Thomas Kohl

Performance of biofuel processes utilising separate lignin and carbohydrate processing.

Novel biofuel pathways with increased product yields are evaluated against conventional lignocellulosic biofuel production processes: methanol or methane production via gasification and ethanol production via steam-explosion pre-treatment. The novel processes studied are ethanol production combined with methanol production by gasification, hydrocarbon fuel production with additional hydrogen produced from lignin residue gasification, methanol or methane synthesis using synthesis gas from lignin residue gasification and additional hydrogen obtained by aqueous phase reforming in synthesis gas production. The material and energy balances of the processes were calculated by Aspen flow sheet models and add on excel calculations applicable at the conceptual design stage to evaluate the pre-feasibility of the alternatives. The processes were compared using the following criteria: energy efficiency from biomass to products, primary energy efficiency, GHG reduction potential and economy (expressed as net present value: NPV). Several novel biorefinery concepts gave higher energy yields, GHG reduction potential and NPV.

Enhanced biofuel processes utilizing separate lignin and carbohydrate processing of lignocellulose

ABSTRACT Enhanced biofuel production routes utilizing separate lignin and carbohydrate processing of lignocellulose are analyzed and compared with two conventional routes; the methanol and methane production via syngas from biomass. The enhanced processes studied are: hydrocarbons production by hydrogenation of biomass based sugars by hydrogen obtained from lignin gasification, and ethanol production by biomass hydrolysis and fermentation and conversion of residual lignin into methanol via syngas. The analysis of processes was done by rigorous flowsheet modeling including power production calculations and realistic heat integration and evaluation based on energy yield, greenhouse gas (GHG) reduction and net present value (NPV). The enhanced processes via separate lignin and sugar processing can run in two modes: either being energy self-sufficient or utilizing external low temperature heat and power. The processes can operate with high efficiency as ‘waste heat and power to gas and liquids’ processes for producing liquid or gaseous fuels especially when excess energy is available e.g. in summer. Of all the processes studied the enhanced hydrocarbon production process integrated with external low temperature heat source gave the largest GHG reduction and highest NPV. External low temperature heat and electricity is converted into fuels in 136% higher heating value (116% lower heating value) efficiency.

Process modeling, synthesis and thermodynamic evaluation of hydrogen production from hydrothermal processing of lipid extracted algae integrated with a downstream reformer conceptual plant

ABSTRACT Hydrothermal processing of organics, particularly the supercritical water gasification process, has showed potential in lab-scale records to valorize the chemical energy stored in biomass. The technology manipulates the varying thermo-physical properties around the critical point of water to convert and upgrade the organic content, as well as extract inorganics. This study provides a systematic evaluation to the process upscaling into energetically efficient commercial demonstration. Conceptual plant flowsheets for a lipid extracted algae feedstock were developed on Aspen plus® for 99.9% purity hydrogen fuel production. The advantageous reactor system configuration is integrated within a layout that includes subsequent power generation and gas purification. The process is coupled with a downstream steam reformer block to maximize the poly-generation of hydrogen fuel, power and thermal heat. To thermodynamically evaluate the plant designs, minimum process utility demands were computed with the pinch analysis method, and different energy recovery scenarios, as well as alternative design configurations for optimal heat recovery were assessed. Finally, a comparative assessment showed that integrating downstream steam reforming with hydrothermal processing lead to an increase in the overall energetic efficiency from 34.2 to 46.2%, in the fuel-equivalent efficiency from 44.1 to 55% and exergetic efficiency from 28.9 to 41.4%.

Prediction of gas composition of Jatropha curcas Linn oil cake in entrained flow reactors using ASPEN PLUS simulation software.

A prediction for product gases of Jatropha curcas Linn (JCL) oil cake gasified in the entrained flow reactor is studied in this paper. ASPEN PLUS commercial software is used to carry out the simulation using Gibbs free energy minimisation with equilibrium phase. A series of simulations and analyses have been carried out to investigate the composition of product gases in JCL oil cake with reactor temperature ranging from 1000 to 1400°C. In the first prediction step, the gas composition of sawdust and rice husk are validated. After this, the simulation model is used to predict JCL oil cake gas composition. Mean error analysis is carried out to identify the maximum and minimum error of the simulation. The results show that with increasing reactor temperature, the amount of carbon monoxide (CO) and hydrogen (H2) increases while the amount of carbon dioxide (CO2) and methane (CH4) decreases. The results of the gas composition of JCL oil cake show that the CO content at a temperature of 1000°C ranges from 41.35% to 53.36%. Composition of other gases such as hydrogen (H2), carbon dioxide (CO2), methane (CH4) is 24.65–32.7%, 4.4–22.99% and 0.94%–19.62%, respectively.