Removal Of Heat Stable Salts Research Articles

Removal of heat stable salts from degraded amine solvent by “BMED+ED” two-stage electrodialysis unit

Due to the degradation reaction and the presence of acidic impurities (HCl, SO2, etc.) in the flue gas, heat stable salts (HSS) are widely present in the aqueous amine solvent for post-combustion CO2 capture. Accumulation of HSS in the solvent can lead to decreased absorption capacity and even corrosion of equipment in post-combustion capture (PCC) pilot plants. This study presents a novel “BMED+ED” two-stage electrodialysis unit for the efficient removal of HSS, including glycolate, formate, Cl−, and SO42−, from degraded amine solvent with an initial loading of approximately 0.38 mol/mol taken from the solvent loop of a PCC pilot plant after over 1000 hours of operation at real conditions. Experimental results showed that 94.93% of HSSs were removed with an initial HSS concentration of approximately 1920 ppm. The amine loss rate in the two-stage electrodialysis unit was much lower than that in a conventional ED unit, as protonated amine is further converted to organic amines by bipolar membrane electrodialysis. The energy consumption of the two-stage electrodialysis unit was 0.1643 kWh/L amine solvent, and the total cost for amine reclaiming was 1.8145 $/kg amine. This method effectively addressed the challenges of high amine loss rate in the traditional ED treatment process and hazardous wastewater disposal.

Removal of Heat Stable Salts from Degraded Amine Solvent by “Bmed+Ed” Two-Stage Electrodialysis Unit

Removal of Heat Stable Salts from Degraded Amine Solvent by “Bmed+Ed” Two-Stage Electrodialysis Unit

Removal of Heat-Stable Salts from Lean Amine Solution Using Bipolar Membrane Electrodialysis

Removal of Heat-Stable Salts from Lean Amine Solution Using Bipolar Membrane Electrodialysis

Design and optimization of a concentric setup for the separation of Heat Stable Salts from industrial lean amine solution using electromagnetic forces

The accumulation of heat-stable salts (HSS) in the gas sweetening amine units causes several problems, including foaming, corrosion, and fouling. Herein, a simple and efficient electromagnetic salt removal (EMSR) process was proposed for the separation of HSS from industrial lean amine solution. In this process, HSS were separated through an electro polarization mechanism instead of electrosorption. For this purpose, a lab-scale concentric flow setup was fabricated using aluminum conduit and rod as an anode and cathode, respectively. The effects of the process operational parameters, including flow rate, applied voltage, residence time, and pH were investigated. At the best-operating conditions, a maximum of 15 % HSS removal percentage was achieved in one pass having the power consumption of 0.003 Wh/L. This study demonstrated the potential usage of EMSR for industrial applications.

Removal of heat stable salts from N-methyldiethanolamine wastewater by anion exchange resin coupled three-compartment electrodialysis

Heat stable salts (HSS) are well-known degradation products of gas desulfurization using N-methyldiethanolamine (MDEA) solvents. Excessive HSS content causes a decrease in desulfurization efficiency, a decrease in the active ingredients of MDEA, and the corrosion of pipelines. In this paper, a self-designed two-compartment electrodialysis (ED) stack, a three-compartment electrodialysis (TED) stack, and an anion exchange resin coupled three-compartment electrodialysis (RTED) stack were assembled to remove the HSS from spent MDEA wastewater. The HSS desalination mechanisms of the three electrodialyzers were investigated, and their HSS removal efficiencies and losses of MDEA were investigated and compared. According to the results, approximately 93.84% of HSS were removed from the spent MDEA wastewater in the RTED, 7.88% higher than those in the TED and 28.57% higher than those in the ED. The loss of MDEA for the RTED was 3.78%, which is 1.78% lower than that for the TED and 17.29% lower than that for the ED. A relatively high sodium hydroxide (NaOH) concentration in the NaOH compartment, but no more than 3%, is beneficial for both improving the HSS removal efficiency and decreasing the loss of MDEA in TED and RTED. Much less fouling of the anion exchange membranes occurs in the RTED process than in the ED process because of the effect of the filled resin and the NaOH compartment. The cost of RTED is estimated to be US $0.88/kg HSS, which is far lower than that of both ED and TED.

Removal of heat stable salts from N-methyldiethanolamine wastewater using electrodialysis: a pilot-scale study

Removal of heat stable salts from N-methyldiethanolamine wastewater using electrodialysis: a pilot-scale study

Effect of Carbon Dioxide Loading on Removal of Heat Stable Salts from Amine Solvent by Electrodialysis.

Heat stable salts (HSS) formed and continuously accumulated in the amine-based solvents due to solvent degradation and impurities in the feed gas can dramatically change the efficiency of the amine scrubbing process. HSS can be removed by using different methods including membrane separation such as electrodialysis (ED). In this work, we studied the effect of CO2 loading of the lean 30 wt % monoethanolamine (MEA) solution on the efficiency of HSS removal and MEA loss. In the model MEA solution containing HSS on the level of 48 meq/L, the carbon dioxide concentration was varied from 0.2 down to 0 mole (CO2)/mole (MEA). The reclaiming of model MEA solution was carried out by lab-scale two-stage ED unit when the concentrate stream after the first stage was additionally treated using ED (second stage) that allowed reducing MEA loss. It was shown that the decrease of carbon dioxide content from 0.2 down to 0 mole (CO2)/mole (MEA) resulted in a substantial reduction of both parameters—the MEA loss and the specific power consumption with respect to extracted HSS (from 140 down 37 kJ per 1 g of recovered HSS anions). This can be explained by the drop in the total concentration of ions formed by the interaction of MEA solution with carbon dioxide. However, the change of CO2 loading is associated with additional power consumption towards further solvent regeneration in the column. Based on the preliminary estimations of power consumption required for additional CO2 stripping with the respect to the power consumption of ED stage, it seems that lean solvent CO2 loading of 0.1 mole/mole provides an optimum for the power input at 25.9 MJ/kg(solvent).

A quest for electrode materials: Heat-stable salts removal from industrial lean amine solution via electro-sorption

The accumulation of heat-stable salts (HSS) deteriorate the performance of gas treatment amine units. In this work, different commercially available electrode materials such as copper, stainless steel, aluminum foil, platinized coated titanium, and nickel foam were tested in a batch mode for the electro-sorption of HSS from industrial lean methyl-diethanolamine (MDEA) solutions. Initially, salt removal was examined by using copper electrodes in two different configurations: inside and outside the designed cell; attributing direct and indirect contact with the lean amine, respectively. The results revealed that indirect electrochemical cell configuration has a zero impact on HSS removal, and hence, all the electrodes were structured inside a cell having direct contact with the MDEA solution. Remarkably, the applied voltage has a significant impact on the removal efficiency of the HSS. Among the tested materials, nickel foam (Ni) and platinized (Pt) coated titanium (Ti) electrodes were the most efficient in the removal of HSS with 6.5% and 9.6% removal at a voltage of 0.8V and 1.2V, respectively. The electrochemical characteristics including areal capacitance and cyclic voltammetry for nickel and Pt coated Ti electrode were also reported. The magnetic forces showed no impact on the removal efficiency of the HSS in the batch mode of operation.

Solvent extraction based reclaiming technique for the removal of heat stable salts (HSS) and neutral degradation products from amines used during the capture of carbon dioxide (CO2) from industrial flue gases

This work used a modified OH-aliquat mixed with a new diluent, namely, 2-ethyl-1-hexanol to separate heat stable salts (HSS), namely, formate, glycolate and oxalate as well as neutral degradation products (i.e. imidazole, N-acethylethanolamine, 2-oxazolidone, N-(2-hydroxyethyl)-succinimide) from monoethanolamine (MEA), 2-amino-2-methyl-1-propanol (AMP), and N-methyldiethanolamine (MDEA) and their blends which are amines/amine blends typically used for carbon dioxide (CO2) capture from industrial flue gases. The new diluent, which has a branched-chain structure, increased the extraction performance of the OH-aliquat up to 50% HSS removal from MEA solution compared to our previous straight-chained 1-octanol diluent. The extractant also performed very well in removing HSS from MDEA and AMP with the ease of HSS extraction increasing in the order of AMP < MEA < MDEA for which the oxalate was removed by nearly 100% regardless of the type of amine and concentration. In blended MEA, AMP and MDEA, the extractant had a higher chemical affinity in removing all HSS when compared with single MEA. The extractant could also remove major neutral degradation products found in MEA solution. High temperature and low CO2 loading conditions were found to be favorable in maximizing the ability of the extractant to remove both product types. This finding revealed that the exact location where the amine slipstream should be taken for simultaneous extraction of all degradation products is at the exit point of the lean-rich amine heat exchanger. The regeneration of extractant using sodium hydroxide solution (NaOH) also indicated the reusability of the extractant as long as its reactive molecules remained. The results obtained from this study are being used for further development of the extraction process that can be used as a permanent replacement for conventional reclaiming techniques.

A novel rectangular assembly for heat stable salts removal from industrial lean amine: Effect of operational parameters

Heat stable salts (HSS) formed in gas sweetening units pose many challenges such as foaming, corrosion and equipment fouling. In this work, we designed a novel electromagnetic (EM) setup which aids the removal of HSS from MDEA without degrading amine and producing secondary waste. Total organic acid (TOA) was taken as a model pollutant to represent HSS ions. TOA was successfully removed by employing electromagnetic forces based on the Lorentz principle, using rectangular setup having parallel electrodes. The direction of the electric field will be perpendicular to the flow path along the channel to enhance the separation of ions at the outlet. In the flow cell, we investigated the effect of voltage, flow rate and magnet position on the removal efficiency and found optimal operating conditions to be at an applied potential of 3 V, the flow rate of 2 mL/min and 1T magnets placed parallel to fluid flow. The experimental results showed that the introduction of electromagnetic forces led to the electrosorption of ions onto the surface of the aluminum electrode whereas polarization occurred when only the electrical field was used. The HSS removal rate with magnets and without magnets in the parallel flow cell was 7.8% and 3.2% respectively.

Removal of heat stable salts from aqueous MDEA solution via electrosorption using carbon-based electrodes

Capacitive Deionization (CDI), an emerging desalination technique, was explored for the removal of heat stable salts (HSS) from the industrial lean methyldiethanolamine (MDEA) solutions. Various carbon-based materials, commercially available and synthetically prepared, were screened for the CDI application. Among different biochar materials, biochar prepared from date palm was the most efficient material for the removal of HSS. The activated biochar from date palm prepared at 550 °C (DPAC550) showed the highest HSS removal with about 20% removal efficiency. The date palm activated carbon was characterized by BET, XRD, SEM, FTIR and Elemental Analysis. Kinetic studies were also performed to determine the uptake capacity of DPAC550. The kinetic studies revealed that the electrosorption of HSS by DPAC550 followed pseudo-first order model. Electrochemical analysis supported the electrosorption behavior of DPAC550 which exhibited a specific capacitance of 269 F g−1 at 10 mV s−1 in 6 M KOH solution. This study clearly demonstrated the potential application of biochar electrodes for the removal of HSS from aqueous MDEA solutions using CDI cells.

Removal of heat stable salts from industrial lean methyldiethanolamine using magnetic alginate/iron oxide hydrogel composite

Heat Stable Salts (HSS) are undesirable contaminates that are generated due to the degradation of the amine solvent. This study deals with the development of a new process for the removal of HSS from amine solvent using magnetic calcium alginate hydrogel composites. The magnetic calcium alginate hydrogel composites was prepared by encapsulating freshly prepared maghemite nanoparticles (γ-Fe2O3) synthesized using a conventional precipitation technique in the calcium alginate beads. The developed magnetic hydrogel composites (CA-Fe2O3) characterized by XRD, SEM and FTIR showed that γ-Fe2O3 are retained homogeneously in the composites matrix. Kinetic and equilibrium batch adsorption experiments revealed that maximum HSS removal of 29.24% was achieved in 240 min with 3.0 g of onto CA-Fe2O3 composites at 25 °C and sorption efficiency increased with an increase in temperature. Adsorption kinetic study was performed using three kinetic models and the pseudo-second order kinetics very well correlated with the experimental data; demonstrating the chemisorption and endothermic nature of sorption. The reusability experiments showed no significant loss in absorption capability even after eight cycles. Additionally, the superparamagnetic behavior showcased by the magnetic composites allowed easy separation of the composites from lean MDEA using an external magnet. Therefore, such magnetic alginate–Fe2O3 hydrogel composites can work as a simple and cost-effective adsorbent for the reclamation of industrial lean MDEA, with the additional advantages of good efficiency, eco-friendliness and being easy to fabricate and recover.

Removal of HSS from industrial amine solution by anionic resin (case study: Ilam gas refinery)

In this research, the removal of heat stable salts was considered as one of the most effective factors in the process of amine degradation. To remove this type of salts, ion-exchange method was used. A resin purification system was investigated to separate the heat stable salt ions of acetate, formaldehyde, chloride, oxalate, thiosulphate, sulphate, and sulphite from alkanolamine solution flowing in the Ilam gas refinery sweetening units. To remove the existing ions in the lean amine solution, a strong anionic resin designated as INDION GS 300 was tested. Ion-exchange systems operated in batch and continuous mode (fixed-bed column) were applied to remove these salts. The effects of different operating variables such as contact time, temperature, and amount of resin were examined. The optimum values of amount of resin and temperature found for both systems were 5 g and 25 °C, respectively. Furthermore, the optimum times for batch and continuous systems were 30 and 10 min, respectively. Results of experiments revealed that around 95.5 and 97% of salts were removed using batch and column operations, respectively. Moreover, the amine solution pH increased from 10 to 11, indicating a corrosion rate reduction in the amine system of the Ilam gas refinery.

Capacitive deionization performance of CNTs-Si-Ag based electrodes for the removal of heat stable salts from methyldiethanolamine (MDEA) solution in natural gas sweetening units

The presence of heat stable salts (HSS) in the gas sweetening absorption columns reduces the absorption capacity of the amine solutions. For the first time, the capacitive deionization (CDI) technique is used to clean the MDEA solutions from HSS. For this purpose, the hybrid material (CNTs-Si-Ag) was synthesized by using the sol–gel process followed by chemical reduction. This hybrid material was then utilized as CDI electrode material in order to remove the HSS from the lean amine solutions. TEM and SEM confirmed the well-ordered interconnected porous network containing silanized CNTs (carbon nanotubes) along with silver (Ag) nanoparticles. Nitrogen adsorption–desorption analysis and electrochemical studies (EIS and CV) evidenced the substantial conductivity, porosity, surface area and specific capacitance of the prepared material. The specific capacitance of the hybrid material was found to be 149.1 F g−1 at 10 mV s−1 heralding substantial electrosorption capacity for the removal of HSS. The continuous CDI experiments showed that the highest SAC of the newly prepared electrode is 21.5 mg g−1 with maximum ASAR of 0.17 mg g−1 min−1 under 1.0 V and the lowest SAC is 17.3 mg g−1 with ASAR of 0.12 mg g−1 min−1 under 0.8 V. This work introduced the CDI as a potential technique that can be used to clean amine solutions advantaged with its low maintenance, easy operation and environment friendliness.

Two-Step Electrodialysis Treatment of Monoethanolamine to Remove Heat Stable Salts

Electrodialysis technology was adapted to removal of heat stable salts from aqueous solutions of alkanolamine absorbents, with monoethanolamine as example. Removal of anions of heat stable salts by electrodialysis from a 30 wt % aqueous solution of monoethanolamine with the degree of carbonation of 0.2 mol of CO2 per mole of monoethanolamine was studied. The two-step removal of heat stable salts by electrodialysis allows the monoethanolamine loss to be reduced and the concentration of residual CO2 in the absorbent solution to be decreased. The suggested two-step electrodialysis treatment scheme allows the concentration of heat stable salts to be maintained on the required level from the viewpoint of their corrosion activity, the total volume of the concentrate to be decreased by 50%, and the monoethanolamine loss to be decreased by 30%. The treatment unit with the circulation volume of the monoethanol absorbent of 100 m3 h–1 was calculated for confirming the efficiency of the two-step electrodialysis treatment scheme. As compared to the one-step electrodialysis treatment scheme, the two-step scheme ensures recovery of 50% of monoethanolamine at the same efficiency of the removal of heat stable salts.

Removal of heat stable salts (HSS) from spent alkanolamine wastewater using electrodialysis

The formation of heat stable salts (HSS) is a tough problem for aqueous alkanolamines solution in gas processing industry. In this study, a self-made electrodialysis stack was assembled to remove the HSS from spent amine wastewater. Results indicated that the optimum current density is 15mA/cm2. An increase in pH is beneficial for amine recovery but is harmful to the lifespan of membranes. The ED process cost is estimated to be 14.6$/t with the energy consumption of 39.4kWh/T. Comparison with the conventional neutralization or replacement methods, ED is not only energy-saving but also environmentally friendly for the removal of HSS from the spent amine wastewater.

New Reactive Extraction Based Reclaiming Technique for Amines Used in Carbon Dioxide Capture Process from Industrial Flue Gases

A new reclaiming technique based on reactive extraction for removal of heat stable salts (HSS) from monoethanolamine (MEA) used in carbon dioxide (CO2) capture process has been developed. The extraction process was based on the use of tri-n-octylamine (TOA), Aliquat 336, OH– modified Aliquat 336, a two-step extraction (modified Aliquat followed by TOA), and mixed extractant (modified Aliquat and TOA) in 1-octanol diluent. The best parameters were 69% OH– modified Aliquat, two-step extraction, and mixed extractant (modified Aliquat and TOA) and under optimum extraction conditions were able to improve the extraction efficiency of the original Aliquat and TOA to over 90%. The two-step extraction and mixed extractant were also capable of managing Cl– contamination in MEA solution. Extraction was found to be independent of temperature whereas efficiency reduced with increase of CO2 loading. Therefore, it is recommended to apply this extraction technique to the lean MEA stream after the rich/lean heat exchanger...

Regeneration of heat stable salts-loaded anion exchange resin by a novel zirconium pentahydroxide [Zr(OH) 5 − ] displacement technique in CO 2 absorption process

Abstract In the CO2 absorption process, heat stable salts (HSS) have been reported to be a major cause of operational problems, such as excessive foaming, corrosion, amine loss, and capacity reduction. Ion exchange technology has been the most effective and economical way for the removal of HSS. However, the disadvantage of this technology is its low regeneration efficiency. This study attempted to improve the low regeneration efficiency of anion exchange resin loaded with HSS by using a novel zirconium pentahydroxide (ZrOH5−) displacement technique. The experimental results showed, in the batch system, that the most effective potential metal-hydroxide regenerant, Zr(OH)5−, exhibited an efficiency that is 15.2% higher than for conventional NaOH, and in the continuous system, Zr(OH)5− had an efficiency that is 28.0–17.8% higher for 1.5–5 bed volume (BV). The differences of the BV corresponded to the breakthrough point for the initial breakthrough and after the 1st and 2nd regenerations were only 1.5–3.9%, which means that there was no significant deterioration of the resin’s performance by Zr(OH)5− regeneration. The mechanism of the general ion exchange steps as well as the regeneration by Zr(OH)5− was determined by performing an FT-IR analysis. These results indicate that the novel Zr(OH)5− displacement technique improves the low regeneration efficiency of the ion exchange process.

음이온교환수지를 이용한 CO2흡수 공정시 발생하는 열안정성염 처리 특성

In this study, we studied the characteristics of ion exchange for treatment of HSS (heat stable salts) which cause performance reduction in CO2 gas capture amine solution using anion exchange resins. The optimum HSS removal efficiency, 96.1% was obtained when using strong base anion exchange resin SAR10 at dosage 0.05 g/mL, 316 K, pH 12 and the best resin regeneration efficiency, 78.8% was obtained using NaOH solution of 3 M at 316 K. The adsorption data were described well by the Freundlich model and the sorption intensity(n) was 2.0951 lying within the range of favorable adsorption. The adsorption selectivity coefficients were increased by increasing valences and size of ion and desorption selectivity coefficients showed a contradictory tendency to adsorption selectivity coefficients. By continuous HSS removal experiments, 13.3 BV of HSS con- taminated solution was effectively treated and the optimum NaOH solution consumption was 5.2 BV to regenerate resins.

Heat Stable Salts (HSS) Removal by Electrodialysis: Reclaiming of MEA Used in Post-combustion CO2-Capture

Abstract Heat-stable salts (HSS) are well-known degradation products in the acid gas removal technologies with alkanolamines, especially in the post-combustion CO2 Capture processes. The traditionally applied HSS removal methods such as purging, filtration, distillation might be economically unattractive in the large scale post-combustion plant case. Electrodialysis could be an alternative method for solvent reclaiming with removal of electrically charged amine degradation products. This work presents the results of electrodialysis reclaiming concept tested under real operation conditions during pilot campaign at Heilbronn post combustion CO2 Capture pilot plant. The HSS removal results and some process specific parameters are presented.