氧化铝激光选区熔化温度场模拟

基于ANSYS模拟分析了激光选区熔化(Selective Laser Melting,SLM)Al_2O_3陶瓷过程中的温度场,研究了激光功率和扫描速率对熔池热行为的影响,并结合实验验证了模型的可靠性。结果表明:当激光功率由100 W增加到200 W时,熔池的最高温从1 619.02 K增加到3 276.79 K,升温速率极值从2.05×106 K/s增加到4.90×106 K/s;当扫描速率由60 mm/s增加到120 mm/s时,熔池的最高温由2 754.45 K减少到1 980.59 K,而升温速率极值由2.65×106 K/s增加到3.57×106 K/s,降温速率极值由2.15×106 K/s增加到2.63×106 K/s;当扫描速率固定为90 mm/s时,熔池的最高温度是影响降温速率值的直接因素,熔池最高温度越高(激光功率越大),降温速率越大。随着激光功率的增加或者扫描速率的减少,熔池的尺寸逐渐增大。对比实验与模拟数据,发现模拟结果能够说明试样的表面质量和粉末的熔化状态随激光工艺参数而变化的趋势。     

低压轴径向节能型氨合成塔的应用

介绍了φ61200低压轴径向节能型氨合成塔内件基本结构、催化剂的装填情况和升温还原过程．总结了该塔实际运行效果和生产操作经验。     

锰硅铁合金冶炼电弧炉中焦炭层电流分配行为的模拟

根据锰硅铁合金冶炼电弧炉内焦炭层熔池的结构特征及相似理论,设计了研究熔池导电行为的模拟实验装置. 以电导率为10.08~17.97 mS/cm的NaCl水溶液和冶金焦粒模拟实际锰硅铁合金冶炼电弧炉熔池内的导电相,研究了冶炼过程熔池内电流在焦炭层与熔渣之间的分配关系. 结果表明,焦炭层厚度Hc、焦炭粒度Dc和导电相的电导率(固相rC,液相rL)与通过熔池底部电流(Ib)和总电流(It)之比Ib/It的关系式为Ib/It=4.36(rL/rC)1.523(DC/HC)0.186, Ib/It随熔融层操作电阻的增大而变小,与锰硅铁合金实际生产状况一致.     

关于炉料中"焦比"对电炉制磷影响的探讨

根据制磷电炉的构造和运行特点 ,引入了炉料焦比的概念。阐述了磷矿和焦炭的化学组成对炉料焦比的影响 ,从电能转换成热能过程出发 ,探讨了炉料焦比和炉料电阻率 (熔池电阻率 )、操作电阻 (熔池电阻 )的关系 ,以及它对电炉的电气参数、几何尺寸和操作运行的影响 ,并指出炉料焦比不仅是电炉设计时必须考虑的因素 ,而且是生产中控制操作电阻的主要因素。     

2~#变换升温技术措施

云天化云峰分公司产能为100kt/a合成氨2#变换装置,大修后进行升温。介绍了变换工艺流程,升温准备工作,升温的操作措施以及工艺控制。升温过程要求逐步加量加压,确保"平稳过度",达到正常工艺指标。     

侧顶复吹条件下AOD转炉熔池内流体流动的数学模拟:模型对侧顶复吹过程的应用及结果

由提出的侧顶复吹条件下AOD熔池内钢液流动三维数学模型的侧吹和顶吹分量对纯侧吹和纯项吹下熔池内流体流动计算结果的叠加,处理和分析了复吹过程中120 tAOD转炉及线尺寸为其1/4的水模型熔池内流体的流动.所得结果显示,该数学模型可用以模拟复吹AOD熔池内流体流动.侧吹气流对复吹AOD熔池内流体流动起主导作用,整个熔池液...     

MIG焊接V型熔池特性的数理模型建立

通过对MIG坡口焊接工艺过程的分析将三维焊接物理过程简化为二维数理模型,建立移动高斯热源模型用于描述电弧与工件的热作用,建立熔池内的CFD模型用以描述熔池内熔化／凝固过程的流动传热传质现象,对典型V型坡口焊接过程进行实验和数值模拟研究,通过与实验得到的工件截面金相图对比分析验证了数理模型的准确性,最后对数理模型中高斯热源参数及熔池流动的驱动力机理模型进行了进一步讨论。结果表明通过合理的模型参数选择二维数理模型可以准确地分析MIG坡口焊过程熔池的演变过程。     

FLUENT在电光源玻璃熔窑的应用研究

采用FLUENT软件求解2座电光源玻璃熔窑熔池玻璃液的三维温度场,数学模拟结果与实际熔池池底侵蚀程度进行了比较。研究表明:不同的窑炉规模和出料口位置对熔池池底的温度会产生较大的影响,温度越高池底侵蚀越大。利用数学模拟法可优化玻璃熔窑结构设计和操作工艺。     

合成车间老系统低变升温还原研究

低变催化剂升温还原的过程和操作要点。     

MIG焊接V型熔池特性的数理模型建立

通过对MIG坡口焊接工艺过程的分析将三维焊接物理过程简化为二维数理模型,建立移动高斯热源模型用于描述电弧与工件的热作用,建立熔池内的CFD模型用以描述熔池内熔化/凝固过程的流动传热传质现象,对典型V型坡口焊接过程进行实验和数值模拟研究,通过与实验得到的工件截面金相图对比分析验证了数理模型的准确性,最后对数理模型中高斯热源参数及熔池流动的驱动力机理模型进行了进一步讨论。结果表明通过合理的模型参数选择二维数理模型可以准确地分析MIG坡口焊过程熔池的演变过程。     

纳米结构表面液体沸腾传热的分子动力学模拟

为了从纳米尺度了解表面结构和润湿性对池沸腾液体与固体壁面的传热性能,本文采用分子动力学方法研究了超亲水至超疏水不同润湿性的液体氩在光滑表面和含凹、凸半球纳米结构表面的沸腾传热过程,分析了三种表面上液氩在受热过程的形态、温度、热流密度等相关参数的变化情况。结果表明,液氩层沸腾过程大致可分为液氩层吸附于固体表面和液氩层从壁面脱离两个加热阶段,当液氩层吸附于固体表面时,温度升高、热流密度及气态氩原子产生速度均大于液氩层脱离壁面时的情况,在这两个阶段亲水表面上氩原子温度变化有明显的拐点,而疏水表面在两个阶段加热过程相差不大。亲水表面上的微结构能吸附更多液氩原子,促进了气泡产生及加速温度、热流密度的变化,而在疏水及超疏水微结构表面,微纳结构与液氩间的气膜层促进了气泡产生,计算结果为池沸腾传热及微结构选择提供了理论依据。     

Improving the load flexibility of industrial air separation units using a pressure-driven digital twin

Air separation units are one of the prime examples for studies on demand side management and (non-)linear model predictive control due to their high power consumption and energy storage potential. These plants separate ambient air into its main components, nitrogen, oxygen, and argon, by means of cryogenic distillation at different pressure levels. Approximately two thirds of the industrially operated air separation units consider the separation of argon either as a value product or for reasons of energy efficiency. However, most of the studies in literature neglect the separation of argon since this requires additional equipment, increases the heat and process integration and, thus, the complexity of process control. In this work, a digital twin of an air separation unit with argon system is used to analyze and to improve load change procedures. Moreover, the potential of applying the digital twin as a soft sensor is demonstrated.     

Argon production from air distillation: Use of a heat pump in a ternary distillation with a side rectifier

A ternary feed mixture ABC can be separated into individual components through the use of a main distillation column with a thermally linked side rectifier. To enhance such a separation, a heat pump can be implemented to transfer heat from the condenser at the top of the side rectifier to the reboiler at the bottom of the main column. In this paper, one such heat pump is described and applied to an air distillation system separating the ternary mixture containing nitrogen, oxygen and argon. The separation is performed by a conventional double column with a crude argon side column. When this system is operated at an elevated pressure to obtain higher product pressures, the separation of oxygen and argon becomes very difficult and leads to reduced argon recovery. The proposed heat pump enhances the separation by providing a supplementary crude argon condensing duty through the vaporization of a liquid oxygen stream from the bottom of the low pressure (LP) column. This scheme improves the liquid/vapour ratio (L/V) in the bottom section of the LP column and, more importantly, increases the vapour feed to the crude argon column. This increased feed rate leads to a substantial increase in argon recovery for the elevated pressure air distillation process.     

Dynamic modeling and collocation‐based model reduction of cryogenic air separation units

High purity distillation columns and multi‐stream heat exchangers (MSHXs) are critical units in cryogenic air separation plants. This article focuses on modeling approaches for the primary section of a super‐staged argon plant. A full‐order stage‐wise model for distillation columns in air separation units (ASUs) that considers key process phenomena is presented, followed by a reduced‐order model using a collocation approach. The extent of model reduction that can be achieved without losing significant prediction accuracy is demonstrated. A novel moving boundary model is proposed to handle MSHXs with phase change. Simulation results demonstrate the capability of the proposed model for tracking the phase change occurrence along the length of the heat exchanger. Dynamic simulation studies of the integrated plant show that the thermal integration between the feed and product streams captured in the primary heat exchanger is critical to accurately capture the behavior of ASUs. © 2016 American Institute of Chemical Engineers AIChE J, 62: 1602–1615, 2016     

A power plant for integrated waste energy recovery from liquid air energy storage and liquefied natural gas

Liquefied natural gas(LNG)is regarded as one of the cleanest fossil fuel and has experienced significant developments in recent years.The liquefaction process of natural gas is energy-intensive,while the regasification of LNG gives out a huge amount of waste energy since plenty of high grade cold energy(-160℃)from LNG is released to sea water directly in most cases,and also sometimes LNG is burned for regasification.On the other hand,liquid air energy storage(LAES)is an emerging energy storage tech-nology for applications such as peak load shifting of power grids,which generates 30％-40％of compres-sion heat(～200℃).Such heat could lead to energy waste if not recovered and used.The recovery of the compression heat is technically feasible but requires additional capital investment,which may not always be economically attractive.Therefore,we propose a power plant for recovering the waste cryo-genic energy from LNG regasification and compression heat from the LAES.The challenge for such a power plant is the wide working temperature range between the low-temperature exergy source(-160℃)and heat source(～200℃).Nitrogen and argon are proposed as the working fluids to address the challenge.Thermodynamic analyses are carried out and the results show that the power plant could achieve a thermal efficiency of 27％and 19％and an exergy efficiency of 40％and 28％for nitrogen and argon,respectively.Here,with the nitrogen as working fluid undergoes a complete Brayton Cycle,while the argon based power plant goes through a combined Brayton and Rankine Cycle.Besides,the economic analysis shows that the payback period of this proposed system is only 2.2 years,utilizing the excess heat from a 5 MW/40MWh LAES system.The findings suggest that the waste energy based power plant could be co-located with the LNG terminal and LAES plant,providing additional power output and reducing energy waste.     

A Comparison of Reducing and Oxidizing Heat Treatments of Hot-Pressed Silicon Nitride

The effects of postfabrication heat treatments in argon and air atmospheres at 1400°C on the microstructure of a hot-pressed silicon nitride are compared. Heating in argon leads to a disappearance of the intergranular glass phase (with the consequent formation of interconnected porosity) and a reduction in the content of silicon oxynitride, and results in a soft, easily abraded surface. On subsequent heating in air, an oxide scale, similar to that produced by oxidation, rich in impurity and additive cations, is formed on the surface. In addition, silicon oxynitride and silica are formed below the scale. On cooling, macroscopic cracking, attributed to the volume increase of SO₂ on transformation to cristobalite, occurs. Material heated first in air and then in argon resembled that of material heated in argon alone.     

Research on crack mechanism and kinetic model of alumina ceramic in the degreasing stage based on stereolithography

Given that the kinetics of the thermal degreasing process of alumina ceramics based on stereolithography apparatus (SLA) has not been investigated, the mechanism of crack generation is still not fully revealed. This paper aims to elucidate the mechanism of crack generation in the degreasing process of alumina ceramics and to establish a kinetic model for alumina ceramics. Two sintering atmospheres, air, and argon, were selected for the degreasing tests at 100°C–700°C. The reaction products and mass changes of alumina ceramics were analyzed by TG-FTIR and TG-DSC (heating rates of 5, 10, and 15°C/min, respectively). Meanwhile, Boswell, Friedman, Ozawa, and DAEM model was used to describe the nonisothermal kinetics of the SLA alumina ceramic degreasing process. The results showed that setting the holding time to 400°C–425°C could promote the slow release of heat from the alumina ceramics. The thermal degreasing stage of the ceramic generated fewer cracks in the argon atmosphere than in the air atmosphere. The corresponding average activation energy values were 105.40 kJ/mol (Boswell model), 112.48 kJ/mol (Friedman model), 108.14 kJ/mol (Ozawa model), and 101.36 kJ/mol (DAEM model). The results of the study could provide an invaluable reference for the fabrication of defect-free SLA alumina ceramics.     

不同润湿表面液体沸腾的分子动力学模拟

采用分子动力学方法研究纳米尺度下液氩在过热基板上的沸腾过程。通过调节固液间相互作用的方式改变壁面润湿性,模拟并分析了壁面润湿性对沸腾过程中能量传递和液体运动情况的影响。结果表明：不同润湿性表面均会发生固液分离的现象,但是固体表面附近吸附的氩原子数密度随润湿性增强而增大;润湿性较强时,液体的能量上升快,热通量高,液体内部温度梯度大,发生固液分离时间早,系统中氩的温度和能量低,上升过程中液氩密度、厚度变化小;润湿性较弱时,液体的能量上升慢,热通量小,液体内部温度梯度小,发生固液分离时间延后,系统中氩的温度、能量更高,上升过程中液氩密度、厚度变化较大。下部气体压力整体上大于上部气体压力,发生固液分离时润湿性越强的表面上液体上下压差越大,首次上升过程能达到的高度越高,所需时间越短。     

Numerical heat transfer analysis for the design of the engineering-scale electrowinning cell in pyroprocessing

A heat transfer analysis of the electrowinning cell was conducted to develop a basic tool for designing of the engineering-scale electrowinner. For calculating the heat transfer properties of argon gas and LiCl–KCl eutectic salt in the electrowinning cell, the ANSYS CFX commercial code was adapted. The simulation model was prepared, and the temperature profiles of the argon gas and the salt were compared with those in the lab-scale electrowinning cell. Using the simulation model, temperature distributions of the engineering-scale electrowinning cell were analyzed. When the heating zone length was 2.5 times longer than the height of the LiCl–KCl salt, the salt temperature was maintained at about 500 °C and its temperature gradient became less than 5 °C. The cooling zone length had an influence on both temperatures of the argon gas under the cell cover as well as the salt. When the cooling zone length was about 0.16–0.19 of the heating zone length, the temperature of the salt was maintained at 500 °C and the argon gas temperature under the cover decreased below 200 °C. The number of the heat shield plates and size mainly affected the temperature gradient of the salt and argon gas under the cover. More than 3 heat shield plates had to be placed in the cooling zone and their diameters should be extended over 410 mm that is over 0.95 of the cell diameter.     

内压缩流程空分的换热与精馏研究

分析和讨论了内压缩空分设备的氧氮两组分、氧氮氩三组分及氧氩两组分和氮氩两组分的相平衡,精馏部分的上塔、下塔、粗氩塔、精氩塔的精馏以及高压主换热器、低压主换热器、过冷器及主冷凝蒸发器等换热设备。希望能促进空气分离设备在理论方面的发展。