Alkanolamine Solvents Research Articles

Ladder-Like Polyphenylsilsesquioxane Membranes for Dissolved Oxygen Removal in Liquid–Liquid Membrane Contactors

The main disadvantage of absorption with aqueous alkanolamine solvents is the solvent degradation under process conditions in the presence of oxygen captured from flue gases. In this communication, the direct dissolved oxygen removal from an amine solvent in liquid–liquid membrane contactors is examined. The membranes from ladder-like polyphenylsilsesquioxanes are used for the first time for this process. The membrane deoxygenation is demonstrated in the O2 removal process from monoethanolamine (MEA) into an aqueous solution of Na2SO3. In this case, the O2 removal efficiency reached up to 40% within 1 h.

Modeling of carbon dioxide absorption into aqueous alkanolamines using machine learning and response surface methodology

This research focuses on modeling CO2 absorption into alkanolamine solvents using multilayer perceptron (MLP), radial basis function network (RBF), Support Vector Machine (SVM), networks, and response surface methodology (RSM). The parameters, including solvent density, mass fraction, temperature, liquid phase equilibrium constant, CO2 loading, and partial pressure of CO2, were used as input factors in the models. In addition, the value of CO2 mass flux was considered as output in the models. Trainlm, trainbr, and trainscg algorithms trained the networks. The results showed that the best number of neurons for MLP with one layer is 16; with two layers, 5 neurons in the first layer and 12 neurons in the second layer; and with three layers, 9 neurons in the first layer, 5 neurons in the second layer, and 1 neuron in the third layer. The best spread in RBF was found to be 2.202 for optimal network performance. Furthermore, statistical data analysis revealed that the trainlm function performs best. The coefficients of determination for RSM, MLP, RBF, and SVM for optimized structures are obtained at 0.9802, 0.9996, 0.9940, and 0.8946, respectively. The results demonstrate that MLP and RBF networks can model CO2 absorption using the trainlm, trainbr, and trainscg algorithms.

Mixing γ-Al2O3, silica-ZIF-8 and activated carbon nanoparticles in aqueous N-methyldiethanolamine+sulfolane as a nanofluid for application on CO2 absorption

Mixing of Al2O3, superactive carbon (SAC), and Si-ZIF-8 nanoparticles in alkanol amine solvents with aqueous and hybrid context were used to study the absorption of carbon dioxide. Hybrid-based nanofluids composed of aqueous N- methyldiethanolamine (MDEA) + Sulfolane (SFL) + small amount of nano particles including-γ-Al2O3, Si-ZIF-8 and SAC in three concentrations levels, were prepared by weighting each components. The Zeta potential of suspensions was found thatγ-Al2O3, Si-ZIF-8 and super activated carbon is stable in aqueous solvents. Absorption measurements were performed using the static method at a temperature of T = 313.15 K, gas partial pressure ranges up to about 1.2 MPa, nanoparticle concentrations of 0.02 – 0.50 by weight percent, and fixed concentration of MDEA (40 wt%) and SFL (30 wt%). It was found that in the hybrid context (i.e., MDEA 40 wt% + SFL 30 wt%), the addition of γ-Al2O3 (0.1 wt%), Si-ZIF-8 (0.02 wt%) and SAC (0.1 wt%) has maximum effect on CO2 absorption. In aqueous context (i.e., MDEA 40 wt%), nanofluids used in the present study have no significant effect on CO2 capacity. The importance of the addition of SFL in nanofluids was discussed, and the experimental solubility data was modeled using Genetic Programming approach. Average absolute relative deviation (AARD), Coefficient of determination R2, as well as Root mean square error (RMSE) were 10.43% & 8.94%, 0.985 & 0.983, 0.051 & 0.054 for training and validating data, respectively. It is found that the determined parameters give satisfactory predictions in the modeling of the solubility.

Reclaiming of Amine CO2 Solvent Using Extraction of Heat Stable Salts in Liquid-Liquid Membrane Contactor

Amine CO2 solvents undergo oxidative degradation with the formation of heat stable salts (HSS). These HSS reduce the sorption capacity of amines and lead to intense corrosion of the equipment. In our work, we propose a membrane-supported liquid-liquid extraction of the HSS from alkanolamines. For this purpose, a hollow fiber membrane contactor was used for the first time. A lab-scale extraction system on the basis of a hollow-fiber liquid-liquid membrane contactor with hollow fiber ultrafiltration polyvinylidenefluoride and polysulfone membranes has been studied. The extraction of the HSS-ions from a 30 wt.% solution of monoethanolamine was carried out using a 0.25-1 M solution of OH-modified methyltrioctylammonium chloride in 1-octanol as an extractant. It has been shown that >90% of HSS ions can be extracted from the alkanolamine solvent within 8 h after extraction. The results obtained confirm the possibility of using membrane extraction with a liquid-liquid membrane contactor for the reclaiming of amine CO2 solvents to increase the general efficiency of carbon dioxide capture.

Toward economical application of carbon capture and utilization technology with near-zero carbon emission

Carbon capture and utilization technology has been studied for its practical ability to reduce CO2 emissions and enable economical chemical production. The main challenge of this technology is that a large amount of thermal energy must be provided to supply high-purity CO2 and purify the product. Herein, we propose a new concept called reaction swing absorption, which produces synthesis gas (syngas) with net-zero CO2 emission through direct electrochemical CO2 reduction in a newly proposed amine solution, triethylamine. Experimental investigations show high CO2 absorption rates (>84%) of triethylamine from low CO2 concentrated flue gas. In addition, the CO Faradaic efficiency in a triethylamine supplied membrane electrode assembly electrolyzer is approximately 30% (@−200 mA cm−2), twice higher than those in conventional alkanolamine solvents. Based on the experimental results and rigorous process modeling, we reveal that reaction swing absorption produces high pressure syngas at a reasonable cost with negligible CO2 emissions. This system provides a fundamental solution for the CO2 crossover and low system stability of electrochemical CO2 reduction.

Modeling of CO2 absorption into 4-diethylamino-2-butanol solution in a membrane contactor under wetting or non-wetting conditions

In this work, 4-diethylamino-2-butanol (DEAB) as a new type of alkanolamine solvent is used for CO2 capture in a hollow fiber membrane contactor (HFMC). A model describing the gas and liquid reactions and transport inside the membrane contactor under the wetting or non-wetting conditions was built. The countercurrent flow of natural gas and solvent was considered in the model. To investigate the influence of solvent type on decarburization efficiency, DEAB was used and compared with other common solvents such as potassium carbonate (K2CO3), triethylamine (TEA) and diethanolamine (DEA). Under the same operating conditions, the impact of parameters such as humidity, gas flow rate, liquid concentration, membrane length on the decarburization performance was examined. The results indicate that DEAB solvent had the best overall performance especially under the wetting conditions. It was noted that increasing liquid concentration, membrane length and decreasing gas flow rate enhanced decarburization.

Investigation of Alkanol-Amine Solvents and their Blends for CO2 Removal from Natural Gas using Aspen-Hysys

The removal of carbon dioxide (CO2) from natural gas is vital towards meeting pipeline sales gas specifications and evading operational complications during the liquefaction of natural gas. Therefore, the removal of CO2 from natural gas is necessary for the efficient utilization of natural gas and for the reduction of global CO2 emission. It is also vital for the effective liquefaction process in the liquefied natural gas project A common and widespread technique used at natural gas plants in Nigeria is the removal of carbon dioxide (CO2) from natural gas through chemical absorption using alkanolamine solutions. In this research, an amine sweetening process is simulated using Aspen HYSYS V10 with a typical Nigerian natural gas composition. The simulation is used to investigate four different kinds of amines and their blends (mixed amines). The investigated amines are Monoethanolamine (MEA), Diethanolamine (DEA), Diglycolamine (DGA) and Methyldiethanolamine (MDEA) while the blends are MDEA + MEA, MDEA + DEA and MDEA + DGA. Results obtained from the simulation show that the mixed amine “MDEA + MEA” with lean amine strength of 11% MEA and 39% MDEA, absorbs 99.97% of CO2 present in the gas and hence, amine blends absorb carbon dioxide from natural gas better than the individual amines. It was also concluded that increasing the composition of the primary or secondary amine while decreasing the composition of the tertiary amine in the lean amine solution (amine blend) led to an increase in the amount of CO2 being absorbed. The study provides useful information on the absorption of CO2 using alkanolamine solvents and their blends in a standard amine sweetening plant.

Force-Field-Based Computational Study of the Thermodynamics of a Large Set of Aqueous Alkanolamine Solvents for Post-Combustion CO2 Capture.

The ability to predict the thermodynamic properties of amine species in CO2-loaded aqueous solutions, including their deprotonation (pKa) and carbamate to bicarbonate reversion (pKc) equilibrium constants and their corresponding standard reaction enthalpies, is of critical importance for the design of improved carbon capture solvents. In this study, we used isocoulombic forms of both reactions to determine these quantities for a large set of aqueous alkanolamine solvent systems. Our hybrid approach involves using classical molecular dynamics simulations with the general amber force field (GAFF) and semi-empirical AM1-BCC charges (GAFF/AM1-BCC) in the solution phase, combined with high-level composite quantum chemical ideal-gas calculations. We first determined a new force field (FF) for the hydronium ion (H3O+) by matching to the single experimental pKa data point for the well-known monoethanolamine system at 298.15 K. We then used this FF to predict the pKa values for 76 other amines at 298.15 K and for all 77 amines at elevated temperatures. Additionally, we indirectly relate the H3O+ hydration free energy to that of H+ and provide expressions for intrinsic hydration free energy and enthalpy of the proton. Using the derived H3O+ FF, we predicted the pKa values of a diverse set of alkanolamines with an overall average absolute deviation of less than 0.72 pKa units. Furthermore, the derived H3O+ FF is able to predict the protonation enthalpy of these amines when used with the GAFF. We also predicted the carbamate reversion constants of the primary and secondary amine species in the data set and their corresponding standard heats of reaction, which we compared with the scarcely available experimental data, which are often subject to significant uncertainty. Finally, we also described the influence of electronic and steric effects of different molecular fragments/groups on the stabilities of the carbamates.

Equilibrium solubility measurement of carbon dioxide in hybrid solvents of aqueous N-methyldiethanolamine blended with 1-Methyl-3-octyl-imidazolium tetrafluoroborate ionic liquid at high pressures

Solubility of CO2 in the hybrid solvents composed of aqueous N-methyldiethanolamine (MDEA) blended with 1-methyl-3-octyl-imidazolium tetrafluoroborate ([Omim][BF4]) ionic liquid (IL) was measured at temperatures from (298.15–343.15 K) and pressures of (0.2–4 MPa). The experimental trials were performed in a static high pressure equilibrium cell to determine the CO2 absorption capacity of novel absorbent solutions based on the isochoric saturation technique. The experimental data showed that, by rising the concentration of IL in the absorbent solutions’, the mole fraction of dissolved CO2 gas enhances gradually. Absorption capacity of these aqueous solutions was assessed and compared with pure ILs and alkanolamine solvents, which indicates the solutions studied in this research as better hybrid solvents in terms of CO2 loading. Furthermore, a semi empirical model is used to correlate the solubility data of this work, which presents a good agreement with an absolute average deviation (AAD %) of below 1%.

Energy, exergy and economic (3E) evaluation of CO2 capture from natural gas using pyridinium functionalized ionic liquids: A simulation study

Sweetening of natural gas is a necessary process step to meet transportation and commercial standards. Amine-based solvents have been conventionally used for absorption-based removal of contaminants, like acid gas from natural gas. The process has inherent high energy penalty issues during solvent recovery and large fugitive emissions due to the solvent's low vapor pressure. Contrarily, ionic liquids (ILs) have lower solution enthalpies and vapor pressure compared to conventional alkanolamine solvents. Hence, ILs can offer an energy-saving pathway for the carbon dioxide removal. However, understanding their application at plant-wide scale is limited. This study presents an energy, exergy and economic (3 E) analysis of an ionic liquid-based process for removing carbon dioxide from natural gas in a simulated environment. Pyridinium cation-based IL is analysed as a CO2 capturing solvent and compared to the monoethanolamine (MEA) and 1,2-dimethoxyethane (DME). Optimal operating conditions for the IL-based carbon capture are evaluated with 99% CH4 recovery and 99% CH4 purity as benchmark conditions. The energy analysis shows that 3-methyl-1-ethylpyridinium bis(trifluoromethylsulfonyl)imide (3MEPYNTF2) ionic liquid provides 90.08% and 80.28% overall energy savings relative to MEA and DME. The exergy analysis further complements the energy analysis as 3MEPYNTF2 is energy proficient with overall anergy of 13.3 MW, while MEA and DME gives a higher value of 57.45 and 30.98 MW, respectively. Furthermore, economic analysis indicates that at average, 3MEPYNTF2 offers savings in overall capital (65.86%), operating costs (81.09%), and total annualized costs (78.33%) compared to MEA and DME. The 3 E analysis suggests that pyridinium cation based ILs are a potential replacement for amine-based high pressure natural gas sweetening processes.

Effects of alkanolamine solvents on the aggregation states of reactive dyes in concentrated solutions and the properties of the solutions.

The aggregation of dyes is a common phenomenon in solutions, particularly concentrated solutions, which seriously affects the dyeing and printing processes. In this study, the effects of alkylamine solvents on the reactive dye aggregation behavior in highly concentrated solutions was studied. Typical cases were conducted with two slightly toxic and environmentally friendly solvents, namely diethanolamine (DEA) and triethanolamine (TEA), and two reactive dyes, namely C. I. Reactive Red 218 (R-218) and C. I. Reactive Orange 13 (O-13). Aggregation states were studied by ultraviolet-visible (UV-Vis) absorption spectroscopy, Gaussian-peak-fitting method and fluorescence spectroscopy. The results showed that both the additives DEA and TEA could reduce the dye aggregation because the solvents, DEA and TEA, can break the iceberg structure and allow easy entry of the molecules into the dye aggregates. Also, the disaggregation caused by DEA was higher as compared with TEA, which may be caused by the weaker hydrogen bond and the relatively smaller steric hindrance effects of DEA. The schematic of disaggregation between R-218 and DEA was also discussed. For R-218, the dimers were disaggregated to monomer, while the higher-ordered aggregates were disaggregated to trimers and dimers for O-13. Moreover, physical properties such as viscosity and surface tension of the solutions were measured. This investigation is instructive for the further dyeing progress with organic bases in the textile industries.

Mass transfer performance of carbon dioxide absorption in a packed column using monoethanoleamine-Glycerol as a hybrid solvent

Environmental concerns caused by chemical solvents need be managed through the advantages of hybrid bio-sourced solvents for CO2 capture. On the other side, to accurately predict the height of a CO2 absorption packed column, it is essential to estimate the mass transfer coefficients. This paper provides the experimental results of mass transfer performance of the aqueous mixture of MEA + Glycerol, as an industrially eco-friendly hybrid solvent, instead of a typical commercial alkanolamine solvent for CO2 capture in a laboratory-scale absorption packed column. For the first time, a predictive statistical model was built to investigate the influence of process variables, involving absorption temperature (30−45 °C), inlet gas flow rate (4−6 L/min), the initial solvent concentration of glycerol (5−15 wt %), and MEA (10−30 wt %) on the CO2 removal efficiency (ef), and the volumetric overall gas-phase mass transfer coefficient (KGaV) in the CO2+MEA + Glycerol system. The results of CO2-absorption showed that rising the glycerol concentration from 5 % to 15 % enhances the values of ef and KGaV by 4.5 % and 24.62 %, respectively, when the other three variables are considered fixed at their midpoints. Therefore, the presence of glycerol, as the promoter in a hybrid mixture of MEA-Gly, significantly gives rise to the mass transfer coefficient and CO2 removal efficiency.

Removal of the total organic acid anions from an industrial lean diglycolamine solvent using a calcium alginate carbon adsorbent, and molecular modeling studies

Diglycolamine (DGA), one of the alkanolamine solvent used in natural gas sweetening unit, produces total organic acid (TOA) anions as degraded products that has detrimental effects over the operational units. In this study, calcium alginate carbon (CAC) adsorbents were used to remove TOA anions from industrial lean DGA solvent. The adsorbents were characterized by TGA, DSC, Raman, FTIR, and SEM analysis. Effects of different parameters such as the adsorption time, adsorbent dosage, and solution temperature were examined in the batch adsorption experiments. The kinetic data were best fitted to the pseudo-second-order model, highlighting chemisorption as the rate-limiting step. This was also validated using molecular modeling by predicting the intermolecular hydrogen bond formation between the organic acid anions and the calcium alginate molecules. The TOA uptake increased with the increase in the solution temperature from 49.9 mg/g at 25 °C to 72.5 mg/g at 55 °C. The CAC beads were regenerated effectively for six adsorption–desorption cycles in a fixed-bed column. The environmentally friendly CAC adsorbent exhibited significant application potential for the removal of TOA anions from lean DGA solvents.

Theoretical investigations on the effect of absorbent type on carbon dioxide capture in hollow-fiber membrane contactors.

Chemical absorption of carbon dioxide from flue or natural gas in hollow-fiber membrane contactors (HFMCs) has been one of the most beneficial techniques to alleviate its emission into the environment. A theoretical research study was done to investigate the change in membrane specifications and operating conditions on CO2 absorption using different alkanolamine solvents. The mathematical model was developed for a parallel counter-current fluid flow through a HFMC. The developed model’s equations were solved based on finite element method. The simulations revealed that the increase in membrane porosity, length and the number of fibers has a positive impact on CO2 removal, while the gas flow rate and tortuosity enhancement resulted in the reduction of CO2 absorption. Furthermore, it was found that 4-diethylamino-2-butanol (DEAB) with approximately 100% CO2 absorption is suggested as the best solvent in this system, but ethyl-ethanolamine (EEA) with only 46% CO2 absorption had the lowest capacity for CO2 absorption (DEAB>MEA>EDA>MDEA>TEA>EEA). It is worth pointing out that the CO2 absorption can be improved using EEA solvent via change in membrane specifications such as increase in membrane porosity, length and the number of fibres.

Comparison of aqueous and non-aqueous alkanolamines solutions for carbon dioxide desorption in a microreactor

An experimental study of CO2 desorption from aqueous and non-aqueous saturated alkanolamine solutions carried out in a tubular microreactor, consisting of a stainless steel microtube with an internal diameter of 800 μm and a total length of 35 cm. We tested a total of six solvent mixtures of water or methanol with monoethanolamine, diethanolamine, or activated methyl diethanolamine in a broad range of operational conditions, including temperature (50–100 °C), rich solvent flow rate (0.5–4.5 ml/min), and amine concentration in the solvent (10 and 50% w/w). CO2 desorption was thoroughly characterized with respect to the mass transfer rate and energy consumption, and both were expected to improve with the use of a microreactor due to short diffusion distances and a larger surface-to-area ratio. An increase in the operating temperature or concentration of the amine resulted in a higher percentage of desorption and enhanced mass transfer rates, as shown by the local mass transfer coefficient based on the liquid phase values herein disclosed. Increasing the rich solvent flow rate also increased the local mass transfer coefficient values (80%–95%); however, the overall percentage of CO2 desorption reduced (25%–35%) due to shorter residence times in the microreactor. Similarly, the energetic desorption efficiency improved for all the solutions with increasing temperature (65–75% reduction) and concentration of amine in the solvent (20–35% reduction), yet again decreasing with an increasing flow rate of rich solvent (5–15%). Compared to the literature values for the packed columns and microreactors, our data showed the overall energy consumption up to an 88% reduction in specific CO2 desorption, demonstrating great potential for the intensification of solvent-mediated, energetically demanding CO2 desorption. In addition, the results showed that the energy consumption for CO2 desorption was reduced by 73% by choosing a non-aqueous in preference to an aqueous alkanolamine solvent.

Absorption of carbon dioxide in mixtures of N-methyl-2-pyrrolidone and 2-amino-2-methyl-1-propanol

It has been suggested that non-aqueous solvents containing amines may provide alternatives to aqueous alkanolamine solvents due to the potentially lower energy requirement for the regeneration of the amine. This paper presents experimental data on the solubility of CO2 and heat of absorption in the organic solvent N-methyl-2-pyrrolidone (NMP) and mixtures of 2-amino-2-methyl-1-propanol (AMP) in NMP. The solubility of CO2 was found to be very low at temperatures above 70 °C, the temperature at which the AMP/NMP solvent can be regenerated. The solubility of CO2 was higher at lower temperatures, particularly when precipitation of the AMP carbamate occurred. The heat of absorption in the AMP/NMP solvent decreased with increasing temperature, from approximately 90 kJ/mol CO2 at 40 °C and low loadings, to approximately 40 kJ/mol CO2 and 65 kJ/mol CO2, at 88 °C and low loadings, for the 15 wt% and 25 wt% AMP in NMP solvents, respectively. The results obtained complement our previous studies, together providing comprehensive data on the vapor–liquid equilibrium and the heat of absorption of CO2, which can be used to model the system.

CO<sub>2</sub> Absorption Solvent Degradation Compound Identification Using Liquid Chromatography-Mass Spectrometry Quadrapole-Time of Flight (LCMSQTOF)

The degradation of the alkanolamine solvent used in the removal of acid gases from natural gas streams due to exposure to contaminants, thermal degradation and presence of oxygen or oxygen containing compounds will change the solvent properties, such as heat transfer coefficient, diffusion coefficient, and mass transfer coefficient of the solvent. Therefore, characterization and quantification of amine degradation product becomes one of the important analyses to determine alkanolamine solvent’s health. In order to identify degradation products of alkanolamine solvent, analytical strategies by using mass spectrometry (MS) as detector have been studied extensively. In this work, due to the low concentration of the amine degradation product, a method was developed for identification of alkanolamine degradation products using LCMS-QTOF technique. A strategy for identification of trace degradation products has been identified. Six (6) alkanolamine degradation products had been identified by using LCMS-QTOF targeted analysis in the blended alkanolamine solvent used in natural gas processing plant. Another fifteen (15) molecular formulas having similarity in chemical structure to alkanolamine degradation products were identified using untargeted analysis strategy, as possible compounds related to degradation products. Using LCMS-QTOF via targeted and untargeted analysis strategy, without tedious column separation and reference standard, enables laboratory to provide a quick and indicative information for alkanolamine solvent’s organic degradation compounds identification in CO2 adsorption, within reasonable analysis time.

Estimation of CO2 equilibrium absorption in aqueous solutions of commonly used amines using different computational schemes

In absorptive removal of CO2 by aqueous alkanolamine solvent, as the most prevalent CO2 capture technique, equilibrium absorption capacity of CO2 is a significant parameter for assessing the efficiency of absorption systems. In this study, unique computational models are presented to estimate CO2 solubility in commonly used amines. A series of models, including genetic algorithm-adaptive neuro fuzzy inference system (GA-ANFIS), particle swarm optimization ANFIS (PSO-ANFIS), coupled simulated annealing-least squares support vector machine (CSA-LSSVM) and radial basis function (RBF) neural networks were developed to estimate CO2 equilibrium absorption capacity in twelve aqueous amine solutions. The model inputs comprise of CO2 partial pressure, temperature, amine concentration in aqueous solution, molecular weight, hydrogen bond donor/acceptor count, rotatable bond count and complexity of the amines. The obtained results affirm that among proposed models, LSSVM exhibits more promising results with an excellent compatibility with experimental values. In detail, both mean square errors and average regression coefficient (R2) of LSSVM model are 0.02 and 0.9338, respectively. Moreover, it is confirmed that the proposed LSSVM model has better accuracy compared to the other models.

Energy and exergy analysis of acid gas removal processes in the LNG production chain

In the energy transition towards a zero-carbon energy sector, natural gas grows much faster than either oil or coal, since it is an environmentally-friendly fuel supported by the continuing expansion of LNG, increasing the availability of gas globally. In recent years, the substantial growth in the world energy demand has increased the interest in the exploitation of natural gas reservoirs previously deemed undesirable due to their high acid gas content. Existing technologies for natural gas purification, such as chemical absorption with alkanolamine solvents, may be not suitable for treating highly contaminated natural gas due to the required higher solvent circulation rate and, consequently, to the energy demand for solvent regeneration. Over the last decades attention has been devoted to the study and development of low-temperature CO2 removal processes. With these new technologies, CO2 is separated as a high-pressure liquid making it easier to be pumped underground for sequestration or utilization in Enhanced Oil Recovery (EOR) projects.The aim of this work is to analyze natural gas purification technologies and liquefaction schemes for the production of LNG starting from the same acid natural gas stream. In particular, two CO2 removal technologies are considered to bring CO2 concentrations down to levels suitable for LNG production: the conventional chemical absorption technology with activated-MDEA (aMDEA) as solvent and the recently patented Dual Pressure Low-Temperature (DPLT) distillation technology. Different commercial technologies are taken into account for the liquefaction of the purified natural gas: Propane-Mixed Refrigerant (C3MR), Mixed Fluid Cascade (MFC), and Single Mixed Refrigerant (SMR). However, since these liquefaction processes are designed for a sweet gas obtained using a conventional acid gas removal technology, some adjustments have been made for their application to a low-temperature sweet gas. The choice to compare a conventional technology with a novel low-temperature one has been made to understand if the synergy between a CO2 removal technology operated at low-temperature and the downstream liquefaction process is advantageous, despite the need for refrigeration also in the CO2 removal step.The different process schemes resulting from the combination of the two CO2 removal technologies with the liquefaction ones have been simulated in Aspen HYSYS® V10 and their performances are assessed and compared by means of energy and exergy analyses, respectively based on the “net equivalent methane” approach and on the exergy efficiency concept.Results suggest that, although the aMDEA absorption process and the DPLT distillation one with downstream NGLs recovery have about the same specific energy consumption when applied to the natural gas stream taken into account in this work considering the CO2 removal step only, the overall process (including the liquefaction of the purified natural gas stream) involving the DPLT distillation technology is characterized by lower consumptions and a higher exergy efficiency.

Degradation Test for Energy-Saving CO2 Absorbent Based on Phase Separation Type Solvent by Aqueous (Amine + Ether) Solution

To mitigate CO2 emission, chemical absorption using alkanolamine solvent is proposed to be the most applicable technology for CO2 capture. However, the alkanolamine solvent possess high energy consumption in regeneration. Thus, it is important that energy consumption in regeneration is reduced. To reduce the energy consumption, we have developed the phase separation solvent for CO2 capture, which consist amine, organic solvent and water. It shows single liquid phase before CO2 absorption though it shows two liquid phases after CO2 absorption. Feature of phase separation solvent is decreasing stripper bottom temperature (e.g. T=90℃). As a result, energy consumption in regeneration can be decreased to 2.9 GJ/t-CO2 or less (Monoethanolamine solvent, 3.8GJ/t-CO2). CO2 solubility of the immiscible type solvent follows the general trend of conventional amine solvents since the ether does not dissolve in amine phase and does not affect the physical property of the amine solution. CO2 solubility in phase separation solvent is almost the same as that of immiscible one at 313 K, though the solubility at 363 K is remarkably small. It means that the phase separation solvent reduces stripper temperature. In addition to reduction of energy consumption, durability is also an important point in order to put into practical use. SO2 is the main acidic impurity in flue gas and will affect amine degradation in CO2 capture. Therefore, this study is conducted durability test under acid gas in order to evaluate the durability of the phase separation absorbent. Durability of the phase separation absorbent under acid gases is evaluated by using test equipment. The compressed gas cylinders provided the feed gases whose flow rates were controlled by mass flow controllers. The gases fed into a static mixer and were mixed. The phase separation solvent is put in a beaker, and absorbs CO2 by blowing mixed acid gas after keeping the constant temperature (323K) with cold water. During regeneration, the phase separation solvent regenerates while keeping the constant temperature (363K) with hot water. In each step, the temperature is kept constant by stirring inside the beaker. To measure amount of absorbed CO2, gas flow rate of outlet during absorption / regeneration is measure by using mass flowmeter. In addition, the composition of the gas at the absorber outlet is analysed by a gas chromatograph.