FSI (FURNACE SORBENT INJECTION) DRY METHOD.
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This method consists in dozing of dry sorbents to furnace chamber. The range of dry sorbents includes: |
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Sorbent dozing methods:
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Dry flue gas desulfurization method (also called direct method) consists in absorption of sulfur by Ca0 originating from pulverized limestone, hydrated lime ordolomite. After its introduction into the furnace chamber, sorbent is decomposed, i.e. decarbonized or dehydrated in accordance with below described reactions:
CaCO3 + Q CaO + CO2
Ca(OH)2 + Q CaO + H2O
and then, lime reacts with SO2 in accordance with below described reactions:
CaO + SO2 CaSO3 + Q
CaO + SO2 + 1/2 O2 CaSO4 + Q
Dehydration occurs at a temperature above 400°C and decarbonization takes place at a temperature above 750°C. Hitherto gathered operating experience demonstrates that the introduction of pulverized limestone into the furnace chamber shall be done within the field of temperatures ranging from 780°C to 1200°C.
Temperature in sorbent injection area is one of the most important parameters determining the achievement of required desulfurization efficiency. Excessively high temperature may cause agglomeration of sorbent particles and intensify the reactions between CaO and minerals contained in coal. Dry method desulfurization efficiency is also affected by following parameters:
- quantity of sorbent injected (Ca/S molal ratio);
- sorbent milling quality;
- alkaline metals contents in sorbent (sorbent purity);
- alkaline metals contents in coal ash;
- residence time (contact time) of sorbent particles in flue gas within the furnace chamber;
- homogeneous mixing of sorbent with flue gas.
Optimisation of all above mentioned factors during the operation is not an easy task, thus, practically achievable dry method desulfurization efficiency amounts to 20 - 40% (maximum: 45%).
