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Valuable Products from Thermal Degradation of Industrial Waste Lignin in the Presence of Chemical Additives
Published in Kailas L. Wasewar, Sumita Neti Rao, Sustainable Engineering, Energy, and the Environment, 2022
Rupali A. Nandanwar, A. R. Chaudhari, J. D. Ekhe
In the components of wood, together with cellulose and hemicellulose, lignin is also the main component. It is a valuable resource for energy and chemicals, also it is considered as the important source of organic raw material [1, 2]. Lignin consisting about 4–35 wt.% of most biomass. In the pulp and paper industry, during the Kraft process of delignification, lignin is separated from cellulose and hemicellulose. Around 70 million tons of lignin is produced per year. Out of this large amount of lignin produced only 3–5% of lignin was utilized commercially, and the rest amount of lignin is only burnt out. Thus, for the pulp and paper industries, the disposal of this produced lignin is big problem [3, 4]. However, due to the generation of very large quantities of lignin, it has the potential to be used as an alternative source of chemicals and hydrocarbon fuels [5–8]. Due to the chemistry and structure of lignin, it is considered as the important raw material for a number of applications. Many researchers worked a lot for the utilization of industrial waste lignin (IWL), e.g., hydrogenation [9, 10], alkali fusion [11], pyrolysis [12] and low molecular weight fuel additives can be prepared from lignin [13, 14].
Feasibility of Treating Pulp Mill Effluent with a Constructed Wetland
Published in Gerald A. Moshiri, Constructed Wetlands for Water Quality Improvement, 2020
The chemical pulping of wood chips takes place under conditions of high heat and pressure in strongly alkaline solutions of sodium sulfide (the kraft process) or in mildly acidic solutions of a basic salt of bisulfite (the sulfite process). The primary intent of this pulping or cooking process is to solubilize the lignin in wood, thus isolating the cellulose fibers. Most of the lignin is recovered (burned for energy), but some enters the wastewater. Various mechanical pulping processes are also utilized whereby much of the lignin is incorporated into the finished product. If a bright white product is required, then several bleaching steps may be used. Most often, bleaching is accomplished with a combination of chlorine, chlorine dioxide, and sodium hydroxide. However, the use of oxygen and hydrogen peroxide has assumed increasing importance. Pulps produced by the mechanical method do not use chlorine bleaching agents.
Literature review
Published in Tejaswini Eregowda, Anaerobic treatment and resource recovery from methanol rich waste gases and wastewaters, 2019
In the Kraft process, white liquor, a mixture of sodium hydroxide (NaOH) and sodium sulphide (Na2S), is used to separate lignin from the cellulose fibres (compound of interest for paper making). Lignin is a phenolic polymeric structure present in plants that supports vascular plant wood. The pulp washing results in a stream of weak black liquor mainly comprising of recoverable chemicals and lignin. Weak black liquor is sent to the Kraft recovery system, where the inorganic pulping chemicals are recovered for reuse, while the dissolved organics are used as a fuel to make steam and power. In the Kraft process, weak black liquor is concentrated in multi-effect evaporators and concentrators to a point where it can be effectively burned in a recovery boiler (65% solids or higher). The condensates from different stages of condensation and evaporation are collectively known as Kraft condensates (Badshah et al., 2012; Tran and Vakkilainnen, 2012). Methanol is generated in the Kraft process by the removal of a methyl group (de-methylation) from lignin and xylan (hemicellulose groups in the plant cell walls) (Zhu et al., 1999).
Electrodialysis reversal applied to tertiary treatment of Kraft pulp mill effluent
Published in Chemical Engineering Communications, 2021
Luan Amaral de Souza, Tatiane Benvenuti, Daniella Cardoso Buzzi, Marco Antônio Siqueira Rodrigues, Franco Dani Rico Amado
About pulp production methods, the Kraft process is used by more than 90% of the industries, because it presents as advantages the recovery of chemical reagents and process sustainability (Hu et al. 2018; Pathak et al. 2019). However, these industries require large amounts of water in the process and generates the largest volume of industrial effluents in the world, containing highly toxic and non-biodegradable compounds (IBÁ 2017; Prabakar et al. 2018; Sharma et al. 2020).