Desulfurization and denitrification system and desulfurization and denitrification method for rotary kiln and cement kiln

Abstract

The invention discloses a rotary kiln, a cement kiln desulfurization and denitrification system and a desulfurization and denitrification method. The rotary kiln comprises a kiln body, the kiln body comprises a kiln head and a kiln tail, the kiln head is provided with a first pulverized coal burner, the middle of the kiln body is provided with an air inlet device, and the position, close to the kiln tail, of the kiln body is provided with an ammonia inlet device. The desulfurization and denitrification method is low in cost and high in efficiency, and ultralow emission of dust, SO2, NOx and the like in the cement kiln flue gas is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of cement kiln flue gas desulfurization and denitrification, and in particular relates to a rotary kiln and a cement kiln desulfurization and denitrification system and a desulfurization and denitrification method. Background Art

[0002] Cement is an important building material and is widely used in construction, infrastructure, and engineering construction. However, the cement production process produces a large amount of nitrogen oxides (NOx) and sulfur dioxide (SO 2 ) and other harmful gases, posing potential risks to the environment and human health. In order to reduce the emission of atmospheric pollutants in the cement production process, protect the environment and improve air quality, the cement industry needs to take corresponding desulfurization and denitrification measures. At present, the domestic thermal power industry has carried out ultra-low emission transformation, which has greatly reduced the emission of nitrogen oxides and sulfur dioxide. Nitrogen oxides in the building materials industry, especially the cement industry, have become the main source of nitrogen oxide pollution. It is urgent for the cement kiln industry to try ultra-low emissions.

[0003] In the cement kiln production process, SO 2 It is mainly produced from coal combustion. Most domestic cement kilns use low-sulfur coal as fuel. SO 2 The content is generally 50~300mg / Nm 3 , but still does not meet the ultra-low emission standard (35mg / Nm 3 ) requirements; the causes of NOx generation are relatively complex, and are mainly divided into thermal and combustion types. Thermal nitrogen oxides are generated when nitrogen reacts with oxygen under high temperature conditions (>1500℃). The flame temperature in the cement kiln is as high as about 1800℃, which is the temperature peak area in the entire clinker burning process. Due to the high temperature that produces thermal NOx, the burner flame is the main source of NOx generated in the cement kiln, accounting for more than 80% of the NOx generated in the entire kiln system. Fuel-type nitrogen oxides are mainly generated by organic nitrogen in raw materials and fuels during combustion or heating. The distribution of these nitrogen oxides in the cement clinker production line shows that although there are several forms of NOx generated in the kiln, they are all formed in the process of increasing the temperature.

[0004] Application publication number CN 111841322 A discloses a denitrification emission method for cement kilns. On the basis of the existing dry cement kiln system, a catalyst is added to the flue gas at the outlet of the preheater system. After the catalyst and the flue gas are mixed, the flue gas containing the reducing agent and nitrogen oxides is catalyzed to undergo a denitrification reaction. The catalyst is collected at the dust collector at the end of the kiln, and enters the preheater system together with the raw material through the raw material warehouse and the raw material elevator, and again catalyzes the flue gas containing the reducing agent and nitrogen oxides to undergo a denitrification reaction. The reducing agent is an ammonia compound or an amine compound, which is added at a newly installed reducing agent filling point on the preheater or using an existing SNCR system. This method has the characteristics of low investment, low operating cost, no blockage, no poisoning, and high reliability. However, the denitrification catalyst in this method is a consumable product and needs to be added continuously; and the nitrogen oxides cannot reach 50mg / Nm 3 Ultra-low emission requirements.

[0005] A Chinese patent with authorization announcement number CN 214764469 U discloses an SCR denitrification reactor for a cement kiln denitrification ultra-low purification system, comprising a reactor body, a flue gas inlet is provided on the top of the reactor body, a flue gas outlet is provided at the bottom of the reactor body, a rectifying grid is provided at the flue gas inlet of the reactor body, a first support beam is provided at the bottom of the reactor body, and limit brackets are provided on both sides of the reactor body. The limit brackets are fixedly connected to the reactor body through a guide device and a steel plate. This method adds an SCR reactor. Since alkaline metals in cement kilns are prone to catalyst poisoning, and the dust content in the flue gas is high, the catalyst is severely worn, the replacement cycle is short, and the operating cost is high.

[0006] The Chinese patent application with publication number CN112679121A discloses a low-emission and low-energy cement clinker production line, which mentions that while ensuring that the reduction zone does not frequently form crust, the pulverized coal is allowed to produce as much CO as possible under anaerobic conditions, so that it reacts with NOx in the pre-decomposition kiln system to reduce NOx emissions. This solution controls the amount of air, controls the combustion of pulverized coal, and then reduces CO and NOx under the action of a catalyst.

[0007] The Chinese patent application with publication number CN116143431A discloses a method for preparing low-alkali cement clinker using clay, which points out that after raw material grinding, homogenization treatment, high solid-gas ratio suspension preheat decomposition, and then firing in a new dry rotary kiln to make clinker, NOx content is effectively controlled, ultra-low emission standards are achieved, and the physical quality of cement is improved. Compared with the patent application, the patent improves the production of cement clinker by changing the raw material composition ratio, but the NOx generated in the flue gas is mainly thermal NOx produced by the reaction of N2 in the air with O2, and fuel NOx generated by the reaction of N element in coal powder with air. Changing the raw material ratio cannot achieve the purpose of controlling NOx generation.

[0008] At present, SNCR technology is mostly used for denitrification of cement rotary kiln flue gas, but the denitrification efficiency is only about 40-50%. Summary of the invention

[0009] The present invention aims to provide a rotary kiln and cement kiln desulfurization and denitrification system and a desulfurization and denitrification method, which can reduce dust, SO 2 , NOx emissions.

[0010] In order to achieve the above object, the technical solution adopted by the present invention is:

[0011] A rotary kiln comprises a kiln body, wherein the kiln body comprises a kiln head and a kiln tail, the kiln head is provided with a first pulverized coal burner, an air inlet of the first pulverized coal burner is connected with a blower, an air inlet device is provided in the middle of the kiln body, and an ammonia inlet device is provided near the kiln tail of the kiln body.

[0012] The ammonia inlet device has the same structure as the air inlet device, and the existing air inlet device can be used. It is located in the raw material preheating section of the rotary kiln. The flue gas temperature in the kiln is about 950-1050°C, which is the optimal temperature range for SNCR denitrification reaction. The ammonia supply device provides ammonia that enters the rotary kiln from the ammonia inlet device to undergo redox reaction with nitrogen oxides produced by combustion, thereby further removing NOx produced by coal powder combustion.

[0013] Compared with the Chinese patent with publication number CN114797432A, both are SNCR reaction processes, but the ammonia injection position is completely different. This patent injects ammonia in the preheating section of the rotary kiln, and the reaction temperature of the decomposition furnace is higher, so the SNCR denitrification efficiency is also higher. Compared with the Chinese patent with publication number CN114797432A, the denitrification efficiency can be increased by 10-20%.

[0014] According to the embodiments of the present invention, the present invention can be further optimized. The following is the technical solution formed after optimization:

[0015] In one of the preferred embodiments, the air inlet device includes a moving ring which surrounds the outer wall of the kiln body and is fixed thereto, the cross-section of the moving ring is a U-shaped groove, the opening of the U-shaped groove faces outward, and the static ring is integrally nested in the inner side of the U-shaped groove of the moving ring, and a plurality of air inlet pipes are installed through the outer wall of the kiln body, and the plurality of air inlet pipes are arranged at intervals along the circumference of the kiln body, a gravity half-open valve is installed at one end of the air inlet pipe located in the kiln body, and the other end of the air inlet pipe is connected to the chamber between the moving ring and the static ring, and an air inlet is installed through the static ring, and the air inlet is connected to the chamber.

[0016] In one of the preferred embodiments, the static ring includes an inner layer spring sheet and an outer layer spring sheet, the inner layer spring sheet elastically abuts against the inner walls at both ends of the U-shaped groove of the dynamic ring, the outer layer spring sheet elastically abuts against the inner walls at both ends of the U-shaped groove of the dynamic ring, an outer annular chamber is formed between the inner layer spring sheet and the outer layer spring sheet, the compressed air inlet is connected to the outer annular chamber, the static ring is provided with a compressed air inlet, the inner layer spring sheet and the dynamic ring directly form an inner annular chamber, and the air inlet is connected to the inner annular chamber.

[0017] The moving ring rotates with the kiln body, and the stationary ring is a semicircular ring structure, which is a fixed part and does not rotate with the rotary kiln. Compressed air is passed between the stationary ring and the moving ring, and the stationary ring and the moving ring are kept in a sealed connection, so that air enters the inner annular chamber through the air inlet and then enters the kiln body through the air inlet pipe. The gravity half-open valve can ensure that the gas enters the kiln body, and at the same time can prevent impurities and dust from entering the kiln body.

[0018] The kiln body is provided with a supporting wheel and a driving device. The supporting wheel supports the kiln body, and the driving device realizes the rotation of the rotary kiln. The kiln head is provided with a kiln head seal. The kiln tail is provided with a kiln tail seal.

[0019] Preferably, the air inlet of the first pulverized coal burner is connected to a blower.

[0020] The invention also discloses a cement kiln desulfurization and denitrification system, comprising the rotary kiln, wherein the kiln tail is connected with a decomposition furnace, and a second pulverized coal burner is installed in the decomposition furnace.

[0021] The raw meal enters from the tail of the rotary kiln, mixes with the injected pulverized coal and burns. After preheating, burning, crystallizing, cooling and other steps, it finally forms clinker and is discharged from the kiln head in a sealed manner. The first pulverized coal burner injects pulverized coal and 60-80% of the combustion air required for complete combustion of pulverized coal, burns with oxygen depletion, and maintains the flame temperature below 1400℃. A large amount of CO and unburned pulverized coal enter the air inlet device and are mixed with the injected 20-40% combustion air required for complete combustion for secondary combustion; the decomposition furnace injects pulverized coal and part of the air again to provide heat for raw meal preheating; the temperature in the rotary kiln and decomposition furnace is controlled by adding pulverized coal and introducing air at multiple stages to avoid local overheating, thereby suppressing the generation of thermal NOx and ensuring the quality of cement clinker.

[0022] In one of the preferred embodiments, the gas outlet of the decomposition furnace is connected to the air inlet of the waste heat boiler, the gas outlet of the waste heat boiler is connected to the air inlet of the dust collector, and the gas outlet of the dust collector is connected to the air inlet of the wet desulfurization and denitrification device.

[0023] The three methods of "air staged combustion + SNCR denitrification + wet denitrification" are combined and improved on the existing basis, such as setting up an air inlet device, supplying air in the calcining section of the rotary kiln, changing the position of ammonia injection, etc. The three work together to achieve ultra-low NOx emissions.

[0024] In one of the preferred embodiments, the cement kiln desulfurization and denitrification system further includes a raw meal homogenization tank, the discharge port of the raw meal homogenization tank is connected to the feed port of the preheater, the discharge port of the preheater is connected to the kiln tail, the air outlet of the decomposition furnace is connected to the air inlet of the preheater, and the air outlet of the preheater is further connected to the air inlet of the waste heat boiler.

[0025] The preheater transfers the heat of the flue gas to the raw meal to preheat the raw meal. After preheating, the raw meal temperature is 700-800℃ and the flue gas temperature is reduced to 300℃.

[0026] In one of the preferred embodiments, the wet desulfurization and denitrification device includes a horizontally arranged main body, one end of the main body is a flue gas inlet, a stepped multi-stage flow equalizer is installed in the middle of the main body, a spray layer is installed on the top of the main body, the air outlet of the main body is connected to the air inlet of the inverter demister, and the flue gas outlet of the inverter demister is connected to the air inlet of the chimney.

[0027] In one of the preferred embodiments, a slurry pool is provided at the bottom of the chimney, a liquid inlet of the slurry pool is communicated with a liquid outlet of the body, and a liquid outlet of the slurry pool is communicated with a liquid inlet of the spray layer.

[0028] The present invention also discloses a desulfurization and denitrification method for the cement kiln desulfurization and denitrification system, comprising the following steps:

[0029] S1. Add raw material at the tail of rotary kiln;

[0030] S2, spraying pulverized coal and 60-80% of the combustion-supporting air required for complete combustion of the pulverized coal into the first pulverized coal burner;

[0031] S3, 20-40% of the combustion air required for complete combustion of the pulverized coal in S2 is introduced into the air inlet device;

[0032] S4. Pulverized coal and air are sprayed into the decomposition furnace.

[0033] In one preferred embodiment, the desulfurization and denitrification method is characterized in that it also includes the following steps:

[0034] S5. After the gas discharged from the decomposition furnace passes through the preheater, waste heat boiler and dust collector, the flue gas temperature is reduced to 90-150°C;

[0035] The flue gas cooled in S6 and S5 enters the wet desulfurization and denitrification device 8 for wet desulfurization and denitrification, and is finally discharged into the atmosphere.

[0036] The waste heat boiler recovers part of the heat in the flue gas to generate steam, and the flue gas temperature is reduced to below 150℃.

[0037] For waste heat recovery, if the flue gas temperature is higher than 150℃, the waste heat recovery effect is not ideal. The design considers the temperature to be lower than 150℃ to recover heat as much as possible.

[0038] Preferably, the raw material added in S1 is preheated to 700-800°C.

[0039] The preheater transfers the heat of the flue gas to the raw meal to preheat the raw meal. After preheating, the raw meal temperature is 700-800℃ and the flue gas temperature is reduced to 300℃.

[0040] Compared with the Chinese patent application with publication number CN112679121A, this patent controls the combustion of pulverized coal by adding air at multiple points, thereby controlling the temperature in the rotary kiln below 1400°C and avoiding the nitrogen in the air. 2 With O 2 At high temperature (1500℃), the reaction produces thermal NO x Due to insufficient air, coal combustion produces a large amount of CO. In the absence of a catalyst, CO cannot react with NO. x The present invention is provided with an air inlet device, and air can be added into the middle of the rotary kiln, so that the temperature control is more accurate.

[0041] Compared with the Chinese patent application with publication number CN116143431A, the present patent application controls the temperature in the kiln below 1400℃ by air classification into the rotary kiln, thus curbing the generation of thermal NOx At the same time, ammonia is sprayed into the preheating section near the kiln tail to remove part of the NO x ; A wet desulfurization and denitrification device is set up at the end to further remove NO 2 The three are combined to improve the denitrification efficiency, NO x Meet ultra-low emission standards.

[0042] The Chinese patent application with publication number CN114797432A discloses a device and method for denitrification by spraying ammonia to adjust the temperature of cement plant flue gas. The device includes a cement preheater, a decomposition furnace, a rotary kiln, a grate cooler, an ammonia gasification device and a conveying pipeline connecting the above components in sequence. The ammonia gasification device is externally connected to an ammonia supply pipeline. The cement preheater and the decomposition furnace are simultaneously connected to the ammonia gasification device through a conveying pipeline. Low-temperature flue gas is transported between the cement preheater and the ammonia gasification device, and high-temperature flue gas is transported between the grate cooler and the ammonia gasification device. The process method controls the ratio of high and low temperature flue gas and the flow rate of ammonia water, and mixes the high and low temperature flue gas with ammonia water in the device for gasification to obtain the optimal temperature suitable for the denitrification reaction. The denitrification reaction and the optimal temperature are disclosed therein. Compared with the present application, this patent sprays ammonia into the decomposition furnace to remove part of NO. x Purpose: The temperature of the decomposition furnace is generally 800-900℃, and ammonia and NO x The best reaction temperature is 850-1100°C. The patent application sprays ammonia gas near the preheating section (temperature 900-1100°C) at the end of the rotary kiln, and the denitrification efficiency is higher than that of the patent application.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] (1) The cement rotary kiln is supplied with pulverized coal and air in stages to control the temperature inside the kiln below 1400°C, which greatly reduces the generation of thermal NOx.

[0045] (2) The combination of staged combustion technology, SNCR technology and wet denitrification technology reduces nitrogen oxide emissions to less than 50 mg / Nm 3 , meeting ultra-low emission requirements.

[0046] (3) Based on the characteristics of cement kiln flue gas volume, low sulfur dioxide concentration and stable operating conditions, a wet desulfurization and denitrification device is designed to achieve ultra-low pollutant emissions while reducing equipment investment costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a structural schematic diagram of a cement kiln desulfurization and denitrification method and device according to the present invention.

[0048] Figure 2 yes Figure 1 Middle AA section view.

[0049] Figure 3 yes Figure 2 Middle BB section view.

[0050] Figure 4 It is a schematic diagram of a wet desulfurization and denitrification device 8.

[0051] In the figure, 1 is a raw material homogenizing bin, 2 is a preheater, 3 is a rotary kiln, 3-1 is a pulverized coal burner, 3-2 is a kiln head seal, 3-3 is a support wheel, 3-4 is an air inlet device, 3-5 is a driving device, 3-6 is an ammonia inlet device, 3-7 is a kiln tail seal, 3-8 is a kiln body, 4 is a decomposition furnace, 4-1 is a second pulverized coal burner, 5 is a waste heat boiler, 6 is a dust collector, 7 is an exhaust fan, 8 is a wet desulfurization and denitrification device, and 9 is a chimney.

[0052] 3-4-1—dynamic ring, 3-4-2—static ring, 3-4-3—air inlet, 3-4-4—compressed air inlet, 3-4-5—outer spring sheet, 3-4-6—outer annular chamber, 3-4-7—inner spring sheet, 3-4-8—inner annular chamber, 3-4-9—intake chamber, 3-4-10—gravity half-open valve.

[0053] 8-1—main body, 8-2—flue gas inlet, 8-3—multi-stage flow equalizer, 8-4—spray layer, 8-5—inverter demister, 8-6—flue gas outlet, 8-7—slurry pool. DETAILED DESCRIPTION

[0054] The present invention will be further described below in conjunction with the accompanying drawings:

[0055] like Figure 1 As shown, a cement kiln desulfurization and denitrification system includes a rotary kiln 3, a kiln tail 3-10 connected to a decomposition furnace 4, and a second pulverized coal burner 4-1 is installed in the decomposition furnace 4.

[0056] The rotary kiln 3 includes a kiln body 3-8, and the kiln body 3-8 includes a kiln head 3-9 and a kiln tail 3-10. The kiln head 3-9 is equipped with a first pulverized coal burner 3-1, and the air inlet of the first pulverized coal burner 3-1 is connected to a blower 10. An air inlet device 3-4 is installed in the middle of the kiln body 3-8, and an ammonia inlet device 3-6 is installed in the kiln body 3-8 near the kiln tail 3-10.

[0057] The kiln body 3-8 is equipped with a supporting wheel 3-3 and a driving device 3-5.

[0058] The supporting wheel 3 - 3 supports the kiln body, and the driving device 3 - 5 realizes the rotation of the rotary kiln 3 .

[0059] The kiln head 3-9 is equipped with a kiln head seal 3-2.

[0060] like Figure 2-3As shown, the air inlet device 3-4 includes a moving ring 3-4-1 which surrounds the outer wall of the kiln body 3-8 and is fixed thereto, the cross-section of the moving ring 3-4-1 is a U-shaped groove, the opening of the U-shaped groove faces outward, and the static ring 3-4-2 is integrally nested in the inner side of the U-shaped groove of the moving ring 3-4-1, and a plurality of air inlet pipes 3-4-9 are installed through the outer wall of the kiln body 3-8, and the plurality of air inlet pipes 3-4-9 are arranged at intervals along the circumference of the kiln body 3-8, and a gravity half-open valve 3-4-10 is installed at one end of the air inlet pipe 3-4-9 located in the kiln body 3-8, and the other end of the air inlet pipe 3-4-9 is connected to the chamber between the moving ring 3-4-1 and the static ring 3-4-2, and an air inlet 3-4-3 is installed through the static ring 3-4-2, and the air inlet 3-4-3 is connected to the chamber.

[0061] The static ring 3-4-2 includes an inner layer spring piece 3-4-7 and an outer layer spring piece 3-4-5. The inner layer spring piece 3-4-7 elastically abuts against the inner walls at both ends of the U-shaped groove of the dynamic ring 3-4-1. The outer layer spring piece 3-4-5 elastically abuts against the inner walls at both ends of the U-shaped groove of the dynamic ring 3-4-1. An outer annular chamber 3-4-6 is formed between the inner layer spring piece 3-4-7 and the outer layer spring piece 3-4-5. The compressed air inlet 3-4-4 is connected to the outer annular chamber 3-4-6. The static ring 3-4-2 is provided with a compressed air inlet 3-4-4. The inner layer spring piece 3-4-7 and the dynamic ring 3-4-1 directly form an inner annular chamber 3-4-8. The air inlet 3-4-3 is connected to the inner annular chamber 3-4-8.

[0062] The cross section of the moving ring 3-4-1 is a U-shaped groove structure, which is fixed along the wall of the rotary kiln 3 and rotates with the rotary kiln. The moving ring 3-4-1 contains 4 to 8 air inlet pipes 3-4-9 connected to the inside of the rotary kiln. A gravity half-open valve 3-4-10 is set at the bottom of the air inlet pipe 3-4-9. When the gravity half-open valve 3-4-10 is located in the upper half of the rotary kiln 3, the valve is opened; when the gravity half-open valve 3-4-9 is located in the lower half of the rotary kiln 3, it is closed by gravity.

[0063] The static ring 3-4-2 is a semicircular ring structure, a fixed part, and does not rotate with the rotary kiln. An air inlet 3-4-3 is arranged on the top, and a compressed air inlet 3-4-4 is arranged on the top side. The outer layer is a semicircular outer layer spring 3-4-5, and the inner layer is a semicircular inner layer spring 3-4-7. The outer ring chamber 3-4-6 is between the outer layer spring 3-4-5 and the inner layer spring 3-4-7. Compressed air is introduced through the compressed air inlet 3-4-4 to play a sealing role. The air inlet 3-4-3 is connected to the inner ring chamber 3-4-8, and the combustion-supporting air enters the inner ring chamber 3-4-8 from here, and then enters the rotary kiln 3 through the air inlet pipe 3-4-9.

[0064] During the operation of the rotary kiln, the moving ring rotates with the kiln to ensure that air can enter the kiln, and the gravity half-open valve prevents the powder in the rotary kiln from entering the moving ring.

[0065] The gas outlet of the decomposition furnace 4 is connected to the air inlet of the waste heat boiler 5 , the gas outlet of the waste heat boiler 5 is connected to the air inlet of the dust collector 6 , and the gas outlet of the dust collector 6 is connected to the air inlet of the wet desulfurization and denitrification device 8 .

[0066] The dust collector 6 is a bag dust collector, which collects raw material dust in the flue gas and stores it in the raw material homogenization warehouse 1. The dust emission in the flue gas is less than 10mg / Nm 3 .

[0067] The smoke exhaust fan 7 provides power for the flow of smoke.

[0068] The cement kiln desulfurization and denitrification system also includes a raw meal homogenization storage 1, the discharge port of the raw meal homogenization storage 1 is connected to the feed port of the preheater 2, the discharge port of the preheater 2 is connected to the kiln tail 3-10, the air outlet of the decomposition furnace 4 is connected to the air inlet of the preheater 2, and the air outlet of the preheater 2 is further connected to the air inlet of the waste heat boiler 5.

[0069] like Figure 4 As shown, the wet desulfurization and denitrification device 8 includes a horizontally arranged main body 8-1, one end of the main body 8-1 is a flue gas inlet 8-2, a stepped multi-stage flow equalizer 8-3 is installed in the middle of the main body 8-1, a spray layer 8-4 is installed on the top of the main body 8-1, the air outlet of the main body 8-1 is connected to the air inlet of the inverter demister 8-5, and the flue gas outlet 8-6 of the inverter demister 8-5 is connected to the air inlet of the chimney 9.

[0070] A slurry pool 8-7 is provided at the bottom of the chimney 9, the liquid inlet of the slurry pool 8-7 is communicated with the liquid outlet of the body 8-1, and the liquid outlet of the slurry pool 8-7 is communicated with the liquid inlet of the spray layer 8-4.

[0071] Furthermore, the wet desulfurization and denitrification device 8 is composed of a main body 8-1, a flue gas inlet 8-2, a multi-stage flow equalizer 8-3, a spray layer 8-4, an inverter demister 8-5, a flue gas outlet 8-6, and a slurry pool 8-7 located at the bottom of the chimney. The flue gas enters the wet desulfurization and denitrification device 8 from the flue gas inlet 8-2, passes through the multi-stage flow equalizer 8-3, and is evenly distributed. It is in reverse contact with the desulfurization and denitrification solution atomized by the spray layer 8-4, and NO2 and SO2 therein are absorbed into the solution and react with the desulfurization and denitrification agents to produce sulfates and nitrates. The purified flue gas passes through the inverter demister 8-5 to remove the water mist in the flue gas, and the purified flue gas is discharged through the chimney 9.

[0072] a. The main body 8-1 is a horizontal square. Compared with the vertical desulfurization tower, it reduces equipment costs and has a desulfurization efficiency of >90%. It is suitable for large flue gas volumes and ultra-low emissions of flue gas with low sulfur dioxide concentration.

[0073] b. The multi-stage flow equalizer 8-3 is distributed in a stepped manner, divided into 2 to 6 levels according to the amount of flue gas, with a perforated plate structure, an opening rate of 30 to 50%, and an aperture of 10 to 30 mm. The opening rate is low and the aperture is small near the flue gas inlet 8-2; the opening rate is high and the aperture is large far from the flue gas inlet 8-2.

[0074] c. The spray layer 8-4 is located on the upper part of the multi-stage flow equalizer 8-3. The atomized particle size is less than 100 μm. It collides with the multi-stage flow equalizer 8-3 to form a secondary atomization layer, thereby improving the gas-liquid contact efficiency.

[0075] d. The inverter demister 8-5 is located on the upper part of the spray layer 8-4, and includes two levels of cyclone plates in opposite directions. The flue gas flow rate is about 5 to 7 m / s. Through the centrifugal action of the cyclone, the atomized droplets are condensed and atomized, and flushing water pipes are distributed in it to keep the inverter demister 8-5 clean.

[0076] e. Slurry pool 8-7, located at the bottom of chimney 9, realizes the circulation of desulfurization and denitrification slurry between spray layer 8-4 and slurry pool 8-7; desulfurization and denitrification agents are mainly alkaline substances such as calcium hydroxide and calcium oxide, which can be limestone, slaked lime, carbide slag solution, etc., and at the same time, a small amount of oxidizing substances such as hydrogen peroxide and potassium permanganate are added to facilitate the absorption of nitrogen oxides.

[0077] Compared with the existing desulfurization absorption tower, the wet desulfurization and denitrification device of the present application has a completely different structure. The wet desulfurization and denitrification device of the present application is square, with a lower height and lower cost. It adds a stepped multi-stage flow equalizer, an inverter demister, etc., which is suitable for large flue gas volume, SO 2 and NO 2 Low concentration (SO 2 Concentration less than 500mg / Nm 3 ), flue gas volume stability. Not suitable for SO 2 The working conditions are high concentration and large changes in flue gas load.

[0078] The present invention also discloses a desulfurization and denitrification method for the cement kiln desulfurization and denitrification system, comprising the following steps:

[0079] (1) Cement raw meal is stored in the cement raw meal homogenization tank 1, heated by the countercurrent high-temperature flue gas through the preheater 2, and enters the tail of the rotary kiln 3. Under the action of the rotation and inclination of the rotary kiln 3, it gradually moves toward the kiln head, and at the same time mixes with the coal powder and air in the rotary kiln 3 to complete the high-temperature calcination reaction. The raw meal is decomposed and burned in the kiln. After the preheating, calcination and cooling stages, it finally forms cement clinker products and is discharged from the kiln head.

[0080] (2) The pulverized coal burner 3-1 injects pulverized coal and 60-80% of the combustion-supporting air required for complete combustion of the pulverized coal, and burns in an oxygen-deficient manner to maintain a flame temperature below 1400°C. A large amount of CO and incompletely burned pulverized coal are generated by the combustion and enter the air inlet device 3-4, where they are mixed with the injected 20-40% of the combustion-supporting air required for complete combustion and burn for a second time to complete the cement raw material calcination reaction; the decomposition furnace 4 injects pulverized coal and part of the air again to provide heat for raw material preheating; the temperature in the rotary kiln 3 and the decomposition furnace 4 is controlled by adding pulverized coal and introducing air at multiple stages to avoid local overheating (exceeding 1400°C), thereby suppressing the generation of thermal NOx; at the same time, ammonia (SNCR) is injected into the raw material preheating section of the rotary kiln to reduce the combustion-type nitrogen oxides generated by the pulverized coal combustion process in the rotary kiln, further remove the nitrogen oxides, and ensure the quality of cement clinker. The flue gas discharged from the decomposition furnace 4 enters the preheater 2 to preheat the cement raw material, and the flue gas temperature is reduced to about 300°C. The heat is further recovered by the waste heat boiler 5. After the dust collector 6 collects the dust, the flue gas temperature is reduced to 90-150°C. It is pressurized by the exhaust fan 7 and enters the wet desulfurization and denitrification device 8 to further remove nitrogen oxides and sulfur dioxide. The purified flue gas is discharged into the atmosphere through the chimney 9. The blower 10 provides combustion-supporting oxygen for the combustion of coal powder in the rotary kiln 3, and the ammonia supply device 11 provides a reducing agent for the SNCR denitrification reaction.

[0081] The cement kiln desulfurization and denitrification method in this embodiment can achieve the purpose of reducing the particulate matter, SO 2 , ultra-low NOx emission. Flue gas volume 1 million Nm 3 / h, nitrogen oxide emission 400mg / Nm 3 , SO 2 Emission 300mg / Nm 3 After the transformation of the present invention, the air and coal powder staged combustion removes about 65% of NOx, the SNCR removes about 60% of NOx, and the wet desulfurization and denitrification device removes about 30% of NOx, and the NOx emission is less than 50mg / Nm 3 , desulfurization efficiency of wet desulfurization and denitrification device> 90%, SO 2 Emissions less than 35mg / Nm 3 The bag filter and wet desulfurization and denitrification device work together to reduce dust emissions to less than 5mg / Nm 3 .

[0082] The contents explained in the above embodiments should be understood as these embodiments are only used to more clearly illustrate the present invention, and are not used to limit the scope of the present invention. After reading the present invention, various equivalent forms of modifications to the embodiments made by those skilled in the art fall within the scope defined by the claims attached to the present invention.

Claims

1. A rotary kiln, comprising a kiln body (3-8), wherein the kiln body (3-8) comprises a kiln head (3-9) and a kiln tail (3-10), characterized in that: The kiln head (3-9) is equipped with a first pulverized coal burner (3-1), the middle of the kiln body (3-8) is equipped with an air inlet device (3-4), and the kiln body (3-8) is equipped with an ammonia inlet device (3-6) near the kiln tail (3-10).

2. The rotary kiln according to claim 1, characterized in that: The air inlet device (3-4) comprises a moving ring (3-4-1) surrounding the outer wall of the kiln body (3-8) and fixed thereto, the cross section of the moving ring (3-4-1) is a U-shaped groove, the opening of the U-shaped groove faces outward, the stationary ring (3-4-2) is integrally nested inside the U-shaped groove of the moving ring (3-4-1), and a plurality of air inlet pipes (3-4-9) are installed through the outer wall of the kiln body (3-8), and the plurality of air inlet pipes (3-4-9) are arranged along the kiln body. The kiln body (3-8) is arranged at intervals in the circumference of the kiln body (3-8), one end of the air inlet pipe (3-4-9) located in the kiln body (3-8) is equipped with a gravity half-open valve (3-4-10), the other end of the air inlet pipe (3-4-9) is connected to the chamber between the dynamic ring (3-4-1) and the static ring (3-4-2), and an air inlet (3-4-3) is installed through the static ring (3-4-2), and the air inlet (3-4-3) is connected to the chamber.

3. The rotary kiln according to claim 2, characterized in that: The static ring (3-4-2) comprises an inner layer spring sheet (3-4-7) and an outer layer spring sheet (3-4-5), wherein the inner layer spring sheet (3-4-7) elastically abuts against the inner walls at both ends of the U-shaped groove of the dynamic ring (3-4-1), and the outer layer spring sheet (3-4-5) elastically abuts against the inner walls at both ends of the U-shaped groove of the dynamic ring (3-4-1), and a spring sheet (3-4-7) and an outer layer spring sheet (3-4-5) are formed between the inner layer spring sheet (3-4-7) and the outer layer spring sheet (3-4-5). The outer annular chamber (3-4-6) is formed, the compressed air inlet (3-4-4) is connected to the outer annular chamber (3-4-6), the static ring (3-4-2) is provided with a compressed air inlet (3-4-4), the inner layer spring sheet (3-4-7) and the dynamic ring (3-4-1) directly form an inner annular chamber (3-4-8), and the air inlet (3-4-3) is connected to the inner annular chamber (3-4-8).

4. A cement kiln desulfurization and denitrification system, characterized in that: It comprises the rotary kiln as claimed in any one of claims 1 to 3, wherein the kiln tail (3-10) is connected to a decomposition furnace (4), and a second pulverized coal burner (4-1) is installed in the decomposition furnace (4).

5. The cement kiln desulfurization and denitrification system according to claim 4, characterized in that: The gas outlet of the decomposition furnace (4) is connected to the gas inlet of the waste heat boiler (5), the gas outlet of the waste heat boiler (5) is connected to the gas inlet of the dust collector (6), and the gas outlet of the dust collector (6) is connected to the gas inlet of the wet desulfurization and denitrification device (8).

6. The cement kiln desulfurization and denitrification system according to claim 5, characterized in that: It also includes a raw material homogenization bin (1), the discharge port of the raw material homogenization bin (1) is connected to the feed port of the preheater (2), the discharge port of the preheater (2) is connected to the kiln tail (3-10), the air outlet of the decomposition furnace (4) is connected to the air inlet of the preheater (2), and the air outlet of the preheater (2) is further connected to the air inlet of the waste heat boiler (5).

7. The cement kiln desulfurization and denitrification system according to claim 5, characterized in that: The wet desulfurization and denitrification device (8) comprises a horizontally arranged main body (8-1), one end of the main body (8-1) being a flue gas inlet (8-2), a stepped multi-stage flow equalizer (8-3) being installed in the middle of the main body (8-1), a spray layer (8-4) being installed on the top of the main body (8-1), an air outlet of the main body (8-1) being connected to an air inlet of an inverter demister (8-5), and a flue gas outlet (8-6) of the inverter demister (8-5) being connected to an air inlet of a chimney (9).

8. The cement kiln desulfurization and denitrification system according to claim 7, characterized in that: A slurry pool (8-7) is provided at the bottom of the chimney (9), the liquid inlet of the slurry pool (8-7) is connected to the liquid outlet of the body (8-1), and the liquid outlet of the slurry pool (8-7) is connected to the liquid inlet of the spray layer (8-4).

9. A desulfurization and denitrification method for a cement kiln desulfurization and denitrification system according to any one of claims 4 to 8, characterized in that The following steps are involved: S1. Add raw material at the tail of rotary kiln; S2, spraying pulverized coal and 60-80% of the combustion-supporting air required for complete combustion of the pulverized coal into the first pulverized coal burner; S3, 20-40% of the combustion air required for complete combustion of the pulverized coal in S2 is introduced into the air inlet device; S4. Pulverized coal and air are sprayed into the decomposition furnace.

10. The desulfurization and denitrification method according to claim 9, characterized in that The following steps are also included: S5. After the gas discharged from the decomposition furnace passes through the preheater, waste heat boiler and dust collector, the flue gas temperature is reduced to 90-150°C; The flue gas cooled in S6 and S5 enters the wet desulfurization and denitrification device (8) for wet desulfurization and denitrification, and is finally discharged into the atmosphere.

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