理想的的固体推进剂粘合剂的分子结构

对粘合剂的分子结构和固体推进剂的力学以及流变性能之间的关系进行了研究.由发动机中药住的操作条件对推进剂力学性能的要求以及已有的加工技术对药浆流变性能的限制出发.反推得出固体推进剂粘合剂理想的分子结构.结构和加工要求是由三种类型的火箭发动机的应用要求决定的:航天转运、运载火箭和弹道导弹以及空对空战术导弹.考虑了可满足这些应用要求的三种一般的配方.除假想的全粘合剂推进剂外,还包括传统的复合和硝酸酯增塑的推进剂配方.对这三类中的各种配方按分子量、交联密度、溶解度参数、链的刚硬性、单体的摩擦系数、填充物的体积分数和增塑剂的体积分数确定了各种聚合物的分子特性.10个聚合物粘合剂系统的特性数据说明了它们的分子结构如何影响制得的推进剂的性能.     

合成氨的生产工艺的现状及发展趋势的探讨

本文通过对合成氨的工艺流程和发展情况对合成氨的生产工艺的现状及发展趋势进行阐述。     

磨边机的磨削过程的数学模型的研究

在参考金属磨削过程动态模型以及对墙地砖磨边机磨削过程分析折基础上,建立了磨边机磨削数学动态模型。该模型反映了砖的形态等因素与磨削力的关系,并提出了改进磨边机磨削质量的途径。     

面向未来的强大的合作伙伴

13馆、A13展位——作为阿博格参加历届K展这一国际展览盛事的传统位置,今年该公司的展位依然保持不变。除此之外,与往届一样,阿博格将以崭新的产品和技术亮相K2010：独特的Selogica特性、大型高性能液电混合机器和实现部件高效生产的复杂生产单元,以及诸多的应用技术和模具技术,都将首次向全球展出。     

优质的产品 完善的服务 理想的选择

<正>企业概述为了满足石油化工、有色冶炼、硫磷工业、环境保护、焦化行业技术的快速发展以及生产规模的不断扩大带来的市场需求,"扬州建业投资有限公司"和"扬州庆松化工设备有限公司"部分股东共同组建了"建业庆松集团有限公司"。新成立的"建业庆松集团有限公司"将传承老公司的优秀业绩、优良传统,发扬新公司的开拓理念、创新精神,     

硫铁矿的pH的研究

在市场经济条件下,矿山必须适应市场和满足用户要求,以好的产品质量来赢得用户和占领市场。提高产品质量关键在于控制矿石品位及杂质等指标的稳定性,出口硫铁矿(以下简称“出口矿”)除了S、Fe、Pb、Zn、Cu、SiO2、C、H2O、粒度的指标控制外,个别客户还要求pH在5~6之间,而我们出口矿S品位在45~48以上的pH一般在2~4之间,为满足客户的需求,我们必须降低出口矿的酸度即提高pH,这关系到配矿的工艺流程。     

亚瑟的老师的困扰

这是你在本章中将看到的第一个Broderbund的“活书”概论——但不是最后一个。毫无疑问,该公司已经生产出一批一流的光盘。这种情形使我想起了1964年3月31日的“本周最流行歌曲前10名排行榜”上,披头士不只有一首歌排名第一,而是同时有五首最好的歌,在前100名流行歌曲排行榜上,披头士还有另外七首,Broderbund公司的情况和这种情况很相似,该公司的光盘产品《只有祖母和我》(Just Grandma and Me),《乌龟和兔子》(Thc Tortoise and the     

物理化学的概念教学的启发式模式的构建

通过对目前物理化学教材内容和讲授模式的分析,针对在概念著述和课堂讲授中存在的误区,结合物理化学家吉布斯的启发式教学典故,本文构建一种"立足客观自然、环环相扣启发"的概念教学模式,以"焓"概念的讲授为例,化抽象为直观,收了良好的教学效果。启发式模式对当前物理化学的概念教学有重要的参考价值。     

复古的，摩登的

这是—个典型的“墙边店”。倚墙的褐色矮柜上,是泛着漆光的有着胡桃木外壳的复古电唱机,墙上装裱好的镜框里,是店主张强收藏的经典唱片。张强打开最华贵的一台唱机,低沉悠扬的蓝调爵士立刻回荡在空旷无人的店堂里。     

丁二酸酐的生产工艺的研究

丁二酸酐的化学简式是C4H4O3丁二酸酐是医药、染料、涂料的主要原材料,同时还是重要的药物和化学试剂成分,另外丁二酸酐可以用于生胃酮、琥珀酸胺噻唑的生产,并且可以广泛的应用于树脂的合成和制备。目前工业上对丁二酸酐的制备主要有以下两种方法：第一种方法就是对顺丁烯二酸酐的直接催化加氢法。现在对顺丁烯二酸酐直接催化加氢的生产工艺流程研究的比较广泛,特别是对丁二酸酐生产工艺中的热力学以及探索新的催化研究体系等方面的研究更为广泛;第二种方法就是直接对丁二酸进行脱水。第二种方法的主要优点就在于它对环境污染较小且不使用苯类溶剂,所以国内外很多丁二酸酐生产厂家都普遍采用第二种方法。     

Fluid flow through compressible soft particle beds

The fluid flow through a soft particle bed was studied theoretically and experimentally in this report. Several correction factors were introduced to modify the Ergun equation and account for the deformed shape and reduced volume of compressed particles in a compressible soft particle bed. To acquire the correction factors, both uni‐compression tests and computational fluid dynamics simulation methods were used. The pressure drop estimated from the customized modeling equation was further compared with the experimental data obtained from a bed composed of calcium‐alginate gel particles. In contrast to the conventional Ergun equation, the pressure drop estimated from the customized modeling equation was highly consistent with the experimental data. The result suggests that the customized modeling equation is a convenient tool for accurately predicting the pressure drop across a compressible soft particle bed. © 2016 American Institute of Chemical Engineers AIChE J, 62: 1716–1727, 2016     

Pressure buildup in gas‐liquid flow through packed beds due to deposition of fine particles

In order to understand the increase in pressure drop in hydrotreating reactors due to deposition of fine solids, experiments were conducted with a model suspension of kaolin clay in kerosene. The suspension was circulated through packed beds of catalyst pellets in the trickle‐flow and pulse‐flow regimes, and the increase in pressure drop measured as a function of particle concentration in the bed. The increase in pressure drop was linear with particle concentrations over the range 0–60 kg.m^?3. A consistent approach to modeling the pressure drop behavior was to determine an effective porosity of the packed bed as a function of the concentration of fine particles, then use this porosity in the Ergun equation as a basis for calculating the two‐phase pressure drop.     

异形多通孔催化剂工程研究(Ⅰ)12孔及24孔颗粒当量直径测定

引　言异形多通孔催化剂载体的外形为薄壁环柱形 ,多通孔由薄片分隔而成 ,是一种组合成形的薄片载体 .对于活性组分呈均匀分布的催化剂 ,多通孔载体有利于减小内扩散过程影响 ,提高选择性 ;对于外表型分布的催化剂 ,外表面积增大有利于增加活性组分负载量 ,提高催化剂活性 .异形多通孔催化剂还具有强化传热和降低反应器床层压力降的优点 .文献 [1,2 ]针对三叶草、蜂窝状载体等异形催化剂颗粒的传热性能及选择性的提高等方面进行了实验研究 .本文具体研究异形多通孔催化剂对床层压力降的影响 ,并测定了异形多通孔颗粒的当量直径 .催化剂颗粒…     

Pressure-drop predictions in a fixed-bed coal gasifier

In the Sasol Synfuels plant in Secunda, Sasol-Lurgi fixed-bed dry-bottom gasifiers are used for the conversion of low-grade bituminous coals to synthesis gas (syngas). The gasifiers are fed with lump coal having a particle size in the range from 5 to 100 mm. Operating experience shows that the average particle size and particle-size distribution (PSD) of feed coal, char and ash influence the pressure drop across the bed and the gas-flow distribution within the bed. These hydrodynamic phenomena are responsible for stable gasifier operation and for the quality and production rate of the syngas. The counter-current operation produces four characteristic zones in the gasifier, namely, drying, de-volatilization, reduction and combustion. The physical properties of the solids (i.e. average particle size, PSD, sphericity and density) are different in each of these zones. Similarly, the chemical composition of the syngas, its properties (temperature, density and viscosity) and superficial velocity vary along the height of the bed. The most popular equation used to estimate the pressure drop in packed beds is that proposed by Ergun. The Ergun equation gives good predictions for non-reacting, isothermal packed beds made of uniformly sized, spherical or nearly spherical particles. In the case of fixed-bed gasifiers, predictions by the Ergun equation based on the average or inlet values of bed and gas flow parameters are unsatisfactory because the bed structure and gas flow vary significantly in the different reaction zones. In this study, the Ergun equation is applied to each reaction zone separately. The total pressure drop across the bed is then calculated as the sum of pressure drops in all zones. It is shown that the total pressure drop obtained this way agrees better with the measured result.     

Flow through packed bed reactors: 1. Single-phase flow

Single-phase pressure drop was studied in a region of flow rates that is of particular interest to trickle bed reactors . Bed packings were made of uniformly sized spherical and non-spherical particles (cylinders, rings, trilobes, and quadralobes). Particles were packed by means of two methods: random close or dense packing (RCP) and random loose packing (RLP) obtaining bed porosities in the range of 0.37–0.52. It is shown that wall effects on pressure drop are negligible as long as the column-to-particle diameter ratio is above 10. Furthermore, the capillary model approach such as the Ergun equation is proven to be a sufficient approximation for typical values of bed porosities encountered in packed bed reactors. However, it is demonstrated that the original Ergun equation is only able to accurately predict the pressure drop of single-phase flow over spherical particles, whereas it systematically under predicts the pressure drop of single-phase flow over non-spherical particles. Special features of differently shaped non-spherical particles have been taken into account through phenomenological and empirical analyses in order to correct/upgrade the original Ergun equation. With the proposed upgraded Ergun equation one is able to predict single-phase pressure drop in a packed bed of arbitrary shaped particles to within ±10% on average. This approach has been shown to be far superior to any other available at this time.     

Experimental investigation of pressure drop in packed beds of irregular shaped wood particles

The knowledge of the pressure drop across a packed bed of irregular shaped wood particles is of great importance for achieving optimal control and maximum efficiency in many applications, such as wood drying, pyrolysis, gasification and combustion. In this work the effect of porosity, average particle size and main particle orientation on the pressure drop in a packed bed is investigated. To this end, particle size distributions and porosities are determined experimentally.Based on the experimental results obtained in this study, the form coefficient C and the permeability K of the Forcheimer equation are calculated for different packed beds. The Ergun equation requires an average equivalent particle diameter that is derived from the measured particle size distribution. This equivalent diameter and the corresponding bed porosity are used in the well known Ergun equation in order to derive adapted shape factors A and B.Since a change in bed porosity and particle size, caused by the degradation of the wood particles and gravity, can be expected in a reacting packed bed, a set of shape factors for use with the Ergun equation is determined that are independent of porosity and particle diameter and fit the experimental data very well.     

管式固定床反应器柱状颗粒床层流体流动模拟与实验研究

针对管式固定床反应器内管束数量多、规模大等特点,选取单个管束作为特征结构。对装填不同直径柱状颗粒的管束,采用程序坐标定位的方法,建立柱状颗粒床层的物理模型。采用DEM与CFD联合数值仿真方法,探究反应管内径与柱状颗粒的等比表面积球当量直径之比(管径比Di/dp)对柱状颗粒床层流体流动的影响,并建立单管固定床反应器试验台,采用差压测试方法进行实验研究。结果表明,当Di/dp由5.37增至12.75时,床层空隙率和流体分布均匀性均得到改善,壁面效应的影响由床层中心减弱到管壁。基于数值模拟及实验结果对Di/dp=12.75的柱状颗粒床层进行床层压降Ergun公式常系数修正,CFD模拟计算的结果与拟合公式吻合较好。研究结果能为固定床反应器压降预测提供参考。     

Flow dynamic in a packed bed filled with Ni-Al2O3 porous catalyst: Experimental and numerical approach

Numerical simulations and experiments have been carried out to explore the effect of particle shapes on the pressure drop and the loss factor in a packed fixed bed filled with a porous catalyst. The packed bed is presented by the Ni-Al₂O₃ catalyst of the different shapes. The commercial program ANSYS Fluent is used for the analysis; more than 20 mln cells are used for computational fluid dynamics (CFD) modeling. The catalyst particles were set as a porous medium with the viscous resistance coefficients and the inertial resistance coefficients. The comparison of the pressure drops between the experimental and simulation results show a good correlation with the divergence of results <8%. To determine the effect of the porosity properties of the medium on the numerical results, two cases of CFD modeling were realized (with taking into account the porous medium properties and without it). The discrepancy between results increases with an increasing gas flow rate.     

THE EFFECT OF SURFACE ROUGHNESS ON PRESSURE DROP IN A PACKED BED

Particle surface roughness is shown to have a significant effect on the pressure drop in a packed bed of adsorbent particles. The packed bed friction factor is determined using three spherical adsorbents of differing degree of surface roughness in the Reynolds number range 1-62. The results were successfully correlated using a correlation of the Ergun type. It is shown that surface roughness significantly increases the friction factor.     

Resistance of wood pellets to low airflow

The pressure drop versus low airflow from 0.000117 to 0.1 m/s was measured across a fixed bed of wood pellets. Wood pellets were on average 6.2 mm in diameter and 12 mm in length. The moisture content of wood pellets ranged from 2.8% to 8.1%. Four equations, Darcy, Shedd, Hukill and Ergun representing flow versus static pressure drop for bulk granules were fitted to the experimental data. At airflows below 0.01 m/s, the predicted pressure drops using all four equations deviated from experimental data. This deviation was the largest for the Darcy equation and the smallest for Ergun equation. © 2011 Canadian Society for Chemical Engineering