Abstract
Soot sludge is a waste stream formed in the fuel oil gasification of formic acid and hydrogen peroxide production. The soot sludge has a high moisture content (95%) and is presently combusted with heavy fuel oil in order to dispose of the sludge. Experimental tests earlier conducted by the authors have shown that the sludge can be convectively dried with sawdust in a fixed bed. By upgrading the sludge from waste to fuel, the utilization of oil can be decreased. In this study, characteristic drying curves (CDC) are determined for the sludge and sawdust mixture. The CDCs are further used to evaluate the economy of the mixture drying in a belt dryer by using the payback period method. Results show that the linear CDCs of the mixture can be used to extrapolate drying data from specific drying conditions to another when the bed height is 200 or 300 mm, and the inlet air temperature 40–100 °C. The economic analysis shows that drying is economical for all inlet air temperatures if the oil price is ≥350 €/t-oil. Sensitivity analyses reveal that the heat, sawdust and emission prices have no remarkable influence on the economy of drying if the oil price does not fall below c. 300 €/t-oil.
Highlights
The production plant of the Eastman Chemical Company [1] forms a waste stream called soot sludge
Characteristic drying curves are determined for a soot sludge and sawdust mixture which has been dried in fixed beds at different bed heights and air temperatures
After an amine-wash of the gas, the gas is led into a separation process in which CO and H2 are separated for the production of formic acid and hydrogen peroxide [26]
Summary
The production plant of the Eastman Chemical Company [1] forms a waste stream called soot sludge. A characteristic drying curve can be used to extrapolate drying data from one set of external conditions to another Characteristic drying curves have been defined in several studies Many of those studies focus on convective air drying of fruits, plants and vegetables in fixed beds as ginger roots [12], eucalyptus [13], banana [14], green sweet pepper [15], cactus [16], spearmint [17], prickly pear fruit [18], rosemary leaves [19], and cellulosic fibres from citrus fruits [20]. Characteristic drying curves are determined for a soot sludge and sawdust mixture which has been dried in fixed beds at different bed heights and air temperatures. Characteristic drying curves are used in an economic analysis in which the profitability is evaluated of the soot sludge drying before combustion
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