改性干水体系中瓦斯水合分离动力学与回收研究

Effect of modified dry water on kinetic and recovery of hydration separation coal mine gas

  • 摘要: 煤炭行业低碳化发展是实现碳中和目标的关键,降低碳排放强度是"双碳"目标的必然要求,因此在碳达峰背景下探寻快速高效分离回收低浓度煤矿瓦斯的方法十分必要。据此基于水合物技术,运用结冷胶、碳纳米管和铜粉对干水进行改性,并以干水作为试验液相,在3.0 MPa,275.2 K条件下静态体系中进行多轮次水合物形成循环试验,考察非改性干水、结冷胶-四氢呋喃(THF)、碳纳米管-THF、铜粉-THF改性干水对25% CH4/67% N2/8% O2混合气的分离动力学和CH4回收效果的影响,并对比了不同改性材料干水重复应用的性能稳定性。结果表明:改性材料中结冷胶体系分离效果最好,与非改性干水体系相比,结冷胶-THF改性干水体系气体消耗量显著增加9.36倍,水合物初始生长速率提高87.45%,CH4平均回收率最大为56.4%。4种结冷胶质量分数(3%、6%、9%、12%)优选结果显示含有9%结冷胶的改性干水体系(GDW)具有较好的动力学稳定性和回收效果。而碳纳米管-THF、铜粉-THF改性干水对瓦斯水合物形成具有轻微的抑制作用,在多轮次水合物形成过程中出现部分解离时,存在自由水和未解离干水的一个最优配比,从而达到最优动力学效果。鉴于结冷胶改性干水的高回收率、良好的循环性和能耗低的特点,有望成为水合物法分离回收低浓度瓦斯的一种新的方法。

     

    Abstract: The low carbon development of coal industry is the key to achieve the "dual carbon" goal, and the reduction of carbon emission intensity is its inevitable requirement. It is necessary to explore the method of rapid and efficient separation and recovery of coal bed methane in the context of carbon peak. In this study, dry water was modified with gellan gum, carbon nanotubes, and copper powder based on hydratre technology.The multiple cycles of hydrate formation were carried out in the static system at a condition of 3.0 MPa and 275.2 K using dry water as the experimental fluid phase. The authors examined the effects ofunmodified dry water, gellan gum-dry water, carbon nanotube-dry water, and copper powder-dry water on the separation kinetics and CH4 recovery effect of 25% CH4/67% N2/8% O2 mixture, and compared the performance stability of dry water with different modified materials for repeated applications. The results indicated that the separation effect of materials is best in gellan gum-dry water.Compared to the unmodified dry water system, the gellan gum-modified dry water system was significantly increased by a factor of 9.36, the initial growth rate of hydrate was improved by 87.45%, and the average CH4 recovery was maximized to 56.4%.The graphite nanofluid containing 9% GDW is preferred among the four GDW systems mass concentrations (3%, 6%, 9%, and 12%) tested in this study. The preferred results showed that the 9% gellan gum-dry water had a better kinetic stability and recovery effect. However, the carbon nanotube-dry water and copper powder-dry water showed a slight inhibitory effect on the CBM hydrate formation. When partial dissociation occurs during multiple cycles of hydrate formation, there exists an optimal ratio of free water and undissociated dry water to achieve optimal kinetics. The high CH4 recovery rate, enhanced repeated kinetics, and low-energy consumption of the GDW system demonstrated a new prospect for the separation of low-concentration CBM gas by hydrate method.

     

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