Abstract:
Abstract: Different structure and the different feeding mode burners affect the emission and the combustion efficiency of various biomass solid fuels. However, how the burner structure and feeding mode impact on the particle emissions is not clearly understood. To investigate this, an experiment was conducted to evaluate gas emissions from three types of feeders: the upper feeding type burner (type A), the horizontal feeding type burner (type B) and the bottom feeding type burner (type C), and types of solid biomass fuels: corn straw, cotton stalks and wood compressed into a cylindrical type (diameter, 8 mm, length, 10-30 mm) burned respectively at maximum power on each type of burner. The gas composition emitted was determined using SEMTECH (Sensors, U.S.) for the number and concentration of particulate from the three kinds of biomass solid fuel burned respectively from three burners via Electrical Low Pressure Impactor (ELPI). The particle size was catalogued into 12 classes, ranging from 0.003-10 μm. The number of particle size emitted and their corresponding mass distribution per second from the three burners were calculated. The experimental results showed that particle mass distribution from the three burners had two peaks respectively in the 5-7 (>0.165-0.637 μm) and 12 (>3.970-10.150 μm) levels accounting for the total particulate mass of 90%. For corn straw pellets in A, B, C type of burner combustion, PM 2.5 (PM below grade 10) accounted 68.5%, 70%, 51% for PM10 of particulate mass, respectively, in contrast to the cotton stalks pellets, which accounted 74.2%, 66.9%, 76.7% for PM10 of particulate mass. For wood pellets combustion in the three burners, on the other hand, PM2.5 accounted 61.8%, 67.8%, 68.1% for PM10 of particulate mass. As compared to the particle mass distribution, the number of particles distributed in three burners only had one peak. The most particulate numbers of corn straw and wood were in the 1-5 level in the type B burner, but in the 3-6 level in the type A and type C burner. The particle numbers of cotton straw was mainly in the 1-5 level in the type C burner, and in the 3-6 level in the type A and type B burner. Three kinds of burners had little influence on the distribution of the particle mass. The test results suggested that agriculture residues used as fuels needed to be burner specific. From the point of view of the total emissions of particulate matter, corn straw should be matched with the type B burner, cotton stalk and wood fuel should be matched with the type A burner. From the aspect of proportion of PM2.5 emission, corn straw fuel should be matched with the type C burner, cotton stalk should be matched with the type B burner, wood should be matched with the type A burner. In addition, the structure of biomass solid fuel burner may have following characteristics: Continuous feeding smoothly; equipped with active slag cleaning device and small slag wave; pressured air flow to ensure the high air ratio. The research provided reference for particulate emission regulations of biomass solid fuel of China.