High Temperature Oxidation Behavior of Creep Resistant Steels in Water Vapour Containing Environments

This study describes the water vapour effect on the oxidation resistance of 9Cr creep resistant steels. Boiler P91 and MarBN steels were oxidized for 3000 h in a simulated humid atmosphere with ~10% water vapour. The oxidation kinetics had a stable course for 1000 h and was evaluated by the weight gain curves for both experimental steels and both oxidation temperatures. The oxidation rate was higher at 650 °C versus 600 °C, as reflected by the oxidation rate coefficient. A significant increase occurred after 1000 h of oxidation, which was related to the local breakdown oxide scale and oxide nodules were formed on steel. This oxidation behavior was influenced by the fact that a compact spinel structure of iron oxides and alloying elements were not formed on the steel. Analysis after 3000 h of exposure showed hematite Fe2O3 formed on the outer layer, magnetite Fe3O4 on the middle layer, and the bottom layer consisted of iron-chromium-spinel (Fe,Cr)2O3.

Modifikasi Proses Pengolahan Boiler Feed Water (BFW) dari All Volatile Treatment (AVT) menjadi Oxygenated Treatment (OT) untuk Produksi Listrik Ramah Lingkungan

In power plant industries, boiler feed water (BFW) quality becomes the main parameter for steam generation, which is used for electricity production. To generate standard BFW for power plants, each impurity within water resources should be removed to prevent corrosion and scale deposition by several processes such as sedimentation, coagulation, polishing, and deaeration. Operation conditions that involved high temperature would trigger corrosion as a crucial factor in the maintenance and practical lifetime of the equipment. In the beginning of the operation, PT. Cirebon Electric Power (CEP) used All Volatile Treatment–Reduction (AVT-R) by injection of both ammonia and hydrazine. In order to optimize the operation, the BFW treatment was changed to All Volatile Treatment–Oxidation (AVT-O) that only uses of ammonia and deaerator for removing the dissolved gas. Based on the actual evaluation, AVT technology showed less performance related to corrosion prevention and high chemical consumption. Therefore, PT. CEP tried to implement modification in the BFW treatment, which is AVT technology to Oxygenated Treatment (OT). This paper is to evaluate the effect of those modifications on corrosion prevention and resource-energy saving. The modification into OT showed valuable results that decrease concentration of dissolved Fe from 1 ppb to 0.1 ppb in the deaerator outlet stream. This data reveals that good corrosion prevention can be achieved through the creation of passive layers, hematite Fe2O3. Oxygen injection into the water circulation system yielded an oxidation atmosphere so that the passive layer, Fe2O3, was formed. In addition to corrosion prevention, this modification also cut the amount of ammonia injection into the system from 2 ppm to 0.12 ppm. Reduction of that ammonia injection provides other benefits such as decreasing the volume of resin regeneration, which becomes only twice a month. This situation also created other benefits such as reducing the regeneration water, chemicals, and wastewater. Thus, the modification could establish the electricity production by PT. CEP more environmentally friendly and sustainable.A B S T R A KPada operasi PLTU, kualitas boiler feed water (BFW) menjadi parameter yang krusial untuk menghasilkan steam yang akan digunakan untuk memproduksi listrik. Untuk mendapatkan BFW sesuai dengan standar yang ada, maka pengotor di dalam air baku industri harus dihilangkan karena dapat menyebabkan korosi dan pembentukan kerak, baik pada pipa maupun peralatan. Kondisi operasi yang melibatkan steam pada suhu tinggi menyebabkan korosi menjadi masalah yang krusial terutama terkait dengan maintenance dan umur efektif pabrik. Pada awal berdirinya, PT. Cirebon Electric Power (CEP) menggunakan teknologi All Volatile Treatment–Reduction (AVT-R) dengan injeksi amonia dan hidrazin. Selanjutnya, dilakukan optimasi melalui perubahan proses menjadi All Volatile Treatment–Oxidation (AVT-O) dengan hanya menginjeksikan amonia dan mengoptimalkan fungsi deaerator untuk menghilangkan pengotor dissolved gas. Berdasarkan data lapangan, teknologi AVT yang digunakan kurang memberikan pencegahan korosi yang baik dan juga jumlah bahan kimia yang digunakan masih relatif banyak. Agar lebih ramah lingkungan dan handal, PT. CEP berusaha untuk melakukan modifikasi terhadap pengolahan boiler feed water (BFW) dari yang semula menggunakan teknologi AVT-O menjadi Oxygenated Treatment (OT). Penelitian ini bertujuan untuk mengevaluasi dampak modifikasi sistem AVT menjadi OT pada pencegahan korosi dan juga penghematan sumber daya. Modifikasi sistem AVT-O menjadi OT berhasil menurunkan konsentrasi dissolved Fe dari 1 ppb menjadi 0,1 ppb pada BFW. Hal ini menunjukkan terjadinya peningkatan pencegahan korosi melalui pembentukan double protective layer yang merupakan kombinasi magnetite (Fe3O4) dan hematite (Fe2O3). Injeksi oksigen ke dalam sistem mengubah kondisi air menjadi suasana oksidasi sehingga mampu mengubah dan membentuk lapisan baru sebagai pencegahan korosi. Selain pencegahan korosi, modifikasi ini juga berhasil menurunkan jumlah injeksi amonia dari 2 ppm menjadi 0,12 ppm dalam siklus air yang ada. Penurunan jumlah injeksi amonia ini akan memberikan keuntungan beruntun berupa berkurangnya frekuensi regenerasi resin dari semula 8 menjadi 2 kali perbulan. Kondisi ini akan menghasilkan penghematan sumber daya berupa kebutuhan air untuk regenerasi, bahan kimia amonia, dan beban pencemaran. Oleh karena itu, modifikasi ini telah membuat proses produksi listrik di PT. CEP lebih ramah lingkungan dan berkelanjutan.Kata kunci: All Volatile Treatment (AVT); efisiensi energi; korosi boiler; Oxygenated Treatment (OT)

Study on the reducibility of iron ore pellets at high temperature

The behaviour of iron ore pellets in a blast furnace must be considered to improve ironmaking operations, especially when a large amount of the pellets is used. This study presents the reduction degree, mineralogical composition, and morphology of the pellet reduced in a gas mixture of 60% CO and 40% Ar at temperatures between 900 and 1,100oC. The pellet was prepared from iron ore from the Cao Bang province, Vietnam, by rotary drum. The obtained results showed that the reduction degree of the pellet increased with increasing reduction time and temperature. The activation energy of the reducing reaction was calculated to be 63.2 kJ/mol, which indicated that reduction occurred more easily in the present condition. X-ray diffraction (XRD) results revealed mineralogical phases such as hematite (Fe2O3), magnetite (Fe3O4), wüstite (FeO), metallic iron (Fe), and fayalite (Fe2SiO4) existing in the pellets when reduced for different times and temperatures. Fe and Fe2SiO4 were found to be the majority in the pellet that was reduced for 90 min at 1,100oC. Scanning electron microscopy (SEM) observations suggested the formation of a liquid phase, e.g., Fe2SiO4, which retarded the reducing reaction because it hindered the diffusion of gas flow inside the pellet. This phenomenon is essential to blast furnace ironmaking because pellets must be completely reduced before they move down to the liquid zone.

Composite Materials Based on Iron Oxide Nanoparticles and Polyurethane for Improving the Quality of MRI

Polyether urethane (PU)-based magnetic composite materials, containing different types and concentrations of iron oxide nanostructures (Fe2O3 and Fe3O4), were prepared and investigated as a novel composite platform that could be explored in different applications, especially for the improvement of the image quality of MRI investigations. Firstly, the PU structure was synthetized by means of a polyaddition reaction and then hematite (Fe2O3) and magnetite (Fe3O4) nanoparticles were added to the PU matrices to prepare magnetic nanocomposites. The type and amount of iron oxide nanoparticles influenced its structural, morphological, mechanical, dielectric, and magnetic properties. Thus, the morphology and wettability of the PU nanocomposites surfaces presented different behaviours depending on the amount of the iron oxide nanoparticles embedded in the matrices. Mechanical, dielectric, and magnetic properties were enhanced in the composites’ samples when compared with pristine PU matrix. In addition, the investigation of in vitro cytocompatibility of prepared PU nanocomposites showed that these samples are good candidates for biomedical applications, with cell viability levels in the range of 80–90%. Considering all the investigations, we can conclude that the addition of magnetic particles introduced additional properties to the composite, which could significantly expand the functionality of the materials developed in this work.

Structural and Magnetic Properties of Nano Composite (Ni1-xSrx Fe12 O19) Prepared by Sol-gel

The compound was prepared by sol-gel method for spontaneous combustion with certain weight ratios (x=0.0,0.1,0.2,0.3,0.4,0.5,0.6,0.7,0.8,0.9), the samples were calcined at a temperature (900oC) for a period of two hours(2h), then studied its structural and magnetic properties.one of the most prominent results that we obtained from the X-ray diffraction technique (XRD) is that compound has several phases. Where the sample (NiFe2O4) appeared to be polycrystalline and the dominant phase in it is the cubic phase, while the other phase is (Hematite)(Fe2O3) A crystal structure rhomboid (Rhombohedral), in addition to these two phases, the phase with the existing quaternary structure appeared (Sr2Fe2O5) its called (Orthorhombic). The results of the magnetic properties that were obtained through the (VSM) device, and one of the most important of these properties is the magnetic hysteresis loop by analyzing the magnetic hysteresis loop at (x=0.3), where the least area of the hysteresis loop or the least width of the hysteresis loop One of the most important parameters of the magnetic properties is the saturation magnetism (μS) and its value ranges from (19.76-3.86) (emu/gr), the highest value was at (X=0.3) and its value is (19.76emu/gr) and in general its value decreases with increasing concentration of strontium. The residual magnetism (Mr) ranges between (7.45-1.58) (emu/gr), where it reached its highest value at (x=0.3) and its value is (7.45emu/gr), and generally its value decreases with increasing concentration of strontium. In addition to that, there is another parameter which is coercion or Magnetic coercivity (Hc) ranges in value (1751.104-209.26) (Oe), reaching its lowest value at (x=0.3), and then increases with increasing strontium concentration until it reaches its highest value at (x=0.9), where it reached its value is (1751.104Oe). The square rate represented by the symbol (μi) has high values. This means that there is a mutual coupling between the soft and hard magnetic phases, which was the highest value at (x=0.3) and its value is (4.93).

New Approaches to Increasing the Superhydrophobicity of Coatings Based on ZnO and TiO2

The work presented is devoted to new approaches to increasing the superhydrophobic properties of coatings based on zinc oxide (ZnO) and titanium dioxide (TiO2). There is an innovation in the use of inorganic coatings with a non-polar structure, high melting point, and good adhesion to ZnO, in contrast to the traditionally used polymer coatings with low performance characteristics. The maximum superhydrophobicity of the ZnO surface (contact angle of 173°) is achieved after coating with a layer of hematite (Fe2O3). The reason for the abnormally high hydrophobicity is a combination of factors: minimization of the area of contact with water (Cassie state) and the specific microstructure of a coating with a layer of non-polar Fe2O3. It was shown that the coating of ZnO structures with bimodal roughness with a gold (Au) layer that is 60-nm thick leads to an increase in the wetting contact angle from 145° to 168°. For clean surfaces of Au and hematite Fe2O3 films, the contact angle wets at no more than 70°. In the case of titanium oxide coatings, what is new lies in the method of controlled synthesis of a coating with a given crystal structure and a level of doping with nitrogen using plasma technologies. It has been shown that the use of nitrogen plasma in an open atmosphere with different compositions (molecular, atomic) makes it possible to obtain both a hydrophilic (contact angle of 73°) and a highly hydrophobic surface (contact angle of 150°).

Production of Ferroboron from Wastes by SHS-metallurgy and influence of Ligatures on the Structure/Properties of Cast Iron

Waste, generated during the industrial process negatively affects the environment, but at the same time it is a valuable raw material and can be used to produce new marketable products. The study of the effectiveness of Self-propagating High temperature Synthesis (SHS) methods, which are characterized by the simplicity of the necessary equipment, the purity of the final product and the high processing speed, is under the wide scientific and practical interest to solve the set problem. The work describes technological aspects of production of ferro boron by the method of SHS - metallurgy from iron-containing wastes of rolled production for alloying of cast iron and results of effect of alloying element on degree of boron assimilation with liquid cast iron. Features of Fe-B system combustion have been investigated and the main parameters to control the phase composition of synthesis products have been experimentally established. Effect of overloads on patterns of cast ligatures formation and mechanisms of structure formation of SHS products was studied. It has been shown that an increase in the content of hematite Fe2O3 in iron-containing waste leads to an increase in the content of phase FeB and accordingly, the amount of boron in the ligature. Boron content in ligature is within 3-14%, and phase composition of obtained ligatures consists of Fe2B and FeB phases. Depending on the initial composition of the wastes, the yield of the end product reaches 91 - 94%, and the extraction of boron is 70 - 88%. Combustion processes of high exothermic mixtures allow obtaining a wide range of boron-containing ligatures from industrial wastes. In view of the relatively low melting point of the obtained SHS-ligature, the positive dynamics of boron absorption by liquid iron is established. According to the obtained data, the degree of absorption of the ligature by alloying gray cast iron at 1450 ° C is 80 - 85%. When combined with the treatment of liquid cast iron with magnesium, followed by alloying with the developed ligature, boron losses are reduced by 5-7%. At that uniform distribution of boron micro-additives in volume of treated liquid metal is provided.

High purity hematite (Fe2O3) from beach sands for soft ferrite magnetic materials application

Actually, the potential and deposites are rich and spread in many place, but the process from raw material to industrial product is not optimal yet. In this work, the manufacture of iron sand was done using direct reduction technique by compact coals as reductor. The carbon compound of coals were using for releasing oxide in magnetite compounds (Fe3O4) of iron sand, so it could be transformed to Fe phase. The iron sand was firstly milled using high energy ball mill (HEBM) for 0, 10, 20, and 40 hours. Then the iron sands samples were mixed with coals, bentonite and compacted using hydraulic press. Then, loaded into furnace and sintered at 700 °C, 800 °C, and 900 °C. As the results, it was identified (using XRF) that the major phase was Fe2O3 (75.40 %). Consistent with XRF results, the phase composition observation by using XRD was shown that the major phase of sample was Fe2O3 (hematite). It was also shown that the crystallite size of the sample was around 8 nm, as calcultaed using Scherrer formula. The magnetic behavior investigation was showed that the decreasing in magnetic saturation value (Ms) and remanent (Br) and followed by increasing the coercivity value (Hc).

Green Synthesis of Hexagonal Hematite (α-Fe2O3 ) Flakes Using Pluronic F127-Gelatin Template for Adsorption and Photodegradation of Ibuprofen

Hematite (-Fe2O3) with uniform hexagonal flakes morphology has been successfully synthesized using a combination of gelatin as natural template with F127 via hydrothermal method. The resulting hematite was investigated as adsorbent and photocatalyst for removal of ibuprofen as pharmaceutical waste. Hexagonal flake-like hematite was obtained following calcination at 500 oC with the average size was measured at 1-3 µm. Increasing the calcination temperature to 700 oC transformed the uniform hexagonal structure into cubic shape morphology. Hematite also showed high thermal stability with increasing the calcination temperatures, however, the surface area was reduced from 47 m2/g to 9 m2/g. FTIR analysis further confirmed the formation Fe-O-Fe bonds, and the main constituent elements of Fe and O were observed in EDX analysis for all samples. Fe2O3-G samples have an average adsorption capacity of 55-25.5 mg/g at 12-22% of removal efficiency when used as adsorbent for ibuprofen. The adsorption capacity was reduced with increasing the calcination temperatures due to the reduction of available surface area of the hexagonal flakes when transformed into cube. Photocatalytic degradation of ibuprofen using hematite flakes achieved 50% of removal efficiency meanwhile combination of adsorption and photocatalytic degradation further removed 80% of ibuprofen in water/hexane mixtures.