Evaluating Kriging as a Tool to Improve Moderate Resolution Maps of Forest Biomass

The USDA Forest Service, Forest Inventory and Analysis program (FIA) recently produced a nationwide map of forest biomass by modeling biomass collected on forest inventory plots as nonparametric functions of moderate resolution satellite data and other environmental variables using Cubist software. Efforts are underway to develop methods to enhance this initial map. We explored the possibility of modeling spatial structure to make such improvements. Spatial structure in the field biomass data as well as in residuals from the map was investigated across 18 ecological zones in the Interior Western U.S. Exploratory tools included directional graphs of summary statistics, three dimensional maps, Moran’s I correlograms, and variograms. Where spatial pattern was present, field and residual biomass were kriged, and predictions made for an independent test set were evaluated for improvement over predictions in the initial biomass map. While kriging has some potential benefit when analyzing the field data and exploring spatial structure, kriging residuals resulted in little or no improvement in the initial biomass map developed using Cubist software. Stationarity assumptions, variogram behavior, and appropriate model fitting strategies are discussed.     

Production of high quality syngas from argon/water plasma gasification of biomass and waste

Extremely hot thermal plasma was used for the gasification of biomass (spruce sawdust, wood pellets) and waste (waste plastics, pyrolysis oil). The plasma was produced by a plasma torch with DC electric arc using unique hybrid stabilization. The torch input power of 100–110 kW and the mass flow rate of the gasified materials of tens kg/h was set up during experiments. Produced synthetic gas featured very high content of hydrogen and carbon monoxide (together approximately 90%) that is in a good agreement with theory. High quality of the produced gas is given by extreme parameters of used plasma – composition, very high temperature and low mass flow rate.     

高层建筑火灾时走廊-前室缓冲区效果数值模拟研究

高层建筑火灾时,正压防烟带入的大量新鲜空气被送入着火层并稀释了烟气,降低了机械排烟效率.提出设置高层建筑条形走廊-前室缓冲区的设想,采用双方程κ-ε模型,对设置缓冲区后排烟效果的影响进行了模拟和分析.结果表明:建有前室缓冲区后,前室内烟气的平均质量分数远小于4.6％,前室在较长时间内处于安全状态.从走廊扩散至竖井的烟气分别经过走廊、前室两次降温,温度下降明显,在竖井中容易形成滞止状态,使其向上方其他楼层扩散的趋势降低,对整栋楼内人员疏散而言更为有利.     

长廊型建筑前室缓冲区对排烟效果的影响

高层建筑发生火灾时,采用加压防烟将会有大量的新鲜空气被送入着火层。这些新鲜空气稀释了烟气,从而降低了机械排烟效率。提出了高层建筑条形走廊前室缓冲区的设想,并通过高层建筑内烟气流动的数学模型,采用双方程三维紊流模型,对相同排烟量情况下前室缓冲区对排烟效果的影响进行了模拟计算和对比分析。结果表明：对条形走廊,前室缓冲区能够提高机械排烟效率近3.6%,同时在前室门附近走廊内形成一段相对安全的区域,有利于人员逃离着火层。     

室内织物火灾烟气危害性分析

室内织物因其容易点燃、燃烧速度快、蔓延迅速等燃烧特性,对室内火灾的发生、发展蔓延及火灾危害都有重要影响.在低强度热源加热条件下,研究了几种常见室内织物如牛仔裤、化纤运动裤、棉布床单、混合织物等温度变化、火灾烟气危害性及喷水对热解烟气的影响.结果表明,棉类织物在低强度火源引燃后烟气毒害成分主要为CO、NOx、SO2,3种毒性气体在7～ 10 min超过人体允许极限值,喷水降低了烟气毒性成分的生成速度与生成量,如牛仔裤热解烟气中CO、SO2的超标时间分别增加了约4min、7 min,NOx则未超标;化纤类织物热解气体超标主要毒性成分为CO、SO2,喷水有利于化纤等聚合物熔融物的流动,在一定程度上反而加快了热量传递,热分解速度加快,有毒有害气体的生成量和产生速度增加.如加水后化纤运动裤热解烟气中,CO超标时间提前了10 min,SO2、NOx烟气也在20 min左右出现了超标情况.     

Pyrolysis Investigation For Bio-Oil Production From Various Biomass Feedstocks In Thailand

This study investigated the bio-oil production from vacuum pyrolysis of potential biomass feedstocks in Thailand. Experiments were carried out on palm empty fruit bunch, rice straw, rice husk, eucalyptus wood, rubber wood (Hevea Brasiliensis), and Teng wood (Shorea Obtuse) in a lab-scale-fixed bed reactor. The results showed that the product distribution was strongly dependent on temperature and biomass properties. Maximum oil yields, i.e., 50–60 wt %, were reached at 450–550°C. Due to mild temperature, most of alkalis originally present in biomass concentrated in product char, and only traces were detected in oil. Two-third of energy in biomass was in the product oil.     

温度对凤眼莲浮岛净化效果影响的研究

以凤眼莲浮床为研究对象,研究不同温度下浮床的净化效率、水生植物生长情况和植物体中氮磷的累积量。研究结果表明,凤眼莲浮岛对TN、TP的去除率与温度并不成正相关。浮岛的处理效果主要与浮岛植物的生物量有关,其处理效率随着生物量的增加而增加。凤眼莲浮岛25℃时处理效率明显高于35℃和15℃。在北方地区浮岛技术的生态学价值要显著于环境工程价值。     

矿井竖巷内火灾燃烧模拟实验研究

简要介绍了矿井竖直巷道内火灾燃烧模拟实验系统和所进行的多次火灾模拟实验情况及其结果,研究分析了火灾时期井下几种常见的固体可燃材料（坑木、风筒布、运输胶带,电缆和煤炭等）的火源燃烧过程和特点,以及沿竖直巷道轴向上火灾烟流的温度参数在火源不同燃烧阶段的变化规律。     

Energy recovery from solid waste fuels using advanced gasification technology

Since the mid-1980s, TPS Termiska Processer AB has been working on the development of an atmospheric-pressure gasification process. A major aim at the start of this work was the generation of fuel gas from indigenous fuels to Sweden (i.e. biomass). As the economic climate changed and awareness of the damage to the environment caused by the use of fossil fuels in power generation equipment increased, the aim of the development work at TPS was changed to applying the process to heat and power generation from feedstocks such as biomass and solid wastes. Compared with modern waste incineration with heat recovery, the gasification process will permit an increase in electricity output of up to 50%. The gasification process being developed is based on an atmospheric-pressure circulating fluidised bed gasifier coupled to a tar-cracking vessel. The gas produced from this process is then cooled and cleaned in conventional equipment. The energy-rich gas produced is clean enough to be fired in a gas boiler (and, in the longer term, in an engine or gas turbine) without requiring extensive flue gas cleaning, as is normally required in conventional waste incineration plants. Producing clean fuel gas in this manner, which facilitates the use of efficient gas-fired boilers, means that overall plant electrical efficiencies of close to 30% can be achieved. TPS has performed a considerable amount of pilot plant testing on waste fuels in their gasification/gas cleaning pilot plant in Sweden. Two gasifiers of TPS design have been in operation in Grève-in-Chianti, Italy since 1992. This plant processes 200 tonnes of RDF (refuse-derived fuel) per day. It is planned that the complete TPS gasification process (including the complete fuel gas cleaning system) be demonstrated in several gas turbine-based biomass-fuelled power generating plants in different parts of the world. It is the aim of TPS to prove, at commercial scale, the technical feasibility and economic advantages of the gasification process when it is applied to solid waste fuels. This aim shall be achieved, in the short-term, by employing the cold clean product gas in a gas boiler and, in the longer-term, by firing the gas in engines and gas turbines. A study for a 90 MWth waste-fuelled co-generation plant in Sweden has shown that, already today, gasification of solid waste can compete economically with conventional incineration technologies.     

Triboelectric charging behavior of wood particles during pellet handling processes

Electrostatic charges accumulated on wood particles through triboelectrification during their transportation and handling processes can cause hazardous electrical discharge which may further trigger dust explosion. In this work, tribo-charging behavior of different kinds of wood particles was investigated by a vibrating plate charging method. It was found that reduction in the work function difference between contact bodies might contribute to the reduction of tribo-charge generation, while the reduction of electrical resistivity of wood pellets could effectively accelerate the charge dissipation. As the particle size decreases, accumulated charges increase significantly. In contrast, higher moisture content of wood particles leads to lower charge accumulation due to an accelerated charge dissipation rate. Tribo-charging behaviors of white pellets, torrefied pellet, steam treated pellets and dark pellets have also been investigated. Compared to the white pellets, they all have shown a reduction on charge accumulation to some extent. However, results suggested that all of them have nearly equivalent tribo-charge density as coal and wheat grains used as references in this study.