CN110849138A - Cement kiln denitration device, cement kiln and cement kiln denitration process - Google Patents
Cement kiln denitration device, cement kiln and cement kiln denitration process Download PDFInfo
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- CN110849138A CN110849138A CN201911306861.1A CN201911306861A CN110849138A CN 110849138 A CN110849138 A CN 110849138A CN 201911306861 A CN201911306861 A CN 201911306861A CN 110849138 A CN110849138 A CN 110849138A
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F27—FURNACES; KILNS; OVENS; RETORTS
- F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
- F27B7/00—Rotary-drum furnaces, i.e. horizontal or slightly inclined
- F27B7/20—Details, accessories, or equipment peculiar to rotary-drum furnaces
- F27B7/36—Arrangements of air or gas supply devices
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/46—Removing components of defined structure
- B01D53/54—Nitrogen compounds
- B01D53/56—Nitrogen oxides
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
- B01D53/81—Solid phase processes
- B01D53/83—Solid phase processes with moving reactants
Abstract
The invention provides a cement kiln denitration device, a cement kiln and a cement kiln denitration process, relates to the technical field of cement kiln denitration, and solves the problem of low denitration efficiency in the prior art. In the cement kiln, a burner connected with a pulverized coal conveying pipe is installed at a coal-fired feeding point of a decomposing furnace, a tertiary air pipe is installed at a tertiary air pipe access point of the decomposing furnace, a raw material feeding point of the decomposing furnace is connected with a blanking pipe, the blanking pipe is connected with a four-stage cyclone, and a lower cone air inlet of the decomposing furnace is connected with a rotary kiln. The process makes all coal powder pyrolyzed in oxygen-deficient environment of reduction zone to produce large amount of CO and inhibit NOxAnd completing the formation of NO in the reduction zonexReduction to N in an environment of high C and CO concentration2So as to improve the denitration efficiency of fuel staged combustion.
Description
Technical Field
The invention relates to the technical field of cement kiln denitration, in particular to a cement kiln denitration device, a cement kiln and a cement kiln denitration process.
Background
The most critical link in cement production is the firing of cement clinker. FIG. 8 shows a typical new type of dry process cement clinker burning system, which is mainly composed of a raw material preheater, a decomposing furnace, a rotary kiln and a clinker cooler. Wherein the flow direction of the materials is as follows: the method comprises the following steps of feeding low-temperature raw materials into a primary cyclone, a secondary cyclone, a tertiary cyclone, a four-stage cyclone, a decomposing furnace, a five-stage cyclone and a rotary kiln. Wherein the flow direction of the high-temperature gas is as follows: the system comprises a rotary kiln, a tertiary air pipe, a decomposing furnace, a five-stage cyclone, a four-stage cyclone, a three-stage cyclone, a two-stage cyclone, a first-stage cyclone and a discharge preheater.
The typical modern novel dry-process cement clinker sintering system has the following technical characteristics:
(1) the coal feeding point is positioned at the upper part of the tertiary air pipe access point of the decomposing furnace;
(2) the oxygen content of the gas which is discharged from the rotary kiln and enters the lower cone of the decomposing furnace is generally controlled to be about 2.5 percent, namely the coefficient a of the excess air is more than 1;
(3) the coal powder enters the decomposing furnace through the circular tube-shaped burner;
(4) feeding points of the materials on the decomposing furnace are all arranged at the upper part of the tertiary air pipe;
(5) the residence time of the gas from the rotary kiln into the lower cone of the decomposing furnace in the reduction zone is generally controlled to be 0.2 seconds.
The waste gas generated by the post combustion in the fuel feeding system is discharged out of the preheater system along with the high-temperature gas, and the ash generated by the combustion is mixed into the materials and finally becomes a part of the cement clinker. The burning of cement clinker requires the consumption of a large amount of fuel, 40% of which is fed to the rotary cement kiln and the remaining 60% of which is fed to the decomposing furnace, which produces a large amount of NO during the burning processxThe generation routes mainly include the following three ways:
(1) thermal NOx
High temperature state N in cement kiln2Gas meets with O2Generated by post-oxidation reactions, about NOxAbout 20% of the total amount.
N2+O2→NO
NO+O2→NO2
Generally, the reaction takes place in large amounts at temperatures above 1500 ℃ and almost NO thermal NO is observed below 1500 ℃xIs generated.
(2) Fuel type NOx
Fuel type NOxIs NO produced by the thermal decomposition and subsequent oxidation of nitrogen compounds contained in the fuel during combustionxAbout account for NOx75% -90% of the total amount of fuel type NOxIs NO produced by coal combustionxThe main source.
HCN+NH3+CN+O2→NOx+H2+CO+......
(3) Transient NOx
Transient NOxIt is believed that the hydrocarbon fuel will rapidly generate NO near the reaction zone when the fuel is over-richx. It is the N in the impinging combustion air of hydrocarbons (CHi) etc. produced during combustion of the fuel2The molecules are produced into CN, HCN, and then HCN and the like are oxidized into NOx. Rapid mode occurs only when there are more CH compounds and the oxygen concentration is relatively low, typically producing very small proportions.
NO contained in exhaust gas discharged from cement kilnxGreater environmental pollution, NOxCombined with water in the air and finally converted into nitric acid and nitrate, so certain measures must be taken to remove NO from the exhaust gas of the cement kiln as much as possiblexSo as to reduce the pollution to the environment.
Control of NOxThe technical measures of emissions can be divided into two main categories: one is so-called source control, which is to control NO in the combustion process by various technical meansxThe formation reaction of (1); the other is so-called tail control, which is to control the NO already generatedxReduced to N by some means2Thereby reducing NOxAnd (4) discharging.
Currently, the most common method in the world is to remove NO from cement kiln waste gasxThe technology is an SNCR technology, an SNCR denitration technology, namely a Selective Non-Catalytic Reduction (hereinafter abbreviated as SNCR) technology is a typical tail control technology, and is a technology which does not use a catalyst, and in the temperature range of 850-1100 ℃, a reducing agent (such as ammonia water, urea solution and the like) containing amino is sprayed into a cement kiln decomposition furnace, so that NO in smoke is converted into ammoniaxClean denitration technology for reducing the nitrogen into harmless nitrogen and water. The SNCR system can be effectiveRemoving NO in flue gasxHowever, there are three more significant disadvantages to SNCR systems: firstly, the operation cost is high, the industrial ammonia water price in the current market reaches about 800 yuan/ton, and the production cost of cement is averagely increased about 3 yuan/ton by using the ammonia water for denitration. Secondly, ammonia escape (ammonia escape means that part of ammonia water sprayed into the cement kiln decomposition furnace by the SNCR denitration system does not participate in NO removalxThe reaction(s) is directly discharged into the atmosphere along with cement kiln exhaust gas in the form of ammonia gas and is harmful to the environment), and the ammonia escape which is difficult to meet the national standard is less than 8mg/m3The emission requirements of (2). Thirdly, the ammonia water sprayed into the cement kiln decomposition furnace by the SNCR system can cause the average increase of the heat consumption of clinker sintering of the cement kiln system to about 1 kilogram of standard coal/ton of cement clinker, so that the production cost of the cement is increased by about 1 yuan/ton of cement.
In recent years, the gradually increased air staged combustion denitration technology and the fuel staged combustion denitration technology are applied as source control for removing NOxThe technology has low efficiency, the denitration efficiency is generally only 40-50%, and NO of the cement kiln cannot be treated by using the air staged combustion denitration technology or the fuel staged combustion denitration technology alonexThe emission value is reduced to be below the index required by the national standard GB 4915-2013 emission Standard of atmospheric pollutants for the Cement industry. At present, the air staged combustion denitration technology and the fuel staged combustion denitration technology are only used as auxiliary means of the SNCR technology, so the denitration technology in the cement industry still cannot leave an SNCR system, and the problems of negative influence of rising operation cost caused by using ammonia water and inevitable ammonia escape caused by using ammonia water for denitration inevitably exist.
Disclosure of Invention
The invention aims to design a cement kiln denitration device, a cement kiln and a cement kiln denitration process, and aims to improve the fuel staged combustion denitration efficiency by improving a method and a device for a fuel staged combustion denitration technology.
The invention is realized by the following technical scheme:
the invention provides a cement kiln denitration device which comprises a decomposing furnace, wherein the decomposing furnace comprises a furnace main body and a lower cone, the lower cone is provided with a lower cone air inlet, the decomposing furnace is provided with a coal feeding point and a tertiary air pipe access point, the coal feeding point is arranged at the lower part of the tertiary air pipe access point, and a reduction area is formed between the coal feeding point and the tertiary air pipe access point.
When the arrangement structure is adopted, the position of the coal feeding point of the fuel coal used by the decomposing furnace is changed from the feeding point position at the upper part of the traditional tertiary air pipe feeding point to the feeding point position at the lower part of the tertiary air pipe feeding point, so that the carbon element in the fuel coal used by the decomposing furnace is used as a reducing agent, a reducing area is established in an oxygen-deficient area in the decomposing furnace, and NO is completely reduced in the reducing areaxReduction to N2The reaction of (1).
In order to further better implement the invention, the following arrangement structure is particularly adopted: the coal feeding point is arranged on the lower cone.
When the arrangement structure is adopted, the coal feeding point can obtain a larger reduction area at the lower cone.
In order to further better implement the invention, the following arrangement structure is particularly adopted: the coal feeding point is arranged close to the lower cone air inlet of the decomposing furnace.
When the structure is adopted, the coal feeding point is near the lower cone air inlet of the lower cone, so that a larger reduction area can be obtained.
In order to further better implement the invention, the following arrangement structure is particularly adopted: the relative distance between the coal feeding point and the air inlet of the lower cone is more than or equal to 100mm and less than or equal to 300 mm.
In order to further better implement the invention, the following arrangement structure is particularly adopted: the volume of the reduction zone satisfies the formula V1＝V2T, wherein V1Volume of the reduction zone, V2And the volume of the gas entering the lower cone from the lower cone air inlet per second is shown, T is the time for the gas entering the lower cone from the lower cone air inlet to stay in the reduction area, and T is 0.2-0.6 s.
When the arrangement structure is adopted, the retention time of the gas entering the lower cone of the decomposing furnace from the rotary kiln in the reducing region is prolonged to at least 0.2 second and at most 0.6 second, and a sufficient reducing region can be established in the lower cone of the decomposing furnace.
In order to further better implement the invention, the following arrangement structure is particularly adopted: and a fireproof lining thickening layer is laid on the surface of the fireproof lining of the inner wall of the lower cone and used for reducing the original ventilation area of the air inlet of the lower cone.
When the structure is adopted, the measure of reducing the sectional area of the air inlet of the lower cone air inlet at the connecting part of the lower cone of the decomposing furnace and the rotary kiln can reduce the ventilation volume in the rotary kiln and reduce the coefficient a of excess air in the rotary kiln, thereby inhibiting NO in the rotary kilnxGenerating and better forming the function of a reduction zone in the lower cone of the decomposing furnace.
In order to further better implement the invention, the following arrangement structure is particularly adopted: the ventilation area of the lower cone air inlet is reduced to 92% -98% of the original ventilation area.
When the structure is adopted, the fireproof lining at the air inlet of the lower cone body is thickened, so that the ventilation area at the air inlet is reduced by about 2% -8% compared with the original design, and the coefficient a of the excess air in the rotary kiln can be closer to 1.
In order to further better implement the invention, the following arrangement structure is particularly adopted: the raw material feeding point of the decomposing furnace comprises an upper raw material feeding point and a lower raw material feeding point, the upper raw material feeding point is arranged at the upper part of the tertiary air duct access point, and the lower raw material feeding point is arranged between the coal-fired feeding point and the tertiary air duct access point.
When the arrangement structure is adopted, part of the low-temperature material from the four-stage cyclone can be fed into the lower cone of the decomposing furnace, the low-temperature material can absorb heat quickly after entering the reduction region, so that the temperature of the reduction region is maintained below 1000 ℃, and high-temperature skinning and new high-temperature NO generation can be avoidedxThe risk of (c).
In order to further better implement the invention, the following arrangement structure is particularly adopted: the relative distance between the feeding point of the lower raw material and the feeding point of the fire coal is more than or equal to 0.4m and less than or equal to 1.5 m.
The invention also provides a cement kiln, which comprises a combustor, a pulverized coal conveying pipe, a tertiary air pipe, a feeding pipe, a four-stage cyclone cylinder, a rotary kiln and the cement kiln denitration device; the coal-fired feeding point of the decomposing furnace is provided with a burner connected with the pulverized coal conveying pipe, the tertiary air pipe is connected with the tertiary air pipe, the raw material feeding point of the decomposing furnace is connected with the blanking pipe, the blanking pipe is connected with the four-stage cyclone cylinder, and the lower cone air inlet of the decomposing furnace is connected with the rotary kiln.
When the arrangement structure is adopted, the feeding point of the pulverized coal conveying pipe connected with the burner at the decomposing furnace is arranged at the lower part of the access point of the tertiary air pipe at the decomposing furnace, so that all pulverized coal can be sprayed into the decomposing furnace from the lower part of the tertiary air pipe to form a reduction zone in the decomposing furnace, and NO is inhibitedxGeneration of and conversion of NOxReduction to N2。
In order to further better implement the invention, the following arrangement structure is particularly adopted: the fuel nozzle of the combustor is of a flaring structure, and the cross section of the fuel nozzle of the combustor is flat and rectangular.
When the structure is adopted, the flaring burner with the flat and rectangular cross section can quickly disperse and mix with the airflow which flows quickly and uniformly in the decomposing furnace once the pulverized coal enters the decomposing furnace, so that NO contained in the gasxThe carbon is contacted and reduced as quickly as possible.
In order to further better implement the invention, the following arrangement structure is particularly adopted: the pipe section of the tertiary air pipe connected into the decomposing furnace is inclined upwards, and an included angle formed between the pipe section and the horizontal plane is 10-30 degrees.
When the structure is adopted, the last section of the newly connected tertiary air pipe entering the decomposing furnace is made into an inclined section which is inclined upwards, so that the mixing speed of the tertiary air after entering the furnace and the ascending air flow of the reduction zone is further delayed, the total volume of the reduction zone is further enlarged, the reduction reaction time is prolonged, and the reduction effect is improved.
The invention also provides a cement kiln denitration process, which comprises the following steps: make decomposition proceedThe coal feeding point of the furnace is positioned at the lower part of the tertiary air pipe access point, and a reduction zone is established in the oxygen-deficient zone between the coal feeding point of the decomposing furnace and the tertiary air pipe access point, so that all coal powder is pyrolyzed in the oxygen-deficient environment of the reduction zone to generate a large amount of CO and inhibit NOxAnd completing the formation of NO in the reduction zonexReduction to N in an environment of high C and CO concentration2The reaction of (1).
Further, the method also comprises one or any combination of the following processes:
firstly, the coefficient a of the excess air in the rotary kiln meets the condition that a is more than or equal to 0.7 and less than or equal to 1;
secondly, the diffusion efficiency of the pulverized coal sprayed into the decomposing furnace from the burner is improved, and NO in the pulverized coal and gas is promotedxAre in sufficient contact;
when the raw material feeding points are multiple, the raw material from the four-stage cyclone is evenly distributed among all the raw material feeding points to restrain the temperature of the reduction region and prevent the generation of high-temperature NOx；
Fourthly, prolonging the retention time of the gas entering the lower cone from the rotary kiln to 0.5 second in the reduction zone;
and fifthly, reducing the mixing rate of the tertiary air entering the decomposing furnace from the tertiary air pipe and the air flow rising from the reduction zone so as to further enlarge the total volume of the reduction zone.
The invention has the following advantages and beneficial effects:
in the invention, the feeding point of the fire coal used by the decomposing furnace is changed from the feeding point at the upper part of the traditional tertiary air pipe access point to the feeding point at the lower part of the tertiary air pipe feeding point, so that the carbon element in the fire coal used by the decomposing furnace can be used as a reducing agent, a reducing area is established in an oxygen-deficient area in the decomposing furnace, and NO is completely reduced in the reducing areaxReduction to N2The reaction of (2) can improve denitration efficiency, no longer use the aqueous ammonia denitration, realize the zero cost operation of cement kiln denitration, solve the problem that the cement kiln uses the ammonia escape that the aqueous ammonia denitration brought.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a schematic view of a feeding point of a cement kiln denitration device;
FIG. 2 is a schematic view of the arrangement of a four-stage cyclone to a lower cone of a decomposing furnace;
FIG. 3 is a schematic structural view of a lower cone air inlet;
FIG. 4 is a schematic view of a burner configuration;
FIG. 5 is a schematic view of the diffusion effect of the burner;
FIG. 6 is a schematic view of the tertiary air duct;
FIG. 7 is a schematic view showing the structure of a decomposing furnace part of a cement kiln (two four-stage cyclones, a decomposing furnace both-side air-intake type);
FIG. 8 is a basic schematic diagram of a cement kiln air staged combustion denitration technology;
labeled as:
1. a primary cyclone; 2. a secondary cyclone; 3. a tertiary cyclone; 4. a four-stage cyclone; 5. a fifth stage cyclone;
6. a decomposing furnace; 6a, a furnace main body; 6b, a lower cone; 6c, feeding coal; 6d, connecting a tertiary air pipe; 6e, a reduction zone; 6f, a lower cone air inlet; 6g of a thickening layer of a refractory lining; 6h, refractory lining; 6i, feeding raw materials; 6j, feeding the raw materials;
7. a tertiary air pipe; 8. a clinker coolant; 9. a rotary kiln;
10. a burner; 10a, a fuel nozzle;
11. a pulverized coal conveying pipe; 12. a discharging pipe; 13. three-way material distributing valve.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be described in detail below. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the examples given herein without any inventive step, are within the scope of the present invention.
Example 1:
the cement kiln denitration device improves the denitration efficiency of fuel fractional combustion by improving a device of fuel fractional combustion denitration technology, and is particularly provided with the following structures as shown in fig. 1, fig. 2, fig. 3, fig. 4, fig. 5, fig. 6, fig. 7 and fig. 8:
the vertical decomposition furnace 6 comprises a furnace main body 6a and a lower cone 6b connected to the bottom of the furnace main body 6a, and a lower cone air inlet 6f is formed in the bottom of the lower cone 6 b. Compared with the traditional decomposing furnace, the decomposing furnace 6 in the embodiment changes the feeding point at the upper part of the traditional tertiary air pipe access point into the feeding point at the lower part of the tertiary air pipe access point for all the coal feeding points 6c of the used coal into the feeding point at the lower part of the tertiary air pipe access point, so that all the coal powder is pyrolyzed in the lower cone 6b of the decomposing furnace under the oxygen-deficient environment between the coal feeding point 6c and the tertiary air pipe access point 6d to generate a large amount of CO so as to form NO to form a NO feeding point, wherein the coal feeding points 6c, the tertiary air pipe access point 6d and the raw material feeding point are taken as the through holes, the coal feeding points 6c are generally multiple, all the coal feeding points 6c are arranged at the lower part of the tertiary air pipe access point, and the reducing area 6e is formed between the coal feeding point 6c and the tertiary airxA reduction zone, in which the pulverized coal is pyrolyzed under a low oxygen environment to effectively inhibit NOxWhile NO has been generatedxCan be reduced into N in the environment with high C and CO concentration2. Thus, the carbon C element in the fuel coal for the decomposing furnace is used as a reducing agent, a reducing zone 6e is established in the oxygen-deficient zone in the decomposing furnace 6, and NO addition is completed in the reducing zone 6exReduction to N2The reaction of (1).
As a preferable arrangement of the coal feeding point in this embodiment, the coal feeding point 6c is provided at the lower cone 6b to obtain a larger reduction area 6e, and the coal feeding point 6c is preferably provided adjacent to the lower cone air inlet 6f of the decomposing furnace 6. Thus, the coal feeding point 6c can obtain a larger reduction area 6e near the lower cone air inlet 6f of the lower cone 6 b. In practical engineering, the coal feeding point 6c is generally controlled within the range of 100-300mm above the lower cone air inlet 6f to obtain a reduction zone 6e as large as possible, so as to ensure the denitration effect, and the relative distance between the coal feeding point 6c and the lower cone air inlet 6f is preferably controlled at 200 mm.
Example 2:
the embodiment is further optimized on the basis of the above embodiment, and in order to further better implement the invention, the following arrangement structure is particularly adopted:
research shows that the higher the excess air factor, i.e. the ratio of the actual air usage to the theoretical air usage, the higher the NOxThe higher the formation concentration and the higher the conversion rate, particularly when the excess air ratio a<1 is NOxThe amount of formation and the conversion rate are drastically reduced. At an excess air ratio of around 0.7, fuel nitrogen is mainly converted to N2。
In a typical modern novel dry cement clinker firing system, the oxygen content of the gas exiting the rotary kiln into the lower cone of the decomposing furnace is generally controlled to be about 2.5%, i.e. the excess air factor a is greater than 1. This aspect results in NO when the coal is burned in a rotary cement kilnxThe generated amount of the air is large, and simultaneously, a certain amount of oxygen is brought into the lower cone of the decomposing furnace, which has negative influence on the reduction zone formed on the lower cone of the decomposing furnace, so that in the embodiment, the measure of reducing the area of the air inlet at the connecting part of the lower cone 6b of the decomposing furnace 6 and the rotary kiln 9 is adopted to reduce the ventilation amount in the rotary kiln 9, so that the coefficient of the excess air in the rotary kiln 9 is very close to 1, and the effect of inhibiting NO in the rotary kiln 9 is achievedxThe function of the reduction area 6e of the lower cone 6b of the decomposing furnace 6 is generated and better formed.
The concrete engineering measure is to lay a layer of thickening layer 6g of the refractory lining on the surface of the refractory lining 6h of the inner wall of the lower cone 6b, or thicken the refractory lining from the production stage for reducing the original ventilation area of the lower cone air inlet 6f, so that the ventilation area of the lower cone air inlet 6f is reduced by about 2-8% compared with the traditional design, even if the lower cone air inlet 6f is reduced by 2-8%The ventilation area of f is reduced to 92-98% of the original ventilation area, the measure of reducing the air inlet sectional area of the lower cone air inlet 6f at the joint of the lower cone 6b of the decomposing furnace 6 and the rotary kiln 9 can reduce the ventilation volume in the rotary kiln 9, reduce the coefficient a of the excess air in the rotary kiln 9, and inhibit NO in the rotary kilnxThe effect of creating and better forming the reduction zone 6e in the lower cone 6b of the decomposing furnace 6 is to bring the excess air factor a in the rotary kiln 9 closer to 1. Wherein, for better denitration effect, the ventilation area at the lower cone air inlet 6f is preferably reduced by about 5% compared with the traditional design, and the air speed of kiln gas entering the decomposing furnace 6 is generally controlled at 30-35 m/s.
Example 3:
the embodiment is further optimized on the basis of the above embodiment, and in order to further better implement the invention, the following arrangement structure is particularly adopted:
in the technical scheme of staged combustion denitration applied in the cement industry at present, the retention time of gas entering a lower cone of a decomposing furnace from a rotary kiln in a reduction zone is generally controlled to be more than 0.2 second. The reason for this is that the volume of the reduction zone is not sufficient or the kiln gas velocity is too high. In order to establish a sufficient reduction zone 6e in the lower cone 6b of the decomposing furnace 6, the height of the tertiary air duct access point 6d, i.e. the height of the position where the tertiary air duct 7 enters the decomposing furnace 6, can be raised in addition to lowering the height of the coal feeding point 6 c.
In this embodiment, in order to further improve the denitration effect of the reduction zone 6e, the retention time of the gas entering the lower cone 6b of the decomposing furnace 6 from the rotary kiln 9 in the reduction zone 6e needs to be prolonged, specifically, the retention time of the gas entering the lower cone 6b from the air inlet 6f of the lower cone in the reduction zone 6e is prolonged to 0.6s at most, preferably 0.5s, and the air speed of the kiln gas entering the decomposing furnace 6 is generally controlled to 30-35 m/s. The volume required for the reduction zone can be calculated as follows: v1＝V2T, wherein V1Volume of the reduction zone 6e, V2Is the volume of gas per second that enters the lower cone 6b from the lower cone inlet 6 f. The residence time of the gas from the rotary kiln 9 into the lower cone 6b of the decomposing furnace 6 in the reduction zone 6e is prolonged to at least 0.2 seconds and at most 0.6 seconds, and can be divided into minutesA sufficient reduction zone 6e is established in the lower cone 6b of the decomposing furnace 6.
Example 4:
the embodiment is further optimized on the basis of the above embodiment, and in order to further better implement the invention, the following arrangement structure is particularly adopted:
in a typical novel dry-process cement clinker sintering system, the feed of a decomposing furnace is from a four-stage cyclone, and the feeding points of the materials on the decomposing furnace are all arranged on the upper part of a tertiary air pipe. In this embodiment, all the coal used for the decomposing furnace 6 is fed to the lower cone 6b of the decomposing furnace 6, and if no measure is taken for suppressing the high temperature of the lower cone 6b, the temperature of the lower cone 6b rapidly rises to 1000 ℃. Excessive zone temperatures present two risks: firstly, liquid phase appears in dust and fire coal particles carried in gas from the rotary kiln at high temperature, and the liquid phase impacts the lining wall in the decomposing furnace to be adhered and deposited to form crust, thereby influencing the normal operation of a cement kiln system; second, new high temperature NO is formed at high temperaturexTotal NO in the systemxThe amount increases, resulting in deterioration of the denitration effect of the staged combustion denitration system.
Then, the measure for suppressing the temperature of the reduction region 6e in the lower cone 6b of the decomposing furnace 6 taken in this embodiment is to feed the low-temperature material from the fourth-stage cyclone 4 into the reduction region 6e of the lower cone 6b of the decomposing furnace 6 by dividing it into portions. The low-temperature material can absorb heat quickly after entering the reduction area 6e, so that the temperature of the reduction area 6e is maintained below 1000 ℃, and high-temperature skinning and new high-temperature NO generation can be avoidedxThe risk of (c).
The specific technical measure is to divide the raw material feeding points of the decomposing furnace 6 into a pair, including an upper raw material feeding point 6i and a lower raw material feeding point 6j used in pair, wherein the upper raw material feeding point 6i is arranged at the upper part of the tertiary air duct access point 6d, such as the furnace main body 6a, and the lower raw material feeding point 6j is arranged between the coal feeding point 6c and the tertiary air duct access point 6d, such as the lower cone 6 b. Thus, the lower raw material feeding point 6j can feed the low-temperature material from the four-stage cyclone 4 into the lower cone 6b of the decomposing furnace 6, and the low-temperature material can absorb heat quickly after entering the reducing area 6e, so that the temperature of the reducing area 6e is maintained below 1000 DEG CCan avoid high-temperature skinning and generate new high-temperature NOxThe risk of (c). The relative distance between the lower raw material feeding point 6j and the coal feeding point 6c is more than or equal to 0.4m and less than or equal to 1.5m, preferably in the range of 0.5-1.0 m.
Example 5:
the embodiment provides a cement kiln based on the above embodiment, and particularly adopts the following arrangement structure:
the cement kiln comprises a primary cyclone cylinder 1, a secondary cyclone cylinder 2, a tertiary cyclone cylinder 3, a four-stage cyclone cylinder 4, a five-stage cyclone cylinder 5, a burner 10, a pulverized coal conveying pipe 11, a tertiary air pipe 7, a blanking pipe 12, a four-stage cyclone cylinder 4, a rotary kiln 9, a clinker cooler 8 and a cement kiln denitration device in embodiment 4.
The connection relationship between different levels of cyclones is the same as that of the traditional cement kiln. Burners 10 are arranged at four coal feeding points 6c of the decomposing furnace 6, and a coal powder conveying pipe 11 is connected with a burner interface of each burner 10. One or two tertiary air pipe access points 6d of the decomposing furnace 6 can be provided according to the existing machine type, and the tertiary air pipe 7 is installed at each tertiary air pipe access point 6 d. The raw material feeding point of the decomposing furnace 6 can have one or two groups according to the existing model, each group of raw material feeding points comprises an upper raw material feeding point 6i and a lower raw material feeding point 6j which are paired, the upper raw material feeding point 6i and the lower raw material feeding point 6j are provided with a blanking branch pipe, the upper raw material feeding point 6i and the lower raw material feeding point 6j which are paired to use are collected and connected to a blanking pipe 12 through the blanking branch pipe, and the blanking pipe 12 is connected to a four-stage cyclone cylinder 4 corresponding to the upstream. A lower cone air inlet 6f at the bottom of the decomposing furnace 6 is connected to the rotary kiln 9.
In order to facilitate the distinction between the cement kiln of the present embodiment and the existing conventional cement kiln, the concrete engineering measures of the cement kiln of the present embodiment are described in a manner of modifying the conventional cement kiln:
the concrete engineering measures are as follows:
1. the feeding point of the pulverized coal conveying pipe 11 connected with the burner 10 in the decomposing furnace 6 is changed from the upper part of the tertiary air pipe 7 to the lower part of the tertiary air pipe 7, namely, the coal feeding point 6c is changed to the lower part of the tertiary air pipe access point 6 d.In practical engineering, the coal feeding point 6c is generally controlled to be about 200mm above the lower cone air inlet 6 f. Thus, all the pulverized coal can be sprayed into the lower cone 6b from the lower part of the tertiary air duct 7, so that all the sprayed pulverized coal is pyrolyzed in the oxygen-deficient environment of the lower cone 6b to generate a large amount of CO so as to form NOxThe reduction zone, the pyrolysis of the fuel coal under the low oxygen environment can effectively inhibit NOxWhile the already generated NO is simultaneously usedxCan be reduced into N in the environment with high C and CO concentration2。
2. The ventilation area of the air inlet of the lower cone of the decomposing furnace is reduced. The specific engineering measure is that the refractory lining 6h at the air inlet 6f of the lower cone is paved with a layer of refractory lining thickening layer for thickening, so that the ventilation area at the air inlet is reduced by about 5 percent compared with the original design. The measure of reducing the area of the air inlet at the joint of the lower cone 6b and the rotary kiln 9 is adopted to reduce the ventilation volume in the rotary kiln 9, so that the coefficient a of the excess air in the rotary kiln 9 is very close to 1, thereby inhibiting NO in the rotary kilnxTo form and better form the reducing zone 6 e.
3. The material separation part which is traditionally fed into the lower part of the decomposing furnace by a four-stage cyclone cylinder is fed into a lower cone 6b of the decomposing furnace. The method comprises the steps of cutting off a feeding pipe 12 of an existing four-stage cyclone 4 entering a decomposing furnace 6 at a proper position, installing a three-way material distributing valve 13, connecting two outlets of the three-way material distributing valve with a feeding branch pipe to an upper raw material feeding point 6i and a lower raw material feeding point 6j, wherein the specific furnace entering point of the lower raw material feeding point 6j is kept at a relative distance of 0.5-1m from a coal feeding point 6 c. Preferably, about 50% of the material discharged from each of the four-stage cyclones 4 is fed into the lower cone 6b, wherein the openings of the upper material feeding point 6i and the lower material feeding point 6j of the decomposing furnace 6 are preferably identical in size, and the pipe diameters of the branched material pipes connected to the upper material feeding point 6i and the lower material feeding point 6j are also identical, so as to ensure that 50% of the material is more accurately discharged.
4. The position of the tertiary air entering the decomposing furnace is increased. The concrete engineering measures are that a tertiary air pipe of an original cement kiln system is put into a decomposing furnace section to be dismantled, and original tertiary air pipe holes on the decomposing furnace are sealed. In the upper part of the reduction zone 6e of the decomposing furnace 6And when the position is newly opened, a tertiary air pipe access point is opened, and the tertiary air pipe is connected with the new tertiary air pipe access point. The position of the new tertiary air pipe access point is according to the formula V1＝V2T and the location of the coal feed point 6c, preferably T ═ 0.5 s.
At present, the mode of feeding the tertiary air pipe into the decomposing furnace of the cement kiln system is commonly provided with two arrangement modes of single-side feeding and two-side feeding. The technical scheme of tertiary air pipe lifting in this embodiment is divided into single-side lifting and double-side lifting. Which lifting scheme is specifically applied will be specifically determined according to the actual situation of the engineering site. Generally, the air is fed into the air inlet on one side, and the technical scheme of lifting on one side is directly used; originally, both sides are air inlet, will give priority to the technical scheme who uses both sides lifting. Because the tertiary tuber pipe of both sides air inlet is by a house steward divide into two branches when being close to the dore furnace, gets into the dore furnace respectively from the both sides of dore furnace, so when the cubic tuber pipe of lifting, also can consider to cut two lateral pipes, directly from the house steward lifting, become a cubic tuber pipe and insert the dore furnace.
In order to further improve the denitration efficiency, the NO of the cement kiln is finally denitrified by separately using the fuel staged combustion denitration technologyxThe emission value is reduced to be below the index required by national standard GB 4915-2013 emission Standard for atmospheric pollutants for Cement industry, so that the SNCR technology is not used for the cement kiln, ammonia water denitration is not used, zero-cost operation of cement kiln denitration is realized, the problem of ammonia escape caused by denitration by using ammonia water for the cement kiln is completely solved, and the structure of the cement kiln in the embodiment needs to be further optimally designed.
The concrete engineering measures are as follows:
5. the traditional cylindrical burner for the decomposing furnace is changed into a novel special low-nitrogen burner for the decomposing furnace. The specific engineering measures are that the fuel jet 10a of the burner 10 faces the decomposing furnace 6, the cross section of the fuel flow is in a flat rectangular structure, and the fuel jet 10a is also in a flaring structure.
The burners used in the traditional cement kiln decomposing furnace are all in a round pipe shape, and the stream of the pulverized coal enters the decomposing furnace through the round pipe-shaped burnersThe surfaces are rounded so that the stream of fuel entering the decomposition furnace is difficult to disperse quickly and mix thoroughly with the rapidly flowing stream of hot gases in the decomposition furnace 6 without having to completely remove all of the NO in the gasxSufficiently contacts with carbon and is reduced, thus resulting in inefficient denitration of the entire reduction zone.
After the pulverized coal is injected into the decomposing furnace 6 by the burner 10 having the flared combustion nozzle 10a with the flat rectangular cross-sectional shape, the fuel flow is changed from the conventional cylindrical shape to the flat rectangular shape and spreads out in a fan shape on the horizontal plane, and can be rapidly dispersed and rapidly and uniformly mixed with the rapidly flowing gas flow in the furnace, so that NO contained in the gas is rapidly and uniformly mixed with the gas flowxCan contact with carbon as soon as possible and be reduced, and finally the aim of reaching the standard of flue gas denitration is achieved.
6. Delaying the mixing speed of the tertiary air and the airflow after the tertiary air enters the decomposing furnace. The specific engineering measure is that the pipe section of the last three meters of the connected tertiary air pipe 7 entering the decomposing furnace 6 is made into an upward inclined section, an included angle formed between the pipe section and the horizontal plane is 10-30 degrees, and the optimal angle is 20 degrees, the last section of the newly connected tertiary air pipe 7 entering the decomposing furnace is made into an upward inclined section, so that the mixing speed of the tertiary air after entering the furnace and the ascending airflow of the reducing area is further delayed, the total volume of the reducing area is further enlarged, the reduction reaction time is prolonged, and the reduction effect is improved.
Example 6:
the embodiment provides a cement kiln denitration process, which particularly adopts the following settings:
basically, the coal feeding point 6c of the decomposing furnace 6 is positioned at the lower part of the tertiary air pipe access point 6d, and a reducing area 6e is established in an oxygen-deficient area between the coal feeding point 6c of the decomposing furnace 6 and the tertiary air pipe access point 6d, so that all coal powder is pyrolyzed in the oxygen-deficient environment of the reducing area 6e to generate a large amount of CO and inhibit NOxAnd the generation of NO is completed in the reduction zone 6exReduction to N in an environment of high C and CO concentration2The reaction of (1).
Preferably, in order to further improve the denitration efficiency, the fuel used alone is finally subjected to staged combustionDenitration technology for removing NO from cement kilnxThe emission value is reduced to the following indexes required by national standard GB 4915-2013 emission Standard of atmospheric pollutants for Cement industry, so that the cement kiln does not use SNCR technology any more, ammonia water denitration is not used any more, zero-cost operation of cement kiln denitration is realized, the problem of ammonia escape caused by denitration by using ammonia water in the cement kiln is completely solved, and the method also comprises one or the combination of any more of the following processes:
firstly, the coefficient a of the excess air in the rotary kiln meets the condition that a is more than or equal to 0.7 and less than or equal to 1;
secondly, the diffusion efficiency of the pulverized coal sprayed into the decomposing furnace 6 from the burner is improved, and the NO in the pulverized coal and the gas is promotedxAre in sufficient contact;
when there are a plurality of raw material feeding points, the raw material from the four-stage cyclone 4 is equally distributed among all raw material feeding points to suppress the temperature of the reduction region 6e and prevent the generation of high-temperature NOx；
Fourthly, prolonging the retention time of the gas entering the lower cone 6b from the rotary kiln 9 to 0.5 second in the reduction zone 6 e;
and fifthly, reducing the mixing speed of the tertiary air entering the decomposing furnace 6 from the tertiary air pipe 7 and the air flow rising from the reduction area 6e so as to further enlarge the total volume of the reduction area 6 e.
The cement kiln denitration process can completely replace the SNCR technology in the cement kiln in the application example 5, or the SNCR technology can be completely replaced by selecting a proper cement kiln according to the process.
The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention.
Claims (10)
1. Cement kiln denitrification facility, including dore furnace (6), dore furnace (6) are including stove main part (6a) and lower cone (6b), lower cone (6b) have lower cone air intake (6f), its characterized in that: the decomposing furnace (6) is provided with a coal feeding point (6c) and a tertiary air pipe access point (6d), the coal feeding point (6c) is arranged at the lower part of the tertiary air pipe access point (6d), and a reduction area (6e) is formed between the coal feeding point (6c) and the tertiary air pipe access point (6 d).
2. The cement kiln denitration device according to claim 1, characterized in that: the vertical relative distance between the coal feeding point (6c) and the lower cone air inlet (6f) is more than or equal to 100mm and less than or equal to 300 mm.
3. The cement kiln denitration device according to claim 1, characterized in that: the volume of the reduction zone (6e) satisfies the formula V1＝V2T, wherein V1Is the volume of the reduction zone (6e), V2And the volume of the gas entering the lower cone (6b) from the lower cone air inlet (6f) per second is T, the time for which the gas entering the lower cone (6b) from the lower cone air inlet (6f) needs to stay in the reduction area (6e) is T, and the T is 0.2-0.6 s.
4. The cement kiln denitration device according to claim 1, characterized in that: and a fireproof lining thickening layer (6g) is laid on the surface of the fireproof lining (6h) on the inner wall of the lower cone (6b) and is used for reducing the original ventilation area of the lower cone air inlet (6 f).
5. The cement kiln denitration device according to any one of claims 1 to 4, characterized in that: the raw material feeding point of dore furnace (6) includes raw material feeding point (6i) and lower raw material feeding point (6j), go up raw material feeding point (6i) set up in tertiary tuber pipe access point (6d) upper portion, lower raw material feeding point (6j) set up in coal-fired feeding point (6c) with between tertiary tuber pipe access point (6 d).
6. The cement kiln is characterized in that: the denitration device comprises a combustor (10), a pulverized coal conveying pipe (11), a tertiary air pipe (7), a blanking pipe (12), a four-stage cyclone cylinder (4), a rotary kiln (9) and the denitration device of the cement kiln, wherein the denitration device is as defined in any one of claims 1 to 5;
the coal-fired feeding point (6c) of dore furnace (6) is installed and is connected combustor (10) of buggy conveyer pipe (11), the tertiary tuber pipe access point (6d) of dore furnace (6) is installed tertiary tuber pipe (7), the raw material feeding point of dore furnace (6) is connected unloading pipe (12), unloading pipe (12) are connected level four whirlwind section of thick bamboo (4), the lower cone air intake (6f) of dore furnace (6) is connected rotary kiln (9).
7. The cement kiln of claim 6, wherein: the fuel nozzle (10a) of the burner (10) is of a flaring structure, and the cross section of the fuel nozzle (10a) of the burner (10) is of a flat rectangle shape.
8. The cement kiln of claim 6, wherein: the pipe section of the tertiary air pipe (7) connected into the decomposing furnace (6) is inclined upwards.
9. The cement kiln denitration process is characterized by comprising the following steps: the coal feeding point (6c) of the decomposing furnace (6) is positioned at the lower part of the tertiary air pipe access point (6d), a reducing area (6e) is established and formed in an oxygen-deficient area between the coal feeding point (6c) of the decomposing furnace (6) and the tertiary air pipe access point (6d), so that all coal powder is pyrolyzed in the oxygen-deficient environment of the reducing area (6e) to generate a large amount of CO, the generation of NOx is inhibited, and the generated NO is completely reduced in the reducing area (6e)xReduction to N in an environment of high C and CO concentration2The reaction of (1).
10. The cement kiln denitration process of claim 9, further comprising one or a combination of any of the following processes:
firstly, the coefficient a of the excess air in the rotary kiln meets the condition that a is more than or equal to 0.7 and less than or equal to 1;
secondly, the diffusion efficiency of the pulverized coal sprayed into the decomposing furnace (6) from the burner is improved, and the pulverized coal is promoted to be fully contacted with NOx in the gas;
when a plurality of raw material feeding points are provided, the raw material from the four-stage cyclone (4) is evenly distributed among all the raw material feeding points to inhibit the temperature of the reduction zone (6e) and prevent the generation of high-temperature NOx;
fourthly, prolonging the retention time of the gas entering the lower cone (6b) from the rotary kiln (9) to 0.5 second in the reduction zone (6 e);
and fifthly, reducing the mixing speed of the tertiary air entering the decomposing furnace (6) from the tertiary air pipe (7) and the air flow rising from the reduction area (6e) so as to further enlarge the total volume of the reduction area (6 e).
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112058064A (en) * | 2020-09-23 | 2020-12-11 | 南京凯盛国际工程有限公司 | Circulating spouting NOx emission reduction system and working method thereof |
| CN114199024A (en) * | 2021-11-23 | 2022-03-18 | 天瑞集团禹州水泥有限公司 | Denitration system for cement kiln decomposing furnace with large reduction area |
| CN117367122A (en) * | 2023-12-07 | 2024-01-09 | 山西卓越水泥有限公司 | Decomposing furnace for cement manufacturing denitration |
-
2019
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112058064A (en) * | 2020-09-23 | 2020-12-11 | 南京凯盛国际工程有限公司 | Circulating spouting NOx emission reduction system and working method thereof |
| CN114199024A (en) * | 2021-11-23 | 2022-03-18 | 天瑞集团禹州水泥有限公司 | Denitration system for cement kiln decomposing furnace with large reduction area |
| CN117367122A (en) * | 2023-12-07 | 2024-01-09 | 山西卓越水泥有限公司 | Decomposing furnace for cement manufacturing denitration |
| CN117367122B (en) * | 2023-12-07 | 2024-02-09 | 山西卓越水泥有限公司 | Decomposing furnace for cement manufacturing denitration |
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