How to measure exhaust gas flow rate and velocity? What instrument?

Both flow rate and velocity are measured using pitot tubes, but due to the large cross-section of the flue, such measurements are very difficult and inaccurate! Both before and after the modification of the branch flue and the main flue, there are temperature and pressure measurement holes available for use! However, measuring flow rate requires setting up several measurement points across the entire cross-section of the flue, based on the theoretical velocity distribution, and then calculating a weighted average – which is very difficult! !

This post was last edited by yggswl on 2015-7-7 18:19. Thank you; it’s clear you understand the matter. Is there no other instrument that displays the information directly? I think there should be one, right? A handheld, portable instrument that provides relatively accurate readings

Modern pitot tubes all come with electronic display instruments

Could you please take a look and tell me which algorithm is correct? It would be great to have an example; http://bbs.hcbbs.com/thread-1417325-1-1.html

The gas flow rate in the coal gas pipes in the basement is easy to measure and calculate. Once the gas flow rate is known, it’s simply a matter of calculating the amount of exhaust gas based on the composition of the gas and the air excess factor Why go to the trouble of measuring exhaust gas flow? Besides, what’s the point?

Considering that exhaust gas may contain impurities, etc., vortex flow meters can be used···········

I guess this friend is planning to carry out exhaust gas desulfurization and denitration, or to make use of waste heat! You are absolutely right; in fact, the amount of exhaust gas can be calculated using the amount of gas used and the air excess factor! !

I’ve done the calculations, but the errors are incredibly large. The flow rate of coke oven gas is 25,000; based on these calculations, the volume of wet exhaust gas is 25,000*5.55 = 138,750. However, the flow rate measured at the chimney indicates that the volume of flue gas is actually around 400,000 – a huge difference. The oxygen content is over 10%. I sometimes think that the engineers at coke oven plants might only focus on ensuring an adequate air excess factor during combustion within the coke ovens. But after combustion, as the exhaust gas reaches the valves and subsequent emission systems, its volume increases significantly. Coke plants don’t pay enough attention to this increase in exhaust gas volume. Yet, in projects related to desulfurization, denitrification, and waste heat recovery, the substantial increase in the volume of flue gas leads to greatly increased costs for such projects. I’m not sure if my reasoning is correct

Then the air excess factor for the main flue should be around 1.8

In coke ovens, especially in their later stages of use, leakage is very severe. The amount of waste gas generated cannot be simply calculated based on the air excess factor; leakage from the partition walls, the main walls of the regenerator, and poor sealing at the valves can all lead to an increase in the amount of waste gas as well as an increase in its oxygen content. It is simple to prove this: measure the oxygen content in the downward airflow of the vertical flue, the oxygen content in the small flue, and the oxygen content at the main flue, and thereby determine which part of the coke oven has severe air leakage. It’s difficult to determine the amount of exhaust gas, and this indeed has a significant impact on subsequent desulfurization and denitrification processes.