A method of reducing gaseous suspended combustion nitrogen oxides

Abstract

The application discloses a method for reducing gaseous suspended calcination nitrogen oxide, and solves the problem of high cost of external equipment for reducing nitrogen oxide emission of a calcination furnace at present.The method comprises the following steps: S1, arranging a lance in a combustion station; and S2, lengthening a flame and dispersing a flame intersection.Compared with the prior art, the application has the following benefits: 1) under the existing working condition and equipment condition, the method of lengthening the flame and dispersing the intersection is adopted in operation, the external flame intersection is avoided, the high-temperature interval is controlled within 950 DEG C, and the formation of NOx can be effectively reduced; 2) the number of the lances can be reduced, and the lengthening of the flame length and the avoidance of the external flame intersection point can be realized; and 3) the wind speed can be increased, and the lengthening of the flame length and the reduction of the intersection point temperature can be realized.

Description

A method for reducing gaseous suspended nitrogen oxides during roasting Technical Field

[0001] This invention relates to the field of gaseous emissions from roasting furnaces, and more particularly to a method for reducing gaseous suspended nitrogen oxides during roasting. Background Technology

[0002] With the increasing environmental awareness of the Chinese people, whether the emissions from industrial furnaces and kilns meet standards has directly affected the survival and development of enterprises. The main emission indicators for alumina calcining furnaces are particulate matter, SOx, nitrogen oxides (NOx), and ammonia slip. The formation and emission of NOx are directly related to combustion temperature, while nitrogen oxides mainly originate from the combustion process; high-temperature combustion of fuel produces large amounts of nitrogen oxides. Atmospheric nitrogen oxides mainly exist in the forms of nitric oxide and nitrogen dioxide.

[0003] There are three pathways for NOx formation during combustion: first, the oxidation of nitrogen in the air at high temperatures, known as thermal NOx; second, the reaction of CH radicals generated from the high-temperature decomposition of carbon and nitrogen compounds in fuel volatiles with nitrogen in the air to produce HCN and N, which then react with oxygen at an extremely rapid rate to generate NOx, known as instantaneous reaction NOx; and third, NOx generated by the oxidation of nitrogen-containing compounds in the fuel during combustion, known as fuel-type NOx. The latter two types of nitrogen oxides do not constitute the majority of NOx and are not the primary source; the main source is thermal NOx generated during the high-temperature combustion of fuel.

[0004] Currently, reducing nitrogen oxide emissions mostly requires technical upgrades to external equipment, which incurs relatively large expenses. Summary of the Invention

[0005] In view of the above situation and to overcome the shortcomings of the prior art, the present invention provides a method for reducing gaseous suspended nitrogen oxides during roasting, which effectively solves the problem that the current roasting furnaces require external equipment to reduce nitrogen oxide emissions, resulting in high costs.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: a method for reducing gaseous suspended calcined nitrogen oxides, comprising the following steps:

[0007] S1, with spray guns installed inside the combustion station;

[0008] S2, lengthens the flame and disperses the flame intersection.

[0009] Preferably, the process also includes step S3, which involves increasing the air velocity towards the roasting furnace.

[0010] Preferably, the combustion station is equipped with three spray guns, two symmetrically positioned and the third crisscrossingly spraying into the furnace.

[0011] Preferably, the combustion station is equipped with two spray guns, which are arranged symmetrically.

[0012] Compared with the prior art, the present invention has the following advantages: 1) Under existing working conditions and equipment conditions, the method of "lengthening the flame and dispersing the intersection point" is adopted to avoid the convergence of the outer flame and control the high temperature range within 950°C, which can effectively reduce the formation of NOx; 2) Reducing the number of spray guns can be used to lengthen the flame length and avoid the intersection point of the outer flame; 3) Increasing the wind speed can be used to lengthen the flame length and reduce the temperature at the intersection point. Attached Figure Description

[0013] Figure 1 is a top view of the distribution of spray guns in a combustion station in the prior art;

[0014] Figure 2 is a main cross-sectional view of the distribution of spray guns in a combustion station in the prior art;

[0015] Figure 3 is a diagram showing the effect of elongating the flame and dispersing the intersection points of the present invention.

[0016] Figure 4 shows the effect of using three spray guns in this invention;

[0017] Figure 5 shows the effect of using two spray guns in this invention. Detailed Implementation

[0018] The present invention will now be described in further detail with reference to the accompanying drawings. The drawings are simplified schematic diagrams, illustrating only the basic structure of the invention, and therefore only show the components relevant to the invention.

[0019] Please refer to Figures 1-5. The technical solution of the present invention is: a method for reducing gaseous suspended calcined nitrogen oxides, comprising the following steps:

[0020] S1, with spray guns installed inside the combustion station;

[0021] S2, lengthens the flame and disperses the flame intersection.

[0022] Preferably, the process also includes step S3, which involves increasing the air velocity towards the roasting furnace.

[0023] The flame is divided into the flame core, inner flame and outer flame. The temperature of the flame increases from the inside to the outside, as shown in Figure 1-2. The distribution of the spray guns in the existing combustion station is shown in Figure 2. It can be seen intuitively from Figure 2 that the highest temperature in the furnace is at the intersection of the outer flames.

[0024] This invention employs a method of elongating the flame and dispersing the intersection point to reduce nitrogen oxide emissions, as shown in Figure 3. Firstly, reducing the number of spray guns can lengthen the flame and avoid the flame intersection point. Secondly, increasing the air velocity can lengthen the flame and lower the temperature at the intersection point. When the feed rate and main furnace temperature of the roasting furnace are stable, since the natural gas intake is constant, adjusting the number of air guns can effectively increase or decrease the air gun injection pressure, thereby changing the flame length within the furnace, adjusting the thermal intensity of the combustion chamber, and artificially adjusting the fuel-air mixing speed to control NOx formation.

[0025] In this invention, four spray guns are arranged in the combustion station. The common practice is to open all of them, but we adopt a method of opening three and keeping one on standby, or opening two and keeping two on standby.

[0026] Practical results:

[0027] a. When three natural gas guns, two symmetrical and one crosswise, are injected into the furnace, the flame becomes longer, the flame intensity in the combustion chamber decreases, the mixing speed of natural gas and preheated air is slowed down, the high temperature zone moves up by 0.7 meters, the furnace temperature is stabilized at 950℃, segmented combustion is achieved, NOx formation is reduced, and the nitrogen oxide concentration is between 20-45 mg / m³.

[0028] b. When the two natural gas guns cross and inject into the furnace, the flame becomes longer, the flame intensity in the combustion chamber decreases, and the mixing speed of natural gas and preheated air is further slowed down. The high temperature zone moves up 1.4 meters, and the PO4TA temperature in the roasting furnace is stabilized at 950℃, achieving segmented combustion, reducing the formation of NOx, and the nitrogen oxide concentration is between 20-45 mg / m³.

[0029] The calcining furnace combustion station employs a method of "lengthening the flame and dispersing the intersection point" to adjust the nitrogen oxide content, achieving segmented combustion. This ensures that the calcining furnace temperature remains stable at 950℃, and the thermal nitrogen oxide content in the calcining furnace is effectively controlled. Meanwhile, the maximum upward shift of the high-temperature zone is 1.4 meters, which has a negligible impact relative to the 20-meter height of the main furnace.

[0030] The embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that various variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom remain within the scope of this invention.

Claims

1. A method for reducing gaseous suspended nitrogen oxides during roasting, characterized in that, The process includes the following steps: S1, arranging spray guns inside the combustion station; S2, lengthening the flame and dispersing the flame intersection point; S3, increasing the wind speed towards the roasting furnace; the methods for lengthening the flame and dispersing the intersection point are: ① reducing the number of spray guns to lengthen the flame length and avoid the outer flame intersection point; ② increasing the wind speed to lengthen the flame length and reduce the temperature at the intersection point; four spray guns are arranged inside the combustion station, and this method uses a three-on-one-on-two or two-on-two-on-one-on-two configuration; a) when three natural gas guns are used, two are symmetrically injected into the furnace and one is crosswise. When the gas is injected into the furnace: the flame becomes longer, the flame intensity in the combustion chamber decreases, the mixing speed of natural gas and preheated air is slowed down, the high-temperature zone shifts upward by 0.7 meters, the furnace temperature is stably controlled at 950℃, and NOx formation is reduced; b. When two natural gas guns cross and inject into the furnace: the flame becomes longer, the flame intensity in the combustion chamber decreases, the mixing speed of natural gas and preheated air is further slowed down, the high-temperature zone shifts upward by 1.4 meters, the furnace temperature is stably controlled at 950℃, and NOx formation is reduced.

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