Influence of Diatomite on Distribution of Heavy Metals in Waste Incineration
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摘要: 选用管式炉作为燃烧反应器，研究了硅藻土对垃圾焚烧过程中重金属Pb、Cd、Cu和Zn分布特性的影响，并运用HSC Chemistry 6.0软件进行热力学模拟。实验结果表明：硅藻土使得重金属更多地分布于底灰中，对重金属的吸附作用随着其质量分数的增加逐步提升。600~800 ℃范围内硅藻土对重金属最佳吸附效率依次为Cd > Zn > Pb > Cu，900 ℃硅藻土对重金属的最佳吸附效率依次为Cd > Pb > Zn > Cu。模拟结果表明硅藻土能够与Pb、Cd、Zn反应生成相应的硅酸盐，对Cu的形态变化无影响。Abstract: The tube furnace was selected as the combustion reactor, the actual domestic waste was used as the raw material. The heavy metal content was measured by inductively coupled plasma atomic emission spectrometer (ICP-AES), and the surface morphology of diatomite before and after incineration was observed by the field emission electron microscope (FE-SEM). The influence of diatomite on the migration characteristics of heavy metals Pb, Cd, Cu and Zn in the waste incineration process at different temperatures (600、700、800、900 ℃) and addition mass fraction (1%, 2%, 3%, 4%) was investigated in this paper. And HSC Chemistry 6.0 was used for thermodynamic simulation calculations. The experimental results showed that diatomite could make heavy metals more distributed in the bottom ash. With the increase in the amount of addition, the adsorption of heavy metals by the diatomite gradually increased. When the experimental incineration temperature was between 600−800 ℃, the adsorption efficiency of diatomite for heavy metals was as follows: Cd> Zn> Pb> Cu; at 900 ℃: Cd> Pb> Zn> Cu. The corresponding temperature of the best adsorption efficiency for Pb was 900 ℃, for Zn was 800 ℃, and for Cd and Cu were 700 ℃. Thermodynamic simulation found that diatomite could react with Pb, Cd, Zn to form corresponding silicates, and had no effect on the morphological changes of Cu. Combined with thermodynamic equilibrium simulation and experimental data analysis, physical adsorption and chemical adsorption coexisted in the adsorption of Pb, Cd and Zn by diatomite, and physical adsorption was the main adsorption for Cu.
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Key words:
- waste incineration /
- diatomite /
- heavy metals /
- migration and distribution /
- thermodynamic simulation
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图 1 实验装置系统示意图
Figure 1. Schematic diagram of experimental device system
1−DSR-30A compressor；2−Air tank；3−Flow controller；4−LZB-10 glass rotameter；5−Quartz glass tube；6−SK2-4-12 tube furnace；7−Corundum boat；8−Temperature controller；9−Fiberglass cartridges；10−Air bottle；11−HNO3 solution；12−H2O2 solution；13−Air bottle
图 3 焚烧前硅藻土表面形貌的FE-SEM图
Figure 3. FE-SEM diagram of diatomite surface morphology before incineration
图 4 焚烧后硅藻土表面形貌的FE-SEM图
Figure 4. FE-SEM diagram of diatomite surface morphology after incineration
图 5 添加不同质量分数硅藻土后Pb在底灰中的归一化分布
Figure 5. Normalized distribution of Pb in bottom ash after adding diatomite with different mass fractions
图 6 添加不同质量分数硅藻土后Cd在底灰中的归一化分布
Figure 6. Normalized distribution of Cd in bottom ash after adding diatomite with different mass fractions
图 7 添加不同质量分数硅藻土后Cu在底灰中的归一化分布
Figure 7. Normalized distribution of Cu in bottom ash after adding diatomite with different mass fractions
图 8 添加不同质量分数硅藻土后Zn在底灰中的归一化分布
Figure 8. Normalized distribution of Zn in bottom ash after adding diatomite with different mass fraction
图 9 硅藻土对Pb分布影响的热力学平衡模拟
Figure 9. Thermodynamic equilibrium simulation of the effect of diatomite on Pb distribution
图 10 硅藻土对Cd迁移分布的热力学平衡模拟
Figure 10. Thermodynamic equilibrium simulation of the effect of diatomite on Cd distribution
图 11 硅藻土对Cu迁移分布的热力学平衡模拟
Figure 11. Thermodynamic equilibrium simulation of the effect of diatomite on Cu distribution
图 12 硅藻土对Zn迁移分布的热力学平衡模拟
Figure 12. Thermodynamic equilibrium simulation of the effect of diatomite on Zn distribution
表 1 垃圾样品的元素分析与工业分析
Table 1. Ultimate and proximate analysis of waste sample
wultimate1)/% wproximate2)/% C H O N Cl Mad Aad Vad FCad 47.29 7.35 1.06 19.33 0.36 3.39 21.56 72.02 3.26 1)Ultimate analysis; 2)Proximate analysis; ad−Air dry basis; M−Moisture; V−Volatile matter; FC−Fixed carbon 
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表 2 热力学模拟初始值
Table 2. Thermodynamic simulation initial value
n/mol C H O N Si Pb Cr Cu Zn 15.72 28.97 4.81 0.28 0.55 7.24×10−5 7.56×10−6 1.18×10−4 1.61×10−4
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表 3 硅藻土对Pb的吸附效率
Table 3. Adsorption efficiency of diatomite to Pb
w(diatomite)/% η/% 600 ℃ 700 ℃ 800 ℃ 900 ℃ 1 15.12 13.59 10.23 22.54 2 26.04 24.26 21.96 36.70 3 32.32 34.75 33.57 54.65 4 43.94 45.68 48.11 64.95
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表 4 硅藻土对Cd的吸附效率
Table 4. Adsorption efficiency of diatomite to Cd
w(diatomite)/% η/% 600 ℃ 700 ℃ 800 ℃ 900 ℃ 1 62.44 111.46 71.10 33.76 2 96.87 149.98 111.63 79.68 3 136.18 235.51 183.65 174.40 4 153.83 283.10 217.11 210.40
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表 5 硅藻土对Cu的吸附效率
Table 5. Adsorption efficiency of diatomite to Cu
w(diatomite)/% η/% 600 ℃ 700 ℃ 800 ℃ 900 ℃ 1 4.63 4.59 0.78 −0.57 2 10.80 11.79 −0.77 1.67 3 8.11 10.94 3.14 1.27 4 12.56 13.94 5.68 4.24
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表 6 硅藻土对Zn的吸附效率
Table 6. Adsorption efficiency of diatomite to Zn
w(diatomite)/% η/% 600 ℃ 700 ℃ 800 ℃ 900 ℃ 1 25.80 24.12 17.60 19.58 2 35.38 35.72 25.82 25.75 3 48.61 57.48 45.07 40.57 4 51.20 58.28 59.77 46.60
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