CN213120085U - Decomposing furnace zone-organized combustion self-denitration system - Google Patents

Abstract

The utility model discloses a decomposing furnace zonal tissue combustion self-denitration system, wherein a kiln gas flue is arranged between a kiln tail smoke chamber and a decomposing furnace, a furnace inlet of the kiln gas flue is connected with the side surface of the decomposing furnace, a branch pipe under tertiary air is connected with the bottom of a cone of the decomposing furnace, and a transverse zonal combustion environment of a central concentrated oxygen zone and a peripheral diluted oxygen zone is formed on the cross section of the decomposing furnace; the tertiary air upper branch pipe is connected with the middle part of the decomposing furnace column, a strong reduction area is arranged in the kiln gas flue, the space in the decomposing furnace below the tertiary air upper branch pipe is a weak reduction area, and the space in the decomposing furnace above the tertiary air upper branch pipe is a burnout area, so that a longitudinal gradient combustion environment combining the strong reduction area, the weak reduction area and the burnout area is formed. The transverse partition combustion environment is realized by enabling tertiary air to longitudinally enter air from the center of the bottom of the decomposing furnace upwards and enabling smoke to tangentially rotate to enter air from the volute type of the side surface of the decomposing furnace; the longitudinal staged combustion environment is realized by staged fuel feeding and tertiary air separation. The utility model discloses realize that subregion tissue burning is from the denitration, improve from denitration efficiency.

Description

Decomposing furnace zone-organized combustion self-denitration system

Technical Field

The utility model relates to a cement industry flue gas denitration technical field especially relates to a dore furnace subregion tissue burning is from deNOx systems.

Background

The decomposing furnace is a key device in the cement production process. The main component of the cement raw material is calcium carbonate, and carbonate in the cement raw material is decomposed into oxides in the decomposing furnace, so that a foundation is provided for the subsequent clinker sintering reaction in the rotary kiln. As the carbonate needs to absorb a large amount of heat for decomposition, a certain amount of fuel needs to be fed into the decomposition furnace for supply. Generally, the fuel in the decomposing furnace accounts for about 60% of the fuel consumption in the whole cement clinker calcining process. The combustion condition of the fuel in the decomposition directly affects the product energy consumption of the whole production system, and the decomposition of the decomposing furnace on the material directly affects the material calcination quality of the rotary kiln, thereby affecting the yield and quality of the cement clinker.

There are various types of decomposing furnaces, and typical furnace types include an on-line type decomposing furnace and an off-line type decomposing furnace. In the linear decomposing furnace, the flue gas discharged from the kiln often enters the furnace from the bottom of the decomposing furnace, and combustion air (high-temperature tertiary air recovered from the grate cooler) enters the furnace from a cone or a cylinder of the decomposing furnace. In the off-line decomposing furnace, the flue gas discharged from the kiln directly enters the preheater and does not enter the decomposing furnace. Compared with an off-line decomposing furnace, the on-line decomposing furnace has stable operation condition and is the mainstream decomposing furnace at present.

Nitrogen oxides are gases generated when fossil fuels and air are combusted at high temperature, and have strong toxicity. The emission of nitrogen oxides affects the quality of the atmosphere and has serious harm to the living environment and health of human beings. The cement industry is the third largest nitrogen oxide emission house behind thermal power generation and automobile exhaust. The NOx in the cement flue gas is mainly generated in the combustion process of fuel in a rotary kiln and a decomposing furnace, wherein the NOx generated in the rotary kiln is mainly used. The type of NOx in rotary cement kilns is mainlyOf the thermal type NOx, i.e. N in combustion air at high temperature₂NOx produced by oxidation. The original soviet scientist Zeldovich proposed an empirical formula for the formation reaction of thermal NOx as:

the higher the flue gas temperature during combustion, the faster the rate of formation of thermodynamic NOx. The calcination temperature of the cement clinker is generally 1350-1450 ℃, and the concentration of NOx in the kiln-out flue gas is usually higher, generally 800-1500 ppm. The flue gas of the rotary kiln is discharged from the kiln and then enters the decomposing furnace through the kiln tail smoke chamber, and the reduction of the concentration of NOx in the discharged flue gas is very important for improving the self-denitration efficiency integrally. In order to enhance environmental protection and actively control nitrogen oxide emissions, strict emission standards are established. At present, selective non-catalytic reduction (SNCR) denitration technology or Selective Catalytic Reduction (SCR) denitration technology is mostly adopted in the cement industry at home and abroad. The SNCR technology or the SCR technology is adopted, NOx in the flue gas is reduced by adding a denitration reducing agent (generally ammonia water, urea and other amino reducing agents), and the method has the advantages of high denitration efficiency, mature and reliable technology and the like, but the one-time investment is high, the reducing agent is consumed in the production process, and extra environmental protection treatment cost is brought.

The fuel combustion self-denitration technology is a combustion technology which inhibits the formation of NOx through an intermediate product formed in the combustion process by controlling the combustion characteristic parameters of the fuel under the condition of not additionally adding a denitration reducing agent. At present, the fuel combustion self-denitration technology comprises an air staged combustion technology and a fuel staged combustion technology. The air staged combustion technology utilizes tertiary air fed into the furnace for staged feeding, an oxygen-poor combustion area is formed at the column section of the decomposing furnace, NOx generated by the self combustion of fuel of the decomposing furnace can be inhibited, the peroxide coefficient of the formed oxygen-poor combustion area is still high, and the integral denitration effect is poor. The fuel staged combustion technology utilizes the staged feeding of fuel entering the decomposing furnace, forms an oxygen-deficient combustion area on the cone part of the decomposing furnace, can effectively reduce NOx in flue gas discharged from the rotary kiln, but the reduction range is generally only about 30%, the main reason for limiting the improvement of denitration efficiency is the shortage of denitration reaction time, the residence time of denitration reaction is short due to the limitation of the equipment space of the online decomposing furnace, and the self combustion of the fuel of the decomposing furnace is difficult to inhibit to generate NOx.

The denitration reaction under the reducing atmosphere mainly comprises the following steps: CO + NO → N₂+CO₂。

Patent WO2019043036a1 "Low NOx calcinar" discloses a decomposition furnace with a denitration function, and provides a decomposition furnace for denitration by fuel staged combustion, which can only reduce NOx generated in a rotary kiln and cannot reduce NOx generated by fuel combustion in the decomposition furnace.

Patent CN201711215096 discloses a "gradient combustion self-denitration process method for a sintering system", which is characterized in that a gradient combustion environment of an extremely-oxygen-poor combustion zone, an oxygen-poor combustion zone and an oxygen-rich burnout zone is formed in a decomposing furnace. The decomposing furnace adopts a single furnace form, and the method of gradient combustion is limited in the decomposing furnace. The method is limited by factors such as the volume of the furnace body of the decomposing furnace, the space of the field and the like, the space of the extremely oxygen-poor area is limited, and the whole denitration effect is still to be improved. Meanwhile, the ignition environment of the fuel in the oxygen-deficient combustion area is the mixed gas of the kiln-out smoke and the tertiary air, and the oxygen concentration is insufficient, so that the ignition and the ignition of the fuel of the decomposing furnace are relatively difficult, and the stability of the cement production process is influenced.

The air intake form of the flue gas and the tertiary air discharged from the kiln is also a key link of the decomposing furnace structure. The temperature of the combustion zone in the decomposing furnace and the atmosphere in the combustion zone are decisive factors influencing the combustion speed of the fuel in the decomposing furnace. The fuel combustion rate can be significantly increased by increasing the temperature of the combustion zone or increasing the oxygen concentration in the combustion zone. However, in the actual production process, the temperature in the combustion zone of the decomposing furnace is limited, and the temperature in the decomposing furnace of most production lines is generally controlled below 1150 ℃. When the temperature of the combustion zone is too high, the liquid phase of the raw materials is easy to appear at high temperature, so that the problem of furnace wall crust is caused, and meanwhile, the burning loss of the refractory materials of the furnace wall is easy to cause due to too high combustion temperature.

In summary, the problems of the prior art are as follows:

(1) in the existing linear decomposing furnace, kiln gas directly enters from the bottom of the decomposing furnace, even though fuel is adopted for staged combustion, a reduction zone is formed in the cone part of the decomposing furnace, and a certain effect is achieved on reducing NOx in the discharged flue gas, but because the discharged flue gas directly enters the furnace, the space of an oxygen-deficient combustion zone is limited, the residence time of the denitration reaction is short, and the denitration efficiency is about 30% generally.

(2) The existing decomposing furnace cannot burn out quickly due to the limitation of the temperature of a combustion area, the burning time needs to be prolonged by improving the volume of the decomposing furnace, so that the burning requirement is met, on one hand, the investment and the occupied space are increased, and on the other hand, the heat dissipation energy consumption of the surface of equipment is increased.

(3) The temperature of the combustion zone of the decomposing furnace is limited by the furnace wall crust, so that the prior art is difficult to further increase the temperature of the combustion zone. The temperature in most production line decomposing furnaces is generally controlled below 1150 ℃. When the temperature of the combustion zone is too high, the liquid phase of the raw materials is easy to appear at high temperature, so that the problem of furnace wall crust is caused. Too high a combustion temperature of the decomposing furnace easily causes burning loss of the refractory material of the furnace wall.

(4) The fuel staged combustion method of the decomposing furnace can only reduce NOx generated in the rotary kiln, but can not reduce NOx generated by the self-combustion of the fuel in the decomposing furnace. And the ignition of the fuel in the decomposing furnace is relatively difficult, the working condition fluctuation is easily caused, and the stability of the cement production process is influenced.

(5) The prior method for gradient combustion of the decomposing furnace is limited to the inside of the decomposing furnace. Is limited by factors such as the volume of the furnace body of the decomposing furnace, the space of the field and the like, and the whole denitration effect is still to be improved.

Along with the improvement of the environmental protection requirement, the denitration operation cost of cement enterprises is further increased, the improvement of the fuel combustion self-denitration efficiency, the reduction of the denitration operation cost and the reduction of secondary pollution are urgent matters in the cement industry. And the reduction of NOx through the intermediate product in the combustion process is an environment-friendly treatment mode for source emission reduction, and is beneficial to reducing the integral operation cost of denitration. Therefore, a combustion self-denitration system of a decomposing furnace with a partition structure is provided, a transverse partition combustion environment of a rich and thin oxygen-containing area of the decomposing furnace and a longitudinal gradient combustion environment of a strong reduction area, a weak reduction area and a burnout area are formed, the retention time of the strong reduction area is prolonged, the denitration effect of the strong reduction area is improved, NOx generated by fuel combustion of the decomposing furnace is inhibited, flue gas self-denitration is realized, and the combustion of the fuel is ensured while the temperature of the combustion area of the decomposing furnace is not increased. Has important significance for popularization and application of the denitration technology with high efficiency and low cost for the flue gas of the cement kiln.

Disclosure of Invention

An object of the utility model is to provide a burning is organized from deNOx systems by zone to decomposing furnace, the utility model discloses a burning is organized by zone to the self-denitration system has realized the burning by zone on the whole, can promote the decomposing furnace on the one hand and take off nitre efficiency by zone, and on the other hand is favorable to promoting the interior fuel burning rate of decomposing furnace.

The utility model is realized in such a way that the decomposing furnace is divided into regions to burn the self-denitration system, which comprises a rotary kiln, a kiln tail smoke chamber connected with the kiln tail of the rotary kiln, the decomposing furnace, a decomposing furnace fuel feeding point, a decomposing furnace raw material feeding point and a tertiary air pipe; the device also comprises a kiln gas flue connecting the kiln tail smoke chamber and the decomposing furnace, and a fuel feeding point of the kiln gas flue; the furnace inlet of the kiln gas flue is connected with the side surface of the cone of the decomposing furnace or the side surface of the bottom of the cylinder of the decomposing furnace, so that the flue gas out of the kiln gas flue enters from the volute type tangential rotational flow on the side surface of the decomposing furnace; the tertiary air pipe is divided into an upper branch pipe and a lower branch pipe, the upper branch pipe comprises a tertiary air lower branch pipe and a tertiary air upper branch pipe, the tertiary air lower branch pipe is positioned under the cone of the decomposing furnace, the tertiary air lower branch pipe is connected with the bottom of the cone of the decomposing furnace, so that tertiary air longitudinally enters from the center of the bottom of the decomposing furnace upwards, and an air flow distribution environment of a central concentrated oxygen area and a peripheral diluted oxygen area is formed on the cross section of the decomposing furnace; the tertiary air upper branch pipe is connected with the middle part of the decomposing furnace cylinder;

a strong reduction area is arranged in the kiln gas flue, excessive fuel is fed into a fuel feeding point of the kiln gas flue, so that strong reduction atmosphere is formed in the kiln gas flue, and NOx in the flue gas discharged from the kiln is fully reduced; the space in the decomposing furnace below the tertiary air upper branch pipe is a weak reduction area, and NOx generated by fuel combustion of the decomposing furnace is inhibited; the space in the decomposing furnace above the tertiary air upper supporting pipe is a burnout zone, so that the oxygen demand for fuel combustion is met; and a longitudinal gradient combustion environment combining a strong reduction area, a weak reduction area and an ember area is formed in a combined combustion space of the kiln gas flue and the decomposing furnace.

Preferably, the fuel feeding point of the kiln gas flue is positioned at the lower part of the kiln gas flue.

Preferably, a kiln gas flue raw material feeding point is arranged on the kiln gas flue, the kiln gas flue raw material feeding point is positioned above a kiln gas flue fuel feeding point, raw material is fed through the kiln gas flue raw material feeding point to control the temperature in the kiln gas flue to be not higher than 1150 ℃, and the problem of skinning caused by overhigh temperature in the flue due to fuel combustion is prevented.

Preferably, at least one fuel feeding point of the decomposing furnace is positioned below a furnace inlet of the kiln gas flue, the fuel of the decomposing furnace is firstly mixed with tertiary air, the combustion of the fuel is facilitated, and the fuel moves upwards along with the tertiary air, so that a combustion area is mainly a central oxygen-rich area of the decomposing furnace.

Preferably, the decomposing furnace raw material feeding points comprise a decomposing furnace raw material lower feeding point and a decomposing furnace raw material upper feeding point, and the two decomposing furnace raw material feeding points are both positioned below the air inlet of the tertiary air upper supporting pipe; the lower raw material feeding point of the decomposing furnace is positioned above the fuel feeding point of the decomposing furnace below the furnace inlet of the kiln gas flue; the upper feeding point of the raw material of the decomposing furnace is positioned in the middle of the column body of the decomposing furnace; the two feeding points adjust the feeding amount through a material distributing valve arranged on a material pipe of the decomposing furnace, and the temperature of a peripheral light oxygen region in the decomposing furnace is controlled to be lower than 1150 ℃ through the raw material amount, so that the problem of high-temperature furnace wall crust is prevented; simultaneously, a part of raw meal is fed into the upper feeding point of the raw meal of the decomposing furnace, so as to reduce the amount of raw meal fed from the lower feeding point and increase the temperature of the lower part of the decomposing furnace.

Still more preferably, the decomposing furnace raw meal lower feeding point is positioned on the decomposing furnace cone or on the lower part of the decomposing furnace cylinder.

Still further preferably, a decomposing furnace bottom column section is arranged between the decomposing furnace cone and the furnace inlet of the tertiary air lower branch pipe, and the decomposing furnace raw material lower feeding point and the decomposing furnace fuel feeding point below the furnace inlet of the kiln gas flue are positioned on the decomposing furnace bottom column section.

Still further preferably, the decomposing furnace cylinder is provided with a decomposing furnace middle reducing opening, and the decomposing furnace middle reducing opening is positioned below a raw material feeding point of the decomposing furnace.

Preferably, tertiary air valves are arranged on the tertiary air upper branch pipe and the tertiary air lower branch pipe, the tertiary air distribution proportion is adjusted through the tertiary air valves, the peroxide coefficient of a weak reduction region in the decomposing furnace is further adjusted, the peroxide coefficient of the weak reduction region is controlled to be 0.8-1.0, and NOx generated by fuel combustion of the decomposing furnace is inhibited.

Preferably, a discharge bin and a material pipe connected with the discharge bin are arranged below a bottom elbow of the tertiary air lower branch pipe, the other end of the material pipe is connected with the kiln tail smoke chamber, and an air locking valve is arranged on the material pipe.

Through the grading design of tertiary air, fuel and raw materials, a longitudinal gradient combustion environment of a strong reduction zone, a weak reduction zone and an ember zone is formed, NOx in the smoke of the rotary kiln is reduced by the strong reduction zone, the weak reduction zone inhibits the generation of fuel type NOx in the combustion process of the fuel in the decomposing furnace, the ember zone enables the fuel to be fully combusted, and NOx is reduced by using a combustion intermediate product CO in the combustion process of the fuel and the decomposition process of the raw materials, so that the self-denitration of the smoke is realized. And the air flow distribution environment of a central concentrated oxygen area and a peripheral diluted oxygen area is formed on the cross section of the decomposing furnace by utilizing the mode that tertiary air longitudinally enters from the bottom of the decomposing furnace upwards and flue gas of a flue gas channel of kiln outlet gas enters from the volute type tangential rotational flow of the side surface of the decomposing furnace, so that the fuel is high in combustion speed in the central concentrated oxygen area and low in combustion speed in the peripheral diluted oxygen area, the temperature of the peripheral diluted oxygen area is not higher than 1150 ℃, the furnace wall is not skinned, the temperature of the central concentrated oxygen area can be increased to 1300 ℃, and the combustion speed of the fuel is increased. The utility model discloses subregion burning dore furnace structure based on dark and light oxygen-containing district sets up the kiln gas flue outside being independent of dore furnace owner stove before the dore furnace, makes strong reduction zone be located the kiln gas flue, has prolonged the dwell time of flue gas in the strong reduction zone by a wide margin, has increased the time of strong reduction zone denitration reaction to reduce the NOx in the kiln flue gas more thoroughly, promote from the complete decomposition of the abundant burning out of the ashes and raw of denitration efficiency assurance fuel simultaneously.

The system is adopted to carry out the decomposing furnace zone-organized combustion self-denitration process, the process adopts a transverse zone combustion environment with a concentrated oxygen zone at the center and a light oxygen zone at the periphery formed on the section of a main combustion zone of the decomposing furnace, and a longitudinal gradient combustion environment combining a strong reduction zone, a weak reduction zone and a burnout zone is formed in a combined combustion space of a kiln gas pipeline and the decomposing furnace, so that self-denitration and fuel burnout are realized; the transverse subarea combustion environment is realized by enabling tertiary air to longitudinally and upwards enter air from the center of the bottom of the decomposing furnace and enabling smoke out of the kiln gas flue to tangentially rotate and enter air from the volute type on the side surface of the decomposing furnace, wherein under the action of a rotating centrifugal force, the smoke out of the kiln gas flue forms a light oxygen area at the periphery of the decomposing furnace, and the tertiary air forms a concentrated oxygen area at the center of the decomposing furnace; the longitudinal gradient combustion environment is realized by feeding tertiary air, fuel and raw materials in a grading manner, the strong reduction area is an area positioned in a kiln gas flue, excessive fuel is fed into the kiln gas flue, the peroxide coefficient of the strong reduction area is controlled to be less than 0.8, NOx in smoke discharged from the kiln is reduced, and the temperature is controlled to be 850-1150 ℃; the weak reduction area is a decomposing furnace area below a tertiary air upper branch pipe, the air distribution ratio of tertiary air is adjusted to control the peroxide coefficient of the weak reduction area to be 0.8-1.0, NOx generated by fuel combustion of the decomposing furnace is inhibited, and the temperature is controlled to be 950-1150 ℃; the burnout zone is a decomposing furnace zone above a tertiary air upper branch pipe, the peroxide coefficient of the burnout zone is controlled to be larger than 1.0, and the oxygen demand of fuel combustion is met.

Preferably, the wind speed at the furnace inlet of the tertiary air lower branch pipe is not lower than 10 m/s.

The utility model has the advantages of it is following and beneficial effect:

1. the utility model discloses utilize cement manufacture line to burn till technology characteristics, developed a dore furnace subregion tissue burning from deNOx systems and technology. Through the grading design of tertiary air, fuel and raw materials, a longitudinal gradient combustion environment combining a strong reduction area, a weak reduction area and an after-burning area with different peroxide coefficients is formed in a combined combustion space of a kiln gas pipeline and a decomposing furnace; through the structural design of the tertiary air entering the furnace and the low-oxygen kiln gas, the tertiary air is vertically jetted upwards from the center of the bottom of the decomposing furnace to enter air, the flue gas enters air from the volute type tangential rotational flow of the side surface of the decomposing furnace, and a transverse subarea combustion environment of a rich-lean oxygen-containing area is formed on the cross section of the decomposing furnace; the two combustion environments are combined, so that the zoned-tissue combustion self-denitration is realized integrally, the self-denitration efficiency can be effectively improved, the full burning of fuel in a decomposing furnace and the complete decomposition of raw materials are not influenced, and the cement clinker production process is not influenced. The system has the advantages of reasonable process, good reliability, strong adaptability and the like, can reduce the environmental protection treatment cost of enterprises, can be popularized and applied in new production lines of cement engineering and old denitration technology improvement, and has strong operability and practicability.

2. The utility model discloses a set up the kiln gas flue that is independent of outside the dore furnace owner stove in the front of the dore furnace, make strong reducing zone be located the kiln gas flue, solved the not enough problem in the strong reducing zone space in the current dore furnace, prolonged the dwell time of flue gas in the strong reducing zone by a wide margin, increased the time of strong reducing zone denitration reaction to reduce the NOx in the kiln flue gas more thoroughly, promote from the efficiency of taking off the nitre.

3. The utility model discloses a fuel makes kiln gas flue form strong reducing atmosphere in grades, and NOx in the flue gas of play rotary kiln here is reduced to N₂(ii) a The lower cylinder of the decomposing furnace forms weak reducing atmosphere by tertiary air, so that the generation of fuel type NOx in the combustion process of fuel in the decomposing furnace is inhibited; therefore, the background concentration of NOx in the flue gas generated in the cement production process is greatly reduced on the whole, the emission reduction of NOx sources in the firing process is realized, the upper column body of the decomposing furnace is provided with oxidizing atmosphere, the fuel is fully burnt out, and the purposes of environmental protection control and green production are achieved.

4. The utility model discloses a make the tertiary air from the vertical perpendicular efflux air inlet that makes progress in decomposition furnace bottom center, the gas flue gas of going out of kiln from decomposition furnace side spiral case formula tangential whirl air inlet, under rotatory centrifugal force effect, the flue gas forms light oxygen district outside the decomposition furnace, and the tertiary air forms concentrated oxygen district at the decomposition furnace center, realizes that fuel is in furnace body center concentrated oxygen district high temperature combustion, the subregion combustion environment of peripheral light oxygen district medium temperature combustion. The temperature of the central concentrated oxygen zone can be increased to 1300 ℃, and the combustion temperature is relatively increased by 100-200 ℃, so that the combustion speed of the fuel is increased; the fuel in the peripheral light oxygen region is combusted under the anoxic condition to generate a reducing intermediate product CO which can continuously reduce NOx in the flue gas, meanwhile, the combustion speed of the fuel is inhibited by the low-oxygen atmosphere, the temperature of the side wall is not increased, the temperature of the peripheral light oxygen region is not higher than 1150 ℃, and the furnace wall is not skinned; the method solves the contradiction between the improvement of the temperature of the combustion zone and the prevention of furnace wall crust, can improve the combustion temperature of the central zone of the decomposing furnace, does not increase the risk of furnace wall crust of the decomposing furnace, widens the limit of peripheral furnace wall crust on the combustion temperature of the decomposing furnace, integrally improves the combustion speed of fuel in the decomposing furnace, improves the burnout degree, reduces the fuel consumption of a firing system, and has very important practical significance.

5. The utility model discloses in locate kiln gas flue and go into the dore furnace fuel feeding point of mouth below for fuel mixes with the tertiary air that oxygen content is high earlier, more is favorable to the ignition of fuel to catch fire, has strengthened the combustion effect of fuel in the dore furnace when realizing from the denitration, realizes energy saving and consumption reduction.

Drawings

Fig. 1 is a schematic structural diagram of a system according to a first embodiment of the present invention;

fig. 2 is a schematic structural diagram of a kiln gas flue according to a first embodiment of the present invention;

fig. 3 is a schematic structural diagram of a tertiary air lower branch pipe according to an embodiment of the present invention;

FIG. 4 is a schematic structural diagram of a decomposing furnace and a furnace inlet of a kiln gas flue according to an embodiment of the present invention;

fig. 5 is a schematic structural diagram of a system according to a second embodiment of the present invention;

fig. 6 is a schematic structural diagram of a system according to a third embodiment of the present invention.

In the figure:

a, flue gas of a rotary kiln; b-tertiary air; c, discharging flue gas; d, charging raw materials;

100-peripheral light oxygen zone; 200-a central concentrated oxygen zone; 300-a strong reduction zone; 400-weak reduction zone; 500-an ember zone;

1-decomposing furnace; 11-decomposing furnace cone; 12-decomposing furnace column; 12 a-a decomposing furnace lower column; 12 b-decomposing furnace upper cylinder; 13-necking down the middle part of the decomposing furnace; 14-a decomposing furnace bottom column section;

21-kiln gas flue; 22-a furnace inlet of a kiln gas flue;

3-tertiary air pipe; 31-tertiary air lower branch pipe; 311-bottom elbow of branch pipe under tertiary air; 32-tertiary air upper branch pipe; 33-tertiary air valve;

41-decomposition furnace fuel feeding point; 42-kiln gas flue fuel feed point;

51-raw material feeding point of decomposing furnace; 52-feeding point on raw meal of decomposing furnace; 53-kiln gas flue raw material feeding point;

6-kiln tail smoke chamber;

71-a discharge bin; 72-a material pipe; 73-a latch valve;

the dotted line with an arrow is the airflow direction; the arrowed direction is realized as the direction of the flow.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail with reference to the following embodiments and accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

In the description of the present invention, it is to be noted that, unless otherwise explicitly specified or limited, the terms "connected" and "connected" are to be interpreted broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood in specific cases to those skilled in the art.

Example 1

Referring to fig. 1-4, an embodiment of the present invention provides a decomposing furnace zone tissue combustion self-denitration system, which includes a rotary kiln, a kiln tail smoke chamber 6 connected to a kiln tail of the rotary kiln, a decomposing furnace 1, a kiln gas flue 21 connecting the kiln tail smoke chamber 6 and the decomposing furnace 1, and a tertiary air duct 3; refractory materials are arranged in the decomposing furnace 1, the kiln gas flue 21 and the tertiary air duct 3.

The rotary kiln flue gas A is flue gas generated by fuel combustion in a rotary kiln, the temperature is generally 900-1150 ℃, the oxygen content is generally within 5%, and the concentration of NOx in the flue gas is generally 800-1500 ppm. The rotary kiln smoke A moves upwards after passing through the kiln tail smoke chamber 6 and enters the kiln gas flue 21, and enters the decomposing furnace cone 11 through the furnace inlet 22 of the kiln gas flue. The furnace inlet 22 of the kiln gas flue is connected with the side surface of the decomposing furnace cone 11 or the side surface of the bottom of the decomposing furnace cylinder 12, in the embodiment, the furnace inlet 22 of the kiln gas flue is connected with the side surface of the decomposing furnace cone 11, so that flue gas out of the kiln gas flue enters the decomposing furnace cone from the volute type tangential rotational flow, the included angle between the air direction of the flue gas entering the decomposing furnace and the horizontal direction is +/-30 degrees, and the flue gas rotates upwards along the outer wall of the decomposing furnace under the centrifugal force after entering the decomposing furnace. The tertiary air B enters the decomposing furnace through the tertiary air pipe 3, the tertiary air pipe 3 is divided into an upper branch pipe and a lower branch pipe, the lower branch pipe 31 of the tertiary air pipe and the upper branch pipe 32 of the tertiary air pipe are included, the lower branch pipe 31 of the tertiary air pipe is positioned under the decomposing furnace cone 11, the lower branch pipe 31 of the tertiary air pipe is connected with the bottom of the decomposing furnace cone 11, after a part of the tertiary air passes through a bottom elbow 311 of the lower branch pipe of the tertiary air pipe, airflow moves vertically upwards, the tertiary air enters the decomposing furnace cone 11 vertically upwards along the center of the bottom of the decomposing furnace cone 11, the air speed of the furnace inlet of the lower branch pipe 31 of the tertiary air pipe is larger than 10m/s, raw materials in the decomposing furnace. The tertiary air valve 33 is arranged on the tertiary air lower branch pipe 31 in the embodiment and used for adjusting the tertiary air quantity of the tertiary air lower branch pipe. An airflow distribution state with the periphery of the kiln-out smoke and the center of the tertiary air is formed on the cross section of the decomposing furnace. The oxygen content in the tertiary air is high and is about 21 percent; the oxygen content in the flue gas discharged from the kiln is low, and is generally within 5 percent. A regional combustion environment of a central concentrated oxygen region 200 and a peripheral diluted oxygen region 100 is formed on the cross section in the decomposing furnace, high-temperature combustion is carried out in the central concentrated oxygen region 200 of the decomposing furnace, the temperature of the central region of the decomposing furnace is favorably improved, the temperature can be improved to 1300 ℃, fuel combustion is accelerated, medium-temperature combustion is carried out in the peripheral diluted oxygen region 100, the temperature is not higher than 1150 ℃, and NOx in smoke is continuously reduced.

The tertiary air upper branch pipe 32 is connected with the middle part of the decomposing furnace cylinder 12. The section a-a of the air outlet of the tertiary air upper supporting pipe 32 divides the decomposing furnace cylinder 12 into a decomposing furnace lower cylinder 12a and a decomposing furnace upper cylinder 12 b.

A strong reduction area 300 is arranged in the kiln gas flue 21, excessive fuel is fed into a fuel feeding point 42 of the kiln gas flue, so that strong reduction atmosphere is formed in the kiln gas flue 21, and NOx in the kiln gas discharged from the kiln is fully reduced; the space in the decomposing furnace below the tertiary air upper branch pipe 32 is a weak reduction zone 400, and NOx generated by fuel combustion of the decomposing furnace is inhibited; the space in the decomposing furnace above the tertiary air upper supporting pipe 32 is a burnout zone 500, and the oxygen demand for fuel combustion is met; a longitudinal gradient combustion environment combining the strong reduction area 300, the weak reduction area 400 and the burnout area 500 is formed in the combined combustion space of the kiln gas flue 21 and the decomposing furnace 1.

The strong reduction area 300 is an area in the kiln gas flue 21, and gas in the strong reduction area 300 is kiln discharge flue gas. The kiln gas flue 21 is provided with a kiln gas flue fuel feeding point 42, excessive fuel is fed through the kiln gas flue fuel feeding point 42, and the peroxide coefficient in the kiln gas flue 21 is controlled to be less than 0.8. Because of insufficient oxygen, the fuel generates a large amount of reducing gas CO in an oxygen-deficient combustion environment and reacts with NOx in the kiln discharge flue gas to reduce the NOx into N₂And the NOx in the flue gas discharged from the kiln is reduced. The kiln gas flue fuel feeding point 42 is positioned at the lower part of the kiln gas flue 21, so that NOx in the kiln gas can fully react with CO. The fuel is partially combusted in the strong reduction area 300 to release heat, in order to prevent the temperature from being overhigh, a kiln gas flue raw material feeding point 53 is arranged on a kiln gas flue 21, the kiln gas flue raw material feeding point 53 is positioned above a kiln gas flue fuel feeding point 42, raw materials are fed through the kiln gas flue raw material feeding point 53, the temperature in the kiln gas flue 21 is controlled not to be higher than 1150 ℃ through raw material heat absorption, and the problem of skinning caused by overhigh temperature in the flue due to fuel combustion is prevented.

In the weak reduction area 400, the flue gas of the kiln outlet gas flue is mixed with the tertiary air in the lower branch pipe of the tertiary air. The tertiary air lower branch pipe 31 is positioned right below the decomposing furnace cone 11, and the furnace inlet 22 of the kiln gas flue is positioned on the side surface of the decomposing furnace cone 11. The tertiary air upper supporting pipe 32 is connected with the middle part of the decomposing furnace column 12, and the weak reduction area 400 is positioned below the air inlet of the tertiary air upper supporting pipe 32. The tertiary air valve 33 is arranged on the tertiary air upper branch pipe 32, the air volume of the tertiary air upper branch is adjusted, and a part of the tertiary air enters the middle part of the decomposing furnace column 12 through short circuit, so that the peroxide coefficient in the weak reduction area 400 is controlled to be 0.8-1.0, and NOx generated by fuel combustion of the decomposing furnace is inhibited. The fuel of the decomposing furnace is ignited and burnt in the weak reduction area 400, and because the burning air is insufficient, a burning intermediate product CO can be formed in the weak reduction area 400, the fuel of the decomposing furnace can be inhibited from generating NOx in the burning process, and the NOx which is not completely reacted in the flue gas of the kiln gas is further reduced; in addition, the fuel fed from the fuel feeding point 42 of the kiln gas flue can not be completely combusted in the kiln gas flue 21, the part of incompletely combusted fuel enters the peripheral light oxygen region 100 of the decomposing furnace along with the kiln gas, is still in an oxygen-deficient combustion state in the peripheral light oxygen region 100 to form a reducing atmosphere, and releases combustion products such as CO and the like, thereby being beneficial to further denitration of the smoke in the light oxygen region, and reducing NOx in the smoke discharged from the kiln and the smoke in the peripheral light oxygen region of the decomposing furnace. At least one fuel feeding point of the decomposing furnace is positioned below a furnace inlet 22 of the kiln gas flue, the fuel at the decomposing furnace is firstly mixed with tertiary air, the combustion of the fuel is more facilitated, and the fuel moves upwards along with the tertiary air, so that a combustion area is mainly a central oxygen concentration area 200 of the decomposing furnace. In order to prevent the combustion temperature in the decomposing furnace from being too high, a decomposing furnace raw material lower feeding point 51 is arranged on the decomposing furnace cone 11 or at the lower part of the decomposing furnace lower column 12a, the decomposing furnace raw material lower feeding point 51 is positioned above the decomposing furnace fuel feeding point 41, the temperature of a combustion area in the decomposing furnace is reduced by absorbing heat of raw materials after the raw materials enter the decomposing furnace from the decomposing furnace raw material lower feeding point 51, the temperature of smoke near the wall of the decomposing furnace is generally required to be lower than 1150 ℃, and the temperature of a peripheral light oxygen region in the decomposing furnace is controlled by the raw materials to prevent the high-temperature skinning of the wall of the. Meanwhile, the decomposing furnace raw material upper feeding point 52 is also arranged on the decomposing furnace lower column body 12a, the gas temperature in the weak reduction area 400 is controlled to be 950-1150 ℃ through the distribution of the decomposing furnace raw material upper feeding point 52, the raw material quantity fed from the decomposing furnace raw material lower feeding point 51 is reduced, and the temperature of the lower part of the decomposing furnace is increased.

The burnout zone 500 is the zone where the upper cylinder 12b of the decomposing furnace is located, and after the tertiary air in the upper branch pipe 32 of the tertiary air enters the burnout zone 500, the coefficient of the excess air in the burnout zone 500 is larger than 1.0, so that the oxygen amount required by fuel burnout is met.

Preferably, a discharge bin 71 and a material pipe 72 connected with the discharge bin 71 are arranged below a bottom elbow 311 of the tertiary air lower branch pipe, and two ends of the material pipe 72 are connected with the discharge bin 71 and the kiln tail smoke chamber 6. When the machine is shut down in an accident, the materials in the decomposing furnace can fall into the discharging bin 71, enter the kiln tail smoke chamber 6 along the material pipe 72 and enter the rotary kiln, and the materials do not need to be cleaned manually. The air locking valve 73 is arranged on the material pipe 72 and is used for preventing the kiln outlet flue gas in the kiln tail smoke chamber 6 from entering the decomposing furnace through air blowby from the material pipe 73.

To sum up, the utility model discloses a hierarchical design of tertiary air, fuel, raw material forms the longitudinal gradient combustion environment in strong reduction district-weak reduction district-burn-out district, utilizes burning intermediate product CO to reduce NOx at the in-process of fuel burning and raw material decomposition, can reduce the NOx in rotary kiln flue gas A, also can restrain the NOx that produces in the fuel burning process in the decomposition stove to reduce the NOx content in the decomposition stove flue gas C of coming out of the stove on the whole, realize burning the in-process and take off the nitre function certainly. And the air flow distribution environment of the central concentrated oxygen area 200 and the peripheral diluted oxygen area 100 is formed on the cross section of the decomposing furnace by utilizing the mode that tertiary air longitudinally enters from the bottom of the decomposing furnace upwards and flue gas of a flue gas channel of kiln outlet gas enters from the volute type tangential rotational flow of the side surface of the decomposing furnace, so that the combustion speed of fuel in the central concentrated oxygen area is relatively high, and the combustion speed in the peripheral diluted oxygen area is relatively low. In order to prevent the furnace wall from skinning, the temperature of the peripheral light oxygen region is controlled to be not higher than 1150 ℃, the furnace wall does not skinning, the combustion temperature in the central concentrated oxygen region 200 is not limited by the furnace wall skinning, the temperature of the central concentrated oxygen region can be increased to 1300 ℃, the combustion speed of the fuel is increased, the burning time of the fuel is shortened, the self-denitration of the decomposing furnace is realized, the combustion speed of the fuel is not reduced, and the purposes of saving energy and reducing consumption are achieved. The utility model discloses subregion burning dore furnace structure based on dark and light oxygen-containing district, set up the kiln gas flue outside being independent of dore furnace owner stove in the front of the dore furnace, make strong reduction zone be located the kiln gas flue, the problem that strong reduction zone space is not enough in the current dore furnace has been solved, the dwell time of flue gas in the strong reduction zone has been prolonged by a wide margin, increase the time of strong reduction zone denitration reaction, thereby reduce the NOx in the kiln flue gas more thoroughly, promote the complete decomposition of the abundant ashes of burning and raw of fuel has been guaranteed simultaneously to the efficiency of taking off the nitre certainly.

Example 2

Unlike the embodiment 1, the decomposition furnace cylinder 12 is provided with a decomposition furnace inner throat 13.

Please refer to fig. 5. Preferably, the decomposing furnace cylinder 12 is provided with a decomposing furnace inner throat 13. The decomposing furnace middle reducing mouth 13 is positioned below the decomposing furnace raw material feeding point 52. Raw materials entering from the raw material feeding point 52 of the decomposing furnace move downwards under the action of gravity, and the section wind speed at the reducing part is increased relative to the section wind speed of the column body by arranging the reducing part 13 in the middle of the decomposing furnace, so that the falling height of the raw materials can be effectively reduced, and the phenomenon of material collapse in the decomposing furnace is prevented.

Example 3

Different from the embodiment 1, a decomposing furnace bottom column section 14 is arranged between the decomposing furnace cone 11 and the furnace inlet of the tertiary air lower branch pipe 31. The lower feed point 51 for raw meal of the decomposing furnace and the feed point 41 for fuel of the decomposing furnace below the furnace inlet of the kiln gas flue are located on the bottom column section 14 of the decomposing furnace.

Please refer to fig. 6. Preferably, a decomposing furnace bottom column section 14 is arranged between the decomposing furnace cone 11 and the furnace inlet of the tertiary air lower branch pipe 31. The tertiary air firstly passes through the column section 14 at the bottom of the decomposing furnace and then enters the cone 11 of the decomposing furnace. At this time, the decomposing furnace fuel feeding point 41 and the decomposing furnace raw material feeding point 51 which are positioned below the furnace inlet of the kiln gas flue are positioned on the decomposing furnace bottom column section 14, and the decomposing furnace bottom column section 14 is not mixed with the flue gas discharged from the kiln, so that the ignition and the ignition of the fuel are facilitated.

Example 4

The system is adopted to carry out the decomposing furnace zone-organized combustion self-denitration process, the process adopts a transverse zone combustion environment with a concentrated oxygen zone at the center and a light oxygen zone at the periphery formed on the section of a main combustion zone of the decomposing furnace, and a longitudinal gradient combustion environment combining a strong reduction zone, a weak reduction zone and a burnout zone is formed in a combined combustion space of a kiln gas pipeline and the decomposing furnace, so that self-denitration and fuel burnout are realized; the transverse subarea combustion environment is realized by enabling tertiary air to longitudinally and upwards enter air from the center of the bottom of the decomposing furnace and enabling smoke out of the kiln gas flue to tangentially rotate and enter air from the volute type on the side surface of the decomposing furnace, wherein under the action of a rotating centrifugal force, the smoke out of the kiln gas flue forms a light oxygen area at the periphery of the decomposing furnace, and the tertiary air forms a concentrated oxygen area at the center of the decomposing furnace; the longitudinal gradient combustion environment is realized by feeding tertiary air, fuel and raw materials in a grading manner, the strong reduction area is an area positioned in a kiln gas flue, excessive fuel is fed into the kiln gas flue, the peroxide coefficient of the strong reduction area is controlled to be less than 0.8, NOx in smoke discharged from the kiln is reduced, and the temperature is controlled to be 850-1150 ℃; the weak reduction area is a decomposing furnace area below an upper branch pipe of the tertiary air pipe, the air distribution ratio of tertiary air is adjusted to control the peroxide coefficient of the weak reduction area to be 0.8-1.0, NOx generated by fuel combustion of the decomposing furnace is inhibited, and the temperature is controlled to be 950-1150 ℃; the burnout zone is a decomposing furnace zone above a tertiary air upper branch pipe, the peroxide coefficient of the burnout zone is controlled to be larger than 1.0, and the oxygen demand of fuel combustion is met.

Preferably, the wind speed at the furnace inlet of the tertiary air lower branch pipe is not lower than 10m/s, so that the raw materials in the cone 11 of the decomposing furnace can be suspended, and the phenomenon of material collapse caused by short circuit of the materials is prevented.

In summary, the decomposing furnace partition tissue combustion self-denitration process of the utility model is characterized in that excessive fuel is fed into a kiln gas flue, and the peroxide coefficient is less than 0.8, so as to form a strong reduction area; the lower cylinder of the decomposing furnace forms weak reducing atmosphere through the air distribution of tertiary air, the peroxide coefficient is 0.8-1.0, the upper cylinder of the decomposing furnace is oxidizing atmosphere, and the peroxide coefficient is more than 1.0; and then a longitudinal gradient combustion environment combining a strong reduction zone, a weak reduction zone and an ember zone with different peroxide coefficients is formed in a combined combustion space of the kiln gas pipeline and the decomposing furnace, the strong reduction zone reduces NOx in the smoke of the rotary kiln, the weak reduction zone inhibits the generation of fuel type NOx in the combustion process of fuel in the decomposing furnace, and the ember zone enables the fuel to be fully combusted. And the air flow distribution environment of a central concentrated oxygen area and a peripheral diluted oxygen area is formed on the cross section of the decomposing furnace by utilizing the mode that tertiary air longitudinally enters from the bottom of the decomposing furnace upwards and flue gas of a flue gas channel of kiln outlet gas enters from the volute type tangential rotational flow of the side surface of the decomposing furnace, so that the fuel is high in combustion speed in the central concentrated oxygen area and low in combustion speed in the peripheral diluted oxygen area, the temperature of the peripheral diluted oxygen area is not higher than 1150 ℃, the furnace wall is not skinned, the temperature of the central concentrated oxygen area can be increased to 1300 ℃, and the combustion speed of the fuel is increased. The utility model discloses reduce NOx's background concentration in the flue gas that the cement manufacture process produced on the whole by a wide margin, restrained the formation of fuel type NOx in the fuel combustion process in the decomposing furnace, realized firing burning process in NOx source and reduced discharging, promoted the complete decomposition of the abundant burn-out and the raw meal of fuel has been guaranteed simultaneously from the efficiency of taking off the nitre, reached the purpose of environmental protection control and green production.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that: it is also possible to modify the solutions described in the foregoing embodiments or to substitute some or all of the technical features of the foregoing embodiments with equivalents, without departing from the scope of the embodiments of the present invention.

Claims (8)

1. A decomposing furnace zone tissue combustion self-denitration system comprises a rotary kiln, a kiln tail smoke chamber connected with the kiln tail of the rotary kiln, a decomposing furnace fuel feeding point, a decomposing furnace raw material feeding point and a tertiary air duct; it is characterized by also comprising a kiln gas flue connecting the kiln tail smoke chamber and the decomposing furnace, and a fuel feeding point of the kiln gas flue; the furnace inlet of the kiln gas flue is connected with the side surface of the cone of the decomposing furnace or the side surface of the bottom of the cylinder of the decomposing furnace, so that the flue gas out of the kiln gas flue enters from the volute type tangential rotational flow on the side surface of the decomposing furnace; the tertiary air pipe is divided into an upper branch pipe and a lower branch pipe, the upper branch pipe comprises a tertiary air lower branch pipe and a tertiary air upper branch pipe, the tertiary air lower branch pipe is positioned under the cone of the decomposing furnace, the tertiary air lower branch pipe is connected with the bottom of the cone of the decomposing furnace, so that tertiary air longitudinally enters from the center of the bottom of the decomposing furnace upwards, and an air flow distribution environment of a central concentrated oxygen area and a peripheral diluted oxygen area is formed on the cross section of the decomposing furnace; the tertiary air upper branch pipe is connected with the middle part of the decomposing furnace cylinder;

a strong reduction area is arranged in the kiln gas flue; the space in the decomposing furnace below the tertiary air upper supporting pipe is a weak reduction area; the space in the decomposing furnace above the tertiary air upper supporting pipe is a burnout zone; and a longitudinal gradient combustion environment combining a strong reduction area, a weak reduction area and an ember area is formed in a combined combustion space of the kiln gas flue and the decomposing furnace.

2. The decomposing furnace zone-organized combustion self-denitration system as claimed in claim 1, wherein the feeding point of the kiln gas flue fuel is positioned at the lower part of the kiln gas flue, the kiln gas flue is provided with a feeding point of kiln gas flue raw material, and the feeding point of the kiln gas flue raw material is positioned above the feeding point of the kiln gas flue fuel.

3. The furnace zoned tissue combustion self-denitrification system of claim 1, wherein at least one of the furnace fuel feeding points is located below the furnace inlet of the kiln gas flue, the furnace raw material feeding points comprise a furnace raw material lower feeding point and a furnace raw material upper feeding point, and both furnace raw material feeding points are located below the air inlet of the tertiary air upper branch pipe; the lower raw material feeding point of the decomposing furnace is positioned above the fuel feeding point of the decomposing furnace below the furnace inlet of the kiln gas flue; the feeding point of the raw material of the decomposing furnace is positioned in the middle of the column body of the decomposing furnace.

4. The decomposing furnace zone-tissue combustion self-denitrification system according to claim 3, wherein the decomposing furnace raw material lower feeding point is positioned on the decomposing furnace cone or at the lower part of the decomposing furnace cylinder.

5. The decomposing furnace zone-tissue combustion self-denitration system as claimed in claim 3, wherein a decomposing furnace bottom column section is provided between the decomposing furnace cone and the furnace inlet of the tertiary air lower branch pipe, and the decomposing furnace raw material lower feeding point and the decomposing furnace fuel feeding point below the furnace inlet of the kiln gas flue are provided on the decomposing furnace bottom column section.

6. The decomposing furnace zone tissue combustion self-denitration system according to claim 3, wherein the decomposing furnace cylinder is provided with a decomposing furnace middle reducing opening which is positioned below a decomposing furnace raw material feeding point.

7. The decomposing furnace zone tissue combustion self-denitrification system according to claim 1, wherein tertiary air valves are arranged on the tertiary air upper branch pipe and the tertiary air lower branch pipe.

8. The decomposing furnace zone tissue combustion self-denitration system according to claim 1, wherein a discharge bin and a material pipe connected with the discharge bin are arranged below a bottom elbow of the tertiary air lower branch pipe, the other end of the material pipe is connected with a kiln tail smoke chamber, and an air lock valve is arranged on the material pipe.

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