A device and method for producing low-sulfur and low-chlorine lime powder by calcining limestone powder

Abstract

The application discloses a device and a production method for producing low-sulfur and low-chlorine lime powder by calcining limestone powder, and belongs to the field of limestone powder production and steelmaking. The decomposition furnace is divided into a high-temperature oxygen-deficient combustion region, a first limestone decomposition region and a second limestone decomposition region. A high-temperature oxygen-deficient CaO-free environment is created in the high-temperature oxygen-deficient combustion region, so as to promote the volatilization of residual KCl and NaCl, and then the residual KCl and NaCl are discharged through bypass air release technology. Limestone is added in the first decomposition region for decomposition, and combustion-supporting air is added in the second limestone decomposition region for strengthening combustion effect. In this way, the decomposition rate of limestone can be improved, the quality of steelmaking lime can be improved, and the steelmaking cost can be reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of producing steelmaking lime powder from limestone powder, in particular to a device and method for producing low-sulfur and low-chlorine lime powder from calcined limestone powder. BACKGROUND

[0002] As an important flux for converter steelmaking, lime for steelmaking plays an important role in modern converter steelmaking process. Lime for steelmaking is mainly used as a slagging material to remove harmful elements P and S in molten steel, which can improve the quality of molten steel. High-activity lime for steelmaking can significantly shorten the initial slagging time of the steelmaking converter and reduce lime consumption per ton of steel, thereby reducing the cost of steelmaking. With the increasing demand for molten steel quality and the requirement for cost reduction and efficiency improvement in steelmaking production, more precise control of the quality of lime for steelmaking is required.

[0003] At present, the requirement for limestone for producing lime for steelmaking in China is relatively high, generally requiring CaO > 52.0%, SiO2 < 2.0%, and S < 0.02% (Qu Baohui, Influence of Limestone Resources on Steel and Iron Metallurgy Industry, Refractories and Lime [J], 47 (2022).4:37-41). The commonly used raw material for producing lime for steelmaking is natural limestone. Natural limestone is the most widely distributed and abundant shale mineral in nature, but due to the complex crystal structure of limestone and the variety of impurities, natural limestone that can be used to produce lime for steelmaking is not abundant. In particular, elements such as potassium, sodium, chlorine, and sulfur in limestone are difficult to remove during calcination in equipment such as rotary kilns and shaft kilns, as high-temperature gases containing volatile KCl and NaCl will meet the low-temperature raw materials and recondense, and SO2 will react with decomposed calcium oxide to form sulfates, thus it is difficult to remove them from the system, resulting in the inability to remove potassium, sodium, chlorine, and sulfur from the final lime for steelmaking, thereby reducing the quality of the lime for steelmaking.

[0004] Therefore, the current production of lime for steelmaking is facing a series of problems:

[0005] First, elements such as chlorine, sulfur, sodium, and potassium cannot be removed in the existing production process of lime for steelmaking in shaft kilns and rotary kilns.

[0006] Second, the presence of elements such as chlorine, sulfur, sodium, and potassium in the lime for steelmaking product leads to a decrease in the quality of the lime for steelmaking, resulting in an increase in the cost of steelmaking.

[0007] Third, the decomposition rate of limestone is low and the content of calcium oxide is not high in the process of suspended preheating and calcination of limestone, which is due to the fact that the combustion of fuel is relatively intense at the beginning, but the oxygen concentration decreases in the later stage, resulting in weak combustion, which affects the decomposition of limestone. SUMMARY

[0008] In view of the problems in the prior art, the present application provides a device and a production method for producing low-sulfur and low-chlorine lime powder from calcined limestone powder, so as to reduce the content of elements such as chlorine, sulfur, sodium and potassium in the finished steel-making lime, and produce high-quality steel-making lime.

[0009] The present application is implemented in the following manner: a device for producing low-sulfur and low-chlorine lime powder from calcined limestone powder, comprising a feeding device, a multi-stage preheating cyclone, a decomposition furnace, a multi-stage cooling cyclone, and a fuel air inlet device; the air outlet of the first-stage cooling cyclone of the multi-stage cooling cyclone is divided into two air flow pipelines, the first air flow pipeline is connected to the bottom of the decomposition furnace, and the second air flow pipeline is connected to the upper part of the decomposition furnace; the fuel pipeline of the fuel air inlet device is connected to the lower part of the decomposition furnace; the material inlet of the decomposition furnace is located in the middle part of the decomposition furnace and is connected to the last-but-one preheating cyclone of the multi-stage preheating cyclone; the material outlet of the decomposition furnace is located in the top part of the decomposition furnace and is connected to the last preheating cyclone of the multi-stage preheating cyclone, so that the interior of the decomposition furnace is sequentially divided into a high-temperature and oxygen-deficient combustion zone, a first limestone decomposition zone and a second limestone decomposition zone according to the air flow direction; the first air flow pipeline and the fuel pipeline are connected to the high-temperature and oxygen-deficient combustion zone, and the second air flow pipeline is connected to the second limestone decomposition zone; the material inlet of the decomposition furnace is located in the first limestone decomposition zone; a first bypass air discharge pipeline is arranged on the decomposition furnace and is located between the material inlet of the decomposition furnace and the fuel pipeline; the first bypass air discharge pipeline is located at the junction of the high-temperature and oxygen-deficient combustion zone and the first limestone decomposition zone.

[0010] The last preheating cyclone of the multi-stage preheating cyclone is connected to the first-stage cooling cyclone of the multi-stage cooling cyclone; the generated calcium oxide is sequentially discharged after being heated by the air entering from the air inlet pipeline; the air inlet pipeline is connected to the inlet air pipe of the last cooling cyclone; and the limestone inlet pipeline of the feeding device is located on the air pipe between the first-stage preheating cyclone and the second-stage preheating cyclone.

[0011] A second bypass air discharge pipeline is arranged on the flue gas pipeline before the outlet of the third-stage preheating cyclone is connected to the material discharge pipe of the first-stage preheating cyclone.

[0012] The production method of the device for producing low-sulfur and low-chlorine lime powder by calcining the above limestone powder has the following material process: limestone powder entering from a limestone powder inlet pipeline is preheated by a multi-stage preheating cyclone, then the limestone powder enters a first limestone decomposition area, combines with high-temperature flue gas in a high-temperature oxygen-deficient combustion area to decompose calcium carbonate, then in a second limestone decomposition area, fuel further burns with high-temperature air fed through a second air flow pipeline, calcium carbonate is further decomposed completely, then enters a final-stage preheating cyclone, and the generated calcium oxide after decomposition is collected here, and then enters a first-stage cooling cyclone, a second-stage cooling cyclone and a third-stage cooling cyclone to exchange heat with air entering from an air inlet pipeline, and finally is discharged from a final-stage cooling cyclone.

[0013] The process flow of the gas is as follows: air enters from an air inlet pipeline, exchanges heat with calcium oxide decomposed from calcium carbonate by sequentially passing through multi-stage cooling cyclones, high-temperature air at the outlet of the first-stage cooling cyclone is divided into two parts, one part directly enters the high-temperature oxygen-deficient combustion area to mix with fuel entering from a fuel pipeline to generate flue gas with a higher temperature, and then mixes with limestone powder in the first limestone decomposition area, the limestone powder is decomposed by heat, then the high-temperature air in the second air flow pipeline mixes with the flue gas to further decompose calcium carbonate completely, and then enters a final-stage cyclone and sequentially passes through a penultimate-stage preheating cyclone to a first-stage preheating cyclone to be discharged from the system.

[0014] The temperature of the high-temperature oxygen-deficient combustion area is controlled at 900-1200℃.

[0015] The second bypass air release pipeline is set at a region of 600-850℃.

[0016] The molar percentage of chloride ions in the raw material limestone powder is greater than or equal to 50% of the sum of potassium ions and sodium ions.

[0017] When the molar percentage of chloride ions in the raw material is less than 50% of the sum of potassium ions and sodium ions, a non-potassium-sodium chloride salt is added to increase the molar amount of chloride ions to be greater than or equal to 50% of the sum of potassium ions and sodium ions.

[0018] When the chloride content in the raw material in the pipeline between the outlet of the decomposition furnace and the final-stage preheating cyclone is greater than or equal to 0.2%, bypass air release is performed, and the first bypass air release pipeline and the second bypass air release pipeline are opened, the air release ratio can be adjusted at 0.1%-20% according to the total air volume of the first-stage preheating cyclone discharge system, and the air release is performed to ensure that the chloride content in the raw material is less than 0.2%, and the percentage is a volume percentage fraction.

[0019] The present application has the following advantages and technical effects:

[0020] (1) The sulfur in steelmaking lime, pyrite sulfur and sulfur-containing organic matter does not enter the steelmaking lime, thus reducing the sulfur content in the steelmaking lime.

[0021] (2) By controlling the ratio of chloride ions to potassium ions and sodium ions, the volatilization of KCl and NaCl is promoted, and the decomposition of sulfate is promoted to release SO2. At the same time, the bypass ventilation technology is used to release this gas rich in potassium, sodium, chloride and sulfur out of the system. Therefore, it can effectively remove sodium, potassium, sulfur and chlorine from lime products.

[0022] (3) By dividing the decomposition furnace into a high-temperature oxygen-deficient combustion zone, a limestone primary decomposition zone, and a limestone secondary decomposition zone, a high-temperature oxygen-deficient and CaO-free environment is created in the high-temperature oxygen-deficient combustion zone to promote the volatilization of residual KCl and NaCl, which are then released through bypass venting technology. Limestone decomposition is added in the primary decomposition zone, and combustion air is reintroduced in the secondary decomposition zone to enhance the combustion effect. This can improve the decomposition rate of limestone while removing sodium, potassium, sulfur, and chlorine, thereby improving the quality of steelmaking lime and ultimately reducing steelmaking costs. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the apparatus and production method for producing low-sulfur and low-chlorine lime powder from calcined limestone powder according to the present invention.

[0024] In the diagram: 1. Primary preheating cyclone, 2. Secondary preheating cyclone, 3. Tertiary preheating cyclone, 4. Quaternary preheating cyclone, 5. Fifth preheating cyclone, 6. Decomposition furnace, 7. Primary cooling cyclone, 8. Secondary cooling cyclone, 9. Tertiary cooling cyclone, 10. First airflow duct, 11. Second airflow duct, 12. First bypass vent duct, 13. Fuel duct, 14. Air inlet duct, 15. Limestone powder inlet duct, 16. Second bypass vent duct, 6a. High-temperature oxygen-deficient combustion zone, 6b. First decomposition zone of limestone, 6c. Second decomposition zone of limestone. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below; obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] In the description of the present application, it is to be understood by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, which are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application.

[0027] In addition, the terms "first", "second" and the like are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated.

[0028] Therefore, the features defined as "first", "second" and the like can explicitly or implicitly include one or more of the features. In the description of the present application, unless otherwise stated, the meaning of "a plurality of" is two or more.

[0029] In the description of the present application, it is to be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connection" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood through specific circumstances.

[0030] As Figure 1The device for producing low-sulfur and low-chlorine lime powder by calcining limestone powder of the present application comprises a feeding device, multi-stage preheating cyclone, decomposition furnace, multi-stage cooling cyclone and fuel feeding device. The outlet of the first-stage cooling cyclone 7 of the multi-stage cooling cyclone is divided into two airflow pipelines. The first airflow pipeline 10 is connected to the bottom of the decomposition furnace 6, and the second airflow pipeline 11 is connected to the upper part of the decomposition furnace 6. The fuel pipeline 13 of the fuel feeding device is connected to the lower part of the decomposition furnace 6. The material inlet of the decomposition furnace is located in the middle part of the decomposition furnace 6 and is connected to the lower outlet of the second-to-last-stage preheating cyclone 4 of the multi-stage preheating cyclone. The material airflow outlet of the decomposition furnace is located in the top of the decomposition furnace 6 and is connected to the inlet of the last-stage preheating cyclone 5 of the multi-stage preheating cyclone. The interior of the decomposition furnace 6 is divided into high-temperature and oxygen-deficient combustion area 6a, limestone first decomposition area 6b and limestone second decomposition area 6c in sequence according to the airflow direction. The first airflow pipeline 10 and the fuel pipeline 13 are connected to the high-temperature and oxygen-deficient combustion area 6a, and the second airflow pipeline 11 is connected to the limestone second decomposition area 6c. The material inlet of the decomposition furnace is located in the limestone first decomposition area 6b. The first bypass air discharge pipeline 12 is arranged on the decomposition furnace and is located between the material inlet of the decomposition furnace and the fuel pipeline 13. The first bypass air discharge pipeline 12 is located at the junction of the high-temperature and oxygen-deficient combustion area 6a and the limestone first decomposition area 6b.

[0031] The lower outlet of the last-stage preheating cyclone 5 of the multi-stage preheating cyclone is connected to the feeding inlet of the first-stage cooling cyclone 7 of the multi-stage cooling cyclone. The generated calcium oxide is discharged after being sequentially cooled by the air entering from the air inlet pipeline 14. The air inlet pipeline 14 is connected to the inlet air pipeline of the last-stage cooling cyclone 9. The limestone inlet pipeline 15 of the feeding device is located on the air pipeline between the first-stage preheating cyclone 1 and the second-stage preheating cyclone 2.

[0032] The second bypass air discharge pipeline 16 is arranged on the flue gas pipeline before the outlet of the third-stage preheating cyclone 3 and the lower discharge pipeline of the first-stage preheating cyclone 1 are combined.

[0033] The production method of the device for producing low-sulfur and low-chlorine lime powder by calcining limestone powder is as follows. The limestone powder entering from the limestone powder inlet pipeline 15 is preheated by the multi-stage preheating cyclone. Then, the limestone powder enters the limestone first decomposition area 6b, is combined with the high-temperature flue gas of the high-temperature and oxygen-deficient combustion area 6a, and is decomposed. Then, in the limestone second decomposition area 6c, the fuel is further combusted with the high-temperature air fed through the second airflow pipeline 11, and the calcium carbonate is further decomposed completely. Subsequently, the calcium oxide generated after decomposition is collected in the last-stage preheating cyclone 5, sequentially enters the first-stage cooling cyclone 7, the second-stage cooling cyclone 8 and the third-stage cooling cyclone 9, exchanges heat with the air entering from the air inlet pipeline 14, and is finally discharged from the last-stage cooling cyclone.

[0034] The process flow of the gas: air enters from the air inlet pipe 14, and is sequentially heat-exchanged with the calcium oxide decomposed from calcium carbonate in the multi-stage cooling cyclone and calcium oxide. The high-temperature air at the outlet of the first-stage cooling cyclone 7 is divided into two parts. One part directly enters the high-temperature oxygen-deficient combustion area 6a and mixes with the fuel entering from the fuel pipe 13 to generate flue gas with higher temperature. Then, the flue gas mixes with the limestone powder in the first limestone decomposition area 6b, and the limestone powder is decomposed by heat. Then, the high-temperature air in the second air flow pipe 11 mixes with the flue gas to further decompose the calcium carbonate completely. Subsequently, the flue gas enters the last-stage cyclone 5, and sequentially flows through the second-to-last-stage preheating cyclone 4 to the first-stage preheating cyclone 1 and is discharged from the system.

[0035] The temperature of the high-temperature oxygen-deficient combustion area 6a is controlled at 900-1200℃.

[0036] The second bypass pipe 16 is set at the area of 600-850℃.

[0037] The molar percentage of chloride ions in the raw limestone powder is greater than or equal to 50% of the sum of the molar percentages of potassium ions and sodium ions.

[0038] When the molar percentage of chloride ions in the raw material is less than 50% of the sum of the molar percentages of potassium ions and sodium ions, a non-potassium-sodium chloride salt is added to increase the molar amount of chloride ions to be greater than or equal to 50% of the sum of the molar percentages of potassium ions and sodium ions.

[0039] When the chloride content in the raw material in the pipe between the outlet of the decomposition furnace 6 and the last-stage preheating cyclone 5 reaches 0.2% or more, bypass air is discharged, and the first bypass pipe 12 and the second bypass pipe 16 are opened at the same time. The air discharge ratio can be adjusted at 0.1%-20% according to the total air volume of the first-stage preheating cyclone 1 discharge system. The air is discharged to ensure that the chloride content in the raw material is less than 0.2%. The percentage is a volume percentage fraction.

[0040] The principle of the present application is as follows:

[0041] Firstly, the present application adopts air staging technology, and air is added in two stages. In the first stage area, air is insufficient, fuel is relatively more, there is no limestone decomposition, and it belongs to the high-temperature oxygen-deficient combustion area, and the temperature can be controlled at 900-1200℃. Since KCL and NaCl continuously circulate in the gasification and solidification processes with the increase of temperature in the system, the particle size of KCL and NaCl crystal dust is small, and the collection efficiency of KCL and NaCl crystal dust in the first-stage cooling cyclone 7 is low. Therefore, KCl and NaCl are gasified into steam after entering the high-temperature oxygen-deficient combustion area 6a in the first air flow pipe 10. Therefore, the first bypass pipe 12 is used to discharge part of the flue gas to destroy the circulation of KCl and NaCl and reduce the potassium and sodium chloride content in the lime product. The air discharge can be in an intermittent or continuous manner.

[0042] Second, according to the relevant research (Cui Yudong, Potassium sodium chloride sulfur volatile characteristics and the influence of clinker calcination, Zhejiang University [D], 2011), at 600-800℃ and 1000-1200℃, there is a peak of each of the volatilization of chlorine, potassium, sulfur, and the increase of chlorine content can promote the volatilization of potassium, sodium, sulfur, improve the decomposition rate of sulfate, stimulate the transfer of sulfur from the solid phase to the gas phase. Because below 800℃, limestone decomposition is less, the content of calcium oxide is low, this part of sulfur dioxide will not be absorbed to regenerate sulfate, thus reducing sulfur emissions. Therefore, the present application proposes requirements for the chlorine content of the raw material, when the chlorine content in the raw material is insufficient, add part of calcium chloride. Because the volatilization rate of chlorine is close to 100% above 800℃, therefore the chlorine in the increased calcium chloride will not enter the steelmaking lime.

[0043] Third, the sulfur in limestone, in addition to sulfate, there are pyrite sulfur and sulfur-containing organic matter, both of which account for more than 50% of the total sulfur content. The pyrite sulfur and sulfur-containing organic matter in the present application react to release SO2 in the secondary preheating cyclone 2 and the tertiary preheating cyclone 3 after entering the device. Here, there is no calcium oxide to adsorb SO2, and SO2 is discharged with the flue gas from the primary preheating cyclone 1, thereby reducing the sulfur entering the steelmaking lime.

[0044] Example 1

[0045] A device for calcining limestone powder to produce low-sulfur and low-chlorine lime powder, comprising a primary preheating cyclone 1, a secondary preheating cyclone 2, a tertiary preheating cyclone 3, a quaternary preheating cyclone 4, a quinary preheating cyclone 5, a decomposition furnace 6, a primary cooling cyclone 7, a secondary cooling cyclone 8, a tertiary cooling cyclone 9, a first air flow pipeline 10, a second air flow pipeline 11, a first bypass air pipe 12, a fuel pipeline 13, an air inlet pipeline 14, a limestone powder inlet pipeline 15, and a second bypass air pipe 16, wherein the decomposition furnace 6 is divided into a high-temperature oxygen-deficient combustion area 6a, a limestone first decomposition area 6b, and a limestone second decomposition area 6c.

[0046] The limestone powder entering from the limestone powder inlet pipeline 15 is preheated by the primary preheating cyclone 1, the secondary preheating cyclone 2, the tertiary preheating cyclone 3, and the quaternary preheating cyclone 4, and then the limestone powder enters the limestone first decomposition area 6b, where it is combined with the high-temperature flue gas of the high-temperature oxygen-deficient combustion area 6a to decompose the calcium carbonate. Then, in the limestone second decomposition area 6c, the fuel further combusts with the high-temperature air passing through the second air flow pipeline 11, and the calcium carbonate is further decomposed completely. Subsequently, the limestone enters the quinary preheating cyclone 5, where the generated calcium oxide after decomposition is collected, and then enters the primary cooling cyclone 7, the secondary cooling cyclone 8, and the tertiary cooling cyclone 9 in turn to exchange heat with the air entering from the air inlet pipeline 14, and finally is discharged from the tertiary cooling cyclone 9.

[0047] Air enters from air inlet pipe 14, and exchanges heat with calcium oxide decomposed by calcium carbonate in turn in three-stage cooling cyclone 9, two-stage cooling cyclone 8, and one-stage cooling cyclone 7. Then, high-temperature air at the outlet of one-stage cooling cyclone 7 is divided into two parts. One part directly enters high-temperature oxygen-deficient combustion area 6a to mix with fuel from fuel pipe 13 to generate flue gas with higher temperature by combustion. Then, the flue gas mixes with limestone powder in limestone first decomposition area 6b, and the limestone powder is decomposed by heat. Then, high-temperature air from second air flow pipe 11 mixes with the flue gas to further decompose calcium carbonate completely. Subsequently, the flue gas enters five-stage preheating cyclone 5, and flows through four-stage preheating cyclone 4, three-stage preheating cyclone 3, two-stage preheating cyclone 2, and one-stage preheating cyclone 1 in turn, and is discharged from the system.

[0048] In production, the temperature of high-temperature oxygen-deficient combustion area 6a is controlled at 1100-1200 degrees Celsius.

[0049] First bypass pipe 12 is arranged between high-temperature oxygen-deficient combustion area 6a and limestone first decomposition area 6b, and before the material from four-stage preheating cyclone 4 is not contacted with flue gas.

[0050] Second bypass pipe 16 is arranged at a dust concentration area with a temperature of 750-850 degrees Celsius and a low dust concentration, and on the flue gas pipe before the outlet of three-stage preheating cyclone 3 and the material pipe of one-stage preheating cyclone 1 are combined. The mole percentage of chloride ions needs to be equal to 60% of the sum of potassium ions and sodium ions.

[0051] When the chloride content in the material in the pipe between the outlet of decomposition furnace 6 and five-stage preheating cyclone 5 is more than 0.2%, bypass is always carried out, and the bypass ratio is 2%.

[0052] When the chloride content in the material in the pipe between the outlet of decomposition furnace 6 and five-stage preheating cyclone 5 is more than 0.2%, bypass is always carried out, and the bypass ratio is 2%.

[0053] Finally, compared with the previous invention CN103387347B of the applicant, the sulfur content in the steelmaking lime is reduced by 40%, the chloride content is reduced by 20%, the potassium content is reduced by 55%, and the sodium content is reduced by 30%.

[0054] Example 2

[0055] The application relates to a method and device for producing low-sulfur and low-chlorine lime powder by calcining limestone powder, which comprises a first-stage preheating cyclone 1, a second-stage preheating cyclone 2, a third-stage preheating cyclone 3, a fourth-stage preheating cyclone 4, a fifth-stage preheating cyclone 5, a decomposing furnace 6, a first-stage cooling cyclone 7, a second-stage cooling cyclone 8, a third-stage cooling cyclone 9, a first gas flow pipeline 10, a second gas flow pipeline 11, a first bypass air release pipeline 12, a fuel pipeline 13, an air inlet pipeline 14, a limestone powder inlet pipeline 15 and a second bypass air release pipeline 16, wherein the decomposing furnace 6 is divided into a high-temperature and oxygen-deficient combustion area 6a, a first limestone decomposing area 6b and a second limestone decomposing area 6c.

[0056] The limestone powder entering from the limestone powder inlet pipeline 15 is preheated by the first-stage preheating cyclone 1, the second-stage preheating cyclone 2, the third-stage preheating cyclone 3 and the fourth-stage preheating cyclone 4, and then enters the first limestone decomposing area 6b to be decomposed in combination with the high-temperature flue gas of the high-temperature and oxygen-deficient combustion area 6a, and then enters the second limestone decomposing area 6c to be further decomposed in combination with the high-temperature air of the second gas flow pipeline 11, and then enters the fifth-stage preheating cyclone 5 to be collected, and then enters the first-stage cooling cyclone 7, the second-stage cooling cyclone 8 and the third-stage cooling cyclone 9 to be heat-exchanged with the air entering from the air inlet pipeline 14, and finally is discharged from the third-stage cooling cyclone 9.

[0057] The air entering from the air inlet pipeline 14 is heat-exchanged with the decomposed calcium oxide in the third-stage cooling cyclone 9, the second-stage cooling cyclone 8 and the first-stage cooling cyclone 7, and then the high-temperature air of the first-stage cooling cyclone 7 is divided into two parts, one part directly enters the high-temperature and oxygen-deficient combustion area 6a to be mixed with the fuel entering from the fuel pipeline 13 to generate flue gas with higher temperature, and then the flue gas is mixed with the limestone powder in the first limestone decomposing area 6b to decompose the limestone powder, and then the high-temperature air of the second gas flow pipeline 11 is mixed with the flue gas to further decompose the calcium carbonate, and then enters the fifth-stage preheating cyclone 5 and sequentially flows through the fourth-stage preheating cyclone 4, the third-stage preheating cyclone 3, the second-stage preheating cyclone 2 and the first-stage preheating cyclone 1 to be discharged from the system.

[0058] During production, the temperature of the high-temperature and oxygen-deficient combustion area 6a is controlled to be 1100-1200 DEG C.

[0059] The first bypass air release pipeline 12 is arranged between the high-temperature and oxygen-deficient combustion area 6a and the first limestone decomposing area 6b, and before the limestone powder discharged from the fourth-stage preheating cyclone 4 is contacted with the flue gas.

[0060] The second bypass pipe 16 is set in a region with a dust concentration of 750-850 degrees Celsius, and the molar percentage of chlorine ions in the third stage is less than 50% of the sum of potassium ions and sodium ions. Calcium chloride is added to increase the percentage to 50.1%.

[0061] When the chlorine content in the raw material in the pipe between the outlet of the decomposition furnace 6 and the fifth stage preheating cyclone 5 is greater than or equal to 0.2%, the bypass is always open, and the bypass ratio is 2%.

[0062] When the chlorine content in the raw material in the pipe between the outlet of the decomposition furnace 6 and the fifth stage preheating cyclone 5 is greater than or equal to 0.2%, the bypass is always open, and the bypass ratio is 2%.

[0063] Finally, compared with the previous invention CN103387347B, the sulfur content in the steelmaking lime is reduced by 35%, the chlorine content is reduced by 18%, the potassium content is reduced by 53%, and the sodium content is reduced by 27%.

[0064] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. An apparatus for producing low sulfur and low chlorine lime powder from calcination of limestone powder, comprising a feeding device, a multi-stage preheating cyclone, a decomposing furnace, a multi-stage cooling cyclone, a fuel feeding device, characterized in that, The first-stage cooling cyclone (7) of the multi-stage cooling cyclone is divided into two air flow pipes, the first air flow pipe (10) is connected to the bottom of the decomposing furnace (6), the second air flow pipe (11) is connected to the upper part of the decomposing furnace (6), the fuel pipe (13) of the fuel feeding device is connected to the lower part of the decomposing furnace (6), the material inlet of the decomposing furnace is located in the middle part of the decomposing furnace (6) and connected to the lower outlet of the second-to-last-stage preheating cyclone (4) of the multi-stage preheating cyclone, the material air flow outlet of the decomposing furnace is located in the top of the decomposing furnace (6) and connected to the inlet of the last-stage preheating cyclone (5) of the multi-stage preheating cyclone, so that the inside of the decomposing furnace (6) is divided into a high-temperature and oxygen-deficient combustion area (6a), a first limestone decomposing area (6b) and a second limestone decomposing area (6c) in sequence according to the air flow direction, the first air flow pipe (10) and the fuel pipe (13) are connected to the high-temperature and oxygen-deficient combustion area (6a), the second air flow pipe (11) is connected to the second limestone decomposing area (6c), the material inlet of the decomposing furnace is located in the first limestone decomposing area (6b), the first bypass air pipe (12) is arranged on the decomposing furnace between the material inlet of the decomposing furnace and the fuel pipe (13), and the first bypass air pipe (12) is located at the junction of the high-temperature and oxygen-deficient combustion area (6a) and the first limestone decomposing area (6b); The lower outlet of the last-stage preheating cyclone (5) of the multi-stage preheating cyclone is connected to the material inlet of the first-stage cooling cyclone (7) of the multi-stage cooling cyclone, the generated calcium oxide is sequentially discharged after heat exchange with the air entering from the air inlet pipe (14), the air inlet pipe (14) is connected to the inlet air pipe of the last-stage cooling cyclone, and the limestone powder inlet pipe (15) of the feeding device is located on the air pipe between the first-stage preheating cyclone (1) and the second-stage preheating cyclone (2).

2. The apparatus for producing low sulphur and low chlorine lime powder by calcination of limestone powder as claimed in claim 1 wherein, The second bypass air pipe (16) is arranged on the flue gas pipe before the outlet of the third-stage preheating cyclone (3) is combined with the lower discharge pipe of the first-stage preheating cyclone (1).

3. A production method of the device for producing low-sulfur and low-chlorine lime powder by calcining limestone powder according to claim 2, characterized in that, The process flow of the material is that the limestone powder entering from the limestone powder inlet pipe (15) is preheated by the multi-stage preheating cyclone, then the limestone powder enters the first limestone decomposing area (6b) and is combined with the high-temperature flue gas of the high-temperature and oxygen-deficient combustion area (6a) to decompose calcium carbonate, then in the second limestone decomposing area (6c), the fuel is further combusted with the high-temperature air fed through the second air flow pipe (11) to further decompose the calcium carbonate completely, and then the calcium oxide generated after decomposition is collected in the last-stage preheating cyclone (5), sequentially enters the first-stage cooling cyclone (7), the second-stage cooling cyclone (8) and the third-stage cooling cyclone (9), is heat-exchanged with the air entering from the air inlet pipe (14), and is finally discharged from the last-stage cooling cyclone. The process flow of the gas: air enters from the air inlet pipe (14), and is sequentially heat exchanged with the calcium oxide decomposed from calcium carbonate in the multi-stage cooling cyclone. The high-temperature air at the outlet of the first-stage cooling cyclone (7) is divided into two parts, one part directly enters the high-temperature anoxic combustion area (6a) and is mixed with the fuel entering from the fuel pipe (13) to generate flue gas with higher temperature, and then is mixed with the limestone powder in the first limestone decomposition area (6b), the limestone powder is decomposed by heat, and then the high-temperature air in the second air flow pipe (11) is mixed with the flue gas to further decompose the calcium carbonate completely, and then enters the last-stage preheating cyclone (5), and sequentially flows through the second-to-last-stage preheating cyclone (4) until the first-stage preheating cyclone (1) is discharged from the system.

4. The process for producing low sulphur and low chlorine lime powder by calcining limestone powder as claimed in claim 3 wherein, The temperature of the high-temperature anoxic combustion area (6a) is controlled at 900-1200℃.

5. The process for producing low sulphur and low chlorine lime powder by calcination of limestone powder as claimed in claim 3 wherein, The second bypass pipe (16) is set at a temperature of 600-850℃. ​ 6. The process for producing low sulphur and low chlorine lime powder by calcination of limestone powder as claimed in claim 3 wherein, The mole percentage of chloride ions in the raw limestone powder is greater than or equal to 50% of the sum of potassium ions and sodium ions.

7. The process for producing low sulphur and low chlorine lime powder by calcining limestone powder as claimed in claim 6 wherein, When the mole percentage of chloride ions in the raw material is less than 50% of the sum of potassium ions and sodium ions, a non-potassium-sodium chloride salt is added to increase the mole amount of chloride ions to greater than or equal to 50% of the sum of potassium ions and sodium ions.

8. The process for production of low sulphur and low chlorine lime powder from calcination of limestone powder as claimed in claim 3 wherein, When the chloride content in the raw material in the pipe between the outlet of the decomposition furnace (6) and the last-stage preheating cyclone (5) is greater than or equal to 0.2%, bypassing is performed, and the first bypass pipe (12) and the second bypass pipe (16) are opened at the same time, the bypassing ratio can be adjusted at 0.1%-20% according to the total air volume of the first-stage preheating cyclone (1) discharge system, and the bypassing is performed to ensure that the chloride content in the raw material is less than 0.2%, and the percentage is a volume percentage fraction. ​

Images