Predictive process mapping for laser powder bed fusion: A review of existing analytical solutions

One of the main challenges in the laser powder bed fusion (LPBF) process is making dense and defect-free components. These porosity defects are dependent upon the melt pool geometry and the processing conditions. Power-velocity (PV) processing maps can aid in visualizing the effects of LPBF processing variables and mapping different defect regimes such as lack-of-fusion, under-melting, balling, and keyholing. This work presents an assessment of existing analytical equations and models that provide an estimate of the melt pool geometry as a function of material properties. The melt pool equations are then combined with defect criteria to provide a quick approximation of the PV processing maps for a variety of materials. Finally, the predictions of these processing maps are compared with experimental data from the literature. The predictive processing maps can be computed quickly and can be coupled with dimensionless numbers and high-throughput (HT) experiments for validation. The present work provides a boundary framework for designing the optimal processing parameters for new metals and alloys based on existing analytical solutions.     

The effect of biomass feeding location on rice husk gasification for hydrogen production

The objective of this study is to investigate the impact of biomass feeding location on rice husk gasification for hydrogen production. By comparing the results between top-feed and bottom-feed of the feedstock of the fluidized bed biomass gasification at the reaction temperature between 600～1000 °C and ER = 0.2, 0.27, and 0.33 without steam, the optimum low heating value was increase by 2.35 kJ/g-rice husk by the top-feed to gasifier. Although the yield of hydrogen was decreased by 42% for the rice husk gasification by the top-feed operation, the yield of CO, CO2, and CH4 were highly increased, which enhancing the heating value of the effluent gas. The study results suggested the potential route of the biomass gasification at the different feeding location.     

Additive manufacturing of bipolar plates for hydrogen production in proton exchange membrane water electrolysis cells

Water electrolysis is a process that can produce hydrogen in a clean way when renewable energy sources are used. This allows managing large renewable surpluses and transferring this energy to other sectors, such as industry or transport. Among the electrolytic technologies to produce hydrogen, proton exchange membrane (PEM) electrolysis is a promising alternative. One of the main components of PEM electrolysis cells are the bipolar plates, which are machined with a series of flow distribution channels, largely responsible for their performance and durability. In this work, AISI 316L stainless steel bipolar plates have been built by additive manufacturing (AM), using laser powder bed fusion (PBF-L) technology. These bipolar plates were subjected to ex-situ corrosion tests and assembled in an electrolysis cell to evaluate the polarization curve. Furthermore, the obtained results were compared with bipolar plates manufactured by conventional machining processes (MEC). The obtained experimental results are very similar for both manufacturing methods. This demonstrates the viability of the PBF-L technology to produce metal bipolar plates for PEM electrolyzers and opens the possibilities to design new and more complex flow distribution channels and to test these designs in initial phases before scaling them to larger surfaces.     

An experimental study on the spray characteristics of pressure nozzle in a fluid bed granulation

The particles with a narrow size distribution are proper products in a fluid bed granulation and coating. As well, the process efficiency is one of the most important parameters, and the wall deposition of sprayed liquid reduces it. The modality of spray volume distribution is a key parameter in the definition of particle size distribution and process efficiency. This work is done in two steps: In the first step, an experimental study on spray characteristics including spray flux distribution, spray cone angle, and discharge coefficient is conducted. Based on the experimental data, the curves of liquid volume flux versus nozzle pressure and height are obtained. The results indicate that the flux distribution changes significantly with even small pressure and height changes. In the second step, the granulation process is carried out in a semi-industrial conical fluid bed, and the particles size distribution curves and the deposited mass on the bed wall are obtained. The results show that the precise determination of the spray flux distribution is an appropriate way to predict the well-advised nozzle pressure/height in order to achieve the narrow particle size distribution and high efficiency of the process.     

负压差对固体进料系统压力分布和气固两相流动规律的影响

A series of experiments on a solid feed system was performed to investigate the effects of negative pressure gradient on the gas-solid flow pattern and hydrodynamic characteristics. Based on the non-fluidized gas-solid two phase flow and particulate mechanics in the standpipe, a method for predicting the pressure of the air passing through the recycle chamber and the pressure drop through the loop seal slit in these systems is also presented. The predicted pressure profile along the negative pressure gradient from the proposed model exhibits a good agreement with the experimental data. The experimental data show that the gas flow in the standpipe is always upward in the negative pressure gradients, while the direction of gas cannot be changed by the drag force. The solid flow rate, the materiel bed height in the recycle chamber (Hf), the pressure drop across the slit (△Pg） decrease with an increasing negative pressure gradient. At a given negative pressure gradient, the superficial gas velocity through the recycle chamber of the loop seal does not affect the pressure drop in standpipe. It increases with an increasing negative pressure gradient.     

厌氧接触+射流曝气+Fenton流化床技术处理制浆造纸废水运行实例

介绍厌氧接触+射流曝气+Fenton流化床技术处理制浆造纸生产废水的工程参数、运行效果和工程效益。六个月的运行数据显示,厌氧单元出水COD平均浓度为1321 mg·L^-1,平均去除率为61%;好氧单元出水COD浓度为185 mg·L^-1左右,平均去除率为78%;深度处理部分COD出水浓度为44 mg·L^-1,平均去除率为73%,可实现废水达标排放。     

高压料床挤压对钢渣易磨性改善的应用研究

在分析了大量钢渣原料的化学成分、矿物组成和粉磨邦德功指数基础上，依据辊压机高压料床挤压粉碎原理，本文采用辊压机对钢渣进行预挤压试验，并参照相对易磨性试验方法，对比了挤压前后钢渣粉磨特性的变化，试验结果表明辊压机高压料床的挤压粉碎作用大大改善了钢渣的易磨性，有效的降低了钢渣的粉磨电耗。     

高温固定流化床费托合成技术及其产物加工路线

与采用低温费托合成主产油品技术相比，产品更为多元化和高值化的高温费托合成技术在目前市场环境下显示出非常明显的优势。本文综述了高温费托合成技术的发展历程及其最新进展，重点介绍了高温费托合成过程中的核心问题，主要包括高温费托合成工艺、固定流化床反应器、费托合成催化剂；介绍了高温费托合成产物分布与特性，讨论了高温费托合成产物的加工路线，并对高温费托合成煤间接液化的工业应用前景和产业化方向进行了展望。结果表明：高温费托合成技术具有产物附加值高、兼顾油品和化学品、技术发展成熟等优势，产物中轻组分含量高、碳数分布较窄、高附加值的α-烯烃含量高；精细化、高端化、差异化加工是实现高温费托合成产物高值化利用的关键。     

Effect of phase maldistribution on performance of two-phase catalytic monolith reactor and its comparison with trickle bed reactor

Monolith reactors are widely considered as an alternative to the conventional trickle bed reactor. For the commercial deployment of monolith reactors, comparative performance studies are required. Reliable comparative and performance studies require a detailed understanding of the effect of phase distribution/maldistribution on the performance studies. In this work, performance and comparative studies were carried out in a relatively large column that was 4.8 cm in diameter. Experiments were performed in the same conditions that were used in studies for which phase distribution data were available. Since the properties of the catalyst used were different in both the reactors, the apparent kinetics were studied to facilitate the comparison. The hydrogenation of alpha-methyl styrene (AMS) was used as a test reaction. From the performance studies, it was found that the effect of maldistribution on the performance was stronger than the catalyst availability. From the comparative studies, it was found that the monolith reactor with maldistributed flow conditions provides higher productivity than the trickle bed reactor.     

电脑横机编织三维全成形口罩结构建模与工艺实践

为探究用电脑横编机开发全成形针织产品的可能性,以针织三维全成形口罩为开发对象,进行结构建模与工艺实践。首先对人体面部尺寸进行测量,以此确定全成形口罩的二维纸样;然后结合全成形口罩规格尺寸进行工艺计算,以四针床电脑横编机和SDS-ONE APEX3系统为开发工具,分别建立针织三维全成形口罩的口罩主体、过滤垫片口袋开口、挂耳带部位的结构模型。结果表明:通过对口罩的规格设计并建立结构模型,同时结合工艺参数的调节并优化其生产技术,可实现兼具美观性与舒适性三维全成形口罩的快速生产,结合功能性原料可开发高附加值的口罩产品。