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1.
应用扫描电镜(scanning electron microscopy,SEM)和能谱(energy disperse X-ray microanalysis,EDX)结合联用技术对稻壳和稻秆在600和815℃下灼烧产生的灰渣的微观形态特征及其元素组成进行了全面地研究,并考察了不同灰化温度对生物质灰的粒度分布、微观形态、颗粒表面、内部结构及元素组成等方面产生的影响。结果表明:灰化温度升高,灰粒的粒度减小,且分布较均匀,稻壳灰中多为团状颗粒,而稻秆灰以棒状颗粒居多;对于600℃稻壳灰,部分灰粒仍保留着稻壳的原始纤维结构,且灰中存在许多松散状的密实小颗粒,但并未出现粘结团聚,而600℃稻秆灰表面存在大量粘连着小颗粒的絮状物,表明此时灰中已经出现低熔点成分熔融而产生的弱粘结;815℃时2种生物质灰粒表面都出现熔融态的碱金属物质和以玻璃体突起形式存在的石英结构,而且都存在明显的团聚结渣现象;稻壳灰与稻秆灰的主要组成元素是C、O、Si、K和Ca,较少的Mg、Al、Fe、P等也被检出,而S只在稻秆灰中检出,稻壳灰中未检出S元素;灰化温度升高,稻壳灰的K含量明显下降,而稻秆灰中K、Na、Ca的含量变化较小,但是Cl、Fe、Al的含量均明显下降;稻秆灰的K、Na、Ca和Cl含量都远高于稻壳灰,稻秆灰比稻壳灰更易造成设备腐蚀、结渣等危害。  相似文献   

2.
应用热重-差热分析法研究了空气和氮气气氛中2种灰化温度(600和815℃)下制得的稻壳和稻秆等生物质灰的灼烧失重特性。结果表明:不同飞灰在空气中灼烧的质量损失均可分为剩余水分的蒸发、有机成分的快速热裂解以及无机成分的缓慢挥发等阶段,而氮气中飞灰的质量损失并未出现明显的分段热解规律;空气中600℃生物质灰的主要质量损失发生在300~550℃之间,而815℃稻壳灰的主要质量损失区间为200~600℃,815℃稻秆灰在300~550℃之间的质量损失只有1.76%;灰化温度升高,飞灰的总质量损失明显降低。空气中不同灰化温度下的稻壳灰在950~1 050℃之间都出现放热峰,但该温度区间并无明显质量损失;815℃的稻秆灰在750℃附近则存在由于KCl熔融吸热引起的吸热峰,而600℃稻秆灰的热解过程则未出现明显的吸热峰;氮气中生物质灰的热解存在2个分隔明显的质量损失速率峰,这是由2种质量损失机制单独作用而成:600~800℃之间的质量损失主要是由不稳定的碳酸盐(Ca CO3、Ma CO3等)受热分解造成,而在800~1 200℃之间的质量损失则主要是由灰中活泼的碱金属氯化物(KCl、Na Cl等)受热进入气相所致;相同灰化温度下的稻壳灰或稻秆灰在空气中热解的总质量损失明显高于氮气。  相似文献   

3.
梁桓  索全义  侯建伟  刘常涛 《土壤》2015,47(5):886-891
掌握不同生物炭材料的结构特征和化学特性是合理利用生物炭的基础。通过无氧炭化法制备了不同炭化温度下的玉米秸秆生物炭和沙蒿生物炭,对比了不同材料和不同炭化温度下生物炭性质的差异。结果表明:炭化温度低于400℃时,两种材料生物炭的孔隙结构保存完整,600℃以上时,两种材料生物炭的蜂窝状结构均遭到破坏,玉米秸秆生物炭被破坏得更严重;同一炭化温度下,玉米秸秆生物炭的比表面积及总孔容和平均孔径均大于沙蒿生物炭,两种生物炭的比表面积随炭化温度的升高均增大,总孔容呈"V"形变化;两种材料的生物炭均呈碱性,炭化温度越高,pH越大,400℃~800℃,每升高10℃,玉米秸秆生物炭和沙蒿生物炭的pH均以0.02的幅度增加,同一温度下,玉米秸秆生物炭的pH大于沙蒿生物炭,在400℃、600℃和800℃下分别比沙蒿生物炭高0.31、0.35和0.29单位;随炭化温度的升高,玉米秸秆生物炭和沙蒿生物炭的C、P、K和灰分含量增加,400℃~800℃,玉米秸秆生物炭的C、P、K含量以炭化温度每升高10℃分别增加2.94、0.11、0.20 g/kg的幅度变化,沙蒿生物炭也以4.35、0.07、0.24 g/kg的幅度增加,与此同时,玉米秸秆生物炭的N、H含量以每升高10℃分别以0.13 g/kg和0.86 g/kg的幅度降低,沙蒿生物炭的N、H含量分别以0.04 g/kg和0.82 g/kg的幅度下降,S含量无明显变化,C/N和C/H增大,且不同材料生物炭的元素含量差异显著;两种材料生物炭的N、P、K有效性随炭化温度的升高均下降,400℃~600℃,玉米秸秆生物炭和沙蒿生物炭的速效N含量分别下降了57.89%和19.05%,800℃时两种生物炭的速效N均接近0 mg/kg,400℃~800℃玉米秸秆生物炭和沙蒿生物炭的速效P含量分别降低了67.41%和52.36%,此时速效K含量也分别降低了45.62%和90.16%。总之,不同材料和炭化温度对生物炭的物理特征和化学特性都有较大影响。  相似文献   

4.
生物质气化技术是将低品位的生物质能转换成高品位能源的有效途径。该文以稻壳和麦秸半焦为试验对象,进行了低温下生物质半焦的水蒸气气化试验,研究了浸渍法制备的碱金属催化剂和气化温度对生物质半焦气化行为的影响。结果显示,对于稻壳半焦气化而言,相同负载量的K基催化剂的催化效果明显优于Na基催化剂,相比非催化时稻壳半焦的碳转化率分别提高了18.2%和13.5%,差异明显。增加K2CO3负载量有利于半焦气化反应的进行,但负载量不宜超过30%。不同的煅烧温度,催化剂的活性组分存在形式有较大差别,负载量为30%的K基催化剂在800℃煅烧后具有最佳的催化效果。相同条件下,麦秸半焦的气体产率和碳转化率均较高,在700℃下添加该催化剂时分别达到130.0mol/kg和95.9%,相比非催化时分别提高了57.0%和34.1%。随着温度的降低,气体产率和碳转化率均明显下降,该文催化条件下的半焦气化温度不宜低于700℃。研究结果可为生物质低温气化高效催化剂的选择提供理论依据。  相似文献   

5.
生物质气化技术是将低品位的生物质能转换成高品位能源的有效途径。该文以稻壳和麦秸半焦为试验对象,进行了低温下生物质半焦的水蒸气气化试验,研究了浸渍法制备的碱金属催化剂和气化温度对生物质半焦气化行为的影响。结果显示,对于稻壳半焦气化而言,相同负载量的K基催化剂的催化效果明显优于Na基催化剂,相比非催化时稻壳半焦的碳转化率分别提高了18.2%和13.5%,差异明显。增加K2CO3负载量有利于半焦气化反应的进行,但负载量不宜超过30%。不同的煅烧温度,催化剂的活性组分存在形式有较大差别,负载量为30%的K基催化剂在800℃煅烧后具有最佳的催化效果。相同条件下,麦秸半焦的气体产率和碳转化率均较高,在700℃下添加该催化剂时分别达到130.0 mol/kg和95.9%,相比非催化时分别提高了57.0%和34.1%。随着温度的降低,气体产率和碳转化率均明显下降,该文催化条件下的半焦气化温度不宜低于700℃。研究结果可为生物质低温气化高效催化剂的选择提供理论依据。  相似文献   

6.
为优化生物质流化床气化工艺,该研究在中试规模流化床实验台上进行了成型树皮和成型秸秆的空气气化试验,研究了空气当量比、气化温度与送风温度对成型树皮和成型玉米秸秆气化特性的影响,同时采用电子探针显微分析仪与X射线光谱分析仪对气化过程中结渣的微观结构与成分进行了分析。结果表明:气化效果随着空气当量比增大先升后降,空气当量比较佳值在0.24左右,此工况下树皮与秸秆合成气热值分别为5.66和3.92 MJ/m~3,气化效率分别为59.62%与33.92%;气化温度增加促进气化效果提升,气化温度从700℃升高至800℃,树皮合成气热值与气化效率分别提升了1.01 MJ/m~3与14.28%;一次风温度的提升对气化效果无显著影响(P0.05),但明显提升了炉膛底部温度,容易导致结渣,不利于设备稳定运行。2种生物质都有明显结渣现象,其表面呈现熔融玻璃状。结渣主要由KAl(SiO3)、K2MgSi_5O_(12)等复杂化合物与SiO_2组成。导致结渣的原因主要是生物质中K、Mg等碱金属元素在床料中富集,与石英砂床料反应形成低熔点熔融盐;树皮含有较多Ca,气化中形成高熔点的CaSO_4进而抑制结渣,而秸秆成灰率高,含有较多的K,导致结渣更为严重。  相似文献   

7.
为了了解风量对稻壳在循环流化床内燃烧温度的影响,在循环流化床试验装置上测量了炉膛内燃烧温度并分析其变化规律以确定稻壳燃烧参数。当风料比为4.2 m3/kg时,二次风与一次风量比1~1.2时燃烧工况较好,炉膛内温度控制在800~850℃;在燃烧过程中有焦炭回料时,炉膛内温度分布均匀,波动范围较小;否则炉膛内温度分布不均匀。稻壳灰熔点为1230℃,但温度1000℃时就出现结焦;在温度700~800℃时出现结团,采取炉膛内温度升高后和流化风速较大时加入石英砂以及点火之初选择1 m/s左右的流化风速,将可以大大减少结团现象。  相似文献   

8.
为了综合水分活度及玻璃化转变理论构建状态图,获得灰枣粉的较佳贮藏条件,该文采用静态称量法和差示扫描量热法测定灰枣粉的吸附特性及玻璃化转变温度。结果表明,膨化干燥灰枣粉水分吸附的平衡干基含水率随水分活度的增加而增加,水分吸附等温线呈J型,描述灰枣粉水分吸附特性的适宜模型为GAB模型(R2=0.9968);灰枣粉的玻璃化转变温度随含水率升高而降低,湿基含水率由0.064 g/g增加到0.175 g/g时,玻璃化转变温度由29.90℃降低到?35.02℃;灰枣粉干基含水率≤0.1223 g/g、贮藏温度≤?0.062°C时其稳定性较好,研究结果为灰枣粉加工、运输等过程中的贮藏条件提供理论参考。  相似文献   

9.
典型生物质颗粒燃料燃烧特性试验   总被引:18,自引:10,他引:8  
为研究生物质颗粒燃料的燃烧特性及污染物排放特性,该文以国外引进的生物质颗粒燃料燃烧器为试验装置,选择了8种典型的生物质颗粒燃料进行试验研究。试验结果表明,挥发份含量越高,含水率越低,生物质颗粒燃料所需的点火时间越短,SO2、NOx等污染物排放质量浓度远低于国家标准,但存在着部分生物质颗粒燃料灰分含量过大、结渣严重等问题。对大多数颗粒燃料来说,软化温度越高,结渣率越低,当软化温度超过1 389℃时,不会发生结渣;Si元素、碱金属元素含量越高,越容易结渣,碱土金属元素含量越高,越抗结渣。玉米秸中Si的质量分数为27.70%,底灰结渣率达到48.84%,落叶松中Si的质量分数仅为9.76%,不结渣;使用添加剂后,玉米秸的底灰结渣率降低了22.77%。这将为设计适合中国国情的生物质颗粒燃料燃烧设备及改善燃料的燃烧性能提供依据。  相似文献   

10.
工业木质素的热裂解试验研究   总被引:3,自引:1,他引:3  
本文研究了木薯水解剩余木质素在N2氛围下的TG和DTG曲线,以及在不同升温速率下热裂解产物的组成随温度的变化情况。试验结果表明,在290~430℃之间热裂解速率最快;在400~800℃之间时,焦炭产量随着温度的升高而降低,焦油产量首先会随着温度升高而增加,在达到一个最大值后,随着温度的进一步升高,部分挥发分的二次热解会使焦油产量降低,气体产量随着温度的升高而增加,H2、CO、CH4和CO2等组分也随着温度的升高而有相应的变化;快速热解在600℃以下有利于焦油和焦炭的生成,在600℃以上有利于气体的生成。通过GC—M S分析发现焦油中的组分主要是苯酚类化合物。  相似文献   

11.
Flameless atomic absorption spectrometry is applied for the determination of Pb in coal, coal ash and fly ash. Lead concentrations in coal and coal ash ranging from respectively 7 to 110 µg g?1 and 120 to 450 µg g?1 are found. A mean concentration of 1520 µg g?1 in fly ash corresponding to a concentration of 117 µg m?3 in the effluent gas suggests the importance of coal combustion as an atmospheric source of Ph. The contribution of coal combustion to the total Pb emissions is conservatively estimated at 6%.  相似文献   

12.
The formation of soil organo-mineral complexes is a key reaction in the carbon cycle in soil, since organic materials acquire a resistance to decomposition due to the formation of the complexes. Adsorption of dissolved organic matter (DOM) onto soil minerals provides a model of this important process. Adsorption of DOM onto samples from Andisols, Inceptisols, and Entisols in batch experiments was compared in terms of the quantitative relationship between the soil properties and the adsorption behavior of DOM. Adsorption behavior was effectively described by a linear initial mass (IM) isotherm, indicating that the adsorption efficiency did not appreciably decline in the range studied even though a large amount of DOM was applied to the soil samples. Samples from Andisols showed a particularly high efficiency of adsorption compared with those from other soils which contained a comparable amount of organic carbon. Explanatory variables useful to predict the efficiency parameter were investigated in 2 steps: firstly the degree of carbon accumulation in the soil samples was examined, and next an index for the amount of ligand exchange sites was examined in combination with the former indices. As a result, an index comprising the total carbon/clay (or total carbon/specific surface area) ratio and the amount of hydroxy ions in the soil extracts with NaF solution was eventually detected. The former represents the degree of carbon occupation on the soil surface, and the latter the amount of ligand exchange sites on labile aluminum. Although the mechanisms involved in the adsorption varied among soils, the selected index was significantly correlated with the adsorption efficiency.  相似文献   

13.

The ability of fly ash to remove fluoride from water and wastewaters has been studied at different concentrations, times, temperatures and pH of the solution. The rate constants of adsorption, intraparticle transport, mass transfer coefficients and thermodynamic parameters have been calculated at 30, 40, and 50 °C. The empirical model has been tested at various concentration for the present system. The removal of fluoride is favorable at low concentration, high temperature and acidic pH.

  相似文献   

14.
Abstract

The weight of the ash resulting from dry ashing spruce needles at 500° C can be predicted with good precision from the concentrations of calcium (Ca), potassium (K), magnesium (Mg), manganese (Mn), and silicon (Si) in the needles. The empirical factors associated with the individual elements are given. There is evidence that they can also be applied to leaves from other plants. The colour of the ash can be related to the Mn concentration in the needles. Dry ashing entails no losses for Ca, cobalt (Co), barium (Ba), K, rubidium (Rb), antimony (Sb), scandium (Sc), and zinc (Zn), whereas a very small loss was observed for cesium (Cs), and a very large for bromine (Br).  相似文献   

15.
Almost all the lignite ash from the coal thermal power plants in Maemoa, Lumpang Province, Thailand is disposed of as solid wastes. However, the number of reclaimed sites for the disposal of the wastes is not sufficient to handle the large amount of wastes. Therefore, the development of a technique for the utilization of lignite ash is essential to preserve the environment and to recycle the waste materials. Lignite ash is composed of inorganic compounds mainly present as glasses resulting from fusion during their combustion. The chemical composition of these glasses is similar to that of volcanic glass in nature and changes easily to zeolite-like substances by hydrothermal treatment with an alkali. Henmi (1987) reported the synthesis of hydroxysodalite, a kind of zeolite, from waste coal ash. Zeolites are crystalline, hydrated aluminosilicates with a three-dimensional crystal structure and have the attractive cation-exchange properties in agricultural applications (Ming and Mumpton 1989). In the present study, attempts were made to synthesize zeolitelike substances from lignite ash from Thailand, in order to develop a new method for the disposal of industrial wastes. Although the synthesis of zeolite-like substances from waste coal ash had been reported in different countries after the publication of Henmi (1987), this method was applied for the first time in Thailand for the treatment of lignite ash.  相似文献   

16.
秸秆灰混凝土力学性能试验及强度预测   总被引:3,自引:2,他引:1  
为了优化混凝性能,减少水泥产业耗能,尝试采用以部分秸秆灰替代水泥制备混凝土。该文通过试验对油菜秸秆灰混凝土拉压性能进行了研究,得到秸秆灰质量分数和水胶比对秸秆灰混凝土拉压性能的影响规律,如当秸秆灰质量分数增大时,混凝土拉压性能呈下降趋势;当水胶比过大时,混凝土力学性能急剧下降。同时提出秸秆灰混凝土抗拉性能与抗压性能间的线性函数关系以及混凝土轴心抗压强度计算公式,并与其他混凝土抗压强度公式进行比对验证。采用小波神经网络的预测方法,引入随机函数,对试验数据抽样进行训练,而后预测数据并与试验数据进行比对,计算误差,并将预测数据用于该文提出的拉压公式进行验证,结果表明验证较好。最后试验结果表明:当秸秆灰替代掺量为10%时,秸秆灰混凝土劈裂抗拉强度下降了25%,抗压强度仅下降了8%;当替代掺量为20%时,抗压强度下降了31%。  相似文献   

17.
To elucidate the influence of climate and vegetation upon the vertical distribution of soil moisture and its seasonal change is one of the fundamental problems in the studies on water economy of volcanic ash soils, that cover the larger parts of Japan, and have characteristic soil-water system.1) Few data are now available in this field, despite the fact that management of volcanic ash soils is practically one of the most urgent problems in Japan.  相似文献   

18.
Fly ash and soil mixtures with a range of fly ash content from 0 to 100% were used to study the adsorption and desorption of herbicides atrazine, propazine, prometryne, propanil, and molinate in batch experiments. The isotherms shapes according to Giles classification (Giles et al., 1960) were S, L, and H as the substrate changed from sandy clay loam (SCL) to fly ash, depending on the percent of fly ash in the mixture. The adsorption isotherms fit the Freundlich equation x/m = K(f) C(1/)(n)(). The K(f) values increase with the increase of the fly ash content. The mean percent amounts of herbicides, for a range of concentration 1-20 mg L(-)(1), adsorbed on the soil were 21.9% for atrazine, 50.7% for propazine, 29.04% for prometryne, 43.14% for molinate, 31.35% for propachlor, and 46.34% for propanil. Mass balance estimations show that the adsorbed amounts of the herbicides increase along with the fly ash content in the sorbent mixture and reach the 99% in the "pure" fly ash. In contrast, the amounts desorbed with water decrease as the fly ash content increases. The n values ranged from 0.82 to 3.05 indicating that the carbon content of fly ash plays a significant role during the sorption process and an increase of heterogenity of solid substrate. The increase of the amounts desorbed with acetone indicates that the sorption of organic compounds onto fly ash is believed to occur principally via the weak induction forces of London or dispersion forces which are characteristic of the physical adsorption process. The results of this research demonstrate that the fly ash shows a significant capacity for adsorption of organic compounds from aqueous solution.  相似文献   

19.
Collembola were extracted from surface layers of four lagoons in east London (UK) of the industrial waste pulverised fuel ash (PFA). One lagoon was subject to seasonal inundation, while the other lagoons were dry, and ranged from 4 to 40 years. Twenty-one species were recorded, with both species richness and community diversity increasing steadily with site age. Early successional species were primarily epi-edaphic, while eu-edaphic species were largely confined to the woodland phase of the succession. The first axis of a canonical correspondence analysis detected the difference between early and late stage sites, while the second axis separated out the wet lagoon community from the dry sites. The data include the first record of Isotoma riparia Nicolet for the UK.  相似文献   

20.
Samples of ash from municipal refuse incinerators in six Connecticut towns as well as samples of incinerated sewage sludge were collected during 1988 and 1989. The samples were analyzed for pH, metal content by HNO3 + H2O2 digestion, extractable metals by solvents including NaOAc, DTPA, H2CO3 and H2O. Two samples were examined for metals that could be leached by H2O from laboratory columns. Most ash samples were highly alkaline and their pH changed slowly, decreasing by about two pH units over a 6-week period. The variability in metal content of ash from different incinerators was similar to that observed in samples obtained from the same facility at different times. Only a portion of the metals were extracted by the solvents in the order NaOAc > DTPA > H2CO3 > H2O. The relative amounts of the total metals in the ash that could be extracted with specific solvents varied widely, suggesting different chemical forms in different ashes. After the initial removal of large concentrations of metals in the leachates from laboratory columns over 2 to 3 days, leaching of metals continued at extremely low concentrations that were generally below drinking water standards.  相似文献   

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