Comparison of coal gasification in fluidized and spouted beds

Abstract

Two sub‐bituminous coals, a bituminous coal and a reject coal of 55% ash were gasified with steam and air in a 0.31‐m dia. reactor operated in the fluidized and spouted bed modes. Inert beds of 1.1 mm dia. Ottawa sand and 2.1 mm dia. gravel provided stable fluidization and spouting respectively, at superficial velocities in the range 1.3–1.6 m/s. Coals of 1.19–3.36 mm diameter were fed to the gasifier at rates up to 45 kg/h and a range of air/coal ratios. For a given coal, results in the two systems were basically similar, although differences in gas heating value, gas yield and thermal efficiency were noted for some coals.

The influence of geometrical factors and feedstock on gasification in a high temperature fluidised bed

“…The value of this ratio before the maximum gives a lower gas heating value as a result of product gas dilution by air nitrogen, despite the higher bed temperature obtainable in such cases. For a spouted bed, Watkinson et al (1983) also have detected a maximum gas heating value by variation of the coal feed rate at constant air flow. This maximum.…”

“…The mass of the bed was measured at the end of experiments after removal of the hot solids from the reactor through its bottom. Changing both the bed volume and the coal feed rate allows variation of the particle residence time over a broader range than when only the coal feed rate is varied (Watkinson et al, 1983), and it also increases the generality of the results.…”

“…The gas heating value is sometimes related in the literature to the ratio of the coal rate to the air rate (Watkinson et al, 1983). Variation of this ratio during the experiments also changes the solid particle residence time in the bed and the bed temperature.…”

“…Variation of this ratio during the experiments also changes the solid particle residence time in the bed and the bed temperature. Watkinson et al (1983) have noted that such experimental data can be used for design purposes, but with a large degree of caution. The most suitable form of presentation, because of its generality, is a relation with the particle residence time as in Figure 3.…”

“…During the presented research a new approach has been made to attain the demanded gas calorific value on using char as feedstock in a fluidised bed gasifier without external heating. It has been aimed also to present the results in a form more applicable for design purposes than the literature data (Watkinson et al, 1983), which are limited to certain ratios of the stream flows.…”