Work

Exergy Analysis of an Innovative System by Combining the Biomass Gasification Unit with the Supercritical Water Unit

Year: 2026

Type: article

Abstract: Contaminants such as tars in the gas from gasifiers hinder the application of biomass gasification technology. Theoretically, tars can be completely removed in the system by combining the biomass gasification unit with the supercritical water unit (SWU). In order to evaluate the system energy utilization in terms of quality, exergy analysis of the process by combining the gasification unit with the SWU is conducted. Besides, the effects of the mass ratio of tars to supercritical water (T/W), the supercritical water reactor (SWR) inlet temperature, and the SWR pressure on the exergy efficiency and the exergy loss are also investigated. Results show that the four units with the largest exergy loss are the gasification process, SWE, compressor, and SWM. The distribution characteristic shows that the system exergy loss is mainly concentrated in the chemical reactions, cooling of product gas, inter-stage cooling of the compressor, irreversibility of the compression process, irreversible adiabatic expansion, temperature gradient, mixing, diffusion, and heat exchange processes. With the increase of T/W from 1.00% to 2.00%, the system exergy efficiency decreases slightly, while the exergy efficiency of dry gas and the system dry exergy efficiency increase. The system exergy efficiency and the system dry exergy efficiency increase slightly with the increase of SWR inlet temperature from 973.15 K to 1073.15 K, while the exergy efficiency of dry gas decreases slightly. With the increase of SWR pressure from 219.00 atm to 265.00 atm, the system exergy efficiency and the system dry exergy efficiency increase slightly, while the exergy efficiency of dry gas is slightly reduced. Considering the slight change of the system exergy efficiency, the difficulty of engineering implementation, and the operating risk, the optimal T/W, SWR inlet temperature, and SWR pressure are 2.00%, 973.15 K, and 219.00 atm, respectively. Sensitivity analysis shows that the system exergy efficiency has low sensitivity to the minor fluctuation of T/W; SWR inlet temperature is a moderately sensitive operating parameter; the system exhibits extremely strong robustness against SWR pressure change; the system exergy performance is weakly sensitive to the compressor efficiency fluctuation; and the system shows weak robustness against SWE efficiency. Factorial design analysis shows that T/W exhibits the largest influence on system exergy efficiency, followed by TSWR and PSWR. The T/W × PSWR interaction produces a minor measurable impact; the T/W × TSWR, interaction has an extremely small effect; and the TSWR × PSWR interaction exerts a negligible effect. When the T/W, the inlet temperature of SWR and the SWR pressure are 2.00%, 973.15 K, and 219.00 atm, respectively, the calculated system exergy efficiency is 54.20%, which is higher than the system exergy efficiency (24.47%) of the baseline case (biomass gasification unit and conventional gas cleaning unit).

Source: Energies

DOI: 10.3390/en19204892

Authors: Wei Wan, Jianchen Wan, Zhaozhao Li

Institution: Huanghe Science and Technology College

Language: English

Topic: Thermodynamic and Exergetic Analyses of Power and Cooling Systems

Subfield: Mechanical Engineering

Field: Engineering

Domain: Physical Sciences

SDGs: Affordable and clean energy, Responsible consumption and production, Climate action

Open Access status: gold

Estimated APC paid: $3,137