Solid Wood Products 



2717 



Figure 22-68. — A comparison of metallurgical chips and pulp chips. (Photo from Wart- 

 Iuftl971.) 



were pine bark. Wartluft (1971) concluded that demand for metallurgical chips 

 should increase at about 6 percent a year. His publication lists the names and 

 locations of 22 plants that used metallurgical chips in 1970. 



Wood species and form. — Hardwoods are preferred because they last longer 

 in the furnace. Most ferro-alloy plants prefer green wood, although some buy 

 dry wood to reduce transportation costs. Metallurgical chips should be free of 

 decay and also of foreign material that might impart impurities to the alloys 

 being produced. Because bark frequently carries dirt, it is undesirable. Howev- 

 er, in 1970 16 of the 22 plants in the United States accepted limited proportions 

 of bark. 



Chip size is the most important specification. In the Ohio and Tennessee River 

 Valleys, desired particle size ranges from 2.5 inches square and 0.5 inch thick to 

 8 inches square by 1 inch thick. Chips larger than these, as well as some very 

 stringy hardwood barks, are excluded primarily by the plant's materials handling 

 equipment. Small particles, including sawdust, generally are of no benefit 

 because they bum too fast. 



Chip manufacture. — For a review of the technology of manufacturing large 

 chips, see: Antezana, L.F. 1985. Maxi-chippers. In Proceedings of the sympo- 

 sium "Comminution of wood and bark" held October 1-3, 1984, Chicago, 

 Illinois; available from the Forest Products Research Society, Madison, 

 Wisconsin. 



See also, section 18-24. 



