Seeking advice from experts in restructuring
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There is a question that has been bothering me: since the raw materials need to undergo pre-hydrodesulfurization before being used, why is it still necessary to add sulfur during the reforming process? It would be great if all the sulfur from pre-hydrodesulfurization could be removed, so that no sulfur would need to be added during reforming
Sulfur injection is intended to maintain the sulfur content in the reaction cycle gas at a certain level, thereby forming a thin film of ferrous sulfide on the pipeline surface, which helps to reduce corrosion of the pipelines. Another point is the passivated catalyst
The amount of sulfur to be injected is determined by testing the sulfur content in the refined oil after sulfur injection; injection can then be stopped. The sulfur content in the raw material is usually over 100, so pretreatment via hydrodesulfurization is necessary to reduce it to 0.5
Sulfur addition is necessary because the sulfur content in the pre-hydrogenated refined oil is too low; therefore, an appropriate amount of sulfur is introduced into the reforming feed to deactivate the catalyst and the metal surfaces of the reactor walls, thereby reducing carbon deposition. The idea of using pre-hydrogenation to control sulfur content after desulfurization is good, but it is very difficult to implement.
The sulfur content of the refined naphtha obtained through pre-hydrogenation must definitely meet the standards; this is probably to avoid corrosion of the equipment
Pre-hydrodesulfurization to below 0.5 PPm is primarily due to the requirements of the reforming catalyst regarding sulfur; high sulfur content in the reforming feed leads to sulfur poisoning of the catalyst, resulting in its deactivation. Sulfur injection is mainly carried out at the start-up of operation; it is not done during normal production. Sulfur injection is intended to suppress the hydrolysis activity of the reforming catalyst in the early stages of operation.
Under normal conditions, sulfur injection is not required during reformation; generally, the sulfur content in the refined oil is controlled. Sulfur acts as a passivator for the catalyst, preventing it from becoming too active and reducing pipeline corrosion. However, the UOP manufacturer provides guidance on a regular basis; it may depend on the reaction conditions. I’m starting to inject sulfur now, and I’ve been doing so continuously; the sulfur injection rate is 0.5 ppm
The purpose of injecting sulfur at the start-up of semi-regenerative reforming is to deactivate the catalyst activity, as Re has a strong hydrocracking capability. Continuous reforming units have been subjected to sulfur injection in recent years, with the requirement that the sulfur content in the feed be kept between 0.25–0.5 ppm; it’s not the case that the lower the sulfur level, the better, as the goal is to prevent carbon deposition on the reactor walls. At present, it is not possible to control the value within the range of 0.25–0.5 during preprocessing; therefore, it is best to remove impurities first and then make appropriate supplements
It is difficult to control the sulfur content in the pre-hydrogenated refined oil at the level of 0.2 to 0.5 ppm required by reforming processes. Ensuring an appropriate sulfur content can prevent coking reactions between the metal in high-temperature areas and the raw materials, thereby providing better protection for the reactor internals.