Guohui Song

Simulation and energy performance assessment of CO2 removal from crude synthetic natural gas via physical absorption process

The paper presents an energy performance assessment of CO2 removal for crude synthetic natural gas (SNG) upgrade by Selexol absorption process. A simplified process simulation of the Selexol process concerning power requirement and separation performance was developed. The assessment indicates that less pressure difference between crude SNG and absorption pressure favors the energy performance of CO2 removal process. When both crude SNG and absorption pressures are 20 bar, CO2 removal process has the best energy performance. The optimal specific power consumption of the CO2 removal process is 566 kJ/kgCO2. The sensitivity analysis shows that the CO2 removal efficiency would significantly influence the total power consumption of the removal process, as well as higher heating value (HHV) and CO2 content in SNG. However, the specific power consumption excluding crude SNG and SNG compressions changes little with the variance of CO2 removal efficiency. If by-product CO2 is compressed for CO2 capture, the process would turn into a CO2-sink for the atmosphere. Correspondingly, an increase of 281 kJ/kgCO2 in specific power consumption is required for compressing the separated CO2.

Estimation of Specific Enthalpy and Exergy of Biomass and Coal Ash

Ash is one of the most studied but poorest understood characteristics. Based on the latest summary on chemical ash composition of varieties of biomass and coal, specific enthalpy, physical, and chemical exergy of biomass and coal ash were calculated then studied statistically. Three correlations were derived for estimating specific enthalpy, physical, and chemical exergy of ash, respectively. Then the ratios of the energy and exergy losses with discharged ash indicate that ash should be taken into account in an accurate exergy analysis of a process that simultaneously involves fuels with high ash content and a high exhaust gas temperature.

Simulation of Bio-syngas Production from Biomass Gasification via Pressurized Interconnected Fluidized Beds

Bio-syngas production from biomass gasification via pressurized interconnected fluidized beds was described. The interconnected fluidized beds technology separates the gasification and combustion processes of biomass, and the heat is transferred from combustor to gasifier by bed materials, while extra heat needed in gasification process is provided by additional biomass burning in the combustor. The simulation of the whole process was carried out with Aspen Plus software. The effects of gasification temperature (T g), gasification pressure (p g) and steam to biomass ratio (S/B) on bio-syngas production were studied. The results showed that gasification temperature, gasification pressure, and S/B had great influences on the bio-syngas composition and to achieve high carbon conversion and yield of high-quality bio-syngas, the suitable gasification temperature is around 750 °C, and the gasification pressure and S/B could not too high.

A techno-economic assessment of SNG production from agriculture residuals in China

ABSTRACT Biomass provides an attractive option for satisfying the demand of the rapid gas consumption growth. A process of BioSNG production via interconnected fluidized beds as gasification system and fluidized bed methanation reactor was modeled using Aspen Plus. The process performances and economic cost of BioSNG production from rice straw, wheat straw, corns stalk, and cotton straw were performed and compared. The exergy efficiency of BioSNG production from the four varieties of biomass ranges from 54.8% to 65.6%. With assumption on price of biomass including transportation of 250 RMB/t, the unit cost of BioSNG is equivalent to that of coal-based SNG. However, sensitivity analysis indicates that the unit cost of BioSNG linearly increases with the increase of biomass price. The exergy efficiency and unit cost results also strongly suggest that the CO2 produced during BioSNG production should be captured rather than treated as waste.

Improving Coal Gasification with in Situ CO2 Capture by Pressurization in Interconnected Fluidized Beds

The technical route of coal gasification with in situ CO2 capture using CaO sorbents was proposed via interconnected fluidized beds (ICFB) system, however, the defect of mismatch between the optimal coal gasification temperature and the optimal sorbents carbonation temperature limited the application. This paper modified the mentioned defect by pressurization. The coal gasification process with CO2 capture was simulated using Aspen Plus. It was analyzed that the effects of gasification temperature, pressure, sorbents/coal ratio on gasification products composition, CO2 capture efficiency. The effect of different bed materials was also discussed. The results indicates the pressure range of 0.7-0.9 MPa with the gasification temperature range of 740-760°C is favorable considering the match of coal gasification and sorbents carbonation temperature. Moreover, the optimal sorbent/coal ratio is about 0.38 under the condition above. The use of CaO sorbents reduces the CO2 concentration in the exit of the gasifier about 53.53%, as well as partly promotes coal gasification degree and H2 yield, compared to quartz sands.