Efficient low-nitrogen ethylene cracking furnace radiation wall premixing burner

Abstract

The efficient low-nitrogen ethylene cracking furnace radiation wall premixing burner comprises a burner shell, a spray gun, an air bellow, guide vanes and a honeycomb steady flow disc, a composite refractory brick is arranged at the top of the burner shell, the spray gun sequentially penetrates through the burner shell and the composite refractory brick, and an air circulation gap is formed between the spray gun and the composite refractory brick. The spray gun comprises a Venturi tube and a spray head, a honeycomb steady flow disc is arranged in the spray head, an umbrella cap of the spray head extends out of the composite refractory brick to enter the hearth, an air box for air inlet is arranged at the bottom of the combustor shell, and primary air enters the Venturi tube to be mixed with fuel gas under the action of the honeycomb steady flow disc. Secondary air enters the hearth through an air circulation gap along an annular channel between the Venturi tube and the combustor shell, guide vanes are arranged in the air circulation gap, and spray holes are formed in the circumferential direction of the spray head. The composite refractory bricks are adopted, waves are arranged close to the surface of the hearth, thermal shock stability and thermal efficiency are improved, flame distribution is uniform, and efficient, stable and clean combustion is achieved.

Description

Technical Field

[0001] This invention relates to the field of ethylene cracking furnace combustion technology, specifically to a high-efficiency, low-NOx ethylene cracking furnace radiant wall premixed burner. Background Technology

[0002] Ethylene cracking furnaces are core equipment in the petrochemical industry, and the performance of their burners directly affects cracking efficiency, energy consumption, and pollutant emissions. Traditional burners for ethylene cracking furnaces have the following shortcomings: Refractory bricks have a simple structure and poor thermal shock stability, making them prone to cracking with frequent start-ups and shutdowns; the simple pore arrangement leads to uneven flame distribution, resulting in low flame stability; and the simple air-fuel mixing method makes it difficult to achieve both low NOx and high thermal efficiency. Therefore, there is an urgent need to design a high-efficiency, low-NOx ethylene cracking furnace radiant wall premixed burner. Summary of the Invention

[0003] The purpose of this invention is to overcome the above-mentioned shortcomings and provide a high-efficiency, low-NOx ethylene cracking furnace radiant wall premixed burner, which solves the problems of uneven mixing of fuel gas and air, unstable flame, high NOx emissions, and easy damage to refractory bricks, and achieves efficient, stable, and clean combustion.

[0004] The objective of this invention is achieved as follows: A high-efficiency, low-NOx ethylene cracking furnace radiant wall premixed burner includes a burner shell, a spray gun, a wind box, guide vanes, and a honeycomb flow stabilizer. The top of the burner shell is provided with composite refractory bricks. The spray gun passes through the burner shell and the composite refractory bricks in sequence. An air flow gap is provided between the spray gun and the composite refractory bricks. The spray gun includes a venturi tube and a nozzle. A honeycomb flow stabilizer is provided inside the nozzle. The umbrella cap of the nozzle extends out of the composite refractory bricks and enters the furnace. An air box is provided at the bottom of the burner shell. Primary air enters the venturi tube and mixes with fuel gas under the action of the honeycomb flow stabilizer. Secondary air enters the furnace through the air flow gap along the annular channel between the venturi tube and the burner shell. Guide vanes are provided inside the air flow gap. The nozzle has spray holes around its circumference.

[0005] Preferably, the nozzle is mushroom-shaped, including a neck constriction section and an umbrella cap, with an expansion ratio D2 / D1 = 2.0-2.5:1, where D2 is the diameter of the umbrella cap and D1 is the diameter of the neck constriction section, and the conical expansion angle of the umbrella cap relative to the axial direction is 15-25°.

[0006] Preferably, the nozzles are arranged around the circumference of the umbrella cap, and each nozzle is distributed in a sinusoidal curve. The nozzles are divided into main nozzles and secondary nozzles according to their size. The main nozzles are arranged at the peaks and troughs of the sinusoidal curve, and several secondary nozzles are distributed between adjacent main nozzles.

[0007] Preferably, the honeycomb flow stabilizer is located in the neck constriction section of the nozzle, and the honeycomb flow stabilizer is made of nickel-based alloy with a SiC coating on its surface, and the honeycomb flow stabilizer has honeycomb holes evenly distributed inside.

[0008] Preferably, the diameter of the main spray hole is 10-15mm, the spacing between adjacent main spray holes is distributed along a sine curve with equal arc length and the spacing is 40-60mm, the main spray hole is inclined and the angle α between the main spray hole and the surface of the refractory brick is 20-30°.

[0009] Preferably, the diameter of the secondary spray hole is 3-5mm, and there are 2-3 secondary spray holes between every two main spray holes. The inclination angle of the secondary spray holes is 15-20°.

[0010] Preferably, the guide vanes are disposed within the airflow gap and 100-150mm from the nozzle, with 8-12 guide vanes evenly distributed circumferentially, and the angle of attack of the guide vanes is 3-5°.

[0011] Preferably, the composite refractory brick includes an insulation layer, a transition layer and a hot surface layer arranged sequentially from the outside to the inside. The hot surface layer has waves on the side surface near the furnace, and the wave height gradually decreases from the center of the composite refractory brick to the edge.

[0012] Preferably, the hot surface layer is made of silicon carbide-based composite ceramic with a SiC content of 65-75 wt% and a porosity that gradually increases from the furnace side to the back side along the thickness direction.

[0013] Preferably, the transition layer is prepared by mixing mullite powder with Al2O3 short fibers, molding and then curing, and the transition layer has an Al2O3 content of 55-65 wt% and a thickness of 75-100 mm.

[0014] The beneficial effects of this invention are: The primary air enters the venturi tube and is fully premixed with the fuel gas under the stabilizing and diverting effect of the honeycomb flow stabilizer. It is then injected into the furnace through the nozzle orifice in a sinusoidal trajectory. The sinusoidal distribution of the nozzle orifice makes the injected fuel gas spatially three-dimensionally distributed, the flame is evenly distributed, and the mixing with air is enhanced to achieve staged combustion. The secondary air enters the annular channel between the burner shell and the venturi tube and flows upward. After passing through the guide vanes in the air flow gap and axially swirling, it enters the furnace and mixes and burns with the fuel injected from the nozzle orifice. The composite refractory bricks have a wavy, uneven surface near the furnace, which provides the strongest stability to the flame root and allows the outer flame to spread naturally, preventing excessive flame diffusion. At the same time, the crests form flame anchoring points, and the troughs increase the flame residence time, thereby improving flame stability. In addition, the increased surface area improves radiative heat transfer efficiency by 28-38%. The composite refractory bricks, with their insulation layer, transition layer, and thermal surface layer arranged sequentially from the outside in, improve thermal shock stability and increase the start-stop cycle life from 800 times to over 2000 times. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of a high-efficiency, low-nitrogen ethylene cracking furnace radiant wall premixed burner according to the present invention.

[0016] Figure 2 This is a schematic diagram of the internal structure of composite refractory bricks.

[0017] Figure 3 This is a schematic diagram of the three-dimensional structure of the nozzle.

[0018] Figure 4 This is a schematic diagram of the internal structure of the nozzle.

[0019] in: 1. Burner shell; 2. Air box; 3. Guide vane; 4. Honeycomb flow stabilizer plate; 5. Composite refractory brick; 5.1. Insulation layer; 5.2. Transition layer; 5.3. Hot surface layer; 5.3.1. Corrugated surface; 6. Air flow gap; 7. Venturi tube; 8. Nozzle; 8.1. Neck contraction section; 8.2. Umbrella cap; 8.3. Main nozzle; 8.4. Secondary nozzle. Detailed Implementation

[0020] See Figure 1-4This invention relates to a high-efficiency, low-NOx ethylene cracking furnace radiant wall premixed burner, comprising a burner shell 1, a spray gun, a wind box 2, guide vanes 3, and a honeycomb flow stabilizer 4. The top of the burner shell 1 is provided with composite refractory bricks 5. The spray gun passes sequentially through the burner shell 1 and the composite refractory bricks 5. An airflow gap 6 is provided between the spray gun and the composite refractory bricks 5. The spray gun includes a Venturi tube 7 and a nozzle 8. The nozzle 8 is provided with a honeycomb flow stabilizer 4. The cap 8.2 of the nozzle 8 extends out of the composite refractory bricks 5 and enters the furnace. The neck constriction section 8.1 of the nozzle 8 is located inside the composite refractory bricks 5. The bottom of the burner shell 1 is provided with an air box 2 for air intake. Primary air enters the Venturi tube 7 and mixes with fuel gas under the action of the honeycomb flow stabilizer 4. Secondary air enters the furnace through the annular channel between the Venturi tube 7 and the burner shell 1 and through the airflow gap 6. The airflow gap 6 is provided with guide vanes 3. The nozzle 8 is provided with circumferential spray holes. The nozzles point towards the composite refractory brick 5. The nozzles are distributed in a sinusoidal curve. The nozzles are divided into main nozzles 8.3 and secondary nozzles 8.4 according to their size. The main nozzles 8.3 are located at the peaks and troughs of the sinusoidal curve. Several secondary nozzles 8.4 are distributed between adjacent main nozzles 8.3. The composite refractory brick 5 includes an insulation layer 5.1, a transition layer 5.2, and a hot surface layer 5.3 arranged sequentially from the outside to the inside. The hot surface layer 5.3 has waves 5.3.1 on its surface near the furnace. The height of the waves gradually decreases from the center of the composite refractory brick 5 to the edge. The peaks and troughs of the waves 5.3.1 form multiple concentric rings. This undulating structure of the waves provides the strongest stabilizing effect at the flame root, allowing the outer flame to spread naturally and preventing excessive flame diffusion. At the same time, the peaks form flame anchoring points, and the troughs increase the flame residence time, thereby improving flame stability. It also increases the surface area and improves the radiative heat transfer efficiency by 28-38%.

[0021] The hot surface layer 5.3 is made of silicon carbide-based composite ceramic with a SiC content of 65-75 wt%. The porosity increases gradually from 5% on the furnace side to 10-15% on the back side along the thickness direction, and the thickness is 65-75 wt%. The silicon carbide-based composite ceramic is prepared by mixing SiC powder (65-75 wt%), Al2O3 powder and a pore-forming agent, and then casting in a gradient manner (the pore-forming agent content is 5%, 10%, and 15% in three castings), followed by sintering at 1400-1500℃.

[0022] The transition layer 5.2 is prepared by mixing mullite powder with Al2O3 short fibers (8-12 μm in diameter and 5-15 mm in length), molding, and then curing. The transition layer has an Al2O3 content of 55-65 wt% and a thickness of 75-100 mm.

[0023] The insulation layer 5.1 is made of aluminum silicate fiber modules with a thermal conductivity of ≤0.08 W / (m·K) and a thickness of 75-100mm.

[0024] The nozzle 8 is mushroom-shaped, including a neck constriction section 8.1 and an umbrella cap 8.2. The nozzle expansion ratio D2 / D1 = 2.0-2.5:1, where D2 is the diameter of the umbrella cap and D1 is the diameter of the neck constriction section. The conical expansion angle of the umbrella cap relative to the axial direction is 15-25°.

[0025] The honeycomb flow stabilizer 4 is located at the neck contraction section 8.1 of the nozzle 8. The honeycomb flow stabilizer 4 is made of nickel-based alloy and coated with a SiC coating with a coating thickness of 50-80 μm. The honeycomb flow stabilizer 4 has evenly distributed honeycomb holes with a side length of 6-10 mm and a wall thickness of 0.8-1.2 mm.

[0026] The main nozzle 8.3 has a diameter of 10-15mm. The spacing between adjacent main nozzles 8.3 is distributed along a sine curve with equal arc length and a spacing of 40-60mm. The main nozzles 8.3 are inclined, and the angle α between the main nozzle 8.3 and the normal to the refractory brick surface is 20-30°. The secondary nozzles 8.4 have a diameter of 3-5mm. There are 2-3 secondary nozzles 8.4 between every two main nozzles 8.3. The angle of inclination of the secondary nozzles 8.4 is 15-20°.

[0027] The guide vanes 3 are set in the air flow gap 6 and 100-150mm away from the nozzle. 8-12 guide vanes 3 are evenly distributed around the circumference. The angle of attack of the guide vanes 3 is 3-5°, forming an axial swirling intensity S=0.2-0.4.

[0028] Wave 5.3.1 forms five concentric annular peaks and five annular troughs on the surface of the hot surface layer 5.3, with a spacing of 40-70 mm between adjacent annular peaks.

[0029] The wavy surface is formed by CNC milling, with a surface roughness Ra≤6.3μm, and is coated with a high emissivity coating (emissivity ε≥0.93) with a coating thickness of 60-100μm.

[0030] The air box 2 is located at the bottom of the burner housing 1 and is used to introduce combustion air.

[0031] The primary air enters the venturi tube 7 and is fully premixed with the fuel gas under the stabilizing and diverting effect of the honeycomb flow stabilizer 4. It is then injected into the furnace through the nozzle 8 in a sinusoidal trajectory. The sinusoidal distribution of the nozzle makes the injected fuel gas spatially distributed in three dimensions, enhancing the mixing with air. The secondary air enters the annular channel between the burner shell 1 and the venturi tube 7 and flows upward. After passing through the guide vanes 3 in the air flow gap 6 and axially swirling, it enters the furnace and mixes and burns with the fuel injected from the nozzle.

[0032] In addition to the above embodiments, the present invention also includes other embodiments. All technical solutions formed by equivalent transformation or equivalent substitution should fall within the protection scope of the claims of the present invention.

Claims

1. A high-efficiency, low-NOx ethylene cracking furnace radiant wall premixed burner, characterized in that: The device includes a burner shell, a spray gun, a bellows, guide vanes, and a honeycomb flow stabilizer. The top of the burner shell is covered with composite refractory bricks. The spray gun passes through the burner shell and the composite refractory bricks in sequence. An air flow gap is provided between the spray gun and the composite refractory bricks. The spray gun includes a venturi tube and a nozzle. A honeycomb flow stabilizer is provided inside the nozzle. The nozzle cap extends out of the composite refractory bricks and enters the furnace. An air inlet bellows is provided at the bottom of the burner shell. Primary air enters the venturi tube and mixes with fuel gas under the action of the honeycomb flow stabilizer. Secondary air enters the furnace through the air flow gap along the annular channel between the venturi tube and the burner shell. Guide vanes are provided inside the air flow gap. The nozzle has spray holes around its circumference.

2. The high-efficiency, low-NOx ethylene cracking furnace radiant wall premixed burner according to claim 1, characterized in that: The nozzle is mushroom-shaped, including a neck constriction section and an umbrella cap. The nozzle expansion ratio D2 / D1 = 2.0-2.5:1, where D2 is the diameter of the umbrella cap and D1 is the diameter of the neck constriction section. The conical expansion angle of the umbrella cap relative to the axial direction is 15-25°.

3. A high-efficiency, low-NOx ethylene cracking furnace radiant wall premixed burner according to claim 1 or 2, characterized in that: The nozzles are arranged around the umbrella cap, and each nozzle is distributed in a sinusoidal curve. The nozzles are divided into main nozzles and secondary nozzles according to their size. The main nozzles are arranged at the peaks and troughs of the sinusoidal curve, and several secondary nozzles are distributed between adjacent main nozzles.

4. A high-efficiency, low-NOx ethylene cracking furnace radiant wall premixed burner according to claim 1 or 2, characterized in that: The honeycomb flow stabilizer is located in the neck constriction section of the nozzle. The honeycomb flow stabilizer is made of nickel-based alloy and coated with SiC coating. The honeycomb flow stabilizer has honeycomb holes evenly distributed inside.

5. The high-efficiency, low-NOx ethylene cracking furnace radiant wall premixed burner according to claim 3, characterized in that: The diameter of the main nozzle is 10-15mm, and the spacing between adjacent main nozzles is distributed along a sine curve with equal arc length, with a spacing of 40-60mm. The main nozzles are inclined, and the angle α between the main nozzle and the surface of the refractory brick is 20-30°.

6. The high-efficiency, low-NOx ethylene cracking furnace radiant wall premixed burner according to claim 3, characterized in that: The diameter of the secondary spray holes is 3-5mm, and there are 2-3 secondary spray holes between every two main spray holes. The inclination angle of the secondary spray holes is 15-20°.

7. The high-efficiency, low-NOx ethylene cracking furnace radiant wall premixed burner according to claim 1, characterized in that: The guide vanes are set in the airflow gap and 100-150mm away from the nozzle. 8-12 guide vanes are evenly distributed circumferentially, and the angle of attack of the guide vanes is 3-5°.

8. The high-efficiency, low-NOx ethylene cracking furnace radiant wall premixed burner according to claim 1, characterized in that: The composite refractory brick includes an insulation layer, a transition layer and a hot surface layer arranged sequentially from the outside to the inside. The hot surface layer has waves on the side surface near the furnace, and the height of the waves gradually decreases from the center of the composite refractory brick to the edge.

9. A high-efficiency, low-NOx ethylene cracking furnace radiant wall premixed burner according to claim 8, characterized in that: The hot surface layer is made of silicon carbide-based composite ceramic with a SiC content of 65-75 wt% and a porosity that gradually increases from the furnace side to the back side along the thickness direction.

10. A high-efficiency, low-NOx ethylene cracking furnace radiant wall premixed burner according to claim 8, characterized in that: The transition layer is prepared by mixing mullite powder with Al2O3 short fibers, molding and then curing. The transition layer has an Al2O3 content of 55-65 wt% and a thickness of 75-100 mm.

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