# Comparative Analysis of Partially Renewable Composite Fuels Based on Peat, Lignite and Plant Oil
## 3 Results and Discussion
### The Material and Energy Balance of Conversion  
The data presented in the previous sections make it possible to determine the expenses of energy consumed from the external source for conversion of the unit weight of the fuel composition. The estimation of the specific energy expenses was performed according following equation:  
\[E_{sp}=\frac{\Delta E}{\Delta m},\]  
where \(\Delta E\) is an energy of absorbed light and \(\Delta m\) is a corresponding weight changes of the sample observed during the time \(\Delta t\). This value shows the general consumption of the heat from external sources that includes the losses for thermal radiation emitted at the steady state temperature as well as light reflection losses. The energy needed for the conversion of the unit weight of the L + RO composition was about 9 MJ/kg. The same value for P + RO was about 54.5 MJ/kg. At the same time, lignite produced quite a lot of heat that contributed to the efficient and relatively fast conversion of the L + RO mixture. The comparison of the findings with the data published earlier on the conversion of a water slurry of peat or lignite [9; 11] shows that the conversion of RO-based compositions requires much higher heating intensity (with corresponding temperatures). At the same time, there is also a significant rise in combustible gas production. Both of the proposed compositions provide a considerably better ratio of combustible-to-non-combustible gases than that obtained for the water slurries in [9]. The comparison of the high-temperature oxidation of peat- and lignite-based fuels (Figure 4) shows that both L + RO and P + RO compositions have rather similar high calorific values. However, partial oxidation during the conversion results in very different heat production and different chemical compositions of the producer gas. The obtained values of energy consumption during the conversion of the L + RO composition are comparable with the ones required for the conversion of the water slurry of bituminous coal processing waste (left three columns in Figure 7) [36]. The samples of coal-water slurry were converted with an air excess coefficient of about 1.3, the value of which is close enough to the conditions of the conversion of the L + RO composition presented in this paper (air excess coefficient -1.5). The conversion of wet peat or wet lignite usually requires external heating with intensities of about 100 W/cm\({}^{2}\)[9]. The conversion of wet peat and wet lignite was performed at air excess coefficient of about 1-1.1. The amount of the air moved into the chamber depended on the duration of the conversion process, which was essentially different for all these fuels. Figure 7 shows the typical amounts of the externally sourced heat required for the conversion of the unit weight of different fuels. Rapeseed oil makes peat and lignite less  
Figure 7: External heating source energy used to convert unit weight of fuel composition. Solid components are peat (P), lignite (L) and bituminous coal processing waste (C). The energy is shown on a log scale. sensitive to heating. The oxidation of pure peat or lignite usually goes with increased production of CO\({}_{2}\) at the set heating intensity. However, the chosen P + RO or L + RO compositions increased production of combustible gases instead (see Figure 5). Therefore, the quasi-renewable composition of lignite (60 wt%) and rapeseed oil (40 wt%) can serve as a cheap and efficient alternative fuel for different industrial purposes. The produced gas mixture has a high calorific value of \(\sim\)20 MJ/kg (and 10.8 MJ/kg for P + RO). In the case of the L + RO composition, the heating value of fuel gas surpasses the energy invested into conversion process. Summarizing the previously presented results, we can formulate the appropriate conversion conditions. The conversion of P + RO compositions requires a fuel temperature above 600 \({}^{\circ}\)C. This temperature threshold should be achieved in a short time to prevent the separate evaporation of the volatile components of the oil.