Industrial wastewater treatment wastes used as oxygen carriers in energy generation processes

The paper contains the results of a study on a promising combustion technology known as chemical looping combustion (CLC). The main advantage of CLC is the production of a highly concentrated CO2 stream without any energy penalty for its separation, together with NOx emissions reduction. The objective of this work was to examine novel oxygen carrier (OC) materials for their practical applications with gaseous fuel/air. We report a simple, economical and environmentally friendly method for the large-scale synthesis of OCs from wastes. The reactivity tests for OCs made from wastewater from a coking plant were performed in a thermogravimetric analyser. For selected temperatures, reduction–oxidation cycles were performed. The effect of temperature on the reaction rates, the effect of waste treatment and the oxygen transport capacity were determined. The waste material demonstrated good thermal stability and maintained its redox behaviour over cycling. ICP-OES and XRD data revealed these materials that contained beneficial amounts of Fe species and silicon oxide, which improved stability. The study showed that these waste materials are excellent examples of raw materials that can enable a decrease in OC production costs with the additional benefit of the practical management of post-wastewater sediments from coke oven wastewater plants

Modelling, simulation, and optimization of hot stove operation

This thesis focuses on modelling and simulation of the operation of a system of three hot stoves used for preheating of the combustion air in the ironmaking blast furnace. A dynamic mathematical model of the stove set was developed for the purpose. Several sample cases were investigated to examine how the hot stoves characteristics, the bypass configuration, and the system operation variables influence the behavior as well as the performance of the entire hot-stove system. In addition, a brief optimization problem has been also studied with the goal to achieve optimum blast temperature. The model developed in this work considers the heat transfer phenomena throughout the hot stove operation sequence as well as the interconnection between the stoves within the system. In addition, the effects of changes in different operation parameters, i.e., system full-cycle duration, stoves on-blast periods, temperature target of the blast, fuel rate, and enrichment by external fuel, on the overall performance of the system were also studied in the simulations. As the model is programmed with adjustable parameters, it can easily be adapted to any other specific hot-stove system to allow for more accurate and applicable outputs

Energy saving technologies and optimisation of energy use for decarbonised iron and steel industry

The iron and steel industry relies significantly on fossil energy use and is one of the largest energy consumers and carbon emitters in the manufacturing sector. Simultaneously, a huge amount of waste heat is directly discharged into the environment during steel production processes. Conservation of energy and energy-efficient improvement should be a holistic target for iron and steel industry. There is a need to investigate and analyse potential effects of application i.e., a number of primary and secondary energy saving and decarbonisation technologies to the basic energy performance and CO2 emissions profile of iron and steel industry. A 4.7Mt annual steel capacity iron and steel plant in the UK is selected as a case study. By carrying out a comprehensive literature review of current primary and secondary energy saving and decarbonisation technologies, suitable technologies are categorised based on their purpose of utilisation and installation positions. It is found that fuel substitution technologies and waste heat recovery technologies have wide application prospects in iron and steel industry. To further investigate effects of these technologies on the UK integrated steelwork, a comprehensive model of iron and steel production processes is built by using the software Aspen Plus. The model is fully validated and is used to examine the specific energy consumption and direct CO2 emissions. Energy consumption and CO2 emissions of whole production chain to produce a ton of crude steel are 17.5 GJ and 1.06 t. Waste heat from hot coke and gas cooling could cover 40% of electricity consumed in the plant if coking process has the maximum coke capacity. To implement primary energy saving and decarbonisation technologies, the performance of blast furnace is optimised first by substituting coke with bio-reducers based on the proposed model. Three biomass substitutions are considered to reduce coke rate and CO2 emissions of ironmaking process. Results show that coke demand of per ton of hot metal and CO2 emissions of the ironmaking process are improved by replacing partial coke with biomass. An optimal coke replacement is operated with 200 kg bio-oil and 222 kg coke when producing one ton of product. The reaction involving bio-syngas has the most potential to reduce CO2 emissions. To find a sustainable way to capture CO2 and recover waste heat onsite, a model of adopting organic Rankine cycle with amine-based CO2 capture in ironmaking process is introduced. In comparison with different reducing agents injected into BF, bio-oil has the most advantage to improve energy consumption of CO2 capture system. CO2 emissions from total sites can be maximumly reduced by 69% through the method of CO2 capture with waste heat recovery technologies. The combination of various decarbonised technologies creates great opportunity to reduce CO2 emissions. A mass-thermal network of iron and steel industry is finally built up, where primary and secondary energy saving technologies are implemented to optimise energy use and reduce CO2 emissions. The general guideline i.e., 5-step method is summarised to optimise the mass-thermal network. Exergy analysis is used to evaluate overall network after applications of energy saving and decarbonisation technologies. Injection of biomass-based syngas can maximumly increase the exergy efficiency of ironmaking process. Sinter and BOF steelmaking processes are related with mass ratio of hot metal. Optimisation insights of energy use and decarbonisation for steelwork are revealed based on exergy efficiency and destruction results

Performance Evaluation of Various Biomasses in a Gasifier Based Cook Stove

Biomass constitutes the biggest sources of energy in rural Asia. However, its utilization in the domestic sector is mostly inefficient and polluting which results in indoor air pollution and resource wastage. Traditional cook stoves predominantly used in the households for domestic cooking have been major contributor to the ill effects related in respiratory and other health problem. Improved cook stoves programs implemented in the developing world attempt to address these problems. Biomass gasification appears to have significant potential in Asia for domestic cooking applications. Gasifier-based cook stove were fuel efficient and emission efficient in comparison to traditional cook stove

Rendimiento de combustibles bajos en carbono en motores de combustión interna

RESUMEN Los combustibles bajos en carbono son clave para la transición hacia un sistema energético sostenible con menos emisiones contaminantes y menos dependiente de los combustibles fósiles. El hidrógeno como vector energético permite una amplia implementación de las fuentes de energía renovables, con una generación de energía limpia más distribuida en las diferentes regiones del mundo. Además, el hidrógeno puede utilizarse en muchos sectores, como el marítimo, con una importante contribución al transporte de mercancías y pasajeros. Asimismo, hay corrientes residuales industriales con un elevado porcentaje de hidrógeno y alto contenido energético, permitiendo su recuperación con motores de combustión interna, una tecnología empleada mundialmente. La primera parte de esta tesis se enfoca en el análisis de un sistema energético europeo en 2050 basado en hidrógeno orientado a barcos, mientras que en la segunda parte se realiza el estudio del gas de coque en un motor, tanto experimentalmente como en un modelo CFD.ABSTRACT Low carbon fuels are key to the transition to a sustainable energy system with lower pollutant emissions and less dependence on fossil fuels. Hydrogen as an energy vector allows a wide implementation of renewable energy sources, with a more distributed clean energy generation across the world. In addition, hydrogen can be used in many sectors, such as the maritime sector, with an important contribution to freight and passengers transport. Likewise, there are industrial waste streams with a high percentage of hydrogen and high energy content, allowing its recovery with internal combustion engines, a worldwide deployed technology. The first part of this thesis focuses on the analysis of a European energy system in 2050 based on hydrogen oriented to ships, while in the second part the study of coke oven gas in an engine is carried out, both experimentally and in a CFD model.This thesis has been financially supported by the European Regional Development Fund within the framework of the Interreg Atlantic Program through the project “HYLANTIC” – EAPA_204/2016 and within the framework of the Interreg SUDOE Program through the project PEMFC-SUDOE (SOE1/P1/E0293 – INTERREG SUDOE/FEDER, UE), “Energy Sustainability at the SUDOE Region: Red PEMFC-SUDOE”. The three months research stay at the Institute of Energy and Climate Research – Techno-Economic Systems analysis (IEK-3) in Forschungszentrum Jülich, Germany, under the supervision of Martin Robinius has been also financed through the “HYLANTIC” project

Graphite as a structural material in conditions of high thermal flux: a survey of existing knowledge and an assessment of current research and development

The state of fundamental knowledge on the subject of graphite and the graphitisation process is reviewed. The principle methods of manufacture may be considered to include (1) conventional graphitisation of a coke filler-binder mix, (2) the compaction at high pressure and temperatures of natural or artificial graphite particles without a binder, (3) pyrolytic graphites derived from gaseous deposition, and (4) conventional graphites impregnated by liquid or gas and re-graphitised. The present state of development of these processes is examined. The erosion of graphite by high velocity gases at high temperatures is due primarily to oxidation effects which occur preferentially at crystallite boundaries. Coatings of carbides and nitrides improve the resistance at temperatures below about 1700 degrees C, but above this, pyrolytic coatings are more successful. The addition of vapourising compounds, iodides and fluorides, or the addition of carbides and nitrides to the graphite mix, are both beneficial, but of little value at very high temperatures. The development of new graphites, either the impregnated type, or those produced by pressure baking, may offer a margin of improvement, as the best surface structure at temperatures of 3000 degrees C and above appears to be simply graphite. Additions may do little to improve the mechanism of erosion, but they may usefully lower the surface temperature. Considerations relating to thermal shock, creep and fabrication are surveyed. Some of the conclusions are: that graphite is of singular importance to high temperature technology; that commercial issues cannot be allowed to impede vigorous development towards more resistant forms; that much is to be gained by viewing graphite from a metals standpoint; that the fundamental theory of the basic crystal mechanics is undeveloped; that the present wide variability in properties should not be regarded overseriously; that non-destructive assessment by damping measurements needs development, that coatings and impregnants are of high priority, and that, of all factors, oxidation is the most serious limitation to use at the present time

Best Available Techniques (BAT) Reference Document:for:Iron and Steel Production:Industrial Emissions Directive 2010/75/EU:(Integrated Pollution Prevention and Control)

The BREF entitled ‘Iron and Steel Production’ forms part of a series presenting the results of an exchange of information between EU Member States, the industries concerned, non-governmental organisations promoting environmental protection and the Commission, to draw up, review, and where necessary, update BAT reference documents as required by Article 13(1) of the Directive. This document is published by the European Commission pursuant to Article 13(6) of the Directive. This BREF for the iron and steel production industry covers the following specified in Annex I to Directive 2010/75/EU, namely: • activity 1.3: coke production • activity 2.1: metal ore (including sulphide ore) roasting and sintering • activity 2.2: production of pig iron or steel (primary or secondary fusion) including continuous casting, with a capacity exceeding 2.5 tonnes per hour. The document also covers some activities that may be directly associated to these activities on the same site. Important issues for the implementation of Directive 2010/75/EU in the production of iron and steel are the reduction of emissions to air; efficient energy and raw material usage; minimisation, recovery and the recycling of process residues; as well as effective environmental and energy management systems. The BREF document contains 13 chapters. Chapter 1 provides general information on the iron and steel sector. Chapter 2 provides information and data on general industrial processes used within this sector. Chapters 3 to 8 provide information on particular iron and steel processes (sinter plants, pelletisation, coke ovens, blast furnaces, basic oxygen steelmaking and casting, electric arc steelmaking and casting). In Chapter 9 the BAT conclusions, as defined in Article 3(12) of the Directive, are presented for the sectors described in Chapters 2 to 8.JRC.J.5-Sustainable Production and Consumptio

Exploiting the potential of chemical looping processes for industrial decarbonization and waste to energy conversion. Process design and experimental evaluations

The impact of anthropogenic activities on the environment is leading to climate changes and exceptional meteorological phenomena all over the world. To address this negative trend, the scientific community agrees that the environmental impact from fossil fuels-based power production must be mitigated by the integration with alternative and sustainable technologies, such as renewable energy. However, the time required for the complete development and diffusion of such technology poses the urgency of finding a midterm solution to significantly reduce CO2 emissions. Carbon capture, utilization, and storage (CCUS) technologies represent an interesting option to mitigate CO2 emissions. CCUS involves (among other possible applications) the separation of the CO2 content from industrial off-gases, its transport and storage or its reconversion to a chemical/fuel. Chemical looping can be considered as an oxyfuel combustion where the oxygen supply comes from the lattice oxygen atoms of a solid. It is based on gas-solid reactions where a solid also known as oxygen carrier, generally a metal oxide, undergoes successive reduction and oxidation steps. In the reduction step, normally occurring at high temperatures (700-1000 °C), the oxygen carrier interacts with a reducing agent, such as coal, natural gas, syngas etc. and loses part of its oxygen atoms. By controlling the degree of reduction of the oxygen carrier is thus possible to achieve a complete oxidation of the reducing agent (the fuel) to CO2 and H2O (chemical looping combustion) or a partial oxidation to a syngas (chemical looping reforming and gasification). In these latter case, the introduction of external CO2 and H2O can be of help to support the reforming or gasification processes. The oxygen carrier in the reduced phase is then sent to an air reactor, where it reacquires the oxygen atoms by an exothermic reaction with air. This process presents several advantages according to the specific application. In chemical looping combustion, intrinsic separation of N2 and CO2 is achieved, because the two streams are involved in two different reaction steps. This largely simplifies the CO2 separation effort for storage or utilization purposes. On the other hand, in chemical looping reforming it is possible to achieve autothermal operation thanks to the exothermicity of the oxidation step in the air reactor, as well as high reforming efficiencies. Similarly, in chemical looping gasification the resulting syngas is characterized by no N2 dilution, lower tar release and possibility of autothermal operation. These benefits enhance the energy efficiency of the process, leading to a better energy utilisation. In this work, strategies for the decarbonisation and circularity of the industrial and power sector are proposed based on the synthesis of hydrogen and hydrogen-derived fuels. In particular, the potential of chemical looping technology is deeply studied aiming at exploiting its ability to reconvert or valorise CO2 or waste streams to a syngas and then to a liquid fuel/chemical, such as methanol or ammonia. This task is carried out through modelling and experimental evaluations. The modelling activities mainly concern design of process schemes involving the chemical looping section for waste or CO2 reconversion and the liquid fuel synthesis section. The experimental evaluations are focused on two crucial that have been limitedly discussed in the literature: the thermochemical syngas production step by oxidation with CO2 and H2O streams, the effect of high-pressure operation on the redox abilities of a typical iron and nickel-based oxygen carrier. In Chapter 1, a general overview on the main research developments on chemical looping technology is provided. A section is reserved for each chemical looping variant, i.e. combustion, reforming and gasification, and a general description of each process is provided along with the summary of the main research achievements. Subsequently, the technology is divided by application in power production and chemicals production. Main findings from techno-economic assessment and process designs are discussed in comparison with benchmark technologies and other clean pathways. In Chapter 2 steel mills are taken as an example of the hard-to-abate industry. A H2-based decarbonization strategy is proposed and assessed by Aspen Plus simulation. The strategy starts from an initial configuration that is characterized by a typical blast furnace-basic oxygen furnace steel mill and consider the introduction of direct reduction – electric arc furnace lines, that are more efficient and involve natural gas as reducing agent rather than coke. Sensitivity analyses are carried out to assess the effect of the introduction of H2/CH4 blendings in the direct reduction plant and of the utilization of scrap material in the electric arc furnace. The impact of each configuration on the CO2 emissions and the energy flows of the plant is assessed by mass and energy balances. The results indicate a promising decarbonization potential of the introduced technologies but require large investments to increase the renewable sources penetration in the energy mix and large availability of H2. Therefore, alternative pathways for an earlier decarbonization of hard-to-abate industries and for large scale syngas/H2 production need to be considered. In Chapter 3, a novel process scheme is proposed involving chemical looping for syngas production. The CO2 content in blast furnace gases is separated with a calcium looping cycle and subsequently injected with H2O into the oxidation reactor of a chemical looping cycle. Assuming an inlet stream of pure CO2, mass balances on the chemical looping plant are carried out to compare the performance of nickel ferrites and iron oxides in terms of required oxygen carrier flow rate to process 1 t/h of CO2. Computational fluid dynamics simulations with integrated reaction kinetics are then carried out to validate the assumptions on the oxygen carrier conversion and syngas compositions. In Chapter 4 and 5, experimental evaluations are carried out on two crucial aspects for the successful operation of a chemical looping plant aiming at syngas production. In Chapter 4, the syngas productivity by CO2 and H2O splitting over a Fe bed is investigated. This is a very important step, and the effect of various parameters was considered. Firstly, the CO2 splitting is analysed for different temperatures with an inlet flow rate of 1 NL/min to ensure a substantial dissociation of the CO2. Subsequently, combined streams of CO2 and H2O are evolved in the reactor. The effect of the total flow rate, reactants molar ratio and bed height is investigated and from the results, the optimal syngas composition is identified. SEM and XRD are used to assess the morphological evolution and the phase changes of the material during the test. On the contrary, in Chapter 5 the effect of high-pressure operation on the redox abilities of two NiFe aluminates is assessed. The aluminates present similar Fe loadings, but different Ni loadings. High pressure operation is crucial for the development of this technology because it facilitates downstream processing of the syngas to liquid fuels. For a comparative analysis, preliminary tests at low pressure are carried out at three temperatures. Subsequently, the effect of reactants flow rate, temperature, total pressure, gas composition is analysed at high pressure conditions. Finally, long term tests are performed both at ambient and high-pressure conditions. Material characterization by SEM, XRD and H2-TPR is used to support the comparative analysis. In Chapter 6, a techno-economic analysis on a process scheme encompassing methanol and ammonia production from chemical looping gases is carried out. Chemical looping hydrogen production is a very versatile technology and allows for the combined production of power and H2 or syngas. With proper calibration of the flow rates, a stream of high purity N2 can also be obtained at the air reactor outlet and used for ammonia synthesis. Back up with an alkaline electrolyser is considered for the supply of the required amount of hydrogen. Sensitivity analyses are carried out on the chemical looping plant to evaluate the effect of fuel flow rate, steam flow rate, and oxygen carrier inlet temperature to the fuel reactor. Subsequently, a techno-economic analysis is carried out evaluating several parameters among which: the specific CO2 emissions, the energy intensity, and the levelized cost of methanol and ammonia. Finally, a comparison with benchmark technologies and other clean alternatives is presented. In this way, the benefits as well as the drawbacks of chemical looping in terms of environmental and economic parameters are assessed and the missing elements to reach industrial competitivity are clarified

Comparative evaluation of GHG emissions from the use of Miscanthus for bio-hydrocarbon production via fast pyrolysis and bio-oil upgrading

This study examines the GHG emissions associated with producing bio-hydrocarbons via fast pyrolysis of Miscanthus. The feedstock is then upgraded to bio-oil products via hydroprocessing and zeolite cracking. Inventory data for this study were obtained from current commercial cultivation practices of Miscanthus in the UK and state-of-the-art process models developed in Aspen Plus®. The system boundary considered spans from the cultivation of Miscanthus to conversion of the pyrolysis-derived bio-oil into bio-hydrocarbons up to the refinery gate. The Miscanthus cultivation subsystem considers three scenarios for soil organic carbon (SOC) sequestration rates. These were assumed as follows: (i) excluding (SOC), (ii) low SOC and (iii) high (SOC) for best and worst cases. Overall, Miscanthus cultivation contributed moderate to negative values to GHG emissions, from analysis of excluding SOC to high SOC scenarios. Furthermore, the rate of SOC in the Miscanthus cultivation subsystem has significant effects on total GHG emissions. Where SOC is excluded, the fast pyrolysis subsystem shows the highest positive contribution to GHG emissions, while the credit for exported electricity was the main ‘negative’ GHG emission contributor for both upgrading pathways. Comparison between the bio-hydrocarbons produced from the two upgrading routes and fossil fuels indicates GHG emission savings between 68% and 87%. Sensitivity analysis reveals that bio-hydrocarbon yield and nitrogen gas feed to the fast pyrolysis reactor are the main parameters that influence the total GHG emissions for both pathways