Discussion on domestic and international coking processes and the development direction of coking in Shandong Province

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Discussion on Coking Processes at Home and Abroad and the Development Direction of Coking in Shandong Province Abstract: This paper introduces the development status of coking technologies worldwide, analyzes the current production situation of the coking industry in Shandong Province, and proposes new technologies that should be adopted for the future development of this industry in Shandong. Keywords: coking; coke oven; mechanical coke production; development trends 1 Status of coking production technology abroad 1.1 enlargement of coke ovens? To improve the production capacity and economic efficiency of coke ovens, the height and width of the carbonization chambers are increased during their design, leading to an trend toward larger coke ovens. The Prospehl Test Plant of the German Institute for Mining Research developed coke ovens with carbonization chambers 450 mm and 600 mm wide. The effective dimensions of the carbonization chamber in coke ovens have been increasing continuously. From 4.5m×11.7m×0.45m (height×length×width) in the 1970s, they increased to 7.1m×15.9m×0.59m in the 1980s. At the Kaiserstuhl Coke Oven Plant in Germany, these dimensions reached 7.18m×18.0m×0.61m in the 1990s, resulting in an effective volume of 78.8 m3 – making it the coke oven with the largest volume in the world today. It is capable of producing 48 tons of coke per batch, with only 120 chambers; the coking time is 25 hours, and the annual production capacity is 2 million tons. ? 1.2 Controlling coking pollution ? Coking plants are among the major sources of environmental pollution. In recent years, as environmental awareness has grown, various countries have established environmental protection standards. Many new technologies have been developed to reduce the dust pollution generated during coal charging in coke ovens, such as: (1) Spraying ammonia water at a pressure of about 3 MPa into the rising pipe or bridge pipe of the coke oven, thereby maintaining a negative pressure of nearly 0.16 kPa at the bottom of the rising pipe and enabling smoke-free coal charging; (2) Installing extraction, combustion, and purification equipment on the coal charging vehicle, and using such equipment to burn organic substances such as coal dust, cyanides, and benzo[a]pyrene; (3) Setting up connecting pipes on the coke side of the roof carbonization chamber, and during coal charging using “U”-shaped pipes to connect the roof carbonization chamber with adjacent carbonization chambers, so that some of the flue gases from coal charging pass through these “U”-shaped pipes to the adjacent chambers before entering the coke gas pipes; (4) Installing ground-based dust collection devices, and using a system in which the coal charging vehicle is connected to fixed suction pipes during coal charging, with the dust being drawn through these pipes to bag filters; (5) Employing a sequential coal charging method by the coal charging vehicle to reduce dust emissions. There are also various types of devices for eliminating coking-related pollution. For example, ventilation hoods can be installed on coking cars; these hoods have an opening at the bottom, and baffles are placed inside them during coke pushing. The heat buoyancy generated by these hoods helps to settle dust particles, allowing 90%–95% of the dust to be captured. A combination of a dust collection hood on the coking car and ground-based collection devices can be used as well – the dust collection hood is connected to fixed pipelines via belt-driven transfer carts, and the dusty gas is pumped to bag filters using fans, which reduces the dust content in the gas to below 20 mg/m3. 1.3 Expanding the sources of coking coal? Expanding the sources of coking coal and using a larger proportion of weakly bindable coals is the main way to reduce coking costs; for this purpose, various new coking technologies have been developed, such as ramming coking, blended coal coking, coal preheating, and shaped coals. Developing large-capacity coke ovens over the next 10 to 30 years, adopting compacting methods for coke production, using blended coals for coking, implementing dry quenching techniques and coal moisture control methods in order to improve the quality of coke, making more use of weakly bindable coals, striving to reduce production costs, and eliminating or mitigating environmental pollution will be the key development directions for China’s and Shandong Province’s coke industry. 2 Status of domestic coking production technology 2.1 Review of the development of coking technology in China? In the early years after the founding of the People’s Republic of China, China only had old coke ovens left over from Japan and Germany; the manufacturing processes were backward, the equipment was poor, and production volumes were very low, far from sufficient to meet the needs of New China’s development. In 1958, China’s first 58-type coke oven, designed and built domestically, was successfully put into operation at the Beijing Coking Plant, marking a revolutionary advancement in the country’s coking industry and urban gas sector. Subsequently, a large number of Type 66 and Type 70 coke ovens emerged like mushrooms after rain, playing an important role in promoting the development of China’s heavy industry. In the late 1970s and 1980s, by studying diligently, adopting new foreign coking technologies, and taking into account China’s national conditions, 6m coke ovens were designed and built. In just a few years, 6m coke ovens were rapidly adopted and spread; to date, 39 coke ovens with a height of over 5m have been built (27 of them are 6m in height, 5 are 5.5m in height, and 4 are 5m in height). Their production capacity amounts to 18 million tons, accounting for 24% of the country’s total coke production, thus playing an important role in the development of China’s coking industry. Entering the 1990s, coking environmental protection technologies, coking automation technologies, as well as various new types of coking technologies and equipment developed rapidly. China’s coking industry has gradually risen to the international forefront in terms of design capacity, product output, and technological level. 2.2 Development of coking technology? By the end of 1998, there were over 170 coking enterprises in China, equipped with 753 various types of coke ovens, resulting in a coking capacity of 80.1 million tons per year. Among these, 177 ovens had a carbonization chamber height of more than 4 meters, with a coking production capacity of 59.19 million tons per year; these accounted for 23.5% of the total number of coke ovens in the country and 73.9% of the total designed coking production capacity. In 1997, the country produced 139.02 million tons of coke, of which 70.672 million tons were produced by mechanical methods and 67.284 million tons by traditional methods. ? As China’s coking industry has developed from scratch, its technical and equipment standards have been continuously improving. In terms of coke ovens, China’s coke oven technology, represented by the 6m coke ovens used in Baosteel’s second phase of production, has reached international advanced levels. The degree of localization of the design and mechanical equipment for these coke ovens exceeds 90%, with 100% localization for the coke oven itself. In the field of gas purification, China has not only developed new technologies such as the ammonia water process, ammonium sulfate process, ADA desulfurization process, ammonia combustion process, and single-tower benzene removal process on its own, but has also acquired internationally advanced technologies through joint design with foreign countries and technology introduction. These include the full-negative-pressure gas purification process, AS washing process for desulfurization, decyanation, and benzene removal, acid removal and ammonia distillation process, ammonium sulfate process without a saturator, FRC process, T-H process for desulfurization and decyanation, Solvian process for desulfurization, cold and hot Fersum anhydrous ammonia processes, and ammonia decomposition-Claus process. Moreover, breakthroughs have been achieved in the localization of equipment and materials, pushing gas purification technologies and equipment to the international forefront. In terms of environmental protection, modern technologies for the coke industry have been developed and mastered, including high-pressure ammonia water spraying for smoke-free coal charging, thermal buoyancy covers, dust collection systems for coal charging and coke pushing in coke ovens, large-scale coke oven machinery equipped with smoke suppression devices, dry quenching processes, biological denitration technology for coke plant wastewater, and activated carbon adsorption technology for wastewater purification. In particular, China has developed its own biological denitrification technology for coke plant wastewater that is at an internationally advanced level; after successful industrial trials at the Xuecheng Coke Plant in Shandong, this technology was applied in the second-phase coke production project of Baosteel, yielding remarkable results. In the field of automatic control in electrical and production processes, PLC technology and DCS distributed computer control technology have been widely used in the construction of new plants and the renovation of existing ones. The technologies related to configuration, software development, control debugging, as well as those concerning hardware and computer equipment, along with signal transmission techniques, have been largely mastered. The degree of localization of materials used in data processing equipment and primary components is also increasing steadily. Latest technologies such as automatic detection and adjustment of temperature and pressure in coke ovens, factory computer management systems, and \"triple-electric integration\" design are also under development and promotion. In the field of chemical product refinement, large-scale advanced processing technologies for tar, coal-based acicular coke, as well as benzene hydrogenation and other techniques for refining crude benzene have been developed and put into use. The variety of industrial naphthalene, anthracene, pyridine and their refined products is increasing, while production volumes keep rising. 2.3 Existing Problems and Development Prospects Although China’s coking industry has achieved significant progress, there are still some issues. For example, coking enterprises are small in scale, with a high proportion of small-scale coke ovens; the refining processes for chemical products are outdated, processing sites are scattered, production volumes are low, and deep processing is insufficient. The coal preparation and coking processes are relatively simple, resulting in low efficiency; they do not suit the characteristics of China’s coking resources. Moreover, the existing ramming coking equipment is also outdated and inefficient. The production of low-quality coke still accounts for a certain proportion, leading to serious waste of resources and environmental pollution, which to some extent hinders the development of large-scale modern coking industries. ? Over the next 30 years, China’s coking industry (machine-made coke) will continue to develop. For a considerable period of time, blast furnaces will remain dominant, and coke consumption will keep increasing. ? As global energy sources such as oil and natural gas will remain at high prices, coking coal resources will become increasingly scarce overall. Although direct reduction and smelting reduction technologies have reached a certain level of development, issues related to energy consumption, efficiency, as well as various challenges associated with the processes and materials used in these technologies still need to be resolved; therefore, it will be difficult for them to compete with blast furnaces for a considerable time to come. Therefore, for some time in the early 21st century, the traditional blast furnace-sintering-blast furnace-converter process will remain dominant in steel production. In steel complexes over the next 20 years, the traditional coke oven-blast furnace smelting process will still retain its advantages. With the development of short-process technologies in steel production, electric furnaces will gradually become an important means for steelmaking. By 2010, more than two-thirds of the world’s crude steel would still be produced by steel complexes using blast furnace processes; therefore, coke will remain an important basic raw material for the metallurgical industry in the coming decades. It can be predicted that over the next 30 years, blast furnaces will continue to play an irreplaceable role in steel production worldwide, especially in developing countries. 3 The Technical Status and Development of Coking Production in Shandong Province? 3.1 The Technical Status of Coking Production? As of the end of 1999, there were 16 coking enterprises in Shandong Province, distributed across 4 sectors – metallurgy, chemicals, coal, and urban construction – in 9 cities and regions. There are a total of 50 coke ovens, with an annual designed production capacity of 4.21 million tons of coke. Among them, there are 10 ovens with a diameter of over 3.2 meters (7 ovens with a diameter over 4 meters, and 3 ovens with a diameter between 3.2 and 3.8 meters). These 10 ovens have an annual designed production capacity of 2.46 million tons of coke, accounting for 58.43% of the total designed production capacity of all the coke ovens. In 1999, Shandong Province produced 3.3965 million tons of machine-made coke in total; of this amount, 2.2426 million tons were produced within the metallurgical sector, while 1.7997 million tons were produced by enterprises under Shandong Provincial Metallurgical Industry Corporation. The province supplied 1,281,159 GJ of commercial gas, as well as 20 types of chemical products. Of the 16 coking enterprises, 14 are responsible for supplying gas for urban residents’ daily use, making positive contributions to supporting industrial production, facilitating people’s lives, and improving the urban environment and quality of life. In terms of technological progress and innovation, the coking enterprises in Shandong Province have successively developed and applied dozens of new processes, technologies, materials, and equipment, such as the single-tower benzene distillation process, flame welding for repairing coke ovens, coking using blended coke powder, smokeless coal charging with high-pressure ammonia water, water seals on rising pipe caps, horizontal tube pre-coolers, spiral plate heat exchangers, treatment of light tar to extract naphthalene, annular packing for benzene distillation towers, biological nitrogen removal for coking wastewater, needle coke, refined naphthalene, cast coke, ramming coking, dry quenching of coke, and the use of ramming coking technology in converting top-charging coke ovens to side-charging ones. These innovations have significantly contributed to the improvement of the coking technology level in Shandong Province. 3.2 Major existing problems: First, the coke ovens are of small size with a high proportion of such ovens; the technical and equipment standards are low, and the environmental protection facilities are inadequate. Secondly, a new large-scale coke oven project was originally planned, but due to a lack of funds, the plan had to be changed. Third, there are few chemical products, processing is scattered, and there are no large-scale centralized processing facilities or plants. 3.3 Development direction? Over the next 10–30 years, the development of large-capacity coke ovens, coal charging by ramming, coking using formulated coals, dry quenching of coke, and coal processing technologies, as well as the centralized and advanced processing of chemical products, are key directions for the development of the coke industry in Shandong Province. These efforts aim to improve the quality of coke, eliminate or reduce environmental pollution, and make greater use of low-cohesion coals. ? Focus on the development and promotion of the following technologies: coal moisture regulation technology; atmospheric and vacuum distillation processes for tar; processes for producing ammonium sulfate using \"vasc/scl+Nasco\" or \"HPF\" and spray saturators; automation of coke oven heating along with technologies for aligning the four locomotives and implementing interlocking systems; new flame welding techniques for coke ovens; dry quenching technology for coke; tamping coal feeding technology for coke production; blending coal types for coke production; technologies to extend the service life of coke ovens; automatic heating technology for coke ovens; coal-rock blending technology for coke production; dust removal techniques during coal loading and coke pushing in coke ovens; energy-saving and consumption-reduction technologies as well as waste heat utilization technologies. In short, during the 10th Five-Year Plan period and in 2010, through technological upgrades and the active adoption of high-tech solutions, Shandong Province’s coking industry will see significant improvements and developments in terms of equipment standards, technical capabilities, and product quality. This will contribute positively to the development of the province’s steel industry as well as to urban and rural economic construction.