酸洗脱除矿物对煤化学组成及润湿性的影响

Effects of Acid Treatment and Mineral Removal on Coal Chemical Composition and Wettability

为探究酸洗处理对煤尘含氧官能团和矿物质变化及对煤尘结构和润湿性的影响,采用盐酸、磷酸、乙酸和盐酸-氢氟酸对榆林煤(YL)进行处理,并利用FTIR,XRD及XRF分析煤尘化学组成及结构变化,借助毛细管上向渗透法研究煤尘的吸湿量,考察煤的灰分、矿物质组成及官能团对润湿性的影响规律。结果表明:酸处理能够脱除煤中的大部分矿物质,对含Si的矿物质元素脱除效果较差,对Ca和K等碱金属矿物的脱除效果较好,盐酸-氢氟酸脱除率最高,为95.3%,盐酸、磷酸、乙酸的单独脱灰率分别为88.4%,84.0%和79.9%。由XRD谱可以看出,酸处理后灰样谱图上的矿物质杂峰数量明显减少,石英峰在处理后增强。通过对XRD参数拟合,发现酸处理破坏了煤中碳的微晶结构,使煤的结构发生了一定程度的解体。FTIR分析表明,酸处理后煤中的羟基官能团含量下降,羧酸和酚羟基C—O的吸收峰占比增加;对灰分含量、矿物质元素组成、官能团变化与润湿性的拟合关系进行分析,发现酸处理降低了灰分含量,降低了煤尘润湿性;无机矿物质元素中Si和Al元素的变化与润湿性的变化规律一致;对比原煤和脱灰煤的润湿性变化与含氧官能团的含量关系,发现在1 050cm-1～1 250cm^(-1)处的酚羟基C—O的峰面积与YL的润湿性变化趋势相反,3 400cm^(-1)～3 450cm^(-1)处羟基的峰面积与YL的润湿性变化趋势相同。

The effects of oxygen-containing groups and minerals on the structure and wettability of coal were explored. The Yulin coal was treated by hydrochloric acid, phosphoric acid, acetic acid and hydrochloric-hydrofluoric acid. By means of FTIR, XRD and XRF, the changes of chemical composition and structure were investigated. The moisture absorption of treated coal to water was measured using capillary upward infiltration method, and the effects of ash, mineral composition and functional group on wettability of coal were set up. The results indicate that most of the minerals in YL coal can be removed by acid treatment, the removal of mineral elements containing Si is poor while the removal of the mineral elements containing Ca and S is better. The hydrochloric-hydrofluoric acid treatment can remove 95.3% of ash, while the other three acids can remove 88.4%, 84.0% and 79.9% of ash respectively. The XRD pattern shows that the quartz peak on the treated coal spectrum is enhanced while the number of mineral peaks on the spectrum of the demineralized sample is significantly reduced after the acid treatment. In addition, it is found by fitting the XRD parameters that the microcrystalline structure of carbon is destroyed and the coal structure is disintegrated at the mean time. The FTIR shows that the content of hydroxyl functional decreases while the proportion of carboxylic acid and phenolic hydroxyl group C-O absorption peaks increases after the acid treatment. The analysis of the fitting relationship between ash content, composition, functional group change and wettability reveales that the treatment reduces the ash content and decreases the wettability of coal. In the inorganic mineral elements of coal, Si and Al elements are consistent with the change of wettability of coal. Compared with the relationship between the wettability and oxygen-containing functional group of YL coal and demineralized coal, the peak area of the phenolic hydroxyl group C-O at 1 050cm^-1 -1 250cm^-1 is opposite to the change of wettability of YL while the peak area of the hydroxyl group at 3 400cm^-1 -3 450cm^-1 is the same as the change of wettability of YL.