Corrosion inspection of carbon nine cold poly resin plant equipment 2, analysis of corrosion mechanism and discussion of anti-corrosion measures
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This post was last edited by cjhti at 2020-4-9 22:40. Carbon nine cold poly resin is used in reactor 1 and reactor 2. The reaction liquid is taken out by the reaction liquid circulation pump, and part of it is cooled by the low-temperature water in the circulating cooler and returned to the reactor, while the other part enters reactor 2 to continue the reaction. The reaction in reactor 2 is an exothermic reaction. The temperature of the reactor is controlled at about 50-55°C, and the flow rate of low-temperature water flowing into the jacket is controlled by the indicator. The reaction liquid is taken out by the reaction liquid taking out pump. The picture below shows the corrosion inspection picture of reactor 2. The material is the same as reactor 1.
Does the reaction medium contain other harmful media, such as chloride ions, and what is the pH value?
C9 petroleum resin is produced through catalytic polymerization using C9 with a distillation range of 140 to 200°C. The main active components in the C9 fraction include vinyl toluene, indene and carbamate indene. The catalyst used generally uses boron trifluoride or the diethyl ether complex of boron trifluoride. The reaction process generally includes initiation reaction, growth reaction, transfer reaction and termination reaction. After the reaction is completed, the sodium hydroxide solution is used to react with the catalyst to deactivate the catalyst, and is separated from the resin oil through water washing. Boron trifluoride hydrolysis with HF and hydrofluoric acid cold polymerization reactor 1 production parameters: Pressure 0.1MPa ； Temperature 55℃, material: S31603+Q345R ； Composite material, 316 thickness is 3mm.
During use, the medium contains sodium hydroxide, boron trifluoride and hydrofluoric acid after hydrolysis. The pitting corrosion on the lining surface is mainly due to the influence of hydrofluoric acid. We know that when using stainless steel, we must avoid the occurrence of chloride ions. The washing water here should contain chloride ions, which increases the risk of pitting corrosion of stainless steel. In addition, the fluoride ions of hydrofluoric acid will also corrode the surface of stainless steel. Because chloride ions and fluoride ions are elements of the same family, the outer electrons also have 7 electrons, but fluoride ions are more active non-metals than chlorine ions. This is only an analysis based on usage conditions. For specific situations, you can ask a professional company to do a qualitative and quantitative analysis. Come up with solutions.
Teacher Wang, for this situation, what are the better repair measures and preventive measures in the later production process? Thanks
Depending on the reactor temperature being controlled at around 50-55°C, paint coating can be used for repair.
Teacher Wang, according to the current production situation, the inner lining is S31603. How about applying titanium nano-coating on this surface? Or another coating? 1. I have done heat exchanger coating before, but only the coating model. I don’t know whether it is titanium nanometer or other coatings. I will confirm again. Made by Karamay Kobe Anticorrosive Co., Ltd. 2. Are there many domestic manufacturers that can produce titanium nano-coatings? Are there any such manufacturers in Xinjiang? 3. If there is a stirrer in the reactor, will it affect the installation of the mechanical seal of the stirrer and the flushing of the stirrer? 4. The initial plan is to repair by grinding and welding. Coating has not been considered yet. Teacher Wang proposed coating and our unit will discuss it later.