September 25, 1915. 



HARDWOOD RECORD 



23 



through the piles. Even with the boards placed edgewise, the stick- 

 ers running vertically, with the heating pipes beneath the lumber, it 

 was found that although the air passed upward through most of the 

 spaces, it was actually descending through others, and very unequal 

 drying resulted. While edge piling would at first thought seem ideal 

 for the freest circulation in an ordinary kiln with steam pipes be- 

 low, it, in fact, produces an indeterminate condition ; air columns 

 may pass downward through some channel as well as upward through 

 others, and probably stagnate in others. Nevertheless, edge piling 

 is greati}' superior to flat piling where the heating system is below 

 the lumber. 



The idea has gradually been developed from these experiments and 

 from a study of conditions in commercial kilns to so arrange the 

 parts of the kiln and the pile of lumber that advantage may be 

 taken of this cooling of the air to assist the circulation ^instead of 

 being a counteracting influence. That this can be readily accom- 

 plished without doing away with the present features of regulation of 

 humidity by means of a spray of water, is clear from the accompany- 

 ing diagram. Fig. 1, which represents a cross section of the im- 

 proved humidity regulated dry kiln. 



In the simplest, typical form, shown in the sketch, the spray cham- 

 bers formerly placed on the sides of the kiln are done away with and 

 are replaced by a single chamber or flue B which runs through the 

 center near the bottom. This flue is only about six or seven feet 

 in height, and together with the water spray F and the bafile plates 

 DD, constitutes the humidity control feature of the kiln. This con- 

 trol of humidity is effected in the same manner as in the former 

 kiln by the temperature of the water used in the spray. This spray 

 completely saturates the air in the flue B at whatever predetermined 

 temperature is required. The baflle plates DD, are to separate all 

 entrained particles of water from the air, so that it is delivered to 

 the heaters in a saturated condition at the required temperature. 

 This temperature is, therefore, the dew point of the air when heated 

 above, and the method of humidity control may, therefore, be called 

 the dew-point method. It is a very simple matter by means of the 

 humidity diagram designed for the purpose,* or by a hydrodeik to 

 determine what dew point temperature is needed for any desired 

 humidity above the heaters. This spray F also accomplishes another 

 thing besides the humidity regulation, namely, it acts as an ejector 

 and forces a circulation of air through the flue B. The heating sys- 

 tem H is concentrated near the outer walls so as to heat the rising 

 column of air. The temperature within the drying chamber is con- 

 trolled by means of any suitable thermostat, actuating a valve on the 

 mean steam line. The lumber is piled in such a way that the stick- 

 ers slope downward toward the center. Referring to the remaining 

 letters on the diagram, M is an auxiliary steam spray pointing 

 downward for use at very high temperatures. C is a gutter to catch 

 the precipitation and conduct it back to the pump, the water being 

 recirculated through the sprays. JJ are auxiliary heating coils, for 

 maintaining tlie temperature of tlie rising column of hot air but may 

 be omitted. G is a pipe condenser for use toward the end of the 

 drying operation. K is a baflle plate for diverting the heated air 

 and at the same time shielding the under layer of boards from direct 

 radiation of the steam pipes. 



The operation is extremely simple. The heated air rises in the 

 spaces HJ at the sides of the pUes of lumber. As it comes in con- 

 tact with the piles, portions of it are cooled and pass downward 

 and inward through the layers of boards into the space G. Here 

 the column of cooled air descends into the spray-flue B where its 

 velocity is increased by the force of the water spray. It then passes 

 out from the baffle plates to the heaters and repeats the cycle. 



Various modifications of this arrangement may be made. For 

 instance, a single track kiln may be used. This form would be 

 represented by simply dividing the diagram vertically into two 

 parts by extending the line E (on the left side) upward to represent 

 the outer wall, and erasing the part to the left of this line. Or 

 again, the spray chambers may be kept on the sides, just as in the 



former kiln, as shown in figure 2. The lumber would then slope 

 in the opposite direction with respect to the center of the kiln, the 

 air would rise in the center and descend on the sides. With this 

 arrangement the flue B may be extended upward to the top of the 

 pile as in the former kiln. In fact, the former kUn may be used to 

 accomplish this reverse circulation, by merely sloping the piles of 

 lumber in the direction shown in figure 2, without any alteration of 

 the parts, except that the steam pipes should be concentrated towards 

 the center or so baffled as to throw the heat towards the center of the 

 pile. Experiment indicates that the method will work satisfactorily 

 with this arrangement, the air rising in the center, descending out- 

 wardly through the lumber, rising to the top of the partitions and 

 again descending in the spray chambers. It is advantageous, how- 

 ever, to lower the partitions and also the spray system so that the 

 tops of the spray chambers are but slightly above the bottom of the 

 pile of lumber. 



One of the greatest advantages of this reversed circulation method 

 is that the colder the lumber when placed in the kiln, the greater is 

 the movement produced, under the very conditions which call for 

 the greatest circulation, — ^just the opposite of the direct circulation 

 method. This is a feature of the greatest importance in winter, 

 when the lumber is put into the kiln in the frozen condition. One 

 truck load'of lumber at 60 per cent moisture may easily contain over 

 seven thousand pounds of ice! Think of the circulation of air 

 needed to melt three and a half tons of ice, before any heating or 

 drying can begin to take place, and this for every truck load placed 

 in the kiln! 



The result is, in fact, self -regulatory : The colder the lumber, 

 the greater the circulation produced; and, moreover, the effect is in- 

 creased toward the cooler and wetter portions of the pile. 



In figure .3 is illustrated diagrammatically how a battery of six 

 trucks, equivalent to three ordinary kilns, may be placed under a 

 single roof without any partitions between. 



Baltimore Exports for August 



The statement of exports of lumber and logs from Baltimore dur- 

 ing August has been completed, and apart from showing a sharp 

 decline as compared with July, it also discloses a continuance of the 

 gains over the corresponding month of last year. This is one of the 

 striking features of the exhibit, which takes on additional interest 

 from the fact that August is the first month which can be compared 

 with the corresponding month of 1915, falling within the war period. 

 Heretofore it has been a case of contrasting the war months with 

 others when supposedly normal conditions prevailed, but from now 

 on the effect of the great conflict upon the exports of lumber and 

 logs can be traced from month to month. The report shows what 

 has been generally known before, that August is one of the dullest' 

 months in the year, war or peace, a decided decline as against July 

 being revealed. The falling off from July to August of the present 

 year, however, is not so heavy as was the shrinkage in 1914, the total 

 value of the exports this year being by some $20,000 larger than 

 that for the same months of 1914. Some of the items altogether 

 wanting in 1914 again take their place on the list, and the exhibit is 

 in the main gratifying. Of course the first shock of the war, as was 

 to have been expected, caused a sharp cessation of shipments, a con- 

 dition that gradually gave way to a revival of confidence when it 

 appeared that the bottom had not dropped out of the business. The 

 comparative statement for August of the two years is as follows: 



$25,655 



• Forest Service Bulletin 104. "Principles of Drying Lumber and 

 Humidity Diagram," Superintendent of Documents, Government Printmg 

 Office, Wasbington, D. C, 5 cents. 



-August, 1915 

 Quantity Value 



Logs — Hickory 



Lumber — 



Oak 710,000 ft. 



White pine 



Shortleaf pine 113.000 ft. 



Poplar 334,000 ft. 



Spruce 111,000 ft. 



.\11 other woods 209,000 ft. 



Sbooks 6.571 



Staves 191,900 



Headings 



.\11 others i 



Doors, sash and blinds 



Furniture 



All other manufactures of wood 



-August, 1914 



4,040 

 11,345 

 3,330 

 9,152 

 6,070 

 9,070 

 900 

 2,800 

 2,200 

 2,300 

 9,660 



Quantity 

 20,000 ft. 



S4S.000 ft. 

 31,000 ft. 



91,000 ft. 



11,000 ft. 



294,000 ft. 



Vain- 

 $ 710 



31,112 

 1,320 



' '3,698 



454 



14,104 



$86,522 



7,280 



"'662 

 7.142 



$66,482 



