Effect mechanisms of different flue gas on adsorption of mercury by powder activated coke

doi:10.11949/j.issn.0438-1157.20181278

Abstract

Abstract:

Under the condition of simulating coal-fired hot flue gas as heat source and medium, quasi-east lignite was used as raw material to carry out carbonization activation (one-step method) to prepare powdery activated coke by one-dimensional settling furnace, and the adsorption capacity of activated coke to Hg⁰ was investigated. Further, the effects of SO₂, H₂O, O₂, CO₂, H₂O+O₂, SO₂+O₂ and H₂O+SO₂+O₂ on Hg⁰ removal efficiency were examined in flue gas. The results indicate that the coke has high adsorption performance for Hg⁰ removal. The N₂ atmosphere was used as comparison, the O₂, SO₂+O₂ and H₂O+SO₂+O₂ are beneficial for Hg⁰ removal, while the H₂O, CO₂, SO₂ and H₂O+O₂ have inhibiting effect on Hg⁰ removal. Furthermore, the spectra of Hg 4f were determined by XPS, in order to explore the mechanism of inhibition and promotion of Hg⁰ adsorption by activated coke under different flue gas. H₂O can inhibit the adsorption of active coke on Hg⁰via covering the active coke sites and blocking the pores, SO₂ can inhibit the adsorption through the competitive adsorption of SO₂ and HgO on the active coke, and CO₂ that adsorbed on the active coke micropore also can inhibit the adsorption of active coke on Hg⁰. In the atmosphere of O₂ and SO₂+O₂, the Hg⁰ is oxidized into HgO and HgSO₃, separately. And the HgSO₃ further oxidized into HgSO₄ by O₂. Besides, in the atmosphere of H₂O+SO₂+O₂, Hg⁰ is oxidized into HgO and HgSO₄.

Key words: powder activated coke, one-step method, mercury adsorption, effect mechanism

摘要：

在模拟燃煤热烟气为热源和介质条件下，以准东褐煤为原料，通过一维沉降炉进行炭化活化（一步法）制备粉状活性焦，考察了活性焦对Hg⁰的吸附能力，探索了SO₂、H₂O、O₂、CO₂、H₂O+O₂、SO₂+O₂及H₂O+SO₂+O₂气氛对活性焦吸附Hg⁰的影响机理。结果表明：一步法获得的活性焦对Hg⁰具有较高的吸附性能。N₂气氛作对比，H₂O、H₂O+O₂、CO₂和SO₂气氛下抑制活性焦对Hg⁰的吸附；O₂、SO₂+O₂和H₂O+SO₂+O₂促进活性焦对Hg⁰的吸附。通过Hg 4f的XPS分析证明了不同气氛组成对活性焦吸附Hg⁰的抑制和促进机理。H₂O覆盖在活性焦活性位上和堵塞孔隙而抑制活性焦对Hg⁰的吸附；SO₂与Hg⁰在活性焦上发生竞争吸附而抑制对Hg⁰的吸附；CO₂ 吸附在活性焦微孔上而抑制对Hg⁰的吸附；O₂气氛下主要形成了HgO, SO₂+O₂气氛下Hg⁰被氧化成HgSO₃，进一步氧化成HgSO₄； H₂O+SO₂+O₂气氛下，Hg⁰被氧化成HgO和HgSO₄。

关键词: 粉状活性焦, 一步法, 汞吸附, 影响机理

CLC Number:

TQ 028.8

Donghai AN, Xiaolin HAN, Xingxing CHENG, Binxuan ZHOU, Ying ZHENG, Yong DONG. Effect mechanisms of different flue gas on adsorption of mercury by powder activated coke[J]. CIESC Journal, 2019, 70(4): 1575-1582.

安东海, 韩晓林, 程星星, 周滨选, 郑瑛, 董勇. 不同烟气组分对粉状活性焦吸附汞的影响机理[J]. 化工学报, 2019, 70(4): 1575-1582.

Figures/Tables 13

Fig.1 System of powder activated coke preparation

Table 1 Proximate and ultimate analyses of coke and burn-off of coal

工业分析/%				元素分析/%					烧失率/%
M_ad	V_ad	A_ad	FC_ad	C_ad	H_ad	O_ad	N_ad	S_ad	烧失率/%
0.88	4.56	33.87	60.69	60.74	0.96	2.09	0.84	0.62	28.7

Fig.2 Experimental system of Hg0 adsorption

Fig.3 SEM images of raw coal (a) and coke (b)

Fig.4 N2 adsorption-desorption isotherm of coke

Table 2 Structure parameters of coke

总比表面积/

(m²/g)

微孔比表面积/

(m²/g)

总孔容/

(cm³/g)

微孔孔容/

(cm³/g)

Fig.5 Pore size distribution of coke

Fig.6 Hg0 adsorption curves under N2 and N2 +6%O2 (a) and adsorption mechanism (b) of coke

Fig.7 XPS analysis of Hg 4f for used coke under N2 (a) and N2 +6%O2 (b)

Fig.8 Hg0 adsorption curves under N2 and N2+0.06% SO2+6%O2 (a) and adsorption mechanism (b) of coke

Fig.10 XPS spectra of Hg 4f under N2+SO2+O2 (a) and N2+0.06% SO2+6% O2+6% H2O (b)

Fig.9 Hg0 adsorption curves under N2 and N2+0.06% SO2+6%O2+6%H2O (a) and adsorption mechanism (b) of coke

Fig.11 Hg0 adsorption curves under N2, N2+0.06% SO2, N2+6% H2O and N2 +6% H2O+6% O2 of coke

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