Papers by Keyword: Autoclave

Abstract: Materials selection for hydrogen service is needed to support the deployment of hydrogen as a fuel as well as the development of codes and standards for stationary hydrogen use, hydrogen vehicles, refueling stations, and hydrogen transportation. Hydrogen energy infrastructure is currently in the process of development and in preparation for mass transportation of hydrogen gas and methane-hydrogen media involves significant use of the existing network of gas pipelines and formation of a network of hydrogen pipelines. Materials property measurement is needed on deformation, fracture and fatigue in hydrogen-containing media. Determination of steel properties such as strength, crack and fatigue resistance are priority to ensure safe design of pipelines transporting hydrogen gas or methane-hydrogen mixture. At the same time, there is a problem in technological support for evaluation of hydrogen compatibility of materials in laboratory conditions for evaluation of hydrogen embrittlement, depending on hydrogen concentration, methods and modes of loading, temperature, pressure and actual properties of materials.

Abstract: In this research, iron oxide nanoparticles were prepared by a new hydrothermal pyrolysis technique at different reaction times. X-ray diffractometer (XRD) characterization showed that the nanoparticles have high crystallinity with a combination of two crystal phases maghemite and magnetite, as the reaction time increase the ratio of magnetite phase to maghemite phase increased. The morphological properties of the samples showed an increase in the particle size from 58 to 108 nm due to the single domain–multidomain transition as showed by scanning electron microscope (SEM). Electron Dispersive X-ray (EDX) spectra showed only peaks of oxygen and iron that verified the formation of iron oxide nanoparticles. The Fourier transform infrared spectroscopy (FT-IR) showed that the absorption peaks at about 578 cm^-1 and 630 cm^-1 correspond to the stretching modes of the Fe-O in magnetite, as the reaction time increased the peak around 630 cm^-1 decreased due to the magnetite phase only. Finally, all the results showed the formation of iron oxide nanoparticles by this new technique that merges spray pyrolysis and hydrothermal techniques with many advantages such as spraying successive parameters in a short time, high-speed, good homogeneity, and pure material with small particle size.

Abstract: Flue Gas Desulfurization (FGD) is a waste incineration process commonly used to eliminate sulfur dioxide (SO₂) from flue gas power plants. FGD by-product recorded a rich gypsum content, also known as calcium sulfate dehydrate (CaSO₄•2H₂O), which has promising practical applications in plaster mould production. Plaster of Paris (POP) with a chemical composition of calcium sulfate hemihydrate (CaSO₄•0.5H₂O) is widely used in plaster mould production because of its quick setting and hardening upon moistened. Naturally, gypsum with 2 molecules of crystalline water can change to 1.5 molecules via the dehydration process. Various dehydration methods were conducted to transform FGD gypsum to hemihydrate. After undergoing different autoclave processes, the phase transition of FGD by-products was identified by X-ray diffraction (XRD) mode and compared with commercial POP. Chemical composition of FGD sludge contains a high amount of calcium oxide (CaO), sulfur trioxide (SO₃) and boron trioxide (B₂O₃), as well as other impurities such as fluorine (F), chlorine (Cl), and magnesium oxide (MgO). Based on phase analysis, sample H1 to H5 show the percentage of hemihdyrate is 1.5%, 19.7%, 2.8%, 1.2%, and 46.1%, respectively, after different dehydration methods.

Abstract: The problem of copper leaching from copper-electrolyte slimes is discussed. To intensify the long and costly process, it is proposed to use a leaching system containing sulfuric acid and hydrogen peroxide as an oxidizing agent. The chemical transformations possible variants at the treatment of slime under the specified conditions and the thermodynamic parameters of the predicted reactions are considered. Solution composition effect on the copper dissolution rate at room temperature was studied in the presence of hydrogen peroxide using the rotating disc technique. It is found that dissolution rate constant at using hydrogen peroxide slightly inferior to dissolution rate constant under autoclaved conditions in an oxygen atmosphere.

Abstract: The problems of autoclave c of cellular concrete are considered. It was shown that the key problem of autoclaving is the appearance of areas of concrete with different dark colors and a reduced strength. The main reason for their occurrence is the presence of air in the porous space of cellular concrete, which prevents heat transfer. Cold air does not allow the concrete to warm up to a temperature of 170-175 °C, which hinders the flow of physical-chemical processes of hardening. The proposed activities that improve the quality of autoclave processing and precluding the formation of «non-steamings» in the concrete: ensure the temperature inside cellular concrete mass of at least 80 °C before curing, the vacuum (P=‒0.5 Bar) before pressure rise in the autoclave, preventing the ingress of air into the autoclave at the beginning of the process.

Abstract: An experimental program was carried out to investigate how to improve the characteristics of steel slag. Mainly the pretreatment methods of cooking and autoclave were used to detect such as free CaO content in the steel slag. The physical and chemical characteristics of steel slag were measured by X-ray diffraction (XRD) and fluorescence (XRF) analysis. The aim of improving the slag utilization is an important way to resolve large production problem, and then the research progress of steel slag utilization at home and abroad are recycled as raw material to be applied. By means of those ways to manage steel slag we have received the following conclusions: With the increase of cooking temperature the content of free CaO is gradually reduced. When temperature higher than 90oC the means could greatly reduce the free CaO content from about 7% wt. to less than 2.5% wt. in 3 h. By means of autoclave pressure upto 1.5MPa could greatly reduce the free CaO content from about 7% wt. to less than 3.2% wt. in 3 h. Through the study of the relevant of steel slag after pretreatment can effectively reduce the free CaO content in the steel slag, improving the stability of the steel slag is advantageous to the seven used in the construction field.

Abstract: In this study, β-wollastonite is produced from a reaction between silica (SiO₂) and calcium oxide (CaO) with the SiO₂/Cao ratio of 55:45. Rice straw ash is chosen as the source for SiO₂ instead of rice husk ash because the straw can yield up to 85% of silica even though this percentage is lower than those silica yielded from rice husk ash. It is found that period of autoclaving and sintering play an important role in producing the wollastonite. As shown in the XRD results, a single phase β-wollastonite is obtained after 8 h of autoclaving and 3 h of sintering at 950 °C. The produced β-wollastonite phase also shows a good crystallinity but needs longer sintering time compared with wollastonite produced using rice husk ash. DTA graph shows a chemical reaction between silica and calcium oxide started to occur at 788.3°C. IR spectroscopic analysis data confirm that the IR peaks at 681, 894 and 931 cm^-1 are due to the β-Wollastonite phase. Form the results obtained, it can be concluded that rice straw ash is comparable to rice husk ash as a precursor in producing β-Wollastonite material.

Abstract: Special industrial application of fiber-cement composites is currently one important issue of concrete industry and research activity. The field of refractory and high-temperature resistance materials is very large and contains the cement composites too. Hydrothermal curing together with using aluminous cement with refractory basalt aggregates and fibers shows high potential for its applications in high temperature. These composite is characterized by compressive strength over 140 MPa and tensile strength in bending 12 MPa (investigated on specimens 40 x 40 x 160 mm). After exposure to temperature 1000 °C these parameters are 60 MPa in compression respective 6 MPa in bending. Achieved values are significantly higher than in the case of laboratory curing condition and there are suitable especially for prefabricated fire resistance cladding or other special application in the industry.

Abstract: In these days, autoclaved aerated concrete research points to the utilization of alternative raw materials such as metakaoline. An effort is made to improve the mechanical and related heat-insulation properties of the products without significant change of present technology and price. This work studies the effect of metakaoline, as an alternative raw material to Portland cement, on final properties of autoclaved aerated concrete, especially the effect on the volume weight and compressive strength. Quantitative and qualitative mineralogical composition, especially the presence and the amount of Tobermorite and Xonotlite were observed by XRD and TG-DTA-EGA methods.

Abstract: This paper has studied using steam injector to recycle waste steam emission from autoclave kettle and it will produce great economic benefits and environmental benefits. Autoclave kettle which is a kind of resistance to high temperature high pressure steam curing equipment, and it’s mainly used for pipe pile, lime-sand brick and aerated concrete production. We will get more technical and economic benefits, if the research results can be popularized and applied in the national building materials products production.