Problem resolution for diesel hydrogenation units
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The 300,000 tons per year diesel hydrogenation unit that was newly commissioned in our plant this year has been experiencing a significant amount of oil in the gas stream from the high-pressure separation tank since it started operating (about 3 to 5 tons per day). All process parameters such as pressure, temperature, and flow rate remain stable, the product quality is good, and the system is stable. However, the issue of oil in the gas stream is quite troubling for us; could it be a problem with the demisting screen? Why? Please analyze how to handle this effectively without stopping the vehicle.
Is it a high score in cold conditions? Is the circulation volume high? It is recommended that you lower the high-level liquid level
It’s possible that, as mentioned upstairs, the liquid level control is set too high; you might try setting it at a lower level. If it has little to do with the liquid level, check whether the temperature of the high-viscosity oil isn’t low enough after cooling, causing some light hydrocarbons to be carried away? Let’s take a look at these first; the data you provided is too little
Try reducing the high-temperature setting or appropriately lowering the speed of the cyclohydrogen compressor
Reduce the post-cooling temperature and decrease the space velocity. Take the analysis of the circulating gas composition; if maintenance is involved, check the catcher
We have also encountered situations where high scores were not achieved in the liquid phase; the solution we adopted was to reduce the reaction temperature by 2 degrees； First reduce the hydrogen-to-oil ratio, then restore it ； Increase the purity of recycled hydrogen. Cause analysis: The presence of liquid in the high-pressure section is due to an excessive amount of gas and a too high flow rate; as a result, the liquid cannot be properly separated, causing the gas to carry liquid phase into the liquid separation tank at the inlet of the circulator. Currently, hydrogenation catalysts used for processing low-quality oils possess a cracking capacity of around 10%, which results in the production of large amounts of light components. The hydrogen-liquid separation capabilities of these catalysts are not sufficient to handle this situation, leading to liquid accumulation in the recycle gas. In severe cases, the liquid inside the high-pressure container separates into layers, which can be observed in a glass plate. Lowering the temperature mainly reduces the reaction depth and weakens the cracking reaction. Reducing the hydrogen-to-oil ratio is intended to temporarily decrease the flow rate of the circulating gas, which is then restored once the liquid accumulation in the circulating gas is resolved. Improving the purity of recycled hydrogen mainly involves reducing the amount of high-molecular-weight gases in the recycled gas and improving the temperature distribution within the catalyst bed. If the liquid to be treated is too severe, it is necessary to temporarily reduce the load and operate at a lower reaction intensity.