Effect of MgO Content on Heat Capacity of Synthetic BF Slag and Heat Release Behavior during Cooling Process

The differential scanning calorimetry (DSC) sapphire analysis was used to measure the specific heat capacity of the BF (BF) slag and observe the CaO-SiO2-MgO-Al2O3-TiO2 5-element slag system with the binary basicity fixed at 1.17. The specific heat capacity of the BF slag and the cooling heat distribution were obtained during the cooling process when the MgO content changing from 7% to 11%. The results showed that the heat released of BF slag was more than 1.2 GJ/ton during the cooling process from 1400 °C to 35 °C, of which the sensible heat was dominant. At MgO content of 9%, the latent heat of crystallization is maximum. The cooling and heat release law of BF slag is directly associated with the phase precipitated in slag cooling and micromorphology.

Process Concept for the Dry Recovery of Thermal Energy of Liquid Ferrous Slags

Slags are valuable by-products of iron- and steelmaking processes. Their efficient reutilization and the recuperation of their thermal energy are key for improving the overall efficiency of these processes. With the innovative approach presented in this work, it is possible to recover thermal heat from liquid slags. The process concept consists of a slag tundish and four subsequent heat exchangers. The liquid slag is poured into the slag tundish which homogenizes the slag and guarantees a constant mass flow. The heat exchangers extract thermal energy from the slag and transfer it to water or oil. The first module cools the slag from the tapping temperature of about 1500 °C down to 850 °C. Inside the second module, more thermal energy is gathered from the already solidified slag cooling the slag down to ambient temperature. The captured energy can be used for various processes, such as gas preheating or generation of steam. The solidified slag is volume stable and forms amorphous phases, depending on its basicity. The process was designed, and the concept was tested on lab-scale demonstrators with an overall heat recovery rate of 42%. Some applications of the recovered slag heat are also presented in this work. Graphical Abstract Scheme of the process concept with the three heat exchangers and buffer unit.

Effect of Cooling Rate on Crystallization Behavior of CaO-SiO2-MgO-Cr2O3 Based Slag

In order to improve the recycling efficiency of stainless-steel slag resources, the effect of different cooling rates on the crystallization behavior of CaO-SiO2-MgO-Cr2O3 based system was studied by using FactSage 7.1, XRD, SEM and IPP 6.0. The results indicated that the spinel is a high-temperature precipitated phase and the cooling rate had less effect on the final grain size of spinel crystals, but had greater influences on the nucleation of spinel crystals and the crystallization of silicates such as α-C2S.When the cooling rate was 12∘C/min, the spinel crystals was the unique precipitation. However, the spinel crystals and α-C2S could produce during the slag cooling process as the cooling rate was1∘C/min. Chromium in silicate phase is inclinable to leaching with the dissolution of silicate phase, so the formation of silicate phase should be controlled. According to the influence of the cooling rate on the formation of spinel crystals and the erosion of spinel crystals by α-C2S, it is suggested that the cooling rate of the stainless-steel slag in industrial treatment should not be lower than 12∘C/min.

The effect of primary copper slag cooling rate on the copper valorization in the flotation process

Technological procedure of slow cooling slag from primary copper production is applied in the purpose of copper recovery in the level of 98.5% to blister. This technological procedure is divided into two phases, first slow cooling of slag on the air for 24 hours, and then accelerated cooling with water for 48 hours. Within the research following methods were used: calculation of nonstationary slag cooling, verification of the calculation using computer simulation of slag cooling in the software package COMSOL Multiphysics and experimental verification of simulation results. After testing of the experimentally gained samples of slowly cooled slag it was found that this technological procedure gives the best results in promoting growth or coagulation of dispersed particles of copper sulfide and copper in the slag, thereby increasing the utilization of the flotation process with a decrease of copper losses through very fine particles.

A Design of Pyrolysis Test System Based on the Co-Processing of Municipal Waste with Rotary Klin

A novel and improved waste pyrolysis test system is developed by process design, pyrolysis host type design and the corresponding counterpart type design. It contains the design of waste pyrolysis pretreatment device, the sealing feeding device, the pyrolysis slag cooling device, the high temperature pyrolysis gas dust removal device and the pyrolysis gas desulfurization dust removal device. This study proposes a good testing model and a production validation on waste combustion under the oxygen-free and high-temperature condition. Thus it offers an effective technical support and guidance on improving the utilization of waste calorific value and preventing the generation of dioxin.