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Studies in Hardwood Distillation 



Arthur D. Little, Inc., chemists and engineers, Boston, Mass., has 

 issued a pamphlet which will prove of interest to persons engaged in 

 the distillation of hardwoods. The pamphlet is the work of Dr. L. F. 

 Hawley. Its purpose is to oiltline certain matters of distillation which 

 are not yet known as well as they should be. There is a series of 

 questions remaining to be answered, but to answer them, further in- 

 vestigations will, in most cases, be necessary; yet they are practical 

 <]uestions and they concern the industrial distillation of hardwoods. 



One of the matters is the variation in yield from different woods. 

 This has never been given proper consideration. In this country the 

 usual raw material consists of mixtures of different species of hard- 

 woods in various unknown proportions, depending upon the natural 

 occurrence of these species in the forest from which the supply wood 

 is obtained. Beech, birch and maple usually predominate, but there 

 are others. Which woods are most valuable, if they can be bought at 

 different prices? 



Of course in a plant already established this question would 

 probably not be of importance because it is likely to have only one 

 certain mixture of species available and it is doubtful whether sorting 

 of the species would be practicable. But in establishing new plants 

 a consideration of the species available and their relative costs is 

 very important. For instance, the question might arise, ' ' Wliich is 

 the most favorable source of raw material, tupelo at $2 per cord or 

 birch at .$2.50?" The solution of this question would depend almost 

 entirely upon the value of the products per cord from the two classes 

 of material, since the cost of distilling the wood and refining the 

 products would differ only slightly. It would therefore bo necessary 

 only to (leterniine the yields per cord from each of the two species 

 and find whether the difference in the value of the products made up 

 for the difference in cost. 



However, in comparing two species which differ considerably in 

 weight per cord, it would be necessary to consider also the difference 

 in cost of distilling the wood and refining the distillate. For in- 

 stance, in comparing oak (weight per cord with 15 per cent moisture 

 about 4,300 pounds) with red gum (weight per cord with 15 per cent 

 moisture about 3,300 pounds) it can be seen that more heat would be 

 required to distil a cord of the former and, assuming the same per- 

 centage of pyroligneous acid, 40 per cent, in both cases, there would 

 be 400 pounds pyroligneous acid per cord to refine in the case 

 of the oak. In distilling the wood the extra fuel would be the only 

 added expense, but in refining the distillate there would be required 

 an increase in capacity of the refining apparatus as well as extra fuel. 

 In comparing the values of two species which differ in weight it is 

 therefore necessary to take into account other things besides just the 

 yield of products and the cost per cord. 



A very similar study is the determination of the relative value of 

 different forms of material from the same species. This question 

 has never been completely solved. There is variation in yield from 

 different parts of the same tree. That question would come up in 

 its practical form in a plant built to distU sawmill waste. What 

 should be the limit in size of limbs and slabs to be distilled? In 

 that case the comparative cost of handling the different sizes of 

 materials would be important. 



Among other questions which can be satisfactorily determined only 

 after more study is that relating to the moisture content of the wood ; 

 how dry it is. The more moisture in it, the more heat is required to 

 distil the material. 



The increased moisture content may increase the length of time 

 required for distillation and therefore reduce the capacity of the 

 retorts; the extra water in the pyroligneous acid requires enlarged 

 refining apparatus: and finally, the yields of acetic acid are inversely 

 proportional to the amount of water in the wood. In determining 

 the optimum moisture content of the wood at any particular plant it 

 would be necessary to balance the cost of drying against the gains 

 due to saving of fuel, to increase of capacity of distilling and refining 

 apparatus, and to increase of yields. This study would require a large 

 amount of both experimentation and calculation. 



Then the question comes up as to the effect of the temperature on 

 the yields. Dr. Hawley says that it is generally understood that slow 

 distillation improves the yield of valuable products, but there does 

 not seem to be any definite conception of how much of an effect can 

 be produced in this way. This lack of information is probably due 

 to the fact that most forms of commercial apparatus are designed for 

 distillation under certain definite conditions, and it is difficult to 

 vary these conditions to any great extent. 



It is declared that the commercial yields of the acetate of lime 

 are only 65 per cent of what the wood is capable of furnishing. 

 Would it be advisable to attempt to attain this increased yield at the 

 necessary extra expense? 



There is opportunity to economize heat in refining. At present about 

 250 per cent of heat is used to do 100 per cent work. Could not the 

 heat be made to do more work, by using the same heat for different 

 processes? 



There are valuable products lost in the tar and others lost in the 

 escaping gases. It is suggested that some of this waste can be recov- 

 ered, provided it will pay to do so ; and that is another matter needing 

 further investigation. 



Baltimore Exporters Not Encouraged 



Any impression that the foreign trade liaiT undergone a positive 

 improvement in the last six weeks, which might have gained currency 

 in the trade, will be very emphatically dissipated by a study of the 

 figures for March as compared with those for the corresponding 

 month of 1913. These figures demonstrate plainly that the tendency 

 in the direction of a curtailment in the forwardings to foreign coun- 

 tries which was a feature of the trade during the greater part of last 

 year is still in progress, and reflection will show that if the decline is 

 no greater it may be attributed to the fact that having continued 

 for so long, there is less room for a contraction than was the case 

 before. The real significance of the showing lies in the fact that a 

 further recession has taken place, and that as yet there is no con- 

 vincing evidence that the trend toward a narrowing movement has 

 been halted. Oak lumber is again in the lead with a decline of 

 nearly fifty per cent, or from 2,174,000 feet in March, 1913, to 

 1,147,000 feet last month. But hickory logs are not far behind, 

 with a shrinkage from 275,000 feet to 174,000 feet. In walnut logs 

 there was a gain, and the classification of ' ' all other logs ' ' makes a 

 better exhibit than might have been supposed. But with regard to 

 walnut logs it is to be said that stocks on the other side are reported 

 to be very large, with prices unremunerative, and a holding back of 

 shipments is earnestly urged. Poplar dropped from 279,000 feet to 

 92,000 feet, leading all other woods in the extent of the deeUne in 

 so far as percentage is concerned, and bearing out the reports received 

 here to the effect that the accumulations on the other side are large 

 and that interest of buyers is at a low ebb. In some items a gain is 

 disclosed, but they do not cut a big figure in the trade, the effect 

 of the statement as a whole being to impose caution upon the ex- 

 porters. The figures are as follows: 



1914, 

 Quantity. 

 174,000 Ft. 



Logs, Hickory 



Logs, Oak 8,000 Ft. 



Logs, Walnut 218,000 Ft. 



Logs, all others 128,000 Ft. 



Lumber, Oak 1,147,000 Ft. 



Lumber, Poplar 92,000 Ft. 



Lumber, Spruce 50,000 Ft. 



Lumber, all others 408,000 Ft. 



Shocks, all others 



Value. 

 .$ 5,97.5 

 350 

 12,940 

 5,388 

 37,156 

 4,667 

 1,875 

 21,110 



1913. 

 Quantity. 

 275,000 Ft. 

 39,000 Ft. 

 184,000 Ft. 

 71,000 Ft. 

 2,174,000 Ft. 

 279,000 Ft. 



41,750 



472.000 Ft. 

 3.646 

 27.330 



Headings 



All other kinds of lumber.. 



Doors 



Furniture 



Trimmings 



All other manufactures ol 

 wood 



Value. 

 $ 8,585 



1,365 

 11,660 



1,625 

 68,010 

 10,004 



21,870 

 4,021 

 3,306 



28,411 

 —29— 



