Attention should be paid to the formation of organic acids and corrosion in the petrochemical reforming extraction system
Thread Content
Attention should be paid to the formation of organic acids and corrosion in the petrochemical reforming extraction systems. The solvents used for solvent extraction, such as triethylene glycol ethers or diethylene glycol ethers, do not cause corrosion to the equipment themselves; however, when they come into contact with the small amounts of air present in the system, they gradually oxidize and deteriorate, forming organic oxidized compounds such as aldehydes, ketones, or acids. Under prolonged operation, the solvent experiences an accelerated oxidation rate in high-temperature and acidic conditions. The organic acids produced cause equipment corrosion and clogging of the sieve pores. The areas affected by corrosion include the gas-water and solvent heat exchangers, the reboiler at the bottom of the stripping tower, and the feed heater of the vacuum distillation tower. The high content of olefins in the raw material is the main factor causing acidification of the system solvent. It should be noted here that hydrogen sulfide corrosion occurs in alkaline solutions, while chloride ions do not cause corrosion in such an environment. Chloride ions cause corrosion in acidic solutions, whereas hydrogen sulfide does not cause corrosion in acidic solutions. HIC (hydrogen-induced cracking) mostly occurs under acidic conditions, but it also occurs under alkaline conditions. Chloride ions corrode stainless steel under acidic conditions, but they do not cause corrosion in stainless steel under alkaline conditions.
In the reforming and extraction systems of the petrochemical industry, the formation of organic acids and corrosion issues must be given due attention. Generally, the solvents used—such as triethylene glycol ethers or diethylene glycol ethers—are not corrosive to the equipment itself, but when they come into contact with the small amount of air present in the system, they may gradually oxidize and produce organic oxygen-containing compounds such as aldehydes, ketones, or acids. The formation rate of these compounds increases under high temperature and acidic conditions. The organic acids resulting from this can corrode equipment and clog the sieve pores; common sites of corrosion include gas-water and solvent heat exchangers, the reboiler at the bottom of the stripping tower, and the feed heater in the vacuum distillation tower. Furthermore, if the olefin content in the raw material is too high, it may also become a major factor in the acidification of the system solvent. It is worth noting that the corrosion caused by hydrogen sulfide occurs mainly in alkaline solutions, whereas in such environments, chloride ions do not cause corrosion. On the contrary, chloride ions may cause corrosion in acidic solutions, whereas hydrogen sulfide does not. The hydrogen-induced cracking (HIC) problem is more common under acidic conditions, but it can also occur under alkaline conditions. Under acidic conditions, chloride ions may corrode stainless steel, but not under alkaline conditions. Therefore, to avoid corrosion by organic acids, it is necessary to regularly inspect and maintain the equipment, and to ensure that the solvents and raw materials used are processed and handled under appropriate conditions. At the same time, it is also necessary to monitor the acidity and alkalinity in the system, as well as the presence of hydrogen sulfide and chloride ions, in order to prevent potential corrosion issues. .