Dennis Creasy and Steven Harper; Appita 2003
An experimental investigation was made of the hydrogenation of kraft black liquor at 350°C with CO gas and sodium or borax as catalysts. It was found that up to 65% of the fuel value of the black liquor could be converted to ail and char. The method may be useful as a means of reducing the load on a recovery boiler and simultaneously displacing fossil fuel from a lime kiln.
There is an obvious attraction in being able to convert lignin and other organics in black liquor from pulping processes to form a fossil fuel replacement. Most previous work in attempting to form liquid fuels from forest products had concentrated on cellulose, and in particularly in converting it into ethanol. Such an approach is obviously not particularly attractive in terms of best use of the organic material, as the cellulose is required for paper production. It still leaves a situation where the lignin can only be used as a fuel in rather specialised furnaces or for the production of minor quantities of specialised lignin derived chemicals. Supercritical extraction has also been studied as a means of separating lignin from cellulose but this approach does not give the lignin in a particularly useful form.