With the green hydrogen starting at 4.45  US$/kg, [1] hydrogen usage seems difficult. Not only the green hydrogen is very expensive, even the gray hydrogen is uneconomical. However, hydrogen production is a possibility when there is oversupply of electric energy.

In California, renewables as solar and wind already able to provide almost 100% of the energy, avoiding fossil fuels as coal and natural gas [2]. Both windy days or sunny days offer the possibility of in-excess production of energy [2], which can be employed for cheap hydrogen production.

Usually, DRI – Direct Reduction of Iron – request high quality iron ore [3], offering a possibility for Brazil in this market. Vale is considering a hub for HBI (hot briquetted iron) in Porto do Açu in Brazil [4]. Other possible hubs are planned for Saudi Arabia, Oman and Dubai, due to the possibility of cheap natural gas [5].

This study addresses economic issues of hydrogen usage in steelmaking.

Although the denomination “steelmaking” is much more  common in English, the world “siderurgy”  also exists in English. The name “siderurgy” comes from the old Greek world for iron: sideros. Steelmaking and Ironmaking revolutionized the history of humankind: There are distincts quality of life for the 4 main hystorical ages: stone age, copper age [1], bronze age, and iron age. 

Nowadays it became clear that the Old Egyptians were less advanced in metallurgy - or ironmaking - than their neighbors: The Tut-ankh-amon dagger is  meteoritic (due to high nickel) and, besides, it probably was imported from Mittani or Hittite lands [2], thats is, present day Turkey .

The transition of bronze to iron and steel was very important for quality of life: In the iron age, furniture could be easily  manufactured, and also ships and boats. This revolutionized the commerce. Bronze was very expensive due to the scarce and essential alloying element  tin (11-12% in bronze). Instead, iron ore can be found almost everywhere.

It is reviewed the complex process that gave origin to smelting [3,4], for steel and iron production:  Magnetite maybe the first ore used for reduction. The origin of first smelting techniques are still uncertain [5]. More and more it became clear that Black Sea regions started the iron smelting process, possibly in areas related to the Chalybes [6], near present day Trebzon.

The present study investigates the advantages and feasibility of the shaft furnace in direct reduction processes, highlighting its energy efficiency and flexibility in the choice of reducing agents. The complexity of the processes involved within the furnace is addressed, dividing it into four distinct zones. Although mathematical models have been developed to predict direct reduction, their application is limited due to the simplification required in the face of the complexity of the phenomena. The integration of the shaft furnace with partial replacement of the charge by self-reducing pellets is explored, demonstrating a potential increase in process efficiency and reduction in CO₂ emissions. This study proposes a multiphase and multicomponent mathematical model to predict the internal temperature distribution of the furnace, validated by simulations on an industrial scale. The results indicate a significant increase in productivity and metalization when using self-reducing pellets, as well as, a reduction in carbon emissions when partially replacing conventional reducing gas with hydrogen. The findings highlight the importance of optimizing operational parameters to maximize the benefits of the shaft furnace in direct iron production.

This study investigates the potential of combined injection of hydrogen as fuel and pulverized charcoal (PCH) in the operation of blast furnaces, aiming to reduce carbon emissions and increase energy efficiency. Through a detailed computational model, we analyzed various operational scenarios with different rates of PCH and hydrogen injection. The results demonstrate that the partial or total replacement of pulverized coal (PC) with PCH can significantly increase blast furnace productivity, reducing coke consumption and carbon emissions. An improvement in internal material distribution and temperature was also observed, with an acceleration in burden descent and a modification in the temperature pattern in the raceway region. Furthermore, it was found that progressive increases in PCH and hydrogen injection can lead to substantial increases in blast furnace productivity, with additional reductions in coke consumption and carbon emissions. These results highlight the potential of combined hydrogen and PCH injection as a viable strategy to promote sustainability and efficiency in the steel industry, aligned with decarbonization and circular economy objectives.

The present situation of the market and applications of rare-earths is reviewed. It is given special attention for discussing the possibility of substitution of  rare-earth magnets by other families of magnets.

Three are the main commercial applications of rare-earths: i) luminescent phosphors, ii) magnets, and iii) catalysis.

For catalysis, the cheap rare-earths as cerium and lanthanum are employed.  Luminescent phosphors are essential in many applications, as lasers and, for example, erbium is used in optical fibers. However, in spite of its relevance, erbium is not expensive as Tb and Dy. 

In LED applications, the rare-earths are used as thin films, and , thus the demand in volume  is not very significant when compared with the demand for magnets. The use of white LED (light emission diode) significantly reduced the demand for europium after 2015, but this application is still relevant. In the 1960s and up the 1980s, Europium was the most expensive rare-earth, due to extreme demand.

The rare-earth market is nowadays driven by Tb, Dy, Nd and Pr, which are employed in rare-earth iron permanent magnets of the RE2Fe14B family (RE=rare earth). For applications in high temperature, dysprosium and terbium are added, and this made the demand and price of Dy and Tb be skyrocketing.

SmCo magnets have the problem of using the expensive element cobalt. Nowadays the demand and price of cobalt increased conbseiderably due to application in rechargeable battteries, and thus, SmCo use in large scale is avoided, but they remain relevant for high temperature applications (above 150oC).

Possible alternatives for rare-earth  permanents magnets are discussed. Among the few options for replacement are the ferrite magnets (BaFe12O19 or SrFe12O19), the Alnico magnes based on shape anisotropy and maybe iron nitrogen. Economic and technical feasibility of these families of magnets are discussed.

Its is given a brief overview about recent mining projects in Brazil, which are focusing on ionic clays, with the objective of extracting the scarce and expensive elements terbium and dysprosium. 

It was recently presented a model [1-3] able to predict the magnetic anisotropy of any sample, This is called the "Simultanoeus Fitting Method" SFM.

According the SFM method, the magnetic anisotropy can be determined, since magnetic measurements are performed at the  (_|_) perpendicular and (//) parallel directions (relative to the alignment direction). The method assumes samples with alignment in one preferential direction, thus with uniaxial anisotropy. This kind of anisotropy is typically found in samples prepared by powder metallurgy, where the alignbment is obtained by applying magnetic fields in grains with single domain size. 

Using the SFM, the crystallographic texture of samples can be determined directly from magnetic measurements, avoiding complicated, laborious and expensive techniques as EBSD - Electron BackSacterred Diffraction.

A symmetrical distribution as for example the Gaussian, is used for describing the crystallographic texture.

Other distribution functions can also be used, since they are symmetrical. This includes Cauchy -Lorentz, Voigt and Pearson VII as possibilities.

It is experimentally found that f=cos(theta)^n or Gaussian distributions describe very well the texture of the samples.

The model allows the re-evaluation of experimental data. Here it is discussed how to apply the model in very different samples.

These samples are SmFeN (magnetocrystalline anisotropy), Alnico, (shape anisotropy [4,5]) and cobalt-needle samples.

In cobalt needle samples the shape anisotropy and the magnetocrystalline anisotropy may have the same order of magnitude.

It is discussed the question of dominant anisotropy.