厌氧发酵作为一种有机固废处理与资源化利用方法，其过程中会伴随着大量含有重金属、病原菌及难以生物降解的有机物等有毒有害物质的沼渣。沼渣产量大、无法及时消纳，不妥善处理会对环境造成严重污染，这成为限制沼气工程发展的瓶颈问题。热解技术作为沼渣处理的一种有效方式受到越来越多的关注，但沼渣单独热解存在能耗高，热解产物品质低，热解产物难利用等方面的问题。因此，针对沼渣热解技术和热解产物利用中所存在的部分实际问题，可以采用与园林废弃物共热解的方式弥补沼渣单独热解的缺陷，其热解产物生物炭是一种比表面积高，多孔的材料，在其表面含有丰富的有氧官能团，是一种潜在的污染物吸附剂和土壤改良剂。沼渣和园林废弃物共热解制备生物炭，不仅对沼渣进行了无害化处理，而且实现了沼渣和园林废弃物的资源化利用，实现了“以废治废”的环保主题。
本文以沼渣和园林废弃物为实验原料，采用热重分析仪研究了沼渣与园林废弃物共热解特性；通过热解-活化反应器研究了园林废弃物与沼渣共热解制备生物炭条件及生物炭的活化条件；通过固定床吸附装置研究了生物炭对二氧化硫的吸附效果，并组建了一套中试规模的热解试验装置。通过以上研究，主要得出以下结论：
（1）热重分析实验表明，园林废弃物热解过程中存在放热反应起到能量补充作用，反应活性高且能耗低，沼渣的热解过程是复杂的持续吸热过程，反应活性低且能耗高，园林废弃物的添加能够促进混合物热解，使反应向低温段移动，促进反应进行。
（2）园林废弃物与沼渣共热解实验表明，物料质量配比和热解温度对生物炭产率和品质有较大影响，热解时间对生物炭影响较小；最佳热解条件为沼渣与园林废弃物质量比7:3、热解温度500 ℃、热解时间30 min，在此条件下下制备的生物炭灰分含量较高，表面有较丰富的官能团，比表面积为185.4 m2/g，孔容为0.17 cm3/g。
（3）生物炭活化实验表明，活化温度和活化时间对生物炭活化效果有较大影响，随着活化温度升高，生物炭碘值和比表面积呈现先上升后降低的趋势，随着活化时间延长，生物炭比表面积和碘值不断降低，最佳活化条件为活化温度800 ℃、活化时间5 min，生物炭经过活化后比表面积达到548.2 m2/g，孔容达到0.5 cm3/g。
（4）活化后生物炭对二氧化硫的吸附实验表明，生物炭对二氧化硫化学吸附效果更好；活化条件对生物炭吸附二氧化硫有较大影响，吸附温度对吸附效果影响较小；生物炭对二氧化硫最大吸附容量为15.31 mg/g；生物炭解吸再生2次后吸附能力出现较大幅度下降。
 

As an organic solid waste treatment and resource utilization method, the process of anaerobic fermentation is accompanied by a large amount of digestate containing toxic and harmful substances such as heavy metals, pathogenic bacteria and organic substances that are difficult to biodegrade. The large production of digestate, which cannot be consumed in time and will cause serious pollution to the environment if not properly treated, has become a bottleneck limiting the development of biogas engineering. Pyrolysis technology has received more and more attention as an effective way of digestate treatment, but there are problems of high energy consumption, low quality of pyrolysis products and difficult utilization of pyrolysis products in digestate pyrolysis alone. Therefore, to address some of the practical problems of digestate pyrolysis technology and pyrolysis product utilization, co-pyrolysis with garden waste can be used to make up for the defects of digestate pyrolysis alone, and its pyrolysis product, biochar, is a material with high specific surface area and porous, containing abundant aerobic functional groups on its surface, which is a potential pollutant adsorbent and soil conditioner. The preparation of biochar by co-pyrolysis of digestate and garden waste not only provides harmless treatment of digestate, but also realizes the resource utilization of digestate and garden waste, which realizes the environmental protection theme of "treating waste with waste".
In this paper, the co-pyrolysis characteristics of digestate and garden waste were investigated with a thermogravimetric analyzer; the conditions of biochar preparation by co-pyrolysis of garden waste and digestate and the activation conditions of biochar were investigated with a pyrolysis-activation reactor; the adsorption effect of biochar on sulfur dioxide was investigated with a fixed-bed adsorption device, and a pilot-scale pyrolysis test device was set up. From the above studies, the following conclusions were mainly drawn:
(1) Thermogravimetric analysis experiments show that the existence of exothermic reactions in the pyrolysis process of garden waste plays an energy-supplementing role, with high reaction activity and low energy consumption, while the pyrolysis process of digestate is a complex continuous heat absorption process with low reaction activity and high energy consumption, and the addition of garden waste can promote the pyrolysis of the mixture and make the reaction move to the low temperature section to facilitate the reaction.
(2) The experiments on the co-pyrolysis of garden waste and digestate showed that the mass ratio of material and pyrolysis temperature had a greater influence on the yield and quality of biochar, while the pyrolysis time had less influence on the biochar; the best pyrolysis conditions were 7:3 mass ratio of digestate to garden waste, 500 ℃ pyrolysis temperature and 30 min pyrolysis time. The specific surface area was 185.4 m²/g, and the pore volume was 0.17 cm³/g.
(3) The activation experiments showed that the activation temperature and activation time had a great influence on the activation effect of biochar, with the increase of activation temperature, the iodine value and specific surface area of biochar showed a trend of increasing and then decreasing, and with the increase of activation time, the specific surface area and iodine value of biochar decreased continuously. After activation, the specific surface area of biochar reached 548.2 m²/g and the pore volume reached 0.5 cm³/g.
(4) The adsorption experiments of activated biochar on sulfur dioxide showed that biochar had a better effect on sulfur dioxide chemisorption; the activation conditions had a greater effect on sulfur dioxide adsorption by biochar, and the adsorption temperature had a smaller effect on the adsorption effect; the maximum adsorption capacity of biochar on sulfur dioxide was 15.31 mg/g; the adsorption capacity of biochar decreased significantly after desorption and regeneration for two times.