Sodium carbonate roasting furnace capable of recycling waste heat and process for co-production of sodium carbonate and calcium carbonate by using same

Abstract

The invention provides a soda ash roasting furnace capable of recycling waste heat and a process for co-production of soda ash and calcium carbonate thereof, and relates to the technical field of waste heat recycling, the soda ash roasting furnace comprises a roasting furnace main body, a base, a waste heat box and an adjusting mechanism; the base is located on the right side of the roasting furnace body, the waste heat box is installed on the upper surface of the base, an air inlet frame and an exhaust frame are installed on the left side and the right side of the waste heat box respectively in a sealed mode, and a smoke pipe is installed on the top of the roasting furnace body in a sealed mode. The adjusting mechanism comprises a middle plate and a back plate, the middle plate is rotationally installed in the middle of the interior of the air inlet frame, the back plate is fixedly arranged on the back of the middle plate, side plates are rotationally connected to the positions, located on the two sides of the middle plate, in the air inlet frame, and a sealing installation pipe is installed on the outer wall of the waste heat box. According to the scheme, angle adjustment of the middle plate and the side plates in the left-right direction is controlled, smoke concentrated in the middle can be forcibly guided to the areas on the two sides, the smoke makes full contact in the whole heat exchange section, and the heat exchange area of the low-temperature areas on the two sides is fully activated.

Description

Technical Field

[0001] This invention relates to the field of waste heat recovery, and more particularly to a soda ash roasting furnace capable of waste heat recovery and its process for co-producing calcium carbonate from soda ash. Background Technology

[0004] In the existing technology, in the industrial process of calcining sodium bicarbonate to produce soda ash, the high-temperature calcination gas and fuel combustion flue gas discharged from the calcination furnace will cause energy waste if the waste heat is directly discharged and cannot be well utilized. Secondly, the flue gas flow field is very unstable during waste heat recovery, which can easily affect the heat exchange effect.

[0005] Therefore, it is necessary to provide a soda ash roasting furnace with waste heat recovery and a process for co-producing calcium carbonate from soda ash to solve the above-mentioned technical problems. Summary of the Invention

[0006] This invention provides a soda ash roasting furnace with waste heat recovery and a process for co-producing calcium carbonate from soda ash, which solves the problems of poor utilization of waste heat in the roasting furnace and unstable distribution of waste heat flue gas flow field during the soda ash roasting process.

[0007] To solve the above-mentioned technical problems, the present invention provides a soda ash roasting furnace with waste heat recovery capability, comprising a roasting furnace body, a base, a waste heat box and an adjustment mechanism; The base is located on the right side of the roasting furnace body, the waste heat box is installed on the upper surface of the base, and an air inlet frame and an exhaust frame are respectively sealed on the left and right sides of the waste heat box. A flue gas pipe is sealed on the top of the roasting furnace body. The adjustment mechanism includes a middle plate and a back plate. The middle plate is rotatably installed in the middle position inside the air intake frame. The back plate is fixed to the back of the middle plate. Side plates are rotatably connected to both sides of the middle plate inside the air intake frame. A sealing installation tube is installed on the outer wall of the waste heat box. An adjustment electric cylinder is installed inside the sealing installation tube. A push rod is installed at the output end of the adjustment electric cylinder. A sliding rod is fixed to the inner wall of the air intake frame below the middle plate. A sliding frame is slidably connected to the outer wall of the sliding rod. Three limiting grooves are opened inside the sliding frame. Guide wheels are rotatably connected to the bottom of the middle plate and the side plates respectively. The waste heat box is equipped with heat exchange tubes, and the left and right ends of the heat exchange tubes are respectively integrated with water inlet pipes and water outlet pipes.

[0008] Preferably, the middle plate and the side plate have the same length, and the middle plate and the side plate are spaced at the same intervals relative to the inside of the air intake frame.

[0009] Preferably, the push rod is slidably connected to the sealing mounting pipe and the waste heat box, and the output end of the push rod is fixedly installed to the side wall of the sliding frame.

[0010] Preferably, the guide wheel is embedded in the three limiting grooves, and the sliding frame can slide along the guide direction of the slide rod.

[0011] Preferably, the heat exchange tube has a continuous "S" shaped structure, the water inlet pipe and the water outlet pipe are respectively sealed and installed with the waste heat box, and the outlet end of the flue gas pipe is connected to the outer wall of the air inlet frame.

[0012] Preferably, it also includes a flow guiding mechanism; The flow guiding mechanism includes a first flow guiding plate and a second flow guiding plate. Both the first flow guiding plate and the second flow guiding plate are rotatably installed inside the waste heat box and located on both sides of the heat exchange tube by torsion springs. A first connecting plate is fixedly provided on the side wall of the first flow guiding plate. A first guide roller is rotatably connected to the bottom of the first connecting plate and on one side of the first flow guiding plate. A second connecting plate is fixedly provided on the side wall of the second flow guiding plate. A second guide roller is rotatably connected to the bottom of the second connecting plate and on one side of the second flow guiding plate.

[0013] Preferably, it also includes auxiliary mechanisms; The top of the waste heat box is sealed with a mounting cover by bolts. The auxiliary mechanism includes a switching seat and a switching cylinder. The switching seat is installed on the top of the waste heat box and inside the mounting cover. The switching cylinder is installed on one side of the switching seat and inside the mounting cover. The left and right sides of the switching seat are respectively sealed with an air outlet pipe and a liquid outlet pipe, and an air inlet pipe and a liquid inlet pipe. The switching seat has a first through hole and a second through hole respectively. The output end of the switching cylinder and inside the switching seat is equipped with a telescopic rod. The outer wall of the telescopic rod is respectively fixed with a first sealing plug and a second sealing plug.

[0014] Preferably, the air outlet pipe and the liquid outlet pipe extend into the waste heat box and are located above the heat exchange tube. Nozzles are installed at equal intervals on the lower surfaces of the air outlet pipe and the liquid outlet pipe. The first through hole connects the air outlet pipe and the air inlet pipe, and the second through hole connects the liquid outlet pipe and the liquid inlet pipe. The outer walls of the first sealing plug and the second sealing plug are tightly fitted to the inner wall of the switching seat.

[0015] The process for co-producing calcium carbonate from soda ash includes the following steps: S1: Mix centrifuged salt and ammonium bicarbonate. The molar ratio of total sodium to total ammonium in the reaction system is 1:0.8-1.4. The reaction is carried out at 30-50℃ for 0.5-2 hours. After filtration and washing, sodium bicarbonate and mother liquor I are obtained. The obtained sodium bicarbonate is calcined to produce soda ash. The calcination needs to be carried out in the main body of the calcining furnace 1. S2: Add HCO3 to mother liquor I obtained in S1 − The Ca(OH)2 required for complete reaction, and the HCO3 during causticization. −The molar ratio of the causticizing residue to Ca(OH)2 is 1:0.5-0.8, the reaction time is 10-30 min, and after the reaction is completed, a causticizing residue, causticizing mother liquor II and ammonia are produced. The causticizing residue can be directly wet-screened to obtain high-purity ultrafine calcium carbonate and a mixed product of calcium sulfate dihydrate and calcium carbonate. The ammonia obtained is recycled to S1. S3: Adjust the pH of the mother liquor II obtained in S2 to 8-9 using sulfuric acid; S4: Add SO4 to mother liquor II obtained in S3 2− The Ca(OH)2 required for complete reaction, and the SO4 during causticization process 2− The molar ratio of Ca(OH)2 to Ca is 1:1-1.5, the reaction time is 10-30 min, and after the reaction is completed, a second-stage causticizing slag, causticizing mother liquor III and ammonia are produced; the obtained second-stage causticizing slag can be mixed with the mixed products in S2 to form calcium-based building material raw materials, and the obtained ammonia is recycled to S1; S5: The causticizing mother liquor III obtained from the evaporation of S4 has an evaporation crystallization temperature of 70-130℃. After filtration and separation, high-purity sodium sulfate and the evaporation mother liquor are obtained. The NH3 and H2O generated during the evaporation process can be reused in S1.

[0016] Compared with related technologies, the soda ash roasting furnace with waste heat recovery and its process for co-producing calcium carbonate from soda ash provided by the present invention have the following beneficial effects: By adjusting the angles of the middle and side plates in the left and right directions, the flue gas concentrated in the middle can be forcibly guided to the two side areas, allowing the flue gas to fully contact the entire heat exchange cross section. This fully activates the heat exchange area of ​​the low-temperature zones on both sides. Secondly, when the dust in the flue gas flows at high speed, it is easy to cause "scouring and wear" in the middle tube bundle, while dust easily accumulates in the low-speed zones on both sides. By using the middle and side plates to guide the flow, the flue gas is diverted to both sides, reducing the flow velocity in the middle area, reducing scouring and wear on the middle tube bundle, and increasing the flow velocity in the two side areas. By using airflow disturbance to reduce dust deposition, the frequency of dust removal can be reduced, effectively improving the service life of the heat exchange tubes. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0018] Figure 1 The optimal structural schematic diagram provided for this invention; Figure 2 for Figure 1 The diagram shows a cross-sectional view of the mounting cover and sealing mounting tube. Figure 3 for Figure 1 The diagram shows a cross-sectional view of the waste heat box. Figure 4 for Figure 3 The diagram shows the installation structure of the waste heat box and heat exchange tubes. Figure 5 for Figure 3 The diagram shows the structure of the adjustment mechanism; Figure 6 This is a schematic diagram of the initial working state of the adjustment mechanism provided by the present invention; Figure 7 for Figure 6 The diagram shows the working state of the control plate and side plate flipping when the adjusting electric cylinder is pushed forward. Figure 8 for Figure 6 The diagram shows the working state of the control plate and side plate flipping when the adjusting electric cylinder is pushed backward. Figure 9 This is a schematic diagram of the flow guiding mechanism provided by the present invention; Figure 10 for Figure 7 The diagram shows the impact of the side plate flipping process on the working state of the first guide plate. Figure 11 for Figure 8 The diagram shows the impact of the side plate flipping process on the working state of the second guide plate. Figure 12 A schematic diagram of the auxiliary mechanism structure provided by the present invention; Figure 13 for Figure 12 A magnified structural diagram of point A shown in the figure; Figure 14 A process flow diagram for the co-production of calcium carbonate from soda ash provided by this invention.

[0019] Explanation of icon numbers: 1. Main body of the roasting furnace; 2. Base; 3. Waste heat box; 4. Flue gas pipe; 5. Intake frame; 6. Exhaust frame; 7. Adjustment mechanism; 71. Middle plate; 72. Side plate; 73. Back plate; 74. Adjustment cylinder; 75. Push rod; 76. Slide rod; 77. Sliding frame; 78. Limiting groove; 79. Guide wheel. 8. Flow guiding mechanism; 81. First flow guiding plate; 82. Second flow guiding plate; 83. First connecting plate; 84. First guide roller; 85. Second connecting plate; 86. Second guide roller; 9. Auxiliary mechanism; 91. Switching seat; 92. Air inlet pipe; 93. Liquid inlet pipe; 94. Air outlet pipe; 95. Liquid outlet pipe; 96. Nozzle; 97. Switching electric cylinder; 98. Telescopic rod; 99. First sealing plug; 910. Second sealing plug; 911. First through hole; 912. Second through hole. 10. Sealed mounting pipe; 11. Mounting cover; 12. Heat exchange tube, 13. Water inlet pipe, 14. Water outlet pipe. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] This invention provides a soda ash roasting furnace with waste heat recovery and a process for co-producing calcium carbonate from soda ash.

[0022] First embodiment: Please see Figures 1 to 8 A soda ash roasting furnace with waste heat recovery capability includes a roasting furnace body 1, a base 2, a waste heat box 3, and an adjustment mechanism 7. The base 2 is located on the right side of the roasting furnace body 1. The waste heat box 3 is installed on the upper surface of the base 2. The left and right sides of the waste heat box 3 are respectively sealed with an air inlet frame 5 and an exhaust frame 6. The top of the roasting furnace body 1 is sealed with a flue gas pipe 4. The adjustment mechanism 7 includes a middle plate 71 and a back plate 73. The middle plate 71 is rotatably mounted in the middle of the air intake frame 5. The back plate 73 is fixed to the back of the middle plate 71. Side plates 72 are rotatably connected to both sides of the middle plate 71 inside the air intake frame 5. A sealing installation pipe 10 is installed on the outer wall of the waste heat box 3. An adjustment electric cylinder 74 is installed inside the sealing installation pipe 10. A push rod 75 is installed at the output end of the adjustment electric cylinder 74. A sliding rod 76 is fixed on the inner wall of the air intake frame 5 below the middle plate 71. A sliding frame 77 is slidably connected to the outer wall of the sliding rod 76. Three limiting grooves 78 are opened inside the sliding frame 77. Guide wheels 79 are rotatably connected to the bottom of the middle plate 71 and the side plates 72 respectively. The waste heat box 3 is equipped with a heat exchange tube 12, and the left and right ends of the heat exchange tube 12 are respectively integrated with an inlet pipe 13 and an outlet pipe 14.

[0023] Please see Figure 5 The user can activate the adjusting electric cylinder 74 to control the forward and backward movement of the push rod 75; Please see 4 and Figure 6In the initial state, the middle plate 71 and the side plate 72 are oriented in the same direction relative to the air inlet frame 5. In this state, the high-temperature flue gas entering from the air inlet frame 5 will pass through the gap between the middle plate 71 and the side plate 72 and flush the heat exchange tube 12 towards the middle section for heat exchange. Please see Figure 4 and Figure 7 The user controls the push rod 75 by adjusting the electric cylinder 74 to drive the sliding frame 77 to move forward. During the movement of the sliding frame 77, it is subjected to force through the three limiting grooves 78 and the corresponding guide wheels 79 in the limiting grooves 78. At this time, the guide wheels 79 move in the limiting grooves 78 and are thus affected by the force, controlling the middle plate 71 and the side plates 72 on both sides to flip to the right. At this time, the flue gas in the air intake frame 5 is blocked and will flush and exchange heat towards the side of the heat exchange tube 12. Please see Figure 4 and Figure 8 If the user controls the push rod 75 to drive the sliding frame 77 to move backward by controlling the electric cylinder 74, the sliding frame 77 will move backward by controlling the middle plate 71 and the side plates 72 on both sides to flip to the left through the three limit grooves 78 and the force guide wheel 79. At this time, the flue gas in the air intake frame 5 will be blocked and will flush and exchange heat towards the other side of the heat exchange tube 12.

[0024] The middle plate 71 and the side plate 72 have the same length, and the middle plate 71 and the side plate 72 are spaced at the same intervals relative to the inside of the air intake frame 5.

[0025] The push rod 75 is slidably connected to the sealing installation pipe 10 and the waste heat box 3, and the output end of the push rod 75 is fixedly installed to the side wall of the sliding frame 77.

[0026] The guide wheel 79 is embedded in the three limiting grooves 78, and the sliding frame 77 can slide along the guide direction of the slide rod 76.

[0027] The heat exchange tube 12 has a continuous "S" shaped structure. The water inlet pipe 13 and the water outlet pipe 14 are respectively sealed and installed with the waste heat box 3. The outlet end of the flue gas pipe 4 is connected to the outer wall of the air inlet frame 5.

[0028] Understandable: Please refer to Figures 3 to 5 The sealing installation pipe 10 seals the entire regulating electric cylinder 74, which ensures the working sealing and stability of the regulating electric cylinder 74. The sliding rod 76 ensures the stability of the sliding frame 77 during the sliding process. Secondly, the guide wheel 79 can reduce the friction between the guide wheel 79 and the limiting groove 78 during the movement, which can improve the service life of the guide wheel 79. This embodiment

[0029] Compared to the traditional air inlet frame 5, flue gas often concentrates in the middle of the heat exchange surface (due to inlet structure or tube bundle arrangement issues) due to inlet structure problems, while low-speed "dead zones" are formed on both sides. This invention, by controlling the angle adjustment of the middle plate 71 and the side plate 72 in the left and right directions, can force the flue gas concentrated in the middle to the two side areas, so that the flue gas can fully contact the entire heat exchange cross section, and the heat exchange area of ​​the low-temperature zone on both sides can be fully activated. Secondly, when the dust in the flue gas flows at high speed, it is easy to form "scouring wear" in the middle tube bundle, while the low-speed zone on both sides is prone to dust accumulation. By forming a guide through the middle plate 71 and the side plate 72, the flue gas is diverted to both sides, reducing the flow velocity in the middle area, reducing the scouring wear on the middle tube bundle, increasing the flow velocity in the two side areas, and using airflow disturbance to reduce dust deposition, the frequency of dust cleaning can be reduced, and the service life of the heat exchange tube 12 can be effectively improved.

[0030] Second embodiment: Please see Figures 9 to 11 It also includes a flow guiding mechanism 8; The flow guiding mechanism 8 includes a first flow guiding plate 81 and a second flow guiding plate 82. The first flow guiding plate 81 and the second flow guiding plate 82 are rotatably installed inside the waste heat box 3 by torsion springs and located on both sides of the heat exchange tube 12. A first connecting plate 83 is fixedly provided on the side wall of the first flow guiding plate 81. A first guide roller 84 is rotatably connected to the bottom of the first connecting plate 83 and on one side of the first flow guiding plate 81. A second connecting plate 85 is fixedly provided on the side wall of the second flow guiding plate 82. A second guide roller 86 is rotatably connected to the bottom of the second connecting plate 85 and on one side of the second flow guiding plate 82.

[0031] Understandable: Please refer to Figure 9 The first guide plate 81 and the second guide plate 82 are initially inclined, so when the flue gas is concentrated in the middle section, the first guide plate 81 and the second guide plate 82 can also play a guiding role.

[0032] Please refer to 10: When the side plate 72 moves to the right, the side plate 72 will abut against the first guide roller 84, which controls the first connecting plate 83 to control the first guide plate 81 to rotate clockwise and increase the inclination surface. Therefore, the flue gas passing through the right side will be guided by the first guide plate 81. Please see Figure 11 When the side plate 72 moves to the left, the side plate 72 will abut against the second guide roller 86, which controls the second connecting plate 85 to control the second guide plate 82 to rotate counterclockwise and increase the inclination surface. Therefore, the flue gas passing through the left side will be guided by the second guide plate 82. Please refer to it again. Figure 10 and Figure 11 When the side panel 72 flips to the left or right, the middle panel 71 will flip simultaneously. When the middle panel 71 flips to the left, the back panel 73 will reduce the space on the right side of the air intake frame 5 to ensure that a large amount of smoke enters the left side. When the middle panel 71 flips to the right, the back panel 73 will reduce the space on the left side of the air intake frame 5 to ensure that a large amount of smoke enters the right side. This embodiment

[0033] During the flow of flue gas, a boundary layer will form on the inner wall of the waste heat box 3 due to the influence of the wall viscosity force. The thermal resistance of the low-speed flue gas in the boundary layer is extremely high. Due to the slow flow rate, the heat exchange efficiency between the flue gas and the wall is extremely low. The first guide plate 81 and the second guide plate 82, which are set at an inclination, will directly cut the low-speed boundary layer attached to the wall, forcing the flue gas to change its flow direction from "parallel flow along the wall" to "oblique impact on the mainstream zone", breaking the stable state of the low-speed layer and allowing the high-temperature mainstream flue gas to contact the heat exchange tube 12 more directly. By guiding the flow, the flue gas adhering to the wall is stirred into the mainstream high-temperature flue gas, promoting the mixing of hot and cold flue gas, eliminating temperature stratification near the wall, and making the flue gas temperature distribution in each area of ​​the waste heat box 3 more uniform. Secondly, the tilt angle of the first guide plate 81 and the second guide plate 82 is determined by the flip angle of the side plate 72. Therefore, the larger the amount of flue gas guided, the larger the tilt angle, which can make the flue gas stirring and reversing more intense.

[0034] Third embodiment: Please see Figure 3 , Figures 12 to 13 It also includes auxiliary mechanisms 9; The top of the waste heat box 3 is sealed with a mounting cover 11 by bolts. The auxiliary mechanism 9 includes a switching seat 91 and a switching cylinder 97. The switching seat 91 is installed on the top of the waste heat box 3 and is located inside the mounting cover 11. The switching cylinder 97 is installed on one side of the switching seat 91 and is located inside the mounting cover 11. The left and right sides of the switching seat 91 are respectively sealed with an air outlet pipe 94, a liquid outlet pipe 95, an air inlet pipe 92, and a liquid inlet pipe 93. The switching seat 91 has a first through hole 911 and a second through hole 912. The output end of the switching cylinder 97 and located inside the switching seat 91 is equipped with a telescopic rod 98. The outer wall of the telescopic rod 98 is respectively fixed with a first sealing plug 99 and a second sealing plug 910.

[0035] Please see Figure 12 and Figure 13 In the initial state, the second sealing plug 910 blocks the first through hole 911, cutting off the air inlet pipe 92 and the air outlet pipe 94. At this time, the cleaning fluid that enters through the liquid inlet pipe 93 will enter the liquid outlet pipe 95 through the second through hole 912. During operation, the user can activate the switching electric cylinder 97 to control the telescopic rod 98 to move the first sealing plug 99 and the second sealing plug 910 backward. The first sealing plug 99 then blocks the second through hole 912, cutting off the inlet pipe 93 and the outlet pipe 95. At this time, the gas that enters the switching seat 91 through the air inlet pipe 92 will be discharged through the air outlet pipe 94.

[0036] Please see Figure 3 and Figure 12Both the gas outlet pipe 94 and the liquid outlet pipe 95 will enter the interior of the waste heat box 3 and be sprayed onto the surface of the heat exchange tube 12 through the fan-shaped nozzle 96.

[0037] The air outlet pipe 94 and the liquid outlet pipe 95 extend into the waste heat box 3 and are located above the heat exchange tube 12. Nozzles 96 are installed at equal intervals on the lower surfaces of the air outlet pipe 94 and the liquid outlet pipe 95. The first through hole 911 connects the air outlet pipe 94 and the air inlet pipe 92, and the second through hole 912 connects the liquid outlet pipe 95 and the liquid inlet pipe 93. The outer walls of the first sealing plug 99 and the second sealing plug 910 are tightly fitted to the inner wall of the switching seat 91. This embodiment

[0038] Waste heat flue gas usually carries impurities (such as sodium salt crystals produced by sodium bicarbonate calcination, unreacted raw material powder, dust, etc.). These impurities will gradually deposit on the surface of heat exchange tube 12, forming an ash layer or scale layer. In severe cases, it may even be necessary to shut down the machine for ash removal and interrupt the waste heat recovery process. Online or semi-online cleaning can be achieved by setting the liquid outlet pipe 95 (without complete shutdown, only the flue gas flow needs to be reduced). The fan-shaped water flow can directly flush the dust and scale on the surface of the heat exchange tube 12. The dust cleaning effect of the "S"-shaped gaps of the heat exchange tube 12 is significant. After cleaning by the liquid outlet pipe 95, there will be residual moisture on the surface of the heat exchange tube 12. The gas outlet pipe 94 dries the heat exchange elements by introducing dry compressed air (or preheated inert gas), which can eliminate "vapor resistance", avoid a sudden increase in flow resistance, avoid the generation of vaporization vapor resistance, keep the flow resistance within the normal range, and at the same time avoid corrosion of the heat exchange tube 12.

[0039] Fourth embodiment: Please combine Figure 14 The process of producing calcium carbonate from soda ash includes the following steps: S1: Mix centrifuged salt and ammonium bicarbonate. The molar ratio of total sodium to total ammonium in the reaction system is 1:0.8-1.4. The reaction is carried out at 30-50℃ for 0.5-2 hours. After filtration and washing, sodium bicarbonate and mother liquor I are obtained. The obtained sodium bicarbonate is calcined to produce soda ash. The calcination needs to be carried out in the main body of the calcining furnace 1. S2: Add HCO3 to mother liquor I obtained in S1 − The Ca(OH)2 required for complete reaction, and the HCO3 during causticization. − The molar ratio of the causticizing residue to Ca(OH)2 is 1:0.5-0.8, the reaction time is 10-30 min, and after the reaction is completed, a causticizing residue, causticizing mother liquor II and ammonia are produced. The causticizing residue can be directly wet-screened to obtain high-purity ultrafine calcium carbonate and a mixed product of calcium sulfate dihydrate and calcium carbonate. The ammonia obtained is recycled to S1. S3: Adjust the pH of the mother liquor II obtained in S2 to 8-9 using sulfuric acid; S4: Add SO4 to mother liquor II obtained in S3 2− The Ca(OH)2 required for complete reaction, and the SO4 during causticization process 2− The molar ratio of Ca(OH)2 to Ca is 1:1-1.5, the reaction time is 10-30 min, and after the reaction is completed, a second-stage causticizing slag, causticizing mother liquor III and ammonia are produced; the obtained second-stage causticizing slag can be mixed with the mixed products in S2 to form calcium-based building material raw materials, and the obtained ammonia is recycled to S1; S5: The causticizing mother liquor III obtained from the evaporation of S4 has an evaporation crystallization temperature of 70-130℃. After filtration and separation, high-purity sodium sulfate and the evaporation mother liquor are obtained. The NH3 and H2O generated during the evaporation process can be reused in S1.

[0040] This embodiment: This invention introduces inexpensive and stable Ca(OH)2 and employs a novel two-stage causticization process to achieve efficient ammonia recycling in the alkali production process, successfully producing high-purity ultrafine calcium carbonate, solid sodium sulfate, and calcium-based building material raw materials. In the Ca(OH)2 two-stage causticization process, due to the high ammonia recycling rate of CaCO3 (2.80 × 10⁻⁶), the ammonia is recycled to form CaCO3. −9 ) and CaSO4·2H2O (3.14×10 −5 The solubility product constants of the two differ significantly at standard temperatures, therefore, staged causticization can be achieved by adjusting the amount of Ca(OH)2 added: Causticization stage I mainly involves HCO3- − The reaction yields a causticizing slag with a high CaCO3 content. Subsequent wet sieving yields high-purity ultrafine calcium carbonate and a mixed product of CaSO4·2H2O and CaCO3 (the particle size difference between calcium carbonate and calcium sulfate dihydrate is significant). Causticizing stage II mainly involves SO4... 2− The reaction occurs, but the added Ca(OH)2 cannot react completely. Therefore, the second-stage causticizing slag mainly consists of CaSO4·2H2O, Ca(OH)2, and a small amount of CaCO3, which can be used as a calcium-based raw material for building materials. The causticizing filtrate mainly consists of sodium sulfate and ammonia water, which can be processed by evaporation and crystallization to obtain high-purity sodium sulfate solid. In addition, there are three ammonia production steps in the process, which can remove NH4+ from the solution. + All of it is converted into NH3, achieving efficient recovery and utilization of ammonia at the front end of the ammonia-soda process for producing soda ash.

[0041] Please refer to the reference again. Figures 1 to 1 4. The working principle of the soda ash roasting furnace with waste heat recovery and the soda ash co-production calcium carbonate process provided by the present invention is as follows: In step S1, the hydrogen carbonate obtained in the fourth embodiment is placed in the main body 1 of the calcining furnace and calcined to produce soda ash. During the calcination process, high-temperature flue gas is generated and discharged from the flue gas pipe 4. The user needs to use an external bag filter to filter out large particles, leaving only the high-temperature flue gas to enter the air inlet frame 5. Then, the heat exchange tube 12 in the air inlet frame 5 and the waste heat box 3 are connected to form waste heat recovery heat exchange. The user passes cold water into the heat exchange tube 12 through the water inlet pipe 13. Finally, the heat heats the cold water in the heat exchange tube 12 and discharges it through the water outlet pipe 14. The steam generated during the heat exchange process can be used for soda ash drying. Step S2, adjust the air intake frame 5; The user-controlled electric cylinder 74 controls the push rod 75 to drive the sliding frame 77 to move forward. During the movement of the sliding frame 77, it passes through the three limit grooves 78 and is subjected to the corresponding guide wheels 79 in the limit grooves 78. The guide wheels 79 move and are subjected to force, which affects the control plate 71 and the side plates 72 on both sides to rotate to the right. At this time, the flue gas in the air intake frame 5 is blocked and will flush and exchange heat towards the side of the heat exchange tube 12. The user controls the push rod 75 to drive the sliding frame 77 to move backward by controlling the electric cylinder 74. During the movement of the sliding frame 77, the middle plate 71 and the side plates 72 on both sides are controlled to flip to the left by the force guide wheel 79 through the three limit grooves 78. At this time, the flue gas in the air intake frame 5 is blocked and will flush and exchange heat towards the other side of the heat exchange tube 12. Step S3: Clean the heat exchange tube 12 after the heat exchange is completed; The cleaning fluid that enters through the inlet pipe 93 will enter the outlet pipe 95 through the second through hole 912 and be sprayed onto the surface of the heat exchange tube 12 through the fan-shaped nozzle 96. After spraying for a period of time, the switching electric cylinder 97 is activated to control the telescopic rod 98 to drive the first sealing plug 99 and the second sealing plug 910 to move backward. The first sealing plug 99 then blocks the second through hole 912, cutting off the liquid inlet pipe 93 and the liquid outlet pipe 95. At this time, the gas that enters the switching seat 91 through the air inlet pipe 92 will be discharged through the air outlet pipe 94. The gas is sprayed onto the surface of the heat exchange tube 12 through the fan-shaped nozzle 96.

[0042] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made under the concept of the present invention using the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A soda ash roasting furnace with waste heat recovery capability, characterized in that, Includes the main body of the roasting furnace, the base, the waste heat box, and the adjustment mechanism; The base is located on the right side of the roasting furnace body, the waste heat box is installed on the upper surface of the base, and an air inlet frame and an exhaust frame are respectively sealed on the left and right sides of the waste heat box. A flue gas pipe is sealed on the top of the roasting furnace body. The adjustment mechanism includes a middle plate and a back plate. The middle plate is rotatably installed in the middle position inside the air intake frame. The back plate is fixed to the back of the middle plate. Side plates are rotatably connected to both sides of the middle plate inside the air intake frame. A sealing installation tube is installed on the outer wall of the waste heat box. An adjustment electric cylinder is installed inside the sealing installation tube. A push rod is installed at the output end of the adjustment electric cylinder. A sliding rod is fixed to the inner wall of the air intake frame below the middle plate. A sliding frame is slidably connected to the outer wall of the sliding rod. Three limiting grooves are opened inside the sliding frame. Guide wheels are rotatably connected to the bottom of the middle plate and the side plates respectively. The waste heat box is equipped with heat exchange tubes, and the left and right ends of the heat exchange tubes are respectively integrated with water inlet pipes and water outlet pipes.

2. The soda ash roasting furnace with waste heat recovery according to claim 1, characterized in that, The middle plate and the side plate have the same length, and the middle plate and the side plate are spaced at the same intervals relative to the inside of the air intake frame.

3. The soda ash roasting furnace with waste heat recovery according to claim 1, characterized in that, The push rod is slidably connected to the sealing installation pipe and the waste heat box, and the output end of the push rod is fixedly installed to the side wall of the sliding frame.

4. The soda ash roasting furnace with waste heat recovery according to claim 1, characterized in that, The guide wheel is embedded in the three limiting grooves, and the sliding frame can slide along the guide direction of the slide rod.

5. The soda ash roasting furnace with waste heat recovery according to claim 1, characterized in that, The heat exchange tube has a continuous "S" shaped structure. The water inlet pipe and water outlet pipe are respectively sealed and installed with the waste heat box. The outlet end of the flue gas pipe is connected to the outer wall of the air inlet frame.

6. The soda ash roasting furnace with waste heat recovery according to claim 1, characterized in that, It also includes a flow guiding mechanism; The flow guiding mechanism includes a first flow guiding plate and a second flow guiding plate. Both the first flow guiding plate and the second flow guiding plate are rotatably installed inside the waste heat box and located on both sides of the heat exchange tube by torsion springs. A first connecting plate is fixedly provided on the side wall of the first flow guiding plate. A first guide roller is rotatably connected to the bottom of the first connecting plate and on one side of the first flow guiding plate. A second connecting plate is fixedly provided on the side wall of the second flow guiding plate. A second guide roller is rotatably connected to the bottom of the second connecting plate and on one side of the second flow guiding plate.

7. The soda ash roasting furnace with waste heat recovery according to claim 1, characterized in that, It also includes auxiliary mechanisms; The top of the waste heat box is sealed with a mounting cover by bolts. The auxiliary mechanism includes a switching seat and a switching cylinder. The switching seat is installed on the top of the waste heat box and inside the mounting cover. The switching cylinder is installed on one side of the switching seat and inside the mounting cover. The left and right sides of the switching seat are respectively sealed with an air outlet pipe and a liquid outlet pipe, and an air inlet pipe and a liquid inlet pipe. The switching seat has a first through hole and a second through hole respectively. The output end of the switching cylinder and inside the switching seat is equipped with a telescopic rod. The outer wall of the telescopic rod is respectively fixed with a first sealing plug and a second sealing plug.

8. The soda ash roasting furnace with waste heat recovery according to claim 7, characterized in that, The air outlet pipe and liquid outlet pipe extend into the waste heat box and are located above the heat exchange tube. Nozzles are installed at equal intervals on the lower surface of the air outlet pipe and liquid outlet pipe. The first through hole connects the air outlet pipe and the air inlet pipe, and the second through hole connects the liquid outlet pipe and the liquid inlet pipe. The outer walls of the first sealing plug and the second sealing plug are tightly fitted to the inner wall of the switching seat.

9. A process for the co-production of calcium carbonate from soda ash, characterized in that, The process for co-producing calcium carbonate from soda ash includes a soda ash roasting furnace with waste heat recovery as described in any one of claims 1-8, and includes the following steps: S1: Mix centrifuged salt and ammonium bicarbonate. The molar ratio of total sodium to total ammonium in the reaction system is 1:0.8-1.

4. The reaction is carried out at 30-50℃ for 0.5-2 hours. After filtration and washing, sodium bicarbonate and mother liquor I are obtained. The obtained sodium bicarbonate is calcined to produce soda ash. The calcination needs to be carried out in the main body of the calcining furnace 1. S2: Add HCO3 to mother liquor I obtained in S1 − The Ca(OH)2 required for complete reaction, and the HCO3 during causticization. − The molar ratio of the causticizing residue to Ca(OH)2 is 1:0.5-0.8, the reaction time is 10-30 min, and after the reaction is completed, a causticizing residue, causticizing mother liquor II and ammonia are produced. The causticizing residue can be directly wet-screened to obtain high-purity ultrafine calcium carbonate and a mixed product of calcium sulfate dihydrate and calcium carbonate. The ammonia obtained is recycled to S1. S3: Adjust the pH of the mother liquor II obtained in S2 to 8-9 using sulfuric acid; S4: Add SO4 to mother liquor II obtained in S3 2− The Ca(OH)2 required for complete reaction, and the SO4 during causticization process 2− The molar ratio of Ca(OH)2 to Ca is 1:1-1.5, the reaction time is 10-30 min, and after the reaction is completed, a second-stage causticizing slag, causticizing mother liquor III and ammonia are produced; the obtained second-stage causticizing slag can be mixed with the mixed products in S2 to form calcium-based building material raw materials, and the obtained ammonia is recycled to S1; S5: The causticizing mother liquor III obtained from the evaporation of S4 has an evaporation crystallization temperature of 70-130℃. After filtration and separation, high-purity sodium sulfate and the evaporation mother liquor are obtained. The NH3 and H2O generated during the evaporation process can be reused in S1.

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