^H^Mi^aa^tTOi)^tWJa^>ii^i^jM}tia^gagiitt^^ 



Making Wood Distillation History 



Editor's Note 

 ThP followine article treats of an entirely new phase in hardwood distillation, showing the possibility of 

 utilizfnasawSt^hayings and similar wastes for this purpose where it has never successfully been used betore. 

 The process itself bids fair to revolutionize hardwood utilization. 



To conserve and render valuable the material which has been 

 regarded as useless has been constantly the subject of the deepest 

 study. Marvelous progress has been made along many lines, but 

 the perfecting of a complete process of vrood distillation has been 

 retarded not only by the lack of uniformity in the size and density 

 of the raw material, but also by the inability to secure such 

 controlled heat penetration as to produce results with reasonable 

 rapidity or certainty. 



The first commercial prominence in the United States given to 

 wood distillation was in southern New York and northern Penn- 

 sylvania forty years ago when a small group of plants, designed to 

 use hardwood in cordwood form for the purpose of making wood 

 alcohol, acetate of lime and charcoal therefrom, was established. 

 Methods of an almost primitive nature were employed in these 

 early plants, resulting in a small yield and an inferior quality of 

 output, which was offset, however, by the prevailing high prices of 

 products, together with the low value of the wood used, which, 

 consequently, allowed the owners to reap a handsome profit. 

 Gradually changing conditions, however, made imperative a 

 greater efficiency. 



It was at about this period that the eminent scientist, Henry M. 

 Pierce, LL.D., carried the industry into Michigan. The displace- 

 ment by him of older for better methods entered largely into the 

 history of the industry. Too much cannot be said of the creditable 

 and successful work accomplished by Dr. Pierce. While his pene- 

 trating mind perceived, at all times, the limitations of this industry, 

 as then operated, he foresaw the great values which would accrue 

 could the operator control with greater accuracy the conditions 

 under which he worked. 



Chief among these limitations was the absolute inability to 

 govern the temperature. Since heat is, obviously, the prime mover 

 in distillation, its accurate regulation must, of necessity, be the 

 master key to open the way to an increased output. 



In the plants of to-day, wood of irregular size, quality and 

 moisture content is placed in retorts or ovens heated externally 

 by the products of combustion from one or more furnaces. The 

 heat penetration is necessarily slow and irregular, owing to the 

 many variable elements mentioned. Some of the problems con- 

 fronting the distillation engineer of the present time, whether 

 dealing with hardwood or resinous wood, are thus presented. 



In order to make the situation clearer, it will be well to outline 

 briefly the present state of the art and to follow this by a descrip- 

 tion of certain methods which are demonstrating their ability to 

 cope with the known difficulties. 



In the field to-day are two general types of plants, retort plants 

 (the older) and oven plants (the newer and larger). 



The standaril retort is a plain horizontal cylinder fifty-two inches 

 in diameter and nine feet long. It holds seven-tenths of a cord. 

 Ovens are of various sizes, usually holding six cords, but are 

 always rectangular in form and provided with tracks on which 

 run small cars to convey the incoming wood, hold it in position 

 while carbonizing, and carry the outgoing hot charcoal to the 

 coolers. The principle employed in each is exactly the same. The 

 time required for a complete "turn-over" is twenty-four hours, 

 which is the same for both types. By a turn-over is meant the 

 time of carbonizing, drawing the charge of charcoal and again 

 filling the apparatus with fresh wood. Therefore, practically the 

 only advantages of the oven over the retort are those of a smaller 

 labor charge in loading and unloading, and also less breakage 

 and loss of charcoal. Hence, it is plain that the first step of wood 

 distillation, i. e., carbonization, is done still in very much the 

 same way that it was twenty or twenty-five years ago. 



The retort was in universal use until the discovery of natural 

 "as. While that fuel was extremely low in price, the oven was 



devised to take advantage of that fact. As the price of gas 

 steadily rose, the ovmers were, one by one, forced to turn to 

 the use of coal, which for a time caused much trouble, due to 

 lack of proper heat distribution. Even now this feature is far 

 from perfect, and it is very doubtful if ovens would ever have 

 reached their present prominence but for the rise and fall of 

 natural gas. 



The carbonization of wood simpl.v means its heating to a rather 

 high temperature and at the same time the exclusion of air. This 

 operation is not as simple as it would at first appear. When heat 

 is applied to the shell of the oven or retort, it is transmitted to 

 the contained wood partly by conduction (to the portions of the 

 wood in contact with the shell) and more by radiation (to wood 

 lying farther from the shell). The first mode of heat transmis- 

 sion is by far the more desirable for the purposes in hand. Cord- 

 wood is by nature a most irregular commodity, in shape, character 

 and moisture content. This fact precludes all thought of auto- 

 matically handling or of equipping retorts to facilitate heat pene- 

 tration. 



When a piece of wood is heated, it naturally first gives up its 

 moisture. After this, if no air be present, the chemical elements 

 of the wood are torn apart by the increasing temperature and then 

 re-combined to form other and totally different substances. For 

 example, it is capable of easy demonstration that there is not a 

 single drop of wood alcohol in a cord of wood. If, however, we 

 carbonize this wood and collect the resulting vapors, we get wood 

 alcohol, the quantity depending on the kind of wood and the 

 way in which carbonization is effected. This is true in a still 

 greater degree of acetic acid, which goes to make the commercial 

 acetate of lime. The quantity of such goods or the "yield" is a 

 subject of first magnitude to the producer and will be discussed 

 later on. 



When the elements are evolved from the wood, they at once 

 re-combine as stated and in so doing generate heat, thus raising 

 materially the temperature of that particular zone or part of the 

 mass. This is known as "exothermic reaction." It has been 

 but little understood and still less controlled, and forms another 

 complication with which the distillation engineer has had to con- 

 tend. When the elements of the wood re-combine, they form gas 

 and at the same time a very complex substance which, when 

 condensed, is known as pyroligneous acid or "raw liquor." These 

 substances leave the retort in the form of heated vapor which 

 is carried to suitable water-cooled surface condensers which lower 

 the temperature of the whole. The gas sweeps on through this 

 condenser chemically unchanged, while the vapors are largely 

 reduced to liquid form. Unfortunately, the gas refuses to give 

 up all its valuable burden of vapors but sweeps a part of them 

 on through and out of the condenser. Much good work has been 

 done in connection with this and in reclaiming the entrained 

 vapors from the gas. The manufacturers have, however, for the 

 most part refused to adopt this or other improvements, preferring 

 to adhere to ancient methods while they attributed their mis- 

 fortune to the tariff, or some equally irrevelant cause. Following 

 this policy, the gas is taken directly to the boiler fire boxes and 

 burned as fuel. 



The residuum remaining in the retort is the charcoal 

 merce. The pyroligneous acid requires further treatment, 

 stated, this treatment consists of the following steps: 



Settling to eliminate portions of the tar. 



Complete distillation to eliminate the balance of Ihe tar which is left 

 behind in the still. 



Addition of lime to neutralize acetic acid and form acetate of Hmo. 



Distillation to take off weak alcohol, the acetate remaining In solution 

 in the still. 



ISe-distillation of the above weak alcohol to bring it up to eighty-two 

 per cent or commercial "crude." 



of com- 

 Briefly 



—26— 



