Maintenance Technology And Practice Of Long Campaign For No.2 Blast Furnace(2nd Generation)in Baosteel

The longevity of blast furnace has enormous economic benefits and technical significance.Baosteel has broken the domestic longevity record in Baosteel No.2 BF(1st generation)and No.3 BF(1st generation)one after another.which represents inheritance and development of longevous technologies of large sized blast furnace in Baosteel.Since Baosteel No.2 BF(2nd generation)was put into production,engineers have summarized and extracted the longevous maintenance technologies and daily production practice systematically,scientific and effective longevous operation and maintenance integrated technologies for large sized BF was developed finally,which can be used for longevous maintenance reference for similar large sized BF.Corrosion mechanism of refractories,damage mechanism of cooler and heat transfer theory of flow of hot iron in hearth and bottom were studied and analyzed firstly,which can offer theoretical direction for BF’s longevous maintenance practice.Then the development and practice of fine operation on longevous technologies were introduced systematically in No.2 BF which include several main aspects as follows.Obey "beneficiated burden material"principle strictly,reduce detrimental elements charging;Adjust and optimize gas flow distribution,activate hearth behaviour;Form appropriate edge gas flow and decrease coal injection rate moderately to stabilize heat load of stack;Enhance management of tapping operation,stabilize taphole working condition,etc.Several longevous maintenance technologies were analyzed theoretically and summarized practically in the end.Such as maintenance law of iron ore titanium-bearing and reasons of unsatisfactory protecting performance;comprehensive measures about reducing circumferential molten iron flow erosion and improving heat transfer in hearth and activating hearth behaviour;The advantages and disadvantages of spray painting on stack,etc.The following conclusions were made.Obey "beneficiated burden material" principle strictly,enhance monitoring and management of the significant physicochemical indexes of the raw materials,especially chemical composition and particle size,etc.Reduce detrimental elements charging such as alkali metals and zinc,etc.Adjust and optimize gas flow distribution through comprehensive gas flow adjustment both at the stack and hearth.Strengthen central gas flow to activate hearth behaviour;Form appropriate edge gas flow to relieve the erosion to the liner of the stack;keep W value between 0.7 and 1.0 and maintain coal injection rate below 170kg/t to stabilize heat load of stack.Enhance fine management of tapping operation,pay attention to daily maintenance of taphole.keep taphole depth between 3.5 and 3.7 m and stabilize taphole working condition.In order to produce enough titaniferous compounds to shield the hearth,make sure that titanium content in molten iron should be above 0.1%when charging titanium ores to shield the hearth.But titanium ores may inactivate hearth behaviour and aggravate circumferential flow so that titaniferous compounds can not easily accumulate and settle down on the erosion position on the hearth.It can’t shield the hearth,on the contrary it worsen permeability and increase fuel consumption of BF.Therefore it is necessary to avoid using titanium ores as far as possible.Comprehensive measures have been taken,such as reducing smelting intensity appropriately;maintaining bottom temperature at high level;enhancing cooling intensity of hearth and hearth grouting and so on,so as to slow down circumferential molten iron flow erosion,improve heat transfer in hearth and activate hearth behaviour.The hearth sidewall erosion could be alleviated finally.Spraying painting on stack is a significant artificial lining method which can stabilize heat load of stack and improve gas utilization rate in a certain time.But due to the difficulty of reblowing and recovery process and the short duration of spraying painting effect,It depends on degree of corrosion of refractories whether choosing spray painting or not.Furthermore it would be best to combine spraying painting operation with intermediate repair plan.Stock level will be descended to tuyere level,so that checking in reblowing process could be avoided perfectly.