Overview of technical principles of flameless combustion

Overview of technical principles of flameless combustionHhaBoiler Burner
1、 Method for judging flameless combustion state.HhaBoiler Burner
There is no very clear specification for the definition of flameless combustion state in the world. At present, what we agree with is the research of Wunning and his son. Through a large number of experiments, they have obtained the relationship between the internal circulation rate and temperature of flue gas when mixing and combustion are conducted simultaneously in the diffusion combustion mode.HhaBoiler Burner
The axial evolution and radial diffusion of fuel jet and oxidizer jet lead to the surrounding air entrainment, which gradually dilutes the combustion products and gases that do not participate in the reaction in the central area of the jet and reaches the "low oxygen" combustion state.HhaBoiler Burner
In addition to these, there are other judging methods. For example, temperature rise is used to determine whether combustion is flameless. Kumar et al. believed that after the normalization of the combustion process, the temperature change in the reactor is about 15%, which can be defined as flameless combustion. Antonio Lavaliere et al. used the inlet temperature and temperature rise to describe the combustion condition. The study also concluded that the inlet temperature is lower than the auto-ignition temperature and the temperature rise is greater than the inlet temperature, which is called feedback combustion. The process of the inlet temperature is higher than its inlet temperature, which is called high-temperature combustion. The inlet temperature is higher than its inlet temperature, which is also called flameless combustion.HhaBoiler Burner
2、 Flameless combustion system.HhaBoiler Burner
In the absence of external heat sources, the reactants are heated to more than 1000 ℃ by recycling the waste heat of combustion flue gas or high-temperature waste heat. The flue gas regulation process in the furnace controls the mixing of fuel, air and flue gas. The volume fraction of oxygen in the combustion area of the furnace is 2% - 5%. The fire boundary extends to the whole furnace, which makes the furnace temperature evenly distributed, greatly improves the combustion efficiency and utilization rate, and forms a new combustion mode different from the traditional luminous flame.HhaBoiler Burner
3、 Flameless combustion characteristics.HhaBoiler Burner
1. High temperature and low oxygen are the basic conditions for achieving flameless combustion. Before reaction, the oxidant should be preheated to reach a certain high temperature or fully preheated, so that the temperature at any position of the furnace is greater than the fuel self-ignition point when the furnace is burning;HhaBoiler Burner
2. The fuel and oxidant shall be fully diluted by such methods as entrainment by high-speed jet or backflow by special structure of burner, and dilution gas filling, so as to keep the oxygen concentration in combustion reaction zone between 2% and 15% as far as possible;HhaBoiler Burner
3. In the flameless combustion mode, the combustion is "soft" and there is no combustion noise. The combustion space spreads over a large range, making the temperature distribution of the whole space uniform and reducing the pollutant emission.HhaBoiler Burner
4、 Realize flameless combustion path.HhaBoiler Burner
1. Fill in nitrogen.HhaBoiler Burner
2. High-speed jet.HhaBoiler Burner
3. Special combustion chamber structure.