Pilot-Scale Evaluation of CO2 Loading Capacity in AMP Aqueous Solution beside the Improvers HMDA-NH3 under a Series of Operational Conditions

Journal of Environmental Treatment Techniques

2018, Volume 6, Issue 4, Pages: 74-80

J. Environ. Treat. Tech.

ISSN: 2309-1185

Journal weblink: http://www.jett.dormaj.com

Pilot-Scale Evaluation of CO Loading Capacity

in AMP Aqueous Solution beside the Improvers

HMDA-NH under a Series of Operational

Conditions

3,4

Amin Ale-Ebrahim Dehkordi , Alireza Jahangiri Amirreza Talaiekhozani A.Heidari

Semiromi

- Chemical Engineering Department, Jami Institute of Technology, Isfahan, Iran

- Faculty of Engineering, Shahrekord University, Shahrekord, Iran

- Department of Civil Engineering, Jami Institute of Technology, Isfahan, Iran

- Applied Nanobiophotonics Center, Shiraz University of Medical Sciences, Shiraz, Iran

-Chemical Engineering Department, Jami Institute of Technology, Isfahan, Iran

Received: 09/08/2018

Accepted: 01/12/2018

Published: 30/12/2018

Abstract

Nowadays, carbon dioxide removal has to be ingeniously managed because of its environmental and health effects. CO as a

heat-trapping greenhouse gas is pumped into the atmosphere through anthropogenic activities. This specific characteristic of CO₂

gas not only adversely impacts the environment but also imposes noxious effects on human life. In spite of all the various and

potential scientific technics for CO₂removal, gas absorption using alkanolamines solvents has played a significant role in

industries in recent decades. In the present research, the equilibrium set up for measuring CO solubility in aqueous solvents was

assembled. CO loading data in aqueous Amp and Amp (3M) activated with HMDA and NH were assessed under the influence

of various operational conditions of CO partial pressures (8.44, 25.33, and 42.22kPa), temperatures (303, 313, and 323K) and

solvent concentrations of (0.5, 1.5 and 3M) for pure AMP and (0.4, 0.8 and 1.2M) for HMDA-NH . The result showed that CO

loading of AMP activated HMDA-NH3 increases with decreasing system temperature and increasing CO partial pressure.

Furthermore adding the HMDA solvent into the system increased CO loading before it followed a slight decrease while adding

NH decreased the amount. Concerning efficiency enhancement, it was comprehended that, HMDA could be considered among

promising improvers while NH as an additive beside AMP or as a based solvent, perform well in CO absorption process only

under specific operational condition.

Keywords: CO solubility, AMP, Ammonia (NH ), Loading

mean global temperature by 1.9 C and the sea level by 3.8

m [2]. To find a solution to this severe environmental

concern and to reduce the amplified greenhouse effects,

^s^e^v^e^r^a^l^C^O2 removal methods have been designed after

tremendous amounts of laboratory works. Some of them

include chemical absorption, physical absorption,

refrigerating methods, membrane separation and biological

absorption. However gas absorption using aqueous

Introduction

The anthropogenic increase of greenhouse gases

concentration in the atmosphere is stated to be the root

cause of global warming. Among these greenhouse gases,

CO is believed to be highly responsible contributing to this

issue. The accumulation of CO₂in the air stems from

diverse sources such as steel plants, cement industry and

coal-fired power plants [1]. It is estimated that, if these

large emitters continue to release CO₂up into the

atmosphere, by the year 2100 the atmosphere may will

alkanolamine solutions as

a mature well-established

technology has proved both efficacious and viable among

others. Some of the most sought-after solutions in this

category which have been exercised by many industry are

monoethanolamine (MEA), diethanoleamine (DEA), and

have loaded up to 570 ppm CO . This will then increase the

Corresponding author: Alireza Jahangiri, Tel.:

989192672218; fax:

‏

9 8 3814424438; E-mail address:

jahangiri@eng.sku.ac.ir.

methyldiethanolamine (MDEA). Owing to

advancement in gas treating technology,

hindered amine 2-amino-2-methyl-1-propanol (AMP) has

recent

‏

sterically

Journal of Environmental Treatment Techniques

2018, Volume 6, Issue 4, Pages: 74-80

been proposed as a different class of chemical absorbent

also used beside to compensate for the low absorption rate

of AMP [8]. NH₃as an additive has several major

dominances over amine solutions such as high CO₂

removal capacity, no degradation, less corrosion, low heat

requirement for regeneration and the potential of capturing

CO , SO and NOx simultaneously [1]. In this regard,

[

3].

Due to several supremacies in absorption capacity,

absorption rate, selectivity, degradation resistance and

regeneration energy over conventional alkanolamines it has

been called

a commercially attractive solvent [4].

Preliminary work on hindered amine solution was

conducted by A.K. Chakraborty et.al. Also pahlavanzadeh

and jahangiri were the priors to undertook the similar

experiment with the introduced CO₂absorption set up

which showed good results [5]. Another study with AMP

solvent was conducted by Anoar Ali Khan et.al to prove

high loading capacity of this hindered amine [1].

Concerning efficiency enhancement, many researchers

made a start on the utilization of blends of alkanolamines,

or an amine based improved solution in varying

concentration. They believed to produce absorbent with

intensified absorption characteristics [4]. In other word, by

this method it could bring together the advantages of each

experiments were carried out with different molar

compositions of AMP (.5, 1.5 and 3 M), AMP+HMDA

(3+.4, 3+.8 and 3+1.2M) and AMP+NH3 (3+1, 3+2 and

3+3M) at three different temperatures of (303, 313, and

323K) and CO₂partial pressures of (8.44, 25.33, and

42.22Kpa). The loading capacities of CO in each blends of

AMP, AMP/NH3 and AMP/HMDA were calculated under

the mentioned operational conditions and the data were all

registered.

Materials and Methods

In order to carry out the experiments, AMP, HMDA

and NH solvents were purchased with purity of 95%, 99%

amine to facilitate CO absorption process. For instance a

and 25% respectively, supplied by Merck Company and a

certain amount of distilled water for preparing aqueous

solution. CO -N gas was prepared by SEPAHAN,

mixture of primary (MEA) and tertiary amine (MDEA)

could benefit from both a high absorption rate of MEA and

a high equilibrium capacity of MDEA [6]. In this field,

there exist several study to show the increasing interest in

performing ^C^O2 absorption experiment using amine

mixtures. As an example Yuli Artanto et.al investigated

industrial and medical gasses production, Company which

is located in ISFAHAN

Laboratory Setup: In order to conduct the CO absorption

process, equilibrium set up for measuring CO solubility in

CO absorption in aqueous mixture of AMP and piperazine

aqueous solvents was assembled which is illustrated in Fig.

(PZ) which showed good results compared to conventional

. This set up have several advantages over the

MEA [7]. Won-Joon Choi et.al investigated CO absorption

conventional static and flow apparatus which have been

into aqueous AMP/HMDA and AMP/MDEA to show the

high CO2 loading capacity and high absorption rate of

HMDA and MDEA additives [6].

The present research focuses on the use of amine blends

which takes advantages of a hindered amine named AMP

applied for several years to measure CO solubility data.

The most important feature is the continuous contact of

both phases during the experiment which practically occurs

in industrial processes. Since you could have precise data

for industrial designing.

with a higher equilibrium CO loading capacity in compare

to conventional amines. Aqueous HMDA and NH₃were

Figure 1: The apparatus for measuring the solubility of gases in liquid (a:Spiral tube, b:Scalling burette, c:Monometre, d:Water

bath, e:Mercury Jack, f:Cell, g:Unloaded Solvent Container, h: Circulating Pump, i: CO Capsule, J:Loaded Solvent Collector,

K:H O injector)

Journal of Environmental Treatment Techniques

2018, Volume 6, Issue 4, Pages: 74-80

The basic elements of the set up are as follows:



Equilibrium cell: It is designed to make an

n 

(2)

equilibrium environment in which the equilibrium



solubility of CO in aqueous solvent solution could be

investigated. The water which enters the equilibrium

cell adjust the temperature to begin the experiments.

Spiral tube: There exist number of turns which is

constant. In these turns the liquid and vapor phase

come into contacts with each other to begin absorption

process. The solute and the solvent decide the

parameters such as number of turns, the slope and the

diameter of the tube. While the solubility of the gas

increases, the number turns should be increased and

the slope should be decreased to guarantee the

equilibrium condition between the solvent and the

solute at the end of the spiral tube.

Scaling Burette: A scaling burette is a requisite

device in order to estimate the volume of the dissolved

gas into the solvent and also to maintain the gas in

the set up. This burette is connected to the spiral tube

at the top and to an internal valve at the bottom. The

valve is in connection with a CO₂capsule and a

mercury vessel. The mercury vessel is located on a

moving platform so as to adjust the level of the

solution in the monometer.

Determining the number of Solvent moles with the

volume, density and molecular mass of the solvent, the

number of solvent moles consumed is calculated from the

following equation:



n 

(3)

M _w

In this regard, V is the solvent volume in milliliters, d is

the solvent density in grams per ml, and MW is the solvent

molecular mass in grams per mole. The number of moles

consumed from each of the solvents is obtained by the

following equation:



ⁿt



(4)

M _w

That n

is the number of total molecules consumed for



Manometer: A manometer is constructed at the

bottom of the spiral tube. It is needed to show the

pressure disagreement in the set up. The manometer is

joint to the spiral tube from one end and is opened to

the atmosphere from the other end.

Water bath: A water bath is applied in the process in

order to supply the water to the equilibrium cell at an

adjusted temperature. This will provide for the

temperature at which the experiments are considered

to be performed.

solvent mixtures, in which:

d 

x d

(5)



^Mw



x ( M ⁾i

(6)





Circulating pump: This device is used to circulate

the water which is supplied from the bath into and out

of the equilibrium cell.

Solvent container: Solvent container is used to inject

the certain amount of solvent into the system at a

constant rate.

In these equations, xi, di and (MW)

are the solvent (i)

mole fraction in the composition, the solvent (i) density,

and the molecular mass of the solvent (i). The following

equation is used to calculate the mole of each solvent

consumed:

CO loading calculations: To obtain CO loading, tests are

n  c n

(7)

needed to measure the amount of CO gas dissolved in a

certain amount of solvent. In each experiment, the amount

of CO dissolved during the test is obtained by reading on

By calculating the amount of CO

moles and the

the burette. Then, using a proper equation of state, with

having the pressure and temperature of the experiment, the

volume of the gas is converted to the number of dissolved

moles. Because the total pressure at which the set up works

is approximately 1 atmosphere, the ideal gas equation of

state is used. Molar volume of the gas could be obtained

from equation 1.

amount of solvent moles according to equations above, the

amount of α which stands for CO

loading could be

obtained by the following equation:

m ol_C_O

 _e_x_p



(8)

m ol_s_o_l_v_e_n_t

Laboratory data related to CO loading in AMP + H O

P  RT

(1)

CO system: In Table 1, CO loadings are calculated

After calculating the molar volume of the gas dissolved

in the test conditions, given the fact that during the test the

volume of the gas is also determined based on the change

in the height of the surface of the mercury, the amount of

according to equation. The calculations were performed

under different operational conditions in AMP

concentrations of (.5, 1.5 and 3M), temperature (303, 313,

and 323K) and CO₂partial pressure (8.44, 25.33, and

42.22kPa). According to the data which are presented in

table 1, Figure 1 displays CO₂loading capacity of pure

AMP under the mentioned operational conditions.

CO moles can be obtained according to equation 2.

Journal of Environmental Treatment Techniques

2018, Volume 6, Issue 4, Pages: 74-80

Laboratory data related to CO loading in AMP + H O

(8.44, 25.33, and 42.22kPa). According to the data which

are presented in table 2, Figure 2 displays the effects of

HMDA additive into AMP (3M) under the mentioned

operational conditions.

CO + HMDA system: In Table 2, CO loadings are

calculated according to equation. The calculations were

performed under different operational conditions in

AMP+HMDA concentrations of (3+.4, 3+1.8 and 3+1.2),

temperature (303, 313, and 323K) and CO partial pressure

Table 1: CO loading in AMP+H O+CO system

AMP Concentration

Temp

^E x p

P_C_O 8 .4 4 kP a

P_C_O 2 5 .3 3 kP a

P_C_O 4 2 .2 2 kP a

AMP (0.5M)

AMP (1.5M)

AMP (3M)

303

313

323

303

313

323

303

313

323

0.0207

0.0160

0.0078

0.0096

0.0080

0.0052

0.0062

0.0040

0.0026

0.1243

0.0722

0.0466

0.0495

0.0399

0.0232

0.0329

0.0279

0.0212

0.3107

0.2005

0.1166

0.1581

0.1261

0.0903

0.0960

0.0797

0.0643

AMP (3M)

.44

25.33

42.22

Partial Pressures (kPa)

.35

.25

.15

.3107

0.2005

.1581

.1243

.0207

0.1261

.0399

.1166

.096

.0903

.0797

.0279

.0722

.016

.0643

.05

.0466 0.0495

.0078 0.0096

.0329

0.0232

0.0212

0.008

0.0052 0.0062

0.004

313

0.0026

313

0.5

323

303

313

323

303

323

0.5

1.5

AMP Concentrations (M)-Temperatuares (K)

Figure 1: The influence of operational conditions on CO loading in different AMP Concentrations of (0.5, 1 and 3M)

Table 2: CO loading in AMP+HMDA+H O+CO system

AMP Concentration

Temp

^E x p

P_C_O 8 .4 4 kP a

P_C_O 2 5 .3 3 kP a

P_C_O 4 2 .2 2 kP a

AMP(3M)+HMDA(0.4M)

AMP(3M)+HMDA(0.8M)

AMP(3M)+HMDA(1.2M)

303

313

323

303

313

323

303

313

323

0.011

0.009

0.007

0.001

0.009

0.007

0.010

0.009

0.007

0.052

0.042

0.037

0.052

0.044

0.039

0.048

0.041

0.037

0.0105

0.096

0.079

0.099

0.088

0.073

0.099

0.089

0.073

Journal of Environmental Treatment Techniques

2018, Volume 6, Issue 4, Pages: 74-80

Laboratory data related to CO loading in AMP+NH +

reason, CO

loading decreases with increase in

H O + CO system: In Table 3, CO₂loadings are

concentration, which has been observed in previous

researches conducted by pure AMP to confirm the accuracy

of the matter[5]. According to Figure 2 HMDA additive

into AMP (3M) made an upward trend toward an

calculated according to equation. The calculations were

performed under different operational conditions in

AMP+NH₃concentrations of (3+1, 3+2 and 3+3M),

temperature (303, 313, and 323K) and CO partial pressure

enhancement in CO loading capacity especially at higher

(8.44, 25.33, and 42.22kPa). According to the data which

CO₂partial pressures, however it was applied in low

are presented in table 3, Figure 3 displays the effects of

NH₃additive into AMP (3M) under the mentioned

operational conditions.

concentrations. For aqueous NH According to Figure 3, it

was found that, no improvement has obtained during the

absorption process while NH was added to AMP system

under the same operational conditions. In order to justify

the behavior of ammonia solvent, Several Previous works

Results and Discussion

on CO absorption using aqueous ammonia were studied. It

Experiments were carried out under the mentioned

was understood that, aqueous ammonia in CO absorption

operational conditions. According to the Figures 1, 2, and

, it was comprehended that for pure AMP, AMP+NH and

process has its best performance while it is applied in

temperatures below 10C. In a case where the temperature

exceeds, Figure 3, ammonia evaporation may occur as a

result which leads to solvent loss during the experiments.

Furthermore, In order to cope with solvent loss during the

absorption process, some researchers have recommended

the use of metal addit ives like Zn, Cu, Ni, and Me into the

aqueous ammonia [9, 10].

AMP+HMDA, CO loading increased with a reduction in

temperature and an increase in CO partial pressures. By

increasing AMP concentration, CO loading decreased. In

practice, during the absorption process with pure AMP, the

increase in CO mole numbers in the solvent is not as well

as the increase in AMP solvent moles when increasing the

concentration. According to equation 8, the denominator

increase is much more than the numerator increase. For this

.44

25.33

42.22

CO2 Partial Pressures (kPa)

.12

0.099

0.089

.096

0.096

.088

.044

.08

.06

.04

.02

0.0797

0.079

.073

.039

0.073

0.037

.0643

.052

0.052

.048

0.042

0.041

0.009

.037

.0329

.0062

.0279

0.0212

0. 0. 011015

0.01

.009

0.009

0.007

323

0.007

323

0.007

323

.004 0.0026

0.001

303

313

323

303

0.4

313

0.4

313

0.8

303

1.2

313

1.2

0.4

0.8

1.2

AMP+HMDA Concentrations (M)-Temperatures (K)

Figure 2: The influence of adding the improver (HMDA) in concentrations of (0.4, 0.8 and 1.2M) into AMP (3M) under variable operational

conditions

Table 3: CO loading in AMP+NH +H O+CO system

AMP Concentration

Temp

^E x p

P_C_O 8 .4 4 kP a

P_C_O 2 5 .3 3 kP a

P_C_O 4 2 .2 2 kP a

AMP(3M)+NH (0.4M)

303

313

323

303

313

323

303

313

323

0.0010

0.0007

0.0002

0.0010

0.0006

0.0003

0.0010

0.0007

0.0003

0.0209

0.0181

0.0161

0.0150

0.0131

0.0117

0.0120

0.0105

0.0094

0.0499

0.0435

0.0398

0.0351

0.0307

0.0282

0.0291

0.0263

0.0237

AMP(3M)+NH (0.4M)

AMP(3M)+NH (0.8M)

AMP(3M)+NH (1.2M)

Journal of Environmental Treatment Techniques

2018, Volume 6, Issue 4, Pages: 74-80

.44

25.33

42.22

CO2 Partial Pressures (kPa)

.09

.08

.07

.06

.05

.04

.03

.02

.01

0.09

.079

.064

.049

.043

.039

0.035

.016 0.015

.032

.006

0.03

.013

0.029

.027

.004

0.028

0.011

0.026

0.01

0.0007 0.0003

313

.023

.009

0.021 0.02

.002 0.001

.018

0.012

0.001

303

0.001

303

0.0007 0.0002

313

0.0006 0.0003

313

323

303

323

0.4

0.8

1.2

AMP+NH Concentrations (M)-Temperatures (K)

Figure 3: The influence of adding the improver (NH ) in concentrations of (0.4, 0.8 and 1.2M) into AMP (3M) under variable

operational conditions

2.22

42.22

CO partial pressure (kPa)

0 3

3 1 3

3 2 3

3 0 3

0 . 4

3 1 3

0 . 4

3 2 3

0 . 4

3 0 3

0 . 8

3 1 3

0 . 8

3 2 3

0 . 8

3 0 3

1 . 2

3 1 3

1 . 2

3 2 3

1 . 2

AMP+HMDA

AMP+NH₃

AMP (3M) ACTIVATED NH -HMDA

Figure 4: Experimental CO loading of the mixed AMP+HMDA in comparison with AMP+NH3

consideration for CO loading calculation which caused a

drop in the amount.

Conclusion

In the present research CO absorption by pure AMP

and AMP activated NH -HMDA was studied under various

operational conditions. HMDA additive increased CO₂

loading capacity of pure AMP while adding aqueous NH₃

to AMP did nothing to enhance the amount. In fact

inappropriate selection of the operational temperature range

higher than the optimum amount, led to ammonia loss

during the CO absorption process. That meant that no NH

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