China's Refractories

Regenerator checkerwork for glass melting furnaces should have high resistance against thermal stress and chemical attack, high mechanical stability, high efficiency to recover the heat from waste gas and low tendency for clogging. This article reviews the innovation of the regenerator checkerwork from the past decades. The state of the art for optimised material choice and optimised checker shapes will be reported.

A new type of magnesia spinel brick containing a novel flexibilizer was developed. The publication presents an investigation on its chemical composition, physical properties and cement clinker resistance. Compared to conventional magnesia spinel bricks, the new brick type shows reduced amounts of alumina, significantly improved hot properties and resistance against cement clinker attack whilst keeping its textural flexibility on the same level. Field trials revealed satisfactory results and confirmed the novel flexibilizer concept.

Mega trends like urbanization, industrialization and growing population drive the demand of daily necessaries and therefore result in increased refractory consumption for waste treatment carried out at elevated temperatures. It is estimated that for burning 1 t of waste about 5.5 kg of refractory materials need to be consumed. In the present study, the corrosion resistance of refractory bricks based on alumina-chromia and alumina-silica was tested by exposing them to slag from hazardous waste incineration. Samples from the cup test were investigated macroscopically and mineralogically. They showed that alumina-chromia bricks had high corrosion resistance when in contact with the tested slags, while alumina-silica bricks containing silicon carbide showed an overall good performance.

Copper smelting furnaces are typically lined with magnesia-chromite refractories, which are exposed to multiple and complex stresses. The selection of the processing route, furnace type, and slag system is dictated by the specific ore type available; which will determine the individual refractory wear. This paper evaluates the common refractory wear mechanisms as observed in the copper Peirce-Smith converter and in the copper anode furnace. The chemical factors include corrosion caused by fayalite type slag and sulphur supply, as well as by Cu-oxide attack. Changes in the temperature during the furnace operation (thermal shock) create stresses in the brick lining which can only be absorbed to a limited extent. Mechanical factors include erosion, caused primarily by the movement of the metal bath, slag and charging material, as well as stresses in the brickwork due to punching. Finally, improper lining procedures can also affect the service life. All these wear parameters lead to severe degeneration of the brick microstructure and a decreased lining life, and in the worst case overheated furnace structures and possibly dangerous hot spots or even breakouts. Therefore, a detailed investigation and understanding of the wear mechanisms through “post-mortem studies” together with thermochemical calculations by FactSage ^TM software is an important prerequisite for the refractory producer. Based on these research results, combined with specific process knowledge, appropriate brick lining solutions for copper processing furnaces can be recommended. In addition to the described efforts to investigate refractory wear and optimise lining qualities, it is also essential to monitor the process and the effect on the refractories to further improve both safety and process. For this purpose, technologies using sensors and novel digital solutions can be applied.

Since early 2020 RHI Magnesita has been running a fully integrated dolomite plant in Chizhou, Anhui Province, P. R. China. The current operation consists of a world-class dolomite mine including a state-of-the art sinter plant equipped with rotary kiln plus a plant where shaped and unshaped doloma products are being manufactured. As raw dolomite has been a technically usable carbonate rock for decades the article describes the way from raw dolomite stone to doloma production.

The article focuses on the influence of operator and process safety and the trends of robotics and digitalisation on a ladle slide gate that was introduced to the market 6 years ago^[1]. After more than 50 installations, customer experience was gathered and new features were added to a system upgrade. These upgrades are related to safety, ease of operation, and low operational costs. Especially a newly introduced “open check” feature increases the confidence level of the operators and can boost performance. With growing requirements to increase safety for people and processes in the ladle preparation area and on the continuous casting floor, automation has become increasingly important in steel plants. A slide gate prototype is currently underway to launch an innovative new gate design striving for full automation. Several critical process steps are already available and successfully used in the steel plants, such as cylinder connection, slag detection integration, and ladle gate preparation area automation. Fully automated operation will be followed by digitalisation, allowing for tracking of performance, safety, and quality. This paper summarises new features available for slide gates and outlines individual initiatives towards fully automated operation and data acquisition examples of digitalisation.

Ladle shrouds (LS) and submerged entry nozzles (SEN) are flow control products used in continuous casting which transfer the liquid steel from the ladle to the tundish and further to the mould. Due to the strongly different and quickly changing temperature conditions before and during steel casting, highly thermal shock resistant refractory materials are required which simultaneously save steel process energy. A new technology embeds a special liner into the refractory body inner surface to reduce the heat transfer through the LS/SEN wall. To better understand the function of this insulation layer a mathematical model was applied. Temperature measurements carried out in the steel plant were compared with the simulation results. The research results indicate potential heat loss reduction and performance improvements in the steelmaking process.

Argon addition into the casting channel reduces the amount of clogging on the refractory wall to allow long sequence casting of aluminium-killed steel grades. The key to minimum surface defects on the final product is to establish the optimum quantity by optimising the gas distribution below the stopper nose. This is achieved by new argon stopper technology which supports low gas quantities with homogeneous gas and bubble distributions to float non-metallic inclusions (NMI) in the continuous casting mould.

Fluid flow in the mold has a significant impact on the quality of continuously cast steel products. Since it is strongly influenced by the SEN design, attention has to be paid on its geometry. In this paper the main principles of a novel SEN type will be described. Water modeling and Computational Fluid Dynamics (CFD) are applied to characterize the flow pattern under different conditions. Furthermore, the interaction with electromagnetic stirring (M-EMS) is analyzed by means of a liquid melt model. Finally, actual steel plant performance data and observations are discussed.

In the continuous casting process of aluminum killed steel grades, nozzle clogging is a common problem. Argon is usually injected into the casting channel through stoppers or nozzles to minimize clogs; however, complex two-phase flow regimes appear, and the flow in the mold might deteriorate. This could result in a higher defect rate in the cast product and should be avoided as much as possible. Therefore, it is important to understand the interaction between process conditions and the refractory products used and their impact on the flow pattern in the mold. In this study, a full-scale water model was established to simulate the slab casting process. Three nozzle shapes and three immersion depths were applied to investigate the flow behavior and liquid level fluctuations by the full-scale water model. The relationship between the flow behavior and continuous casting parameters was evaluated. The results provide guidance for the design and production of the refractory nozzle and the operation of the continuous casting plant.