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• Detailed reaction pathway of soybean stem was proposed. • Kinetic model of soybean stem gasification in SCW was established. • The kinetic model was used in tubular reactor for further analysis. • Sensitivity and steady analysis of reactor was conducted. • Dynamic characteristic of reactor with parameters fluctuating was studied. Supercritical water gasification (SCWG) technology is considered as a potential technology to realize resource utilization of biomass waste. Both experimental and modeling researches are performed to guide the development and scale-up of this technology. Among these researches, dynamic study of the reactor is an important aspect. However, related published literature is relatively limited. In this study, a one-dimensional dynamic model was developed, and a kinetic model of soybean stem containing detailed reaction pathway of biomass was established based on the lumped parameter method. It was calculated through fitting experiment data (obtained at 600, 650, and 700℃ three temperatures and pressure of around 25 MPa), after which it was applied to the tubular reactor for further analysis. Sensitivity analysis of the reactor displayed that H 2 mole fraction was most sensitive to the inlet temperature, which increased or decreased by around 10 % when the temperature had a ± 5 % fluctuation. Dynamic simulation results showed that the gasifier responds quickly under a transient change of concentration. Gasification efficiency decreased from 83.8 % to 41.9 % at 500 s, kept constant for 240 s, and then increased to 83.4 % and stabilized at this value. Total response time was 900 s. Molar fraction of CO, CO 2 and CH 4 increased by 0.8 %, 0.66 %, 3.08 % respectively. While that of H 2 decreased by 4.54 % within 660 s. As for fluctuation of flowrate, gasification efficiency increased by 3.4 % when residence time increased from 527 s to 584 s. Mole fraction of H 2 and CO 2 increased with time, while that of CH 4 and CO decreased, and response time was 900 s. [ABSTRACT FROM AUTHOR]

Biomass combined heat and power plants (CHPPs) can operate target-specifically because of their controllability while supporting decarbonization in district heating. The transition from the German Renewable Energies Act funding, which has promoted biomass CHPPs but is now about to expire, to direct marketing, is a major economic challenge for many biomass-heating grids. To successfully accomplish it, the flexible operation of biomass CHPPs, compared to the previous baseline-operation, is becoming an increasingly important requirement if participation in the electricity markets is to remain profitable. This paper presents a techno-economic assessment of flexible CHPP operation in a modeled district heating system with a CHPP, a peak load boiler and a thermal heat storage. The simulation model compares two cases - a natural gas and a wood-chip gasifier CHPP. The analysis of the results investigates the parameters that need to be adapted to make biomass-fired CHPP heating grids more efficient compared to fossil-fired CHPP heating grids in a flexible operating scenario. It highlights the technical and economic superiority of a fossil-fired CHPP in flexible operation in comparison to the wood gasifier system. The introduction of a CO 2 -tax on natural gas as a fuel, currently under discussion in Germany, would increase the competitiveness of the wood gasifier. • Simulation model of a district heating system. • Model units are wood or natural CHP plant, peakload boiler and heat storage. • Three scenarios for CHP plant dispatch under consideration of electricity prices. • Focus on dynamic differences of the CHP plant operation strategy. • Results show limitations in operational flexibility of the wood gas CHP plant. [ABSTRACT FROM AUTHOR]