Temperature for isothermal dehydrogenation in diesel hydrogenation

Generally around 250 degrees and 20 kfg/cm2

Around 250 degrees, 2.5 Mpa

This does not mention the temperature of the oil in the constant-temperature zone.

Isothermal dehydrogenation has only been adopted in recent years, which indicates that there has been a deeper understanding of hydrogen corrosion. Principle of isothermal dehydrogenation: Hydrogen molecules are small; at high temperatures, as the steel expands due to heat, these hydrogen molecules penetrate into the crystal structure of the steel. When operation stops and the temperature drops, hydrogen molecules combine with carbon molecules to form methane. Methane molecules are larger and cannot escape from the steel’s crystal structure, which leads to cracks in the steel. This is extremely dangerous for medium-pressure hydrogenation units; therefore, isothermal dehydrogenation is necessary. The medium used is an inert gas, usually nitrogen. The pressure requirement is primarily determined by the operating conditions of the circulating compressor; it is generally between 2.0–3.0 MPa, with the compressor operating at full capacity ； The temperature is generally divided into three stages: 275°C, 250°C, and 225°C, with each temperature being maintained for 8–24 hours; the duration of this constant-temperature period can be extended appropriately depending on the hydrogen content in the circulating gas. During the operation, first remove all the oil and gas from the catalyst bed, then purge the system with nitrogen – generally until the hydrogen content is below 10%, and ideally below 0.5%. After that, start the isothermal dehydrogenation process; be sure to keep the cooling rate slow during this step! 5-10℃/h! This will result in a better dehydrogenation effect. Generally, about 10-15% (v) can be recovered. I have been working in hydrogenation for many years; feel free to write to me to exchange ideas!