Materials and experimental

1.1. Raw materials and characterizations

In this study British coal, rice husk and palm kernel shell originated from Perlis were em­ployed as fuel. These fuels were open air dried for 2 to 3 days to remove moisture. The proxi­mate and ultimate analyses were performed on coal and rice husk are summarized in Table 1.

Figure 1, is a schematic diagram of the Atmospheric Fluidised Bed combustor used in this investigation. The system comprises of a 0.15m diameter and 2.3m high combustion cham­ber, allows for bed depths of up to 0.3m using 850qm sand, cyclone, screw feeder and gas analyzer. The combustor body is constructed from 1 cm thick 306 stainless steel and covered in Kaowool insulation to prevent excessive heat loss during operation. Fluidising air was in­troduced at the base of the bed through a nozzle distributor and provided fluidisation and combustion air. Start up of the bed was achieved using an in-bed technique; Propane was introduced directly into the distributor plate by injectors and mixed with air in the nozzles, providing a combustible mixture at the nozzle exit. Bed and freeboard temperatures were

measured at 8 different heights above the distributor plate by means of sheathed Ni/Cr-Ni thermocouples (TC) type K. Fuel was fed pneumatically into the bed surface from a sealed hopper through an inclined feeding pipe the flowrate for which flow rate was controlled by a screw-feeder. A cyclone was fitted to the combustor exit and the carryover from the bed was collected for analysis. CO and 02 were measured using a Xentra 4904 B1 continuous emissions analyzer, whereas C02 was measured using a non-dispersive infrared absorption spectrometry analyser. A fly ash sample was collected from the catch pot after finishing the combustion run. The fly ash sample was then weighed and analysed to determine the total amount of unburned carbon of the fuels in the test. The percentage of combustion efficiency was computed using Equation 1. Based on the values of combustion efficiency from experi­ments where duplicate runs were conducted under almost identical conditions, the combus­tion efficiency values should be within ±2%.