What are the flow meters used to measure the airflow in coke ovens?

In most cases, elliptical orifice plates or elbow flow meters are used to measure coke oven gas;

There are various measurement methods; in addition to using orifice plates with elliptical openings or elbow flow meters, venturi tubes or laminar flow probes can also be used for measurement. During use, changes in the composition of coke oven gas as well as temperature and pressure compensation need to be taken into account.

What are the flow meters used to measure the airflow in coke ovens? Is its display correct when running on nitrogen? What is the magnitude of the error? If a throttling device is used to measure flow, the error is quite large; what do you think about using vortex flow meters instead? I have no practical experience; this is just a suggestion!

We use various methods for measuring the flow rate of coke oven gas; here is a brief overview: 1. Use of orifice plates: ① Standard orifice plates: These are hardly ever used, having been employed only once due to an error in the engineering design. The performance of such orifice plates can be imagined – since coke oven gas consists of multiple components, substances such as naphthalene, benzene, and ammonia adhere to the edges of the orifice plates, making accurate measurement impossible. These plates must be cleaned every year； ②Using elliptical orifices is basically feasible, but attention must be paid to the method of pressure sampling. Pressure sampling via corner connections or flanges often results in clogged sampling holes; it is better to use a radial distance-based sampling method (i.e., D–1/2D). Through calculations, we have changed the sampling method to this radial distance approach, and the results have been good. ③ 2. Use of elbow flow meters: I believe this is not a viable option – it’s better to avoid them. Although such meters do result in less pressure loss of the fluid medium, the pressure of coke oven gas is already very low; as a result, the actual differential pressure across the elbow used for pressure measurement is very small. The maximum differential pressure is generally below 500 Pa, and in cases of normal operating flow rates, it is usually below 100 Pa. This leads to unstable data collection. Based on its working principle, a bent-tube flow meter is best suited for measuring gas media that have a high operating pressure ； 3. Measurement using a venturi tube or a flow meter (probe): It can be used. 4. V-shaped cone: We have used it; to be honest, it’s best not to use it with coke oven gas. The reasons are as follows: There are several reasons why the V-shaped cone should be used with caution: a) Dirty media, such as untreated blast furnace gas or coke oven gas. The pressure tap on the cone is often clogged, requiring a lot of repetitive work ； b Low-temperature, humid media: The problem is blockage; especially in the north, freezing causes blockages. Steam is used to clean the negative-pressure pipelines, but blockages occur again after a short time ； Use c with caution in applications that require high precision; for example, it is not suitable for energy billing purposes. 5. Annular orifice plates: They perform well when high precision is not required! It is also a radial distance pressure tapping method. The original design was for measuring coke oven gas; now that nitrogen is being used, the measurements will definitely be inaccurate. Hehe, I think what you mean by using nitrogen is that it’s used for purging when the coke oven gas is not in use for maintenance purposes. As for the extent of the error, it can be calculated. It’s too late tonight; if you’re interested, we can discuss this further later. Additionally, steam is the best choice for purging coke oven gas! Well, that’s enough for now; it’s time to rest, haha

The 5th floor is really professional; I learned a lot there!

I recommend using vortex flow meters, those with temperature and pressure compensation

Flow rate is closely related to density; when your flow meter is calibrated using coke oven gas, it will inevitably have errors when used to measure nitrogen. The magnitude of these errors is roughly proportional to the square root of the ratio of their densities.

I am also working on selecting a flow meter, and I need to take into account factors such as the gas composition, pressure, flow rate, and operating environment. It’s quite difficult to make a choice. Could you please advise me, experts on the 5th floor: my plant’s gas contains water, dust, and tar, the pipelines experience vibration, and the flow rate is low. What kind of flow meter should I choose?