Kinetics of thermolysis and burning of solid biofuel particles. Part 1. Experimental installation and research procedure
Further increase of biomass used for energy production requires improvement of burning technologies. An actual task is CO, NOx, and particulate emission reduction at biomass burning
and especially at straw burning. Technological problem of biomass burning is the low intensity of furnace process in comparison to that for traditional fossil fuels.
Proper burnout of volatile substances will prevent formation and emission of soot and resins particles. Stable ignition and intensive burning out of volatile substances is possible at a concerted rate of their release and blowing air supply. Known dependencies, which describe the fuel thermolysis kinetics and volatile release in an inert atmosphere at low temperatures up to
600K, are unacceptable for thermolysis in the oxidizing environment at high temperature, when volatile immediately reacts with oxidizer with energy release and creating temperature conditions around the particle which differ from initial conditions thus causing thermolysis acceleration. In previous works, the thermolysis duration in an oxidative environment at temperatures 400...900 C for wood chips, wood pellets, particles of straw and straw pellets
were described. But to calculate furnace processes it is necessary to know not only process duration but also rates of biofuel particle thermal decomposition throughout the thermolysis period.
In standard derivatograph, the kinetics of fuel particle thermolysis is examined at the heating rate of working space up to 50…99 C per minute. At that duration of particle heating to 400…900 C is 5…10 minutes, whereas thermal decomposition of solid biofuel particle in oxidative conditions occurs during 10...200 seconds. Standard equipment is not available and cannot provide the necessary heating rate, therefore the creation of experimental thermogravimetrical installation was needed.
Experimental thermogravimetrical installation was created; its principle of operation lays is in measurement and registration the mass of solid biofuel particle at its "shock" heating in oxidative conditions. Biofuel particle is placed on the structure, located on the scales, and then named structure is covered with muffle preheated to the desired temperature. A range of working muffle temperature is up to 900 C, the accuracy of temperature control is ±10oC, discreteness of particle mass measurements – 0.01 g, discreteness of time countdown – 0.2s. The process is fast running, so the image of instrument scales are recorded with camcorder and data read at the slow playing of video on a computer.
For studied biofuels moisture content, ash and volatiles were measured. For experiments, 0.5 g particles of biofuels were cut off from dry pellets having correct shape without visible defects.
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