Highly efficient CO2 capture with simultaneous iron and CaO recycling for the iron and steel industry

An efficient CO2 capture process has been developed by integrating calcium looping (CaL) and waste recycling technologies into iron and steel production. A key advantage of such a process is that CO2 capture is accompanied by simultaneous iron and CaO recycling from waste steel slag. High-purity CaO-based CO2 sorbents, with CaO content as high as 90 wt%, were prepared easily via acid extraction of steel slag using acetic acid. The steel slag-derived CO2 sorbents exhibited better CO2 reactivity and slower (linear) deactivation than commercial CaO during calcium looping cycles. Importantly, the recycling efficiency of iron from steel slag with an acid extraction is improved significantly due to a simultaneous increase in the recovery of iron-rich materials and the iron content of the materials recovered. High-quality iron ore with iron content of 55.1–70.6% has been recovered from waste slag in this study. Although costing nearly six times as much as naturally derived CaO in the purchase of feedstock, the final cost of the steel slag-derived, CaO-based sorbent developed is compensated by the byproducts recovered, i.e., high-purity CaO, high-quality iron ore, and acetone. This could reduce the cost of the steel slag-derived CO2 sorbent to 57.7 € t−1, appreciably lower than that of the naturally derived CaO. The proposed integrated CO2 capture process using steel slag-derived, CaO-based CO2 sorbents developed appears to be cost-effective and promising for CO2 abatement from the iron and steel industry

Reactivity of modified iron silicate slag as sustainable alternative binder

A possible solution to decrease the CO2 footprint caused by cement industry and to enhance the transition to circular economy is to use slags as Supplementary Cementitious Materials (SCM). The study presented here focuses on valorizing and investigating the reactivity and mechanical properties of blended binder systems combining modified iron silicate (MFS) slag and Ordinary Portland cement (OPC). MFS slag is a fumed by-product synthesized during the production of copper metal (Cu). This slag can be used as possible alternative SCM due to its pozzolanic behavior. To study the replacement level in relation to reactivity and strength development, replacement levels of 15, 30 and 50 wt% of MFS-slag in OPC are analyzed. The work can be divided into two categories, 1) assessing the reactivity through thermogravimetric analysis (TGA) and 2) evaluating the compressive strength (as a function of time) of mortar with MFS-slag after 2, 7, 28 and 90 days. TGA at 7, 15, 28 and 90 days allows to determine the reduction of portlandite (CH) content which gives an indication of the pozzolanic reactivity. Reactivity of the MFS-slag blended systems is also determined relative to inert filler blended systems to discern between the reactive behavior of the MFS-slag and the filler effect

Cooling Process Analysis of a 5-Drum System for Radioactive Waste Processing

A cooling system design for the processing of radioactive waste drums is investigated in this work, with the objective of providing insights for the determination of the air flow rate required to ensure an acceptable slag temperature (323 K or below) after 5 days. A methodology based on both 3D and 2D axisymmetric Computational Fluid Dynamics (CFD) modelling is developed. Transient temperature distributions within the drums in time and space determined by the heat transfer characteristics are studied in detail. A sensitivity analysis is also carried out assuming different physical properties of the radioactive slag. It was found out that for all variations analyzed, the maximum temperature of slag at the end of five days cooling is below 323 K, where the maximum outlet air temperature for a minimum air inlet velocity of 1 m/s is between 320 K and 323 K depending on the radioactive slag properties. When glass-like radioactive slag properties are assumed, the internal heat conduction within the slag is limiting the overall heat transfer, therefore requiring significantly longer cooling times

The complex binder based on Portland cement andash-and-slag wastes from thermal power stations

Increase in the balance of boiler and furnace fuel of the energy sector of the Republic of Belarus the proportion of own energy resources (milling peat and wood chips) places priority on resolving the issues of utilization of ash-and-slag wastes and reducing the area of ash-and-slag disposal sites, which cause irreparable damage to the environment. A considerable amount of research has been devoted to the utilization of ash-and-slag wastes. There are more than 300 technologies of their recycling and use. Ash and slag wastes are used in the production of concrete, mortars, ceramics, heat and water insulating materials, road construction. The world experience shows the potential of 70-80% utilization of ash and slag, as, for example, in some European countries. However, the cost of the recycling of ash-and-slag wastes with the production and simultaneous neutralization of wastes can be higher than the cost of the production. One of the directions of the use of ash and slag wastes is the production on their basis of new types of complex binder that have increased strength and low prime cost. The replacement of a part of cement with active mineral additive allows to achieve significant saving of binder. The existing methods of the production of complex binders include the stages of joint or separate grinding of cement clinker and mineral additive with following mixing. Significant energy costs for grinding increase the cost of binder. In this regard, the development of the effective complex binder with the use of ash-and-slag wastes of the Belarussian state district power station in Orekhovsk using resource-saving technology is the actual research objective

The reaction of slag in cement: theory and computer modelling

In this study, theoretical models available for the reaction of both pure slag\ud (alkali-activated) and slag-blended cement are reviewed. They were developed by using stoichiometric computations

Velocity and temperature distributions of coal-slag layers on magnetohydrodynamic generators walls

Approximate analytical expressions are derived for the velocity and temperature distributions in steady state coal slag deposits flowing over MHD generator walls. Effects of slag condensation and Joule heating are included in the analysis. The transport conditions and the slag temperature at the slag-gas interface are taken to be known parameters in the formulation. They are assumed to have been predetermined either experimentally or from the slag properties and the gas dynamic calculations of the free stream flow. The analysis assumes a power law velocity profile for the slag and accounts for the coupling between the energy and momentum conservation equations. Comparisons are made with the more exact numerical solutions to verify the accuracy of the results

To develop a new mineral carbonation process that have a high efficiency in CO2 absorption into industry slag using low energy mechanical milling

Increase in the CO2 emission in atmosphere due to the combustion of fossil fuels has caused serious global warming. Electricity generation, tranportation, and industrial waste are the main sectors indentified to contribute to the emission of CO2 in Malaysia. In dealing with this issue, the absorption of CO2 into industrial waste was experimentally studied by the utilization of mechanical grinding method. This research is to aim a development of new mineral carbonation process that has a high efficiency in the capture and storage of CO2 with low energy consumption. In the first stage of this study, the behavior of CO2 absorption on electric arc furnace and ladle furnace slag was studied by low energy mechanical milling It was found that the absorption is occured during milling. CO2 was stored into the slag mainly as CaCO3. Thus this indicates that the CO2 can be stored permanently inside the slag with this method. In the next stage, the effect of dissolution of metal element into water on the behavior of CO2 absorption was investigated by leaching test experiment. It was found that , concentration value of Fe in pure water is higher but in river water the concentration is lower, the dissolve concentration decreased with the increased in the number of the leaching time. Concentration will be increased at the earlier stage before it decreased at final of concentration. This case because the liquid became saturated and cannot be to dissolved. After the pH steeply increased gradually at an early stage of the elution of slag, it slightly decreased. The pH decreased with the increased in the number of elution. The changes of pH in leaching test it seemed to depend on the content of CaO in the slag. For mechanism of CO2 absorption, morphological change of slag were study and the slag were characteried by using XRD, FE-SEM, and EDS

Influence of physic-mechanical properties on a choice of metallurgical slags processing technology

Проаналізовано фізико-механічні властивості шлаків після первинної переробки – тер-мічного (термоудар) і механічного впливу на розплав, схильність відвальних шлаків до розпаду – структурним перетворенням, і можливі види механічної переробки для отримання різних видів шлакової продукції. Наводиться технологічна схема переробки відвальних шлаків (можливе застосування також і для шлаків поточного випуску) з витяганням металу і отриманням широкого спектру шлакової продукції, включаючи в'яжучі матеріали.Проанализированы физико-механические свойства шлаков после первичной переработки – термического (термоудар) и механического воздействия на расплав, склонность отвальных шлаков к распаду – структурным превращениям, и возможные виды механической переработки для получения разных видов шлаковой продукции. Приводится технологическая схема переработки отвальных шлаков (применимо и для шлаков текущего выпуска) с извлечением металла и получением широкого спектра шлаковой продукции, включая вяжущие материалы.Physical and mechanical properties of the slag after the initial processing – thermal (thermal shock) and mechanical impact on the melt, the dump slag inclination to disintegration – structural transformations and the possible kinds of mechanical processing to produce different types of slag products were analyzed. Technological scheme of dump slag (it can also be applied to the current release slags) with metal extraction and of slag products wide range, including cementations materials were given

Functional glass-ceramic foams from \u2018inorganic gel casting\u2019 and sintering of glass/slag mixtures

The here described investigation was essentially aimed at exploring the chemical stabilization and reutilization of iron-rich slag from copper metallurgy, by the manufacturing of glass-ceramic foams. The foams were developed according to a new method, recently reported for pure recycled soda-lime glass. Mixtures of soda-lime glass/slag powders (with slag content ranging from 10 to 30\u202fwt%), suspended in alkaline aqueous solution, underwent progressive low temperature (80\u202f\ub0C) hardening, owing to the formation of hydrated calcium silicate compounds (CSH). Before complete setting, an extensive foaming could be achieved by vigorous mechanical stirring, with the help of a surfactant. After foaming, glass/slag mixtures could be sintered at 800\u20131000\u202f\ub0C; the mutual interaction caused an extensive crystallization, with precipitation of CaFe silicates and iron oxides (hematite and magnetite), promoting the mechanical properties (up to 4.4\u202fMPa, with a porosity of about 80%). Leaching test confirmed the stabilization of pollutants, from the slag, in the final ceramics. Owing to the separation of iron oxides, particularly magnetite, the newly obtained foams exhibited a ferrimagnetic behavior, that could be exploited in electromagnetic shielding applications