Operating noise issues in methanol converters using coke oven gas
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Dear colleagues: Our 150,000-ton methanol production plant using coke oven gas has been in normal operation for over a year now. During normal operation, the converter emits relatively loud noises; there are mainly two types of such noises: 1. There is a sharp and loud sound coming from the elbow fitting connected to the burner, located after the check valve in the oxygen pipeline at the top – it sounds similar to whistling. 2. The intermittent airflow impact sound at the bottom of the converter is quite noticeable. Our current load is around 93% of the designed load; we have not increased it further due to the loud noise generated by the converter. Note: When the converter is operating at a low load, there is basically no noise at the top or bottom; however, as the operating load reaches over 85% of the design value, the noise becomes increasingly noticeable. I would like to ask everyone: what are the main reasons for this, and how should it be checked and dealt with? If it cannot be processed, what aspects should be given special attention?
Let me guess: Is the first reason sharp noises being produced due to foreign objects or sharp edges at the elbows or flanges? This is consistent with what you said – low load results in no sound, while high volume leads to loud sound. Take it apart to take a look during maintenance. Regarding the second point, I have heard of a situation like that, but it is caused by an excessively high gas flow rate and low pressure; I’m not sure if that is the case here Also, check if the steam volume in the oxygen inlet pipeline is too high
1. The catalyst loading height is too high, resulting in limited space in the combustion chamber and incomplete combustion reactions; calculate the required combustion space and remove excess catalyst! 2. The methane content in coke oven gas is too high, exceeding 25%, which results in a vigorous combustion reaction! 3. The amount of steam added is too low; it is necessary to maintain an appropriate water-vapor ratio of around 0.75, and a water-carbon ratio of around 2.5! 4. The pressure drop for each material is too high; adjust it to around 0.2 MPA! 5. The oxygen purity is insufficient; the purity of oxygen used for analysis and control should be greater than 99.97%. 6. Is the temperature at the outlet of the preheating furnace too low, resulting in small explosions in the combustion chamber? 7. Increase the vapor in the oxygen and ensure thorough mixing; give it a try and see how it goes
If the burner is damaged, the furnace should be shut down and the burner removed for inspection.
During the parking for maintenance, we removed the burner and the check valves and elbows of the oxygen pipelines at the top and inspected them several times; no problems were found； What you mentioned about low gas pressure and high flow rate is somewhat true; indeed, the pressure in our conversion system is lower than the designed pressure, by about 20%. Additionally, what is the optimal amount to control for the oxygen-enriched steam? We are roughly at: oxygen/vapor = around 1.4.
1. There should be no issues with the combustion space; it’s basically the same as what was designed by the design institute, around 4800–4900 mm. 2. The methane content in our actual coke oven gas is not high, generally ranging around 21-22%. 3. Our water vapor ratio is indeed not high, around 0.4. (But it’s not clear whether this is the reason; if the water vapor ratio is increased, the carbon dioxide content in the converted gas rises, so we keep the water vapor ratio at a relatively low level.) 4. The pressure drops for each material are currently as follows: oxygen-gas = 0.25–0.3 MPa ； Steam-oxygen = around 0.15 MPa. 5. The oxygen purity analysis has basically been problem-free. 6. The outlet temperature of the preheating furnace should be maintained between 530–550°C. 7. What is the optimal flow rate for the oxygen-enriched steam? We have been keeping it at around oxygen/steam = 1.4.
Reply to 6# tzy_02598: From what you’ve described, it seems to be the process designed by Huahua No.2 Hospital, right? There should be no major issues with the indicators; it’s just that the water vapor ratio is too low, which makes carbon deposition more likely. Is the sound coming from the curved part above produced by a metal burner? It is necessary to calculate the flow rate of the oxygen-vapor mixture to determine how much vapor should be mixed into the oxygen; the flow rate for non-metallic burners is 30 meters per second, while that for metallic burners is 70 meters per second. Personal suggestion.
Actually, the main issue is with the burner distributor in the conversion furnace; uneven gas distribution is causing the airflow noise. The original poster actually doesn’t need to worry; they can continue to increase the load.
Reply to 7# tzy_02598: Yours has high steam pressure while ours is only 0.68