Before we understand what is hydrogen-rich exhaust, let's talk about hydrogen. Compared with methane, the main component of gasoline and natural gas, hydrogen has a high energy per unit mass, a wide combustible limit, and a fast burning rate, which is a good fuel.
1. The unit mass of hydrogen has a high calorific value, which is about 2.7 times of the low calorific value of gasoline.
2. The ignition energy of hydrogen is very low, and the burning speed is fast, which is 7 times faster than the flame propagation speed of gasoline.
3. The explosion of hydrogen in the air is wide, ranging from 4% to 75%, and the explosion range in oxygen is 4.5%-95%, so the hydrogen-air mixture is prone to deflagration. In addition, the burning speed of hydrogen is very fast, which is easy to cause tempering, causing the gas pipeline to explode, forming a shock wave, causing casualties to personnel and high risk.
4. The diffusion coefficient of hydrogen in the air is very large, 12 times that of gasoline, so hydrogen is easier to mix with air to form a uniform mixture than gasoline.
5. Less harmful emissions. The main product of hydrogen combustion is water, which does not produce carbon monoxide (CO) and hydrocarbons (HC).
So, the question is, what is hydrogen-rich exhaust?
The main components of the hydrogen-rich tail gas are hydrogen and methane. The density and low calorific value decrease with the increase of hydrogen content; the theoretical combustion temperature increases with the increase of hydrogen content; the flame propagation speed increases exponentially with the increase of hydrogen content, and the change is the most intense. Therefore, the density, low calorific value, theoretical combustion temperature and flame propagation speed of the hydrogen-rich tail gas are gradually approached to pure hydrogen with the increase of the hydrogen content.
The advantages of hydrogen-rich tail gas as a fuel are obvious. The pollution is low, and the advantages of hydrogen are all available. However, there is a disadvantage that tempering occurs when burning. Therefore, the general burner is not suitable for using hydrogen-rich tail gas as a fuel, and if it is necessary to use it, a special anti-tempering design is required.
——Author：ebico