Development and Application of Multi-phase Nitrides Bonded Silicon Carbide Lintel Blocks for Dry Quenching Furnaces

Multi-phase nitrides bonded silicon carbide lintel blocks were prepared using industrial SiC(SiC≥98 mass%,3-0.5,≤0.5 and≤0.044 mm),Si powder(Si≥98 mass%,≤0.044 mm),and SiO2 micropowder(SiO2≥96 mass%,d50=0.15 pm)as raw materials,and calcium lignosulfonate as the additive,batching,mixing,and molding on a vibration pressure molding machine,drying and then firing at 1420℃for 10 h in high-purity N2.The apparent porosity,the bulk density,the cold modulus of rupture,the hot modulus of rupture,and the linear expansion coefficient of the samples were tested.The phase composition and the microstructure of the samples at different nitriding depths(50,100,and 150 mm)were analyzed by XRD and SEM.The field application effects of the blocks were studied.The results show that:(1)the multi-phase nitrides bonded silicon carbide refractories can dynamically adjust their own phase composition and minimize structural and thermal stresses,improving the service life of key parts of dry quenching furnaces;(2)calcium lignosulfonate can improve the nitriding micro-environment of multi-phase nitrides bonded silicon carbide lintel blocks,successfully increasing the effective nitriding thickness of the blocks to 300 mm;(3)Sinosteel LI RR provides a unique concept in the design of materials and block types as well as the stable and scientific overall structure,promoting the industrialization process of dry quenching furnaces with long service life in China.

Application of Mullite Composite Lining Plates in Rotary Coke Tanks for Coke Dry Quenching Equipment

To reduce the burning loss and the spalling and to improve energy efficiency,the mullite composite lining plates were used to replace cast steel or alloy lining in rotary coke tanks for coke dry quenching equipment.The results show that:the dense mullite composite lining plate in the cone part has the density of 2.20 g·cm^(-3) and the wear test,s volume loss of 4.08 cm^(3),and the light weight mullite composite lining plate in the straight cylinder part has the density of 1.95 g·cm^(-3) and the wear test,s volume loss of 17.6 cm^(3).After using,there is no shrinkage gap,no burn loss or holes in the plates,indicating good sealing of the mullite composite lining plates.The lining plate for the cone part has low burning loss,without spalling for more than half a year.The outer surface temperature of coke tanks adopting the cast steel or the alloy lining is 480 to 570℃,while that of the ones adopting mullite composite lining plates is 120 to 170℃,showing a largely improved insulating property.Adopting mullite composite lining plates on the basis of the current coke tank cage,the lining plates can be timely treated and wholly replaced,improving the service life and reducing the maintenance workload.

Steel Fiber Toughening Mullite-SiC Castables for Coke Dry Quenching Furnace Corbel Pillar

The mullite-SiC castables for coke dry quenching（CDQ）furnace corbel pillar were prepared by taking mullite and silicon carbide as aggregates,silicon carbide powder,fused silica powder,α-Al2O3powder and silica fume as matrix,calcium aluminate cement as binding system,and extra-adding steel fibers to extend the CDQ furnace refractory life.The effects of steel fiber types（melt pumping meniscus,cut straight,wavy indentation,cold-drawn hook）and steel fiber extra-additions（0,1%,2%,3%by volume）on the properties of mullite-SiC castables were investigated.Then the toughening mechanism of steel fiber in the castables was analyzed according to the load-displacement curves.The results show that：（1）the toughening effects of the melt pumping meniscus steel fiber with rough surface and colddrawn hook steel fiber with strong anchoring effect with the matrix are better than those of cut straight steel fiber and wavy indentation steel fiber;（2）the suitable amount of steel fiber（less than 2%）in mullite-SiC castables not only significantly improves the mechanical properties,thermal shock resistance and wearing resistance,but also improves the fracture energy by 49.0%and slows the crack growth;（3）the bond strength and mechanical anchoring force between steel fiber and castable interface are key elements of steel fiber reinforced castables.

Research and Application of Wear Resistant Refractories for Cooling Zone of Large Scale Coke Dry Quenching Ovens

In order to prolong the service life of the cooling zone of large scale coke dry quenching ovens,six kinds possible refractories for the cooling zone of large scale coke dry quenching ovens： SiC containing brick A,SiC containing brick B,mullite-andalusite brick,spinel containing brick,zirconia containing brick,corundum-mullite brick and grade B mullite brick,were analyzed in properties. It is found that the cooling zone lining adopting SiC containing bricks or mullite-andalusite bricks has much longer service life. Based on this,a new type of wear resistant brick was developed. The brick has a compressive strength of 135 MPa,a wear loss of 2. 10cm^3（only a quarter of that of the grade B mullite brick）,and a higher bulk density than the grade B mullite brick. The application of the brick in a 140t·h^（-1）coke dry quenching oven showed that it performed better than the grade B mullite brick. The cooling zone adopting the new bricks has a lower coke discharging temperature,which is beneficial to the enhancement of heat recovery efficiency and steam power generation.

Mathematical Model for Fluid Flow and Heat Transfer in the Cooling Shaft of Coke Dry Quenching Unit

A mathematical model based on non-Darcian flow and two-phase model is developed for fluid flow and heat transfer in the cooling shaft of Coke Dry Quenching (CDQ) unit. The potential flow model is employed to simulate coke descending. Governing equations are solved by the SIMPLE algorithm on the collocated, non-orthogonal and body-fitted grids. The velocity of circulating gas and the temperature of coke and gas are obtained to study the effects of coke size distribution on flow and heat transfer behavior in the cooling shaft. It is found that the non-uniformity of gas velocity and the unevenness of coke temperature in the radial direction can be reduced if coke size distribution is improved. The gas velocity field and the temperature distribution of coke and gas are presented.

Numerical and experimental study on coke size distribution in bell-type charging in the CDQ shaft

The mechanism of coke size segregation in the radial direction of pre-chamber in coke dry quenching （CDQ） shaft was investigated by experiment and numerical analysis. The experimental apparatus was a cold three-dimensional semicircle model for bell-type charging, which was used to study the influences of different kinds of bells and different stock line levels on the radial distribution of coke size in the radial direction of a pre-chamber. A mathematical model was used, which is capable of estimating the radial average size distribution as well as the radial deposit distribution of each particle size for multiple size coke with a few fixed parameters. The calculated results agree well with the experimental data, which proves the reliability of both experimental study and numerical analysis.

SAIL—striding towards the future with the touch of green

Steel plays a vital role in every facet of our life.Like DNA in our body,steel plays a crucial role in the development of any society.From infrastructure,defence,transportation,research & development and even in day to day life,everywhere steel is used.Per capita consumption of steel is treated as an important index for the socioeconomic development of any country.The rapid and continuing growth of steel industry during last few decades bears testimony to the indispensability of steel as a vital resource for economic development.Though steel as a product is eco friendly,the process of making steel is associated with lot of energy and environmental ramifications.According to International Energy Outlook 2009,iron and steel industry account for about 20%of the total industrial energy consumption.Hence this industrial sector can play a pivotal role to influence the energy and environmental scenario of any country. As a responsible corporate citizen,Steel Authority of India Limited,the largest steel producer in India,has taken various initiatives over the years towards the protection of environment and reduction in energy consumption.This has resulted in the reduction of energy consumption by almost 15.45%over a period of last 10 years.The initiative is also evident in the company's growth plan which aims at almost doubling the production capacity in the near future from the existing level of 13.5 Mt/a.Implementation of tate of it lean echnologies like CDQ,TRT,and waste heat recovery from sinter plants,maximizing CDI & CTI in blast furnaces,augmentation of pollution control devices with more efficient equipment are on the anvil.These reaffirm our commitments for clean and sustainable environment. This paper gives an overview of the efforts taken by SAIL over the years for energy conservation and environmental protection with special emphasis on a few projects like by product fuel for power generation,use of energy efficient burners,maximizing the use of thyristors in place of motor generators,coke dry quenching facility, etc.

Optimization and Simulation of Inclined Channel Area Lining for CDQ Ovens

The mechanical force borne by the lintel and“brackets”in the inclined channel area of CDQ and the thermal stress generated by the top-down temperature gradient were simulated by ANSYS software.The following conclusions are drawn.(1)The mechanical force has very mild effect on the damage of the“brackets”.(2)The temperature gradient caused by the uneven temperature distribution of CDQ oven is the key factor affecting the“bracket”damage.The different expansion of refractory materials in various parts results in the thermal stress concentration which tears the“brackets”.(3)The structure adjustment of the“brackets”has very little effect on the thermal stress distribution.(4)The multi-phase nitride bonded silicon carbide for CDQ can effectively alleviate the stress concentration at the“brackets”,realizing the long-life and stable operation.