g10 physical & analytical chemistry assignment

KKEK1135 PHYSICAL AND ANALYTICAL CHEMISTRY

SOLUBILITY OF ACID GASES IN AQUEOUS ALKANOLAMINES

ARISYA BINTI AHMAD ZAINI KEK150AZWAN BIN SHARI@DISIPELIHANNA SOFIA BINTI CHEK WIRAMAN KEKNURJAA BINTI ARIFFIN KEK150121NOR ANISA BINTI NASRUDIN KEKNUR AMANINA BINTI MOHD ARIEF KEK150120

GROUP 11

DEPARTMENT OF CHEMICAL ENGINEERINGUNIVERSITY OF MALAYA18 DECEMBER 2014

ABSTRACTAcid gas removal, or more commonly known as amine scrubbing, gas sweetening and acid gas removal, refers to a series of processes to remove acid gases such as hydrogen sulfide (HS) and carbon dioxide (CO) form gases in various industries using aqueous solutions of various alkylamines (or simply referred to as amines). This unit process is common in refineries, petrochemical plants and even natural gas processing plants. It is mainly to prevent corrosion and operational problems, as well as increasing heating value of the gas.Hydrogen sulfide needs to be removed as it is highly toxic and very poisonous, extremely corrosive with the presence of water and can cause catalyst poisoning in refinery vessels. As for carbon dioxide, it is removed as it has no heating value, corrosive with the presence of water and if the gas is heading to cryogenic plants, the presence of carbon dioxide may induce solidification. The most widely applied technology in the industry to facilitate the removal of these acid gases is by absorption and/or desorption process by aqueous alkanolamines as chemical solvents.Some of the different amines used in gas treating are: Diethanolamine (DEA) Monoethalamine (MEA) Methyldiethanolamine (MDEA) Triethanolamine (TEA) Aminomethyl propanol (AMP)This process of absorption is reflected by an acid-base mechanism. Hydrogen sulfide and carbon dioxide form weak acids in water or aqueous solutions, while the alkanolamines act as weak organic bases. When the sour gas stream is contacted with the aqueous alkanolamines solutions, the acid gas and the amine base react to form an acid-base complex, which is a salt. The process then follows up with the disposal or treating of the acid gas, and regenerating of amine solution for reuse.INTRODUCTIONThe acid gas under study in this topic is hydrogen sulphide. Hydrogen sulfide is a colorless gas with an offensive stench and is said to smell like rotten eggs.The gas can be detected at a level of 2 parts per billion. To put this into perspective, 1 mL of the gas distributed evenly in a 100-seat lecture hall is about 20ppb. Commercially hydrogen sulfide is obtained from "sour gas" natural gas wells.Hydrogen sulfide is used in chemicals industries to manufacture sodium sulfide and thiophenes, while in laboratory and analysis, is used to calibrate environmental emission monitoring, industrial hygiene monitors and trace impurity analyzers and as balance gas for some calibration mixtures.Acid Gas Partial Pressure : 1kPa, 10kPa, 30 kPa, 50kPa, 100kPa, 200kPa,500kPa, and 1000kPa.Absorption Temperature : 30C, 40C, 60C.

FIGURE 1 The apparatus for measuring the solubility of gases in water

CALCULATIONSThe system under study is the aqueous solution of Aminomethyl propanol associated with the acid gas hydrogen sulfide. The dissociation of Aminomethyl propanol in aqueous solution is given by equation of,(1)Other dissociations in the system are given by the equation below, (2) (3)(4)Charge neutrality for the system is given by the equation,(5)The mole balances involved in the system is reflected by the equation,(6)(7)Dissociation equations in the system : (8)(9)(10)(11)

To obtain the concentration of carbon dioxide soluble in the given amount of Aminomethyl propanol under specific pressure and temperature we use the Henry Laws equation, expressed in the form of,(12)By rearranging equation (8),

By rearranging equation (12),

By combining equation (9) and (12),

By the combination of (10), (11) and newly obtained equation for [],

From equation (11),

From all the above equations, we noticed that every other concentration can be calculated by calculating the concentration of H+ ions.From electroneutrality equation and the combination of newly derived equation , we can calculate the concentration of H+ ions.

The equation above is solve by the infamous method of Newton-Rhapson using the software Matlab and the goal seek method by using the software excelFrom mole balance of carbon dioxide, we obtained the solubility of carbon dioxide given by the equation,

Equilibrium constants for the system are calculated using the relationship below,For aminomethyl propanol : For first dissociation of carbon dioxide: For second dissociation of carbon dioxide: For water : Henry constant for carbon dioxide at various temperature is calculated using the relation given by,

Assumptions made during calculations : 1) Activity coefficient, is equal to 1

- 19 -

List of values and symbols: = 1, 10, 30, 50, 100, 200, 500, 1000 kPa = 1, 2, 3 and 4MP = PressureT = TemperatureKH = Henrys constant for carbon dioxideKW = Dissociation constant for waterKa = Dissociation constant for aminomethyl propanolKa1 = 1st dissociation constant for carbon dioxideKa2 = 2nd dissociation constant for carbon dioxideT = 303K, 313K, 333K

ResultsConcentration = 1MTemperature 303KPressure (kPa)[CO2][H][ HCO3 ][OH][CO32-][C4H11NOH]

10.1057570991.62378E-063.02E-023.15E-051.0056E-075.87E-020.13591324

101.0575709925.36612E-069.12E-029.54E-069.2077E-081.82E-011.14882125

303.1727129769.68037E-061.52E-015.29E-068.488E-083.05E-013.32446067

505.287854961.27613E-051.92E-014.01E-068.1405E-083.84E-015.47970794

10010.575709921.88488E-052.60E-012.72E-067.4628E-085.20E-0110.8354913

20021.151419842.83531E-053.45E-011.81E-066.5963E-086.91E-0121.4968184

50052.87854965.05089E-054.85E-011.01E-065.1964E-089.69E-0153.3632716

1000105.75709928.1393E-056.02E-016.29E-074.0022E-081.20E+00106.358693

Temperature 313KPressure (kPa)[CO2][H][ HCO3 ][OH][CO32-][C4H11NOH]

10.0867077831.56839E-062.78E-023.83E-059.2058E-085.48E-020.11446169

100.6408678895.17654E-068.41E-021.16E-056.246E-081.70E-010.95116458

301.9226036679.21017E-061.42E-016.51E-065.9193E-082.84E-012.7430146

503.2043394451.21498E-051.79E-014.94E-065.6691E-083.58E-014.51451717

1006.4086788891.7888E-052.43E-013.35E-065.2307E-084.86E-018.91411142

20012.817357782.67928E-053.25E-012.24E-064.6631E-086.50E-0117.6664755

50032.043394454.7363E-054.60E-011.27E-063.7305E-089.19E-0143.8133994

100064.086788897.56439E-055.75E-017.93E-072.9251E-081.15E+0087.2832081


10.0640867891.3639E-062.46E-025.31E-058.3601E-084.77E-020.08866277

100.6408678894.50525E-067.44E-021.61E-057.6619E-081.49E-010.71526531

301.9226036678.0022E-061.26E-019.05E-067.2858E-082.51E-012.04826044

503.2043394451.05458E-051.59E-016.87E-066.9918E-083.18E-013.36325445

1006.4086788891.54514E-052.17E-014.69E-066.5139E-084.34E-016.6256011

20012.817357782.29694E-052.92E-013.15E-065.8953E-085.83E-0113.1092029

50032.043394454.00855E-054.18E-011.81E-064.8392E-088.36E-0132.4614689

100064.086788896.31318E-055.31E-011.15E-063.9019E-081.06E+0064.6177009

Graph of Solubility, , against Partial Pressure, P for 1M Amine

Concentration = 2MTemperature 303KPressure (kPa)[CO2][H][ HCO3 ][OH][CO32-][C4H11NOH]

10.1057570991.17136E-064.18E-024.37E-051.8272E-060.042694690.07378065

101.0575709923.74572E-061.31E-011.37E-051.7869E-060.130409170.59414829

303.1727129766.66453E-062.20E-017.68E-061.6933E-060.2208095131.69656509

505.287854968.74337E-062.80E-015.86E-061.6397E-060.2800415642.78393593

10010.575709921.27615E-053.84E-014.01E-061.5394E-060.3840270635.47970427

20021.151419841.88491E-055.20E-012.72E-061.4113E-060.51962376910.8354868

50052.87854963.24798E-057.54E-011.58E-061.1882E-060.75376853826.8161674

1000105.75709925.05106E-059.69E-011.01E-069.8264E-070.96939511753.3632552


10.0867077831.11435E-064.39E-024.59E-052.0189E-060.0406591120.06288528

100.8670778353.59942E-061.36E-011.42E-051.9351E-060.1256354410.49400428

302.6012335056.36646E-062.31E-018.04E-061.8556E-060.2119804451.40317234

504.3353891758.34891E-062.93E-016.13E-061.7983E-060.2691074872.29803376

1008.670778351.21535E-054.03E-014.21E-061.6973E-060.3691062444.51446376

20017.34155671.79058E-055.47E-012.86E-061.5639E-060.5001223878.91386914

50043.353891753.06579E-057.99E-011.67E-061.3337E-060.7268534822.0318899

100086.70778354.73581E-051.03E+001.08E-061.1178E-060.93724506543.8134473


10.0640867899.73293E-075.03E-025.26E-052.6465E-060.0356039760.04926322

100.6408678893.14855E-061.56E-011.63E-052.5289E-060.1107697560.37366188

301.9226036675.55655E-062.64E-019.21E-062.436E-060.1875421691.05178375

503.2043394457.27094E-063.37E-017.04E-062.3711E-060.238505241.71741514

1006.4086788891.05364E-054.65E-014.86E-062.2583E-060.3280500823.36339616

20012.817357781.54516E-056.34E-013.31E-062.1001E-060.4468899166.62559891

50032.043394452.61987E-059.35E-011.95E-061.8263E-060.65579724816.3415369

100064.086788894.00863E-051.22E+001.28E-061.5602E-060.85484346732.4614606



10.1057570999.51947E-075.14E-025.38E-052.9258E-073.48E-020.05239904

101.0575709923.04215E-061.61E-011.68E-052.8649E-071.07E-010.40617695

303.1727129765.37893E-062.73E-019.52E-062.7492E-071.82E-011.14860392

505.287854967.04483E-063.48E-017.27E-062.6712E-072.32E-011.87846186

10010.575709921.02141E-054.79E-015.01E-062.5414E-073.20E-013.68503424

20021.151419841.49712E-056.54E-013.42E-062.3659E-074.36E-017.26851778

50052.87854962.54143E-059.63E-012.01E-062.0525E-076.42E-0117.9472987

1000105.75709923.88702E-051.26E+001.32E-061.7548E-078.40E-0135.6722735


10.0867077839.14705E-074.76E-026.56E-052.7065E-073.23E-020.04476569

100.6408678892.91697E-061.49E-012.06E-051.9671E-079.95E-020.33876722

301.9226036675.14565E-062.54E-011.17E-051.8964E-071.69E-010.95166927

503.2043394456.72973E-063.23E-018.92E-061.8478E-072.16E-011.55292919

1006.4086788899.73647E-064.47E-016.16E-061.7655E-072.98E-013.03927848

20012.817357781.4249E-056.11E-014.21E-061.6487E-074.07E-015.98417067

50032.043394452.40614E-059.05E-012.49E-061.4455E-076.03E-0114.7527994

100064.086788893.66056E-051.19E+001.64E-061.2491E-077.93E-0129.298958


10.0640867897.93942E-074.22E-029.12E-052.4672E-072.81E-020.03543569

100.6408678892.55713E-061.31E-012.83E-052.3783E-078.76E-020.25731523

301.9226036674.49578E-062.24E-011.61E-052.3083E-071.49E-010.71542202

503.2043394455.86935E-062.86E-011.23E-052.2572E-071.90E-011.1632906

1006.4086788898.47202E-063.96E-018.55E-062.1667E-072.64E-012.26810231

20012.817357781.23453E-055.43E-015.86E-062.0408E-073.62E-014.45345271

50032.043394452.06794E-058.10E-013.50E-061.8183E-075.41E-0110.9512674

100064.086788893.11721E-051.08E+002.32E-061.6005E-077.17E-0121.7206761



10.1057570998.19813E-075.97E-026.25E-053.7302E-060.0300739610.04137212

101.0575709922.62854E-061.86E-011.95E-053.6285E-060.0933289990.31096464

303.1727129764.63294E-063.17E-011.11E-053.504E-060.1588446910.87244663

505.287854966.04762E-064.05E-018.47E-063.4274E-060.2024389141.42317285

10010.575709928.74387E-065.60E-015.86E-063.2791E-060.2800553042.78392794

20021.151419841.27616E-057.67E-014.01E-063.0788E-060.3840300385.47940243

50052.87854962.14477E-051.14E+002.39E-062.725E-060.57081540113.505015

1000105.75709923.24802E-051.51E+001.58E-062.3764E-060.75377446926.8161627


10.0867077837.81476E-076.27E-026.55E-054.1052E-060.0286877520.03560273

100.8670778352.5197E-061.94E-012.03E-053.9488E-060.0896374950.25995754

302.6012335054.43498E-063.31E-011.15E-053.8238E-060.1525754030.72391838

504.3353891755.78644E-064.23E-018.85E-063.7438E-060.1945464691.17787698

1008.670778358.34893E-065.86E-016.13E-063.5967E-060.2691079682.29803349

20017.34155671.21535E-058.06E-014.21E-063.3946E-060.3691074014.51446307

50043.353891752.03407E-051.20E+002.52E-063.0297E-060.54944639811.1059628

100086.70778353.06583E-051.60E+001.67E-062.6673E-060.72685943322.0318853


10.0640867896.92331E-077.07E-027.40E-055.2304E-060.0254569260.02812606

100.6408678892.205E-062.22E-012.32E-055.1564E-060.0788838660.19821977

301.9226036673.87408E-063.79E-011.32E-055.0112E-060.134577220.54553991

503.2043394455.05025E-064.85E-011.01E-054.9148E-060.1719228110.88404571

1006.4086788897.27092E-066.73E-017.04E-064.7422E-060.238504661.71741546

20012.817357781.05364E-059.29E-014.86E-064.5166E-060.3280497633.36339635

50032.043394451.75275E-051.40E+002.92E-064.0803E-060.4921562488.24988337

100064.086788892.6215E-051.87E+001.95E-063.648E-060.65607238416.3413373


Graph of Concentration of SpeciesVs Partial Pressure

T = 300CConcentration of Aminomethyl propanol = 4M

CONCLUSION

Based on the graph, the pattern of the graph shows the higher the temperature, the lower the solubility of carbon dioxide in aminomethyl propanol. The pattern of the graph also shows that when partial pressure of carbon dioxide increases, the solubility of carbon dioxide increases as well. From the graph of species concentration, when the concentration of amine increases, solubility decreases.

REFERENCE1. http://en.wikipedia.org/wiki/Carbon_dioxide2. http://en.wikipedia.org/wiki/Aminomethyl_propanol3. http://en.wikipedia.org/wiki/Henry's_law4. http://http://www.chemicalland21.com/specialtychem/nh/2-AMINO-2-METHYLPROPANOL.htm5. http://en.wikipedia.org/wiki/Amine_gas_treating6. A. Jahangiri , H. Pahlavanzadeh & A. Mohammadi (2014) The Modeling of CO2 Removal From a Gas Mixture by 2-amino-2-methyl-1-propanol (AMP) Using the Modified Kent Eisenberg Model, Petroleum Science and Technology, 32:9, 1104-1113

g10 physical & analytical chemistry assignment

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