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Review of Slurry Bed Residue Hydrogenation Technology 2016-09-11 Oil and Petrochemical Industry News http://mmbiz.qpic.cn/mmbiz/V30nKrJZmDSl2LZFy4X313tq*atE1A80zxgNic8icwaqdZV1ibxqqRzDLWNjzrJwnGMlib8jHh2wAPDD0C11pIXEfQ/0?wx_fmt=jpeg The slurry bed hydrocracking technology evolved from coal liquefaction techniques developed in the 1940s. Suspension bed hydrocracking is a process in which thermal cracking and hydrogenation reactions occur at high temperature and pressure, in the presence of hydrogen along with fully dispersed catalysts and/or additives. The catalysts or additives used in suspended-bed reactors have a fine particle size and are in powder form; they remain suspended in the reactants, which helps to effectively suppress the formation of coke. The suspended-bed hydrogenation technology has virtually no restrictions on the impurity content of the feedstock; it can even be used to process asphalt and oil sands. Since the slurry bed hydrocracking technology can overcome the limitation of low residue conversion rates, the use of this technology for processing residue has become a hot topic and focus in the refining industry in recent years. There are currently 5 types of residue slurry bed hydrocracking technologies being developed for industrial use: ① EST technology by Italy’s Eni company ； ②BP’s BPVCC technology ； ③PDVSA’s HDHPLUS technology ； ④UOP’s Uniflex technology in the United States ； ⑤Chevron’s VRSH technology in the United States. The main process conditions for hydroprocessing residue in suspension beds abroad are shown in the table below: Process conditions for major overseas residue suspension-bed hydrocracking technologies. Company: ESTBP, VCC, HDHPLUS, Uniflex, VRSH. Catalysts: Oil-soluble, powder-type; powder-type, nanoscale iron-based; water-soluble molybdenum catalysts; solid catalysts; solid catalysts; solid catalysts; molybdenum catalysts. Reaction temperature/°C: 400–425, 440–470, 440–470, 435–470, 410–450. Reaction pressure/MPa: 10–20, 18–23, 17–20, 12.7–14.1, 14–21. Feedstock: Low-quality residue with high sulfur, high metals, high residue, and high asphaltenes. Products: High yield of diesel; high yield of ultra-low sulfur diesel; high yield of ultra-low sulfur diesel; high yield of diesel; high yield of diesel. Conversion rate: >97%, 85%–95%, 85%–92%, >90%, nearly 100%. Unconverted oil: 2.5%–3.8%, <5%, <10%, <10%, —. Advantages and disadvantages of suspension-bed residue hydrocracking technology: Suspension-bed hydrocracking technology is an innovative approach that enables a significant increase in conversion rates for the deep processing of residue, and it has the following advantages: ① It has very strong adaptability to different feedstocks ； ②Empty-tube reactor, without any special internal components; simple structure and low installation cost ； ③High residue conversion rate (operable at ≥90% conversion), high light oil yield, high diesel-to-gasoline ratio, low chemical hydrogen consumption, and low processing costs ； ④The process is simple and flexible to operate; it can be run at both high and low conversion rates ； ⑤The catalyst is simple and inexpensive, and can be continuously replenished and removed ； ⑥There are no issues with bed blockage or pressure drop, nor is there any overheating of the reactor. The disadvantage of the suspended-bed hydrocracking technology is poor product quality, high metal content and carbon residue levels in the tail oil, as well as poor reprocessing performance. During the hydrocracking process in a suspended-bed reactor when operated at high conversion rates, it is difficult to make use of small amounts of residue. Additionally, due to the poor quality of the feedstock, coking tends to occur easily in the reactor, circulation pipelines, and pump equipment. For the large-scale industrialization of suspended-bed hydrogenation technology, it is necessary to further address the technical challenges related to reactors and related engineering scale-up. II. Research Progress in Foreign Suspended-Bed Residue Hydrocracking Technology In recent years, some internationally renowned oil companies have increased their investment in research and development related to suspended-bed residue hydrocracking technology in order to improve the degree of crude oil processing, and have made breakthrough advances. The progress in this area has mainly focused on optimizing the process flow, scaling up the technology on a larger scale, and developing new catalysts. (1) Process advancements: The key to hydrotreating residue lies in properly controlling the degree of conversion, gradually transforming large molecules such as asphaltenes that tend to aggregate, while maintaining the stability of the entire colloidal system, thereby preventing the formation of a \"second liquid phase\" that could lead to coking. Only by controlling the reaction before the conversion limit and maintaining dynamic equilibrium throughout the reaction system can heavy oil be converted step by step. The EST process employs an advanced control system during the reaction process, and optimizes the process parameters based on the quality of the feed oil, thereby keeping the residue in a stable state. This ensures that the reaction stops before the reactants reach their conversion limit, effectively preventing the precipitation of asphaltenes, coking, and equipment scaling, and thus ensuring long-term operation of the plant. The EST process employs a scheme of circulating unconverted oil; the unconverted residue flowing out of the deasphalting unit is mixed with fresh crude oil with a high aromatic content, which helps to restore the colloidal stability of the circulating oil. After multiple cycles, the system reaches a stable state, thereby enabling the reconversion of asphaltenes and preventing coking during the reaction process. In the EST process, to limit the accumulation of metals (nickel and vanadium) in the feedstock residue oil, a small amount (less than 3%) of unconverted tail oil must be discharged. The BPVCC process is an integrated process in which a suspended-bed thermal reaction system and a trickle-bed hydrogenation system operate at the same temperature and pressure, connected by a thermal separator that ensures complete separation of the converted products from the unconverted tail oil. Compared to other technologies, the advantage of this integration process is lower investment costs, higher product quality, and higher thermal efficiency. The reaction system of the BPVCC technology employs several reactors in series to overcome the adverse effects of backmixing. Recently, Intevep (PDVSA’s Center for Petroleum Research and Technical Support) and IFP have jointly developed an improved process called HDHPLUS. This new process is suitable for processing low-quality heavy/residue oils with high impurity levels; it can remove all metals from the feedstock. Compared to the previous process, HDHPLUS yields higher amounts of distillate oil and significantly reduces the amount of residue produced. The core of the Uniflex process is an upflow reactor, combined with a reactor feed distributor and optimized process parameters; reactions take place under nearly adiabatic conditions, which allows for an increased residence time of the heavy components in the feed on the catalyst and reduces secondary cracking reactions. The Uniflex process heats the feed oil and recycled hydrogen to the reaction temperature respectively ； The reaction effluent has the reaction terminated by quenching at the reactor outlet ； A portion of the depressurized heavy gas oil is recycled back to the slurry bed reactor for further conversion. The Uniflex process uses part of the unconverted residue as fuel oil for nearby cement plants, achieving comprehensive utilization of heavy oil. The VRSH process employs a multi-reactor series configuration; based on the complete conversion of the feed oil, it utilizes a combination of multiple reaction/separation steps to enable the stepwise conversion of different light and heavy components in the feed oil. This approach reduces the severity of the reactions, allowing for continuous hydrogenation processing while controlling coke formation. Furthermore, some VGO is introduced between Reactor 1 and Reactor 2 to improve the colloidal stability of the feedstock and suppress coking of the reactants. This approach is consistent with the theoretical basis of the EST process; although the methods are different, they achieve the same result. (2) Progress on the project: ENI is preparing to build two industrial plants. The first unit was built at the Sannazzaro refinery in Italy, with a processing capacity of 1.15 million tons per year; it came online in 2013 and is currently the facility that brings hydrocracking technology using a slurry bed for residue treatment closest to industrial implementation. The second plant is located at the Taranto refinery in Italy, with a processing capacity of 700,000 tons per year; the date of commissioning has not been determined. There are currently three BPVCC suspended-bed hydrocracking industrial plants under construction: the first one is located at China’s Yanchang Petroleum Group, with a processing capacity of 500,000 tons per year. It uses coal tar as raw material and mainly produces diesel; it came online in 2013 ； The second plant is also located in China’s Yanchang Petroleum Group, with a processing capacity of 500,000 tons per year. It uses refinery vacuum residue and coal dust as raw materials to produce diesel primarily, and it began operations in 2014 ； The third set of industrial facilities is being built in Russia to process heavy, low-quality vacuum residue, with commissioning expected in 2015. In 2006, PDVSA announced a partnership with the French company Axens to build two HDHPLUS industrial units. The first unit was built at the Puerto La Cruz refinery in Venezuela to process vacuum residue; it is under construction and is set to come online in 2016 ； The second set is planned to be built at the El Palito refinery in Venezuela. UOP has improved the design of the Uniflex unit, reducing both the investment costs and operating expenses for it. The first industrial unit using Uniflex technology was built at the refinery in Karachi, Pakistan, to process vacuum residue; it is scheduled to come online in 2016, at which time it will produce 2 million tons of diesel and 225,000 tons of lubricants per year. An industrial demonstration plant for VRSH technology (175,000 tons per year) is under construction, and there is still a long way to go before it can be used on an industrial scale. Currently, COPL, a subsidiary of China National Offshore Oil Corporation, is working together with Chevron to advance the industrialization of this technology as well as its introduction to global markets. (3) Advances in catalysts: The EST process uses oil-soluble molybdenum compounds as catalysts. During the reaction, the molybdenum-based catalyst decomposes in situ to produce nanoscale MoS2 catalyst particles, which are uniformly dispersed in the feed oil and react upon contact with hydrogen. At the reaction temperature, the feed oil undergoes C–C bond cleavage to generate free radicals; catalysts with concentrations as high as several thousand μg/g can effectively prevent these free radicals from recombining and forming more coke. As a result, the activity of the hydrogenation reaction is significantly increased, and coke formation during the reaction is suppressed. According to recent reports, BPVCC uses a non-metallic catalyst, which is a waste product from the aluminum refining industry or lignite semi-coke, containing nickel and iron; it is in powder form, and its usage level is usually no more than 2% (by mass), making it relatively inexpensive. The catalyst used in HDHPLUS is a natural mineral abundant in Venezuela, containing 4%–5% vanadium and 1% nickel. It not only has hydrogenation conversion capabilities but also can suppress the formation of gases and coke, with strong metal tolerance. The catalyst amount is 2% to 5%. The catalyst cost for HDHPLUS is low, but the amount added needs to be reduced to avoid excessive solid waste discharge. Intevep claims that 99% of the solid catalyst can be separated and recovered from the unconverted tail oil. The HDHPLUS process was used in a pilot plant to study two methods for treating solid wastes: one involves using the waste catalyst as a raw material in the metallurgical industry ； Another approach is to regenerate the spent catalyst, and the two methods can be used together. The Uniflex process uses inexpensive iron-based nanodispersed catalysts. In addition to having good hydrogenation properties, these catalysts also possess a large specific surface area, which helps to prevent the aggregation of coking precursors, suppress the formation of intermediate phases, and facilitate the conversion of macromolecules such as asphaltenes into smaller molecules, thereby reducing the amount of coke formed. Currently, UOP is developing a second-generation catalyst that can reduce catalyst consumption by 50% compared to current catalysts, while maintaining higher catalytic performance, thereby further lowering operating costs. The catalysts in the VRSH process can be recycled. The catalyst, which has been sulfided at low, medium, and high temperatures, is mixed with a gas mixture of H2 and H2S along with the feed oil and fed into a slurry bed reactor. After hydrogenation conversion and product separation, part of the oil from the bottom of the distillation tower is returned to the reactor for further conversion. The heavier fractions undergo solvent deasphalting, and the residue containing the catalyst as well as metal sulfides such as nickel and vanadium is processed in a partial oxidation zone, where these metal sulfides are converted into oxides such as MoO3, NiO, and V2O5. These oxides are then reduced in a reduction zone, with V2O5 being converted to V2O4. Subsequently, ammonia water is used to dissolve the substances; MoO3 dissolves due to its reaction with ammonia water, while NiO and V2O4 remain undissolved. In this way, nickel and vanadium are removed. Excess ammonia is removed by heating, and the molybdenum in the catalyst is recovered. After undergoing sulfiding at low, medium, and high temperatures as well as ammonia removal treatment, the catalyst returns to its initial state, thus completing its circular use. III. Development trends of suspended-bed residue hydrocracking technology. Suspended-bed residue hydrogenation is a hydroconversion technique for residues with good application prospects, and further improvement and refinement are needed. Based on the research progress in new suspended-bed hydrogenation technology, the future trends in research can be generally summarized as follows. (1) Residue colloid system: Residue is a complex colloid system. During the reaction process, it is necessary to understand the compatibility in terms of quantity, properties, and composition of the various reactant components, as well as the solubility of hydrogen in the feed oil. Additionally, it is important to consider the relationships between reaction temperature, conversion limits, and catalyst concentration, in order to accurately control the temperature in the suspended-bed reactor. Process optimization can be used to address issues related to residues and coking, enabling efficient integration with existing hydroprocessing units. (2) Reactor hydrodynamic properties and mass and heat transfer processes: Suspended-bed hydrogenation reactions involve three phases – gas, liquid, and solid. Studying the flow, mass transfer, and heat transfer mechanisms of the reactants within the suspended bed can provide theoretical guidance for the design and development of such reactors as well as for their industrial scale-up. (3) Development of highly active dispersed catalysts: At present, the active component in many catalysts used for suspension-bed hydrogenation reactions is molybdenum, and its cost remains high; this makes the recovery and recycling of such catalysts necessary. Developing new catalysts, improving the catalytic hydrogenation efficiency of catalysts for heavy components such as asphaltenes, simplifying catalyst recovery methods, reducing catalyst usage, and lowering catalyst costs are also important research directions for slurry bed hydrogenation reactions. (4) Residue utilization and environmental protection issues: Early suspension-bed hydrogenation processes generated some residue containing solid powders. Although newer suspension-bed hydrogenation technologies focus on the complete conversion of heavy oil, a certain amount of residual oil is still produced during actual industrial operation (usually <1%). Finding appropriate ways to handle and utilize this residue and residual oil in order to avoid environmental pollution is also an important area of research. http://mmbiz.qpic.cn/mmbiz/V30nKrJZmDSCynvIbYzzicZN1PAUSEeCjr9fs6PMNGtYEV76HxAD6IR9meGBMgD5ktf9waC334KoThibO58qojbg/0?wx_fmt=jpeg Note: This excerpt is from \"Advances in Chemical Engineering\", authored by Zhang Qingjun et al., Fushun Research Institute of Petroleum Chemistry