将“内六方”转变为“内十二方”——浅析钢管定(减)径时的内多边形现象

简述了三辊式定(减)径机的传动方式以及目前普遍使用的相邻机架辊缝的相位关系;分析了热轧钢管使用三辊式定(减)径机时产生"内六方"缺陷或缺欠的主要原因;提出了用增加定(减)径机机座工位、改变机架的布置方式和传动方位、减小相邻机架辊缝相位角的想法,以期达到将"内六方"转变为"内十二方",提高钢管壁厚精度的目的。     

Accelerated Mold Test on Dried Pine Sapwood Boards: Impact of Contact Heat Treatment

Abstract

We test the hypothesis that the combination of kiln drying of double-stacked boards and contact heat treatment will reduce the susceptibility of treated boards to colonization by mold fungi. Winter-felled Scots pine (Pinus sylvestris L.) sapwood boards were double-stacked in an industrial kiln in ‘‘sapwood out’’ and ‘‘sapwood in’’ positions. Dried samples were then contact heat-treated using a hot press at three different temperatures (140°C, 170°C, and 200°C) for three different periods (1, 3, and 10 min). An accelerated mold test was performed in a climate chamber where naturally mold-infected samples were used as a source of mold inocula. Contact heat treatment degraded the saccharides that accumulated at dried surfaces, and reduced the mold growth. The threshold temperature and time for inhibiting mold growth were 170°C for 10 min. However, for industrial application, the most feasible combination of temperature and time would be 200°C for 3 min. We concluded that double stacking/contact heat treatment used is an environmentally friendly alternative to chemicals for reducing mold on Scots pine sapwood boards.     

Redox Control in Solvent Extraction Studies Using a PEEK AKUFVE Unit

Abstract

When studying actinides or other elements with different possible oxidation states it is important to control which state is present in solution. Earlier redox control has been done by adding some other element to the solution but this approach introduces additional uncertainties. Since the sixties the AKUFVE apparatus has been used for precise solvent extraction studies. Now this equipment has been improved with redox control facilities, additional thermal control, and all parts in contact with the liquids are made of polyetherether ketone (PEEK) to minimize sorption.     

MODELING VACUUM-CONTACT DRYING OF WOOD: THE WATER POTENTIAL APPROACH

ABSTRACT

A two-dimensional mathematical model for vacuum-contact drying of wood is presented. The moisture and heat equations are based on the water potential concept whereas the pressure equation is formulated considering unsteady state conservation equation of dry air. Most of the model parameters were determined during independent experiments. The set of equations is then solved in a coupled form using the finite element method. The validation of the model is performed using experimental results obtained during vacuum-contact drying of sugar maple sapwood. The experimental and calculated data are in good agreement. Nevertheless, some discrepancies are observed which can be attributed to the boundary conditions used and to the fact that heat transfer by convection was neglected.     

POLYCYCLIC AROMATIC HYDROCARBONS IN PRODUCTS OF A BEET SUGAR FACTORY IN VOJVODINA: LEVELS AND INTAKES

The levels of 16 EPA polycyclic aromatic hydrocarbons (PAHs) were investigated in samples of sugar beets and their products representative for a beet sugar factory located in the central part of Vojvodina, the main agricultural region in Serbia. The sum of the detected PAHs ranged from 51 pg g ^?1 ww for molasses to 391 pg g ^?1 ww for dried sugar beet pulp. The concentration of benzo(a)pyrene (BaP) for all sample types was about or less than 100 pg g ^?1 ww, which is far less than the existing Serbian and EU tolerances set for some foodstuffs. The Serbian intake of BaP via total sugar consumption that ranged from 70–85 g per capita day ^?1 , was assessed to be from 0.029 to 0.035 ng kg ^?1 b.w. day ^?1 . Furthermore, the toxic equivalency factor (TEF) approach was used to estimate the carcinogenicity of PAH mixture found in analyzed samples.     

Mild alkaline pre-treatments loosen fibre structure enhancing methane production from biomass crops and residues

Three ligno-cellulosic substrates representing varying levels of biodegradability (giant reed, GR; fibre sorghum, FS; barley straw, BS) were combined with mild alkaline pre-treatments (NaOH 0.05, 0.10 and 0.15 N at 25 °C for 24 h) plus untreated controls, to study pre-treatment effects on physical-chemical structure, anaerobic digestibility and methane output of the three substrates. In a batch anaerobic digestion (AD) assay (58 days; 35 °C; 4 g VS l⁻¹), the most recalcitrant substrate (GR) staged the highest increase in cumulative methane yield: +30% with NaOH 0.15 N over 190 ml CH₄ g⁻¹ VS in untreated GR. Conversely, the least recalcitrant substrate (FS) exhibited the lowest gain (+10% over 248 ml CH₄ g⁻¹ VS), while an intermediate behaviour was shown by BS (+15% over 232 ml CH₄ g⁻¹ VS). Pre-treatments speeded AD kinetics and reduced technical digestion time (i.e., the time needed to achieve 80% methane potential), which are the premises for increased production capacity of full scale AD plants. Fibre components (cellulose, hemicellulose and acid insoluble lignin determined after acid hydrolysis) and substrate structure (Fourier transform infra-red spectroscopy and scanning electron microscopy) outlined reductions of the three fibre components after pre-treatments, supporting claims of loosened binding of lignin with cellulose and hemicellulose. Hence, mild alkaline pre-treatments were shown to improve the biodegradability of ligno-cellulosic substrates to an extent proportional to their recalcitrance. In turn, this contributes to mitigate the food vs. fuel controversy raised by the use of whole plant cereals (namely, maize) as feedstocks for biogas production.     

论特高压在我国能源安全中的核心地位

石油的不可再生性和稀缺性使其面临枯竭,我国能源发展应体现人口与资源承载量和环境容量相协调的生态文明特征。电能可替代多种能源,尤其是石油,未来将在我国能源安全中处于核心地位。我国发电能源与电力消费呈逆向分布,造成主要可再生发电能源大量浪费,煤炭由于运输受限而不能满足消费地需要,因此能源运输问题成为影响我国能源安全的症结。对我国而言,特高压是符合远距离运输的综合最优方案,能实现我国能源的合理配置,未来将成为节能减排的主力,并将引起交通领域的重大变革。     

PM2.5问题与热电联产行业

由于我国大气污染形势严峻,国务院在2013年9月发布《大气污染防治行动计划》,各地方政府纷纷采取多项措施治理大气污染.总体上看,这些治理措施将对热电联产行业产生正面的影响,但也将不可避免地出现某些负面影响.本文将对此进行探讨,并提出5项具体的研究项目供本行业的行政管理人员和技术人员参考.     

现代生物能源第二波研发和产业化浪潮

液态和气态生物燃料一直是生物能源研发的"重中之重"。纤维素乙醇这种所谓的"第二代生物燃料"的开发热持续了近10年,但始终未能突破商业化生产的技术、经济瓶颈。物料预处理成本和酶成本过高,是木质纤维素乙醇产业化的两大根本性障碍,同时还存在着其他不确定性。而基于热化学平台和糖平台的新型液体生物燃料正在走上世界能源舞台。近年来生物质气化-合成油、生物质裂解提质油、EL类生物燃油、生物MTG油、CBGTL油、藻类油/燃气、生物质气化-合成天然气等各种新型的生物燃料不断涌现,而且研发和产业化速度很快,若干品种的研发已处于产业化的前夜,有望在今后2~4年内实现商业化。它们不但符合"先进生物燃料"关于碳减排的要求,而且还是所谓的"可直接使用生物燃料",即能以任何比例与常规汽柴油调合,或完全单独用于现有的发动机,无需像燃料乙醇那样必须有专用的储运设施。液态和气态生物能源正在迎接研发和产业化的第二波浪潮,中国在其中也占有了一席之地。在这样的大背景下,上述新型生物燃料的主要原料木质纤维素类物料的重要性将愈发凸显。     

高铅渣制孔铸锭技术创新

针对我国顶吹和底吹-鼓风炉炼铅工艺,所产高铅渣均为致密熔结物,结合青海西豫有色金属有限公司目前生产现状,鼓风炉还原需要二次配料以适应鼓风熔炼,与烧结块比增加了还原难度、能耗高、渣含铅高、床能力低及炉顶温度高等缺点。因此,将高铅渣的物化性质在较小的投资下,优化转换甚至高于烧结块的物化性质,更加适应于鼓风炉的熔炼,从而解决这一难题,起到节能降耗的作用。创新方案实施及对节能方面进行了较详细的分析论证。