20KW Combustion Experimental And NO_x Emissions Characteristics Of MILD Combustion

MILD combustion is a new energy saving and environmental protection technology.MILD combustion is a technology with high combustion efficiency, strong heat radiationand low NOx emissions. This article specially concerned on the combustion characteristicsand the modeling/design theory of MILD combustion, by aid of both experimental andnumerical investigations.The design and manufacture of the20kW MILD combustion facility is introduced. TheMILD combustion experiments for natural gas and pulverized coal had been taken toexplore the combustion characteristics of MILD combustion under different type of fuel.The organization of MILD combustion, distribution characteristic of flame temperature andNOx emission are mainly analyzed. The results indicate that MILD combustion can berealized by diffusion combustion under gaseous fuel and solid particles fuel such aspulverized coal and biomass. The NOX emissions had been suppressed in methane andpulverized coal MILD combustion and the NOX emissions was much lower than theconventional combustion. Comparing to the gaseous MILD combustion, the realization ofMILD combustion under solid particles fuel such as pulverized coal and biomass demandsmore strict organization condition. First, solid particles fuel combustion require moreintense level of furnace flue gas entrainment to overcome the influence of gravity. Second,the particle diameter of the solid particle fuel may also have great affect. What is more, thecontinuation of the fuel feeding is a great challenge to overcome.The low emission of NOx is a main advantage of MILD combustion. To understand theformation of nitrogen oxides from fuel-N, the investment of both experimental andnumerical had been taken. A simulation study of methane+air flames doped with ammonia(10000ppm of the fuel) is reported in the counter-flow diffusion flame model. What’s more,the CH4-NH3MILD combustion experiment had been taken for further research. The resultdemonstrate that the reduction reactions of the N radical at MILD condition are much moreintensity in comparison with that at AC condition. On the country, the oxidant reactions aremore intensity under AC condition. Meanwhile, the importance of the pathway NO→ N2O→N2under MILD condition is highlighted which is extremely weak underconventional combustion. These phenomena can be the reasons cause the reduction of NOxemissions in MILD combustion. The CH4-NH3MILD combustion experiment shows thatthe value of Fuel-NOX emissions under conventional combustion is about2~3times highthan which under MILD combustion. It demonstrates that the great advantage of Fuel-NOXemissions reduction characteristic under MILD combustion. During gaseous fuel MILDcombustion, we found that there is a critical equivalence ratio under MILD combustion.The CO and NO concentration increased with the increased of the equivalence ratio. Thevalue of the critical equivalence ratio under gaseous fuel MILD combustion were at a rangeof0.8~0.9.