Creating Values from Biomass Pyrolysis in Sweden: Co-Production of H2, Biocarbon and Bio-Oil

Ilman Nuran Zaini,Weihong Yang,Kurt Sjöblom,Nanta Sophonrat

doi:10.3390/pr9030415

Abstract

Hydrogen and biocarbon are important materials for the future fossil-free metallurgical industries in Sweden; thus, it is interesting to investigate the process that can simultaneously produce both. Process simulations of biomass pyrolysis coupled with steam reforming and water-gas-shift to produce H2, biocarbon, and bio-oil are investigated in this work. The process simulation is performed based on a biomass pyrolysis plant currently operating in Sweden. Two co-production schemes are proposed: (1) production of biocarbon and H2, and (2) production of biocarbon, H2, and bio-oil. Sensitivity analysis is also performed to investigate the performance of the production schemes under different operating parameters. The results indicated that there are no notable differences in terms of the thermal efficiency for both cases. Varying the bio-oil condenser temperature only slightly changes the system’s thermal efficiency by less than 2%. On the other hand, an increase in biomass moisture content from 7 to 14 wt.% can decrease the system’s efficiency from 79.0% to 72.6%. Operating expenses are evaluated to elucidate the economics of 3 different cases: (1) no bio-oil production, (2) bio-oil production with the condenser at 50 °C, and (3) bio-oil production with the condenser at 130 °C. Based on operation expenses (OPEX) and revenue alone, it is found that producing more bio-oil helps improving the economics of the process. However, capital costs and the cost for post-processing of bio-oil should also be considered in the future. The estimated minimum selling price for biocarbon based on OPEX alone is approx. 10 SEK, which is within the range of the current commercial price of charcoal and coke.

Highlights

Metal production is one of the main industries highly dependent on fossil fuels and emitting a large amount of CO2
An intermediate pyrolysis process with electrically heated screw reactor is chosen in the simulation to resemble Envigas pyrolysis process for biocarbon production
This value is in the same range of heat required for pyrolysis biomass with a moisture content of 7 wt.% can be converted into 217.2 kg of biocarbon

Summary

Introduction

Metal production is one of the main industries highly dependent on fossil fuels and emitting a large amount of CO2. A significant part of CO2 comes from coal, coke, oil, and natural gas used in steel production processes including sintering, coke making and blast furnace [3]. Blast furnaces, which account for the largest CO2 emission in the steel plant, approximately consume 250–300 kg of coke per ton hot metal produced [4]. Some of the methods to reduce CO2 emission from metallurgical processes are to apply new technologies and to use renewable fuels. This includes the use of H2 as a reduction agent instead of coke (HYBRIT project [5]) and the replacement of coal and coke with biocarbon/charcoal from biomass [6]

Methods

Results

Conclusion