不同温度及气氛条件下生物炭的制备与还田效果研究

发布时间：2018-04-14 01:19

  本文选题：生物炭 + 气氛　； 参考：《华中农业大学》2017年硕士论文

【摘要】：生物炭(Biochar)是生物质在缺氧或限氧的条件下热解而形成的固体产物。制备生物炭的原料来源广泛,富含碳及一系列植物所需的大量和微量养分元素,且具有丰富的多孔结构。近年来,生物炭对于农业土壤的改良成为研究热点。然而,生物炭的理化性质受制备条件(温度、气氛、原料、热解速度等)的影响。本文针对生物炭研究中对较佳还田品质生物炭的研究不足、以及还田后的效果反馈和自身氮素供给等问题,以稻草秸秆和~(15)N标记的麦秆为原料,在不同的热解气氛(CO_2和N2)和热解温度下制备生物炭,通过产率计算、EA、FESEM-EDS、BET、EA-IRMS等多种表征手段,研究了制备条件对生物炭理化性质的调控;通过盆栽实验,考察了不同条件制备的生物炭还田对植物长势的影响。研究结果可为较佳还田品质生物炭的制备及还田应用提供基础理论依据。主要研究结果如下:(1)对于稻秆基生物炭,同一热解气氛下,生物炭产率和养分元素总量随热解温度的升高而降低,生物炭的pH、总孔体积和比表面积呈现上升的趋势。稻秆在300 ℃时不能完全热解,生物炭的孔结构随着热解温度的升高而逐渐发育,但过高的热解温度(800℃)会破坏生物炭的炭架结构。生物炭中介孔分布较多,微孔、介孔和大孔数分别在800℃、400℃和600℃时达到最大。同一热解温度下,综合比较400℃ CO_2气氛下制备的稻秆生物炭具有较佳的养分特性和孔结构。(2)盆栽实验结果表明,由于生物炭自身的多孔结构,加入土壤后,提高了土壤的孔隙度,土壤颗粒黏附在生物炭的表面或进入生物炭孔隙结构中,降低了土壤颗粒的黏结力,改善了土壤的物理特性。生物炭施入后土壤的pH和速效养分均得到了不同程度的提高,对植株的生长均起到了正向促进作用。相对于高温(800 ℃)生物炭,低温(400 ℃)生物炭具有更优的养分特性,对土壤的肥力提升程度更大,植株长势更优。相对于N2气氛制备的生物炭,CO_2气氛制备的生物炭对土壤pH的提升程度更大,其处理组土壤硝化作用更强,得出400 ℃ CO_2气氛下制备的生物炭具有较佳的还田效果。(3)利用~(15)N标记麦秆生物炭还田盆栽实验结果表明,生物炭还田后能释放一定N素养分,生物炭的N素供给受热解温度和热解气氛的影响。400℃ CO_2气氛下制备的生物炭还田后能为植株提供更多的N素养分,对土壤N素利用率的提升程度最大,对植株干物质积累的促进作用最大。
[Abstract]:Biochar is the solid product of biomass pyrolysis under the condition of hypoxia or oxygen limitation.Biochar is made from a wide range of sources, rich in carbon and a series of plants for a large number of nutrients and trace elements, and has a rich porous structure.In recent years, the improvement of agricultural soil by biochar has become a hot spot.However, the physicochemical properties of biochar are affected by the preparation conditions (temperature, atmosphere, raw material, pyrolysis rate, etc.).In this paper, in view of the lack of research on the better quality of bio-carbon in the study of biochar, as well as the effect feedback and nitrogen supply after returning to the field, straw straw and wheat straw labeled with 15N were used as raw materials.Biochar was prepared at different pyrolysis atmospheres and pyrolytic temperatures. The effects of preparation conditions on the physicochemical properties of biochar were studied by means of the calculation of yield of EAFSEM-EDSE-BETEA-IRMS, and pot experiments were carried out to study the effect of the preparation conditions on the physicochemical properties of biochar.The effects of biochar on plant growth under different conditions were investigated.The results can provide a theoretical basis for the preparation and application of biochar with better quality.The main results are as follows: (1) under the same pyrolysis atmosphere, the yield of biochar and the total amount of nutrient elements decreased with the increase of pyrolysis temperature, and the pH, total pore volume and specific surface area of biochar increased.Rice straw can not be pyrolyzed completely at 300 鈩，

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