The application of the metal element rhenium in equipment

09Cr2AlMoRE exhibits good resistance to chloride and sulfide stress corrosion, as well as a certain level of resistance to uniform corrosion; it is primarily used in tower top condensers and air coolers. Heat exchangers manufactured using longitudinal flow mixed tube bundles made of 09Cr2AlMoRE material can not only address the corrosion issues caused by H2S and HCl in petrochemical plants, but also enhance heat transfer and achieve efficient energy savings.

On the application scope of 09Cr2AlMoRE – Shu Runtao, Wuhan Runzhi Da Petrochemical Equipment Co., Ltd. 09Cr2AlMoRE is a special steel resistant to wet H2S corrosion; it is a new steel grade developed by utilizing the corrosion-resistant elements Cr-Al-Mo in low-alloy form, as well as the micro-alloying effect of rare earth elements in steel. It exhibits excellent resistance to stress corrosion and uniform corrosion in H2S-containing environments. 09Cr2AlMoRE steel tubes and forgings are mainly used to manufacture tube bundles for heat exchangers and air coolers. The 09Cr2AlMoRE steel heat exchangers have been successfully used in over 40 petrochemical enterprises, and extensive practical experience has been accumulated through their use. In line with a commitment to responsibility toward products and users, the scope of use for this steel is defined as follows: Since 09Cr2AlMoRE is a new steel grade developed specifically for resistance to hydrogen sulfide corrosion, it is suitable for use in corrosion environments containing H2S at any concentration. In liquids, it isn’t the higher the H2S content that leads to more severe corrosion. When H2S is between 50 and 1600 ppm, corrosion intensifies as the concentration increases; when H2S ≥ 1600 ppm, the corrosion rate gradually decreases. The corrosion of 09Cr2AlMoRE by H2S takes the form of slow, uniform corrosion, and it is not sensitive to stress corrosion. I. This steel is primarily suitable for use in environments with wet hydrogen sulfide, acidic water, and hydrogen corrosion; it should be used in the following types of conditions: 1. Hydrogen sulfide corrosion environments with a low amount of chloride ions (≤300 ppm), such as at the top of atmospheric pressure towers. It is not recommended for use if the chloride content is higher than 300 ppm. 2. Hydrogen sulfide corrosion environment containing HCN: 09Cr2AlMoRE is suitable for use in corrosion environments with HCN levels ≤500 ppm. 09Cr2AlMoRE is suitable for use in the condensers of catalytic absorption stabilization systems (HCN-H2S-CO2-H2O). 3. CO2 in liquid media: 09Cr2AlMoRE is suitable for use in low-temperature (≤120°C) corrosive environments with any concentration of CO2. Corrosion caused by CO2 in a liquid medium is not severe, and CO2 in its gaseous state causes almost no corrosion. 4. High-temperature hydrogen corrosion: 09Cr2AlMoRE exhibits excellent high-temperature properties; in hydrogenation systems, it shows outstanding resistance to hydrogen corrosion, hydrogen blistering, and hydrogen-induced cracking. 5. Corrosion in wastewater treatment systems: Although the acidic water in wastewater treatment systems still contains chloride ions, carbon dioxide, and alkaline amines, the high concentration of sulfides present in the wastewater allows for the formation of a complete S-Cr-Al-Fe protective film on the metal surface. As a result, this material exhibits good performance in acidic water environments, which is different from the corrosion conditions at the top of atmospheric pressure towers (where there is a gas-liquid interface) as well as from the corrosion conditions in circulating water (where no protective film can be formed). 6. It can be used in circulating water, but the erosive damage caused by chloride ions to the pipe ends must be taken into consideration. In circulating water, the main sources of corrosion are oxygen depolarization corrosion resulting from the concentration cell formed by dissolved oxygen in the aqueous and scale phases, as well as erosion and stress corrosion caused by Cl‑ ions in the water. In some circulating waters, the Cl‑ ion concentration exceeds 100 ppm, and the presence of large amounts of biological sludge and solid particles also leads to erosion corrosion on the surfaces of pipe welds. To prevent the circulating water from causing erosive damage to the pipe ends, the tube sheet surface of these pipe ends should be coated for protection. Note: Media with severe corrosion should be placed on the tube side. II. 09Cr2AlMoRE steel is not suitable for use in the environments found in oil refining plants. 1. Since 09Cr2AlMoRE steel is highly sensitive to high-temperature alkalis, its use is not recommended in any environment with temperatures above 90°C. Specifically as follows: a. In the reboiler of the decarburization system in the hydrogen production plant, both bubble corrosion caused by the potassium carbonate alkaline solution and alkali embrittlement occur simultaneously at this location. b. The rich and lean liquid heat exchangers and reboilers in the desulfurization system: Methyl diethanolamine (MDEA) or ethanolic amine (RNH2) readily react with oxygen (O), partially converting to formic acid. At temperatures above 100°C in the reboilers, the scouring corrosion caused by formic acid bubbles is quite severe; uniform corrosion also increases significantly. Moreover, at temperatures above 90°C, alkali embrittlement due to ammonia formation is likely to occur. The combined corrosion of acids and alkalis, along with cavitation corrosion, present on the reboiler have a significant destructive effect on this material. 2. This steel cannot be used in an environment subject to corrosion by high-temperature naphthenic acids. 3. This steel is not suitable for use in corrosive environments with sulfuric acid dew points. No product is perfect; it always has its own limitations. Although 09Cr2AlMoRE has good corrosion resistance, it remains a low-alloy steel, so its inherent corrosion resistance is still limited. It can address the stress corrosion problem that is difficult to overcome in austenitic stainless steels; however, in high-temperature sulfur-corrosive environments, its resistance to high-temperature sulfur corrosion and erosion corrosion remains inferior to that of stainless steels. Its ability to resist uniform corrosion in hydrogen sulfide-corrosive environments is more than 5 times better than that of carbon steel, but its good corrosion resistance is still relative. This steel is not resistant to corrosion in high-temperature corrosive environments involving naphthenic acid (RCOOH≥230°C), and its use is not recommended.