Effect of calcite on desulfurization and denitration performance of activated coke and its mechanism
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摘要: 方解石是煤中主要含钙矿物质，通过物理混合在脱灰宁夏无烟煤上负载不同含量的方解石制备活性焦，并分析其对制备及脱硫脱硝的影响。结果表明，方解石对活性焦的孔结构和表面化学性质起调控作用。在脱硫过程中，随着方解石含量的增加，活性焦的硫容呈先升高后下降趋势，NX-2%CaCO3-AC表现出最佳的脱硫能力（84.0 mg/g），方解石的加入增加了π−π*含量，促进了SO2氧化过程；在脱硝过程中，CaCO3的添加促进了脱硝，添加2%CaCO3的脱硝率（16.9%）比未添加的活性焦的脱硝率（7.9%）提升了1.14倍，主要是由于碱性基团数量的提高；同时脱硫脱硝过程中，活性焦CaO的存在对脱硫脱硝具有不同程度的促进作用。与单独脱硫/脱硝相比，硫容升高，脱硝效率降低，主要是由于竞争性吸附及铵盐的生成。Abstract: Different contents of calcite (CaCO3) were loaded on a deminerized Ningxia anthracite during the activated coke (AC) preparation, the influence of which on the preparation, desulfurization and/or denitrification of AC was investigated. The results show that calcite can regulate the pore structure and surface chemistry of AC. The total specific surface area and the micropore specific surface area decrease from 746 m2/g and 645 m2/g to 408 m2/g and 244 m2/g, respectively, when the calcite addition is up to 8%. The total volume and the micropore volume also decrease with the increase in the content of calcite, while the volume of mesopores and macropores increases. As the calcite addition rises, the oxygen-containing functional group and π−π* are increased linearly, and the sulfur capacity of AC first increases and then decreases during single desulfurization, the NX-2%CaCO3-AC having the best desulfurization capacity (84.0 mg/g). The increase in the content of π−π* by the addition of calcite promotes the SO2 oxidation process, and also promotes the denitrification process, the NO conversion (16.9%) with the addition of 2%CaCO3 is 1.14 times higher than that of AC (7.9%), mainly owing to the increase in the number of basic groups. However, during simultaneous desulfurization and denitrification, the presence of CaO in the AC promotes the sulfur capacity but decreases the NO removal efficiency due to the competitive adsorption and ammonium salt generation.
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Key words:
- calcite /
- activated carbon /
- surface chemistry /
- sulfur capacity /
- NO conversion
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图 1 活性焦脱硫脱硝反应装置示意图
Figure 1 Schematic diagram of desulfurization and denitrification by AC
图 4 N2吸附-脱附等温线(a)和孔径分布(b)
Figure 4 N2 adsorption/desorption isotherms (a) and pore size distributions (b)
图 5 活性焦的表面化学性质
(a): XPS survey spectra of AC; (b):oxygen percentages of AC; (c): high-resolution C 1 s spectrum of AC; (d): atomic percentage distribution of the major functional group of AC
Figure 5 Surface chemical properties of AC
图 6 活性焦的硫容（a）；活性焦的的硫容与表面氧含量（b）和π−π*含量（c）的关系
Figure 6 (a) ACs’ sulfur capacity; the relationships between sulfur capacities and oxygen percentages (b) and π−π* bonds percentages (c) of AC
图 8 活性焦的脱硝效率(a)；活性焦的脱硝效率与表面氧含量（b）和π−π*含量（c）的关系
Figure 8 ACs’ NO conversion (a); the relationships between NO conversion and oxygen percentages(b) and π−π* bonds percentages(c) of AC
图 10 活性焦同时脱硫脱硝的硫容（a）和脱硝效率（b）
Figure 10 ACs’sulfur capacity (a) and NO conversion (b) of simultaneous desulfurization and denitrification
表 1 原煤的工业分析和元素分析
Table 1 Proximate and ultimate analyses of raw coal
Proximate analysis wad/% Ultimate analysis wdaf/% M V A FC C H St N Oa 0.67 11.22 6.12 81.99 91.33 2.82 0.27 1.27 4.14 M: moisture; A: ash; V: volatile matter; a: by difference 
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表 2 原煤的灰成分分析
Table 2 Ash component analysis of raw coal
Component w/% SiO2 Al2O3 CaO SO3 Fe2O3 TiO2 MgO Na2O K2O 39 28.3 11.3 7.92 10.4 0.97 3.08 3.17 0.7
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表 3 方解石添加含量对活性焦制备过程中的参数变化和孔结构的参数变化
Table 3 Parameters of ACs with different contents of calcite during AC preparation
Sample Weight loss/% Burn-off/% Yield/% Pore structure analysis by BET SBET/
(m2·g−1)Smic/
(m2·g−1)Smic/
SBET/%vmic
(cm3·g−1)vmec+mac
(cm3·g−1)vtotal
(cm3·g−1)dave/nm NX-AC 20.02 40.10 47.91 746 645 86 0.25 0.07 0.32 1.72 NX-2%CaCO3-AC 20.46 54.30 36.35 516 385 75 0.15 0.12 0.27 2.10 NX-4%CaCO3-AC 20.40 64.00 28.66 460 400 87 0.15 0.10 0.16 1.41 NX-6%CaCO3-AC 20.26 65.50 27.51 413 232 56 0.09 0.19 0.28 2.71 NX-8%CaCO3-AC 19.30 66.00 27.44 408 244 60 0.10 0.16 0.26 2.55
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