CN113154382B - A kind of low NOx burner and using method - Google Patents

Abstract

The invention relates to a low NOx burner, which is characterized in that it includes a gas connecting pipe, a primary air connecting pipe, a secondary air connecting pipe, a high-temperature flue gas pipe, a low-temperature flue gas pipe and a burner brick; the secondary air connecting pipe The pipe is connected to the burner mouth of the burner brick, and the secondary air connecting pipe is nested in the gas connecting pipe and the primary air connecting pipe in turn. Connect with low temperature flue gas pipe. In the present invention, metal catalytic balls are arranged in the gas pipeline, and the metal catalytic balls are heated by the residual heat of flue gas in the heating furnace, so that NH ₃ in the gas is pyrolyzed to form N ₂ and H ₂ , and then the deammoniated high-temperature gas is burned, greatly Reduce NOx due to fuel nitrogen. To achieve clean combustion of gas. At the same time, the preheating temperature of gas and central air is increased to reduce fuel consumption.

Description

A kind of low NOx burner and using method

technical field

The invention relates to the technical field of thermal energy saving, in particular to a low NOx burner.

Background technique

As one of the key pollutants to be controlled, NOx is the main source of pollution causing acid rain and photochemical smog, which has caused great harm to human health, various crops and the ecological environment. With the implementation of the new environmental protection law, the requirements for gas emissions from iron and steel enterprises are becoming more and more stringent. From 2015 to 2020, the NOx indicators of steel rolling process heating furnaces and heat treatment furnaces in iron and steel enterprises will be reduced to 300mg/Nm ³ . The low emission standard, the NOx index of the heating furnace and heat treatment furnace in the steel rolling process is reduced to 200mg/Nm ³ , which is more stringent than the original regulation.

NOx in the iron ^and steel industry mainly comes from the fuel combustion process, mainly including coal combustion, coke _combustion , fuel oil combustion and industrial secondary gas combustion. The N ₂ in the gas produces NO, N ₂ O, NO ₂ and a small amount of N ₂ O ₃ , N ₂ O ₄ , N ₂ O ₅ under the action of high temperature. There are many N compounds in solid fuel, and the generated flue gas is seriously affected by fuel nitrogen, and the amount of NOx generated is high. Generally, flue gas denitrification treatment is required in the later stage. However, the industrial gas preparation process passes through the fine desulfurization process, and the fuel nitrogen is reduced to a low level. Low levels of NOx can be achieved simply by controlling the generation of thermal nitrogen during combustion.

In the production process of industrial coke oven gas, it is necessary to use ammonia spray to remove the tar and other components in the raw coal gas. There will be a part of ammonia in the purified gas, and this part of ammonia will be oxidized during the combustion of the gas to form NOx. That is, the fuel nitrogen in the gas has an important influence on the formation of NOx, especially at low temperature.

Patent CN201811208892.9 is a fully premixed flameless combustion low-nitrogen burner, which discloses that the burner is provided with a combustion net lining extending toward the inside of the combustion tube, and the side of the combustion net lining facing the outside of the combustion tube is provided with a combustion net . The combustion net is arranged on the inner lining of the combustion net, so that the premixed gas of air and natural gas can pass through the combustion net uniformly, so that the premixed gas can be evenly burned on the surface of the combustion net, and avoid local high temperature in the combustion cylinder , to ensure the normal operation of the burner. Simply disperse the flame through the combustion net, and preheat the existing air gas to a certain temperature. The organization of the flame does not depend on the mixing, but only on the flow rate. This method cannot effectively reduce the concentrated combustion of the flame.

The device and method for reducing the generation of nitrogen oxides in coke ovens extract exhaust gas from the exhaust gas channel of the coke oven and forcefully send it into the air channel of the coke oven to mix with the air; dilute the oxygen content in the air with the exhaust gas. The invention does not need to change the internal structure of the coke oven, can significantly reduce the concentration of nitrogen oxides in exhaust gas and the absolute discharge of nitrogen oxides, and improves the surrounding atmospheric environment of enterprises. Reducing the oxygen content of the air can reduce the generation of thermal NOx, but the reduction of _O2 will cause insufficient combustion, reduce fuel efficiency and increase energy loss.

Patent CN201811155404.2 Radiant tube emission system and method for reducing nitrogen oxide emissions, combining _NOx reduction in combustion process with catalytic reaction _NOx reduction, two-stage reduction of _NOx content in flue gas, _NOx content can be reduced to an extremely low level , greatly reducing equipment costs. The reduction of NOx content by catalytic means is similar to post-treatment, and at the same time, the transformation cost of the burner is relatively high, which will greatly increase the energy cost.

Combining the above analysis and the search results of related patents, reducing the fuel nitrogen in the gas plays an important role in the low NOx combustion of the gas.

Contents of the invention

The technical problem to be solved by the present invention is to provide a low NOx burner, increase the preheating temperature of coal gas and central primary air, and reduce fuel consumption. Realize deammonization of the gas before the burner of the burner, and reduce the amount of NOx produced by the combustion product.

To achieve the above object, the present invention adopts the following technical solutions:

A low NOx burner, comprising a gas connecting pipe, a primary air connecting pipe, a secondary air connecting pipe, a high-temperature flue gas pipe, a low-temperature flue gas pipe and a burner brick; the firing of the secondary air connecting pipe and the burner brick The mouth is connected, and the secondary air connecting pipe is nested in the gas connecting pipe and the primary air connecting pipe in turn. The gas connecting pipe is equipped with a heat exchanger. One end of the heat exchanger is connected to the high-temperature flue gas pipe, and the other end is connected to the low-temperature flue gas pipe.

The heat exchanger includes several heat exchange tubes. The heat exchange tubes are arranged in the ventilation cavity between the gas connection pipe and the primary air connection pipe, and extend through the gas connection pipe to the outside of the gas connection pipe. The outlet of the trachea pipe is connected to the inlet of the low-temperature flue gas pipe at the other end. Steel mesh is installed on both sides of the heat exchange pipe to connect with the inner wall of the gas connection pipe. The cavity is filled with metal catalytic balls.

The outlet of the gas connecting pipe penetrates into the burner mouth of the burner brick by 10 mm to 30 mm.

The high-temperature flue gas pipe 5 passes through the burner brick 4 and enters the heating furnace.

The low-temperature flue gas pipe is connected with the chimney.

The high-temperature flue gas pipe is provided with an ejector fan.

The burner mouth of the burner brick gradually expands from the gas inlet side to the heating furnace.

A thermocouple is installed on the high-temperature flue gas pipe close to the heat exchanger.

The metal catalytic balls include nickel balls, copper-manganese alloy balls, and zinc-titanium alloy balls.

A method for using a low NOx burner. The gas enters the burner from the gas connection pipe and is mixed with the primary air entering the primary air connection pipe for primary combustion. The primary air volume accounts for 30% to 50% of the combustion air volume. The primary combustion of the gas is strong reduction The air excess coefficient is 0.65~0.85, and the temperature of the primary combustion is 1300℃~1500℃; the ejector fan on the high temperature flue gas pipe extracts the high temperature flue gas of 1200℃~1400℃ in the furnace, and at the same time controls the ejector fan mixed Enter 15% to 50% cold air to achieve a mixed air temperature of 900 to 1100°C. The mixed air is sent to the heat exchange tube of the heat exchanger, and the heat exchange tube heats the metal catalyst in the ventilation cavity between the primary air pipe and the gas connection pipe. Balls, the metal catalytic balls where the gas is heated, make the NH ₃ in the gas decompose at high temperature to form N ₂ and H ₂ . During the process of the gas passing through the high-temperature metal catalytic balls, the preheating temperature reaches 500 ℃ ~ 800 ℃, and then the deamination The high-temperature gas and the low-pressure air entering the secondary air connection pipe perform secondary combustion, and the high-temperature flue gas produced is sent into the furnace by the burner brick for material heating.

When the ammonia content in the gas is less ^than 300mg/Nm ³ , keep the gas flow rate in the pipeline at 5m/s~15m/s ^; 13.5m/s, when the ammonia content in the gas is 500mg/Nm ³ ～1000mg/Nm ³ , control the gas flow rate 3.5m/s～12m/s, when the ammonia content in the gas> 1000mg/Nm ³ , control the gas flow rate 2m/ s～11>3m/s.

Compared with prior art, the beneficial effect of the present invention is:

In the present invention, metal catalytic balls are arranged in the gas pipeline, and the metal catalytic balls are heated by the waste heat of flue gas in the heating furnace, so that NH ₃ in the gas is pyrolyzed to form N ₂ and H ₂ , and then the high-temperature deammoniated gas is burned, greatly Reduce NOx due to fuel nitrogen. To achieve clean combustion of gas. At the same time, the preheating temperature of gas and central air is increased to reduce fuel consumption.

Description of drawings

Fig. 1 is a structural schematic diagram of the present invention.

Fig. 2 is a structural schematic diagram of the heat exchanger.

In the figure: gas connecting pipe 1, low-temperature flue gas pipe 2, secondary air connecting pipe 3, burner brick 4, high-temperature flue gas pipe 5, ejector fan 6, thermocouple 7, metal catalytic ball 8, steel mesh 9, Primary air connection pipe 10, heat exchange pipe 11.

detailed description

The specific embodiment of the present invention is further described below in conjunction with accompanying drawing:

As shown in Figures 1-2, a low NOx burner includes a gas connecting pipe 1, a primary air connecting pipe 10, a secondary air connecting pipe 3, a high-temperature flue gas pipe 5, a low-temperature flue gas pipe 2 and a burner brick 4; The secondary air connecting pipe 4 is connected to the burner mouth of the burner brick 4, and the burner mouth of the burner brick 4 gradually expands from the gas inlet side to the heating furnace.

The secondary air connecting pipe 4 nests the gas connecting pipe 1 and the primary air connecting pipe 10 sequentially, and the outlet of the gas connecting pipe 1 protrudes into the burner mouth of the burner brick 4 by 10 mm to 30 mm.

A heat exchanger is arranged inside the gas connecting pipe 1, and the heat exchanger includes several heat exchanging pipes 11. The heat exchanging pipes 11 are arranged in the ventilation cavity between the gas connecting pipe 1 and the primary air connecting pipe 10, and run through the gas connecting pipe. 1 extends to the outside of the gas connecting pipe 1, one end leads to the outlet of the high-temperature flue gas pipe 5, and the other end leads to the entrance of the low-temperature flue gas pipe 2, the high-temperature flue gas pipe 5 passes through the burner brick 4 into the heating furnace, and the high-temperature flue gas pipe 5 is provided with ejector blower fan 6. A thermocouple 7 is provided on the high-temperature flue gas pipe 5 close to the heat exchanger. The low temperature flue gas pipe is connected with the chimney.

Both sides of the heat exchange tube 11 are provided with a steel mesh 9 connected to the inner wall of the gas connecting pipe 1. The steel mesh 9 is a stainless steel mesh. The filled metal catalytic balls 8 are nickel balls.

A method for using a low NOx burner. The gas enters the burner from the gas connection pipe and is mixed with the primary air entering the primary air connection pipe for primary combustion. The primary air volume accounts for 30% to 50% of the combustion air volume. The primary combustion of the gas is strong reduction The air excess coefficient is 0.65~0.85, and the temperature of the primary combustion is 1300℃~1500℃; the ejector fan on the high temperature flue gas pipe extracts the high temperature flue gas of 1200℃~1400℃ in the furnace, and at the same time controls the ejector fan mixed Enter 15% to 50% cold air to achieve a mixed air temperature of 900 to 1100°C. The mixed air is sent to the heat exchange tube of the heat exchanger, and the heat exchange tube heats the metal catalyst in the ventilation cavity between the primary air pipe and the gas connection pipe. Balls, the metal catalytic balls where the gas is heated, make the NH ₃ in the gas decompose at high temperature to form N ₂ and H ₂ . During the process of the gas passing through the high-temperature metal catalytic balls, the preheating temperature reaches 500 ℃ ~ 800 ℃, and then the deamination The high-temperature gas and the low-pressure air entering the secondary air connection pipe perform secondary combustion, and the high-temperature flue gas produced is sent into the furnace by the burner brick for material heating. When the ammonia content in the gas is less ^than 300mg/Nm ³ , keep the gas flow rate in the pipeline at 5m/s~15m/s ^; 13.5m/s, when the ammonia content in the gas is 500mg/Nm ³ ～1000mg/Nm ³ , control the gas flow rate 3.5m/s～12m/s, when the ammonia content in the gas> 1000mg/Nm ³ , control the gas flow rate 2m/ s～11>3m/s.

Example

A low NOx burner, comprising a gas connecting pipe 1, a primary air connecting pipe 10, a secondary air connecting pipe 3, a high temperature flue gas pipe 5, a low temperature flue gas pipe 2 and a burner brick 4; the secondary air connecting pipe 4 is connected with the burner mouth of the burner brick 4, and the burner mouth of the burner brick 4 gradually expands from the gas inlet side to the heating furnace.

The secondary air connecting pipe 4 nests the gas connecting pipe 1 and the primary air connecting pipe 10 in sequence, and the outlet of the gas connecting pipe 1 protrudes into the burner mouth of the burner brick 4 by 20mm.

A heat exchanger is arranged inside the gas connecting pipe 1, and the heat exchanger includes several heat exchanging pipes 11. The heat exchanging pipes 11 are arranged in the ventilation cavity between the gas connecting pipe 1 and the primary air connecting pipe 10, and run through the gas connecting pipe. 1 extends to the outside of the gas connecting pipe 1, one end leads to the outlet of the high-temperature flue gas pipe 5, and the other end leads to the entrance of the low-temperature flue gas pipe 2, the high-temperature flue gas pipe 5 passes through the burner brick 4 into the heating furnace, and the high-temperature flue gas pipe 5 is provided with ejector blower fan 6. A thermocouple 7 is provided on the high-temperature flue gas pipe 5 close to the heat exchanger. The low temperature flue gas pipe is connected with the chimney.

Both sides of the heat exchange tube 11 are provided with stainless steel mesh 9 to connect with the inner wall of the gas connecting pipe 1, and the ventilation cavity between the gas connecting pipe 1 and the primary air connecting pipe 10 between the two stainless steel meshes 9 is filled with metal catalytic balls 8 . The metal catalytic balls 8 are nickel balls.

A method for using a low-NOx burner. Coal gas enters the burner from a gas connecting pipe and is mixed with primary air entering the primary air connecting pipe for primary combustion. The ammonia content in the gas is <300mg/Nm ³ , and the gas pressure is controlled at 1000Pa to 3000Pa. Keep the gas flow rate in the pipeline at 5m/s-15m/s, the primary air volume accounts for 30%-35% of the combustion-supporting air volume, the primary combustion of gas is strong reducing combustion, the air excess coefficient is 0.68, and the primary combustion temperature is 1300℃～1350℃; The ejector fan on the high-temperature flue gas pipe extracts the high-temperature flue gas at 1200°C to 1400°C in the furnace, and at the same time controls the ejector fan to mix in 15% cold air to achieve a mixed air temperature of 900-1000°C, and the mixed air is sent to the furnace In the heat exchange tube of the heat exchanger, the heat exchange tube heats the metal catalytic ball in the ventilation cavity between the primary air pipe and the gas connecting pipe, and the gas is heated by the metal catalytic ball, so that the NH ₃ in the gas is pyrolyzed to form N ₂ and H _2. When the gas passes through the high-temperature metal catalytic ball, the preheating temperature reaches 500℃～600℃, and then the high-temperature deammonized gas is combusted with the low-pressure air entering the secondary air connecting pipe, and the high-temperature flue gas produced is produced by the combustion The nozzle brick is sent into the furnace for material heating.

The invention utilizes the residual heat of the flue gas of the heating furnace to realize the deammonization of the gas in front of the burner mouth, reduce the generation of NOx of the combustion product, increase the preheating temperature of the gas and the central air, and reduce the fuel consumption.

The outlet of the gas connecting pipe penetrates into the burner mouth of the burner brick, so that the gas nozzle is longer than the secondary air nozzle, so that the gas and air in the secondary combustion area can be completely diffused and burned, and the flame temperature in the secondary mixed combustion area can be effectively reduced. Realize the goal of reducing thermal NOx.

For those skilled in the art, without departing from the principle of the present invention, the present invention can also be improved and modified, and these improvements and modifications also fall within the protection scope of the claims of the present invention. The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto, any person familiar with the technical field within the technical scope disclosed in the present invention, according to the technical solution of the present invention Equivalent replacements or changes to the concepts thereof shall fall within the protection scope of the present invention.

Claims (6)

1. A low NOx burner is characterized by comprising a coal gas connecting pipe, a primary air connecting pipe, a secondary air connecting pipe, a high-temperature flue gas pipe, a low-temperature flue gas pipe and a burner block; the secondary air connecting pipe is connected with a burner nozzle opening of the burner block, the secondary air connecting pipe is sequentially nested with the gas connecting pipe and the primary air connecting pipe, a heat exchanger is arranged in the gas connecting pipe, and the heat exchangerOne end of the high-temperature flue gas pipe is connected with the high-temperature flue gas pipe, and the other end of the high-temperature flue gas pipe is connected with the low-temperature flue gas pipe; the heat exchanger comprises a plurality of heat exchange tubes, the heat exchange tubes are arranged in a ventilation cavity between a gas connecting pipe and a primary air connecting pipe, penetrate through the gas connecting pipe and extend to the outer side of the gas connecting pipe, one end of each heat exchange tube is introduced into an outlet of a high-temperature flue gas pipe, the other end of each heat exchange tube is introduced into an inlet of a low-temperature flue gas pipe, steel meshes are arranged on two sides of each heat exchange tube and connected with the inner wall of the gas connecting pipe, and a ventilation cavity between the gas connecting pipe between the two steel meshes and the primary air connecting pipe is filled with metal catalytic balls; the use method of the low NOx burner comprises the following steps that coal gas enters the burner through a coal gas connecting pipe and is mixed with primary air entering a primary air connecting pipe to be subjected to primary combustion, the primary air quantity accounts for 30% -50% of combustion-supporting air quantity, the primary combustion of the coal gas is strong reducing combustion, the air excess coefficient is 0.65-0.85, and the temperature of the primary combustion is 1300-1500 ℃; the ejection fan on the high-temperature flue gas pipe extracts the high-temperature flue gas with the temperature of 1200-1400 ℃ in the hearth, simultaneously controls the ejection fan to mix 15% -50% of cold air, realizes the mixed air temperature of 900-1100 ℃, the mixed air is sent into the heat exchange pipe of the heat exchanger, the heat exchange pipe heats the metal catalytic ball in the ventilation cavity between the primary air pipe and the gas connecting pipe, and the gas passes through the heated metal catalytic ball to ensure that NH in the gas is ₃ Pyrolysis to form N ₂ And H ₂ Preheating coal gas to 500-800 deg.c in the process of passing through the high temperature metal catalytic ball, secondary burning the deaminized high temperature coal gas and the low pressure air entering the secondary air connecting pipe to produce high temperature fume, and feeding the fume into the furnace via the burner brick to heat the material; when the ammonia content in the coal gas is less than 300mg/Nm ³ Keeping the flow speed of coal gas in the pipeline at 5-15 m/s, and when the ammonia content in the coal gas is 300mg/Nm ³ ～500mg/Nm ³ Controlling the flow rate of the coal gas to be reduced by 4.5-13.5 m/s, and controlling the ammonia content in the coal gas to be 500mg/Nm ³ ～1000mg/Nm ³ Controlling the gas flow rate to be 3.5-12 m/s.

2. The burner of claim 1, wherein the outlet of the gas connecting tube extends 10mm to 30mm into the burner port of the burner block.

3. The burner of claim 1, wherein the hot flue gas duct is introduced into the furnace through a burner block.

4. A low NOx burner according to claim 1, characterised in that the low temperature flue pipe is connected to a chimney.

5. A low NOx burner as claimed in claim 1, wherein the burner ports of the burner blocks are enlarged from the gas inlet side into the furnace.

6. The burner of claim 1, wherein a thermocouple is provided on the hot flue gas duct adjacent to the heat exchanger.

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