Analysis and solutions to the causes of the heating furnace burner licking the furnace tube

What is the impact on fuel or furnace when the fuel gas consumption is large in winter? Please explain the combustion quality problems that can be analyzed from the following influencing factors (provided that the heating furnace hardware does not change): 1. Changes in heating furnace load 2. Changes in fuel properties 3. Changes in fuel quantity 4. Changes in fuel pressure 5. Changes in combustion air quantity 6. Changes in combustion air temperature If the load becomes larger, more heat sources need to be input, exceeding the design conditions of the burner? After the burner nozzle opening is determined, changes in fuel properties have a greater impact on combustion quality, etc.

Thanks! The furnace underwent a burner renovation last year, and the design load has increased compared to before the renovation (the burner load is now surplus according to the design). It is designed to use natural gas as fuel. As the ambient temperature drops in winter, the fuel gas consumption increases by about 100Nm3/h, and the above phenomenon occurs.

I think it is caused by poor mixing of methane hydrogen and combustion air. 1. The flame increases, indicating that the fuel gas at the bottom is not fully burned and floats up under the action of buoyancy. During the floating process, it is constantly "looking for" oxygen to burn. At this time, the fuel speed is reduced, so the flame spreads and even burns in the furnace tube. 2. Possible solutions: 1) Is it possible to increase the gas pressure in front of the furnace appropriately to increase the fuel flow rate, which is beneficial to the mixing of fuel and air. Heavy fuel demand in winter may cause mains pressure to decrease ； 2) Open the wind deflector appropriately. 3) If necessary, improve the layout of the air duct at the bottom of the furnace (for example, forced ventilation). 4) Increase the size of the burner's air inlet to reduce the air inlet resistance loss. You can do the above methods 1) and 2) first. I have been engaged in the design of burners (for my own engineering use). Welcome to communicate and discuss.

Is the pressure in the furnace abnormal? Boilers generally maintain a slight negative pressure in the furnace, which is conducive to heat absorption. I think the phenomenon mentioned by the poster is that the pressure in the furnace is not well controlled, and it is necessary to adjust the air volume.

Blue Dot’s analysis also makes sense. It is recommended that the owner check the negative pressure of the radiant roof and the oxygen content of the flue gas at the radiant outlet. The normal values ​​of the two should be -2mmH2O and 2~4% respectively.

Thank you friends! The pressure in the furnace is about -80KPa, and the oxygen content of the flue gas is 3.2%.

The air supply to the burner is insufficient and the air duct layout needs to be improved.

The fuel gas consumption increases to a certain level and the furnace buzzes? I don’t have much exposure to heating furnaces in the chemical industry. In metallurgical heating furnaces, the general noise is caused by flame combustion and high-speed gas flow, especially the high-speed burner, which makes a lot of noise due to the high ignition and ejection speed. As the amount of gas increases, the amount of high-temperature smoke also increases. The outlet area remains unchanged but the speed increases, causing buzzing?

-The negative pressure of 80Pa refers to the radiation bottom, right? If it is a radiant roof, the negative pressure will be too high. You can tell me the temperature of the furnace and the approximate height of the radiation chamber, and I can calculate the pressure difference between the bottom and top of the furnace.

Furnace temperature: 670 degrees ； radiation chamber height: 16.9 meters. Thanks!

The negative pressure generated by the chimney effect of the radiation chamber itself is 15.5MMH2O, 152Pa. If the negative pressure at the top of the furnace is 80Pa, the negative pressure at the bottom of the furnace should be 232Pa. Doesn't it seem right? Is it a tube heating furnace?

The heating furnace we install is a cylindrical tube heating furnace with the burner at the bottom of the furnace and U-shaped coils arranged on the furnace wall. The fuel is natural gas (the pressure in front of the flow regulating valve is 0.2MPa and the pressure behind the valve is 0.1MPa). The negative pressure pressure measuring point is at the top of the radiation chamber. The oxygen content of the flue gas at the outlet of the radiation chamber is about 3.2%. It is equipped with a waste heat recovery system and forced ventilation.

Can you try to close the opening of the flue baffle of the convection outlet a little smaller? Approximately how much heat does each burner produce? What is the approximate size of the burner inlet? How many burners are there in total?

Open the bottom damper and the combustion will be sufficient.

study* After a while, the negative pressure of the heating furnace should be controlled between -10 and -40 Pa. Our installation is also a cylindrical tube heating furnace, which is similar to the previous owner's situation. However, because it is a furnace in the early 1980s, the facilities are relatively backward. In the past, we would only operate based on operating experience. This time, we installed a negative pressure gauge for maintenance. We will see how it goes after the construction starts. The pressure of gas before entering the furnace should be controlled at 4~1kgf/cm2

The pressure in the furnace is about -80KPa, and the oxygen content of the flue gas is 3.2%. -80pa is about the same. -20 - -50pa is best.