Quench hydrogen and quench oil in the hydrogenation unit

Hydrogenation units generally use quench hydrogen, primarily to control the temperature of the reactor bed and prevent the reactor from overheating or experiencing excessive temperature rises. As for the amount of quench hydrogen required to achieve a certain temperature reduction, there are too many factors to consider, so it needs to be determined through practical experience

Hydrogen used in hydrogenation is quenched hydrogen, while in coking units quenched oil is used. The quenched hydrogen is actually recycled hydrogen, and its purpose is to control the increase in reaction temperature, preventing excessive temperature rises that could lead to intensified cracking reactions or even temperature spikes, thereby damaging the catalysts and equipment. It’s difficult to determine exactly how much hydrogen is needed for this purpose, as no one has calculated it, and it isn’t really meaningful to do so. (It is related to many factors such as the properties of the raw materials, catalyst activity, and hydrogen purity.) When introducing cold hydrogen, care should be taken not to open the flow rate too much at once; instead, adjustments should be made in small increments to prevent pressure fluctuations caused by drastic changes in the degree of reaction, which could pose safety risks to the equipment.

Large-scale units use quench oil, which is the oil produced as a result of the reaction; Dalian Petrochemical’s 3.6 million tons per year hydrogen cracking facility also makes use of quench oil.

No way. If quench oil is used in hydrocracking, it will result in a too low hydrogen-to-oil ratio. I’ve read that in large reactors, quench hydrogen is generally preferred; quench oil is hardly ever used. If anyone here has information on quench oil, please share it so that we can all learn from it.

I’m hearing about this for the first time; I hope some materials can be shared for reference

In hydrogenation processes, quenched hydrogen is used, while quenched oil is rarely employed; cold hydrogen is generally used in cases of overheating, but the use of oil leads to an increase in raw materials and more reactions taking place

Our diesel hydroprocessing unit is equipped with both cold hydrogen and cold oil; the cold oil actually serves as a bypass for the feed and product heat exchangers, and it does not increase the feed volume. During operation, if the temperature rises slightly, cold hydrogen (circular hydrogen) is used; if the temperature rise is severe, cold oil (feedstock) must be introduced to quickly bring the temperature under control. As for the amount, it is generally controlled based on the flight temperature; no calculation is done for it, and it doesn’t have much practical significance.

I think what was said upstairs implies the opposite idea: for a slight rise in temperature, oil can be used; but if a significant rise in temperature occurs and oil is still used, then with the same ingredients as you mentioned, wouldn’t the reaction be more intense and produce more heat?

I’m not very well-informed; I’ve never heard of using quench oil for hydrogenation. If anyone has relevant information, please share it. During the initial operation of the system, conducting quench hydrogen tests can provide some preliminary data, but it’s only for reference purposes.

Generally, only the term \"quenching hydrogen\" is used; \"quenching oil\" is mostly associated with coking. I guess the quench oil you’re referring to is a bypass line of the high-pressure heat exchanger; in an emergency, it is used to reduce the temperature at the inlet of the reaction furnace, that is, to lower the temperature at the reactor inlet.

There is no quench oil in the hydrogenation unit; only quench hydrogen is available

I have only encountered rapid-cooling hydrogen; I hope those on the 4th floor who have experienced this situation can provide some detailed information on how to use the rapid-cooling oil line and its advantages.

Quench oil has been encountered twice: the quench oil used in the heavy oil hydrogenation (VR) unit at Qilu Petrochemical. The quench oil used in naphtha hydrogenation units, as well as that in the AXENS process package, is all quench oil. Then there’s the heat exchanger bypass mentioned above; that can’t be called quench oil – it should only be referred to as a temperature control bypass line. Since I was there to learn about * and OT devices, I only observed the process of quench oil; I didn’t study its characteristics in detail. I have my own opinions, but since I’m not sure about them, I won’t share them to avoid misleading anyone. Could some expert please explain this???

In my opinion, for hydrocracking, it’s better to use hydrogen. Re-hydrocracking the oil that has already been hydrocracked is not only wasteful and increases costs, but it also leads to deeper cracking, which reduces the yield of liquid products and increases the risk of catalyst coking. With refinement, especially in the case of naphtha and similar substances, there are no drawbacks such as coking or reduced liquid yield, and quench oil can also be used. However, using quench oil requires an additional set of high-pressure pumps and high-pressure pipelines.

Is oil used because it has a high specific heat capacity, allowing for less amount to be used? Or is it because heavy oils such as residue oil are too dense, and using hydrogen for mixing might result in uneven distribution; that’s why oil is used. I’m not sure about this. It’s just my personal opinion – I welcome experts to provide clarification.

In our facility, one set of gasoline hydrogenation uses quench oil, while another set of diesel hydrogenation uses quench hydrogen; the specific reasons for this are not clear. Quench oil is simply low-boiling-point oil that is circulated; the extent to which the temperature of the bed can be reduced by using quench oil depends on various factors such as the processing volume, the quality of the feed oil, and the reaction temperature. However, the installed equipment should undergo an emergency cooling oil test during its first startup, and records of the control valve positions, the cooling oil flow rate, and the temperature drop in the bed layer must all be kept for archiving. The quench hydrogen is the circulating hydrogen at the compressor outlet; the specific requirements for it are the same as those for the quench oil, and the relevant data can be found with the plant’s technical supervisor.

Quench oil is the term used in cracking units. Hydrogenation oil is adding fuel to the fire.