(752f) Intensification of Biorefinery Operations Using Building Blocks

Bioenergy is an attractive form of energy since it requires renewable sources that can be produced locally and used as raw materials for its production. One of the possible routes for bioenergy production is through lignocellulosic biorefineries, which utilize various biomass sources, e.g. corn stover, wood, rice straw and forest wastes, to produce biodiesel, steam and power in addition to pulp and paper [1]. Increasing awareness towards sustainable and modular technologies highlights the need for novel processing pathways leveraging on process intensification principles that can yield drastic improvements in several metrics, including economics, energy consumption and chemical footprint [2]. Recent developments in process intensification resulted in development of Integrated biorefinery concept with two new processing pathways: (i) pre-extraction of hemicellulose from biomass and its conversion to ethanol, and (ii) production of syngas from gasification of black liquor [3]. However, there exist further unexplored opportunities for intensification of the biorefineries to enhance the reaction yield and mass/heat transfer within the several parts of the process, e.g. digestion of pulp, evaporation of black liquor, etc. [4].

Recently, a new method for systematic process intensification, which relies on building block-based representation of chemical process flowsheets, has been introduced [5]. These building blocks can be integrated to form a two-dimensional grid embedding numerous non-trivial process alternatives [6-9]. Each block can be assigned with several physicochemical phenomena, e.g. reaction, vapor-Liquid equilibrium, solid-liquid equilibrium, etc., combination of which can yield various intensification pathways. In this work, we extend this novel representation methodology to various operations that take place in a biorefinery. Pulping which occurs in a pulp digester lies at the heart of a pulp mill and, here, we develop a new representation based on fundamental building blocks to represent the pulp digestion process. Mass transfer boundary layer is represented by the boundary shared by two neighboring blocks in different phases and digestion process is represented within the interior of the block. This building-block based representation is modeled using a mixed-integer nonlinear programming (MINLP) problem so as to minimize the energy consumption and increasing the yield of the process while searching for several intensified pathways. The proposed approach is demonstrated through several case studies focusing on the conventional Kraft pulping process, Kraft pulping process with pre-extraction of hemicellulose, Kraft pulping process with pre-extraction of hemicellulose and short fibers.

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[8] Li, J., Demirel, S.E., & Hasan, M. M. F. (2019). Building Block-Based Synthesis and Intensification of Work-Heat Exchanger Networks (WHENS). Processes, 7(1), 23.

[9] Demirel, S. E., Li, J., and Hasan, M. M. F. (2019). A General Framework for Process Synthesis, Integration, and Intensification. Industrial & Engineering Chemistry Research. DOI: 10.1021/acs.iecr.8b05961.