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

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

Promotion effect and mechanism of the addition of Mo on the enhanced low temperature SCR of NOx by NH3 over MnOx/γ-Al2O3 catalysts

A series of Mn/γ-Al2O3 and MnMo/γ-Al2O3 catalysts were prepared by using Incipient Wetness Impregnation (IWI) method. The catalytic performance tests showed that the Mn3Mo1.25/γ-Al2O3 demonstrated a higher SCR performance (NO conversion of around 96%) at a broad low temperature range (150 to 300°C). The characterization showed that the addition of Mo to the Mn/γ-Al2O3 catalysts could promote the dispersion of MnOx on the surface of γ-Al2O3. The adsorption of NO could form two different species, nitrites and nitrates on the surface of the catalyst. The presence of nitrites is beneficial to low temperature SCR. It is also found that the existence of Mo in the catalyst favours the formation of Mn3+, which plays a critical role in the adsorption of NH3 and therefore improves NH3 adsorption capacity of the MnOx/γ-Al2O3 catalysts. The low temperature SCR of the Mn3Mo1.25/γ-Al2O3 catalyst was found to mainly follow L-H mechanism, but E-R mechanism also plays a role to some extent. Moreover, it is also found that the addition of Mo not only mitigates the deactivation of catalysts, but also broadens the effective temperature range of the SCR catalyst

Chalcogenide Glass-on-Graphene Photonics

Two-dimensional (2-D) materials are of tremendous interest to integrated photonics given their singular optical characteristics spanning light emission, modulation, saturable absorption, and nonlinear optics. To harness their optical properties, these atomically thin materials are usually attached onto prefabricated devices via a transfer process. In this paper, we present a new route for 2-D material integration with planar photonics. Central to this approach is the use of chalcogenide glass, a multifunctional material which can be directly deposited and patterned on a wide variety of 2-D materials and can simultaneously function as the light guiding medium, a gate dielectric, and a passivation layer for 2-D materials. Besides claiming improved fabrication yield and throughput compared to the traditional transfer process, our technique also enables unconventional multilayer device geometries optimally designed for enhancing light-matter interactions in the 2-D layers. Capitalizing on this facile integration method, we demonstrate a series of high-performance glass-on-graphene devices including ultra-broadband on-chip polarizers, energy-efficient thermo-optic switches, as well as graphene-based mid-infrared (mid-IR) waveguide-integrated photodetectors and modulators

A Review of Sludge-to-Energy Recovery Methods

The increasing volume of sewage sludge from wastewater treatment facilities is becoming a prominent concern globally. The disposal of this sludge is particularly challenging and poses severe environmental hazards due to the high content of organic, toxic and heavy metal pollutants among its constituents. This study presents a simple review of four sewage to energy recovery routes (anaerobic digestion, combustion, pyrolysis and gasification) with emphasis on recent developments in research, as well as benefits and limitations of the technology for ensuring cost and environmentally viable sewage to energy pathway. This study focusses on the review of various commercially viable sludge conversion processes and technologies used for energy recovery from sewage sludge. This was done via in-depth process descriptions gathered from literatures and simplified schematic depiction of such energy recovery processes when utilised for sludge. Specifically, the impact of fuel properties and its effect on the recovery process were discussed to indicate the current challenges and recent scientific research undertaken to resolve these challenges and improve the operational, environmental and cost competitiveness of these technologies

Numerical and experimental study of VM type pulse tube cryocooler with multi-bypass operating below 4 K

International audienceThe Vuilleumier (VM) type pulse tube cryocooler (VPTC) is a new kind of 4 K cryocooler which had been experimentally verified. This paper presents the recent advances on a 4 K VPTC in our laboratory. First, the mechanism of multi-bypass was numerically studied using Sage software. The results showed that the function of the multi-bypass is not only similar to a double-inlet, but also to an orifice, which makes the VPTC work like a two-stage cryocooler. Based on the simulation results, the performance of VPTC was experimentally studied. Under its optimal operating conditions, a no-load temperature of 3.7 K has been obtained, which is the first demonstration of a single-stage VPTC obtaining temperatures below 4 K. It can supply about 14mW cooling power at 4.2 K and about 100 mW cooling power at 35 K simultaneously, which has potential application as the pre-cooler for an adiabatic demagnetization refrigerator (ADR). Finally, based on this VPTC, a new mK cooling chain for HUBS (Hot Universe Baryon Surveyor) satellite is proposed and its prospect has also been theoretically analyzed