Biomass Gasification: An Overview of Technological Barriers and Socio-Environmental Impact

Biomass gasification has been regarded as a promising technology to utilize bioenergy sustainably. However, further exploitation of biomass gasification still needs to overcome a significant number of technological and logistic challenges. In this chapter, the current development status of biomass gasification, especially for the activities in China, has been presented. The biomass characters and the challenges associated with biomass collection and transportation are covered and it is believed that biomass gasification coupled with distributed power generation will be more competitive in some small communities with large amount of local biomass materials. The technical part of biomass gasification is detailed by introducing different types of gasifiers as well as investigating the minimization methods of tar, which have become more and more important. In fact, applying biomass gasification also needs to deal with other socio-environmental barriers, such as health concerns, environmental issues and public fears. However, an objective financial return can actually accelerate the commercialization of biomass gasification for power and heat generation, and in the meantime, it will also contribute to other technical breakthroughs

Thermoacoustic heat pump utilizing medium/low-grade heat sources for domestic building heating

Thermoacoustic heat pumps are a promising heating technology that utilizes medium/low-grade heat to reduce reliance on electricity. This study proposes a single direct-coupled configuration for a thermoacoustic heat pump, aimed at minimizing system complexity and making it suitable for domestic applications. Numerical investigations were conducted under typical household heating conditions, including performance analysis, exergy loss evaluation, and axial distribution of key parameters. Results show that the proposed thermoacoustic heat pump achieves a heating capacity of 5.7 kW and a coefficient of performance of 1.4, with a heating temperature of 300 °C and a heat-sink temperature of 55 °C. A comparison with existing absorption heat pumps reveals favorable adaptability for large temperature lift applications. A case study conducted in Finland over an annual cycle analyzes the economic and environmental performance of the system, identifying two distinct modes based on the driving heat source: medium temperature (≥250 °C) and low temperature (<250 °C), both of which exhibit favorable heating performance. When the thermoacoustic heat pump is driven by waste heat, energy savings of 20.1 MWh/year, emission reductions of 4143 kgCO$_2$/year, and total environmental cost savings of 1629 €/year are obtained. These results demonstrate the potential of the proposed thermoacoustic heat pump as a cost-effective and environmentally friendly option for domestic building heating using medium/low-grade heat sources

Highly efficient steam reforming of ethanol (SRE) over CeO x grown on the nano Ni x Mg y O matrix: H 2 production under a high GHSV condition

Steam reforming of ethanol (SRE) over non-noble metal catalysts is normally conducted at high temperature (>600°C) to thermodynamically favour the catalytic process and carbon deposition mitigation. However, high temperature inhibits water-gas shift reaction (WGSR) and therefore restrains the yield of H2 and leads to the formation of an excessive amount of CO. The modification of non-noble metal catalyst to enhance WGSR is an attractive alternative. In this study, CeOx was firstly loaded onto a nano-scaled NixMgyO matrix and subsequently used as the catalyst for hydrogen production via SRE. Morphology of the catalyst materials was characterized by using a series of technologies, while H2-temperature programmed reduction (H2-TPR), CO-temperature programmed deposition (CO-TPD), and X-ray photoelectron spectroscopy (XPS), were employed to study the surface nickel, ceria clusters, and their interactions. The catalytic activity and durability of the catalyst were studied in the temperature region of 500°C to 800°C. The CeOx-coated nano NixMgyO matrix exhibited an outstanding hydrogen yield of 4.82 mol/molethanol under a high gas hourly space velocity (GHSV) of 200 000 hour−1. It is found that the unique Ni0-CeOx structure facilitates the adsorption of CO on the surface and therefore promotes the effective hydrogen production via WGSR. Moreover, this modified NixMgyO matrix was found to be a more robust and anticoking nanocatalyst because of reversible switch between Ce4+ and Ce3+. © 2019 John Wiley & Sons, Ltd

Kinetic and thermodynamic investigations of CO2 gasification of coal chars prepared via conventional and microwave pyrolysis

This study examined an isothermal CO2 gasification of four chars prepared via two different methods, i.e., conventional and microwave-assisted pyrolysis, by the approach of thermogravimetric analysis. Physical, chemical, and structural behaviours of chars were examined using ultimate analysis, X-ray diffraction, and scanning electronic microscopy. Kinetic parameters were calculated by applying the shrinking unreacted core (SCM) and random pore (RPM) models. Moreover, char-CO2 gasification was further simulated by using Aspen Plus to investigate thermodynamic performances in terms of syngas composition and cold gas efficiency (CGE). The microwave-induced char has the largest C/H mass ratio and most ordered carbon structure, but the smallest gasification reactivity. Kinetic analysis indicates that the RPM is better for describing both gasification conversion and reaction rates of the studied chars, and the activation energies and pre-exponential factors varied in the range of 78.45–194.72 kJ/mol and 3.15–102,231.99 s−1, respectively. In addition, a compensation effect was noted during gasification. Finally, the microwave-derived char exhibits better thermodynamic performances than the conventional chars, with the highest CGE and CO molar concentration of 1.30% and 86.18%, respectively. Increasing the pyrolysis temperature, gasification temperature, and CO2-to-carbon molar ratio improved the CGE

Production of H2-rich syngas from lignocellulosic biomass using microwave-assisted pyrolysis coupled with activated carbon enabled reforming

This study focuses on the use of a microwave reactor that combines biomass pyrolysis, at mild temperature, with catalytic reforming of the pyrolytic gas, using activated carbon, for generating hydrogen-rich synthesis gas. The traditional pyrolysis of biomass coupled with the reforming of its pyrolytic yields were also conducted using an electrically heated reactor. The bio-oil attained from conventional pyrolysis was higher in comparison to the yield from microwave pyrolysis. The reforming of the pyrolytic gas fraction led to reductions in bio-oil yield to <3.0 wt%, with a simultaneous increase in gaseous yields. An increase in the syngas and H2 selectivity was discovered with the reforming process such that the use of microwave pyrolysis with activated carbon reforming produced 85 vol% synthesis gas fraction containing 55 vol% H2 in comparison to the 74 vol% syngas fraction with 30 vol% H2 obtained without the reforming. Cracking reactions were improved with microwave heating, while deoxidation and dehydrogenation reactions were enhanced by activated carbon, which creates a reduction environment. Consequently, these reactions generated H2-rich syngas formation. The approach implemented in this study revealed higher H2, syngas yield and that the overall LHV of products has huge potential in the transformation of biomass into high-value synthesis gas

Kinetic study of the pyrolysis of microalgae under nitrogen and CO2 atmosphere

In this study, three primary components of algae (lipid, carbohydrate and protein) and one microalgae (spirulina) were pyrolyzed using a thermogravimetric analyser (TGA) under nitrogen and CO2 atmosphere at four heating rates. It was found that protein decomposed first, followed by carbohydrate and then lipid. The kinetic study revealed that the lowest activation energy for the initiation of the pyrolysis of ovalbumin (protein) is ∼70 kJ/mol. Oil droplet showed higher activation energy of 266.5 kJ/mol during its pyrolysis in the CO2 atmosphere, which suggests that algal lipid is more difficult to decompose in the CO2 atmosphere. However, for the pyrolysis of cellulose (carbohydrate), the activation energy (∼310 kJ/mol) is similar under two different gas atmospheres tested. This study showed that CO2 atmosphere favors the pyrolysis of algae with high protein content and low lipid content, since the existence of CO2 promotes the cracking of VOCs (volatile organic compounds) as well as the reaction between VOCs and CO2

Dose-effect relationship analysis of TCM based on deep Boltzmann machine and partial least squares

A dose-effect relationship analysis of traditional Chinese Medicine (TCM) is crucial to the modernization of TCM. However, due to the complex and nonlinear nature of TCM data, such as multicollinearity, it can be challenging to conduct a dose-effect relationship analysis. Partial least squares can be applied to multicollinearity data, but its internally extracted principal components cannot adequately express the nonlinear characteristics of TCM data. To address this issue, this paper proposes an analytical model based on a deep Boltzmann machine (DBM) and partial least squares. The model uses the DBM to extract nonlinear features from the feature space, replaces the components in partial least squares, and performs a multiple linear regression. Ultimately, this model is suitable for analyzing the dose-effect relationship of TCM. The model was evaluated using experimental data from Ma Xing Shi Gan Decoction and datasets from the UCI Machine Learning Repository. The experimental results demonstrate that the prediction accuracy of the model based on the DBM and partial least squares method is on average 10% higher than that of existing methods

Nanocarbon-based catalysts for esterification: Effect of carbon dimensionality and synergistic effect of the surface functional groups

Carbon-based solid acid catalysts represented outstanding hydrothermal and mechanical properties but lower catalytic performances and stabilities. Therefore, more comprehensive investigations should be conducted to optimize their catalytic performances. The correlations between catalytic performance, carbon dimensionality and composition of oxygen-containing functional groups of nanocarbon-based catalysts were investigated. The dimensionality of carbon materials had notable effect on the catalytic reactivity and the layered 2-D structure could maximize the solid/liquid interface and minimize the mass transfer resistance and thus favor the catalytic esterification. GO-50, prepared with 50 mL concentrated H2SO4, exhibited outstanding catalytic activity and had 3 times higher turnover frequency (TOF) value than that of H2SO4. In GO-50, the -SO3H groups were identified as the primary catalytic active sites, while the carboxyl groups enhanced the inherent activity of -SO3H, thus facilitating the esterification. The -COOH/-SO3H molar ratio played significant roles and desirable -COOH/-SO3H molar ratio would promote esterification significantly. The esterification kinetics catalyzed by GO-50 was studied and the apparent activation energy of esterification by GO-50 is 1.5 times lower than that by H2SO4. The esterification mechanism by GO-50 was also proposed. Furthermore, GO-50/Poly (ether sulfones) (PES) membrane was prepared and employed in esterification and the optimal reaction conditions were systematically studied

Investigation on Co–Modified NixMgyO solid solutions for hydrogen production from steam reforming of acetic acid and a model blend

This paper is focused on the Co-modified NixMgyO solid solutions (10wt% Ni, 2-6wt% Co) for the steam reforming of acetic acid and a model blend. The pristine rocksalt structured NixMgyO solid solution and the modified NixMgyO-Co catalysts were synthesized via hydrothermal method and co-impregnation. The activity of the catalysts was evaluated in the temperature range of 500-800 °C with a steam/carbon molar ratio of 3 and a gas hourly space velocity (GHSV) of 57,000 h-1. Low cobalt content (Co loading = 2wt%) catalysts exhibited significant promotion of H2 yield via enhancement of both water-gas shift (WGS) reaction and methane decomposition. A 30-hour test at 700 °C achieved excellent acetic acid conversion rate and H2 yield of 99.1% and 86.9%, respectively. However, the catalysts with higher cobalt loading (Co loading ≥ 4wt%) suffered a much quicker deactivation mainly due to carbon deposition. In addition, the catalysts were also tested on a model blend combined acids, alcohols and aromatic species and exhibited outstanding performance with carbon conversion above 90% and H2 yield above 70% for 100 h

Novel two-stage fluidized bed-plasma gasification integrated with SOFC and chemical looping combustion for the high efficiency power generation from MSW: a thermodynamic investigation

A novel municipal solid waste (MSW)-based power generation system was proposed in this study, which consists of a bubbling fluidized-bed (BFB)-plasma gasification unit, a high-temperature solid oxide fuel cell (SOFC), a chemical looping combustion (CLC) unit and a heat recovery unit. Process simulation was conducted using Aspen PlusTM and validated by literature data. The energetic and exergetic assessment of the proposed system showed that the net electrical efficiency and exergy efficiency reached 40.9 % and 36.1 %, respectively with 99.3 % of carbon dioxide being captured. It was found that the largest exergy destruction took place in the BFB-Plasma gasification unit (476.5 kW) and accounted for 33.6 % of the total exergy destruction, which is followed by the SOFC (219.1 kW) and then CLC (208.6 kW). Moreover, the effects of key variables, such as steam to fuel ratio (STFR), fuel utilization factor (Uf), current density and air reactor operating temperature, etc., on system performance were carried out and revealed that the system efficiency could be optimized under STFR = 0.5, Uf = 0.8 and air reactor operating temperature of 1000 ºC. Furthermore, the proposed process demonstrated more than 14% improvement in net electrical efficiency in comparison with other MSW incineration and/or gasification to power processes