Some Thoughts and Suggestions on the Access Requirements for the Coking Industry

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Some Thoughts and Suggestions on the \"Access Conditions for the Coking Industry\" Dong Hai To curb the trend of low-level repetitive construction and reckless expansion in the coking industry, promote the upgrading of the industrial structure, regulate industry development, and maintain market order, the **National Development and Reform Commission issued the \"Access Conditions for the Coking Industry\" on December 16, 2004, hereinafter referred to as the \"Conditions\". The “Conditions” have played an effective controlling role in approving the construction, renovation, and expansion of coke ovens. Meanwhile, the **National Development and Reform Commission has also approved 108 operating coking enterprises that meet the specified criteria; their total coking production capacity amounts to 125 million tons. This has played a positive role in facilitating the timely phasing out of outdated enterprises and coking ovens. After two years of operation, the \"Conditions\" have fulfilled the role intended when they were established, but certain provisions still have shortcomings. To this end, relevant issues were raised for discussion with relevant parties and experts, and revision suggestions were put forward in order to ensure that the \"Conditions\" provide better guidance for the future development of the coking industry. 1 Discussion on clause 1.1 of item II.(II) in the \"Conditions\", regarding the requirement that \"the height of the carbonization chambers in newly built, renovated, or expanded coke ovens must be 4.3 meters or more (including 4.3 meters), with an annual production capacity of 600,000 tons or more\": (1) Raising questions. The height of the coke oven chamber mentioned in this clause does not specify whether it refers to a coke oven fed with coal from the top or one fed with compacted coal. Since there are differences between the two in terms of process technology and equipment development levels, when the coal charging method is not specified explicitly, it should generally be understood as a top-charging coke oven. Given the distribution of coking coal resources in our country, developing ramming coal charging for coking is one of the important measures for making rational use of these resources, and it is a technology that is encouraged for promotion. Therefore, this clause should specify separately the required height of the carbonization chamber for top-charging coke ovens and for tamping-charging coke ovens. (2) Determination of the carbonization chamber height. As early as the 1960s, the international community began building coke ovens with a carbonization chamber height of 6 meters or more, considering ovens with a height of less than 5 meters as medium-sized coke ovens. Our country also built its first 5.5m coke oven at Panzhihua Iron and Steel Plant in 1970. In 1985, Baosteel introduced 6m coke ovens, and in 1987, the first 6m coke oven designed in China was built at the Beijing Coking Plant. In 1996, the former Ministry of Metallurgical Industry issued the \"Technical Specifications for Coking Process Design\" (YB9069－96) to guide the preparation and approval of project proposals and feasibility studies for the construction, renovation, and major repairs of coke ovens in coking plants (workshops). Based on the development level of the national economy, the scale of construction, and the progress in equipment standards at that time, these regulations classified coke ovens into three categories: large, medium, and small. Among them, coke ovens with a carbonization chamber height of 5 m or more are classified as large coke ovens. Those with a height of between 5m and 3m are medium-sized coke ovens. It can be seen that the 4.3m coke oven was classified as a medium-sized coke oven over 10 years ago, and it does not conform to future development trends. In July 2006, Article 13 of Chapter 4 of the \"Steel Industry Development Policy\" issued by the National Development and Reform Commission under Order No. 35 set the height of the carbonization chambers in newly built coke ovens at 6 meters or more. At present, China has built over 90 coke ovens with carbonization chambers reaching 6 meters in height, boasting a total production capacity of around 50 million tons. In addition, companies such as Taiyuan Iron and Steel, Maanshan Iron and Steel, and Yankuang have already built coke ovens with carbonization chambers 7.63 m high, while several other enterprises are planning to build or are currently constructing coke ovens that are 6 m, 7 m, or 7.63 m high. Although the \"Policy\" is aimed at steel enterprises, considering the layout of China’s coking industry and the technological development trends in related sectors, it is not advisable to establish separate coking plants in the future. Even if a few independent coking plants are building new or upgrading existing coke ovens, it is appropriate for the height of their carbonization chambers to approach 6 meters. Regarding rammed coal-charging coke ovens, foreign countries built rammed coke ovens with a carbonization chamber height of 6 meters in the 1980s, which are currently the tallest such ovens in the world. Our country has also developed and built 5.5m ramming coke ovens. To this end, this clause of the \"Conditions\" should specify that the height of the carbonization chamber in top-charging coke ovens shall be 6 m or more, and that the height of the carbonization chamber in ramming-charging coke ovens shall be 5 m or more. (3) Regarding the determination of the annual coking production capacity. The minimum limit set for the annual coking production capacity at 600,000 tons is clearly too low. Based on an annual coke production capacity of 600,000 tons, only 2 coke ovens with a capacity of 4.3 meters each are required. Once the 4.3m coke ovens are no longer considered suitable for use, and 6m top-charging coke ovens or 5m rammed coke ovens are used instead, just one such oven is needed to meet a demand of 600,000 tons. Moreover, constructing 1 coke oven is highly inappropriate in terms of process configuration. With 2 coke ovens, its production capacity can reach 1 million tons. When the production scale is 600,000 tons, no matter which advanced process technology is used, it is not economically or technically feasible. Therefore, to accommodate the revision of the height of the coke oven charging chamber. It is appropriate for this clause to revise the production capacity of newly built or renovated coke ovens to over 1 million tons. 1.2 Discussion on the requirement that “the scale of a newly built coal tar processing unit should be such that it can handle 100,000 tons per year or more of anhydrous tar.” As early as 1983, the former Ministry of Metallurgical Industry, following the guidance of the State Council’s Science and Technology Leadership Group, brought together experts and scholars from relevant research institutions, design institutes, universities, and certain enterprises in the steel industry. After nearly half a year of research and analysis, and further evaluation by over 400 experts over a period of about 3 months, they formulated the “Technical and Equipment Policies for the Steel Industry,” which were issued for trial implementation in the same year under document number “(83) Ye Ke Zi No. 1998”. This Policy stipulates that for coal tar processing, \"no new construction or major repairs shall be carried out on tar processing facilities with a capacity of 100,000 tons or less (including 100,000 tons)\". Since the issuance of this Policy, no organizations, enterprises, or individuals have raised any objections to it, which indicates that the Policy has been accepted by all parties. The \"Conditions\" have regressed compared to the 1983 level; they do not conform to the trend of expansion and consolidation, and are therefore inappropriate. Centralized processing of coal tar facilitates the use of various advanced process technologies and equipment, which not only helps with energy conservation and environmental protection but also enables the development of new tar-based products. In the 1980s, when evaluating the introduction of German technology for building a tar processing plant at the Shijiazhuang Coking Plant, analysis of various process technologies and economic indicators showed that an annual tar processing capacity of 200,000 tons represented the minimum economically viable scale. At present, our country already has the capability and infrastructure to design and manufacture a single tar processing unit with a capacity of 200,000 tons. Therefore, this clause in the Conditions should be revised to state that the capacity of a new coal tar processing unit must be 200,000 tons per year or more. Units of 100,000 tons and below will no longer undergo major overhauls. 2 Discussion on clause 2.(iii).1 of the \"Conditions\" regarding the requirement that \"for newly built or expanded coke ovens, dry quenching units should, in principle, be constructed simultaneously (in water-scarce areas and steel enterprises)\". The statement in this clause, “in principle (in water-scarce areas and steel enterprises)…”, does not fully align with the requirement in Article 13, Chapter 4 of the Steel Industry Policy, which stipulates that coke ovens for new projects must be equipped with dry quenching devices simultaneously. With a focus on energy conservation and environmental protection, the regulations should explicitly require that steel companies installing new coke ovens or upgrading/reconstructing existing ones must simultaneously build dry quenching devices. Given the fact that in independent coking enterprises, there is no proper way to dispose of wastewater contaminated with phenol, cyanide, and other pollutants after biochemical treatment, and such wastewater can only be treated through wet quenching, temporary special treatment can be applied to new coke ovens or those being upgraded or expanded by such enterprises (which should generally be subject to strict control). Therefore, this clause should be revised to state that when constructing new coke ovens or upgrading/reconstructing existing ones, steel companies must simultaneously install dry quenching equipment ； Independent coking enterprises should strive to install dry quenching units, provided that they can reduce the generation of phenol-cyanide wastewater and have proper methods for treating it. 3 Discussion on clause 3.(ii).2 of the «Conditions» regarding «H2S in the coal gas produced by coking enterprises for industrial or other uses ≤ 300 mg/m3». SO2 is a major pollutant among air pollutants in our country, and the task of controlling it will remain extremely arduous for a considerable period to come. In gas, H2S is converted to SO2 upon combustion, and the amount of SO2 produced is almost equal to that of H2S (the molecular weight of H2S is 34, while that of SO2 is 64). Therefore, strictly controlling the H2S content in gas is highly beneficial for reducing the formation of SO2. At the same time, gas with high H2S content is also not suitable for steel companies to use in the production and further processing of high-quality, specialty steels (such as stainless steel and electrical steel), as well as in applications like methanol synthesis and pure hydrogen extraction. Currently, among the several coke oven gas desulfurization technologies widely used in coking production, with the exception of a few, strict management and careful operation can ensure that the H2S content in the desulfurized gas remains below 200 mg/m3. If the H2S content in the gas is reduced from 300 mg/m3 to 200 mg/m3, approximately 80 tons of SO2 generated by burning coke oven gas can be reduced for every 1 million tons of coke produced. Therefore, it is recommended to revise the H2S content in desulfurized gas to ≤200 mg/m3. 4 Discussion on clause 4.(ii) of the «Conditions» regarding «tonnage of coke consumed per ton of washed coking coal (dry coal) ≤ 1.33 t (i.e., total coke yield ≥ 75%»». As is well known, the tonnage of coke consumption per unit of washed coking coal (dry coal) does not include losses due to transportation, storage, and other processes other than coking; it is determined by the dry-base volatiles of the coal used in charging the furnace. The consumption of washed coking coal increases as the volatiles content rises, meaning that the overall coking rate decreases as volatiles increase. This does not change according to people's will. The factors determining the volatiles content of coal blend can essentially be attributed to two main aspects: the resource conditions of the coal and the quality requirements for coke. Each enterprise determines the volatility of the coal blend at a specific time, based on its own conditions. Given the conditions under which coking coal resources are found in our country, and while ensuring the quality of coke, appropriate coal preparation techniques should be employed; it is advisable to use more coal with higher volatile matter and lower ash content, as it has weaker bonding properties. Technologies such as Baosteel’s blended coal technology and ramming coal loading technology are all effective measures. When the volatiles content of the coal blend is slightly high, although the coke yield decreases, the production of gas and chemical products increases accordingly. Under the condition of effective recycling of chemical products, it is entirely possible to achieve quite good economic results. It is also in line with **long-term interests** from the perspective of protecting scarce and high-quality coking coal resources. Therefore, it is recommended to modify the clause “ton of coke produced per ton of washed clean coal (dry coal) ≤ 1.33 t (i.e., overall coke yield ≥ 75%)” to “the ton of coke produced per ton of washed clean coal (dry coal) or the overall coke yield shall be determined by taking into account factors such as the volatile matter content of the dry basis of the coal used in furnace charging at each plant, as well as the operating procedures of the coke ovens.” Verification can be carried out using the following formula; practice has shown that equation (1) better reflects the actual situation. Kdj = (100－Vdm)/(100－Vdj)×100＋a (%) (1) Kdj = 103.7－0.75 Vdm－0.0067tj (%) (2) Where: Kdj – coking efficiency, %; Vdm – dry-base volatiles of the coal used in charging, %; Vdj – dry-base volatiles of the coke, %; a – the carbon increase resulting from secondary cracking after the volatiles in the coal escape; the value of a is generally taken as 1.1±0.3; tj – temperature at the center of the coke cake (measured 15 minutes before coke extraction), °C. 5 Discussion on clause 4.(i).6 of the “Conditions” regarding “coking oven gas utilization rate ≥ 95%”. Section II.(III).2 of the “Conditions” stipulates that “coking oven gas must be fully recovered and utilized,” which is not entirely consistent with the ≥95% utilization rate specified in Section IV.(I).6. In fact, with stable gas users, gas storage tanks of sufficient capacity, and strict management in place, there is basically no issue with the inability to recycle coke oven gas. Gas release occurs only in the event of a malfunction in the coke oven, gas purification system, or gas transmission system, or during scheduled maintenance or equipment replacement. The probability of this occurring in coking production is very low, and efforts should be made to keep it as low as possible from the perspectives of safety, energy conservation, and environmental protection. When the utilization rate of coke oven gas is 95%, for a company that produces 1 million tons of coke per year, this means that 60,000 m3 of gas can be released daily. This amount corresponds to the daily gas consumption of 60,000 urban residents; in terms of coal, this is equivalent to 50 tons of coal, meaning that more than 18,000 tons of coal are lost per year. This is not only an astonishing waste but also a serious pollution of the environment. According to the \"Statistics on Environmental Protection in Steel Enterprises in 2004\" published by the China Iron and Steel Association, the coke production of 48 steel enterprises was approximately 60 million tons, with a comprehensive utilization rate of coke oven gas at 98.17%. Upon further analysis, among the 48 enterprises: 26 had an utilization rate of ≥98.5%, accounting for 54%, and their gas production accounted for 61.4% of the total gas production of all 48 enterprises; 25 enterprises had a utilization rate of ≥99%, accounting for 52%, and their gas production accounted for 52.6% of the total production; 16 enterprises had a utilization rate of 100%, accounting for 33.3%, and their gas production accounted for 31.9% of the total production of all 48 enterprises. From the above analysis, it can be seen that setting the lower limit for the utilization rate of coke oven gas at 95% is on the low side. Indicators for improving the utilization rate of coke oven gas help to restrict the development of enterprises without stable gas supply ； It helps to encourage existing enterprises to accelerate the installation and improvement of relevant equipment, thereby improving the utilization of gas ； It helps to encourage enterprises to strengthen their management. Therefore, it is recommended to revise the utilization rate of coke oven gas to ≥99%. It is hoped that the above suggestions will help further strengthen the regulatory and guiding role of the \"Access Requirements for the Coking Industry.\" Please feel free to advise if they are appropriate. （200710241）