Individual Pellets Research Articles

A Numerical Study of the Thermochemical and Aerodynamic States of H2‐intensive Direct Reduction Shaft Furnace

In the urgent pursuit of deep decarbonization, the steel industry has paid significant attention to the hydrogen‐intensive direct reduction process, where the H2‐to‐CO (volume) ratio of feed gas for the shaft furnace (SF) is increased compared to the current level. In this work, the reduction process of iron oxide pellets in the SF is investigated numerically to clarify how the in‐furnace thermochemical and aerodynamic states are affected by increasing hydrogen content, with the goal to provide guidelines for more efficient operations of the unit. Multiscale modeling is conducted to investigate the complicated gas–solid countercurrent reactive flows in the SF where the reduction behavior of an individual iron oxide pellet is described using a three‐interface unreacted shrinking core model. The results show that an increase in the hydrogen content leads to a lower temperature level and hence a deteriorated thermochemical state. It also induces a lower gas pressure drop over the in‐furnace packed bed.

Particle-resolved computational modeling of hydrogen-based direct reduction of iron ore pellets in a fixed bed. Part I: Methodology and validation

In the pursuit of more sustainable steelmaking, stakeholders are engaging in a transformative exploration of hydrogen-based direct reduction as an alternative to conventional blast furnaces. As a bridging step between single iron ore pellets and industrial shaft furnaces, direct reduction modeling in a fixed bed configuration can play a central role for subsequent process optimization. However, this task involves numerous challenging steps: generation of a realistic packed bed structure along with a good quality mesh and, foremost, reliable transport and kinetic processes for the individual pellets. Therefore, the present work formulates a sound methodology to progress from single particle considerations to 3D-CFD simulations of iron ore reduction using hydrogen in fixed beds, further supported by validations regarding the bed structure and the overall reduction against experimental data from the literature of a 500 g iron ore bed. The current results offer new insights into the direct reduction process, revealing, for instance, the non-uniform reduction of pellets within the bed, the presence of gas pockets, or the importance of the temperature deviation due to the endothermic reduction of iron oxides with hydrogen.

Fuelling of deuterium–tritium plasma by peripheral pellets in JET experiments

A baseline scenario of deuterium–tritium (D–T) plasma with peripheral high-field-side fuelling pellets has been produced in JET in order to mimic the situation in ITER. The isotope mix ratio is controlled in order to target the value of 50%–50% by a combination of tritium gas puffing and deuterium pellet injection. Multiple factors controlling the fuelling efficiency of individual pellets are analysed, with the following findings: (1) prompt particle losses due to pellet-triggered edge-localised modes (ELMs) are detected, (2) the plasmoid drift velocity might be smaller than that predicted by simulation, (3) post-pellet particle loss is controlled by transient phases with ELMs.The overall pellet particle flux normalised to the heat flux is similar to that in previous pellet fuelling experiments in AUG and JET.

Lightweight concrete with low-carbon artificial aggregates recycled from biomass ash and slurry waste

The development of artificial aggregates (AAs) significantly reduces carbon emissions of concrete production since the aggregates account for about 70% volume of all concrete ingredients. Therefore, a type of low-carbon AAs was prepared with full solid wastes of biomass ash (BA) and slurry waste (SW) through a pelletizing technique and carbonation curing methods. This study focused on evaluating the feasibility of AAs produced by the synergistic effect of BA and SW; identifying and optimizing the pelletization parameters through the response surface methodology (RSM) with experimental tests; analyzing the effects of blending amounts of BA on the properties of AAs; discussing the improvement of carbonation curing methods for AAs production; assessing the properties of the prepared lightweight concrete (LWC) with AAs. The results indicate the addition of 20 wt% BA lightened the bulk density of AAs by about 13% but weakened strength by nearly half due to its porous characteristics. The appropriate incorporation of 5 wt% BA could improve the individual pellet and cylinder compressive strength by about 2% and 16%, respectively. AAs cured in pressurized carbonation of 3 d and wet carbonation of 10 min demonstrated similar enhancement effects. Pressurized and wet carbonation curing showed respective superiorities in terms of improving effect and curing efficiency. The effects of inclination angle and moisture content on the average particle size are more significant than those of rotation speed, while rotational speed has a dominant effect on the bulk density. RSM simulations identified the optimal inclination angle, rotation speed, and moisture content as 45°, 38.5 r/min, and 37.5%, respectively. The LC40 high-strength LWC can be prepared by using full substitution pre-wetting AAs.

Behaviour of sewage sludge based lightweight aggregate in geopolymer concrete

The global challenge of sewage sludge disposal has encouraged innovative solutions aimed at reducing environmental impact while simultaneously addressing the growing demand for sustainable construction materials. This study aimed to develop treated raw sewage sludge-based lightweight aggregates with strength comparable to commercially available aggregates. Two methods, namely cold bonding and sintering, were employed for the formation of aggregates. The sintering method produced well-formed and hard aggregates, while the cold bonded aggregates exhibited weakness and disintegrated under the slightest pressure. The optimal mix for quality aggregates was found to be 10%–20% sewage sludge, 70%–80% fly ash, and 10% lime using the sintering method. In the sintering method, an increase in sewage sludge content resulted in the reduction of bulk density and specific gravity by 13% and 4% respectively due to the high organic content in sewage sludge, volatile gas release, and porous structure formation. When 10% to 20% sewage sludge content was added, water absorption of the aggregates also increased by approximately 2%. Physical properties such as individual pellet strength. aggregate crushing value reduced by 18%, 20% respectively and the aggregate impact value increased by about 9%. These aggregates were then used to produce lightweight geopolymer concrete, which exceeded the design strength by 7% for the aggregate containing 20% sewage sludge and demonstrated excellent physical properties. The use of waste-based aggregates offers advantages including savings in cost, sustainability, resource conservation, waste reduction, and reduced environmental impact, making them a valuable alternative to natural crushed stone aggregates in specific applications.

Evidence for the transportation of aggregated microplastics in the symplast pathway of oilseed rape roots and their impact on plant growth

As an emerging contaminant, microplastics are absorbed by crops, causing diverse impacts on plants. Plants may have different physiological responses to different uptake modes of microplastics various stage of growth. In this study, the distribution of polystyrene (PS) microspheres in the roots of oilseed rape and the physiological responses at different growth stages were investigated by confocal laser scanning microscope, scanning electron microscopy, and biochemical analysis. This study, conducted via scanning electron microscopy, discovered that agglomerates of microspheres, rather than individual plastic pellets, were taken up by plant roots in solution for the first time. The agglomerates subsequently migrate into the vascular bundles of the root system. Moreover, this study provided the proof for the first time that PS is transported in plants via the symplast system. On the physiological and biochemical function, the exposure of PS at the flowering and bolting stages caused oxidative stress on oilseed rape. That is, the addition of PS with different particle sizes significantly increased peroxidase (POD), malondialdehyde (MDA), photosynthetic rate, chlorophyll content and inhibited superoxide dismutase (SOD) content in oilseed rape at different developmental stages. These changes regulated the chloroplast structure and chlorophyll synthesis, maintained a high photosynthetic rate, and mitigated the toxicity of PS. In addition, correlation analysis showed that MDA and citric acid contents were significantly positively correlated with chlorophyll contents (p < 0.05), which suggested that the 80 nm PS treatment stimulated organic acid secretion in oilseed rape at the bolting stage to maintain a higher chlorophyll content. This study expands the current understanding of the effects of microplastics on crop growth, and the results holding significant implications for exploring the impact of microplastics on vegetables during various developmental stages and for future risk assessment.

Effect of Rearing System and Physical form of the Total Mixed Ration on Growth Performance of Local Male Lambs

The University of Anbar’s Department of Animal Production hosted this experiment on their sheep farm from October 18, 2022, through January 6, 2023. Twenty-two local male lambs, ranging in age from 3.3 to 3.5 months, and averaging 20.2±2.28 kilograms were included. The purpose of the experiment was to determine the influence of the rearing system and physical form of the total mixed ration on the growth and feeding performance of local male lambs. Lambs were randomly distributed into four treatments. T1 (group housing + loose diet) included 6 Lambs distributed in three group cages (2 Lambs /cage), T2 (group housing + pellet diet) included 6 Lambs distributed in three group cages (2 Lambs /cage), T3 (individual housing + loose diet) included 5 Lambs distributed in five individual cages (1 lamb / cage), and T4 (individual housing + pellet diet) included 5 Lambs distributed in five individual cages. A total of 63 days were devoted to the actual experiment. All lambs were fed ad-libitum to the Pelleted and loose total mixed ration. Throughout the duration of the experiment, the parameters of growth and nutritional performance were estimated. The results of present experiment showed that the individual rearing system significantly improved daily feed intake and dry matter intake compared with grouped rearing system. The pelleted total mixed ration was superior to the loose total mixed ration in growth performance (final body weight, total weight gain, daily weight gain) and feeding performance (feed conversion ratio, feeding efficiency), and decreased the cost of producing 1 kg of weight gain. The results showed that the growth and feeding performance of local male lambs were significantly boosted by the interaction between individual housing and pellet diet. Researchers found that fattening lambs’ productivity might be improved with the use of individual housing combined with a pellet diet.

Influence of Integration of Iron Ore Tailings on the Physio-mechanical and Microstructure Properties of Fly Ash–Based Coarse Aggregates

Abstract The goal of this experimental study is to produce fly ash (FA)-based coarse aggregates by adding iron ore tailings (IOT) to the FA-based precursor as an additional mix component. The involvement of different types of binders—influential factors of both pelletization and geopolymerization that govern the production of FA-based coarse aggregates—was experimentally designed by adopting Taguchi’s experimental design. An evaluation was conducted utilizing response indexes at three curing periods to study the accumulation of all the influencing factors in the production process as well as on the engineering features of IOT admixed FA-based coarse aggregates. Aggregate impact and crushing values, individual pellet strength (IPS), and specific gravity and water absorption values were measured. According to experimental findings, IOT addition considerably affects the engineering characteristics of FA-based coarse aggregates. The heat resistance of the produced aggregates was found to be improved by the presence of different sodium oxide dosages and blending ratios (IOT:FA) based on analysis through scanning electron microscopy and thermogravimetric differential thermal analysis. The role of IOT in associative formation of calcium silicate hydrate is demonstrated by increasing calcium hydroxide, which supports increasing IPS values of produced aggregates. From the 1st to the 200th day of curing age, Fourier-transform infrared spectroscopy studies between the best- and worst-performing mixes showed two things: first, the emergence of new peaks with time, and second, the observation of major bands shifting to lower and higher wavenumbers, which was found to be directly correlated to the performance of the aggregates.

Direct reduction of iron ore pellets by H2-CO mixture: An in-situ investigation of the evolution and dynamics of swelling

The iron and steel metallurgy industry faces the question of how to replace carbon in iron ore reduction to reduce CO2 emission in basic industries and achieve the expectation of "double carbon". This study investigates the reduction swelling of individual iron ore pellet under mixed H2-CO atmospheres and at temperatures of 800–1000 ℃ by in-situ observation. The progression is surveyed by infrared imaging, scanning electron microscopy (SEM), and optical microscopy (OM). To evaluate the internal relationship between dynamic reaction control and swelling behavior during the reduction process, the dynamic resistance calculations are compared using OM slice images and the variation in the pellet’s compressive strength. The advantage of H2 in suppressing the reduction swelling greater when below 950 ℃ and is strengthened by increasing its proportion. With the increase of H2 content, metallic iron whiskers easily form iron shells on the outer layer of pellets, while they are easy to aggregate and fill in pores and cracks inside the pellets, leading to shrinkage of pellets after maximum swelling. The dynamic resistance calculations indicates that, at 950 ℃, the reaction process is mainly controlled by internal diffusion under 94 % CO, and by a combination of internal diffusion and interfacial chemical reactions under H2/CO = 1.0, while the reaction process is mainly controlled by the interfacial chemistry with the increase of H2.

MINIMALLY DESTRUCTIVE RADIOCARBON DATING OF CAPRINE DUNG

ABSTRACTArchaeological dung pellets are time capsules of ancient herbivore diets and gut flora, informing on past agropastoral activity, ecology, and animal health. Improving multi-proxy approaches is key to maximizing this finite archaeological resource. Through experiments with standard pretreatments used in radiocarbon (14C) dating, we address a fundamental problem in maximal multi-proxy analysis: How to chronometrically date individual caprine pellets while conserving as much as possible for additional analyses? We applied acid-alkali-acid (AAA) or acid-only pretreatments to 37 samples of ancient and recent sheep/goat dung pellets from sites in the Negev desert, Israel, measuring weight-loss due to pretreatment. Shavings of outer surfaces and remaining inner pellets of four pairs were dated and compared. We found that (i) sample-specific factors affect pretreatment survivability, including preservation quality and initial sample size; (ii) given sufficient start weight, AAA can be used to pretreat sheep/goat coprolites; (iii) 100 mg appeared a desirable minimum sample weight before pretreatment; and (iv) shavings of coprolites’ outer surface produced 14C dates equivalent to dates obtained from inner coprolites. Whereas standard coprolite analysis protocols discard shavings removed from outer surfaces to avoid contamination, our findings indicate their efficacy for 14C dating. This offers an important addition to workflows for multi-proxy coprolite analysis.

Synchrotron radiation-based microcomputed tomography for three-dimensional growth analysis of Aspergillus niger pellets.

Filamentous fungi produce a wide range of relevant biotechnological compounds. The close relationship between fungal morphology and productivity has led to a variety of analytical methods to quantify their macromorphology. Nevertheless, only a µ-computed tomography (µ-CT) based method allows a detailed analysis of the 3D micromorphology of fungal pellets. However, the low sample throughput of a laboratory µ-CT limits the tracking of the micromorphological evolution of a statistically representative number of submerged cultivated fungal pellets over time. To meet this challenge, we applied synchrotron radiation-based X-ray microtomography at the Deutsches Elektronen-Synchrotron[German Electron Synchrotron Research Center], resulting in 19,940 3D analyzed individual fungal pellets that were obtained from 26 sampling points during a 48 hAspergillus niger submerged batch cultivation. For each of the pellets, we were able to determine micromorphological properties such as number and density of spores, tips, branching points, and hyphae. The computed data allowed us to monitor the growth of submerged cultivated fungal pellets in highly resolved 3D for the first time. The generated morphological database from synchrotron measurements can be used to understand, describe, and model the growth of filamentous fungal cultivations.

Synchrotron Microanalytical Characterization and K/Ar Dating of the GL-O-1 Glauconite Reference Material at the Single Pellet Scale and Reassessment of the Age of Visually Mature Pellets

The K/Ar chronology of glauconite pellets is a long-used method for directly dating marine sedimentary deposits. Many papers have explored the processes that form glauconite and the factors that lead to greater reliability in the ages. Although K/Ar ages of glauconite are generally in agreement with other measures of stratigraphic age, there are examples of occurrences with ages too old and examples with ages too young. This paper seeks to build on the accumulated knowledge of glauconite, using synchrotron radiation to non-destructively characterize individual pellets and then consecutively measure the argon and potassium to obtain a K/Ar age. This strategy provides the advantage of measurements on a single aliquot while avoiding recoil loss of 40Ar in the nuclear reactor during irradiation for 40Ar/39Ar dating. We have used the glauconite reference material GL-O-1 to showcase several non-destructive methods for evaluating the maturity of individual pellets. In our argon measurements, we have found that the radiogenic argon concentration of large bulk samples underestimates the values for individual visually mature pellets, and we determined a K/Ar age of 101.0 ± 0.3 Ma (1σ SEM), M.S.W.D. 0.54 from 15 of 16 visually mature individual pellets. This age is 6% older than the reference value of 95.03 ± 1.11 Ma (1σ), and it is in good agreement with constraints from the U-Pb dating of volcanic minerals near the Albian–Cenomanian boundary.

Physico-mechanical and energy properties of pellets made from ground walnut shells, coniferous tree cones and their mixtures

The aim of this study was to verify the possibility of obtaining good-quality pellets from mixtures of materials with different particle structures and shapes. The paper describes the pressure agglomeration of ground walnut shells and coniferous tree cones as well as their three mixtures. The process involved the production of pellets with a diameter of 6 and 8 mm at the temperatures of 95 and 120°C by applying the force of 5 and 6 kN. The fraction distribution of the particles from which the pellets were made was assessed. It was found that the pellets made only of cones, as opposed to those made only of nutshells, have a fairly even distribution, i.e. the particles were of similar size. The size parameters of the pellets (length and diameter) were measured, on the basis of which the density of individual pellets was calculated. Compressive stresses of the pellets were tested on an endurance testing machine. It was found that the pellets with a greater share of nut shells were less durable than those made with the addition of ground cones. The pellets with a diameter of 6 mm and formed at a temperature of 120°C also showed a higher strength than those with a diameter of 8 mm and compacted at a temperature of 95°C. Increasing the force did not statistically significantly improve the compressive strength of the pellets. Tests of the elemental composition and the amount of ash allowed for concluding that pellets are a good energy material, as evidenced by their average calorific value of about 19 MJ kg−1. Due to exceeding the permissible limit of nitrogen content (ISO 17225), the pellets made solely of cones were classified as quality class B, while the addition of ground walnut shells shifted them to class A2.

The Nutrient Dynamics of Major and Minor Nutrients on Pelleted and Unpelleted Dry Fodders

Background: Farmers are facing the challenges to providing adequate availability of feed and fodders to livestock during dry period (lean period) which poses a major threat in livestock productivity. This study delineates, pelleting of feed and fodder helps to meet out the fodder requirement during lean period consequently improving the livestock productivity. Methods: The experiment was conducted at Forage Pelleting Unit, Department of Forage Crops in Agricultural College and Research Institute, Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu from March 2020 to June 2022 to identify the best suitable dry fodder crops for quality pellets production. The laboratory experiment was conducted and laid out in completely randomized block design with 11 treatments and three replications. The treatment consists of D1: Rice straw, D2: Maize stover, D3: Maize husk, D4: Sorghum straw, D5: Ragi straw, D6: Pearl millet stover, D7: Wheat straw, D8: Groundnut haulms, D9: Groundnut shells, D10: Sugarcane tops, D11: Blackgram husk were selected and produced into individual dry fodders pellets. Then, the selected dry fodders were harvested with the help of fodder harvester cum chaffer. The chaffed material was then dried using a solar drier at 70°C for one day to attaining the ideal moisture of 12%. Then, dried materials were grinded by fodder pulverizer and then grinding material was conveyed through conditioning with passing the steam at 60 to 70°C. Then, the conditioning material was passes through a pelletizer with 6 mm die diameter. Result: The observation on macro minerals (calcium, magnesium, potassium) and micro minerals (cobalt, zinc, manganese) were analyzed by using an Inductive Coupled Plasma Mass Emission Spectroscopy. The unpelleted and pelleted dry fodders showed a significant variation in the major and minor nutrients. In this regards, the calcium content recorded higher in groundnut haulms (D8) with 1.027 per cent and whereas ragi straw (D5) were recorded higher magnesium and potassium contents with 0.433 per cent and 2.178 per cent respectively. The minor nutrients like cobalt, manganese and zinc contents varied significantly due to pelleting process. From this study, rice straw (D1) recorded higher cobalt content with 0.378 per cent and whereas, ragi straw (D5) recorded higher zinc content (16.45 per cent) and while, manganese contents were registered higher in pearl millet straw (D6) with 54.88 per cent.

A Critical Investigation of Certificated Industrial Wood Pellet Combustion: Influence of Process Conditions on CO/CO2 Emission

The pollutants emission into the atmosphere is largely related to human activity and health, whereas, of many factors, domestic heating systems greatly impact the emission rate. The measures taken to reduce the emission of harmful compounds to the atmosphere are slowly starting to bring the intended effects and a downward trend in emissions of such gases as carbon monoxide (CO), nitrogen oxides (NOx), and sulfur dioxide (SO2) is noticeable. The conducted tests allowed the determination of the combustion characteristics of individual pellet types available on the European market. During the tests, pellets were supplied to a 25 kW fixed-bed boiler with a constant mass flow of 3 kg·h−1, and the air-flow ratio was manipulated and presented in the form of the excess air coefficient λ (1.8–3.08). Pellets certificated with the ENPlus as A1 were found not meeting the requirements, mainly in the ash content, which negatively affected their combustion performance gradually and caused exceeded CO emissions up to 1000 mg·Nm−3. Pellets of declared lower classes were more beneficial for combustion in terms of emission factors.

Simulation Tool for the Development of a Staged Combustion Pellet Stove Controller

Optimizing the combustion control concepts on a pellet stove with very low heat output is time-consuming and costly. In order to shorten the required laboratory test time, a 0-D transient tool was developed within the ERA-NET project “LowEmi-MicroStove”, which simulates a 4 kW pellet stove with staged combustion and heat transfer. This approach was chosen in order to greatly simplify the description of the combustion processes and so reduce the computational complexity and simulation time. The combustion of a bed of pellets is modeled as a superposition of the combustion cycles of individual pellets, assuming no interactions between pellets. A test setup was developed and used to determine the ignition and burning cycle of individual pellets. The description of the CO emissions behavior is based upon an empirically grounded relation which is in turn based on the air/fuel ratio and the combustion chamber temperature. For the validation of the 0-D simulation results, a test rig for a 4 kW pellet stove was built. Despite its simplistic approach, good agreement was found between the simulation and 4 kW pellet stove test results for the mean values and temporal fluctuations of flue gas temperature and oxygen and carbon monoxide content during start up, stable operation and load changes. The simulation could thus be used to quantify the effect of air flow rates and distribution as well as load changes on performance and draw conclusions regarding different process control strategies. A control strategy which can operate the stove at high temperatures near the air stoichiometric limit with acceptable CO emissions has been proven to be the most promising. Additionally, the model can be used to quantify the effects of variations in other process parameters, for example the impact of fluctuations in the pellet feed. Due to its effectiveness and simplicity, this model approach can be applied for the development of control strategies for other staged, pellet combustion systems.

Semi-automatic detection and segmentation of wooden pellet size exploiting a deep learning approach

The production of wood pellets was born as a response to the need to manage the residual sawdust of wood processing. Nowadays, the standard UNE EN ISO 17225-2:2021 determine the general requirements of the fuel specifications and their classes. Among these, the length of the pellet plays an important role in defining its behaviour in different contexts, starting from the way the spaces are occupied both in static (storage) and dynamic (feeding) conditions. The geometric-dimensional aspects of pellets are of particular importance for the density, the energy density, and the effective thermal capacity of thermal plants, affecting also the flowability. Despite the extreme importance of such parameters, the pellet measurement is carried out using a precision caliper on a group of individual pellets taken from laboratory samples. This method is time-consuming and returns dimensional values in very small quantities, raising the issue of sample representativeness. Considering the impact of the quality parameters, it is important to examine alternative solutions. In this light, this work has the task of testing and verifying the efficiency of a system that uses a deep neural network, to determine the geometric-dimensional parameters of wood pellets. Thus, the implemented system detects, segments, and determines the dimensions of wood pellets in a bunch. This problem is not trivial, due to the irregular lighting conditions that affect the quality of the images and the overlapping of the wood pellets. To evaluate the performance of the deep neural network approach, several experiments have been carried out, in different lighting conditions and for validation purposes, we considered also PVC pellets, which have a known and fixed dimension. The comparison between real environment data and the validation set, despite a slight tendency towards underestimation in length, shows great performances in terms of RMSE.

Energy Consumption Depending on the Durability of Pellets Formed from Sawdust with an Admixture of FFP2 Masks

At present, we are still feeling the effects of the COVID-19 pandemic in connection with the huge amount of waste generated. However, the reuse of the produced waste in other processes requires energy consumption. This article deals with the reuse of face masks FFP2, which were added as an admixture to spruce or beech sawdust and then processed into pellets. During the production process of the pellets, energy consumption was measured and further converted to one ton of pellets, and also the consumption was reflected in the price of electricity. After storage, the mechanical durability and dimensions of the individual pellets were measured, and their density was calculated. Based on the results, it can be concluded that spruce pellets with 10% face masks FFP2 (consumption 747.41 kWh; durability 97.53%) and beech pellets with 5% face masks FFP2 (consumption 721.27 kWh; durability 97.38%) achieved higher values of mechanical durability and also consumed more energy than the remaining samples with lower values of durability without considering the sample with spruce sawdust and 5% FFP2 face masks (consumption 872.63 kWh; durability 91.68%). The production of spruce pellets with 5% FFP2 face masks was affected mainly by cold outside weather.

Decision paths to reduce costs and increase economic impact of geothermal district heating in Geneva, Switzerland

Geothermal district heating could play an important role towards climate change mitigation, but its slow uptake implies that it is cost competitive only under specific sets of conditions, including drilling success and design of the district heating. Even in cases when geothermal district heating may be less cost competitive than other alternatives, expenditure that occurs during its development brings indirect economic impact that could also benefit domestic economy. Using the case study of the State of Geneva in Switzerland, this paper analyzes cost competitiveness and economic impacts of 5′892 decision paths (combinations of decisions) to develop geothermal district heating, including the choice of auxiliary heat source, and uses comprehensive sensitivity analysis to identify the most influential decisions. The right share of geothermal coverage in the heat mix to achieve an optimum combination of investment costs and geothermal heat production, and the integration of waste incineration as auxiliary heat source are crucial for cost competitiveness. High economic impact multipliers are created by geothermal systems incorporating individual pellet boilers as auxiliary heat source. High share of domestic impact consistently occurs in the case of standalone geothermal installations, especially when they are used with second or third generation of district heating. Combining geothermal district heating from medium and deep wells (1′500 m and 2′500 m) with heat from waste incineration creates synergies where above-average cost competitiveness and economic impacts are achieved.

Direct reduction of iron ore pellets by H2 and CO: In-situ investigation of the structural transformation and reduction progression caused by atmosphere and temperature

With the aim of reducing CO2 emissions in basic industries, the sector of iron and steel metallurgy is also faced with the question of how carbon can be replaced in ore reduction. By means of in-situ observation, this study investigates the direct reduction (DR) of individual iron ore pellets under an atmosphere of hydrogen (H2) and carbon monoxide (CO) and at temperatures between 800 °C and 1100 °C at atmospheric pressure. The progress of the reduction, i.e. the phase change and the structural change, is analysed by X-ray diffraction (XRD) and scanning electron microscopy equipped with energy-dispersive X-rays (SEM-EDX). To evaluate the porosities of the pellets, analytical porosimetry is compared to optical porosimetry findings obtained by analysing images of sections in the SEM (hereinafter called SEM porosimetry). Furthermore, the swelling behaviour is evaluated by video analysis and the reduction swelling index (RSI) is determined. The results show a higher reduction progress and a higher RSI under H2 atmosphere than under CO atmosphere. Higher temperatures lead to faster reduction progress and to significant changes in the structural composition of the reduced pellets.