Analysis of the low-carbon development path for China’s refining industry

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Analysis of the Low-Carbon Development Path for China’s Refining Industry Li Mingfeng, Wu Hao, Li Yanjun, Qin Kang, Yu Bo (Sinopec Research Institute of Petroleum Processing, Beijing) Abstract: The “dual carbon” goals represent both a contemporary challenge for the refining industry and an important opportunity for it to achieve high-quality development. Low-carbon development in this industry requires balancing overall and partial aspects, as well as development and emission reduction, short-term and medium-to-long-term considerations, and selecting appropriate emission reduction strategies based on specific scenarios. Energy-efficient utilization, resource-efficient utilization, resource recycling, the use of renewable resources, low-carbon refining processes, green hydrogen-based refining, the chemical utilization of CO2, and intelligent technologies can provide support for low-carbon development at various stages of industry growth, helping to achieve the industry’s dual-carbon goals at an earlier date. Keywords: oil refining, low-carbon development, green hydrogen, biofuels. 1 Policy requirements for low-carbon development in the oil refining industry. In 2020, China officially announced its \"dual carbon\" goals, which aim to peak carbon dioxide emissions by 2030 and achieve carbon neutrality by 2060. ****The State Council attaches great importance to efforts to address climate change, formulates scientific strategic plans, and incorporates the goals of reaching carbon peak and carbon neutrality into the overall framework for ecological civilization development. At present, China has completed the top-level planning for achieving carbon neutrality, and has essentially established a \"1+N\" policy framework, which is continuously being improved. Supporting policies covering various industries and sectors are being introduced one after another. At the same time, **** continues to standardize the framework for achieving carbon peak and carbon neutrality, requiring that actions be taken in an orderly manner rather than through blanket or short-term measures to reduce carbon emissions, while upholding the two key principles of energy security and stable economic growth. On October 24, 2021, the **Central Committee and the State Council officially issued the \"Opinions on Fully, Accurately, and Comprehensively Implementing the New Development Concept to Advance Work Related to Reaching Carbon Peaks and Achieving Carbon Neutrality,\" which provided a systematic plan for this work, outlining the overall requirements, main goals, and key measures. Low-carbon development goals have been set, including advancing the construction of a low-carbon circular economic system, reducing carbon intensity, and increasing the share of non-fossil energy consumption. On October 26, 2021, the State Council issued the \"Action Plan for Reaching Carbon Peak by 2030\" (hereinafter referred to as the \"Plan\"), setting the goal of reducing energy consumption per unit of GDP by 13.5% by 2025 compared to 2020, and reducing carbon dioxide emissions per unit of GDP by 18% by that same date. The Plan also sets clear goals and requirements for the low-carbon development of the petrochemical and refining industries: by 2025, the domestic capacity for primary processing of crude oil is to be kept below 1.0 Gt, with the capacity utilization rate for key products to be increased to over 80% ； Guide enterprises to change their energy consumption patterns, and encourage the use of electricity, natural gas, etc. as alternatives to coal ； Adjust the raw material structure, expand sources of hydrogen-rich raw materials for import, and promote the use of lighter-weight raw materials in the petrochemical industry ； Enterprises are encouraged to carry out energy-saving upgrades and transformations, as well as to promote the hierarchical use of energy and the recycling of materials. In February 2022, **four departments including the National Development and Reform Commission jointly issued the \"Guidelines for Energy Conservation and Carbon Reduction Transformations in Key Sectors of High-Energy-Consuming Industries (2022 Edition)\", which explicitly called for efforts to promote energy conservation and carbon reduction reforms in the refining industry. The measures proposed included advancing the development and application of advanced separation technologies and fractionated refining techniques, promoting the use of advanced energy-saving equipment, as well as optimizing energy systems and hydrogen systems. In August 2022, the Ministry of Industry and Information Technology, the National Development and Reform Commission, and the Ministry of Ecology and Environment jointly issued the \"Implementation Plan for Reaching Carbon Peak in the Industrial Sector\", which calls for giving top priority to energy and resource conservation, improving utilization efficiency, optimizing the structure of energy use and raw materials, promoting circular production models among enterprises, and advancing the low-carbon, intelligent, and systematic use of energy. **The policy provides clear strategic guidance and methodological guidelines for the oil refining industry’s efforts to achieve carbon neutrality, yet the industry’s low-carbon development also faces numerous challenges. The work related to achieving carbon peak and carbon neutrality is both a tough challenge and a long-term endeavor; it is necessary to advance relevant efforts in phases and step by step, in line with the set goals. 2 Challenges to the low-carbon development of the refining industry 2.1 Structural overcapacity in refining capacity In recent years, China’s refining capacity has continued to increase; as can be seen from Figure 1, it has grown by more than 50% since 2010, reaching 910 Mt/a in 2021. As refining capacity continues to increase, the problem of structural overcapacity becomes more apparent. This is evident in several ways: first, the overall refining utilization rate across the country is relatively low. Although the operating rate of refineries increased from 66% in 2015 to around 78% in 2021, it is still some distance below the 90% level seen in developed countries ； Secondly, the scale of oil refining is relatively small; the average national oil refining capacity is 4.58 Mt/a, which is far below the world average of 8.12 Mt/a ； Third, there is an excess of refined oil and basic chemical products, but a severe shortage of high-end chemical products. In addressing structural overcapacity and the insufficient production capacity for high-end chemical products, it is necessary to take into account the needs of low-carbon development. Figure 1: China’s refining capacity. 2.2 There is an urgent need for transformation and development in the refining industry. The process of achieving carbon peak and carbon neutrality in China will inevitably lead to changes in the energy structure; energy used for transportation will gradually be replaced by new energy sources. After reaching a peak in the near future, demand for refined oil products will inevitably show a downward trend. The structural imbalances between supply and demand in the refining industry prompt a shift toward chemical manufacturing in this sector. According to the International Energy Agency (IEA), by 2030, chemical feedstocks will account for more than one-third of the growth in oil demand, and this proportion is set to rise to 50%. During the petroleum processing stage, energy consumption varies significantly depending on the desired product and the degree of conversion, which in turn leads to substantial variations in carbon emissions during the refining process. During the transition of refineries from producing finished oil products to manufacturing chemical products, higher levels of raw material conversion inevitably lead to increased energy consumption and carbon emission intensity. Therefore, during the transition from oil refining to chemical manufacturing, refineries will face significant challenges in terms of carbon emissions. 2.3 The energy utilization efficiency in oil refining needs to be improved urgently. The International Energy Agency states that to achieve carbon neutrality as outlined in the set goals, energy savings and efficiency improvements must contribute 37% to global CO2 emission reductions. Multiple estimates indicate that energy conservation and improvements in energy efficiency will account for over 70% of the contribution to China’s goal of reaching carbon peak by 2030. According to the guidelines issued in the \"Implementation Guidelines for Energy Conservation and Carbon Reduction Transformations in Key Sectors of High-Energy-Consuming Industries (2022 Edition)\\", as of the end of 2020, approximately 25% of the production capacity in China’s refining industry had energy efficiency levels above the benchmark, while about 20% had efficiency levels below that benchmark; thus, there is significant potential for energy conservation and carbon reduction transformations in this sector. At the same time, the energy efficiency of China’s refining enterprises remains low compared to world-class standards; it is therefore urgent to improve energy utilization efficiency through optimizations in various aspects such as energy conversion, energy use, and energy recovery. 2.4 Technological innovation and application need to be promoted. Oil refining companies facing low-carbon development encounter dual challenges in terms of technological breakthroughs and application. Firstly, the production processes with high carbon emissions lack effective technologies for reducing carbon emissions. Although various demonstration projects related to carbon capture, storage, and utilization (CCUS) have been carried out, the technical and economic viability of these technologies still needs to be improved, and there is still a gap before they can be applied on a large scale ； The technology for the large-scale application of green hydrogen and green electricity is not yet mature. Secondly, constrained by complex process industrial systems, low-carbon unit technologies can only realize their maximum low-carbon value on the basis of overall process optimization, making it more difficult to integrate new technologies with existing processes. Third, the digitalization process in the petrochemical industry started later compared to other industries, and smart low-carbon energy systems featuring multiple energy source integration have not yet been applied in the refining industry. 3 Current Status of Carbon Emissions in the Refining Industry. As an industry that provides essential transportation fuels and raw materials for the basic chemical industry in China, the refining industry plays an irreplaceable role in the development of the national economy; however, it also emits large amounts of carbon dioxide in the process. According to statistics, greenhouse gas emissions from the global chemicals and petrochemical industries account for 5.8% of total emissions, of which 3.6% comes from energy use and 2.2% from industrial processes. China emits nearly 600 Mt of carbon emissions each year in the processes of oil refining and basic chemical production, accounting for about 6% of the country’s total carbon emissions; therefore, reducing carbon emissions is a practical and urgent task for the refining industry. Depending on the scale of the refinery and its processing processes, there are significant differences in carbon emissions from refineries. The carbon emission intensity of the refining segment in fuel-based refineries (carbon dioxide emissions per unit of crude oil processed) is approximately 0.15–0.30 t/t, while that in integrated refining and chemical plants is around 0.20–0.45 t/t. The chemical transformation of the refining industry will lead to a substantial increase in carbon emissions at the production level. However, from a life cycle perspective, thanks to the carbon sequestration effect of chemical products, the carbon emissions throughout the life cycle of crude oil are significantly reduced after it is processed in integrated refining plants. 4 Composition of carbon emissions in refineries: With the introduction of China’s \"dual carbon\" goals, refineries are in urgent need of identifying the sources and intensity of carbon emissions within their operations. They must also be able to assess trends in carbon emissions promptly when making adjustments to their production plans, in order to effectively monitor or predict such emissions and develop targeted strategies for reducing carbon emissions. Table 1 shows the carbon emission composition of typical oil refineries. It can be seen that there is a significant difference in emission intensity between fuel-based refineries and integrated refining and chemical processing plants, at 0.181 t/t and 0.346 t/t respectively. Fuel-based refineries have a lower emission intensity, mainly because their processes are relatively shorter and their plant complexity is relatively lower. In terms of emission types, the process emissions from integrated refining and petrochemical plants are significantly higher, mainly due to the high carbon emissions associated with catalytic cracking coking and hydrogen production during the chemical transformation process. In the process of achieving carbon peak and carbon neutrality in integrated refining plants, in addition to using green energy and green hydrogen, more consideration should be given to employing CCUS technology to address carbon emissions from manufacturing processes. Table 1 Composition of carbon emissions in typical refineries Figure 5 Pathways for low-carbon development in the refining industry 5.1 Further promoting energy conservation and carbon reduction 5.1.1 Optimization of steam power systems Refinery steam power systems are characterized by multiple levels of parameters, various fuel sources, diverse demands for steam production and supply, as well as multiple operational cycles; they are located at the forefront of the energy conversion process. The optimization of steam power systems is easily influenced by process units, other utilities, as well as auxiliary and ancillary production systems. In efforts to conserve energy within petrochemical enterprises, the energy-saving effects of optimizing steam power systems are primarily reflected in reduced consumption of electricity, steam, and fuel gas; thus, it constitutes a vital component of energy conservation and carbon reduction in refineries. By using process simulation to assist in establishing a complete mathematical model of the steam power system, formulating mixed-integer nonlinear programming problems and optimizing their solutions, it is possible to optimize the equipment in the steam system as well as the driving methods of the power sources, optimize the steam network, and optimize the distribution of steam – thereby achieving energy savings and reduced carbon emissions. For refineries with a capacity of tens of millions of tons, optimizing the steam power system can reduce carbon dioxide emissions by 30–100 kt per year. Sinopec Jinling Branch took into account the three stages of steam generation, transmission, and consumption, and developed models of the power stations and steam pipelines. As a result of optimizing the steam system, electricity generation increased by 7,227 kW, 30 tons per hour of low-pressure steam was saved, and an annual reduction in carbon dioxide emissions of around 55 kt was achieved. After the optimization project for the plant’s steam pipeline network system was implemented at the Petrochemical Complex of Sinopec Shengli Oilfield Co., Ltd., steam consumption was reduced by 10 tons per hour, resulting in annual economic savings of over 5 million yuan; moreover, nearly 20 kilotons of carbon dioxide were reduced each year. 5.1.2 Efficient utilization of low-temperature waste heat: Low-temperature waste heat is the heat that remains unused in a production system even after internal heat recovery; it originates from the conversion of fuel thermal energy. The proper utilization and recovery of such waste heat are important aspects of energy conservation and carbon reduction. Based on relevant data estimates, the amount of medium- and low-temperature waste heat available in China’s refining and chemical enterprises at 80–150 °C is 20–30 GW. To improve the efficiency of utilizing low-temperature waste heat in refineries, diagnosis and analysis can be carried out using process simulation and computational fluid dynamics. In accordance with the principle of \"matching temperatures and utilizing heat at each stage,\" comprehensive optimization of the low-temperature heat resources across the entire refinery can be achieved based on the balance of the plant’s steam power system. For refineries with a processing capacity of tens of millions of tons, optimization through efficient utilization of low-temperature waste heat can result in a reduction of the overall energy consumption by around 2% even if the efficiency of low-temperature heat recovery increases by only 10%; meanwhile, carbon dioxide emissions can be reduced by approximately 40 kt/a. Table 2 shows the energy savings and carbon reduction effects achieved through low-temperature heat optimization in a 5.0 Mt/a refinery. As can be seen from Table 2, after low-temperature thermal optimization, the consumption of steam, fuel gas, and electricity all decreased to varying degrees. Table 2: Energy savings and carbon reduction data after low-temperature heat optimization at a certain refinery. Figure 1: The units are tons of oil equivalent (tOE), with 1 tOE equal to 41.868 GJ. 5.1.3 Integration and optimization of heat exchange networks Heat exchange networks play a crucial role in energy recovery within refineries; improving the efficiency of heat exchange is an important means for refineries to save energy, reduce carbon emissions, and enhance economic performance. The integrated optimization of heat exchange networks can employ a combination of pinch analysis and mathematical programming to conduct thorough simulations of the heat exchange networks in the entire plant as well as individual units. Detailed diagnosis and sensitivity analysis of these networks are carried out, and operational optimization and retrofitting measures are proposed based on the energy consumption characteristics and constraints of each unit, thereby achieving an optimized allocation and comprehensive utilization of energy resources. Furthermore, by establishing an intelligent optimization platform for heat exchanger networks, optimization schemes for such networks can be automatically generated based on the processes and optimization objectives of different refineries, thereby providing more cost-effective solutions for energy conservation and efficiency improvement. The integrated optimization technology for heat exchange networks can be widely applied to thermal integration among various units within a refinery and across the entire plant. By improving energy utilization efficiency, it helps reduce the consumption of fuel gas and steam in heating furnaces, thereby achieving energy conservation and carbon emission reduction. Taking a million-ton-class atmospheric and vacuum distillation unit as an example, optimization of the heat exchange network integration can reduce the unit’s energy consumption by 1–3 kgOE/t (1 kgOE = 41.868 MJ), cut CO2 emissions by 20–50 kt/a, and increase economic benefits by 15–30 million yuan/year. By applying heat exchange network integration optimization technology, Sinopec Jinan Branch adjusted and optimized the heat exchange network of its atmospheric and vacuum distillation units, resulting in an increase in the final temperature of heat exchange by 5 °C and a reduction in the load on the heating furnaces by 6.58%. Through the optimization of its heat exchange network, the atmospheric and vacuum distillation unit of a domestic enterprise managed to raise the final temperature of the heat exchange network by 10 °C, reduce energy consumption by 0.7 kgOE/t, and achieve an increase in economic benefits of approximately 1.26 million yuan per year. 5.2 Improving resource utilization efficiency
5.2.1 Optimizing crude oil supply
Crude oil is the main raw material for refineries; its cost accounts for approximately 90% of the total production costs in refineries. Therefore, the proper selection and utilization of crude oil play a crucial role in refineries. The efficient utilization of crude oil resources can be achieved, on the one hand, through the development and application of new technologies, and on the other hand, by making proper selections of crude oil and adjusting processing methods. Optimization models tailored to the actual production conditions of refineries are developed to optimize crude oil selection and operational processes; overall process optimization is carried out by integrating refinery process models. This approach not only helps to maximize corporate profitability but also enables efficient management of the refinery’s carbon assets. Research findings show that changes in crude oil properties have a significant impact on the plant’s energy consumption and carbon emissions. Taking a hydrocracking refinery with a processing capacity of tens of millions of tons as the research subject, and based on the types of crude oil actually processed by the enterprise, comparison scenarios with different crude oil compositions were established to examine the impact of crude oil properties on energy consumption and carbon emissions during the production process. The results are shown in Table 3. As can be seen from Table 3, as crude oil becomes lighter and has lower sulfur content, both the overall energy consumption and carbon emissions of the plant show a downward trend, with significant reductions. Table 3: Properties of mixed crude oil and overall plant energy consumption and carbon emission levels. Figure 5.2.2 Molecular refining (component refining): Molecular refining (component refining) is a viable approach for improving the efficiency of oil refining and reducing its energy consumption. Its core principle involves using advanced separation techniques to separate the hydrocarbon components of crude oil or its various fractions, followed by the refining of these separated components. The conventional approach is to maximize the production of chemical products through the direct catalytic cracking of 10 Mt/a of crude oil. As shown in Figure 2, after the crude oil is processed in a catalytic cracking unit, the cracked dry gas, liquefied gas, and gasoline are further processed in subsequent units to yield ethylene, propylene, C4 liquefied gas, and benzene, toluene, xylene (BTX) products. The cracked diesel is processed in a diesel aromatic reforming (RLA) unit; the reformed gasoline is then subjected to aromatic extraction to produce BTX products, while the reformed diesel is fed back into the catalytic cracking unit. Figure 2: Basic design scheme for a chemical-type refinery. Taking a refinery with a crude oil processing capacity of 10 Mt/a as an example, a processing flow diagram is designed based on the concept of component-based refining, as shown in Figure 3. Crude oil is separated into light, medium, and heavy fractions using a distillation unit; thereafter, the saturated fractions are isolated using respective separation devices before being fed into a catalytic cracking unit for further processing ； The light fraction of unsaturated hydrocarbons is used to produce triphenyl products through hydrodesorption, the medium fraction of unsaturated hydrocarbons undergoes catalytic cracking after hydrogenation, while the heavy fraction of unsaturated hydrocarbons is fed into coking units for processing ； Catalytic cracking of dry gas, liquefied gas, and gasoline enables the separation of ethylene, propylene, C4 liquefied gas, and triphenyl products through subsequent processing units. Catalytic cracking of diesel and the unsaturated components in middle distillates is carried out in a circulating oil hydrogenation-catalytic cracking unit, which can produce methylnaphthalene oil and anthracene oil. Figure 3: Chemical-type component separation refinery scheme. A comprehensive study of the overall process was conducted for both the conventional scheme and the component-based refining scheme, with a comparison of the product distributions; in the component-based refining scheme, the yields of ethylene, propylene, and triphenyl products were all higher than those in the conventional scheme ； Meanwhile, by separating the unsaturates from the feedstock of the catalytic cracking unit, the total amount of coke formed in the catalytic cracking process under this component-based refining scheme is lower than that in conventional schemes. By comparing the economic benefits of the two options at a crude oil price of $60 per bbl (1 bbl≈159 L), it was found that the product value generated by the fractional distillation approach was higher than that of the conventional approach. Although the operating cost per ton of oil and the depreciation costs associated with capital investment in the fractional distillation approach were higher than those in the conventional approach, its gross profit per ton of oil was still 185 yuan higher. Due to the reduction in coking amount in the catalytic cracking unit under the component-based refining scheme, the total carbon emissions associated with this scheme are 445.7 kt/a less than those of the conventional scheme. Meanwhile, as the value of the products produced under the component-based refining scheme increases, the carbon emission intensity per 10,000 yuan of product value is 0.26 t less than that of the conventional scheme, representing a reduction of 9.2%. 5.2.3 Efficient utilization of hydrogen resources: As the quality of crude oil deteriorates, environmental protection requirements become increasingly stringent, and there is a pressing need for transformation in the chemical industry, refineries’ demand for hydrogen is rising year by year. The cost associated with using hydrogen continues to increase, making it the second largest cost factor for refineries, after crude oil itself. However, hydrogen production facilities are expensive (with a cost of 10,000–20,000 yuan per ton of hydrogen), consume a large amount of energy (with an average overall energy consumption of over 1,000 kgOE/t), and generate high levels of carbon emissions (the carbon emissions from hydrogen production using natural gas are approximately 11 tons per ton of hydrogen). Therefore, conducting integrated design and optimization of hydrogen systems in refineries to improve hydrogen utilization is an important approach for petrochemical enterprises to save energy, reduce carbon emissions, and enhance efficiency. To achieve efficient utilization of hydrogen resources, refining companies need to shift their approach to hydrogen use from a crude form of hydrogen balance to a more refined form of hydrogen management. They should focus on four key areas: optimizing the raw materials used in hydrogen production, managing hydrogen consumption in equipment that uses hydrogen, recycling hydrogen resources, and optimizing the integration of hydrogen networks. By doing so, it is possible to make use of hydrogen resources in a more efficient and systematic manner, improve the efficiency of hydrogen utilization within the system, and minimize hydrogen consumption, energy consumption, and carbon dioxide emissions. This helps companies achieve low-carbon and high-quality development. The technical approach for the integrated optimization of hydrogen network systems includes: ① Using hydrogen pinch analysis to diagnose the current operating conditions of the hydrogen system in refineries, identifying the bottlenecks in hydrogen usage, and conducting a thorough analysis of the potential for hydrogen savings and the directions for optimization ； ②Strict simulations of hydrogen-consuming devices are carried out to implement hydrogen-saving management for such devices, achieve coordinated optimization of the hydrogen network and hydrogen-consuming devices, and integrate the optimization of the hydrogen distribution network with the optimal operating conditions of hydrogen refueling stations ； ③A mathematical programming model for the superstructure of hydrogen networks is developed to optimize the topology of hydrogen networks under practical constraints. The mixed-integer nonlinear programming model can take into account constraints such as pressure limits, logical restrictions, the mathematical models of purification and compression units, investment costs, and payback periods. With minimizing the total annual cost as the objective function, it effectively balances the relationships among hydrogen savings, investment costs, and operating costs ； ④Taking into account the overall layout of the refinery, as well as the pressure in the pipeline network and the hydrogen consumption patterns of the regional hydrogenation units, and after carefully weighing the engineering investment costs against operational expenses, the existing hydrogen pipeline network is fully utilized for optimization and modification, thereby achieving integrated optimization of the hydrogen network system. For refineries with a processing capacity of tens of millions of tons, optimizing the hydrogen system is expected to improve the efficiency of hydrogen utilization by 2%–5%, reduce carbon dioxide emissions by 20–50 kt per year, and generate economic benefits of around 30–60 million yuan per year. After optimizing its hydrogen system, the Shijiazhuang Refining and Chemical Branch of Sinopec in China saw its overall hydrogen utilization rate rise from 76% to 88%. After the implementation of the optimization plan for the operating load of the hydrogen production unit, the purchased hydrogen volume can be reduced by 10,493 m³/h, resulting in an annual cost savings of 11.8858 million yuan ； After the implementation of the optimized hydrogen cascade utilization plan, 420 m3/h of externally purchased hydrogen was reduced, resulting in annual cost savings of 3.8758 million yuan ； After the implementation of the optimized plan for the comprehensive recovery of hydrogen and light hydrocarbons, 12,014 m3/h of externally purchased hydrogen was reduced, resulting in an annual economic benefit of 97.3821 million yuan. By implementing optimization measures such as hierarchical utilization of hydrogen resources and refined management, Sinopec Qilu Branch has managed to increase crude oil processing volume while keeping the hydrogen production units either shut down or operating at reduced capacity, resulting in annual savings of around 89 million yuan in hydrogen costs. The results of the optimization of the hydrogen system at Sinopec’s Shengli Oilfield Branch show that the optimization model can effectively reduce the operating costs of this system. By implementing measures such as optimizing the raw materials used in hydrogen production units, optimizing the reaction processes within these units, and installing new PSA units for hydrogen recovery, an annual economic benefit of 15.44 million yuan is achieved. These measures not only help save hydrogen but also significantly reduce the process emissions from the hydrogen production units in the refineries. 5.3 In-depth adjustment of the industrial structure: As the \"dual carbon\" policies are implemented more thoroughly, it will inevitably lead to significant changes in the energy structure. Oil’s role as a primary source of energy will gradually diminish, and its function will shift from serving as a main fuel for transportation to being used in the production of chemical products. As shown in Table 4, although the carbon emissions during the production phase of chemical-type refineries increased significantly, their carbon emission intensity over the entire life cycle decreased by more than 50%. If technologies such as green electricity, electric heating, and CCUS are used to address electricity-related emissions, fuel combustion emissions, and process emissions in future production processes, the oil refining industry can achieve zero carbon emissions throughout its lifecycle. Chemical-type refineries feature low carbon emissions throughout their life cycle, representing the low-carbon development direction for refining and petrochemical enterprises. Table 4 Comparison of carbon emission intensity among different types of refineries. Figure 5.4 Promoting the circular economy. 5.4.1 Chemical recycling of waste plastics. As a downstream product of the refining industry, plastics in China are produced in an annual amount of 95 Mt, while 63 Mt of waste plastics are generated each year. At present, one-third of waste plastics in our country are processed through physical recycling, one-third through incineration, and another one-third through landfilling. Traditional treatment methods not only result in significant land use and pollution but also generate large amounts of CO2. As an emerging technology that has received significant attention in recent years, the chemical recycling of waste plastics not only helps to reduce carbon emissions during the processing of waste plastics as well as the carbon footprint associated with the production of new plastics, but it also **helps to reduce China’s reliance on imported crude oil. In recent years, Sinopec Research Institute of Petroleum Processing Co., Ltd. has developed the waste plastic pyrolysis (RPCC) technology and completed pilot-scale tests. Based on the integration of chemical utilization of waste plastics in petroleum-based refineries, studies were conducted on refinery carbon emissions and product carbon footprints, with the results shown in Tables 5 and 6. As can be seen from Tables 5 and 6, using waste plastic oil to replace crude oil in fuel-based refineries results in a 58.9% reduction in carbon emissions during the processing process ； When waste plastic oil is used to maximize the production of polyolefins, the carbon footprints of polyethylene and polypropylene products (in terms of CO2 emissions per unit of polyolefin) are 1.48 and 1.17 t/t respectively, representing reductions of 26.4% and 24.0% compared to polyolefins derived from crude oil. Whether it is producing oils from waste plastics or producing polyolefins through the chemical recycling of waste plastics, carbon emissions and the carbon footprint of the products are significantly reduced, resulting in substantial emission cuts. Table 5: Carbon emission intensity associated with the chemical utilization of waste plastics in fuel-based refineries – Image. Table 6: Carbon footprint of polyolefins produced from waste plastics – Image. 5.4.2 Bioenergy technologies: Petroleum resources are non-renewable, and their use results in large amounts of net carbon dioxide emissions. Faced with both the crisis related to petroleum resources and environmental issues, scientists have turned their attention to renewable resources. As an important component of sustainable raw materials, bio-oils remain the primary source for bio-jet fuel. The oil-based raw materials are pre-treated to remove certain impurities before undergoing hydrogenation; during this process, oxygen, sulfur, nitrogen, and other heteroatoms in the raw materials are removed. Subsequently, hydrocarbon components for bio-jet fuel are produced through hydrogenation, and their composition is similar to that of conventional jet fuel. According to current standards, up to 50% of conventional jet fuel can be replaced by bio-jet fuel, and no modifications to an aircraft’s existing fuel or propulsion systems are required when using bio-jet fuel. The emission reduction effects of biojet fuels vary depending on the different raw materials and processing methods used. According to calculations, compared to petroleum-based jet fuel, the carbon dioxide emission reduction over the entire life cycle of jet fuel produced from used fats and oils ranges from 67% to 94%. Microalgae are single-celled organisms capable of photosynthesis, which allows them to convert carbon dioxide and inorganic nitrogen into organic carbon (mainly sugars and lipids) and organic nitrogen (mainly proteins) with extremely high efficiency, granting them great practical value. On the one hand, microalgae can achieve “addition,” producing large amounts of biomass rich in fats and proteins ； On the other hand, it enables a \"subtraction\" approach by absorbing and sequestering the carbon dioxide and NOx released from the use of fossil fuels, thereby contributing to the achievement of goals related to peak carbon emissions, carbon neutrality, and the control of air pollution. With a scale of 3,400 mu, microalgae cultivation can absorb 10 kt of carbon dioxide annually, while producing approximately 5,400 tons of high-protein microalgal biomass, which has a market value of up to 70 million yuan. 5.5 Resource utilization of carbon dioxide: CCUS technology is one of the key technologies globally for addressing climate change. Given its ability to capture and convert large amounts of carbon dioxide, it is regarded as an effective and necessary means of achieving carbon neutrality. According to the International Energy Agency, carbon dioxide captured through CCUS could account for one-sixth of the total carbon dioxide emissions that need to be reduced by 2050. The resource utilization of carbon dioxide mainly includes the production of fuels and chemicals from carbon dioxide. The hydrogenation of carbon dioxide can yield polycarbon organic compounds with higher economic value, and the direct production of jet fuel from carbon dioxide via hydrogenation is considered a transformative strategic technology. The design of new materials and catalysts based on new research strategies, as well as the development of catalytic systems, are key to achieving the hydrogenation conversion of carbon dioxide. The modular high-efficiency technology developed by the China Institute of Petroleum Science for the hydrogenation of carbon dioxide into jet fuel enables a one-pass conversion rate of 41.6% for carbon dioxide, along with a selectivity of 51.1% for kerosene fractions. Compared to petroleum-based jet fuel, the CO₂ hydrogenation process for producing jet fuel results in a reduction of nearly 3 tons of carbon emissions per ton of fuel over its entire life cycle. Given China’s current annual consumption of 33 Mt of jet fuel, even if only 10% of this amount were replaced by such fuel, it would lead to an annual carbon emission reduction of approximately 10 Mt. The technology of converting carbon dioxide into methanol through hydrogenation not only enables the sustainable utilization of carbon dioxide but also transforms green electricity generated from wind and solar energy into chemical energy that can be stored and transported. It represents a green and low-carbon energy storage technology, and serves as an important technical foundation for achieving carbon neutrality. The reaction of carbon dioxide with green hydrogen to produce 1 ton of methanol can result in a reduction of 2 tons of carbon dioxide emissions. Compared to methanol produced from coal, and based on China’s current methanol production volume of 97 Mt/year, even with a 10% substitution rate, an annual carbon emission reduction of around 20 Mt can be achieved. 5.6 Green Hydrogen in Refining According to a report by the World Energy Council, hydrogen can be classified as “gray,” “blue,” and “green” based on its source of production. Grey hydrogen mainly comes from fossil fuels; depending on the raw materials used for hydrogen production, the carbon emissions associated with traditional hydrogen production processes are approximately 10–23 t/t. Blue hydrogen is hydrogen produced from fossil fuels, but the carbon dioxide generated during the hydrogen production process is captured and stored. Green hydrogen is hydrogen produced by electrolyzing water using green electricity; the hydrogen production process generates no carbon emissions, but the cost is currently relatively high. In 2020, China’s hydrogen production exceeded 25 Mt, with the refining and chemical industries accounting for 25% of the hydrogen consumption. As product quality improves and the refining industry undergoes transformation, demand for hydrogen is set to continue rising. Since the production of green hydrogen does not generate carbon emissions, green hydrogen refining will be one of the key approaches to achieving deep decarbonization in the oil refining industry. In the medium to long term, as the demand for carbon reduction increases and green hydrogen technology advances along with improved cost-effectiveness, the hydrogen supply structure will gradually shift from hydrogen produced from fossil fuels, which is associated with high carbon emissions, to green hydrogen derived from renewable energy sources. Taking a refinery with a processing capacity of tens of millions of tons as an example, if all the hydrogen used as feedstock is replaced by green hydrogen, the refinery’s carbon emissions can be reduced by more than 2.0 Mt per year. 5.7 Promoting the development of smart refineries On December 28, 2021, eight departments including the Ministry of Industry and Information Technology jointly issued the \"14th Five-Year Plan for Intelligent Manufacturing Development.\" It specifies that by 2025, the majority of manufacturing enterprises above a certain scale will have achieved digitalization and networking, while key enterprises in major industries will have begun to utilize intelligent technologies ； By 2035, digital and networked capabilities will be fully adopted by manufacturing enterprises above a certain scale, with key enterprises in major industries basically achieving intelligence ； It supports enterprises in building intelligent workshops/factories based on standards, using innovation to drive change in order to improve quality, efficiency, and productivity, reduce resource and energy consumption, streamline the industrial and supply chains, and contribute to achieving the goals of carbon peak and carbon neutrality. Digital transformation, networked collaboration, and intelligent innovation are the irreversible trends in the oil refining industry today. The construction of smart refineries should be based on the inherent characteristics of the industry and focus on intelligent features. It should rely on data from production operations, use simulation of process equipment as a means, and emphasize collaborative optimization at all levels, in order to achieve optimized process flows, efficient allocation of resources, and intelligent decision-making support. Real Time Optimization (RTO) is a key element that facilitates the vertical integration of production planning, scheduling, operation optimization, and real-time control in refineries. It enables the real-time adjustment of operating conditions of the plants based on changes in factors such as the properties of raw materials, product specifications, and market demands, thereby ensuring that the production units operate under the most optimal conditions possible. Based on real-time optimization technology, it is possible to fully utilize the operational potential of existing production facilities without requiring significant investment in new equipment. This enables the key technical and economic indicators to reach or exceed those of advanced facilities of the same type, thus effectively achieving the goals of improving quality, increasing production, saving energy, and reducing consumption – all of which contribute to the safe, efficient, green, and low-carbon development of enterprises. Taking the atmospheric and vacuum distillation units in petrochemical plants with production capacities in the tens of millions of tons as an example, by applying real-time optimization techniques, the light oil yield can be increased by 1%–3%, the overall energy consumption can be reduced by 1–2 kgOE/t, carbon dioxide emissions can be decreased by 20–40 kt/a, and the economic benefits can increase by 15–80 million yuan per year. Sinopec Maoming Branch applied the real-time model to its 5.0 Mt/a atmospheric and vacuum distillation unit, resulting in economic benefits of approximately 40.5 million yuan per year. Mamdouh Gadalla and others optimized the crude oil distillation unit at an Egyptian refinery, ultimately reducing energy consumption and carbon dioxide emissions by 17%. 6 Conclusion **Policies provide strong strategic guidance and methodological guidelines for the petrochemical industry in its efforts to achieve carbon neutrality, but at the same time, the refining industry also faces numerous challenges in pursuing low-carbon development. As a complex process-based industrial sector, the refining industry faces various challenges in the process of carbon emission reduction, including limited basic data, numerous constraints, and heavy emission reduction targets. There is a structural surplus in refining capacity; the efficiency of energy utilization in refining needs to be improved urgently, and further progress is required in technological innovation and application. The low-carbon development of the refining industry requires an integrated approach that takes into account both the overall and individual aspects, balances development with emission reduction, and considers short-term and long-term perspectives. Through technologies such as energy-saving techniques, efficient utilization of crude oil and hydrogen resources, advanced refining unit technologies, process reengineering based on component analysis, use of renewable resources, resource recycling, smart refineries, green hydrogen-based refining, and CCUS, sustainable low-carbon development in the refining industry can be achieved. The content of this article is taken from the first issue of 2023 of \"Petroleum Refining and Chemical Engineering\"; it has been compiled and published by Shihua Yuan. Please indicate the source when reproducing it, and those wishing to submit articles in collaboration with Shihua Yuan should contact us via WeChat at the end of the article!