January 1, 1921 



THE INDIA RUBBER WORLD 



247 



CONTROLLING CHIMNEY LOSSES TO SAVE FUEL 



THE rubber manufacturer who congratulates himself on his 

 economical management is distinctly shocked when reminded 

 that while he may be saving at the spigot he is wasting at the 

 bung-hole. Yet such a blow to the pride of many a manufac- 

 turer was delivered by one of the foremost combustion engineers 



Where the Heat Goes in the Average Botler Plant 



of America,' in an address on "Saving Fuel by Controlling Chim- 

 ney Losses," read before the Fuel Section of the 1920 National 

 Exposition of Chemical Industries in New York. 



Not that the average rubber manufacturer has been unaware 

 that a considerable amount of the latent heat in coal, which 

 latter commodity is getting perceptibly scarcer as well as dearer, 

 is lost in ordinary furnace combustion. He has known it quite 

 well and has tried his best, with good boiler equipment and 

 trained firemen, to minimize such loss. But what he has not 

 sufficiently realized is the large e.xtent of the loss, not merely in 

 smoke, which seldom exceeds one per cent of the loss through 

 the stack, but in the other products of combustion, the total 

 wastage in this way ranging often up to 40 and even 50 per cent of 

 the fuel used. The most conservative estimate of government 

 investigators" is that out of 100 tons of coal burned under fac- 

 tory boilers, the heat of 35 tons is entirely lost in the flue gases. 

 On the other hand, in boiler plants equipped with the latest 

 scientific devices for controlling heat loss, the wastage is re- 

 duced to as low as 20 per cent. 



Coming as another surprise to many having to do with steam 

 production is the noted engineer's contention that atmospheric 

 oxygen — or fresh air — must not be fed freely to the burning coal 

 to get the most nearly perfect combustion, and incidentally the 

 utmost heat. Indeed, firemen are shown how excess air plainly' 

 dilutes the heat and overtaxes the temperature possibilities of the 

 furnace. Nor do many firemen realize that in burning a ton 

 of coal of average fineness they use up a column of air a foot 

 square and three miles high. Often conscientious enough in 

 handling coal, they could serve their employers better were they 

 more economical in handling that which costs nothing at all — 

 fresh air. 



Shorn of technical terminology, the simple chemistry of efficient 

 coal combustion in boiler plants is that the most important fur- 

 nace product (apart from the heat itself) is carbonic acid gas, 

 i.e., carbon dioxide or COj ; and the greater the quantity of this 

 gas that is produced in proportion to the amount of fuel con- 

 sumed, the more certain it is that the coal user is getting the 

 maximum of heat from his fuel. Overaeration — in other words, 

 too much draft — means the carrying off of the carbon in the 

 coal before it is perfectly oxidized, and hence low COj percentage ; 

 while underaeration means semioxidation or imperfect combus- 

 tion of carbon and the resultant production of too much carbon 



monoxide, CO, the familiar poison gas of ill-ventilated stoves. 

 The ideal condition is where the production of COj is 21 per 

 cent of tile fine gases anil exactly equals the 21 per cent of 

 oxygen in the air passed through the coal. Forty per cent of 

 excess air will reduce' the COi content to 15 per cent, 100 per 

 cent excess will bring it down to 10.5 per cent, and a 200 per 

 cent excess to 7 per cent. 



The remedy proposed is the installing of a plain- 

 reading CO, gage on the boiler front to guide the 

 firemen, and a CO. recording meter in the engineer's 

 office to give daily charts checking up the firemen's 

 work. It is said that with such devices to observe 

 CO, production and graduate air supply, excess loss 

 of heat can be controlled in 99 out of every 100 

 cases, and that such instruments afford a practically 

 unfailing index to proper draft regulation, pro- 

 vided, of course, that due pracaution be taken to 

 prevent air infiltration through the brick furnace 

 setting, that firebeds be kept within suitable thickness, 

 etc. In 24-hour tests made recently in a small New 

 England plant, where the firenjen had probably never 

 heard of COj before but who willingly regulated 

 their work according to the COj production in- 

 dicator, an immediate saving in coal of 9.9 per cent 

 was readilv demonstrated. 



COTTON FIRE HOSE IGNITED UNDER TEST 



Several weeks ago, engineers of the Fire Department of Boston, 

 Massachusetts, were testing a powerful motor fire pump, to which 

 was attached a new length of double-jacket rubber-lined cotton 

 hose. The pump was operated at capacity, with the hose outlet 

 reduced to one-third the usual size and the water passing at an 

 angle from the engine to the hose, striking a spot in the hose 

 about eight inches from the engine coupling. Under these con- 

 ditions heat, due to friction, was generated sufficient to ignite the 

 cotton jackets and cause actual flame. 



By request of Fire Commissioner John R. Murphy, an investi- 

 gation of this occurrence was conducted by Professor Augustus 

 H. Gill of the Massachusetts Institute of Technology, whose report 

 to the Commissioner is quoted in part as follows : 



A thorough examination of the samples shows that the fire took 

 place between the two cotton casings. Further examination reveals 

 the fact that on each side of the burnt hole the casing is very 

 severely chafed. This chafing, coming from the vibration pro- 

 duced in the hose by the pumping, was in my opinion, sufficient to 

 produce great heat and finally active combustion. It seems to me 

 that the cotton casing of the hose is not as closely woven as it 

 should be, as is the case with certainly one other make of fire 

 hose. It would seem that the tension on the cords in the process 

 of weaving was not sufficiently high. 



I have not made a chemical analysis of the rubber lining to as- 

 certain the percentage of free sulphur, for I cannot see how this 

 would be material. The sulphur here is finely scattered through- 

 out the rubber lining and does not occur in pockets or lumps. 



In conclusion, I am of the opinion that the occurrence was due 

 to excessive friction between the cotton casings produced by the 

 vibration of the hose in service. 



ACID FORMED IN FIRE HOSE^ 



Several years ago considerable excitement was caused in various 

 New England city fire departments because of the presence of acid 

 found in lengths of fire hose which had been suspended on racks 

 while partially filled with water. The technical work involved 

 in a thorough and complete research on this matter was turned 

 over to the chemical department of the Underwriters' Labora- 

 tories. Tests have been going on for more than a year under 

 two distinct divisions. One was the practical aspect in which 

 commercial full length samples of fire hose were used, and the 

 other the laboratory investigation done on a situll scale with 

 various rubber compounds and ingredients. 



'F F. UehlinR, combustion engineer. New York City. 

 Technical paper No. 205, United States Bureau of Mines. 



* r-abo'atories* Data. Vol. 1. November. 

 Laboratories. Chicago, Illinois. 



1920. paRe 144. fiuicrwriters' 



