112 resultados para Supercondutividade de alta temperatura


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Recent studies are investigating a new class of inorganic materials which arise as a promising option for high performance applications in the field of photoluminescence. Highlight for rare earth (TR +3 ) doped, which have a high luminous efficiency, long decay time and being able to emit radiation in the visible range, specific to each element. In this study, we synthesized ZrO2: Tb +3 , Eu +3 , Tm +3 nanoparticles complex polymerization method (CPM). We investigated the influences caused by the heat treatment temperature and the content of dopants in zirconia photoluminescent behavior. The particles were calcined at temperature of 400, 500 and 600 ° C for two hours and ranged in concentration of dopants 1, 2, 4 and 8 mol% TR +3 . The samples were characterized by thermal analysis, X-ray diffraction, photoluminescence of measurements and uv-visible of spectroscopies. The results of X-ray diffraction confirmed the formation of the tetragonal and cubic phases in accordance with the content of dopants. The photoluminescence spectra show emission in the region corresponding simultaneous to blue (450 nm), green (550 nm) and red (615 nm). According to the results, ZrO2 particles co-doped with rare earth ions is a promising material white emission with a potential application in the field of photoluminescence

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A polyester film has a vast application field, due some properties that are inherent of this kind of material such as, good mechanical resistance, chemical resistance to acids and bases and low production cost. However, this material has some limitations as low superficial tension, flat surface, low affinity to dyers, and poor adhesion which impede the use of the same ones for some finality as good wettability. Among the existent techniques to increase the superficial tension, plasma as energy source is the more promising technique, because of their versatility and for not polluting the environment. The plasma surface polymeric modification has been used for many researchers, because it does not affect the environment with toxic agents, the alterations remains only at nanometric layers and this technique shows expressive results. Then, due to its good acceptance, polyester films were treated with oxygen plasma varying the treatment time from 10 to 60 min with an increase of 10 min to each subsequent treatment. Also, the samples were treated with a gas mixture (nitrogen + oxygen) varying the percentage of each gas the mixture from 0 to 100%, the treatment time remaining constant to all treatments (10 min). After plasma treatment the samples were characterized by contact angle, surface tension, Raman spectroscopy, Infrared attenuated total reflection (IR-ATR) and atomic force microscopy, with the aim to study the wettability increase of treated polyester films as its variables. In the (O2/N2) plasma treatment of polyester films can be observed an increase of superficial roughness superior to those treated by O2 plasma. By the other hand, the chemical modification through the implantation of polar groups at the surface is obtained more easily using O2 plasma treatment

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Textile production has been considered as an activity of high environmental impact due to the generation of large volumes of waste water with high load of organic compounds and strongly colored effluents, toxic and difficult biodegradability. This thesis deals with obtaining porous alumina ceramic membranes for filtration of textile effluent in the removal of contaminants, mainly color and turbidity. Two types of alumina with different particle sizes as a basis for the preparation of formulation for mass production of ceramic samples and membranes. The technological properties of the samples were evaluated after using sintering conditions: 1,350ºC-2H, 1,450ºC-30M, 1,450ºC-2H, 1,475ºC-30M and 1,475ºC-2H. The sintered samples were characterized by XRD, XRF, AG, TG, DSC, DL, AA, MEA, RL, MRF-3P, SEM and Intrusion Porosimetry by Mercury. After the characterization, a standard membrane was selected with their respective sintering condition for the filterability tests. The effluent was provided by a local Textile Industry and characterized at the entry and exit of the treatment plant. A statistical analysis was used to study the effluent using the following parameters: pH, temperature, EC, SS, SD, oil and grease, turbidity, COD, DO, total phosphorus, chlorides, phenols, metals and fecal coliform. The filtered effluent was evaluated by using the same parameters. These results demonstrate that the feasibility of the use of porous alumina ceramic membranes for removing contaminants from textile effluent with improved average pore size of 0.4 micrometre (distribution range varying from 0,025 to 2.0 micrometre), with total porosity of 29.66%, and average percentages of color removal efficiency of 89.02%, 92.49% of SS, turbidity of 94.55%, metals 2.70% (manganese) to 71.52% (iron) according to each metal and COD removal of 72.80%

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The isolation of adjacent zones encountered during oilwell drilling is carried out by Portland-based cement slurries. The slurries are pumped into the annular positions between the well and the casing. Their rheological behavior is a very important component for the cementing process. Nowadays, several alternative materials are used in oilwell cementing, with goal the modification and the improvement of their properties, mainly the increase of the fluidity. And this can be reached by using plasticizers additives able to account for different oilwell conditions, yielding compatible cement slurries and allowing enough time for the complete cementing operation. If the rheological properties of the slurry are properly characterized, the load loss and flow regime can be correctly predicted. However, this experimental characterization is difficult. Rheological models capable of describing the cement slurry behavior must be capable of predicting the slurry cement deformation within reasonable accuracy. The aim of this study was to characterize rheologically the slurries prepared with a especial class of Portland cement, water and plasticizers based on lignosulfonate, melamine and polycarboxylate at temperatures varying from 27°C to 72°C. The tests were carried out according to the practical recommendations of the API RP 10B guidelines. The results revealed a great efficiency and the dispersive power of the polycarboxylate, for all temperatures tested. This additive promoted high fluidity of the slurries, with no sedimentation. High lignosulfonate and melamine concentrations did not reduce the rheological parameters (plastic viscosity and yield stress) of the slurries. It was verified that these additives were not compatible with the type of cement used. The evaluated rheological models were capable of describing the behavior of the slurries only within concentration and temperature ranges specific for each type of additive

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Metal-Ceramic (M/C) Zirconia-stainless steel interfaces have been processed through brazing techniques due to the excellent combination of properties such as high temperature stability, high corrosion resistance and good mechanical properties. However, some M/C interfaces show some defects, like porosity and cracks results in the degradation of the interfaces, leading even to its total rupture. Most of time, those defects are associated with an improper brazing parameters selection to the M/C system. In this work, ZrO2 Y-TZP and ZrO2 Mg - PSZ were joint with the stainless steel grade 304 by brazing using a eutectic silver-copper (Ag28Cu) interlayer alloy with different thermal cycles. Ceramic surfaces were previous mechanically metallized with titanium to improve adhesion of the system. The effect of temperature on the M/C interface was studied. SEM-EDS and 3 point flexural bend test were performed to evaluate morphology, chemical composition and mechanical resistance of the M/C interfaces. Lower thermal cycle temperatures produced better results of mechanical resistance, and more regular/ homogeneous reaction layers between braze alloy and metal-ceramic surfaces. Also was proved the AgCu braze alloy activation in situ by titanium

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Fuel cells are considered one of the most promising ways of converting electrical energy due to its high yield and by using hydrogen (as fuel) which is considered one of the most important source of clean energy for the future. Rare earths doped ceria has been widely investigated as an alternative material for the electrolyte of solid oxide fuel cells (SOFCs) due to its high ionic conductivity at low operating temperatures compared with the traditional electrolytes based on stabilized zirconia. This work investigates the effect of gallium oxide (Gallia) as a sintering aid in Eu doped ceria ceramic electrolytes since this effect has already been investigated for Gd, Sm and Y doped ceria electrolytes. The desired goal with the use of a sintering aid is to reduce the sintering temperature aiming to produce dense ceramics. In this study we investigated the effects on densification, microstructure and ionic conduction caused by different molar fraction of the dopants europium (10, 15 and 20%) and gallium oxide (0.3, 0.6 and 0.9%) in samples sintered at 1300, 1350 and 1450 0 C. Samaria (10 and 20%) doped ceria samples sintered between 1350 and 1450 °C were used as reference. Samples were synthesized using the cation complexation method. The ceramics powders were characterized by XRF, XRD and SEM, while the sintered samples were investigated by its relative density, SEM and impedance spectroscopy. It was showed that gallia contents up to 0.6% act as excellent sintering aids in Eu doped ceria. Above this aid content, gallia addition does not promote significant increase in density of the ceramics. In Ga free samples the larger densification were accomplished with Eu 15% molar, effect expressed in the microstructure with higher grain growth although reduced and surrounded by many open pores. Relative densities greater than 95 % were obtained by sintering between 1300 and 1350 °C against the usual range 1500 - 1600 0 C. Samples containing 10% of Sm and 0.9% of Ga reached 96% of theoretical density by sintering at 1350 0 C for 3h, a gain compared to 97% achieved with 20% of Sm and 1% of Ga co-doped cerias sintered at 1450 0 C for 24 h as described in the literature. It is found that the addition of gallia in the Eu doped ceria has a positive effect on the grain conductivity and a negative one in the grain boundary conductivity resulting in a small decrease in the total conductivity which will not compromise its application as sintering aids in ceria based electrolytes. Typical total conductivity values at 600 and 700 °C, around 10 and 30 mS.cm -1 respectively were reached in this study. Samples with 15% of Eu and 0.9 % of Ga sintered at 1300 and 1350 °C showed relative densities greater than 96% and total conductivity (measured at 700 °C) between 20 and 33 mS.cm -1 . The simultaneous sintering of the electrolyte with the anode is one of the goals of research in materials for SOFCs. The results obtained in this study suggest that dense Eu and Ga co-doped ceria electrolytes with good ionic conductivity can be sintered simultaneously with the anode at temperatures below 1350 °C, the usual temperature for firing porous anode materials

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Ionic oxides with ABO3 structure, where A represents a rare earth element or an alkaline metal and B is a transition metal from group VIII of the periodic table are potential catalysts for oxidation and good candidates for steam reforming reaction. Different methods have been considered for the synthesis of the oxide materials with perovskite structure to produce a high homogeneous material with low amount of impurities and low calcination temperatures. In the current work, oxides with the LaNiO3 formula had been synthesized using the method of the polymeric precursors. The thermal treatment of the materials took place at 300 ºC for 2h. The material supported in alumina and/or zirconia was calcined at 800 ºC temperature for 4h. The samples had been characterized by the following techniques: thermogravimetry; infrared spectroscopy; X-ray diffraction; specific surface area; distribution of particle size; scanning electron microscopy and thermo-programmed reduction. The steam reforming reaction was carried out in a pilot plant using reducing atmosphere in the reactor with a mixture of 10% H2-Argon, a mass about 5g of catalyst, flowing at 50 mL.min-1. The temperature range used was 50 - 1000 oC with a heating rate of 10 oC.min-1. A thermal conductivity detector was used to analyze the gas after the water trapping, in order to permit to quantify the consumption of hydrogen for the lanthanum nickelates (LaNiO3). The results showed that lanthanum nickelate were more efficient when supported in alumina than when supported in zirconia. It was observed that the methane conversion was approximately 100% and the selectivity to hydrogen was about 70%. In all cases were verified low selectivity to CO and CO2

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The development of activities in the oil and gas sector has been promoting the search for materials more adequate to oilwell cementing operation. In the state of Rio Grande do Norte, the cement sheath integrity tend to fail during steam injection operation which is necessary to increase oil recovery in reservoir with heavy oil. Geopolymer is a material that can be used as alternative cement. It has been used in manufacturing of fireproof compounds, construction of structures and for controlling of toxic or radioactive waste. Latex is widely used in Portland cement slurries and its characteristic is the increase of compressive strength of cement slurries. Sodium Tetraborate is used in dental cement as a retarder. The addition of this additive aim to improve the geopolymeric slurries properties for oilwell cementing operation. The slurries studied are constituted of metakaolinite, potassium silicate, potassium hydroxide, non-ionic latex and sodium tetraborate. The properties evaluated were: viscosity, compressive strength, thickening time, density, fluid loss control, at ambient temperature (27 ºC) and at cement specification temperature. The tests were carried out in accordance to the practical recommendations of the norm API RP 10B. The slurries with sodium tetraborate did not change either their rheological properties or their mechanical properties or their density in relation the slurry with no additive. The increase of the concentration of sodium tetraborate increased the water loss at both temperatures studied. The best result obtained with the addition of sodium tetraborate was thickening time, which was tripled. The addition of latex in the slurries studied diminished their rheological properties and their density, however, at ambient temperature, it increased their compressive strength and it functioned as an accelerator. The increase of latex concentration increased the presence of water and then diminished the density of the slurries and increased the water loss. From the results obtained, it was concluded that sodium tetraborate and non-ionic latex are promising additives for geopolymer slurries to be used in oilwell cementing operation

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The state of Rio Grande do Norte presents a great potentiality for the production of ceramic tiles because of having natural raw material in quantity and quality making its economical exploration possible, beyond the great energetic differential of the state, the natural gás. This works aims to study the influence of the dolomite and granulometry concentration and calcinations temperature in the obtaining of formulations for porous coverings which have to be coherent to the project,s specifications. The experiments have involved the physical-chemical and mineralogical characterizations of raw materials and mechanical tests in the dry and burnt proof bodies preceding a mixture experiment planning with the use of the response surface methodology, in order to get the best raw materials combinations to produce a ceramic mass with specific properties. The twelve ceramic masses studied in this work were prepared by the via dry process, characterized, shaped by uniaxial pressing and sinterized in the temperatures of 940ºC, 1000ºC, 1060ºC, 1120ºC and 1180ºC, using a fast burning cycle. The crystalline phases formed during the sintering in the temperatures in study have revealed the presence of anorthite and diopside beyond quartz with a remaining phase. These phases were the main responsible ones by the physical- mechanical properties of the sinterized proof bodies. The proof bodies after the sintering stage have presented water absorption higher than 10% and a good dimensional stability in all studied temperatures. However, the flexural breaking strength results in the temperatures of 940ºC, 1000ºC and 1060ºC, under the temperature zone of the vitrification of ceramic whiteware do not reach the flexural breaking strength specific for the porous wall tile (15 MPa), but in the temperature of 1120ºC next to the vitrification temperature zone, some whiteware ceramic (formulations) has reached the specified value for the porous wall tile. The results of this work have showed that the studied raw materials have great importance for used in the production of porous wall tiles (BIII)

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Nowadays, industries from all sectors have great concerns over the disposition of the residues generated along the productive process. This is not different in the mineral sector, as this generates great volumes of residues. It was verified that the kaolin improvement industry generates great volumes of residue basically constituted of kaolinite, muscovite mica and quartz, which are basic constitution elements to formularisations of ceramics masses to the production of covering of stoneware tiles type. This happens because the methodology applied to the improvement process is still very rudimentary, what causes a very low yield, only ¼ from all the material volume that enters the improvement process, in the end, is marketable. The disposal of this residue, in a general way, causes a very big negative environmental impact, what has justified the researches efforts aiming to find a rational solution to this problem. In this way, the intention of this present work is the utilization of this residue in the manufacture of products to high quality ceramics covering, stoneware tiles in an industrial scale. For this purpose, the influence of the addition of the residue to a standard ceramics mass used by a ceramics sector company, already established in the market, with the intention of verifying the possibility of use of this residue as the mass complementary raw material and even the possible partial or total substitution of one of the components of the mass for the raw material in evidence will be studied. To the accomplishment of this work, the kaolin improvement residue generated by an industry of exploitation and improvement of kaolin, located in the region of Equador-RN, in the levels 1,2,4,8, 16 and 32% will be added to the standard mass already used for the production of stoneware tiles. The raw materials used, kaolin residue and the standard mass, were characterized through DRX, FRX, DTA, TGA and dilatometry. After the sintering of the bodies of test, tests of water absorption, apparent porosity, post burning linear retraction, apparent specific mass and flexural strength (3 point bending) were realized to determinate the technological properties of these materials. The results show the studied residue can be considered raw material of great potential to the industry of floor and ceramics covering of the stoneware tiles type

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The State of Paraíba is one of the most dynamic states of Brazil, strategically located in the northeast, is notable for the excellent potential for integration of different transportation modes forming the states of Rio Grande do Norte, Pernambuco and Alagoas. The dynamic that occurs with port activity causes changes in the space where it is installed. And the elements of this space are always more than suffering direct or indirect influences as the flow in the port is expanded. Therefore, this region became subject to the accidental spillage of oil, because it presents a heavy traffic of ships of various sizes that can run aground or collide with oil causing accidental events. The study of geomorphological and sedimentological compositions of seafloor becomes important as more is known about the relationships between these parameters and associated fauna, and can identify their preferred habitats. The database background, acoustically collected along the proposed study area, is a wealth of information, which were duly examined, cataloged and made available. Such information can serve as an important tool, providing a geomorphological survey of the sedimentary area studied, and come to subsidize, in a flexible, future decision making. With the study area Port of Cabedelo, Paraíba - Brazil, this research aimed to evaluate the influence of the tidal surface and background in modeling the seabed, including the acquisition of information about the location of submerged rocky bodies and the depth of these bodies may turn out to be natural traps for the trapping of oil in case of leaks, and obtain the relationship between types of bed and the hydrodynamic conditions present in the region. In this context, for this study were collected bathymetric data (depth) and physical oceanographic (height of water column, water temperature, intensity and direction of currents, waves and turbidity), meteorological (rainfall, air temperature, humidity, winds and barometric pressure) of the access channel to the Port of Cabedelo / PB and its basin evolution (where the cruise ships dock), and includes tools of remote sensing (Landsat 7 ETM +, 2001), so that images and the results are integrated into Geographic Information Systems and used in the elaboration of measures aimed at environmental protection areas under the influence of this scale facilities, serving as a grant to prepare a contingency plan in case of oil spills in the region. The main findings highlight the techniques of using hydroacoustic data acquisition together bathymetric surveys of high and low frequency. From there, five were prepared in bathymetric pattern of Directorate of Hydrography and Navigation - DHN, with the depth in meters, on a scale of 1:2500 (Channel and Basin Evolution of Access to Port of Cabedelo), where there is a large extent possible beachrocks that hinder the movement of vessels in the port area, which can cause collisions, running aground and leaking oil. From the scatter diagram of the vectors of currents, it can be seen as the tidal stream and undergoes a channeling effect caused by the bidirectional effect of the tide (ebb and flood) in the basin of the Port of Cabedelo evolution in NW-direction SE and the highest speed of the currents occurs at low tide. The characterization weather for the period from 28/02 to 04/07/2010 values was within the expected average for the region of study. The multidisciplinary integration of products (digital maps and remote sensing images), proved to be efficient for the characterization of underwater geomorphological study area, reaching the aim to discriminate and enhance submerged structures, previously not visible in the images

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The use of biofuels remotes to the eighteenth century, when Rudolf Diesel made the first trials using peanut oil as fuel in a compression ignition engine. Based on these trials, there was the need for some chemical change to vegetable oil. Among these chemical transformations, we can mention the cracking and transesterification. This work aims at conducting a study using the thermocatalytic and thermal cracking of sunflower oil, using the Al-MCM-41 catalyst. The material type mesoporous Al-MCM-41 was synthesized and characterized by Hydrothermical methods of X-ray diffraction, scanning electron microscopy, nitrogen adsorption, absorption spectroscopy in the infrared and thermal gravimetric analysis (TG / DTG).The study was conducted on the thermogravimetric behavior of sunflower oil on the mesoporous catalyst cited. Activation energy, conversion, and oil degradation as a function of temperature were estimated based on the integral curves of thermogravimetric analysis and the kinetic method of Vyazovkin. The mesoporous material Al-MCM-41 showed one-dimensional hexagonal formation. The study of the kinetic behavior of sunflower oil with the catalyst showed a lower activation energy against the activation energy of pure sunflower oil. Two liquid fractions of sunflower oil were obtained, both in thermal and thermocatalytic pyrolisis. The first fraction obtained was called bio-oil and the second fraction obtained was called acid fraction. The acid fraction collected, in thermal and thermocatalytic pyrolisis, showed very high level of acidity, which is why it was called acid fraction. The first fraction was collected bio-called because it presented results in the range similar to petroleum diesel

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In this study, was used a very promising technique called of pyrolysis, which can be used for obtaining products with higher added value. From oils and residues, since the contribution of heavier oils and residues has intensified to the world refining industry, due to the growing demand for fuel, for example, liquid hydrocarbons in the range of gasoline and diesel. The catalytic pyrolysis of vacuum residues was performed with the use of a mesoporous material belonging the M41S family, which was discovered in the early 90s by researchers Mobil Oil Corporation, allowing new perspectives in the field of catalysis. One of the most important members of this family is the MCM-41, which has a hexagonal arrangement of mesopores with pore diameters between 2 and 10 nm and a high specific surface area, making it very promising for use as a catalyst in petroleum refining for catalytic cracking, and their mesopores facilitate the access of large hydrocarbon molecules. The addition of aluminum in the structure of MCM-41 increases the acidity of the material, making it more positive for application in the petrochemical industry. The mesoporous material of the type Al-MCM41 (ratio Si / Al = 50) was synthesized by hydrothermal method starting from the silica gel, NaOH and distilled water added to the gel pseudobohemita synthesis. Driver was used as structural CTMABr. Removal of organic driver (CTMABr) was observed by TG / DTG and FTIR, but this material was characterized by XRD, which was observed the formation of the main peaks characteristic of mesoporous materials. The analysis of adsorption / desorption of nitrogen this material textural parameters were determined. The vacuum residues (VR's) that are products of the bottom of the vacuum distillation tower used in this study are different from oil fields (regions of Ceará and Rio de Janeiro). Previously characterized by various techniques such as FTIR, viscosity, density, SARA, elemental analysis and thermogravimetry, which was performed by thermal and catalytic degradation of vacuum residues. The effect of AlMCM-41 was satisfactory, since promoted a decrease in certain ranges of temperature required in the process of conversion of hydrocarbons, but also promoted a decrease in energy required in the process. Thus enabling lower costs related to energy expenditure from degradation during processing of the waste

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Originally aimed at operational objectives, the continuous measurement of well bottomhole pressure and temperature, recorded by permanent downhole gauges (PDG), finds vast applicability in reservoir management. It contributes for the monitoring of well performance and makes it possible to estimate reservoir parameters on the long term. However, notwithstanding its unquestionable value, data from PDG is characterized by a large noise content. Moreover, the presence of outliers within valid signal measurements seems to be a major problem as well. In this work, the initial treatment of PDG signals is addressed, based on curve smoothing, self-organizing maps and the discrete wavelet transform. Additionally, a system based on the coupling of fuzzy clustering with feed-forward neural networks is proposed for transient detection. The obtained results were considered quite satisfactory for offshore wells and matched real requisites for utilization

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The occurrence of heavy oil reservoirs have increased substantially and, due to the high viscosity characteristic of this type of oil, conventional recovery methods can not be applied. Thermal methods have been studied for the recovery of this type of oil, with a main objective to reduce its viscosity, by increasing the reservoir temperature, favoring the mobility of the oil and allowing an increasing in the productivity rate of the fields. In situ combustion (ISC) is a thermal recovery method in which heat is produced inside the reservoir by the combustion of part of the oil with injected oxygen, contrasting with the injection of fluid that is heated in the surface for subsequent injection, which leads to loss heat during the trajectory to the reservoir. The ISC is a favorable method for recovery of heavy oil, but it is still difficult to be field implemented. This work had as an objective the parametric analysis of ISC process applied to a semi-synthetic reservoir with characteristics of the Brazilian Northeast reservoirs using vertical production and vertical injection wells, as the air flow injection and the wells completions. For the analysis, was used a commercial program for simulation of oil reservoirs using thermal processes, called Steam, Thermal and Advanced Processes Reservoir Simulator (STARS) from Computer Modelling Group (CMG). From the results it was possible to analyze the efficiency of the ISC process in heavy oil reservoirs by increasing the reservoir temperature, providing a large decrease in oil viscosity, increasing its mobility inside the reservoir, as well as the improvement in the quality of this oil and therefore increasing significantly its recovered fraction. Among the analyzed parameters, the flow rate of air injection was the one which had greater influence in ISC, obtaining higher recovery factor the higher is the flow rate of injection, due to the greater amount of oxygen while ensuring the maintenance of the combustion front