Effect of ionic liquid on the spontaneous combustion characteristics of noncaking pulverized coal
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摘要: 為了研究煤粉儲運過程中堆積煤粉在漏風環境下氧化升溫導致其氧化自燃特征，揭示[BMIM][BF4]離子液體抑制煤粉氧化阻燃反應機制。本文選用高效阻化劑[BMIM][BF4]離子液體對紅柳煤礦(HL)不粘煤煤粉進行阻化處理，通過煤粉恒溫氧化實驗測定5%、10%、15%質量分數的[BMIM][BF4]處理煤粉的自燃臨界參數，即煤粉臨界自燃溫度Tm和著火延遲時間ti，分析[BMIM][BF4]對煤粉加熱、自熱反應的影響；測試同一高溫環境下(各煤粉均被點燃)[BMIM][BF4]對煤粉的宏觀阻化特性；通過FT-IR實驗表征[BMIM][BF4]對煤粉的微觀阻化特征，驗證煤粉自燃臨界參數變化規律。結果表明：[BMIM][BF4]能夠抑制煤粉自熱反應并提高煤粉Tm和ti值，降低煤粉自燃危險性，且其質量分數越大，煤粉自燃臨界參數越大，其中15%質量分數的[BMIM][BF4]處理煤粉的Tm為156 ℃，較原煤粉冗余度提高+26 ℃，ti為80 min，較原煤粉著火延遲32 min。在同一環境溫度Ta下(Ta>Tm)，[BMIM][BF4]處理煤粉的中心點溫度、耗氧速率、CO產生量均小于原煤粉，且[BMIM][BF4]的阻化效果隨質量分數的增大而增大。[BMIM][BF4]的阻化作用體現在強電負性氟原子與煤中羥基氫原子形成較強的氫鍵，溶解破壞煤中羥基基團，阻斷煤氧鏈式反應。Abstract: To study the oxidation behavior induced by the spontaneous combustion of accumulated pulverized coal during its storage and transportation within an air leakage circumstance during increased oxidation and temperature and to reveal the mechanism of [BMIM][BF4] ionic liquid inhibiting oxidation and flame retardant characteristics of pulverized coal, this paper used a high-efficiency inhibitor [BMIM][BF4] ionic liquid to inhibit the noncaking coal pulverized coal of the Hongliu coal mine (HL), measuring the critical parameters (critical spontaneous combustion temperature, Tm, and ignition delay time, ti) of pulverized coal spontaneous combustion treated using [BMIM][BF4] at 5%, 10%, and 15% mass fraction. This work also analyzed the influence of [BMIM][BF4] on the heating and self-heating of the pulverized coal. Macroscopic resistance characteristics of [BMIM][BF4] to the pulverized coal were tested under the same high-temperature circumstance (all pulverized coals were ignited). Furthermore, an Fourier transform infrared experiment was used to characterize the microscopic resistance characteristics of the pulverized coal by [BMIM][BF4] to verify the variation of the critical parameters during pulverized coal spontaneous combustion. Results show that [BMIM][BF4] can efficiently inhibit the self-heating reaction of the pulverized coal, increase the Tm and ti values of the pulverized coal, and reduce the risk of pulverized coal spontaneous combustion. Moreover, a higher [BMIM][BF4] mass fraction results in a greater critical parameter of pulverized coal spontaneous combustion. Among them, the Tm of the coal powder treated by [BMIM][BF4] at a 15% mass fraction is 156 ℃, which is +26 ℃ longer than the original pulverized coal redundancy, and the ti is 80 min, which is 32 min later than the original pulverized coal ignition. Under a similar experimental temperature, Ta (Ta>Tm), the center point temperature, oxygen consumption rate, and CO production of pulverized coal treated by [BMIM][BF4] are all lower than those of the original pulverized coal, and the inhibition effect is enhanced with the increase in the mass fraction of [BMIM][BF4]. Meanwhile, the inhibited effect of [BMIM][BF4] is reflected in the strong electronegative fluorine atoms forming strong hydrogen bonds with the hydroxyl hydrogen atoms in coal, dissolving and destroying the hydroxyl groups in the coal and blocking the coal oxygen chain reaction.
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圖 3 原煤粉在兩種環境溫度下的氧化進程. (a) 原煤粉中心點溫度變化; (b) 原煤粉氧氣質量分數變化
Figure 3. Oxidation process of the original pulverized coal at two ambient temperatures: (a) temperature change at the center point of the original pulverized coal; (b) oxygen mass fraction change of the original pulverized coal
圖 4 離子液體處理煤粉在兩種環境溫度下的升溫曲線. (a) 5%?[BMIM][BF4]; (b) 10%?[BMIM][BF4]; (c) 15%?[BMIM][BF4]
Figure 4. Temperature rise curves of the pulverized coal treated by ionic liquid at two ambient temperatures: (a) 5%?[BMIM][BF4]; (b) 10%?[BMIM][BF4]; (c) 15%?[BMIM][BF4]
圖 8 紅外光譜曲線. (a) [BMIM][BF4]的吸光度; (b) 15%?[BMIM][BF4]與原煤粉的吸光度對比
Figure 8. Infrared spectrum curve: (a) absorbance of [BMIM][BF4]; (b) comparison of absorbance between 15%?[BMIM][BF4] and original pulverized coal
圖 9 煤粉主要吸收峰面積變化
Figure 9. Change of the main absorption peak area of the pulverized coal
表 1 煤樣工業分析
Table 1. Industrial analysis of the coal sample
Sample Mass fraction/% Moisture (Mad) Ash (Aad) Volatiles (Vad) Fixed carbon (FCad) HL 2.62 16.18 35.27 45.93 
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表 2 煤樣元素分析
Table 2. Element analysis of the coal sample
Sample Mass fraction/% Carbon (Cad) Hydrogen (Had) Oxygen (Oad) Nitrogen (Nad) Sulfur (Sad) HL 68.11 4.61 6.54 1.78 0.16
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表 3 [BMIM][BF 4]和煤粉的配比
Table 3. Mixing ratio of [BMIM][BF4] and pulverized coal
Samples Mass fraction of [BMIM][BF4]/% Pulverized coal: Water: Ionic liquid (mass ratio) 5%?[BMIM][BF4] 5 100∶47.5∶2.5 10%?[BMIM][BF4] 10 100∶45∶5 15%?[BMIM][BF4] 15 100∶42.5∶7.5
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表 4 煤粉自燃臨界參數
Table 4. Critical parameters of pulverized coal spontaneous combustion
Pulverized coal Tm/℃ ti/min Original pulverized coal 130 48 5%?[BMIM][BF4] 136 55 10%?[BMIM][BF4] 142 67 15%?[BMIM][BF4] 156 80
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