Indian Journal of Chemical Technology Vol. 11 January 2004 pp. 127-134

Studies on soda and soda-AQ pulping of binata

C H Tyagia, Dharm Dutta* & Dhuruba Pokharelb aDepartment of Paper Technology, Indian Institute of Technology Roorkee, Saharanpur Campus Saharanpur 247 001, bBhrakuti Paper Mills Ltd, Received 28 February 2003; revised received 28 July 2003; accepted 19 August 2003

Eulaliopsis binata was cooked by soda and soda–AQ pulping processes and results were compared with alkali-O2, al- kali-O2-AQ and NSSC pulping processes. Even the nodes are not resistant to the action of cooking liquor and consequently at 14 % alkali dose whole is reduced to a clean and regular pulp giving 48 % screened pulp yield of Kappa number 16. A screened pulp yield of 49.8 % at Kappa no 15.7 was obtained at 12 % alkali and 0.5 % AQ. In order to get 80 % (ISO) brightness, the pulp was bleached by single stage hypochlorite bleaching, O2 delignification followed hypochlorite bleach- ing, peroxide bleaching, O2 delignification followed by peroxide, CEH and OCEH bleaching sequences. Various paper grades like news print, light weight writing and printing paper, cigarette tissue, condenser paper, high grade bond, ledger and other cultural papers can be manufactured by selecting an appropriate pulp brightness and blending with long fibred pulp. IPC Code: D21B1/04

Certain unique morphological characteristics of Eula- other paper making characteristics of Eulaliopsis bi- liopsis binata make it suitable in imparting some nata. unique property of specialty grade paper. The chemi- cal composition of also gives some Experimental Procedure indication, as to where these fibres will fit into paper Morphological studies making system. Eulaliopsis binata due to its open and The hand-chopped culms of Eulaliopsis binata loose anatomical features and low lignin contents were boiled with concentrated solution of HCl to makes it suitable to pulp easily with milder cooking separate cellulosic fibres by dissolving middle la- condition, to produce readily bleachable grade pulp. mella. The fibres were washed and stained with The fibre dimensions along with water drainage char- Hertzberg stain. Morphological characteristics of acteristics of the pulps, also indicate that they do not Eulaliopsis binata were determined with the help of require extensive refining to develop fibrillation, hy- microscope and compared with bamboo fibres. The dration and inter fibre bonding. results are reported in Table1. The action of AQ is indeed, so striking that it was 2 originally half suspected of magical properties , but it Proximate chemical analysis soon gained the respectable status of catalyst as the Hand-chopped Eulaliopsis binata was disintegrated 3,4 mechanism of its action was pieced togather . There into powder in wood mill and a fraction passes is a wide spread agreement that AQ operates as a re- through -48 mesh size but retained on +80 mesh size dox catalyst by promoting an efficient transfer of was used for proximate chemical analysis. The results electron from a source (carbohydrate) to a sink are reported in Table 2. (lignin)5,6. Thus, the degradation and solubilization of lignin are accelerated (faster pulping) and by end Pulping studies Hand-chopped Eulaliopsis binata was cooked in group oxidation the carbohydrates are stabilized WEVERK rotary digester of capacity 0.02 m2 by against the attack of alkali (higher pulp yield). soda, soda-AQ, alkali-O alkali-O -AQ and NSSC The purpose of the present communication is to 2, 2 pulping processes. The pulp was washed, screened evaluate the morphological, chemical, pulping, and and crumbled. The pulp was beaten at different PFI ______*For correspondence (E-mail: [email protected]; Fax : revolutions and evaluated for various physical 0132 2727354) properties. The black liquor generated during pulp 128 INDIAN J. CHEM. TECHNIOL., JANUARY 2004

squeezing was analyzed for COD using Dralange Table 1 — Morphological characteristics of Eulaliopsis binata Lasa photometer in each pulping stage. The results are and bamboo reported in Tables 3-9. Particulars Eulaliopsis Bamboo Light Colour binata Bleaching studies Brownish green To achieve the targeted brightness the following yellow bleaching sequences were tried: H, OP, OH, CEH, P, Density, g/cm3 ⎯ 0.521 and OCEH. For conducting all the bleaching se- Fibre length, (L) mm 2.4 1.7 quences the laboratory manual for the pulp and paper Fibre width (D), μm 9.97 23.50 laboratory, NTH and SCAN standards were followed. Lumen diameter (d), μm 5.75 9.5 For the estimation of pulp strength the viscosity has Cell wall thickness (w), 2.11 7.0 been determined by capillary tube viscometer using μm cupriethylenediamine solution (CED). The results are Flexibility coefficient 57.67 40.4 reported in Tables10-15. (d/D) × 100 Slenderness ratio L/D 266 72.0 Results and Discussion Rigidity coefficient 0.42 0.59 Table 1 shows the morphological characteristics of 2w/D sabai grass and bamboo. The average fibre length of Wall fraction (2w/D) × 42 59 sabai grass is 2.4 mm compared to those of 1.7 mm 100 for bamboo. The fibre diameter of bamboo is 23.60 Runkel ratio 2w/d 0.73 1.47

μm, which is 2.5 times, more than sabai grass. The slenderness ratio or felting power of sabai grass is 266 in some characteristics than that of bamboo fibres. against 72 in case of bamboo. Due to high slenderness Microscopic examination reveals that sabai grass ratio, it is expected that such type of fibres shall have fibres are long, thin, and slender and taper off to low degree of collapsing and conformability. There- pointed ends with some parenchymatous cells. The fore, such type of paper gives more tear, porosity, fibres are of two types, thin walled lignified fibres and bulk and opacity. thick walled libriform fibres. The parenchymatous The runkel ratio of Eulaliopsis binata resembles to content is about 30 % of the total cells. The paren- that of bamboo but due to less fibre diameter, the chymatous cells measure 30-220 µm in length and 10- flexibility and the degree of collapseness of fibre, 50 µm in width. When these cells are present in ex- both of which control the degree of conformability cess it shows linting problems in pressing, drying and within the paper sheet and as such the size and num- calendaring. The epidermal cells are not removed in ber of inter fibre bonds is improved in case of Eulali- acidic or neutral medium. Thus, in acidic pulping, the opsis binata. The runkel ratio is related to fibre den- pulp fibres remain with the epidermal cells which ad- sity7,8, hence breaking length, bursting strength and versely affect the pulp quality. The epidermal cells double fold is determined by fibre density. However, can be dissolved to some extent during alkaline pulp- the mechanical properties along with other properties ing process, so this method is more suitable for sabai of paper related to wet plasticity may be increased by grass. fibrillation and high hemicellulose content (around 33 A Bauer-McNett fibre classification of soda pulp %). The fibre length is of secondary importance in was carried out in Bauer-McNett fibre classifier hav- ing meshed no +28, +48, +100, +200 and -200. determining the breaking length with other properties. The effect of fibre length has been ascribed to stress Mesh size Fibre weight, % dissipation; the longer the fibre, the greater the area +28 46.7 over which the stress is dissipated9,10. The fibre length +48 20.7 of sabai grass is 2.5 times more than the fibre length +100 9.7 of bamboo. Hence, it is expected that all the mechani- +200 1.2 cal strength properties of sabai grass will be better +28 fractions represent long slender fibres with than the mechanical strength properties of bamboo. some typical epidermal cells. Fairly long fibres and The rigidity coefficient, runkel ratio and wall fraction lot of epidermal cells are observed in +48 fraction and of sabai grass is also in close proximity with bamboo. fibres are short in comparison to fibres of +28 frac- Based on morphological characteristics, the sabai tion. In +100 fractions, short fibres and epidermal cell grass is quite comparable and even somewhat better bundles varying in dimensions oriented in different TYAGI et al. : STUDIES ON SODA AND SODA-AQ PULPING OF EULALIOPSIS BINATA 129

directions are observed. +200 fractions contain lot of Table 2 — Proximate chemical analysis of Eulaliopsis binata thin-walled parenchyma cells and rarely seen epider- bagasse and bamboo mal cells with some very short fibres, while -200 frac- Particulars (%) Eulaliopsis Bagasse14 Bamboo15 tion consists of lot of fine thin walled parenchymatous binata13 cells. Cold water solubility 3.60 5.91 7.60 Table 2 indicates the proximate chemical analysis Hot water solubility 9.50 7.85 8.50 of sabai grass along with bamboo. Sabai grass is rich Alcohol-benzene 4.10 6.30 3.40 in cellulose and having low lignin content. The diges- solubility (1:2 v/v) tion can be carried out under milder process condi- One per cent NaOH 39.70 33.60 26.80 tions along with less bleach consumption. The yield solubility of good quality pulp is slightly more than that of Lignin 22.00 20.30 24.30 Pentosan 23.90 23.86 18.30 bamboo. Moreover in comparison to bamboo, the sa- Holocellulose ⎯ 70.60 71.50 bai grass produces a stronger and more durable paper. Hemicellulose ⎯ 28.45 27.60 Sabai grass is singularly homogenous in quality α-cellulose 49.00 42.00 43.50 throughout the whole plant. Even the nodes are not β -cellulose ⎯ ⎯ 13.40 resistant to the action of cooking liquor and conse- γ -cellulose ⎯ ⎯ 14.00 quently it is reduced to a clean and regular pulp by Ash 6.00 3.80 2.10 simple digestion. Sabai grass consists of 33.2 % pec- Silica ⎯ 2.10 1.40 toses, which have positive significant effect on the Acetyl content ⎯ ⎯ 2.50 size, number, and strength of bonds11,12 and refining of Methoxyl content ⎯ ⎯ 3.10 pulp. Table 3 ⎯ Experimental conditions and results for soda Table 3 shows the experimental conditions and re- pulping of Eulaliopsis binata sults of soda pulping of sabai grass. The screened pulp yield drops from 48.8 to 48 %, whereas kappa Particulars Set 1 Set 2 number drops from 22.3 to 16.1 when sabai grass is O d weight of sample, g 100 100 delignified to H-Factor 1632 at alkali doses of 12 and NaOH charged, % (as such) 12 14 14 % (as such) respectively while keeping other vari- Liquor to wood ratio 5:1 5:1 ables constant like bath ratio 1.5, maximum cooking Max cooking temp, °C 160 160 temperature 160°C and maximum pulping time 4 h. Temp rising time, min 70 70 Table 4 shows the property of hand-sheets beaten Temp keeping time, min 4.0 4.0 Whole cycle H-factor 1632 1632 in PFI mill to 18, 35, 42 and 49 °SR respectively after Screened pulp yield, % 48.8 48.0 12 % soda pulping. Both tensile index and elongation Screening rejects, % 0.48 0.09 power increase with increase in °SR i.e. from 37.71 to pH of black liquor 10.6 11.1 85.55 kNm/kg and 1.70 to 2.73% respectively. In the Kappa number 22.3 16.1 similar manner, both tensile energy absorption and Brightness, % (ISO) 26.59 29.23

Table 4 ⎯ Properties of hand-sheets prepared using 12% soda pulping Particulars Unbeaten Pulp beaten at different PFI revolutions pulp 250 500 1000 °SR 18 35 42 49 Basis weight, g/m2 67.86 65.09 64.61 63.91 Tensile index, kNm/kg 37.71 68.01 78.49 85.55 Elongation, % 1.70 2.18 2.56 2.73 Tensile energy absorption, J/kg 411.4 942.3 1258 1472 Breaking length, km 3.844 6.933 8.001 8.720 Tear index, Nm2/kg 7.9 9.9 10.6 9.5 Density, kg/m3 452 521 505 542 Gurley’s porosity, s 0.43 2.68 2.82 3.57 Brightness, % (ISO) 26.59 27.30 27.91 27.42 Opacity, % 99.51 100.14 99.91 99.05

130 INDIAN J. CHEM. TECHNIOL., JANUARY 2004

breaking length increase with increase in °SR i.e. which can further be reduced on industrial scale. The from 411.4 to 1472 J/kg and 3.844 to 8.720 km re- relative screened pulp yield was also improved by spectively. Tear index first increases from 7.9 to 10.6 approximately 4 % in case of soda-AQ pulping and Nm2/kg then declines with further increase in °SR. the kappa number was reduced by approximately 3 % Table 5 shows the property of hand-sheets beaten than soda pulping. in PFI mill to 18, 35, 42 and 49 °SR respectively after Tables 7 and 8 indicate the property of hand-sheets 14 % soda pulping. Table 5 follows the same pattern beaten in PFI mill at various freeness levels. The as in case of soda pulping at 12 %. All the properties strength properties in these two cases are found to be like tensile index, tensile energy absorption, breaking length and tear index show an improvement over the Table 6 ⎯ Experimental conditions and results for soda-AQ pulp- aforesaid properties of pulp delignified at 12 % alkali ing of Eulaliopsis binata dose. Particulars Set 3 Set 4

Table 6 shows the experimental conditions and re- O d weight of sample, g 100 100 sults of soda-AQ pulping of sabai grass. The screened NaOH charged, % (as such) 10 12 pulp yield slightly decreases from 51.8 to 49.8 % AQ charged, % 0.5 0.5 while kappa number drops from 21.1 to 15.7 when Liquor to wood ratio 1:5 1:5 Max cooking temp, °C 160 160 sabai grass is delignified to H-Factor 1632 at alkali Temp rising time, min 70 70 doses of 10 and 12 % (as such) respectively while Temp keeping time, min 4.0 4.0 keeping other variables constant like AQ dose 0.5 %, Whole cycle H-factor 1632 1632 bath ratio 1.5, maximum cooking temperature 160°C Screened pulp yield, % 51.8 49.8 Screening rejects, % 0.46 0.07 and maximum pulping time 4 h. When soda-pulping pH of black liquor 10.2 10.6 process is compared with soda-AQ process, there is a Kappa number 21.1 15.7 net saving of 2 % alkali with little addition of AQ, Brightness, % (ISO) 24.85 27.15

Table 5 ⎯ Properties of hand-sheets prepared using 14 % soda pulping Particulars Unbeaten Pulp beaten at different PFI revolutions pulp 250 500 1000 0SR 22 35 44 49 Basis weight, g/m2 69.17 65.18 63.41 62.76 Tensile index, kNm/kg 52.68 78.84 78.20 81.75 Elongation, % 1.69 2.50 2.58 2.71 Tensile energy absorption, J/kg 536.5 1249 1280 1399 Breaking length, km 5.370 8.037 7.971 8.334 Tear index, Nm2/kg 9.2 10.6 10.3 10.1 Density, kg/m3 501 534 515 532 Gurley’s porosity, s 1.10 3.22 3.60 4.43 Brightness, % (ISO) 29.23 29.016 29.43 29.20 Opacity, % 99.30 100.13 99.16 99.04

Table 7 ⎯ Properties of hand-sheets prepared using 10 % soda-AQ pulping Particulars Unbeaten pulp Pulp beaten at different PFI revolutions 250 500 1000 °SR 17 31 41 53 Basis weight, g/m2 67.07 63.06 64.93 66.18 Tensile index, kNm/kg 37.55 68.56 74.13 83.86 Elongation, % 1.54 2.12 2.25 2.73 Tensile energy absorption, J/kg 370.5 925.4 1077 1459 Breaking length, km 3.828 6.989 7.557 8.549 Tear index, Nm2/kg 8.4 10.3 10.5 9.6 Density, kg/m3 445 517 523 567 Gurley’s porosity, s 0.43 2.52 3.03 7.8 Brightness, % (ISO) 24.85 25.27 25.58 25.29 Opacity, % 99.25 99.45 99.48 99.53

TYAGI et al. : STUDIES ON SODA AND SODA-AQ PULPING OF EULALIOPSIS BINATA 131

Table 8 ⎯ Properties of hand-sheets prepared using 12 % soda-AQ pulping Particulars Unbeaten Pulp beaten at different PFI revolutions pulp 250 500 1000 °SR 22 35 45 54 Basis weight, g/m2 66.18 64.68 64.92 63.46 Tensile index, kNm/kg 51.54 76.96 76.99 84.53 Elongation, % 1.84 2.46 2.37 2.63 Tensile energy absorption, J/kg 604.8 188 1155 1409 Breaking length, km 5.253 7.845 7.848 8.617 Tear index, Nm2/kg 9.3 9.5 9.6 9.1 Density, kg/m3 479 525 536 568 Gurley’s porosity, s 0.83 3.18 4.75 8.12 Brightness, % (ISO) 27.15 27.80 27.81 27.5 Opacity, % 99.52 99.10 99.37 99.42

Table 9 ⎯ A comparison between cooking conditions, pulp evaluation results and paper properties of soda, soda-AQ, alkali-O2, al- ♠ kali-O2-AQ and NSSC pulps of Eulaliopsis binata Pulping Cooking process Kappa Pulp ♣Pulp Pulp Strength properties of unbleached pulp processes no. yield yield bright- Alkali Max Max °SR Tear Tensile Burst Porosity % % ness dose temp cooking index index index ,s %ISO 2 % °C time, min mNm Nm/g KPam /g 2/g Soda 14∇ 160 240 16.1 48.00 43.20 81.5 53 9.6 83.86 8.7 4.43 Soda-AQ∗ 12∇ 160 240 15.7 49.80 44.50 80.0 54 9.1 84.53 8.9 8.12 Alkali- 13∇ 165 120 14.2 51.24 46.30 83.4 52 9.2 86.43 9.2 7.21 ψΦ O2 ∇ Alkali-O2- 13 165 120 13.4 51.78 46.50 82.7 53 9.3 86.78 9.1 7.14 AQψΦ∗ Kraft⊗ 12∇∇ 165 90 12.5 52.30 46.90 82.0 51 9.4 86.60 9.5 8.2 NSSC♦ ⎯ 160 240 34.5 51.30 ⎯ ⎯ 48 9.0 65.25 9.3 - 2 = Unbleached pulp, ♣ = Pulp bleached by CEHH sequence, ♠ = Bath ratio 1:3.5, ∗ = 0.1% AQ, ψ = 0.1% MgSO4, Φ = O pressure 8 2 kg/cm , ⊗ = Sulphidity 20% ♦= Na2SO3, 18% and Na2CO3, 4%, ∇ = as NaOH, ∇∇ = as Na2O more or less same. However, these properties show a Table 10 ⎯ Experimental conditions and results for single marginal improvement over properties of soda pulps stage hypochlorite bleaching cooked at 12 and 14 % respectively. On the basis of Particulars Hypochlorite bleaching above results 12 % soda-AQ pulping may be taken as Sequence 1 Sequence 2 an optimum alkali dose. It is worth mentioning that before opting this process, the economic analysis Pulp consistency, % 7 5 Temperature, °C 38 38 should be carried out. Chemical charge, % 2.5 8.0 Table 9 shows the pulp evaluation characteristics Retention time, h 2.0 3.0 of soda, soda-AQ, alkali-O , alkali-O -AQ, kraft and Initial pH 11.2 11.2 2 2 Final pH 10.0 9.5 NSSC pulps of sabai grass. The addition of 0.5 % AQ Residual Cl2, % 0.0 0.32 at 12 % alkali dose not only helps to preserve pulp Brightness, % (ISO) 48.4 69.7 yield with viscosity improvement but saves 2 % al- Viscosity, cm3/g 654 591 COD, kg/T 27.4 63.1 kali. O2 in alkaline medium accelerates the delignifi- cation process due to its selectivity towards lignin and ing hypochlorite (NaOCl) doses i.e. 2.5 and 8.0 % on hence both pulp yield and strength are improved. OD pulp basis. The brightness of pulp improves to Kraft pulp shows an improvement both in pulp yield 3 48.8 % (ISO) with pulp viscosity 654 cm /g and COD and kappa number over alkali-O and alkali-O -AQ 2 2 27.4 kg/T when pulp is treated with 2.5 % hypo processes. In case of NSSC pulping process the pulp charge. On the other hand, the pulp brightness im- yield is lower but kappa number is very high i.e. 34.5. 3 proves to 69.7 % (ISO) with pulp viscosity 591 cm /g In order to get targeted brightness, a single stage and COD 63.1 kg/T at hypo charge of 8.0. Table 10 hypochlorite bleaching was conducted with the vary- clearly indicates that on increasing hypo charge from 132 INDIAN J. CHEM. TECHNIOL., JANUARY 2004

Fig. 1—Trends of chlorine consumption for single stage hypo (8 %) bleaching

Table 11 ⎯ Experimental conditions and results for oxygen Table 12 ⎯ Experimental conditions and results for single delignification followed by hypochlorite bleaching stage hydrogen peroxide bleaching Particulars Sequence 3 Particulars Sequence 4 Oxygen Hypochlorite P Pulp consistency, % 10 7 Pulp consistency, % 10 Temperature, °C 95 38 Temperature, °C 80 Chemical charge Chemical charge NaOH, % 1.5 1.5 H2O2, % 2.5 MgSO4, % 0.3 - NaOH, % 2.5 Oxygen pressure, bar 6 - EDTA, % 0.5 Retention time, h 0.75 Retention time, h 1 2 Initial pH 12 Initial pH - 11.4 Final pH 11 Final pH 11.7 10.2 Brightness, % (ISO) 49.0 Kappa number 7.7 - Viscosity, cm3/g 702 Brightness, % (ISO) 36.3 62.2 COD, kg/T 15.8 Viscosity, cm3/g 705 684 COD, kg/T 25.1 22.3 load. Peroxide bleaching gives brightness 49.0 % 2.5 to 8.0 % the brightness goes up by 21 units with (ISO) with pulp viscosity 702 cm3/g and COD load increase in pollution load by about 36 units. Fig. 1 15.8 kg/T. In order to boost up the brightness another indicates that in case of 8 % hypo bleaching about effort has been made to use O2 delignification prior to 86 % of the available Cl2 was consumed in first 15 peroxide bleaching. The results are reported in min. The consumption of available Cl2 was 95 % at a Table 13. A brightness level of 49.3 % (ISO) was retention time of 3 h. achieved by using OP bleaching sequence with good Table 11 indicates that the kappa number has re- pulp strength and less pollution load. duced to 51 % after O2 delignification. It results in a Table 14 shows the results and conditions of CEH decrease in hypo charge to 1.5 %. OH bleaching se- bleaching sequence in order to achieve targeted quence gives brightness 62.2 % (ISO) with pulp vis- brightness 80 % (ISO). Pulp brightness 80.9 % (ISO) cosity 684 cm3/g and COD load 22.3 kg/T. is obtained with tolerable pulp strength. As it was ex- Table 12 shows single stage peroxide bleaching pected, that, this sequence will generate high pollution and its impact on brightness, viscosity and pollution load, the value of COD was found to be 93.8 kg/T TYAGI et al. : STUDIES ON SODA AND SODA-AQ PULPING OF EULALIOPSIS BINATA 133

Table 13 ⎯ Experimental conditions and results for oxygen Table 14 ⎯ Experimental conditions and results for chlorina- delignification followed by hydrogen peroxide bleaching tion-extraction-hypochlorite bleaching Particulars Sequence 5 Particulars Sequence 6

Oxygen H2O2 C E H

Pulp consistency, % 10 10 Pulp consistency, % 2 10 7 Temperature, °C 95 80 Temperature, °C Ambient 60 38 Chemical charge Chemical charge, % NaOH, % 1.5 2.5 Molecular Cl2, % 3.14 - - MgSO4, % 0.3 - NaOH, % - 2.5 1.5 EDTA. % 0.5 Retention time, h 0.75 1.0 1.5 Oxygen pressure, bar 6 - Initial pH 1.5 11.7 11.5 Final pH 1.2 11.5 9.8 Retention time, hr 1 0.5 Brightness, % (ISO) 40.4 52.15 80.9 Initial pH - 12.7 Viscosity, cm3/g 669 - 645 Final pH 11.7 12.2 COD, kg/T 54 21.3 18.5

Kappa number 7.7 - Brightness, % (ISO) 36.3 49.3 Viscosity, cm3/g 705 694 Table 15 ⎯ Experimental conditions and results for oxygen COD, kg/T 25.1 17.3 delignification followed by CEH bleaching

Particulars Sequence 7

O C E H

Pulp consistency, % 10 2 10 7 Temperature, °C 95 Ambient 60 38 Chemical charge Molecular Cl2, % - 1.55 - 1.5 NaOH, % 1.5 - 2.5 - MgSO4, % 0.3 - - - Oxygen pressure, bar 6.0 - - -

Retention time, h 1.0 0.75 1.0 1.5 Initial pH - 1.5 - 11.7 Final pH 11.0 1.2 - 11.0 Brightness, % (ISO) 36.3 50.0 60.2 81.5 1 Viscosity, cm3/g 705 - - 671 Kappa number 7.7 - - - COD, kg/T 25.1 24.2 12.4 10.5

Fig.2—Viscosity and brightness for different bleaching sequences Eulaliopsis binata shows lower degree of col- which is very high in comparison to the other bleach- lapsness and conformability within the paper sheet ing sequences attempted. due to high slendernsess ratio. Sabai grass consists of In order to mitigate the pollution load oxygen de- high percentage of hemicellulose, thereby affecting lignification is carried out prior to CEH bleaching the number and strength on bonds. The pulp yield sequence. It can be concluded from Table 15 that the ranges between 48- 51.3 % when sabai grass is im- pulp brightness is boosted up to 81.5 % (ISO), where pregnated with various pulping processes such as soda as total value of COD is reduced to 72.2 kg/T. and soda-AQ, alkali and alkali-O2-AQ and NSSC pro- Figure 2 gives a comparison between viscosity and cesses. Soda-AQ pulping process shows a net saving brightness for different bleaching sequences of sabai of 2 % alkali in comparison to soda pulping process. grass. In OCEH bleaching sequence the brightness is The relative screened pulp yield was also improved little higher than that of CEH bleaching sequence. The by approximately 4 % in case of soda –AQ pulping pulp strength is better in case of OCEH than that of and the kappa number was reduced by approximately CEH bleaching and also with a reduction of 23 % in 3 % than soda pulping. In OCEH bleaching sequence the pollution loads (Fig. 3). brightness of 81.9 % (ISO) was achieved than that of Conclusions 80.9 % (ISO) brightness in CEH bleaching sequence. 134 INDIAN J. CHEM. TECHNIOL., JANUARY 2004

Fig.3—Viscosity, COD and brightness for different bleaching sequences The pulp strength is better in case of OCEH than that 3 Lowendahl L & Samelson O, Tappi, 61 (2) (1978) 43. of CEH bleaching and also with a reduction of 23 % 4 Fleming B I & Bolker H T, Tappi, 61 (6) (1978) 19. 5 Iiyama K & Nakana J, Wood Res Soc, 24 (10) (1978) in the pollution load. 766. 6 Alfar W H & Farrington A, Appita, 33 (1) (1979) 33. Recommendations 7 Bray M W & Curran C F, Paper Trade J, 105 (20) (1937) 39. Due to comparatively narrower fibre diameter and 8 Pillow M Y, Childester G H & Bray M W, South Pulp Paper high cost of sabai grass fibre, it is essential to carry J, 4(7) (1941) 6. out blending studies with other pulp in order to manu- 9 Gallay W, In The Formation and Structure of Paper edited by F Bolam (Brit Paper and Board Maker’s Tech. Asso), 1962. facture cultural papers. By selecting appropriate blend 10 Arlov A P, Norsk Skogind, 13 (10) (1959) 342. of pulp a variety of specialty like wood free writing 11 Stone J E, Pulp Paper Mag Canada, 64 (12) (1963) T528. and printing, glassine and grease proof, condenser, 12 Swanson J W, Pulp Paper Mag Canada Tappi, 39 (5) (1956) cigarette paper, light weight printing and writing, fire 257. 13 Dhuruba Pokharel & Tyagi Chandrahas, A study of the work paper, high grade bond, ledger and other cul- technological aspects of Sabai grass for paper making, tural papers can be developed. Project Report, The University of Trondheim, The Norwegian Institute of Technology, Department of Chemical References Engineering Trondheim, Norway, 1990. 1 The Wealth of India, Raw Materials, III, D-E (CSIR 14 Singh Sunderpal, Studies on some potential non-woody Publication, New Delhi), 1952. fibrous for pulp and paper making, Ph.D. Thesis, 2 Hanson J P & Michaela W T, Pulp Paper Mag Canada, (5) University of Roorkee, Roorkee, 1987. (1978) 86. 15 Clark J D A, Paper Trade J, 115 (26) (1942) 36.