube sheet by expansion fitting. Acetylene gas and hydrogen chloride gas pass through the converter from bottom to top after being mixed and dehydrated, thereby undergoing an addition reaction to produce vinyl chloride gas. The reaction temperature is 120~180°C. Leaks began to occur after more than 1 year of use, with the longest duration being 18 months and the shortest being less than 13 months. The main cause of corrosion is water in the feed gas. Secondly, the quality of the hot water in the shell side is poor, with a low pH value and high chloride ion content. Analysis: Carbon steel exhibits good corrosion resistance in dry, high-concentration hydrogen chloride gas, with a corrosion rate of 0.05–0.5 mm/year; however, when the hydrogen chloride gas contains more than 0.02% moisture, the corrosion rate increases rapidly. Similarly, carbon steel is also corrosion-resistant in chlorine with extremely low moisture content (including liquid chlorine), whereas moisture in chlorine causes severe corrosion of carbon steel. Therefore, for carbon steel equipment used to handle dry chlorine (liquid chlorine) and hydrogen chloride gas, it is extremely important to control the moisture content.