Meijie Zhang

Mathematical Modeling on Erosion Characteristics of Refining Ladle Lining with Application of Purging Plug

According to parameters of the refining ladle with argon bottom blowing, the mathematical model describing the erosion behavior of ladle lining materials was established, the flow process of molten steel and thermal transmission of ladle lining were coupled, and the erosion of ladle lining in the condition of blowing argon at the bottom was researched. It has been found that either single or double blowing is applied, the larger erosion rates are mainly distributed in the slag line and the area of ladle lining near purging plugs, and the erosion is accelerated with the gas flow rate increasing, so the areas with higher erosion rates of the lining should be enhanced to avoid early partial damage. The erosion rate of ladle lining with double blowing is larger and the distribution of erosion is obviously different as the gas flow rate is increasing; serious erosion areas are in the slag line region and the higher erosion areas are concentrated on the slag lining and extended toroidally. And, as the distance between the purging plug and the lining of ladle is shortened, the partial erosion is easy to deteriorate and the refractories in the area with higher erosion rate need specialized selection and design. Meanwhile, the purging plug should be located away from the lining wall under the condition of good blowing effect in order to avoid increasing of the partial erosion and shortening of the lining service life.

Potash Erosion Resistance of Chromium-Containing Materials

Compared with the traditional entrained flow gasifier, coal catalytic gasifier has the advantages of low reaction temperature, high production efficiency and low energy consumption, but it also has higher requirements for potash erosion resistance. Chromium-containing material is commonly used as lining material for gasification furnaces. In this paper, potash erosion resistance of chromium-containing raw materials and products were respectively researched by using powder tabletting sintering and potassium vapor erosion method. The potash erosion resistance are characterized by XRD and SEM. The study show that:(1)There are obvious potassium salt deposition on the surface of chromium-containing raw materials and products after potash erosion experiment. Potash reacts with chrome-corundum and magnesium-chrome spinel to form K2CrO4,and reacts with chromium oxide to form K2Cr2O7 at 750°C. (2)Potassium vapor enters into chromium-containing products through pores and leads to crack formation and volume change, which destroy the structure and reduce high temperature volume stability of material.

Application of Molten Salt Method in Hercynite Composite Powder Synthesis at Elevated Temperature

With molten salt method, a series of the hercynite powders were prepared using FeCl2·4H2O, active alumina and iron powder as raw material and KCl molten salt as reaction medium. The phase composition and micro-morphology were studied by techniques of XRD and SEM. The results showed that a high purity hercynite-alumina powder can be synthesized by molten salt synthesis method after heat treatment at 1000 °C in reducing atmosphere, the main phases were hercynite and α-Al2O3, and the increasing iron powder content can raise hercynite production quantity with developed crystal grain, the grain size was increased from 6μm to 10μm.

Effects of Matrix Densification Based on Particle Packing on Lightweight Al2O3-MgO Castables

The property of refractory matrix was dominated by both the maineral composition and particle packing behaviors. In this study, the theoretical packing density of refractory castables was calculated to design the particle size distribution (PSD) of its matrix. Four lightweight Al2O3-MgO castables with different matrix PSD (represented by q-value) were prepared and examined. Results show that a suitable q-value was needed to ensure acceptable properties including sintering characteristics, strength and slag resistance, which deteriorated distinctly at high q ( > 0.31). For the sample with q = 0.28, the matrix showed dense and uniform mirostructure, and the properties of castable reached a favorable compromise among sintering characteristics (apparent porosity = 14.8%, bulk density = 3.02g∙cm-3, permanent linear change < 0.6%), strength (cold modulus of rapture = 12.4MPa, cold crashing strength=155.5MPa), and resistance against both slag corrosion (Ic = 22.4%) and penetration (Ip = 11.5%). The sample with q = 0.25 showed the highest strength and resistance against slag corrosion, but its slag penetration resistance was lower due to the existence of cracks between aggregates and matrix.

Application of Electromagnetic Field Theory in the Study of Iron-Rich Slag Resistance Mechanism of Low Carbon MgO-C Refractories

Electromagnetic field (EMF) can promote the reaction between the Fe/Mn ion in slag and MgO-C refractories to form Mn-doped MgFe2O4 spinel. In order to further study the morphology and characteristics of Mn-doped MgFe2O4 spinel, the experiments were respectively carried out in medium-frequency induction furnace and resistance furnace. MgO-C refractories containing 6 wt.% carbon and iron-rich slag containing 53.62 wt.% Fe2O3 were used. The results show that the penetration layer in the slag line under EMF is obvious and the reduced Fe from FexO is distributed homogeneously in this layer. However in the resistance furnace having no EMF, there is not MgFe2O4 spinel but MgAl2O4 spinel formed. The iron content in Mn-doped MgFe2O4 spinels decrease dramatically from the erosion layer to penetration layer, while the manganese content in the spinel remains unchangeable.

The Influence of Thermal Radiation on Effective Thermal Conductivity in Porous Material

Effective thermal conductivity is an important parameter of porous materials for measurement of heat insulation performance. Two-dimensional geometrical models based on micrographs of real material were constructed in this paper and the finite element approach was applied for thermal analysis, the effective thermal conductivity was calculated. The influence of radiation heat transfer, temperature, and porosity on thermal conductivity were analyzed. The results show that conduction heat transfer plays an important role in total heat transfer and the influence of radiation heat transfer was small at low temperature. Because of the increase in radiation heat transfer, the temperature gradient decreased obviously at high temperature and the heat flux lines passed through the pores and became relatively smooth; thus the radiation heat transfer plays an important role in total heat transfer at high temperature and the influence of radiation heat transfer cannot be ignored. Thermal conductivity for a high porosity value will be greater than thermal conductivity for a low porosity value at high temperature. This paper provides guidance for predicting thermal conductivity and reducing the heat transfer efficiency of porous materials at high temperature.

Preparation and Properties of Low-Temperature Glaze Used in Coke Oven Cordierite Bricks

According to analyze service condition and extent of damage of cordierite bricks used in coke oven, the experiment was prepared by using spodumene powder, cordierite powder and fused silica as main starting materials, borax as the flux. The effect of borax on melting properties and thermal shock resistance of low-temperature glaze used in coke oven cordierite brick was investigated. The results showed that the melting temperature of glaze is close to the theoretical calculation, Seger formula can be equally applied to metallurgical industry. With the amount of borax increasing, the melting temperature of the glaze reduced. When the amount increased to 22%, borax dissolved in the mullite phase, which increased the content of glass phase in glaze. When the temperature is 1000°C, glaze layer formed and spreaded evenly on the surface of cordierite lining bricks and didn’t flowing. After five thermal shock, glazed surface didn’t appear crack, the requirements were achieved that glaze can be generated in the carbonization chamber temperature of coke oven without pre-firing. When the amount of borax continues to increase, the viscosity of glaze decreases, which results in flowing.

Crack Security Influence on Refractory Design with Thermo-Mechanical Stress

The fracture growth is one of primary causes which the refractory of ladle destroys. We have carried on the computation and the analysis to the ladle temperature field and the stress field coupling by he finite-element method. Attributes the crack state-of-art stress strain field using the J-integral, has established in the ladle refractory in the thermal load and under the molten steel load function its crack secure relations, and obtained the crack security change rule. These results have provided the support rationale to the equipment safe operation.

Simulation and Optimization of Melted Iron Desulfurization Process in Torpedo with Blowing Gas and Spray

According to the practical physical dimension and processing parameters of torpedo in a factory, Eulerian multiphase model was applied and adopting porous media model for the gas flow through the porous refractory, desulphurization process model was coupled, the desulphurization process of melted iron in torpedo with bottom blowing were computed using mathematical simulation approach, effect of bottom blowing technique was discussed. The results show that: Compared with the desulphurization behavior of melted iron in torpedo without bottom blowing, porous refractories were located at the bottom of torpedo in order to mixing melted iron by blowing gas, even using 30m3/h gas flow rate, desulphurizing result is improved. As the gas flow rate increased, the desulphurizing result become better. The desulphurizing result of bottom blowing between inlet and the end at the bottom of torpedo is better, especially the position of 2500mm. Blowing in 260s after the end of dust can avoid resulfuring and decrease sulfur content.

Numerical Simulation of Temperature Field and Thermal Shock Resistance Property of Permeable Brick

The temperature distribution of the permeable brick was modeled using CFX software. The influence of magnesia and corundum on thermal shock resistance of non-cement bonded alumina-based permeable brick was investigated. The results indicated that, in the gas blow process, the high temperature regions near the working face of the brick gradually expanded with the increase of the gas flow rate. Therefore the inner part of the brick had the complex and large change of thermal stress. Further experiments demonstrated that thermal shock resistance of alumina-magnesia based castable refractory was better than that of alumina-chrome based castable refractory. With the increase of magnesia amount, the alumina-magnesia based castable refractory had more cycles of heating and water-cooling. When different kinds of corundum were added in the raw materials, the sample with tabular corundum showed the best thermal shock resistance, the one with white fused corundum performed worse and the one with fused dense corundum performed worst.