Hydrocracking slow-release agent

Do you mean a corrosion inhibitor? As the name implies, a corrosion inhibitor is used to prevent corrosion; it is generally added at the top of the stripping tower, where the H2S concentration is high

A corrosion inhibitor is a substance that, when added in small amounts to a corrosive medium, can significantly slow down the rate of metal corrosion. Corrosion inhibitors can adsorb on metal surfaces to form a monomolecular water-resistant protective layer. Most corrosion inhibitors possess functional groups containing atoms such as oxygen and sulfur; these polar functional groups adhere to the metal surface, creating a monomolecular protective film. The polar functional groups bond with metal atoms through electron pairs, while the hydroxyl groups in the corrosion inhibitor molecules cover the metal surface, forming the outer layer of this molecular film. This layer separates the metal from the corrosive aqueous environment, preventing contact between the metal surface and acidic substances. It also helps to neutralize acidic components in the fluid, adjusting its acidity and thus serving to protect the metal. Since active sulfur compounds such as H2S present in the distillation system can cause corrosion to the equipment, corrosion inhibitors are added to prevent such corrosion and protect the equipment. In hydrocracking, it is generally injected into the pipeline at the top outlet of the hydrogen sulfide stripping tower, before the air cooler. If the hydrogen sulfide concentration at the top of other distillation towers is high, it will also be injected.

When I went to check it out that day, I only remembered the pipelines at the top of the stripper; there seemed to be another part whose name I couldn’t recall

We also inject at the top of the pre-distillation tower to prevent corrosion by hydrogen sulfide at the tower top

It is generally installed at the top of the stripping tower and the butane removal tower to prevent acidic gases from corroding the equipment

We also have pipelines with corrosion inhibitors for reprocessing; it’s similar to what was mentioned upstairs – they’re located at the top of the distillation tower as well. However, I haven’t seen them being used. I’m not sure why; maybe the corrosion isn’t severe enough?

Corrosion inhibitors are added at the top of the distillation column after hydrogenation in the hydrogenation unit, as well as before air cooling, to prevent hydrogen sulfide from corroding the pipelines.

There are mainly two types: 1. Hydrogenation high-pressure corrosion inhibitors, which are added before high-pressure air cooling, along with water； 2. In the low-pressure section, at the areas subject to wet hydrogen sulfide corrosion, these are mainly the vaporization lines of the hydrogen sulfide removal stripper, regenerator, distillation column, etc

There are three types of corrosion inhibitor action mechanisms: ① Phase-forming film mechanism. Corrosion inhibitors form a protective film on the metal surface through oxidation or deposition, preventing contact between the medium and the metal. ②Mechanism of adsorption membranes. Corrosion inhibitors bind to the active metal centers through physical or chemical adsorption, preventing the medium from coming into contact with these active metal centers, thereby protecting the metal. Physical adsorption refers to the binding of corrosion inhibitors to metal active centers through the attractive forces between molecules or ions ； Chemical adsorption refers to the formation of complexes between corrosion inhibitor molecules and metal atoms, with their hydrophilic groups bonding to the metal and their hydrophobic groups staying away from it. Such corrosion inhibitors are mostly organic corrosion inhibitors. ③Electrochemical mechanism. Such corrosion inhibitors slow down the corrosion of metals by increasing the anodic or cathodic resistance to corrosion. The injection point of the corrosion inhibitor is generally located in the oil and gas outlet pipeline at the top of the hydrogen sulfide removal stripping tower.

Hydrogenation corrosion inhibitors are divided into: high-pressure air-cooling corrosion inhibitors, which are generally sodium polysulfide and are added to water. Corrosion inhibitors for separation towers are generally added at the top of the separation tower and the butane removal tower; they are available in both water-soluble and oil-soluble forms, with a typical addition level of 10–20 PPM.