Causes of ignition tube burn-through failure
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A 75t/h circulating fluidized bed was put into operation in 2014, using 0# diesel and employing a bottom-fired ignition method. Fault symptom: The outer wall of the ignition cylinder turns red every time it is ignited. Both furnaces experienced the accident of the ignition tube burning through on two occasions each. Inspections after shutting down the furnace revealed carbon buildup inside the ignition cylinder (see the location indicated in the diagram). Process description: After ignition, the mixing air was fully opened, the ignition air was slightly reduced; the flame monitor showed normal readings, and observations through the viewing port were also normal, with no significant black smoke observed. The designed oil pressure is 1.5 Mpa, while the actual pressure during use ranges from 0.6 to 1.5 Mpa (in most cases, the oil pressure can only be kept below 0.8 Mpa). When coal is added to increase the oil pressure, the outer wall heats up significantly. An atomization test was conducted before each ignition (we had no experience in this area and relied solely on visual judgment). Possible reasons: 1. The pore size of the atomizer’s misting element is too large (according to the boiler manufacturer’s specifications, the pore sizes are 0.8 mm, 1.0 mm, 1.6 mm, and 2.0 mm; parameters from misting tests were recorded, with a designed fuel supply rate of 200 kg/h). In practice, however, a pore size of 2.0 mm is used (there is no misting element, only a swirl plate with a pore size of 2.0 mm), which results in poor misting. As the oil pressure increases, the amount of oil supplied rises sharply, leading to excessive carbon buildup in the front section of the ignition chamber due to incomplete combustion and uneven flow. This causes severe deviation of the flame, resulting in damage to the refractory materials and the outer wall. ——For the turnkey project, the installation unit does not accept this explanation; it insists that there is a problem with the air distribution. 2. The incorrect installation angle of the flame stabilizer causes the internal flame to deviate. 3. The air distribution technique is not mastered; as a result, the pressure inside the ignition cylinder is lower than that inside the water-cooled air chamber, leading to carbon buildup due to incomplete combustion. The ratio of ignition air to mixing air is incorrect. ——I don’t quite agree with this; the monitoring points are only the temperature of the water-cooled air chamber and the oil pressure. This issue may occur in the initial stage, with black smoke coming out. Setting the mixed air flow to maximum helps cool the cylinder wall. I would appreciate it if experienced friends could analyze the carbon buildup inside the lighter and the perforations on its outer wall, and provide suggestions for improvement.
I’ve encountered situations where the burner gets damaged due to the boiler being started up; it’s not something that can be resolved with just a few words – a solution needs to be determined based on the actual circumstances. Please add me on QQ at 1390099052; it’s about burners
There are certain issues with the burner itself; this is a Pinonic fuel burner
This post was last edited by dongjiang1001 on 2015-1-9 at 17:10. Based on years of experience, I think the issue lies with the power output of the oil gun. I have previously modified similar oil guns by redesigning their misting nozzles; feel free to contact me via private message if you need help!
Hello, friend. After reading your reply to me, you’re being too kind. I’ve taken a look at your ignition air duct drawings and would like to share the following points with you: 1. I’m very familiar with the area that has been damaged; we experienced damage there before as well, and we replaced the steel plate and refractory materials at that time. Generally, when this area gets damaged, it is first the refractory material that falls off or large cracks appear; only then does the steel plate get carbonized, resulting in a large reddish area visible on the surface. I’m not sure what type of fire-resistant material you use; we use ceramic fiber compact blocks, and at that time, about 7 or 8 of them started to fall off. 2. The atomization experiment is always observed visually, no matter where it is conducted; therefore, it’s sufficient to be more rigorous during its execution. 3. The nebulization tablets must be cleaned carefully each time, and the carbon buildup on the nozzle of the oil gun also needs to be removed. I’m not very familiar with the specifications of your nebulization tablets; ours are much larger. The same goes for oil pressure; your parameters are relatively low. However, as long as full combustion is ensured and the wind temperature in front of the air chamber does not exceed the specified limits, try to keep it as close to the design value as possible. 4. The flame stabilizer should be installed vertically, with the fuel injector inserted perpendicularly at the center of the flame stabilizer. If the angle of the swirl vanes on the flame stabilizer matches that specified in the drawings, there should be no problems. 5. As for the air distribution issue, it’s hard to say for sure; the air volume must not be below the critical value for fluidization. There should be regulations regarding air pressure, as ensuring proper fluidization is a prerequisite for avoiding air stagnation.
We have manufactured many of these smoke generators that are installed under beds. Based on the information you provided, the most likely causes are as follows: 1. The atomization effect of the oil gun is poor. For such simple mechanical atomization oil guns, an atomization pressure of 1.5–2.0 MPa is required; too low a pressure results in poor atomization, which leads to incomplete combustion of diesel and subsequent carbon buildup； 2. The flue gas generator itself was not designed properly, resulting in unstable flames and localized high temperatures; the main issues lie in the flame stabilization cover of the oil gun and the air distribution system. If your company needs renovation, please contact me. 80823993@qq.com Please indicate HaiChuan