Basic knowledge of oil refining units – definitely worth saving!

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Introduction: In recent years, the construction of petrochemical enterprises has been in full swing. Many friends, whether as the client side or the supplier side, are gradually joining this field... What kind of entity are refining and chemical enterprises, after all? Here, this article guides you through understanding what the actual production process at a oil refinery entails... 1. Overall processing flow The overall processing flow is the overarching aspect of oil refining; to gain an understanding of how a refinery operates, one must start from this macro perspective. In terms of the overall processing process, it mainly includes the total processing scale, the composition of the facilities throughout the plant, and the material balance of the entire plant. The overall processing route reflects the way crude oil is processed. Compared to traditional processing methods of the past, the currently popular approaches are full hydrogenation routes or those based on ethylene and aromatics; carbon removal processing routes have gradually become obsolete. After determining the processing route, we need to pay special attention to the processing sequence of components from heaviest to lightest, such as residue oil, wax oil, diesel, kerosene, naphtha, and liquefied gas. It is also important to pay attention to the technology used in the processing of each type of distillate oil, as well as the level of advancement of that technology. The five types of balance across the entire plant represent another aspect that refineries need to consider at a macro level: once the overall processing route of the plant has been determined, it is necessary to understand how balances such as the overall material balance, hydrogen balance, sulfur balance, fuel balance, steam balance, and the balance of components used in the blending of gasoline and diesel are achieved and maintained. II. Classification of refining units: Following the processing sequence from crude oil to various fractions mentioned earlier, it is necessary to provide a classified description of these units. Specifically, these include the following: 1. The selection of crude oil is the fundamental starting point for refinery design. With over 2,000 different types of crude oil worldwide, each type having distinct properties, the processing procedures and design requirements also vary accordingly. These differences have a significant impact on factors such as the refinery’s product structure, product quality, equipment corrosion protection, and the requirements for utility systems. Therefore, when evaluating a refinery, it is essential to first determine what type or types of crude oil the refinery is designed to process, in order to understand its processing characteristics. 1) Crude oil processing units: The choice of crude oil processing units is quite simple; it either involves atmospheric distillation or atmospheric-vacuum distillation. Generally, when designing such units, consideration is given to both the acid value and sulfur content of the crude oil. For companies that place a strong emphasis on crude oil quality, atmospheric and vacuum distillation is an inevitable option; some companies go a step further and choose units equipped with vacuum deep extraction functions, such as Qingdao Refining & Chemical Co. Atmospheric and vacuum distillation unit: In production, the atmospheric and vacuum distillation unit is a purely physical process that does not use any catalysts. The unit consists of a heat exchange section, an electro-desalting section, a primary distillation section, and atmospheric and vacuum distillation sections. Its products are essentially intermediate products destined for downstream processing, such as non-condensable gases, naphtha, kerosene, diesel, wax oil, and vacuum residue. Naphtha and gases are sent to a light hydrocarbon recovery unit to recover light hydrocarbons, while the naphtha is separated into light and heavy fractions and sent to the next unit. Kerosene and diesel are sent to the hydrogenation unit, while wax oil is either sent to catalytic cracking, hydrocracking, or wax oil hydrogenation. Residuum also has various destinations; depending on the processing route, it is sent to residuum hydrotreating or delayed coking. 2) The pathway taken by residue in a residue processing unit is a crucial factor in distinguishing between different processing routes in a refinery: it can either undergo hydroprocessing or decarbonization, i.e., coking. In terms of composition, residue is divided into atmospheric residue and vacuum residue. Atmospheric residue is generally blended and processed as a feedstock for catalytic cracking, or used as a feedstock for residue hydrotreating. Reduced-pressure residue can be used in units for heavy oil catalytic cracking, coking, residue hydrogenation, solvent deasphalting, etc. Resid hydrotreating units: Currently, amidst the trend of heavy oil lightening, resid hydrotreating has become a unit that attracts significant attention from various enterprises. From a process standpoint, residue hydrotreating is divided into fixed-bed, fluidized-bed, and slurry-bed types. The difference mainly lies in the reaction part. Overall, the plant consists of a reaction section, a fractionation section, and a utilities section. The raw materials are vacuum residue and some catalytic slurry, while the products include hydrogenated residue as well as some naphtha and diesel. The hydrogenated residue is subsequently sent to catalytic cracking for further processing as raw material. Resid hydrotreating plays a crucial role in heavy oil processing; however, it is characterized by high investment and operating costs, as well as relatively stringent requirements for equipment. Coking units: Delayed coking is a major heavy oil processing technology that lightens heavy hydrocarbons through thermal cracking and condensation reactions. Coking units have advantages such as low investment and operating costs, simple processes, mature technology, strong adaptability to various feedstocks, and a high oil-to-coal ratio. They are capable of processing a wide range of heavy and low-quality feedstocks, including straight-run residue, pyrolysis tar, deoiled asphalt, coal tar, clarified oil, and visbreaker residue. As a result, in traditional decarboxylation processes, coking units are often referred to as the \"trash bins\" of refineries. A conventional delayed coking unit consists of several components, including coking, fractionation (some units also include gas recovery), coke handling, a flare system, and treatment of cold and cut coke water. In terms of operation, the coking unit’s operational flexibility can be enhanced by adjusting parameters such as temperature, pressure, and recycle ratio. Coking products include coke, coker gas oil, coker diesel, coker gasoline, and dry coker gas. 3) The wax oil from the wax oil processing unit generally goes to catalytic cracking, hydrocracking, or wax oil hydrogenation units. Hydrocracking unit: Domestic hydrocracking units use reduced-pressure wax oil and hydrogen as raw materials, and are important devices for integrating oil refining and chemical processing within refineries. In terms of the process route, it is generally divided into single-stage series, single-stage with two reagents, parallel feeding, staged feeding, reverse series, etc. Typical products include: tail oil, heavy naphtha, diesel, jet fuel, light naphtha, liquefied gas, dry gas, etc. Among them, light naphtha and tail oil used for deethylation serve as raw materials, and tail oil can also be used as a raw material for lubricants. Heavy naphtha is used to produce aromatics via dehydrogenation. Aviation fuel and hydrogenated diesel can be sold as products directly, or hydrogenated diesel can be used in blending before being shipped out. Catalytic cracking unit: Both catalytic cracking and hydrocracking are methods used to process waxy oils, and the changes take place in the front part of the unit, namely in the reaction and regeneration sections. A great variety of types have been developed around the reverse regeneration process and the corresponding catalysts. In terms of the main categories of equipment, they can be divided into reverse regeneration systems, distillation systems, stabilization systems, and three types of machines. Based on the classification of process routes, a variety of processes such as FCC, RFCC, DCC, MGG, ARGG, MGD, FDFCC, HCC, MIP, and MIO have been developed. In terms of products, these include light diesel, stabilized gasoline, liquefied gas, dry gas, oil slurry, etc. Light diesel goes to diesel hydrogenation; stabilized gasoline goes to gasoline hydrogenation or SZorb (gasoline adsorption desulfurization). Liquefied gas and dry gas are sent for the refinement of corresponding products. A small portion of the catalytic slurry is recycled, and if there is a coking unit downstream, it is used for blending in coke production or for blending in residue hydrogenation. In recent years, due to environmental pressures, most catalytic cracking units have adopted flue gas desulfurization and denitration technologies for flue gas treatment. Desulfurization technologies include the EDV sodium method, domestically produced renewable amine methods, and domestic sodium methods, while denitration technologies include LoTOx ozone and SCR, among others. Wax oil hydrogenation unit: The wax oil hydrogenation unit is also commonly referred to as hydrogenation treatment. Its function is to carry out hydrogenation desulfurization, denitration, and olefin saturation reactions in order to produce refined wax oil with a sulfur content of less than 0.2% for use as a catalyst feedstock; simultaneously, it produces small amounts of diesel and naphtha as by-products. In terms of process, it includes the reaction section (including the compressor), the distillation section, and the utility section. The combination of wax oil hydrogenation and catalytic cracking can significantly reduce the impurity content in the catalytic feedstock, improve its crackability, enhance the operational performance of catalytic cracking units, and at the same time reduce SOX and NOX emissions from the flue gases. 4) Naphtha processing units: Naphtha is a key component in the integration of oil refining and the chemical industry. Naphtha can be used as a raw material for ethylene and reforming, as well as as a solvent oil and a component in gasoline blends. In terms of origin, naphtha is divided into straight-run naphtha and reprocessed naphtha. Straight-run naphtha mainly comes from atmospheric and vacuum distillation, while secondary processed naphtha originates from units such as hydrocracking, reforming, coking, residue hydrogenation, wax oil hydrogenation, and diesel hydrogenation. Units using naphtha as raw material include catalytic reforming, aromatic extraction, isomerization, etc. Catalytic reforming unit: Catalytic reforming is an important production unit in refineries; it is a process in which naphtha is converted into reformate oil rich in aromatics, with hydrogen being produced as a by-product, under conditions of specific temperature, pressure, hydrogen presence, and the use of catalysts. The reformate can be used directly as a blending component for motor gasoline. It can also undergo aromatic extraction to produce benzene, toluene, and xylene. The by-produced hydrogen serves as one of the main sources of hydrogen for hydrogenation units in oil refineries (such as hydrotreating and hydrocracking). There are also many variations in the processes and catalysts used in catalytic reforming. In terms of processes, there are semi-regenerative reforming and continuous reforming. Abroad, there is UOP’s stacked type and AXENS’s side-by-side type. Domestically, there are the low-pressure batch reforming process (not entirely continuous) developed independently in our country, the continuous catalytic reforming process, the ultra-low pressure continuous catalytic reforming process, and the counter-current moving bed continuous reforming process. In the past two years, due to the dual pressures of excess domestic refining capacity and the transition to China’s National VI emission standards, many refining and petrochemical enterprises, including independent refineries, have been investing in reforming units to prepare for industrial upgrading. Aromatic extraction unit: Aromatic extraction is currently the primary method used in the chemical industry to separate aromatics from non-aromatics, and it is mainly employed to isolate high-purity BTX aromatic products from gasoline fractions such as reformed oil and hydrocracked gasoline. The process aspects include the raw material distillation section, aromatic extraction section, aromatic separation section, and utility section. Aromatic extraction technology comprises two different processes: liquid-liquid extraction and extractive distillation. The liquid-liquid extraction process separates components based on the differences in the solvent’s solubility for aromatics and non-aromatics. The extraction distillation process achieves distillation separation by selecting an appropriate solvent to alter the relative volatility of non-aromatic and aromatic components. The products of aromatic extraction include raffinate oil, toluene products, and C8+ reformate oil, etc., which mainly supply the C8+ reformate oil and toluene feedstocks required by p-xylene (PX) plants. Depending on the solvent used, liquid-liquid extraction processes can be classified into methods such as the Udex process, the Sulfolane process, the Arosolvan process (N-methylpyrrolidone), the DMSO process (dimethyl sulfoxide), and the Formex process (N-formylmorpholine). Among these, the Sulfolane process is the most widely applied. The extraction distillation processes include the MORPHYLANE process and the sulfolane extraction distillation process. Relatively speaking, the sulfolane extraction distillation process is more widely used. The sulfolane extraction distillation process is represented by the extraction distillation processes developed by GTC in the United States, UOP in the United States, and RIPP of the Chinese Academy of Petroleum Sciences. The extractive distillation process is characterized by a short process flow, easy operation, low investment requirements, and minimal land usage; therefore, in recent years, most newly built aromatic extraction units have adopted this process. C5/C6 isomerization unit: Alkane isomerization is one of the key processes for producing high-octane gasoline components. The principle involves converting the n-alkanes of C5 and C6 present in the feedstock light naphtha into their corresponding branched-chain isomers, thereby increasing the front-end octane number of gasoline and ensuring uniform anti-knock properties throughout the fuel. There are various isomerization processes for C5 and C6 n-paraffins, depending on the octane number of the reaction products. These include simple single-pass processes, pre-deisopentanization single-pass processes, nC5 cycle processes, as well as processes that completely remove isoparaffins from the feed oil. Different process technologies can be employed based on the required octane number of the isomerized oil. In terms of processes, there are UOP’s Penex isomerization process, Axens’ Isomerization process, the RISO isomerization technology developed by the China Academy of Petroleum Sciences, as well as an isomerization process jointly developed by East China University of Science and Technology, Jinling Petrochemical, and SEI; there is also Anadig’s AISO isomerization process, among others. The main product of the C5/C6 isomerization unit is high-octane isomerate, which serves as a gasoline blending component in the formulation of finished gasoline. 5) Product refining unit – Hydrorefining unit: Hydrorefining refers to the process in which, under the action of a catalyst, hydrogen, and specific pressure and temperature conditions, organic compounds containing sulfur, nitrogen, and oxygen undergo hydrolysis, while olefin and aromatic molecules undergo hydrogenation saturation. Product refining mainly includes gasoline hydrorefining, gasoline adsorptive desulfurization (S Zorb), diesel hydrorefining, and jet fuel hydrorefining, etc. Apart from gasoline adsorption desulfurization (S Zorb), the other three types of hydroprocessing processes are similar in terms of technology; their plant configurations consist essentially of a reaction section, a distillation section, a hydrogen compressor, a recycle hydrogen desulfurization unit, and utility systems. The products are refined gasoline, diesel, and jet fuel. In terms of hydrorefining, there are numerous processes and catalyst technologies available both domestically and internationally, with the focus lying mainly on catalysts; they will not be listed one by one here. Gasoline adsorption desulfurization (S Zorb) unit: The S Zorb unit was developed by Sinopec by acquiring ConocoPhillips’ patents. The unit mainly consists of the feed and desulfurization reaction section, adsorbent regeneration section, adsorbent circulation section, product stabilization section, and the utility systems within the unit. At the process technology level, it combines the features of catalytic cracking and catalytic reforming, enabling the sulfur content in gasoline to be easily reduced to below 10PPM. 6) LPG processing units, which use LPG as raw material, mainly include gas fractionation, MTBE production, and alkylation. Gas fractionation unit: Gas fractionation is a distillation process that separates different components based on the differences in their relative volatilities; it is primarily used in conjunction with catalytic cracking units. The plant mainly consists of a propane removal section, an ethane removal section, a purified propylene section, and utility sections. The main products are purified propylene, propane fractions, mixed C4 fractions, and ethane gas. MTBE plant: MTBE was once widely used as an excellent component for high-octane gasoline, and it is produced primarily from liquefied gas and carbon tetrahydrocarbons derived from catalytic and coking units, along with methanol as a raw material. The MTBE production process is primarily an etherification process. Depending on the type of etherification reactor, the MTBE synthesis methods include fixed-bed reaction technology, slurry-bed reaction technology, catalytic distillation reaction technology, slurry-bed-catalytic distillation reaction technology, mixed-phase reaction technology, and mixed-phase reaction distillation technology, among others. In the gasoline blending market, MTBE and alkanes used to account for the majority of the components in high-octane blended gasoline, but everything changed on September 13, 2017. On September 13, the “Implementation Plan on Expanding the Production of Biofuel Ethanol and Promoting the Use of Ethanol Gasoline for Vehicles”, jointly issued by 15 ministries and commissions including the National Development and Reform Commission, the National Energy Administration, and the Ministry of Finance, stipulates that by 2020, the use of ethanol gasoline for vehicles shall be promoted nationwide in China. Due to the limits on oxygen content in National VI gasoline, the widespread use of ethanol-based gasoline means that the good times for MTBE are also coming to an end. Alkylation unit: Alkylated oil is a high-quality component for gasoline, featuring a high octane rating, low vapor pressure, low sulfur content, and no aromatics. Contrary to the bleak situation of MTBE, alkylation units have been quite popular in recent years. Especially within the Sinopec and CNPC systems, to successfully complete the upgrade to National VI gasoline, both groups have carried out extensive construction of alkylation units. In terms of alkylation, more than a dozen technology suppliers have emerged, depending on different process routes and catalysts. Alkylation techniques can be divided into liquid acid alkylation and solid acid alkylation based on the phase state of the catalyst. Depending on the catalyst used, liquid acid alkylation can be divided into hydrofluoric acid alkylation, sulfuric acid alkylation, and ionic liquid alkylation. The first two processes are highly mature, with multiple units already in operation. The ionic liquid process is currently a research hotspot in this field. There are already industrial applications in China; Sinopec has planned the construction of multiple ionic liquid-based alkylation units within its system. From a technical perspective, the treatment of waste acid is an important issue in alkylation plants, and all different process routes have to deal with this problem. 7) Refining and chemical enterprises that have established hydrogen production facilities in the past two years have increased their investment in hydrogenation facilities. Therefore, the source of hydrogen becomes the first issue to consider. Currently, the main sources of hydrogen production are catalytic reforming, hydrogen production from dry gas/natural gas, and hydrogen production from coal. Dry gas/natural gas hydrogen production plants: The hydrogen production processes using dry gas and natural gas rely primarily on light hydrocarbon steam reforming technology and pressure swing adsorption (PSA) purification technology. The light hydrocarbon steam reforming process boasts advantages such as low investment, low energy consumption, high operational reliability, and flexibility; moreover, it has many successful industrial applications. Its process units mainly consist of five parts: raw material pretreatment, hydrocarbon steam reforming, waste heat recovery, carbon monoxide shift, and hydrogen purification. At the industrial level, the commonly used conversion processes can be divided into three types: conventional conversion, pre-conversion, and convective conversion processes. At the purification level, it can be divided into conventional purification and PSA purification. Coal gasification plant: The production process of the coal-to-hydrogen plant involves mixing coal slurry with pure hydrogen; after passing through gasification and purification units, hydrogen gas with a purity of approximately 97.5%, along with acidic gases, is produced. The main representative advanced coal gasification technologies both domestically and internationally include dry pulverized coal feeding, coal-water slurry gasification, and lump (crushed) coal gasification. Coal dry powder feeding technologies include Shell’s SCGP technology, Siemens’ GSP gasification technology, the single-nozzle powder coal gasification technology developed jointly by East China University of Science and Technology, Sinopec Ningbo Research Institute, and CNOOC Chemical Co., Ltd., as well as the two-stage dry coal powder gasification technology developed by Xi’an Thermal Power Institute ； Wet coal-water slurry feeding technologies include GE’s single-nozzle coal-water slurry gasification technology in the United States, the multi-nozzle opposed gasification technology jointly developed by East China University of Science and Technology and Yankuang Group, the staged entrained-flow gasification technology co-developed by Tsinghua University and Dalike Technology Co., Ltd., as well as the multi-component slurry technology developed by Northwest Institute of Chemical Industry, among others ； Regarding coal feeding, there is Germany’s Lurgi pressurized gasification technology and BGC Company’s BGL gasification technology from the UK. Based on the operating conditions of currently commissioned coal gasification plants, the entrained-flow gasification technology is developing at the fastest pace industrially; among them, the wet-feed gasification technology is more mature. 8) The sulfur recovery unit within the integrated sulfur recovery facility is a crucial component in maintaining sulfur balance in refineries. The sulfur brought in with the crude oil is, aside from a very small amount that is carried away with the products or emitted during the processing, captured by sulfur recovery units. Therefore, the scale of the sulfur treatment unit is closely related to the sulfur content of the crude oil processed by the refinery and its processing procedures. The sulfur recovery unit includes units such as acidic water stripping, solvent regeneration, sulfur recovery, flue gas treatment, solvent regeneration, and liquid sulfur molding and packaging. In terms of processes, the main sulfur recovery and flue gas treatment processes used in recent years include Super Claus, SCOT, MCRC, RAR, HCR, LS-SCOT, and Super-SCOT, among others. Domestically, the sulfur recovery catalyst technology developed by the Research Institute of Qilu Petrochemical Company and the Southwest Natural Gas Research Institute, as well as the complete sulfur recovery technology (ZHSR) developed by Zhenhai Petrochemical Engineering Company, have seen successful applications. In the acidic water stripping process, the three commonly used processes in China are single-tower pressurized side-stream extraction stripping, single-tower low-pressure full-blowing stripping, and two-tower pressurized stripping. III. Storage and Transportation System The storage and transportation system is an important component of a refinery; it is responsible for the receipt and storage of crude oil, as well as the storage and transfer of intermediate and final products. A storage and transportation system generally includes crude oil tank farms, intermediate raw material tank farms, finished product tank farms, sludge oil tank areas, pump houses, low-pressure fuel gas recovery facilities, flare systems, tank truck washing facilities, railway loading facilities and washing equipment, as well as chemical reagent systems. In the integrated refining and chemical enterprises built in recent years, due to their high standard of construction, the automation systems that were previously easily overlooked in storage and transportation systems have been enhanced as there are increasing demands for optimizing production processes and improving management efficiency. In particular, some corresponding technical measures have been gradually adopted to optimize the scheduling of crude oil arrival at the plant, the blending processes, as well as the on-site blending of products such as gasoline and diesel before they are shipped out. IV. Utility Services: Water, electricity, steam, and air in the utility systems are essential elements for maintaining the proper operation of a refinery. Deionized water, deoxygenated water, and condensate are mainly supplied to the boilers and steam-generation equipment in the power station and various units, with a portion also being used in the chemical processes. The production water supply system is responsible for providing water for the entire plant’s production processes, for circulation purposes, for fire fighting, for laboratory use, for landscaping, and for cleaning floors. The circulating water is managed by the circulating water plant, which is responsible for supplying circulating cooling water to most of the refining units and power systems. The used circulating hot water from these units is sent directly back to the cooling towers in the circulating water plant for cooling before being reused. During the use of circulating water, it can be replenished with fresh water or recycled water from wastewater treatment plants. To ensure the stable operation of refinery production, two separate power sources are generally used for power supply; each of these sources is capable of meeting the electrical needs of the refinery’s main installations and equipment. Some companies also have their own power generation facilities to ensure a supply of electricity in emergency situations. Refineries require large amounts of steam at various pressure levels during their production process; therefore, their steam distribution systems typically include steam at pressures of 3.5 MPa, 1.0 MPa, and 0.5 MPa. Some companies also utilize high-pressure steam at 9.8 MPa. The sources of steam in refineries are diverse, including steam generated by power stations, as well as steam of various grades produced by waste heat boilers and steam generators in certain units. The purified and unpurified air used in the production equipment is mainly supplied by the air compressor station, and is generally used for the production process of the equipment, as well as for instruments and purging purposes. Oxygen and nitrogen for production and maintenance are supplied by the air separation plant. V. Laboratory System: The central laboratory system is responsible for testing most of the materials and their physical properties throughout the production process of the entire plant. The main testing instruments include nearly a hundred types of analysis and testing equipment, such as chromatographs, distillers, spectrometers, sulfur analyzers, density meters, pour point and cloud point testers, freezing point and cold filter point determiners, flash point testers, kinematic viscosity meters, nuclear magnetic resonance devices, acid value testers, and acidity meters. In accordance with the requirements of the production facility, material analysis and testing are carried out in line with the analysis schedule, providing a basis for decision-making in the facility’s production. VI. In modern refining and chemical enterprises with automatic control and information technology, automatic control systems and related information systems are essential components. Automatic control and information systems can be classified into the operation control layer, production execution layer, production management layer, and enterprise management layer. At the operational control level, there are the DCS systems for each set of equipment as well as the automatic control systems for various related units; such systems are primarily designed to achieve automation in the production process and improve operational efficiency. The control time granularity is on the second level. On top of DCS and related automatic control systems, many enterprises have adopted advanced control systems, which we abbreviate as APC. APC addresses the issues of stable operation and, to some extent, optimized operation; at the APC level, the concept of optimization begins to be implemented, and the time granularity for APC operations is on a minute basis. At the APC level, in recent years some companies have begun to implement real-time optimization systems, namely RTO. RTO is an optimization mechanism that lies between the production execution layer and the operational control layer. Its inputs come from the production execution layer, while its outputs are sent directly to APC. The optimization strategies from the production execution layer are transformed into control signals through RTO and APC, which are then applied to the corresponding control valves. The time granularity of RTO is hours. In addition to the RTOs used in production facilities, storage and transportation units are equipped with systems for online blending of crude oil and finished oils, which are responsible respectively for optimizing the blending of crude oil and ensuring quality control of finished oils before they leave the facility. Similar applications exist in other production units, which will not be detailed here. At the production execution level, the main system is the Manufacturing Execution System, or MES, which is responsible for managing production activities across the entire plant. Its primary task is to ensure material balance and energy management from the work teams to the individual units and throughout the whole plant, with a time granularity of daily. The corresponding enterprise business department user is the Production Management Department. At the same time, at the level of enterprise production planning and scheduling, there are corresponding plan optimization applications and scheduling optimization software systems. At the operational management level, ERP systems dominate. VII. Summary: The \"2017 Report on the Development of the Oil and Gas Industry at Home and Abroad\" shows that in 2017, China’s refining capacity was 770 million tons per year. In 2018, it will exceed 800 million tons per year for the first time, exacerbating the problem of excess refining capacity. Many refining and chemical companies, including CNPC, Sinopec, CNOOC, as well as China National Chemical Corporation, Sinochem Group, Yanchang Petroleum, and domestic regional refineries, are facing the challenge of transitioning toward higher-value chemical products and new material sectors. With the transformation of oil refining companies, many of the refining facilities that were once prominent in this industry will also gradually undergo changes. Whether this process happens slowly or quickly, the role of these refining facilities in converting oil into chemical raw materials will continue to be significant for a long time to come, as they continue to innovate. Copied from the Internet, for new friends to learn*!