DISPERSANT
Dispersant helps in distributing the active chemical ingredients evenly throughout the boiler. It enables the chemical to reach even the inaccessible parts in the boiler, ensuring that all parts in a boiler are treated.
CATALYST
Catalysts reduce the ignition temperature of carbon and other combustible complexes of Sulphur-carbon, etc. This enables the combustibles to burn off at much lower temperature and at much fast rate. The organic foulants are thus removed by the combustion catalyst.
OXIDIZERS
Oxidizers aid combustion of organic material in the deposits in presence of the catalyst. Nascent oxygen can modify the inorganic clinker structure by changing it to a higher oxidation state.
CORROSION INHIBITORS
They neutralize acid deposits formed in boilers and reduce the formation of Sulphur trioxide by poisoning the vanadium and iron catalysts. They raise the dew point of acid and reduce cold end corrosion.
SLAG MODIFIERS
These chemicals raise the ash fusion temperature. Thus molten mass is not easily formed. A devitrification catalyst further modifies the slag making it amorphous.
COLD END CORROSION
Cold end corrosion in boilers is due to precipitation of sulphuric acid from flue gases. In the presence of excess air and high flame temperature, sulphur in the fuel is oxidized to sulphur trioxide. Impurities in the fuel like vanadium and corrosion products catalyze the reaction. Sulphur trioxide reacts with the water vapour in flue gas and forms sulphuric acid and starts precipitating below dew point. Approximately 130-160oC is the dew point range for commonly used fuels. Such corrosion is generally observed in heat recovery units, air pre-heaters, economizers, chimneys, etc.
EFFICIENCY
Fireside deposits are generally poor conductors of heat. Accumulation of such deposits on metal surface reduces the heat conduction to a large extent. As little as 1 mm thick deposition can result in about 2% loss of efficiency. The build up of such deposits depends on the operating conditions, fuel characteristics and boiler design. The reduced heat transfer in boiler is reflected in higher flue gas temperature. Increased stack losses reduce the overall boiler efficiency. In order to maintain peak boiler efficiency, it is necessary to clean the deposits regularly, which need a shut down. Periodic cleaning is troublesome and energy is wasted in cooling and reheating the boiler. Also, the boiler is not available during the shut down period. It is therefore essential to remove or prevent fireside deposition in any combustion equipment.
