中小型沼气工程撬式沼气提纯系统设计与应用

根据中国中小型沼气工程分布范围广、地区差异性大、统筹规划难的现状，考虑到中小型沼气工程中出现的沼气净化提纯效率低、净化提纯效果差、成本高等问题，该研究设计了1套撬装式集约型的沼气提纯净化系统，分别从脱硫系统、脱碳系统、控制系统等方面设计出适合于装置制造的工艺方法。系统集成了干法脱硫、膜法脱碳和分子筛工艺，在进气量为500 Nm3/d、粗沼气压力为104 kPa的沼气工程条件下，进行了工程应用试验。通过检测，该装置稳定运行35 min后，提纯气中CH4质量分数可以达到97.88%，CO2低于2.5%，H2S质量浓度仅为16.7 mg/m3，CH4回收率为86.5%。设备运行成本为0.09元/Nm3沼气，且投资回收期仅为1.5 a。经过对比，该装置的提纯指标达到了国内生物天然气相关标准，且具有移动灵活、提纯效率高、成本低等优点。通过对本装置的应用研究表明，沼气提纯净化可实现中小型沼气工程生物天然气的高值化利用，为中小型沼气工程的发展拓宽途径。

Design and application of skid type biogas purification system for small- and medium-scale biogas projects

Small-and medium-scale biogas systems are widely distributed in China. Nevertheless, the overall strategic planning of biogas project is highly difficult, due mainly to the large difference in geographic regions. According to the different daily production of biogas (Q), biogas projects in China can be divided into four categories: extremely large (Q>5 000 Nm3/d), large (5 000 Nm3/d>Q>500 Nm3/d), medium (500 Nm3/d>Q>150 Nm3/d), and small (150 Nm3/d>Q>5 Nm3/d). At present, there are more than 100 000 biogas projects of various types in China, among which there are more than 66 000 large-scale biogas projects, more than 10 000 medium-sized biogas projects, and more than 80 000 small-scale biogas projects. Many previous studies focused on biogas purification on the large and super large biogas engineering, serving as the future development trend of industrialization. Purified biogas after purification can be used for vehicle fuel or incorporated into the natural gas pipeline network, thereby to achieve its high value usage. The fermentation of raw materials in small-and medium-sized biogas projects are usually from village wastes and manure from farms. There are still problems in the small-and medium-scale biogas system, such as regional dispersion, large quantity, difficulty in the overall planning, high purification cost, and low efficiency. The generated biogas is mostly used in low-value utilization ways, such as cooking, lighting, and power generation, far beyond the high-value utilization. Therefore, it is very urgent to extend the potential application of purification system in the small and medium-sized biogas projects. In this study, a set of skid-mounted integrated biogas purification system was designed, aiming to improve the efficiency, performance, and cost-saving systems in small- and medium-sized biogas projects. Technical methods were designed suitable for the manufacture system of desulfurization, decarburization, and control. Specifically, the dry desulfurization, membrane decarburization, and molecular sieve technology were integrated into the set of the system. An engineering application test was carried out, under the conditions of biogas intake capacity of 500 m3/d, and biogas pressure of 104 kPa. After 35 minutes of stable operation, the content of CH4 in the purified biogas reached 97.88%, the content of CO2 was lower than 2.5%, the content of H2S was as low as 11 mg/kg, and the recovery efficiency of CH4 reached 86.5%. The operating cost of equipment was 0.09 yuan/Nm3 biogas, and the payback period was only 1.5 a. In comparison, the purification performance of the apparatus met the requirements of biological natural gas standard of China, indicating the advantages of flexible movement, high purification efficiency, and low cost. To meet the needs of different engineering requirements for biogas purification equipment, the device can be designed, according to different material gas in different biogas producing scale. The stability of adjusted equipment was still needed to improve in the further, particularly on the equipment adaptability, and stability characteristics for the different types of biogas engineering. The application of this apparatus can realize the valorization of biogas, and further widen the fields for the development of small and medium-sized biogas projects.