A robust predictive tool for estimating CO2

Annual emission of a large quantity of Greenhouse Gases(GHG)endangers the environment and is the main reason ofglobal warming and climate is estimated that a considerable amount of global warming,approximately more than 55%,is related to the CO2,which is present in the ,decreasing CO2 emissions is a harsh necessity and requires immediate attention[1–4].

Absorption by aqueous alkanol-amine solutions is the mostcommon method for processes dealing with CO2 elimination from flue gas streams[5–7].The most preferred chemical solvents for absorption of CO2 are the aqueous solution of amines(primary,secondary,tertiary,and sterically hindered)due to their amazing thermal degradation resistance,low hydrocarbons loading capacity,high rate of absorption,and reasonable cost[8].Nevertheless,high consumption of energy,equipment corrosion,fouling,and foaming are inevitable drawbacks of utilizing amine solutions[8].

In recent decades,Ionic Liquids(ILs)have been suggested as new CO2 to their low vapor pressures,they have low vaporization ,ILs face some problems as CO2 solvent including high viscosity,high cost,and low CO2 loading[9].In the past decade,as a potential substitute for alkanol-amines,amino acid salt solutions have been welcomed[10].Despite that,alkanolamines are cheaper;the amino acid salt solutions are superior in many ways.Due to their ionic essence,they have high chemical reactivity,low vapor pressures,and low viscosities,are stable to oxidative degradation,and capable of establishing proper binding energy with CO2[11].CO2 absorption by amino acid salt solutions may produce some precipitation in the liquid phase,which shifts the reactions in the direction of forming more products and consequently an increase of CO2 absorption[12,13].

Some investigators have studied the absorption of CO2 via amino acid salt glycinate solutions were investigated by Song et al.[14]for CO2 used solutions of 10 wt%,20 wt%,and 30 wt%for CO2 absorption with the range ofpartialpressure from 0.1 to 200 kPa at the temperatures 303,313,and 323 K.The outcomes stated that the loading capacity reduces by increasing concentration ofthe amino acid salt.Mu?oz etal.[15]studied CO2 absorption with 1-molar solution of the potassium salts of threonine,proline,serine,arginine,ornithine,histidine,glycine,and taurine at 293 K and 100 kPa.They concluded that these amino acid salt solutions have a CO2 loading like monoethylamine(MEA).

Portugal et al.[15]used potassium threonate and potassium glycinate for CO2 stated that despite no precipitation was observed during the experiments,the order of magnitude for CO2 absorption using the amino acid is equal to the MEA.In addition,they found out that an increase in the potassium glycinate concentration decreases the CO2 and Brilman[16]studied the potassium L-prolinate solution in absorbing CO2.They concluded the CO2 loading decreases with increasing molar concentration of potassium addition,they observed some precipitation in the absorption process using 3-molar L-prolinate solution at 285 K.

Wei et al.[17]examined the CO2 loading capacity of potassium taurate aqueous solution along with density and indicated that the CO2 loading increases when the concentration of potassium taurate etal.[32]investigated the CO2 absorption at low partial pressures using potassium results indicated that the CO2 solubility decreases by increase in the concentration of potassium lysinate and operating temperature.

Literature experimental data for equilibrium solubility of CO2 into some amino acid salt solutions are collected and they are limited in the range of operating conditions and ,the CO2 loading for amino acid salt solutions depends on the solvent type,temperature,pressure,and concentration of are several experimental data on CO2 absorption with amino acid salt solutions in the literature[10,11,14,18,19].Nevertheless,they cover only a narrow range of temperature and concentration,which does not satisfy the requirements for addition,equilibrium data points are needed to assess the system ,the experimental measurements in all ranges for all types of solutions are impractical and rather developing methods for estimating CO2 loading of amino acid salt solutions is of vital importance.

Several thermodynamic models could be found in the literature that can predict the CO2 some empirical base models such as Kent–Eisenberg[20]which is applicable to some CO2 absorption systems[21],non-idealities are assumed lumped in equilibrium models which are developed using the excess Gibbs free energy,such as the models introduced by Austgen et al.[22],Clegg and Pitzer[23],the electrolyte-NRTL modelofChen and Evans[24],and Deshmukh and Mather[25].There are some equations of state(EoS)which try to designate non-idealities of the amino acid absorption models such as SAFT and CPA could be applicable for predicting CO2 absorption using amino acid salts,albeit the lack of data on critical and some physical properties of amino acid solutions is a major problem.

In this study,we are trying to develop a rebuts predictive mathematical model for estimating CO2 solubility in potassium based amino acid salt solutions by using neural networks and assess the in fluential parameters of the absorption process with resultant model.

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