24 



HARDWOOD RECORD 



February 



1922 



By C. J. M. 



These lines are particularly recommended to the consideration of 

 those Captains of the woodworking industry who are obliged to buy 

 more or less coal or other fuel to supplement the shavings and scrap 

 wood, which, resulting as a byproduct of their operations, are 

 passed on to the boiler furnaces for production of power and heat. 



It is in such plants that the full fuel value of shavings should be 

 completely utilized, because unless this full fuel value is obtained, 

 then the additional purchased fuel, or at least part of it, represents 

 waste of money, pure and simple, caused by the improper combustion 

 of the fuel by-product of the plant. 



As an interesting example, the writer recalls the investigation of 

 the steam boiler operation of a woodworking plant of reasonable 

 magnitude, which required approximately $15,000 worth of coal (at 

 pre-war prices) per annum, in addition to the dry shavings (mostly 

 hardwood) and wood scrap, delivered to the boilers. The investiga- 

 tion promptly disclosed an exceedingly wasteful application of the 

 shavings, which were not considered in the light of a valuable fuel, 

 but rather as a factory waste which had to be gotten rid of by incin- 

 eration in a boiler furnace on top of a perfectly good bed of glowing 

 lump coal. 



Briefly told, about 40 per cent, or $6,000, of this coal bill was 

 saved through a more economic use of the shavings, and an addi- 

 tional 12 per cent, or $1,800, was saved through the remedy of obvi- 

 ous defects in condition and operation of the steam equipment. 



Combustion engineering has qjade great progress in the last 

 decade, but not in woodworking plants generally, and the conditions 

 above described are by no means very rare. The gentlemen at the 

 top of the woodworking establishments will find that a real oppor- 

 tunity exists for profitable conservation of by-product fuel in most 

 of their boiler plants, provided they shall divorce these plants from 

 customary methods of least resistance and shall enforce rational, 

 economic conditions of fuel feeding and combustion. 

 Hardwoods Have Good Heat Value 



Engineering textbocjks usually state the heat value of hardwood, 

 in comparison to that of bituminous coal, as 2:1, that is, two pounds 

 of hardwood will make as much heat as will one pound of bituminous 

 coal. While nothing is stated, generally, about the moisture content 

 of the wood, ordinary, air-dry condition, of 15 to 20 percent is 

 presumed. 



In daily practice, however, many steam boiler plants of woodwork- 

 ing establishments do not realize even this 50 per cent heat value 

 from their shavings. In fact, there are some woodworking plants 

 which do not obtain as much as 25 per cent of the true fuel value 

 from their by-product, and further, there are still other woodwork- 

 ing plants which, at times at least, actually spend good money for 

 coal with which to burn their shavings at more than a 100 per cent 

 loss. This may seem unbelievable, but the statement is based on 

 observation. 



On the other hand, the following description of a highly econom- 

 ical steam producing plant, using about 60 tons of shavings per day, 

 may prove more refreshing and perhaps profitable. 



A short time ago the writer, as a member of a committee of engi- 

 neers, made an investigation in the boiler plant of a large industry 

 near Chicago, which had been reported as obtaining most economic 

 results from its shavings and scrapwood fuel (the bulk from kiln- 

 dried hardwood and a small percentage from dry pine). 



The findings of this investigation substantiated in fact that each 

 pound of the entire 60 tons of shavings actually did produce as 

 much steam as three-fourths of a pound of the fair grade Illinois 

 coal which was being used, under highly economical conditions of 

 stoker firing and combustion, in boilers of the same size and make, 

 adjoining those burning the shavings. The exact percentage ob- 

 tained from the wood was 76 per cent of the amount of steam as 



produced by one pound of coal. Thus if one ton of the coal cost 

 $4, then one ton of the shavings had a fuel value of $3, both deliv- 

 ered into the furnace. 



The shavings were fed automatically, but not through the usual 

 spout from a Cyclone separator. Instead, the separator delivered 

 the shavings and hogged scrap to a horizontal drag conveyor above 

 the boiler house, and from this were filled the individual boiler bins, 

 solid with the shavings. From the bottom of these bins the shavings 

 were conveyed in concentrated form, by mechanical means, to the 

 furnaces and there introduced, without admission of air above the 

 fire, and at the instant of entering the furnace were spread, in an 

 effective manner, by means of small steam jets, so as to cover the 

 entire grate surface quite uniformly. 



Automatic Feed Gains Heat 



Wishing to determine just what credit these automatic feeding 

 devices were entitled to in the economic performance of the plant, 

 the writer arranged with the plant engineer of another large Chicago 

 manufactory to run a complete test on shavings skillfully hand-fired 

 with admission of minimum excess air, and burned under similar 

 conditions of science and common sense. 



This test disclosed that with careful handflring (with the shovel 

 from boiler room floor), each pound of shavings from kiln-dried wood 

 (mixed about SO per cent hardwood and 20 per cent pine), would 

 produce a trifle over 65 per cent as much steam as would one pound 

 of Clinton County (Illinois) coal, when likewise burned under same 

 favorable conditions. 



In this case, if therefore the coal likewise cost $4 per ton, then 

 the fuel value of the shavings was $2.60 per ton, both delivered to 

 the firing floor. 



Comparing the automatic shavings feed with hand firing, under 

 the conditions stated, we find a difference of 11 per cent in favor of 

 the concentrated automatic feed, which difference at the costs 

 stated, would have a money value of about 40 cents per ton of 

 shavings. 



Other and similar cases of extreme results may be cited in illus- 

 tration of a condition of waste, existing in a great industry, which 

 waste is perhaps suspected but not suflSciently appreciated in its 

 full importance to the individual manufacturer and to the entire 

 industry. 



What are the essential factors which control the economic com- 

 bustion of shavings and make possible a high rate of economy in 

 one case, and almost complete loss of the fuel value of the shavings 

 in another, and what is the remedy? 



Essentials for Burning Shavings 



There are but three essential conditions necessary to the economic 

 combustion of shavings. These are: 



FIEST: Continuous, uniform feeding of the shavings in concen- 

 trated mass, and in sufficient volume to keep grates thoroughly 

 covered to uniform depth, but not too deep to choke the air supply. 



SECOND: Thorough spreading over the entire grate area, care- 

 fully avoiding all bare spots through which excess air could enter. 



THIRD: A correctly proportioned, uniformly maintained air 

 supply, through the grates only, and by no means above the fire, 

 carefully avoiding excessive amount of air, over and above that 

 required to support complete combustion, plus such small addition 

 as may be necessary to effect thorough distribution of the air 

 throughout the shavings. 



None of these conditions is properly fulfilled in the generally em- 

 ployed, convenient method of feeding shavings to the boiler furnace 

 through a spout or chute direct from the Cyclone separator, which 

 method, because of its convenience, has cost the woodworking 

 industry of this countrv millions of dollars in wasted fuel. 



