ST2B-1-3: Cleaner Technology: Application to Paper Mulberry Pulp and Paper Industry

Thumrongrut Mungcharoen1 and Saeksan Papong1

ABSTRACT The objective of this project is to introduce cleaner technology (CT) to paper mulberry pulp and paper industry. By auditing the production process, data was analyzed and recommendation practices or CT-option was introduced in order to reduce wastes at the source and, lower production cost. The case study was a handmade paper operation in Nongmuangkai, Prae Province with a total production capacity of 1,000 sheets/day. Losses during the processes of cooking, bleaching and washing were 7,890, 2,680 and 224 kg pulp/yr, respectively or in terms of cost 150,000, 107,000 and 35,000 baht/yr, respectively. CT-options using stainless steel tank for bleaching could decrease the amount of bleaching chemicals used in the process to around 1,400 kg/yr equivalent to 35,000 baht/yr. Similarly, improvement of bleaching could decrease by 800 kg the chemical used or 19,000 baht per yr. In the cooking process, using black liquor instead of water as a soaking solvent can reduce by 400 kg the cooking chemicals or 6,400 baht/yr. The countercurrent system which was suggested for the washing process could decrease 1,400 m3 of water consumption per year or 8,400 baht/yr.

INTRODUCTION Hand-made paper from paper mulberry is a kind of small industry. This industry helps farmer gain better income so it plays an important role in the rural economy especially in the upper-north of . In addition to hand-made paper enterprises some machine operated paper mills also exist. However, their processing and management are not well developed. This results in losses of raw materials, chemicals and high energy consumption while producing varieties of wastes to the rural

1Department of Chemical Engineering Faculty of Engineering, , 10900, Thailand Final Report The Research Project for Higher Utilization of Forestry and Agricultural Plant Materials in Thailand (HUFA) environments especially rivers. Cleaner technology is an alternative to reduce wastes and minimize cost of production at the same time. Review to cleaner technology in paper mulberry pulp and paper production Recently, many environmental friendly pulping procedures have been investigated, such as steam explosion pulping, organosolv pulping, extended delignification, oxygen or ozone pulping and biopulping (Young and Akhtar, 1998). Modeling and simulation of a technique for paper mulberry pulping process has been studied by installing an evaporator in the process of alkaline-oxygen, steam explosion, conventional and organosolv pulping. By these means 70-78% of the effluent could be reused in the process (Leaspisitthagroon and Teeratatorn, 2000). In the bleaching process environmental friendly procedures are under investigation, such as oxygen bleaching, ozone bleaching, peroxide bleaching and bio-bleaching (McDonough, 1995). Moreover, mass and heat exchange network technology or pinch technology are applied in order to reduce water consumption and energy in the production process (Gullichsen and Fogelholm, 1999. A counter current washing process is one of the best techniques to save water as shown in Figure 1. Water consumption can be calculated from the first equation (Bissop, 2000).

1/n QR=[(Cp / Cn) + 1/n] QD (1)

QR is flow rate of washing water, QD is drag out flow rate, CP is concentration of total suspended solid in cooking or bleaching tank, Cn is concentration of allowable total suspended solid and n is number of inlined tank.

Figure 1. Counter washing process (Bissop, 2000)

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Cleaner technology in paper mulberry pulp and paper industry is an alternative for this industry. Based on studies of cooking paper mulberry bark by steam explosion, it seems that the finished pulp can be easily bleached with H2O2. The steam explosion method is also an alternative to NaOH cooking techniques (Punsuvon and Kobayashi, 1999). Formacell is another cooking technique which can result in a high quality pulp, in addition the sulfate method and almost all chemicals can be reused in the process. (Nakbenjapron and Kraisurapong, 1999). Hydrogen peroxide bleaching is promoted instead of chlorine as it produces less pollution (Vatanawong et al., 1999). However, there are limitations in H2O2 bleaching because H2O2 can be decomposed easily by pH, temperature and heavy metal ion eg. Mn2+ Cu2+ and Fe3+ as shown in the second equation (Fairbank et al., 1989).

Mn+ - - H2O2 + HO 2 O2 + OH + H2O(2)

Case study: Paper mulberry pulp and paper industry General information of factory A The experimental mill used in this study is a small unit with a production capacity of about 250,000 sheet/year. Consumption of paper mulberry bark is 20 T/yr., NaOH 2 T/yr. (10% of the bark) and bleaching with Ca(ClO)2 1.6 T/yr. In the year 2000, primary cleaner technology was introduced to the mill. It was found that by decreasing NaOH to 8% of the bark and bleaching with H2O2 (50% wt) and Na2SiO3 resulted in cost reduction of 43,400 baht/yr. as shown in Figure 2.

Figure 2. Section cost of factory for a year

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Selected to CT focus for detail assessments Comparison of resource consumption in the case study and reference data are shown in Table 1.

Table 1. Comparison of resource consumption Key factor Expected value Resources Case study Reference# Unit/ADT % Baht/yr Inner bark 2.911 2.083a ton 28.44 113,760 Water 521 167 a m3 67.95 12,500** Chemical 466 208 a kg 55.36 51,450 Fire wood 42.89* 21.06 a GJ 50.90 4,580 Electrical 567 530##b kW-hr 6.53 522 Remark: ADT= Air Dry T of Paper * heat of combustion of wood at 20% MC is 16.37 MJ/kg (Schwleges, 1980) ** assume the water cost is 6 baht/m3 # capacity of reference data is 300 sheets/day ## electricity data is selected from beating and utility section a Maneetheph (1995) ab AIT (1997)

Scores ranking can be classified based on economic, technical and environmental points of view. Based on an economic perspective, scores are ranked 1, 2 and 3 when cost of production save less than 35,000, 35,000-70,000 and more than 70,000 baht/yr (Table 1). Technically if probability is less than 20% the score is ranked 1. Scores are ranked 2 and 3 when probabilities are 20-50% and over 50%, respectively. From environmental point of view less effect, medium effect and high effect the scores are ranked 1, 2 and 3, respectively.

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Table 2. Selecting CT focus Weighted score Resource/waste Total score Ranking Economic Environment Technical Inner bark/pulp 3 3 2 8 1 Chemical 2 2 3 7 2 Water/waste water 1 3 3 7 2 Fire wood 1 2 3 6 4 Electrical 1 2 1 4 5

Detailed Assessment Pulp balance, water balance and chemical balance were selected for detailed analysis, data is presented in Figures 3 and 4 and Table 3, respectively.

Figure 3. Loss of inner bark/pulp from production process

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Figure 4. Water consumption and wastewater from production process

Table 3. Loss of quantity and value for chemical balance Chemical Annual consumption Waste Loss value (kg/yr) (kg/yr) (baht/yr) NaOH 1,700 80 1,280

H2O2 (50% wt) 1,600 34 900

Na2SiO3 800 n.a. -

Cleaner Technology Option Cleaner technology for raw material and chemical balance focused on the cooking and bleaching process. The water balance concentrated on washing after cooking and bleaching: Cooking process Cooking of po saa bark in black liquor instead of water reduces NaOH consumption to 400 kg/year, a saving of 6,400 baht/yr. The brightness of pulp of cooking by this method was shown in Figure 5.

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Figure 5. Effect of soaking with black liquor on brightness

Bleaching process Improvement of the bleaching process was carried out by replacing the iron tank with one made from stainless steel. As a result consumption of H2O2 and Na2SiO3 could be reduced to 800 kg/yr and 600 kg/yr, respectively, a saving of 35,000 baht/yr. If the owner does not want to change to the stainless steel tank he can improve conditions in the bleaching process by decreasing the amount of

H2O2 and Na2SiO3 which can save 44 kg/yr of both chemicals, a cost saving of 19,000 baht/yr. The brightness of pulp produced by the modified process is shown in Figure 6.

Figure 6. Comparison of pulp brightness between factory and modified process

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Washing process after cooking and bleaching Water consumption in the washing process could be minimized by means of counter current flow and by reusing bleaching washing water for washing after cooking. This will minimize water consumption by 1,400 m2/yr. or 8,400 baht/yr. However, there seems to be no data on the application of counter current flow in paper mulberry pulp mill. Water consumption in counter current method is calculated from the first illustrated equation. In the cooking process Cp=11,400 mg/L, Cn= 200 mg/L,

QD=3.4 L/kg pulp and in bleaching process Cp= 190 mg/L, Cn= 25 mg/L and QD= 4.6 L/kg pulp as shown in Figure 7. When the washing process uses a 3 tank system, water consumption is decreased from 9,100 L/1000 sheets to 1,900 L/1000 sheets.

Figure 7. Water consumption of washing process of the rinsing tanks

Cleaner technology option for implementation Selected CT-options for implementation are shown in Table 4. It is clear that using a stainless steel tank for bleaching instead of iron tank showed highest score for application. Improvement of bleaching condition and soaking of paper mulberry bark in black liquor instead of water were the second choices followed by counter current flow, respectively.

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Table 4. Selected CT-option for implementation Weighted score Economic Environment Technical Total CT-options Rank Saving Score Reducing Score Score (baht/yr) 1. Soaking Saa-bark 6,400 1 58 kg NaOH/ADT 2 3 6 3 with BL

2. Use stainless steel 35,000 3 58 kg/H2O2/ADT 33 91

bleacher 85 kg Na2SiO3/ADT

3. Improved 19,000 2 30 Kg H2O2/ATD, 23 72

Bleaching 58 kg Na2Sio3/ADT Condition 4. Stages counter 8,400 1 200 m3/ADT 3 1 5 4 current washing

CONCLUSION Recommended cleaner technology has been applied in paper mulberry pulping process especially the cooking and bleaching process. By assessment of cleaner technology (CT) option in one demonstration pulp and paper mill, some options of CT were selected. The most applicable CT is the replacement of stainless steel tank for bleaching process. This option can minimize chemical use to 1,400 kg in the pulp and paper process per year, a value of 6,400 baht/yr. Improvement of optimum bleaching condition can decrease chemicals consumption by 800 kg/yr or 19,000 baht/yr. In the cooking process, using black liquor instead of water as soaking solvent can reduce 400 kg of cooking chemical or 6,400 baht/yr. In order to decrease water consumption in washing after the cooking and bleaching process a counter current system is suggested. This procedure could decrease water by 4,400 m3 per yr or 8,400 baht/yr. From the recommended CT-options waste can be minimized. Moreover, cost of production can also be reduced.

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ACKNOWLEDGEMENTS This project was financially supported by the National Research Council of Thailand and Kasetsart Agricultural and Agro-Industrial Product Improvement Institute (KAPI).

REFERENCES AIT. 1997. Technology, Energy Efficiency and Environmental Externalities in the Pulp and Paper Industry. School of Environmental, Resources and Development, Asian Institute of Technology, Bangkok. 88 p. Bissop, P.L. 2000. Pollution Prevention: Fundamentals and Practice. McGraw-Hill, Boston. pp. 421- 453. Fairbank, M.G., J.L. Colodette, T. Ali, F. McLellan and P. Whiting. 1989. The Role of Silicate in Peroxide Brightening of Mechanical Pulp:4. The Role of Silicate as a Buffer During Peroxide Brightening. J. pulp & paper science. 15(4): J132-J135. Gullichsen, J. and C.J. Fogelholm. 1999. Chemical Pulping : vol. B. Tappi Press, Helsinki. 497 p. Leaspisitthagroon, S. and N. Teeratatorn. 2000. Modeling and Simulation of Noval Technique for Mulberry Pulping Process base on cleaner Technology. Chemical Engineering Project, Department of Chemical Engineering, Kasetsart University, Bangkok. 108 p. Maneetheph P. 1995. The study in Cost and Benefit of House-hold Saa-paper Industry at Sankumpang, Chiangmai Province. M.E. Thesis, Krirk University Bangkok, Thailand. McDonough, T.J. 1995. Recent Advances in Bleached Chemical Pulp Manufacturing Technology. Part I : Extended Delignification, Oxygen Delignification, Enzyme Applications and ECF and TCF Bleaching. Tappi J. 78(3): 55-62. Nakbenjaporn P. and T. Kraisurapong. 1999. Production of Pulp using the Formacell Process from Paper Mulberry. Chemical Engineering Project, Department of Chemical Engineering, Kasetsart University, Bangkok. 108 p. Punsuvon V. and Y. Kobayashi. 1999. Steam Explosion Pulping Paper Mulberry Bast. 10th International Symposium on Wood and Pulping Chemistry. Yokohama, Japan, June 7-10. pp. 684-687.

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Schwleges, B. 1980. Power from Wood. Power 124(2): s.l-s.32. Vatanawong R., T. Ratanarojmongkol and J. Chaisanit. 1999. High Quality Paper Mulberry Pulp for Handicraft. Proceeding of Production and Utilization of Paper Mulberry. Kasetsart University, Bangkok, Thailand, March 10. pp. 54-83. Young, R.A. and M. Akhtar (eds) 1998. Environmental Friendly Technologies for the Pulp and Paper Industry. John Wiley & Sons, INC., New York. 577 p.

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