Frequent high-temperature alarms in the continuous reforming reduction zone caused a CCR interlock

As the temperature difference decreases, the natural reformation reaction becomes less efficient, and the aromatic content at the bottom of the tower decreases. As the original poster said, it’s because the activity of the catalyst has decreased. On the other hand, it’s related to the composition of the feed material; perhaps the material has become lighter, which has led to a decrease in the temperature difference. Additionally, it’s necessary to check whether the catalyst has sintered properly and whether its carbon content is too high. As for the interlock due to excessively high temperatures in the reduction section, we sometimes encounter such problems as well. Usually, we check the carbon content of the regenerated catalyst, and also determine whether there are issues with the flow of the catalyst inside the reduction section; increasing the catalyst circulation rate might help.

This post was last edited by Golden Sunshine 1974 on 2012-8-17 at 12:55. There are no abnormalities in catalyst charring or circulation; the thermocouples in the reduction zone have also been calibrated numerous times. The temperature and flow rate of the reducing gas are within normal ranges, with the highest carbon content in the catalyst being only 5.0% (in order to increase the load on the facility, we used raw materials with a lower composition than before, ranging from 80 to 158, in order to reduce the catalyst’s carbon content). We also tried adjusting the catalyst circulation rate, but with little effect. Strangely enough, even after the interlock system turned off the electric heater due to a high temperature alarm of 549 degrees in the reduction zone, the temperature there continued to rise, reaching up to 580 degrees. We conclude that there is indeed a phenomenon of excessive temperature rise in the reduction section; poor reduction efficiency leads to a decrease in catalyst activity, which affects the reforming reaction, and the purity of the recycled hydrogen is also as low as 82%； It was said upstairs that abnormal flow of the catalyst in the reduction zone causes this phenomenon; is it a blockage in the material leg? However, the level fluctuations in the reduction zone are very small. If there are abnormalities in the flow of the catalyst in the reduction section, it would lead to significant fluctuations in the level of material in that zone. Could you please provide more details on the results of your investigations into the causes when an alarm for high temperature in the reduction zone was triggered in your facility? In my opinion, the recent abnormalities in the system might be related to the insulation we added to the pipelines used for transporting the regenerated catalyst. In previous winters, the temperature in the reduction zone would often trigger a low-temperature interlock at around 400 degrees. To save energy, the company installed insulation on these pipelines in order to raise the temperature of the catalyst as it entered the reduction zone. Although the low-temperature interlock problem no longer exists, during summer the temperature in the reduction zone tends to cause high-temperature interlocks. I once read an article stating that according to UOP’s experience, using cold reforming catalysts in the reduction section yields the best results. However, I’m not sure what the appropriate temperature should be for reforming catalysts entering the reduction zone. I hope fellow experts can help analyze this issue. O(∩_∩)O Thank you!

If the reaction temperature drops suddenly, the most likely cause is a change in the quality of the raw materials; changes in catalyst activity lead to such drops, either due to poisoning or for some other reason. Of course, there are other possible explanations as well. I wonder whether, along with a decrease in the octane rating of your product, the hydrogen production also decreases significantly – by a large margin – and whether it never returns to its previous level after that drop. As for the high-temperature interlock in the reduction zone, I haven’t encountered it before. But for the regeneration lift pipe, insulation is required according to the design; I’m not sure why yours isn’t insulated. The lift gas pressure is 150, and the lift pipe has a high-temperature interlock – if I remember correctly, it’s set at 220. If your riser design does not include insulation, then dechlorinated hydrogen should be used. If the temperature in the reduction zone rises, there must be a hydrocracking reaction occurring; check whether the olefin content in the hydrogen is high. What type do you use for the feed heat exchanger, from that manufacturer?

The temperature rise in the reduction zone is mainly caused by the hydrocracking of hydrocarbons with C2+ composition under the high-temperature and hydrogen-rich conditions in that zone, which releases a large amount of heat. This issue can be addressed from the following three aspects: (1) Using higher-purity hydrogen for reduction in order to increase the purity of the reducing hydrogen. (2) Check the operation of the hydrogen-lifted condensate tank to determine whether there is any internal damage to the tank, and whether the orifice plates in the lower pipelines are blocked, which could result in a high level of hydrocarbons in the tank; as a consequence, some of these hydrocarbons may be carried along with the lifted hydrogen to the reduction zone. (3) Control the amount of reducing hydrogen to prevent the reaction gas from flowing back into the reduction zone.

Without actual trend charts, a detailed analysis is not possible! But it’s certain that there are problems with the technical management of the LZ device! You can look throughout the entire device to identify where there are instabilities, and then determine what the root cause is!

Check whether there are any issues with the coalescer; this will help determine whether components with high reactivity are entering the reduction section. What is the temperature of the hydrogen entering the coalescer? If the temperature is high, the heavier components will also be present in it.

This post was last edited by Golden Sunshine 1974 on 2012-8-19 at 12:27. The hydrogen gas we use for reduction has not been dechlorinated, and the temperature is at room temperature, around 35 degrees. The filter elements in the hydrogen condensation filter were replaced last year (we replaced them when there were issues last year); the design of the regeneration pipeline does not include any insulation, with a designed temperature of 177 degrees, but it has now dropped to 165 degrees. As mentioned by someone on the fourth floor, there are olefins present in the hydrogen gas used for reduction. Indeed, we observed an abnormal increase in the propylene content in the recycled hydrogen gas, rising from the normal level of 0.03% to 0.14%. It is preliminarily assumed that foam is being carried along with the gas in the product separator, resulting in small amounts of olefins and light components ending up in the recycled hydrogen gas. To address this issue, we have adjusted the load on the plant as well as the hydrogen-to-hydrocarbon ratio, in an attempt to reduce the gas flow rate in the product separator below the critical value in order to prevent foam from being carried along. However, these efforts have not yielded satisfactory results. Regarding the suggestion on the fifth floor to upgrade the orifice plate at the bottom of the hydrogen condensation filter, we also checked for liquid hydrocarbons by draining fluid, and it seems to be unobstructed ； The pressure difference in the reduction section is also kept relatively stable at 1.5 KG/CM2, preventing the reactant stream from rising to the reduction section. The question now is whether it is the problem with the defoaming screen of the product separator that affects the reforming reaction and subsequently impacts catalyst reduction, or whether poor catalyst reduction affects the reforming reaction. If hydrogenolysis occurs during the reduction stage and leads to a rise in temperature, it is possible to try reducing the load, decreasing the severity of the reaction conditions, and improving the purity of hydrogen in order to enhance the reduction reaction. However, if the issue really lies with the defoaming screen, then the only option is to shut down the plant for maintenance.