CN101968220B - Low nitrogen oxide burning process as well as burning device and application - Google Patents

Abstract

The invention relates to a low-nitrogen oxide combustion process, a combustion device and an application. Utilize the partially premixed combustion process with the oxygen-lean oxygen concentration of 13%-21% and the stoichiometric ratio of hydrocarbon fuels of 1.1-1.3 to suppress the formation of temperature-type NOx, while using the oxygen concentration of 21%-30% Oxygen enrichment organizes the supplementary combustion process outside the main combustion zone to reduce the generation of soot and CO; the overall stoichiometric ratio of the entire combustion process is controlled below 1.0. Specifically, the partial premixing and combustion process of oxygen-deficient and hydrocarbon fuel prepared by air separation equipment is used to form a reductive main combustion zone downstream of the flame stabilizer, which can effectively inhibit the formation of temperature-type NOx; The form is fed from the outside of the main combustion area to organize the supplementary combustion process of the remaining fuel and thermal decomposition products, which can effectively reduce the generation of soot and CO in the combustion products. The invention has the characteristics of high combustion efficiency, low pollutant emission, stable flame and uniform flame temperature field, and is suitable for ground gas turbines, fuel gas boilers, heating furnaces and other power equipment.

Description

Low nitrogen oxide combustion process and combustion device and application

technical field

The present invention relates to a low-nitrogen oxide combustion process, a combustion device and its application, specifically a kind of premixed combustion using oxygen-poor (13%≤O ₂ ≤21%) tissue and utilizing oxygen-rich (21%≤O ₂ ≤30%) clean and high-efficiency combustion technology (oxygen-poor partial premixing-oxygen-enriched supplementary combustion process) and combustion device to complete the burnout process.

Background technique

Traditional combustion technology mostly adopts diffusion combustion, using rotating jets or cross jets to realize the mixed combustion process between fuel and air, oxygen-enriched or even pure oxygen. Although this method improves the combustion efficiency, it will form local combustion in the region of the jet mixing boundary layer. The high temperature zone of the reaction results in a substantial increase in the generation of nitrogen oxides (NOx). Based on the formation mechanism of NOx in the diffusion combustion process, scholars from various countries have successively proposed low-NOx combustion technologies such as air staged combustion, rich-lean combustion, flue gas recirculation, rich combustion/quenching/lean combustion, etc., by reducing the temperature of the main combustion zone or oxygen concentration, Measures such as shortening the residence time of oxygen in the high temperature zone and reducing NOx in the flue gas can achieve the purpose of reducing the amount of NOx generated during the diffusion combustion process. However, there is always a contradictory relationship between reducing pollutant emissions and enhancing combustion. During the implementation of the above-mentioned low NOx combustion technologies, the generation of soot and CO may increase due to poor fuel/oxygen mixing.

Compared with diffusion combustion, the premixed combustion process is not restricted by factors such as component diffusion, and its combustion efficiency is higher, which is not only conducive to reducing the volume of the combustion chamber, but also can control the flame temperature by controlling the concentration of fuel or oxygen in the premixed gas and NOx production. Lean premixed combustion and lean premixed prevaporized combustion developed based on the above theory are currently the most promising low NOx combustion technologies. The basic principle is to pre-mix the fuel and air at a lower stoichiometric ratio, and organize the swirl combustion process; because the flame temperature is relatively low, the amount of NOx generated is small, and because the oxygen is sufficient and the fuel/oxygen mixture Uniform, so the generation of soot and CO is far less than the diffusion flame. Therefore, lean-burn premixed combustion can achieve a cleaner and more efficient combustion process. But it is precisely because the working conditions of the lean-burn premixed swirl flame are too close to the lean-burn flameout limit, and the large swirl intensity and turbulence intensity are easy to induce unstable vortex precession in the shear boundary layer (Processing Vortex Core), it is easy to cause local quenching in the flame surface, resulting in periodic pulsation of flame heat release; in some cases, the pulsating flame heat release will excite and oscillate with the sound pressure oscillation in the combustion chamber, forming the so-called thermoacoustic Coupled oscillation will eventually lead to dynamic instability or even extinguishment of the premixed flame.

Through experimental and theoretical research on NOx emission characteristics and flame dynamics stability of lean-burn premixed swirl combustion process, the patent applicant found that using porous media to stabilize the flame and using partial premixed/circular gas injection can effectively reduce premixed combustion The amplitude of the process thermoacoustic coupling oscillation can control the production of NOx, soot and CO in a lower range. Based on the above-mentioned experimental and theoretical analysis results, a method of organizing partial premixed combustion using oxygen-poor (13%≤O ₂ ≤21%) and using rich oxygen (21%≤O ₂ ≤30%) to organize the burnout process is proposed. Low NOx high-efficiency combustion technology, and designed a combustion device based on this technology.

Contents of the invention

The object of the present invention is to provide a low-nitrogen oxide combustion process, combustion device and application, which is an "oxygen-poor partial premixing-oxygen-enriched supplementary combustion system" that effectively reduces the amount of NOx, soot and CO generated during the combustion of hydrocarbon fuels. "Combustion technology and combustion devices based on it. On the one hand, the present invention combines the advantages of air staged combustion, rich-lean combustion, lean-burn premixed combustion and oxygen-enriched combustion technologies; It has the characteristics of good stability and uniform flame temperature field, and is widely used.

A low-NOx combustion process provided by the present invention includes the steps of: using lean oxygen and hydrocarbon fuel to organize a partial premixed combustion process to suppress the generation of NOx, and at the same time using rich oxygen to organize a supplementary combustion process outside the main combustion zone, To reduce the generation of soot and CO; the overall stoichiometric ratio of the entire combustion process is controlled below 1.0.

A kind of low nitrogen oxide combustion process provided by the present invention comprises the steps:

Utilize the partially premixed combustion process with the oxygen-lean oxygen concentration of 13%-21% and the stoichiometric ratio of hydrocarbon fuels of 1.1-1.3 to suppress the formation of temperature-type NOx, while using the oxygen concentration of 21%-30% Oxygen enrichment organizes the supplementary combustion process outside the main combustion zone to reduce the generation of soot and CO; the overall stoichiometric ratio of the entire combustion process is controlled below 1.0.

The oxygen-deficient (slow gas) with an oxygen concentration between 13% and 21% is used to realize a partial premixed combustion process with a stoichiometric ratio of 1.1-1.3 to the hydrocarbon fuel.

The supplemental combustion process in which the overall equivalence ratio of the oxygen-enriched tissue is less than 1.0 with an oxygen concentration between 21% and 30% produced by membrane oxygen-enrichment equipment.

The partial premixing combustion process is a partial premixing process of oxygen-deficient and hydrocarbon fuel organized in a premixing chamber of a combustion device by using radial swirl flow and straight jet flow.

The partial premixed combustion process utilizes a swirling flow flame stabilizer and a porous medium flame stabilizer to realize the stability of a partially premixed flame and form a main combustion zone with a reducing atmosphere.

The supplementary combustion process uses tangential swirling flow to organize the burnout process of enriched oxygen with an oxygen concentration of 21%-30%, unburned fuel and thermal decomposition products, and controls the overall stoichiometric ratio below 1.0.

A low nitrogen oxide combustion device provided by the present invention mainly includes: a fuel inlet pipe, an oxygen-poor inlet pipe, radial swirl blades, a premixing chamber, a flame stabilizer, an oxygen-enriched inlet pipe and tangential swirl blades.

The combustion device is a cylindrical three-layer sleeve structure. The fuel inlet pipe is located at the axis as a central sleeve, its beginning end is connected with the fuel pipeline, and its end is connected with the premixing chamber. The oxygen-depleted inlet pipe is located outside the fuel inlet pipe, radial swirl blades (a set of 8 pieces are optional) are arranged around the premixing chamber, and tangential swirl blades are connected with the inner wall of the outer sleeve; After the oxygen-deficient inlet pipe enters the middle sleeve, it enters the premixing chamber through the radial swirling blades in the form of rotating jets, and forms part of the premixed combustible gas with the fuel. The tangential swirl flame stabilizer (or porous medium flame stabilizer) is located at the center of the outlet at the top of the premix chamber, and part of the combustible premixed gas enters the combustion chamber through the tangential swirl flame stabilizer (or porous medium flame stabilizer), forming The main combustion zone of the reducing atmosphere. The oxygen-enriched inlet pipe is connected tangentially to the outer sleeve of the combustion device. The oxygen-enriched air prepared by the air separation equipment enters the outer sleeve through the oxygen-enriched inlet pipe, and then flows through the tangential swirling blades at the outlet of the outer sleeve to enter in the form of a rotating jet. The combustion chamber forms a secondary combustion zone with an oxidizing atmosphere outside the main combustion zone.

The combustion device is cylindrical as a whole, and the fuel inlet pipe, oxygen-poor inlet pipe and oxygen-enriched inlet pipe are all round pipes; the premixing chamber is a cylindrical chamber; The end cover is welded; the tangential swirl blade 7 is a set of straight blades, which are welded to the inner wall of the outer sleeve; the tangential swirl flame stabilizer (or porous medium flame stabilizer) 5 consists of a set of twisted blades, and the inner and outer ends of the blade are They are respectively welded to the inner wall of the central cylinder and the outer circular tube (the porous medium flame stabilizer is a porous ceramic body fastened in the circular tube).

Features of the present invention are described in detail as follows:

"Oxygen-enriched" involved in the present invention refers to an oxygen/nitrogen mixed gas with an oxygen concentration of 21%-30% prepared by air separation technology (such as membrane oxygen-enriched preparation technology), while "poor oxygen" refers to Refers to the slow gas with an oxygen concentration of 13%-21% produced after air separation (usually, the slow gas with this concentration is mostly discharged directly into the atmosphere without being used). The above-mentioned "oxygen-enriched" and "oxygen-poor" concentrations can be guaranteed by adjusting the working parameters of the oxygen-enriched preparation equipment.

The "oxygen-deficient partial premixing-oxygen-enriched supplementary combustion technology" involved in the present invention refers to the premixed combustion of "oxygen-deficient" and carbon-hydrogen gas fuels according to a certain stoichiometric ratio Φ (1.1≤Φ≤1.3), Form the main combustion zone with a reducing atmosphere; at the same time, outside the main combustion zone, "oxygen-enriched" is fed into the secondary combustion zone with an oxidizing atmosphere by means of a rotating jet; during the entire combustion process of hydrocarbon fuels, the overall chemical The equivalent ratio Φ is less than 1.0. The use of "oxygen-deficient partial premixing" can reduce the flame temperature in the main combustion zone by 150-200°C, thereby effectively suppressing the formation of temperature-type NOx; at the same time, the reducing atmosphere in the main combustion zone also helps to reduce NOx to N ₂ . The use of "oxygen-enriched supplementary combustion" helps to increase the combustion speed and burnout degree of the remaining hydrocarbon fuel and its thermal decomposition products outside the main combustion zone, and can effectively reduce the volume content of soot and CO in the combustion products. The research results show that under the same working conditions, compared with lean-burn premixed combustion, the use of "oxygen-lean partial premixed-oxygen-enriched supplementary combustion" technology can reduce the concentration of NOx in flue gas by more than 75%, soot and CO The amount of production is equivalent, and the flame stability is greatly improved.

The invention can be used for power equipment such as ground gas turbines, fuel gas boilers and fuel gas heating furnaces.

On the one hand, the present invention combines the advantages of air staged combustion, rich-lean combustion, lean-burn premixed combustion and oxygen-enriched combustion technologies; The invention has the characteristics of good stability and uniform flame temperature field, and the invention is widely used.

Description of drawings

Figure 1a is a schematic cross-sectional view of a combustion device (swirl flame stabilizer).

Figure 1b is a schematic cross-sectional view of the combustion device (porous medium flame holder).

Fig. 2 is a view of the combustion device A-A.

Figure 3a is a schematic diagram of the velocity field in the combustion chamber under lean-burn premixed conditions.

Figure 3b is a schematic diagram of the velocity field in the combustion chamber under the condition of oxygen-lean partial premixing-oxygen-enriched supplementary combustion.

Figure 4a is a schematic diagram of the temperature field in the combustion chamber under lean-burn premixed conditions.

Figure 4b is a schematic diagram of the temperature field in the combustion chamber under the condition of oxygen-lean partial premixing-oxygen-rich supplementary combustion.

Figure 5a is a schematic diagram of the NO concentration field in the combustion chamber under lean-burn premixed conditions.

Figure 5b is a schematic diagram of the NO concentration field in the combustion chamber under the condition of oxygen-poor partial premixing-oxygen-enriched supplementary combustion.

Detailed ways

The present invention is described in detail as follows with reference to accompanying drawing:

Fig. 1a and Fig. 1b are cross-sectional views of a combustion device using a swirl flame stabilizer and a porous medium flame stabilizer respectively, and Fig. 2 is a view of the combustion device A-A.

In the figure, 1 is the hydrocarbon fuel inlet pipe, 2 is the oxygen-poor inlet pipe, 3 is the radial swirl vane, 4 is the premixing chamber, 5 is the swirl flame stabilizer or porous medium flame stabilizer, and 6 is the oxygen-enriched inlet Tube, 7 is a tangential swirl vane.

The combustion device involved in the present invention is designed based on the above-mentioned technical theory, and can rationally organize the high-efficiency and low-NOx combustion process of hydrocarbon fuels. The combustion device is mainly composed of a fuel inlet pipe 1 , an oxygen-lean inlet pipe 2 , a radial swirl blade 3 , a premix chamber 4 , a flame stabilizer 5 , an oxygen-enriched inlet pipe 6 and a tangential swirl blade 7 .

The combustion device is cylindrical and has a three-layer sleeve structure. The fuel inlet pipe 1 is located at the axial center as a central sleeve, its beginning end is connected with the fuel pipeline, and its end is connected with the premixing chamber 4 . The oxygen-deficient inlet pipe 2 is located outside the fuel inlet pipe 1, and the radial swirl vanes 3 (a group of 8 pieces) are arranged around the premixing chamber 4. Then it enters the premix chamber 4 through the radial swirl blade 3 in the form of rotating jet, and forms part of the premixed combustible gas with the fuel. The tangential swirl flame holder (or porous medium flame holder) 5 is located at the center of the outlet at the top of the premix chamber 4, and part of the combustible premixed gas enters the combustion via the tangential swirl flame holder (or porous medium flame holder) 5 Chamber, the main combustion area that forms a reducing atmosphere. The oxygen-enriched inlet pipe 6 is connected tangentially to the outer sleeve of the combustion device, and the oxygen-enriched air prepared by the air separation equipment enters the outer sleeve through the oxygen-enriched inlet pipe 6, and then flows through the tangential swirl blade 7 at the outlet of the outer sleeve to rotate The jet flow enters the combustion chamber, forming a supplementary combustion zone with an oxidizing atmosphere outside the main combustion zone.

The combustion device is cylindrical as a whole, and the fuel inlet pipe 1, the oxygen-poor inlet pipe 2, and the oxygen-enriched inlet pipe 6 are all circular pipes; the premixing chamber 4 is a cylindrical chamber; the radial swirl blades 3 are a set of straight blades, Welded with the upper and lower end caps of the premixing chamber 4; the tangential swirl blades 7 are a set of straight blades welded to the inner wall of the outer sleeve; the tangential swirl flame stabilizer (or porous medium flame stabilizer) 5 consists of a set of twisted Blades, the inner and outer ends of the blades are respectively welded to the central cylinder and the inner wall of the outer circular tube (the porous medium flame stabilizer is a porous ceramic body fastened in the circular tube).

The hydrocarbon gas fuel enters the premixing chamber 4 through the central fuel inlet pipe 1 in the form of direct flow; oxygen-deficient enters the premixing chamber 4 through the oxygen-deficient inlet pipe 2 and the radial swirl vanes 3 in the form of swirling flow according to a certain stoichiometric ratio φ The two complete the mixing process in the premix chamber 4 to form part of the premixed combustible gas; part of the premixed combustible gas is sprayed and burned through the swirl or porous medium flame stabilizer 5 to form the main combustion zone of the reducing atmosphere. Enriched oxygen is sent from the outside of the main combustion zone through the oxygen-enriched inlet pipe 6 and tangential swirl vanes 7 in the form of a rotating jet, and reacts with the remaining fuel and thermal decomposition products flowing out of the main combustion zone to form a supplementary combustion zone.

The present invention utilizes membrane method oxygen-enrichment preparation equipment (membrane method oxygen-enrichment preparation equipment, Henan Nengxin Energy Saving Technology Co., Ltd., product model: MZYR-25 to MZYR-300, oxygen-enrichment preparation volume 400 cubic meters/hour to 2500 cubic meters/hour) Or other air separation equipment to prepare oxygen-enriched oxygen with an oxygen concentration of 21%-30% and lean oxygen at 13%-21%; use lean oxygen and hydrocarbon fuels with a certain stoichiometric ratio Φ (1.1≤Φ≤1.3) in the preset The mixing chamber is uniformly premixed, and the main combustion zone of the reducing atmosphere is formed downstream of the swirl flame holder and the porous media flame holder; while the overall stoichiometric ratio is kept below 1.0, the oxygen-enriched gas is transferred from the It is sent from the outside of the main combustion zone to make it burn with the remaining fuel and thermal decomposition products to form a supplementary combustion zone with an oxidizing atmosphere.

In the case of keeping the overall equivalence ratio Φ=0.625 the same, the simulation studies the NOx generation in the combustion chamber under the conditions of lean-burn premixed combustion and oxygen-lean partial premixed-oxygen-enriched supplementary combustion. The simulation parameters are: center lean oxygen concentration is 18%, and the outer oxygen enrichment concentration is 24%. The simulation results are shown in the figure:

Figure 3a is a schematic diagram of the velocity field in the combustion chamber under lean-burn premixed conditions. Figure 3b is a schematic diagram of the velocity field in the combustion chamber under the condition of oxygen-lean partial premixing-oxygen-enriched supplementary combustion. The velocity distribution trends of the two are basically the same, but the center swirl velocity of the latter is slightly higher, the annular jet velocity is slightly lower, and the average velocity is slightly lower.

Figure 4a is a schematic diagram of the temperature field in the combustion chamber under the condition of lean-burn premixing; Figure 4b is a schematic diagram of the temperature field in the combustion chamber under the condition of oxygen-lean partial premixing-oxygen-enriched supplementary combustion; The field is more uniform.

Figure 5a is a schematic diagram of the NO concentration field in the combustion chamber under lean premixed conditions; Figure 5b is a schematic diagram of the NO concentration field in the combustion chamber under oxygen-lean premixed-oxygen-enriched supplementary combustion conditions; it can be seen that the NO concentration comparison (mass fraction) As a result, the NO concentration of the latter was reduced by more than 75%.

Claims (9)

1. low-nitrogen oxide combustion technique; It is characterized in that the step that it comprises: utilize oxygen concentration to be the oxygen deprivation of 13%-21% and hydrocarbon fuel histochemistry equivalent proportion partly-premixed combustion process for 1.1-1.3; To suppress the generation of NOx; Utilize oxygen concentration to organize the afterburning process in the outside, primary zone simultaneously, to reduce the growing amount of soot and CO for the oxygen enrichment of 21%-30%; The overall stoichiometric ratio of whole combustion process is controlled at below 1.0.

2. technology according to claim 1 is characterized in that utilizing film oxygen enriching equipment to produce the oxygen deprivation of oxygen concentration between 13%-21%, and realization is the partly-premixed combustion process of 1.1-1.3 with hydrocarbon fuel histochemistry equivalent proportion.

3. technology according to claim 1, the oxygen enrichment of oxygen concentration between 21%-30% that it is characterized in that utilizing film oxygen enriching equipment to produce realize that overall stoichiometric ratio is less than 1.0 afterburning process.

4. technology according to claim 1 is characterized in that described partly-premixed combustion process is in the premixer of burner, to utilize radial vortex and direct projection stream to organize the partly-premixed process of oxygen deprivation and hydrocarbon fuel.

5. technology according to claim 1 is characterized in that described partly-premixed combustion process is utilize eddy flow flame holder or porous media flame holder implementation part premixed flame stable, forms the primary zone of reducing atmosphere.

6. technology according to claim 1 is characterized in that described afterburning process is to utilize the oxygen enrichment of tangential swirl tissue oxygen concentration 21%-30% and the after-flame process of uncombusted fuel and thermal decomposition product, and controls overall stoichiometric ratio below 1.0.

7. the burner of the described low-nitrogen oxide combustion technique of claim 1 is characterized in that mainly comprising: fuel inlet pipe, oxygen deprivation inlet tube, radial vortex blade, premixer, flame holder, oxygen enrichment inlet tube and tangential swirl blade;

The fuel inlet pipe is positioned at shaft core position as cylindrical central sleeve, and its top links to each other with fuel channel, and its end links to each other with the premixer; The oxygen deprivation inlet tube is positioned at the fuel inlet pipe outside; The radial vortex blade shroud is arranged around the premixer; Flame holder is positioned at top exit center, premixer, and the oxygen enrichment inlet tube is connected with sleeve tangential, the burner outside, and the tangential swirl blade is connected with outside sleeve lining face; Burner integral body is cylindrical, three layers of tube-in-tube structure.

8. burner according to claim 7 is characterized in that described flame holder is tangential swirl flame holder or porous media flame holder.

9. the application of low-nitrogen oxide combustion technique according to claim 1 is characterized in that can be used for ground gas turbine, oil-burning gas-fired boiler and fuel-firing gas-firing heating furnace power-equipment.

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