Numerical Investigation On Oxygen Coal Combustion Behavior In The Raceway Of Blast Furnace

At present,the blast furnace ironmaking is faced with some serious problems,such as,resource shortage,environmental pollution,and so on.Therefore,it is the development direction of the blast furnace to further increase the coal rate and decrease coke rate.To significantly increase the coal rate,the main issue to solve is the full combustion of coal particles in the raceway region.It is shown that oxygen-enrichment is one of the most effective method.The high oxygen-enrichment and full oxygen are the development trend of blast furnace.To further understand the effect of high oxygen-enrichment and full oxygen on coal combustion,the coal combustion in the raceway region under the high oxygen-enrichment and full oxygen is investigated using simulation method.In hot blast oxygen-enrichment way,the oxygen concentration around the coal particles increases slightly,and the coal burnout increases a little.For local oxygen-enrichment way,the room-temperature oxygen is injected into the blowpipe by some method.The local oxygen-enrichment way can significantly increases the oxygen content around the coal particles.However,the room-temperature oxygen has some adverse effect on coal combustion.Therefore,an appropriate local oxygen-enrichment way and amount is very important for coal combustion.Firstly,the coal combustion in the oxygen-coal lance is investigated.It shows that the room-temperature oxygen flowing from the annulus of the oxygen-coal lance increases the oxygen concentration around the coal particles,but limits the dispersion and devolatilizations of coal particles.When the oxygen-enrichment amount by oxygen-coal lance is 2%,the coal burnout reaches the maximum with an increase of 2.17%.However,when the oxygen-enrichment amount is 6%,the coal burnout has a decrease of 5.74%.Furthermore,the coal combustion is investigated under different arrangements of two oxygen-coal lances.It is shown that the coal burnout has an obvious increase under eccentric double oxygen-coal lance.When the intersection angle is 40° and the oxygen-enrichment amount is 2%,the coal burnout increases the most with an increase of 12.51%.Secondly,the coal combustion under oxygen coal double lance is investigated.The room-temperature oxygen is injected by an alone lance.The effect of oxygen stream on the coal particles dispersion is avoided,and the cooling effect of room-temperature oxygen decreases.It is shown that the coal burnout further increases by rising the coal lance or reducing the oxygen lance.When the coal lance rise 15 mm and the oxygen amount is 3%,the coal burnout reaches the maximum with an increase of 12.79%.If some oxygen is injected in hot oxygen-enrichment and the remain oxygen is injected by oxygen lance,the coal burnout will further increase.The coal burnout has an increase of 14.52%under 4%oxygen-enrichment amount by hot air and 2%oxygen-enrichment amount by oxygen lance.Thirdly,the coal combustion behavior under oxygen blast furnace is investigated.In oxygen blast furnace the room-temperature oxygen is injected,and the preheated top gas with CO2 stripped is recycled into the furnace.The coal combustion behavior under the base case is investgated.The oxygen concentration of base case is 90%,and the recycled gas temperature is 900?.It is shown that the coal burnout of base case increased by 16.1%compared to that of traditional blast furnace.On this foundation,the effect of oxygen content,oxygen temperature,recycled gas temperature,and so on,on coal combustion is investigated.It is shown that the coal burnout increases with the increase of oxygen content.When the oxygen content is 100%,the coal burnout has an increase of 18.6%compared to that of traditional blast furnace.Furthermore,the coal burnout increases with increase of recycled gas temperature.Finally,the coal flow and combustion behavior in the raceway and coke bed is investigated.Furthermore,the characteristic of gas temperature and content is investigated.It is shown that the coal particles mainly flow along the horizontal direction,and the phenomenon becomes more obvious with increase of the coal particles diameter.