Influence of direct reduced iron on the energy balance of the electric arc furnace in steel industry

A model of the EAF energy efficiency was developed based on a closed mass and energy balance of the EAF melting process. This model was applied to industrial EAFs in steel industry charged with scrap or with mixes of scrap and DRI. Complex mass and energy conversion in the EAF was simplified with the introduction of mass and energy conversion efficiencies for the conversion of oxygen and the energy conversion of electrical energy in the electric arcs, chemical energy from the oxidation reactions in the melt and energy from the combustion of burner gas. It turned out that close agreement with observed process parameters from 16 EAFs is obtained by slight variations of the efficiency values. Especially the sensitivity of the steel temperature from the energy conversion efficiency of the electric arc energy indicates the importance of efficient foaming slag operation in EAF steel making. Characteristics and process parameters of DRI charged EAFs are discussed. Model results for a series of case studies illustrate the correlations between DRI chemical composition, DRI portion, oxygen consumption, etc. with electrical energy demand in order to indentify cost-effective EAF process conditions.     

Energy efficiency and the influence of gas burners to the energy related carbon dioxide emissions of electric arc furnaces in steel industry

Determining the complete energy balance of an electric arc furnace (EAF) provides an appropriate method to examine energy efficiency and identify energy saving potentials. However, the EAF energy balance is complex due to the combined input of electrical energy and chemical energy resulting from natural gas (NG) combustion and oxidation reactions in the steel melt. In addition, furnace off-gas measurements and slag analysis are necessary to reliably determine energy sinks. In this paper 70 energy balances and energy efficiencies from multiple EAFs are presented, including data calculated from plant measurements and compiled from the literature. Potential errors that can be incorporated in these calculations are also highlighted. The total energy requirement of these modern EAFs analysed ranged from 510 to 880 kWh/t, with energy efficiency values (η = ΔH_Steel/E_Total) of between 40% and 75%. Furthermore, the focus was placed on the total energy related CO₂ emissions of EAF processes comprising NG combustion and electrical energy input. By assessing multiple EAF energy balances, a significant correlation between the total energy requirement and energy related specific CO₂ emissions was not evident. Whilst the specific consumption of NG in the EAF only had a minor impact on the EAF energy efficiency, it decreased the specific electrical energy requirement and increased EAF productivity where transformer power was restricted. The analysis also demonstrated that complementing and substituting electrical energy with NG was beneficial in reducing the total energy related CO₂ emissions when a certain level of substitution efficiency was achieved. Therefore, the appropriate use of NG burners in modern EAFs can result in an increased EAF energy intensity, whilst the total energy related CO₂ emissions remain constant or are even decreased.     

Effect of pore characteristics on hydrogen reduction kinetics based on a novel analysis approach combined model-fitting and iso-conversion

Carbon reductant used in metallurgy industry is a considerable source of carbon dioxide emissions. Growing concerns over greenhouse effect have urgently prompted research in the application of hydrogen energy as an alternative. However, some basic kinetic problems in the hydrogen reduction process have not been clarified and resolved yet, such as the activation energy fluctuations caused by neglect of pore characteristics, along with the overly subjective division of the whole reaction process to analyze rate limiting mechanisms. In this study, a novel approach for acquiring instantaneous activation energy is proposed that is able to identify the activation energy at every reaction moment and thereby provide a quantitative basis for kinetics segmentation and rate-limiting mechanism determination. Moreover, due to the space requirements, the activation energy for the reaction stage controlled by nucleation and nuclei growth has a strong correlation with specific surface area. Whereas the restriction mechanisms of chemical reaction and diffusion are closely related to the average pore size. These results reveal that the different pore characteristics and changes in value have a direct influence on the corresponding rate limiting mechanisms and restriction degrees.     

A short overview on purification and conditioning of syngas produced by biomass gasification: Catalytic strategies,process intensification and new concepts

Application of the process intensification concept to biomass gasification is relatively recent, but is arousing growing interest by providing true opportunities for developing cost-effective high quality syngas, particularly for small to medium-scale installations, adapted to the economic context of most regions in the world. In this highly swarming context towards process intensification, this article provides an overview of the different strategies which are reported in the literature to perform syngas or H₂ purification and conditioning into the gasifier. A promising avenue towards process intensification consists in integrating several functionalities into suitable fluidized bed gasifiers, such as catalytic tar cracking/reforming, CO₂ elimination, H₂ separation and the elimination of particles and other contaminants. The development of new catalytic integrated gasification concepts is also proposed to achieve high conversion performances while pursuing significant process intensification. This strategy is illustrated by relevant examples such as the design of short contact time partial oxidation catalytic reactors, the implementation of specific reaction media such as supercritical water or molten metal, or the realisation of a close contact between solid catalysts and lignocellulosic biomass. Most of these different technologies are not mature yet and research effort has to be performed for optimizing each of these approaches, calling for a multidisciplinary and multi-scale approach integrating catalysis, chemistry, reaction and process engineering. The design of new advanced gasification reactor concept still has to be pursued in order to achieve the challenging one-step production of a high quality syngas from biomass gasification. The implementation of such innovative biomass gasification breakthrough concepts could be one of the most promising ways of process intensification resulting in a significant cut down of the production costs of synthesis gas and H₂ derived from biomass.     

Optimization of an energy district for fuel cell electric vehicles: Cost scenarios of a real case study on a waste and recycling fleet

This paper analyses the planning and operation of an energy district that aims to integrate a hydrogen supply chain for feeding vehicles based on fuel cell technology. A model of an energy district and an optimization algorithm based on the economic parameters are presented and validated leveraging an existing energy district, simulating several scenarios depending on different economic conditions and technical parameters. The model of the energy district evaluates energy balances, distinguishing hydrogen and electrical energy flows; the districts can include an FCEV fleet, electrical loads, energy generators, storage system and an electrolyser for producing hydrogen from the green energy surplus produced in the district as well as drawing energy from the power distribution network. The algorithm, based on MILP, is used for optimizing the flows in the district; indeed, it evaluates all the technical and economic constraints at a certain timestamp and provides optimal scheduling of the energy units. Model and algorithm have been used to evaluate different scenarios that were identified by varying the economic parameters (i.e., prices of electrical energy and hydrogen) as well as district design (i.e., upgrading sizes of the generators and electrolysers). Energy district parameters have been identified exploiting real data collected in an existing district located in Terni (Italy) owned by the local multi-utility ASM Terni S.p.A. It already includes a fleet for waste management, PV plants, office buildings and warehouses. Through parameters combination, 1125 OPEX and 729 CAPEX simulated scenarios have been evaluated and reported; each scenario assesses the daily variation of variables' economic trends covering the timeframe from 2030 to 2050. Results of simulations highlight the most convenient economic contexts as well as the envisioned amount of expenditures for adopting FCEV in the presented district or similar ones. For the case study, the forecasted cost of the hydrogen district, including FCEVs, is fully comparable to current costs, resulting in some cases even cheaper.     

A critical review on the current technologies for the generation,storage, and transportation of hydrogen

Hydrogen production, storage, and transportation are the key issues to be addressed to realize a so-called clean and sustainable hydrogen economy. Various production methods, storage methods, and hydrogen transportations have been listed in the literature, along with their limitations. Therefore, to summarize the state of the art of these proposed technologies, a detailed discussion on hydrogen production, storage, and transportation is presented in this review. Also, to discuss the recent advancements of these methods including, hydrogen production, storage, and transportation on their kinetics, cyclic behavior, toxicity, pressure, thermal response, and cost-effectiveness. Moreover, new techniques such as ball milling, ultrasonic irradiation, ultrasonication, alloying, additives, cold rolling, alloying, and plasma metal reaction have been highlighted to address those drawbacks.Furthermore, the development of modern hydrogen infrastructure (reliability, safety, and low cost) is needed to scale up hydrogen delivery. This review summarizes promising techniques to enhance kinetic hydrogen production, storage, and transportation. Nevertheless, the search for the materials is still far from meeting the aimed target for production, storage, and transportation application. Therefore, more investigations are needed to identify promising areas for future H₂ production, storage, and transportation developments.     

The introduction of electric vehicles in the private fleet: Potential impact on the electric supply system and on the environment. A case study for the Province of Milan,Italy

The study analyses the possible impact of the electric vehicles’ recharging activities on the electric supply system for the Province of Milan and on the global environment with a 2030 time horizon. In particular, the impact on the electric grid is seen both in terms of total electric energy consumption and in power requested to the grid. Because of the long recharging time required by the car batteries, the probability to have thousands of cars contemporary plugged-in at a given time is not negligible. On the other hand, the impact on the environment is seen in terms of CO₂ emissions reduction. Even if, at the moment, the Italian electric energy mix is mainly generated by means of thermal power stations making use of not renewable fossil fuels, the efficiency of these plants is much higher than the efficiency of a vehicle’s engine.     

A generic framework for recycling of battery module for electric vehicle by combining the mechanical and chemical procedures

By year 2020, due to enormous growth of production of electric vehicles, it is estimated that approximately 250 000 tons of battery must be disposed or recycled. Till date, the technology to recycle this much amount of batteries in a single year does not exist. Nor, do the methods for recycling are standardized and regulated because of differences in configurations of battery packs. This article conducts a systematic review on research of recycling methods for battery pack used in various stages such as from the dismantling/ disassembly of the battery pack, the detection of the residual energy of the battery, and the recycling/recovery of materials from the battery. The review summarizes basically the 2 main aspects of recycling of battery pack: the mechanical procedure and the chemical recycling. The work describes the existing recycling technology in these 2 aspects and identifies the important research problems in the process of recycling of battery pack such as (1) complexity of dismantling process of battery pack; (2) diversity of connectors used in battery pack; (3) safety of dismantling of battery pack; (4) instability of chemical materials in battery; (5) the chaos of the recycling market; and (6) emerging battery dismantling technologies. One important direction suggested is the automation of battery pack disassembly, which is a main factor towards formulation of generic framework for recycling of battery pack in an efficient manner. Based on these gaps, the present work also proposes a framework for the recycling of battery pack by combining the semi‐automation mechanical procedure of battery pack and enhanced chemical recycling of battery for recovery of vital materials. Future work for authors is to work on establishing and validation of proposed framework. The advantages of the proposed framework are compared with that obtained from the existing framework. The proposed framework when used shall result in efficient and effective recycling of battery module and promote greener environment.     

In situ thermal and acoustic performance and environmental impact of the introduction of a shape-stabilized PCM layer for building applications

Energy consumption in buildings accounts for up to 34% of total energy demand in developed countries. Thermal energy storage (TES) through phase change materials (PCM) is considered as a promising solution for this energetic problem in buildings. The material used in this paper is an own-developed shape stabilized PCM with a polymeric matrix and 12% paraffin PCM, and it includes a waste from the recycling steel process known as electrical arc furnace dust (EAFD), which provides acoustic insulation performance capability. This dense sheet material was installed and experimentally tested. Ambient temperature, humidity, and wall temperatures were measured and the thermal behaviour and acoustic properties were registered. Finally, because of the nature of the waste used, a leaching test was also carried out. The thermal profiles show that the inclusion of PCM decreases the indoor ambient temperature up to 3 °C; the acoustic measurements performed in situ demonstrate that the new dense sheet material is able to acoustically insulate up to 4 dB more than the reference cubicle; and the leaching test results show that the material developed incorporating PCM and EAFD must be considered a non-hazardous material.     

A review on the economic dispatch and risk management of the large-scale plug-in electric vehicles (PHEVs)-penetrated power systems

Nowadays, the deterioration of ecological environment and the ever rising gas price make green transportation our relentless pursuit. Energy-saving, low-emission even zero-emission electric vehicles (EVs) have been considered as one solution to the problem. With the rapid development of plug-in electric vehicle (PHEV) and forceful support and incentives from the government, PHEV and its supporting facilities are being gradually popularized. When randomly being connected to the power grid in large scale, PHEVs will bring new challenges to power grid in operation and management. This paper presents an overall review on historical research on power system integrated with electric vehicles and especially focuses on economic dispatch of PHEV in the electricity market. The paper also discusses the joint scheduling problem considering other renewable energy resources and risk management of PHEV-penetrated power systems.     

A proposal for a novel multi-functional energy system for the production of hydrogen and power

A novel multi-functional energy system with two kinds of fuels (coal and natural gas) and two kinds of products (hydrogen and electricity) is proposed. The proposed system takes advantage of the complementary properties of coal and natural gas by integrating natural gas/steam reforming together with the combustion of coal. Coal is indirectly gasified by combustion so that the need for an air separation unit is eliminated. At the same time, a part of superior natural gas fuel, which is burnt in the reformer, is replaced with inferior coal fuel. Hence, energy utilization is improved effectively. In addition, the novel system is investigated by means of the EUD (energy-utilization diagram) methodology and then compared with the reference system, which is composed of four conventional systems. As a result, the thermal efficiency of the new system may be expected to reach 75%. Moreover, a comparison with the reference system shows that the proposed system provides a 10% energy savings. The promising result obtained here provides an attractive option for an effective utilization of coal and natural gas.     

Simulation and experimental study of the NOx reduction by unburned H2 in TWC for a hydrogen engine

The unburned H₂ can be used to reduce NO emission in conventional TWC (three-way catalyst) for a hydrogen internal combustion engine when it works at equivalence ratio marginally higher than the stoichiometric ratio. To explore the effects and feasibility of this reaction, a Perfectly Stirred Reactor simulation model of TWC has been built with simplified mechanisms. Experiments on a 2.3 L turbocharged hydrogen engine are used to verify the conclusion. It shows that rising initial temperature accelerates the reduction of NO and the maximum reaction rate occurs at 400 °C temperature. The conversion efficiency of NO remains approximately 0 when temperatures below 300 °C. The efficiency reaches a peak value of approximately 98% with 400 °C and declines gradually. The unburned H₂ to NO mixing ratio greater than 1.5 in TWC guarantees 100% NO conversion efficiency. The experiments indicate that the NOx concentration decreases from 2056 ppm to 41 ppm at the stoichiometric ratio after the treatment of TWC and NOx reaches 0 ppm with a rich ratio. Results also demonstrate that the suitable reaction temperatures for TWC locate in the range of 400 °C–500 °C. Therefore, if the temperature and the mixing ratio are appropriate, it can achieve zero emissions with NOx reduction by unburned H₂ in conventional TWC for a hydrogen engine.     

Hexadecacarbonylhexarhodium as a novel electrocatalyst for oxygen reduction and hydrogen oxidation in the presence of fuel cell contaminants

The electrocatalytic activity for oxygen reduction and hydrogen oxidation of a discrete metal carbonyl cluster with a well defined molecular and crystal structure, Rh₆(CO)₁₆, is reported. The exchange current density of this compound for oxygen reduction is one order of magnitude higher than that of platinum, and its resistance degree to PEM fuel cell contaminants such as methanol and CO is as high as 2 mol L⁻¹ and 0.5%, respectively. These properties make the metal complex a potential alternative for use as electrode in polymer electrolyte membrane fuel cells.     

Sonolytic and ultrasound-assisted techniques for hydrogen production: A review based on the role of ultrasound

Among the cleanest combustibles, hydrogen represents the energy carrier of the near future, thereby, techniques for hydrogen synthesis have been the subject of several research studies. The integration of ultrasound to several techniques as a promising combination has known in recent years an increasing interest owing to the physical and chemical roles of sonication and the eventual created synergetic effects. The present review aims to inspect the various techniques using ultrasound as a direct or auxiliary pathway for the generation of hydrogen. Experimental and numerical studies related to the use of power ultrasound as an isolated technique are reviewed in terms of approaches, configurations, and qualitative and quantitative observations. The combination of power ultrasound with other techniques such as electrolysis, catalysis, and photolysis, is then examined and discussed, particularly in regards to the role of ultrasound in the “ultrasound-assisted” hydrogen production, but also the expected magnitude of the kinetics enhancement and energy-saving when integrating ultrasound. It was reported in several works that the use of ultrasound for hydrogen generation may lead to an increase in the rate of produced hydrogen achieving 25%, and an improvement in energy efficiency in the range of 5–18%, while some other studies reported limited enhancement in the order of 1%. Overall, ultrasound irradiation has the advantages of enhancing mass transport, bubbles detachment from catalysts and electrodes surfaces, efficient degassing, and cleaning effect. The technological state of the art and the engineering designs are also reported with the perspective of adopting the sono-production of hydrogen at the industrial scale.     

A novel Pt loading method for WO3 gasochromic film and the morphology control of the film by two-step solvothermal synthesis

Controlling the morphology and structure of nanofilms is an important way to improve their properties. Herein, we report a two-step solvothermal method for preparing nanostructured WO₃ film composed of single crystal WO₃ nanowires, by which much more flexible morphology control than the traditional one-step method is realized. The film prepared by this method combines the morphological characteristics of two one-step films by changing the solution composition during each step. To obtain gasochromic film, a novel method named “charging-immersing” method is used to load catalyst Pt on the WO₃ film. In this novel method, WO₃ film is first charged and then immersed in the K₂PtCl₄ solution, reducing Pt nanoparticles from solution. The variation of transmittance, coloring rate (in 4% H₂/Ar) and bleaching rate (in the air) of the film synthesized by two-step method at the wavelength of 1000 nm are 76.2%, 4.57%/s and 1.29%/s, respectively. While the properties of two one step films are 69.2% and 40.9%, 2.73%/s and 1.72%/s, 0.063%/s and 1.42%/s, respectively. The combination of morphology leads to the combination of performance advantages because new morphology (thin WO₃ nanowires and relatively large Pt nanoparticles) is more conducive to the dissociation of H₂ and diffusion of H and O atoms during gasochromism. This study offers a novel strategy for morphology control of nanostructured WO₃ film prepared by solvothermal method and loading catalyst Pt on it.     

A comparison of high-speed flywheels, batteries, and ultracapacitors on the bases of cost and fuel economy as the energy storage system in a fuel cell based hybrid electric vehicle

Fuel cells aboard hybrid electric vehicles (HEVs) are often hybridized with an energy storage system (ESS). Batteries and ultracapacitors are the most common technologies used in ESSs aboard HEVs. High-speed flywheels are an emerging technology with traits that have the potential to make them competitive with more established battery and ultracapacitor technologies in certain vehicular applications. This study compares high-speed flywheels, ultracapacitors, and batteries functioning as the ESS in a fuel cell based HEV on the bases of cost and fuel economy. In this study, computer models were built to simulate the powertrain of a fuel cell based HEV where high-speed flywheels, batteries, and ultracapacitors of a range of sizes were used as the ESS. A simulated vehicle with a powertrain using each of these technologies was run over two different drive cycles in order to see how the different ESSs performed under different driving patterns. The results showed that when cost and fuel economy were both considered, high-speed flywheels were competitive with batteries and ultracapacitors.     

A comparative study on a novel combination of spherical and membrane tubular reactors of the catalytic naphtha reforming process

Refineries have been looking for ways of improving the performance of the reformer by enhancing the octane number of the product via increasing the aromatics content. To reach this goal, more improved configurations should be investigated. The aromatics production rate could be enhanced by shifting the reactions to the production side by using hydrogen perm-selective membranes. In the present study, we have investigated theoretically the best combination of membrane tubular reactors and spherical radial-flow reactors for the conventional naphtha reforming unit consist of three fixed-bed reactors. Hydrogen permeation through the membrane shifts the reaction to the product side (aromatics and hydrogen) according to the thermodynamic equilibrium. Spherical reactors reduce the pressure drop in the catalytic naphtha reforming units and consequently increase the efficiency. The results show higher aromatics production in the new configurations compared with the membrane tubular and conventional reactors despite using lower membrane surface area.     

A preliminary study of a novel catalyst Al2O3·Na2O·xH2O/NaOH/Al(OH)3 for production of hydrogen and hydrogen-rich gas by steam gasification from cellulose

The new catalyst, Al₂O₃·Na₂O·xH₂O/NaOH/Al(OH)₃, was made by means of hydrolyzation and hydration of sodium aluminum oxide (Al₂O₃·Na₂O). Hydrogen and hydrogen-rich gas were produced through the reaction of cellulose with the catalyst and steam. In order to avoid production of tar, the gasification temperature is controlled at ≤673 K. The temperature of producing hydrogen is controlled at about 473–623 K. The conversion degree of hydrogen from cellulose at about 473–673 K could come up to 59.63%. The production of hydrogen-rich gas was set at about 673 K. The gasification residue could be used as material for combustion. Al₂O₃·Na₂O could be regenerated from the byproducts Al₂O₃ and Na₂CO₃ produced in the combustion process. The catalyst could be re-prepared from the regenerative Al₂O₃·Na₂O.     

A quasi-Delphi study on technological barriers to the uptake of hydrogen as a fuel for transport applications—Production, storage and fuel cell drivetrain considerations

The introduction of hydrogen in transport, particularly using fuel cell vehicles, faces a number of technical and non-technical hurdles. However, their relative importance is unclear, as are the levels of concern accorded them within the expert community conducting research and development within this area. To understand what issues are considered by experts working in the field to have significant potential to slow down or prevent the introduction of hydrogen technology in transport, a study was undertaken, primarily during 2007. Three key technology areas within hydrogen transport were selected - hydrogen storage, fuel cell drivetrains, and small-scale hydrogen production - and interviews with selected experts conducted. Forty-nine experts from 34 organisations within the fuel cell, automotive, industrial gas and other related industries participated, in addition to some key academic and government figures. The survey was conducted in China, Japan, North America and Europe, and analysed using conventional mathematical techniques to provide weighted and averaged rankings of issues viewed as important by the experts. It became clear both from the interviews and the subsequent analysis that while a primary concern in China was fundamental technical performance, in the other regions cost and policy were rated more highly. Although a few individual experts identified possible technical showstoppers, the overall message was that pre-commercial hydrogen fuel cell vehicles could realistically be on the road in tens of thousands within 5 years, and that full commercialisation could take place within 10-15 years, without the need for radical technical breakthroughs. Perhaps surprisingly, the performance of hydrogen storage technologies was not viewed as a showstopper, though cost was seen as a significant challenge. Overall, however, coherent policy development was more frequently identified as a major issue to address.     

Effect of hydraulic retention time on hydrogen production from sewage sludge and wine vinasse in a thermophilic acidogenic CSTR: A promising approach for hydrogen production within the biorefinery concept

The aim of the present study was to investigate the effect of hydraulic retention time (HRT) on hydrogen production from sewage sludge:wine vinasse (50:50 v/v) in a laboratory-scale continuously stirred tank reactor under thermophilic conditions. For this purpose, nine HRT ranging from 5.0 to 0.25 days were tested. Maximum hydrogen production and specific hydrogen production of 0.90 LH₂/L_reactor/d and 35.19 mLH₂/g VS_added were respectively obtained at a HRT of 0.5 days. Eubacteria was the main group (65–79%) for all the tested HRT. Decreasing HRT was inversely correlated with hydrogen production and microbial population. HRT of 0.5 days is optimal for the growth of the acidogenic population and therefore this population is more active and maximum microbial activity (15.28·10^?10 LH₂/cells) was also achieved at this HRT.