The evolution of the ASA (active surface area) of the samples with carbon conversion was obtained by measuring the CO and CO2 desorption rate during the TPD tests of samples partially burned off at various carbon conversions.
The raw data of desorption from a given sample, characterised by a given carbon conversion, were then normalised with respect to the SSA of the same sample. In this way for each carbon conversion of the sample we obtained the amount of CO and C02 desorbed per unit sample surface. The results are shown as profiles of CO and CO2 desorption per unit sample surface in function of the desorption temperature in Figs. 7 and 8, respectively.
Fig. 7. Desorption of CO complexes per unit Specific surface area of char of the blend coal K-cocoa shells at different partial bum off as a function of desorption temperature.
Fig. 8. Desorption of C02 complexes per unit SSA of char of the blend coal K-cocoa shells at different partial bum off as a function of desorption temperature.
Fig. 7 shows that when the carbon conversion changes from 0 to 26%, the CO desorption profile’s maximum increases slightly and moves from 1100 К to 900 K. Further increasing X gives rise to a decrease of the profile’s maximum that remains, however, at the same temperature (about 900 K). As a result the quantity of CO desorbed per unit sample surface area decreases but its desorption is easier since occurs at lower temperatures. At 1100 К where there was the maximum of the CO desorption profile at X= 0% there is the presence of a shoulder. Fig. 8 shows that as the carbon conversion changes from 0 to 26%, the C02 desorption profile maximum strongly increases and moves from 950 К to 900 K. Further increasing X gives rise to an increase of the profile’s maximum that shifts, however, again at about 950 K. As a result the quantity of C02 desorbed per unit sample surface area increases.
Fig. 9. Comparison between TPO tests of coal K-cocoa shells blend chars after partial burning at X= 0%, 26%,
55% and 73%.