The feed to the process was rather assumed to be in the form of weak black liquor. However, the addition of sodium hydroxide was not included in process simulation because of the possibility of using the sodium hydroxide material stream available in a pulp mill as an active cooking chemical. The reactions were also performed under mild alkaline conditions to ensure solubilization of the lignin. (32) Briefly, kraft lignin precipitated using the LignoBoost technology was treated with molecular oxygen under different reaction conditions to identify the best conditions for obtaining a biocompatible, oxidatively depolymerized lignin stream. The process design was based on first-hand experimental data, obtained from a study on the oxidative depolymerization of kraft lignin as a means of pretreatment for microbial conversion. (28) Three lignin conversion routes to biobased aromatics have been analyzed: noncatalytic pyrolysis, hydrothermal upgrading, and direct hydrodeoxygenation the last route is found to be the most economically promising. (27) In another study, the feasibility of synthesizing lignin micro- and nanoparticles via an aerosol/atomization method has been evaluated, where manufacturing costs were quoted as being in the range of 600–1170 $/t. The techno-economics of large-scale production of colloidal lignin particles, involving solubilization with tetrahydrofuran and ethanol, has also been assessed, where an internal rate of return of 17% was reported. (24) Capacity design and risk analysis of biophenol/resin production from kraft lignin have also been presented, (25,26) demonstrating that the viability of such a biorefinery depends on the selling price of the product on the market and variations in the cost of lignin. (23) Process intensification has been combined with simulation to compare different strategies for the production of vanillin/methyl vanillate from kraft lignin, for example, extraction with organic solvents, nanofiltration, and adsorption with zeolite the last alternative shows additional savings in energy and cost of 0.2 and 7.4%, respectively. Energy and exergy calculations have been performed on catechol production based on lignin extracted from olive tree pruning. The findings of this study underline the need for further research to develop efficient lignin conversion technologies with attractive yields in order to increase profitability on an industrial scale.Ī limited number of studies have recently been carried out on the technical design and viability of novel lignin valorization processes. A quantitative investigation of process sustainability resulted in an E-factor of ∼1.6 for the entire synthetic route, that is, 38% material efficiency. A sensitivity analysis was carried out to assess the impact of the vanillin selling price and the cost of lignin on the profitability of the process. Assuming an interest rate of 10% and a plant lifetime of 10 years, the return on investment was calculated to be 14%, indicating that such a biorefinery is viable. A heat-integrated process design is suggested, and the energy demands and the CO 2 emissions are evaluated and compared. The production capacity of aromatic chemicals, including vanillin, vanillic acid, guaiacol, and acetovanillone, was 0.3 kg aromatics/kg net lignin use. Mass and energy balances and main design data were determined for a 700 t/y kraft lignin biorefinery.
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Modeling, simulation, and analysis were performed based on experimental data to assess the viability of the process.
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This study presents a conceptual design for a recently demonstrated process for lignin oxidative depolymerization. The valorization of lignin into chemicals currently presents a challenge, and its facilitation is key in the development of viable lignocellulosic biorefinery processes. Lignin is the most abundant aromatic biopolymer on Earth, and its aromatic structure makes it a promising platform for the production of biobased chemicals and other valuable building blocks.