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Article

Research Progress on Iron- and Steelmaking Iste Slag-Based Glass-Ceramics: Preparation and GHG Emission Reduction Potentials

by
Zichao Wei
1,2,
Xiaomin Liu
3,
Guangwen Hu
3,*,
Kai Xue
1,2 and
Yufeng Wu
3
1
School of Economics and Management, University of Chinese Academy of Sciences, Beijing 100049, China
2
Binzhou Institute of Technology, Weiqiao-UCAS Science and Technology Park, Binzhou 256606, China
3
Institute of Circular Economy, Faculty of Materials and Manufacturing, Beijing University of Technology, Beijing 100124, China
*
Author to whom correspondence should be addressed.
Sustainability 2023, 15(24), 16925; https://doi.org/10.3390/su152416925
Submission received: 6 September 2023 / Revised: 10 November 2023 / Accepted: 23 November 2023 / Published: 18 December 2023
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Abstract

:
Promoted by carbon neutrality and solid iste policies, iron- and steelmaking iste slag (ISWS)-based glass-ceramics have drawn attention because of their contribution to achieving the net-zero carbon emissions goal for the iron- and steelmaking industry. However, a holistic estimation of the preparation, property and GHG (greenhouse gas) emission abatement of ISWS-based glass-ceramics is still under exploration. In this paper, research progress on preparing glass-ceramics from ISWS discharged from the traditional iron- and steelmaking industry is reviewed. Then, the influence of ISWS’s chemical characteristics on the preparation of glass-ceramics and the products’ performance are discussed. In addition, the potential of GHG emission reduction related to the promotion of ISWS-based glass-ceramics is measured. It is found that ISWS-based glass-ceramics can avoid 0.87–0.91 tons of CO2 emissions compared to primary resource routes. A scenario simulation is also conducted. If the technology could be fully applied in the ironmaking and steelmaking industries, the results suggest that 2.07 and 0.67 tons of indirect CO2 reductions can be achieved for each ton of crude steel production from blast furnace–basic oxygen furnace (BF-BOF) and electric arc furnace (EAF) routes, respectively. Finally, a “dual promotion” economic mode based on national policy orientation and the high demands on metallurgical iste slag (MWS)-based glass-ceramics is proposed, and the application prospects of MWS-based glass-ceramics are examined. These application prospects will deepen the fundamental understanding of glass-ceramic properties and enable them to be compounded with other functional materials in various new technologies.

1. Introduction

The iron- and steelmaking industry (ISI) is a typical energy- and resource-intensive industry that is responsible for approximately 7–10% of global energy consumption and GHG emissions and also generates a large amount of industrial solid iste (ISW). Currently, this ISW, which carries a high volume of iste heat, has a very low recycling rate—around 30%. The remaining ISW is usually untreated and discarded, leading to energy iste, land loss, and environmental problems, such as soil and water pollution.
Against the background of carbon neutrality, net-zero carbon emissions not only promote the decarbonization transition of iron- and steelmaking technologies but also invoke the comprehensive utilization (CU) of ISW because of its potential in reducing GHG emissions from the life-cycle perspective by replacing many virgin resources. While previous studies on the CU of ISW have been highlighted during the past decades, most have focused on the performance of the recycled products. However, the CU of ISW is also capable of reducing the life cycle of GHG emissions of the ironmaking and steelmaking processes because its physical and chemical properties satisfy the requirements of many industrial products. In addition, the heat from the high-temperature iste contained within the ISW can save substantial energy needed for production if properly used. This reutilization is expected to compensate for high energy consumption and GHG emissions during the ironmaking and steelmaking processes, especially under circumstances where full-decarbonization technologies for ironmaking and steelmaking are neither economically nor industrially ready for the transition.
According to data released by the World Steel Association, global iron- and steelmaking iste slag (ISWS) emissions in 2021 exceeded 750 million tons. Among these emissions, those of steel slag, BFS, and ferroalloy slag are 304 million tons, 390 million tons, and 60 million tons, respectively. On the other hand, considering the cost restriction for the industry in the short term, energy savings and resource recycling play a very important role for GHG emission reduction from a life-cycle perspective. Thus, if this ISWS can be properly treated, it could result in high level of GHG emission abatement, primary virgin resource replacement, and environmental pollution avoided for the iron- and steelmaking industries.
Currently, there are many technology routes for the CU of ISWS. Considering the huge amount of ISWS generated per year and its physical and chemical properties, it is necessary to design a holistic recycling strategy for it. As one of the most promising recycling options for ISWS, glass-ceramics have a number of outstanding characteristics, such as excellent hardness, acid and alkali resistance, and wear resistance. However, the current industrialized process for preparing glass-ceramics usually requires high-cost chemical ingredients, such as Li2O, B2O3, Al2O3, etc., and high consumption of energy to provide high-melting-temperature conditions. Additionally, the preparation of glass-ceramics is physically and chemically suitable for ISWS CU due to the similarity in oxide compositions (Table 1).
These features suggest the feasibility of GHG emission reduction for the ISI by coupling it with ISWS-based glass-ceramics. While the preparation of ISWS-based glass-ceramics can be found in existing studies, a holistic evaluation of the preparation and properties of ISWS-based glass-ceramics and their potential contribution to GHG emission abatement for the ISI are still under exploration [11,12]. This discourages the industrial-level utilization of ISWS-based glass-ceramics in collaboration with the ISI, because the technology readiness, market acceptance, and contribution to GHG emission reduction are still unclear. To this end, this paper intends to fill the gap between the preparation technologies and potential GHG emission reduction for ISWS-based glass-ceramics against the background of carbon neutrality, so as to provide feasible solutions for the net-zero transition of the ISI.
This paper investigates the research progress of preparing glass-ceramics from ISWS discharged from the ISI and discusses the influence of ISWS chemical characteristics on the preparation of glass-ceramics and the products’ performance. On this basis, the potential of GHG emission reduction related to the promotion of ISWS-based glass-ceramics is estimated under different scenarios.
The significance of this paper includes: First, a holistic evaluation of ISWS-based glass-ceramics preparation technologies is conducted to reveal the technology readiness for industry-scale utilization of ISWS-based glass-ceramics in collaboration with the ISI; second, the impacts of chemical characteristics on the performance of ISWS-based glass-ceramics are analyzed, which helps to diagnose the feasible industrial glass-ceramics products for ISI; third, the GHG emission reduction potentials of ISWS-based glass-ceramics is evaluated, which help to improve the GHG emission reduction contribution and market acceptance of ISWS-based glass-ceramics and provide feasible solutions for the net-zero transition of the ISI.

2. ISWS for the Preparation of Glass-Ceramics

2.1. Blast-Furnace-Slag-Based Glass-Ceramics

BFS is the iste slag discharged from the blast furnace during the smelting process of pig iron. Although the composition of BFS produced in the ironmaking process is complex, its main components are still CaO, Al2O3, MgO, and SiO2. Considering the composition of BFS and the maximum utilization rate of iste slag, BFS is often used as the raw material for the preparation of CMAS-based glass-ceramics (Table 2) [1,13].
For BFS-based glass-ceramics, many studies have reported the crystallization mechanism of nucleating agents and their effects on CMAS-based glass-ceramics [21]. The main reason is the fact that the BFS contains little nucleating agent (such as Cr2O3), resulting in crystal growth limited to low-density interstitials [6]. Therefore, adding a nucleating agent to BFS is an important approach. Cr2O3, Fe2O3, TiO2, etc. are the commonly used nucleating additives for BFS-based glass-ceramics, which are often used to control the crystallization and crystal growth rate of the glass phase [17]. Among them, Cr2O3 is known for its extremely high efficiency in inducing the formation of diopside crystals in CMAS-based glass systems. The reason why Cr2O3 is preferred as a nucleating agent could be divided into two theories: (ⅰ) Cr2O3 is an insoluble oxide that forms an intermediate phase with certain components during heat treatment, resulting in phase separation [6]. (ⅱ) Cr3+ is a high-field ion, occupying the interstitial position, and sorting with the surrounding O2− to form phase separation [22]. As a commonly used nucleating agent, Cr2O3 promoted the precipitation of diopside, the main phase of glass-ceramics, by forming chromium-containing spinel [14].
The content of nucleating agent is considered to be an important factor affecting the crystallization and mechanical strength of BFS-based glass-ceramics. For example, samples with the addition of TiO2 (2 wt%) struggled to achieve bulk crystallization of titanium-containing BFS-based glass and only exhibited two-dimensional crystallization [23]. On the contrary, adding a small amount of Cr2O3 (1.44 wt%) could induce the crystallization of titanium-containing BFS-based glass. The crystal phase in the obtained glass-ceramics is relatively uniform and dense, resulting in a high flexural strength (101.7 MPa) of the sample [13]. The above studies show that adding a certain amount of Cr2O3 could effectively promote crystallization. In addition, the variation of Cr2O3 content would induce the transformation of the crystallization mode of the basic glass, from two-dimensional crystal to three-dimensional crystal, and dendrites are gradually refined [2]. For example, CMAS-Cr2O3 glass-ceramics is prepared with BFS as the main raw material. The research indicates that the content of Cr2O3 significantly affected the crystallization mechanism and microstructure of BFS glass-ceramics. When the content of Cr2O3 is less than 0.5 wt%, the samples exhibit surface crystallization. With the increase in Cr2O3 content (1.0–2.5 wt%), the samples exhibit massive crystals (main crystal phase diopside). When the content of Cr2O3 is greater than 2.5 wt%, the dendrite (diopside) is gradually refined, and the second phase particles (subcrystalline spinel) are precipitated in the glass-ceramics [4]. Another study indicates that the addition of 0.2 wt% Cr2O3 could promote the rapid growth of dendrites in the glass. When the Cr2O3 content increases from 0.2 wt% to 0.8 wt%, the dendrites in BFS-based glass-ceramics gradually decrease, while the granular crystals gradually increase until the dendrites almost become granular crystals (less than 1 μm). When the concentration of Cr2O3 is more than 0.8 wt%, the number of granular crystals gradually decreased, while dendrites gradually accumulated [2]. The conclusions of these two studies are similar, and both indicate that higher Cr2O3 content is beneficial to the accumulation of the host phase diopside. The moderate content of Cr2O3 would disaggregate the network, which is beneficial to the formation of finer crystals, resulting in a higher flexural strength and Vickers hardness for the glass-ceramics.
The above studies mainly expound the influence of single nucleating agent on the system. There are also some studies on the effect of composite nucleating agents on system crystallization, and it is considered that composite nucleating agents could significantly accelerate the crystallization behavior of glass [24]. These accelerated crystallization behaviors are mainly reflected in the influence on the activation energy and crystal growth index. For example, the use of composite nucleating agents CaF2 and TiO2 could reduce the activation energy of CMAS-based glass-ceramics to 392.2 kJ/mol and accelerate the crystallization rate. The synergistic effect of the composite nucleating agents CaF2 and P2O5 could increase the crystal growth index n to 3.07, making the system exhibit overall crystallization behavior [25]. It should be pointed out that in the process of optimizing the preparation of BFS-based glass-ceramics, the composite nucleating agent (such as Cr2O3/TiO2) could affect many aspects of glass-ceramics, such as the crystal structure, grain size, crystal distribution, etc., but would not change the crystalline type of glass-ceramics [26].
The above research indicates that the addition of crystal nucleating agent improved the crystallization ability of BFS-based glass-ceramics to a certain extent. The addition of crystal nucleating agent would also lead to variation in the crystallization mechanism and mechanical properties of glass-ceramics. Cr2O3 is considered as a suitable nucleating agent for CMAS-based glass-ceramics, and the addition of composite nucleating agents could significantly accelerate the crystallization behavior of this glass system.

2.2. Steel-Slag-Based Glass-Ceramics

The f-CaO in steel slag is prone to volume expansion during hydration, resulting in product cracking, which seriously restricts its application in traditional industries (such as cement) [27]. In contrast, in the process of preparing glass-ceramics with steel slag as raw material, this f-CaO limitation could be overcome by acting as a fixed component of glass-ceramics. In addition, since the steel slag contains Cr2O3, Fe2O3, and/or CaF2 components with nucleation functions, adding additional nucleating agents during the preparation of steel-slag-based glass-ceramics could be avoided.
Similar to BFS, the CMAS system is also chosen to apply in steel-slag-based glass-ceramics (Table 3). In addition, the presence of a Cr component in the form of Cr3+ and Cr6+, especially the highly toxic Cr6+ which is easily soluble in water, causes steel slag to pose a great threat to the environment and human body [6]. Therefore, many reports focus on the solidification of Cr in steel slag by glass-ceramics. Wet reduction methods, ferroalloy recovery methods, and glass-ceramic solidification methods have been developed for Cr detoxification [28]. In particular, the glass-ceramic solidification method attracts much attention due to its ultra-high detoxification efficiency. For example, chromium-containing stainless steel slag is used as a raw material to prepare glass-ceramics with excellent properties by the melting method, in which the heavy metal element Cr is well solidified in the crystal lattice. The study indicates that the Cr-containing crystalline phase grew inward from the surface of the sample until the fine-grained crystals were uniformly distributed inside the sample. The crystallinity of glass-ceramics increases with the stainless steel slag, that is, Cr is better solidified with the increase in crystallinity [22]. Another study expresses a similar viewpoint, indicating that the heavy metal Cr is not only incorporated into the spinel lattice but also encapsulated by pyroxene. This is basically consistent with the nucleation mechanism of Cr2O3, that is, the heavy metal Cr in the glass sample reacts with MgO and FeO to form spinel, which provides heterogeneous nucleation sites for the growth of the pyroxene phase [6].
In addition, considering the high CaO content (34.93–49.73 wt%) in steel slag, the doping method is commonly used to obtain high-performance steel-slag-based glass-ceramics. Solid iste such as iste glass, tailings, and other analytical reagents (such as SiO2, CaO, Al2O3, Na2CO3) are the commonly used dopants to reduce or dilute the concentration of CaO in steel slag. Meanwhile, a large amount of CaO improves the melting efficiency and melt fluidity of the iste slag, which is beneficial to the casting of liquid glass. However, an extremely high CaO concentration would affect the melt viscosity, crystallization, and sintering temperature. There are many cases involving a doping method. For example, SiO2, Al2O3, and Na2CO3 are utilized as dopants of stainless steel slag to prepare stainless-steel-slag-based glass-ceramics with extremely high strength and hardness by a casting method. The flexural strength of the resultant sample is as high as 137.83 MPa, which exceeded that of other MWS-based glass-ceramics and natural stone (7–15 MPa) [20]. The Mohs hardness of the obtained sample is 7, which is also higher than that of natural marble (3–5) and granite (5.5). The good mechanical properties are attributed to the presence of a large number of interwoven grains and high-strength diopside crystal phases in the samples prepared after doping. The corrosion resistance test results (K < 0.1%) indicate that the sample has higher acid and alkali resistance than the samples containing akermanite and gehlenite crystal phases. In addition to using the doping method to reduce the influence of high CaO content in the steel slag on the preparation of glass-ceramics, the method of leaching calcium ions from the steel slag could also be used with ammonium salts. This involves the reaction of Ca2+ and CO2 in the steel slag to form high-purity calcium carbonate (PCC) precipitation to reduce the concentration of Ca2+. Carbothermal reduction is further used to extract iron from ammonia-dipped steel slag, and the reduced slag is used to prepare high-value-added CMAS-based glass-ceramics [31]. The study indicates that the crystallization activation energy E of the obtained samples is as high as 660.664 kJ/mol, and the Avrami indices calculated under different heating rates are all less than 3, indicating that the crystallization mode of the glass involved surface crystallization. It should be mentioned that the crystallization activation energy E reflected the crystallization ability of the glass to a certain extent, and the higher crystallization activation energy of this sample indicated the lower crystallization ability of basic glass. It is worth mentioning that it is necessary to add SiO2 and Al2O3 auxiliary reagents in the reduced slag during the preparation of glass-ceramics to obtain suitable basic glass compositions [34].
In addition to reducing the CaO content in the steel slag, component ratio regulation, new processes, and the introduction of crystal nucleating agents are also several important ways to obtain high-performance steel-slag-based glass-ceramics. In the case of preparing CMAS-based glass-ceramics with stainless steel slag as the main raw material, the effect of SiO2/MgO ratio on the crystallization behavior, structure, and properties of stainless-steel-slag-based glass is studied. It is worth mentioning that, similar to Ca2+, the Mg2+ ions acted as a glass network modifying ions to disrupt the [Si-O] network and generate NBO groups [35], resulting in enhanced particle motion and reduced glass viscosity. The research indicated that with the decrease in SiO2/MgO ratio, the crystallization activation energy of the sample decreased and the crystallization index increased. The crystallization activation energy E reflected the crystallization ability of the system glass to a certain extent. That is, a reduced crystallization activation energy meant an enhanced crystallization ability of the glass system [31]. When the SiO2/MgO ratio is adjusted from 7.57 to 4.45, the flexural strength increases from 102.01 to 176.21 MPa [4]. In addition to improving the performance of glass-ceramics by adjusting the ratio of raw material components, high-performance products could also be obtained by developing new processes. Different from conventional sintering methods, the spark plasma sintering (SPS) method is a method that relies on pulsed direct current (DC) and pressure to intensify sintering and has the advantages of short sintering time, fast cooling rate, and controllable pressure [36]. The microstructural transformation study of stainless-steel-slag-based CAMS glass-ceramics prepared by SPS indicated that under pressure, diopside grew directionally and exhibited a crystal size gradient, which made the hardness of the sample as high as 16.3 GPa. Gaussian calculations and Raman shift results indicated that the increase in sintering temperature is beneficial to obtain stable highly polymerized groups (Q2 and Q3), resulting in the formation of a uniform glass network and samples with good mechanical properties. In addition to the above methods, the introduction of crystal nucleating agents is another effective method to improve the performance of slag-based glass-ceramics. Especially when fluorides are introduced to prepare glass-ceramics containing cuspidine crystal phase, the resultant samples often exhibit attractive mechanical properties. A typical example is the preparation of glass-ceramics with high flexural strength by introducing Na2SiF6. The influence of fluorine content (0–6 wt%) on the structure and properties of steel-slag-based glass-ceramics has been studied. The research indicated that the main crystal phases of the obtained glass-ceramics are nepheline and cuspidine, the flexural strength is as high as 177.76 MPa, and the volume shrinkage rate is only 0.06%. The high flexural strength of the samples is attributed to the variation in crystal form and degree of crystallinity, especially the size of the crystal phase. The amount of fluoride is considered to be a key factor affecting the number of nuclei. The reason is that the formation of fluoride required the consumption of Ca2+ and F−, resulting in the increase in bridging oxygen and DOP in the glass structure. When Ca2+ is consumed, excess F− and [Si2O7]6− would inhibit the increase in non-bridging oxygen and the decrease in DOP in the glass structure. It is worth mentioning that Na2SiF6 is generally used instead of CaF2 to avoid the increase in CaO content in the slag [5].
In a word, the high CaO content and trace Cr element in steel slag have brought about many restrictions to the resource utilization of steel slag. The addition of exogenous iste residues or reagents to dilute CaO is a common way to prepare steel-slag-based glass-ceramics. Product performance could be optimized through component ratio control and the addition of special reagents. In the future, it will be necessary to develop more new processes similar to the spark plasma sintering (SPS) method to obtain products containing special crystal phases (such as cuspidine) and having excellent properties.

2.3. Ferroalloy-Slag-Based Glass-Ceramics

According to ferroalloy varieties, ferroalloy slag includes Mn-Fe slag, silicon manganese slag, Fe-Cr slag, nickel ferrous slag, and so on. Among them, the yield of Mn-Fe slag is much higher than that of other ferroalloy slag [37]. This is related to the poor manganese characteristics of manganese ore resources in our country, and the overall grade of manganese ore resources is about 10% lower than the world average [7].
Compared with BFS and steel slag, there are few studies on the preparation of glass-ceramics from ferroalloy slag. In addition to the limited slag inventory, there are some other possible reasons, such as high content of CaO in ferroalloy slag and some substances with high melting points (e.g., spinel, 1857 °C, Fe-Cr, 2135 °C). The application status of different kinds of ferroalloy slag on glass-ceramics is analyzed as follows.

2.3.1. Mn-Fe-Slag-Based Glass-Ceramics

Mn-Fe slag is a kind of slag with very high CaO content (>40 wt%). The high CaO content of Mn-Fe slag is believed to be related to the smelting process of Mn-Fe alloy, in which a large amount of CaO is added to adjust the ratio of CaO/SiO2 (1.3~1.5) [29]. Although this process improved the smelting efficiency of Mn-Fe alloys, it also led to an increase in CaO content in Mn-Fe slag.
More than 70 wt% Mn-Fe slag is currently used to synthesize high-calcium CMAS-based glass-ceramics [8]. However, the CMAS system has a high limit on the CaO composition, and samples with a CaO content below 20% are favorable for the crystallization of diopside in the system. That is, in the absence of additives or pretreatment, the maximum utilization rate of Si-Mn slag in the CMAS system is only 50% [8]. In addition to affecting the utilization rate, extremely high CaO content also has a negative impact on the crystallization of the system, which would easily lead to rapid crystallization of the system and affect sintering.
In order to solve these problems, adding SiO2 and Al2O3 reagents to increase the ratio of SiO2/CaO is an important way to prepare Mn-Fe-slag-based glass-ceramics in CMAS systems. This approach could increase the utilization rate of Mn-Fe slag to 70wt%. In addition, the low SiO2/CaO ratio tended to promote an increase in the content of oligomeric silica tetrahedra in the glass mesh (such as chevron-shaped akermanite), which led to rapid crystallization of the melt during cooling. Conversely, with the increase in the SiO2/CaO ratio, the anionic groups in the glass change from a low degree of polymerization to a dendritic diopside–wollastonite with a high degree of polymerization, resulting in an increase in crystal uniformity [19].
Another study also solved the problem of rapid crystallization of high-calcium Mn-Fe slag by adding Al2O3 to Mn-Fe slag [7]. The main crystal phase of the obtained glass-ceramic samples is akermanite. With the increase in Al2O3, the crystal phase varied from akermanite to gehlenite, and the content of diopside in the secondary crystal phase increased gradually. The reason is speculated to be that the increase in Al2O3 content not only reduced the non-bridging oxygen (Onb) radicals but also formed more [AlO4] to participate in the formation of the glass network [38]. The study also indicated that akermanite and gehlenite crystallized more easily than wollastonite and diopside under high-calcium conditions. It should be mentioned that akermanite is an oligomeric silicate network, resulting in samples with flexural strengths as low as 67 MPa.
In general, CaO-rich Mn-Fe slag is suitable for use as high-calcium-type CMAS-based glass-ceramics, in which the main existing forms of the silicon–oxygen tetrahedron (Qn) are Q0 and Q1. Adding SiO2 and Al2O3 reagents is beneficial to increase the polymerization degree of Qn and obtain more stable glass. The increase in Qn polymerization degree easily led to the variation of the main crystal phase of glass-ceramics, from akermanite to diopside–wollastonite [8].

2.3.2. Si-Mn-Slag-Based Glass-Ceramics

Si-Mn slag is an industrial by-product formed in the process of producing Si-Mn alloy by the carbothermic reduction method and has the characteristics of high manganese content. Traditionally, Si-Mn slag is often utilized as a dopant for high-value-added products such as mineral wool, glass-ceramics, permeable bricks, cement, and concrete [10].
In recent years, some new functional elements in Si-Mn slag have been developed to exert greater value, such as Mn, which is beneficial to improve the luminescence properties and crystalline properties of glass-ceramics. For example, color-controlled transmatrix glass-ceramics based on Mn-doped CaF2 are prepared by a traditional high-temperature smelting method using Si-Mn slag as raw material. In general, tetrahedral-coordinated Mn2+ acted as a green luminescent center, while octahedral-coordinated Mn2+ exhibited orange to red luminescence [39]. The different luminescence properties of manganese ions in the material are closely related to the nanocrystals formed in the material. The results indicated that the intensity of the emission peak also increased and shifted to longer wavelengths as the content of Si-Mn slag increased, which is attributed to the increased probability of cross-relaxation between Si and Mn. This work provided a new method for comprehensive utilization of Si-Mn slag [9].
In addition, Mn2+ in Si-Mn slag is considered to have the effect of strengthening glass crystallization during heat treatment. For example, bustamite–diopside–anorthite glass-ceramics are prepared from Saudi Si-Mn slag by a melt-casting process. It is speculated that Mn2+ in Si-Mn slag is an important factor to promote the crystallization of Si-Mn-slag-based vitreous phase. The reason is that the manganese coordination may change from an Onb-consuming tetrahedron to Onb-supplying octahedron, resulting in reduced polymerization degree and enhanced crystallinity of the system [7]. In addition, in these typical multiphase glass-ceramics, the interface energy between glass phases is considered to be lower than the interface energy between glass phase and crystal phase, thereby reducing the barrier of nucleation and promoting the devitrification behavior of the system.
In conclusion, the luminescent properties of Mn2+ and its promoting effect on the crystallization properties of glass bring more opportunities for the high-value utilization of Si-Mn slag. Its luminescence mechanism is similar to that of rare earth ions, that is, the transition metal ion Mn2+ lacked the outermost electron shielding, resulting in a small change in the field strength, which led to a significant change in its luminescence properties [40]. From this point of view, Si-Mn slag has a great research potential in providing luminescent centers and color control factors of optically trans-basic glass-ceramics in the future.

2.3.3. Fe-Cr-Slag-Based Glass-Ceramics

Fe-Cr slag is the iste slag produced in the process of smelting Fe-Cr alloy with carbon as a reducing agent. At present, the recycling of Fe-Cr slag is mainly based on the recovery of alloys and chromium concentrates in the slag, and the remaining residues are used for the production of refractory materials, concrete, colored cast stones, and building materials. In contrast, there are few studies on the preparation of glass-ceramics from Fe-Cr slag. The reason may be related to the fact that Fe-Cr slag contains many high-melting-point substances, such as spinel (melting point, 1857 °C), iron–chromium alloy (melting point, 2135 °C), and so on [11]. Although these high-melting-point substances could act as nucleating agents and reduce the addition of external nucleating agents, they would also lead to problems such as high melting point and high viscosity of basic glass.
In the existing research, the Fe-Cr-slag-based glass-ceramics are generally prepared by theoretical calculation coupled with the addition of auxiliary reagents. For example, CMASN-based glass-ceramics with pyroxene and nepheline as the main crystal phases are prepared by using Fe-Cr slag and iste glass as the main raw materials and fluorite as the flux. In order to determine the slag ratio range, phase diagrams corresponding to different ratios are calculated by FactSage 7.3 software. The research indicated that both the theoretical calculation and the addition of CaF2 are beneficial to reduce the melting temperature of the glass, which largely alleviated the problem of high viscosity caused by high-melting-point substances in the Fe-Cr slag [11]. Note that a wide range of applicable material ratios could be obtained by calculation, which is beneficial to maximize the utilization rate of Fe-Cr slag. In addition to adding flux, TiO2 could also be added to form a TiO2-Cr2O3 composite nucleating agent with Cr2O3 in Fe-Cr slag to reduce the glass transition temperature and crystallization temperature. TiO2 is considered to be an effective crystal nucleating agent for glass-ceramics, which is related to the existence of [TiO4] four-coordination and [TiO6] six-coordination forms of TiO2 [41]. In the molten state at high temperature, the [TiO4] tetrahedron is quite different from the [SiO4] structure in the glass network, which led to the difficulty of complete mixing and the appearance of more and more phase interfaces. In this case, the presence of [TiO4] tetrahedra is favorable for phase separation and heterogeneous nucleation. At the same time, Cr2O3 in the Fe-Cr slag precipitated in the form of titanium spinel and chromium spinel nuclei, respectively, during the cooling process of the melt, which provided a non-uniform nucleation interface for the further nucleation of the basic glass. That is, the presence of Cr2O3 is beneficial to reduce the nucleation barrier. In other words, the composite nucleating agent reduced the nucleation temperature of the system, resulting in high-performance Fe-Cr-slag-based glass-ceramics at a low energy consumption.

2.3.4. Ni-Fe-Slag-Based Glass-Ceramics

The Ni-Fe slag contains a large amount of SiO2, MgO, and CaO components, and lacks the Al2O3 component required by the CMAS system. Therefore, Ni-Fe-slag-based glass-ceramics could be obtained by formula design and the addition of AI2O3-based auxiliary reagents. For example, CMAS-based glass-ceramics are prepared by using Ni-Fe slag as raw material and fly ash with high Al2O3 content as a doping reagent [42]. With the increase in Ni-Fe slag content from 40% to 55%, the increased Mg2+ and Ca2+ content in glass led to the increase in anorthite and enstatite crystal phase content in glass-ceramics. Although the increase in Ni-Fe slag content had little effect on the nucleation temperature and crystallization temperature of glass-ceramics, it significantly increased the flexural strength of glass-ceramics from 66 MPa to 87 MPa. In another study, the composition and properties of Ni-Fe-slag-based glass-ceramics are optimized by adding Al2O3-containing BFS and MgO auxiliary materials to Ni-Fe slag at the same time [3]. The research indicated that when the content of the two mixed slags reached 90% and also 2wt% of MgO is added, the obtained glass-ceramic structure is dense and only contained minerals of the pyroxene family (including diopside, ordinary pyroxene, and clinoptiloxene). It is worth noting that the slag crystallization temperature needed to be controlled at 900 °C and annealed at 650 °C. At this time, the glass-ceramics exhibited excellent mechanical properties, with flexural and compressive strengths as high as 210 MPa and 1162 MPa, respectively. However, if the content of Ni-Fe slag or MgO is further increased, the forsterite crystal phase would precipitate and the mechanical properties of glass-ceramics would also be significantly reduced.
In summary, a large number of studies on MWS-based glass-ceramics in the iron and steel industry have been developed, especially the CMAS system. Various schemes are adopted to promote the crystallization of MWS-based glass-ceramics and reduce the influence of slag basicity on sample preparation. All these works make a positive contribution to the maximum utilization of MWS.

3. Characteristics of ISWS for Preparing Glass-Ceramics

It is noticed that the basicity of ISWS may affect the preparation of glass-ceramics, which as a result influences the performance of the end product. Considering the industrial process of iron- and steelmaking, this paper will analyze if the inherent characteristics of ISWS will have influences on the preparation of glass-ceramics.
During the preparation of ISWS-based glass-ceramics, the influence of alkalinity is mostly associated with melt viscosity, crystallization, crystallization temperature, and other factors of basic glass, which lead to the variation in the mechanical properties of the end products.

3.1. Melt Viscosity

Studies have revealed that the increase in alkalinity will decrease the melt viscosity [19], while the melt viscosity is the key controller for pelletizing behavior [43]. The variation in melt viscosity is attributed to the conversion of melt network structure. Samples containing a large amount of CaO generally showed lower viscosity in the molten state, making the pelletizing process smoother. In contrast, silica-rich iste residue increased the viscosity of the system due to the polymerization of the silicate component, which is not conducive to granulation. That is, the influence of alkalinity on the viscous activation energy is related to the Ca2+ ion concentration [44]. At low concentrations, Ca2+ ions with high ionic field strength participated in the destruction of network structure, resulting in a decrease in the viscous activation energy. At high concentrations, Ca2+ ions led to an increase in activation energy by causing the aggregation of network building blocks. That is, as the alkalinity increased, the viscous activation energy first decreased and then increased.

3.2. Crystallization

Studies have indicated that high alkalinity would lead to a decrease in the stability and an increase in the crystallization ability of basic glass [45]. The possible reason is that the high alkalinity promotes the diffusion rate of ions, resulting in the variation of interphase tension. In the system, as the content of modified oxides (such as Ca2+, Mg2+) increased and the content of glass-forming oxides (SiO2 and Al2O3) decreased, the degree of polymerization of basic glass network decreased and the crystallization capacity increased. That is, the amount of non-bridging oxygen in the glass mesh increased and the amount of bridging oxygen decreased, and the precrystallized ions needed to overcome less energy to complete the crystallization process [30].
It is suggested that these phases with high concentrations of Ca2+ and Mg2+ cations acted as heterogeneous nucleation sites. The strong tendency for phase separation promoted a reduced nucleation barrier and crystallization activation energy, leading to an increased probability of crystallization [4]. This is confirmed by the enhanced XRD peak intensity and newly added unknown crystal phase peaks of the steel slag low-temperature-sintered samples [35]. In addition, thermal analysis testing is also used to demonstrate that glass crystallization ability increases with increasing alkalinity. It is considered that the alkaline oxide CaO could destroy the network structure of silicate glass, resulting in a shift of the exothermic peak of the thermal analysis curve to a low temperature and a decrease in the glass viscosity. The crystallinity of basic glass is further demonstrated to increase with increasing alkalinity through a decrease in the intensity of the amorphous peak [46]. It is worth mentioning that high alkalinity is believed to facilitate the three-dimensional crystallization of basic glass [30].

3.3. Crystallization Temperature and other Properties

In a CBS glass system, the sintering temperature of glass-ceramics decreased with the increase in alkalinity [47]. Additionally, during the study of the influence of composition on sinter crystallization and properties, it is found that the glass transition temperature Tg and crystallization peak temperature Tp increased with decreasing alkalinity. It is considered that the low alkalinity facilitated the formation of a tight network structure in the glass matrix, making it difficult for the components to diffuse massively and rapidly at the crystallization temperature. Therefore, samples with lower alkalinity had higher Tp than that previously [48]. There are also studies holding different conclusions. For example, in the CMAS system glass-ceramics prepared from BFS, the crystallization temperature represented an upward trend with the decrease in alkalinity [19]. These opposite variation trends may be attributed to the factors such as raw material components in different systems, viscous activation energy of melts, and so on.
In the glass-ceramics of the quaternary CMAS system, it is considered that the reduction of alkalinity is beneficial to increase the flexural strength of glass-ceramics. The reason may be that the decrease in alkalinity led to a decrease in the amount of non-bridging oxygen and an increase in the degree of polymerization of the glass network, resulting in an increase in the flexural strength of the sample structure. Another study suggested that silicon slag with higher alkalinity is beneficial to obtain samples with more dense and uniform microstructure [46]. High-alkalinity steel slag is beneficial to obtain glass-ceramic samples with higher Vickers hardness and flexural strength, because a high-alkalinity sample is conducive to the precipitation of nepheline crystal phase with high mechanical strength. Low-alkalinity samples could promote the densification process by extending the sintering time and delaying crystallization, thereby increasing the mechanical strength of glass-ceramic samples [48].

4. Corrosion Resistance Analysis of ISWS-Based Glass-Ceramics

Corrosion resistance is an important characteristic of glass-ceramics, and the analysis of corrosion resistance increases the guarantee for the application of ISWS-based glass-ceramics. Studies have indicated that corrosion generally occurred in the ion exchange stage of H+ in acid solution and metal ions (such as K+, Na+, Ca2+, Mg2+) in the glass phase [4]. In contrast, the crystalline phase in glass-ceramics remained unchanged throughout the etching process. The reason is that H+ with a smaller radius is more likely to exchange with the metal ions on the surface of the glass phase, which led to the weakening of the surface stress between the crystalline phase and the glass phase, resulting in cracks in the sample. On the other hand, the glass phase and the crystal phase had different thermal expansion coefficients, which led to cracks at the glass–crystal interface [49]. Under acidic conditions, these cracks are easily attacked by H+, leading to corrosion. Generally, the mass loss of glass-ceramic samples would not exceed 1.5% in alkaline solution (NaOH) and 8% in acidic (HNO3) solution [18].
Based on the high-field-strength properties, doping of rare earth ions is considered as a channel to improve the corrosion resistance of glass-ceramic samples [50]. In addition to doping with rare earth ions, increasing crystallinity had also been demonstrated to play an important role in the corrosion resistance of glass-ceramics [44]. As the crystallinity increased, the metal ions were more easily distributed in the crystalline phase. As the content of metal ions in the glass phase decreased, its resistance to acidity increased [51]. That is, glass-ceramics with a higher degree of crystallinity (such as bulk crystallization) meant stronger corrosion resistance. Multiple experimental cases showing that Cr2O3-rich glass-ceramic samples had excellent corrosion resistance also fully verify this conclusion.

5. Sensible Heat Utilization in ISWS-Based Glass-Ceramics

According to Dai’s estimation [52], the utilization of iste heat (1400–1650 °C) of hot ISWS has great potential for the low-carbon and green development of the iron- and steelmaking industry. The traditional technologies for ISWS iste heat recovery and utilization include water quenching, physical recovery, and chemical recovery. Water quenching is a typical hot-slag-processing technology, which obtains glassy by-products through water cooling. This technology has the disadvantages of large water consumption and difficult iste heat recovery [53]. The recovery of iste heat after pelletizing or crushing the hot slag into pieces is a common physical treatment method, with a heat recovery efficiency of 40–60%. Part of the hot slag is also applied as a heat carrier and a catalyst for high-temperature reaction, and its heat recovery efficiency could reach 95% [52]. The above studies had their own advantages in iste heat recovery, but they also had the disadvantages of low efficiency and process discontinuity in dealing with the iste heat utilization of large-scale hot slag.
Compared with traditional iste heat utilization technologies, on-site thermal modification of hot slag or in situ comprehensive utilization technology to prepare high-value products has become a new trend in iste heat utilization. These technologies mostly focus on the modification of the furnace or the composition of slags so as to reduce the iste heat generated during the previous ironmaking process and maintain the performance of the targeted products. Dai et al. [52] developed a novel modifying furnace, consisting of a cyclone furnace (CFu) and modifying chamber (MCh), with which structure the hot ISWS can be transformed efficiently into glass-ceramics, while the iste heat is collected and utilized. Thermal modification is also an effective way to change the mineral composition of steel slag to improve the comprehensive utilization rate, and it is beneficial to improve the iron recovery rate by changing the structure of iron minerals [27]. For example, in situ modification of hot slag by adding silica to induce the formation of anorthite has been investigated to obtain a stable structure that can inhibit the leaching of heavy metals (such as Ba, V, Cr) [12].
On the other hand, the direct emission of sensible heat in hot slag could easily have a serious negative impact on the environment, especially the toxic or corrosive gases generated at high temperature, such as CO, CO2, SO2, NO2, and so on [54,55]. Through iste heat recovery and reuse methods, the pollution problems caused by exhaust emissions could be greatly alleviated. This can not only reduce the serious corrosion and even damage to the equipment caused by the high-temperature gas but also avoid the emission of these harmful gases into the atmosphere.

6. Potentials of GHG Emission Reduction for ISWS-Based Glass-Ceramics

Based on the previous study, this section intends to measure the carbon reduction effect of ISWS-based glass-ceramics and assess its contribution to the achievement of carbon neutrality in the iron- and steelmaking industry.
The evaluation is conducted under the framework in Figure 1.
The framework consists of two parts: Abatement effects and industrialized scale. The former indicates the GHG emission reduction effects of ISWS-based glass-ceramics at the technology level, and the latter indicates the industrialized scale forecast of the ISWS-based glass-ceramics technology.
(1)
Abatement effects
This part is evaluated by comparing the GHG emissions from the technical routes of the ISWS-based glass-ceramics and traditional glass-ceramics. Based on the standards of carbon emission accounting, the GHG emissions of the two technical routes are calculated focusing on Scale I and Scale II in this paper, and the data are obtained from the environmental evaluation reports of certain glass-ceramics factories in China.
(2)
Industrialized Scale
This part is to simulate the industrial GHG emission reduction potentials of the ISWS-based glass-ceramics if industrialized at certain levels using the scenario simulation methods.

6.1. GHG Emissions from Glass-Ceramic Production

(1)
Primary resource route
The primary resource route for producing glass-ceramics is illustrated in Figure 2.
According to the accounting standard of carbon emissions, the GHG emissions for the whole route are calculated based on Scale I (direct energy consumption, mostly natural gas consumption in this case) and Scale II (mostly electricity in this case). The production data are obtained from a glass-ceramic factory in Changshu, China.
(2)
ISWS-based route
The ISWS-based route for producing glass-ceramics is illustrated as Figure 3 and Figure 4. As illustrated, the ISWS-based route is distinguished as BFS and steel slag routes considering the different slags produced during ironmaking and steelmaking processes.
According to the accounting standard of carbon emissions, the GHG emissions for the whole route are calculated based on Scale I (direct energy consumption, mostly natural gas consumption in this case) and Scale II (mostly electricity in this case).

6.2. Future Scenario Settings of Ironmaking and Steelmaking

This section focuses on the future scenario of ironmaking and steelmaking development, which will determine the industrialized scale of ISWS-based glass-ceramics. Two aspects are considered here:
First is the GHG emission reduction contribution of the ISWS-based glass-ceramic route for the ironmaking and steelmaking processes; second is the policy development and technology innovation that will also promote and reshape the whole industry, which in turn influence the overall GHG emission reduction of the ISWS-based glass-ceramics.
The current production structure in ironmaking and steelmaking industries is mostly dominated by the BF-BOF route and EAF route. Thus, it is necessary to evaluate the GHG emission reduction potentials for each ironmaking and steelmaking route if the ISWS-based glass-ceramics are introduced into each process.
(1)
BF-BOF route
The BF-BOF route refers to a comprehensive process consists of ironmaking and steelmaking, in which the blast furnace (BF) mostly concentrates on the ironmaking process, and the basic oxygen furnace (BOF) is mostly responsible for the steelmaking process (see Figure 5). Thus, the ISWS generated during this route consists of BFS and steel slag.
(2)
EAF route
The EAF route refers to electric arc furnace steelmaking, of which the process focuses on using steel scrap to produce crude steel (see Figure 6). Different from BF-BOF that uses iron ore to produce pig iron then the crude steel, EAF only contains the steelmaking processes, thus the ISWS generated from this route only consists of steel slag.

6.3. Potentials of GHG Emission Reduction for ISWS-Based Glass-Ceramics

Based on the method mentioned above, the GHG emissions generated for different routes of glass-ceramics are illustrated in Table 4.
According to the calculation, the overall GHG emissions generated from the primary resource route of glass-ceramics is around 907.70 kg CO2. This is obviously higher than that of both the ISWS-based glass-ceramics, which is 33.51 kg CO2 and 2.67 kg CO2, respectively. It reveals the huge potentials of GHG emission reduction for ISWS-based glass-ceramics if they are applied in ironmaking and steelmaking industries. In addition, the production of ISWS-based glass-ceramics also has the potential to consume the iron- and steelmaking solid istes, which generates environmental benefits.
As for the ISWS routes for glass-ceramic production, it is noticed that the BFS-based route has more carbon emissions produced per ton of glass-ceramics compared to that of the steel-slag-based route, which indicates that the steel-slag-based route is more environmentally efficient. However, as steel slag is only generated in steelmaking processes, the application of this route requires further discussion.

6.4. Scenario Simulation

Based on the calculation above, we conduct a multiscenario simulation in which different levela of technology application are considered. Five scenarios are simulated in this analysis with the ISWS-based glass-ceramic technology application scale varying from 0% to 100% so as to reveal the technology’s potential in reducing the overall GHG emissions from the ironmaking and steelmaking industries.
In every scenario, the two ironmaking and steelmaking routes are considered, and the GHG emissions for each are composed of the direct carbon emissions from the ironmaking and steelmaking process, along with the production of glass-ceramics. Assumptions for this scenario simulation also includes:
(1)
From the macro level, the glass-ceramics are assumed to have the same quality regardless of their production routes;
(2)
The differences between scenarios for each technology route are only attributed to the application scale of the technology.
The slags produced in each period (ironmaking and steelmaking period, respectively) are all used for glass-ceramics (BFS for BFS route, steel slags for steel slag route) in the 100% application level scenario. Equally, the same amount of glass-ceramics are produced using primary resources in the 0% application level. As for the rest of the levels, the ratios for both slags are changed evenly.
Scenario simulation results are displayed in Figure 7.
As illustrated, the application of ISWS-based glass-ceramics has obvious potential to reduce overall GHG emissions by redesigning the whole industrial chain.
For the BF-BOF route, both BFS and steel slag routes for glass-ceramics are considered. The results reveal that when the application scale approaches 25%, 50%, 75%, and 100%, the indirect GHG emission reduction potentials will reach 0.52, 1.03, 1.54, and 2.07 tons of CO2e per ton of crude steel production plus the associated glass-ceramics (2.35 tons).
For the EAF route, the emissions related to electricity consumption for the furnace are also considered. The results suggest that when the application scale approaches 25%, 50%, 75%, and 100%, the indirect GHG emission reduction potentials will reach 0.17, 0.34, 0.50, and 0.67 tons of CO2e per ton of crude steel production the associated glass-ceramics (0.75 tons).
It is obvious that the increase in application scale will cause overall GHG emission reduction for the industries as a whole. While the assumption that the market demand for glass-ceramics is unlimited in this scenario simulation is too ideal, this reveals the trends and potentials for the ISWS-based glass-ceramics.
In addition, the iste heat carried in the ISWS is not included in the scenario simulation, therefore the estimation of the potentials is underestimated because the direct consumption of natural gas for heating in the preparation of glass-ceramics is reduced, which resulted in the reduction of GHG emissions for the production of glass-ceramics. In the future scenario, in which the electricity decarbonization and efficiency improvements are considered, the GHG emission reduction potentials will be further expanded, especially when the EAF route surpasses the BF-BOF route to dominate the future iron- and steelmaking production.
However, it should also be noticed that the market demand for glass-ceramics is not unlimited, which means that the theoretic estimation of the GHG emission reduction potentials is often overestimated. Furthermore, the product quality between the primary resources and ISWS-based glass-ceramics is still under discussion, which brings uncertainties to the promotion and application of ISWS-based glass-ceramics.

7. Conclusions

This paper investigates the research development progress of ISWS-based glass-ceramics and estimates the contributions in GHG emission reductions for ironmaking and steelmaking industries. The results suggest great utilization potentials for these technologies against the background of carbon neutrality.
  • Based on a comprehensive summary of the types, different ISWS types are discussed from the perspective of glass-ceramic preparation, including blast furnace slag, steel slag, and ferroalloy slag;
  • the inherent characteristics of these slags are analyzed focusing on their impacts on the preparing process of the glass-ceramics, the influence of the alkalinity due to the contents of ISWS on the melt viscosity, crystallization, crystallization temperature, and other properties. The performance of the ISWS-based glass-ceramics is tested according to existing literature;
  • the GHG emission reduction of the ISWS-based glass-ceramics is estimated and calculated, and it is found that the ISWS-based glass-ceramics can avoid 0.87~0.91 tons of CO2 emissions compared to the primary resource routes. The scenario simulation suggests if the technology could be fully applied in association with the ironmaking and steelmaking industries, 2.07 and 0.67 tons of indirect CO2 reductions can be achieved for each ton of crude steel production from BF-BOF and EAF routes, respectively.
It is concluded that ISWS-based ceramics can provide promising utilization options for high-value-added solid iste reutilization products, which can promote environmental protection and resource conservation for industrial solid iste treatment. Despite the inherent physical and chemical characteristics due to the slags’ element content, recent studies have revealed the mechanism of the crystallization of the ISWS-based glass-ceramics and produced expected and market-accepted end products which satisfy the final demands. In addition, the preparation and utilization of the ISWS-based glass-ceramics suggest great potential in GHG emission reduction, which provides a promising improvement option for the ironmaking and steelmaking industries against the background of carbon neutrality.

8. Limitations of This Paper

It should be noticed that, due to the lack of detailed data and full knowledge of the whole industry, we did not discuss all types of ISWS slags and neglect the quality differences of the glass-ceramics, hence the potentials of GHG emission abatement for the whole iron- and steelmaking industry may be over- or underestimated. Meanwhile, the result may also be affected by the consumers‘ willingness to pay, as the competitiveness of recycled products (the ISWS-based glass-ceramics) on the market is an important factor for the application.

Author Contributions

Conceptualization, Y.W. and K.X.; methodology, X.L. and G.H.; validation, Y.W.; formal analysis, Z.W. and X.L.; investigation, Z.W. and X.L.; writing—original draft, Z.W. and X.L.; writing—review and editing, G.H.; supervision, Y.W.; project administration, Z.W. All authors have read and agreed to the published version of the manuscript.

Funding

This work is financially supported by the Fundamental Research Funds for the Central Universities.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The data presented in this study are available on request from the corresponding author.

Acknowledgments

The authors appreciate the suggestions and enthusiastic support of the editors and reviewers.

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 1. Evaluation framework for ISWS based glass-ceramics.
Figure 1. Evaluation framework for ISWS based glass-ceramics.
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Figure 2. Glass-ceramic production route of factory in Changshu, China.
Figure 2. Glass-ceramic production route of factory in Changshu, China.
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Figure 3. ISWS-based glass-ceramic production route (BFS).
Figure 3. ISWS-based glass-ceramic production route (BFS).
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Figure 4. ISWS-based glass-ceramic production route (steel slag).
Figure 4. ISWS-based glass-ceramic production route (steel slag).
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Figure 5. BF-BOF route for ironmaking and steelmaking.
Figure 5. BF-BOF route for ironmaking and steelmaking.
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Figure 6. EAF route for steelmaking.
Figure 6. EAF route for steelmaking.
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Figure 7. GHG emission reduction potentials for two iron- and steelmaking routes. (a) BF-BOF route. (b) EAF route.
Figure 7. GHG emission reduction potentials for two iron- and steelmaking routes. (a) BF-BOF route. (b) EAF route.
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Table 1. Content ranges of chemical components for different ISWS.
Table 1. Content ranges of chemical components for different ISWS.
/SiO2Al2O3CaOMgOTFeMnO2TiO2K2ONa2OCr2O3Refs.
BFS25.59–38.2111.38–15.8836.79–50.746.13–9.960.34–1.480.13–0.90.84–6.710.48–1.750.23–0.740.02[1,2,3]
Steel slag11.4~27.812.7–7.0034.93–49.736.42–12.510.43–30.83.5–3.770.02–0.80–0.560–0.350.2–4.53[4,5,6]
Mn-Fe slag40.77–40.874.46–4.4941.72–41.786.87–6.910.263.99////[7,8]
Si-Mn slag41.5–453.5–9.022.0–43.76.5–22.00.0–0.754.5–12.00–0.22/0–0.12/[9]
Cr-Fe slag28.24–63.943.18–30.61.66–3.37.51–21.82.19–4.40–0.18/0–4.050–4.315.91–8.92[10]
Table 2. Raw materials and sample properties for BFS-based glass-ceramics.
Table 2. Raw materials and sample properties for BFS-based glass-ceramics.
Raw MaterialsSystemMethodHeat Treatment ConditionsMain PhasesBulk Density (g/cm3)Flexural Strength (MPa)Vickers Microhardness (GPa)Refs.
BFS, SiO2, Al2O3, MgO, Na2CO3, Cr2O3CMASCasting method1450 °C 3 h,
600 °C 2 h		Diopside, spinel/123 MPa7.76[14]
BFS, granite tailingsCMASCasting method1550 °C 2 h,
600 °C 0.5 h		Diopside, wollastonite2.92–3.48/8.6 [15]
BFS, SiO2, borax, MgO, Al2O3, Cr2O3CAMSCasting method1500 °C 2 h,
600 °C 3 h		Diopside, spinel2.97196.69/[16]
BFS, SiO2, Cr2O3/Casting method1500 °C 3 h,
600 °C 3 h		Anorthite, diopside, akermanite/94.370.97[2]
BFS, SiO2 MgO, Al2O3, Na2CO3, Cr2O3CMASCasting method1450 °C 18 h,
600 °C 5 h		Diopside, spinel///[17]
BFS, fly ash, glass culletCASSintering method1450 °C 2 h,
957 °C 2 h		Anorthite2.66–2.85/0.63–0.65[18]
BFS, SiO2, CaO, MgO, Al2O3, Cr2O3CMASMelting method1500 °C 1 h,
800 °C 2 h		Diopside, augite, gehlenite2.78182.86 7.34[19]
BFS, chemically pure reagentsCASCasting method1500 °C 1 h,
780 °C 2 h, 880 °C 3 h		Akermanite,
gehlenite, nepheline		/81.31/[20]
Table 3. Raw materials and sample properties of steel-slag-based glass-ceramics.
Table 3. Raw materials and sample properties of steel-slag-based glass-ceramics.
Raw MaterialsSystemMethodHeat Treatment ConditionsMain PhasesBulk Density (g/cm3)Flexural Strength
(MPa)		Vickers Microhardness (GPa)Refs.
SS, Na2CO3, Na2B4O7, etc.CAMSSpark plasma sintering1450 °C 3 h, 700–850 ℃ 3 minDiopside 2.79–2.8367–1349.7–16.3[29]
SS, carbonate, Na2SiF6/Casting method1400 °C 3 h,
550 ℃ 1 h		Nepheline, cuspidine/177.76 MPa/[5]
SS, fly ashCMASCasting method1450 °C 2 h,
922 °C 1 h		////[30]
SS, MgO, SiO2, CaO, Na2CO3CMASMelting method1500 °C 2 h,
600 °C 3 h		Diopside
Anorthite		2.9222.9 7.15[22]
SS, SiO2, powdered coalCMSAMelting method1500 °C 1 h,
800 °C 1 h, 970 °C 1 h		Melilite, diopside///[31]
SS, chemical reagentCMASCasting method1500 °C 3 h, annealing crystallizationAugite, anorthite, wollastonite///[1]
SS, oxides, carbonatesCMASCasting method1000 °C 1 h,
1500 °C 3 h,
600 °C 0.5 h		Wollastonite/145.6/[32]
SS, SiO2, emery powder, CaO, MgO, TiO2/Casting method1350 °C 1 h,
550 °C 2 h		Diopside ///[33]
Table 4. GHG emissions generated from different glass-ceramic routes.
Table 4. GHG emissions generated from different glass-ceramic routes.
RoutesKg CO2 Emissions Per Ton of Glass-CeramicsKg CO2 Emissions Consumed Per Ton of ISWS
Primary resource route907.70-
BFS-based route33.5150.26
Steel-slag-based route2.676.16
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Wei, Z.; Liu, X.; Hu, G.; Xue, K.; Wu, Y. Research Progress on Iron- and Steelmaking Iste Slag-Based Glass-Ceramics: Preparation and GHG Emission Reduction Potentials. Sustainability 2023, 15, 16925. https://doi.org/10.3390/su152416925

AMA Style

Wei Z, Liu X, Hu G, Xue K, Wu Y. Research Progress on Iron- and Steelmaking Iste Slag-Based Glass-Ceramics: Preparation and GHG Emission Reduction Potentials. Sustainability. 2023; 15(24):16925. https://doi.org/10.3390/su152416925

Chicago/Turabian Style

Wei, Zichao, Xiaomin Liu, Guangwen Hu, Kai Xue, and Yufeng Wu. 2023. "Research Progress on Iron- and Steelmaking Iste Slag-Based Glass-Ceramics: Preparation and GHG Emission Reduction Potentials" Sustainability 15, no. 24: 16925. https://doi.org/10.3390/su152416925

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