Central high pressure natural gas combustion system and method

Abstract

This invention belongs to the field of combustion technology, and specifically relates to a central high-pressure natural gas combustion system and method. The combustion system is characterized by a three-layer sleeve-type integral structure consisting of an outer sleeve, a middle sleeve, and an inner ring. The outer sleeve mainly forms a low-pressure natural gas channel, formed by the inner wall of the outer ring and the outer wall of the secondary outer ring, through which low-pressure natural gas is introduced. The middle sleeve mainly forms a combustion air channel, formed by the inner wall of the secondary outer ring and the outer wall of the high-pressure natural gas nozzle, through which combustion air is introduced. The inner ring has a high-pressure natural gas channel, through which high-pressure natural gas is introduced into the flame via the high-pressure natural gas nozzle. This invention, by introducing high-pressure natural gas into the inner ring and low-pressure natural gas into the outer ring, with combustion air introduced between them, ensures thorough mixing of the natural gas and combustion-supporting gases, effectively extending the flame length and enhancing the stability of flame combustion.

Description

Technical Field

[0001] This invention belongs to the field of combustion technology, and in particular relates to a central high-pressure natural gas combustion system and method. Background Technology

[0002] Natural gas is a clean energy source. Rotary kilns, as crucial equipment in steel, cement, and lime industries, emit significant amounts of pollutants. Ensuring complete combustion within the kiln is key to energy conservation and emission reduction. Proper burner design helps accelerate energy structure optimization. Due to burner structure limitations and environmental constraints, the flame length after combustion of fuel gas and auxiliary combustion gases is often insufficient for fully roasting materials during actual production. Therefore, rationally designing the burner structure is beneficial for improving energy utilization and roasting material yield, which has become an important task in combustion technology research.

[0003] However, the flame produced by natural gas combustion is relatively weak and tends to rise. Existing natural gas burners, designed primarily for combustion efficiency, flame stability, flue gas temperature, and NOx emissions, suffer from problems such as short flame length and poor flame stability. This further leads to poor flue gas uniformity within the kiln, which is highly detrimental to rotary kiln production and unsuitable for its requirements. Therefore, there is an urgent need to design a new type of natural gas burner that can meet the long-flame combustion requirements of rotary kilns while ensuring flame stability. Summary of the Invention

[0004] The purpose of this invention is to provide a central high-pressure natural gas combustion system and method that extends the flame length so that the flame length after combustion of the fuel gas and the combustion-supporting gas is sufficient to fully roast the material.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] The central high-pressure natural gas combustion system of the present invention is characterized by comprising a three-layer sleeve-type integral structure consisting of an outer sleeve, a middle sleeve, and an inner ring. The outer sleeve mainly consists of a low-pressure natural gas channel formed by the inner wall of the outer ring and the outer wall of the secondary outer ring, through which low-pressure natural gas is introduced. The middle sleeve mainly consists of a combustion air channel formed by the inner wall of the secondary outer ring and the outer wall of the high-pressure natural gas nozzle, through which combustion air is introduced. The inner ring is provided with a high-pressure natural gas channel, through which high-pressure natural gas is introduced into the flame via the high-pressure natural gas nozzle.

[0007] The outer diameter of the high-pressure natural gas channel is 1 / 2 to 1 / 5 of the outer diameter of the low-pressure natural gas channel. The natural gas pressure of the low-pressure natural gas channel is 0.2 kPa to 0.8 kPa, and the natural gas pressure of the high-pressure natural gas channel is 4 kPa to 5 kPa.

[0008] The high-pressure natural gas nozzle is equipped with a movable adjusting spring at its end, and the high-pressure natural gas nozzle is made of high-temperature and corrosion-resistant materials.

[0009] The high-pressure natural gas nozzle is made of high-temperature and corrosion-resistant materials.

[0010] A combustion method utilizing a central high-pressure natural gas combustion system, characterized by comprising:

[0011] (1) Open the corresponding natural gas valve and perform other gas supply operations to confirm that the natural gas has been delivered to the burner nozzle, and ensure that the natural gas pressure reduction system is safe and reliable, the pressure in front of the burner is stable at 5 kPa, and ensure that the combustion air passage is unobstructed.

[0012] (2) Turn on the combustion air blower, confirm that the combustion air system is operating normally, and pre-adjust the combustion air flow rate to the flow rate required for combustion;

[0013] (3) Open the low-pressure natural gas supply valve, test the ignition stability, and perform the ignition operation; use the ignition electrode to ignite, measure and record the ignition time, fuel, combustion air pressure, temperature and flow rate at different ignition energies (2000V~7000V); perform automatic ignition once every 3min~5min, perform no less than 10 ignitions in total, and the single ignition time is ≤5s;

[0014] (4) After the low-pressure natural gas and combustion air are ignited and burned, they enter the rotary kiln. The low-pressure natural gas and combustion air are fully mixed in the mixing zone and burned evenly. The flue gas temperature range is 1800℃~2000℃.

[0015] (5) To test the stability of combustion, under the maximum allowable air volume, gradually increase the air and fuel supply until abnormal combustion occurs (the flame monitor cannot detect the flame). Measure and record the natural gas flow rate, air flow rate, flue gas composition, and furnace temperature, etc.; to maintain stable combustion of the burner, gradually and alternately reduce the fuel and air supply until the flame is unstable; measure and record the natural gas flow rate, air flow rate, flue gas composition, and furnace temperature, etc.; when the burner is burning fuel normally within its load regulation range, the CO2 content change in the flue gas should not exceed ±1.5% when monitored by the flue gas analyzer.

[0016] (6) Adjust the position of the high-pressure natural gas nozzle;

[0017] (7) After the flame is uniform and stable, high-pressure natural gas enters the rotary kiln through the high-pressure natural gas nozzle, causing the natural gas to burn under high heat intensity and form high-temperature flue gas. The flow velocity of the high-temperature flue gas is 200m / s~300m / s, and the flue gas temperature range is 2000℃~2200℃. As the low-pressure natural gas produces a high-temperature and high-speed airflow after burning, high-pressure natural gas is injected into the middle of the airflow. The high-speed airflow uses a large amount of kinetic energy to wrap the natural gas and send it deep into the rotary kiln for combustion. The high-temperature and high-speed airflow, as the medium after burning, does not participate in combustion, isolates the internal fuel from the external air, and plays a role in stabilizing the flame. It will not cause the burner to detach, thereby effectively extending the length of the combustion flame.

[0018] Advantages of this invention:

[0019] (1) The central high-pressure natural gas combustion system and method of the present invention introduces high-pressure natural gas through the inner ring and low-pressure natural gas through the outer ring, and introduces combustion air between the two, so that the natural gas and the combustion-supporting gas are fully mixed, effectively extending the length of the combustion flame and enhancing the stability of the flame combustion.

[0020] (2) The central high-pressure natural gas combustion system and method of the present invention have a reasonable structure and strong scientific nature, realizing the efficient combustion and utilization of natural gas. In addition, it provides a design scheme to improve combustion efficiency, thereby improving energy utilization and productivity. Attached Figure Description

[0021] Figure 1 This is a front view of the structure of the central high-pressure natural gas combustion system of the present invention.

[0022] Figure 2 This is a side view of the structure of the central high-pressure natural gas combustion system of the present invention. Detailed Implementation

[0023] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0024] like Figure 1 As shown, the central high-pressure natural gas combustion system of the present invention is characterized by comprising a three-layer sleeve-type integral structure consisting of an outer sleeve, a middle sleeve, and an inner ring. The outer sleeve mainly consists of a low-pressure natural gas channel 2 formed by the inner wall of the outer ring 3 and the outer wall of the secondary outer ring 1, through which low-pressure natural gas is introduced. The middle sleeve mainly consists of a combustion air channel 5 formed by the inner wall of the secondary outer ring 1 and the outer wall of the high-pressure natural gas nozzle 4, through which combustion air is introduced. The inner ring is provided with a high-pressure natural gas channel 6, through which high-pressure natural gas is introduced into the flame via the high-pressure natural gas nozzle 4.

[0025] The central high-pressure burner has a combustion capacity of 100 kcal / h, and its parameters are shown in Table 1. For large industrial rotary kilns, the combustion capacity is generally above 3000 kcal / h.

[0026] Table 1 Parameters of the Central High-Pressure Burner

[0027]

[0028] The total natural gas flow rate is 120m³. 3 The ratio of low-pressure natural gas was changed to 0.1, 0.15, 0.2, 0.25, and 0.3 per hour. When the low-pressure natural gas ratio was 0.1, the flame length fluctuated between 4.99m and 5.26m, and the flame radius fluctuated between 0.24m and 0.44m. When the low-pressure natural gas ratio was 0.2, the flame length fluctuated between 4.74m and 4.85m, and the flame radius fluctuated between 0.21m and 0.27m, with reduced flame fluctuation. When the low-pressure natural gas ratio was 0.3, the flame length fluctuated between 4.18m and 4.24m, and the flame radius fluctuated between 0.14m and 0.2m.

[0029] The high-pressure natural gas nozzle 4 is equipped with a movable adjusting spring at its end, allowing for free adjustment of the nozzle height while maintaining stability. The telescopic rod employs a movable spring device, with an adjusting screw at the bottom of the spring to allow for flexible height changes and maintain stability at various heights. The high-pressure natural gas nozzle is made of high-temperature and corrosion-resistant materials.

[0030] The high-pressure natural gas nozzle 4 is made of high-temperature and corrosion-resistant materials.

[0031] The combustion flame produced by mixing low-pressure natural gas and combustion air is on the same central axis as the combustion flame produced by mixing high-pressure natural gas and combustion air.

[0032] The high-temperature flue gas ejected by the high-speed burner can draw in a large amount of lower-temperature flue gas from inside the kiln, creating a strong flue gas recirculation and stirring effect, which makes the temperature distribution inside the kiln uniform and is very beneficial for the uniform roasting of pellets. Depending on the ejection velocity, the amount of recirculated flue gas varies, ranging from 20 to 300 times.

[0033] Low-pressure natural gas with a low flow rate mixes more easily with primary combustion air, producing a stable and high-quality flame. The relatively high-speed, high-pressure natural gas introduced through the inner ring effectively prevents flame detachment and maximizes the flame length. Furthermore, the rotary kiln's wide heat load adjustment range and convective heat transfer-based operation broaden its applicability.

[0034] A combustion method utilizing a central high-pressure natural gas combustion system, characterized by comprising:

[0035] (1) Open the corresponding natural gas valve and perform other gas supply operations to confirm that the natural gas has been delivered to the burner nozzle, and ensure that the natural gas pressure reduction system is safe and reliable, the pressure in front of the burner is stable at 5 kPa, and ensure that the combustion air passage is unobstructed.

[0036] (2) Turn on the combustion air blower, confirm that the combustion air system is operating normally, and pre-adjust the combustion air flow rate to the flow rate required for combustion;

[0037] (3) Open the low-pressure natural gas supply valve, test the ignition stability, and perform the ignition operation; use the ignition electrode to ignite, measure and record the ignition time, fuel, combustion air pressure, temperature and flow rate at different ignition energies (2000V~7000V); perform automatic ignition once every 3min~5min, perform no less than 10 ignitions in total, and the single ignition time is ≤5s;

[0038] (4) After the low-pressure natural gas and combustion air are ignited and burned, they enter the rotary kiln. The low-pressure natural gas and combustion air are fully mixed in the mixing zone and burned evenly. The flue gas temperature range is 1800℃~2000℃.

[0039] (5) To test the stability of combustion, under the maximum allowable air volume, gradually increase the air and fuel supply until abnormal combustion occurs (the flame monitor cannot detect the flame). Measure and record the natural gas flow rate, air flow rate, flue gas composition, and furnace temperature, etc.; to maintain stable combustion of the burner, gradually and alternately reduce the fuel and air supply until the flame is unstable; measure and record the natural gas flow rate, air flow rate, flue gas composition, and furnace temperature, etc.; when the burner is burning fuel normally within its load regulation range, the CO2 content change in the flue gas should not exceed ±1.5% when monitored by the flue gas analyzer.

[0040] (6) Adjust the position of the high-pressure natural gas nozzle 4;

[0041] (7) After the flame is uniform and stable, high-pressure natural gas enters the rotary kiln through the high-pressure natural gas nozzle 4, so that the natural gas burns under high heat intensity to form high-temperature flue gas. The flow velocity of the high-temperature flue gas is 200m / s~300m / s, and the flue gas temperature range is 2000℃~2200℃. As the low-pressure natural gas produces a high-temperature and high-speed airflow after burning, high-pressure natural gas is injected in the middle of the airflow. Using the large amount of kinetic energy of the high-speed airflow, the natural gas is wrapped and sent into the depth of the rotary kiln for combustion. The high-temperature and high-speed airflow, as the medium after burning, does not participate in the combustion, isolates the internal fuel from the external air, and plays a role in stabilizing the flame. It will not cause the burner to detach, thereby effectively extending the length of the combustion flame.

[0042] This invention proposes a central high-pressure natural gas combustion system and method, characterized by the central introduction of high-pressure natural gas. The burner is optimized to effectively extend the flame length and improve energy utilization and productivity.

[0043] The central high-pressure natural gas combustion system and method of the present invention introduces high-pressure natural gas through an inner ring and low-pressure natural gas through an outer ring, with combustion air introduced between them, so that the natural gas and combustion-supporting gas are fully mixed, effectively extending the length of the combustion flame and enhancing the stability of the flame combustion. The present invention has a reasonable structure and strong scientific nature, realizing the efficient combustion and utilization of natural gas. In addition, it provides a design scheme to improve combustion energy efficiency, thereby improving energy utilization and productivity.

Claims

1. A combustion method using a central high pressure natural gas combustion system, characterized by include (1) Open the corresponding valve for natural gas supply to confirm that natural gas has been delivered to the burner nozzle and ensure that the natural gas pressure reduction system is safe and reliable, the pressure in front of the burner is stable at 5 kPa, and ensure that the combustion air passage is unobstructed. (2) Turn on the combustion air blower, confirm that the combustion air system is operating normally, and pre-adjust the combustion air flow rate to the flow rate required for combustion; (3) Open the low-pressure natural gas supply valve, test the ignition stability, and perform the ignition operation; use the ignition electrode to ignite, measure and record the ignition time, fuel, combustion air pressure, temperature and flow rate under different ignition energies; perform automatic ignition once every 3 min to 5 min, and perform no less than 10 ignitions in total, with a single ignition time ≤ 5 s; (4) After the low-pressure natural gas and combustion air are ignited and burned, they enter the rotary kiln. The low-pressure natural gas and combustion air are fully mixed in the mixing zone and burned evenly. The flue gas temperature range is 1800 ℃~2000 ℃. (5) To test the stability of combustion, under the maximum allowable air volume, gradually increase the air and fuel supply until the flame detector can no longer detect the flame. At this time, measure and record the natural gas flow rate, air flow rate, flue gas composition, and furnace temperature. To maintain stable combustion in the burner, gradually and alternately reduce the fuel and air supply until the flame is unstable. Measure and record the natural gas flow rate, air flow rate, flue gas composition, and furnace temperature. When the burner is burning fuel normally within its load regulation range, the CO2 content change in the flue gas should not exceed ±1.5% as monitored by the flue gas analyzer. (6) Adjust the position of the high-pressure natural gas nozzle; (7) After the flame is uniform and stable, high-pressure natural gas enters the rotary kiln through the high-pressure natural gas nozzle, so that the natural gas burns under high heat intensity to form high-temperature flue gas. The flow velocity of the high-temperature flue gas is 200 m / s to 300 m / s, and the flue gas temperature range is 2000 ℃ to 2200 ℃. Since the low-pressure natural gas produces a high-temperature and high-speed airflow after burning, high-pressure natural gas is injected in the middle of the airflow. The high-speed airflow uses a lot of kinetic energy to wrap the natural gas and send it deep into the rotary kiln for combustion. The high-temperature and high-speed airflow is the medium after burning and does not participate in combustion. It isolates the internal fuel from the external air, plays a role in stabilizing the flame, and will not cause the burner to detach, thereby effectively extending the length of the combustion flame. The central high-pressure natural gas combustion system includes a three-layer sleeve-type integral structure consisting of an outer sleeve, a middle sleeve, and an inner ring. The outer sleeve is a low-pressure natural gas channel formed by the inner wall of the outer ring and the outer wall of the secondary outer ring, through which low-pressure natural gas is introduced. The middle sleeve is a combustion air channel formed by the inner wall of the secondary outer ring and the outer wall of the high-pressure natural gas nozzle, through which combustion air is introduced. The inner ring is equipped with a high-pressure natural gas channel, through which high-pressure natural gas is introduced into the flame via the high-pressure natural gas nozzle.

2. The combustion method using a central high-pressure natural gas combustion system according to claim 1, characterized in that... The outer diameter of the high-pressure natural gas channel is 1 / 2 to 1 / 5 of the outer diameter of the low-pressure natural gas channel. The natural gas pressure of the low-pressure natural gas channel is 0.2 kPa to 0.8 kPa, and the natural gas pressure of the high-pressure natural gas channel is 4 kPa to 5 kPa.

3. The combustion method using a central high-pressure natural gas combustion system according to claim 1, characterized in that... The high-pressure natural gas nozzle is equipped with a movable adjusting spring at its end, and the high-pressure natural gas nozzle is made of high-temperature and corrosion-resistant materials.

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