Novel Design of an Integrated Pulp Mill Biorefinery for the ...

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3.1.1.1 Chemical Processing The woodchips are then impregnated with white liquor and cooked at a high temperature for several hours. The four prime components of the white liquor solution are: NaOH, Na2CO3, Na2S, and Na2SO4. For the calculations, the following concentrations are used below [87]. Table 8: White liquor composition. Compound White Liquor Composition (kg/ADt) White Liquor Usage (kg/day) White Liquor Usage (kg/s) NaOH 293 586000 6.78 Na2CO3 85 170000 1.97 Na2S 156 312000 3.61 Na2SO4 31 62000 0.72 The pulp is then washed in order to separate the pulp from the cooking liquors. This removes a large amount of the lignin in the wood. The resulting byproduct, cooking liquor, is called black liquor due to its color. Pulp is sent to an oxygen delignification system where more lignin is removed before it is bleached in a bleach plant. The bleaching occurs by cycling the pulp through a series of acid and alkaline stages. This stage reduces the amount of lignin in the pulp so that the pulp is an acceptable brightness for consumers. Finally the pulp is dried and sent to a paper mill to be manufactured into paper. Black liquor is the combination of the lignin residue with water and the chemicals used for the extraction. When the black liquor is extracted from the system, it is taken as a “weak wash”. Around 13% – 17% of the weak wash is the energy dense black liquor solids. In order to recover the active sodium from the black liquor, the water must be removed from the system. This is done in a six stage process through a series of evaporators, and the demand of the steam is a function of liquors being processed. A pulp plant will use the recovery boiler to oxidize the black liquor in order to produce steam and electricity for the entire plant. The smelt created by the oxidation of the black liquor is quenched in water and recovered. The resultant solution is called green liquor and injected into a chemical recovery system. For purposes of calculations, green liquor will contain the following amounts in the pulp mill KAM2 pulp mill [87]: Table 9: Green liquor composition. Compound Green Liquor Composition (kg/ADt) Green Liquor Produced (kg/day) Green Liquor Produced (kg/s) NaOH 10 20000 0.23 Na2CO3 477 954000 11.04 Na2S 161 322000 3.73 Na2SO4 32 64000 0.74 The green liquor is then causticized where the Na2CO3 reacts with quicklime (CaO) and water (H2O) to form sodium hydroxide (NaOH) and calcium carbonate (CaCO3). The calcium 40
carbonate is fired in a lime kiln to reduce it to quicklime to be reused, and the sodium hydroxide is used in the pulping process. Consumption of chemicals can vary from mill to mill and is regarded as confidential. Approximately 10-20 kg of NaOH and 5-10 kg of CaO per metric ton of pulp are consumed during the recovery process. Using data found for the reference mill, the following amount of chemicals are required to be added to the system in the KAM2 mill [87]. Table 10: Chemical compound addition. Chemical Addition Compound Requirement (kg/ADt) Addition (kg/day) Addition (kg/s) NaOH 14 28000 0.32 CaO 16 32000 0.37 3.1.1.2 Energy Demand When the KAM2 mill does not include a gasifier, there is a sufficient amount of electricity produced in the recovery boiler as well as an excess amount of bark which can be sold. A schematic of what the KAM2 Eco-Cyclic Pulp Mill process includes is found below with each stage's respective heat and electricity demand. Energy and electricity demand data is published as a function of the amount of air dried tonnes of pulp (ADt) processed. In the KAM2 mill, 2000 ADt/day is removed from the washer to be processed into paper. Using the available values, 58.42 MW of electricity and 300.24 tonnes of steam per day are required. Table 11: Steam Demand Pulp Mill. Medium Pressure Steam Low Pressure Steam Daily Steam Consumption of (GJ/Adt) (GJ/Adt) 2000 ADt Woodyard 0 Digester 1.39 0.29 3360 Brown Stock Washing 0 Oxygen Delignification 0.38 760 Bleach Plant 1.43 0.27 3400 Final Screening 0 Pulp Dryer 2.21 4420 Black Liquor Evaporation 0.95 2.71 7320 Recausticising 0 Cooling Towers 0 Raw Water Treatment 0 Wastewater Treatment 0 Bleaching Chemicals 0 Other (including losses) 0.15 0.2 700 Sum 4.3 5.68 Total Mill Steam use per day 19960 GJ/day 300.24 t/h Using an ECF process of bleaching, 1.71 tonnes of black liquor is recovered per tonne of pulp [88]. As a result, the reference mill produces 3420 tonnes dry solids per day. The recovery boiler typically produced 15.7 GJ/ADt of pulp, steam and 655 kWh/ADt of pulp, electricity [22]. 41
Page 1 and 2: Novel Design of an Integrated Pulp
Page 3 and 4: Table of Contents List of Figures .
Page 5 and 6: List of Figures Figure 1: Price of
Page 7 and 8: 1 Introduction The global transport
Page 9 and 10: 2 Background 2.1 Pulp Mill Backgrou
Page 11 and 12: 2.1.2.2 Chemical Pulping The most c
Page 13 and 14: sodium sulfide and sodium carbonate
Page 15 and 16: process described in the section on
Page 17 and 18: 2.2.1 Low-Temperature Black Liquor
Page 19 and 20: Figure 2: Chemrec gasification proc
Page 21 and 22: Table 3: Average syngas composition
Page 23 and 24: DME than that could be obtained fro
Page 25 and 26: U.S. Patent[58] and European Patent
Page 27 and 28: Figure 4: Topsøe gas phase technol
Page 29 and 30: DME Workshop, Japan (Sept. 7, 2000)
Page 31 and 32: 2.4.1. Fischer-Tropsch Reactors The
Page 33 and 34: kpH 2 pCO Cobalt rate = 2 (2.4.1) (
Page 35 and 36: invention of Fischer-Tropsch in the
Page 37 and 38: Table 7: hydrocarbons and associate
Page 39: 3 Process Design 3.1 Pulp Mill 3.1.
Page 43 and 44: lost and the pulp that provides tha
Page 45 and 46: Table 16: General operating paramet
Page 47 and 48: Table 19: Ash analysis of Pittsburg
Page 49 and 50: Table 22: Experimental syngas compo
Page 51 and 52: 3.2.5 Process Options and Flexibili
Page 53 and 54: Nitrogen compounds Nitrogen from th
Page 55 and 56: 3.3.2.3 Reactors A single-step gas
Page 57 and 58: Table 27: FT-diesel fuel synthesis
Page 59 and 60: 3.5.2 Power Generation Process Desi
Page 61 and 62: Figure 21: Schematic of biorefinery
Page 63 and 64: ar) reacts with the fuel in the com
Page 65 and 66: Figure 25showed the detailed energy
Page 67 and 68: 4. Design Summary The DME design an
Page 69 and 70: Figure 27: Mass and energy flow of
Page 71 and 72: References 1. Åhman, M., G. Modig,
Page 73 and 74: 42. R.A. Peascoe, J.R.K., C.R. Hubb
Page 75 and 76: PerformanceSimulation. 2006, Prince
Page 77 and 78: Appendix Appendix A MP Steam Demand
Page 79 and 80: Appendix B: Composite Fuel Blend to
Page 81 and 82: DME Density = 0.67 kg/L (at 20 °C)
Page 83 and 84: Air Separation Unit Requirements Ba
Page 85 and 86: Purge gas: CO conversion is 60%, 40
Page 87 and 88: Appendix D: FTD Synthesis Two diffe
Page 89 and 90: Table D.3: The hydrocarbon product
Page 91 and 92:
Figure D.3 Mass and energy balance
Page 93 and 94:
Table D.3 Mass and energy balance o
Page 95 and 96:
Appendix E: Heat and Power Generati
Page 97 and 98:
Energy H2O absorbed MW 46.71 Using
Page 99 and 100:
Combustion 2CO+O2→ 2CO2 + 566 kJ/
Page 101 and 102:
Specific Heat (cp) b kJ/kgK 1.072 E
Page 103 and 104:
Specific Heat of Steam (cp) kJ/kgK
Page 105:
Appendix F: Concept Map 105
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