8 BULLETIN 85, U. S. DEPARTMENT OF AGRICULTURE. 



allowed the uncondensed steam to escape to the atmosphere. The ex- 

 haust box was built up of cypress lumber, being about 12 inches square 

 by 14 feet long. The heat contained in the exhaust steam from the 

 five steam turbine driven separators and five reciprocating pumps was 

 sufficient for pasteurizing 17 per cent cream at the rate of 18,360 

 pounds, or 0.18 tons, per hour. This was actually done during the 

 first hour of test. The initial temperature of the cream was 49.5° F., 

 and it was raised to a pasteurizing temperature of 147° F., or through 

 a range of 97.5° F. 



As 1 boiler horsepower is equivalent to the evaporating of 34i 

 pounds of water from and at 212° F., the boiler horsepower per hour 

 required for pasteurizing under the above conditions was 67.1. It is 

 therefore obvious that had this exhaust steam been allowed to go to 

 waste and live steam been taken direct from the boiler for pasteuriz- 

 ing, the boiler capacity of the plant would have had to be increased 

 by this amount, viz., 67.1 horsepower. In other words, there was a 

 saving in boiler capacity, by using the heat in the exhaust steam for 

 pasteurizing, of 67.1 horsepower. As has been previously explained, 

 it was necessary to employ some such arrangement as that illustrated 

 in the diagram in order to avoid putting a back pressure on the turbine 

 separators, although tliis arrangement entailed a loss of heat due to 

 the double heat transfer from the exhaust steam to the water and from 

 the water to the cream. 



Assuming that the boiler and furnace efficiency was 50 per cent 



and that the coal used had a heating value of 12,500 B. t. u. per 



pound, then the fuel saved per hour with this arrangement is 



67 1 X 34 5 X 970 4 



— T o\nn'v -n =359 pounds. If the pasteurizing equipment is 



run 4 hours a day for 310 days in the year, the annual saving in 



359 X 4 X 310 



fuel is — — fttttt: = 198.7 tons, which at $4 per ton would amount 



2,240 r 



to S794.80. In addition to the fuel saved, there is a further saving 

 due to the decreased boiler capacity of the plant. 



It is evident that if the exhaust steam from the separators and 

 pumps had been allowed to escape it would have been necessary 

 to have taken live steam from the boilers for the purpose of pasteur- 

 izing, and this would have taken an additional 70-horsepower boiler, 

 which would have cost approximately $14.75 per boiler horsepower 

 installed, or $1,032.50. Figuring the interest on the money invested 

 at 6 per cent per annum and depreciation and repairs at 10 per cent, 

 there is a saving in addition to the fuel of $165.45, making a total 

 saving of $794.80 + $165.45 = $960.25, to say nothing of the increased 

 labor of firing the boiler. Adding this to the actual cost would 

 bring the cost of pasteurizing 100 pounds of cream in this particular 

 plant up to $0.0512, or an increase of 12.3 per cent. The fuel cost, 



