煤系氦气资源潜力及其提取工艺设计

Resource potential and extraction technique design for helium in coal measures

  • 摘要: 【目的】氦气为重要的战略稀缺资源,目前工业中使用的氦气主要来源于天然气,而煤系氦气通常为氦气含量较高的煤层气,是常规氦气资源的重要补充。在工业上,通过天然气液化过程中对蒸发气体进行提氦是获取氦资源的重要途径之一,但关于煤系氦气的研究多集中在氦气的成因、富集规律和地球化学特征研究等方面,而在煤系氦气资源特征和提取工艺的研究相对较少。【方法】以鄂尔多斯盆地东北缘三交北区块煤系氦气资源为例,分析其区域氦气资源特征,并在现有LNG工厂的基础上设计三交北区块天然气中的氦气提取工艺。【结果】结果表明:(1) 三交北区块煤系天然气资源丰富,但氦气资源量较低,为壳源氦,氦气摩尔体积分数为0.01%~0.30%,平均0.07%,属低氦区,但氦气资源量整体较为稳定,其地质储量可达1114.56万m3,累计产量70.07万m3,故可将其作为提氦的原料气来源,并对LNG生产过程中产生的蒸发气体进行提氦。(2) 选取低温提氦工艺,使用前膨胀制冷+氮气循环制冷两塔分离技术,将提取过程划分为气体过滤、催化脱氢、脱水干燥、氦气提取、氦气充装和液氧催化6个单元。【结论】本设计采用氮气循环系统高效制冷,优化能量回收,减少对原料气直接压缩的依赖,提供了稳定的低温环境,使其对氦气浓度波动不敏感,使工厂产生的蒸发气体资源能得到合理充分利用,尤其适合低丰度氦气资源的高效提取,对提高煤系氦气提取工艺和企业经济效益具有积极作用和重要意义。

     

    Abstract: Objective Helium is an important strategic scarce resource. Presently, helium used in industry originates primarily from natural gas. In contrast, helium in coal measures, generally emerging as coalbed methane (CBM) with a high helium content, serves as a vital supplement to conventional helium resources. In industry, helium extraction from boil off gas (BOG) during natural gas liquefaction is recognized as an important way to obtain helium resources. However, existing studies on helium in coal measures mostly focus on the genesis, enrichment patterns, and geochemical characteristics of helium, while there is a lack of studies on its resource characteristics and extraction techniques. Method This study investigated the helium resources in coal measures in the Sanjiaobei Block along the northeastern margin of the Ordos Basin as an example to analyze the characteristics of regional helium resources. Furthermore, a technique for helium extraction from natural gas in the block was designed based on a existing liquefied natural gas (LNG) plant in the block. Results The results indicate that the Sanjiaobei Block features abundant coal-measure gas but relatively low helium resources. Crust-derived helium is identified in this block, with molar volumetric fractions ranging from 0.01% to 0.30% (average: 0.07%). This establishes the Sanjiaobei Block as the low-helium area. Nevertheless, the helium resources in this block prove stable generally, with geological reserves and cumulative production reaching up to 11.1456 million m3 and 0.7007 million m3, respectively. Therefore, these helium resources can be treated as a feed gas source for helium extraction. This study conducted helium extraction from BOG produced during LNG production. The low-temperature helium extraction technique was selected, for which the two-tower separation technique combining pre-expansion refrigeration and nitrogen cycle refrigeration was employed. The helium extraction process consisted of six units: gas filtration, catalytic dehydrogenation, dehydration and drying, helium extraction, helium charging, and liquid oxygen catalysis. Conclusions The design proposed in this study adopts a nitrogen circulation system (NCS) for efficient refrigeration and optimizes energy recovery, reducing the dependence on direct compression of feed gas. Furthermore, this design provides a stable low-temperature environment that is insensitive to helium concentration fluctuations, enabling the rational and full utilization of BOG gas produced in the plant. This renders the design especially suitable for efficient extraction of low-abundance helium resources produced in the plant. The findings of this study will play a positive and significant role in improving both the technique for helium extraction in coal measures and the economic benefits of relevant enterprises.

     

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