Combined Decarbonization of Electrical Energy Generation and Production of Synthetic Fuels by Renewable Energies and Fossil Fuels

Power generation from renewable energy sources and fossil fuels are integrated into one system. A combination of technologies in the form of a carbon capture utilization (CCU)-combined power station is proposed. The technology is based on energy generation from fossil fuels by a coal power plant with CO₂ recovery from exhaust gases, and pyrolysis of natural gas to hydrogen and carbon, completed by reverse water-gas shift for the conversion of CO₂ to CO, which will react with hydrogen in a Fischer-Tropsch synthesis for synthetic diesel. The carbon from the pyrolysis can replace other fossil carbon or can be sequestered. This technology offers significant CO₂ savings compared to the current state of technology and makes an environmentally friendly use of fossil fuels for electricity and fuel sectors possible.     

A review on production,storage of hydrogen and its utilization as an energy resource

Energy price is rising due to rapid depletion of fossil fuels. Development of renewable and non-polluting energy resources is necessary for reducing pollution level caused by those conventional fuels. Researchers have recognized hydrogen (H₂) as such an energy source. Hydrogen is a potential non-carbon based energy resource, which can replace fossil fuels. Hydrogen is considered as the alternative fuel as it could be generated from clean and green sources. Despite many advantages, storage of hydrogen is a serious problem. Due to high inflammability, adequate safety measures should be taken during the production, storage, and use of H₂ fuel. This review article elucidates production methods and storage of hydrogen. Besides this safety related to H₂ handling in refilling station, and automobiles has also been discussed. Study shows that safety program and awareness could be fruitful for increasing the acceptance of hydrogen as fuel.     

Komplementäre Dekarbonisierung der Erzeugung von Elektroenergie und Gewinnung synthetischer Kraftstoffe durch Erneuerbare Energien und fossile Energieträger

The concept of complementary decarbonisation of power generation from renewable energy sources and fossil fuels consists of their integration in one system. A technology network in the form of a CCU‐combined power plant is proposed for the energy generation from fossil fuels by a coal power plant with CO₂ recovery from the exhaust gases and a pyrolysis of natural gas to hydrogen and carbon as a basic technology. This technology network is completed by a reverse water‐gas shift reaction for the conversion of the CO₂ to CO, which will react with the hydrogen in a Fischer‐Tropsch synthesis for synthetic diesel. The recovered energy from the exothermic Fischer‐Tropsch synthesis meets the energy needs of CO₂ scrubbing. The carbon from the pyrolysis can replace other fossil carbon or can be sequestered.     

Design aspects of the cyclic hybrid adsorbent-membrane reactor (HAMR) system for hydrogen production

As a result of stricter environmental regulations worldwide, hydrogen is becoming an important clean energy source. For it to replace fossil fuels in mobile applications, however, it will require the creation of a production and delivery infrastructure equivalent to the one that currently exists for fossil fuels, which is an immense task. As an alternative and interim step towards the new hydrogen economy, various groups are currently studying steam reforming of methane (SRM) for the on-board generation of hydrogen, or for on site production, in order to alleviate the need for compressed or liquid hydrogen storage. One such technology is the hybrid adsorbent-membrane reactor (HAMR) system, which couples reaction and membrane separation steps with adsorption on the reactor and/or membrane permeate side. Our early studies involved the development of a mathematical model for the HAMR system applied to hydrogen production through SRM. Recently, experimental investigations with the water-gas shift reaction, using microporous membranes and hydrotalcite-type CO₂ adsorbents, were carried out in order to validate the HAMR design model. In this paper, we focus on the practical process design aspects of the HAMR hydrogen production process. A continuous, four-bed HAMR process scheme is proposed and investigated both experimentally and through modeling studies.     

天然气制氢工艺技术研究进展

在未来的能源结构中氢能将占有越来越重要的地位。天然气制氢作为最经济的化石资源制氢过程在未来的20a仍然将在氢能领域占据主要地位。综述了国内外天然气制氢的技术工艺研究现状,进展及发展方向。介绍了各工艺的优缺点,现存的问题及各工艺需解决的关键问题。     

Sustainable clean coal power generation within a European context - The view in 2006

The future use of coal will require strict environmental compliance with an increasing need to minimise emissions of CO₂, particularly from power plants. A pan-European approach is being established to ensure that EU industry can have available, by 2020, fossil fuel power plants that are either capable of capturing almost all their CO₂ emissions in an economically viable manner, or are designed to include CO₂ capture systems (“capture-ready”). The overall aim is to provide a significant impetus to research, development, demonstration and deployment activities such that coal and other fossil fuels can be used in a sustainable manner.     

Recent progress in hydrogenase and its biotechnological application for viable hydrogen technology

Despite increasing interest in hydrogen (H₂) as an alternative energy carrier, the current production of H₂ still depends on fossil fuels. Biotechnological hydrogen production can provide a more sustainable way to generate H₂. Hydrogenases are key enzymes involved in hydrogen metabolism of microorganisms with roles of H₂ oxidation or evolution. They have potential applications in H₂ production in vivo, in vitro and fuel cell. Important achievements have been made over the past decade in our understanding of hydrogenase and its biotechnological application as catalyst for H₂ production and fuel cell. This review summarizes recent progress in the study of hydrogenases, involving strategies for biosynthesis, maturation process, isolation of novel hydrogenases, heterologous expression system, structural feature of oxygen (O₂)-tolerant hydrogenases, and biotechnological applications for viable H₂ technology.     

Addressing the CO2 dilemma

Perspectives are offered for reducing the impact of huge amounts of CO₂ produced today from power generation and transportation vehicles. The origins of the dilemma between the world’s increasing use of hydrocarbons as an energy source and the cogeneration of CO₂ which results as a co-product are discussed. Hydrocarbons will provide much of the fuel needs for these major, global industries for the next 20 years and meet 60% of the world’s energy demand. With the growth of both power generation and transportation vehicles around the world, CO₂ levels will continue to increase in the atmosphere. Renewables such as wind, dams, and biomass will not be able to handle all the energy demand. Technology breakthroughs are needed to reduce the world’s dependence on fossil fuels, which will be aggravated by the drive to use more coal. Current approaches for removing CO₂ are discussed as well as near term and future options with particular focus on how catalysis can offer some solutions. In particular, solar photocatalysis based approaches offer a potentially viable energy solution.     

Comparing Molecular Mechanisms in Solar NH3 Production and Relations with CO2 Reduction

Molecular mechanisms for N₂ fixation (solar NH₃) and CO₂ conversion to C2+ products in enzymatic conversion (nitrogenase), electrocatalysis, metal complexes and plasma catalysis are analyzed and compared. It is evidenced that differently from what is present in thermal and plasma catalysis, the electrocatalytic path requires not only the direct coordination and hydrogenation of undissociated N₂ molecules, but it is necessary to realize features present in the nitrogenase mechanism. There is the need for (i) a multi-electron and -proton simultaneous transfer, not as sequential steps, (ii) forming bridging metal hydride species, (iii) generating intermediates stabilized by bridging multiple metal atoms and (iv) the capability of the same sites to be effective both in N₂ fixation and in CO_x reduction to C2+ products. Only iron oxide/hydroxide stabilized at defective sites of nanocarbons was found to have these features. This comparison of the molecular mechanisms in solar NH₃ production and CO₂ reduction is proposed to be a source of inspiration to develop the next generation electrocatalysts to address the challenging transition to future sustainable energy and chemistry beyond fossil fuels.     

Kinetics and Reactor Modeling of Hydrogen Production from Glycerol via Steam Reforming Process over Ni/CeO2 Catalysts

As a result of skyrocketing prices, environmental concerns and depletion associated with fossil fuels, renewable fuels are becoming attractive alternatives. In this respect, the demand for biodiesel has increased tremendously in recent years. Increased production of biodiesel has resulted in a glut of glycerol that has reduced the demand for this once valuable commodity. Consequently, finding alternative uses for glycerol is a timely proposition. One alternative is producing renewable hydrogen from this cheap commodity. Only a handful of studies have been conducted on producing hydrogen from glycerol. Previous studies have mainly focused on finding effective catalysts for glycerol steam reforming. This paper extends previous knowledge by presenting kinetic parameters in relation to glycerol steam reforming over Ni/CeO₂ and a reactor modeling. The study found that the activation energy and the reaction order for the glycerol steam reforming reaction over Ni/CeO₂ catalyst were 103.4 kJ/mol and 0.233, respectively.     

Möglichkeiten zur Wasserstoff-Erzeugung mit verminderter Kohlendioxid-Emission für zukünftige Energiesysteme

Hydrogen production possibilities for future energy systems with reduced carbon dioxide emission. All possible hydrogen production methods which are of technical importance or could become technically important have been systematically classified. The conventional processes based on fossil raw materials, as well as hydrogen production from biomass, are considered with a view to the separation of CO₂ or the minimization of CO₂ emission by using nuclear energy or solar energy, or by using electric energy generated from these primary energies. In addition, possibilities of hydrogen production with carbon separation are investigated. The nonfossil processes using thermal, electric or radiation energy are treated briefly, and water electrolysis is described in more detail. Finally, the hydrogenation of fossil raw materials is discussed, which would lead to mixed carbon-hydrogen energy systems.     

Selective catalytic reduction of NO x over Ag/Al2O3 using various bio-diesels as reducing agents

The effect of bio-diesel compounds (vegetable methyl and ethyl laurate and hexadecane) as reducing agents on the selective catalytic reduction of NO _x over a 2 wt.% Ag/Al₂O₃ was investigated. These components were found to have a two-fold effect on the SCR over Ag/Al₂O₃. First, the reduction activity below 400 °C was higher with bio-diesel than with n-octane, which is a representative compound for fossil fuels. This effect is attributed to the presence of the ester group in these molecules. However, the conversion above 400 °C decreased sharply and was considerable lower than with n-octane. The most interesting observation was found when the reduction efficiency of bio-diesel components was tested in the presence of hydrogen. The well known low temperature boosting effect of hydrogen was visible not only at lower temperatures, but also above 400 °C. Mechanistically the observation is extremely interesting and indicates that hydrogen effect cannot directly be connected to reduction of surface nitrates, which can be operative only at low temperature domain.     

Long-term scenarios for energy and environment: Energy from the desert with very large solar plants using liquid hydrogen and superconducting technologies

Among the long-term energy scenarios identified by major international organizations in order to drastically reduce fossil fuels consumption and to develop a sustainable energy system within the 21st century, the exploitation of desert areas for large-scale renewable energy production, must be seriously considered. Desert areas are characterized by large land availability, with high levels of solar radiation and wind. However, apart from generating costs (which should fall down in future), two main problems have to be faced. First, fluctuations of renewable power availability may lead to electric grid instability, reducing the quality of energy supply. Second, since deserts are typically far from energy-demanding areas, large power transport lines are needed. The system proposed in this paper resorts to the use of liquid hydrogen (LH₂) for energy storage, and to the combined transport of electric energy and LH₂ with a MgB₂ superconducting line. The system allows flexible delivering of energy in electric and chemical form, depending on end-users demands.     

Bioethanol production from biomass: carbohydrate vs syngas fermentation

Environmental problems associated with the use of fossil fuels as well as their expected scarcity in the near future requires a search for new alternative fuels produced from renewable sources. Bioethanol is a biofuel that can be obtained from biomass and waste as feedstocks through fermentation. Two major routes allow conversion of the feedstocks to fermentable substrates, i.e. the hydrolytic route and the thermochemical route. In the hydrolytic route, the feedstock undergoes a pretreatment stage first, aimed at facilitating the subsequent hydrolytic treatment. Chemical, physical or biological pretreatments can be applied. Lignocellulosic feedstocks are mainly composed of cellulose, hemicellulose and lignin. The pretreatment attacks the lignin and hemicellulose polymers and makes cellulose more accessible in the next, hydrolytic, stage. The hydrolytic treatment uses enzymes to convert the cellulose polymer to simple, fermentable, sugars, mainly glucose. Simple sugars obtained from hemicellulose and cellulose are then fermented by yeasts to bioethanol. In the thermochemical alternative, the feedstock is gasified, yielding syngas – a mixture largely composed of CO, CO₂ and H₂ – which can be fermented anaerobically, usually by clostridia, to ethanol or other products. In both cases, downstream processes are then applied to recover and purify the biofuel. The different stages involved in both alternatives are described, and both processes are compared in terms of their main characteristics and development stage. © 2015 Society of Chemical Industry     

Use of carbon dioxide as feedstock for chemicals and fuels: homogeneous and heterogeneous catalysis

CO₂ is considered to play a key role in an eventual climate change, due to its accumulation in the atmosphere. The control of its emission represents a challenging task that requires new ideas and new technologies. The use of perennial energy sources and renewable fuels instead of fossil fuels and the conversion of CO₂ into useful products are receiving increased attention. The utilization of CO₂ as a raw material for the synthesis of chemicals and fuels is an area in which scientists and industrialists are much involved: the implementation of such technology on a large scale would allow a change from a linear use of fossil carbon to its cyclic use, mimicking Nature. In this paper the use of CO₂ as building block is discussed. CO₂ can replace toxic species such as phosgene in low energy processes, or can be used as source of carbon for the synthesis of energy products. The reactions with dihydrogen, alcohols, epoxides, amines, olefins, dienes, and other unsaturated hydrocarbons are discussed, under various reaction conditions, using metal systems or enzymes as catalysts. The formation of products such as formic acid and its esters, formamides, methanol, dimethyl carbonate, alkylene carbonates, carbamic acid esters, lactones, carboxylic acids, and polycarbonates, is described . The factors that have limited so far the conversion of large volumes of CO₂ are analyzed and options for large‐scale CO₂ catalytic conversion into chemicals and fuels are discussed. Both homogeneous and heterogeneous catalysts are considered and the pros and cons of their use highlighted. © 2013 Society of Chemical Industry     

Biohydrogen Production: Strategies to Improve Process Efficiency through Microbial Routes

The current fossil fuel-based generation of energy has led to large-scale industrial development. However, the reliance on fossil fuels leads to the significant depletion of natural resources of buried combustible geologic deposits and to negative effects on the global climate with emissions of greenhouse gases. Accordingly, enormous efforts are directed to transition from fossil fuels to nonpolluting and renewable energy sources. One potential alternative is biohydrogen (H₂), a clean energy carrier with high-energy yields; upon the combustion of H₂, H₂O is the only major by-product. In recent decades, the attractive and renewable characteristics of H₂ led us to develop a variety of biological routes for the production of H₂. Based on the mode of H₂ generation, the biological routes for H₂ production are categorized into four groups: photobiological fermentation, anaerobic fermentation, enzymatic and microbial electrolysis, and a combination of these processes. Thus, this review primarily focuses on the evaluation of the biological routes for the production of H₂. In particular, we assess the efficiency and feasibility of these bioprocesses with respect to the factors that affect operations, and we delineate the limitations. Additionally, alternative options such as bioaugmentation, multiple process integration, and microbial electrolysis to improve process efficiency are discussed to address industrial-level applications.     

Using Fourier transform infrared spectroscopy to determine toxic gases in fires with lithium‐ion batteries

Batteries, in particular lithium‐ion (Li‐ion) batteries, are seen as an alternative to fossil fuels in the automotive sector. Li‐ion batteries, however, have some safety issues including possible emissions of toxic fluorine‐containing compounds during fire and other abuse situations. This paper demonstrates the possibilities to use the Fourier transform infrared technique to assess some of the most important compounds, including hydrogen fluoride and the far less often measured POF₃ and PF₅. The study is conducted in the cone calorimeter with different solvents used in Li‐ion batteries. The measurements show that, in addition to hydrogen fluoride, with a known high toxicity, POF₃ is emitted and can be quantified using Fourier transform infrared. Copyright © 2016 John Wiley & Sons, Ltd.     

Microbial photosynthesis in the harnessing of solar energy

The shortage of fossil fuels restricts the world supply of reduced carbon compounds and energy sources. Biotechnology offers the most feasible route to renewing the supplies of reduced carbon compounds. This involves recycling of CO₂ through photosynthesis. Conventional agriculture has little or no potential for supplying biomass and its derivatives on sufficient scale to offer an alternative to the fossil fuels. The agricultural wastes, on the whole, are intractable to conversion into useful carbon and energy sources and in any case are not available in amounts to provide a significant alternative to the fossil fuels. In contrast, microbial photosynthesis, optimised in photobioreactors, has vast potential to provide organic matter on a scale to match the consumption of fossil fuels. The quantitative study of microbial photosynthesis as a biotechnological route to biomass has been neglected. As a result there is a chaos of conflicting data on fundamental parameters, for example, the photosynthetic efficiency of biomass production. New photosynthetic biotechnology with fully controlled continuous-culture systems is providing unequivocal values for the parameters. For the scale-up of microbial photosynthesis a tubular-loop reactor is proposed.     

Hydrocracking of Fischer‐Tropsch Wax with Tungstovanadophosphoric Salts as Catalysts

The synthesis of liquid hydrocarbons from CO₂ and H₂, based on renewable energy and H₂O electrolysis, respectively, in a power‐to‐liquid process is a promising concept for the substitution of fossil fuels. Such a process is based on Fischer‐Tropsch synthesis followed by hydrocracking to convert waxy products into transportation fuels such as gasoline and diesel oil. Heteropolyacid cesium salts as catalysts show appropriate activity for hydrocracking, and the selectivity in cracking model hydrocarbons and Fischer‐Tropsch wax can be tuned by the vanadium content of the catalyst. Thermal stability and surface properties were investigated, and the catalysts are compared with a classical H‐Y‐type zeolite used for hydrocracking.     

Hydrogen production from biomass: The behavior of impurities over a CO shift unit and a biodiesel scrubber used as a gas treatment stage

Most of the hydrogen produced is derived from fossil fuels. Bioenergy2020+ and TU Wien have been working on hydrogen production from biomass since 2009. A pilot plant for hydrogen production from lignocellulosic feedstock was installed onsite using a fluidized bed biomass gasifier in Güssing, Austria. In this work, the behavior of impurities over the gas conditioning stage was investigated. Stable CO conversion and hydration of sulfur components could be observed. Ammonia, benzene, toluene, xylene (BTX) and sulfur reduction could be measured after the biodiesel scrubber. The results show the possibility of using a commercial Fe/Cr-based CO shift catalyst in impurity-rich gas applications. In addition to hydrogen production, the gas treatment setup seems to also be a promising method for adjusting the H₂ to CO ratio for synthesis gas applications.