## 3 Results
### Elements in Ash and Deposit  
The behaviour of trace elements during combustion depends on their concentration, the form of occurrence, and how they are bonded to the organic or inorganic components of the coal and the combustion conditions [61]. Elements bonded in organic matter are vaporised and subsequently escape into the atmosphere or are adsorbed on small particles of ash during combustion in the boiler. Most elements that have a higher affinity for the inorganic matrix are usually non-volatile and tend to stay in the ash or fly ash [62].  
[PERSON] et al. [43] sorted the elements by the concentration of ash-forming elements in plant ash (141 biomass varieties) in the following order: O > Ca > K > Si > Mg > Al > Cl > P > Fe > Na > S > Mn > Ti. Elements Ca, Cl, K, Mg, Mn, Na, P, and S in ash from natural biomass normally show higher contents than the respective values for coal ashes, while Al, Fe, Si, and Ti show significantly lower values [43].  
Based on the concentrations of major elements in ash from WM briquette combustion, the elements show a similar arrangement of Ca >> Si = K > Fe > Al > Mn > S > P > Ti as elements in ash from plant ash [43]. The series of trace elements in ash from WM burning is as follows, according to trace element concentration: Zn > Cl > Cu > Pb > Ni = Cr = As. Calcium levels in ash are up to five times higher than those of Si, a ratio that is maintained in deposits. The ash from WM has a significantly higher Fe content than plant ash [43]. Differences in Fe content are already evident in WM briquettes, which contain up to 15 times more Fe than wood biomass, according to [PERSON] et al. [63]. In addition,  
\begin{table}
\begin{tabular}{l c c c c c c c c c c c c c c c c c} \hline \hline
**Coal** & **Al** & **Si** & **Ca** & **Mg** & **Fe** & **Ti** & **P** & **S** & **K** & **Cl** & **Mn** & **Cr** & **Ni** & **Cu** & **Zn** & **Pb** & **As** \\ \hline
**Briguette** & & & & & & **\%** & & & & & & & & & **mg/kg** & & & \\ \hline
**CB** & 0.9 & 2.08 & 0.54 & & 0.46 & 0.14 & 0.024 & 0.22 & 0.11 & 86 & 273 & 33 & 24 & 19 & 22 & 10 & 2.54 \\
**REKORD** & & & & & & & & & & & & & & & & & & \\ \hline
**Company** & 0.07 & 0.23 & 1.14 & 0.17 & 0.50 & & & 0.2 & 0.03 & & & & & & & & & \\ \hline
**Ixap.** & 0.71 & 3.04 & 0.79 & 0.20 & 0.56 & 0.07 & 0.0068 & 0.54 & 0.11 & 41.5 & 86 & & & & & & & \\ \hline
**Lapite** & 0.74 & & & 1.86 & 0.11 & 0.67 & 0.03 & & & & 0.04 & 120 & 72.7 & 13.3 & 32 & 19.5 & 28 & ND & 1.77 \\
**Coal dark** & & & & & & & & & & & & & 100 & 15.0 & 9.0 & 15 & 18 & 6.6 & 7.6 \\
**Ignite** & 1.5 & & & 0.46 & 0.11 & 1.30 & 0.08 & 0.043 & 0.18 & & 43 & 15.0 & 14 & 16 & 53 & 11 & 24 \\ \hline \end{tabular}  
* \({}^{*}\) [PERSON] et al. [43], ** [PERSON] and [PERSON] [60], ** [PERSON] and [PERSON] [59], *** [PERSON] et al. [56].  
\end{table}
Table 6: Content of inorganic elements in CB and their comparison with literature values and coal Clarke values.  
Si has about nine times higher content in WM, and Al up to twenty times higher content than [PERSON] et al. [63] reported for wood. Increased Fe, Al, and Si concentrations may be related to the brushing of furniture wood. Garnet, aluminium oxide, silicon carbide and alumina-zirconia are used as abrasives.  
When comparing the concentrations of elements in fuel (Table 7) and ash, the position of P has changed because it is highly volatile. The order of trace elements in ash has remained unchanged compared to the input fuel.