Techno-Economic and Carbon Footprint Analyses of a Coke Oven Gas Reuse Process for Methanol Production

Jean-François Portha,Solène Valentin,Jean-Marc Commenge,Laurent Falk,Wilmar Uribe-Soto

doi:10.3390/pr9061042

Abstract

This paper focuses on the best way to produce methanol by Coke Oven Gas (COG) conversion and by carbon dioxide capture. The COG, produced in steelworks and coking plants, is an interesting source of hydrogen that can be used to hydrogenate carbon dioxide, recovered from flue gases, into methanol. The architecture of the reuse process is developed and the different process units are compared by considering a hierarchical decomposition. Two case studies are selected, process units are modelled, and flowsheets are simulated using computer-aided design software. A factorial techno-economic analysis is performed together with a preliminary carbon balance to evaluate the economic reliability and the environmental sustainability of the proposed solutions. The production costs of methanol are equal to 228 and 268 €/ton for process configurations involving, respectively, a combined methane reforming of COG and a direct COG separation to recover hydrogen. This cost is slightly higher than the current price of methanol on the market (about 204 €/ton for a process located in the USA in 2013). Besides, the second case study shows an interesting reduction of the carbon footprint with respect to reference scenarios. The carbon dioxide capture from flue gases together with COG utilization can lead to a competitive and sustainable methanol production process depending partly on a carbon tax.

Highlights

The iron and steel industry is one of the main energy-intensive industrial sectors together with the cement manufacturing in the world
A conventional methanol synthesis plant using natural gas to produce syngas by steam methane reforming, with an emission factor of 0.768 tCO2 /tMeOH, a value for a conventional weighted-average methanol plant in Europe [29]; A coking plant producing coking coal, flue gases, and Coke Oven Gas (COG), which is used as a fuel in a power plant; A power plant producing electricity by the combustion of
The new methanol synthesis plant including all processes already presented in cases studies A1 and A2 (COG treatment unit, CO2 capture by chemical absorption, methanol synthesis and purification process, and either methane reforming for case study A1 or hydrogen recovery by Pressure Swing Adsorption (PSA) for case study A2), The coking plant producing the same quantity of coking coal, flues gases

Summary

Introduction

The iron and steel industry is one of the main energy-intensive industrial sectors together with the cement manufacturing in the world. Around 2 tons of CO2 are emitted for each ton of steel manufactured, using the blast furnace route [4] This route produces by-product gases offering interesting perspectives in terms of a potential recycling. Three main off-gases are generated: The Blast Furnace Gas (BFG), the Basic Oxygen Furnace Gas (BOFG), and the Coke Oven Gas (COG) These gases, produced transiently and containing CO, CO2 , and CH4 among other gases, are classically used for energy integration in the steel mills or even burnt in flares without any profit. To mitigate these greenhouse gases emissions, Carbon Capture and Utilization (CCU) could offer some potential interesting solutions. The utilization of CO2 in the chemical industry (200 Mt/y) currently represents a minor fraction of the total anthropogenic emissions (32,000 Mt/y) but can still be improved [5]

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