For high-nitrogen, low-sulfur feedstocks processed in hydrogenation refining units, what aspects should be considered during long-term operation?

High-nitrogen oils require an operating hydrogen partial pressure at a high level to achieve better denitration results. The raw materials used in your facility are of good quality; be careful to control the float level properly to avoid salt accumulation that could block the floats and lead to false signals

The pressure of a standard device is related to the equipment itself, and it cannot be adjusted much. For production units, it is also not possible to adjust the space velocity too much. The most common method is to adjust the temperature; as long as the temperature meets the requirements for nitrogen removal, that’s sufficient. Excessively high temperatures are detrimental to the catalyst, and in some cases they can even affect the efficiency of nitrogen removal

There are still such low sulfur levels these days! Where does the residue oil you use for coking come from? Not much hydrogen is required for the hydrogenation of this oil; however, an oil of such high quality may not be easy to work with. The temperature rise is likely to be low. It’s more economical and profitable to mix in some oil with a higher sulfur content

Firstly, high-pressure hydrogen pipelines are designed to prevent nitrogen salts from crystallizing and blocking the pipelines, especially in the heat exchanger areas, by increasing the amount of water used for washing the reaction products； Secondly, the pH value of sulfur-containing wastewater with high or low acidity, as well as that of the wastewater in the reflux tank at the top of the distillation tower, may be above 8. While preventing sulfides from causing equipment corrosion, attention must also be paid to nitrogen salt crystallization. In particular, the corrosion inhibitors added at the top of the distillation tower are all weakly alkaline chemical agents (in some cases, ammonia salts are added to make them weakly alkaline in order to reduce costs); therefore, such inhibitors should be added in small quantities or after being heavily diluted. It is best to add them in intermittent doses after thorough dilution, in order to avoid an increase in ammonia salt crystallization due to the addition of these inhibitors, which could lead to blockages in air coolers or condensers. Finally, strengthen monitoring of the sulfur-containing wastewater in the following areas and conduct analyses (for iron ions, nitrogen content, sulfur content, chloride content, and pH value); adjust the amount of water injected as well as the amount of corrosion inhibitor added intermittently based on these analyses.

The properties of your raw materials are very similar to ours; we recommend that you first choose the right refined catalyst. Based on our experience, the FH-98 catalyst is a quite good option. Secondly, strengthen the management of raw materials: 1. Where possible, install nitrogen blanketing in the raw material storage areas ； 2. Strengthen raw material filtration; it is strictly prohibited to operate the filter without a connecting line. Additionally, the temperature rise across the reactor beds should be distributed reasonably; generally, it is necessary to keep the temperature rise in each bed similar, with all beds increasing simultaneously when the reaction temperature is raised. Also, when loading the catalyst, it is best to replace the ceramic balls at the top with active support agents.

There are really few S’s. I believe that the fouling of the catalyst bed caused by dienes in coker gasoline, which leads to an increase in pressure drop, could be a factor affecting long-term operation. The current catalyst grading and packing scheme can handle this issue effectively; however, if the diene content is very high, a diene saturation reactor is needed, one that uses lower temperatures of around 140–240 degrees to saturate the dienes

The hydrodesulfurization reaction is somewhat different from hydrodenitration, as both hydrodesulfurization and hydrodenitration are exothermic reactions. From a thermodynamic perspective, higher temperatures are unfavorable for the reaction equilibrium; however, lower temperatures are unfavorable from a kinetic perspective. Therefore, we choose temperatures and pressures that represent a balance point – one that is favorable from both thermodynamic and kinetic points of view. Among these factors, thermodynamics has a more significant impact on denitration compared to desulfurization. Thus, in denitration processes, it’s not necessarily true that higher temperatures lead to better denitration results.

In my opinion, it is mainly due to the crystallization of ammonium salts and the reaction between hydrogen sulfide and NH3 to form ammonium sulfide

What aspects are there regarding static and dynamic equipment? Colleagues.

When processing such raw materials, it is necessary to regularly monitor the hydrogen sulfide concentration in the circulating hydrogen. If this concentration falls below 500PPM, sulfurizing agents must be added periodically to restore the catalyst’s activity; otherwise, prolonged loss of sulfur in the catalyst will affect its efficiency

1. Use a highly efficient catalyst. 2. Appropriately reduce the space velocity. 3. Increase the reaction temperature.