内循环锥形流化床秸杆富氧化化技术研究

开发研究了适合软件软秸杆气化的富氧气化工艺及锥形流化床气炉。在600－820℃气化温度范围内，研究了催化剂（CaO、NaOH）、流化速度、床层压降对煤气热值的影响，以稻划草为原料在CaO催化剂作用下，煤气中的重烃含量高达4．81％，对两循环锥形流化床气化炉在秸杆气化过程中的稳定性和安全性进行了,研究结果表明：采用内循环锥形流化床气化炉及富氧气化工艺安全、稳定，所产生的煤气具有焦油含量低、煤气热值高等特点。     

生物质流态化气化技术研究

论述了在锥形流态化气化炉内，对生物质原料进行气化和催化气化的工程化应用试验研究。研究结果表明：麦草原料气化所产生的煤气热值比稻草和稻壳都高，木屑气化所产生煤气热值最高，非催化气化条件下，流化床气化产生的煤气热值比下吸式气化炉产生的煤气热值提高40％左右；催化气化试验发现，CaO能明显提高煤气热值、降低C0组分，Na2CO3催化气化能提高气体H2的含量。但是对气化产生的气体热值，流态化空气气化中，在710℃以下低温时，无明显的影响，当温度达到800℃时，添加催化剂能明显提高气体的热值。     

生物质催化气化工业应用技术研究

在富氧条件下研究了生物质在流态化气化炉和吸式气化炉中的气化过程，探索了催化剂对气化过程及焦油裂解过程的影响，研究了工艺参数对煤气质量的影响，给出了最佳的工艺操作参数范围。煤气热值最高达9.93MJ/Mm^3。     

生物质流态化催化气化技术研究

研究了流态化气化炉用于生物质化的可行性和安全性，在富氧条件下研究了木屑气化工艺过程。探索了催化剂对气化过程及焦油裂解过程的影响，给出了一个最佳的工艺操作参数范围。煤气热值最高可达9.93MJ／Nm^3。     

CaO对木屑水蒸气气化制取富氢燃气的影响

以木屑为生物质原料,水蒸气为气化介质,CaO为催化剂,在固定床气化炉中进行生物质催化气化制取富氢燃气,考察了CaO与木屑中碳元素的物质的量比(n(Ca)/n(C))、气化温度和水蒸气流量对生物质水蒸气气化特性的影响。结果表明,当n(Ca)/n(C)由0增加至1.0时,H_2体积分数由45.58%增至58.62%,产气率由1.04 m~3/kg增至1.38 m~3/kg,当n(Ca)/n(C)继续增至1.5时,两者均有增加,但是变化不明显;气化温度从700℃增至750℃时,产气中H_2体积分数由51.78%增至58.62%,CO_2由19.89%降至12.60%,继续升高温度,H_2体积分数逐渐降低,燃气热值也降低;水蒸气流量由0.1 g/(min·g)增至0.34 g/(min·g)时,H_2的体积分数由58.62%增至62.55%,水蒸气流量继续增大时,H_2的体积分数和产氢率降低,燃气热值也降低。通过实验选择的最佳气化条件为以CaO为催化剂,n(Ca)/n(C)为1,气化温度750℃,水蒸气流量为0.34 g/(min·g),此时,制取的富氢燃气中H_2体积分数达到最大为62.55%,产氢率为85.08 g/kg,燃气热值为11.41 MJ/m~3。     

循环流化床粉煤气化炉

循环流化床粉煤灰气化炉采用新型布风技术、合理的炉型结构,强化床内循环;采用新型飞灰循环技术,改进床外循环;采用外部流化床反应器取代传统的返料器,实现既返料又反应(燃烧和气化)的双重功效,从而提高粉煤气化的吨煤产量和气化强度,提高煤的利用率。采用高温空气气化工艺,减少污染物的     

两步进气法和水蒸气对竹材下吸式固定床气化性能的影响

以毛竹加工剩余物为研究对象,采用自制的两步进气下吸式固定床气化炉,在当量比(ER)一定的情况下,研究进气比例(AR,0%和60%)和水蒸气/生物质质量比(ms/mb,0,0.045,0.112,0.153,0.211,0.245和0.305)对气化炉性能(炉内温度分布、原料消耗率和气化强度)和可燃气指标(温度、成分、热值和焦油含量)的影响。结果表明:1)与一步进气法相比,两步进气法(AR为60%时)可显著提高气化炉炉温,并且分别在2个进气位置出现2个温度峰,分别为热解区的606℃和氧化区的856℃,可燃气的温度也增加至377℃; 2)两步进气法可显著提高可燃气的可燃组分含量和热值,降低焦油含量,CO含量、H_2含量和低位热值的最大值分别为17.47%、14.67%和4.54 MJ/Nm^3,焦油含量最低值为55.4 mg/Nm^3; 3)随着m_s/m_b从0.045增加至0.305,气化炉内各反应区的温度逐渐降低,与空气气化剂相比,虽然热值并未增加,但是可燃气中H_2和CO的含量发生变化,导致V(H_2)/V(CO)比例逐渐增加至1.01,有助于应用于合成气的研究。本研究为竹材废弃物的能源化利用提供了新的途径和基础数据。     

生物质氧气气化制备中热值燃气的工艺优化及其示范工程

在高温固定床反应器中,进行松木屑氧气气化制备燃气特性研究,考察了气化温度和用量比(ER)对氧气气化制备燃气的热值、产气率以及燃气中各组分体积分数的影响。将获得的最佳工艺参数,在生物质气化制备燃气用于工业锅炉的示范工程中进行了调试和验证。研究结果表明：在气化温度850～950℃时,随着用量比的增加,燃气热值呈现先升高后降低的趋势,在用量比为0.24时,燃气热值最高;气化温度对木屑的氧气气化有显著的影响,气化温度升高,燃气热值以及燃气中H₂、CO、CH₄体积分数随之升高,产气率先升高后降低,在900℃时达到最高。气化温度900℃、用量比0.24为最佳的气化条件,此时气化制备的燃气热值为13.14 MJ/m³,产气率为0.98 L/g,燃气中H₂、CO、CH₄和C₂H_m的体积分数分别为17.64%、 39.78%、 12.45%和2.76%。将该参数应用于示范工程得到燃气热值为10.90 MJ/m³,产气率约为1.02...     

竹材下吸式固定床气化中试试验及其产物的增值应用

生物质气化技术可将物质原料转化为高热值可燃气和生物质炭,可燃气可用于供热或发电,生物质炭可制成高比表面积活性炭.以毛竹为原料,采用一套产能为340 kW的下吸式固定床气化发电系统,研究气化工艺对可燃气品质和气化炉性能的影响,并采用KOH化学活化法开展气化副产物竹炭的活化试验,研究活化工艺对活性炭性能及其吸附甲基橙染料的...     

木屑高温水蒸气气化制备富氢燃气的特性研究

在高温固定床反应器内,无催化剂作用下,进行了木屑高温水蒸气气化制取富氢燃气的特性研究。实验主要研究3 g原料,反应温度(750～1 050℃)及水蒸气流量(0～1.5 g/min)对燃气组分、产氢率、燃气热值(QLHV)等气化过程评价指标的影响。实验结果表明:反应温度和水蒸气流量对燃气组分影响很大,较高的反应温度和加入适量的水蒸气有利于氢气的产生,但随着反应温度的升高和水蒸气流量的增加会使燃气热值降低。在1 000℃时,水蒸气流量为1.02 g/min时,燃气中氢气体积分数可达51.03%,产氢率为71.08 g/kg(以干燥基计,下同),为理论最大产氢率(172.02 g/kg)的41.32%。考虑到实际操作过程,在反应温度为850℃时,水蒸气流量的最佳值为1.02 g/min。木屑高温水蒸气气化所得燃气热值在11～13 MJ/m3范围内变化。研究结果证明,高温水蒸气气化是生物质制取富氢燃气的一种有效方法。     

Browsing Damage on Pine (Pinus sylvestris and P. contorta) by a migrating moose (Alces alces) Population in Winter: Relation to Habitat Composition and Road Barriers

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.     

Effects of Root Freezing on the Physiology and Growth of Picea glauca,Picea mariana and Pinus banksiana Seedlings Under Different Soil Moisture Regimes

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.     

Decomposition and nutrient loss from prunings of different contour hedgerow species in tea plantations in the sloping highlands of Sri Lanka

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.     

Effects of Seed Weight and Seed Type on Early Seedling Growth of Pinus sylvestris under Harsh and Optimal Conditions

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.     

Potential to harness superior nutritional qualities of exotic baobabs if local adaptation can be conferred through grafting

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.     

Modelling of adequate pretwist for obtaining straight timber

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.     

Stand Structure in Pine,Spruce and Deciduous Forests: A Comparison Between Finnish and Russian Karelia

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.     

Growth and Terminal Bud Formation in Picea abies Seedlings Grown with Alternating Diurnal Temperature and Different Light Qualities

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.     

CAD与建筑设计的关系

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。     

Growth of Phlebiopsis gigantea in wood of seven conifer species

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.