Improvements and Performance Evaluation of a Fluidized Bed Gasifier

Author : Rasco, Sherwin Miranda
Major Adviser : Capareda, Sergio C.
Committee Members : Alcanzare, Edilberto A.; Valencia, Sixto A.
Year : 1995
Month : August
Type : Thesis
Degree: BS
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The DAMET fluidized bed gasifier (FBG) was modified, tested and evaluated. Actual operations show that the FBG exhibited poor fluidizing characteristics and operated at spouted bed rather fluidized bed conditions. Because of poor fluidization characteristics, caking and slagging of rice hull ash occurred.

Samples of the flue gas leaving the reactor were collected and were tested for their N₂, H₂, CO and CH₄ content at various air to fuel (A/F) ratios. The average volumetric percentages of N₂, H₂, CO and CH₄ were 76.10, 0.35, 11.04 and 0.79 percent, respectively. The remaining 11.72 % being unidentified gases. Between A/F ratios of 1.62 to 3.01, as A/F ratio increased, the amount of N₂ decreased while the amounts of H₂, CO and CH₄ increased. As a result, the higher heating value of the gas also increased. The same trends were also observed with increasing bed temperature. Higher heating values varied from 1.28 to 1.93 MJ/m³ averaging 1.61 MJ/m³.

At A/F ratios between 1.62 to 3.01 and bed temperatures between 276.10 and 457 °C, both hot and cold gas efficiencies of the FBG increased. Hot gas efficiencies ranged from 31.07 to 54.85 percent averaging 25.87 percent. It was noted that the gasifier produced gases of highest heating values with the greatest efficiencies between A/F ratios of 2.5 to 3 or between 360 to 460 °C.

Before conducting related studies utilizing the equipment, it was recommended to first improve the equipment, specifically the bed fluidizing characteristics by developing a compressor blower and air distributor that would satisfy good fluidization requirements.

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