KINETIC STUDY OF N E U T R A L SULFITE PULPING OF ASPEN CHIPS N. C . S. CHAR11 Forest Products Division, Owcnr-Illinois, Int., Toledo, Ohio 43607
A delignification rate expression suitable for digester design and control in neutral sulfite pulping of aspen chips has been developed. The rate equation takes into account the effects of temperature, concentration of cooking liquor, and time of reaction on pulping rate in the temperature range of 338' to 385' F. and concentration range of 7.5 to 30 grams of NazSOa per liter expressed as Na2.O. A molal ratioof 4 parts of Na2C03 per 3 parts of NazSOa was used in the cooking liquors. A rigorous method has been developed to compute the equivalent cooking times based on time-temperature data for a given cook. Data on yields and lignin contents a t different concentrations and temperatures on Ross diagrams show the relative rates of removal of lignin and nonlignin fractions. For H-factor computations, tables on relative rates have been prepared in the temperature range of 21 2 ' to 400' F. An excellent correlation has been observed between H-factor and yield. Graphs showing H-factor-yield relationships a t various concentrations are presented.
HE earliest investigations on the kinetics of the sulfite T p r o c e s s were conducted by Stangeland (1932) and Yorston (1934, 1935). Stangeland measured the rates of solution of spruce wood meal "incrustants" in calcium bisulfite liquor a t various temperatures and reported that the rate of solution of the "incrustants" obeyed the laws of a first-order reaction. T h e incrustants included all substances present in the wood except those determined as Cross and Bevan cellulose. Stangeland explained his results by assuming a n initial very rapid sulfonation followed by a n acid hydrolysis, the rate of which governed the over-all reaction. Yorston determined the rate of delignification at 266' F. and found that the rate of lignin removal deviated considerably from first-order reaction with respect to lignin. Corey and Mitass (1936) cooked two samples of spruce wood meal at several temperatures and assuming a first-order relation showed that variation in reaction rate with temperature followed the Arrhenius equation between 212' and 284' F. Calhoun et al. (1939) showed that the rate of pulping is a function of liquor concentration as well as lignin content. Goldfinger (1941) analyzed the data of Corey and Maass (1936) and Calhoun et al. (1939) and indicated that there is a change in the order of reaction during the cook. Rawlings and Staid1 (1925) were the first to study the effect of cooking aspen wood with a solution of sodium sulfite in the temperature range of 248" to 365' F. Their data showed that a t temperatures above 338' F., hydrolysis resulting in loss of cellulose takes place to a greater extent. Bray and Eastwood (1931) studied the effect of cooking black gum sawdust with a solution of sodium sulfite and sodium bicarbonate in the temperature range of 284' to 338' F. Their results showed that increasing the temperature of digestion by 18' F. roughly doubles the rate of reaction. Dorland et al. (1954) studied the effect of cooking aspen chips with a solution of sodium sulfite and carbonate a t 338' F. I n the range of concentrations studied, they found that yield drops as cooking time is increased but not with increasing chemical concentrations. Doraiswamy (1952) pulped aspen wood meal with a solution
1
Present address, Owens-Illinois, Inc., Valdosta, Ga. 31601
372
I & E C PROCESS D E S I G N A N D DEVELOPMENT
of sodium sulfite in the temperature range of 338' to 428' F. and determined the rates of removal of lignin and carbohydrates. He found that a critical yield, defined as the yield a t which the rate of lignin removal equals the rate of carbohydrate removal, exists at each temperature. Findley and Nolan (1956) determined the effects of temperature, concentration, and time on the neutral sulfite semichemical pulping of red maple in the temperature range of 324' to 367' F. Their data indicated that two apparently first-order, simultaneous or consecutive reactions might control the rate of pulping. Walters and May (1960) conducted isothermal cooks with aspen chips in the temperature range of 343' to 410' F. and found that increasing pulping temperatures greatly accelerated the over-all pulping reaction rates. Pulps produced a t higher temperatures contained slightly higher percentages of residual lignin than the lower temperature pulps of the same yield. Elton (1962) studied the kinetics of neutral sulfite delignification of loblolly pine with emphasis on the effects of morphological characteristics of springwood and summerwood on the over-all delignification rate. H e found that the dissolution of lignin can be divided into three periods, each of which is characterized by a different reaction rate. Wilder and H a n (1962) developed the rate expressions for neutral sulfite pulping based on the data of Walters and May (1960) and found that delignification occurs in two stages, initially a high rate followed by a slower rate. Most of the literature cited to date has not taken into account the variation of concentration during the pulping reaction in developing the kinetic model. The high temperature studies were mostly conducted using wood meal or sawdust, which is unrealistic from a practical point of view of cooking chips. This is substantiated by a recent hypothesis by Nolan (1961), stating that delignification begins a t the outside surface of the wood chip and that the reaction interface moves slowly inward toward the center of the chip. Rigorous computation of equivalent cooking times based on the kinetic model have not been incorporated in the data presented to date. T h e object of the present study is to develop a rate expression taking into account the effects of temperature, time, and concentration of cooking liquor on the neutral sulfite pulping reaction.
Theory
n
T h e neutral sulfite pulping reaction can be assumed to take place in the following steps: A. Diffusion of chemical from the cooking liquor to the wood structure. B. Adsorption of the chemical at the surface of the lignin particles. C. Sulfonation ansd hydrolysis of lignin. D . Desorption of the reaction products from the reaction surface. E. Diffusion of the reaction products into the liquid phase. T h e rate of delignification as represented by steps B, C, and D can be represented as proportional to the reactant concentrations raised to a n arbitrary power as suggested by Wilder and H a n (1962).
where rL
= delignification rate,
grams (of lignin removed
(100 grams of oven-dry wood) (minute)
e =
time, minutes
E = Arrhenius activation energy, calories per gram mole R = gas constant = 1.987, calories per gram mole, ’ K. T’ = reaction temperature, ’ K. L
grams of lignin in pulp
= lignin concentration,
s =
100 grams of oven-dry wood concentration of Na4S03 in cooking liquor (grams per liter as NanO)
m,c,d = constants Defining
b=--
1.8 E
R
(3) where T i s the temperature in on both sides of the equation,
OR.
Taking natural logarithms
b lnrL=Ir~m--+clnL+dInS
T
(4)
Experimental
Aspen (Populus trernuloides) logs were debarked in a wet barker and chipped in a 10-knife Carthage chipper a t the Owens-Illinois mill in Tomahaivk, Wis. T h e chip fraction retained between 1 by l ’ / ~and 1 by ‘/zinch screens was used for the pulping experiments. T h e chips contained an average moisture content of 49.9% but the exact moisture content was determined prior to each experiment. T h e experimental setup used in this investigation is shown schematically in Figure 1. T h e cooks were made in a 2-cu. foot stainless steel digester with circulation and indirect heating. T h e liquor was made u p by dissolving chemically pure sodium sulfite and sodium carbonate in water to give the desired concentrations. Three levels of liquor concentrations were studied: liquor A consisting of 30 grams per liter of NaZS03 and 40 grams per liter of NazC03: liquor B consisting of 15 grams per liter of T\’azso3and 20 grams per liter of N a ~ C 0 3 , and liquor C consisting of 7.5 grams per liter of NaZS03 and 10 grams per liter of NanCOa, all expressed as NanO. To assure that the chemicals from the cooking liquor diffused completely to the wood surface before the reaction step, the chips were soaked overnight in the cooking liquor in a sealed
CIR cu L ATIN
GA
Figure 1 .
Schematic flow d i a g r a m of the digester system
PUMP
container with a stainless steel perforated plate on the top of the chips, so that the chips were submerged in the cooking liquor during this operation. For each of the cooks, 1000 grams of oven-dry chips were used. A high liquor to wood ratio of 20 to 1 was used in order to maintain a liquor composition essentially constant during the cook. T h e digester was preheated to 150’ F. before charging with the chips and the cooking liquor. After the digester was capped, the circulating pump was turned on, allowing the liquor to circulate through the chips before a temperature of 212’ F. was reached. T h e temperature of the cooking zone is determined by a thermocouple in the liquor circulating line. T h e desired cooking schedule was maintained by means of a n automatic programmer, shown in Figure 2. T h e programmer controls the steam flow to the indirect heat exchanger in such a manner as to maintain the desired rate of temperature rise and time of cooking at the desired temperature. Direct steam was used only if the indirect method failed to maintain the scheduled cooking temperature. T h e time-temperature plots were graphically recorded by the programmer. At the completion of the cook, the chips Tvere blown into the stainless steel bloiv tank and the cooked chips were collected in a screened pot. T h e digester was filled with water again, heated with direct steam for 2 minutes, and blown again. This operation was repeated until the digester was completely cleaned out. T h e chips were washed and defibered in a Sprout-Waldron disk refiner, the resulting pulp was spin-dried, crumbled, and bagged, and the moisture content was determined. T h e yield was computed on a n oven-dry basis. T h e lignin content of pulps was determined in accordance with Tappi Standard Method T 222 M-54. Even though this may not represent the total lignin as defined by \$’alters and M a y (1960), the author assumed that the soluble lignin was a certain fraction of the acid-insoluble lignin and would not materially affect the “relative rates” of reaction as defined by Vroom (1957). T h e equivalent cooking time was computed from the d a t a on time-temperature graphs on the automatic programmer described earlier. This is done by a trial-and-error procedure described as follows: Starting with a value of 36,100 for E as derived by Wilder and H a n (1962) for initial delignification rate, the equivalent cooking time, oes, was computed from the relation:
(5) where T,’ is the final desired temperature of cooking in K. T h e integration was done on a digital computer using Simpson’s rule. Tables were then prepared giving the lignin content, L, of pulp (based on oven-dry wood) as a function of eeq. T h e d a t a were then graphically differentiated by plotting AL/A&,,, us. Be, and drawing a curve such that
VOL. 7
NO. 3
JULY 1 9 6 8
373
Figure 2.
Experimental setup for delignification rate studies
-(- d L /d
0
20 40 6 0 8 0
€4
100 120 140 160
T I M E , MIN.
Figure 3. rate data
Differentiation
of
delignification
PERCENT YIELD
A plot showing this method of differentiating the d a t a is presented in Figure 3. T h e constants m, b, c, and d of Equation 4 were then computed from a least squares analysis of experimental data. T h e value of E was then computed from the relation
bR E=1.8
(7)
T h e equivalent cooking times were recomputed using this value o f E and following the procedures descrihed above. This process was repeated till successive values of E did not differ significantly from each other. T h e resulting rate equation for delignification based on this trial-and-error procedure is:
374
I&EC PROCESS D E S I G N AND D E V E L O P M E N T
Figure 4. Ross diagram showing relative rcites o f lignin and nonligriin fractions for liquor A
where
L
= lignin content
e
= time, minutes
of pulp,
grams of lignin
100 grams of oven-dry wood
= reaction temperature, R. S = concentration of N a z S 0 3 in cooking liqu, liter NasSOs (as NasO)
T
Experimental and calculated values of delignincanon Tares are compared in Table I. Defining Y as the per cent yield, values of L/(Y - L) are also tabulated as a function of Y for all these runs in Table I and plotted in a Ross diagram as presented in Figure 4 for
Table 1.
Delignification Rate Data on Neutral Sulfite Pulping of AspenWood Chips
Cottcn. of N a d O a in Cooking Liquor, Grams per Liter as NazO 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0
T f m P* t F. 338 338 338 338 338 350 350 350 350 350 360 360 360 360 370 370 370 370 375 375
30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 15.0 15.0 15.0 15.0 15.0 15 .O 15.0 15.0 15 .O 15.0
375 375 380 380 380 380 385 385 385 385 338 338 338 338 338 350 350 350 350 350
18.9 25.6 10.3 15.4 2Q.9 26.5 8.4 15.8 23.8 28.9 17.6 38.2 69.5 94.3 168.6 16.2 35.3 69.6 90.7 154.8
47 48 49 50 51 52 53 54 55 56 57 58 59 60
15.0 15.0 15.0 15.0 15 .O 15 .O 15.0 15 . O 15.0 15 .O 15.0 15.0 15.0 15 .O 15.0 15.0 15.0 15 .O 15 .O 15 .O
360 360 360 360 370 370 370 370 375 375 375 375 380 380 380 380 385 385 385 385
61 62 63 64 65 66 67 68 69 70 71 72 73 74
7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5
338 338 338 338 338 350 350 350 350 350 360 360 360 360
Run No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
334 35 36 37 38 39 40 41 42 43 44 45
44
Equivalent Cooking Time, Mi;.,
Lignin in Pulp Based on
:2;2
Lignin in Pulp,, %, Yield, 70, Y L = L'Y/lOO L 83.6 17.41 14.56 76.7 15.74 12.08 66.1 14.31 9.46 61.3 13.06 8.01 52.3 11.35 5.94 82.5 17.13 14.14 72.2 15.34 11.08 62.1 13.73 8.53 57.2 12 56 7.19 49.2 5.21 10.58 73.8 11.62 15.74 68.2 10.08 14.78 62.3 8.23 13.21 47.6 4.61 9.68 76.8 12.57 16.36 68.6 10.35 15.08 63.1 13.88 8.76 59.3 7.82 13.18 71.8 11.18 15.57 66.1 9.42 14.25
Y - L 69.04 64.62 56.64 53.29 46.36 68.36 61.12 53.57 50.01 43.99 62.18 58.12 54.07 42.99 64.23 58.25 54.34 51.48 60.62 56.68
13.87 12.76 15.37 13.92 13.15 12.50 15.19 13.57 11-91 11.12 17.73 16.18 14.91 14.02 12.21 17.44 16.14 14.54 13.70 11.86
62.4 57.5 67.9 62.7 56.4 52.4 69.3 57.4 51.6 49.7 85.8 78.7 70.4 65.8 56.4 84.6 76.7 66.9 62.7 54.3
8.66 7.34 10.44 8.73 7.42 6.55 10.53 7.79 6.15 5.53 15.22 12.74 10.50 9.23 6.89 14.76 12.38 9.73 8.59 6.44
17.9 27.2 34.8 90.5 8.4 17.2 24.9 28.5 11.6 17.5 19.8 26.5 8.5 14.9 22.6 28.3 9.5 16.7 25.5 31.2
16.30 15.17 14.48 11.17 17.02 15.49 14.45 13.93 15.87 15.06 14.58 13.58 16.28 14.98 13.61 12.91 15.69 13.98 12.71 12.16
76.8 71.1 66.5 51.8 80.7 71.5 66.6 63.8 73.9 68.7 67.4 61.7 75.4 67.6 61.1 57.6 72.2 62.8 55.3 52.1
32.7 44.9 72.4 98.7 164.7 28.4 46.6 67.1 95.3 161.3 18.7 37.5 68.6 105.4
17.12 16.58 15.79 14.85 13.05 17.21 15.96 15.42 14.06 12.65 16.85 15.19 13.42 11.89
83.8 79.6 74.2 69 .O 62.2 81.8 76.9 72.3 68.4 57.9 79.8 70.5 60.7 53.2
e
16.8 35.5 66.9 97.5 159.3 15.7 37.3 68.6 94.7 157.9 16.3 23.7 37.5 98.7 8.8 15.4 22.6 27.4 10.4 15.8
L Y - L 0.2108 0.1869 0.1670 0.1503 0.1281 0.2068 0.1812 0.1592 0.1437 0.1184 0.1868 0.1734 0,1522 0.1072 0.1957 0.1776 0.1612 0.1519 0.1844 0.1661
0.159 0.107 0.064 0.043 0.023 0.187 0.111 0.061 0.042 0.022 0.243 0.176 0.113 0.032 0.416 0.271 0.186 0.154 0.393 0.272
0.144 0.096 0.056 0.039 0.020 0 228 0.134 0.075 0.052 0.025 0.226 0.166 0.106 0,030 0.405 0.265 0.184 0.144 0.384 0.264
53.74 50.16 57.46 53.97 48.98 45 85 58.77 49.61 45.45 44.17 70.58 65.96 59.90 56.57 49.51 69.84 64.32 57.17 54.11 47.86
0.1611 0.1463 0.1816 0.1617 0.1514 0.1428 0.1791 0.1570 0.1353 0.1251 0.2156 0.1931 0.1752 0.1631 0.1391 0.2113 0.1924 0.1701 0.1587 0.1345
0.220 0.157 0.408 0.273 0.194 0.144 0.502 0.264 0.157 0.122 0.131 0.092 0.061 0.046 0.023 0.155 0,104 0.060 0.047 0.025
0.220 0.153 0.404 0.273 0.191 0.146 0.501 0.259 0.155 0.123 0.119 0.080 0.052 0,039 0.021 0.187 0.127 0.075 0.057 0.030
12.52 10.79 9.63 5.79 13.74 11.08 9.63 8.89 11.73 10.35 9.83 8.38 12.28 10.13 8.32 7.44 11.33 8.78 7.03 6.34
64.28 60.31 56.87 46.01 66.96 60.42 56.97 54.91 62.17 58.35 57.57 53.32 63.12 57.47 52.78 50.16 60.87 54.02 48.27 45.76
0.1947 0.1789 0.1693 0.1258 0.2051 0.1833 0.1690 0.1619 0.1886 0.1773 0.1707 0.1571 0.1945 0.1762 0.1576 0.1483 0.1861 0.1625 0.1456 0.1385
0.205 0.151 0.122 0.041 0.376 0.234 0.172 0,151 0.335 0.240 0.215 0.159 0.438 0,283 0.186 0.144 0.428 0.253 0.158 0.121
0.199 0.144 0.112 0.037 0.368 0,230 0.169 0.142 0.319 0.242 0,216 0.153 0.430 0.282 0.184 0.144 0.439 0.252 0.155 0.123
14.35 13.20 11.72 10.25 8.12 14.08 12.28 11.15 9.62 7.33 13.45 10.71 8.15 6.33
69.45 66.40 62.48 58.75 54.08 67.72 64.62 61.15 58.78 50.57 66.35 59.79 52.55 46.87
0.2066 0.1987 0,1875 0.1744 0.1501 0.2079 0.1900 0.1823 0.1636 0.1449 0.2027 0.1791 0.1550 0.1350
0.087 0.074 0,053 0.042 0.026 0.103 0.079 0,061 0.045 0.026 0.179 0.109 0.062 0.036
0.078 0.065 0.050 0,037 0.022 0.126 0.093 0.075 0.054 0.030 0.174 0.105 0.058 0.033 (Continued)
I
VOL.
I
7 NO. 3 J U L Y 1 9 6 8
375
Table 1.
Run No. 75 76 77 78 79 80
Concn. of Na&O, in Cooking Liyuor, Grams per Liter as Na20 7.5 7.5 7.5 7.5 7.5 7.5
375 375 380 380 380 380 385 385 385 385
7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5
81
82 83 84 85 86 87 88 89 90
Temp., O F. 370 370 370 370 375 375
Table II.
Eyuivalent Cooking Time, Min.,
e' 16.3 20.8 26.9 35.6 11.0 19.7
(Continued)
Lignin in Pulp Based on Lignin Oven-Dry in Pulp, 70, Yield, yo, Wood, yo, L' Y L = L'Y/700 Y L 16.25 76.6 12.45 64.15 15.65 72.8 11.40 61.40 14.96 69.1 10.34 58.76 14.28 65.3 9.33 55.97 16.70 78.4 13.10 65.30 59.74 15.38 70.6 10.86
21.4 25.8 9.8 16.6 25.2 29.0 7.7 16.3 21.7 30.3
-
15.15 14.60 16.63 15.30 14.11 13.73 16.90 15.14 14.31 13.13
69.4 67.6 77.3 70.1 63.9 61.8 77.8 68.2 62.1 58.3
10.52 9.87 12.86 10.73 9.02 8.49 13.15 10.33 8.89 7.66
58.88 57.73 64.44 59.37 54.88 53.31 64.65 57.87 53.21 50.64
L Y -L 0.1940 0.1856 0.1759 0.1666 0.2006 0.1817
Exptl. 0.228 0.190 0.155 0.119 0.312 0,208
Calcd. 0.221 0.182 0.147 0.118 0.303 0.201
0.1786 0.1709 0,1995 0.1807 0.1643 0.1592 0 2034 0.1785 0.1670 0.1512
0.194 0.164 0.358 0.248 0.167 0.146 0.446 0.258 0.196 0.136
0.187 0.163 0.355 0.239 0.163 0.143 0.454 0.268 0.193 0.139
Relative Rate Values for the KFactor in Neutral Sulfite Pulping of Aspen Wood
Temp., O F.
Relative Rate
TgmP*3 F.
Relative Rate
Temp., O F.
Relative Rate
Temp., O F.
Relative Rate
7 p F. P.,
Relative Rate
212 213 214 215 216
1.o 1.0 1.1 1.2 1.2
253 254 255 256 257
10.9 11.5 12.2 12.9 13.6
294 295 296 297 298
92.5 97.1 102.0 107.1 112.5
335 336 337 338 339
626.8 655.2 684.7 715.5 747.6
376 377 378
%
3521.1 3664.7 3813.9 3968.7 4129.4
217 218 219 220 221
1.3 1.4 1.5 1.6 1.7
258 259 260 261 262
14.3 15.1 16.0 16.9 17.8
299 300 301 302 303
118.1 123.9 130.1 136.5 143.3
340 341 342 343 344
781.1 815.9 852.2 890.1 929.5
381 382 383 384 385
4296.2 4469.3 4649 .0 4835.4 5028.8
222 223 224 225 226
1.8 1.9 2.0 2.2 2.3
263 264 265 266 267
18.8 19.8 20.9 22.1 23.3
304 305 306 307 308
150.3 157.7 165.4 173.5 181.9
345 346 347 348 349
970.5 1013.3 1057.8 1104.2 1152.5
386 387 388 389 390
5229.5 5437.7 5653.7 5877.7 6110.1
227 228 229 230 231
2.4 2.6 2.7 2.9 3.1
268 26 9 270 27 1 272
24.5 25.9 27.3 28.7 30.3
309 310 311 312 313
190.7 199.9 209.6 219.7 230.2
350 351 352 353 354
1202.8 1255.1 1309.6 1366.3 1425.3
391 392 393 394 395
6351 .O 6600.8 6859 9 7128.4 7406.8
232 233 234 235 236
3.3 3.5 3.7 3.9 4.2
273 274 275 276 277
31.9 33.6 35.4 37.3 39.3
314 315 316 317 318
241.3 252.8 264.8 277.4 290.5
355 356 357 358 359
1486.6 1550.5 1617.0 1686.1 1758.0
396 397 398 399 400
7695.5 7994.6 8304.6 8625.9 8958.8
237 238 239 240 241
4.4 4.7 4.9 5.2 5.5
278 279 280 281 282
41.3 43.5 45.8 48.2 50.7
319 320 321 322 323
304.3 318.6 333.6 349.2 365.5
360 361 362 363 364
1832.8 1910.5 1991.4 2075.5 2162.9
242 243 244 245 246
5.9 6.2 6.6 7.0 7.4
283 284 285 286 287
53.4 56.1 59 .O 62.1 65.3
324 3,25 $2 6 327 328
382.6 400.4 418.9 438.3 458.6
365 366 367 368 369
2253.7 2348.2 2446.4 2548.4 2654.4
247 248 249 250 251 252
7.8 8.3 8.7 9.2 9.8 10.3
288 289 290 291 292 293
68.6 72.2 75.9 79.7 83.8 88.0
329 330 331 332 333 334
479.7 501.7 524.7 548,6 573.6 599.7
370 371 372 373 374 375
2764.5 2879.0 2997.8 3121.3 3249.6 3382.8
376
I & E C PROCESS D E S I G N A N D D E V E L O P M E N T
I
liquor A. Similar trends were observed for liquors B and C. I n general, these figures show that, a t a given yield, slightly higher amounts of carbohydrates are lost to attain the same yields a t higher temperatures. T h e relative reaction rates a t various temperatures can be computed using the rate a t 212' F. to be unity. Thus:
.80n -I
W70> I-
where p is the relative rate of reaction and T' is the temperature in ' K. Using the constants developed in Equation 8, the relative reaction rate is computed from the relationship : -27,975
p = e
-1
560V a
W
P
50-
40
1 1 [T - 072
I
0
500
I
1000
I
I
1500 2000
I
I
i
2500
3bOO
3500
H- F A C T O R
where T is in R. T h e results of relative reaction rates as a function of reaction temperature are presented in Table 11. T h e values of H-fact'or are computed for each of these cooks using the relationship " = -o;
suSpd0
(11)
A comparison of the relationships between H-factor and yield a t different concentrations of cooking liquor can be observed in Figure 5 . Acknowledgment
T h e author gratefully acknowledges the valuable suggestions of William W . Marteny during the work. Special thanks are due to Salvatore Cellura, Robert Lewandowski, and Thomas F. Reynolds, who conducted the experimental work, and to Paul A. Hotmer and his stafl for their valuable help in programming and processing the datar through the computer. literature Cited
Bray, M. W., Eastwood, P. R., Paper Trade J . 93 (17), 38-42 (1931). Calhoun, J. M., Yorston, F. H., Maass, O., Can. J . Res. 17 (4), 121-32 (1939).
Figure 5. Comparison of relationship between H-factor and yield at different concentrations
Corey, A. J., Maass, O., Can. J . Res. 14, 336-45 (1936). Doraiswamy, K., Ph.D. dissertation, University of Wisconsin, Madison, Wis., 1952. Dorland, R. M., Leask, R. A,, McKinney, J. N., Pulp Paper Mag. Can. 5 5 (3), 258-62 (Convention Issue, 1954). Elton, E. F., Ph.D. dissertation, Institute of Paper Chemistry, Appleton, Wis., 1962. Findley, M. E., Nolan, FV. J., T a p p i 39 ( l l ) , 758-68 (1956). Goldfinger, G., Paper T r a d e J . 112(24),29-31; (15),27-30(1941). Nolan, W. J., Tappi 44 ( l l ) , 753-62 (1961). Rawlings, F. G., Staidl, J. A., Paper Trade J . 81 (8), 49-51 (1925). Stangeland, E., Papir-J. 20 (16), 170-3; (18), 193-7; (20), 21417: 124). 272-411932). Vroom; K.'E., P u b Paper Mag. Can. 58 (3), 228-31 (Convention Tssur. 1957). -_-
Walters, W. Z,, May, M. N., T a p p i 43 ( l l ) , 881-6 (1960). Wilder, H. D., Han, S. T., T a p p i 45 ( l ) , 1-9 (1962). Yorston. F. H., Proiect 70 M, Forest Products Laboratories, Montreal, Progr. Rkpt. 2 (1934). Yorston, F. H., Project 70 M, Forest Products Laboratories, Montreal, Progr. Rept. 3 (1935). RECEIVED for review July 19, 1967 ACCEPTEDFebruary 20, 1968 52nd Annual Meeting, Technical Association of the Pulp and Paper Industry, New York, N. Y . , February 20-23, 1967.
V O L 7 NO. 3 J U L Y 1 9 6 8
377
