Navegando por Assunto "Dióxido de carbono"

Agora exibindo 1 - 19 de 19

Acesso aberto (Open Access)
Absorção de gases da queima de combustíveis fósseis em torre de recheio estruturado utilizando lama vermelha
(Universidade Federal do Pará, 2013-03-11) SANTOS, Iara Ferreira; SOUZA, José Antônio da Silva; http://lattes.cnpq.br/6157348947425968; SOUZA, Célio Augusto Gomes de; http://lattes.cnpq.br/0800747860976046
The production of alumina from the Bayer process produces 1-3 tons of waste per ton of aluminum. This residue is known red mud, compound of minerals insoluble in concentrated sodium hydroxide, hematite and other iron oxides, quartz and titanium oxides. The red mud has in its composition varied levels of NaOH, depending on the specific industrial plant used. The purpose of this study is to evaluate the process of absorption of gases from a boiler countercurrent with a suspension of red mud, in a spray tower and a packed column. Experiments were performed varying the type of absorption tower, temperature of the liquid phase and solids content in liquid phase to evaluate the reduction in content of gases of combustion in the output of absorption tower and pH variation with time of operation, it was possible to identify the time required for the occurrence of red mud neutralization, and also a reduction in the content of carbon dioxide, thereunto were performed measurements of the concentrations of gasesin the input and output packed column, and also measurements of temperature and pH. The absorption of CO2 existing in the gases of combustion for suspension of red mud occurs by the carbonation process, where the gas reacts with NaOH present in red mud, with water as catalyst. The results obtained after the experiments were satisfactory, and it was concluded that the process performed in absorption towers is efficient for pH reduction of red mud and reducing the content of CO2 freed to atmosphere, providing a double profit for the environment.
Acesso aberto (Open Access)
Absorção do dióxido de carbono por resíduo de bauxita em torres de absorção
(Universidade Federal do Pará, 2013-03-04) BOTELHO, Fernando Aracati; MACÊDO, Emanuel Negrão; http://lattes.cnpq.br/8718370108324505; SOUZA, José Antônio da Silva; http://lattes.cnpq.br/6157348947425968
One of the most discussed environmental problems on the world scene today is global warming and its implications. Although the greenhouse effect is a natural phenomenon, the increase in emissions of gases such as CO2 from the combustion process may favor its aggravation. Following this line, there is interest in conducting research to minimize the release of this gas in the atmosphere. This work aims to study the process of absorption of carbon dioxide by aqueous phase of bauxite residue (soda and dissolved ions in solution) in spray tower and tower saddles random (both pilot scale), as well as check the pH change in this absorption process to both towers. Evaluate pH change and CO2 absorption capacity by considering the following variables: the type of absorption tower, using the supernatant as the absorbent means and the use of the suspension heated by resistances. The results showed that the suspension of bauxite residue absorbed significant amount of CO2, both the spray tower as the tower saddles. The average absorption rate was around 8.42% for the spray tower and 9.34% for the tower saddles. The ability carbonating the suspension of 27%-p was about 33.3 kg CO2 per tonne of waste and there was a substantial reduction of the alkalinity of the residue by reaction with gaseous effluents with a mean decrease of 4.0 and 3.5 pH units for the tower saddles and sprinkler respectively.
Acesso aberto (Open Access)
Comparative study on the quality of oil extracted from two tucumã varieties using supercritical carbon dioxide
(Universidade Federal do Pará, 2016-06) COSTA, Bárbara Elizabeth Teixeira; SANTOS, Orquídea Vasconcelos dos; CORRÊA, Nádia Cristina Fernandes; FRANÇA, Luiz Ferreira de
The vast Amazon region has considerable territorial peculiarities and plant species diversity, sometimes from the same botanical family, which can exhibit significant differences in physicochemical properties. From this diversity, two species stand out – Amazonas tucumã (Astrocaryum aculeatum Meyer) and Pará tucumã (Astrocaryum vulgare Mart.). The research focus is to analyze, comparatively, these oleaginous fruits, their similarities, particularities and potentials regarding the oil quality extracted from two tucumã varieties from the states of Amazonas and Pará, obtained using supercritical carbon dioxide, under different extraction parameters. The results demonstrate the biometric particularities of each species, highlighting the Amazon fruit, which also showed higher oil yield using supercritical CO2 extraction. The fatty acid quality and profile aspects of the oils show their unsaturated predominance, considering carotenoid content and how the extraction temperature can influence the nutritional quality of the oils. The statistical analyses indicated that the Amazon tucumã oil is superior to the Pará tucumã oil. However, in terms of added value both oils have potential applications in various industrial segments.
Acesso aberto (Open Access)
Desenvolvimento de unidade piloto de transferência de massa gás/líquido: redução da reatividade do resíduo da indústria de alumina através da reação com gases de combustão
(Universidade Federal do Pará, 2013-02) VENANCIO, Luis Carlos Alves; SOUZA, José Antônio da Silva; http://lattes.cnpq.br/6157348947425968; MACÊDO, Emanuel Negrão; http://lattes.cnpq.br/8718370108324505
The bauxite refining using the Bayer process produces 0.7 to 2.0 tons of the residue known as red mud and about 1.0 ton of CO2 for each ton of alumina produced. The bauxite residue, although not particularly toxic, poses risks to the environment due to its large volume and reactivity. According to the latest technology, part of the moisture is removed and it is stacked on sealed areas specially constructed. More than 95% of the bauxite residue that has been produced (2.6 Bt until 2007) was discarded, especially in ponds on land. This thesis shows the design, construction and operation of a pilot scale gas liquid mass transfer unity with the objective of testing the reduction of the reactivity of the bauxite residue through a reaction with flue gas. As an additional gain, there is a reduction of carbon dioxide and sulfur dioxide emissions. This unity, with three reactors, was designed in order to consume minimal power, process the effluent as efficiently as possible and minimize the investment cost. Twenty-five experiments were realized with duration from 80 to 520 minutes each. The gases were analyzed at the entry and exit with electrochemical cells and non-dispersive infrared sensors. The pH was monitored during and after the reaction in order to evaluate the short and long-term results as well as the stability of the reactions. It was demonstrated the viability of reacting the bauxite residue with the flue gas from the refinery without previous processing with the stabilization pH reaching 10.5.
Acesso aberto (Open Access)
Desorption of heavy metals from ion exchange resin with water and carbon dioxide
(2006-06) SILVA, Denilson Luz da; BRUNNER, Gerd
Adsorption and regeneration of ion exchange resins were studied using a subcritical solution of a CO2-H2O mixture and a fixed bed column. The commercial Amberlite IRC-50/IRC-86 cation exchange resins and Amberlite IRA-67 anion exchange resin were tested for heavy metals (Pb, Cu, Cd) adsorption from a solution with different initial metal concentrations at different temperatures. After adsorption, the loaded resins were regenerated with water and carbon dioxide at different temperatures and a pressure of 25 MPa. The efficiency of the IRC-50 resin was lower than that of the IRC-86 resin for the adsorption of metals like Cd, Cu and Pb. Results obtained for desorption of these metals indicated that the process could be used for Cd and in principle for Cu. Sorption of metal ions depended strongly on feed concentration. Mathematical modeling of the metal desorption process was carried out successfully as an extraction process. For this purpose, the VTII Model, which is applied to extraction from solids using supercritical solvents, was used in this work.
Acesso aberto (Open Access)
Determinação de parâmetros de transferência de massa do processo de extração supercrítica
(Universidade Federal do Pará, 2013-03-01) SANTANA, Ádina Lima de; MACHADO, Nélio Teixeira; http://lattes.cnpq.br/5698208558551065; ARAÚJO, Marilena Emmi; http://lattes.cnpq.br/8983914018546682
Supercritical fluid extraction of liquid and solid materials sparked interest for industrial applications in recent decades, particularly under the concept of green chemistry and biorefineries, so it is essential to make a modeling of this process in order to optimize and simulate operating conditions process. The objective of this work consists in determining the parameters of mass transfer of supercritical extraction of solid matrix by employing carbon dioxide as solvent, from kinetic data extraction and five systematic evaluation of mathematical models to describe the kinetics extraction of oils from the peel and pulp of buriti, oil from açaí and oleoresin from turmeric, measured in Supercritical Extraction Laboratory, Faculty of Chemical Engineering (UFPA) in order to contribute to the study of scale-up and production cost analysis. Were evaluated the models of Tan and Liou, Goto et al. (1993), Martinez et al. (2003), Esquível et al. (1999), and Sovová (1994). The extraction kinetics modeling was performed using computer applicatives developed and validated in this work from different experimental data published in the literature. Facing 40 kinetic measurements with different extraction equipment, bed settings, types of raw materials, preparation of materials, pressure and temperature and other process parameters (especially income and global flow solvent), was built an overview of results ability of the models on the mass transfer in more different curves describing the overall extraction. Generally, the model Goto et al. (1993) and Sovová (1994) showed the best predictions to experimental data of raw materials treated in this work with smaller values of chi-square, relative errors, range and standard error and R2 values close to unity.
Acesso aberto (Open Access)
Dinâmica do carbono em pequenas bacias de drenagem sob uso de agricultura familiar na Amazônia Oriental
(Universidade Federal do Pará, 2007) ROSA, Maria Beatriz Silva da; FIGUEIREDO, Ricardo de Oliveira; http://lattes.cnpq.br/2388049759708934
This research was designed to evaluate carbon dynamics in Eastern Amazon, where the main land use is small holder farming, and was conducted in three small catchments. Carbon dynamics was evaluated considering hydrological and biogeochemical measurements in Cumaru, Pachibá and São João streams from June 2006 to May 2007. Aquatic environment and fluvial hydrogeochemistry were characterized through in situ measures of electrical conductivity, temperature, pH and dissolved oxygen concentration. Water samples were collected and analyzed to determine dissolved organic carbon (DOC) concentrations and carbon dioxide partial pressures (pCO2). Concentrations of dissolved inorganic carbon (DIC) were calculated from pCO2 values. Despite being calculated from pCO2 values, CO2 fluxes were also measured in situ. Instantaneous discharge was measured in each month field campaign and used to calculate DOC annual fluxes. Soil and land use characterization in the study watersheds, as well as precipitation and discharge rates, were considered for results interpretation. Main results were: 1) Stream water physic-chemical characteristics in the study catchments respond to the acid soils, riparian vegetation, and the hydrological and biogeochemical processes in the terrestrial and aquatic ecosystems, and present some seasonal variation. 2) Dissolved carbon concentrations was correlated with pH and dissolved oxygen in stream water; 3) DOC fluxes weighted by area were higher than in other Amazonian watersheds and even higher during rainy season; 4) DOC fluxes and CO2 evasion seem to respond positively to riparian vegetation and mature forest, and negatively to agriculture; 5) CO2 evasion rates were higher than in other Amazonian rivers corroborating the hypothesis that small catchments are important sources of atmospheric CO2 in the region.
Acesso aberto (Open Access)
Efluxo de CO₂ do solo e biomassa de raízes finas ao longo de um gradiente topográfico na Floresta de Caxiuanã-PA
(Universidade Federal do Pará, 2013-05-07) CASTRO, Sirlene de Lima; CATTANIO, José Henrique; http://lattes.cnpq.br/1518769773387350
The objective of this research was to understand the role of small topographic elevations in the soil carbon dioxide (CO2) efflux comparing different seasonal period in the National Forest of Caxiuanã, oriental Amazon. Were selected two transects with about 17m topographic gradient, the first initiated near the border of a permanent stream and the second standing near an intermittent stream, denominate in this work as Transect1 and Transect2, respectively. In each transect were selected four locations for the collection and measurement of data called lowland, middle lowland, middle plateau and plateau. At these sites were conducted CO2 efflux and soil temperature analysis, and soil samples for organic carbon analysis and fine root (<2 mm) biomass studies at different depth intervals. It was observed a significant difference in the soil organic carbon concentration compared in the soil surface layer (0-10 cm) in lowland topography, where the transect that begins in the board of the intermittent stream had the significantly higher organic carbon content. It was also observed a soil organic carbon reduction with depth, but there were no differences in organic carbon content with topographic variation. Bringing together both transects, the results related to superficial fine root biomass, it was found mean values of 382.47 ± 25.46 g m-2 for the dry months and 298.24 ± 23.50 g m-2 for the rainy months. In general there was a reduction in fine root biomass by increasing the soil depth, and in the surface layer (0-30 cm) is concentrated to greater root biomass with more than 80% of total root biomass for both transects. There were significant differences in root biomass among and within transects. For the same time, it was founded higher CO2 efflux in the lowland topography compared to the plateau. Seasonal variation also has effect on soil CO2 efflux, with the month of August (transitional month) having the highest CO2 effluxes and March (rainy month) the lowest CO2 efflux, independent of topographic position.
Acesso aberto (Open Access)
Efluxo de dióxido de carbono do solo na transição floresta-sistema agroflorestal no município de Tomé Açu, Pará
(Universidade Federal do Pará, 2015-08-31) PINHEIRO, Larissa Paulina Souza; VASCONCELOS, Steel Silva; http://lattes.cnpq.br/0719395243841543
The soil carbon dioxide (CO2) efflux corresponds to the principal flow of carbon from the biosphere to the atmosphere. Tropical soils, which usually show high moisture and temperature, offer very favorable conditions for the production of CO2 resulting from, the decomposition of organic matter, root respiration and microbial respiration, increasing soil CO2 emission to the atmosphere. Soil management practices influence the controlling factors of the soil carbon stock and CO2 emission. A greater understanding of this influence has stimulated studies on all ecosystems, which, among other things, seek to identify and/or develop practices that increase carbon storage and reduce the emission of soil CO2, as is the case of agroforestry. Due to the large global scientific interest in understanding the physical and biological processes involving CO2 fluxes between the surface and the atmosphere, the aim of this research was to evaluate the effects of the transition from secondary forest to oil palm-based agroforestry systems on the soil CO2 efflux and soil biotic and abiotic factors. The experiment was conducted in the municipality of Tomé Açu, northeast Pará, in a project which has been investigating models of palm oil production systems in agrosilvicultural arrangements in the context of smallholder agriculture. The soil CO2 efflux was measured with a portable photosynthesis measurement system (LI-6400) coupled to a soil respiration chamber. We also measured soil gravimetric moisture and temperature, soil respiration (SR), microbial biomass carbon (MBC), soil organic carbon, fine roots stock and litter stock in two AFS and a remaining secondary forest. Measurements of CO2 efflux and soil and plant sampling were taken between January and April 2015 and were carried out fortnightly. The soil CO2 efflux was mainly influenced by soil temperature and moisture in both agroforestry systems. The forest-AFS transition significantly affected the soil CO2 efflux, fine roots, MBC and SR. The transition from secondary forest to AFS with oil palm and the spatial variability of the species or arrangement of the systems affected the soil quality. These changes may be linked to impacts of changes in the structure and species composition of the systems and the management of soil organic matter.
Acesso aberto (Open Access)
Emissão de dióxido de carbono e estoque de carbono em sistemas convencionais e alternativo de produção agropecuária no Nordeste paraense
(Universidade Federal do Pará, 2011-08-25) LEMOS, Elane Cristina Melo; VASCONCELOS, Steel Silva; http://lattes.cnpq.br/0719395243841543
Use of agricultural conservation practices such as slash-and-mulch, as an alternative to slash-and-burn, is less harmful to biogeochemical cycling and helps to mitigate climate change. The aim of this study was to estimate soil carbon emission and stocks in smallholder agricultural units in Northeast of Pará. The study was carried out in the municipality of Mãe do Rio. Average annual temperature in this area varied from 25 to 28 °C and rainfall typically is higher than 2500 mm; predominant soil is Yellow Dystrophic Oxisol with texture varying from medium to clayey. In this research, we selected three land use systems (Schizolobium amazonicum plantation, Manihot esculenta crop, and silvopastoral), which were compared with a reference area (regrowth forest); we established four 20 m x 20 m plots in each system. We measured monthly soil CO2 efflux as well as soil carbon stock and aboveground litter carbon stock. Analysis of variance was used to test the effects of land use systems and regrowth forest effects on carbon emission and stock; Tukey test at 5% was used to compare treatment means. The silvopastoral system showed the highest monthly soil CO2 emissions, which were observed during the rainy season; this system also had the largest annual emission. Soil carbon stock was significantly higher in the regrowth forest was 157 ± 31,10 Mg ha-1 (0-100 cm). Litter stock was higher for the non-woody fraction than the woody fraction for both land use and regrowth forest systems. The largest stock of carbon in non-woody litter (overall mean = 4.31 ± 3,0 Mg ha-1) was observed in January 2010. Our results suggest that the land use systems that do not use fire in land preparation, such as the slash-andmulch system, helped to maintain carbon biogeochemical cycling.
Acesso aberto (Open Access)
Estoques e fluxos de carbono em plantações florestais jovens de Acacia mangium e Schizolobium parahyba var. Amazonicum na Amazônia Oriental
(Universidade Federal do Pará, 2010) FREITAS, Jorge Fernando Barros de; VASCONCELOS, Steel Silva; http://lattes.cnpq.br/0719395243841543
Forest plantations are considered as an alternative land use to mitigate the effects of climate change due to their potential for carbon sequestration in tree species. However, there is little information about carbon stocks and fluxes in forest plantations commonly used in the tropics, especially in the Amazon. The aim of this study was to quantify aboveground carbon stock and soil carbon dioxide (CO2) efflux in Acacia mangium Willd and Schizolobium parahyba var. amazonicum at different spacings. The study was conducted in Dom Eliseu, Pará, whose climate has a mean annual temperature around 25 ºC, annual rainfall varies from 2250 to 2500 mm; predominant soil is A moderate typic dystrophic Oxisol loamy soil. In this study we selected two species (A. mangium and S. parahyba var. Amazonicum) at two spacings (4.0 x 2.0 m and 4.0 x 3.0 m) with two replications, resulting in 4 treatments and 8 plots studied for a period of one year, from 2.5 to 3.5 years old. The plots measured 48 m x 60 m. We measured: height, diameter at breast height, soil CO2 flux, and estimated aboveground carbon stock. Mean soil CO2 efflux in plantations of A. mangium was 5.61 ± 1.30 Mg C ha-1 yr-1, and for S. parahyba the overall average was 7.07 ± 1.50 Mg C ha-1 yr-1. Annual accumulation of carbon in above-ground biomass A. mangium was 16.41 ± 1.16 and 14.03 ± 0.82 Mg C ha-1 yr-1 in 4.0 x 2.0 m and 4.0 x 3.0 m and 3.0 m, respectively. In S. parahyba the annual accumulation rate was 8.93 ± 1.87 Mg C ha-1 yr-1. A. mangium plantations accumulated more carbon in aboveground biomass than S. parahyba, with lower annual soil CO2 efflux smaller in relation to S. parahyba in both spacings. Overall A. mangium plantations in the 4.0 x 2.0 m spacing are recommended for carbon sequestration projects. In relation to S. parahyba, the 4.0 x 3.0 m would be recommended due to the same efficiency in carbon sequestration with lower requirement of inputs (seedlings) compared to 4.0 x 2.0 m. Continuos monitoring of the studied plantations would be very suitable to better understand the carbon dynamics.
Acesso aberto (Open Access)
Extração de oleoresina de Cúrcuma (Curcuma longa l) com CO2 supercrítico
(1997-12) CHASSAGNEZ MÉNDEZ, Angel Luis; CORRÊA, Nádia Cristina Fernandes; MEIRELES, Maria Angela de Almeida
Turmeric (Curcuma longa L) is one of the most used source of natural color in the food industry. Curcuminoids can be obtained from the roots of this plant. These pigments impact a yellow color and they might be able to substitute synthetic dyes. Turmeric oleoresin extraction experiments have been carried out with supercritical CO2 to investigate the influences of the pretreatment of the rhizomes on oleoresin. The extractions were conducted at the Department of Chemical Engineering of the Federal University of Pará (Universidade Federal do Pará). Turmeric was dried at 70ºC and 105ºC. Extractions have been carried out at pressures of 200, 250 and 300 bar and a temperature of 45ºC. Results shown the total yield and the content of curcumin present in the oleoresin. Amount of oleoresin extracted from the material dried at 70ºC was larger while most of the curcuminoids remained in the solid material.
Acesso aberto (Open Access)
Fluxos de dióxido de carbono e metano de um lixão na Amazônia
(Universidade Federal do Pará, 2018-08-03) PINHEIRO, Layse Teixeira; CATTANIO, José Henrique; http://lattes.cnpq.br/1518769773387350
This work had as aim the quantification of greenhouse gases, carbon dioxide and methane from the uncontrolled Aurá landfill, known as the "Aurá Lode", in addition to collecting information from the place after its partial closure in 2015 .The research had a qualitative analysis of environmental aspects of the site and an experimental part, with the development of flow chambers, to capture the gases through the covering of cells other than the landfill. The measurements were performed in two ways, the first with 24 chambers distributed in three distinct points of two cells with relatively different ages and 90 chambers, distributed in grid, in a closed cell. These measurements occurred in a less rainy period and had their points located through geographic coordinates. A portable gas analyzer was used to simultaneously obtain the gas concentration in ppm. The flow calculations involved the selection of the intervals of each chamber, determination of the regression line of the gas concentrations by time, barometric equation and insertion of the data obtained in the main flow equation. The values of methane emissions in the cells titled A, B and C were 191,226 g m² d-¹, 397.7 g m² d-¹ and 36.30 g m² d-¹, respectively. The carbon dioxide fluxes reached 10,554.1 g m² d-¹, 11,786.65 g m² d-¹ and 7,529.77 g m² d-¹.
Acesso aberto (Open Access)
High pressure vapor-liquid equilibria of palm fatty acids distillates-carbon dioxide system
(1997-12) MACHADO, Nélio Teixeira de; BRUNNER, Gerd
Vapor-Liquid equilibria of palm fatty acids distillates/carbon dioxide system has been investigated experimentally at temperatures of 333, 353, and 373 K and pressures of 20, 23, 26, and 29 MPa using the static method. Experimental data for the quasi-binary system palm fatty acids distillates/carbon dioxide has been correlated with Redlich-Kwong-Aspen equation of state. Modeling shows good agreement with experimental data. Selectivity obtained indicates that supercritical carbon dioxide is a reasonable solvent for separating saturated (palmitic acid) and unsaturated (oleic+linoleic acids) fatty acids from palm fatty acids distillates in a continuous multistage countercurrent column.
Acesso aberto (Open Access)
A influência da variabilidade espacial e sazonal sobre o efluxo de dióxido de carbono do solo em ambientes modificados na FLONA Caxiuanã-PA
(Universidade Federal do Pará, 2014) TEIXEIRA, Ana Paula Assunção; CATTANIO, José Henrique; http://lattes.cnpq.br/1518769773387350
This study aimed to investigate the influence of spatial and seasonal variability on the efflux of CO2 from the soil to the atmosphere by comparing with heat sensitive streams and latent heat as with the environmental variables (air and soil temperature, relative humidity and volumetric soil moisture) and total organic carbon in soil. This study was conducted in environments modified naturally (AMN) and antropicamente (AMA) on the FLONA of Caxiuanã, PA, during the transitional period of rainy-dry season and dry period in the year 2013. We have seen that the opening of anthropogenic and natural gaps promote variations of environmental factors arriving at the interior of the modified environments, causing greater intensity in the heat flux, favoring thus the spatial variability of CO2 efflux. The AMN showed an increase of CO2 efflux from the period of transition from the rainy–dry season to the dry period, where the highest rates of efflux occurred in the afternoon with the removal of the gap to the interior of the forest under closed canopy in east and west the gap. Contrasting with the AMA where it was verified reduction of rates of efflux of the transitional period of rainy– dry season to the dry period. Correlations between soil temperature and soil moisture with the CO2 efflux presented significant correlation mainly in the center of the gaps, influenced by heat transport more intense at this location. In this way, the CO2 efflux receives influence of environmental micrometeorological variables, soil physical and chemical characteristics and contribution of total organic carbon, showing variations of behavior with the opening of natural gap and anthropized in the Amazon rainforest.
Acesso aberto (Open Access)
A mass transfer model applied to the supercritical extraction with CO2 of curcumins from turmeric rhizomes (Curcuma longa L)
(2000-09) CHASSAGNEZ MÉNDEZ, Angel Luis; CORRÊA, Nádia Cristina Fernandes; FRANÇA, Luiz Ferreira de; MACHADO, Nélio Teixeira de; ARAÚJO, Marilena Emmi
Increasing restrictions on the use of artificial pigments in the food industry, imposed by the international market, have increased the importance of raw materials containing natural pigments. Of those natural substances with potential applications turmeric rhizomes (Curcuma longa L), are one of the most important natural sources of yellow coloring. Three different pigments (curcumin, desmetoxycurcumin, and bis-desmetoxycurcumin) constitute the curcuminoids. These pigments are largely used in the food industry as substitutes for synthetic dyes like tartrazin. Extraction of curcuminoids from tumeric rhizomes with supercritical CO2 can be applied as an alternative method to obtain curcuminoids, as natural pigments are in general unstable, and hence degrade when submitted to extraction with organic solvents at high temperatures. Extraction experiments were carried out in a supercritical extraction pilot plant at pressures between 25 and 30 MPa and a temperature of 318 K. The influence of drying pretreatment on extraction yield was evaluated by analyzing the mass transfer kinetics and the content of curcuminoids in the extracts during the course of extraction. The chemical identification of curcuminoids in both the extract and the residual solid was performed by spectrophotometry. Mass transfer within the solid matrix was described by a linear first-order desorption model, while that in the gas phase was described by a convective mass transfer model. Experimental results showed that the concentration profile for curcuminoids during the supercritical extraction process was higher when the turmeric rhizomes were submitted to a drying pretreatment at 343 K.
Acesso aberto (Open Access)
Modelagem e simulação de sistemas multicomponentes a altas pressões aplicada a separação de compostos bioativos
(Universidade Federal do Pará, 2014-04-30) SILVA, Welisson de Araújo; ARAÚJO, Marilena Emmi; http://lattes.cnpq.br/8983914018546682
Large applications using supercritical fluids related to the fractionation of natural products have been studied in recent decades. This work had as objective the thermodynamic modeling of phase equilibrium of binary and multicomponent systems of vegetable oils related compounds (fatty acids, triglycerides, squalene, α-tocopherol and methyl and ethyl esters of fatty acids) with supercritical carbon dioxide, using the cubic equations of state of Soave-Redich-Kwong (SRK) and Peng-Robinson (PR), with the Quadratic and Mathias-Klotz-Prausnitz mixing rules, to build a database of binary interaction parameters between these constituents and between these constituents with carbon dioxide, with an emphasis on the interactions related to bioactive compounds. The equations of PR and SRK showed efficiency in correlation of binary systems equilibrium data. For most binary systems experimental data fit, with the mixing rules with two binary interaction parameters, obtained good results and cash equivalents when compared with the mixing rules with three parameters. For multicomponent systems, when the experimental data were correlated with the PE program, employing both equations with quadratic mixing rule, shown convergence, best results for phase equilibrium description and the representativeness of the thermodynamic analysis of separation through the distribution coefficients were obtained. For the CO2 (1)/(2) oleic acid/linoleic acid (3) system, the prediction of equilibrium with an interaction parameters matrix of binary systems proved equivalent in relation to the use of multicomponent systems interaction parameters. In relation to the CO2 (1)/Methyl Myristate (2)/Methyl Palmitate (3) system the results obtained from the calculation using the interaction parameters matrix of binary systems, as with the parameters of interaction of multicomponent system, showed average deviation similar to the temperature of 323.15 K. For the CO2 (1)/Squalene (2)/(3)/Triolein oleic acid (4) system, the best results were obtained by the Quadratic mixing rule with the multi-component system interaction parameters. In relation to the CO2 (1)/(2) oleic acid/Palmitic acid (3)/Squalene (4) system, the results obtained using the interaction parameters matrix of binary systems showed average deviations below 8%. The calculation of the ELV for the CO2 (1)/Methyl Myristate (2)/Methyl Palmitate (3)/Methyl Oleate (4)/Methyl Stearate (5) system, with the EDEflash and PE program with Quadratic mixture rule, using the interaction parameters matrix from binary systems showed similar results. For the CO2 (1)/Ethyl Palmitate (2)/ Ethyl Stearate(3)/ Ethyl Oleate (4)/ Ethyl Linoleate (5) (palm oil ethyl esters) system, the prediction of the ELV with the SRK combined with Quadratic mixing rule, using the interaction parameters matrix from binary systems, presented results with deviations below 4% in both phases at 333.15 K.
Acesso aberto (Open Access)
Separation of satured and unsaturated fatty acids from palm fatty acids distillates in continuous multistage countercurrent columns with supercritical carbon dioxide as solvent: a process design methodology
(1997-12) MACHADO, Nélio Teixeira de; BRUNNER, Gerd
In this work the separation of multicomponent mixtures in counter-current columns with supercritical carbon dioxide has been investigated using a process design methodology. First the separation task must be defined, then phase equilibria experiments are carried out, and the data obtained are correlated with thermodynamic models or empirical functions. Mutual solubilities, Ki-values, and separation factors aij are determined. Based on this data possible operating conditions for further extraction experiments can be determined. Separation analysis using graphical methods are performed to optimize the process parameters. Hydrodynamic experiments are carried out to determine the flow capacity diagram. Extraction experiments in laboratory scale are planned and carried out in order to determine HETP values, to validate the simulation results, and to provide new materials for additional phase equilibria experiments, needed to determine the dependence of separation factors on concetration. Numerical simulation of the separation process and auxiliary systems is carried out to optimize the number of stages, solvent-to-feed ratio, product purity, yield, and energy consumption. Scale-up and cost analysis close the process design. The separation of palmitic acid and (oleic+linoleic) acids from PFAD-Palm Fatty Acids Distillates was used as a case study.
Acesso aberto (Open Access)
Trocas turbulentas noturnas de CO2 entre a floresta de Uatumã, Amazonas, e a atmosfera
(Universidade Federal do Pará, 2014-07-04) MAFRA, Ana Carolina Batista; SÁ, Leonardo Deane de Abreu; lattes.cnpq.br/0107976161469463; ARAÚJO, Alessandro Carioca de; lattes.cnpq.br/6188087583954899
We study the nocturnal boundary layer - NBL above an area of primary tropical forest northeast of the state of Amazonas, the Sustainable Development Reserve of Uatumã, distant 15 km of the Uatumã River, located about 380 km northeast of the city of Manaus, Amazonas. It is intended to determine some of the characteristics of the NBL, particularly nocturnal turbulence regimes by identifying the differences related to vertical exchanges of CO2, according to the methodology proposed by Sun et al. (2012). Fast response data will be used for the atmospheric scalar and vector quantities, as CO2 concentration and wind speed, respectively. The methodology allows characterization of NBL in three regimes of dynamic stability: 1) weak turbulence, mean low wind speed; 2) strong turbulence, with high wind speed, and 3) intermittent turbulence events with "top -down ". From this characterization, we have investigated some of the main statistical characteristics of each turbulent regime. As would be expected, the turbulent fluxes of CO2 increases with the characteristic scale of turbulent velocity, VTKE, associated with turbulent kinetic energy measured above the forest canopy. The CO2 exchange increases considerably with the regime 2,with higher values of the mean wind speed, | V |, and with the occurrence of strong mixing in the atmospheric boundary layer, ABL, not predominantly generated by surface forcings .