共查询到20条相似文献，搜索用时 46 毫秒
1.
以油菜秸秆为原料,采用真空热解系统作为生物质热解液化试验装置,以热解终温、体系压力、升温速率和保温时间为试验因子,生物油产率为试验指标,在单因素试验的基础上,采用响应面法对生物油产率进行进一步优化,利用Design Expert 8.0.6软件分析得出生物油产率的二次多项式模型方程,对热解工艺参数进行寻优,并对优化结果进行了试验验证。研究结果表明,热解终温、体系压力和升温速率是影响生物油产率的主要因素,而保温时间对生物油产率的影响较小;最佳热解工艺参数为:热解终温494.0℃,体系压力5.0 kPa,升温速率18.4℃/min,保温时间60.0 min,在此条件下,生物油产率可达43.50%,与预测值43.63%较为接近。 相似文献
2.
木质生物质快速热解生物油产率影响因素分析 总被引：14，自引：1，他引：14
木质生物质能是可再生能源的重要组成部分,快速热解技术是国内外木质生物质能源化的热点研究课题.本文在简要总结木质生物质快速热解技术的基础上,着重对快速热解过程中热解温度、升温速率、压力、气相滞留时间、木质生物质物料特性、催化剂、热解反应器等因素对生物油产率的影响进行了论述,阐明了提高生物油产率的快速热解工艺条件. 相似文献
3.
《林产工业》2015,(9)
采用热重分析仪研究稻壳、松木屑和玉米秸秆在热解终温600℃下的热解过程,并运用TG-FTIR研究其热解过程中挥发分气体的析出规律。结果表明:随热解温度升高,其热解反应固体残余率逐渐减少,产量具有较为明显的差异:稻壳(41.8%)玉米秸秆(29.3%)松木屑(20.8%)。有机气体在FTIR图谱中主要集中在1 000~2 000cm~(-1),醛类和酸类是吸光度峰值最大的气相产物。生物质热解油的主要形成阶段主要集中在300~520℃,为增大生物质热解油产量,最佳制油温度应控制在450℃左右。分别运用DAEM和F-W-O法对10、20、30、50℃/min下松木屑的热解进行动力学计算,求解的平均活化能分别为144.92kJ/mol和146.01kJ/mol,当转化率达到0.70时,对应的热解温度为450℃左右。 相似文献
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5.
生物燃油的特性及应用 总被引：2，自引：1，他引：2
生物质快速热解制取生物油是目前世界上生物质能研究开发的前沿技术，快速热解是采用中等反应温度(400～550℃）、较短的停留时间(1s以内)、在无氧条件下高速升温对生物质原料进行快速热解的过程。生物质热解生成炭、可冷凝气体(生物燃油)和可燃气体(不可冷凝)。随着热解工艺类型和反应条件的不同， 相似文献
6.
椰壳热解炭化热分析研究 总被引：1，自引：0，他引：1
椰壳是一种优质活性炭原料,利用同步热重-差热分析仪(TG-DTA)对椰壳的热失重、热效应、热稳定性进行研究,分析了椰壳热解炭化的机理。作者还探讨了椰壳热解温度、升温速度对其炭化得率、分解速率的影响。实验结果表明:在5种升温条件下,椰壳热分析曲线都有两个失重阶段。热解温度区间在200~410℃之间。控制第二失重阶段是椰壳热解炭化的关键,提高升温速率在一定程度上会有利于椰壳热解反应的进行。当升温速率为20℃/m in,此时分解热焓为792.15 J/g,失重为31.925%。热解终温宜选择575℃。为椰壳的炭化工艺优化提供理论依据。 相似文献
7.
热解工艺对木醋液制备及性质的影响 总被引：2，自引：0，他引：2
《林产化学与工业》2018,(5)
以杉木屑为原料,在固定床反应器上探讨了热解条件对杉木屑制备木醋液及其性质的影响,结果表明:热解温度是主要影响因素,在热解温度450℃、升温速率10℃/min、氮气流量100 mL/min的热解工艺下,粗木醋液产率可达57.13%,精制醋液产率可达38.20%。杉木屑热解制备得到的木醋液的6类主要化学成分中,酸类和酚类物质为主要成分,约占总含量的2/3,其次是醇类、酮类和醛类,酯类含量较少。热解工艺条件对木醋液的组成和含量有显著影响,热解温度影响酸类、酚类和醇类含量,升温速率影响酸类和醇类含量,氮气流量影响酚类和醇类含量,酮类、醛类和酯类含量基本不受影响。 相似文献
8.
在1 kg/h的小型鼓泡流化床热解反应装置中增设一热过滤装置,对杉木快速热解制取生物油进行了研究,考察了热过滤装置对生物油产率和品质的影响。结果表明:热解油(未经热过滤)和过滤油(经过热过滤)的产率随热解温度的升高先上升后下降,并都在475℃时达到最大值,分别为58.1%和50.7%。热过滤装置的引入降低了生物油的产率(下降5%~10%),且热解温度越高,过滤油产率下降越明显。相比于热解油Ⅰ,过滤油Ⅰ的含水率从13.77%增加到15.83%,p H值从2.18上升到2.23,热值由20.47 MJ/kg降低到19.53 MJ/kg,但固体含量、碱金属和碱土金属均有显著下降,总体下降约75%,减少了生物油中自聚反应的发生。在老化实验过程中,过滤油Ⅰ的含水率、黏度分别增加了10.2%和57.6%,但较热解油Ⅰ变化幅度小;通过GC-MS分析其组成变化,发现过滤油Ⅰ中各组分含量变化幅度较热解油Ⅰ小,表明热过滤使其中不利反应的发生得到了抑制,稳定性较好,显示出热过滤装置对生物油品质提升的良好促进作用,有利于生物油的储存、运输和使用。 相似文献
9.
生物质三组分真空热解特性及液化产物成分分析 总被引：1，自引：0，他引：1
以微晶纤维素、木聚糖和碱性木质素分别作为生物质3组分(纤维素、半纤维素和木质素)的模型物,利用傅立叶变换红外光谱技术(FT-IR)对生物质3组分结构进行了表征,并对3组分进行了真空热解特性分析,同时利用气质联用技术(GC-MS)对3组分真空热解液化后的生物油进行了成分分析,初步探讨了各组分的真空热解液化机理。研究结果表明,纤维素含有吡喃环、β-糖苷键等特征结构,真空热解时失重区间较窄(250~400℃),真空热解油产率较高(73.79%),产物主要有2,5-二甲基呋喃(9.32%)、2,6-二甲氧基苯酚(5.72%)和左旋葡聚糖(17.04%)等;木聚糖中存在β-糖苷键、阿拉伯糖侧链等结构,支链多,热稳定性差,真空热解油主要含有乙酸(10.11%)、羟基丙酮(18.42%)和糠醛(13.15%)等;木质素中含有较多的芳香族类物质结构,热解缓慢,失重区间较宽(185~550℃),热解终了时固体残留物较多,为29.67%,真空热解油中苯酚(16.24%)、愈创木酚(20.37%)等酚类物质较多。 相似文献
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11.
《Scandinavian Journal of Forest Research》2012,27(5):427-435
In Scandinavia, moose (Alces alces L.) sometimes cause severe browsing damage to economically-important pine. Moose-vehicle accidents have spurred construction of fences along roads, and these may interfere with moose migration between summer and winter ranges, or the road alone may be a barrier. If this happens and moose build up along roads, landowners may suffer economically. Therefore, this study investigated whether roads, fences or other factors influence the use of young pine stands by moose. Eighty stands along roads in northern Sweden were evaluated in which individually-browsed branches were counted on 9972 pines. Moose browsing was not significantly related to birch (Betula pendula Roth, B. pubescens Ehrh.) density, nor did it differ between pines (Pinus contorta Douglas or P. sylvestris L.). However, increased pine density, site productivity and proximity to a highway were associated with increased browsing. Further large-scale studies are needed to understand moose habitat selection and the effects of roads. 相似文献
12.
《Scandinavian Journal of Forest Research》2012,27(3):206-217
The root systems of 2-yr-old Picea glauca, Picea mariana and Pinus banksiana seedlings were submitted to various frost temperatures during an artificial frost to induce different levels of root damage. Frost-damaged and control seedlings were placed in a greenhouse under high and low soil moisture regimes. Seedling growth and physiology were evaluated periodically. Seedling survival was reduced when root damage reached levels of 60-80%. Root systems of all three species showed partial to total recovery by the end of the experiment. In general, root freezing damage caused reductions in seedling growth, with these reductions becoming less significant over time. Root damage had little to no effect on black spruce and jack pine seedling physiology, while white spruce CO 2 uptake decreased with increasing root damage. Shoot nitrogen content of all three species decreased slightly with increasing root damage. 相似文献
13.
Contour hedgerows of multipurpose tree species in the sloping tea lands of Sri Lanka are expected to reduce soil erosion and
also add significant amounts of plant nutrients to the soil via periodic prunings. The objective of this experiment was to characterize the biomass decomposition pattern and quantify the
amount of nutrients added through prunings of six tree species (Calliandra calothyrsus, Senna spectabilis, Euphatorium innulifolium, Flemingia congesta, Gliricidia sepium and Tithonia diversifolia) currently being used in hedgerows associated with tea. Withered leaf and stem prunings (50 g) were enclosed in 2-mm litter
bags, placed at 5-cm depth and retrieved after one, three, six, nine and 12 weeks. Loss of initial dry weight, N, P and K
was measured. Single exponential decay function adequately described both dry weight and nutrient loss. Tree species differed
significantly in their rate of breakdown with decomposition constants (k) varying from 0.0299 to 0.2006 week−1 for leaves and from 0.0225 to 0.0633 week−1 for stems. Gliricidia showed the highest k for leaves with the rest in the following descending order: Senna > Tithonia ≥ Euphatorium > Calliandra > Flemingia. A similar pattern was observed for loss of all nutrients with Calliandra and Flemingia always having lower k values than the rest. Although N immobilization was not observed, immobilization of P and K was observed
during the first week of incubation in some species, particularly in stem prunings. Annual biomass of prunings differed significantly
between tree species in the following descending order: Calliandra > Senna > Flemingia > Tithonia > Gliricidia > Euphatorium. Calliandra added the greatest amount of nutrients annually to the soil with Euphatorium adding the least. Calliandra prunings provided the annual total K requirement and 49% of the N requirement of mature tea. However, none of the species
provided more than 5% of the P requirement. It is concluded that among the tree species tested, Calliandra and Flemingia are the most suitable for contour hedgerows in tea plantations of this agroclimatic region because of their higher soil nutrient
enrichment capacity and slower decomposition rates which would minimize leaching losses.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
14.
《Scandinavian Journal of Forest Research》2012,27(2):118-130
The effects of seed weight and seed type on seedling growth of Pinus sylvestris (L.) were studied by seeding individually weighed orchard and stand seed in different mixtures under harsh (direct seeding in field) and optimal (seeding in nursery) conditions. In the nursery experiment an increase in the seed weight from 3 to 7 mg increased the seedling height by 10-27% and total weight by 27-113%, and decreased the height/diameter ratio by 5-6% after 2 yrs. With elimination of seed weight effects, orchard seedlings were 2% taller than stand seedlings in year 2. Without elimination of seed weight effects, orchard seedlings were 7-13% taller. In the field experiment an increase in the seed weight from 3 to 7 mg increased seedling height by 18-65%, stem volume by 81-274% and the number of top-buds by 23-34% in year 5. After elimination of seed weight effects, orchard seedlings were 7-13% taller than stand seedlings and without elimination of seed weight effects 20-21% taller after 5 yrs. Even after elimination of both seed weight and genetic effects orchard seedlings were 3-9% larger than stand seedlings in the field experiment. In conclusion, the influence of seed weight and seed type on growth traits and slenderness is highly significant and the influence seems to be greater in harsh conditions. 相似文献
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Steven Maranz Amadou Niang Antoine Kalinganire Djeneba Konaté Bocary Kaya 《Agroforestry Systems》2008,72(3):231-239
Baobab leaves form an important part of the local diet in Sahel countries and elsewhere in Africa. Existing leaf nutritional
data and agroforestry performance information are based solely on Adansonia digitata L., the baobab of continental Africa. The introduction potential of Adansonia species from the center of diversity in Madagascar and from Australia remains untapped. To assess this potential, the mineral
contents and B1 and B2 vitamin levels of dried baobab leaves were determined for five-year old trees of A. digitata, A. gibbosa (A. Cunn.) Guymer ex D. Baum, A. rubrostipa Jum. & H. Perrier (syn. A. fony Baill.), A. perrieri Capuron and A. za Baill. grown in an introduction trial in Mali. Nutritional data were evaluated against survival and vigor to identify promising
germplasm. Leaf vitamin and crude protein contents were highest in the Madagascar species, especially A. rubrostipa (B1 88 mg 100 g−1, B2 187 mg 100 g−1, protein 20.7% dry weight). However, the local species far outperformed the introductions in survival, tree height, basal
diameter and resistance to termites. We suggest grafting as a way of harnessing the vigor of well-adapted local baobab varieties
to the superior nutritional profiles of A. rubrostipa and others. Cross-species grafting tests in Adansonia were successful, thus creating new agroforestry possibilities with different scion/rootstock combinations. 相似文献
16.
《Wood material science & engineering》2013,8(2):76-84
Abstract Wood in general and wooden studs in particular are often distorted owing to uneven shrinkage during the drying process in the sawmill. Twist is often the most detrimental of all types of distortion, and it is caused by spiral grain in combination with variations in moisture content. For sawmills, the objective is to produce dried, straight boards, and one method of dealing with boards with excessive spiral grain is to sort them out and then dry them in a pretwisted position to obtain straight boards after drying. A model using the finite element (FE) method for the simulation of drying twist distortions was first calibrated against laboratory experiments in which boards were dried with and without restraints and pretwists. After the calibration, the FE results were compared with industrial test results for boards that were dried without restraints or with restraints with zero pretwist, i.e. straight restraints. The FE model used an elastic–ideally plastic material model to obtain permanent deformations. The calibration was to set the yield stresses so that there was a good match between FE results and results from the laboratory experiments. The comparison between the industrial test results and the FE results showed that the FE model is capable of realistic simulations of drying boards with and without restraints and presumably also pretwists. 相似文献
17.
Astra Zaluma Lauma Bruna Darta Klavina Natalija Burnevica Kristine Kenigsvalde Andis Lazdins Talis Gaitnieks 《Forest Pathology》2019,49(6)
Heterobasidion parviporum and Heterobasidion annosum are widely distributed root‐rot fungi that infect conifers throughout Europe. Infection of conifer stumps by spores of these pathogens can be controlled by treating fresh stumps with a competing non‐pathogenic fungus, Phlebiopsis gigantea. In this study, growth of three Latvian strains of P. gigantea and the biological control agent ‘Rotstop’ strain was evaluated in stem pieces of Norway spruce, Scots pine, lodgepole pine, Douglas‐fir, Weymouth pine, Siberian larch and Sitka spruce. The growth rates of one H. parviporum and one H. annosum isolate were also measured in the same stem pieces. The growth rate of P. gigantea varied greatly in wood of different conifer species. It was higher in the three pine species, lower in Norway spruce and lowest in Sitka spruce and Siberian larch, and in Douglas‐fir, this fungus did not grow. The largest area of wood occupied by P. gigantea was in lodgepole pine. Growth of Latvian isolates of P. gigantea in the wood of Pinus and Picea species was comparable to that of the Rotstop isolate. Consequently, stump treatment with local P. gigantea isolates should be recommended. However, our results suggest that Douglas‐fir stump treatment against Heterobasidion by P. gigantea may be ineffective and other stump treatment methods should be considered. 相似文献
18.
《Scandinavian Journal of Forest Research》2012,27(1):53-61
This study investigated the stand structure in pine, spruce and deciduous forests in the border district of Finland and Russia. A total of 46 mature forest stands was selected as pairs, the members of each pair being as similar as possible with respect to their forest site type, age, moisture and topography. The stands were then compared between the two countries by means of basal areas and number of stems. The proportions of dominating tree species were 2-12% lower, and correspondingly the proportions of secondary tree species higher, in Russian forests. The density of the forest stock was also higher in each forest type in Russia. The forests in the two countries differed most radically in terms of the abundance of dead trees. The amount was two to four times higher in Russian deciduous and spruce forests, and in pine forests the difference was 10-fold. The stand structures indicated that Russian coniferous stands, in particular, were more heterogeneous than intensively managed pine and spruce stands in Finland. 相似文献
19.
《Scandinavian Journal of Forest Research》2012,27(1):15-27
The root collar diameter and the height:diameter ratio are of particular importance in container-grown seedlings where a high density in the containers may produce spindly seedlings. Temperature regimes and light quality are known to affect plant growth. The aim of this study was to identify responses in Picea abies (L.) Karst. seedlings grown with light providing different red:far-red ratios and under temperature regimes with alternating day (DT) and night temperature (NT) from negative (DT < NT) to positive (DT > NT) difference (DIF) between DT and NT. Experiments were conducted in controlled environment chambers and in a daylight phytotron. Only limited thermoperiodic responses appeared in P . abies seedlings with respect to seedling height and dry weight accumulation. The formation of terminal buds, however, was clearly delayed in seedlings grown at negative DIF. The results indicate a requirement for day extension light that is high in far-red, to prevent terminal bud formation under natural short-day conditions. An extended study should be conducted to clarify the minimum level of light intensity and the optimal light quality needed to prevent terminal bud formation under natural short-day conditions. 相似文献
20.
本文分析了CAD在设计中引起的正面和负面影响,并进行了系统的阐述,从而使设计者在应用中能够保持客观的态度。 相似文献