硝酸镁法生产浓硝酸的过程控制

结合实际生产情况,介绍硝酸镁法生产浓硝酸的主要控制指标(系统负压、温度、硝酸镁浓度、物料配比等)及调节手段,从而达到优质高产低耗的目的。     

Sonderlösungen bei der brandschutztechnischen Bewertung von Konstruktionsdetails

Special‐purpose solutions in the fire‐protective evaluation of construction details Very often components or construction details in existing buildings but also in new buildings cannot be evaluated with regard to its fire resistance ability considering established technical building regulations. There are no regulations for the evaluation of such components or construction details as these specific construction details have not been evaluated by a certified test authority. However, these components and construction details very often can be classified in fire resistance classes e. g. by evaluating fire tests, with regard to DIN 4102‐4, on the basis of similar proof of usability or only by pragmatic considerations. Since introducing the technical approval of the fire protection Eurocodes more often engineering methods of fire protection are used based on these Eurocodes by using temperature assessment in order to secure the evaluation results. Within this essay we show methods and ways of fire‐protective evaluation for components and construction details. The approach of proof including dimensions of possible upgrade measurements if necessary are being illustrated by examples of use out of practical experience. At the same time different materials such as steel, concrete and wood will be treated with different fire‐proof products. The essay is to explain ways of evaluation of components and construction details involving fire‐proof requirements including upgrade measurements also especially for existing buildings.     

Experimentelle und numerische Untersuchungen von Brandszenarien vor Fassaden unter Berücksichtigung verschiedener Abstände

Experimental and numerical investigations of fire scenarios in front of façades considering various distances Constructional boundary conditions, e. g. walls or façades, close to ignition sources affect the fire formation and the plume. It is already known, that boundaries (e. g. walls) constrain the entrainment of air and oxygen into the plume and the combustion of gas or flammable products is completed at larger heights. How far the location of the fire sources, the building geometry and the heat release rate affect the characteristics of a flame is investigated at the Institut für Baustoffe, Massivbau und Brandschutz (iBMB) of TU Braunschweig in line with a series of experiments with a square gas burner. For the implementation of the fire tests the test rig in Braunschweig is provided with extensive measurement techniques to determine heat flux, wall‐bounded temperatures, temperatures for plume measurements and upward velocity. In this paper the data of the fire tests are discussed and compared with the results of a CFD‐Model and selected empirical calculation approaches.     

Exploring Hf-Ta-O precipitation upon ablation of Hf-Ta-Si-C coating on C/C composites

To improve the ablation resistance of C/C composites, a Hf-Ta-Si-C coating was fabricated by chemical vapor co-deposition. The ablation resistances of Hf-Si-C and Hf-Ta-Si-C coatings were characterized comparatively. After introducing Ta, the ablation resistance, smoothness and integrity of the ablated coating improved. Hf-Si-O and Hf-Ta-Si-O glass wires were observed. To investigate the reaction processes of the two types of glass wires, TEM observation was carried out and coupled to molecular dynamics simulations. These illustrated that Hf and Ta atoms tend gather together at high temperature. To investigate the effect of Hf-Ta-O precipitation on the ablation behavior, supplementary experiments were carried out on bulk ceramics with the same target composition, confirming that precipitation reaction could accelerated the formation of a smooth and intact oxide layer, playing a positive role in protecting C/C composites.     

超高性能混凝土抗压强度尺寸效应及收缩特性

研究了钢纤维体积分数、膨胀剂种类及掺量对不同尺寸的超高性能混凝土(UHPC)试件28d抗压强度及自成型27h后至180d收缩特性的影响.结果表明:以40mm立方体试件抗压强度为基准,不掺膨胀剂时100mm立方体试件的抗压强度换算系数为0.75～0.80,而掺有膨胀剂的100mm立方体试件抗压强度换算系数为0.74～0.80;UHPC的收缩形式以自收缩为主,约占其总收缩量的87.0%～92.7%,掺加钢纤维能够有效降低其收缩量;试验选用的EA1膨胀剂因水化速率过快,在UHPC收缩测试前已基本完全水化,造成试件内部自干燥作用加强,因此增大了UHPC的收缩量;选用的EA2膨胀剂能与空气中的水蒸气及试件内部的水分发生反应并产生持续的膨胀效果,因此在实际应用时应注意控制其掺量,以保证UHPC的体积稳定性.     

温湿度控制系统设计

温室是设施农业的重要组成部分,提高温室的自动控制和管理水平可充分发挥温室农业的高效性。通过传感器技术、外围接口电路,实现了对温度实时采集、智能监控。     

用修正淬透性系数法对反应堆压力容器锻件RTNDT数值的预估

分析反应堆压力容器(RPV)锻件制造过程中关键化学元素含量及基准无塑性转变温度(RTNDT)数值,通过引入修正淬透性系数,建立了反映RTNDT变化规律的修正淬透性系数函数表达式,并给出了实例验证,结果表明,通过本文建立的修正淬透性系数函数式可以比较精确地预估RPV锻件的RTNDT值。     

重要厂用水系统设计水温对冷链换热器热工设计的影响分析

核电厂重要厂用水系统设计水温(TSEC)是影响冷链换热器热工设计的重要参数,随着TSEC的增大,冷链换热器的热工设计工况趋于恶劣,导致换热面积和设备尺寸逐渐增大。本文以冷链换热器的典型热工设计工况为设计输入,针对不同的TSEC,采用热混合设计方法,得到了对应TSEC下的冷链换热器板片方案。分析了冷链换热器总通道数量、流道占比、总传热系数随TSEC的变化情况,发现对于特定的热工设计工况,冷链换热器只能在一定的TSEC范围内实现压降和换热裕量的完全匹配,且存在一个临界温度,当TSEC高于该温度后,板片数量会迅速增大,应尽量避免TSEC高于该临界温度。     

快干羟基丙烯酸酯乳液的合成及性能研究

采用核壳乳液聚合方法制备了羟值为1.5%的低羟丙烯酸酯乳液。研究了聚合物理论Tg、壳中羟基质量分数、核聚合物Hansch参数对双组分漆膜干燥速度的影响。结果表明:漆膜干燥速度随理论Tg、壳中羟基质量分数及核聚合物Hansch参数的增加而加快,当Tg为50℃、壳中羟基质量分数为1.1%、核聚合物Hansch参数为3.43时,漆膜于25℃、60%相对湿度下的实干时间可缩短至95 min,在大巴、工程机械涂装等需要快干的领域具备潜在应用价值。     

耐火钢与普通结构钢高温强度的比较试验

对两种耐火钢(FR)与普通结构钢在常温到高温700℃之间的力学性能比较试验研究结果显示,耐火钢比普通结构钢具有更好的高温力学性能,耐火钢在约650℃时的屈服强度为常温下强度的50%,而普通结构钢在550℃时的屈服强度就已降到常温下强度的50%。同时耐火钢的高温(600℃)蠕变也比普通结构钢的小。研究结果表明在建筑设计中用耐火钢替代需要采取防火措施的普通结构钢更经济安全。