PRODUCING SODA PULP FROM ASPEN". 



37 



cost of wood, soda ash, and bleaching powder. The vertical distances 

 between curves A and B represent cost of soda ash alone, and those 

 between curves B and C represent cost of bleaching powder alone. 



The cost values were obtained by calculations from the amounts 

 of wood, soda ash, and bleaching powder consumed, based on the 

 experimental results. 1 A 90 per cent recovery of the cooking chem- 

 icals charged to the digester was assumed in determining the amounts 



26 

 24 



22 

 «o 

 5 20 



_i 



© 18 



o 



I ,6 



A. 14 



_l 



3 



Ik 



O 



z 10 

































\ 















\ 















\ 













\ 





^e 





_^" 



>? 



»•* 







\ 



V 



S* 



*< 



i 



A 







V 



^^ 











.10 



.20 30 .40 



POUNDS NaOH PER POUND OF WOOD 















" 1 





















































\\ 





c 













\ 



























\ 



^ vS. 



















A 













2 4 6 8 10 12 

 DURATION AT MAX. PRESSURE-HOURS 



18 



CO 



t- 



w 16 



o 

 u 



14 

 12 



10. 



c ■ 



"""A 



60 



TO 80 90 100 110 120 



MAX. PRESSURE -PDS. PER SQ IN. 



c 



_j_ — ~~~ — " 



a" 



40 50 60 70 80 90 100 110 



CONCENTRATION NaOH-GRAMS PER UTEJt 



Fig. 20. — Effects of cooking conditions on cost items per ton of pulp. A, wood; B, wood and soda 

 ash; and C, wood, soda ash, and bleaching powder. 



of soda ash consumed or lost per ton of pulp. The basic units for 

 costs are assumed average values as follows: 



Wood, $9 per solid cord (100 cu. ft.); soda ash (58 per cent Na 2 0), 

 SI per 100 pounds; bleaching powder (35 per cent available chlorine), 

 $1.55 per 100 pounds. 2 The bone-dry weight of aspen wood is taken 

 as 26.68 pounds per cubic foot of clear wood, green volume. 



i These amounts were calculated by interpolating from the yield curves (fig. 4), the loss on bleaching 

 curves (fig. 10), and thecurves for soda ash and bleaching powder employed per ton of pulp (figs. 18 and 19), 

 and not from actual test data. On this account platted points have been omitted. 



2 Reasonable maximum, average, and minimum values for a "solid cord" of aspen f. o. b. mill are $11, 

 $9, and $6, as determined from statistical reports received from a number of mills. Correspondence with 

 pulp manufacturers brought the information that reasonable maximum, average, and minimum unit 

 costs as defined above may be assumed with a fair degree of accuracy as follows: For soda ash, $1.20, $1, 

 and $0.85; for bleaching powder, $2.05, $1.55, and $1.10. These values do not depend upon market fluctua- 

 tions alone, but vary through the range given, due largely to differences in freight charges lor mills in 

 different localities. The actual selling price of "58 per cent" soda ash is 10/48 greater than the manufac- 

 turer's or market quotations, since the latter are based on the old standard of "48 per cent" soda ash. 



