Elsevier

Energy

Volume 230, 1 September 2021, 120729
Energy

Economically feasible thermochemical process for methanol production from kenaf

https://doi.org/10.1016/j.energy.2021.120729Get rights and content

Highlights

  • Green methanol production is a promising technology to convert Kenaf.

  • A process including a two-step of gasification and catalytic upgrading is designed.

  • Economic feasibility is evaluated by considering process scale.

  • Sensitivity analysis identify the relative significance of the major key parameters.

Abstract

This paper presents a thermochemical process design and techno-economic analysis for the production of methanol (MeOH) from Kenaf cultivated in Korea. The proposed process combines three main subsystems to allow for the processing of 2000 tons of kenaf a day: kenaf-to-syngas, syngas-to-MeOH, and a combined heat and power cycle. In the first subsystem, clean syngas is produced from kenaf via a two-step carbonization and steam gasification process. The clean syngas is then catalytically upgraded to MeOH using a commercial Cu/ZnO/Al2O3 catalyst. The third subsystem allows for the generation of heat and electricity to close the energy balance by combusting the biomass residues. Energy analysis and optimization of the heat exchanger network allowed for all energy requirements to be satisfied internally, high overall energy efficiency (60.6%), and the selling of 3.3 MW of excess electricity. Furthermore, an economic feasibility analysis of the process showed that the minimum selling price of MeOH (99.9 wt%) was 0.413 US$/kgMeOH. Importantly, the process economics could be in the range of the market price with respect to incorporating different types of H2 production technology into the process.

Introduction

As the simplest alcohol, methanol (MeOH) is used as a building block for producing conventional products and fuels, and is therefore an important raw material in the global chemical industry; 30% of chemical production uses MeOH as a raw material (e.g., olefin, formaldehyde, acetic acid, chloromethanes, dimethyl ether, gasoline, biodiesel) [1,2]. Further, MeOH demand continues to grow in the renewable energy industries, due to its use as a hydrogen (H2) carrier and production [3,4]. However, as the main industrial feedstocks natural gas and coal [5], MeOH production releases environmental pollutants and carbon dioxide (CO2). Renewable feedstocks therefore must be investigated for sustainable MeOH production.

Lignocellulosic biomass has been identified as the most abundant renewable feedstock for MeOH production [6]. In particular, kenaf, an inedible crop cultivated in South Korea, has a fast growth cycle (five months), high productivity per unit area (30 tons per ha), and high CO2 absorption (30–40 tons per tree), and thus offers potential as a sustainable feedstock [7]. Lignocellulosic biomass is thermally or electrolytically decomposed to syngas [8], which can then be catalytically upgraded to MeOH [9,10]. Raw syngas produced during thermal gasification contains many contaminants, including hydrogen sulfide (H2S), tar, and particulate matter, which decrease the efficacy of the catalysts used for syngas upgrading; thus, expensive syngas cleaning steps are required before upgrading [11]. To address this issue and develop contaminant-free H2-rich syngas, the lab-scale two-step gasification of biomass via carbonization and steam gasification has recently been proposed [12]. This method may provide an economically viable process for producing MeOH without syngas cleaning steps.

Techno-economic analysis (TEA) is an effective methodology in which process models are used to quantify the technical and economic performance of a process and are commonly used to examine the economic feasibility of scaling up a process from the lab scale to a biorefinery [[13], [14], [15]]. Previous researchers have employed TEA on thermochemical pathways in which MeOH was synthesized from lignocellulosic biomass as an initial step for producing gasoline, ethanol, or acetic acid [16,17]. However, the economic feasibility of a standalone process producing MeOH from lignocellulosic biomass has not yet been detailed.

This work therefore aims to techno-economically evaluate the production of MeOH via a two-step thermochemical and catalytic pathway using readily available lignocellulosic biomass as a feedstock. To do so, we simulate a large-scale integrated process by using Aspen Plus Simulator involving the production of MeOH from kenaf including the gasification of Kenaf and the subsequent catalytic upgrading of syngas to MeOH. Moreover, we compare the economic value of MeOH for the developed process with the market price of MeOH for the conventional pathway.

Section snippets

Methods

The kenaf-to-MeOH process was analyzed via a process model design upscaling the lab scale results presented in sections 2.1 Kenaf-to-syngas thermochemical reaction route, 2.2 Syngas-to-MeOH catalytic reaction route, and a subsequent TEA in section 2.3.

Results and discussion

The results of the process simulation, energy integration, and economic evaluation are discussed for the integrated kenaf-to-MeOH process, respectively. The overall reaction pathway is summarized in Fig. 1.

Conclusions

This work detailed the techno-economic analysis of a novel sustainable process for the thermochemical production of MeOH from kenaf, a local lignocellulosic biomass source in Korea. To do so, a large-scale process producing 1123.9 t/d of MeOH from 2000 t/d of kenaf was simulated based on lab-scale experimental data. Optimization of the heat exchanger network and the usage of a CHP unit allowed all internal heating and electricity requirements (including the 289.8 MW required for kenaf

CRediT authorship contribution statement

Hoyoung Park: Investigation, Simulation, Writing- Original draft preparation. Jaewon Byun: Writing- Original draft preparation and Reviewing. Jeehoon Han: Conceptualization, Investigation, Writing- Original draft preparation, Reviewing, and Editing.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgment

This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2019R1I1A3A01061118) and Technology Development Program to Solve Climate Changes of the National Research Foundation (NRF) funded by the Ministry of Science, ICT & Future Planning (2020M1A2A2080858).

References (37)

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