**6.3 The emissions**

During the combustion test continuous measurements of the harmful gases like CO, NOX, SO2 and relative oxygen behind the boiler. were made by the Technical University of Ostrava. Furthermore single measurements of other emissions like cadmium, mercury, lead, arsen and their compounds, polychlorinated dibenzodioxines PCDD, polychlorinated dibenzofurans PCDF, polychlorinated bifenyls PCB, polycyclic aromatic hydrocarbons PAU, gaseous anorganic chlorine and fluor compounds, hard pollutants TZL, were also by the company TESO Ostrava. The measured values of the pollutants were re-counted to 6 % O2. The pollutants are illustrated in Table 17. The table provides evidence that the components CO, NOX, TZL, PCDD/F, HF, Hg meet the requirements of the public notice No. 354/2002 of the Codes of Law but the emissions of SO2 and HCl do not. This can be attributed to the fact that the sorbent dosing to the boiler was put out of action during the combustion test and thus the process of the conversion of both SO2 to CaSO4 and HCl to CaCl2 could not occur.


\*) … limit values given by No. 354/2002 of The Codes Of Law.

Table 18. The chosen emissions of the pollutants (6 % O2, 101,32 kPa, 0 °C)

Regarding the boilers and reducing their emissions of SO2, the fine grounded lime stone CaCO3 is continually added directly to the furnace. The lowerig emissions of SO2 approx. by 100 mg.m-3N was observed during the combustion test with the the shut-down

rust pop up even if the chlorine content in the fuel is low. The ratio Cl/SO2 has an impact on the high-temperature chlorine rust intensity. As for the chlorine content in the fuel sludge, it is evident that it does not exceed the volume found in the hard coal. The HCl concentration in waste gases influence the low-temperature rust intensity. In this particular case the rust rust in the recuperative air heater needs to be considered as well. Another characteristic of the operational efficiency of the combustion equipment is the silting of the heat transfer surfaces. It is important to notice the research on the thermoplastic characteristics of he ash. These characteristics are demonstrated by the following temperatures: tA – softening point , tB – melting point a tC – pour point. The lowest temperature for the mixture of the sludge and coal

During the combustion test continuous measurements of the harmful gases like CO, NOX, SO2 and relative oxygen behind the boiler. were made by the Technical University of Ostrava. Furthermore single measurements of other emissions like cadmium, mercury, lead, arsen and their compounds, polychlorinated dibenzodioxines PCDD, polychlorinated dibenzofurans PCDF, polychlorinated bifenyls PCB, polycyclic aromatic hydrocarbons PAU, gaseous anorganic chlorine and fluor compounds, hard pollutants TZL, were also by the company TESO Ostrava. The measured values of the pollutants were re-counted to 6 % O2. The pollutants are illustrated in Table 17. The table provides evidence that the components CO, NOX, TZL, PCDD/F, HF, Hg meet the requirements of the public notice No. 354/2002 of the Codes of Law but the emissions of SO2 and HCl do not. This can be attributed to the fact that the sorbent dosing to the boiler was put out of action during the combustion test and thus the process of the conversion of both SO2 to

**concentration Limit values \*)**

NOX mg.m-3N 80 238 Meets the requirements

TZL mg.m-3N 11 26 Meets the requirements

HF mg.m-3N 0.2 1 Meets the requirements

Hg mg.m-3N 0.0013 0,05 Meets the requirements

Regarding the boilers and reducing their emissions of SO2, the fine grounded lime stone CaCO3 is continually added directly to the furnace. The lowerig emissions of SO2 approx. by 100 mg.m-3N was observed during the combustion test with the the shut-down

PCDD/F ng(TE).m-3N 0.006 0,1 Meets the requirements

Table 18. The chosen emissions of the pollutants (6 % O2, 101,32 kPa, 0 °C)

SO2 mg.m-3N 560 333 Does not meet the requirements

HCl mg.m-3N 17 10 Does not meet the requirements

is approx. 1220 °C for the half-reductive atmosphere.

CaSO4 and HCl to CaCl2 could not occur.

**emission unit Measured** 

\*) … limit values given by No. 354/2002 of The Codes Of Law.

**6.3 The emissions** 

desulphurisation. This reduction in SO2 content in the waste gases is obtainable only under the condition of additional combustion of the sewage sludge. The additive gets into the sewage sludge during the process of the sludge hygienisation by the lime dosing at the sewage plant. Furthermore it is hydrated on Ca(OH)2 by the sludge humidity. The lime hydrate is rid of CaO while entering the fluidized bed boiler. The CaO then reacts with the SO2 and the CaSO4. The amount of the additives in the sludge lowers the lime stone consumption as the primary source (Szeliga 2008). The analysis of heavy metals and microelements in the combusted fuels (the energy coal, the coal sludge, the sewage sludge) were carried out in the laboratories of The Technical University of Ostrava. The evaluation was made for the single coal combustion and then for the mixture of coal and sludge. The redistribution of heavy metals and microelements during the additional combustion of the sewage sludge to the combustion hard residues and the emissions are a matter of further research. The combustion test proves there are further opportunities for additional fuel combustion in the fluidized bed boilers. The advantages of this kind of sewage sludge usage are mainly in the reliable decomposition and oxidation of the organic harmful elements and significant sludge volume reduction. Another suitable way of using the sludge is to reduce its humidity, which improves fuel efficiency, transport and manipulation. The disadvantage of the thermic usage of the sewage sludge is higher concentration of heavy metals and microelements entering the combustion equipment. Co-combustion of coal and sewage is possible only if there is appropriate content of heavy me tals in the sewage sludge entering the combustion process. The monitoring and analyses of heavy metals in the sewage sludge are nessesary.
