Tons Of Steel Research Articles

Development of energy saving technology of coke dry quenching

Application of coke dry quenching technology provides saving of energy resources, decreasing of environment pollution and increase of metallurgical coke quality. Despite of advantages of coke dry quenching facilities, an additional quantity of circulating gas is generated because of quenching technology peculiarities. This additional circulating gas must be released out of the cooling agent circuit resulting in environment pollution. Existing and proposed methods of reduction of emissions into atmosphere of excess circulating gas considered. It was shown, that utilization of the excess circulating gas as a fuel is the most effective solution of the considered problem. The solution comprise stabilization and support of combustible components composition in the circulating gas at the level of approved indices, joining of excess gas flows out of the dry quenching facility chambers, it enrichment by some amount of high calorie gas (coke or natural) and supply to gas uses. This technical solution was first realized by ArcelorMittal at the coke plant of the steel-works after E. Zendzimir in Krakov, Poland. In 2017 at the EVRAZ NTMK coke plant a project of the dry coke quenching facility modification was realized, comprising utilization of excess circulating gas, which has a considerable technical difference comparing with ArcelorMittal project. According to technology flowsheet, the excess circulating gas is collected out of operating chambers into a collector, cleaned of dust in a bag filter, chilled, enriched by a high calorie gas and delivered into the gas pipe of BF gas for further utilization as a fuel. To increase efficiency of the technology and to reduce the natural gas consumption for calorie content of enriched gas stabilization and supply it into the BF gas pipe line, the CO and H2 content in the circulating gas of the coke dry quenching facility is kept at the level of 12–15 and 4–5 % correspondently. Implementation of the technical modification of the coke dry quenching facility with elimination of harmful substances emissions within the excess circulating gas provided decrease of harmful substances emissions at JSC EVRAZ NTMK – 4 kg per ton of steel.

The Integrated Environmental Health Impact of emissions from a steel plant in Taranto and from a power plant in Brindisi, (Apulia Region, Southern Italy)

to estimate the environmental and health impact attributable to PM2.5 emissions from the ex-ILVA steel plant in Taranto and the ENEL power plant in Brindisi (Apulia Region, Southern Italy). a SPRAY Lagrangian dispersion model was used to estimate PM2.5 concentrations and population weighted exposures following the requirements of the Integrated Environmental Authorization (IEA) of the two plants under study. Available concentration-response functions (OMS/HRAPIE and updates) were used to estimate the number of attributable premature deaths. residents in the 40 municipalities of the domains of the VDS (assessment of health damage, according to the Regional Law n. 21/2012) of Brindisi (source: Italian National Institute of Statistics 2011 Census) and residents in Taranto, Statte, and Massafra (source: cohort study). mortality from natural causes, cardiovascular and respiratory diseases, and lung cancer attributable to PM2.5. Incremental lifetime cumulative risks (ILCRs) for lung cancer associated to PM2.5 exposure. there was a reduction of the estimated impacts from the pre to the post IEA-scenarios in both Taranto and Brindisi. In Taranto, ILCRs greater than 1x10-4; were estimated in 2010 and 2012; the ILCR was greater than 1x10-4; in the district of Tamburi (near the plant) also for the 2015 scenario. ILCRs estimated for Brindisi were between 1x10-6; and 4x10-5;. the Integrated Environmental Health Impact Assessment confirmed the results of the VDS conducted according to the toxicological risk assessment approach. An unacceptable risk was estimated for Tamburi also for the 2015 scenario, characterized by a production of 4.7 million tons of steel, about half compared to one foreseen by the IEA (8 mt.).

Residential building material stocks and component-level circularity: The case of Singapore

The residential built environment plays a crucial role in supporting many human activities. In urban areas however, high-rise residential buildings require significant investment of material resources, which are stacked for a long time over the building's lifetime. Assessing the Material Stock (MS) of buildings has been the focus of several studies for insights into in-use materials and their potential availability as secondary resources. The study of material circularity, or the potential to reuse materials emerging from end-of-life buildings, has so far been mostly limited to metals. This study argues that material stock analysis at individual material or material categories e.g. mineral, or metals, need to be complemented with building component stock estimations to enhance the potential for secondary resource recovery. Based on a bottom-up stock analysis approach, we estimate both the material and component stock of public housing developments in the city-state of Singapore and associated annual in- and out-flows. Results show that public housing in this city, which accommodates over 80 percent of its residents, accounts for 125.7 million tons of non-metallic minerals, 6.52 million tons of steel, 6.45 million windows, 8.61 million doors, 1.97 million toilet accessories, 15.33 million lighting fixtures, 0.99 million kitchen accessories (such as cookstove, kitchen cabinets) and 52.54 million m2 of tiles. The average stock of materials for these residential buildings is estimated at 27.4 tons of non-metallic minerals per capita and 1.4 tons of steel per capita. The average annual inflow of materials has been estimated to be 1.94 million tons for concrete and 0.1 million tons of steel, with a considerably low outflow of 0.31 million tons concrete and 0.02 million tons of steel, implying growth in these material stocks. This study provides a methodological approach to quantify building material and component stock and flows, which can be used by policy makers, urban planners and designers to consider responsible resource consumption. In particular, material and component stock estimations like that reported in this study contribute towards component-level circularity in the built environment.

Thermostatic cover for improving energy and technological efficiency of steel mills

The article proposes a technical solution for reducing the energy costs of casting process and providing more stable production conditions, specifically, the use of a thermostatic cap. Two variants of steel casting are considered: with and without the application of a thermostatic cover using the example of a bucket with a capacity of six tons of steel. The technical challenge is to reduce heat losses through the bucket neck to ensure the stability of the melting temperature throughout the casting and to reduce the temperature of metal release from the steelmaking unit. The design of the thermostatic cover with specifications, as well as the duration of process steps in the steel casting with and without the use of a thermally insulated cap are described. The balance calculations were carried out using MathCAD environment, which confirmed significant energy savings with a slight increase in casting time associated with the appearance of an additional technological operation for installing the thermostatic cover after pouring. Using ANSYS Academic software, a study was carried out on the thermal fields of the ladle and steel at various stages of casting for two options, which confirmed the effectiveness of using a thermostatic cover.

CALCULATION OF THREE-LAYER LARGE DIAMETER PIPES ON THE PC «LIRA»

ObjectivesThis article discusses the evaluation of the possibility of application of three-layer pipelines. For this purpose, the stress-strain state of three-layer pipes under the action of internal pressure is investigated. The largest in the modern world are considered to be the main pipewater. They are mainly used to transport oil and gas from production sites to processing plants. Pipelines are intended for movement of liquid, gases and other environments and first of all it is water pipelines. As you know, main and technological pipelines are IP-elite club that cares only metal buildings, the construction of which consume Xia millions of tons of steel. On the other hand, one of the main indicators of efficiency of trunk pipelines is their material consumption. As a rule, trunk pipelines have a long length, and therefore an unreasonable increase in the even thickness of the pipe walls by at least 1 mm leads to an overspending of steel by de-siyatki and even hundreds of thousands of tons. In this regard, to the calculations of the main pipe wires for strength should be given the most serious attention.MethodsThe calculation is carried out by numerical methods, namely with the help of finite element meto-da (FEM), implemented in the PC "LIRA".ResultsThe calculation of the pipes is performed on the load from the transported medium applied to the inner contour of the pipe. In this case, for the three-layer pipe (the first option) and for the pipes of the second and third options, the ring tensile stresses and strains were determined. The isofields of tensile and shear stresses are given, the comparative graphical dependence of ring tensile stresses is constructed.Conclusion.The obtained numerical results showed that the selected calculation scheme (var.1), that is, the representation of the continuous section of the pipe in the form of a three-layer, is correct. The discrepancies between the data obtained are related to the rotation of the section along the radius of the pipe. In General, the results of calculations showed the possibility of using a three-layer pipe wall for transportation of various media.Acknowledgment.This work was supported by a grant from the President of the Russian Federation (MK-6112.2018.8)

Measures to Decrease and Utilize Steelmaking Slag

Steelmaking slag is artificially produced to remove, among others, the phosphorus from molten steel; approximately 120 kg of slag is formed per ton of steel. At present, steelmaking slag is mostly used for road construction and civil engineering materials. However, the slag cannot be sold at a high price and, in advanced countries, its market for civil work is shrinking and regulations to protect the environment are becoming more severe. There are two solutions to the problem of steelmaking slag: one is to decrease the generation of slag, and the other is the development of reuse methods. In this paper, the measures to decrease slag formation are first discussed based on the mass-balance calculation, and then the present and future states of slag valorization in Japan are reviewed. In the first part, the importance of the hot-metal dephosphorization process and the recycling of decarburized slag is clarified. In the second part, as a new field of slag valorization, the use of slag in marine environments is explained. Several studies to extract phosphorus and manganese from slag were also introduced.

Hybrid model associating thermodynamic calculations and artificial neural network in order to predict molten steel temperature evolution from blowing end of a BOF for secondary metallurgy

Abstract The developed model is an association of thermodynamic calculations for dissolution of alloys, slag formers and the deoxidation reaction in the molten steel with two artificial neural network (ANN) models trained with industrial data, to predict the molten steel temperature drop from the blowing end of the BOF until the first measurement at secondary metallurgy. To calculate the associated energy for deoxidation, an experiment was designed to set up the parameters for oxygen partitioning among deoxidants, with timed aluminum addition during teeming being the main parameter. The temperature control in the teeming stage presented a standard deviation for the error of prediction of 5.46 oC, for transportation from the rinsing station to the secondary metallurgy of 2.79 oC. The association of all calculations presented an error standard deviation of 7.49 oC. The operational validation presented superior accuracy compared with the current method for controlling the temperature, resulting in a reduction in the aluminum consumption for heating at secondary metallurgy with a potential economy of U$ 4.07 million per year for a steel shop producing 5 million tons of steel yearly. The artificial neural network model confirmed its capacity for modeling a complex multivariable process and the separation of thermodynamic calculation provides a better adaptability to different steel grades with different teeming strategies.

Measurement of metallic iron in steel making slags

An integrated steel plant generates 200–250 kg of steel making slag for every tonne of steel produced. These slags contain non-uniformly distributed iron in metallic form, inevitably carried into the slag pot during de-slagging. The steel slag is subjected to crushing/magnetic separation to generate different sizes of slag products with varying metallic values. Based on size and metallic content, these products are recycled in sinter base mix, iron making units and as scrap in steel making process. Hence accurate analysis of Fe-metallic in these samples is imperative for better process control. Due to non-uniform mixing and solidification of steel & slag in de-slagging and dumping practice, precise quantification of the metallic portion in these samples is extremely difficult. Existing methods followed by slag processing agencies has always been doubtful. Moreover, uniformity of constituents in a small sample size cannot be ensured even by best of the sampling techniques. In the present work, all the slag products have been subjected to different measurement techniques to develop a method to determine the metallic iron content accurately in the steel-making slags. Separate methods have been formulated for low metallic and high metallic content slag samples based on the dominant characteristics. Specific density balance and grinding-sieving methods are proposed for more practical and accurate measurement. Best sampling technique and optimum sample size have also been suggested for each method. In addition to increase in the efficiency of the process, where it is recycled, accurate analysis of Fe-metallic in slag helps in improving the magnetic separation technique and the process of its application.

Assessment of hydrogen direct reduction for fossil-free steelmaking

Climate policy objectives require zero emissions across all sectors including steelmaking. The fundamental process changes needed for reaching this target are yet relatively unexplored. In this paper, we propose and assess a potential design for a fossil-free steelmaking process based on direct reduction of iron ore with hydrogen. We show that hydrogen direct reduction steelmaking needs 3.48 MWh of electricity per tonne of liquid steel, mainly for the electrolyser hydrogen production. If renewable electricity is used the process will have essentially zero emissions. Total production costs are in the range of 361–640 EUR per tonne of steel, and are highly sensitive to the electricity price and the amount of scrap used. Hydrogen direct reduction becomes cost competitive with an integrated steel plant at a carbon price of 34–68 EUR per tonne CO2 and electricity costs of 40 EUR/MWh. A key feature of the process is flexibility in production and electricity demand, which allows for grid balancing through storage of hydrogen and hot-briquetted iron, or variations in the share of scrap used.

Research on modelling and optimization of hot rolling scheduling

Multiple species and random change in batch order forms has become the core business of Steel Intelligent Production Enterprises, necessitating new requirements for scheduling real-time adaptability and precision in the steel scheduling model. In this paper, a digital twin intelligent agent with cyberspace physical space integration is proposed as the unified driving source. First, an Open Multiple Objective Travelling Salesmen Problem model was established. For constraints such as a minimum rolling unit plan, process specification and a minimum power consumption per ton of steel, the NSGA-II algorithm was used to obtain a Pareto front for these constraints. With the help of appropriate penalty coefficients for the Pareto front, the constraints were defined as 3D-coordinates among cities of the Travelling Salesmen Problem. Combining the simulated annealing (SA) algorithm and the multi-objective particle swarm optimization (PSO) algorithm, the PSO algorithm was redefined and modified by introducing the metropolis criterion of the SA algorithm twice. This was used to obtain two extremes of the particle swarm, including the individual optimal solution and the global optimal solution to avoid local extrema. A model based on SA-MOPSO was thus obtained. Then, with the help of real-time mapping between the steel production line and the information model, the double-flow digital twin agent was established. This agent can achieve production scheduling model dynamic development and maturation itself. Finally, taking the steel hot rolling production line as a case in point, training and trial application of the model were performed to verify its adaptive development ability. Simulation results show that the algorithm discussed in this paper can solve the problem of hot rolling scheduling and provide support for decision-makers.

Carbothermic reduction of Electric Arc Furnace Dust via thermogravimetry

Abstract Electric Arc Furnace Dust (EAFD) is a solid waste originated from electric steelmaking furnaces. Currently, according to some authors, there is an estimated generation of 15 to 25 kg of dust per ton of steel produced. The formation of the dust is related to the following steps of the process: furnace charge, metal volatilization, iron vaporization under the arc, drag of solid particles and, mainly by the collapse of CO bubbles from metallic bath decarburation. The dust has metals that are harmful to the environment. Otherwise, it is mostly composed of the elements iron, zinc and oxygen. Due to increasing costs for disposal and because it is considered a hazardous waste, industry is looking at the possibility of returning the dust to the steelmaking process. One of the alternatives is by reintroducing the waste in an electric melting shop using self-reducing agglomerates as part of the furnace burden. In this study, self-reducing mixtures are prepared with EAFD and petroleum coke (PET), presenting chemical and physical characterizations. An evaluation about the behavior of the mixtures is carried out in thermobalance, regarding the possibility of use in measuring accurate PET content in self-reducing pellets. As results it could be stated that the elements of economic interest, Zn and Fe, represent, respectively, 34.23 and 22.80%, in weight. These elements are present in chemical species frankilinite, zincite and magnetite and the reducible oxygen was estimated as 17.90%. Also, it was concluded the optimal content of petroleum coke in the mixtures varies from 10 to 15%, in weight. Therefore, the utilization potential of the thermogravimetric technique in the industrial field for adjustment of carbon content in batches of self-reducing pellets is satisfactory.

Improvement in Manufacturing Technology for Coiled and Sheet Rolled Product in a VMZ Casting and Rolling Complex

Research is conducted within the scope of the Clean Steel project into reasons for variation of the metal level in a crystallizer and breakouts of the crystallizing metal skin in a thin-slab CCM, and also a study of reasons for defect formation in hot-rolled strip. Examples are provided of improved monitoring and control of the VMZ casting and rolling complex (CRC) technology. Implementation of the monitoring production technology – evaluation of metal product quality – operational adjustment of technology concept makes it possible to reduce the CCM emergency situation index to less than 0.5 ton/105 tons of steel, and also to determine factors influencing the formation of transverse cracks over a rolling mark, and to remove defect formation.

Assessment of low-carbon iron and steel production with CO2 recycling and utilization technologies: A case study in China

Substance flow analysis (SFA) and energy and economic assessment were used in this study to analyze the utilization of CO2 in the steelmaking system based on four scenarios: the conventional blast furnace-basic oxygen furnace (BF-BOF) process (Baseline case), the BF-BOF process with waste heat and energy recovery (Case-1), the BF-BOF process with CO2 hydrogenation (Case-2), and the CO2-CH4 dry reforming process coupled with an electric arc furnace (EAF) (Case-3). The results suggest that Case-2 is competitive not only in carbon emission but also in energy consumption and economy as it reduces carbon emission and energy consumption by 136 kg and 53.7 kgce respectively. It also increases profits by 9.38 US$ per ton of steel compared to the Baseline case, thus promising to mitigate predicaments in China’s present iron and steel industry. With higher levels of hydrogen in the composition of natural gas, Case-3 reduces carbon emission by 40% more than the Baseline case, but its energy consumption is close to that of the Baseline case. Besides, the production cost is 34% higher in Case-3 than in the Baseline case, owing to the high natural gas price in China. Only when the natural gas price falls to the American value, which is 70% lower than that of China, will Case-3 be economically feasible. In short, high production energy consumption and production costs lead to a lack of technical and economic impetus for Case-3 in the current market, even if it is associated with relatively low carbon emission. The key to solving this problem lies in identifying methods to realize reduced gas production with high efficiency and low cost.

ОЦЕНКА ВЛИЯНИЯ КОНСТРУКЦИЙ МНОГОЯРУСНЫХ КИСЛОРОДНЫХ ФУРМ НА ЭФФЕКТИВНОСТЬ ПРОДУВКИ КОНВЕРТЕРНОЙ ВАННЫ С ДОЖИГАНИЕМ ОТХОДЯЩИХ ГАЗОВ

The aim of the work is to carry out an economic assessment of the effect of various structures of multi-tiered oxygen lances and methods for flushing the converter bath with the afterburning of waste gases on the efficiency of the production of iron-carbon semi-products in a modern metallurgical plant. The study was conducted for the process of steel smelting in converters of combined blowing with supply of oxygen from above and neutral gas through the bottom in the conditions of using conventional and multi-tiered oxygen tuyeres. Studies on the afterburning of converter gas in the converter cavity showed that, in proportion to the increase in the proportion of CO2 in the exhaust gases, the costs of steel production are reduced. Compared with the use of tuyeres of classical construction, they amount to 3.23 US dollars / ton of steel for double-circuit, 6.81 US dollars / ton of steel for bunk, and 11.61 US dollars / ton of steel for three-tier. It was determined that when using the classic design of the upper oxygen tuyere, the lower heat of combustion of the converter gas is 10 MJ / m3. In comparison with the classical design, the two-tier, double-circuit and three-tier tuyeres ensure a reduction in the lower heat of combustion of the converter gas by 8,5; 4.4 and 27.1% (rel.), Respectively. On the basis of the data obtained, it is possible to draw a conclusion about the effectiveness of using the technology of combined blowing of the converter bath with the afterburning of exhaust gases in the converter cavity.

Up-gradation of banded iron ores for pellet grade concentrate

As per national steel policy vision 2030, around 500 million tons of quality iron ore is required to produce 300 million tons of steel. In this context, the use of low grade banded iron ores (Fe∼ 30-45%, 40-50% silica) is inevitable. Reduction roasting followed by magnetic separation technique is employed to treat such ore. In this work, banded iron ore with 32% Fe is enriched to a concentrate of ∼53-57% Fe using reduction roasting followed by low-intensity magnetic separation technique. A concentrate of 35% recovery with 53% Fe grade was achieved using Wet High-Intensity Magnetic separator at 12000 Gauss. In case of microwave reduction roasting a concentrate of 57.19% Fe grade and 17.82%wt. recovery is obtained at optimum conditions (540W, 3 minutes and 7% charcoal). Whereas, in muffle furnace reduction roasting 52.95%Fe grade and 47.38%wt. recovery concentrate is obtained at 900°C, 8% charcoal and 30 minutes time.

Methods of steel manufacturing - The electric arc furnace

Initially, the carbon content was reduced by mixing “the iron” with metallic ingots in ceramic crucibles/melting pots, with external heat input. As time went by the puddling procedure was developed, a procedure which also assumes a mixture with oxidized iron ore. In 1856 Bessemer invented the convertor, thus demonstrating that steel can be obtained following the transition of an air stream through the liquid pig iron.The invention of Thomas, a slightly modified basic-lined converter, fostered the desulphurization of the steel and the removal of the phosphate from it.During the same period, in 1865, in Sireuil, the Frenchman Martin applies Siemens’ heat regeneration invention and brings into service the furnace with a charge composed of iron pig, scrap iron and iron ore, that produces a high quality steel [1].An act worthy of being highlighted within the scope of steelmaking is the start-up of the converter with oxygen injection at the upper side, as there are converters that can produce 400 tons of steel in approximately 50 minutes.Currently, the share of the steel produced in electric arc furnaces with a charge composed of scrap iron has increased. Due to this aspect, the electric arc furnace was able to impose itself on the market.

Paper making in a low carbon economy

Paper and pulp manufacturing industry produces versatile products from renewable feedstock that are easily recycled. It is the fourth largest industrial sector in terms of energy use. Much of the energy used comes from biomass derived fuels or high efficiency combined heat and power plants so the industry is not considered as carbon intensive. But at production paper making emits five times the CO₂/tonne of steel; this is gradually removed from the atmosphere by the growth of replacement trees which can take between 7 and 90 years. This study reviewed existing literature to establish estimates for future energy requirements, and way that these could be met with minimum carbon emissions in a world where there are electricity grids with low carbon intensities, high recycling rates and growing demand for sustainable biomass. It was found that energy consumption could be reduced by 20% using technologies that have been demonstrated at an industrial scale. Most virgin pulp is made using the kraft chemical processing method. It was found that it should be possible to eliminate all fossil fuel use from this process, by combustion of by-product while exporting a small amount of electricity. Recycled paper is becoming the largest source of pulp. In this case the waste streams cannot provide sufficient energy to power the process, but process heat can be produced by burning some of the collected waste paper in steam plants or by using electric heat pumps. The energy needed to produce high quality office paper is nearly twice that required for non-deinked packaging paper. This couples with the lower pulp yields obtained with high quality pulp means that the environmentally preferred option for energy supply to the recycling process is dependent on the grade of pulp being produced.

16.02: “La Belle Liégeoise”, the new footbridge in Liège

ABSTRACTThe new footbridge in Liège, known as “La Belle Liégeoise”, was opened on 2 May 2016. Located upstream of the landscape window created by the new Guillemins Esplanade, this bridge provides a connection for soft transport modes from the railway station across the Meuse to La Boverie Park, maintaining clearance for navigation.The site presents a dissymmetry: an urban bank faces a wooded bank. Reflecting this, the structure of the main section on the left bank develops a suspended typology, while the second section on the right bank is supported by struts.The main span over the Meuse is 163 metres for a total length of 294 metres. The 5.5 metre wide decking is positioned laterally to the supporting structure.The footbridge is accessible to “soft” transport modes via the provision of ramps made of variable height steel boxes, supporting the 3.5 metre wide decking of azobé wood. On the right bank, the bridge crosses La Boverie Park through the canopy, offering a new vision of this urban park.The desire to design a thin and elegant structure integrated into the site, combined with the need to restrict navigation on the Meuse as little as possible, led to the obvious use of steel for the main structure.Construction involved 740 tonnes of steel. Structural elements 15 metres long were trucked onto a temporary assembly site. These elements were assembled on the ground in six sections, the largest weighing 400 tonnes for a 150 metre length. These six sections were finally transported by barge, lifted and positioned by three floating cranes. The most impressive section, consisting of the suspended part, was transported horizontally before being re‐erected on site.Finite element analysis was used to determine the reduction elements and check for strength and stability. Funicular geometry tends to maximize the axial forces of elements. For some critical elements (hangers, suspension, pylon, etc.) non‐linear calculations were performed. The same applied for determining the reverse deflection, which reaches 160 cm in the main span.Adopting a minimalist design for the nodes, the hanger connections are welded, meaning the screed or assembly members do not have to be visible.This particularly slender type of structure is sensitive with respect to its vibratory dynamic behaviour. Tuned mass dampers were designed to allow the project to meet the required conditions of comfort.Bureau Greisch, in association with the landscaping architect Corajoud, was responsible for the full architectural and structural design for the footbridge.

Novel concept of recycling sludge and dust to BOF converter through dispersed in-situ phase induced by composite ball explosive reaction

Recycling of iron and steelmaking dusts is a key issue in environmental protection efforts and to ensure efficient utilization. In this investigation, we developed a novel recovery process that uses a dispersed in-situ phase induced by an explosive reaction of composite balls of iron and steelmaking dusts. We designed and prepared composite balls for this function using a laboratory model batch-type balling disc (at 12 r/min) and optimized the feeding modes in 180-t and 260-t basic oxygen furnace (BOF) converters. The results indicate that feeding composite balls into BOF converters is an effective novel technology for recovering iron and steelmaking dusts. The period after hot metal charging and prior to the oxygen-blowing process is the most reasonable time to feed composite balls. Composite ball treatment is not appropriate for steel production with sulfur requirements lower than 80 ppm. The maximum composite ball feeding amount is 40 kg/t and the iron yield rate is better than 95%. Compared with the conventional recycling process of sludge and dust, this novel technology is more convenient and efficient, saving up to 309 RMB per ton of steel. Further investigation of this novel recycling technology is merited.

Using forest area for carbon footprint analysis of typical steel enterprises in China

Steel industry is an important mainstay industry and key greenhouse gas emitter of China. Employing life cycle assessment method of cradle-to-gate and establishing material flow model for steel production processes, this paper analyzed carbon footprints of steel enterprises to reduce carbon emission efficiently. Taking the function of forest to capture carbon into account, carbon footprint was expressed as the forest area instead of carbon dioxide equivalent (CO2e). Taking five typical steel enterprises (J, A, T, N, B) in China as examples, the carbon footprint per ton of steel in each process was calculated and its influence factors were analyzed. Results show that (1) from the perspective of process, the carbon footprint of iron-making, in which a large amount of coke and coal is consumed, is the largest, followed by the process of coking and sintering; (2) analyzing the type of gas, CO2 contributes over 70% of the total carbon footprint in the whole production process; (3) the average carbon footprint per ton of steel was 0.325hm2/t. Among five companies, carbon footprints of company N were up to 0.342hm2/t, while company B had the lowest carbon footprint, at only 0.291hm2/t. The gaps of carbon footprint are mainly due to geographical differences, energy consumption construction and product equipment and technology. The carbon footprint of enterprises was compared with the local carbon capacity, and analysis results show that the steel output and local forest areas could be significant factors determining whether the carbon emissions discharged by steel mills exceed the local carbon capacity and cause environment problems. According to analysis results, corresponding opinions and policies were proposed.