Chemical and thermodynamic processes in clay brick firing technologies and assosciated atmospheric emissions metrics-a review

Abstract

Atmospheric emissions arising from brick manufacturing installations are a significant source of atmospheric pollution globally. Brick kiln input and firing variables, chemical reactions and thermodynamic processes occurring within the firing chamber of brick kilns, impact on the outcome of fired bricks, as well as the quantity and nature of pollutants emitted into the atmosphere. A review of these chemical reactions and thermodynamic processes, as well as their atmospheric emissions and associated process metrics, was conducted to evaluate the sensitivity of emission metrics to these reactions and processes occurring at a specific period within the firing chamber. Brick kiln emission concentrations and process metrics exhibit wide ranges of data variability during a firing cycle, implying that they are sensitive to these chemical reactions and thermodynamic processes. Kiln emission control efforts aimed at modifying the combustion and firing process in order to alter the chemical reactions and thermodynamic processes in a way that will result in the release of lower quantity of emissions, are proffered. Kiln technologies were ranked from lowest to highest potential for atmospheric pollution based on available emission metrics as follows: Vertical shaft<Zig-zag<US coal-fired< Clamp< Fixed chimney Bull’s trench<Tunnel<Down draft<Bull’s trench.