No abstract

Batches of Pinus pinea char particles with average diameters of 2.2, 2.8, and 3.6 mm were burned in a bubbling fluidized bed at temperatures of 600, 700, and 750 °C, with a velocities ratio U/U mf = 9. The results show that only primary fragmentation occurs with an average fragmentation ratio of 1.5. No effect of the secondary fragmentation phenomena is observed. The increase in the number of particles in the bed because of fragmentation is accounted over the burning time, and its effect is evaluated on the determination of the global combustion resistance.

We herein present some results obtained from the burning of chars derived from wood originated in the semi-arid region of northeastern Brazil (Cariri Paraibano) in a fluidized-bed reactor. A series of tests was performed in air and 10:90% (v/ v) mixtures of oxygen and nitrogen. The average diameter of the burning particles ranged from 1.8 to 3.6 mm for bed temperatures of both 750 and 850°C. The temperature of the burning particles was determined using an energy balance at the surface of the particle. The maximum difference in the temperature between the particles and the bed was 82°C, when the particles were burned in air. This difference decreased to 41°C when the particles were burnt in a 10:90% (v/v) mixture of oxygen and nitrogen. Both kinetic and diffusive data were collected, in response to the general lack of this type of data in the literature relating to the design of fluidized-bed combustors.

No abstract

This paper reports some experimental aspects of the combustion of batches of vegetable chars in a fluidized-bed laboratory reactor at temperatures of 600, 700, and 750 o C. Data on the volumic concentrations of carbon oxides and volatile organic compounds along the combustion process are presented and discussed. Tests show that the carbon conversion rate is not only due to combustion, but there are pyrolysis phenomena that accompany it and contribute to the global conversion rate of the carbon. The burned-out and consumed mass fractions of carbon were determined, and it was observed that these two quantities differ, particularly for lower bed temperatures. Vegetable chars when suffering combustion in low-temperature fluidized beds release tars in the form of vapors that escape from the bed without burning.