PROPOSAL FOR THE USE OF THE "FESFIX" ABSORBER - REACTANT DURING THE COMBUSTION OF ALTERNATIVE SOLID FUELS /HOUSEHOLD SOLID WASTE (HSW)/ AND COAL/ AS AN ABSORBENT OF SULPHUR AND CHLORINE IN FLUIDIZED BED FURNACES.
The solid absorbers such as Al2O3, Fe2O3, MnO, a CaCO3 can be used to bind the S, Cl content of the flue gases produced by the combustion of solid fuels /household solid waste (HSW), coal/. Such absorbers are added to the flue gases in the flue pipe /heat-exchanger/ or directly into the combustion chamber of the fluidized-bed furnace, where the absorbents bind S (sulphur) and Cl (chlorine). Depending on the type of the solid absorbent and the fuel, these processes take place at temperatures of approx. 100 to 500 °C or higher, where the flue gases contain S and Cl particles of fine ash (approx. 5 - 3000 ppm) in solid form, which can be collected on an electrostatic /95 - 98%/ or bag-fabric filter /99.8%/.
The FeSfix is a solid absorbent, an iron-oxide based black reactant (Table 1), an iron concentrate consisting of more than 70% of iron oxides, such as FeO and Fe2O3. Due to its fine-grained granulometry (nanopowder of 5 to 200 micrometres), it has a large active surface with high reactivity. Its chemical and mechanical properties allow its use as a solid absorbent - reactant for the removal of unwanted elements such as S (sulphur) and Cl (chlorine) from the flue gases produced during the combustion of solid fuel (HSW, coal). When FeSfix is used as a solid absorbent - reactant, no extra reaction energy is required, unlike during the use of limestone (CaCO3), and no extra CO2 is produced:
FeO + SO2 = FeSO3
Fe2O3 + SO2 = Fe2(SO2)3
The solid particles, thus generated, are collected on electrostatic or bag-fabric filters together with the ash.
Based on a partial operating experiment in the combustion of solid alternative fuels, HSW and coal, we propose using the FeSfix absorber - reactant /see Table 1/ as a substitute for ground limestone (CaCO3), as an absorbent of undesirable S and Cl elements in the flue gases, which are produced during the combustion of HSW and coal in fluidized-bed furnaces.
We take the opportunity to propose the FeSfix absorber - reactant due to the good experience of its use for the removal of sulphur in biogas production in biogas plants. Its operation is based on iron oxides (FeO, Fe203), which bind to the hydrogen sulphide (H2S) found in the ferments during the anaerobic fermentation in the biogas plants.
The additional desulphurisation methods using the principle of activated carbon adsorption are not an economically optimal method. It is well known that the H2S inhibits the process of methane formation and the H2S also replaces the trace elements required for the methanogenic bacteria. This results in a significant reduction in the biogas production.
Therefore, the best solution is to include the current biogas desulfurization process into the anaerobic fermentation process.
The FeSfix usage to solid fuel burning (HSZH, coal) fluid in furnaces
Its advantages also include its chemical stability, which does not change even at the higher humidity of the storage environment, however, its handling and dosing into the technological process requires more care.
FeSfix is packed in paper bags or in big-bags, according to the demand and the quantity used by the customer. It is recommended storing it in a dry place.
The comparison of FeSfix and CaCO3 as a solid absorber of Sulphur in coal combustion:
| Coal | 1% S | CaCO3 | Energy | CO2 | FeSfix | Energy | C | ||
| 100 kg | S | 2000 kg | 1 MW | 880 kg | 200 kg | 0 | 0 |
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