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The condition and state of the hearth of the blast furnace is of considerable importance since the life length of the refractories governs the campaign length of the furnace, but it is also of significance as it affects the drainage of iron and slag and the hot metal temperature and composition. The paper analyses the hearth of a blast furnace using a model of the lining wear based on the solution of an inverse heat conduction problem, studying the changes in the lining state throughout the campaign. Different operation states are detected, characterized by smooth and efficient hot metal production and by erratic behavior with large disturbances in the hearth state. During the periods of poor performance, the hearth exhibits a cycling state with stages of excessive skull growth on the unworn refractory, followed by periods of dissolution of the skull and lining erosion. An explanation of the transitions is sought by a stating and solving a force balance for the deadman with the aim to clarify whether it is floating or sitting. A connection between the thermal cycles in the hearth and the hot metal sulfur content is finally demonstrated.

The porosity distribution of burden layers in the blast furnace (BF) plays an important role for the gas distribution and gas–solid two-phase interaction. In this work, the porosity distribution along the radial and vertical directions of the BF throat was studied by the discrete element method combined with some experimental verification. The simulated radial porosity distribution of coke burden layer shows general agreement with experimental findings, which in practice depends on the charging matrix. When a layer of burden moves from the top to the bottom, its structure will become more compact, so the porosity will decrease. However, the changes occur while 4–5 new layers are built on top of the layer in question, after which the porosity stabilized at an equilibrium point. For the full burden bed, the porosity of coke layers is larger than that of ore layers, but both layers have larger porosity than mixed layer formed by sinter charged on coke, especially when the particle size difference between ore and coke is large.Graphic abstract

A mathematical model for the design of small-scale supply chains for liquefied natural gas (LNG) has been developed. It considers the maritime delivery of LNG from supply ports to satellite terminals and land-based transports from the terminals to consumers on or off the coast. Both tactical and strategic aspects in the supply chain design are addressed by optimizing the maritime routing of a heterogeneous fleet of ships, truck connections, and the locations of the satellite terminals. The objective is to minimize the overall cost, including operation and investment costs for the selected time horizon. The model is expressed as a mixed-integer linear programming problem, applying a multi-period formulation to determine optimal storage sizes and inventory at the satellite terminals. Two case studies illustrate the model, where optimal LNG supply chains for a region with sparsely distributed island (without land transports) and a coastal region at a gulf (with both sea and land transports) are designed. The model is demonstrated to be a flexible tool suited for the initial design and feasibility analysis of small-scale LNG supply chains.

Intensifying hydrogen use in the blast furnace is a key technology for significant coke and CO2 emissions reductions. The most straightforward approach is the implementation of high hydrogenous gas injection rates in the BF tuyeres. Yet this solution has not been widely implemented due to a lack of understanding of the impact on the furnace’s internal state. In this paper, a newly developed BF mathematical model is presented and validated on operation data. The model is next applied to investigate the effect of hydrogenous gas injection on the overall performance and internal state of the furnace. The current state of an industrial BF is used as a starting point, increasing the injection of coke oven gas, natural gas or pure H2 to the maximum where the limits for a safe and stable process are still obeyed. All three gases were found capable of significantly decreasing the coke rate, but only coke oven gas and pure H2 allowed for a significant reduction of the CO2 emissions. It was found that the indirect reduction of H2 is intensified by hydrogen enrichment partially at the expense of indirect reduction by CO. Furthermore, the water gas shift reaction is intensified at increased hydrogenous gas injection, affecting the CO and H2 utilization of the top gas. The study gives an insight into the feasibility of BF processes with high hydrogenous gases injection into the tuyeres and the resulting coke savings.

The breakthrough route involving a reduction shaft furnace operated with pure hydrogen gas (here called H2-SF) and the electric arc furnace is widely accepted as one of the most viable future alternatives for industrial-scale production of primary steel with minor CO2 emissions. It has been clarified that the largest portion of the total energy for the entire route is consumed by the H2-SF operation, but this unit has not yet received much attention and should therefore be explored. For this, a mathematical model of a reduction shaft furnace is presented in this paper, where a set of simulations were also performed to shed more light on the operation of the H2-SF equipped with a top gas recycling system. The results show that a high gas feed rate is required for guaranteeing a smooth H2-SF operation due to the strong heat demand. An increase in the feed temperature of the gas or in furnace height can reduce the required gas feed. However, an excessive length may conversely result in an increase in the total energy consumption. The model and its results are expected to be helpful for gaining a better understanding of the complex processes in and constraints of the H2-SF.

Steelmaking industry faces urgent demands for both steel slag utilization and CO 2 abatement. Ca and Mg of steel slag can be extracted by acid solution and used to prepare sorbents for CO 2 capture. In this work, the calcium-based sorbents were prepared from stainless steel slag leachate by co-precipitation, and the initial CO 2 chemisorption capacity of the calcium-based sorbent prepared from steel slag with the Ca and Mg molar ratio of 3.64:1 was 0.40 g/g. Moreover, the effect of Ca/Mg molar ratio on the morphology, structure, and CO 2 chemisorption capacity of the calcium-based sorbents were investigated. The results show that the optimal Ca/Mg molar ratio of sorbent for CO 2 capture was 4.2:1, and the skeleton support effect of MgO in calcium-based sorbents was determined. Meanwhile, the chemisorption kinetics of the sorbents was studied using the Avrami-Erofeev model. There were two processes of CO 2 chemisorption, and the activation energy of the first stage (reaction control) was found to be lower than that of the second stage (diffusion control).

Wear of the hearth refractory and buildup (“skull”) formation play important roles for the life length of the ironmaking blast furnace. The extent of these factors during the campaign can be estimated by solving a sequence of inverse heat-conduction problems, but this requires thermocouple measurements in the lining and the effect of liquid flow is often disregarded. The model developed in the present paper aims at providing a theoretical estimation of the asymptotic inner profile of the hearth by a CFD-based approach that estimates both the iron flow and the refractory erosion and possible skull. The profile, shaped by the flowing hot metal, solidified skull, and remaining refractory, is obtained through an iterative process based on the calculated fluid flow and temperature distribution in the domain. The paper presents the assumptions behind the model, its main equations and the solution procedure, as well as a set of illustrative examples that show the versatility of the approach. The results of the model can be used to estimate the potential strengths and weaknesses of a specific hearth design and also how the lining state would be affected by changes in the boundary conditions.

This work studied the effect of B2O3 (analytical reagent) on the parameters of a sintering pot test, as well as the metallurgical properties and microstructure of the sinter samples, to determine the feasibility of applying solid waste containing B2O3 in vanadium–titanium sintering. The results show that along with B2O3 addition, the mechanical strength of the sinter first increases and then decreases; the maximum strength was found upon the addition of 3.0% of B2O3. The low-temperature reduction and pulverization rate of the vanadium–titanium sinter were also improved, while the start and end temperatures of softening showed a decreasing trend. The microstructure of the sinter was found to change from plate structure to particle and point structure, with uniformly distributed small areas. The sintering pots created by B2O3 addition had low total porosity but a greater pore diameter than pots created without the reagent.

A proper burden and porosity distribution of the bed in the upper shaft are important prerequisites for realizing a stable and efficient operation of the ironmaking blast furnace. The discrete element method was used to investigate the effects of the static friction coefficient between burden particles and shaft angle on the burden profile and porosity distribution in the bed formed by charging the burden with a bell-less charging equipment. The results indicate that a large static friction coefficient makes the particles stay closer to the impact point (i.e., where they fall) from the rotating chute. A large mixed region of the burden bed decreases the gas permeability, and an increase in the burden particle roughness will worsen this problem. The burden surface shape becomes flatter with an increase in the shaft angle. These findings explain the effect of particle properties and wall geometry on the inner structure of the burden bed.

Due to demands of lower costs and higher productivity in the steel industry, the volume of operating blast furnaces has grown during the last decades. As the height is limited by the allowable pressure drop, the hearth diameter has grown considerably and, along with this, also draining-related problems. In this paper a mathematical model is developed for simulating the drainage in the case where an impermeable region exists in the blast furnace hearth. The model describes the quasi-stationary drainage process of a hearth with two operating tapholes, where the communication between the two pools of molten slag and iron can be controlled by parameterized expressions. The model also considers the case where the buoyancy of the liquids is sufficient for lifting the coke bed. The implications of different size of the liquid pools, communication between the pools, bed porosity, etc . are studied by simulation, and conclusions concerning their effect on the drainage behavior and evolution of the liquid levels in the hearth are drawn. The simulated liquid levels are finally demonstrated to give rise to a pressure profile acting on the hearth which agrees qualitatively with signals from strain gauges mounted in the hearth wall of an industrial ironmaking process.