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Introduction: The Japanese coke industry, which developed alongside the growth of the steel industry, boasts world-class coal utilization technologies and coke oven operation techniques. However, as the coke ovens age, they will reach the end of their service life one after another over the next decade. If the existing coke ovens are not upgraded, it will lead to a severe shortage of coke. Furthermore, the current coke production technologies face issues such as resource constraints, environmental pollution, and particularly harsh working conditions; therefore, simply rebuilding coke ovens cannot meet the needs of societal development. European and American countries are also facing the same problem of developing new coke production methods: technology is a challenge for the global steel industry. There are two main directions for the development of coke production technology in the 21st century, focusing primarily on the effective utilization of low-cohesiveness coal and environmental improvement, as well as reducing energy consumption. In response, many new coking technologies have been developed, such as the \"giant coking reactor–single-hole coking system\" created by European coking experts, and the SCOPE21 process developed in Japan. This article mainly introduces the development trends of the SCOPE21 process, a coking technology designed to meet the requirements of the 21st century. 1 Traditional coke production process 1.1 Coal carbonization The current coke production process involves the carbonization of coal in coke ovens; the coal fed into the ovens has a moisture content of around 9%, or its moisture level is reduced to about 6% after preheating, and it is then heated to 950°C–1,050°C within the oven for carbonization. The dry distillation process is divided into 4 stages: (1) Dehydration and softening zone: The temperature is raised to around 380°C; the coal entering the furnace first loses water and then becomes soft ； (2) Thermal decomposition temperature range: When heated to around 460°C, the coal begins to undergo thermal decomposition, softening and melting at the same time; further heating leads to the formation of semi-coke ； (3) Carbonization temperature range: As the heating temperature increases, the semi-coke shrinks, and the dry distillation reaction is essentially completed at 900°C ； (4) Coke formation area: To avoid uneven heating inside the coke oven and resulting variations in coke quality, it is usually heated to around 1,000°C. 1.2 Problems in traditional coke production processes and corresponding improvement measures: The existing coke production processes typically use highly caking coals that are in short supply, resulting in low production efficiency and poor thermal efficiency. At the same time, there are also issues such as gas leaks contaminating the environment. Therefore, when developing new coking processes, it is necessary to carry out a thorough reform of the existing processes. 1.2.1 Effective utilization of weakly caking coal: In existing coking technologies, only about 20% of weakly caking coal can be used; new technologies aim to increase this ratio to 50%. The caking property of the coal is improved by preheating it, and its bulk density is enhanced through briquetting techniques that utilize fine coal powder. 1.2.2 Increasing productivity: To achieve the goal of a significant increase in productivity, by preheating the coal before it enters the furnace, ensuring high thermal conductivity of the carbonization chamber walls, using thinner chamber walls, and providing uniform heating, it is possible to produce coke at temperatures lower than those used in conventional carbonization processes (900°C–1,000°C), thereby significantly reducing the coking time. The portion with insufficient dry distillation temperature is reheated using a coke dry quenching device (CDQ) to ensure product quality. 1.2.3 Improving the environment: The coal fed into the furnace is transported using a plug-type conveying method; the operating pressure of the coke oven is adjusted, and sealed dust collection is implemented during coal extraction to reduce dust levels, thereby completely eliminating smoke, dust, odors, and other pollutants generated during coke production. Furthermore, low NOx emissions are achieved by improving the heating gas combustion device. 1.2.4 Energy-saving technologies: High-temperature preheating of the coal fed into the furnace raises the starting temperature for carbonization ； Through medium and low-temperature dry distillation, the temperature at which coke is taken out of the furnace was reduced, and the heat required for heating the coke oven was decreased. Furthermore, energy savings are achieved through the recovery of the sensible heat from the generated gas and combustion exhaust gases. 2 SCOPE21 Process 2.1 Overview The Japan Coal Utilization Center and the Japan Iron and Steel Federation jointly developed the “21st Century New Coke Oven Manufacturing Technology (SCOPE21)” over a period of 10 years from 1994 to 2003. The SCOPE21 process is a new process designed for the 21st century, aimed at making effective use of coal resources, improving productivity, and achieving innovation in environmental/energy-saving technologies; the process flow is shown in Figure 1. http://www.nmtech.com.cn/jishuwang/upload1/070710929591101.jpg First, the raw coal is dried and graded; the coarse coal particles and fine coal powder are each heated rapidly to 350°C–400°C. The fine coal powder is then compressed into pellets and mixed with the coarse coal powder, thereby improving the cohesion of weakly cohesive coal and enabling a significant increase in productivity as well as energy savings. Second, the preheated coal powder is fed into a chamber-type coke oven, which is constructed from thin-walled refractory bricks with high heat conductivity. The coal is taken out of this oven at a temperature lower than that used in conventional carbonization (medium- and low-temperature carbonization), and then sent to the reforming combustion chamber of the CDQ for reheating, in order to achieve the desired quality of coke, thereby improving production efficiency and reducing environmental impact. 2.2 Key Technology Development Phase 2.2.1 Development of Key Technologies From 1997 to 2001, through laboratory experiments and pilot-scale tests, the drying, heating, and grading characteristics of coal during pretreatment, as well as the modification effects during rapid heat treatment, were investigated and confirmed. Furthermore, the main coke oven unit uses a fuel test furnace equivalent to that in actual plants to develop a combustion system capable of uniform heating for high productivity and low NOx emissions. 2.2.2 Laboratory experiments: First, the performance of the key equipment in the SCOPE21 process – the coal preprocessing unit (drying and grading → rapid heating → thermal shaping → high-temperature coal transportation) – was evaluated and the laboratory setup was designed. With the aim of collecting high-quality data, a test bench was constructed at the Nagoya Steel Plant of Nippon Steel & Sumitomo Metal Corporation. The equipment’s capacity for coal processing is 0.6 t/h, which is one-tenth of that of industrial testing equipment. The experimental operations were carried out from October 1998 to March 2000. The experiment used a fluidized bed drying and grading device for coal particle grading, with the particle size of the coal particles being controlled by regulating the flow rate of the coal gas. The relationship between air flow velocity and coal particle size is shown in Figure 2. At the same time, the heating characteristics of coal were confirmed; its temperature rise behavior was essentially consistent with the results of the model analysis, achieving the heating target of 300°C. Figure 3 shows the characteristics of the heating equipment in the wind-heating system. For coarse coal particles (0.5 mm–6.0 mm) for which uniform heating is difficult, if the temperature of the hot air meets the requirements and the temperature variation among the particles remains within 50°C, it is estimated that such coarse coal can also be heated to around 380°C. http://www.nmtech.com.cn/jishuwang/upload1/070710930347775.jpg http://www.nmtech.com.cn/jishuwang/upload1/070710931033989.jpg 2.2.3 Pilot Testing and Industrial Trials: A series of devices including coal pretreatment units and retorting furnaces were developed for pilot testing, with the aim of verifying the development concepts and obtaining the engineering data necessary for the design of actual equipment. Experimental operations were carried out from March 2003 to March 2004. 2.2.3.1 The production capacity of the equipment is 6 t/h, which is approximately 1/20 of that of the actual machine. There are 2 retorting furnaces; the length of each furnace is half that of the actual unit, while its height and width remain the same as those of the actual unit. The experimental results regarding the optimal combustion system are also included, and this equipment enables the collection of the required design data. 2.2.3.2 Pilot-scale operations The pilot-scale operations were generally divided into two phases: one operation at a low furnace temperature (furnace temperature of 1,100°C–1,150°C) and two operations at a high furnace temperature (1,200°C–1,280°C), and these operations lasted for about a year. The total number of dry distillation tests reached 440, basically achieving the development goals. (1) Coke quality: The quality parameters of the test coal are shown in Table 1, with a 50% ratio of coking coal to weak coking coal. Additionally, coal pretreatment involves heating the coarse-grained and fine-grained coal together in a gas flow tower to 380°C after the fluidized bed is heated to 300°C. http://www.nmtech.com.cn/jishuwang/upload1/070710932073275.jpg shows the average strength of the coke produced in the experiments. http://www.nmtech.com.cn/jishuwang/upload1/070710932463189.jpg indicates that this strength is 2.5 higher than the estimated value of 82.3 obtained using the current manufacturing processes; thus, a good strength level is achieved, confirming that it is feasible to use 50% weak-cohesion coal in the mixture. Coupled with the increased density of the coal pile in the furnace, rapid heating was achieved. (2) Productivity Under conditions of a coal loading temperature of 330°C and a furnace temperature of 1,250°C, under normal wet-coal operation, the coking time is 17.5 hours; whereas this equipment requires only 7.4 hours to complete the coking process. Additionally, due to the increased density of the coal fed into the furnace, productivity can be increased by 2.4 times, as shown in Figure 4. It can also be confirmed that not only is high-temperature, high-speed carbonization possible, but shaping the fine-particle coal can also effectively enhance the strength of the coke. http://www.nmtech.com.cn/jishuwang/upload1/070710933229430.jpg (3) Improvement of the environment: The use of plug-type conveying methods for transporting high-temperature coal enables stable transportation at speeds of over 350 t/h ； The NOx emissions during combustion in the retorting furnace were exactly consistent with the test results of the combustion apparatus, achieving low NOx emission levels of below 100×10^-6 at the target furnace temperature of 1,250°C ； Regarding: Leak prevention measures for plant distillation furnace gas, while verifying the effect of pressure adjustment inside the furnace during dry distillation, data on local dust accumulation at the time of gas discharge is collected for practical design purposes ； Compared with the existing process in 1990, the SCOPE21 process reduces energy consumption by 21% when using a comprehensive energy evaluation (energy consumed vs. energy recovered from CDO). Electricity consumption increases in the coal pretreatment process, but gas consumption in the retorting furnace **decreases**. 2.2.4 Conceptual design and economic performance of actual equipment 2.2.4.1 Premises for equipment scale The coke production capacity corresponds to that of large blast furnaces (with an iron output of 10,000 t/d), amounting to 4,000 t/d (1.5 Mt/year) of coke; this includes facilities such as coal crushing, coal preprocessing, high-temperature coal transportation, dry distillation furnaces, and CDQ units. 2.2.4.2 Equipment performance parameters The main equipment parameters are listed in Table 2. Compared with the existing process, the production efficiency has increased by 2.4 times; as a result, the number of dry distillation furnaces in the SCOPE21 process has decreased from 126 to 53. Although coal preprocessing equipment has been added, the floor area required is half of that in the previous system. http://www.nmtech.com.cn/jishuwang/upload1/070710933589939.jpg http://www.nmtech.com.cn/jishuwang/upload1/070710934496003.jpg 2.2.4.3 Equipment costs and economic efficiency: Compared with the current process, although the SCOPE21 process involves additional items such as coal pretreatment equipment and environmental protection facilities, the significant reduction in the number of retorting furnace units results in an approximate 16% decrease in equipment costs. Although the SCOPE21 process incurs higher costs for electricity/fuel gas in coal pretreatment, the use of large amounts of low-caking coal results in lower raw material costs compared to existing processes; as a result, the total cost of coke production (variable costs plus fixed costs) is reduced by approximately 18%. 4 Conclusion The SCOPE21 process is a coking technology tailored to the requirements of the 21st century. It achieves the incorporation of 50% weakly caking coal by increasing the density of the coal pile, rapid heating, and uniform distribution of the coal ； Compared to the current process, production efficiency can be increased by 2.4 times, energy consumption can be reduced by about 20%, and the total cost of coke production (variable costs + fixed costs) can be lowered by approximately 18%.