【Q&A Question 123】2018.05.03

This post was last edited by Blue Flame on 2018-5-3 09:08. Answer: a) Ensure proper nitrogen sealing of the raw material buffer tank to prevent the raw oil from oxidizing； The oxygen content in the inert gas is required to be below 5 μg/g. b) Enhance the dehydration of crude oil to prevent catalyst aging and agglomeration ； The design of catalysts for hydrogenation units generally requires that the water content in the feed oil be below 300 μg/g ； c) Use backwash filters to remove impurities from the feed oil, preventing catalyst impurities from clogging the catalyst bed ； d) Add a protective agent at the reactor inlet for demetallization to prevent catalyst poisoning ； Controlling the metal content in the feed is one of the important methods to ensure the operating cycle of the catalyst. Since heavy metals generally combine with heavy hydrocarbon molecules (to form nickel porphyrins and vanadium porphyrins), strictly controlling the 95% distillation point temperature or dry point of the feed is the main method for controlling metal content. e) Strengthen upstream operations to control from the source ； It is generally required that the iron content in the feed to the hydrogenation unit be no more than 1 μg/g. f) Additionally, from a process perspective, it is necessary to control the hydrogen partial pressure, the hydrogen-to-oil ratio, and the hydrogen sulfide content in the recycled hydrogen, in order to prevent catalyst deactivation ； g) It is also necessary to strengthen the monitoring of the quality of crude oil and fresh hydrogen on a regular basis

Ensure the hydrogen partial pressure, hydrogen-to-oil ratio, and hydrogen sulfide content in the circulating hydrogen

To prevent a decline in catalyst activity, the following adjustments are generally made in the process: 1. Control the air seal of the raw material buffer tank to ensure that the crude oil does not get oxidized. The protection of crude oil mainly involves preventing it from coming into contact with air during storage. Studies have shown that, in addition to sulfonic acids formed by the oxidation of aromatic thioethers in the oil reacting with pyrroles to produce precipitates, olefins can react with oxygen to form oxidation products; these oxidation products can then polymerize with active heteroatom compounds containing sulfur, oxygen, and nitrogen to form precipitates. Therefore, when crude oil containing impurities such as aromatic thiol compounds, olefins, sulfur, and nitrogen comes into contact with air, the oxygen in the air accelerates the condensation reactions of the unstable components in the oil, resulting in the formation of high-molecular-weight polymers, gums, and other precursors to coking, as well as sediment. These coking precursors can easily undergo further condensation and coking in areas with higher temperatures, such as the oil generation/feed oil heat exchangers and the top of the reactor. Therefore, protecting the crude oil from contact with oxygen is a very necessary measure to prevent coking at the top of the heat exchanger and catalyst bed. The protection of crude oil mainly involves inert gas nitrogen protection, and sometimes gas protection is also used. Fill the space above the oil surface with oxygen-free nitrogen to isolate the crude oil from oxygen. During the operation of the unit, regular sampling of the protective gas for the crude oil should be carried out to analyze the oxygen content. To provide better protection for the crude oil and prevent it from oxidizing, the oxygen content in the inert gas is required to be below 5 mg/g. 2 Strengthen the dehydration of crude oil to prevent catalyst aging and agglomeration. The treatment of crude oil also includes its dehydration. Water content in crude oil poses various hazards. Firstly, water in the feed material can cause fluctuations in the operation of the heater, leading to unstable temperatures at the outlet of the heater; as a result, the reaction temperature also fluctuates, which affects the quality of the product ； Secondly, if a large amount of water enters the raw materials suddenly, the vaporization of this water causes pressure changes in the equipment, which creates problems for various control circuits ； Thirdly, water present in the crude oil can cause damage to the catalyst; if exposed to water for an extended period of time, it can lead to the aging and agglomeration of the active metal components on the surface of the catalyst, resulting in a decrease in its activity ； When the water content in the feed oil is too high, it will lead to a decrease in catalyst strength, particle agglomeration of the catalyst, and blockage of the reactor. This unit is designed primarily for thermal feeding and volume replenishment in the tank area; therefore, the crude oil contains essentially no water. If a small amount of water is present, it is usually left to settle and lose water in the crude oil buffer tank within the unit. The design of catalysts for hydrogenation units generally requires that the water content in the feed oil be below 300 mg/g. 3 Use backwash filters to remove impurities from the crude oil, thereby preventing catalyst impurities from clogging the catalyst bed. Crude oil generally contains a certain amount of mechanical impurities; especially when the acid value of the crude oil is high, it can corrode pipes and containers, resulting in an increase in mechanical impurities. These impurities will deposit in the catalyst bed, causing an increase in reactor pressure drop and rendering the plant inoperable. This device is equipped with a backwash filtration system for the feed oil. During operation, it is necessary to check the filtration system regularly to ensure its proper functioning and to guarantee that all impurities in the feed oil are removed before it enters the reactor. 4 Add a protective agent at the reactor inlet for demetallization to prevent catalyst poisoning ； Heavy metals, particularly nickel (Ni), vanadium (V), copper (Cu), lead (Pb), etc., will deposit in the pores of the catalyst, covering its surface active centers and reducing its activity; it is necessary to increase the reaction temperature to compensate for this loss in catalyst activity. Large amounts of metals, including corrosive iron, can have an adverse effect on catalysts. Metals such as Ni and V can easily cause catalyst poisoning; even trace amounts of these metals can lead to the permanent deactivation of the catalyst and reduce the operational lifespan of the device. At the same time, metals such as Ni and V are permanent poisons that cannot have their activity restored through catalyst regeneration; therefore, even after one cycle of operation, the hydrogenation activity of the catalyst still does not meet the required standards, and it is necessary to replace the catalyst due to metal-induced deactivation. By adding a protective catalyst at the inlet of the refining reactor to remove metals, catalyst poisoning can be prevented. 5 Strengthen upstream operations to control the issue at its source. The Fe ions brought in along with the raw materials are a problematic catalyst poison; although their impact on catalyst activity is relatively minor, they easily form sulfides that deposit on the surface of the catalyst bed. Due to their rapid reaction rate, they typically accumulate in the form of a crust at the top of the catalyst bed, resulting in an increase in the pressure drop across the bed. When the bed pressure drop reaches a certain level, it affects the operation of the recycle compressor, crushes the catalyst, and causes chaos in the fluid flow within the reactor, leading to the shutdown of the plant. Fe ions are present in the feedstock in two forms: one as suspended particles, and iron in this form can be minimized by installing a feed filter to reduce the amount of iron particles (such as iron oxides) that enter the catalyst bed ； Another form is the formation of oil-soluble substances with hydrocarbon compounds (such as iron naphthenate), which cannot be resolved by filtration; this requires an increase in the amount of protective agent used. There are also two sources of Fe: one is iron naphthenate, which is oil-soluble and already present in crude oil; the other is Fe that enters the distillates as a result of equipment corrosion during the storage, transportation, and atmospheric/ vacuum distillation of crude oil. It is generally required that the iron content in the feed to the hydrogenation unit be no more than 1 ppm/g. Similar to Fe, high metal contents of Ca, Mg, and Na can also lead to metal deposition on the surface of the catalyst bed. However, since ions such as Ca, Mg, and Na are less likely to be generated during the subsequent processing of crude oil, most of these metals in the oil originate from the crude oil itself; therefore, by properly managing processes such as crude oil desalting, the quality of the feedstock can basically be ensured. Arsenic (As) and silicon (Si) are poisons for hydrogenation catalysts; even a small amount of these elements deposited on the catalyst can lead to a significant decrease in its activity. Silicon mainly enters the hydroprocessing feed oil from upstream coking units, and the use of defoamers in these coking units results in silicon being present in the coked wax oil. Silicon in the hydrogenation feedstock is not easy to remove completely, but even a small amount of silicon deposited on the catalyst can block the pores on its surface, reduce the catalyst’s activity, increase the pressure drop across the catalyst bed, shorten the operational cycle of the equipment, and render the catalyst unusable for regeneration. So it is controlled from the upstream atmospheric and vacuum distillation unit. 6 Additionally, from a process perspective, it is necessary to control the hydrogen partial pressure, the hydrogen-to-oil ratio, and the hydrogen sulfide content in the recycled hydrogen, in order to prevent catalyst deactivation.

a) Ensure proper nitrogen sealing of the raw material buffer tank to prevent the raw oil from oxidizing； The oxygen content in the inert gas is required to be below 5 μg/g. b) Strengthen the dehydration of crude oil to prevent catalyst aging and agglomeration ； The design of catalysts for hydrogenation units generally requires that the water content in the feed oil be below 300 μg/g ； c) Use a backwash filter to remove impurities from the feed oil, thereby preventing catalyst impurities from clogging the catalyst bed ； d) Add a protective agent at the reactor inlet for demetallization to prevent catalyst poisoning ； Controlling the metal content in the feed is one of the important methods to ensure the operating cycle of the catalyst. Since heavy metals generally combine with heavy hydrocarbon molecules (to form nickel porphyrins and vanadium porphyrins), strictly controlling the 95% distillation point temperature or dry point of the feed is the main method for controlling metal content. e) Strengthen upstream operations to control from the source ； It is generally required that the iron content in the feed to the hydrogenation unit be no more than 1 μg/g. f) Additionally, from a process perspective, it is necessary to control the hydrogen partial pressure, the hydrogen-to-oil ratio, and the hydrogen sulfide content in the recycled hydrogen, in order to prevent catalyst deactivation ； g) It is also necessary to strengthen the monitoring of the quality of crude oil and fresh hydrogen on a regular basis.

Control the air seal of the raw material buffer tank to ensure that the crude oil does not get oxidized. The protection of crude oil mainly refers to preventing it from coming into contact with air during storage.

Specifically, the following adjustments should be made: 1. Control the air seal of the raw material buffer tank to ensure that the crude oil does not get oxidized. 2 Strengthen the dehydration of crude oil to prevent catalyst aging and agglomeration. 3 Use a backwash filter to remove impurities from the feed oil, preventing catalyst impurities from clogging the catalyst bed. 4 Add a protective agent at the reactor inlet to remove metals and impurities. 5 Control the impurity content in the raw materials to prevent them from entering the reactor and causing an increase in reactor pressure drop. 6 In terms of process control, it is necessary to maintain the hydrogen partial pressure, hydrogen-to-oil ratio, and hydrogen sulfide content in the circulating hydrogen, in order to prevent catalyst deactivation.

Control the reaction temperature well； hydrogen-to-oil ratio ； Control the properties of raw materials, etc

a) Ensure proper nitrogen sealing of the raw material buffer tank to prevent the raw oil from oxidizing； The oxygen content in the inert gas is required to be below 5 μg/g. b) Strengthen the dehydration of crude oil to prevent catalyst aging and agglomeration ； The design of catalysts for hydrogenation units generally requires that the water content in the feed oil be below 300 μg/g ； c) Use a backwash filter to remove impurities from the feed oil, thereby preventing catalyst impurities from clogging the catalyst bed ； d) Add a protective agent at the reactor inlet for demetallization to prevent catalyst poisoning ； Controlling the metal content in the feed is one of the important methods to ensure the operating cycle of the catalyst. Since heavy metals generally combine with heavy hydrocarbon molecules (to form nickel porphyrins and vanadium porphyrins), strictly controlling the 95% distillation point temperature or dry point of the feed is the main method for controlling metal content. e) Strengthen upstream operations to control from the source ； It is generally required that the iron content in the feed to the hydrogenation unit be no more than 1 μg/g. f)? Additionally, from a process perspective, it is necessary to control the hydrogen partial pressure, the hydrogen-to-oil ratio, and the hydrogen sulfide content in the recycled hydrogen, in order to prevent catalyst deactivation ； g) It is also necessary to strengthen the monitoring of the quality of crude oil and fresh hydrogen on a regular basis.

a) Ensure proper nitrogen sealing of the raw material buffer tank to prevent the raw oil from oxidizing； The oxygen content in the inert gas is required to be below 5 μg/g. b) Enhance the dehydration of crude oil to prevent catalyst aging and agglomeration ； The design of catalysts for hydrogenation units generally requires that the water content in the feed oil be below 300 μg/g ； c) Use backwash filters to remove impurities from the feed oil, preventing catalyst impurities from clogging the catalyst bed ； d) Add a protective agent at the reactor inlet for demetallization to prevent catalyst poisoning ； Controlling the metal content in the feed is one of the important methods to ensure the operating cycle of the catalyst. Since heavy metals generally combine with heavy hydrocarbon molecules (to form nickel porphyrins and vanadium porphyrins), strictly controlling the 95% distillation point temperature or dry point of the feed is the main method for controlling metal content. e) Strengthen upstream operations to control from the source ； It is generally required that the iron content in the feed to the hydrogenation unit be no more than 1 μg/g. f) Additionally, from a process perspective, it is necessary to control the hydrogen partial pressure, the hydrogen-to-oil ratio, and the hydrogen sulfide content in the recycled hydrogen, in order to prevent catalyst deactivation ； g) It is also necessary to strengthen the monitoring of the quality of crude oil and fresh hydrogen on a regular basis.

a) Ensure proper nitrogen sealing of the raw material buffer tank to prevent the raw oil from oxidizing； The oxygen content in the inert gas is required to be below 5 μg/g. b) Enhance the dehydration of crude oil to prevent catalyst aging and agglomeration ； The design of catalysts for hydrogenation units generally requires that the water content in the feed oil be below 300 μg/g ； c) Use backwash filters to remove impurities from the feed oil, preventing catalyst impurities from clogging the catalyst bed ； d) Add a protective agent at the reactor inlet for demetallization to prevent catalyst poisoning ； Controlling the metal content in the feed is one of the important methods to ensure the operating cycle of the catalyst. Since heavy metals generally combine with heavy hydrocarbon molecules (to form nickel porphyrins and vanadium porphyrins), strictly controlling the 95% distillation point temperature or dry point of the feed is the main method for controlling metal content. e) Strengthen upstream operations to control from the source ； It is generally required that the iron content in the feed to the hydrogenation unit be no more than 1 μg/g. f) Additionally, from a process perspective, it is necessary to control the hydrogen partial pressure, the hydrogen-to-oil ratio, and the hydrogen sulfide content in the recycled hydrogen, in order to prevent catalyst deactivation ； g) It is also necessary to strengthen the monitoring of the quality of crude oil and fresh hydrogen on a regular basis.