SU1420028A1 - Method of heating furnace with stepped-suspended bed - Google Patents

Abstract

This invention relates to metallurgy, to methods for enriching iron ore. The purpose of the invention is to increase productivity. The method is carried out in an oven of a step-weighted layer, in which the drying, heating and gas stages of the charge are formed. Thermal forcing is carried out by setting air flow coefficients of 1.1-1.4, 2.9-3.0 and 0.4-0.8 in each zone, respectively. The use of the invention increases productivity by 4-7%.

Description

The invention relates to the preparation of iron ore in ferrous metallurgy, namely to the magnetizing roasting of hard iron

RUDTsEL of the invention - an increase in individual process performance; heat treatment of the charge in a step-weighted layer.

: The operation in step-weighted layer furnaces is defined as follows.

The calcined material is moved under the influence of high-speed conveying jets in the state of gas suspension and is subsequently subjected to drying, heating and thermal burning. The furnace is heated by supplying gaseous liquid fuel through the transporting tuyeres and by incorporating solid fuel into the ore stream. All fuels are burned directly in the gas suspension flow. The polydisperse iron ore material loaded into the furnace, containing external and hydrated moisture, can immediately be subjected to a sharp thermal shock (grinding individual pieces only improves the quality of the finished product) to remove moisture at the highest possible rate and force the particles to reach operating temperatures.

The creation of high temperatures in the furnace is carried out by using in the first rows of tuyeres a high-temperature heat transfer fluid (obtained, for example, in remote furnaces, or using a mixture of fuel and recirculation gases) as the transporting jet. As a result, the formed gas mixture is exposed to sufficiently high temperatures already at the head of the furnace and is transported directly to the volume of the jet under the conditions of burning the mixture of fuels. In this case, the temperature of the coolant is set to exceed the softening temperature of the ore. Sintering of the particles with each other does not occur due to the release of water vapor from them and the surface of the particles in the wet state. The described temperature conditions are provided by burning gaseous fuels with an air flow rate of 1.1-1.4. With a lower coefficient of air flow (less than 1.1), there is a partial melting of small particles and clogging (accelerated exit

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lining of the furnace lining. With a higher air flow rate (over 1.4), the conditions for meeting the combustion products with the raw mixture do not ensure stable ignition of solid fuels, respectively, the consumption of scarce fuels (for example, natural gas, fuel oil) increases and the specific productivity of the process decreases.

The formation of high-temperature coolant is accompanied by the supply of external fuel (for example, natural gas) through the tuyeres of the furnace head in the amount of 60-80% of the total process flow. This, along with the above, provides the ultimate reduction in the consumption of scarce natural gas in the process. When a smaller amount of external fuel is burned in the furnace head (less than 60% of the total), the temperature in the furnace is set insufficiently for stable heating of the charge particles and ignition of coal, which leads to a decrease in the specific productivity of the process. When a large amount of external fuel is burned in the furnace head (more than 80% of the total), it is not possible to control the gaseous medium in the subsequent 1X process zones of the furnace, and as a result, the quality of the finished product deteriorates.

After the removal of moisture from the mixture, it is subjected to intensive heating (the second stage of the process) under conditions of supply through the tuyeres of the fuel-air mixture with an air flow rate of 2.9-3.0. At a lower air flow rate (less than 2.9), the gas suspension temperature exceeds 1150 ° C, the development of speculation begins, and an emergency stop of the unit becomes necessary. With a higher air flow rate (over 3.0), undesirable phase changes in the transported charge no longer occur, and the specific productivity of the process decreases.

After heating, the ore particles are subjected to reducing heat treatment (the third stage of the process). For this, the fuel-air mixture transported through the tuyeres is supplied with an air flow rate of 0.4-0.8. With a lower ratio

Air flow (less than 0.4) The combustion of the fuel in the gas suspension becomes unstable, the flame can be attenuated and the process can be stopped. With a higher air flow rate (more than 0.8), the number of reducing components in the gas suspension decreases, which leads to either a decrease in the degree of ore reduction or a decrease in the productivity of the process.

Example 1 (for medium mode parameters). The prepared raw mixture, for example a mixture of 93% iron ore and 7% coal, is loaded into the furnace of a step-weighted layer and transported. Through the transporting tuyeres, an air-fuel mixture with an air flow rate of 1.2 is fed and burned directly in the working space to form a heat transfer fluid with a temperature of 1265 C. At this temperature, the mixture is kept equal to 2.90. Its further reduction is unacceptable, since already with the air flow factor of 2.8, the formation of drusen occurs and an emergency stop of the unit occurs. Time

0.30 min (30% of the total time of the ore locking at the second stage of the process), feeding in the first three poured equal to 0.1 min (10% of the total amount of transporting tuyeres of the furnace 70% of the external (for example, natural) gas). The mixture is then heated at temperatures precluding its sintering. To do this, the air flow rate of the mixture transported through the tuyeres is set at 2.95 and the mixture is charged at a temperature of up to 1180 ° C for 0.15 min (15% of . total process time.) At the end of the heating, the ore particles are subjected to recovery deep firing at temperatures close to the ore softening temperature and fuel combustion with the formation of reducing components in the gas phase. The air flow rate in the mixture transported through the tuyeres is set to 0.7 for this, and the treatment time of the particles is 0.55 minutes (55% of total process time).

The ore that is restored to 60-80% and the residue of the solid reducing agent is loaded into the pre-reduction (stabilization) chamber, kept in a heated, downward, non-filterable layer, cooled and sent for subsequent processing,. or a warehouse of finished products.

Example 2 (for minimum values of operational parameters). After loading, the raw mixture is injected | | t in contact with the coolant having

special process time). Reducing the time below the specified does not provide heating of the ore particles to the required 30 process temperatures.

After heating, the ore particles are subjected to reductive roasting at temperatures close to the softening temperature of the ore and combustion of fuel with

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ponents in the gas phase. For this, the air flow rate in the mixture transported through the tuyeres is set to Oj4. This coefficient of air flow is minimally acceptable. So, with an air flow rate of 0.35, it is possible to stop burning carbon in a gas suspension.

The recovery time of dispersed materials with a particle size up to 0.10 mm is set equal to 70% of the total (0.7 min). The recovered ore and the remaining solid fuel are loaded into the secondary recovery chamber.

Claims (1)

The application of the invention provides an increase in the unit productivity of up to | 0.90 t / m h and an increase in the degree of ore reduction in front of the reduction chamber by 40-70%. Invention Formula The method of heating the furnace of a step-weighted layer is mainly for temperature that exceeds the softening temperature of the ore by supplying for this through an air-fuel mixture transporting tuyeres with an air flow rate of 1.10 m / m. When the coefficient of air flow of 1.05 occurs nastylevane on the lining of the furnace and accelerated its exit from build At the first stage, the ore is kept for 0.2 minutes (20% of the total process time). The heat treatment mode with the specified operating parameters is applicable to the most Dispersed materials with grain size up to 0.07-0.10 mm. In the second stage (warming up), the air flow rate in the mixture transported through the tuyeres is set to 2.90. Its further reduction is unacceptable, since already with the air flow factor of 2.8, the formation of drusen occurs and an emergency stop of the unit occurs. Time The second stage ore holdings are set to 0.1 min (10% of the total process time). Reducing the time below the specified does not provide heating of the ore particles to the required 30 process temperatures. After heating, the ore particles are subjected to reductive roasting at temperatures close to the softening temperature of the ore and combustion of fuel with five the formation of restorative com0 five 0 five ponents in the gas phase. For this, the air flow rate in the mixture transported through the tuyeres is set to Oj4. This coefficient of air flow is minimally acceptable. So, with an air flow rate of 0.35, it is possible to stop burning carbon in a gas suspension. The recovery time of dispersed materials with a particle size up to 0.10 mm is set equal to 70% of the total (0.7 min). The recovered ore and the remaining solid fuel are loaded into the secondary recovery chamber. The application of the invention provides an increase in the unit productivity of up to | 0.90 t / m h and an increase in the degree of ore reduction in front of the reduction chamber by 40-70%. Invention Formula The method of heating the furnace of a step-weighted layer is mainly for 514200286 magnetizing roasting of iron ores, 40-70% of the total continuum-including air supply and heat treatment, distinguishing between gaseous or liquid fuels, and so that, in order to increase the conveying tuyeres, enter the productivity, the coefficient of solid fuel into the stream of ore and the three-flow rate of air transported by staged combustion in the working air through the combustion tuyeres in the first, second part of the fuel-air furnace, the swarm and the third stages of the process, with the duration of the first, are equal to 1.1 1.4, 2.9-3.0 swarm and the third stage of the process, equal to Q and 0.4-0.8 m / m, respectively, 20-40, 10-20 and