Options of energy conservation in the brick and tile making industry in Uganda
Bricks and tiles are ceramic building materials used in almost all buildings for construction as they are locally available. As a developing country, Uganda’s brick and tile industry is estimated to be growing at a rate of 4 % and this is due to the growing share of the construction sector. However, in Uganda the brick and tile making is an energy intensive process requiring an average of 2.85 MJ/kg to produce one (1) kg of industrial bricks and tiles (World-Bank/UNDP/Bilateral-Aid, 1989) compared to an average of 1.72 MJ/kg in the industrial brick and tile manufacturing for developed countries like Sweden and Spain (ECT, 1998). Excessive energy consumption during firing and the lack of expertise are highlighted as the major issues associated with the brick and tile industry in Uganda. Therefore it becomes inevitable to make a transition from these inefficient firing technologies to more sustainable and environment-friendly technologies. Therefore, this study was conducted to establish options of energy conservation in the brick and tile industry, Uganda Clays Limited as the case study. A mathematical modeling approach was adopted to predict the gas and solid temperature profiles in the Hoffman kiln zones. The modelling entailed formulating and solving a system of energy balance and mass balance equations, in the form of ordinary differential equations. Explicit curve fit expressions representing the general characteristics of the firing process were derived using MATLAB, R2012a bvp4c code. The energy consumption of the Hoffman kiln was also reviewed. The results obtained, reveal that the specific energy consumption of the Hoffman kiln is 2.46 MJ/kg. This indicates that the Hoffman kiln at Uganda Clays is up to 30% more energy intensive than Hoffman kilns in developed countries. The mathematical model results were verified against the measured experimental results from the process and a good agreement was achieved. In the preheating, firing and cooling zones, the mathematical model results diverged from the experimental measurements with an error of 20.64%, 3.3% and 8.48% respectively. Characterization of the kiln indicated that for efficient heat transfer from gas to the tiles, the flow rate of flue gas in the preheating zone should be in the range of (0.03 – 0.05) kg/s. In the firing zone, the fuel feed rate should be reduced from the current 0.008 kg/s to 0.005 kg/s and in the cooling zone, the air flow rate should be 0.04 kg/s.