CANE SUGAR. 



In a sugar factory the main steam pipes will be at a temperature of say 

 324 F., and the back pressure pipes at a temperature of say 224 F. ; the 

 average of these is 274 F, and assuming an equal area in main and back 

 pressure piping it will be sufficient then to take the steam piping as having an 

 excess temperature over the air of 200 F. From the table above then each 

 square foot of unprotected piping will lose 580 B.T.U. per hour, and per 1000 

 square feet the loss is 580,000 B.T.TL If each pound of megass gives for use 

 in the factory 2922 B.T.U., the loss per hour per 1000 square feet is very nearly 

 2000 Ibs. ; if 80 per cent, of this loss be economized by lagging, the loss per 

 hour per 1000 square feet of pipe area is reduced to 400 Ibs. amounting in a 

 day of 24 hours to 9600 Ibs. of megass. This rough and imperfect calculation 

 is introduced to show the magnitude of heat losses in steam pipes and the 

 differences which may be found between compact and straggling factories and 

 between careful and careless equipment. 



Heat Value of Megass as influenced by the 'Extrac- 

 tion.' The samples of megass, the heat value of which was determined by 

 Geerligs, contained but little sugar, and were representative of well exhausted 

 megass ; the thermal value of sugar is lower than that of the cellulose and 

 xylan, so that with less well crushed megass the thermal value per pound of 

 dry matter will tend to decrease, but only to a relatively small extent. 

 Megass approximating to 46-5 per cent, carbon gave a thermal value approx- 

 imating to 8350 B.T.U. per lb., or 17,978 B.T.U. per Ib. of carbon. It might 

 be sufficient to use this value in calculating the thermal value of a megass 

 from its analysis which should include determinations of the cellulose, xylan, 

 sugar and glucose. 



Incidentally it may be remarked that these determinations of Geerligs 

 and others show how incorrect is the use of ' Welter's ' rule which states that 

 the heat of combustion of an organic compound is the heat of combustion of 

 its elements, after deducting the hydrogen which will go to form water ; with 

 the carbohydrates this would imply that their heat of combustion is the same 

 as that of the carbon they contain. The heat of combustion of carbon is 

 14,400 B.T.U., so that a megass containing 46 ! 5 per cent, carbon would only 

 afford -465 x 14,400 = 6696 B.T.U. as compared with the 8350 B.T.U. 

 found on actual experiment. 



Use of the Waste Gases to dry Megass. In Mauritius many 

 factories have erected apparatuses known as secheries for the purpose of the 

 utilization of a part of the waste heat of the flue gases. A secherie, Fig. %24, 

 consists of a large stone or brick chamber into which the flue gases are 

 exhausted by means of fans ; it is usually about 40 ft. long with an internal 

 breadth of six or seven feet, and about 30 ft. high. The green megass is 

 delivered into the sechene by the carrier a falling on to the upper endless belt I ; 

 three such belts are usually provided ; from the lowest the megass falls on to 



418 



