The specific roles of light and heavy fractions in diesel hydrogenation
Thread Content
Who can explain in detail the role of high and low scores? I know that high and low pressures are both used to separate the three phases, but high pressure is not conducive to the separation of gas and liquid phases, so why is a high pressure level designed?
The oil produced by hydrogenation is first heat-exchanged with the feed oil; after water cooling, it enters a cold high-pressure separator. Following gas-liquid separation, the refined oil is sent to the refined oil buffer tank. The recycled hydrogen coming out of the cold high-pressure separator is mixed with make-up hydrogen, compressed by a recycled hydrogen compressor, and then sent to be mixed with the feedstock for use as cold hydrogen. Most of the gas separated at high pressure is re-suppressed using a recycle hydrogen compressor and then returned to the system for use as \"recycle hydrogen\". "Most of the recycled hydrogen is mixed with the feed solvent oil and fed into the reaction system to maintain the desired \"hydrogen/oil\" ratio, remove the heat generated by the reaction, and help keep the reaction temperature stable ； A small portion of the exhaust gas is also sent out from the high-pressure separator outlet through a pressure-reduction system and can be used as fuel; by adjusting the amount of exhaust gas sent out, it is possible to maintain the purity level of the hydrogen circulating in the system.
Reply 1# whatsmore: The high-pressure separator is used for circulating hydrogen; oil is produced as a result of reactions, and sulfur-containing wastewater is separated. The circulating hydrogen returns to the compressor inlet where it is pressurized for reuse. The oil produced goes to the low-pressure separator, where acidic gases are separated, and oil is again produced as a result of reactions; sulfur-containing wastewater is separated there as well. The gaseous phase separated at low pressure contains hydrogen sulfide and some light hydrocarbons, while the oil produced undergoes distillation. If separation is carried out at low pressure, due to the low pressure, impurity gases such as hydrogen sulfide are present in the gas phase; as a result, the hydrogen purity in this gas is low. If such gas is to be recycled back into the reaction system, it must be pressurized using a compressor, which increases the load on the new hydrogen generator and lowers the hydrogen partial pressure in the system. I’m not sure if you understand what I mean
High pressures are necessary in order to be able to control the pressure of the reaction system; otherwise, it’s not possible to maintain a certain hydrogen partial pressure. High pressures are certainly not conducive to gas-liquid separation, so another stage with lower pressure is set up for flashing and separation. The hot, high-pressure stream enters the tower, so there’s no need to worry about separation issues. Additionally, water needs to be added to the reaction system, so the high-pressure stream can remove some of the water, while all the water in the low-pressure stream is removed in the end
Thank you for the answers from the people above; I now understand that a high design value is intended to increase the hydrogen concentration in the recycled hydrogen and reduce the content of sulfur-containing gases, while a low value serves to separate acidic gases.
A high design value is intended to increase the hydrogen concentration in the recycled hydrogen and reduce the content of sulfur-containing gases, while a low value serves to separate acidic gases.
High scores ensure the release of hydrogen, while low scores further release some of the hydrogen sulfide and acidic gases, thereby reducing corrosion in subsequent processes
It is said that it can also save energy and reduce the need for cooling equipment.
Due to the high pressure in the high-pressure fraction, a large amount of hydrogen dissolves into the oil. After going from the high-pressure fraction to the low-pressure fraction, the gas in this lower pressure fraction not only contains acidic gases but also a significant amount of hydrogen; therefore, this low-pressure gas is highly valuable for recovery. Our facility sends this low-pressure gas to hydrocracking for further recovery and reuse
Reply to 9# james_jyj1001: The hydrogen concentration in the low-pressure sulfur-containing gas is already very low. Are there any additional steps needed before it is sent to hydrocracking?
Reply to 10# whatsmore: Before carrying out cracking, the hydrogen in the low-pressure gas needs to be purified using methods such as membrane separation or PSA; the purity of the hydrogen required for cracking should be over 95%