Rotary kiln with double dividing walls
By designing a double-wall structure and honeycomb baffle separation in the rotary kiln, combined with the wall heating and direct heating technology, the problem of difficulty in calcining small-grain limestone in traditional kilns is solved, and efficient calcination and high-quality finished products are achieved.
Patent Information
- Application Number
- CN202510197317.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-21
- Publication Date
- 2025-05-30
AI Technical Summary
Traditional rotary kilns are difficult to calcinate small-particle limestone, resulting in low raw material utilization and poor quality of finished products.
A double-wall rotary kiln is designed, using a honeycomb baffle to separate the heat transfer layer and form multiple chamber areas. The combination of wall heating and direct heating is used to improve the calcination efficiency of limestone.
Efficient calcination of fine-grained limestone less than 1mm is achieved, and the utilization rate of raw materials and the activity of finished limes is improved. The calcined limestone is the finished product after being released from the kiln, saving subsequent treatment steps.
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Figure CN120062977A_ABST
Abstract
Description
Technical Field
[0001] This application belongs to the technical field of industrial kilns and provides a double partition rotary kiln. Background Art
[0002] The main kiln types for calcining lime include shaft kilns and rotary kilns, and generally use lump raw materials. Traditional rotary kilns can calcine limestone with a particle size of 10 mm to 30 mm, but are not suitable for limestone raw materials with a smaller particle size. Summary of the Invention
[0003] In view of this, the embodiments of this application provide a double partition rotary kiln to solve the problem that it is difficult for current rotary kilns to calcine limestone with a small particle size.
[0004] The embodiments of this application provide a double partition rotary kiln, including: a rotary kiln chamber, characterized in that the rotary kiln chamber includes a first partition heat transfer layer, a second partition heat transfer layer and an outer sleeve arranged in sequence from inside to outside; the first partition heat transfer layer, the second partition heat transfer layer and the outer sleeve are all cylindrical; a honeycomb baffle is arranged inside the cylinder surrounded by the first partition heat transfer layer; the honeycomb baffle divides the inner part of the first partition heat transfer layer into a left inner chamber and a right inner chamber; the middle chamber is between the first partition heat transfer layer and the second partition heat transfer layer; the outer chamber is between the second partition heat transfer layer and the outer sleeve.
[0005] A left flue gas passage is arranged between the left inner chamber and the outer chamber; a right flue gas passage is arranged between the right inner chamber and the outer chamber; the left flue gas passage is close to the left end of the rotary kiln chamber; the right flue gas passage is close to the right end of the rotary kiln chamber.
[0006] Regenerative burners are respectively arranged at both ends of the rotary kiln chamber. A feed inlet is arranged on the kiln head hood of the rotary kiln chamber, and a discharge outlet is arranged on the kiln tail hood of the rotary kiln chamber; both the feed inlet and the discharge outlet are communicated with the middle chamber.
[0007] Specifically, the first partition heat transfer layer and the second partition heat transfer layer are made of stainless heat-resistant steel.
[0008] Specifically, refractory bricks are arranged inside the outer sleeve.
[0009] Specifically, a plurality of air ducts are arranged in the middle chamber; both ends of each air duct are communicated with the left flue gas passage and the right flue gas passage respectively.
[0010] Specifically, when the double partition rotary kiln is operating, two regenerative burners located at both ends of the rotary kiln chamber alternately burn fuel and combustion-supporting gas; the preheated powder material is conveyed into the middle chamber through the feed port, and the high-temperature gas is conveyed into the middle chamber through the discharge port; the feed port is located at the higher-positioned kiln head. During the rotation of the rotary kiln chamber, the powder material entering the middle chamber gradually spirals downward and runs to the discharge port at the kiln tail; when the left regenerative burner is burning and the right regenerative burner is storing heat, the high-temperature flue gas formed by the burning of the left regenerative burner flows along the left flue gas channel towards the honeycomb baffle, and the honeycomb baffle divides the flue gas into two parts; the honeycomb baffle makes the first part of the flue gas turn back and enter the outer chamber through the left flue gas channel, flow along the outer chamber to the right end and enter the right inner chamber through the right flue gas channel; the second part of the flue gas enters the right inner chamber through the honeycomb baffle; the high-temperature flue gas flowing through the left inner chamber, the right inner chamber and the outer chamber simultaneously conducts partition heating and calcination on the powder material in the middle chamber; at the same time, the high-temperature gas entering the middle chamber directly heats and calcines the powder material in the middle chamber; the two parts of the flue gas for partition heating and calcination converge in the right inner chamber and are then discharged together through the right regenerative burner; when the flue gas flows through the right regenerative burner, it heats the regenerator therein, so as to preheat the fuel through the regenerator after combustion reversal; after reversal, the left regenerative burner stores heat and the right regenerative burner burns, and the flow direction of the flue gas is opposite to that described above.
[0011] Specifically, the first part of the flue gas accounts for about 70% of the total flue gas volume, and the second part of the flue gas accounts for about 30% of the total flue gas volume.
[0012] Specifically, the high-temperature flue gas is high-temperature CO 2 , high-temperature flue gas, high-temperature nitrogen, high-temperature oxygen-containing gas or high-temperature combustible gas; the temperature of the high-temperature flue gas is the same as the temperature of the calcined powder material in the middle chamber.
[0013] Specifically, when the high-temperature flue gas is a high-temperature oxygen-containing gas, pulverized coal is incorporated into the powder material entering the middle chamber.
[0014] The double partition rotary kiln provided by the embodiment of the present application can calcine small-grained limestone, improve the raw material utilization rate, improve the activity of the finished lime, and is beneficial to resource conservation and environmental protection. Compared with the prior art, the advantages of the present invention are: ① high raw material utilization rate, capable of calcining fine-grained limestone less than 1 mm, improving the utilization rate of limestone mines, and enabling the use of raw materials that cannot be used by shaft kilns and ordinary rotary kilns. ② The product out of the kiln is the finished product and does not require further crushing and screening. ③ The CO 2 content in the middle chamber 8 is high. ④ The limestone obtained by calcination has good quality and high activity (can reach more than 430 ml / 4NHCl), and the overburning and underburning rate is low (can be lower than 0.1%). BRIEF DESCRIPTION OF THE DRAWINGS
[0015] To more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.
[0016] Figure 1 is a schematic structural diagram of a double-wall rotary kiln provided in Embodiment 1 of the present application; Figure 2 is a schematic structural diagram of a lifter plate arranged in the inner chamber of the double-wall rotary kiln; Figure 3 is a schematic connection diagram of a hot blast stove and a double-wall rotary kiln provided in Embodiment 1 of the present application; Figure 4 is a schematic connection diagram of a composite heating furnace and a double-wall rotary kiln provided in Embodiment 4 of the present application; Figure 5 is a schematic connection diagram of a hot blast stove and a double-wall rotary kiln provided in Embodiment 5 of the present application; Figure 6 is Figure 5 a sectional view along the A-A direction in; Figure 7 is Figure 5 a sectional view along the B-B direction in.
[0017] Among them, 1 - rotary kiln chamber, 2 - first inter-wall heat transfer layer, 3 - second inter-wall heat transfer layer, 4 - outer sleeve, 5 - honeycomb baffle, 6 - left inner chamber, 7 - right inner chamber, 8 - middle chamber, 9 - outer chamber, 10 - left flue gas passage, 11 - right flue gas passage, 12 - regenerative burner, 13 - feed inlet, 14 - discharge outlet, 15 - upper combustion chamber, 16 - lower combustion chamber, 17 - burner, 18 - regenerator, 19 - high-temperature gas outlet, 20 - heat collection hood, 21 - cyclone dust collector, 22 - heat exchanger, 23 - air duct, 24 - high-temperature gas inlet, 25 - high-temperature gas outlet, 111 - first cavity, 112 - second cavity, 113 - third cavity, 114 - burner. Detailed implementation manners
[0018] In the following description, for the purpose of illustration rather than limitation, specific details such as specific system structures and technologies are presented to thoroughly understand the embodiments of the present application. However, those skilled in the art should clearly understand that the present application can also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to avoid unnecessary details from interfering with the description of the present application.
[0019] To illustrate the technical solution described in this application, the following will be described through specific embodiments. Embodiment 1
[0020] Embodiment 1 of this application provides a double-wall rotary kiln for calcining lime, which can be used to calcine limestone with a particle size less than 0.1 cm. Figure 1 The structure of the double-wall rotary kiln in Embodiment 1 is shown. As Figure 1 shown, the double-wall rotary kiln includes a rotary kiln chamber 1, and the rotary kiln chamber 1 includes a first wall heat transfer layer 2, a second wall heat transfer layer 3, and an outer sleeve 4 arranged in sequence from the inside to the outside. The first wall heat transfer layer 2, the second wall heat transfer layer 3, and the outer sleeve 4 are all cylindrical. Inside the cylinder surrounded by the first wall heat transfer layer 2, there is a honeycomb baffle 5, and the honeycomb baffle 5 divides the inside of the first wall heat transfer layer 2 into a left inner chamber 6 and a right inner chamber 7. The middle chamber 8 is between the first wall heat transfer layer 2 and the second wall heat transfer layer 3, and the outer chamber 9 is between the second wall heat transfer layer 3 and the outer sleeve 4. There is a left flue gas channel 10 between the left inner chamber 6 and the outer chamber 9, and a right flue gas channel 11 between the right inner chamber 7 and the outer chamber 9. The left flue gas channel 10 is close to the left end of the rotary kiln chamber 1, and the right flue gas channel 11 is close to the right end of the rotary kiln chamber 1. Heat storage burners 12 are respectively arranged at both ends of the rotary kiln chamber 1. The rotary kiln chamber 1 is provided with a feed inlet 13 on the kiln head hood, and a discharge outlet 14 on the kiln tail hood. The feed inlet 13 and the discharge outlet 14 are both communicated with the middle chamber 8.
[0021] The first wall heat transfer layer 2 and the second wall heat transfer layer 3 are made of stainless heat-resistant steel, which has good thermal conductivity. The outer sleeve 4 can also be made of metal material, and refractory bricks are arranged inside the outer sleeve 4 to avoid heat dissipation. In addition, a heat collection hood 20 can be arranged outside the outer sleeve 4 to collect the heat dissipated by the rotary kiln chamber through the kiln shell. Nitrogen or carbon dioxide can be filled in the heat collection hood 20 to prevent the temperature of the metal-made outer sleeve 4 from overheating. The heat collection hood 20 can also prevent gas from leaking at the fish scale seal. The pressure of the gas in the heat collection hood 20 should be slightly higher than the pressure of the gas in the kiln to avoid gas leakage in the kiln. A ploughshare as Figure 2 shown can also be arranged in the middle chamber 8, and the powdery material in the middle chamber 8 is lifted by the ploughshare, so as to help the powdery material be evenly heated. Multiple ploughshares are allowed to be arranged in the middle chamber 8.
[0022] Figure 1When the double partition rotary kiln shown operates, the preheated limestone powder is conveyed into the middle chamber 8 through the feed inlet 13 near the kiln head, and the high-temperature gas is conveyed into the middle chamber 8 through the high-temperature gas inlet 24 near the kiln tail. The feed inlet 13 is located at the relatively high kiln head. During the rotation of the rotary kiln chamber 1, the limestone powder entering the middle chamber 8 gradually spirals downward to the discharge outlet 14 at the kiln tail. The two regenerative burners 12 located at both ends of the rotary kiln chamber 1 burn alternately, and the two regenerative burners 12 use fuel and combustion-supporting gas for combustion. Figure 1 The flow direction of the flue gas when the left regenerative burner 12 burns is shown. When the left regenerative burner 12 burns and the right regenerative burner 12 stores heat, the high-temperature flue gas formed by the combustion of the left regenerative burner 12 flows along the left flue gas passage 10 to the honeycomb baffle 5, and the honeycomb baffle 5 divides the flue gas into two parts. The honeycomb baffle 5 causes the first part of the flue gas (about 70% of the flue gas) to fold back and enter the outer chamber 9 through the left flue gas passage 10, flow along the outer chamber 9 to the right end and enter the right inner chamber 7 through the right flue gas passage 11. The second part of the flue gas (about 30% of the flue gas) enters the right inner chamber 7 through the honeycomb baffle 5. The high-temperature flue gas flowing through the left inner chamber 6, the right inner chamber 7 and the outer chamber 9 simultaneously conducts partition heating and calcination on the limestone powder in the middle chamber 8. At the same time, the high-temperature gas entering the middle chamber 8 directly heats and calcines the limestone powder in the middle chamber 8 to accelerate the heating speed. In the middle chamber 8, the high-temperature gas conducts countercurrent heating and calcination on the limestone powder, and then discharges from the high-temperature gas outlet 25 out of the double partition rotary kiln. The two parts of the flue gas for partition heating and calcination converge in the right inner chamber 7 and then are discharged together after passing through the right regenerative burner 12. When the flue gas flows through the right regenerative burner 12, it heats the regenerator therein, so that after the combustion is reversed, the combustion-supporting gas can be preheated through the regenerator, or the fuel can be preheated by using the regenerator, or both the combustion-supporting gas and the fuel can be preheated by using the regenerator.
[0023] After the reversal, the left regenerative burner 12 stores heat and the right regenerative burner 12 burns, and the flue gas flow direction is opposite to that described above.
[0024] The temperature of the high-temperature gas entering the middle chamber 8 is the same as the temperature of the limestone powder calcined in the middle chamber 8, and the high-temperature gas can be high-temperature CO 2 , high-temperature flue gas, high-temperature nitrogen, high-temperature oxygen-containing gas, high-temperature combustible gas or an appropriate mixed gas. When the high-temperature gas is a high-temperature gas containing oxygen, pulverized coal or other carbon-containing substances can be simultaneously incorporated into the powder entering the middle chamber 8. This part of the pulverized coal self-ignites in the middle chamber 8 with the high-temperature oxygen-containing gas (the high-temperature oxygen-containing gas is in excess), so as to directly calcine the limestone powder in the middle chamber 8. To prevent incomplete self-ignition of the pulverized coal in the middle chamber 8 and the occurrence of flue gas, the high-temperature oxygen-containing gas introduced into the middle chamber 8 can be in excess, so that the pulverized coal and the pulverized coal pyrolysis gas in the middle chamber 8 can be fully self-ignited.
[0025] When pure high-temperature CO is introduced into the middle chamber 8 2 the limestone powder in the middle chamber 8 can be calcined and decomposed to obtain CaO and high-temperature pure CO 2 CaO is discharged as a product from the discharge port 14, and at the same time, the high-temperature pure CO 2 can be used as a by-product. The high-temperature gas discharged from the double-wall rotary kiln passes through the cyclone dust collector 21 and the heat exchanger 22 and exchanges heat with air through the partition wall and then is discharged from the chimney, or is returned to the hot blast stove for recycling, or stored. When using high-temperature CO 2 as the high-temperature gas entering the middle chamber 8 for direct heating and calcination, it is necessary to recover the pure CO 2 discharged from the double-wall rotary kiln.
[0026] The high-temperature gas can be prepared by using the hot blast stove Figure 3 shown in the figure. Figure 3 The hot blast stove shown in the figure is provided with two combustion chambers, namely the upper combustion chamber 15 and the lower combustion chamber 16. The two ends of the upper combustion chamber 15 and the lower combustion chamber 16 are respectively provided with corresponding burners 17 and regenerators 18. The upper combustion chamber 15 and the lower combustion chamber 16 are respectively provided with a combustion exhaust gas outlet and a high-temperature gas outlet 19. The combustion exhaust gas outlets of the two combustion chambers are respectively communicated with the corresponding regenerators 18.
[0027] The upper combustion chamber 15 and the lower combustion chamber 16 alternately carry out heat storage and preheating, and the working process is as follows: When the upper combustion chamber 15 burns with liquid or gas fuel, the lower combustion chamber 16 does not burn. The combustion exhaust gas formed by the combustion in the upper combustion chamber 15 flows through the corresponding regenerator 18, heats the regenerator and then is discharged from the chimney. Although the lower combustion chamber 16 does not burn, the regenerator corresponding to the lower combustion chamber 16 has been preheated during the previous combustion of the lower combustion chamber 16. The gas to be heated enters the regenerator 18 corresponding to the lower combustion chamber 16, and after being heated by the regenerator, it is transformed into high-temperature gas. The high-temperature gas is discharged from the high-temperature gas outlet 19 corresponding to the lower combustion chamber 16 and is transported to Figure 1 the middle chamber 8 of the double-wall rotary kiln shown in the figure, so as to calcine the materials in the middle chamber 8.
[0028] After switching, when the lower combustion chamber 16 burns with liquid or gas fuel, the upper combustion chamber 15 does not burn. The combustion exhaust gas formed by the combustion in the lower combustion chamber 16 flows through the corresponding regenerator 18, heats the regenerator and then is discharged from the chimney. At the same time, the gas to be heated enters the regenerator 18 corresponding to the upper combustion chamber 15, and after being heated by the regenerator, it is transformed into high-temperature gas. The high-temperature gas is discharged from the high-temperature gas outlet 19 corresponding to the upper combustion chamber 15 and is transported to Figure 1 the middle chamber 8 of the double-wall rotary kiln shown in the figure, so as to calcine the materials in the middle chamber 8.
[0029] In a specific embodiment, refractory materials or other substances can be used to replace the high-temperature resistant stainless steel to construct the first partition heat transfer layer 2 and the second partition heat transfer layer 3.
[0030] The operation process of the double partition rotary kiln for calcining lime in Example 1 is as follows: The 200-mesh limestone powder is preheated to 300 °C by the suspension preheating device and then enters the middle chamber 8 through the feed inlet 13. At the same time, the high-temperature CO preheated to 1300 °C by the hot blast stove 2 enters the middle chamber 8 through the high-temperature gas inlet 24. The limestone powder entering the middle chamber 8 gradually spirals downward and runs to the discharge outlet 14 at the kiln tail. When the left regenerative burner 12 is burning and the right regenerative burner 12 is storing heat, the high-temperature flue gas temperature in the left inner chamber 6 is about 1300 °C - 1400 °C, the high-temperature flue gas temperature in the outer chamber 9 is about 1300 °C, and the high-temperature flue gas temperature in the right inner chamber 7 is about 1200 °C - 1300 °C. When the right regenerative burner 12 is burning and the left regenerative burner 12 is storing heat, the high-temperature flue gas temperature in the right inner chamber 7 is about 1300 °C - 1400 °C, the high-temperature flue gas temperature in the outer chamber 9 is about 1300 °C, and the high-temperature flue gas temperature in the left inner chamber 6 is about 1200 °C - 1300 °C. The high-temperature flue gas flowing through the left inner chamber 6, the right inner chamber 7 and the outer chamber 9 simultaneously conducts partition heating and calcination on the limestone powder in the middle chamber 8. At the same time, the high-temperature CO entering the middle chamber 8 2 conducts direct heating and calcination on the limestone powder in the middle chamber 8 to accelerate the heating speed. The calcined product is cooled by the suspension cooling device using cooling air. The low-temperature CO after indirect heat exchange between the middle chamber 8 and air through the heat exchanger 22 can be used 2 as the cooling air of the suspension cooling device. The temperature of the CO after cooling the lime product increases and can be transported to the suspension preheating device to preheat the raw materials. The air after indirect heat exchange through the heat exchanger 22 can be used as the combustion-supporting gas of the hot blast stove. The 200-mesh limestone powder is discharged from the furnace in five minutes, the activity of the product is above 430 ml / 4NHCl, and the overburning and underburning rate is below 0.1%. In Example 1, high-temperature CO 2 is used to directly heat the material, and the CO heated by the hot blast stove 2 is transported to the middle chamber 8. Since high-temperature CO is used in Example 1 2 for circulation, pure CO can be by-produced while calcining lime 2 . 2
[0031] In actual production, high-temperature oxygen-containing gas can be used as the circulating gas between the middle chamber 8 and the hot blast stove. When high-temperature gas containing 3% oxygen is introduced into the middle chamber 8, 3% pulverized coal can be incorporated into the material. In this case, the calcination heat comes from four sources, namely the inner partition wall, the outer partition wall, the high-temperature gas introduced into the middle chamber 8, and the pulverized coal combustion in the middle chamber 8.
[0032] The above method of directly introducing high-temperature gas into the material and directly heating the material by using the sensible heat carried by the high-temperature gas itself is also applicable to other rotary kilns or shaft kilns, such as sleeve kilns, beam kilns, and double-chamber kilns, etc. Example 2
[0033] Figure 1 The double-wall rotary kiln shown can also be used for calcining yellow gangue powder. Yellow gangue contains aluminum oxide, silicon dioxide, and iron oxide. When calcining yellow gangue powder, yellow gangue powder mixed with pulverized coal and high-temperature air can be fed into the middle chamber 8. During the calcination process, the pulverized coal entering the middle chamber 8 self-ignites with the high-temperature air in the middle chamber 8, thereby directly calcining the yellow gangue powder in the middle chamber 8. To prevent incomplete self-ignition of the pulverized coal in the middle chamber 8 and the occurrence of flue gas polluting the yellow gangue, the high-temperature air fed into the middle chamber 8 can be made excessive, so that the pulverized coal in the middle chamber 8 burns completely.
[0034] When pulverized coal is incorporated into the yellow gangue powder input into the middle chamber 8 without introducing high-temperature air, the pulverized coal incorporated into the yellow gangue powder can react with Fe 2 O 3 to carry out a reduction reaction to generate Fe 3 O 4 and CO. Fe 3 O 4 has magnetism, and this characteristic can be used to screen out Fe 3 O 4 from the calcined yellow gangue powder. The yellow gangue powder contains water, and the water reacts with the pulverized coal incorporated into the yellow gangue powder at high temperature to generate CO and H 2 . CO and H 2 can be used as circulating gas. After being discharged from the middle chamber 8 of the double-wall rotary kiln, it is heated by the hot blast stove shown in Figure 3 and then returned to the middle chamber 8 of the double-wall rotary kiln as high-temperature gas, thereby providing heat for calcining the yellow gangue powder. The pulverized coal incorporated into the yellow gangue powder should ensure that all Fe 2 O 3 is reduced to Fe 3 O 4 , and at the same time, the calcined yellow gangue powder does not contain pulverized coal, and it is also necessary to ensure that Fe 3 O 4 will not be oxidized again to transform into Fe 2 O 3 .
[0035] In addition to incorporating pulverized coal into the yellow gangue powder as a reducing agent, it is also allowed to use CO and H 2 to replace pulverized coal as a reducing agent. CO and H can be mixed into the combustion exhaust gas (mainly composed of N 2 and CO 2 ) discharged from the regenerative burner 122 , forming a mixed gas containing N 2 , CO 2 , CO and H 2 . The mixed gas is heated to about 1000 °C by a hot blast stove and then transported to the middle chamber 8. In the middle chamber 8, CO and H in the mixed gas 2 reduce Fe 2 O 3 in the yellow gangue powder, generating Fe 3 O 4 .
[0036] In Example 2, the first partition heat transfer layer 2 and the second partition heat transfer layer 3 are made of high-temperature resistant stainless steel, and the temperature for calcining the yellow gangue powder in the middle chamber 8 is about 700 °C - 800 °C. Example 3
[0037] Figure 1 The double partition rotary kiln shown can also be used for the dry distillation of straw to obtain high-temperature gas. During the dry distillation of straw, the high-temperature gas obtained by dry distilling the straw after removing the wood vinegar liquid can be fed into the middle chamber 8, so that the high-temperature gas removing the wood vinegar liquid directly heats the straw in the middle chamber 8, thereby improving the thermal efficiency of the straw dry distillation. It should be noted that the temperature of the high-temperature gas fed into the middle chamber 8 should be consistent with the temperature required for the straw dry distillation.
[0038] In Example 3, the first partition heat transfer layer 2 and the second partition heat transfer layer 3 are made of high-temperature resistant stainless steel, and the temperature for the dry distillation of straw in the middle chamber 8 is about 500 °C - 800 °C. Example 4
[0039] Figure 1 When the double partition rotary kiln shown is used in combination with a composite heating furnace, it can be used for iron reduction. In Example 4, the double partition rotary kiln can be simplified to a single partition rotary kiln, that is, the second partition heat transfer layer 3 is cancelled; at the same time, the honeycomb baffle 5 is cancelled, and the left inner chamber 6 and the right inner chamber 7 are combined into one inner chamber.
[0040] The composite heating furnace can be used for coal gasification, such as Figure 4As shown in the figure, the composite heating furnace includes three cavities, namely the first cavity 111, the second cavity 112, and the third cavity 113. The first cavity 111 and the third cavity 113 are arranged on both sides of the second cavity 112. Burners 114 are provided at the tops of the first cavity 111 and the third cavity 113, and no burner is provided at the top of the second cavity 112. The bottoms of the first cavity 111, the second cavity 112, and the third cavity 113 are interconnected and share the same molten iron bath 10. Molten iron can flow between the three cavities, but the gases between the three cavities are not connected, and the waste residues generated by gasification are also not connected. Fuel pulverized coal and combustion-supporting air are supplied to the burners 114 at the tops of the first cavity 111 and the third cavity 113, and the molten iron bath is heated by combustion. Pulverized coal for gasification and gasifying agent are supplied to the three cavities through feeding equipment. Low-calorie gas is generated in the first cavity 111 and the third cavity 113, and high-calorie gas is generated in the second cavity 112. The low-calorie gas contains combustion exhaust gas and CO discharged from the burner 114, with a calorific value of 50 kcal to 1000 kcal and a temperature of about 2000 °C. The main component of the high-calorie gas is CO, with a calorific value of up to 3000 kcal and a temperature of about 1500 °C. The yields of the two gases can be controlled by controlling the addition amount of pulverized coal for gasification. The outer wall and the base of the composite heating furnace are designed with interlayers and are cooled by water, or heat-conducting oil, or air. The partition walls used to divide each cavity are also designed with interlayers and are cooled by water, or heat-conducting oil, or air. Under the condition of keeping the molten iron flowing, the more pulverized coal for gasification is supplied, the more gas is produced.
[0041] Iron oxide powder mixed with pulverized coal and high-temperature reducing gas are input into the middle chamber 8 of the single-chamber rotary kiln. The particle sizes of both the iron oxide powder and the pulverized coal are 200 mesh, and the proportion of the pulverized coal is about 20% - 40% of the iron oxide powder. The temperature of the high-temperature reducing gas is about 1500 °C, and its components are CO and H 2 , and part of the CO and all of the H 2 come from the hot blast stove, and the remaining CO comes from the CO produced in the second cavity 112 of the composite heating furnace. The high-temperature CO and H 2 can be used for both reduction reactions and heat supply. The pulverized coal acts as a reducing agent to reduce the iron oxide in the middle chamber 8 to produce CO. The regenerative burners at both ends of the single-chamber rotary kiln are cancelled, and low-calorie gas with a temperature of about 2000 °C produced by the composite heating furnace is introduced into the inner chamber of the single-chamber rotary kiln, and the sensible heat carried by the low-calorie gas is used to indirectly heat the materials in the middle chamber 8 through the partition wall. After the low-calorie gas discharged from the inner chamber of the single-chamber rotary kiln is cooled to 300 °C by the waste heat boiler, it can be recycled or provided to other users. In the middle chamber 8 of the single-chamber rotary kiln, the iron oxide powder is reduced to iron powder. The CO and H 2 discharged from the middle chamber 8 of the single-chamber rotary kiln are dust-removed by the cyclone dust collector 21 and cooled by the heat exchanger 22, and then part of them is returned to the hot blast stove and the other part is recycled.
[0042] The metallization rate of the iron powder produced by the single-wall rotary kiln is above 95%, and the carbon content in the iron powder is not less than 2.0. The iron powder is transported to the second cavity 112 of the composite heating furnace and enters the molten pool as a raw material to be melted into molten iron.
[0043] In Example 4, refractory material is used to make the first partition heat transfer layer of the single-partition rotary kiln. During the iron reduction process, the temperature in the middle chamber 8 is about 1100°C, and the temperature in the inner chamber is about 1200°C. Example 5
[0044] Embodiment 5 of the present application provides a double-wall rotary kiln for calcining lime, which can be used in conjunction with a hot blast furnace to calcine limestone with a particle size of less than 0.1 cm. Compared with the double-wall rotary kiln in Embodiment 1, the double-wall rotary kiln in Embodiment 5 removes the honeycomb baffle 5 and the regenerative burners 12 at both ends, and only a burner 17 is set at the rear end of the kiln; the left inner chamber 6 and the right inner chamber 7 are combined into one inner chamber; a plurality of air ducts 23 are set in the middle chamber 8, as shown in FIG. Figure 5 , Figure 6 and Figure 7 .
[0045] like Figure 5 As shown, a certain proportion of coal powder is added to the limestone powder, and after being preheated by the suspension preheating device, it enters the middle chamber 8 of the double-wall rotary kiln from the kiln head. 2 Heated by hot air furnace to become high temperature CO 2 , add a certain proportion of pure oxygen into it, and mix it with O 2 High temperature CO 2 It is transported from the kiln tail to the inner and middle chambers 8. The amount of coal powder added to the limestone powder is related to the high temperature CO 2 Medium 2 The amount of addition is related to that of coal powder, which can be mixed with 2% and 3% of O 2 The high temperature CO entering the middle chamber 8 2 It flows from the kiln tail to the kiln head along the middle chamber 8, directly heating the materials in the middle chamber 8, and then discharged from the kiln head. 2 O 2 It is burned with coal powder mixed with limestone powder to directly calcine the material. 2 After burning with pulverized coal, CO 2 .
[0046] The O-doped 2 High temperature CO 2It is divided into three parts. The first part flows from the kiln tail to the kiln head along the inner chamber, and conducts indirect heating on the materials in the middle chamber 8; the second part enters the outer chamber 9 from the left flue gas passage 10 near the kiln tail and flows from the kiln tail to the kiln head along the outer chamber 9, conducts indirect heating on the materials in the middle chamber 8, and then returns to the inner chamber from the right flue gas passage 11 near the kiln head; the third part enters each air duct 23 arranged in the middle chamber 8 from the left flue gas passage 10 near the kiln tail, flows from the kiln tail to the kiln head along the air duct 23 respectively, conducts indirect heating on the materials in the middle chamber 8, and then returns to the inner chamber from the right flue gas passage 11 near the kiln head; finally, the high-temperature CO of the three parts 2 merges and is discharged from the double-intermediate-wall rotary kiln at one end of the inner chamber near the kiln head. The high-temperature CO discharged from the double-intermediate-wall rotary kiln 2 enters the suspension preheating device. On the one hand, the sensible heat carried by it is used to preheat the materials in the suspension preheating device; on the other hand, the O 2 incorporated therein burns with the pulverized coal in the limestone powder, thereby preheating the materials.
[0047] The burner 17 provided at the kiln tail end of the double-intermediate-wall rotary kiln burns with fuel and pure oxygen, and the combustion generates high-temperature CO 2 , and this part of high-temperature CO 2 flows in the same direction as the high-temperature CO 2 produced by the hot blast stove and transported into the inner chamber.
[0048] In addition, the high-temperature CO discharged from the hot blast stove 2 can be directly transported to the suspension preheating device to calcine the materials throughout the process while preheating the materials.
[0049] Figure 5 There are a total of five heat sources for calcining lime in the double-intermediate-wall rotary kiln shown. One is the high-temperature CO flowing through the inner chamber 2 , the second is the high-temperature CO flowing through the outer chamber 9 2 , the third is the high-temperature CO flowing through each air duct 23 in the middle chamber 8 2 , the fourth is the high-temperature CO flowing through the middle chamber 8 2 , and the fifth is the heat generated by the combustion of the pulverized coal incorporated in the middle chamber 8 and the O 2 entering the middle chamber 8. The first three heat sources all use the indirect heating method to calcine the materials in the middle chamber 8; the last two heat sources both use the direct heating method to calcine the materials in the middle chamber 8.
[0050] In Example 5, refractory materials are used to make the first intermediate-wall heat transfer layer 2, the second intermediate-wall heat transfer layer 3 and the air duct 23, and the temperature for calcining lime in the middle chamber 8 is about 1300 °C to 1400 °C.
[0051] The above-described embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present application, and should all be included within the protection scope of the present application.
Claims
1. A double-wall rotary kiln, comprising: A rotary kiln chamber (1), characterized in that the rotary kiln chamber (1) comprises a first partition wall heat transfer layer (2), a second partition wall heat transfer layer (3) and an outer sleeve (4) which are arranged in sequence from the inside to the outside; the first partition wall heat transfer layer (2), the second partition wall heat transfer layer (3) and the outer sleeve (4) are all cylindrical; a honeycomb baffle (5) is arranged inside the cylinder surrounded by the first partition wall heat transfer layer (2); the honeycomb baffle (5) divides the interior of the first partition wall heat transfer layer (2) into a left inner chamber (6) and a right inner chamber (7); a middle chamber (8) is between the first partition wall heat transfer layer (2) and the second partition wall heat transfer layer (3); and an outer chamber (9) is between the second partition wall heat transfer layer (3) and the outer sleeve (4); A left smoke passage (10) is provided between the left inner chamber (6) and the outer chamber (9); a right smoke passage (11) is provided between the right inner chamber (7) and the outer chamber (9); the left smoke passage (10) is close to the left end of the rotary kiln chamber (1); and the right smoke passage (11) is close to the right end of the rotary kiln chamber (1); Both ends of the rotary kiln chamber (1) are respectively provided with regenerative burners (12); A material inlet (13) is provided on the kiln head cover of the rotary kiln chamber (1), and a material outlet (14) is provided on the kiln tail cover of the rotary kiln chamber (1); the material inlet (13) and the material outlet (14) are both in communication with the middle chamber (8).
2. The double-wall rotary kiln according to claim 1, characterized in that: The first partition wall heat transfer layer (2) and the second partition wall heat transfer layer (3) are made of stainless heat-resistant steel.
3. The double-wall rotary kiln according to claim 2, characterized in that: Refractory bricks are arranged inside the outer sleeve (4).
4. The double-wall rotary kiln according to claim 3, characterized in that: A plurality of air ducts (23) are arranged in the middle chamber (8); two ends of each air duct (23) are respectively connected to the left smoke channel (10) and the right smoke channel (11).
5. A method for calcining materials using a double-partitioned wall rotary kiln as claimed in any one of claims 1 to 4, characterized in that: When the double-partitioned-wall rotary kiln is in operation, two regenerative burners (12) located at both ends of the rotary kiln chamber (1) use fuel and combustion-supporting gas to burn alternately; The preheated powder is conveyed into the middle chamber (8) through the feed port (13), and the high-temperature gas is conveyed into the middle chamber (8) through the discharge port (14); the feed port (13) is located at a higher position at the kiln head, and during the rotation of the rotary kiln chamber (1), the powder entering the middle chamber (8) gradually spirals downward to the discharge port (14) at the kiln tail; when the left regenerative burner (12) burns and the right regenerative burner (12) stores heat, the high-temperature flue gas generated by the combustion of the left regenerative burner (12) flows along the left flue gas channel (10) to the honeycomb baffle (5), and the honeycomb baffle (5) divides the flue gas into two parts; the honeycomb baffle (5) allows the first part to flow into the flue gas channel (10); the second part flows ... Part of the flue gas turns back and enters the outer chamber (9) through the left flue gas passage (10), flows along the outer chamber (9) to the right end and enters the right inner chamber (7) through the right flue gas passage (11); the second part of the flue gas enters the right inner chamber (7) through the honeycomb baffle (5); the high-temperature flue gas flowing through the left inner chamber (6), the right inner chamber (7) and the outer chamber (9) simultaneously heats and calcines the powder in the middle chamber (8); at the same time, the high-temperature gas entering the middle chamber (8) directly heats and calcines the powder in the middle chamber (8); the two parts of the flue gas heated and calcined by the partition wall merge in the right inner chamber (7) and are discharged together through the right regenerative burner (12); The flue gas heats the heat storage element in the right heat storage burner (12) when flowing through it, so that the fuel is preheated by the heat storage element after the reversing combustion; After the reversal, the left regenerative burner (12) stores heat and the right regenerative burner (12) burns, and the direction of the flue gas is opposite to that described above.
6. The method for calcining materials in a double-wall rotary kiln as claimed in claim 5, characterized in that: The first part of the smoke accounts for about 70% of the total smoke, and the second part of the smoke accounts for about 30% of the total smoke.
7. The method for calcining materials in a double-wall rotary kiln as described in claim 6, wherein the high-temperature flue gas is high-temperature CO2, high-temperature flue gas, high-temperature nitrogen, high-temperature oxygen-containing gas or high-temperature combustible gas; the temperature of the high-temperature flue gas is the same as the temperature of the calcined powder in the middle chamber (8).
8. The method for calcining materials in a double-partitioned wall rotary kiln as claimed in claim 6, wherein when the high-temperature flue gas is a high-temperature oxygen-containing gas, coal powder is added to the powder entering the middle chamber (8).