24 



BULLETIN 343, U. S. DEPARTMENT OP AGRICULTURE. 



to consume the 345 horsepower. When the wood was steamed for 

 6 hours at 20 pounds, a cylinder pressure of 60 pounds and speed of 

 187 revolutions per minute were necessary to use up the power. 



There are shown in figure 17 the relation of horsepower consump- 

 tion per ton, horsepower to the grinder, and production in 24 hours 

 to the steaming pressure when wood, which had been cooked at differ- 

 ent pressures, was ground at constant cylinder pressure and varying 

 speed of rotation of the pulp stone. It will be noted that the horse- 

 power consumption per ton increases with the speed, corresponding 





























































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50 60 70 80 90 100 ■ 



HORSEPOWER PER TON [BONE DRY] HORSEPOWER TO GRINDER TONS (B0HE DRY) IN 24 HOURS 



Fig. 14.— Relation of power consumption and rate of production to speed. (Spruce runs 188 to 191, in- 

 clusive.) 



to increase in the pressure of steaming, and this increase is due to a 

 reduction in the rate of production of the pulp. 



When wood is steamed for a certain number of hours and at a fixed 

 pressure, then ground with a certain amount of power to the grinder 

 but under varying speed of rotation of the pulp stone, it is found that 

 the horsepower consumption per ton increases in a similar manner to 

 that given in figure 18. In other words, at low speed and high pres- 

 sure more power is necessary to grind a ton of pulp in 24 hours than 

 at high speed and low pressure. This is due, again, to the reduction 

 in the rate of production. 



