Exhaust gases treatment standards

We have also included environmental costs in the calculation, such as wastewater treatment, exhaust gas treatment, and disposing of off-spec material (after allowing for metal credit). These costs add up to 0.5-1 USD/kg of final product. In addition, 0.5-1 USD/kg in quality costs are typically required for automotive standards. We have not included R D costs in the calculation. 

Exhaust Gas Treatment The gas effluent must be treated to comply with environmental regulations. The exhaust gas from the reactor contains traces of organic matter and unreacted SO3 and SO2 gases. The first two impurities are removed by the electrostatic precipitator. The remaining SO2 gas is removed by the reaction with caustic soda solution flowing countercurrently inside the scrubbing column. The concentration of the residual SO2 in the exhaust gas vented into atmosphere is kept at 5 ppm maximum, well below the allowable standards. 

Compliance with the EuroIII standards (2000) forced the fitting of Diesel oxidation catalysts (DOC) in the exhaust line [for the after-treatment of unburnt hydrocarbons (HC) and carbon monoxide (CO)]. Additionally, the exhaust gas recirculation (EGR) was adapted to reduce the engine-out emissions of nitrogen oxides (NOx). 

Moreover, the new system entails an increase in the overall production yield ( 1%) obtained by recovering the partially sulfonated materials generated by contacting the exhaust gas with the sprayed amount of LAB. The impact of this recovered stream on the quality of the final LAS-sulfonic acid is limited to a minor increase in the unsulfonated matter content and color. The overall gas scrubbing efficiency has proven to be the same ensured by the standard ESP-based gas treatment units. 

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