## 3 Results  
### Basic Information about the Burning Process  
The amounts of ash obtained by burning 1 kg of fuel in BEC2 and BEC3 are approximately equivalent to the laboratory results of the determination of ash in fuel according to ISO 18122:2015 [27] (Table 1). Burning 1 kg of CB under laboratory conditions would yield 55 g/kg of ash, while burning in BEC2 yielded 56.5 \(\pm\) 8.9 g/kg and BEC3 54.1 \(\pm\) 11.0 g/kg (Figure 1). Additionally, the amounts of deposits produced were comparable for both boilers. These were 0.43 \(\pm\) 0.03 g/kg for the EC2 boiler and 0.52 \(\pm\) 0.05 g/kg  
\begin{table}
\begin{tabular}{l l l l} \hline \hline
**Matrix** & **Parameter** & **Standard/Methods** & **Equipment** \\ \hline A, D, F & Ash & ISO 18122:2015 [27] & Laboratory furnace LAC LH, \\ A, D, F & Ultimate analysis (C,H,N) & ISO 16948:2015 [28] & Czech Republic \\ A, D, F & S—determination & ISO 16994:2016 [27] & Themoscientific \\ F & Calorific value & ISO 18125:2017 [29] & Calorimeter AC 500, LECO, USA \\ A, D, F & Elemental analysis—X-ray & U.S. EPA 2007, method 6200 [30] & Innov-X analyser, Olympus \\ F & Moisture & ISO 18134-2:2017 [31] & Memmert UN30, Germany \\ A, D & Water leachate & EN 12457-2 [32] & Overhead shaker CFL 3040, Germany \\ WL & Major anions (chloride) & U.S. EPA 1997, Method 300.1 [33] & Professional IC Vario \\ F(coal), A & Grain size analysis & ASTM D293/D293M—18 [34] & Vibratory sieve shaker Analysette \\ F(bio), A & Grain size analysis & ISO 17827-2:2016 [35] & 3 Spartan, Fritsch, Germany \\ \hline \end{tabular} Explanation: A—Ash; Bio—b Biomass; D—Deposit; F—Fuel, WL—Water leachate.  
\end{table}
Table 3: Overview of standardised methods used.  
for the EC3 boiler (Figure 2). While burning PB under laboratory conditions produced 127 \(\pm\) 23 g/kg of ash in BEC2, and 118 \(\pm\) 45 g/kg of ash in the EC3 boiler, the amounts of deposits captured differed for the BEC2 and BEC3 boiler. The higher amounts of deposits were collected in the BEC3 boiler (0.94 \(\pm\) 0.13 g/kg), while in BEC2, it was 0.57 \(\pm\) 0.04 g/kg of fuel. The difference is caused by the higher uptake of inorganic particles in the BEC3 deposits (22.7 \(\pm\) 3.84%) than in BEC2 (19.5 \(\pm\) 1.73%), which confirmed the higher efficiency of the EC3 boiler in capturing inorganic particles resulting from the condensation of the gaseous component. The biggest difference is shown in the results obtained by burning WM when substantially smaller amounts of ash were produced. In BEC3, the amount of ash obtained (7.86 \(\pm\) 0.29 g/kg of fuel) was lower than the ash determined according to ISO 18122:2015 [27] (9.5 g/kg of fuel).  
In this case, when the content of inorganic elements in the input fuel is minimal, the amounts of deposits captured in BEC3 is lower (0.19 \(\pm\) 0.04 g/kg of fuel) than in BEC2 (0.97 \(\pm\) 0.16 g/kg of fuel). As a result, only 13.82 \(\pm\) 1.21% of the inorganic component was captured in the deposits from BEC3, compared to 21.81 \(\pm\) 1.05% in BEC2. When burning in BEC2, the temperature was probably lower, which did not allow further thermal decomposition of the major mineral phase of Ca (calcite). The X-ray diffraction method determined the calcite content in deposits from BEC2 10.56 \(\pm\) 2.02% and in deposits from BEC3 3.58 \(\pm\) 0.64% (normalised to 100%). In the deposits from the EC3 boiler,  
Figure 1: Amounts of ash (**a**) and deposits (**b**) formed by the combustion of 1 kg of fuel.  
Figure 2: Amounts of inorganic component (ash) in deposits (**a**) and amounts of unburned carbon in deposits (**b**).  
1.69% of Ca is in the form of calcite, which corresponds to 31% of the total Ca bound in the crystalline phase. In the deposits from the EC2 boiler, 4.75% of Ca is bound in the crystalline phase, which is equivalent to 54.5% of the total Ca content in the deposit. The higher temperature in the EC3 boiler was confirmed by the predominant amorphous character of the deposit particles.