城市污泥制备成型衍生燃料技术综述

城市污泥的处理与处置问题是世界共同关注的问题之一,传统的污泥处理方式已难以满足日益严格的环保要求,污泥的燃料化利用是世界的共识。由于污泥的挥发分含量高、固定碳含量低,污泥难以直接稳定地焚烧,且污泥中淀粉类糊化和蛋白质类变性能够促进氢键和架桥作用,充分利用城市生活污水处理厂污泥制备成型燃料是目前污泥燃料化的新兴方式。本文详细阐述了现有的污泥成型技术,包括污泥干化成型、半干化成型和湿式成型技术等,重点阐明了其各自的优缺点,指出污泥干化成型是未来污泥成型的主要方式。     

加入造粒石墨对低水泥氧化铝基浇注料性能的影响

分别采用成型后造粒(A l2O3-C造粒Ⅰ)以及直接造粒(A l2O3-C造粒Ⅱ)两种不同的方法对天然鳞片石墨进行处理。研究了这两种造粒石墨的加入对低水泥氧化铝基浇注料物理性能、抗氧化性能以及抗渣性能的影响。结果表明:1)石墨含量较低、热处理温度较低(110℃)时,含A l2O3-C造粒Ⅰ的试样的常温抗折强度、耐压强度均优于含A l2O3-C造粒Ⅱ的试样的;2)石墨含量较高、热处理温度较高(1 500℃)时,含A l2O3-C造粒Ⅰ的试样的常温抗折强度、耐压强度则不如含A l2O3-C造粒Ⅱ的试样的;3)含同种造粒石墨的试样,其石墨含量越低,抗氧化性能越好;4)石墨含量对含A l2O3-C造粒Ⅱ试样的抗渣侵蚀性影响较大,浇注料中引入A l2O3-C造粒Ⅱ比引入A l2O3-C造粒Ⅰ更有利于改善试样抗渣侵蚀性。     

镁橄榄石用于铁矿球团的试验研究

应用镁橄榄石粉末，并配以膨润土或新型wkd粘结剂，对武钢大冶铁精矿进行了实验室及工业投笼球团试验。试验研究表明：镁橄榄石粉的添加对生球质量的提高可以起到一定程度的促进作用，但镁橄榄石粉不能完全代替粘结剂，仍然需要与粘结剂配合使用；镁橄榄石粉的添加对造球工艺参数不会造成影响；适当提高焙烧温度是保证球团各项指标合格的关键，其中抗压强度、FeO含量等主要与焙烧温度有关，与镁橄榄石配比无明显关系。另外，冶金性能研究也表明：随着镁橄榄石用量的增加，球团还原度有一定提高，低温还原粉化率、膨胀性能和软熔性能显著改善。     

喷雾造粒对固相烧结SiC陶瓷的影响

采用离心式喷雾造粒技术对SiC浆料进行造粒,研究了喷雾造粒对SiC粉体的流动特性、成型行为、烧结性能、力学性能及显微结构的影响机制。研究结果表明:喷雾造粒后,碳化硅粉体流动性得到较大改善,素坯密度增加,微观结构致密;固相烧结后,碳化硅陶瓷的烧结性能提高,陶瓷显微结构得到改善。     

热处理温度对有机硅树脂结合不烧铝碳滑板性能的影响

以板状刚玉、石墨、Al粉、Si粉和B4C为主要原料,有机硅树脂作结合剂制备了不烧铝碳滑板试样。研究了在空气中先经240℃24h预处理,然后分别于400℃、600℃、800℃、1000℃、1350℃和1450℃保温3h处理后试样的烧结性能、物相组成和显微结构等变化规律。结果表明:热处理温度对有机硅树脂结合不烧铝碳滑板的性能、物相变化和显微结构影响显著。热处理温度为240~600℃时,有机硅树脂裂解产生质量损失,使试样内部结构松散,显气孔率显著增大,常温耐压强度较低;800~1000℃时,试样边缘部分B4C、Al、Si优先氧化,生成须状Al2O3和针状硼酸铝,有利于边缘骨料与基质结构紧密结合,同时,试样内部局部有柱状氮化物生成,相应的体积密度明显增加,显气孔率急剧下降,常温耐压强度达到最高值;温度>1000℃,试样中石墨大量氧化而留下很多气孔,同时Al、Si等氧化反应加剧,试样质量增加和体积膨胀明显,体积密度下降,显气孔率上升,常温耐压强度有下降趋势。     

Pilot scale test of producing nickel concentrate from low-grade saprolitic laterite by direct reduction-magnetic separation

The enrichment of Ni from a low-grade saprolitic laterite ore,which has been pre-treated by high pressure grinding roller（HPGR） to be 74% passing 0.074 mm and contains 0.92% Ni,18.47% Fe,10.61% MgO and 42.27% SiO2,was conducted by using pelletizing,rotary kiln reduction and magnetic separation process on a semi industrial scale,and the effects of reduction duration,mass ratio of coal to pellets（C/P）,the types of magnetic separator,the sections of grinding-separation and the grinding fineness on the recovery of Ni and Fe were examined.It is shown that nickel concentrate containing 3.13 % Ni and 59.20 % Fe was achieved at recoveries of 84.36 % and 71.51% for Ni and Fe,respectively under the following conditions：reducing at （1120±40） ℃ for 120 min,C/P being 1.0,wet grinding of reduced pellets up to 70%-87% passing 0.074 mm and a magnetic field intensity of 238.8 kA/m during the first section of grinding-magnetic separation,and a grinding fineness of 84%-91% passing 0.045 mm and a magnetic intensity of 39.8 kA/m during the second section of grinding-magnetic separation.The enriched Ni containing concentrate has a low content of S and P,and can be used for further processing to produce high-grade ferronickel alloy.     

火法铜渣改质还原提铁试验研究

为有效回收铜渣中有价金属铁,模拟链篦机-回转窑工艺对火法铜渣进行了提铁试验研究。结果表明,含铁量为40.2%的铜渣,配加2%的B型添加剂,成球性能良好,且生球指标在碱度适宜条件下优良;采用模拟链篦机-回转窑工艺进行造球、熔炼试验,在碱度1.2、配碳量为理论碳当量的1.5倍、1 450 ℃下熔炼50 min,可以获得还原率79.7%、铁品位90.6%的二次铁资源。     

连铸用铝碳滑板的热应力仿真分析

使用ANSYS等有限元分析软件,针对钢带缩短量、滑板面压、紧固件强制位移等不同因素,通过施加适当的初始条件和边界条件,计算连铸用滑板在预热过程中的稳态热应力场及浇钢过程中的瞬态热应力场。并对不同因素影响下的热应力场结果进行比较,为改进实际生产中滑板的安装及使用方法提供理论依据。     

Supercritical carbon dioxide extraction of pelletized Jalapeño peppers

The effects of process pressure (220–500 bar) and temperature (35–65 °C) on yield and extract quality of pelletized Jalapeño peppers (Capsicum annuum L) treated with supercritical carbon dioxide (ScCO₂) were studied. Compaction was inadequate when using whole air‐dried pepper flakes conditioned to high moisture as raw material, which resulted in high porosity pellets and low bed densities. Thus, reference pellet samples were produced from Jalapeño pepper flakes that were finely ground and conditioned to low moisture. Pressures ≥290 bar did not affect cumulative extraction of reference pellet samples at 45 °C. On the other hand, the extraction rate of reference pellet samples at 360 bar increased with process temperature, as a result of increments in solubility, improvements in mass transfer properties, and/or improvements in solute desorption from the solid matrix. With regard to pretreatment, finely ground pepper samples were extracted in half the time of reference pellets (120 versus 270 min) at 360 bar and 45 °C; increasing sample moisture prior to pelletization increased extraction yield; and decreasing particle size prior to pelletization increased extraction rate slightly. These results suggest that sample moisture is partially co‐extracted by ScCO₂, and that the extraction rate of pelletized Jalapeño peppers is controlled by internal mass transfer mechanisms. Chlorophyllian pigments were removed in the final stages of the extraction process. Furthermore, pigment extraction increased with process pressure at 45 °C, and it increased slightly with process temperature at 360 bar. On the other hand, the concentration of capsaicinoids in extract samples remained constant during ScCO₂ extraction. Copyright © 2003 Society of Chemical Industry     

Microstructure-Extractability Relationships in the Extraction of Prepelletized Jalapeño Peppers with Supercritical Carbon Dioxide

There is a need to increase vessel loads for high‐pressure batch processes such as supercritical fluid extraction of solid substrates, but a precompacting treatment such as pelletization may negatively affect mass transfer rates. This work was aimed to quantify the effect of the microstructure of Jalapeño pepper pellets on the extraction rate and yield of oleoresins when using supercritical CO₂ at 40 °C and 320 bar as the solvent, so as to contribute with basic information that will help optimize pelletization treatments for solid substrates. Four types of substrates were obtained by considering 2 initial particle sizes and 2 initial moisture levels before pelletization, and the inner porosity and tortuosity of the resulting pellets were estimated. The internal mass transfer was favored in pellets showing a better distribution and connectedness of pores, and the extraction rate and yield improved when using pellets from flakes instead of milled flakes, with initial sample moisture exhibiting a more limited effect. A reduction in the particle size of the pellets improved mass transfer but caused a reduction in packing density, and these 2 factors had opposite effects on the “volumetric yield” of the process (mass of recovered solute per unit time and per unit volume of extraction vessel), which was also affected by prepelletizing sample conditioning.