Showing papers in "Industrial & Engineering Chemistry Research in 2002"
TL;DR: A review of the existing gas separation applications and the expected growth of these and potential new applications of gas separation membranes over the next 20 years are described in this paper, and improvements in gas separation technology needed to produce these changes in the membrane industry are also discussed.
Abstract: During the past 20 years, sales of membrane gas separation equipment have grown to become a $150 million/year business. More than 90% of this business involves the separation of noncondensable gases: nitrogen from air; carbon dioxide from methane; and hydrogen from nitrogen, argon, or methane. However, a much larger potential market for membrane gas separation lies in separating mixtures containing condensable gases such as the C3+ hydrocarbons from methane or hydrogen, propylene from propane, and n-butane from isobutane. These applications require the development of new membranes and processes. In this review, the existing gas separation applications are surveyed, and the expected growth of these and potential new applications of gas separation membranes over the next 20 years are described. The improvements in gas separation technology needed to produce these changes in the membrane industry are also discussed.
1,764 citations
TL;DR: The perturbed-chain SAFT (PC−SAFT) equation of state is applied to pure associating components as well as to vapor−liquid and liquid−liquid equilibria of binary mixtures of associating substances as discussed by the authors.
Abstract: The perturbed-chain SAFT (PC−SAFT) equation of state is applied to pure associating components as well as to vapor−liquid and liquid−liquid equilibria of binary mixtures of associating substances. For these substances, the PC−SAFT equation of state requires five pure-component parameters, two of which characterize the association. The pure-component parameters were identified for 18 associating substances by correlating vapor pressure and liquid density data. A comparison to an earlier version of SAFT confirms the good results for pure substances. When only one associating compound is present in a mixture, the PC−SAFT equation of state does not require mixing rules for the association term. Using one binary interaction parameter kij for the dispersion term only, the model was applied to azeotropic and nonazeotropic vapor−liquid equilibria at low and at high pressures, as well as to liquid−liquid equilibria. Simple mixing and combining rules were adopted for mixtures with more than one associating compound...
969 citations
TL;DR: In this paper, an activity coefficient model using molecular solvation based on the COSMO-RS method is proposed, which requires only a single radius for each atom in the solvation calculations, one universal parameter to discern hydrogen-bond acceptors and donors, and two universal parameters to determine segment interactions.
Abstract: An activity coefficient model using molecular solvation based on the COSMO-RS method is proposed. In this model, quantum mechanical COSMO calculations are performed to obtain the screening charges for molecules in a perfect conductor. A statistical mechanical model that considers molecules to be a collection of surface segments is developed for the calculation of segment activity coefficients using these screening charges. Activity coefficients for molecules are then obtained by summing the contributions of the segments. This model requires only a single radius for each atom in the COSMO solvation calculations, one universal parameter to discern hydrogen-bond acceptors and donors, and two universal parameters to determine segment interactions. This is a significantly fewer number of parameters for phase equilibrium calculations than group contribution methods such as the UNIFAC (168 parameters) and modified UNIFAC (612 parameters) models. The resulting completely a priori prediction method results in abso...
721 citations
TL;DR: In this paper, the authors measured thermogravimetric curves at a heating rate of 5 K/min for several hardwoods (beech, alder, birch, and oak) and softwoods (Douglas fir, two pine species, redwood, and spruce), whose chemical composition varies within the usual standards.
Abstract: Thermogravimetric curves have been measured at a heating rate of 5 K/min for several hardwoods (beech, alder, birch, and oak) and softwoods (Douglas fir, two pine species, redwood, and spruce), whose chemical composition varies within the usual standards. The analysis of the devolatilization characteristics is based on the introduction of several reaction temperatures. A comparison between hardwoods and softwoods shows that, in the latter case, the decomposition starts at lower temperatures, the hemicellulose shoulder is more delayed, and both the hemicellulose and cellulose zones are wider. Furthermore, the yields of char are higher. However, a devolatilization mechanism, consisting of three parallel reactions and the same set of activation energies for hemicellulose, cellulose, and lignin (100, 236, and 46 kJ/mol), can describe the high-temperature (>553 K) degradation behavior of all of the woods with a good accuracy. Modifications for the extension of the mechanism at lower temperatures are required o...
678 citations
TL;DR: In this paper, a CaO sorbent obtained from precipitated calcium carbonate (PCC) was used in a reaction-based process for the separation of carbon dioxide (CO2) from flue gas.
Abstract: This study is focused on improving the reactivity of a CaO sorbent for its use in a reaction-based process for the separation of carbon dioxide (CO2) from flue gas. The separation process consists of cyclical carbonation (of a metal oxide) and calcination (of the metal carbonate formed) reactions to yield concentrated CO2 from flue gas. CaO sorbents synthesized from naturally occurring limestone and dolomite were microporous in nature. Pore filling and pore pluggage of these micropores limited the conversion of CaO in the carbonation reaction to about 45−50% of the stoichiometric limit. A wet precipitation process was tailored to synthesize high-surface-area precipitated calcium carbonate (PCC). The pores of PCC predominantly lie in the mesoporous range (5−20 nm). The CaO sorbent obtained from PCC (PCC-CaO) was less susceptible to pore pluggage and attained over 90% conversion. PCC-CaO was also capable of maintaining its high reactivity (>90%) over two carbonation−calcination cycles.
533 citations
TL;DR: In this paper, a two-stage process is proposed to generate bio-oil, followed by catalytic steam reforming of the biooil, or a fraction thereof, to produce hydrogen.
Abstract: Biomass, a product of photosynthesis, is a renewable resource that can be used for sustainable production of hydrogen. We propose an approach that combines production of hydrogen with valuable coproducts and shows promising economics. The concept is based on a two-stage process: fast pyrolysis of biomass to generate bio-oil, followed by catalytic steam reforming of the bio-oil, or a fraction thereof, to produce hydrogen. The preferred option is separation of the bio-oil into a lignin-derived fraction, which could be used for producing phenolic resins or fuel-blending components, and a carbohydrate-derived material, which would be reformed to produce hydrogen. The coproduct strategy can also be applied to residual fractions derived from pulping operations or ethanol production and to effluents from other biomass conversion technologies such as transesterification of vegetable oils or food processing residues. In addition, all of the biomass-derived liquids can be coprocessed with natural gas to produce hy...
478 citations
TL;DR: A critical review of the literature on heat-exchanger network synthesis, the most commonly studied problem in process synthesis, and several classification schemes of this body of work based on a number of modeling and algorithmic criteria are presented.
Abstract: This paper provides a critical review of the literature on heat-exchanger network synthesis, the most commonly studied problem in process synthesis. After a review of solution methods, we present the chronological milestones in the development of the field and we discuss separately each of 461 related works leading up to the turn of the century. Then, we present several classification schemes of this body of work based on a number of modeling and algorithmic criteria. Finally, we offer a critical assessment of the current status of research in this area and provide suggestions for future research.
428 citations
TL;DR: In this paper, a systematic method for the analysis of hydrogen distribution systems based on the concept of hydrogen surplus is proposed, where the minimum flow rate of fresh hydrogen required by the refinery before any system design is set.
Abstract: Increasingly strict environmental and product-quality regulations, the shrinking market for high-sulfur fuels, and the price benefit of processing heavier and more sour crude oils has pushed oil refiners to increase their hydrocracking and hydrotreating capacities. The resulting increase in hydrogen consumption and limited or even decreased generation are creating tight hydrogen balances in many refineries throughout the world. The efficient use of hydrogen is a necessity, with refineries facing eroded margins due to constrained refinery operations or the need for significant investments in hydrogen generation and purification. This paper addresses the problem of refinery hydrogen distribution. A systematic method for the analysis of hydrogen distribution systems based on the concept of hydrogen surplus is proposed. This method sets targets for the minimum flow rate of fresh hydrogen required by the refinery before any system design. The analysis method is used to provide quantitative insights and to iden...
393 citations
TL;DR: In this article, a design method for PID controllers based on the direct synthesis approach and specification of the desired closed-loop transfer function for disturbances is proposed, which results in very good control for a wide variety of processes including those with integrating and/or non-minimum phase characteristics.
Abstract: A design method for PID controllers based on the direct synthesis approach and specification of the desired closed-loop transfer function for disturbances is proposed. Analytical expressions for PID controllers are derived for several common types of process models, including first-order and second-order plus time delay models and an integrator plus time delay model. Although the controllers are designed for disturbance rejection, the set-point responses are usually satisfactory and can be tuned independently via a set-point weighting factor. Nine simulation examples demonstrate that the proposed design method results in very good control for a wide variety of processes including those with integrating and/or nonminimum phase characteristics. The simulations show that the proposed design method provides better disturbance rejection than the standard direct synthesis and internal model control methods when the controllers are tuned to have the same degree of robustness.
383 citations
TL;DR: In this paper, the use of low-cost adsorbent has been investigated as a replacement for the current expensive methods of removing dyes from wastewater for fly ash generated in National Thermal Power plant.
Abstract: The use of low-cost adsorbent has been investigated as a replacement for the current expensive methods of removing dyes from wastewater. As such, fly ash generated in National Thermal Power plant w...
375 citations
TL;DR: The statistical associating fluid theory (SAFT) is a powerful model for thermodynamic property and phase equilibrium calculations for fluid mixtures as mentioned in this paper, but it has several limitations that are discussed here.
Abstract: Statistical associating fluid theory (SAFT) is a powerful model for thermodynamic property and phase equilibrium calculations for fluid mixtures. In this paper, the model development, modifications, and generalizations proposed over the past decade are reviewed. Emphasis is given to developments resulting in equations of state applicable to real fluids. In addition, theoretical models are reviewed. Applications are discussed, and representative calculations are presented with emphasis on aqueous systems and polymers. Despite its wide acceptance, SAFT has several limitations that are discussed here.
TL;DR: The perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state is applied to binary and ternary mixtures of polymers, solvents, and gases as mentioned in this paper.
Abstract: The perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state is applied to binary and ternary mixtures of polymers, solvents, and gases. The three pure-component parameters required for nonassociating molecules were identified for six polymer compounds. The phase equilibrium of polymer systems, which often involves high-pressure liquid−liquid mixtures as well as vapor−liquid mixtures at lower pressures, was investigated. Using a constant binary interaction parameter (kij), the PC-SAFT equation of state gives good correlations of the appropriate phase behavior over wide ranges of conditions. Comparisons to an earlier version of SAFT reveal an improvement of the proposed model.
TL;DR: In this article, the photochemistry of elemental mercury in simulated flue gases was examined using quartz flow reactors, and the implications of photochemical oxidation of mercury with respect to direct ultraviolet irradiation of flue gas for mercury control, analysis of gases for mercury content, and atmospheric reactions are discussed.
Abstract: Photochemical reactions of mercury with various constituents in flue gas produced by burning coal could be an attractive alternative to dry sorbent- or wet scrubber-based processes for mercury control. The sensitized oxidation of elemental mercury using 253.7-nm ultraviolet radiation has been extensively studied. The photochemistry of elemental mercury in simulated flue gases was examined using quartz flow reactors. Mercury-containing simulated flue gases at temperatures between 80 and 350 °F were irradiated with 253.7-nm ultraviolet light. Results are presented for the photochemical removal of elemental mercury from simulated flue gases, as well as from nitrogen mixtures that contain oxygen, water vapor, or nitrogen oxide. Optimization of the process parameters, including light intensity, is discussed. The implications of photochemical oxidation of mercury with respect to direct ultraviolet irradiation of flue gas for mercury control, analysis of gases for mercury content, and atmospheric reactions are d...
TL;DR: In this article, small inorganic particles strongly enhance water-crude oil emulsion stability when interactions with asphaltenes promote particle adsorption at the oil−water interface.
Abstract: Small inorganic particles strongly enhance water−crude oil emulsion stability when interactions with asphaltenes promote particle adsorption at the oil−water interface. A variety of particle types have been studied to investigate the controlling factors for particle-stabilization effectiveness. Emulsion stabilities were determined by the extent of water resolved after centrifugation and the electric field required for emulsion breakdown. All particles used were hydrophilic and stabilized oil-in-water emulsions if small enough to be interfacially active. When dried and exposed to asphaltene-containing oil phases, the particles stabilized water-in-oil emulsions. Decreased extents of preadsorbed water, decreased particle sizes, and increased particle concentrations enhanced water-in-oil emulsion stability. Investigations with model emulsions showed that an intermediate state of asphaltene aggregation, near the point of incipient precipitation, is required for particle modification and emulsion stabilization....
TL;DR: In this paper, the mechanical, permeance, and selectivity stabilities of carbon molecular sieve (CMS) hollow fiber membranes have been investigated for CO2/CH4 separation.
Abstract: Carbon molecular sieve (CMS) hollow fiber membranes have been investigated for CO2/CH4 separation. High-pressure (up to 1000 psia), mixed-gas feeds of 10% CO2/90% CH4 on the shell side were examined for three different temperatures (24, 35, and 50 °C). The mechanical, permeance, and selectivity stabilities of the CMS membranes under high pressure were encouraging and could be industrially relevant for many high-pressure applications, such as CO2 removal from natural gas. Two asymmetric polyimide precursor fibers, 6FDA/BPDA-DAM and Matrimid 5218, were pyrolyzed under vacuum to form the CMS membrane fibers. When pyrolyzed under identical protocols, the two types of CMS fibers had different permeation properties and physical characteristics. Modifications of the pyrolysis protocol and conditions were explored. Increasing the final pyrolysis temperature was shown to dramatically increase the CO2/CH4 selectivity (>600) of the CMS membranes but was detrimental to the CO2 permeance. On the other hand, using a he...
TL;DR: In this article, the rate of evolution of NH3, which is indicative of the overall rate of degradation, was measured continuously in a batch system sparged with air at 55 °C, typical of absorbers for CO2 removal from flue gas.
Abstract: Oxidative degradation of monoethanolamine (MEA) was studied at 55 °C, typical of absorbers for CO2 removal from flue gas. The rate of evolution of NH3, which was indicative of the overall rate of degradation, was measured continuously in a batch system sparged with air. Dissolved iron from 0.0001 to 1 mM yielded oxidation rates from 0.37 to 2 mM/h in MEA solutions loaded with 0.4 mol CO2/mol MEA. Ethylenediaminetetraacetic acid (EDTA) and N,N-bis(2-hydroxyethyl)glycine effectively decreased the rate of oxidation in the presence of iron by 40−50%. Ferrous caused oxidation in unloaded MEA with stoichiometry from 0.1 to 0.33 mol NH3/mol Fe2+. Fe2+ from 0.0001 to 3.2 mM yielded rates from 0.12 to 1.1 mM/h. Ferric did not appear to catalyze oxidation in unloaded MEA.
TL;DR: In this paper, crosslinkable 6FDA-based copolyimides were synthesized by using 3,5-diaminobenzoic acid (DABA) as one of two diamine monomers.
Abstract: To suppress undesirable plasticization effects in CO2/CH4 separations, crosslinkable 6FDA-based copolyimides were synthesized by using 3,5-diaminobenzoic acid (DABA) as one of two diamine monomers. DABA contains a carboxylic acid group that can be used to crosslink the polymer chains with ethylene glycol and aluminum acetylacetonate. These chemistries were compared for effectiveness in suppressing CO2 plasticization on the basis of pure CO2 permeation and sorption data up to 800 psia. The time and pressure dependencies of permeation and sorption were analyzed to characterize the plasticization phenomenon and how it can be controlled by covalent crosslinking. Mixed-gas permeation data are reported up to a total feed pressure of 850 psia for the separation of 50:50 CO2/CH4 mixtures at 35 °C. Selectivity losses with increasing feed pressure are modeled to further understand the effects of plasticization, dual-mode sorption, gas-phase nonidealities, and bulk flow on membrane performance. Additionally, a short...
TL;DR: In this article, a desulfurization and denitrogenation process for light oils has been investigated based on the chemical oxidation of sulfur- and nitrogen-containing compounds using hydrogen peroxide and acetic acid as oxidizing agent.
Abstract: A desulfurization and denitrogenation process for light oils has been investigated based on the chemical oxidation of sulfur- and nitrogen-containing compounds using hydrogen peroxide and acetic acid as oxidizing agent. Sulfur and nitrogen compounds, when dissolved in n-tetradecane and xylene, were oxidized under moderate conditions and were removed successfully. By use of this basic process, although nitrogen content of actual light oils was reduced to <22% of the corresponding feed values, sulfur content failed to be reduced to the required deep desulfurization level (0.05 wt %). This is because the alkyl-substituted sulfones, produced during the oxidation of sulfur compounds, remain in the resulting light oils, owing to their high hydrophobicity. These, however, may be removed from the light oils by subsequent extraction, using an acetonitrile/water azeotropic mixture, such that the sulfur contents of the light oils were decreased to <0.05 wt %, while maintaining a high oil recovery yield.
TL;DR: In this paper, a simplified model for the reaction pathways related to hydrogen production was proposed for glucose conversion and COD degradation in supercritical water, assuming pseudo-first-order kinetics.
Abstract: Gasification of 0.6 M glucose in supercritical water was investigated at a temperature range from 480 to 750 °C and 28 MPa with a reactor residence time of 10−50 s. The yield of hydrogen among gaseous products increased very sharply with increasing temperature above 660 °C. On the other hand, the yield of carbon monoxide decreased with temperature, most probably due to the role of a water−gas shift reaction. Carbon gasification efficiency reached 100% at 700 °C. A simplified model was proposed for the reaction pathways related to hydrogen production. The rates for glucose conversion and COD degradation were obtained by assuming pseudo-first-order kinetics.
TL;DR: In this article, a new sorbents for desulfurization of liquid fuels were developed using π-complexation, and the experimental heats of adsorption for πcomplexation are in excellent agreement with theoretical molecular orbital predictions.
Abstract: New sorbents for the desulfurization of liquid fuels were developed using π-complexation. Vapor-phase adsorption isotherms were investigated to understand the interaction between benzene/thiophene and various kinds of sorbents, including Ag−Y, Cu−Y, Na−Y, H−USY, Na−ZSM-5, activated carbon, and modified activated alumina. Compared to Na−Y, Cu−Y and Ag−Y adsorbed significantly larger amounts of both thiophene and benzene at low pressures, as a result of π-complexation with Cu+ and Ag+. Molecular orbital calculations confirmed that the relative strengths of π-complexation lie in the order thiophene > benzene and Cu+ > Ag+. The experimental heats of adsorption for π-complexation are in excellent agreement with theoretical molecular orbital predictions. Na−ZSM-5 and activated carbon could also adsorb small amounts of thiophene and benzene at low pressures. The sorbent capacities for thiophene at the low pressure of 2.3 × 10-5 atm were 0.92 molecule/Cu+ and 0.42 molecule/Ag+ and followed the order Cu−Y and Ag−Y...
TL;DR: In this article, a review of SBR technology for treating wastewaters is presented, which includes relevant experiments carried out at the laboratory, pilot-plant, and industrial scales.
Abstract: This review paper intends to provide an overall vision of SBR technology as an alternative method for treating wastewaters. This technology has been gaining popularity through the years, mainly because of its single-tank design and ease of automatation. The bibliographic review carried out here shows the efficiency and flexibility of this technology, as it is able to treat different kinds of effluents such as municipal, domestic, hypersaline, tannery, brewery, and dairy wastewaters; landfill leachates; etc.; under different conditions. The review includes relevant experiments carried out at the laboratory, pilot-plant, and industrial scales.
TL;DR: In this article, the potential of Arundo donax stems, Brazil nutshells, sugarcane bagasse, and sawdust from a native wood species (Prosopis ruscifolia) to sequester trace metals from wastewater was comparatively examined using dilute aqueous solutions of Cd(II)/Ni(II) ions as models.
Abstract: The potential capability of Arundo donax stems, Brazil nutshells, sugarcane bagasse, and sawdust from a native wood species (Prosopis ruscifolia) to sequester trace metals from wastewater was comparatively examined using dilute aqueous solutions of Cd(II) or Ni(II) ions as models. Brazil nutshells showed the best effectiveness (>90%) for the uptake of both metals from solutions of 20 mg/L initial concentration for dosages larger than 0.2−0.4 mg/L, even superior to those obtained for a commercial activated carbon and/or red marine algae (Corallinales) used for comparison under identical conditions. Equilibrium isotherms of cadmium on the lignocellulosic and algae samples and of nickel on the nutshells were determined and properly described by the Langmuir model. The highest maximum sorption capacity of Cd(II) ions was obtained for the nutshells (Xm = 19.4 mg/g) among the lignocellulosic samples. The trend in the estimated Xm values was found to be consistent with their contents of lignin and total surface ...
TL;DR: The production of aldehydes that are microbial inhibitors may occur when hexoses and pentoses in an aqueous solution are exposed to temperatures above 150 °C under acidic conditions common to acid-....
Abstract: The production of aldehydes that are microbial inhibitors may occur when hexoses and pentoses in an aqueous solution are exposed to temperatures above 150 °C under acidic conditions common to acid-...
TL;DR: In this paper, the modified UNIFAC (Dortmund) parameters have been refitted to an extended database and new groups for different amides, used as selective solvents, have been introduced.
Abstract: The group contribution method modified UNIFAC (Dortmund) has become very popular because of its large range of applicability and the reliable results predicted for vapor−liquid equilibria, solid−liquid equilibria, activity coefficients at infinite dilution, azeotropic data, and excess enthalpies over a wide temperature range. However, in a few cases, especially at high and low temperatures, poor results are obtained. To overcome this problem, the modified UNIFAC (Dortmund) parameters have been refitted to an extended database. Additionally, new groups for different amides, used as selective solvents, have been introduced. Altogether, 43 new or revised pairs of group interaction parameters for modified UNIFAC (Dortmund) are given.
TL;DR: Pretreatment by liquid flow past solids increases hemicellulose removal yields particularly at higher flow rates, but current first-order homogeneous kinetic models indicate that the amount of water should not be important.
Abstract: Pretreatment is an essential, but expensive, step in biologically converting biomass to fuels and chemicals, and acids added or released during the reaction hydrolyze hemicellulose to sugars and expose cellulose for enzymatic digestion with good yields. Pretreatment by liquid flow past solids increases hemicellulose removal yields particularly at higher flow rates, but current first-order homogeneous kinetic models indicate that the amount of water should not be important. However, these models suffer from inconsistencies, and the effect of varying sugarcane bagasse concentrations on xylose monomer and oligomer yields was experimentally measured in a batch reactor without adding acids or other chemicals at 200 °C. A greater drop in pH was observed at higher solids concentrations, as anticipated. Furthermore, only about 7−13% of the total xylose recovered in solution was as monomers at the maximum total xylose yield point, with the rest being oligomers, and although monomer yields could be increased at lon...
TL;DR: In this paper, simple solutions of hydrogen peroxide; peroxide activators such as carbonate, bicarbonate, and molybdate; and organic cosolvents afford rapid, broad-spectrum decontamination of chemical warfare agents, even at low temperatures (−30 °C).
Abstract: Simple solutions of hydrogen peroxide; peroxide activators such as carbonate, bicarbonate, and molybdate; and organic cosolvents afford rapid, broad-spectrum decontamination of chemical warfare agents, even at low temperatures (−30 °C). Such solutions are nontoxic, noncorrosive, and environmentally friendly. With bicarbonate activator, the decon solution can be comprised solely using food-grade materials. In situ generation of peroxy anion OOH- effects perhydrolysis of the nerve agents O-ethyl-S-[2-(diisopropylamino)ethyl]-methylphosphonothioate (VX) and pinacolyl methylphosphonofluoridate (GD or Soman) to yield nontoxic products. For the blister agent bis(2-chloroethyl) sulfide (HD or mustard), peroxo species HCO4- and Mo(OO)42- afford oxidation, initially, to the nonvesicant sulfoxide.
TL;DR: In this article, three different types of modified alginate beads were examined for the removal of arsenic; the most efficient type was found to be doped with alginates and subsequently coated with iron oxides.
Abstract: The application of biopolymers (alginate), as sorbent supports, for the removal of arsenic from contaminated water has been investigated in the present study. Calcium alginate beads were placed in a column to form a fixed bed and treated (doped/coated) with hydrous ferric oxides. Three different types of modified alginate beads were examined for the removal of arsenic; the most efficient type was found to be doped with alginate and subsequently coated with iron oxides, whereas the other two types were calcium alginate beads doped or coated with iron oxides. The total amount of iron loaded on this material was found to be 3.9 mg of Fe/g of wet alginate bead. Approximately 230 bed volumes of a 50 μg/L As(V) solution were treated before the breakthrough point was reached, whereas the removal of As(III) was not as efficient, reaching the breakthrough point after the treatment of only 45 bed volumes. The results were modeled using the bed depth service time and empty bed residence time models.
TL;DR: In this article, the piperazine (PZ)/methyldiethanolamine (MDEA)/water/carbon dioxide system was studied for the vapor−liquid equilibrium, speciation, and amine solubility.
Abstract: Vapor−liquid equilibrium, speciation, and amine solubility were studied for the piperazine (PZ)/methyldiethanolamine (MDEA)/water/carbon dioxide system. Solubility data for carbon dioxide in these solutions were obtained using a wetted-wall contactor. Solubility data for anhydrous PZ solid in water were obtained by adding PZ flakes to an agitated flask. In a 0.6 M PZ/4 M MDEA solution at 313 K, the partial pressure of carbon dioxide approaches one-tenth of the value in 4 M MDEA at low loading. This performance is between that of monoethanolamine (MEA) blends and diethanolamine (DEA) blends. The solubility data are modeled using the electrolyte NRTL model. The model is verified using 13C and 1H NMR data at high loading. The resulting model shows that the piperazine carbamate is the major reaction product at low loading (<0.1) while the protonated piperazine carbamate is the major reaction product at high loading. The piperazine dicarbamate species is present in higher concentration than in the simple PZ/H2...
TL;DR: Using mixtures as refrigerants in the design of refrigeration systems offers significant opportunities in the search for more energy-efficient and compact designs as mentioned in this paper, however, the design for mixed-refr...
Abstract: Using mixtures as refrigerants in the design of refrigeration systems offers significant opportunities in the search for more energy-efficient and compact designs. However, the design of mixed-refr...