碳中和的实质问题是能源的问题，根据贯彻“绿水青山就是金山银山”的理念，国务院在2021年10月发布了《关于2030年前碳达峰行动方案的通知》明确了行动方案。作为清洁能源的替代品生物质天然和可再生氢能作为重要组成部分摆在了所有环卫设施建设人的面前。如何选择这两种能源是项目建设的关键问题，也是实现碳达峰落地的实质性问题。以实际项目案例进行沼气制生物天然气和可再生氢能对比，对其他项目选择做出参考。

　　The essence of carbon neutrality lies in the issue of energy. In accordance with the concept of "green mountains and clear waters are as valuable as mountains of gold and silver", the State Council issued the "Notice on the Action Plan for Carbon Peak before 2030" in October 2021, which clarified the action plan. Biomass natural and renewable hydrogen energy, as an important component of clean energy alternatives, are placed in front of all sanitation facility builders. How to choose these two types of energy is a key issue in project construction and a substantive issue in achieving carbon peak implementation. Compare biogas to biogas and renewable hydrogen energy through actual project cases, and provide reference for the selection of other projects.

　　1 前言

　　1 Preface

　　天然气和氢气均被认定为清洁能源，我国在当前主要是使用煤炭、石油作为能源，也是第一大碳排放的原料。为了实现碳达峰、碳中和，需要加快使用清洁能源替代传统能源。我国承诺在2030年实现碳达峰，主要途径是对产业结构、能源结构进行调整。在2060年实现碳中和，主要是通过能源过程、工业生产过程、农业、土地利用等全口径全流程实现零排放。我国承诺实现上述目标的时间远远短于发达国家所用的时间，做出的努力必将远远大于这些国家。同样作为可再生能源和清洁能源，国家相关部委从2019年至今一直密集发布天然气和氢气作为可再生能源产业的指导意见。国家发改委等10大部委在2019年发布《关于促进生物天然气产业化发展的指导意见》中要求构建生物天然气发展规划体系，组织编制生物天然气中长期发展规划。而2022年国家发改委和能源局联合研究制定《氢能产业发展中长期规划（2021~2035年）》“十四五”时期，我国将初步建立以工业副产氢和可再生能源制氢就近利用为主的氢能供应体系。同样的产业发展指导意见和发展规划，均明确了无论是生物天然气还是氢能作为可再生能源的属性。目前可再生能源主要原材料为农作物秸秆、畜禽粪污、城市餐饮垃圾、城市生活垃圾填埋场等。结合目前我国实行的生活垃圾分类收集处置的方针，规模化和产业化的生物天然气主要来源是城市湿垃圾处理设施。

　　Natural gas and hydrogen are both recognized as clean energy sources. Currently, China mainly uses coal and oil as energy sources, which are also the largest sources of carbon emissions. In order to achieve carbon peak and carbon neutrality, it is necessary to accelerate the use of clean energy to replace traditional energy. China has committed to achieving carbon peak by 2030, mainly through adjusting its industrial and energy structure. To achieve carbon neutrality by 2060, the main approach is to achieve zero emissions through a full range of processes including energy, industrial production, agriculture, and land use. Our country's commitment to achieving the above goals is much shorter than the time taken by developed countries, and the efforts made will undoubtedly be much greater than those of these countries. As both renewable and clean energy sources, relevant national departments have been intensively issuing guidance on natural gas and hydrogen as renewable energy industries since 2019. In 2019, the National Development and Reform Commission and 10 other ministries issued the "Guiding Opinions on Promoting the Industrialization Development of Bionatural Gas", which required the construction of a development planning system for biogas and the organization of the preparation of medium - and long-term development plans for biogas. In 2022, the National Development and Reform Commission and the Energy Administration jointly studied and formulated the "Medium - and Long Term Plan for the Development of the Hydrogen Energy Industry (2021-2025)". During the 14th Five Year Plan period, China will initially establish a hydrogen energy supply system mainly based on the nearby utilization of industrial by-product hydrogen and renewable energy hydrogen production. The same industry development guidance and development plan have clearly defined the attributes of both biogas and hydrogen as renewable energy sources. At present, the main raw materials for renewable energy are crop straw, livestock and poultry manure, urban catering waste, and urban household waste landfills. Based on the current policy of classified collection and disposal of household waste in China, the main source of large-scale and industrialized biogas is urban wet waste treatment facilities.

　　2 项目情况介绍

　　Introduction to Project 2

　　位于某市的湿垃圾处理项目，处理规模为500吨/日，其中厨余垃圾300t/d，餐饮垃圾200t/d。主要工艺采用厌氧发酵方式产生沼气。经过计算沼气量约为32000m3/d，这些沼气是经过厌氧发酵产生，主要成分是CH4、CO2和H2S。沼气的成分如表1所示：

　　The wet waste treatment project located in a certain city has a processing capacity of 500 tons/day, including 300t/d of kitchen waste and 200t/d of catering waste. The main process uses anaerobic fermentation to produce biogas. After calculation, the amount of biogas is about 32000m3/d. These biogas are produced through anaerobic fermentation and mainly consist of CH4, CO2, and H2S. The composition of biogas is shown in Table 1:

　　分析后可以看出，经过厌氧发酵后的沼气在热值、华白指数等指标，与我国现行国标天然气相差甚远，不能直接输送至天然气管道。需要对CO2、O2以及其他杂质进行脱除。

　　After analysis, it can be seen that the biogas produced by anaerobic fermentation has a significant difference in calorific value, Huabai index and other indicators compared to the current national standard for natural gas in China, and cannot be directly transported to natural gas pipelines. CO2, O2, and other impurities need to be removed.

　　3 生物质天然气工艺流程及产品指标

　　3. Biomass natural gas process flow and product indicators

　　前端工艺产生的沼气进入气柜储存、均质、稳压，稳压后经沼气风机升压至20~25kPa后送入湿法脱硫系统将硫化氢脱至50mg/m3以下。湿法脱硫后气体含大量水分，经气液分离之后送入干法脱硫系统将硫化氢脱至10mg/Nm3以内。脱硫后沼气经预处理系统除尘、除水、调温后，由沼气压缩机增压至变压吸附工作压力0.5MPa。压缩后沼气经除油、除水后进入挥发性有机化合物（VOC）脱除塔吸附除臭，进一步预处理净化原料气。原料气最终进入变压吸附装置进行脱碳精制，精制得到的天然气产品经调压计量及加臭后送入市政燃气管网。变压吸附顺放气高压部分顺放至沼气螺杆压缩机，低压部分顺放至预处理沼气罗茨风机入口，吸附提纯解析气部分回流至沼气罗茨风机入口，其余大部分解析气送至火炬系统燃烧或直接排空。具体工艺流程如图1生物质天然气工程流程图和表2生物质天然气指标表所示。

　　The biogas generated by the front-end process enters the gas holder for storage, homogenization, and stabilization. After stabilization, it is pressurized to 20-25kPa by the biogas fan and sent to the wet desulfurization system to remove hydrogen sulfide to below 50mg/m3. After wet desulfurization, the gas contains a large amount of moisture. After gas-liquid separation, it is sent to the dry desulfurization system to remove hydrogen sulfide to less than 10mg/Nm3. After desulfurization, the biogas is subjected to dust removal, water removal, and temperature regulation through a pretreatment system, and then pressurized by a biogas compressor to a pressure swing adsorption working pressure of 0.5 MPa. After compression, the biogas enters the volatile organic compound (VOC) removal tower for adsorption and deodorization after oil and water removal, and further pretreats and purifies the raw gas. The raw gas ultimately enters the pressure swing adsorption unit for decarbonization and refining. The refined natural gas product is regulated, metered, and odorized before being sent to the municipal gas pipeline network. The high-pressure part of the pressure swing adsorption gas is discharged to the biogas screw compressor, the low-pressure part is discharged to the inlet of the pre-treatment biogas Roots blower, the adsorption and purification gas is refluxed to the inlet of the biogas Roots blower, and the rest of the gas is sent to the flare system for combustion or directly discharged. The specific process flow is shown in Figure 1 Biomass Natural Gas Engineering Flow Chart and Table 2 Biomass Natural Gas Index Table.

　　4 氢气工艺流程及产品指标

　　4 Hydrogen process flow and product indicators

　　工艺流程由制氢装置和二氧化碳液化装置组成。制氢装置以沼气为原料，采用的工艺路线为沼气湿法甲基二乙醇胺（MDEA）脱碳→蒸汽转化→合成气湿法MDEA脱碳→变压吸附（PSA）分离得到产品氢气。二氧化碳液化装置以制氢装置中产生的二氧化碳尾气作为原料，采用的工艺路线为CO2压缩→预冷却→分子筛干燥/净化→液化精馏得到食品级CO2产品。工艺流程如图2PSA制氢工艺流程图和表3产品氢气指标表所示。

　　The process flow consists of a hydrogen production unit and a carbon dioxide liquefaction unit. The hydrogen production unit uses biogas as the raw material and adopts the process route of wet process of methane based methylenediethanolamine (MDEA) decarbonization → steam reforming → synthesis gas wet MDEA decarbonization → pressure swing adsorption (PSA) separation to obtain product hydrogen. The carbon dioxide liquefaction unit uses the carbon dioxide tail gas generated in the hydrogen production unit as raw material, and adopts the process route of CO2 compression → pre cooling → molecular sieve drying/purification → liquefaction distillation to obtain food grade CO2 products. The process flow is shown in Figure 2PSA hydrogen production process flow chart and Table 3 product hydrogen index table.

　　5 方案对比

　　Comparison of 5 Plans

　　从湿垃圾处理项目本身作为市政基础的稳定运行考虑，对沼气制天然气和氢气从安全性、经济性进行比较。首先我们对天然气和氢气在物化性质与危险特性进行对比，详见表4天然气和氢气的物化性质与危险特性对比表。从特比可以看出，氢气的爆炸极限远大于天然气。同时氢气在遇到超过400℃的热源或明火后会爆炸，与天然气比较有较大的活性。在中等规模项目中较难控制。

　　Considering the stable operation of the wet waste treatment project as a municipal foundation, a comparison is made between the safety and economy of biogas to natural gas and hydrogen production. Firstly, we compare the physicochemical properties and hazardous characteristics of natural gas and hydrogen, as shown in Table 4. From the comparison, it can be seen that the explosive limit of hydrogen is much greater than that of natural gas. At the same time, hydrogen gas will explode when exposed to heat sources or open flames above 400 ℃, and has greater activity compared to natural gas. Difficult to control in medium-sized projects.

　　从项目本身的经济性进行比较，如表5所示为生物质天然气与制氢经济比较：考虑本项目选址的周边条件考虑。项目选址附近有市政天然气管道，可以加压后直接输送。而氢气输送有两种方法，分别是与天然气并网输送和加压至20MPa采用拖车运输。第一种与天然气并网输送技术并不成熟，而采用加压后拖车运输费用较高。根据上述比较，本项目最终选择厌氧发酵沼气PSA工艺制生物质天然气。

　　Comparing the economic viability of the project itself, Table 5 shows the economic comparison between biomass natural gas and hydrogen production: taking into account the surrounding conditions of the project site selection. There is a municipal natural gas pipeline near the project site, which can be pressurized and directly transported. There are two methods for hydrogen transportation, namely grid connected transportation with natural gas and trailer transportation when pressurized to 20MPa. The first type of grid connected transportation technology for natural gas is not yet mature, and the cost of using pressurized trailer transportation is relatively high. Based on the above comparison, this project ultimately chooses the anaerobic fermentation biogas PSA process to produce biomass natural gas.

　　6 结束语

　　6 Conclusion

　　碳达峰、碳中和的目标是可再生能源的革命，同时推动能源结构多元化进程。在生物质能源中利用厌氧技术产生的生物质气体作为可再生能源回收利用，是可循环经济的重要议题之一。然而在相关配套设施上仍然存在差距，如相较于天然气管道，氢气管道配套建设仍不完善，目前国内仍没有适用于氢气长输管道的设计、建造和验收标准。需要加快对于氢气产业的终端用户的扶持力度，如氢能汽车等。生物质可再生能源取代传统化石能源是必然之路，对于节能减排的效果立竿见影。

　　The goal of peaking carbon emissions and achieving carbon neutrality is a revolution in renewable energy, while promoting the diversification of energy structure. The utilization of biomass gas generated by anaerobic technology in biomass energy as a renewable energy source for recycling is one of the important issues in the circular economy. However, there are still gaps in related supporting facilities, such as the incomplete construction of hydrogen pipelines compared to natural gas pipelines. Currently, there are no design, construction, and acceptance standards applicable to hydrogen long-distance pipelines in China. We need to accelerate support for end-users in the hydrogen industry, such as hydrogen powered vehicles. The replacement of traditional fossil fuels with renewable biomass energy is an inevitable path, which has an immediate effect on energy conservation and emission reduction.

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