【作者】 韦茂贵；

【导师】 谢光辉；

【作者基本信息】 中国农业大学 ， 生物质工程， 2014， 博士

【摘要】 木薯茎秆是加工固体颗粒燃料和燃料乙醇等多用途的生物质原料。本试验在我国木薯主产区进行生产田取样和正交设计大田试验,研究木薯茎薯比、直燃利用的原料特性(简称燃料特性)及非结构性糖含量随地点、品种及收获时间的变化规律,探讨木薯茎秆资源量评估的方法及其原料品质分级指标,为木薯茎秆利用的工艺设计和产业发展提供理论依据。试验结果如下：(1)鲜基的茎薯比(茎秆产量/块根产量)均值为0.63,其95%置信度的区间为0.56-0.70。主栽品种华南205的茎薯比均值为0.58,置信区间为0.52-0.64。茎薯比受生长环境和品种及其交互作用的影响。块根收获指数折茎薯比的折算系数也受生长环境和品种的影响。利用折算系数A’将查阅文献获得的收获指数折为茎薯比的方法可行,当收获指数为0.55-0.63时,可用系数A(0.89-1.1)折算为茎薯比。收获指数与茎薯比呈显著负相关。(2)地点因素对木薯茎秆燃料特性(热值(GCV)、去灰分热值(GCVaf)、灰分、N、S、Cl、P、K和Mg含量)的影响最大,品种的影响次之,收获时间的影响最小。茎秆Ca含量受品种的影响最大。偏最小二乘判别分析(PLS-DA)对地点判别的结果显示,引起茎秆燃料特性地点间差异的主要指标为K、灰分、Cl、GCV和GCVaf。其中,K、灰分和Cl含量与土壤理化性质相关,其偏最小二乘线性模型的判别系数R2分别为0.954、0.873和0.789。木薯茎秆灰分含量为1.70-6.69%。用成灰元素的摩尔比及K2O-(CaO+MgO)-P2O5的成分三角坐标图来预测茎秆燃烧时灰分行为,结果表明：木薯茎秆的灰熔点>1500℃,燃烧时底灰熔融结渣的可能性小。茎秆的K和Cl含量分别为1.0-27.8g kg-1和0.2-6.3g kg-1,个别地区(如武鸣和隆安)的茎秆燃烧时会有大量飞灰颗粒产生,易引起颗粒物排放超标、氯化物在换热器表面沉积和腐蚀设备。木薯茎秆的N含量为6.0-21.6g kg-1,燃烧时引起酸性气体排放超标的可能性大。(3)木薯茎秆非结构性糖(可溶性糖和淀粉)的含量和产量受地点因素的影响最大,受品种因素的影响次之,收获时间的影响最小。茎秆淀粉含量为干重的14-42%,产量为0.2-2.1t ha-1,平均产量1.2t ha-1,比只收获块根淀粉增加17.9%。加上可溶性糖,茎秆的非结构性糖产量为0.30-0.59t ha-1,可生产燃料乙醇1408-9246L ha-1,比只利用块根加工燃料乙醇增加6.51-52.94%。在块根收获期内,茎秆淀粉含量与块根淀粉含量呈正相关,判别系数为0.573。正相关关系在不同品种间稳定存在。选择块根淀粉含量高的品种,获得高淀粉含量茎秆的几率大。(4) PLS-DA对地点判别的结果表明,Cl、K和淀粉含量变化是引起木薯茎秆原料化学特性地点间差异的主要原因。引起同一地区的茎秆原料化学特性品种间差异的主要指标为S、Ca、K、Cl和淀粉含量。若木薯茎秆全部用于加工燃料乙醇和固体颗粒燃料,会造成每公顷14-130kgN、1.05-20kg P、3.85-195kg K和3.15-63.65kg Ca的损失。可持续加工利用木薯茎秆,除考虑原料品质外,还要考虑营养元素K、N和Ca的回收还田,以保持土壤肥力。更多还原

【Abstract】 Cassava (Manihot esculenta Crantz.) stem is a multipurpose feedstock for solid biofuel and bioenthanol. The current study was composed of a full factorial design experiment (DE;3cultivars x3locations x5harvest times) in2011to examine variations in stem residues index (SRI), fuel characteristic, and non-structural carbohydrate with location, cultivar, and harvest time; and the field surveys (FS) in2008,2010, and2012of validateing the relations found in the DE. The study sites covered the main cassava cultivation area in Guangxi Zhuang Autonomous Region (Guangxi), which has the largest cassava production in China. The general goal was to improve the basic knowledge of cassava stem properties and their variation for the utilisation of existing crop residues in the regions where cassava is cultivated. The results are as follow:The average of288plants’SRI (stem production/root production) is0.63and its95%confidence interval is0.56-0.70. The mean SRI of the dominant cultivar South China205(SC205) is0.58and its95%confidence interval ranged from0.52to0.64. SRI was affected by location, cultivar, and their interaction. Location has stronger effects on SRI than cultivar. The95%confidence interval of the coefficient between cassava root harvest index (HI) and SRI was ranged from0.89to1.1, which can be adopted for the calculation when the range of HI is0.55-063. There is a strong negative relationship between HI and SRI.Location (growth environment) had the largest effects on most of all the fuel characteristics, excluding Ca, followed by cultivar. Ca content was strongly affected by cultivar. Based on the results of the partial least squares-discriminate analysis (PLS-DA), the variation of stem K, ash, Cl, gross calorific value (GCV), and ash-free gross calorific value (GCVaf) contributed to the variance of the cassava stem fuel characteristic among locations. The K, ash, and Cl contents in cassava stem had strongly correlation with the soil properties and the R2of the particial least square (PLS) models were0.954,0.873, and0.789, respectively. The ash content in cassava stem ranged from2.03%to6.69%, and is rather10times higher than soft wood. However, based the mole ratio between the major-ash forming elements and the ternary diagram analysis of K2O-(CaO+MgO)-P2O5system, cassava stems may have rather high ash-fusion temperatures (mostly>1500℃), suggesting light and limited sintering during combustion, if any. The K and Cl contents of cassava stem ranged1.0-27.8g kg-1and0.2-6.3g kg-1, respectively. Cassava stems from Wuming and Longan exhibit a risk of particle emissions and corrosive Cl-rich deposit when combusted. The N content of cassava stem is6.0-21.6g kg-1and rather higher than soft wood also, it may cause excessive acid gas emission during combustion.The location, i.e., growth environment had stronger effects on stem starch, soluble sugar, and starch+sugar (SS) contents and yield than cultivar and harvest time. The stem starch content and the yield ranged of14-42%and0.2-2.06t ha-1, respectively. The average of stem starch yield is1.2t ha-1, gives a17.9%higher than the starch yield which extracted from the root only. The range of stem non-structural sugar yield is0.30-0.59t ha-1, which ended up to1408-9246L ha-1ethanol yield and gave6.51-52.94%higher than the bioethanol yield which produced by the root only. There is significant positive correlation (R2=0.573) between stem and root starch contents. Those positive correlations among cultivars are all significant, that suggests a potential of selecting the cultivar with higher root starch can get higher stem starch content.The results of PLS-DA, againsted the dummy variable location, indicate that the variation of the stem Cl, K, and starch contents contributed to the differences of the cassava stem chemical characteristics in locations. Variations of S, Ca, K, Cl, and starch contents gave meaningful information about the differences in cultivars. Using the cassava stem for bioenergy purposes, such as solid biofuel and bioethanol, may cause14-130kg N,1.05-20kg P,3.85-195kg K, and3.15-63.65kg Ca lose per hektare. Therefore, the nutrient elements K, N, and Ca in the cassava stem should be returned to the field for maintaining the soil fertility.更多还原