Synthesis of Al2O3-SiC composite powders from coal ash in NaCl-KCl molten salts medium

Magnesium aluminate spinel (MgAl2O4) porous ceramics were in-situ synthesized by heating the mixture of Al2O3 and MgCO3 with MgCl2 salt at 1400~1600 °C for 3 h, and then characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The morphology of as-prepared MgAl2O4 porous ceramics was dependent on the addition of MgCl2, and it indicated that the MgCl2 molten salt not only acted as a template for pore formation of the porous ceramics, but also provided a liquid environment for the synthesis of MgAl2O4.

Synthesis and Characterization of Magnesium Aluminate Spinel Porous Ceramics by Novel Molten Salt Method

Semi-empirical balance-based computational model of air-cooled condensers with the A-frame layout

On-site investigations show that an asynchronous load feature would greatly influence the operation of water systems for centralized air conditioning. However, the manner of defining the load feature and relating it to its influence quantitatively is still unclear. This article quantitatively describes the asynchronous load demand feature and reveals its relationship with the loss of pump power and heat transfer ability in a centralized air-conditioning water system. The Lorenz curve and the Gini index are introduced in this study and used as indices to depict load features. For a large-scale use in office buildings, shopping malls, and other buildings, the fan coil unit and the variable air volume systems are investigated in this study. The loss of pump power on valves and heat transfer ability under different load profiles are analyzed. This study develops a new perspective of analyzing load patterns and quantitatively explores reasons for the resulting losses in pump power and heat transfer ability in ...

Influence of load feature on the water distribution system in a centralized air-conditioning system

While the solidification macrostructure of continuous cast billets is an important factor influencing the final performance and rolling yield of oil casing steel, the continuous casting process parameters have a direct influence on the solidification structure. This study simulated the solidification process of the continuous casting round billets of oil casing steel using a cellular automaton–finite element (CAFE) model. According to the simulation results, at a superheat degree of 20–35 K, a casting speed of 1.9–2.1 m/min, and a secondary cooling specific water flow of 0.34–0.45 L/Kg, the solidification structure had a relatively high equiaxed crystal ratio and small average grain radius. Guided by the simulation results, this paper establishes optimal process schemes for producing 26CrMoVTiB steel round billets, comparatively analyzes the equiaxed crystal ratio and central shrinkage of round billets produced according to these schemes, and defines the optimal continuous casting process conditions, which are: superheat degree = 25 K, casting speed = 2.1 m/min, and specific water flow = 0.35 L/Kg. When adopting these process parameters, the 26CrMoVTiB steel round billets demonstrate a tiny central shrinkage and an equiaxed crystal ratio of 45.2%.

Acquiring High-Quality Oil Casing Steel 26CrMoVTiB under Optimal Continuous Casting Process Conditions

An improved genetic algorithm is presented for the water consumption of the secondary cooling zone based on the heat transfer model of the off-line bloom caster. This study is to control the existing cooling systems and the steel casting practises in order to produce steel with best possible quality. The fitness function of improved genetic algorithm is founded according to the metallurgical criteria. This algorithm coupled with heat transfer model and metallurgical criteria, added dynamic coding method and self-adapting mutation on the original genetic algorithm can increase water distribution adaptively and improve the process efficiency. The simulation results of T91 bloom show that the optimised distribution reduced by 2% of water consumption comparing to that of before optimisation. The maximum surface cooling rate and the rate of temperature rise reduced, and the equiaxed rate increases. The function is built for explaining the relationship between the casting speed and water distribution.

/pdf/the-optimisation-of-the-secondary-cooling-water-distribution-4f096k4ifu.pdf

The optimisation of the secondary cooling water distribution with improved genetic algorithm in continuous casting of steels

MgAl2O4 (MA) powder has been synthesised by heating an equimolar composition of commercial Al2O3 and calcined MgO via a molten salt synthesis (MSS) method Phase compositions, microstructures, elements distributions, particle size and specific surface area of as-synthesised MA at various temperatures were investigated The synthesis reaction of MA from Al2O3 and MgO is incomplete at 1000 and 1100°C for 4 h in KCl–MgCl2 molten salts MgAl2O4 powder can be produced via the MSS method at 1200°C for 4 h, which is ∼200°C lower than that of conventional solid–solid reaction (SSR) method Fine MA particles can be formed at 1000, 1100 and 1200°C for 4 h, and most of them aggregate With the increase in reaction temperature from 1000 to 1200°C, the particle size of as-synthesised MA powder decreases and specific surface area increases The average grain size and the specific surface area of the fabricated powder at 1200°C for 4 h are 757 μm and 07566 m2 g-1, respectively Single MA crystalline phase is detected 

Facile synthesis of MgAl2O4 with high crystallinity from KCl–MgCl2 composite molten salts

Solidification structure is critical in the control of the mechanical properties and quality during the continuous casting process. The thermo-physical properties of 13Cr steel added some rare metals, such as Mo, V, Nb, are measured to better understand the solidification structure of 13Cr bloom. A computational model using CA-FE (cellular automation-finite element) method coupled with heat transfer model is developed to describe the solidification structure in continuous casting process. It is found that the calculated solidification structure is in good agreement with the observed data. The influence of casting speed and superheat on the solidification structure of the bloom is studied in detail. In order to obtain more equiaxed crystal ratio and low degree of the segregation in the bloom, the optimized casting speed 0.6 m/min and superheat less than 25 °C are determined for the caster. Using the optimized manufacturing parameters, these samples are 60% with the equiaxed zone ratio of 8%–10% and below the degree of segregation 1.05.

Ying Li

Papers

The optimisation of the secondary cooling water distribution with improved genetic algorithm in continuous casting of steels

Facile synthesis of MgAl2O4 with high crystallinity from KCl–MgCl2 composite molten salts

Analysis of 13Cr bloom solidification structure using CA-FE model