During the sintering process, the purpose of the ignition is to supply a certain amount of heat to the surface layer of the mixture, so that the solid fuel therein is ignited and burned, and the surface layer mixture is sintered under the action of the high temperature flue gas and the carbon combustion heat release of the ignition furnace, and the surface layer is accumulated. The heat is transferred to the next layer of the mixture to burn the next layer of solid fuel.
(1) Ignition temperature
The firing temperature depends mainly on the melting temperature of the sintered product, due to sintering of iron ore, various molten eutectic temperature of the mixture is between 1030 ~ 1220 ℃, so little sintering temperature difference ignition, typically 1050 Fluctuations between ~1250 °C. For thick layer operation and low temperature sintering process, the lower limit should be taken; for thin layer operation and high temperature "melt" sintering process, the upper limit should be taken.
(2) Ignition time
Theoretically, the ignition time refers to the time when the material surface passes through a certain temperature zone. Some people set the temperature above 1100 °C, and some people have set it above 1000 °C. Since the coke powder is heated to about 700 °C, it starts to burn. Therefore, the ignition furnace The design generally stipulates that the residence time of the mixture in the ignition section is the ignition time. In a certain temperature range, the ignition time is related to the ignition temperature, that is, to the total heat supplied during ignition. Coal low heat value gas, combustion flame temperature is low, the ignition timing needs to be longer. Under normal circumstances, the ignition time is 0.8 ~ 1.2min.
(3) Oxidizing atmosphere of ignition
Increasing the oxygen content of the flue gas ensures that the surface solid fuel is fully combusted, which not only improves the fuel utilization rate, but also improves the quality of the surface sinter. According to the experience of the former Soviet Union, for the traditional ignition process, the oxygen content in the flue gas increased by 1%, the utilization factor of the sintering machine increased by 0.5%, and the solid fuel consumption decreased by 0.3 kg/t.
For the strip flame direct ignition technology actively promoted in the past ten years, since the width of the flame zone is narrow and the passage time of the material layer is short, the combustion temperature of the flame zone is required to be as high as possible. If the excess air volume is increased, The combustion temperature is low and ignition is difficult. Therefore, in addition to the high calorific value of natural gas or coke oven gas, the excess air coefficient can be slightly increased. For a mixed gas with a low calorific value and a wide range of applications, the excess air ratio can only be maintained at about 1.05 to 1.1, if hot air is not used. The role of the oxidizing atmosphere of the flue gas is difficult to reflect.
(4) After the ignition, the high temperature material surface of the ignition section is insulated , and the surface solid fuel is not completely burned and extinguished due to the large amount of heat radiated to the environment having the black body nature and the quenching effect of the inhaled ambient air, which not only reduces the fuel but also reduces the fuel. The utilization rate also reduces the quality of the surface sinter, so it needs to be insulated after ignition. For the traditional thin material layer sintering process, it is necessary to supply a certain amount of heat in the heat preservation section; for the thick material layer sintering, because the running speed of the trolley is slow, the heat preservation section does not supply heat, and the heat preservation effect is also ideal. Under normal circumstances, the holding time is 0.5 ~ 1.0min.
(1) Ignition temperature
The firing temperature depends mainly on the melting temperature of the sintered product, due to sintering of iron ore, various molten eutectic temperature of the mixture is between 1030 ~ 1220 ℃, so little sintering temperature difference ignition, typically 1050 Fluctuations between ~1250 °C. For thick layer operation and low temperature sintering process, the lower limit should be taken; for thin layer operation and high temperature "melt" sintering process, the upper limit should be taken.
(2) Ignition time
Theoretically, the ignition time refers to the time when the material surface passes through a certain temperature zone. Some people set the temperature above 1100 °C, and some people have set it above 1000 °C. Since the coke powder is heated to about 700 °C, it starts to burn. Therefore, the ignition furnace The design generally stipulates that the residence time of the mixture in the ignition section is the ignition time. In a certain temperature range, the ignition time is related to the ignition temperature, that is, to the total heat supplied during ignition. Coal low heat value gas, combustion flame temperature is low, the ignition timing needs to be longer. Under normal circumstances, the ignition time is 0.8 ~ 1.2min.
(3) Oxidizing atmosphere of ignition
Increasing the oxygen content of the flue gas ensures that the surface solid fuel is fully combusted, which not only improves the fuel utilization rate, but also improves the quality of the surface sinter. According to the experience of the former Soviet Union, for the traditional ignition process, the oxygen content in the flue gas increased by 1%, the utilization factor of the sintering machine increased by 0.5%, and the solid fuel consumption decreased by 0.3 kg/t.
For the strip flame direct ignition technology actively promoted in the past ten years, since the width of the flame zone is narrow and the passage time of the material layer is short, the combustion temperature of the flame zone is required to be as high as possible. If the excess air volume is increased, The combustion temperature is low and ignition is difficult. Therefore, in addition to the high calorific value of natural gas or coke oven gas, the excess air coefficient can be slightly increased. For a mixed gas with a low calorific value and a wide range of applications, the excess air ratio can only be maintained at about 1.05 to 1.1, if hot air is not used. The role of the oxidizing atmosphere of the flue gas is difficult to reflect.
(4) After the ignition, the high temperature material surface of the ignition section is insulated , and the surface solid fuel is not completely burned and extinguished due to the large amount of heat radiated to the environment having the black body nature and the quenching effect of the inhaled ambient air, which not only reduces the fuel but also reduces the fuel. The utilization rate also reduces the quality of the surface sinter, so it needs to be insulated after ignition. For the traditional thin material layer sintering process, it is necessary to supply a certain amount of heat in the heat preservation section; for the thick material layer sintering, because the running speed of the trolley is slow, the heat preservation section does not supply heat, and the heat preservation effect is also ideal. Under normal circumstances, the holding time is 0.5 ~ 1.0min.
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