A high-efficiency waste heat recovery system for the flue gas of an AOD furnace

Abstract

The present invention discloses a high-efficiency waste heat recovery system for the flue gas of an AOD furnace, which is provided with a flue gas waste heat recovery pipeline and a steam waste heat recovery pipeline. The high-temperature flue gas generated by the AOD furnace exchanges heat with the vaporization flue to generate high-temperature saturated steam and cooled flue gas. The cooled flue gas recovers waste heat through the flue gas waste heat recovery pipeline, and the high-temperature saturated steam recovers waste heat through the steam waste heat recovery pipeline. At least a dust removal device and a heat storage device are sequentially connected to the flue gas waste heat recovery pipeline. The technical solution of the present invention reduces the dust content of the flue gas entering the boiler, avoids the influence of the reciprocating change of the flue gas temperature on the heat exchange tubes of the boiler, prolongs the service life of the boiler, improves the heat exchange efficiency, and finally improves the waste heat recovery rate of the entire process.

Description

Technical Field

[0001] The present invention belongs to the field of flue gas waste heat recovery equipment, and particularly relates to a high-efficiency waste heat recovery system for the flue gas of an AOD furnace. Background Art

[0002] An AOD furnace is a process device for smelting stainless steel. Its production process is similar to that of a converter, both being intermittent. Due to the requirements of the smelting process, the decarburization speed of the AOD furnace is much slower than that of the converter, resulting in a longer smelting cycle (the smelting cycle of a 120t AOD furnace is 100 minutes, while that of the converter is 30 minutes). The temperature and composition of the flue gas generated are also quite different from those of the converter. The temperature of the flue gas at the furnace mouth of the AOD furnace is as high as 1600°C, but as the smelting time prolongs and the decarburization speed gradually decreases, the temperature of the flue gas at the furnace mouth will drop to 100°C. Therefore, the "quality" of the waste heat in the AOD furnace flue gas is much worse than the sensible heat of converter gas. Currently, some enterprises have partially recovered the waste heat of the AOD furnace flue gas, and a few enterprises still symbolically recover a small amount of waste heat. How to reduce the energy consumption loss in this waste heat recovery process and improve the waste heat recovery rate is of great significance for enterprises' energy conservation and emission reduction.

[0003] The existing recovery process first passes the high-temperature dusty flue gas of the AOD furnace through the vaporization flue under negative pressure, and the temperature drops to ~850°C. At the same time, ~2.5MPa saturated steam (primary high-pressure saturated steam) is generated. The cooled flue gas then enters the waste heat boiler, and the flue gas temperature drops to ~200°C, generating ~2.5MPa saturated steam (secondary high-pressure saturated steam) again. After the flue gas is discharged from the boiler, it enters the pulse bag filter for purification, and then enters the induced draft fan. The flue gas pressure becomes positive pressure and finally is discharged into the atmosphere through the chimney. The primary and secondary high-pressure saturated steam generated during the entire smelting process each corresponds to 1 steam drum. The high-pressure saturated steam led out from the 2 steam drums enters the accumulator, and the accumulator converts the intermittent primary and secondary high-pressure saturated steam into continuous low-pressure saturated steam (~1.2MPa). The low-pressure saturated steam will enter the steam turbine to drive the generator to generate electricity as the main steam, ultimately realizing the waste heat power generation of the high-temperature flue gas of the AOD furnace.

[0004] The existing recovery process first converts the sensible heat of the flue gas into the enthalpy of saturated steam and then into electric energy. This electric energy is transported to the designated substation through cables and then sent to the electrical facilities after secondary distribution. In this process, from waste heat recovery to the secondary utilization of electric energy, there are losses in multiple electric energy transmissions and conversions, and the recovery efficiency is relatively low.

[0005] The high-temperature dusty flue gas directly enters the boiler after passing through the vaporization flue, which has a great impact on the service life of the boiler heat exchange tubes. In order to extend the service life of the heat exchange tubes, there are significant restrictions on the flue gas flow rate, and the boiler volume has to be designed to be relatively large. However, when the flow rate is too low, dust will adhere to the surface of the heat exchange tubes, affecting the heat exchange effect and ultimately reducing the recovery rate of flue gas waste heat. At the same time, internal ash removal facilities need to be considered, which ultimately leads to an increase in the initial investment and unsatisfactory actual use effects.

[0006] Due to the drastic changes in the flue gas parameters of the AOD furnace, when the flue gas volume is large and the temperature is high, a large amount of saturated steam will be generated. When the flue gas volume is small and the temperature is low, no steam will be generated. The existing process relies on a regenerator to smooth out the peaks and valleys of the intermittent steam to produce continuous main steam. However, due to the complex production process of the AOD furnace and the rapid changes in the flue gas, it is very difficult to obtain a suitable type selection of the regenerator through thermal calculations. In actual production, the regenerator is often too small, resulting in a large amount of steam being discharged during the steam production peak. At the same time, the reciprocating change of the flue gas temperature reduces the service life of the boiler heat exchange tubes and is also not conducive to improving the waste heat recovery rate. Summary of the Invention

[0007] In view of the defects and deficiencies in the prior art, the present invention provides a high-efficiency waste heat recovery system for the flue gas of an AOD furnace, which avoids the losses in the power transmission and conversion during the existing recovery process and improves the waste heat recovery rate.

[0008] To achieve the above object, the technical solutions adopted by the present invention include:

[0009] A high-efficiency waste heat recovery system for the flue gas of an AOD furnace is provided with a flue gas waste heat recovery pipeline and a steam waste heat recovery pipeline.

[0010] The high-temperature flue gas generated by the AOD furnace exchanges heat with the vaporization flue to generate high-temperature saturated steam and cooled flue gas. The cooled flue gas recovers waste heat through the flue gas waste heat recovery pipeline, and the high-temperature saturated steam recovers waste heat through the steam waste heat recovery pipeline.

[0011] At least a dust removal device and a heat storage device are sequentially connected to the flue gas waste heat recovery pipeline.

[0012] The dust removal device is provided with a dust removal furnace body. A buffer smoke exhaust cavity is semi-embedded at the top of the dust removal furnace body, and an oxygen supply pipeline is connected and surrounded outside the middle part of the dust removal furnace body. The outer diameter of the buffer smoke exhaust cavity gradually increases away from the top of the dust removal furnace body.

[0013] The heat storage device is at least provided with a heat storage furnace body. At least a plurality of heat storage sections are stacked in sequence along the axial direction in the heat storage furnace body. Heat storage bricks are arranged in the heat storage sections. The heat storage bricks are blocks provided with through holes along the axial direction. High-temperature flue gas is input from the top of the heat storage furnace body and discharged from the bottom of the heat storage furnace body after being stored in a plurality of heat storage sections. Low-temperature flue gas is input from the bottom of the heat storage furnace body and discharged from the top of the heat storage furnace body after being stored in a plurality of heat storage sections.

[0014] Optionally, a cavity tube is provided in the buffer smoke exhaust cavity, and a buffer smoke exhaust pipe is connected to the cavity tube; the buffer smoke exhaust pipe is a pipe body structure with a gradually increasing outer diameter; the height of the buffer smoke exhaust pipe is 1 / 3 to 3 / 4 times the height of the furnace body; the outer diameter range of the buffer smoke exhaust pipe is 1.5 to 2.5 m; the depth of the buffer smoke exhaust cavity embedded in the furnace body is 1 to 2 m.

[0015] Optionally, an annular gap is formed between the buffer smoke exhaust cavity and the dust removal furnace body, and the volume of the annular gap is 80 to 90 m 3 。

[0016] Optionally, the oxygen supply pipeline includes an oxygen supply main pipe and a plurality of oxygen supply branch pipes; the oxygen supply branch pipes are connected circumferentially around the outside of the dust removal furnace body; the dust removal furnace body is sequentially provided with a smoke inlet section, a buffer combustion section and a sedimentation ash discharge section along the axial direction; the buffer smoke exhaust cavity is embedded along the smoke inlet section and the buffer combustion section; the oxygen supply pipeline is arranged around the outside of the buffer combustion section;

[0017] The smoke inlet section is a conical cavity structure, and a smoke inlet pipe is connected to the smoke inlet section; a smoke exhaust pipe is connected to the top of the buffer smoke exhaust cavity, and a CO detector is arranged on the smoke exhaust pipe;

[0018] The sedimentation ash discharge section is a conical cavity structure, and an ash discharge valve is arranged at the bottom of the sedimentation ash discharge section; a maintenance opening is arranged on the side wall of the sedimentation ash discharge section.

[0019] Optionally, the plurality of heat storage sections at least include a first heat storage section, a second heat storage section and a third heat storage section; classified according to the heat storage temperature from high to low, the heat storage temperature or heat storage coefficient of the first heat storage section, the second heat storage section and the third heat storage section decreases in sequence; the heat storage bricks are porous blocks with a polygonal cross-section, the pore diameter is 20 to 25 mm, and the number of pores is 7 to 9.

[0020] Optionally, a flue gas diversion section is further arranged below the plurality of heat storage sections; the flue gas diversion section is composed of a plurality of hollow plates;

[0021] A refractory support section is further arranged below the flue gas diversion section, and the refractory support section is supported by a plurality of uniformly distributed struts; a third heat insulation pipe and a fourth heat insulation pipe are connected to the outside of the heat storage furnace body of the refractory support section; a third valve is arranged on the third heat insulation pipe, and a fourth valve is arranged on the fourth heat insulation pipe.

[0022] Optionally, a flue gas diversion section is further provided on the regenerative furnace body in front of the multiple heat storage sections. The flue gas diversion section is a cylindrical cavity structure. A first adiabatic pipeline and a second adiabatic pipeline are provided to communicate with the outside of the regenerative furnace body for the flue gas diversion section. A first valve is provided on the first adiabatic pipeline, and a second valve is provided on the second adiabatic pipeline. A flue gas buffer section is further provided on the regenerative furnace body in front of the flue gas diversion section. The flue gas buffer section is a conical converging structure.

[0023] Optionally, the flue gas waste heat recovery pipeline includes an adiabatic flue, a dust removal device, a heat storage device, a waste heat boiler, a bag filter, a draft fan, and a chimney that are connected in sequence.

[0024] Optionally, the steam waste heat recovery pipeline includes a steam pipeline, a first steam drum, a steam accumulator, a steam turbine, a clutch, and a generator that are connected in sequence. The generator supplies power for the flue gas discharge of the flue gas waste heat recovery pipeline.

[0025] Optionally, the steam generated by the steam waste heat recovery pipeline is converted into electric energy, and the electric energy supplies power for the flue gas discharge of the flue gas waste heat recovery pipeline.

[0026] The technical solution of the present invention reduces the dust content of the flue gas entering the boiler, and at the same time avoids the influence of the reciprocating change of the flue gas temperature on the heat exchange tubes of the boiler, prolongs the service life of the boiler, improves the heat exchange efficiency, and finally improves the waste heat recovery rate of the entire process. Description of the Drawings

[0027] The drawings are used to provide a further understanding of the present disclosure, and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present disclosure, but do not constitute a limitation to the present disclosure. In the drawings:

[0028] Figure 1 is a schematic structural diagram of the AOD furnace flue gas waste heat high-efficiency recovery system of the present invention;

[0029] Figure 2 is a schematic structural diagram of the dust removal device of the present invention;

[0030] Figure 3 is a structural diagram of the heat storage device of the present invention;

[0031] Figure 4 is Figure 3 a schematic structural diagram of the heat storage bricks in ;

[0032] Each label in the figure represents: 1-vaporization flue, 2-adiabatic flue, 3-dust removal device, 4-heat storage device, 5-waste heat boiler, 6-bag filter, 7-draft fan, 8-chimney, 9-steam pipeline, 10-first steam drum, 11-second steam drum, 12-steam accumulator, 13-steam turbine, 14-clutch, 15-generator, 16-frequency converter;

[0033] 31 - Buffer smoke exhaust cavity, 311 - Buffer smoke exhaust pipe, 32 - Dust removal furnace body, 321 - Smoke inlet section, 322 - Buffer combustion section, 323 - Sedimentation slag discharge section, 3231 - Inspection opening, 33 - Oxygen supply main pipe, 331 - Oxygen supply branch pipe, 34 - Smoke inlet pipe, 35 - Smoke exhaust pipe, 351 - CO detector; 3a - Oxygen supply main pipe valve, 3b - Oxygen supply branch pipe valve, 3c - Ash discharge valve.

[0034] 41 - Flue gas buffer section, 42 - Flue gas diversion section, 43 - First regenerative section, 44 - Second regenerative section, 45 - Third regenerative section, 46 - Flue gas diversion section, 47 - Refractory support section, 471 - Support pillar; 4a - First valve, 4b - Second valve, 4c - Third valve, 4d - Fourth valve, 4e - First adiabatic pipeline, 4f - Second adiabatic pipeline, 4g - Third adiabatic pipeline, 4h - Fourth adiabatic pipeline. Specific embodiments

[0035] The following will describe the specific embodiments of the present disclosure in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only for the purpose of illustration and explanation of the present disclosure, and are not intended to limit the present disclosure.

[0036] In the present disclosure, the "axial direction" refers to the axial direction where the intermediate shaft assembly or the two - shaft assembly is located. In the present disclosure, the "upper", "lower", "left", and "right" are all based on the orientation in the figure. The "top", "bottom", and "side" are such that the upper in the picture is the "top", the lower is the "bottom", and the periphery is the "side". Unless otherwise specified, the above regulations apply to all contents of the present disclosure.

[0037] During the AOD furnace smelting process, first, primary furnace gas is generated in the furnace. After the furnace gas floats out of the molten steel surface, it starts to burn. Until the furnace mouth part still contains a large amount of CO. Since the furnace mouth part is semi - open, when a large amount of air meets this furnace gas, intense combustion occurs, generating high - temperature dust - containing flue gas.

[0038] Combined with Figure 1, the high-efficiency waste heat recovery system for the flue gas of the AOD furnace of the present invention is provided with a flue gas waste heat recovery pipeline and a steam waste heat recovery pipeline; the high-temperature flue gas generated by the AOD furnace exchanges heat with the vaporization flue to generate high-temperature saturated steam and cooled flue gas; the cooled flue gas recovers waste heat through the flue gas waste heat recovery pipeline, and the high-temperature saturated steam recovers waste heat through the steam waste heat recovery pipeline; at least a dust removal device and a heat storage device are sequentially connected on the flue gas waste heat recovery pipeline; the dust removal device is provided with a dust removal furnace body 32, a buffer smoke exhaust cavity 31 is semi-embedded at the top of the dust removal furnace body 32, and an oxygen supply pipeline is connected and surrounded outside the middle of the dust removal furnace body 32; the outer diameter of the buffer smoke exhaust cavity 31 gradually increases away from the top of the furnace body; the heat storage device is at least provided with a heat storage furnace body, and at least a plurality of heat storage sections are stacked in sequence along the axial direction in the heat storage furnace body; heat storage bricks are arranged in the heat storage sections, and the heat storage bricks are blocks provided with through holes along the axial direction; the high-temperature flue gas is input from the top of the heat storage furnace body and discharged from the bottom of the heat storage furnace body after being stored in a plurality of heat storage sections; the low-temperature flue gas is input from the bottom of the heat storage furnace body and discharged from the top of the heat storage furnace body after being stored in a plurality of heat storage sections.

[0039] Specifically, the flue gas waste heat recovery pipeline includes an adiabatic flue 2, a dust removal device 3, a heat storage device 4, a waste heat boiler 5, a bag filter 6, a draft fan 7 and a chimney 8 that are connected in sequence.

[0040] Specifically, the steam waste heat recovery pipeline includes a steam pipeline 9, a first steam drum 10, a steam accumulator 12, a steam turbine 13, a clutch 14 and a generator 15 that are connected in sequence; the generator 15 supplies power for the flue gas discharge of the flue gas waste heat recovery pipeline. For another example, a second steam drum 11 is also connected to the waste heat boiler 5, and the steam of the second steam drum 11 and the steam of the first steam drum 10 are aggregated and supplied to the steam accumulator 12. The power generation efficiency of the generator 15 can also be controlled by a frequency converter 16, and then the working speed of the draft fan 7 can be controlled.

[0041] The overall working process is summarized as that the steam generated by the steam waste heat recovery pipeline is converted into electric energy, and the electric energy supplies power for the flue gas discharge of the flue gas waste heat recovery pipeline. The specific process is as follows: The high-temperature dusty flue gas first enters the vaporization flue 1 and exchanges heat with it. The temperature of the flue gas drops to about 850 °C, and a small amount of dust will be deposited in the vaporization flue; the cooled flue gas enters the primary dust removal device 3 through the adiabatic flue 2, and the flue gas after rough dust removal enters the heat storage device 4 (internally provided with heat storage lattice bricks, which absorb the surplus heat when the flue gas temperature is high and transfer the surplus heat to the low-temperature flue gas when the flue gas temperature is low, so as to reduce the temperature fluctuation of the flue gas and have a certain effect of purifying the flue gas dust), and then enters the waste heat boiler 5 to exchange heat with the boiler, and the temperature of the flue gas drops to about 200 °C; then it enters the pulse bag filter 6 for secondary dust removal, and the low-dust flue gas is finally sent into the chimney 8 through the draft fan 7 and discharged into the atmosphere.

[0042] When the high-temperature flue gas exchanges heat with the vaporization flue, the 2.5 MPa saturated steam (intermittently generated according to the change of the flue gas) enters the first steam drum 10 through the steam pipeline 9. After the flue gas is cooled for the first time, it enters the waste heat boiler and exchanges heat again to generate 2.5 MPa saturated steam (intermittently generated according to the change of the flue gas) and enters the second steam drum 11. The steam discharged from the first steam drum 10 and the second steam drum 11 enters the steam accumulator 12 and is converted into continuous 1.2 MPa saturated steam. This low-pressure saturated steam enters the steam turbine 13 as the main steam, thereby driving the large power-consuming facility - the induced draft fan 7 in this process. The steam turbine 13, the clutch 14, the motor generator 15, and the induced draft fan 7 are coaxial. In the present invention, a frequency converter 16 (meeting the air volume adjustment function of the dust removal fan) is provided in supporting with the motor generator 15 (generating electricity with the surplus after the main steam drives the dust removal fan).

[0043] Combined with Figure 2 , the dust removal device of the present disclosure is provided with a dust removal furnace body 32. A buffer smoke exhaust cavity 31 is semi-embeddedly arranged at the top of the dust removal furnace body 32, and an oxygen supply pipeline is connected and surrounded outside the middle part of the dust removal furnace body 32; the outer diameter of the buffer smoke exhaust cavity 31 gradually increases along the direction away from the top of the dust removal furnace body 32. The device of the present disclosure removes most of the dust in the semi-closed nickel-iron ore smelting furnace flue gas, and at the same time burns out the residual CO in the flue gas, avoiding the blockage of the flue gas pipeline, eliminating the dust removal and ash cleaning facilities of the subsequent heat exchange equipment, and reducing the primary investment; the structural form of this device (inner and outer sleeve type); multiple layers of compressed air ring pipes are arranged on the straight section of the outer sleeve, and a number of branch pipes are arranged in the circumferential direction and inserted into the straight section to mix in air; an electric control valve is arranged on each layer of the ring pipe to dynamically adjust the amount of air mixed in according to the flue gas temperature and CO content, and a device for adjusting the mixed air is provided to ensure that the CO in the flue gas is burned out, and at the same time avoid mixing in excessive air and reducing the flue gas temperature, so as to improve the recovery rate of the flue gas waste heat.

[0044] In the embodiment of the present disclosure, the buffer smoke exhaust cavity 31 is provided with a cavity pipe, and a buffer smoke exhaust pipe 311 is connected to the cavity pipe; the buffer smoke exhaust pipe 311 is a pipe body structure with a gradually increasing outer diameter. The structural setting of the buffer smoke exhaust pipe 311 ensures that the flue gas flow velocity gradually increases on the premise of having enough flue gas running space.

[0045] In the embodiment of the present disclosure, the height of the buffer smoke exhaust pipe 311 is 1 / 3 to 3 / 4 times the height of the dust removal furnace body 32. For example, when the height of the conventional dust removal furnace body 32 is 4 m, the height of the buffer smoke exhaust pipe 311 can be 1.3 to 3 m. The height setting of the buffer smoke exhaust pipe 311 ensures that the flue gas can sink to settle the dust, and at the same time ensures that the flue gas flow velocity gradually increases and is discharged from the smoke exhaust pipe 35 at the top, realizing efficient and rapid treatment.

[0046] In an embodiment of the present disclosure, the outer diameter of the buffer exhaust pipe 311 ranges from 1.5 to 2.5 m, preferably from 2 to 2.5 m, and gradually increases in a conical shape. And preferably, the maximum outer diameter of the buffer exhaust pipe 311 is at least half of the outer diameter of the dust removal furnace body 32, ensuring that there is sufficient operating space after the flue gas enters, and realizing the settlement of dust and then discharging.

[0047] In an embodiment of the present disclosure, the depth of the buffer exhaust cavity 31 embedded in the dust removal furnace body 32 is 1 to 2 m, preferably 1.5 m. That is to say, the depth of the buffer exhaust cavity 31 embedded in the dust removal furnace body 32 is at least 1 / 2 to 3 / 4 times the height of the furnace body, ensuring that there is sufficient annular gap between the buffer exhaust cavity 31 and the dust removal furnace body 32, and at the same time, there is sufficient height for the exhaust treatment of the flue gas.

[0048] In an embodiment of the present disclosure, an annular gap is formed between the buffer exhaust cavity 31 and the dust removal furnace body 32, and the volume of the annular gap is 80 - 90 m 3 preferably 85 m 3 which is convenient for the flue gas to stay in the device for a sufficient time and is beneficial to the settlement of dust.

[0049] In an embodiment of the present disclosure, the oxygen supply pipeline includes an oxygen supply main pipe 33 and a plurality of oxygen supply branch pipes 331; the oxygen supply branch pipes 331 are circumferentially connected and arranged around the outside of the dust removal furnace body 32. This makes the air evenly distributed along the radial direction of the device, ensuring sufficient combustion of CO involved.

[0050] In an embodiment of the present disclosure, the dust removal furnace body 32 is sequentially provided with a smoke inlet section 321, a buffer combustion section 322, and a sedimentation and ash discharge section 323 along the axial direction; the buffer exhaust cavity 31 is embedded along the smoke inlet section 321 and the buffer combustion section 322; the oxygen supply pipeline is arranged around the outside of the buffer combustion section 322. An oxygen supply main pipe valve 3a and an oxygen supply branch pipe valve 3b are provided on the oxygen supply main pipe 33 and the oxygen supply branch pipes 331. The valves can be electric butterfly valves. Through the setting of the above valves, the air flow rate entering the buffer combustion section 322 can be adjusted at any time, thereby controlling the combustion degree of CO. It is necessary to ensure that CO is completely burned out, and at the same time, not introduce too much low-temperature air to avoid affecting the subsequent recovery of flue gas waste heat, and achieve a balance between dust removal and flue gas waste heat recovery.

[0051] In an embodiment of the present disclosure, the smoke inlet section 321 is a conical cavity structure. A smoke inlet pipe 34 is connected to the smoke inlet section 321, preferably connected laterally; a smoke exhaust pipe 35 is connected to the top of the buffer exhaust cavity 31, also preferably arranged laterally. A CO detector 51 is provided on the smoke exhaust pipe 35 to detect whether CO is completely burned to adjust the oxygen supply amount.

[0052] In an embodiment of the present disclosure, the sedimentation ash discharge section 323 is a conical cavity structure, and an ash discharge valve 3c is provided at the bottom of the sedimentation ash discharge section 323; a maintenance opening 3231 is provided on the side wall of the sedimentation ash discharge section 323. In the case of long-term or multiple operations of the device, if the sedimentation ash discharge section 323 becomes blocked, it can be cleaned by manual entry.

[0053] In the production process of the semi-closed nickel-iron ore smelting furnace, first, primary furnace gas is generated in the furnace. When the furnace gas reaches the furnace mouth part, it still contains a large amount of CO. Since the furnace mouth part is semi-open, a large amount of air meets the furnace gas and burns violently, generating high-temperature dust-containing flue gas (temperature: 700 - 900 °C, dust content ~ 35 g / NM3). This high-temperature dust-containing flue gas enters the anti-bonding device of the present disclosure through the smoke inlet pipe 34. When the flue gas passes through the device at a relatively low speed (2 m / s), the dust in it settles sufficiently in the gap between the inner and outer sleeves due to inertia, and the remaining CO burns out completely (a proper amount of compressed air is mixed into the oxygen supply pipeline). The purified flue gas continues to enter the buffer smoke exhaust cavity 31 and leave the device, and finally is sent to the subsequent heat exchange equipment through the smoke exhaust pipe 35 to complete the recovery of the waste heat of the flue gas.

[0054] Figure 2 The anti-bonding device of the present disclosure is of a sleeve type structure. The inner cylinder is in the shape of a "horn" (made of Q235 - B), that is, the buffer smoke exhaust cavity 31, and heat-insulating spray coatings are provided on both the inner and outer sides; the outer sleeve is the dust removal furnace body 32, which is divided into an upper conical section, a straight section, and a lower conical section, namely the smoke inlet section 321, the buffer combustion section 322, and the sedimentation ash discharge section 323 in sequence. Heat-insulating spray coatings are provided on the inner side, and at the same time, 2 layers of oxygen supply branch pipes 331 are provided on the straight section of the outer sleeve (the number of ring pipes can be increased according to the size of the device, and electric butterfly valves are provided at the inlet section of each layer of ring pipe to adjust the amount of mixed air), and a number of branch pipes are provided on the circumferential direction of the ring pipe and inserted into the straight section; a dust discharge pipe is provided at the lower conical end of the outer cylinder, and the ash accumulated in the conical section is regularly discharged through the ash discharge valve c. At the same time, a maintenance opening 231 is provided in the conical section. The opening degree of the oxygen supply branch pipe valve b (electric butterfly valve) on each layer of oxygen supply branch pipe 331 is adjusted according to the parameters fed back by the temperature and CO detector 51 to ensure that the CO burns out completely while avoiding excessive air and reducing the flue gas temperature.

[0055] Taking a 33MW semi-closed nickel-iron ore smelting furnace as an example, the daily nickel output is 230 t / d. If it is blocked once a month, the cleaning time for one time is 10 h, 6 man-hours are required each time, and one crane shift is needed. Then the cost for cleaning the pipeline once is: 1000 (profit per ton of nickel iron) * 230 * (10 / 24) + 6 * 180 (labor cost) + 2000 (crane shift cost) = 98913 yuan. It can save nearly 1.2 million yuan in cleaning costs in a year; if the subsequent heat exchange equipment saves the dust removal and ash cleaning facilities, it can reduce the weight by 10 t, then it can save an investment of 200,000 yuan at a time; this device can reduce the erosion of the heat exchange equipment by dust and extend the service life of the heat exchange equipment itself.

[0056] Combined with Figure 3 and 4 For the heat storage device of the present disclosure, at least a heat storage furnace body is provided, and a plurality of heat storage sections are stacked in sequence along the axial direction at least inside the heat storage furnace body; heat storage bricks are arranged in the heat storage sections, and the heat storage bricks are blocks with through holes arranged along the axial direction. High-temperature flue gas is input from the top of the furnace body and discharged from the bottom of the furnace body after being heat-stored by a plurality of heat storage sections; low-temperature flue gas is input from the bottom of the furnace body and discharged from the top of the furnace body after being heat-stored by a plurality of heat storage sections. It adapts to the requirements of the physical and chemical properties of the heat storage body for the gradually changing flue gas temperature. Since in the treatment process of the AOD furnace, the temperature of the discharged flue gas will decrease in a curve, there will be higher-temperature flue gas and lower-temperature flue gas. In the solution of the present disclosure, the high-temperature flue gas refers to the flue gas discharged from the AOD furnace with a temperature above 500 °C, and the low-temperature flue gas refers to the flue gas with a temperature of 200-500 °C. Such a setting form changes the treatment paths of the high-temperature flue gas and the low-temperature flue gas, not only can the waste heat of the flue gas be stored to the greatest extent, but also the treatment efficiency of the overall device can be improved, and the service life of the device can be increased.

[0057] In an embodiment of the present disclosure, the plurality of heat storage sections at least include a first heat storage section 43, a second heat storage section 44, and a third heat storage section 45; classified by the heat storage temperature from high to low, the heat storage temperatures of the first heat storage section 43, the second heat storage section 44, and the third heat storage section 45 decrease in sequence. For example, when treating high-temperature flue gas, the running path of the high-temperature flue gas is sequentially processed by the first heat storage section 43, the second heat storage section 44, and the third heat storage section 45, giving full play to the appropriate heat storage temperature of each heat storage section, improving the heat storage efficiency as much as possible, saving materials, and increasing the service life of the device.

[0058] In an embodiment of the present disclosure, for example, the height ratio of the first heat storage section 43, the second heat storage section 44, and the third heat storage section 45 is 5:2:3. According to the flue gas distribution characteristics, it is divided into three heat exchange sections: high temperature, medium temperature, and low temperature. The materials and physical and chemical indexes of the heat storage bodies in each section are different, and the set height of each section is also different. Such a reasonable configuration of the heat storage body is to meet the requirements of the heat storage body for high temperature resistance and mechanical properties for the gradually decreasing / increasing flue gas temperature.

[0059] In an embodiment of the present disclosure, as Figure 4 shown, the heat storage brick is a porous block with a polygonal cross-section, the pore diameter is 20-25 mm, and the number of pores is 7-9. The heat storage bricks (lattice bricks) in the heat storage device 4 are arranged in the third section of the furnace body, and different materials (such as silica bricks, high-aluminum bricks, clay bricks, etc.) are used according to the high and low temperature zones of the flue gas. The heat storage brick can be hexagonal and porous, and the pore diameter can be a round hole of 20 mm or 25 mm, and the number can be 7 or 9, etc. Using different materials can reflect different heat storage capacities, and the structure of multiple pores can increase the contact area and improve the heat exchange efficiency.

[0060] In an embodiment of the present disclosure, a flue gas diversion section 46 is further provided under multiple heat storage sections; the flue gas diversion section 46 is composed of multiple hollow plates. For example, the flue gas diversion section 46 is composed of multiple high-temperature-resistant cast iron polygons as units. The size and number of holes of each unit are the same as those of the heat storage bricks, guiding the low-temperature flue gas from the bottom into the heat storage bricks correspondingly, and at the same time bearing a certain weight of the heat storage bricks, ensuring that the flue gas enters the holes of the heat storage bricks evenly and improving the heat exchange efficiency.

[0061] In an embodiment of the present disclosure, a refractory support section 47 is further provided under the flue gas diversion section 46. The refractory support section 47 is supported by columns 71 and bears the weight of the heat storage bricks and the flue gas diversion section 46 in the furnace; for example, it can be made of heat-resistant materials such as silica bricks, high-aluminum bricks, clay, cast iron, etc. into cylindrical columns, which have a certain heat resistance and can also have a certain gravity-bearing capacity.

[0062] In an embodiment of the present disclosure, a third adiabatic pipeline 4g and a fourth adiabatic pipeline 4h are connected to the outside of the furnace body to communicate with the refractory support section 47; a third valve 4c is provided on the third adiabatic pipeline 4g, and a fourth valve 4d is provided on the fourth adiabatic pipeline 4h. The inlet and outlet channels of the flue gas can be adjusted at any time to realize the switching of the high-temperature flue gas and low-temperature flue gas treatment procedures.

[0063] In an embodiment of the present disclosure, a flue gas diversion section 42 is further provided on the furnace body in front of multiple heat storage sections. The structure of the flue gas diversion section 42 is a cylindrical cavity structure, ensuring the radial uniform distribution of the flue gas in the heat storage device 4. So as to facilitate the uniform entry of the flue gas into the porous heat storage bricks. At the same time, a certain buffer space is given to the incoming flue gas, and the flue gas is subjected to heat storage treatment after the flow rate is slightly reduced, which is beneficial to uniform heat absorption.

[0064] In an embodiment of the present disclosure, a first adiabatic pipeline 4e and a second adiabatic pipeline 4f are connected to the outside of the furnace body to communicate with the flue gas diversion section 42; a first valve 4a is provided on the first adiabatic pipeline 4e, and a second valve 4b is provided on the second adiabatic pipeline 4f. The inlet and outlet channels of the flue gas can be adjusted at any time to realize the switching of the high-temperature flue gas and low-temperature flue gas treatment procedures.

[0065] In an embodiment of the present disclosure, a flue gas buffer section 41 is further provided on the furnace body in front of the flue gas diversion section 42. The flue gas buffer section 41 is a tapered closing structure, and can also be a closing structure similar to a vault, ensuring a certain clearance and playing a role in buffering the flue gas.

[0066] As Figure 3 shown, the working process of the heat storage device of the present disclosure is as follows:

[0067] After the high-temperature flue gas of the AOD furnace passes through the primary dust removal device, it enters the first adiabatic pipeline 4e. At this time, the first valve 4a is opened and the third valve 4c is closed. The high-temperature flue gas passes through the furnace body of the regenerator device from top to bottom and is sent to the waste heat boiler through the fourth adiabatic pipeline 4h. When the decarburization speed of the AOD furnace decreases and the flue gas temperature drops, the regenerator bricks in the regenerator device 4 have been heated. The first valve 4a is closed and the third valve 4c is opened. The flue gas passes through the regenerator bricks from bottom to top through the third adiabatic pipeline 4g and is sent to the waste heat boiler through the second adiabatic pipeline 4f.

[0068] The regenerator device 4 can stabilize the flue gas temperature and has a certain dust removal effect to extend the life of the waste heat boiler, reduce or even avoid the discharge of steam volume, and ultimately improve the waste heat recovery rate of the process. The upper part of the regenerator device 4 is of arch top type, the middle part is the regenerator body (set as three temperature zones of high, medium and low according to the flue gas temperature distribution), and the lower part is the flue gas diversion device and refractory support columns (resistant to 400 °C); with a reasonable pipe system structure, the high-temperature flue gas is led out from top to bottom, and the low-temperature flue gas is led out from bottom to top.

[0069] The waste heat recovery efficiency and economic benefits of the AOD furnace flue gas waste heat high-efficiency recovery system solution of the present invention are compared with the existing solution (the existing solution introduced in the background technology) as shown in Table 1 below:

[0070] Table 1

[0071]

[0072] Note: Taking a 3X120t AOD furnace as the comparison benchmark

[0073] Taking 2x120t AOD as an example, the saturated steam generation is about 50t / h. If the dust content of the flue gas is reduced through the primary dust removal device 3 and the regenerator device 4, and the temperature fluctuation of the flue gas is smoothed to increase the heat exchange efficiency by 5%, 50*0.05 = 2.5t / h more steam will be generated (equivalent to 312.5 degrees of electricity). If 1 degree of electricity costs 0.5 yuan, then 312.5*0.5*24*350 = 1.3125 million yuan can be saved.

[0074] If 2 sets of 30t boilers are configured (each boiler costs 1.5 million yuan and has a service life of 3 years), and the boiler life is extended by 1 year, 2 sets of devices can save 1.5 / 3*2 = 1 million yuan;

[0075] In summary, if the device of the present invention is used to recover the waste heat of 2 sets of 120t AOD flue gas, the income can be 3.118 + 1.3125 + 1 = 5.4305 million yuan.

[0076] For the entire system of the present invention, the waste heat of the flue gas is converted into steam enthalpy. The steam enters the steam turbine 13 to do work and directly drives the induced draft fan 7, avoiding multiple transmissions and conversions of electric energy and improving the waste heat recovery rate. A dust removal device 3 is arranged in front of the waste heat boiler 5 to reduce the dust content of the flue gas entering the boiler, prolonging the boiler life and heat exchange efficiency. A heat storage device 4 is arranged in front of the waste heat boiler 5 to store the "surplus" heat of the high-temperature flue gas when the decarburization speed of the AOD furnace is intense. When the decarburization speed of the AOD furnace decreases and the flue gas temperature drops suddenly (basically not suitable for waste heat recovery), the heat storage device 4 converts the stored thermal energy to the low-temperature flue gas, thereby smoothing the influence of temperature fluctuations on the heat exchange tubes of the subsequent waste heat boiler. At the same time, since the heat storage device 4 stabilizes the flue gas temperature, it also avoids the phenomenon that the subsequent steam accumulator 12 cannot recover the excessive steam and has to be discharged when the flue gas is at a high temperature, and solves the problem of difficulty in selecting a steam accumulator in actual production. Additionally, in Figure 1 it also shows that the flue gas from the secondary dust removal and tertiary dust removal during the production process in the workshop is directly connected to the bag filter 6 for subsequent flue gas emission.

[0077] The preferred embodiments of the present disclosure have been described in detail above in conjunction with the accompanying drawings. However, the present disclosure is not limited to the specific details in the above embodiments. Within the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

[0078] It should be noted that, in addition, the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present disclosure will not separately describe various possible combination methods.

[0079] Furthermore, any combination can be made between various different embodiments of the present disclosure as long as it does not violate the idea of the present disclosure, and it should also be regarded as the content disclosed by the present disclosure.

Claims

1. An efficient waste heat recovery system for the flue gas of an AOD furnace, characterized in that, Set up a flue gas waste heat recovery pipeline and a steam waste heat recovery pipeline; The high-temperature flue gas generated by the AOD furnace exchanges heat with the vaporization flue to generate high-temperature saturated steam and cooled flue gas; the cooled flue gas recovers waste heat through the flue gas waste heat recovery pipeline, and the high-temperature saturated steam recovers waste heat through the steam waste heat recovery pipeline; At least a dust removal device (3) and a heat storage device (4) are sequentially connected to the flue gas waste heat recovery pipeline; The dust removal device is provided with a dust removal furnace body (32), a buffer smoke exhaust cavity (31) is semi-embedded at the top of the dust removal furnace body (32), and an oxygen supply pipeline is connected and surrounded outside the middle of the dust removal furnace body (32); the outer diameter of the buffer smoke exhaust cavity (31) gradually increases away from the top of the dust removal furnace body (32); The heat storage device (4) is at least provided with a heat storage furnace body, and at least a plurality of heat storage sections are stacked in sequence along the axial direction in the heat storage furnace body; heat storage bricks are arranged in the heat storage sections, and the heat storage bricks are blocks with through holes arranged along the axial direction; high-temperature flue gas is input from the top of the heat storage furnace body and discharged from the bottom of the heat storage furnace body after being stored in a plurality of heat storage sections; low-temperature flue gas is input from the bottom of the heat storage furnace body and discharged from the top of the heat storage furnace body after being stored in a plurality of heat storage sections; The buffer smoke exhaust cavity (31) is provided with a cavity pipe, and a buffer smoke exhaust pipe (311) is connected to the cavity pipe; the buffer smoke exhaust pipe (311) is a pipe body structure with a gradually increasing outer diameter; the height of the buffer smoke exhaust pipe (311) is 1 / 3 to 3 / 4 times the height of the dust removal furnace body (32); the outer diameter range of the buffer smoke exhaust pipe (311) is 1.5 to 2.5 m; the depth of the buffer smoke exhaust cavity (31) embedded in the dust removal furnace body (32) is 1 to 2 m; The described buffer smoke exhaust cavity (31) and the dust removal furnace body (32) form an annular gap, and the volume of the annular gap is 80-90m 3 ; The oxygen supply pipeline includes an oxygen supply main pipe (33) and a plurality of oxygen supply branch pipes (331); the oxygen supply branch pipes (331) are connected and surrounded outside the dust removal furnace body (32) along the circumferential direction; the dust removal furnace body (32) is sequentially provided with a smoke inlet section (321), a buffer combustion section (322) and a sedimentation ash discharge section (323) along the axial direction; the buffer smoke exhaust cavity (31) is embedded along the smoke inlet section (321) and the buffer combustion section (322); the oxygen supply pipeline is surrounded outside the buffer combustion section (322); the smoke inlet section (321) is a conical cavity structure, and a smoke inlet pipe (34) is connected to the smoke inlet section (321); a smoke exhaust pipe (35) is connected to the top of the buffer smoke exhaust cavity (31), and a CO detector (351) is arranged on the smoke exhaust pipe (35); the sedimentation ash discharge section (323) is a conical cavity structure, and an ash discharge valve (3c) is arranged at the bottom of the sedimentation ash discharge section (323); a maintenance port (231) is arranged on the side wall of the sedimentation ash discharge section (323); The plurality of heat storage sections at least include a first heat storage section (43), a second heat storage section (44) and a third heat storage section (45); classified according to the heat storage temperature from high to low, the heat storage temperature or heat storage coefficient of the first heat storage section (43), the second heat storage section (44) and the third heat storage section (45) decreases in sequence; the heat storage bricks are block bodies with a polygonal cross-section and holes, the hole diameter is 20 to 25 mm, and the number of holes is 7 to 9; A flue gas diversion section (46) is further provided below the plurality of heat storage sections; the flue gas diversion section (46) is composed of a plurality of hollow plates; a refractory support section (47) is further provided below the flue gas diversion section (46), and the refractory support section (47) is supported by a plurality of uniformly distributed struts (471); a third adiabatic pipeline (4g) and a fourth adiabatic pipeline (4h) are provided in communication with the outside of the regenerative furnace body for the refractory support section (47); a third valve (4c) is provided on the third adiabatic pipeline (4g), and a fourth valve (4d) is provided on the fourth adiabatic pipeline (4h). A flue gas diversion section (42) is further provided on the regenerative furnace body in front of the plurality of heat storage sections, and the flue gas diversion section (42) is a cylindrical cavity structure; a first adiabatic pipeline (4e) and a second adiabatic pipeline (4f) are provided in communication with the outside of the regenerative furnace body for the flue gas diversion section (42); a first valve (4a) is provided on the first adiabatic pipeline (4e), and a second valve (4b) is provided on the second adiabatic pipeline (4f); a flue gas buffer section (41) is further provided on the regenerative furnace body in front of the flue gas diversion section (42), and the flue gas buffer section (41) is a tapered closing structure.

2. The high-efficiency recovery system for the waste heat of the AOD furnace flue gas according to claim 1, wherein The flue gas waste heat recovery pipeline includes an adiabatic flue (2), a dust removal device (3), a heat storage device (4), a waste heat boiler (5), a bag filter (6), a draft fan (7) and a chimney (8) that are connected in sequence.

3. The high-efficiency waste heat recovery system for the AOD furnace flue gas according to claim 1 or 2, characterized in that, The steam waste heat recovery pipeline includes a steam pipeline (9), a first steam drum (10), a steam accumulator (12), a steam turbine (13), a clutch (14) and a generator (15) that are connected in sequence. The generator (15) supplies power for the flue gas discharge of the flue gas waste heat recovery pipeline.

4. The high-efficiency waste heat recovery system for the AOD furnace flue gas according to claim 1 or 2, characterized in that The steam generated by the steam waste heat recovery pipeline is converted into electric energy, and the electric energy supplies power for the flue gas discharge of the flue gas waste heat recovery pipeline.

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