9A BULLETIN 343, U. S. DEPARTMENT OF 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 
REVOLUTIONS PER MINUTE 
60 70 60 90 100 10 150 200 250 300 350 400 a es Se SS ee ee 
*° NORSEROWER PER TON (BONE DRY] HORSEPOWER TO GRINDER TONS [BONE DRY] IN 24 HOURS 
Fic. 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. 
