The treatment of carbon based fuels with AFC-705 has a significant effect on trace sulfur combustion chemistry. In diesel engines, gasoline engines and open flame applications (boilers) the use of AFC-705 treated fuel will significantly reduce sulfur oxide (SOx) emissions, and related sulfur acid corrosion problems.
AFC-705 does not react with the sulfur in the fuel nor does AFC-705 have any effect on the sulfur content of the fuel. AFC-705 does not effect fuel specifications at recommended treatment levels. Fuel containing one percent sulfur prior to AFC-705 treatment will still contain one percent sulfur after AFC-705 treatment. However, the use of AFC-705 will determine where the sulfur ends up and what its chemical state will be after combustion.
The combustion of sulfur in fuels invariably leads to the formation of sulfur dioxide S + O2 -->SO2 (1) and sometimes sulfur trioxide 2SO2 + O2 -->2SO3 (2). Sulfur trioxide formation is catalyzed by vanadium pentoxide (V5+ ). This is the most stable oxidation product of vanadium, when vanadium containing fuels are burned in air 4V + 5O2 -->2V2O5 (3). The catalytic effect is thought to relate to the reversible dissociation 2V2O5 -->2V2O4 + O2 (4) at temperatures between 700o -1125o C. The sulfur trioxide reacts with water vapor to form sulfuric acid SO3 + H2O -->H2SO4 (5) which is primarily responsible for acid corrosion problems in combustion equipment.
AFC-705 affects the production of gaseous SOx emissions. It enhances the formation of CO2 during the combustion phase thus limiting the amount of SOx produced during the exhaust phase. The increased production of CO2 reduces the amount of excess O2 available for other reactions. The difference in the amount of CO2 produced during the combustion and the exhaust phases correlates to a temperature differential. This temperature differential results in lower exhaust temperatures and shorter heat transfer times.
Minerals contained in fuel are generally oxidized to metal oxides during the combustion process. When vanadium is oxidized to V5+ the production of sulfur trioxide increases due to reversible dissociation, and sulfuric acid is ultimately formed. The use of AFC-705 inhibits the formation and reversible dissociation of V5+ during the exhaust phase by limiting the available O2, high temperatures, and time periods needed for these reactions to occur.
This greatly reduces the catalytic effect V5+ has on the formation of Sulfur trioxide and thus the formation of sulfuric acid. By reducing the catalytic effect of vanadium, AFC-705 promotes the combination of SOx compounds with other minerals in the fuel such as Na and Ni. This leads to the formation of stable mineral salts and mixed mineral sulfates found in the clinker or fly ash.
In this manner, AFC-705 decreases the gaseous sulfur emissions by increasing the particulate portion of the combustion residue products. AFC-705 treated fuels will therefore show slightly higher sulfate content in the ash than untreated fuel.
