Hot air circulating system for increasing temperature of hearth of roasting machine

Abstract

The utility model provides a hot air circulation system for raising the temperature of a hearth of a roasting machine, which comprises a forced air drying section, an air draft drying section, a preheating section, a roasting section, a soaking section, a first cooling section, a second cooling section and a third cooling section which are sequentially arranged, the second cooling section comprises a front second cooling section and a rear second cooling section which are independently arranged, and a partition wall is arranged between the front second cooling section and the rear second cooling section. Outlets of the front secondary cooling section and the primary cooling section are communicated with flue gas inlets of the soaking section and the roasting section through pipelines, and an outlet of the rear secondary cooling section is communicated with a flue gas inlet of the preheating section through a pipeline. According to the hot air circulating system, the secondary cooling section is divided into two parts, flue gas recovered by the rear part with lower temperature enters the preheating section and does not enter the roasting section, but flue gas with higher temperature in the front section is recovered and introduced into the roasting section, so that the hot air temperature of the roasting section is increased, the temperature of a hearth is increased, and the energy consumption is reduced under the same condition. And the pellet quality requirement can also be met by using the low-calorific-value fuel, so that the production cost is reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of iron and steel metallurgy, in particular to a hot air circulation system for improving the furnace temperature of a roasting machine. Background Technique

[0002] With the development of the high-proportion pellet ore smelting technology in China, the large-scale development of pellet ore has become an inevitable trend in the steel industry. As the mainstream process, the belt roasting pellet has absolute advantages in terms of low carbon, energy conservation and emission reduction. As Figure 1 shown, the existing hot air process flow of the belt roasting pellet is as follows: qualified green pellets enter from the head of the roasting machine, and after being dried by blowing, dried by suction, preheated, roasted, soaked, cooled for the first time, and cooled for the second time, the temperature is reduced to 120 °C and finally discharged from the tail. First, the hot air from the second cooling section is sent into the bottom of the blowing drying section by the blowing drying fan to dry the green pellets. The dried flue gas is purified by the dust collector and then discharged into the chimney through the blowing exhaust fan; the hot waste gas at about 400 °C in the rear end of the roasting section and the air box of the soaking section is sent into the furnace hood of the suction drying section by the regenerative air blower to fully dry the green pellets; the function of the preheating section is to heat and raise the temperature of the pellets, decompose the crystal water and carbonate, and carry out the oxidation reaction. The main heat sources are three aspects: 1) the hot air flow in the first cooling section; 2) the flue gas of the regenerative air blower; 3) the heat supplied by the burner installed in the preheating section. The waste gas in the preheating section, the suction drying section and the front end of the roasting section is sent to the purification system by the main suction fan and finally discharged into the atmosphere; the preheated pellets enter the roasting section, and part of the heat is provided by the burner. The air required for combustion is mainly provided by the hot air in the first cooling section; then it enters the soaking section, and the hot air in the furnace hood of the first cooling section passes through the pellet layer under the action of suction, so that the lower-layer pellets are further completely oxidized; in the first cooling section, the cooling air blower introduces the atmosphere into the air box to penetrate the material layer to cool the high-temperature pellets, and the heat-exchanged hot air is sent to the soaking section, the roasting section and the preheating section respectively; the second cooling section continues to cool the material layer, and finally cools the pellets to below 120 °C and then transports them to the screening area. The air temperature after heat exchange is about 300 °C, which is introduced into the blowing drying section to dry the green pellets, completing the whole air circulation.

[0003] The above technology has the following deficiencies: Since the material temperature in the first cooling section gradually decreases, the air temperature after heat exchange also gradually decreases. After mixing, it will reduce the overall air temperature and the furnace temperature in the roasting section, and a large amount of high-calorific value fuel is required to supplement the furnace temperature. In the conventional design, it is required that the calorific value of the gaseous fuel is not less than 9200 kJ / m 3 , therefore, its production cost is high. Content of the Utility Model

[0004] The main purpose of the utility model is to provide a hot air circulation system for improving the furnace temperature of a roasting machine, aiming to reduce the fuel cost by increasing the furnace temperature of the roasting machine.

[0005] To achieve the above object, the utility model provides a hot air circulation system for improving the hearth temperature of a roasting machine, which includes a blast drying section, an exhaust drying section, a preheating section, a roasting section, a soaking section, a first cooling section, a second cooling section and a third cooling section arranged in sequence. Among them,

[0006] The second cooling section includes a front second cooling section and a rear second cooling section which are independently arranged. A partition wall is arranged between the front second cooling section and the rear second cooling section. The outlets of the front second cooling section and the first cooling section are both connected to the flue gas inlets of the soaking section and the roasting section through pipelines. The outlet of the rear second cooling section is connected to the flue gas inlet of the preheating section through a pipeline.

[0007] Preferably, the flue gas outlet of the soaking section is connected to the inlet of the first cooling section through a pipeline via a first cooling circulation fan.

[0008] Preferably, a cold air mixing air inlet is also arranged at the air inlet of the first cooling circulation fan to suck in cold air from the atmosphere for cooling.

[0009] Preferably, second cooling fans are installed on the pipelines at the inlets of the front second cooling section and the rear second cooling section to suck in cold air from the atmosphere and introduce it into the second cooling section for cooling.

[0010] Preferably, the front second cooling section and the rear second cooling section share a second cooling fan. The pipelines at the inlets of the front second cooling section and the rear second cooling section are connected to the air outlet pipe of the second cooling fan through a main pipeline.

[0011] Preferably, the flue gas outlet of the blast drying section is connected to the inlet of the first cooling section through a pipeline.

[0012] Preferably, the flue gas outlet of the third cooling section is connected to the flue gas inlet of the blast drying section through a pipeline via a third cooling fan and a blast drying fan.

[0013] Preferably, the flue gas outlet of the roasting section is connected to the flue gas inlets of the preheating section and the exhaust drying section through a pipeline via a recuperative fan.

[0014] Preferably, partition walls are arranged between the blast drying section and the exhaust drying section, between the exhaust drying section and the preheating section, between the roasting section and the soaking section, between the front and rear second cooling sections, and between the second cooling section and the third cooling section to prevent air leakage between sections.

[0015] Preferably, the flue gas outlets of the exhaust drying section, the preheating section and the roasting section are all connected to a flue gas purification device through a pipeline via a main exhaust fan.

[0016] The hot air circulation system for improving the hearth temperature of the roasting machine proposed by the utility model divides the second cooling section into two parts. The flue gas recovered from the lower temperature part at the back enters the preheating section instead of the roasting section, while the flue gas at the higher temperature in the front part is recovered and introduced into the roasting section, thereby increasing the hot air temperature in the roasting section and further increasing the hearth temperature. Under the same conditions, using a calorific value of 7500 kJ / m3 The low calorific value fuel can also meet the pellet quality requirements, thus reducing the production cost. At the same time, the hot air circulation system of the present invention has a simple structure, reasonable layout and high heat utilization rate, and can use low calorific value fuel, which is worthy of application and promotion. Moreover, the third cooling section is changed to induced draft cooling. (In the prior art, affected by the heating sequence of the material, the temperature is from top to bottom, the surface material is high, and the bottom temperature is low. The cooling air in the second cooling section starts to cool from the bottom, greatly reducing the cooling effect on the surface material). Its cooling sequence is reasonable, realizing uniform cooling of the pellets and avoiding temperature differences in the upper, middle and lower material layers. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 FIG. 7 is a schematic structural diagram of a belt roasting pellet production system in the prior art;

[0018] Figure 2 FIG. 11 is a schematic structural diagram of a preferred embodiment of the hot air circulation system for increasing the temperature of the roasting furnace hearth of the present invention.

[0019] In the figure, 1, main induced draft fan; 2, blast drying fan; 3, regenerative air fan; 4, first cooling circulation fan; 5, second cooling fan; 6, third cooling fan; 7, medium temperature air duct; 8, high temperature air duct; 9, cold air duct; 10, partition wall; 11, furnace hood; 12, furnace hearth; 13, air box; 14, blast drying section; 15, induced draft drying section; 16, preheating section; 17, roasting section; 18, soaking section; 19, first cooling section; 20, front second cooling section; 21, rear second cooling section; 22, third cooling section; 23, second cooling section.

[0020] The realization, functional features and advantages of the object of the present invention will be further described with reference to the embodiments and the accompanying drawings. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0022] It should be noted that in the description of the present invention, the orientation or positional relationship indicated by the terms "horizontal", "longitudinal", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0023] The present invention provides a hot air circulation system for increasing the temperature of the roasting furnace hearth of a roasting machine.

[0024] Referring to Figure 2 , in this preferred embodiment, a hot air circulation system for improving the furnace temperature of a roasting machine includes a blast drying section 14, an exhaust drying section 15, a preheating section 16, a roasting section 17, a soaking section 18, a first cooling section 19, a second cooling section 23, and a third cooling section 22 arranged in sequence. Among them,

[0025] The second cooling section 23 includes a front second cooling section 20 and a rear second cooling section 21 arranged independently. A partition wall 10 is provided between the front second cooling section 20 and the rear second cooling section 21. The outlets of the front second cooling section 20 and the first cooling section 19 are both connected to the flue gas inlets of the soaking section 18 and the roasting section 17 through pipelines, and the outlet of the rear second cooling section 21 is connected to the flue gas inlet of the preheating section 16 through a pipeline.

[0026] Furthermore, the flue gas outlet of the soaking section 18 is connected to the inlet of the first cooling section 19 through a pipeline via a first cooling circulation fan 4. Compared with the prior art, in which the high-temperature materials in the soaking section 18 enter the first cooling section 19, and since the bottom of the first cooling section 19 is in direct contact with the cold air from the atmosphere, the high-temperature pellets are suddenly quenched, resulting in excessive internal stress in the pellets and cracks. In this application, the blast air at the inlet of the first cooling section 19 is sourced from the soaking section 18. Therefore, the first cooling section 19 uses hot air cooling, and the hot air comes from the waste flue gas discharged from the soaking section 18. This cooling method is more reasonable, effectively preventing cracks caused by excessive internal stress in the pellets and ensuring the product strength. At the same time, the low-temperature waste flue gas is recycled, reducing the flue gas emissions, which is beneficial to energy conservation and emission reduction. Moreover, by recovering the flue gas, the temperature of the flue gas at the outlet of the first cooling section 19 is increased, and then the temperature of the flue gas entering the roasting section 17 can be increased, thereby increasing the furnace temperature of the roasting machine.

[0027] Furthermore, a cold mixing air inlet is provided at the air inlet of the first cooling circulation fan 4 to inhale cold air from the atmosphere for cooling. When the temperature is too high, cold air can be inhaled from the atmosphere for cooling.

[0028] Furthermore, a second cooling fan 5 is installed on the pipelines at the inlets of the front second cooling section 20 and the rear second cooling section 21 to inhale cold air from the atmosphere and introduce it into the second cooling section 23 for cooling. In this embodiment, the front second cooling section 20 and the rear second cooling section 21 share a second cooling fan 5, and the pipelines at the inlets of the front second cooling section 20 and the rear second cooling section 21 are connected to the air outlet pipe of the second cooling fan 5 through a main pipeline.

[0029] In this embodiment, the flue gas outlet of the blast drying section 14 is connected to the inlet of the first cooling section 19 through a pipeline. The flue gas outlet of the third cooling section 22 is connected to the flue gas inlet of the blast drying section 14 through a pipeline via a third cooling fan 6 and a blast drying fan 2, thereby recycling the low-temperature waste flue gas, reducing the flue gas emissions, which is beneficial to energy conservation and emission reduction.

[0030] Furthermore, the flue gas outlet of the roasting section 17 is connected to the flue gas inlets of the preheating section 16 and the suction drying section 15 through a pipeline via the regenerative air blower 3, thereby recycling the low-temperature waste flue gas, reducing the flue gas emissions, and being conducive to energy conservation and emission reduction.

[0031] Furthermore, partition walls 10 are provided between the blowing drying section 14 and the suction drying section 15, between the suction drying section 15 and the preheating section 16, between the roasting section 17 and the soaking section 18, between the front secondary cooling section 20 and the rear secondary cooling section 21, and between the secondary cooling section 23 and the tertiary cooling section 22 to prevent air leakage between the sections.

[0032] The flue gas outlets of the suction drying section 15, the preheating section 16, and the roasting section 17 are all connected to the flue gas purification equipment through pipelines via the main suction fan 1. After being purified by the flue gas purification equipment, it is finally discharged into the atmosphere through the chimney.

[0033] The working process of this hot air circulation system for increasing the furnace temperature of the roasting machine is as follows:

[0034] The first cooling section 19 adopts hot air self-circulation cooling to reduce the thermal stress generated by cold air cooling and prevent the high-temperature pellets from cracking due to rapid cooling. First, the hot air blower 4 extracts about 100°C of hot air discharged from the blowing drying section 14 as the cooling air. After being pressurized, it is blown into the air box of the hot air first cooling section 19 to cool the high-temperature pellets at 1200°C. After passing through the material layer of the first cooling section 19, the hot air is heated to ~1150°C by the pellets and enters the high-temperature air pipeline 8. Under the suction of the first cooling circulation fan 4, part of the hot air flows back to the furnace of the soaking section 18. After the 1150°C hot air exchanges heat with the material layer in the soaking section 18 and enters the air box, the temperature drops to ~600°C and then mixes with the hot air discharged from the blowing drying section 14 at about 100°C again, and the temperature drops to 300°C. Then it is re-blown into the air box of the first cooling section 19 by the first cooling circulation fan 4 to complete a cycle. The remaining ~1150°C hot air mixes with the hot air at the front end of the secondary cooling section 23 after passing through the first cooling section 19 and is evenly distributed through the branch pipes of the high-temperature air pipeline 8 and enters the furnace of the roasting section 17 to participate in the oxidation and combustion reactions.

[0035] The secondary cooling section 23 is divided into a front section and a rear section. The secondary cooling fan 5 sucks in cold air from the atmosphere and blows it into the bottom air box of the secondary cooling section 23 to cool down the high-temperature pellet bed from the primary cooling section 19. After the cold air and the hot pellet bed complete heat exchange, the hot air in the front secondary cooling section 20 and the rear secondary cooling section 21 will no longer be mixed, but will be separately sent to different areas through their respective hot air main pipes. The high-temperature hot air at 1000 - 1100 °C in the front secondary cooling section 20 is transported through the high-temperature air pipeline 8 to the roasting section 17, and is mixed with the remaining high-temperature hot air from the primary cooling section 19. Compared with the conventional ventilation design, the air temperature can be increased by ~180 °C. After the high-temperature hot air mixture completes the iron ore oxidation, high-temperature roasting, and combustion reactions in the furnace of the roasting section 17, it is discharged from the air box of the roasting section 17. Then, the hot air in the air box at the rear end of the roasting section 17, with a temperature of 350 - 450 °C, is extracted by the regenerative air blower 3 and transported to the front ends of the suction drying section 15 and the preheating section 16.

[0036] With the cooling effect of the air in the secondary cooling section 23, the temperature of the pellet bed gradually decreases, and the air temperature in the rear secondary cooling section 21 also drops to 500 - 700 °C. This part of the hot air is transported through the medium-temperature air pipeline 7 at the top of the furnace to the preheating section 16. Among them, the branch pipe at the front end of the medium-temperature air pipeline 7 is mixed with a part of the hot flue gas from the regenerative air blower 3 to form a reasonable temperature gradient in the furnace of the preheating section 16 to preheat the pellet bed.

[0037] After the hot flue gas at the front ends of the suction drying section 15, the preheating section 16, and the roasting section 17 completes the drying, preheating, and roasting functions, it is extracted by the main suction fan 1. After flue gas purification, it is finally discharged to the atmosphere through the chimney.

[0038] The tertiary cooling section 22 is for suction cooling. The upper part of the furnace hood is connected to the atmosphere through the cold air pipeline 9, and cold air is sucked in from the environment to cool the pellet bed. Since the temperature distribution of the material on the cross-section of the roasting machine is from top to bottom, high at the top and low at the bottom, suction cooling can better reduce the temperature of the upper layer of the material. The cold air enters the tertiary cooling section 22 and passes through the pellet bed under the suction of the tertiary cooling fan 6 to complete the cooling of the pellet bed. After uniform cooling, the pellet ore is discharged from the roasting machine to become a qualified product. The cold air after heat exchange is also heated to 250 - 300 °C and is sent to the blowing drying section 14 through the blowing pipeline. After being pressurized by the blowing drying fan 2, it is blown into the air box of the blowing drying section 14 to dry the green pellet bed.

[0039] The hot air temperature after completing the drying function drops to about 100 °C, and is sent back to the air inlet of the primary cooling circulation fan 4 through the pipeline. After being mixed with the high-temperature hot air from the soaking section 18, it is blown into the air box of the primary cooling section 19 to complete the cycle. The hot air discharged from the blowing drying section 14 has a high humidity, and the moisture content of the hot air is about ~7%. The heat radiation capacity of saturated water vapor is greater than that of dry air, so it is beneficial to raise the furnace temperature.

[0040] The hot air circulation system for improving the hearth temperature of the roasting machine proposed in this embodiment divides the secondary cooling section 23 into two parts. The flue gas recovered from the lower-temperature part at the back enters the preheating section instead of the roasting section, while the flue gas with a higher temperature from the front section is recovered and introduced into the roasting section, thereby increasing the hot air temperature in the roasting section 17 and further raising the hearth temperature. Under the same conditions, low-calorific-value fuel with a calorific value of 7500 kJ / m 3 can also meet the pellet quality requirements, thus reducing production costs. At the same time, this hot air circulation system has a simple structure, reasonable layout, and high heat utilization rate, and can use low-calorific-value fuel, making it worthy of application and promotion. Furthermore, the tertiary cooling section 22 is changed to induced draft cooling. (In the prior art, affected by the material heating sequence, the temperature decreases from top to bottom, with the surface material having a higher temperature and the bottom material having a lower temperature. The cooling air in the secondary cooling section 23 starts cooling from the bottom, greatly reducing the cooling effect on the surface material.) Its cooling sequence is reasonable, achieving uniform cooling of the pellets and avoiding temperature differences in the upper, middle, and lower material layers.

[0041] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structural transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, shall be equally included in the patent protection scope of the present invention.

Claims

1. A hot air circulation system for increasing the furnace temperature of a roasting machine, characterized in that, It includes a blowing drying section, an exhaust drying section, a preheating section, a roasting section, a soaking section, a first cooling section, a second cooling section, and a third cooling section arranged in sequence. Among them, the second cooling section includes a front second cooling section and a rear second cooling section arranged independently. A partition wall is provided between the front second cooling section and the rear second cooling section. The outlets of the front second cooling section and the first cooling section are both connected to the flue gas inlets of the soaking section and the roasting section through pipelines. The outlet of the rear second cooling section is connected to the flue gas inlet of the preheating section through a pipeline.

2. The hot air circulation system for increasing the furnace temperature of a roasting machine according to claim 1, characterized in that, The flue gas outlet of the soaking section is connected to the inlet of the first cooling section through a pipeline via a first cooling circulation fan.

3. The hot air circulation system for increasing the temperature of the roasting furnace hearth according to claim 2, wherein, A cold injection air inlet is also provided at the air inlet of the first cooling circulation fan to suck in cold air from the atmosphere for cooling.

4. The hot air circulation system for increasing the temperature of the roasting furnace hearth according to claim 1, characterized in that Second cooling fans are installed on the pipelines at the inlets of the front second cooling section and the rear second cooling section to suck in cold air from the atmosphere and introduce it into the second cooling section for cooling.

5. The hot air circulation system for increasing the temperature of the roasting furnace hearth according to claim 4, characterized in that The front second cooling section and the rear second cooling section share one second cooling fan. The pipelines at the inlets of the front second cooling section and the rear second cooling section are connected to the air outlet pipe of the second cooling fan through a main pipeline.

6. The hot air circulation system for increasing the furnace temperature of a roasting machine according to claim 1, characterized in that, The flue gas outlet of the blowing drying section is connected to the inlet of the first cooling section through a pipeline.

7. The hot air circulation system for increasing the furnace temperature of the roasting machine according to claim 1, wherein The flue gas outlet of the third cooling section is connected to the flue gas inlet of the blowing drying section through a pipeline via a third cooling fan and a blowing drying fan.

8. The hot air circulation system for increasing the temperature of the roasting furnace hearth according to claim 1, characterized in that, The flue gas outlet of the roasting section is connected to the flue gas inlets of the preheating section and the exhaust drying section through a pipeline via a recuperative fan.

9. The hot air circulation system for increasing the furnace temperature of the roasting machine according to claim 1, characterized in that, Partition walls are provided between the blowing drying section and the exhaust drying section, between the exhaust drying section and the preheating section, between the roasting section and the soaking section, and between the second cooling section and the third cooling section to prevent air leakage between sections.

10. The hot air circulation system for increasing the hearth temperature of a roasting machine according to any one of claims 1 to 9, characterized in that, The flue gas outlets of the exhaust drying section, the preheating section, and the roasting section are all connected to a flue gas purification device through a pipeline via a main exhaust fan.

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