Who knows how to deal with the problem of excessive temperature rise in hydrocracking reactions

Release pressure, shut down the furnace! ! !!!!!!!!!

1. Cut off the feed to the reaction vessel. 2. Reduce the temperature of the heating furnace (there is no need to shut it down completely). 3. Prevent over-temperature and over-pressure incidents

Possible reasons for excessive temperature rise include: 1. Abnormalities in the reaction heating furnace, resulting in an excessively high outlet temperature； 2. Sudden changes in the amount and properties of raw materials, with a sharp increase in Co and CO2 content in the new hydrogen ； 3. The system pressure drop is high, resulting in a significant reduction in circulating hydrogen ； 4. Failure of rapid cooling hydrogen regulation ； 5. If there is a circulating oil system, there may be significant changes in the temperature of the circulating oil or an interruption in its circulation. Treatment method: 1. If an abnormal temperature rise occurs at any point within the reactor, promptly adjust the temperature at the outlet of the reaction heating furnace as well as the amount of quenching hydrogen, in order to reduce the reactor temperature and bring it back to normal levels ； 2. If any temperature in the reactor exceeds the normal temperature by 15 degrees Celsius, it is necessary to reduce the feed rate urgently, or even stop the feed altogether, and use the rapid cooling hydrogen valve to cool the temperatures at the entrances to each catalyst bed as well as the temperatures within those beds to the levels required before starting up the feed process ； 3. Under normal circumstances, the cooling rate can be slower; the standard cooling rate should be 2 degrees Celsius per 5 minutes. If necessary, the cooling rate can be increased. 4. If venting at 0.7 MPa/min is not sufficient to control the rapid rise in temperature, or if the reaction temperature exceeds the normal value by 28 degrees or reaches 428 degrees Celsius, start venting at 2.1 MPa/min and follow the emergency pressure relief procedure.

I need it too! ! ! :lol

Thermocouples must be regularly calibrated to ensure there are no deviations; their inspection cannot be neglected.

III. Excessive temperature in the catalyst bed The hydrocracking reaction process is generally exothermic. Furthermore, the reaction rate also increases as the temperature rises. Therefore, if the reactor temperature control is inadequate (such as interactions between quench hydrogen and the heat exchangers for feed/effluent in the heater), the reaction rate and temperature will rise spirally. A gradual increase in temperature is usually referred to as an offset. A large temperature deviation with a rapid rise is known as \"surge temperature\". In both cases, since there are no obvious signs of the offset developing into a runaway temperature, the accident handling procedures are the same. Due to the limited position of the thermocouple used to measure the catalyst temperature. Therefore, when flight temperature conditions occur, the phenomenon may sometimes not be obvious. If the reaction temperature is high enough (around 480°C), it can lead to thermal cracking and **increase heat release. If thermal cracking occurs to a significant extent, the reactor bed temperature can rise above 800°C within a few minutes; this has happened before. In the event of a temperature deviation, if the temperature of either bed layer reaches 425°C, quench hydrogen must be used both upstream and downstream of that bed layer. With this method, when the high-temperature reactants reach the downstream bed layer, the temperature is reduced to some extent, and the deviation can be confined to the preceding bed layers. (1) Phenomenon of excessive temperature in the catalyst bed: 1. The temperatures at all points in the catalyst exceed the normal values. 2. The temperature reading at one or several bed layers exceeds the normal value, causing abnormal temperature increases in the temperature readings of the layers below as well. Reason: 1. Low system pressure or reduced amount of circulating hydrogen prevents heat from being carried away. 2. A sudden decrease or interruption in feed and fresh hydrogen results in less cooling material in the system, disrupting the balance and causing overheating. 3. Sudden changes in the composition of the feed oil and fresh hydrogen lead to a sharp increase in reaction heat. 4. The outlet temperature of F-4101 is excessively high. 5. Failure in rapid cooling hydrogen regulation. 6. The catalyst exhibits unstable initial activity, with sudden increases in activity at certain points that intensify the reaction, leading to local overheating and excessive temperatures. 7. Uneven distribution of reaction feedstock or recycled hydrogen across the catalyst surface leads to local overheating and temperature excess. Remedial measures: 1. Regardless of the cause of overheating, it is necessary to immediately reduce the temperature of each bed layer to normal levels or lower ； 2. To address the overall over-temperature of R-4101, a combination of reducing the furnace outlet temperature and using cold hydrogen should be employed to bring down the temperature. If the over-temperature is not severe, it is not necessary to act too quickly in order to minimize damage to the equipment. If the temperature rise is severe (with temperatures at various points in the bed exceeding 5°C), there is a risk of runaway temperature; in such cases, the temperature must be reduced significantly, to 30°C below normal levels. Only after the operation stabilizes can the temperature be increased back to normal. 3. If the temperature at a certain point rises abnormally, it is necessary to apply a two-sided pressure approach to the bed layer where that point is located: while reducing the temperature at the inlet of that bed layer, the temperature at the inlet of the bed layer below it should also be reduced immediately in order to contain this temperature wave. It is better to reduce the temperature further rather than allow the wave to affect the bed layer below. Once this temperature wave has passed, the temperatures of that bed layer and the one below it can be restored to normal levels. If the temperature at a certain point in R-4101 exceeds the normal value by more than 15°C, the likelihood of a sudden temperature spike is very high. In addition to taking the measures mentioned above, it is also necessary to significantly reduce the temperature at the reactor outlet; depending on the situation, the reactor can be shut down automatically to cool it down by 30°C below normal levels, and then the temperature can be increased gradually once stability is restored. 4. If the reaction temperature exceeds the normal value of 28°C at any point or reaches 425°C, the 0.7 MPa/min venting system shall be activated, and emergency pressure relief procedures shall then be followed. 5. The risk of excessive temperature rise in R-4101 is lower than that in the cracking reactor R-4102. If the purification reactor overheats, measures taken should not be excessive, and the temperature should not be reduced too much, to avoid high levels of organic nitrogen in the effluent from poisoning the cracking catalyst. The intensity of treatment for the refined reaction catalyst depends primarily on the heating rate and any changes in that rate. If the rate increases and shows a tendency to keep rising, immediate action must be taken to significantly lower the furnace temperature and introduce more cold hydrogen to curb this increase; adjustments can then be made once the heating rate slows down noticeably. If the heating rate is not fast, first take appropriate measures to lower the temperature at the furnace outlet and introduce cold hydrogen to prevent further temperature rise, after which gradually reduce it back to the normal temperature. Only when the temperature rises significantly should the furnace be shut down and the temperature of the bed layer lowered further. When the temperature of R-4101 rises, the amount of cold hydrogen at the inlet of R-4102 should be increased to counteract the high temperature of the refined outlet and prevent temperature waves from entering the cracking reactor and causing overheating; once the refining process is back to normal, R-4102 can be adjusted back to its normal level. 6. When adjusting the furnace during outdoor operations, care should be taken to adjust the number of burners to prevent the pressure behind the valves from dropping too low, which could lead to shutdown of the furnace. (II) Excessive temperature rise: If the temperature of a certain bed layer reaches around 425°C and continues to rise, this indicates an excessive temperature rise rather than a local hot spot. In such cases, follow these steps: 1. Shut down the reaction heater F-4101 via interlock. 2. Stop hydrogen supply and open the 7 bar emergency relief valve to reduce pressure. 3. Increase the speed of the circulation compressor to ensure that the maximum amount of gas passes through the reactor. 4. Increase the flow rate of quench hydrogen to its maximum value in order to cool the catalyst bed at the downstream end. 5. If the system pressure does not drop fast enough, activate a 14 bar pressure relief. 6. Minimize the bypass flow rate of the feed/outlet heat exchanger. 7. When the pressure drops, open the liquid-controlled valve that connects the hot high-pressure side and the cold high-pressure side, if necessary, to enhance the system’s oil reduction. 8. Once the pressure reaches 3.0 MPa, stop venting to the flare to maintain system pressure. If the temperature remains stable, maintain pressure by adding hydrogen. Otherwise, adhere to the principle of releasing pressure to a slight positive pressure. 9. The recycle gas should continue to circulate, and the longer the better (if the temperature of the reactor outlet is too high, the recycle compressor will be forced to stop). 10. Fractionation and reaction proceed in a cyclic manner; the product is directed to the unqualified tank while the gas is sent to the flare, and the steam injection volume for T4201, T4202, and T4203 is reduced or stopped. 11. The low-pressure gas desulfurization system shuts off the feed gas; the product is directed to the flare line, while the amine solution circulation is maintained ； The liquefied gas desulfurization system is operating normally. Once the temperature is under control, proceed to normal shutdown as soon as possible. If the temperature still cannot be controlled, stop the liquid feed to the reactor and continue to reduce the pressure until all temperatures stabilize. If necessary, when the system pressure is below 3.0 MPa, the reactor is purged with 99.9% pure nitrogen. If the cycle compressor can operate at low load, it can continue to use recycled hydrogen to cool the hot spots of all catalysts at low pressure. On the other hand, before increasing the system pressure to restart the circulator, the hot spots are cooled by a single pass with supplemental hydrogen or nitrogen.

Temperature deviation: For the bed layer where a temperature deviation occurs, increase the flow of cold hydrogen to lower the inlet temperature and adjust the bed layer temperature back to the normal range. At the same time, closely monitor and regulate the inlet temperature of the bed layer below, to prevent any deviation in that layer’s inlet temperature as well. Flight temperature: The 0.7 MPa/min pressure relief system should be activated to reduce the reaction pressure, the furnace should be shut down, new hydrogen supply should be stopped, and feed supply should be halted as appropriate; efforts should be made to keep the recycle hydrogen compressor running. Increase the amount of quench hydrogen to its maximum value, expand the parallel circuits of the feed/reactant heat exchangers, lower the temperature of the stream entering the reactor, and increase the cooling rate. If the temperature rise cannot be controlled, activate the pressure relief system at 2.17 MPa/min to release pressure. At the same time, pay attention to the high and low liquid levels as well as the inlet temperature of the recycle hydrogen to prevent damage to the recycle hydrogen compressor.

Reduce the furnace temperature, increase the flow of cold hydrogen, reduce the reaction rate or even stop feeding material; if that doesn’t work, then shut down the 7 bar venting system urgently

Flight temperature is different from over-temperature. Over-temperature refers to a situation where the temperature suddenly exceeds the normal control temperature by 8°C or the safe design temperature of the reactor. Flight temperature occurs when the temperature goes beyond the controllable range and emergency measures must be taken; the rate of increase in temperature in such cases is usually greater than 56°C per minute, accompanied by intense demethanization reactions. The total temperature rise can exceed 800°C. In modern design, excessive temperature will automatically trigger the high-pressure relief device. It should be operated in accordance with the high-pressure relief procedures; it is imperative to avoid stopping the pressure release midway, as this could lead to secondary overheating and the formation of catalyst hot spots, resulting in more serious consequences such as damage to the reagents and equipment.