生物炭制备过程中养分元素迁移转化机制研究

发布时间：2018-02-28 12:04

本文关键词： 生物炭养分元素气氛温度　出处：《华中农业大学》2016年硕士论文　论文类型：学位论文

【摘要】：生物炭是在无氧或者缺氧的条件下,生物质热解后形成的含碳量较高、稳定性较强的固体产物。稻秆作为制备生物炭的原材料具有来源广泛、数量巨大、可再生能力强等特点。生物炭作为潜在的土壤改良剂,其还田后对土壤及农作物生长的影响受到研究者的广泛关注。然而,制备条件对生物炭养分特性的影响机制研究相对缺乏。本论文主要以稻秆为原料,在不同热解条件下制备生物炭,通过热解产物产率计算、EA,XPS、SEM-EDS、BET、GC-MS等多种方法研究了不同热解条件对热解产物中碳、氮、磷、钾等养分元素的影响,揭示了生物炭制备过程中养分元素的迁移转化机制。其主要成果和结论如下:(1)CO_2气氛下制备的生物炭产率、pH、养分元素的总量比N_2气氛高;生物炭产率、养分元素的总量随温度升高而降低,而生物炭pH呈上升趋势;生物炭产率、养分元素不受进气流速的影响,但进气流速增大生物炭pH呈下降趋势;随着升温速率的增大,生物炭产率、pH、养分元素的总量呈下降趋势。对不同制备条件下的生物炭产率、pH、养分元素进行层次分析,从而得出CO_2气氛下,当温度为400oC、升温速率为20oC/min、进气流速为0L/h时制备的生物炭较好。(2)随温度的升高,生物油中碳、氮元素先增加再减少,其中酚类物质是生物油的主要成分,生物油中含氮物质由含杂环氮物质向其他含氮类物质转化;气体产物中碳、氮元素处于增长的趋势;CO_2气氛下生物油中酚类、酰胺类物质相对含量高于Ar气氛;CO_2气氛下气体产物中碳、氮总量高于N_2气氛。(3)CO_2气氛下生物炭中碳、氮元素总量高于Ar气氛下,CO_2气氛下生物炭中炭架结构稀疏,C与O的结合明显增加;热解时稻秆中的蛋白质、游离氨基酸、胺、吡咯、生物碱、无机盐迁移转化为生物炭中的氨基化合物、酰胺、腈、吡咯、胺、无机盐等物质,生物炭中氮元素主要是与碳元素相结合。(4)稻秆中的磷、钾元素基本保留在生物炭中,稻秆中有机磷转化为K2HPO3、(NaPO3)3、P4O10等物质保留在生物炭中,稻秆中卤化钾、KNO3、KNO_2一部分以原来形态保留在生物炭中,一部分转化为钾络合物、石墨层-钾保留在生物炭中。(5)随温度升高,生物炭比表面积增加,生物炭主要以微孔和介孔为主;碳、氮、磷、硫元素相对总量减少,钾元素相对总量增加,无机氮、无机磷、无机硫相对含量增加,可利用性钾相对含量减少,但是无机氮、磷、可利用性钾相对总量减少,无机硫相对总量增加。因此,说明400oC的生物炭品质较好。(6)CO_2气氛下制备的生物炭比表面积、总孔体积高于N_2气氛,且生物炭中无机氮、无机磷、无机硫、可利用性钾相对含量高于N_2气氛。由此表明CO_2气氛下制备的生物炭品质优于N_2气氛下制备的生物炭。
[Abstract]:Biochar is a solid product with high carbon content and strong stability after pyrolysis of biomass under anaerobic or anoxic conditions. Rice stalks as raw materials for the preparation of biochar have a wide range of sources and a large number. Biochar, as a potential soil modifier, has attracted extensive attention from researchers for its effects on soil and crop growth after being returned to the field. The effect of preparation conditions on the nutrient properties of biochar is relatively lacking. In this paper, biochar was prepared from rice straw under different pyrolysis conditions. The effects of different pyrolysis conditions on carbon, nitrogen, phosphorus, potassium and other nutrient elements in pyrolysis products were studied by calculating the yield of pyrolysis products. The main results and conclusions are as follows: the biochar yield is pH and the total nutrient content is higher than that in N\ -2 atmosphere, the biochar yield is higher than that in N\ -2 atmosphere, the biochar yield is higher than that in N\ -2 atmosphere, and the total amount of nutrient elements is higher than that in N\ -2 atmosphere, the main results and conclusions are as follows. The total amount of nutrient elements decreased with the increase of temperature, but the pH value of biochar increased; the yield of biochar, nutrient element was not affected by the inlet gas flow rate, but the pH value of biochar decreased with the increase of inlet gas velocity; with the increase of heating rate, the pH value of biochar increased. The pH value of biochar yield and the total nutrient element were decreased. The pH of biochar yield and nutrient element under different preparation conditions were analyzed, and the results showed that under the atmosphere of CO_2, the pH and nutrient elements of biochar were analyzed. When the temperature is 400oC, the heating rate is 20oC / min, and the inlet flow rate is 0L / h, the carbon and nitrogen elements in bio-oil increase first and then decrease with the increase of temperature, in which phenols are the main component of bio-oil. Nitrogen in bio-oil is transformed from heterocyclic nitrogen to other nitrogen-containing compounds, and carbon and nitrogen elements in gas products are in an increasing trend. In the atmosphere of CO-2, phenols are found in bio-oil. The relative content of amides is higher than that of carbon in gas products in ar atmosphere, and the total amount of nitrogen is higher than that in biochar in NSP _ 2 atmosphere. The total amount of nitrogen element was higher than that in ar atmosphere, the binding of carbon frame structure sparsely C and O in biochar was obviously increased, the protein, free amino acid, amine, pyrrole, alkaloid in rice stalk were increased during pyrolysis, and the content of amino acid, pyrrole, alkaloid, amino acid, pyrrole, alkaloid, Inorganic salts were transferred to amino compounds, amides, nitriles, pyrrole, amines, inorganic salts and other substances in biochar. The transformation of organic phosphorus from rice straw to K _ 2HPO _ 3N _ 3N _ 4O _ (10) was retained in biochar. Some of Kno _ (3) O _ (2) in rice culm was retained in biochar, some was transformed into potassium complex, and graphite layer and potassium remained in biochar (.5) with the increase of temperature, and Kno _ (3) O _ (2) remained in biochar, and K _ (3) O _ (2) was changed into K _ (2) HPO _ (3). The specific surface area of biochar was increased, and the microporous and mesoporous carbon was the main one, while the relative total amount of carbon, nitrogen, phosphorus and sulfur decreased, the relative total amount of potassium increased, the relative content of inorganic nitrogen, inorganic phosphorus and inorganic sulfur increased. The relative content of available potassium decreased, but the relative total amount of inorganic nitrogen, phosphorus and available potassium decreased, and the relative total amount of inorganic sulfur increased. The total pore volume was higher than that in N _ 2 atmosphere, and the relative contents of inorganic nitrogen, inorganic phosphorus, inorganic sulfur and available potassium in biochar were higher than those in N _ 2 atmosphere, which indicated that the quality of biotic carbon prepared in CO_2 atmosphere was better than that in N _ 2 atmosphere.
【学位授予单位】：华中农业大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：S156.2

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