In gas boilers, is natural gas burning or exploding?

Why isn’t anyone answering? Please help! Why doesn’t natural gas explode in a boiler? ? ? ? ?

When the oxygen content in the boiler exhaust is 0, 9.1% by volume of natural gas falls within the explosive range (the volume percentage of natural gas remains within the explosive range when the exhaust oxygen content is between 3% and 5%)； Does the oxygen content in the exhaust gas refer to that of the exhaust gas after combustion, or that of the exhaust gas before combustion?

First, you haven’t understood the concepts of deflagration and combustion, as well as detonation. Second, the flame during the combustion phase can be divided into several sections, with varying oxygen contents in each section. Third, it’s not enough to only look at the oxygen content in the furnace or the exhaust gases; what’s important is to consider the oxygen content ahead of the flame. There’s so much to say about this.

Is the combustion chamber in this boiler of the deflagration type?

Gas and air are in the same proportion. Combustion: It is in a constant steady state, with pressure remaining unchanged; the amount of gas that enters is expelled after combustion. Detonation or deflagration is unsteady-state, with a short duration and sudden pressure changes. Conduct an experiment: use a container that is not sealed; when gas and air are introduced into it, the mixture can burn and smoke will be emitted. And if the container is sealed and already contains a mixture of gas and air, ignition will cause an explosion. Just like in internal combustion engines, small tricycles make a humming sound; all of these are considered to be cases of deflagration. In other words, during combustion, chemical energy is converted only into thermal energy. But deflagration needs to be converted into kinetic energy (first it’s thermal energy; due to energy-mass equivalence, only part of it becomes kinetic energy). In a boiler, only thermal energy is required, not kinetic energy; moreover, pressure changes caused by kinetic energy have a decisive impact on the safety of the boiler, therefore the furnace must be a space with a constant pressure. How to maintain this condition is the relationship between the combustion rate and air intake that needs to be considered during design.

The difference between explosion and combustion is probably the speed of combustion; it’s mentioned in the book

I’ve learned it! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !

Both combustion and explosion are essentially oxidation reactions of combustible substances in air. The difference lies in the different oxidation rates. Combustible materials, oxidizers, and ignition sources are the three basic conditions for combustion and explosion, collectively known as the three elements. Combustion is not the same as explosion, as the combustion rate remains constant and heat is released in a timely manner, whereas an explosion is a process in which energy is accumulated over an instant or a very short period before being released – this is the difference between combustion and explosion.

Thank you for your answer! According to the information I’ve reviewed, the process in boilers where combustible gases are mixed with air in advance and then burned is called flameless combustion. Explosions and deflagrations are both phenomena that occur when explosive gas mixtures come into contact with fire. So can I understand it this way: explosions and deflagrations of combustible gases both fall under the category of flameless combustion, with explosions being flameless combustion that occurs in enclosed spaces, and deflagrations being flameless combustion that occurs in open spaces? Boilers, on the other hand, represent a continuous flameless combustion process in an open space (that is, a continuous deflagration process).

It is the oxygen content in the exhaust gases after combustion.