Brubaker, William

Western Dry Kiln Clubs

Western Dry Kiln Clubs. Meeting (31st : 1980)

Undetermined

ScholarsArchive@OSU

ENERGY SAVINGS IN DRY KILNS - SOMETHING OLD, SOMETHING NEWWilliam BrubakerWellons, Inc.Sherwood, OregonLet's start with something old, first. In earlier days,when electric power was expensive, dry kilns were sold with 2-speed motors to drive the line shaft fan system. The reason forthis is that the greatest air circulation requirements in a drykiln occur during the first half of the schedule, which is aboutwhen the lumber reaches fiber saturation point (approximately 28%to 30% moisture content). After that level has been reached, aircirculation needs are greatly reduced and fans can be droppeddown to slow speed, thus using only half the initial horsepower.About ten years ago, I discovered that a mill in NorthernCalifornia had ten dry kilns, each powered with a 50 H.P. 2-speedmotor driving the fans. No one in the mill could remember everrunning the fans at slow speed. Power was fairly cheap by then,so why should anyone be concerned about using less electricity?I suggested they try one kiln charge with the fans at low speedduring the last half of the schedule, and then check the lumbercarefully on the dry sorter against a charge dried with fans onhigh speed only. They found absolutely no difference and havebeen utilizing the 2-speed fan schedule ever since.This may not sound very important until you calculate thesavings in dollars. Assuming a power cost of five cents perkilowatt hour today (it was one-half cent ten years ago), 500horsepower (ten 50 H.P. motors), operating 340 days a year, 24hours a day, will consume $141,530 in electrical power. Runningthe low speed one-half the time will reduce the total power con-sumption 25%, or a savings of $35,380 per year--at today's powerprices!Saving electrical power in the dry kilns can contribute moreto reducing your energy bill than any other place in the plant--simply because your kilns run practically all year long, 24 hoursa day, or over 8,000 hours annually. In comparison, your sawmilland planing mill, running two 8 hour shifts, are in operationonly 4,000 hours per year.We've talked about something old, now let's talk about some-thing new. It is not uncommon in sawmills to have 300 to 400 H.P.(or more) in dry kiln fan motors. Recognizing the time-testedreliability of the line shaft fan system in dry kilns, Wellonsset out to improve their dry kiln with a fan system which greatlyreduces or even eliminates electrical power requirements. Fiveyears ago, we unveiled two dry kilns with a new fan system inwhich we intended to accomplish:1. Lower electrical horsepower requirements.2. Non-reversing fans.3. Reversible air flow.4. Normal or above normal air flow in either direction.All of these objectives were met. With 40% to 50% lesshorsepower, we have a fan system which never turns off during the25kiln drying cycle, air circulation which can be reversed auto-matically (as frequently as every 15 minutes to as little as everyfive hours) and very acceptable air flow by today's high efficien-cy line shaft standards.The accompanying figures illustrate how the air travels andreverses. On a standard line shaft (Figure 1) looking at a planview, the zig-zag fan ducts are arranged with alternating right-and left-hand fans. The air flows in the direction of the arrows(Figure 2) in counter clockwise rotation of the fan, and theopposite direction (Figure 3) in clockwise direction. If wecould, in effect, move fan wall A (Figure 4) to position X, andfan wall B to position Y, air would be forced to move in theopposite direction (Figure 5). By making these fan walls (Figure6) into "jalousie louvers" a 90° rotation closes one louver andopens the adjacent one (Figure 7).Okay, let's go to something old again. Years back, in theold mills, steam was used to drive almost everything. So, ofcourse, all of you are one step ahead of me--since the line shaftonly needs to turn in one direction, why not do it with a steamturbine? Right! And that's just what we're in the process ofdoing. We'll use 150 PSIG steam and turn the turbine (using thePRESSURE of the steam to do the work in turning the turbine) anduse the 15 PSIG exhaust steam to supply the heating coils andsteam spray humidification (using the HEAT in the steam to do theheating job in the dry kiln heating coils). Interestingly enough,only about 10% more fuel is required to generate steam at 150PSIG, instead of 15 PSIG (starting from water at 212°F, in bothcases, assuming 60% boiler efficiency). Having your cake andeating it, too? You bet!2627

Energy savings in dry kilns - something old, something new

https://ir.library.oregonstate.edu/downloads/9k41zf65c

Energy savings in dry kilns - something old, something new

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