CN108506929A - A kind of fuel oil flameless combustion apparatus and its system equipment - Google Patents

Abstract

The invention provides a fuel oil flameless combustion device and system equipment thereof. The fuel oil flameless combustion device includes a burner body, a fuel nozzle, an igniter, a fully diffused jet swirler and an open jet swirler, and its system equipment includes: a furnace, a flue gas recirculation fan, a blower and a combustion device connected in series . The full-diffusion jet swirler produces internal swirl and forms a fully-diffused jet in the furnace, while the open-jet swirler generates external swirl and forms an open jet in the furnace, and the mutual interference between the open jet and the full-diffusion jet produces turbulent kinetic energy. The gas dynamic field composed of the recirculation stable combustion zone and the turbulent kinetic energy interference zone can quickly reduce the oxygen concentration in the furnace to about 3%, reaching the conditions of strong turbulent kinetic energy and low oxygen concentration in the furnace, and when the furnace temperature is greater than the ignition temperature Under this condition, the flameless volumetric combustion of fuel oil is realized, so that the _NOx emission concentration of the oil-fired boiler is less than 80mg/Nm ³ .

Description

A fuel oil flameless combustion device and its system equipment

technical field

The invention belongs to the technical field of thermal energy engineering combustion, and relates to a fuel oil flameless combustion device and system equipment thereof.

Background technique

At present, the methods for reducing NO _x by fuel combustion include: air staging, fuel staging, flue gas recirculation, etc. However, it is very difficult to reduce the NO _x emission concentration of fuel combustion to less than 120mg/Nm ³ . The main methods for gas to reduce NO _x are high-temperature air combustion and surface combustion. The flameless combustion of high-temperature air gas has been used in large-scale industries, but it cannot be used in industrial boilers. uniform security issues. Therefore, it has important theoretical significance and practical value to develop a new type of burner that can reduce the NO _x emission concentration of oil-fired boilers.

Contents of the invention

The purpose of the present invention is to provide a fuel oil flameless combustion device which can form a low-oxygen environment in the furnace so as to realize the flameless combustion of fuel oil in the furnace.

Another object of the present invention is to provide a fuel oil flameless combustion device, which can realize continuous flameless combustion of fuel oil in the furnace, and then reduce the _NOx emission concentration in the boiler flue gas.

To achieve the above object, the solution of the present invention is:

A fuel oil flameless combustion device, which includes: a burner body, a fuel nozzle, an igniter, a fully diffused jet swirler and an open jet swirler.

Among them, the mixture of flue gas and air is recirculated in the burner body. The maximum volume concentration of oxygen in the mixed gas is about 10%, for example, 10±2%.

Fuel nozzles are used to create atomized fuel jets. The burner body adopts a 45° swirl. The axial partial velocity of the rotating jet is 20‐50m/s. The atomization angle of the atomized fuel jet is 10-60°. The atomized average particle size of the atomized fuel jet is 100-110 μm.

The igniter ignites the jet of atomized fuel.

The full-diffusion jet swirler is arranged on the peripheral side of the fuel nozzle, so that a part of the mixed gas in the burner body produces a full-diffusion jet. The inner diameter of the fully diffused jet cyclone is 60-150mm, the volume flow rate is 20-40%, and the swirl number is 0.5-1.5.

The open jet swirler is arranged on the peripheral side of the fully diffused jet swirler, so that the mixed gas in the rest of the burner body produces an open jet. The open-jet cyclone has a volume flow rate of 60‐80% and a swirl number of 0.25‐1.

A fuel oil flameless combustion equipment, which includes: a furnace, a flue gas recirculation fan, a blower and a fuel oil flameless combustion device connected in series in sequence. The fuel oil flameless combustion device includes a burner body, a fuel nozzle, an igniter, a fully diffused jet swirler and an open jet swirler.

The fuel nozzle atomizes the fuel to form an atomized fuel jet and sprays it into the furnace. The oxygen volume concentration in the furnace is about 3%, for example, 3±1%. The burner body adopts a 45° swirl. The axial partial velocity of the rotating jet is 20‐50m/s. The atomization angle of the atomized fuel jet is 10-60°. The atomized average particle size of the atomized fuel jet is 100-110 μm.

The igniter ignites the jet of atomized fuel.

The furnace absorbs heat, burns atomized fuel jets and exhausts smoke. The volumetric heat load in the furnace is 600‐3000kW/m ³ . The maximum temperature of the furnace is less than 1400°C. Furnace temperature fluctuation coefficient is less than 20%. The emission concentration of NO _x in the flue gas of the oil-fired boiler is less than 80mg/Nm ³ .

The flue gas recirculation fan sends part of the flue gas to the blower, and the recirculation ratio of this part of flue gas is 80‐150%.

The blower sends the mixed gas formed by circulating flue gas and air to the burner body of the combustion device. The highest volume concentration of oxygen in the mixed gas is about 10%.

The full-diffusion jet swirler is arranged on the peripheral side of the fuel nozzle, so that a part of the mixed gas in the burner body produces a full-diffusion jet in the furnace. The inner diameter of the fully diffused jet cyclone is 60-150mm, the volume flow rate is 20-40%, and the swirl number is 0.5-1.5.

The open jet swirler is arranged on the peripheral side of the fully diffused jet swirler, so that the mixed gas in the remaining part of the burner body produces an open jet flow in the furnace. The open-jet cyclone has a volume flow rate of 60‐80% and a swirl number of 0.25‐1. The open jet flow and the fully diffused jet flow produce a turbulent kinetic energy superposition area, a backflow stable combustion area and a turbulent kinetic energy interference area in the furnace.

Owing to adopting said scheme, the beneficial effect of the present invention is:

The fuel oil flameless combustion device of the present invention utilizes a full-diffusion jet swirler to generate an internal swirl and form a full-diffusion jet in the furnace, and simultaneously utilizes an open jet swirler to generate an outer swirl and form an open jet in the furnace. The open jet and The interference of the fully diffused jet produces a gas dynamic field composed of the turbulent kinetic energy superposition area, the backflow stable combustion area and the turbulent kinetic energy interference area, which quickly reduces the oxygen concentration in the furnace to about 3%, reaching the conditions of strong turbulent kinetic energy and low oxygen concentration in the furnace , under the condition that the furnace temperature is higher than the ignition temperature, the flameless volumetric combustion of fuel oil is realized, so that the NO _x emission concentration of the oil-fired boiler is less than 80mg/Nm ³ .

Description of drawings

Fig. 1 is a schematic structural view of the fuel oil flameless combustion equipment of the present invention.

Fig. 2 is a schematic structural view of the fuel combustion device of the present invention.

Fig. 3 is a schematic diagram of the three-zone gas dynamic field of the furnace of the present invention.

Fig. 4 is a numerical simulation diagram of the oxygen mass fraction of the central section of the furnace in the first embodiment of the present invention.

Fig. 5 is a numerical simulation diagram of the temperature of the central section of the furnace in the first embodiment of the present invention.

Fig. 6 is a numerical simulation diagram of the speed of the center section of the furnace in the first embodiment of the present invention.

Fig. 7 is a numerical simulation diagram of the oxygen mass fraction of the central section of the furnace in the second embodiment of the present invention.

Fig. 8 is a temperature numerical simulation diagram of the central section of the furnace in the second embodiment of the present invention.

Fig. 9 is a numerical simulation diagram of the speed of the center section of the furnace in the second embodiment of the present invention.

Reference signs:

Igniter 1, oil inlet pipe 2, oil return pipe 3, flame detector 4, streamlined head 5, furnace 6, combustion device 7, blower 8, flue gas recirculation fan 9, oil, wire outlet pipe 10, central pipe 11, Fuel nozzle 12, open jet swirler 13, fully diffused jet swirler 14, mixed gas of flue gas and air 15, turbulent kinetic energy superposition area 16, backflow stable combustion area 17, turbulent kinetic energy interference area 18, burner body 19, Combustion device outlet 20, boiler outlet 21.

Detailed ways

The invention provides a fuel oil flameless combustion device and fuel oil flameless combustion equipment containing the device.

As shown in FIG. 1 , the fuel oil flameless combustion equipment of the present invention includes: a furnace 6 , a flue gas recirculation fan 9 , a blower 8 and a combustion device 7 . The furnace 6, the flue gas recirculation fan 9, the blower 8 and the combustion device 7 are sequentially connected in series through pipelines. T in Figure 1 represents a thermometer, P represents a pressure gauge, and Q represents a flow meter.

As shown in FIG. 2 , the combustion device 7 includes a burner body 19 , a fuel nozzle 12 , an igniter 1 , a fully diffused jet swirler 14 and an open jet swirler 13 .

Wherein, the fuel nozzle 12 can make the fuel generate an atomized fuel jet, and spray it into the furnace 6 for combustion. The fuel nozzle 12 is arranged at the center of the burner outlet 20 of the furnace 6 . The outlet of the burner body adopts a 45° swirl mouth, the axial partial velocity of the rotating jet is 20-50m/s, the atomization angle of the atomized fuel jet generated is 10-60°, and the atomization mean particle size (SMD) is 100‐110 μm.

The igniter 1, the oil inlet pipe 2, the oil return pipe 3 and the flame monitor 4 are arranged in the center pipe 11, and the space of the center pipe 11 is separated from the space of the combustion device body by the streamlined head 5. The side wall of the center pipe 11 is also provided with an oil and wire lead-out pipe 10 for supplying fuel oil and laying wires of the igniter 1 and the flame detector 4 .

The furnace 6 is used to absorb heat, burn atomized fuel and discharge smoke. The front end of the furnace 6 corresponds to the outlet 20 of the combustion device, and the outlet 21 of the boiler discharges flue gas. The volume heat load in the furnace 6 is 600-3000kW/m ³ , the maximum temperature of the furnace is less than 1400°C, and the temperature fluctuation coefficient is less than 20%. The oxygen concentration in the furnace 6 is about 3%.

One end of the flue gas recirculation fan 9 is connected to the boiler outlet 21 of the furnace 6 through a pipe, and the other end is connected to the blower 8 through a pipe. The flue gas recirculation fan 9 retransmits part of the flue gas from the boiler outlet 21 to the blower 8, so that this part of the flue gas is circulated, and the rest of the flue gas is discharged into the atmosphere.

One end of the air blower 8 is connected to the flue gas recirculation fan 9 in a pipeline, and the other end is connected to the burner body 19 of the combustion device 7 . The blower 8 makes the recirculated flue gas and normal temperature air uniformly mixed to form a mixed gas 15, and the mixed gas is delivered to the burner body 19 of the combustion device 7, and the volume concentration of oxygen in the mixed gas in the burner body 19 is about 10%. . The ratio of recirculated flue gas is 80‐150%. The recirculation ratio of flue gas refers to the percentage of the amount of flue gas in the external circulation and the theoretical flue gas amount.

The full-diffusion jet swirler 14 is arranged on the peripheral side of the fuel nozzle 12 to make a part of the mixed gas generate a full-diffusion jet in the furnace 6 . The fuel nozzle 12 is located at the center of the central pipe 11, and the swirlers 14 and 13 are both annular surfaces. The full-diffusion jet swirler 14 generates an internal swirl flow with an inner diameter of 60-150mm, a volume flow rate of 20-40%, and a swirl number of 0.5-1.5. The internal swirling flow is a fully diffused jet.

The open jet swirler 13 is arranged on the peripheral side of the fully diffused jet swirler 14 , so that the remaining part of the mixed gas generates an open jet flow in the furnace 6 . The open-jet swirler 13 produces an external swirling flow with a volume flow rate of 60-80% and a swirl number of 0.25-1. The external swirling flow is an open jet. The volumetric flow rate refers to the ratio of the outer swirl gas flow to the total mixed gas flow. The swirl number is a parameter to measure the strength of fluid rotation, and it is defined as the ratio of the axial flux of the tangential momentum of the fluid to the axial momentum flux.

The degree of rotation of the internal swirling flow generated in the fully diffused jet swirler 14 and the outer swirling flow generated in the open jet swirler 13 can be characterized by the swirl number n, and the calculation formula is n=M/KL . Where M is the rotational moment of momentum of the corresponding swirl; K is the axial momentum of the swirl, and the axial direction refers to the extension direction of the central axis of the swirl; L is the size of the nozzle that ejects the swirl. When the swirl number n increases to a certain value, the central area near the jet outlet of the swirler will form an internal recirculation zone, and this flow state is called an open swirling jet. When the swirl number n continues to increase, the entrainment ability of the outer boundary of the jet is strong, and the air supply condition is not good, which will make the pressure of the outer boundary lower than the central pressure, and the entire jet will open outwards, forming a fully diffused rotating jet.

As shown in Figure 3, open jets and fully diffused jets exist in the furnace 6 at the same time, and their mutual interference will produce a gas dynamic field composed of three areas: the turbulent kinetic energy superposition area 16, the backflow stable combustion area 17, and the turbulent kinetic energy interference area 18. It has the characteristics of large recirculation zone, strong turbulent kinetic energy and low oxygen atmosphere. The atomized fuel jet generated by the fuel nozzle 12 is injected into the backflow stable combustion zone 17, and diffuses with the gasification of the fuel. The turbulent kinetic energy superposition zone 16 and the backflow stable combustion zone 17 rapidly reduce the oxygen concentration in the furnace 6 to about 3%, reaching the conditions of strong turbulent kinetic energy and low oxygen concentration in the furnace 6, and under the condition that the furnace temperature is higher than the ignition temperature, the The flameless volumetric combustion of fuel oil makes the _NOx emission concentration of the oil-fired boiler less than 80mg/Nm ³ .

In a word, the fuel oil flameless combustion device of the present invention adopts the combined air distribution of open jet swirl and fully diffused jet swirl to radially classify the oxygen entering the furnace, and the full diffusion jet swirl and open jet swirl interfere with each other to form three The gas dynamic field characteristic of the zone, the turbulent kinetic energy superposition zone and the reflow stable combustion zone make the oxygen concentration in the furnace rapidly decrease to about 3%. Mesoscopically, the turbulent mixing time in the furnace is less than the chemical reaction time of fuel combustion, so the reaction is volumetric combustion. Apparently, the flame front in the furnace disappears, the furnace is bright, and the temperature field is uniform, so as to achieve high-efficiency combustion and achieve the purpose of ultra-low _NOx pollutant control.

The present invention will be further described below in conjunction with the embodiments shown in the accompanying drawings.

Embodiment one

This embodiment provides a fuel oil flameless combustion equipment, and the heat load of the boiler is 389kW. The diameter of the furnace is 400mm and the length is 1973mm. The fuel injection rate of the fuel nozzle is 33kg/h, and the average particle size of atomization is 100μm. The temperature of the recirculated flue gas is 52°C, and the ratio of the recirculated flue gas is 80%. The recirculated flue gas is uniformly mixed with the air and then enters the double-swirl air distributor (that is, the fully diffused jet swirler and the open jet swirler). The diameter of the inner ring of the full-diffusion jet swirler is 80 mm, and the volume flow rate of the inner swirling flow is 20%. The volumetric flow rate of the external swirling flow of the open jet cyclone is 80%. The outlet of the burner body adopts a 45° swirl, and the axial partial velocity of the rotating jet is 25m/s. Numerical simulations were carried out on the oxygen mass fraction distribution, temperature distribution and velocity distribution of the central section of the furnace, and the simulation results are shown in Fig. 4, Fig. 5 and Fig. 6. Fig. 4 is the distribution of oxygen mass fraction in the central section of the furnace. It can be seen that the oxygen concentration in the main combustion zone in the furnace is basically below 3%; Fig. 5 is the temperature distribution in the central section of the furnace, the highest temperature is 1400K, and the temperature distribution in the main combustion zone is relatively uniform; Fig. 6 is the velocity distribution of the central section of the furnace. It can be seen that the overall velocity field is relatively uniform, and the air velocity is 5-10m/s.

Embodiment two

This embodiment provides a fuel oil flameless combustion equipment, and the heat load of the boiler is 3110kW. The diameter of the furnace is 800mm and the length is 3973mm. The fuel injection rate of the fuel nozzle is 260kg/h, and the average particle size of atomization is 110μm. The temperature of the recirculated flue gas is 120°C, and the ratio of the recirculated flue gas is 150%. The recirculated flue gas is uniformly mixed with the air and then enters the double-swirl air distributor (that is, the fully diffused jet swirler and the open jet swirler). The diameter of the inner ring of the full-diffusion jet swirler is 150mm, and the volume flow rate of the inner swirling flow is 40%. The volume flow rate of the external swirling flow of the open jet cyclone is 60%. The outlet of the burner body adopts a 45° swirl, and the axial velocity of the rotating jet is 50m/s. Numerical simulations were carried out on the oxygen mass fraction distribution, temperature distribution and velocity distribution of the central section of the furnace. The simulation results are shown in Fig. 7, Fig. 8 and Fig. 9. Fig. 7 is the distribution of oxygen mass fraction in the central section of the furnace. It can be seen that the oxygen concentration in the main combustion zone in the furnace is basically below 3%; Fig. 8 is the temperature distribution in the central section, the highest temperature is 1400K, and the temperature distribution in the main combustion zone is relatively uniform; Fig. 9 is the velocity distribution of the central section. Due to the increase of the axial jet velocity of the flue gas, the air velocity in the main combustion zone is increased to 10-30m/s.

The above description of the embodiments is for those of ordinary skill in the art to understand and use the present invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments, and apply the general principles described here to other embodiments without creative effort. Therefore, the present invention is not limited to the above-mentioned embodiments. Improvements and modifications made by those skilled in the art according to the disclosure of the present invention without departing from the scope of the present invention should fall within the protection scope of the present invention.

Claims (10)

1. A fuel oil flameless combustion device, characterized in that: it comprises: The burner body, through which a mixture of flue gas and air passes; Fuel nozzles for generating atomized fuel jets; an igniter for igniting said jet of atomized fuel; A full-diffusion jet swirler is arranged on the peripheral side of the fuel nozzle to make a part of the mixed gas in the burner body generate a full-diffusion jet; and The open-jet swirler is arranged on the peripheral side of the full-diffusion jet swirler, so that the mixed gas in the remaining part of the burner body produces an open jet. 2. The combustion device according to claim 1, characterized in that: the maximum volume concentration of oxygen in the mixed gas in the burner body is 10±2%. 3. The combustion device according to claim 1, characterized in that: the inner diameter of the fully diffused jet swirler is 60-150mm, the volume flow rate is 20-40%, and the swirl number is 0.5-1.5; and/ Or, the volume flow rate of the open-jet cyclone is 60-80%, and the swirl number is 0.25-1. 4. The combustion device according to claim 1, characterized in that: the outlet of the burner body adopts a 45° swirl, and the axial partial velocity of the rotating jet is 20-50m/s; and/or, the atomization The atomization angle of the fuel jet is 10-60°; and/or, the average atomization particle diameter of the atomized fuel jet is 100-110 μm. 5. A fuel oil flameless combustion device, characterized in that: it includes: a furnace, a flue gas recirculation fan, a blower and a fuel oil flameless combustion device connected in series in sequence; the fuel oil flameless combustion device includes a burner body, a fuel oil Nozzles, igniters, full diffuse jet swirlers and open jet swirlers; the fuel nozzle generates an atomized fuel jet and sprays it into the furnace; the igniter ignites the atomized fuel jet; The furnace absorbs heat, burns the atomized fuel jet and discharges smoke; The flue gas recirculation fan sends part of the flue gas to the blower; The blower sends the mixed gas formed by the part of the flue gas and air to the burner body of the fuel oil flameless combustion device; The full-diffusion jet swirler is arranged on the peripheral side of the fuel nozzle, so that a part of the mixed gas in the burner body produces a full-diffusion jet in the furnace; The open-jet swirler is arranged on the peripheral side of the full-diffusion jet swirler, so that the mixed gas in the remaining part of the burner body generates an open jet in the furnace, and the open jet is connected with the full-diffusion jet swirler. The diffusion jet produces a turbulent kinetic energy superposition zone, a backflow stable combustion zone and a turbulent kinetic energy interference zone in the furnace. 6. The fuel oil flameless combustion equipment according to claim 5, characterized in that: the recirculation ratio of the part of the flue gas is 80-150%; and/or, the emission concentration of NO _x in the boiler flue gas is less than 80mg/Nm ³ . 7. The fuel oil flameless combustion equipment according to claim 5, characterized in that: the volumetric heat load in the furnace is 600-3000kW/m ³ ; and/or, the maximum temperature of the furnace is less than 1400°C; and /or, the furnace temperature fluctuation coefficient is less than 20%. 8. The fuel oil flameless combustion equipment according to claim 5, characterized in that: the highest volume concentration of oxygen in the mixed gas in the burner body is 10±2%; and/or, the oxygen in the furnace The volume concentration is 3±1%. 9. The fuel oil flameless combustion equipment according to claim 5, characterized in that: the inner diameter of the fully diffused jet swirler is 60-150 mm, the volume flow rate is 20-40%, and the swirl number is 0.5-1.5 and/or, the open-jet cyclone has a volume flow rate of 60-80% and a swirl number of 0.25-1. 10. The fuel oil flameless combustion device according to claim 1, characterized in that: the burner body adopts a 45° swirl, and the axial partial velocity of the rotating jet is 20-50m/s; and/or, the The atomization angle of the atomized fuel jet is 10-60°; and/or, the atomized average particle diameter of the atomized fuel jet is 100-110 μm.