Figure 15.2. CO, CO2, and HC concentration in gases produced during pyrolysis of cellulose.
section of the reactor was varied from 600 to 1400 K. The measurement results on the concentration of gaseous species (CO, CO2, and HC) generated from the pyrolysis of cellulose in the controlled mixing history reactor are shown in Figure 15.2. The results are also compared with the calculated results. The results show an increase in CO and a decrease in CO2 and unburned hydrocarbons with an increase in pyrolysis temperature. This is an indication of dissociation of the cellulose into low-molecular-weight products (e.g., CO, CO2, and unburned hydrocarbons) at high temperatures. The calorific value of the gases at high temperatures is high, thus indicating a good source of energy recovery. Good trends were obtained between the experimental and calculated results except for the CO2 that had very low concentrations at higher temperatures.
The solid residue from pyrolysis experiment was collected, measured, and further tested to examine its characteristics. The amount of solid residue collected at different temperatures is shown in Figure 15.3. It can be seen that the amount of solid residue collected decreases rapidly with an increase in pyrolysis temperature. This is due to the high heating rate that results in lower activation energy and a larger preexponential coefficient of the devolatilization reaction . Further analysis showed that the solid residue from cellulose pyrolysis is primarily pure carbon.
The devolatilization reactions during pyrolysis will be completed only when the heat has fully penetrated the waste particle [32-34]. Therefore, the size and shape of the solid waste particles are important parameters that affect the pyrolysis reactions. The fed particles must have a characteristic size that is designed for a particular operating temperature, heating rate, and residence time.
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