Quicklime is an essential reducing agent in the steel smelting process and its calcination from limestone is accompanied by considerable energy consumption. As a relatively economical lime kiln, the Parallel Flow Regenerative (PFR) lime kiln is used as the main equipment for the production of quicklime by various steel industries. PFR lime kilns generally use natural gas as the fuel gas. Although natural gas has a high calorific value and is effective in calcination, with the increasing price of natural gas and the pressure saves energy and protect the environment, it makes sense of exploring the use of cleaner energy sources or other sub-products as fuel gas. The use of blast furnace gas (BFG) as a low calorific value fuel gas produced in the steel smelting process has been of interest. This paper therefore develops a set of mathematical models for gas-solid heat transfer and limestone decomposition based on a Porous Medium Model (PMM) and a Shrinking Core Model (SCM) to numerically simulate a PFR lime kiln using BFG in order to investigate the feasibility of calcining limestone with low calorific fuel gas and to provide a valuable reference for future development of such processes and the kiln structure improvement.

Limestone of different particle sizes is often calcined together to improve production efficiency, but the calcination effect of mixed particle size limestone is difficult to guarantee. To investigate the effect of different particle size combinations on calcination, this study uses a porous media model and a shrinking core model to simulate the calcination process for a single particle size and two mixed particle sizes in a Parallel Flow Regenerative lime kiln (PFR lime kiln). The results of the study show that an increase in void fraction has a small effect on the gas temperature. The temperature also does not change with particle sizes. At the same time, the decomposition is poor near the wall and better the closer to the center of the calcination zone. In addition, when the particle sizes differ by 2 times, the decomposition of small limestone particles had less influence, and the decomposition of large particles was also better. When the particle sizes differ by 3 times, the decomposition of both limestone sizes is more affected, especially for the larger limestone size, where only the outer surface is involved in the decomposition.

As an excellent reducing agent, lime has an important role in the steel production process. Annular Shaft Kiln (ASK) has been widely used in the lime production industry for its low cost, low footprint, high chemical activity, easy construction, and easy maintenance. Due to the high temperature generated inside ASK during operation, it is hard to observe the limestone decomposition process and the field distribution in the lime kiln. The simulation analysis of temperature field, velocity field and decomposition field in the limestone calcination process by CFD provides practical guidance for future lime product quality control, ASK design and operation parameters’ control. This study is based on an ASK that was put into production. Based on the finite volume method, this paper combines the porous medium model and the shrinking core model to establish a set of mathematical models that can describe the temperature and flow field distribution inside the ASK, as well as the limestone decomposition process and the heat and mass transfer process inside the ASK. According to the feedback from the production site, the mathematical model is in good agreement with the production results.

The arc furnace is an important equipment in the production of manganese ferroalloys. In the smelting process, it produces high temperature flue gas above 700 K, which has high utilization value. During the pelleting process, moisture exists on the surface and inside of the pellets, which, if directly fed into the arc furnace, will lower the temperature of the furnace, affecting the production, and will also cause the pellets to burst, resulting in pressure fluctuations in the furnace and other hazards. The preheating shaft kiln reduces the moisture content of the pellet while preheating the pellet by utilizing high temperature flue gas. In this paper, through the establishment of porous media and shrinking core coupling mathematical model, to achieve the prediction of the heating and drying process of the pellets of various particle sizes, which is in good agreement with the production monitoring data. The results show that 9~11 mm pellets have the best preheating effect in terms of tail gas temperature, pellet temperature and preheating time.

Shallow geothermal energy refers to geothermal resources within 200 m below the surface, which has the advantages of stable temperature, strong sustainability, environmental protection and economy, and has been widely used by residents in various regions since ancient times. With the acceleration of industrialization and urbanization and the further expansion of human demand for energy, the development and utilization of shallow geothermal energy has gradually moved from the surface to the deep. In this process, researchers have conducted in-depth research on geothermal energy heat exchange equipment, temperature measurement and other technologies, and introduced artificial intelligence to predict underground temperature and humidity, and made a lot of progress. Focusing on the ground source side of shallow geothermal energy, this paper comprehensively expounds the research progress in the past 10 years from the aspects of the observability of geothermal energy utilization, the thermal response testing technology of buried pipe, the heat transfer model and the application of artificial intelligence, summarizes the difficulties at this stage, and points out the direction of future solutions.

As an essential slagging raw material in blast furnace ironmaking, quicklime, which requires high chemical activity, is produced in parallel flow regenerative (PFR) lime kilns. The PFR lime kiln supports a wide range of fuels and can calcine a wide range of particle sizes while maintaining a high reactivity, which enhances the high temperature hard-burnt issue caused by rotary kilns. In this study, the bed porosity under dual sizes structure has been obtained with the help of discrete element model based on porous medium model, and the distribution of gas-solid temperature and decomposition rate in dual sizes PFR lime kiln under the condition of low grade fuel has been simulated by numerical method, and the accuracy of the model has been verified by the monitoring data of control system. The results showed that calcination with 100+30 mm dual sizes improved the production efficiency compared to single sizes.