HARDWOOD DISTILLATION 217 



Yields. 



The yield of products at hardwood distillation plants varies considera- 

 bly. The yield at any particular plant depends upon the following factors : 



1. Temperature, that is, the maximum and minimum temperatures 

 used during the exothermic process. 



2. The rapidity of heating. Too rapid heating will cause a much 

 smaller and lower grade of product. Usually about ten hours is the time 

 required to get wood up to the highest temperatures. If heating is done 

 too rapidly the color of the pyroligneous acid is much darker and the 

 yields are consequently much lower. 



3. The species of wood. There is a general consensus of opinion 

 among the New York plants that maple is the best wood with beech next 

 and birch third. Oak and hickory are also desirable species, but if there 

 is too much soft maple, basswood, poplar, gray birch or other inferior 

 species, the yields will be lowered. 



4. The condition of the wood. It is generally assumed that the dryer 

 and more thoroughly the wood is seasoned, the better will be the product. 

 It is also true that heartwood yields much larger and better products than 

 sapwood, and body wood is much more desirable than limb wood. 



5. Efficiency of the plant. This is determined by the character of 

 the machinery and equipment, arrangement of the apparatus and many 

 other factors connected with the efficiency of an operation. 



The products of hardwood distillation are as follows: Wood alcohol, 

 acetate of lime, charcoal, wood tar and wood gas. The latter two are 

 practically always used as fuel under the boilers or retorts. 



From an investigation of the 25 plants in New York State it was 

 determined that ah average yield of 42.7 bu. of charcoal are obtained 

 per cord of wood from all of the plants. There was a maximum yield of 

 50 bu. of charcoal per cord and a minimum yield of 38 bu. 



The average estimated yield of acetate of lime* was 199.47 lb. per 

 cord of wood. The minimum was 171 lb. and the maximum 220 lb. 



In wood alcohol the average yield was 9.9 gal. of 82 per cent wood 

 alcohol per cord of wood. The minimum was 8 gal. and the maximum 

 ii gal. per cord. 



It is estimated that between 23 and 28 gal. of wood tar are secured 

 per cord with an average of about 25 gal. It is estimated that about 

 11,500 cu. ft. of gas are secured per cord of wood. 



These figures are based upon the individual estimates of the various 

 wood distillation plants of the state. Altogether much better yields 



are secured from the oven plants than from the cylindrical retort plants. 



UNIVERSITY OF CALIFORNIA 



DEPARTMENT OF CIVIL ENGINEERING 

 BERKELEY. CALIFORNIA 



