Effect of straw charcoal as a “Carbon Neutral” carbon source on the melting behavior of mold flux
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摘要: 炭质材料作为保护渣中不可或缺的原料之一，主要发挥调控保护渣熔化行为的作用。“双碳”背景下，现有炭质材料存在固定碳、N和S含量高等导致碳、NOx和SO2高排放问题，严重影响生态环境。其次存在不可再生及成本高等问题，急需寻找一种可再生且环境友好型的炭质材料进行代替。研究提出了一种“碳中性”、可再生以及储量丰富的固体废弃物秸秆炭作为保护渣新型碳源，研究了炭黑C611和秸秆炭各自的基本物理性能，系统分析了碳的种类和含量对保护渣熔化行为的影响规律。研究结果表明：秸秆炭的比表面积和平均粒径均大于炭黑C611，固定碳含量低于炭黑C611。随着秸秆炭含量增加，保护渣的软化温度、熔化温度和流动温度均明显升高，其中秸秆炭对熔化温度的影响效果最为明显。随着秸秆炭含量增加，保护渣的熔化速度降低，当碳含量为8%时，秸秆炭对保护渣熔化速度的控制效果与炭黑C611相同。Abstract: Carbonaceous materials are one of the essential components in mold flux, mainly serving to regulate its melting behavior. Under the background of the “dual carbon” strategy, conventional carbon materials exhibit high contents of fixed carbon, nitrogen, and sulfur, resulting in excessive emissions of CO2, NOx, and SO2, which pose serious environmental concerns. Moreover, their non-renewability and high cost further limit their sustainable application. Therefore, it is urgent to explore the renewable and environmentally friendly alternatives. The research proposed a “carbon-neutral”, renewable and abundant solid waste, straw charcoal, as a new type of carbon source for protective slag. The respective basic physical properties of carbon black C611 and straw charcoal were investigated, and the influence of carbon types and contents on the melting behavior of mold fluxes were systematically analyzed. The results indicate that straw charcoal possesses a higher specific surface area and larger average particle size than carbon black C611, though its fixed carbon content is relatively lower. With increasing straw charcoal content, the softening temperature, melting temperature, and flowing temperature of mold flux increase noticeably, with the melting temperature being the most affected. As the carbon content of straw increases, the melting rate of the mold flux decreases. When the carbon content is 8%, the control effect of straw charcoal on the melting rate of the protective residue is the same as that of carbon black C611.
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Key words:
- straw charcoal /
- carbon black C611 /
- physical properties /
- mold flux /
- melting behavior /
- ontinuous casting
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图 2 样品熔化过程示意
（a）原始样品；（b）样品高度75%；（c）样品高度50%；（d）样品高度25%
Figure 2. Schematic diagram of sample melting process
图 3 两种炭质材料的燃烧特性
(a)秸秆炭; (b)炭黑C611
Figure 3. Combustion characteristics of two carbon materials
图 4 两种炭质材料的扫描电镜和能谱
(a)秸秆炭; (b)炭黑C611; (c)秸秆炭能谱; (d)炭黑C611能谱
Figure 4. SEM and EDS images of two carbonaceous materials
图 6 不同碳含量下保护渣的软化温度
Figure 6. Softening temperature of mold flux with different carbon contents
图 7 不同碳含量下保护渣的熔化温度
Figure 7. Melting temperature of mold flux with different carbon contents
图 8 不同碳含量下保护渣的流动温度
Figure 8. Flow temperature of mold flux with different carbon contents
图 9 不同碳含量下保护渣的熔化区间
Figure 9. Melting range of mold flux with different carbon contents
图 10 碳含量对保护渣熔化速度的影响
Figure 10. Melting speed of mold flux with different carbon contents
表 1 保护渣基础渣系的化学组成
Table 1. The chemical composition of the basic slag system of mold flux
% NO. CaO SiO2 Al2O3 Na2O CaF2 MgO A 30.5 30.5 5.0 12.0 20.0 2.0 
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表 2 保护渣配碳比例
Table 2. Carbon ratio in mold flux
% NO. A Straw charcoal Carbon black C611 S4 96 4 0 S6 94 6 0 S8 92 8 0 S10 90 10 0 C4 96 0 4 C6 94 0 6 C8 92 0 8 C10 90 0 10
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表 3 炭质材料元素分析
Table 3. Elemental analysis of carbon materials
% Carbon materials C N O H S Straw charcoal 44.56 0.62 35.35 4.11 0.13 Carbon black C611 72.84 1.02 14.38 2.9 0.35
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表 4 炭质材料工业分析
Table 4. Industrial analysis of carbon materials
Carbon materials Industrial analysis/% Calorific value/(MJ·kg−1） Ash content Volatile matter content Moisture content Fixed carbon content Straw charcoal 5.13 12.25 11.87 80.51 33.79 Carbon black C611 1.41 5.48 4.17 94.47 36.40
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表 5 炭质材料物性分析
Table 5. Physical and chemical properties analysis of carbon materials
Carbon materials Average particle size/μm Specific surface area/(m2·g−1） Straw charcoal 59.34 1267.42 Carbon black C611 8.98 116.10
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