Changes in Microstructure and Chemical Composition of Deadman Coke of a 2800 m³ Industrial Blast Furnace

Abstract

The paper examined the changes in microstructure and inorganic elements in their true mineral forms of the coke samples from various hearth locations using X-ray diffraction (XRD) and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) after the blow out and cool down of a 2 800 m 3 industrial blast furnace. The results illustrate that all deadman coke samples from fines to lumps were confirmed to be highly graphitized. Furthermore, the deadman coke was filled up with the accumulated KAlSiO 4 during its descent process and the blast furnace slag which consisted of Ca 2 MgSi 2 O 7 -Ca 2 Al 2 SiO 7 system and Ca 2 ZnSi 2 O 7 phases. Besides the slag phases, the iron was also observed in the deadman coke soaked in the iron layer. Those cause that the mass of the deadman coke is about 1.62-2.82 times larger than that of the feed coke under the same conditions. Thus it may make the deadman which was designed to float sit on the hearth bottom as the permeation of the slag and the liquid iron into the deadman coke was not taken into consideration during the design process. We concluded that the slag phase below the taphole level is primarily derived from the blast furnace slag. Moreover, the deadman coke carrying final slag may come in contact with the hearth bottom and react with ceramic pad or carbon brick with a sitting deadman, thereby it results in degrading the hearth lining. Meanwhile, the slag phases below the taphole level can provide the material for the formation of skull to protect the hearth lining.

Analysis of the Coke Particle Size Distribution and Porosity of Deadman Based on Blast Furnace Hearth Dissection

“…Previous studies on hearth coke behaviors have focused on coke graphitization, mineral transformation, mineral yield, open porosity and microstructure, etc., through the dissection of furnace after blow-out. [10][11][12][13][14] Although the information of the particle size distribution of deadman coke and deadman porosity is critical for understanding the blast furnace hearth phenomenon, the relevant study is rare and insufficient. Jiao et al investigated the mean size of hearth coke using image-processing technique and found the hearth coke size was about 32 mm-34 mm.…”

Microstructure and Phase of Carbon Brick and Protective Layer of a 2800 m³ Industrial Blast Furnace Hearth

“…The KAlSiO 4 observed in the skull may be attributed to the fact that KAlSiO 4 deposited in the deadman coke enters into the blast furnace slag with the dissolution of coke carbon into hot metal. 30)…”

“…Then the blast furnace slag that penetrated into the pores of the coke is also brought into the salamander indirectly. 30) With the dissolution of deadman coke into hot metal, the blast furnace slag in the deadman coke is exposed and attached to the hot surface of the carbon brick below the taphole level under the suitable conditions to form skull, protecting blast furnace linings from erosion. 30) Accordingly, the Ca 2 Al 2 SiO 7 and Ca 2 MgSi 2 O 7 in the skull are derived from blast furnace slag in deadman coke, rather than the ash in the feed coke.…”

“…Position The relevant parameters of the studied blast furnace have been described in detail in our previous work. 30) The furnace bottom was lined with semi-graphite carbon brick, micro porous carbon brick and ceramic pad from bottom to top, as shown in Fig. 1 (a).…”

Coke Microstructure and Graphitization Across the Hearth Deadman Regions in a Commercial Blast Furnace

“…Meanwhile, the coke in the iron layer below the taphole centerline and the interaction between coke and hot metal was not studied. Niu et al 11) studied the coke mineral phase and the microstructure of hearth deadman coke in a blast furnace hearth. They thought that the final slag can permeate into the coke pores and react with coke minerals.…”