Improvements And Production Practices Of Hot Blast System In No.2 Blast Furnaces Of SHAGANG

In the production of blast furnace,the operation of high air temperature has become the goal that operators pursued for.It is an important measure that not only to reduce coke,increase production and improve the quality of pig iron,but also to improve the combustion rate of injected fuel,improve the effect of injection and provide favorable conditions for increasing the amount of coal injection.No.2 blast furnace of SHAGANG was put into production in 2004.It has three improved high-temperature and long-life internal combustion hot blast furnaces.Since 2015,the hot blast system has experienced such phenomena as high pipeline temperature,brick dropping at the hot blast outlet,inclined partition wall,reduced heat transfer efficiency of the heat exchanger,and gas leakage at the air inlet device,which have severely restricted the use level of the blast furnace air temperature and also brought significant safety hazards to production.In order to ensure the safety and the optimization of production indexes,the ironmaking plant has organized scientific and technical personnel to solve the above problems for many times.This work makes an in-depth analysis of the problems encountered by hot blast system of No.2 blast furnace in recent years.It analyzes and studies the influencing factors,emergency treatment measures,equipment transformation,system optimization and other aspects.Through specific production practices,some conclusions are drawn,and the main results are as follows:(1)The problems of damage and falling off of refractory materials and excessive surface temperature are mainly caused by the expansion and contraction of refractory materials or the local displacement of hot blast pipe,resulting in cracks or partial detachment of refractory materials.Pipe production grouting,excavation and other measures have been taken during production to alleviate the phenomenon of high surface temperature,but these measures cannot fundamentally solve the problem.(2)Through the analysis of the force of the pipe system,the structural design problem of hot blast pipe system of SHAGANG NO.2 blast furnace was found.Through improving the design of tubular refractories and steel structures,the original design defects were eliminated by eliminating expansion joints at the lower part of the original pipeline,redesigning expansion joints,adding special-shaped bricks,reasonably configuring types of resistant materials and other measures,which provided a foundation for the application of high air temperature.After modification,hot blast stove pipe surface temperature is generally fall below 100?;the fluctuation state of the main and branch pipes junctions was eliminated,and the problem of excessive temperature,redness,deformation and cracking of the three-mouth pipe shell was solved.(3)The problems of high temperature of the local steel shell,difficulty in improving air temperature,decreasing arch temperature at the end of air supply,collapse of hot blast outlet and so on in hot blast furnace are analyzed.The main reasons are considered as follows:over burning of grate and short circuit at the lower part of burner;there are different degrees of peeling of the upper lattice brick;gas leakage occurs through short circuit location,etc.The above problems are solved by filling the gap with the castable,adding steel plate lining to the pipes and grouting the gaps.In addition,strengthen the quantitative analysis of exhaust gas and temperature monitoring.Through the above measures to ensure the normal production of hot blast furnace,eliminate the potential safety hazards.(4)The characteristics of the hot blast outlet collapse position of the hot blast stove were analyzed.It was concluded that the hot blast branch pipe is deep into the furnace,which is difficult to maintain,so the hot construction(casting)method was selected for the hot blast outlet pouring operation.The treatment practice of NO.2 and 3 hot blast stoves showed that no further collapse of hot blast furnaces has occurred.The temperature of the steel shell at the hot blast outlet is stable at 160?.(5)Through the implementation of BCS(Boiler Optimization Control Technology)and waste gas heat recovery technology,the hot gas stove combustion gas and combustion air preheating,and fully automatic optimization of the furnace are realized,and the self-control rate reaches 90%.Above,the gas is saved by 2%or more at the same air supply temperature,the furnace time is shortened.(6)In order to ensure the anterograde and efficient production of the blast furnace,a top combustion stove was designed and built to avoid the problem of long-term low air temperature operation caused by blast furnace repair.The new hot blast stove has a simple and the system layout of the new and old hot blast furnace is fully considered in the design,so as to benefit the old as much as possible.It realizes the docking optimization of the new pipe and the original pipe system,saves investment and reduces the blast furnace off time.Adopting stable and reliable hot blast pipe system compensation and material resistant structure technology,high degree of automation,perfect safety equipment,is conducive to saving gas consumption The installation and masonry of the new hot blast stove are implemented in accordance with strict construction standards and procedures to ensure the construction quality of the new furnace.(7)Through adding a new hot blast stove the air temperature is raised to 1180?,which creates favorable conditions for efficient production of the blast furnace.Through the production practice research in this paper,the new hot blast stove can effectively improve the collapse and damage of the hot blast stove in the later stage of life,and at the same time,without affecting the blast furnace production situation,the hot blast system is upgraded,and it is also expected to provide useful reference for the production and operation of SHAGANG and domestic similar hot blast stove in the future.