• Energy Research

End-of-life tires are an increasingly important environmental burden. Since retreading is only partly possible, safe and economic methods of disposal need to be developed. Pyrolysis of ELTs, and subsequent upgrading/application of the produced energy carriers, is considered a valuable treatment method. In order to design the process, numerous operation units have to be taken into account. Char, vapour and gas are formed in the reactor. The char is purified from ZnO with a leaching process. The pyrolysis vapour is separated into a condensable fraction (oil) and a non-condensable fraction (gas) thanks to a cross-flow condenser with air as indirect cooling medium. The remaining gas is compressed to 6 bar: a part of it is continuously converted in electricity for process use, while another part is stored for power generation at peak demand time. A flowsheet of the process is established and environmental and assessment of investments and production are discussed. For the pyrolytic treatment of 3 ton/hr of ELTs, the required heat for the reactor is 271 kW at 380 °C, provided by electrical heating elements. A reactor volume is determined for a residence time of about 6 h. For the cross-flow condenser, indirectly air-cooled, a heat-transfer area of about 13.2 m2 is required. The compression of the gas the pressurized pyrolytic gas storage tank depends upon the excess pyrolytic gas produced during operation. The char cooler requires a heat-transfer area of 10.2 m2, when indirectly cooled by water. Operating parameters of the leaching and subsequent recovery of Zn2+ complete the design. The product added-value and the large-scale capacity make the process economically viable, although the ROI is between 2 and 3 years.

Abstract Very few industrial processes only produce the target product, but other materials not desired by the manufacturer are also obtained. These unwanted products constitute the residues of the processes and their discharge contributes to the overall environmental impact. The concept of preventing pollution is gaining increased importance, and certain industries that are particularly similar in nature, could benefit from PPP (Pollution Prevention Program) cross-fertilization. Implementing PPP sets important targets and benefits. A number of codes of good practice lead to PPP, both from a management and technical viewpoints. The fast development of technology and pollution standards implies important challenges for environmental engineers, environmental research and development. Although there is no general route to success, there are however a number of pollution prevention and waste reduction schemes that apply. These alternatives and procedures are illustrated in the paper. It is clear that environment-caring companies will be more readily accepted by their human environment. It is also evident that the engineer of the 21st century faces new and complex environmental challenges. Research remains the backbone of successful development.

Abstract Presently, hydrogen is for ∼50% produced by steam reforming of natural gas – a process leading to significant emissions of greenhouse gas (GHG). About 30% is produced from oil/naphtha reforming and from refinery/chemical industry off-gases. The remaining capacity is covered for 18% from coal gasification, 3.9% from water electrolysis and 0.1% from other sources. In the foreseen future hydrogen economy, green hydrogen production methods will need to supply hydrogen to be used directly as fuel or to generate synthetic fuels, to produce ammonia and other fertilizers (viz. urea), to upgrade heavy oils (like oil sands), and to produce other chemicals. There are several ways to produce H2, each with limitations and potential, such as steam reforming, electrolysis, thermal and thermo-chemical water splitting, dark and photonic fermentation; gasification, and catalytic decomposition of methanol. The paper reviews the fundamentals and potential of these alternative process routes. Both thermo-chemical water splitting and fermentation are marked as having a long term but high “green” potential.

Spent grains from microbreweries are mostly formed by malting barley (or malt) and are suitable for a further valorization process. Transforming spent grains from waste to raw materials, for instance, in the production of nontraditional flour, requires a previous drying process. A natural convection solar dryer (NCSD) was evaluated as an alternative to a conventional electric convective dryer (CECD) for the dehydration process of local microbrewers’ spent grains. Two types of brewer’s spent grains (BSG; Golden ale and Red ale) were dried with both systems, and sustainability indices, specific energy consumption (eC), and CO2 emissions were calculated and used to assess the environmental advantages and disadvantages of the NCSD. Then, suitable models (empirical, neural networks, and computational fluid dynamics) were used to simulate both types of drying processes under different conditions. The drying times were 30–85 min (depending on the drying temperature, 363.15 K and 333.15 K) and 345–430 min (depending on the starting daytime hour at which the drying process began) for the CECD and the NCSD, respectively. However, eC and CO2 emissions for the CECD were 1.68–1.88 · 10−3 (kW h)/kg and 294.80–410.73 kg/(kW h) for the different drying temperatures. Using the NCSD, both indicators were null, considering this aspect as an environmental benefit.

Sulphur dioxide (SO2) is mostly emitted from coal-fueled power plants, from waste incineration, from sulphuric acid manufacturing, from clay brick plants and from treating nonferrous metals. The emission of SO2 needs to be abated. Both wet scrubbing (absorption) and dry or semi-dry (reaction) systems are used. In the dry process, both bubbling and circulating fluidized beds (BFB, CFB) can be used as contactor. Experimental results demonstrate a SO2-removal efficiency in excess of 94% in a CFB application. A general model of the heterogeneous reaction is proposed, combining the external diffusion of SO2 across the gas film, the internal diffusion of SO2 in the porous particles and the reaction as such (irreversible, 1st order). For the reaction of SO2 with a fine particulate reactant, the reaction rate constant and the relevant contact time are the dominant parameters. Application of the model equations reveals that the circulating fluidized bed is the most appropriate technique, where the high solid to gas ratio guarantees a high conversion in a short reaction time. For the CFB operation, the required gas contact time in a CFB at given superficial gas velocities and solids circulation rates will determine the SO2 removal rate.

Abstract Electricity from concentrated solar power (CSP) plants, gains an increasing interest and importance. To fully match the supply-demand principle, CSP processes include a thermal energy storage and back-up fuel supply. Novel CSP concepts are needed with specific targets of increased efficiency and reliability, and of reduced CAPEX and OPEX. The use of particle suspensions offers significant advantages since applicable in all sub-sections of the complete CSP as heat carrier from the receiver, to the heat storage, and ultimately to the power block. The use of particles in the steam generation (power block) is a common fluidized bed boiler technology. This paper will present the entire particle-based concept, while also discussing the potential to use biomass-based energy carriers as back-up heat supply. Process data and expected effects on the process economy of the system will be discussed.

Abstract Hydrogen is a common reactant in the petro-chemical industry and moreover recognized as a potential fuel within the next 20 years. The production of hydrogen from biomass and carbohydrate feedstock, though undoubtedly desirable and favored, is still at the level of laboratory or pilot scale. The present work reviews the current researched pathways. Different types of carbohydrates, and waste biomass are identified as feedstock for the fermentative bio-hydrogen production. Although all techniques suffer from drawbacks of a low H2 yield and the production of a liquid waste stream rich in VFAs that needs further treatment, the technical advances foster the commercial utilization. Bacterial strains capable of high hydrogen yield are assessed, together with advanced techniques of co-culture fermentation and metabolic engineering. Residual VFAs can be converted. The review provides an insight on how fermentation can be conducted for a wide spectrum of feedstock and how fermentation effluent can be valorized by integrating fermentation with other systems, leading to an improved industrial potential of the technique. To boost the fermentation potential, additional research should firstly target its demonstration on pilot or industrial scale to prove the process efficiency, production costs and method reliability. It should secondly focus on optimizing the micro-organism functionality, and should finally develop and demonstrate a viable valorization of the residual VFA-rich waste streams.