Optimizing combustion performance by controlling density of the highly permeable SiC fiber porous media

The highly permeable SiC fiber porous media (FPM) were prepared with impressive combustion performance by optimizing the density. The fiber paper was firstly prepared by suction filtration of chopped SiC fibers. Different layers of fiber paper were laminated to the same thickness and then BN interfaces and SiC shells were deposited to weld the fibers, resulting in the FPM with different densities. The permeability, thermal physical properties and combustion performance of the FPM with different densities were studied. Results show that two types of pore structures exist in the FPM. One is the smaller pores near the fiber joints while the other is larger pores far from that. The increase in lamination layer will result in decreased porosity and pore size. Meantime, as the lamination layer increases, thermal diffusivity decreases while the infrared radiation coefficient, thermal capacity and thermal conductivity increase. In the combustion tests, the FPM with 5 layers of fiber paper shows excellent combustion effect, high gas conversion efficiency and low NO_x emission. The combustion temperature is about 800 °C. The NO_x and CO content in the flue gas is 3 ppm and 6 ppm, respectively, at a low emission level.