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

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conventionally handled in a Tomlinson recovery boiler for chemicals recovery and production of heat and power. Although the recovery boiler has been used successfully for years, it has several disadvantages that allow for the consideration of a replacement strategy. First, the recovery boiler is capital intensive, yet it is relatively inefficient for producing electricity from black liquor [3]. In addition, gasification virtually eliminates safety concerns due to explosion hazards for the recovery boiler. Equally as important, black liquor gasification technology performs better than conventional and advanced boiler technology [1]. Chemrec AB has designed a gasification process for black liquor to produce an energy rich synthesis gas centered on a high-temperature (950-1000°C), high-pressure (32 bar) oxygenblown gasifier. The design is similar to the Shell slagging entrained-flow gasifier for coal gasification. The goal of this project is to design an integrated gasification process design with a U.S. pulp mill to generate high-quality syngas while also achieving a high chemical recovery yield and generating additional heat and power for the pulp mill and potential sale of electricity to the grid. Supplementing black liquor gasification with coal is a means to substantially increase the yield of fuels produced from gasification to syngas for further conversion to DME or Fischer- Tropsch fuels. 8
2 Background 2.1 Pulp Mill Background 2.1.1 Harvesting and Chipping The pulping process begins at the site where trees are harvested. When all factors are taken into account, the most important idea behind cost minimization is that “optimizing forest fuel supply essentially means minimizing transport costs” [6]. Two main options are available for the transpiration of wood to the mill, one as solid logs and one as wood chips, where the wood is chipped in the forest. Chipping is advantageous because it increases the bulk volume which can be transported. The main disadvantages of chipping in the forest are the decreased length of time for which chips can be stored. After their size reduction, microbial activity in the chips increases, releasing poisonous spores, and energy is lost within the wood increasing the risk of self ignition [7]. Recently the idea of storing the wood as bundles has arisen as a viable option to improve forest-fuel logistics. Large eight cylinder machines are used to drive two compression arms which bundle the wood similar to the way a person rolls a cigarette. The figure below shows the difference between shipping loose residuals on the same size truck as a bundle [7]. This new technology reduces the impact of transporting forest-fuel matter across larger distances. Figure 1: Price of wood as a function of transportation distance. There are a number of available technologies for debarking wood entering the plant. Three main technologies at the head of the industry are ring style debarkers, cradle debarkers, and enzyme assisted debarking [8]. Ring style debarkers fall into two categories, wet and the more common dry debarkers. Wet debarkers remove bark by rotating logs in a pool of water and knocking the logs against the drum. Dry debarkers eliminate the use of about 7-11 tons of water per ton of wood, thus reducing water and energy use [9]. Wet debarkers need 0.04 GJ per ton of debarked logs of energy, while ring style debarkers use approx. 0.025 GJ per ton of debarked logs [10]. A Cradle Debarker has an electricity demand of 90 kWh and can debark 120 cords an hour [11]. An Enzyme assisted 9
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: 1 Introduction The global transport
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 and 40: 3 Process Design 3.1 Pulp Mill 3.1.
Page 41 and 42: carbonate is fired in a lime kiln t
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
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ar) reacts with the fuel in the com
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Figure 25showed the detailed energy
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4. Design Summary The DME design an
Page 69 and 70:
Figure 27: Mass and energy flow of
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References 1. Åhman, M., G. Modig,
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42. R.A. Peascoe, J.R.K., C.R. Hubb
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PerformanceSimulation. 2006, Prince
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Appendix Appendix A MP Steam Demand
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Appendix B: Composite Fuel Blend to
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DME Density = 0.67 kg/L (at 20 °C)
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Air Separation Unit Requirements Ba
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Purge gas: CO conversion is 60%, 40
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Appendix D: FTD Synthesis Two diffe
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Table D.3: The hydrocarbon product
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Figure D.3 Mass and energy balance
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Table D.3 Mass and energy balance o
Page 95 and 96:
Appendix E: Heat and Power Generati
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Energy H2O absorbed MW 46.71 Using
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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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