Climate change and fossil fuel depletion are the main reasons leading to hydrogen technology. There are many processes for hydrogen production from both conventional and alternative energy resources such as natural gas, coal, nuclear, biomass, solar and wind. In this work, a comparative overview of the major hydrogen production methods is carried out. The process descriptions along with the technical and economic aspects of 14 different production methods are discussed. An overall comparison is carried out, and the results regarding both the conventional and renewable methods are presented. The thermochemical pyrolysis and gasification are economically viable approaches providing the highest potential to become competitive on a large scale in the near future while conventional methods retain their dominant role in H2 production with costs in the range of 1.34–2.27 $/kg. Biological methods appear to be a promising pathway but further research studies are needed to improve their production rates, while the low conversion efficiencies in combination with the high investment costs are the key restrictions for water-splitting technologies to compete with conventional methods. However, further development of these technologies along with significant innovations concerning H2 storage, transportation and utilization, implies the decrease of the national dependence on fossil fuel imports and green hydrogen will dominate over the traditional energy resources.

A comparative overview of hydrogen production processes

Hydrogen production, storage, transportation and key challenges with applications: A review

Biomass gasification is a widely used thermochemical process for obtaining products with more value and potential applications than the raw material itself. Cutting-edge, innovative and economical gasification techniques with high efficiencies are a prerequisite for the development of this technology. This paper delivers an assessment on the fundamentals such as feedstock types, the impact of different operating parameters, tar formation and cracking, and modelling approaches for biomass gasification. Furthermore, the authors comparatively discuss various conventional mechanisms for gasification as well as recent advances in biomass gasification. Unique gasifiers along with multi-generation strategies are discussed as a means to promote this technology into alternative applications, which require higher flexibility and greater efficiency. A strategy to improve the feasibility and sustainability of biomass gasification is via technological advancement and the minimization of socio-environmental effects. This paper sheds light on diverse areas of biomass gasification as a potentially sustainable and environmentally friendly technology.

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An overview of advances in biomass gasification

Recent development in the treatment of oily sludge from petroleum industry: A review

Thermal degradation of PVC: A review.

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CO2 gasification kinetics of Shenhua bituminous coal by isothermal thermogravimetric analysis

An attempt was made to prepare hollow silica microspheres by an oil-in-water emulsion which proposed to use waste polystyrene organic solution as oil phase. Effects of the kinds and amounts of surfactants and the concentration of waste polystyrene solution on the nanosized hollow silica microspheres were studied. The prepared hollow silica microspheres were characterized by TEM, XRD, TG-DTA and particle size distribution analyzer. The experimental results showed that the waste polystyrene organic solution was successfully treated as oil core and the cores could be removed at about 350 degrees C. Meanwhile, the obtained hollow microspheres were amorphous with an average particle size of 40nm. The hollow silica microspheres could be obtained with the selected surfactant.

A Green Approach to Preparing Nanosized Hollow Silica Microspheres with Waste Polystyrene

Kinetics is the study of rates of chemical processes, which includes investigations of how different experimental conditions can influence the speed of a chemical reaction and the reactions mechanism. In this paper, the influences of several parameters including particle size and mass of copper-based oxygen carrier, reaction gas flow rate and temperature on the conversion rate of oxygen carrier in chemical looping combustion was investigated. The results of experiment reveal that the conversion rate of oxygen carrier is influenced by the reaction temperature, mass of the oxygen carrier and the reaction gas flow rate. The conversion rate of oxygen carrier is improved with decreasing the mass of the oxygen carrier and increasing the reaction gas flow rate within a certain extent in the chemical looping combustion process. The particle size has very little effect on the conversion rate, and 800 °C is an advisable reaction temperature for chemical looping combustion process of copper-based oxygen carrier with methane and air.

Study on the Kinetics of Chemical Looping Combustion of Copper-Based Oxygen Carrier

Coal thermochemical conversion processes unavoidably generate gaseous pollutants, endangering the environment or influencing synthetic processes downstream. In order to display the differences in release behaviors of nitrogen among different coal thermochemical conversion stages, nitrogen release characteristics of Shenhua bituminous coal under Ar, CO2, and air atmospheres were investigated using X-ray photoelectron spectrum (XPS) and thermogravimetry-mass spectrometry (TG-MS). Results indicate that the reaction atmosphere has an important influence on nitrogen release. The total released mass of nitrogen when using 100 g raw coal in the whole experiment under Ar, CO2, and air atmospheres is 0.54, 0.64, and 0.75 g, respectively. The organic forms of nitrogen in raw coal and coal char are pyridine nitrogen (N-6), pyrrole nitrogen (N-5), quaternary nitrogen (N-Q), and nitrogen oxide (N-X). While in the coal ash, the sub-peaks of N-Q and N-X disappear entirely, leaving only N-5 and N-6 sub-peaks. The released nitrogen-containing gas consists of NH3, HCN, NO, and NO2 during experiments in CO2 and air atmospheres. However, only NH3 and HCN are detected during experiments in Ar atmosphere. The revolution characteristics of NH3 and HCN under Ar and CO2 atmospheres are similar. This article is protected by copyright. All rights reserved. 

Release of nitrogen during thermochemical conversion of Shenhua bituminous coal under Ar,
 
 CO
 2
 
 , and air atmospheres

A thermodynamic study on a toluene chemical looping reforming process with six metal oxides was conducted to evaluate the product distribution for selecting an appropriate oxygen carrier with thermodynamic favorability towards high syngas yield. The results show that a suitable operation temperature for most oxygen carriers is 900 °C considering syngas selectivity and solid C formation whether the toluene is fed alone or together with fuel gas. The syngas selectivity of all oxygen carriers decreases with the increasing equivalence ratio, but the decrease degrees are quite different due to their different thermodynamic natures. With the increasing amounts of H2 and CO, the syngas selectivity for various oxygen carriers correspondingly decreases. The addition of CO2 and H2O(g) benefits reducing the solid C formation, whereas the addition of CH4 leads to more solid C being produced. Under the simulated gasification gas atmosphere, a synergetic elimination of solid C and water–gas shift reactions are observed. In terms of syngas selectivity, Mn2O3 possesses the best performance, followed by CaFe2O4 and Fe2O3, but NiO and CuO exhibit the lowest performance. BaFe2O4 presents a high H2 selectivity but a very poor CO selectivity due to the formation of BaCO3, which has a high thermodynamic stability below 1200 °C. Nevertheless, Mn2O3 is more likely to form solid C than feeding toluene alone and has a lower melting point. Considering syngas selectivity, carbon deposit and melting point, CaFe2O4 exhibits the highest performance concerning the tar chemical looping.

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Evaluation of Different Oxygen Carriers for Chemical Looping Reforming of Toluene as Tar Model Compound in Biomass Gasification Gas: A Thermodynamic Analysis

Zhiqi Wang

Papers

CO2 gasification kinetics of Shenhua bituminous coal by isothermal thermogravimetric analysis

A Green Approach to Preparing Nanosized Hollow Silica Microspheres with Waste Polystyrene

Study on the Kinetics of Chemical Looping Combustion of Copper-Based Oxygen Carrier

Release of nitrogen during thermochemical conversion of Shenhua bituminous coal under Ar, CO 2 , and air atmospheres

Evaluation of Different Oxygen Carriers for Chemical Looping Reforming of Toluene as Tar Model Compound in Biomass Gasification Gas: A Thermodynamic Analysis