3220 Chapter 26 



26-6 LIQUEFACTION 



U.S. BUREAU OF MINES PROCESS 



Wood can be converted to an oil by reaction with synthesis gas and an alkaline 

 catalyst under high temperature and pressure (Lindemuth 1978) (fig. 26-36). 

 The synthesis gas can also be produced from wood by gasification. Preparation 

 for liquifaction includes drying and grinding the wood before blending with 

 recycled oil to produce a wood oil slurry of about 30 percent solids. The slurry, 

 synthesis gas, and the alkaline catalyst (sodium carbonate solution) are then 

 reacted at 600° to 700°F and 2,000 to 4,000 psi for various lengths of time. The 

 oil is separated from unreacted wood and ash and part is recycled to blend with 

 incoming wood. The waste stream contains catalyst and unreacted wood. 



Figure 26-36. — Wood liquefaction scheme. (Drawing after Lindemuth 1978.) 



In the original process, which was developed by the U.S. Bureau of Mines, ^ 

 carbon monoxide plus steam and/or hydrogen was used as a reducing mixture in 

 the presence of alkaline catalysts (Na2C03 or HCO^Na) at temperatures up to 

 750°F and pressures as high as 5,000 psi (Appel et al. 1975). Under these 

 conditions it was found that cellulosic materials such as urban refuse, sawdust, 

 bovine manure, and sewage sludge could be converted to heavy oils. However, 

 it was noted that materials containing larger quantities of lignin or other non- 

 carbohydrates may require more severe reaction conditions. Bark, which has a 

 high phenolic content that would consume considerable quantities of the alkaline 

 catalyst, may not be suitable for this process as originally designed. 



A unit in Albany, Oregon is testing the feasibility of using the U.S. Bureau of 

 Mines process to liquefy wood and other biomass on a large scale. Incoming 

 wood chips, which normally have a moisture content of about 50 percent (wet 

 basis), are dried to about 1 to 5 percent moisture content in a gas-fired rotary 

 dryer. The dried wood is then hammermilled to about 50 mesh before being 

 slurried with recycled product oil. A catalyst solution of sodium carbonate is 

 added and carbon monoxide gas is sparged through the mixture. Results to date 



