GBOUND-WOOD PULP. 33 



(2) When wood is cooked under conditions of constant pressure 

 and varying lengths of time the maximum power consumption per 

 ton of pulp is obtained after cooking for six hours. This holds true 

 regardless of the pressure at which the cooking takes place, between 

 and 75 pounds gauge pressure. 



(3) Wood which is cooked at high pressure requires more power 

 per ton of pulp when ground under the same conditions of cylinder 

 pressure, speed, and surface of stone than wood which is cooked at 

 lower pressure, if the duration of the cook is the same. Likewise, the 

 production of pulp in 24 hours is materially less when the wood ground 

 has been cooked at high pressure than if it had been cooked at low 

 pressure. 



(4) The yield per cord is influenced very greatly by the length of 

 time the cooking is carried on and the pressure of the cook, being 

 much lower for high pressures than for low and also for long cooking 

 periods than for short. 



(5) The power to the grinder increases with speed and pressure of 

 grinding and decreases with the degree of sharpness of stone. There 

 is also a very slight increase in the power required with increase of 

 temperature, other conditions remaining constant, while the thick- 

 ness of stock in the grinder pit has almost no influence. Under like 

 conditions of all other factors the power to the grinder is less for 

 steamed wood than for green or seasoned wood untreated. 



(6) With a fixed amount of power to the grinder and a fixed grind- 

 ing pressure, the speed of the pulp stone will vary greatly, depending 

 on the length of time the wood has been steamed and the steaming 

 pressure. Unsteamed wood will grind at low speed, while that 

 steamed a long time will grind at high speed with the same amount 

 of power to the grinder. 



(7) There is little if any difference in the quality of pulp obtained 

 as a result of using either the boiling or steaming process. The color, 

 length of fiber, and yield are practically the same if the boiling or 

 steaming is carried on at the same temperature. 



(8) The amount of pulp produced in grinding cooked wood with a 

 fixed amount of power to the grinder is less at high pressure and low 

 speed than it is at low pressure and high speed. This results in a 

 greater horsepower consumption per ton of pulp at high pressure and 

 low speed. 



UNCOOKED WOOD. 



(1) The rate of production varies directly with pressure, speed, and 

 degree of sharpness of stone. Less pulp is obtained in 24 hours using 

 seasoned wood than with green, and still less using steamed wood, all 

 other conditions being the same. The temperature influences the 

 rate of production to some extent ; less pulp is produced at low tem- 

 peratures. 



14S52°— Bull. 343—16 3 



