Energy and exergy analysis of a biomass based ceramic plant

Abstract

The manufacture of relatively low commercial value ceramic products for construction is an energy intensive industry. It is important to improve and optimize the energy equation of the plant operation while simultaneously introducing renewable primary energy sources for the heat supply. The present paper concerns the analysis of the energy usage in a brick plant. This unit operates continuously on a 3 shift schedule. The overall annual production of five types of bricks is over 62 kton and the main energy consumption unit is the furnace. For this unit, the thermal load is supplied mainly by biomass coupled with fuel oil (80%–20% split, respectively) which yield a maximum temperature of 950 °C. The process is controlled by adjusting the air mixing in the kiln. A secondary furnace provides the heat for a rotating dryer for biomass drying which is supplied to the main furnace. The fuel is a mixture of various sources and its characteristics were determined by means of an elemental analysis, ash content and the measurement of the heat value. Measurements of mass fluxes along with the operating temperature on critical elements of the plant and chemical composition of the flue gases were used to calculate the energy balances to the plant. Because of the diversity of the product mix the production was normalized using the mass/surface area ratio of the various types of bricks. From the results, the energy intensity is 44 kg of oil equivalent per ton. The exergy analysis of the plant shows that most of the energy degradation occurs in the kiln. The analysis also enabled to assess the influence of the replacing fossil fuel by biomass on the increase of exergy efficiency of the plant.This work was financed by FCT, under the Strategic Project UID/SEM/04077/2013. The authors acknowledge the contribution of Amaro de Macedo S.A., for providing access to the plant