Charcoal Blast Furnace Research Articles

History of the iron furnace using the physical-chemical blast furnace model

The physical–chemical blast furnace model first built by Michard and Rist has proven to be a very efficient tool to predict and drive the present blast furnaces. It mostly describes the iron blast furnace as a counter current gas-solids dual heat and oxygen exchanger. The onset of coke gasification (orelse of iron oxide direct reduction), leads to a two-zones exchange model. This theory is used to look back at the operation of the earlier and smaller iron furnaces such as the early XIXth century charcoal blast furnace or the much older low shaft furnaces. It shows the interest of using physical-chemical models to better understand the operation of past production tools.

Cogeneration of energy in the reuse of blast furnaces gases in a steel manufacturing company / Cogeração de energia na reutilização gases de altos-fornos de uma empresa siderúrgica

In the present work, using the tools and the concepts of energy for the steelmaking process, a detailed study of the electric energy generation system (Cogeneration) in a non-integrated steel mill coupled with a thermoelectric plant was carried out, where the production process of this steel industry, which is located in a city in the Midwest region of Minas Gerais (Brazil), was analyzed. A pig iron producer that sells in the internal and external markets, this steel industry is continuously seeking to increase its competitiveness in the steel sector and to become an ecologically sustainable company. The intention is to propose a better utilization of the gases generated in the production of pig iron in a charcoal blast furnace. That is, since the gas flow from the blast furnace, which serves as fuel in the combustion process in the boiler, does not have a regular or constant flow, it is necessary to monitor the air/fuel ratio almost in real time, in order to obtain the highest power in the turbo-generator set of the steam system. Through the energy analyses performed for each of the components of the energy generation cycle of the steel mill, improvement proposals are suggested to increase the energy efficiency of the components and, consequently, of the cycle as a whole.

Predicting and Explaining Pig Iron Production on Charcoal Blast Furnaces: A Machine Learning Approach

Pig iron, the source for a variety of iron-based products, is traded in commodity markets. Therefore, enhanced productivity has significant economic implications for the producers. Pig iron is mainly produced inside of tall, vertical, thermodynamic reactors called blast furnaces that run 24 hours a day. The blast furnaces are too complex to model explicitly and are generally regarded as black boxes. In this study, we design, develop, and deploy novel machine learning models on a rich data sample covering more than 20 production variables spanning nine years of actual operational period, collected at one of the largest pig iron production plants in Brazil. We show that, given the blast furnace parameters, machine learning models are capable of unveiling novel insights by illuminating the black box and successfully predicting production levels at different configurations. These prediction models can be used as decision aids to improve production efficiencies. We also perform a sensitivity analysis of the trained models to identify and rank the input variables according to their relative importance. We present our findings, which are largely in line with the existing literature, and confirm their validity, practicality, and usefulness through consultations with subject matter experts.

Mill scale and flue dust briquettes as alternative burden to low height blast furnaces

The present work evaluated the behavior of self-reducing briquettes produced from mill scale and blast furnace flue dust at high-temperature and reducing atmosphere conditions, aiming to recycle these wastes through low height blast furnaces. Briquettes prepared in three different carbon/oxygen mass ratios were submitted to interrupted high-temperature tests in CO-reducing atmospheres and evaluated in terms of reduction and mechanical strength behavior. Metallic iron was identified in the samples obtained even at low temperature and moderate CO partial pressure, which revealed the high reducibility of these briquettes comparatively to lump iron ores. It was observed that self-reducing reactions play an important role at low temperatures (up to 900 °C), while at high temperatures the external atmosphere had a greater influence. The mechanical strength of the briquettes was strongly affected by self-reducing reactions and the proportions of wastes. At 900 °C the briquettes swelled, which was more pronounced when blast furnace flue dust increased in the briquettes. Briquettes with the lowest carbon/oxygen mass ratio (0.25) presented the best performance to use in blast furnaces reactors. A mass balance considering this briquette for recycling mill scale and blast furnace flue dust from integrated steel mills through low height charcoal blast furnace showed to be an attractive route to improve the sustainability of iron and steelmaking industry.

Use of slag (GBFS) generated in charcoal blast furnace as raw material in alkali-activated cement

Alkali-activated cements are low-environmental-impact binders and can be obtained from the alkaline activation of wastes such as slags and fly ashes, and solutions of hydroxides and silicates. In this study, two types of slag, A and B, generated in charcoal and coke blast furnaces, respectively, were activated with NaOH in contents of 4, 5 and 6% to obtain alkali-activated slag (AAS). Samples were submitted to calorimetry and compressive strength tests, and investigative microstructure analysis. The results showed that cement obtained with slag A (AAS_A) presented a much superior performance than AAS_B, which was related to the higher degree of hydration, higher formation of amorphous CSH with a higher incorporation of aluminum ions (C–(A)S–H). For AAS_B, the activator content was not able to improve the compressive strength. Calorimetry measurements showed a small interaction between slag B and the activator. The results contribute to the appreciation of slags generated in charcoal blast furnaces, which may become raw material for low-environmental-impact cements, in this case, AAS.

The operation of charcoal blast furnaces in the XIXth century

Processing conditions in charcoal blast furnaces and their related internal phenomena are described, with good precision in papers and books by Hassenfratz, Karsten, Dumas, and especially Ebelmen in 1841, using, for the first time, the newly developed techniques of chemical analyses of gases and solids. Reviewing their publications at the light of more recent physical chemistry data and further developed blast furnace models, brings about a more detailed evaluation of the internal phenomena occurring inside charcoal blast furnaces and about their operating point. As industrial measurements have been carried out on small size blast furnaces, it may also bring a contribution to the archeology of early blast furnace metallurgy.

Alkali activated cement made from blast furnace slag generated by charcoal: Resistance to attack by sodium and magnesium sulfates

In Brazil, 20% of annual steel production where the furnaces are fueled using charcoal, with growth prospects the increase in the use of charcoal as a substitute for coke. The slags from coal blast furnaces (coke) have a large percentage of CaO, while those produced in charcoal blast furnaces have a low CaO-SiO2 ratio. This study investigated the behavior of alkali activated slag (AAS) made from GBFS generated by charcoal under attack by sulfates. Acceleration of the attack was achieved using miniature paste prisms and cylinder specimens. Sulfate-resistant blended cement samples (PC) were used for comparison. The results showed that AAS presented good performance in sodium sulfate solution, superior to that of the sulfate-resistant blended cement, such that no expansion, loss of compressive strength or degradation of C-S-H were observed. However, when AAS was subjected to magnesium sulfate solution, decalcification of C-S-H, formation of gypsum and alteration of physical, chemical and mechanical properties were observed. Also, the decreasing in compressive strength was much more intense for AAS. The tests using miniature past specimens were efficient at accelerating the sulfate attack, but the intense shrinkage of AAS indicated the need to monitor the mechanical performance.

An investigation of the carbonation of alkaline activated cement made from blast furnace slag generated by charcoal

In Brazil, 20% of annual steel production is from charcoal, with growth prospects due to the increase in the use of charcoal as a substitute for coke. The slags from coal blast furnaces (coke) have a large percentage of CaO to remove the present sulfur while those produced in charcoal blast furnaces have a low CaO-SiO2 ratio. Alkali-activated slag (AAS) is a type of cement obtained mostly from GBFS, which has good mechanical properties for engineering and low environmental impact in its production process. This process is based on the activation of the slag by an alkaline solution, such as hydroxides or silicates. However, because the product of hydration consists essentially of CASH, carbonation in AAS has been investigated. Also, studies dedicated to AAS from charcoal (low CaO/SiO2) are not common. Therefore, the goal of this paper was to study the behavior of GBFS-based AAS from charcoal under carbonated conditions by accelerated tests and compare it with that of Portland cement. The results showed that AAS presented higher carbonation depths (127.1 mm) than Portland cement (PC) (77.1 mm) and a sharp decrease in compressive strength from 37 to 28 MPa, which was related to intense shrinkage, decalcification of CSH and formation of vaterite. Although the slag from charcoal has more Al2O3 (13%) and MgO (6%), it was unable to form aluminosilicate or hydrotalcite, which could reduce the susceptibility of AAS carbonation.

Analysis of charcoal blast furnace slags by laser-induced breakdown spectroscopy.

Laser-induced breakdown spectroscopy (LIBS) was used for the analysis of charcoal blast furnace slags. Plasma was generated by an application of a 1064nm wavelength Nd:YAG laser beam to the surface of pellets created from the slags. The presence of Al, Ca, Fe, K, Mg, Mn, and Si was determined by identifying their characteristic spectral signatures. Multivariate analysis was performed for the quantification of these elements. The predicted LIBS results were found in agreement with the inductively coupled plasma optical emission spectrometry analysis. The limit of detection for Al, Ca, Fe, K, Mg, Mn, and Si was calculated to be 0.10%, 0.22%, 0.02%, 0.01%, 0.01%, 0.005%, and 0.18%, respectively.

Combustibility and reactivity of coal blends and charcoal fines aiming use in ironmaking

Charcoal is a very important reducing agent in Brazil, the world’s largest steel industry based on charcoal blast furnace. Charcoal generates large amounts of charcoal fines during its production and processing. A good alternative for harnessing this fuel is the injection into coke-based blast furnaces via PCI process (Pulverized Coal Injection), a key technology for reducing use of coke in ironmaking. This study aimed to evaluate the combustibility and reactivity to CO2 of binary blends of charcoal fines and coals with purpose to PCI. Moreover, it was also attempted to identify the reasons for the different behavior of coals. The work was carried out by thermogravimetric analysis (TGA). The proportions of charcoal used were 10, 20 and 50% in mass. Charcoal showed the highest combustibility and reactivity among tested fuels and the blends formulated had higher combustibility and reactivity than single coals.

ESTUDO DO REAPROVEITAMENTO DO GÁS DE TOPO DE ALTO-FORNO A CARVÃO VEGETAL PARA REDUÇÃO DO FENÔMENO DE CREPITAÇÃO EM GRANULADOS DE MINÉRIO DE FERRO

The phenomenon of particle size degradation of minerals due to decreptation is presented as source of fines. In the present work, a study of iron ores decrepitation by employing a system of thermal pretreatment of iron ore was carried out reusing exhaust gases from a mini charcoal blast furnace located in the state of Minas Gerais. The experiments were carried out in two periods of seven days each one, where in the first period the pretreatment system was deactivated and in the second period was activated. The results showed an improvement in the burden permeability by the reduction of the granules decreptation when it was used the thermal pretreatment, reflecting in a increasing of production

Analysis of synthetic natural gas injection into charcoal blast furnace

Recently, the synthetic natural gas (SNG) has been available for large consumers in the Brazilian domestic market. The SNG is a suitable fuel with potential use to several processes and facilities of the steel industry. This paper investigates the injection of SNG into charcoal blast furnaces as a substitute for granular charcoal charged from the top and pulverized charcoal injections with potential increase of productivity and decrease of specific CO2 emissions. In order to study the effect of replacement of granular charcoal and injection of pulverized charcoal the well known Blast Furnace Five Fluid Model (BF-FFM) is applied to describe detailed phenomena within the process. This model treats the blast furnace as a five-phase reactor, accounting for gas, lump solids (raw iron ore, sinter, pellets and granular charcoal), hot metal, pulverized charcoal, and molten slag. The model is based on conservation equations for mass, momentum, energy and chemical species numerically solved based on the finite volume method (FVM). The SNG has high amount of H2 and strongly affects the inner conditions of the reactor and only a comprehensive model with detailed chemical reaction rates can properly predict the inner parameters of the process and hence furnish useful information to design smooth operational conditions. The simulation results obtained in this study indicated that smooth operations using SNG up to 25Nm3/t of pig iron could be achieved simultaneously by increasing the productivity up to 58% and with a decrease of 40kg/thm on the granular charcoal charged.

Stability of black carbon in soils across a climatic gradient

The recalcitrant properties of black carbon (BC) grant it to be a significant pool of stable organic C (OC) in soils. Up to now, however, the longevity of BC under different climates is still unclear. In this study, we used BC samples from historical charcoal blast furnace sites to examine the stability of BC across a climatic gradient of mean annual temperatures (MAT) from 3.9 to 17.2°C. The results showed that OC concentration and OC storage in the BC‐containing soils at a soil depth of 0–0.2 m were 9.0 and 4.7 times higher than those in adjacent soils, respectively. Organic C in the BC‐containing soils was more stable, with a significantly lower amount of the labile OC fraction (4.4 mg g−1 OC versus 27.5 mg g−1 OC) and longer half‐life of the recalcitrant OC fraction (59 years versus 9 years) than the adjacent soils determined by incubation experiments. The stability of BC was primarily due to its inherently recalcitrant chemical composition as suggested by short‐term incubation and solid state 13C nuclear magnetic resonance spectra of isolated BC particles. A significant negative relationship between OC storage and MAT further indicated that OC storage was decreased with warmer climate. However, the lack of a relationship between MAT and BC mineralization suggested that the stability of the remaining BC was similar between sites with very different MAT. Despite the fact that warming or cooling result in immediate consequences for BC stocks, it may have little impact on the stability of remaining BC over the period studied.

Natural oxidation of black carbon in soils: Changes in molecular form and surface charge along a climosequence

The aim of this work was to investigate changes in molecular form and surface charge of black carbon (BC) due to long-term natural oxidation and to examine how climatic and soil factors affect BC oxidation. Black C was collected from 11 historical charcoal blast furnace sites with a geographic distribution from Quebec, Canada, to Georgia, USA, and compared to BC that was newly produced (new BC) using rebuilt historical kilns. The results showed that the historical BC samples were substantially oxidized after 130 years in soils as compared to new BC or BC incubated for one year. The major alterations by natural oxidation of BC included: (1) changes in elemental composition with increases in oxygen (O) from 7.2% in new BC to 24.8% in historical BC and decreases in C from 90.8% to 70.5%; (2) formation of oxygen-containing functional groups, particularly carboxylic and phenolic functional groups, and (3) disappearance of surface positive charge and evolution of surface negative charge after 12 months of incubation. Although time of exposure significantly increased natural oxidation of BC, a significant positive relationship between mean annual temperature (MAT) and BC oxidation (O/C ratio with r = 0.83; P < 0.01) explained that BC oxidation was increased by 87 mmole kg C −1 per unit Celsius increase in MAT. This long-term oxidation was more pronounced on BC surfaces than for entire particles, and responded 7-fold stronger to increases in MAT. Our results also indicated that oxidation of BC was more important than adsorption of non-BC. Thus, natural oxidation of BC may play an important role in the effects of BC on soil biogeochemistry.

PROCESS CONTROL MODEL FOR CHARCOAL BLAST FURNACES IN BRAZIL

In the present paper, a simple process control model for charcoal blast furnaces is presented. The main feature of the model is that it is based on carbon balance and requires low investment in instrumentation. The process model described in the present work has been tested through trial runs and has proved to be an important tool to maintain a stable furnace operation.

The Blast Furnace at Rockley, South Yorkshire

At Rockley, Yorkshire (SE338021) there survives the stone stack of a blast furnace which archive sources suggest was built in about 1700 and was used with charcoal until at least 1741. Antiquarian suggestions of a later period of operation using coke have received archaeological support in excavations carried out between 1978 and 1982. These established the layout of the blowing and casting houses, as well as the position of a head race, and of a water wheel of which only fragments survived. Of particular significance was a stone-lined casting pit, inserted into the floor of the casting house. The results of this excavation provide new impetus for research on the adaptation of charcoal blast furnaces for the use of coke.

The Iron Industry of the Weald.

This revised and expanded second edition (the first appeared in 1985) provides a definitive regional study of the charcoal iron industry, as well as a major addition on Wealden history generally. The new edition reprints the whole of the original text (and all the illustrations), covering the geology of the Weald (by Bernard Worssam); prehistoric, Roman, and Medieval ironmaking; the rise and fall of the charcoal blast furnace in the Weald; and the archaeology and technology of the industry during the blast furnace period. The extensive gazetteers of sites, which are an essential feature of the book, have been revised and extended in the light of recent fieldwork and research, as has the bibliography. There is also a completely new index, compiled by Ann Hudson, which now includes the gazetteers, as well as the main text.