氯化焙烧粉煤灰脱除Pb、Cd的机理及其应用

黄齐真; 石林; 何柳青

doi:10.3969/j.issn.1000-6532.2023.06.029

氯化焙烧粉煤灰脱除Pb、Cd的机理及其应用

1.
华南理工大学　环境与能源学院，广东　广州　510006

2.
工业聚集区污染控制与生态修复教育部重点实验室，广东　广州　510006

基金项目: 国家科技支撑计划项目（2015BAD05B05+2）；中山市社会公益与基础研究项目（2020B2004）。

详细信息

作者简介: 黄齐真（1996-），男，硕士研究生，主要从事固体废物资源化利用研究

通讯作者: 石林（1975-），男，教授，博士，主要研究方向为环境科学与资源利用

中图分类号: TD95

收稿日期: 2021-04-07

刊出日期: 2023-12-25

Mechanism and Application Research on Removal of Pb and Cd from Coal Fly Ash by Chlorinating Calcination

1.
School of Environment and Energy, South China University of Technology, Guangzhou, Guangdong, China

2.
The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters of Education, Guangzhou, Guangdong, China

More Information

Corresponding author: Shi Lin, celshi@163.com

Received Date: 07 April 2021

Publish Date: 25 December 2023

摘要

摘要:
这是一篇冶金工程领域的论文。采用氯化钙作为氯化剂，对粉煤灰中重金属进行了脱除实验。考查了焙烧温度、焙烧时间和CaCl₂添加量对重金属去除率的影响。将实验结果与热力学计算结果相结合，阐明了粉煤灰氯化焙烧脱除重金属的机理，并对焙烧过程的动力学模型进行了讨论。此外，以粉煤灰为原料制备土壤调理剂，通过盆栽实验研究其肥效。研究发现，添加16%氯化钙和高温锻烧40 min后，混合物中 Pb和 Cd的含量分别下降了89.26%和76.88%，而余量仅为10.22 g/t和0.54 g/t。粉煤灰中含有的石英、莫来石、氧化铝、氧化钠等组分促进CaCl₂的分解。PbO和CdO不直接与CaCl₂反应，而是主要与CaCl₂分解生成的HCl反应生成挥发性氯化物。动力学结果表明，Pb和Cd的氯化挥分行为受界面化学反应控制，Pb氯化挥发的表观活化能为84.54 kJ/mol，Cd氯化挥发的表观活化能为44.96 kJ/mol。盆栽实验表明，制备的土壤调理剂能改善土壤环境，促进香葱对营养物质的吸收，改善香葱品质，添加CaCl₂能降低产品中的重金属含量，提高有效钙含量。研究提供了一种综合利用粉煤灰的方法。
- 冶金工程 /
- 粉煤灰 /
- 氯化焙烧 /
- 重金属去除 /
- 土壤调理剂
Abstract:
This is an essay in the field of metallurgical engineering. Calcium chloride was used as chlorination agent to conduct the heavy metals removal experiments for coal fly ash, investigating the effects of calcination temperature, calcination time and amount of CaCl₂ on the removal rate of heavy metals. The results of calcination experiments and thermodynamic calculation demonstrate the mechanism of heavy metals removal in fly ash by using chlorinating volatilization method; further, the kinetic model of chlorinating process was discussed. Moreover, the coal fly ash, as raw material, was used to produce soil conditioner which was studied to discover its fertilizing effect by pot experiments. Studies found that the remaining contents of Pb and Cd in mixture were 10.22 g/t and 0.54 g/t, respectively, which meant 89.26% of Pb and 76.88% of Cd were decreased after addition of CaCl₂ at high calcination temperature for 40 min. The mineral of mullite, quartz, alumina and disodium oxide in fly ash contributed to the decomposition of CaCl₂. PbO and CdO mainly reacted with HCl formed by the decomposition of CaCl₂ to form volatile chloride, meaning the oxides do not directly react with CaCl₂. thermodynamic models fitting implied that the chlorination of Pb and Cd were controlled by the chemical reaction, and the apparent activation energy of reactions was 84.54 and 44.96 kJ/mol, respectively. Further, the pot experiments showed that the synthesized soil conditioner can improve the condition of the soil, promote nutrient absorption of chives, and improve the quality of chives. The effective calcium content of soil conditional product was increased after the reduction of heavy metals by adding CaCl₂. This research provides a method for comprehensive utilization of fly ash.
- Metallurgical engineering /
- Coal fly ash /
- Chlorinating calcination /
- Heavy metal removal /
- Soil conditioner

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图 1 粉煤灰的XRD

Figure 1.

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图 2 焙烧温度对Pb、Cd脱除率的影响

Figure 2.

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图 3 在CaCl₂添加量为16%的条件下，焙烧温度为600~1000 ℃的样品及原始粉煤灰的XRD

Figure 3.

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图 4 CaCl₂添加量对Pb、Cd去除率的影响

Figure 4.

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图 5 样品（16% CaCl₂添加、1000 ℃焙烧）的SEM

Figure 5.

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图 6 样品（16% CaCl₂添加、1000 ℃焙烧）的能谱分析

Figure 6.

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图 7 焙烧时间对Pb、Cd去除率的影响

Figure 7.

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图 8 反应（2）~（7）吉布斯自由能与温度的关系

Figure 8.

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图 9 反应（8）~（14）吉布斯自由能与温度的关系

Figure 9.

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图 10 反应（15）~（20）吉布斯自由能与温度的关系

Figure 10.

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图 11 1000 ℃时Pb、Cd氯化反应F（x）与时间关系（曲线（1）F（x）=α；曲线（2）F（x）=1−2α/3− (1−α)^2/3；曲线（3）F（x）=1−(1−α)^1/3）

Figure 11.

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图 12 Pb的氯化挥发1-(1-α)^1/3与时间t的关系

Figure 12.

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图 13 Cd的氯化挥发1-(1-α)^1/3与时间关系

Figure 13.

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图 14 Pb和Cd氯化的阿伦尼乌斯曲线

Figure 14.

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图 15 不同条件下制备土壤调理剂的XRD

Figure 15.

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图 16 土壤调理剂对土壤pH值、矿质元素的影响

Figure 16.

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表 1 粉煤灰样品的主要成分/%

Table 1. Chemical components of the CFA sample

SiO₂	Al₂O₃	Fe₂O₃	CaO	MgO	K₂O	TiO₂	Na₂O	SO₃	As*	Cd*	Cr*	Hg*	Pb*
51.17	31.12	6.17	4.81	1.76	1.38	1.29	1.11	0.31	41.2	2.8	76.9	3.0	112.0
*单位为g/t

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表 2 CaCl₂对土壤调理剂有效硅、有效钙的影响

Table 2. Effect of CaCl₂ on the content of the effective silicon content and the effective calcium in soil conditioner

CaCl₂ 加入量/ %	有效硅/%	有效钙 /%
0	18.78	28.07
4	19.02	29.25
8	19.26	29.49
12	19.34	30.86
16	19.42	31.48
20	18.99	31.80

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表 3 土壤调理剂的主要成分/%

Table 3. Main components of the soil conditioners

SiO₂	Al₂O₃	Fe₂O₃	CaO	MgO	K₂O
29.77	9.98	2.03	33.65	7.78	4.52

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表 4 CaCl₂对土壤调理剂中重金属全量的影响

Table 4. Effect of the CaCl₂ on the content of heavy metals in soil conditioners

CaCl₂ 加入量 /%	Pb / (g/t)	Cd / (g/t)	As / (g/t)	Hg / (g/t)	Cr / (g/t)
0	41.20	0.85	13.05	0.91	23.03
4	12.72	0.55	10.65	0.90	19.15
8	11.45	0.48	9.16	0.89	18.87
12	11.06	0.41	9.02	0.88	18.56
16	9.85	0.30	8.58	0.87	18.25
20	10.17	0.32	8.82	0.86	18.22
水平（GB/T 23349-2009）	200	10	50	5	500

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表 5 土壤调理剂对香葱株高和产量的影响

Table 5. Effect of soil conditioners on plant height and yield of chives

	植被高度 /cm	产量 /g	产率 /%
CK	25.08	98.76	-
T1	26.57	125.98	27.56
T2	28.15	144.34	46.15
T3	29.31	159.54	61.54

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