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SUMMARYBrick making in developing countries, which relies on biomass fuel, is facing energy shortage. This paper reports a study aiming to develop an energy-efficient brick kiln. The drying, preheating, firing and cooling of bricks were studied by computer simulation of a fixed bed model and resulted in a new design of downdraft brick kiln. The new kiln has four chambers to serve the four processes separately but simultaneously. A heat recovery feature was incorporated in the kiln operation. A kiln was constructed for full-scale experimentation. The experiments showed that the specific energy consumption could be as low as 2·3 MJ kg\ of brick, which was only half of that presently consumed in traditional open top updraft kilns. The energy efficiency of the new kiln was 62·6% on average.

Biomass-red cogeneration not only is an environmentally friendly energy production, but also possesses high energy conversion ef ciency. Generally, the wood product industry requires both heat and electricity. Combined heat and power generation (cogeneration) using wood residue has a three-fold bene t: waste minimization, reduction of an energy-related production cost and additional income from selling the excess electricity to the utility. In reality, the process heat demand uctuates according to the production activities in the factory. The uctuation of process heat demand affects the cogeneration ef ciency and the electricity output and, consequently, the nancial return, since the prices of heat and electricity are different. A study by computer simulation to establish a guideline for optimum operation of a process heat uctuating cogeneration power plant is presented. The power plant was designed for a sawmill and an adjacent plywood factory using wood wastes from these two processes. The maximum boiler thermal load is 81.9 MW while the electricity output is in the range 19-24 MW and the process heat 10-30 MW. Two modes of operation were studied, namely the full (boiler) load and the partial (boiler) load. In the full load operation, the power plant is operated at a maximum boiler thermal load, while the extracted steam is varied to meet the steam demand of the wood-drying kilns and the plywood production. The partial load operation was designed for the partially fuelled boiler to provide suf cient steam for the process and to generate electricity at a desired capacity ranging from the rmed contract of 19 MW to the turbine maximum capacity of 24 MW. It was found that the steam for process heat has an allowable extracting range, which is limited by the low pressure feed water heater. The optimum operation for both full and partial load occurs at the lower limit of the extracting steam. A guideline for optimum operation at various combinations of electricity output and steam demand is presented. The maximum achievable overall ef ciency is 64.6 per cent when the power plant is operated at partial (boiler) load condition for 19 MW electricity and 30 MW process heat. The full load operation, although having lower overall ef ciency, is preferable nancially because of the higher unit price of electricity in comparison with heat.

This work aimed to investigate the potential of plastic waste in old landfill as a resource to produce pelletized RDF. Old landfill contents at different ages of 4-5, 5-10 and over 10 years old were excavated and sorted. The combustible part consisted mostly of plastics at 34.0, 21.9 and 22.1% at younger to the older age in order. The non-combustible part composted of soil-like material from 63.8 to 76.3% which made up of daily cover soil and organic debris. High calorific value of the plastic waste of 33.11-43.41 MJ/kg was not diluted by the mixing of binder. Heated compaction method was used in the formation of RDF pellets in this study. Bulk density was linearly increased with higher compaction pressure (R2 = 0.9655). Besides, the vertical compressive strength of the formed pellets increased by 82 kg/cm2 when the compaction pressure changed from 7 to 21 kg/cm2 and started to decrease when it was above 21 kg/cm2. Meanwhile the horizontal compressive strength was rather stable and appeared independent of the compaction pressure. Calorific value of the RDF produced was high because no binder of lower calorific value was used, enabling it to meet the specified European standard for its calorific value.