Self-sustained physical activation at pilot-scale integrated in a commercial wood gasification plant: A path to renewable activated carbon, PAH removal and electrical efficiency improvement

Abstract

A pilot-scale reactor for self-sustained physical activation was integrated into an industrial wood gasification plant (300kWel) with the aim of upgrading its carbon-rich by-product, gasification char (GC). The resulting products were activated carbon (AC) and a combustible gas, which was used to generate electricity in the plant’s gas engine. Physical activation of GC is frequently endorsed in literature and has great economic potential. However, a significant research gap remains, possibly due to challenges inherent to GC, including a soft skeleton, high degree of graphitisation, ash content, and reduced porosity. Key achievements include: (i) activation product gas with a heating value of 3.2MJ/Nm3, (ii) maximal theoretical electrical efficiency improvement of the gasification plant by 12.5%; (iii) a 150% increase in GC porosity, reaching 661m2/g; (iv) a 400% improvement in organic micropollutant adsorption capacity compared to GC, achieving approximately 2/3 of the capacity of commercial AC; and (v) significant reduction of polycyclic aromatic hydrocarbons (PAH) content, frequently measuring below broadly recognised threshold values for biochar. This novel co-production of low PAH, high porosity AC and combustible gases represents a promising approach for advancing a carbon negative economy, improving the fuel utilisation rate of gasification plants and producing high value-added products.

Keywords

• Gasification char
• Activated carbon
• Pilot-scale physical activation
• Biochar
• Polycyclic aromatic hydrocarbons (PAH)