生物質炭復合團塊在高爐中的反應行為

張壯壯; 王強; 唐惠慶; 薛慶國

doi:10.13374/j.issn2095-9389.2020.11.30.002

生物質炭復合團塊在高爐中的反應行為

doi: 10.13374/j.issn2095-9389.2020.11.30.002

北京科技大學鋼鐵冶金新技術國家重點實驗室，北京 100083

基金項目: 國家自然科學基金資助項目（U1960205）

詳細信息

通訊作者:
E-mail：hqtang@ustb.edu.cn

中圖分類號: TF537
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出版歷程
- 收稿日期: 2021-04-30
- 網絡出版日期: 2022-05-11
- 刊出日期: 2022-07-01

Reaction behavior of the biochar composite briquette in the blast furnace

State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, Beijing 100083, China

More Information

Corresponding author: E-mail: hqtang@ustb.edu.cn

摘要

摘要: 研究了生物質復合團塊在高爐中的反應行為，該復合團塊主要成分(質量分數)為：11.1% C、72.7% Fe₃O₄、11.25% FeO、0.77% Fe和4.67% 脈石。并對高爐環境下復合團塊的反應行為進行了建模，通過高爐氣氛下的等溫動力學實驗確定模型參數并進行了模型驗證。進一步，結合模型模擬，模擬高爐環境的實驗和團塊微觀結構分析，對模擬高爐條件下和實際高爐條件下團塊的反應行為進行了分析。研究結果表明：模擬高爐條件下，在60 min (973 K) 到120 min (1273 K) 期間，團塊的微觀結構發生明顯變化，其微觀結構由渣相網絡結構向金屬鐵網絡結構轉變。在實際高爐中，復合團塊的反應進程主要包括三個階段：團塊的高爐煤氣還原（473~853 K）、團塊的高爐煤氣還原和部分自還原（853~953 K）以及團塊的完全自還原（953~1150 K）。在團塊自還原參與階段，與燒結礦相比，團塊內氧化鐵還原速率更快；與焦炭相比，團塊內生物質炭氣化速率更高。同時，在此階段，團塊有提高高爐煤氣利用率和降低高爐熱儲備區溫度的作用。
- 生物炭 /
- 復合團塊 /
- 高爐煉鐵 /
- 反應模型 /
- 反應行為
Abstract: Blast furnace (BF) ironmaking is considered to be the most popular technology to meet the increasing steel demand worldwide, but it is responsible for the most CO₂ emissions in the blast furnace-basic oxygen furnace production process. The utilization of biomass/biochar in BF ironmaking is an effective countermeasure to reduce its CO₂ emission, as biomass/biochar is a renewable carbon source and environment neutron. Charging the biochar composite briquette (BCB) is a convenient method to introduce biomass/biochar into BF. The present research investigates the reaction behavior of the BCB in the BF. The BCB for the BF was prepared using cold briquetting followed by low-temperature heat treatment. The BCB was composed of 11.1% carbon, 72.7% magnetite, 11.25% wustite, 0.77% metallic iron, and 4.67% gangue (all in mass fraction). The BCB reaction model in the BF was developed considering the step-wise gaseous reduction of iron-oxide particles, CO₂ gasification of biochar particles, internal gas diffusion in the BCB, and mass transfer between the BCB and the environment. Isothermal BCB reaction tests were conducted for model validation. Using the model, the changes of the BCB iron-oxide reduction fraction and biochar conversion rate and the BCB microstructure evolution under simulated BF conditions were analyzed. The model was also applied to predict the change of the BCB iron-oxide reduction fraction, change of the BCB biochar conversion, change of the BCB CO generating rate, and change of the BCB CO₂ generation rate along a solid flowing path near the mid-radius in an actual BF. Results showed that under simulated BF conditions, the BCB underwent fast self-reduction and structure changes (forming low-melting compounds and transforming from the slag matrix to the iron network) from 60 min (973 K) to 120 min (1273 K). In an actual BF, the BCB reaction route is mainly divided into three stages: (1) reduction by BF gas (473–853 K), (2) reduction by the BF gas and partial self-reduction (853–953 K), and (3) full self-reduction (953–1150 K). In the stages involving BCB self-reduction, the iron oxide in the BCB reduces faster than the sinter, and the biochar gasifies faster than the coke. Moreover, in these stages, the BCB has the functions of increasing the BF gas utilization efficiency and lowering the temperature level of the BF thermal reserve zone.
- biochar /
- composite briquette /
- blast furnace /
- reaction model /
- reaction behavior

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圖 1 模擬高爐條件下氣體成分和溫度變化曲線

Figure 1. Simulated blast furnace (BF) gas composition and temperature profiles

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圖 2 反應模型

Figure 2. Model concept

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圖 3 團塊的XRD圖譜

Figure 3. XRD pattern of the BCB

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圖 4 團塊樣品的SEM圖像.（a）燒結氧化鐵基體; （b）生物質炭顆粒的微觀形貌

Figure 4. SEM images of the BCB sample: (a) sintered iron-oxide texture; (b) microstructure of biochar particles

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圖 5 模擬高爐條件下部分反應后復合團塊冷抗碎強度的變化

Figure 5. Change of the BCB cold crushing strength after partial reaction under simulated BF conditions

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圖 6 用于確定a_gs的數據點

Figure 6. Selected data points for determining a_gs

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圖 7 不同實驗方案下實驗和模型預測的質量損失曲線對比

Figure 7. Measured and model-predicted mass-loss curves under different scenarios

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圖 8 生物質炭復合團塊樣品的圖像. (a) 原始圖像; (b) 在方案Ⅰ下反應后圖像;(c) 在方案Ⅱ下反應后圖像; (d) 在方案Ⅲ下反應后圖像

Figure 8. Images of the BCB sample: (a) original; (b) after reaction under scenario Ⅰ; (c) after reaction under scenario Ⅱ; (d) after reaction under Scenario Ⅲ

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圖 9 模擬高爐條件下生物質炭復合團塊還原行為. (a)還原分數隨時間的變化; (b)生物炭轉化率隨時間的變化

Figure 9. BCB reduction behavior under simulated BF conditions: (a) change in reduction fraction with time; (b) change in biochar conversion with time

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圖 10 不同時間下生物質炭復合團塊的XRD譜. (a) 60 min; (b) 90 min; (c) 120 min

Figure 10. XRD patterns of BCB at different times: (a) 60 min; (b) 90 min; (c) 120 min

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圖 11 不同時間生物質炭復合團塊的掃描電鏡圖像. (a) 60 min; (b) 90 min; (c) 120 min

Figure 11. SEM images of BCB at different times: (a) 60 min; (b) 90 min; (c) 120 min

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圖 12 （a）用于建模的固體流動路徑的圖示;（b）高爐變量沿路徑的變化

Figure 12. (a) Illustration of solid flowing path for modeling; (b) change of BF variables along the path

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圖 13 實際高爐中的生物質炭復合團塊反應行為.（a）沿路徑的還原分數變化;（b）沿路徑的生物炭轉化率變化;（c）沿路徑的CO和CO₂生成速率變化;（d）在1150至1168 K溫度下CO和CO₂的生成速率變化

Figure 13. BCB reaction behavior in the BF: (a) change in reduction fraction along the path; (b) change in biochar conversion along the path; (c) changes in generation rates of CO and CO₂ along the path; (d) changes in generation rates of CO and CO₂ from 1150 to 1168 K

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圖 14 生物質炭復合團塊和高爐煤氣在生物質炭復合團塊自還原區區域的CO還原勢

Figure 14. CO potentials of the BCB and the BF gas in the zone with BCB self-reduction

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表 1 制備用生物炭工業分析(質量分數)

Table 1. Proximate analysis of the prepared biochar fines %

Volatile	Moisture	Fixed carbon	Ash
3.91	2.95	88.23	4.91

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表 2 等溫團塊動力學實驗方案

Table 2. Scenarios for isothermal biochar composite briquette ( BCB) kinetic tests

Scenario	Temperature/K	CO₂ volume fraction/%	CO volume fraction /%	N₂ volume fraction /%
Ⅰ	1073	20	30	50
Ⅱ	1173	15	35	50
Ⅲ	1273	10	40	50

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表 3 模型中涉及的反應

Table 3. Reactions involved in the model

No.	Reaction	Reaction rate/(mol·m^–3·s^–1)	Ref.
1	$ {\text{3 F}}{{\text{e}}_{\text{2}}}{{\text{O}}_{\text{3}}}\left( {\text{s}} \right) + {\text{CO}}\left( {\text{g}} \right) = 2{\text{ F}}{{\text{e}}_{\text{3}}}{{\text{O}}_{\text{4}}}\left( {\text{s}} \right) + {\text{C}}{{\text{O}}_{\text{2}}}({\text{g}}) $	${R_i} = \dfrac{ {({P_{ {\text{CO} } } } - {P_{ {\text{C} }{ {\text{O} }_{\text{2} } } } }/{K_i})/(8.314T)} }{ {({K_i}/({k_i}(1 + {K_i}))} }{(1 - {f_i})^{2/3} }{a_ {\text{gs} } }$(i=1,2,3), ${K_1} = \exp ({\text{7} }{\text{.255 + 3720} }/T),$ ${k_1} = \exp ( - 1.445 - 6038/T),$ ${K_2} = \exp (5.289 - 4711/T),$ ${k_{\text{2}}} = \exp ( - {\text{2}}{\text{.515}} - {\text{4811}}/T),$ ${K_3} = \exp ( - 3.127 + 2879.63/T),$ ${k_3} = \exp (0.805 - 7385/T)$	[24,27]
2	$ {\text{F}}{{\text{e}}_{\text{3}}}{{\text{O}}_{\text{4}}}\left( {\text{s}} \right) + {\text{CO}}\left( {\text{g}} \right) = 3{\text{ FeO}}\left( {\text{s}} \right){\text{ + C}}{{\text{O}}_{\text{2}}}({\text{g}}) $
3	$ {\text{FeO}}\left( {\text{s}} \right) + {\text{CO}}\left( {\text{g}} \right) = {\text{Fe}}\left( {\text{s}} \right){\text{ + C}}{{\text{O}}_{\text{2}}}({\text{g}}) $
4	$ {\text{C}}\left( {\text{s}} \right) + {\text{C}}{{\text{O}}_{\text{2}}}\left( {\text{g}} \right) = 2{\text{ CO(g)}} $	$\begin{gathered} {R_4}{\text{ = } }{\rho _{ {\text{C,0} } } }{k_{\text{4} } }{\left( { {\text{1} } - {f_{\text{4} } } } \right)^{ {\text{2/3} } } }{\text{(} }{P_{ {\text{C} }{ {\text{O} }_{\text{2} } } } }{\text{/1} }{\text{.01} } \times {\text{1} }{ {\text{0} }^{\text{5} } }{\text{)/} }{M_{\text{C} } }_{\text{, } } \hfill \\ {k_4} = 1{\text{5} }00\exp ( - 13{\text{1} }00{\text{0} }/RT) \hfill \\ \end{gathered}$	[28]

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表 4 生物質炭復合團塊的礦物組成（質量分數）

Table 4. Mineralogical composition of BCB %

Carbon	Magnetite	Wustite	Metallic iron	Gangue
11.10	72.21	11.25	0.77	4.67

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表 5 不同的實驗方案下團塊的反應參數和實驗測量值及模型預測值

Table 5. Measured and model-predicted parameters of the BCB reduced under different scenarios

Scenario	BCB reduction fraction		BCB biochar conversion
Scenario	Measurement	Model prediction	Measurement	Model prediction
I	0.14	0.16	0.10	0.20
II	0.44	0.49	0.33	0.53
III	0.85	0.90	0.86	0.94

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