【Q&A Question 074】March 15, 2018
Thread Content
This post was last edited by Internet Invisible Man on 2018-3-15 at 13:44. [Q&A Question No. 074] 2018.03.15: Briefly describe the impact of pressure on hydrorefining Since the hydrogenation reaction is a volume-reducing reaction, increasing the pressure is beneficial to the reaction, with the most significant effect on nitrogen removal. For the catalyst itself, higher pressure reduces carbon deposition, thereby extending its lifespan; however, excessively high pressures increase the operating costs associated with equipment investment. (Unless otherwise specified, all questions and answers are based on hydrogenation units.) ) Due to the limitations on the number of posts in the “One Question per Day” section, “One Image per Day” has been moved to the registered devices section; you can access it through the directory I posted. For management purposes, if you need to access content from a few days ago, please go to the summary post below to enter the “My Registration Season” event – (Note: This event is currently underway in the Chemical Engineering section). https://bbs.hcbbs.com/forum.php?mod=viewthread&tid=18978 For the daily questions section related to chemical engineering technology training in 2018: https://bbs.hcbbs.com/forum.php?mod=viewthread&tid=1888971 For the daily image summary section related to registration equipment in 2018: https://bbs.hcbbs.com/forum.php?mod=viewthread&tid=1888970 For the Q&A section related to hydrogen production and hydrogenation technologies in 2018: https://bbs.hcbbs.com/forum.php?mod=viewthread&tid=1888968 For the daily questions section related to LNG technology in 2018: https://bbs.hcbbs.com/forum.php?mod=viewthread&tid=1888973 For the Q&A section from 2017 (updates have started): https://bbs.hcbbs.com/thread-1657793-1-1.html For the daily questions section from 2017 (updates have started): https://bbs.hcbbs.com/thread-1657794-1-1.html For the daily image summary section from 2017: https://bbs.hcbbs.com/forum.php?mod=viewthread&tid=1875160 For the list of daily questions related to LNG in 2017: https://bbs.hcbbs.com/forum.php?mod=viewthread&tid=1804162 For the Q&A section from 2016 (all updates completed): https://bbs.hcbbs.com/thread-1597792-1-1.html
Answer: Since the hydrogenation reaction is a reaction that increases volume, increasing pressure is beneficial for the reaction, with the most significant effect on nitrogen removal. As for the catalyst itself, higher pressure reduces carbon deposition, thereby extending its lifespan. However, excessively high pressure increases the operating costs associated with equipment investment.
The control of reaction pressure depends on factors such as the equipment’s capacity, the required degree of hydrogenation, and the amount of hydrogen to be added. The effect of pressure on the reaction is achieved through hydrogen partial pressure. Increasing the hydrogen partial pressure of the system can accelerate the hydrogenation reaction, as well as the rates of desulfurization, denitration, and olefin saturation. Therefore, after increasing the pressure, the resulting product has a low bromine value, contains fewer sulfur and nitrogen compounds, and exhibits good oil stability. At the same time, increased pressure can also suppress coking in the bed, which helps maintain catalyst activity and improve its stability. The adjustment of reaction pressure must be based on the guarantee of product quality; reaction pressure can be increased by increasing the amount of fresh hydrogen, reducing the reaction temperature, or decreasing the space velocity.
Increasing the reaction pressure enhances the depth of hydrorefining, which is beneficial for both hydrodesulfurization and hydrodenitration, but the degree of impact on each is different. Increasing the reaction pressure significantly improves the denitrification rate, but has little effect on the desulfurization rate. The main reason is that the denitrification rate is low while the desulfurization rate is high; at lower pressures, there is sufficient time for desulfurization to occur. The selection of reaction pressure is related to the properties of the feedstock; the higher the nitrogen and aromatic content in the feedstock, the higher the reaction pressure required. An excessively high hydrogen partial pressure leads to increased equipment investment, as well as higher operating costs. Therefore, the reaction pressure should be determined based on the requirements of the target product and the properties of the raw materials used in the processing.
The effect of reaction pressure is manifested through the hydrogen partial pressure, which in turn is determined by the operating pressure, hydrogen-to-oil ratio, purity of the recycled hydrogen, and the gasification rate of the feedstock. The reactions of hydrogen desulfurization of sulfur-containing compounds and hydrogen saturation of olefins proceed rapidly, achieving high conversion rates even at low pressures ； The hydrogenation denitration reaction of nitrogen-containing compounds is slow; therefore, the reaction pressure must be increased or the space velocity reduced to achieve a certain degree of denitration. For aromatic hydrocarbon hydrogenation reactions, increasing the reaction pressure not only improves the conversion rate but also enhances the reaction rate.
Since the hydrogenation reaction is a reaction that results in a decrease in volume, increasing the pressure is beneficial for the reaction; this effect is most noticeable in terms of nitrogen removal. For the catalyst itself, higher pressure reduces carbon deposition, thereby extending its lifespan. However, excessively high pressures increase the operating costs associated with equipment investment.
The higher the pressure, the greater the depth of the reaction.
Answer: Since the hydrogenation reaction is a reaction that increases volume, increasing pressure is beneficial for the reaction, with the most significant effect on nitrogen removal. For the catalyst itself, higher pressure reduces carbon deposition, thereby extending its lifespan; however, excessively high pressure increases the operating costs associated with equipment investment.
This post was last edited by Xin Zai Tian Bian on 2018-3-15 at 10:58. It’s good to review old material to gain new insights: 1. Pressure is one of the main control parameters in the hydrogenation process, and it is generally represented by the hydrogen partial pressure. It usually depends on factors such as the hydrogen-to-oil ratio of the system, the purity of the circulating hydrogen, and the gasification rate of the feedstock in the bed. II. Increasing the hydrogen partial pressure is beneficial for the hydrogenation reaction. 1. Hydrorefining is usually a volume-reducing reaction; increasing the pressure promotes the reaction to proceed in the desired direction, thereby accelerating it. 2. Increasing the hydrogen partial pressure can improve the removal rate of impurities such as sulfur, nitrogen, and metals, and promote the hydrogenation saturation reaction of polycyclic aromatics. 3. An increase in hydrogen partial pressure can suppress coking reactions and protect the catalyst. III. When the material is in liquid phase within the bed layer, increasing the system pressure is not favorable for the reaction. (At this point, it is necessary to rely on increasing the hydrogen-to-oil ratio and raising the hydrogen partial pressure while keeping the system pressure constant. ）
The pressure selected for hydrorefining is primarily determined by catalyst life and product quality. Since hydrogenation is a process that reduces volume, increasing pressure is beneficial for the reaction, with the greatest impact on nitrogen removal. Increasing the pressure also prolongs the catalyst’s lifespan, but it requires higher pressure resistance from the equipment and results in greater investment costs
The pressure in hydrorefining is primarily determined by considerations of catalyst life and product quality. Since hydrogenation is a process that involves volume reduction, increasing the pressure is beneficial for the reaction, with the greatest impact on nitrogen removal. Higher pressure also extends the catalyst’s lifespan, but it requires higher pressure resistance from the equipment, resulting in increased investment costs.