Study on the composition and structure characteristics and dry decarbonization separation of coal water slurry gasification fine slag
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摘要: 本研究以水煤浆气化细渣(CWSFS)为研究对象，将其通过湿法筛分分级，采用工业分析、XRF、XRD、BET、SEM等手段考察粒度组成与结构特征的关系，并提出CWSFS的分类方法，用以指导煤气化灰渣的分质高值化利用；再采用粉碎解离-气流分级联合处理方法开展了水煤浆气化细渣的干法分选研究。结果表明，不同粒级CWSFS，在固定碳含量、灰组成、矿物类型上有明显差异。≥74 μm粒级的CWSFS中，固定碳含量＞60%、发热量＞20 MJ/kg，比表面积较高，主要为残炭，并含有磁铁矿和板钛矿；13−74 μm粒级的CWSFS中，固定碳含量为20%−60%、发热量为11−19 MJ/kg，比表面积较小，矿物类型主要为辉石、白铁矿和赤铁矿等；0−13 μm粒级的CWSFS中，固定碳含量低于20%、发热量低于10 MJ/kg，主要为富含铝、铁、钙等非晶态玻璃相、石英和少量铁橄榄石、白云母等矿物。根据不同粒级CWSFS的特征，将上述三个组分分别定义为高炭组分、中炭组分和低炭组分。干法分选试验表明，与圆盘粉碎-分级工艺相比，采用气流粉碎-分级工艺可获得产率为29.60%、烧失量高达93.76%的产品，气流粉碎有助于提高残炭的分级分离富集率。Abstract: Efficient separation and high-valued utilization of coal gasification ash or slag limit the clean and green development of coal chemical industry. In this paper, a coal-water slurry gasification fine slag (CWSFS) was studied by wet screening and classification. The relationship between the particle composition with different sizes and the structural characteristics was investigated by means of proximate analysis, XRF, XRD, BET and SEM. A classification method of CWSFS was proposed to guide the high-valued utilization of coal gasification slag. Then, dry separation of a coal-water slurry gasification fine slag was carried out using a combined treatment method of crushing and dissociation and airflow classification. The results show that the CWSFS particles of different sizes have obvious differences in fixed carbon content, ash composition and mineral types. For the CWSFS with the particle size above 74 μm, the fixed carbon content is more than 60%, the calorific value is more than 20 MJ/kg, the specific surface area is relatively high and the main component is the residual carbon that contains magnetite and brookite. For the CWSFS with particle sizes between 13−74 μm, the fixed carbon content is between 20%−60%, the calorific value is between 11−19 MJ/kg, the specific surface area is small and the main mineral types are pyroxene, marcasite and hematite, etc. For the CWSFS with a particle size between 0−13 μm, the fixed carbon content is less than 20% and the calorific value is less than 10 MJ/kg, which mainly includes the amorphous glass phase that was rich in aluminum, iron and calcium, quartz and a small amount of fayalite, muscovite and other minerals. According to the fixed carbon content of CWSFS with different particle sizes, the above three components with varying particle size ranges are defined as high-carbon component, medium-carbon component and low-carbon component, respectively. The dry separation test shows that the air flow crushing and classification process can achieve a higher product yield of 29.60% and a high ignition loss of 93.76%, compared to the traditional disc crushing-classification process. Airflow crushing was proved to be able to effectively increase the dissociation degree of residual carbon and greatly improve the separation and enrichment rate of residual carbon.
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图 1 粉碎-气流分级流程示意图
Figure 1 Combined process of crushing and airflow classification
(a): disc crushing and airflow classification; (b): airflow crushing and airflow classification
图 2 水煤浆气化细渣各粒级固定碳含量
Figure 2 Fixed carbon content of different particle size grades of CWSFS
图 3 水煤浆气化细渣各粒级的XRD谱图
Figure 3 XRD spectra of size-segmented CWSFS
Q: Quartz; M: Magnetite; H: Hematite; D: Diopside; B: Brookite; 2M: Muscovite; A: Anhydrite; N: Nepheline; 2F: Fayalite; 3F: Marcasite
图 8 CWSFS圆盘粉碎-气流分级后各产品烧失量及产率
Figure 8 Ignition loss and yield of each product after crushed and combined airflow classification
图 9 气流粉碎各产品产率及烧失量
Figure 9 Yield and loss on ignition of each product in airflow crushed
图 10 不同粉碎方式下CWSFS各产品的SEM照片
Figure 10 SEM images of CWSFS products using different crushing methods
表 1 水煤浆气化细渣的工业分析和元素分析
Table 1 Proximate and ultimate analyses of coal-water slurry gasification fine slag
Proximate analysis w/% Ultimate analysis wad/% Qgr,d/(MJ·kg−1) Mad Aad Vdaf FCad C H O N St 6.41 29.15 20.86 43.58 54.17 2.31 3.25 1.11 3.60 25.13 
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表 2 水煤浆气化细渣粒度特性
Table 2 Characteristics of CWSFS in different particle size grades
Particle size/μm Yield/% Ash content/% Fixed carbon content/% Loss on ignition/% Calorific value/(MJ·kg−1) ＞98 50.83 15.99 70.35 85.52 26.214 74−98 5.66 24.55 61.88 73.21 23.835 45−74 13.89 37.79 39.93 68.95 15.223 22−45 6.41 49.97 28.31 57.57 13.249 13−22 7.86 50.05 25.86 47.3 12.198 0−13 15.35 59.25 19.34 45.7 9.081 Total 100 29.18 43.58 72.59 25.126
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表 3 水煤浆气化细渣各粒级氧化物含量
Table 3 Oxide content of size-segmented CWSFS
Particle size/μm Composition w/% SiO2 Al2O3 Fe2O3 CaO K2O TiO2 SO3 ZnO Cr2O3 MnO SrO CuO V2O5 ＞98 0 38.55 21.16 25.21 1.03 1.68 10.26 0.34 0 0.40 0.67 0.25 0 74−98 23.66 20.43 18.06 24.25 1.15 1.46 9.69 0.27 0 0.37 0.21 0 0 45−74 16.84 18.99 29.61 22.50 1.61 1.55 7.38 0 0 0.52 0.59 0 0.14 22−45 33.88 22.55 15.49 19.02 1.73 1.28 5.38 0 0 0.28 0.14 0 0.10 13−22 40.72 21.71 12.52 15.86 1.78 1.24 4.69 0.78 0.17 0.22 0 0 0 0−13 34.91 24.10 15.72 16.29 2.04 1.69 3.09 0.98 0.41 0.26 0 0 0 CWSFS 21.09 27.96 20.70 19.83 1.85 1.64 5.28 0 0.28 0.37 0.58 0 0
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表 4 水煤浆气化细渣EDS分析
Table 4 EDS analysis of CWSFS
Morphology Particle size/μm Element w/% C O Na Al Si S K Ca Ti V Fe Sr Porous irregular particles ＞98 75.7 15.1 0.18 1.03 3.36 0.9 0.21 1.05 0.13 0 1.81 0.57 74−98 85.3 7.84 0.13 0.75 2.8 0.72 0.17 0.71 0.15 0.04 0.79 0.64 Block particles ＞98 76.1 12 0.44 1.31 2.94 2.09 0.21 2.22 0.09 0.07 1.61 0.93 74−98 73.5 20.2 0.2 0.82 2.24 0.24 0.12 0.87 0.12 0 1.09 0.63 45−74 73.8 19.4 0.2 0.99 2.44 0.32 0.17 1.06 0.11 0.01 0.89 0.67 22−45 63.7 21.5 0.24 1.42 5.95 1.4 0.35 1.57 0.13 0.03 1.74 2 13−22 54 19.7 0.4 2.7 9.94 1.48 0.6 2.9 0.29 0 4.84 3.16 Spherical particles ＞98 9.86 41.5 2.86 6.44 11.5 1.02 0.51 6.03 0.4 0 18.2 1.75 74−98 9.66 43 2.8 6.25 11 0.71 0.46 5.59 0.3 0.14 18.2 1.87 45−74 26.7 36.8 2 4.92 8.82 0.94 0.41 4.63 0.25 0 13.2 1.31 22−45 17.6 42.5 2.81 7.13 1.98 0.69 0.44 6.16 0.3 0 19 1.37 13−22 24.7 34.6 2.3 6.6 10.9 0.6 0.4 5.61 0.31 0 12.3 1.68 0−13 20.5 36.8 3.01 6.82 10.4 0.74 0.52 5.98 0.21 0 13.8 1.24 Floccule 0−13 35.9 39.5 2.27 4.7 7.35 0.2 0.57 2.51 0.26 0.05 6.18 0.59
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表 5 水煤浆气化细渣各粒径的孔隙特征参数
Table 5 Pore characteristic parameters of size-segmented CWSFS
Particle size/μm Specific surface area/(m2·g−1) Total pore volume/(cm3·g−1) Average aperture/nm ＞98 67.80 0.041 6.21 74−98 216.93 0.147 5.52 45−74 41.26 0.024 7.42 22−45 46.47 0.044 7.08 13−22 59.01 0.070 7.57 0−13 58.86 0.092 9.80 CWSFS 44.59 0.052 7.12
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表 6 水煤浆气化细渣的分类指标及不同类型组分的组成结构特征
Table 6 Classification indexes of CWSFS and composition and structure characteristics of different types of components
Classification index Type Structure and composition characteristics of different types of components fixed carbon content/% calorific value/(MJ·kg−1) particle size range/μm micro morphological characteristics pore structure
characteristics (specific
surface area)/
(m2·g−1)main mineral composition ＞60 ＞20 high carbon component ＞74 porous irregular particle, block particle >67 magnetite, brookite 20−60 11−19 medium carbon component 13−74 block particle, spherical particle 40−60 pyroxene, marcasite, hematite ＜20 ＜10 low carbon component ＜13 floccule <60 quartz, fayalite,
muscovite
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表 7 不同粉碎方式下球形颗粒的面积统计
Table 7 Statistical results of spherical particle projected area using different crushing methods
CWSFS product Total area of spherical
particles/μm2Ratio of spherical particles to
total sample area/%Disc crushed for 3 min 253.8817 9.4034 Disc crushed for 6 min 189.4517 5.8623 Disc crushed for 9 min 56.4101 1.7996 Airflow crushed
graded frequency 20 Hz58.3324 1.7501 Airflow crushed
graded frequency 35 Hz130.1613 4.3221 Airflow crushed
graded frequency 50 Hz183.0621 5.4915
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