Analysis of combustion emissions and char from CCA- and ACQ-treated wood

This study used Taiwania cryptomerioides Hay as a specimen to be treated with CCA-3 or ACQ-1 preservatives. CCA and ACQ-treated woods, the preservatives themselves as well as their individual ingredients during combustion were investigated. The emission gas concentrations of O2 and CO2, the emission contents (CO, SO2, NOx) , and the temperature of the emission gases were measured using a flue-gas analyzer at the exit of a 45 deg flammability testing cabinet as specified in the continuous emission monitoring (CEM) techniques. The specimens were analyzed with an energy dispersive X-ray spectrometer (EDX), and were examined in a 45 deg flammability testing cabinet before and after the analysis. The residual elements in the char were also analyzed using an elemental analyzer (EA). The results indicated that the emission gas temperatures of all samples rose rapidly to about 200-250 deg C and then slowed down to a temperature range of 200 deg C, shown as a plateau curve. The concentration of O2 decreased from 20.7% to about 17.0-19.8% linearly, and was contrary to the concentration of CO2 increased from 0.2% to about 1.8-2.8%. Both O2 and CO2 then approached the shape of a plateau curve until the end of the combustion time, and were closely related during the combustion. The highest emission quantity of CO was about 179.3 ppm for the ACQ specimen, 157.0 ppm for As2O5, and about 85.5 ppm for BKC. The emission quantity of SO2 for each type of sample was zero. The maximum NOx for the ACQ specimens and ACQ-1 preservatives were about 23.5-26 5 ppm, and about 32.0 ppm for BKC. The result of the EDX analysis indicated that the main element was C (77.89%), and that the relative proportion of Cu was 2.67% for the ACQ specimen, but that ACQ-1 was left with a high amount of Cu, of 50.14%. The result of the EA analysis inferred that the ACQ specimen could produce NOx gases during combustion, because the amount of N (1.42%) was higher for ACQ-1 than for the other specimens, and the BKC was almost burned out.