Questions about burners

The proportional adjustment of the burner refers to the ratio of the maximum combustion capacity to the minimum combustion capacity under stable burner operation! ——That’s absolutely right. So, once the structure of the burner is determined, this ratio value depends only on the amount of gas supplied by the pipelines, and accordingly, it is related to the adjustment range of the control valves for the gas and air! Is my understanding correct? ————What you’re saying has basically nothing to do with the burner adjustment ratio. For a single burner (with the exception of combined burners, which are more complex and will not be discussed here), in the case of externally mixed gas burners, the thermal load for combustion generally does not exceed 1/5, while the adjustment ratio of a typical control valve is around 1/300. What happens if the pressure in the gas and air supply lines of the burner is too high or too low? I think that excessive gas pressure or a mixture velocity greater than the flame propagation speed can cause flame separation, while the opposite situation leads to backfire – is that correct? ——What you’re referring to is probably a gas burner. Flameout generally occurs only in externally mixed gas burners. Ordinary burners are equipped with flame stabilizing devices, and flameout happens when the gas flow rate is too high; however, pressure is not a definitive indicator of this phenomenon. This is because there is a limit to the spray velocity of the gas emitted by a typical nozzle; above this limit, no matter how high the pressure, the velocity does not increase any further. Backflow generally occurs in semi-premixed or fully premixed gas burners, and it happens when the injection velocity is lower than the flame propagation velocity. What happens to combustion if the air pressure is too high or too low? ——If the air pressure is too high and not adjusted, the excess air coefficient will increase, resulting in a reduced efficiency in heat utilization. Is the length of the flame adjusted by regulating air pressure when the gas is stable? ——The intensity of the flame is first related to the structure of the nozzle. Secondly, it is related to the supply pressure and quantity of the fuel gas; generally, when the supply quantity is high, both the flame diameter and flame length increase. When the combustion air coefficient is between 1 and 3, its impact is minimal. So how can a reasonable air excess factor be ensured? ——There are many ways to do this; generally, it is sufficient to measure the oxygen content in the combustion products. If complete combustion is to be ensured, then the length of the flame remains constant, right? ——On the condition of ensuring complete combustion, when the air excess factor is less than 3 and the combustion temperature is above 1000 degrees, the flame length remains essentially unchanged. When the air coefficient is greater than 3, the combustion rate decreases due to the lower temperature in the combustion zone, and the flame lengthens. Looking forward to everyone's advice! Thank you! This post was last edited by *ngefei on 2007-12-8 23:10]

“\"Proportional adjustment of the burner\" refers to the coordinated adjustment of fuel and air in the burner in a proportional manner. The ratio of the maximum combustion capacity to the minimum combustion capacity under stable combustion conditions refers to the \"burner load adjustment ratio\".

“\"Proportional adjustment of the burner\" refers to the coordinated adjustment of fuel and air in the burner in a proportional manner. Based on the above concepts, I can assume that if the amount of gas remains constant, then the ratio can be adjusted by controlling the amount of air, right? How can the air excess factor be ensured? (1.05-1.1) I believe there is only one optimal combustion condition for a burner with a fixed structure (taking a high-speed natural gas burner as an example); in this condition, the air excess coefficient lies between 1.05 and 1.1, right? I have encountered situations where an excessive amount of air blew out the flame. So, how much air is needed to blow out the flame? Is this related to the structure of the burner itself?

The flame length is first related to the structure of the nozzle. If I were to create two burners with different capabilities, I could also achieve flames of the same length by changing the size of the nozzle, right? A burner with a fixed structure can adjust the flame length by adjusting the gas volume and gas pressure, right? But does the burner’s capacity also change while adjusting the gas volume?

There are dedicated air-fuel ratio control valves; these valves come pre-set with basic parameters, and the ‘ratio’ is adjusted on-site according to actual conditions, in order to control the excess air coefficient required under different fuel supply levels. There are two types: pressure-controlled proportional valves and mechanical proportional valves. First, the air (fuel) supply pressure or valve opening is adjusted separately, after which the pressure of the fuel (air) or the valve opening is controlled by pressure (or by a proportional control mechanism). The standard operating condition of a burner with a defined structure is the designed operating condition. As for the \"best combustion condition,\" it depends on what you consider to be the best such condition. For some heating furnaces that require a high excess air coefficient or incomplete combustion, do you still think the ideal excess air coefficient lies between 1.05 and 1.1? It’s difficult to answer the question of why an excessive amount of air can extinguish the fire; it mainly comes down to on-site adjustments, and it’s somewhat related to, but not entirely dependent on, the structure of the burner. :Determining responsibility for problem P is a really tricky task. Under variable operating conditions, the flame length and diameter of a good burner should be adjustable (at a constant combustion capacity), and this is controlled by the burner’s air distribution regulator. A burner with a fixed structure can adjust the flame length by regulating the gas flow rate and gas pressure. The capacity of the burner will certainly change while adjusting the gas flow rate. I’d like to learn more about the various burners available at http://www.sminqing.cn/; although they are relatively simple, there are many different types of them. It’s not for advertising. :P, take another look at information on the thermal equipment and similar items for various types of heating furnaces.

Reply 1: This can generally be achieved, provided that the load differences between the burners are not too large. Additionally, the flame diameter also changes. Reply 2: The situation is usually as follows: first, the load range of the burner is specified; the burner is designed according to specific requirements, so there is generally a corresponding relationship between the load and the length and diameter of the flame. However, for some special types of burners, such as flameless burners, such a corresponding relationship does not exist. Last edited by *ngefei on 2007-12-13 13:53]

If by “adjustment of the burner ratio” you mean adjustment within a certain range, then there is nothing wrong with that. Due to certain practices in China, different people have varying concepts and understandings of this issue. The air coefficient is generally determined based on specific requirements. For burners at the top of reactors used in ammonia synthesis or methanol production, it is required that the residual oxygen content in the combustion products be below 3%, so the air coefficient is less than 1.1. For other types of tubular heating furnace burners, the air coefficient is usually between 1.3 and 1.5. Increasing the air coefficient helps to reduce high temperatures in the combustion zone and prevent localized overheating. In some hot blast furnaces, the air coefficient can be greater than 2; in some cases, it is even higher

Currently, there are two ways of adjusting burners: on-off control (discontinuous adjustment) and proportional control (continuous adjustment). On-off control means that the capacity of the burner changes in steps from ignition to full power, and it is generally used in small and medium-sized burners. The continuous control mode refers to the power of the burner varying continuously between full load and minimum load, thereby enabling optimal control. In the two-stage regulation, the output power is approximately 50%-70% in the first stage and 100% in the second stage. The continuously adjustable power range can reach 1:20. Proportional control is just one method of adjustment; the performance indicator for burners should be their capacity, that is, KJ/h. The above are my humble opinions; I look forward to your guidance.

What everyone has said is correct, but modern burner designs have higher requirements: a low excess air coefficient, complete combustion, a bright flame, good rigidity, and reduced formation of nitrogen oxides. As for the length and shape of the flame, it depends on the requirements of the heating furnace itself.

It’s a good article, but I’m not sure if it applies to the upper nozzle

This is a description of the basic performance of a burner, not limited to those with flames directed upward and mounted at the bottom.

This is related to the amount of gas and the volume of secondary air; one cannot focus solely on the burner.

1. There is a close relationship between the cooling method and the degree of protection; in particular, if water is not added in time at the moment of ignition, the burner will be damaged immediately. 2. There is room to improve the service life through better material selection. 3. Oxygen level regulation is important; controlling the oxygen content helps to extend the lifespan of the pilot burner. 4. Reasonable system control can extend the lifespan of the equipment.

The poster already mentioned when posting that the burner uses gas as fuel; it’s likely a gaseous fuel. For ordinary heating furnaces (tubular furnaces), their air coefficient is generally less than 1.4:1. A conventional hot air furnace is designed to produce hot air at a certain temperature; for example, the hot air used in drying devices has a different air coefficient than what you mentioned. This is especially true for hot air furnaces with forced ventilation where there is positive pressure inside the furnace. Taking natural gas as an example for fuel, if the temperature of the hot air required for drying is 700 degrees, you can calculate how much additional air is needed for combustion and temperature mixing; it is possible to achieve a temperature of 3 degrees or even higher, rather than it being impossible. The length of the flame is related to mixing, but the influence of furnace temperature cannot be ignored. In a conventional ammonia synthesis converter, it is easy to tell what the flame length is at the beginning of operation and what it is during normal use. Moreover, at the beginning of operation (when the furnace is cold), the thermal load on the burners is relatively low; during normal operation, this thermal load is higher. The flame length is also longer under normal operation compared to when the system is just starting up. Doesn’t this illustrate that point? This post was last edited by wuming on 2008-5-8 21:45.]