Analysis and Prospect of Waste Heat Utilization from Blast Furnace Slag Flushing

Estimating the residual heat of blast furnace slag flushing in China,classifying and introducing the current proposed methods of slag flushing waste heat utilization,and listing existing cases.In order to better save energy and water in the slag flushing process of blast furnaces,an ideal comprehensive cascade utilization system scheme for annual recovery of waste heat is proposed.Based on the measured waste heat data of a steel plant,design calculations are carried out to further analyze the economic feasibility of the new scheme and provide reference for its promotion and application.

Prospects of utilization of waste dumped low-grade limestone for iron making: A case study

Low grade dumped limestone sample having high silica of 8.1%, 36.8% CaO, and 3% Al2O3 has been studied with the aim to reduce the silica level to below 3% for its utilization in iron making. Beneficiation study of the sample was initiated with desliming of the feed sample of -100 μm to remove the siliceous ultrafine particles and to improve the feed quality. Flotation study was carried out by column flotation technique varying the collector dosage, superficial air flow velocity and froth depth to assess their effect on silica reduction and CaO recovery. It was observed that increased collector dosage and superficial air velocity increases the recovery of CaO, and increase in the froth depth reduces the mass flow and silica content in the concentrate. The best result was found at 1.25 cm/sec superficial air velocity, 25 cm froth depth, 1.25 kgpt collector dosage and concentrate assayed 47.3% CaO, 2.8% silica with 72% CaO recovery.

Thermal treatment and utilization of Al-rich waste in high calcium fly ash geopolymeric materials

The Al-rich waste with aluminium and hydrocarbon as the major contaminant is generated at the wastewater treatment unit of a polymer processing plant. In this research, the heat treatment of this Al-rich waste and its use to adjust the silica/alumina ratio of the high calcium fly ash geopolymer were studied. To recycle the raw Al-rich waste, the waste was dried at 110℃ and calcined at 400 to 1000℃. Mineralogical analyses were conducted using X-ray diffraction （XRD） to study the phase change. The increase in calcination temperature to 600, 800, and 1000℃ resulted in the phase transformation. The more active alumina phase of active θ-Al2O3 was obtained with the increase in calcination temperature. The calcined Al-rich waste was then used as an additive to the fly ash geopolymer by mixing with high calcium fly ash, water glass, 10 M sodium hydroxide （NaOH）, and sand. Test results indicated that the calcined Al-rich waste could be used as an aluminium source to adjust the silica/alumina ratio and the strength of geopolymeric materials. The fly ash geopolymer mortar with 2.5wt% of the Al-rich waste calcined at 1000℃ possessed the 7-d compressive strength of 34.2 MPa.

Pathways for Sustainable Utilization of Waste Chicken Eggshell

Chicken eggshell is one of the most common wastes generated from households,restaurants and other food processing outlets.Waste Chicken Eggshells(WCES)also constitutes an environmental nuisance and ends up discarded at dumping site with no consideration of further usage.The main constituent of WCES is calcium carbonate from which calcium or calcium oxide can be extracted for various applications.This current effort reviews recently published literature on the diverse applications of WCES.The considered utilization avenues include catalysts for biofuel production,construction industry,wastewater purification,industrial sector,food industry,medical,and agricultural applications.The specific areas of application apart from the transesterification reactions include cement additives and replacement in concrete,asphalt binder,adsorbent of metals and dyes,production of hydroxyapatite,food supplement and fortification,dentistry,therapeutics,bone formation,drug delivery,poultry feeds as well as organic fertilizer.For most of the identified applications,the WCES is subjected to pretreatment and other modification techniques before utilization.The conversion of WCES to valuable products is a cost-effective,safe,environmentally friendly,non-toxic and viable means of waste disposal and utilization.More investigations are needed to further explore the benefits derivable from this bioresource.

Synthesis of Activated Carbon from Polyethylene Terephthalate(PET)Plastic Waste and Its Application for Removal of Organic Dyes from Water

Synthetic plastics are often considered to be materials that cannot be broken down by natural processes.One such plastic,polyethylene terephthalate(PET),is commonly used in everyday items but when these products are discarded,they can cause serious harm to the environment and human health.In this study,PET plastic waste was used to create activated carbon using a physical activation process that involved using CO2 gas.The researchers investigated the effects of different temperatures,carbonization,and activation times on the resulting activated carbon’s surface area.The activated carbon was then analyzed using scanning electron microscopy(SEM),X-ray diffraction(XRD),FTIR,and BET.The activated carbon created from PET plastic waste showed excellent absorption properties for methylene blue in aqueous solutions across a wide range of pH levels.By creating activated carbon from plastic waste,not only are environmental issues addressed,but high-value activated carbon is produced for environmental remediation purposes.

Production of pig iron from red mud waste fines using thermal plasma technology

Red mud, an insoluble residue produced during alkali leaching of bauxite, is considered as a low-grade iron ore containing 30% to 50% iron. The present paper deals with the use of thermal plasma technology for producing pig iron from red mud waste fines. The smelting reduction of red mud was carried out in a 35 kW DC extended arc thermal plasma reactor. Red mud was properly mixed with fluxes and graphite （fixed carbon, 99%） as a reductant as per stoichiometric requirement. The effect of various process parameters like a reductant, fluxes and smelting time on iron recovery was studied and optimized. An optimum condition for the maximum recovery of iron was obtained. A new thermal plasma process applicable to direct iron making from red mud waste fines that would achieve significant utilization of red mud was proposed.

A novel process for comprehensive utilization of vanadium slag

Traditional processes for treating vanadium slag generate a huge volume of solid residue and a large amount of harmful gas,which cause serious environmental problems.In this study,a new process for the comprehensive utilization of vanadium slag was proposed,wherein zeolite A and a V2O5/TiO2 system were synthesized.The structural properties of the as-synthesized zeolite A and the V2O5/TiO2system were characterized using various experimental techniques,including X-ray diffraction,X-ray fluorescence,scanning electron microscopy,and infrared spectroscopy.The results reveal that zeolite A and the V2O5/TiO2 system are successfully obtained with high purity.The results of gas adsorption measurements indicate that the prepared zeolite A exhibits high selectivity for CO2 over N2 and is a candidate material for CO2 capture from flue-gas streams.

Utilization of Low-Alkalinity Cementitious Materials in Cemented Paste Backfill of Gold Mine Tailings

The purpose of this paper was to explore the possility of using low alkalinity cementitious materials as binders,in which ground blast furnace slag and fly ash acted as a partial replacement of ordinary Portland cement,and CaSO_(4),Na_(2)SO_(4),and CaO were used as a sulfate activator and alkali activated additives,to solidify gold mine tail-ings for preparation of a green,inexpensive cemented paste backill(CPB).For this target,the effects of cement/tailings ratio,superplasticizer dosage,solid content,tailings fineness on the mechanical properties of the CPB were inves tigated.Additionally,the hydration mechanism of the CPB was analyzed based on X-ray diffraction and scanning electron microscopy results.The results showed that the fuidity of the CPB slurry could be improved by adding polycarboxylic acid superplasticizer.The unconfined compressive strength(UCS)of the CPB specimens was increased with the increase of cement/tailings ratio and solid content.Under the same experi-mental conditions,the 28 d UCS of the CPB specimens was 3.8-4.9 times higher than that of ordinary Portland cement.The softening coefficient of the CPB specimens was increased with the increasing cement/tailings ratio,ranging from 0.83 to 0.92.The shrinkage rate of the CPB specimens was decreased from 0.70%to 0.54%with the increase of cement/tailings ratio from 1:12 to 1:4 The UCS of the full tailings CPB was the highest,followed by the fine tailings CPB specimens,and the UCS of the coarse tailings CPB specimens was the lowest.The low alka-linity binder was proved to be a promising material to improve the engineering performances of the CPB.The optimal mixing ratio is 1:6 cement/tailings ratio,0.15 wt% superplastizer dosage,and 70 wt%solid content.Pre-pared by this mixing ratio,the UCS values of the CPB after 3,7,and 28 d curing ages reached 1.85,5.87,and 9.16 MPa,respectively,which were suitable as CPB for the Zhaoyuan gold mine in terms of strength requirements.

Review of the fabrication and application of porous materials from silicon-rich industrial solid waste

Porous materials have promise as sound insulation, heat barrier, vibration attenuation, and catalysts. Most industrial solid wastes, such as tailings, coal gangue, and fly ash are rich in silicon. Additionally, a high silicon content waste is a potential raw material for the syn- thesis of silicon-based, multi-porous materials such as zeolites, mesoporous silica, glass-ceramics, and geopolymer foams. Representative sil- icon-rich industrial solid wastes (SRISWs) are the focus of this mini review of the processing and application of porous silicon materials with respect to the physical and chemical properties of the SRISW. The transformation methods of preparing porous materials from SRISWs are summarized, and their research status in micro-, meso-, and macro-scale porous materials are described. Possible problems in the application of SRISWs and in the preparation of functional porous materials are analyzed, and their development prospects are discussed. This review should provide a typical reference for the recycling and use of industrial solid wastes to develop sustainable “green materials.”

Solid State Reaction Yielding a Mineral Utilizing Silica Obtained from an Agricultural Waste

Wollastonite, a mineral of wide industrial applications was synthesised from rice husk ash silica and limestone. A number of raw batches consisting of these starting materials, in 1:1 molar ratio, were heat treated to produce it through solid state reaction from 900℃ to 1300℃. The conducted reaction was monitored by XRD step by step. Amount of Wollastonite formed at every temperature was also studied to some extent. Analyses of the obtained data indicated that the target mineral formation was quite effective and almost proportional to a rise in temperature up to 1200℃. The results from both, XRD and chemical analysis were found in fair agreement with one another

New Advanced Technology on Waste Resourcelization of the Black Pulping Liquor

Combining the characteristics of the black pulping liquor that contains a lot of lignin and other biomass resources, the technology of comprehensive waste utilization is employed. The reconstructive preparation of modified urea-formaldehyde glue by adding black pulping liquor and the application in extruding the medium density fibre board using this modified urea-formaldehyde glue is researched. Results show that when applying the preparation technology that alkaline reaction and then weak acid reaction, the appropriate preparation process is as follows： the adding urea process is divided into three stages （proportion 2 ： 1 ： 1） ; the pH value is 8.0, and the reaction time is 40 min in the addition reaction stage; the pH value will be naturally reduced to 3.5 -5.0, and the reaction time is 45 min in the aggregation reaction stage; the pH value is 8.0 in the urea complement stage. And the optimal condition of the reconstructive preparation the modified ureaformaldehyde glue is adding the condensed black pulping liquor after hydroxymethylation in the beginning of polycondensation reaction by 5% proportion. The application in extruding medium density fibre board with this modified urea-fosmaldehyde glue is proved feasible.

Site Selection of Waste Slag Yard and Design of Protective Measures in Water Supply Project of Drawing from the Songhua River in Central Cities of Jilin

Water supply project of drawing from the Songhua River in central cities of Jilin is taken as research object.On the basis of analyzing project characteristics and natural conditions of the project area,site selection of waste slag yard of water diversion project and design of water and soil conservation measures are discussed.Rationality of site selection of waste slag yard and pertinence of prevention and control measures of water and soil loss in waste slag yard are analyzed,and comprehensive utilization of waste slag in large-scale production and construction projects is explored.

Recycling Spent LiCoO_(2)Battery as a High-efficient Lithiumdoped Graphitic Carbon Nitride/Co_(3)O_(4)Composite Photocatalyst and Its Synergistic Photocatalytic Mechanism

The ever-increasing quantity of spent lithium-ion batteries(LIBs)is both a potential environmental pollutant and a valuable resource.The spent LIBs recycling mainly aimed at the separation of valuable elements.Some issues still exist in these processes such as high energy consumption and complex separation procedures.This study avoided element separation and proposed a facile approach to transform spent LiCoO_(2) electrode into a lithium(Li)-doped graphitic carbon nitride(g-C_(3)N_(4))/Co_(3)O_(4) composite photocatalyst through one-pot in situ thermal reduction.During the thermal process,melamine served as the reductant for LiCoO_(2) decomposition and the raw material for g-C_(3)N_(4) production.Li was in situ doped in g-C_(3)N_(4) and the generated Co_(3)O_(4) was in situ integrated,forming a Li-doped g-C_(3)N_(4)/Co_(3)O_(4) composite photocatalyst.This special composite exhibited an enhanced photocatalytic performance,and its photocatalytic H2 production and RhB degradation rates were 8.7 and 6.8 times higher than those of g-C_(3)N_(4).The experiments combined with DFT calculation revealed that such enhanced photocatalytic efficiency was ascribed to the synergy effect of Li doping and Co_(3)O_(4) integrating,which extended the visible light absorption(450-900 nm)and facilitated the charge transfer and separation.This study transforms waste into a high-efficient catalyst,realizing high-valued utilization of waste and environmental protection.

Recovery of alkali and alumina from Bayer red mud by the calcification–carbonation method

Red mud produced in the Bayer process is a hazardous solid waste because of its high alkalinity; however, it is rich in valuable components such as titanium, iron, and aluminum. In this study, a novel calcification-carbonation method was developed to recover alkali and alumina from Bayer red mud under mild reaction conditions. Batch experiments were performed to evaluate the potential effects of im- portant parameters such as temperature, amount of CaO added, and CO2 partial pressure on the recovery of alkali and alumina. The results showed that 95.2% alkali and 75.0% alumina were recovered from red mud with decreases in the mass ratios of Na2O to Fe2O3 and of Al2O3 to Fe2O3 from 0.42 and 0.89 to 0.02 and 0.22, respectively. The processed red mud with less than 0.5wt% Na2O can potentially be used as a construction material.

Recovery of iron from copper slag by deep reduction and magnetic beneficiation

Aiming at recovering iron from high-iron-content copper slag, this article introduced a combination technol- ogy of deep reduction and magnetic beneficiation, investigated the iron recovery efficiency and optimized the technical conditions. When coke powder with 86wt% fixed carbon was used as a reductant, iron was successfully extracted from the copper slag. Under the optimized condition of the coke powder content of 14wt%, the calcium-to-silicon mass ratio （Ca/Si） of 0.2, the roasting temperature of 1300℃, the roasting time of 3 h, the grinding time of 20 min, and the magnetic field intensity of 61 kA-m-1, the iron recovery rate of the copper slag can reach 91.82%, and the extracted iron powder has an iron grade of 96.21%. With the characteristics of high iron grade and low impurity content, the extracted iron powder can be used as high-quality raw materials of weathering steel.

Rapid recovery of polycrystalline silicon from kerf loss slurry using double-layer organic solvent sedimentation method

The rapid development of photovoltaic （PV） industries has led to a shortage of silicon feedstock. However, more than 40% silicon goes into slurry wastes due to the kerf loss in the wafer slicing process. To effectively recycle polycrystalline silicon from the kerf loss slurry, an innovative double-layer organic solvent sedimentation process was presented in the paper. The sedimentation velocities of Si and SiC particles in some organic solvents were investigated. Considering the polarity, viscosity, and density of solvents, the chloroepoxy propane and carbon tetrachloride were selected to separate Si and SiC particles. It is found that Si and SiC particles in the slurry waste can be successfully separated by the double-layer organic solvent sedimentation method, which can greatly reduce the sedimentation time and improve the purity of obtained Si-rich and SiC-rich powders. The obtained Si-rich powders consist of 95.04% Si, and the cast Si ingot has 99.06% Si.

New technology for recycling materials from oily cold rolling mill sludge

Oily cold rolling mill （CRM） sludge is one of metallurgical industry solid wastes. The recycle of these wastes can not only protect the environment but also permit their reutilization. In this research, a new process of ＂hydrometallurgical treatment ＋ hydrothermal synthesis＂ was investigated for the combined recovery of iron and organic materials from oily CRM sludge. Hydrometallurgical treatment, mainly including acid leaching, centrifugal separation, neutralization reaction, oxidizing, and preparation of hydrothermal reaction precursor, was first utilized for processing the sludge. Then, micaceous iron oxide （MIO） pigment powders were prepared through hydrothermal reaction of the obtained precursor in alkaline media. The separated organic materials can be used for fuel or chemical feedstock. The quality of the prepared MIO pigments is in accordance with the standards of MIO pigments for paints （ISO 10601-2007）. This clean, effective, and economical technology offers a new way to recycle oily CRM sludge.

Coupling effect of pond ash and polypropylene fiber on strength and durability of expansive soil subgrades:An integrated experimental and machine learning approach

This study explores the coupling effect of pond ash(PA)and polypropylene(PP)fiber to control the strength and durability of expansive soil.The PA is used to chemically treat the expansive soil and PP fiber is adopted as reinforcement against tensile cracking.The sustainable use of PA and PP fiber are demonstrated by performing mechanical(i.e.unconfined compressive strength,split tensile strength and ultrasonic pulse velocity),chemical(pH value,electrical conductivity and calcite content),and microstructural analyses before and after 2nd,4th,6th,8th and 10th freezing-thawing(F-T)cycles.Three curing methods with 7 d,14 d and 28 d curing periods are considered to reinforce the 5%,10%,15%and 20%PA-stabilized expansive soil with 0.25%,0.5%and 1%PP fiber.In order to develop predictive models for mechanical and durability parameters,the experimental data are processed utilizing artificial neural network(ANN),in association with the leave-one-out cross-validation(LOOCV)as a resampling method and three different activation functions.The mechanical and durability properties of the PA-stabilized expansive soil subgrades are increased with PP fiber reinforcement.The results of ANN modeling predict the mechanical properties perfectly,and the correlation coefficient(R)approaches up to 0.96.

Preparation of CaO-Al_2O_3-SiO_2 system glass from molten blast furnace slag

To use the potential heat of molten blast furnace slag completely, a CaO-Al2O3-SiO2 system glass （MSG） was prepared from the molten industrial slag. The corresponding method proposed in this study utilized both slag and its potential heat, improving the production rate and avoiding the environmental pollution. Using appropriate techniques, an MSG with uniform color and superior performances was produced. Based on the experimental results and phase diagram, the chemical composition of MSG by mass is obtained as follows：CaO 27%-33%, SiO2 42%-51%, Al2O3 11%-14%, MgO 6%-8%, and Na2O＋K2O 1%-4%. Thermodynamic processes of MSG preparation were analyzed, and the phases and microstructures of MSG were investigated by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The results show that alkali metal oxides serve as the fluxes, calcium oxide serves as the stabilizer, and alumina reinforces the Si-O network. XRD and SEM analyses show that, the prepared MSG displays the glass-feature patterns, the melting process is more complete, and the melt viscosity is lowered with an increase in calcium oxide content;however, a continuous increase in slag content induces the crystalli-zation of glass, leading to the formation of glass subphase. The optimum content of molten slag in MSG is 67.37wt%. With respect to bend-ing strength and acid/alkali resistance, the performance of MSG is better than that of ordinary marble.

Development of carbon composite iron ore micropellets by using the microfines of iron ore and carbon-bearing materials in iron making

Iron ore microfines and concentrate have very limited uses in sintering processes. They are used in pelletization; however, this process is cost intensive. Furthermore, the microfines of non-coking coal and other carbon-bearing materials, e.g., blast-furnace flue dust （BFD） and coke frees, are not used extensively in the metallurgical industry because of operational difficu]ties and handling problems. In the present work, to utilize these microfines, coal composite iron oxide micropellets （2-6 mm in size） were produced through an innovative technique in which lime and molasses were used as binding materials in the micropellets. The micropellets were subsequently treated with CO2 or the industrial waste gas to induce the chemical bond formation. The results show that, at a very high carbon level of 22wt% （38wt% coal）, the cold crushing strength and abrasion index of the micropellets are 2.5-3 kg/cm2 and 5wt%-9wt%, respectively; these values indicate that the pellets are suitable for cold handling. The developed micropellets have strong potential as a heat source in smelting reduction in iron making and sintering to reduce coke breeze. The micropellets produced with BFD and coke fines （8wt%-12wt%） were used in iron ore sin- tering and were observed to reduce the coke breeze consumption by 3%-4%. The quality of the produced sinter was at par with that of the conventional blast-furnace sinter.