Absorption of Nitric Oxide from Flue Gas using Ammoniacal ...mecheng1.uwaterloo.ca/~tanz/research/NOx.pdf · Absorption of Nitric Oxide from Flue Gas using Ammoniacal Cobalt(II) Solutions

Absorption of Nitric Oxide from Flue Gas

using Ammoniacal Cobalt(II) Solutions

by Hesheng Yu

Supervisor: Dr. Zhongchao Tan

2013-03-16

APRIL Group

1

Outline

2013-03-16

APRIL Group

2

1. Background

2. Selection of Absorbent

3. Determination of Equilibrium Constants

4. Kinetic Study

5. Effect of Oxygen and Absorbent Regeneration

6. Mass Transfer in Industrial Gas-Liquid Contactors

7. Conclusions

2013-03-16

APRIL Group

3

1. Background

2013-03-16

APRIL Group

4 4

2.49 2.40

3.33 3.65 3.80 3.96 4.14

4.53

5.19 5.29 5.64

5.96

0

1

2

3

4

5

6

7

201020092008200720062005200420032002200120001999

Nit

rog

en

Oxid

es (

Mt)

Year

NOx Emissions from Conventional Power Plants in U.S., 1999-2010

Mobile Stationary

2013-03-16

APRIL Group

5 5

Nitrogen Oxides Facts

Formula Name Nitrogen

Valence

Properties

N2O nitrous oxide 1 colorless gas

water soluble

NO

N2O2

nitric oxide

dinitrogen dioxide

2 colorless gas

slightly water soluble

N2O3 dinitrogen trioxide 3 black solid

water soluble, decomposes in water

NO2

N2O4

nitrogen dioxide

dinitrogen tetroixe

4 red-brown gas

very water soluble, decomposes in

water

N2O5 dinitrogen pentoxide 5 white solid

very water soluble, decomposes in

water

2013-03-16

APRIL Group

6

NOx Hazards & Threats:

Tropospheric Ozone Acid Rain

2013-03-16

APRIL Group

7

NOx Control Technologies

NOx Control

Technologies

Fuel Switching

Combustion

Modification

Flue Gas

Treatment (FGT)

Reduce nitrogen content

Less Excess Air

Staged combustion

Flue gas recirculation

Low-NOx burners

Water/steam injection

Selective catalytic reduction

Selective non-catalytic reduction

Combined plasma photolysis

Adsorption

Wet scrubbing

(not very realistic)

(20-70%)

Required to meet increasingly stringent

(<15ppm) emission regulation (cost-effective)

2013-03-16

APRIL Group

8

Absorbent for Wet Scrubbing

Absorbent

Strong Oxidant

for conversion

NO into NO2

Reagent for

formation of a

nitrosyl complex

ClO2/NaClO2

KMnO4

O3

H2O2/ with NH3

FeSO4

Fe(II)-EDTA

Ammoniacal Cobalt(II) Ions

H2O2

Advantages of Ammonical Cobalt(II) Complexes:

Fast reaction

Positive effect of oxygen on NO absorption

Easy regeneration

Potential to simultaneously remove NO and SO2

Environmentally friendly by-products – Nitrate and nitrite

2013-03-16

APRIL Group

9

Ammonia – Cobalt(II) System

(with concentrated ammonium)

Reaction Number

𝐶𝑜(𝐻2𝑂)62++𝑁𝐻3 ⇌ 𝐶𝑜(𝑁𝐻3)(𝐻2𝑂)5

2++𝐻2𝑂 (1-1)

𝐶𝑜(𝑁𝐻3)(𝐻2𝑂)52++𝑁𝐻3 ⇌ 𝐶𝑜(𝑁𝐻3)2(𝐻2𝑂)4

2++ 𝐻2𝑂 (1-2)

𝐶𝑜(𝑁𝐻3)2(𝐻2𝑂)42++𝑁𝐻3 ⇌ 𝐶𝑜(𝑁𝐻3)3(𝐻2𝑂)3

2++𝐻2𝑂 (1-3)

𝐶𝑜(𝑁𝐻3)3(𝐻2𝑂)32++𝑁𝐻3 ⇌ 𝐶𝑜(𝑁𝐻3)4(𝐻2𝑂)2

2++𝐻2𝑂 (1-4)

𝐶𝑜(𝑁𝐻3)4(𝐻2𝑂)22++𝑁𝐻3 ⇌ 𝐶𝑜 𝑁𝐻3 5(𝐻2𝑂)

2+ +𝐻2𝑂 (1-5)

𝐶𝑜(𝑁𝐻3)5(𝐻2𝑂)2+ +𝑁𝐻3 ⇌ 𝐶𝑜(𝑁𝐻3)6

2++𝐻2𝑂 (1-6)

𝑁𝐻𝟒+ ⇌ 𝑁𝐻3 + 𝐻+ (1-7)

Reactive Complexes

2013-03-16

APRIL Group

10

Ammonia - Cobalt (II) System for different pH values at

T=30 oC

0

10

20

30

40

50

60

70

80

90

100

3.5 4.5 5.5 6.5 7.5 8.5 9.5 10.5 11.5 12.5

Perc

en

tag

e (

%)

pH value

Co2+

[CoA]2+

[CoA2]2+

[CoA3]2+

[CoA4]2+

[CoA5]2+

[CoA6]2+

CoA6

CoA5

CoA4

Co2+

CoA

A=NH3

[NH4+] = 2mol∙L-1

pH =7.5

2013-03-16

APRIL Group

11

2𝑁𝑂 + 2[𝐶𝑜 𝑁𝐻3 6]2+⇌ 𝐶𝑜 𝑁𝐻3 5𝑁2𝑂2 𝑁𝐻3 5𝐶𝑜

4+ + 2𝑁𝐻3 (1-8)


4+ (1-9)

Light Yellow Pink or Red

Reactions of NO Absorption into Penta- and Hexa-

amminecobalt(II) solutions

2013-03-16

APRIL Group

12

2. Selection of Absorbent

2013-03-16

APRIL Group

13

Experimental Setup for Absorbent Selection

Scrubbing bottle

Water Jacket

Column Reactor

Valve 5

Valve 3

Valve 4

Valve 2

Valve 1

Beaker

Testo 350 XL

Mixer Connector

NO O2 N2

Mass flow meters

Thermostatic Bath

2013-03-16

APRIL Group

14

Comparison of NO Reduction between Different Absorbents

Hydrogen Peroxide

Fe(II)-EDTA

2013-03-16

APRIL Group

15

40

50

60

70

80

90

100

0 15 30 45 60 75 90 105 120

NO

Rem

ova

l (%

)

Time (min)

19

35

50

Inlet flow rate = 500ml/min,

NO = 500 ppm, O2 = 5.0%, pH = 10.5, Cobalt (II) = 0.06 mol∙L-1

Effect of Temperature on NO Removal Efficiency

2013-03-16

APRIL Group

16

3. Determination of Equilibrium

Constants

2013-03-16

APRIL Group

17

Laboratory Setup for Equilibrium Study

2013-03-16

APRIL Group

18

Picture of Main Section of Testing Rig

2013-03-16

APRIL Group

19

Validation of Complex Reactivity – NO Absorption Curve

99.65%

2013-03-16

APRIL Group

20

Validation of Complex Reactivity – Colour Change


4+ + 2𝑁𝐻3 (3-1)


4+ (3-2)

Light Yellow Pink or Red

2013-03-16

APRIL Group

21

Brief Calculation of Equilibrium Constants


4+ + 2𝑁𝐻3 (3-1)


4+ (3-2)

[Co(NH3)5-6]2+

e is given by mass balance of cobalt(II)

where aw = water activity; fNH3 = the activity coefficient of the ammonia;

Gm = molar flow rate, mol∙s-1

KNO5 = the equilibrium constant of Reaction 3-1, L3∙mol-3；

KNO6 = the equilibrium constant of Reaction 3-2, L3∙mol-3；

PT = total pressure, atm;

yin, yout = NO concentration at inlet and out, ppm;

η = NO removal efficiency

2013-03-16

APRIL Group

22

𝑙𝑛𝐾𝑁𝑂5 = 3598.5 ∙

1

𝑇+ 16.759 (R2=0.994) (3-3)

𝑙𝑛𝐾𝑁𝑂6 = 1476.4 ∙

1

𝑇+ 26.597 (R2=0.970) (3-4)

𝐾𝑁𝑂5 = 1.90 × 107exp(

3598.5

𝑇) (3-5)

𝐾𝑁𝑂6 = 3.56 × 1011exp(

1476.4

𝑇) (3-6)

Rewritten as,

where KNO5 --- the equilibrium constant of Reaction 3-1, L3∙mol-3；

KNO6 --- the equilibrium constant of Reaction 3-2, L3∙mol-3；

T --- temperature, K

Equilibrium Constants of Reactions (3-1) and (3-2)

2013-03-16

APRIL Group

23

4. Kinetic Study

2013-03-16

APRIL Group

24

Double-Stirred Tank Reactor

2013-03-16

APRIL Group

25

Laboratorial Setup for Kinetic Study

2013-03-16

APRIL Group

26

Picture of actual laboratorial setup for kinetic study

(a) flue gas simulation system (b) double stirred tank section

2013-03-16

APRIL Group

27

𝑁𝑁𝑂 = (1

𝐻𝑘𝐺+

1

𝐷𝑁𝑂2

𝑚 + 1𝑘𝑚𝑛5 𝐵5

𝑛𝑐𝑁𝑂𝑖𝑚−1 +

2𝑝 + 1

𝑘𝑝𝑞6 𝐵6

𝑞𝑐𝑁𝑂𝑖𝑝−1

)−1𝑐𝑁𝑂𝑖 (4-3)

According to film theory and enhancement factor for parallel reactions, the rate of NO

absorption into ammoniacal cobalt(II) solutions, presented in Reactions 4-1 and 4-2, can

be described as follows:

where NNO --- NO absorption rate, mol∙m-2∙s-1； H --- Henry Law constant, L∙atm∙mol-1； kG --- gas-phase mass transfer coefficient, mol∙s-1∙m-2∙atm-1；

DNO --- molecular diffusivity of NO in liquid phase, m2∙s-1;

m, n, p, q, reaction orders with respect to reactant;

k --- reaction rate, unit is dependent upon reaction orders


4+ + 2𝑁𝐻3 (4-1)


4+ (4-2)

Calculation Scheme

2013-03-16

APRIL Group

28

Determination of Reaction Order with regard to NO

m=p=1 can be given by the obvious

linear relationship between NNO and cNOi

as shown in the figure. Therefore,

substituting of m=p=1 into Eq. 4-3 gives

𝑘1𝑛5 𝐵5

𝑛 + 𝑘1𝑞6 𝐵6

𝑞=

𝑐𝑁𝑂𝑖𝑁𝑁𝑂

−1

𝐻𝑘𝐺

−2

𝐷𝑁𝑂(4−4)

𝑁𝑁𝑂 = (1

𝐻𝑘𝐺+

1

𝐷𝑁𝑂2

𝑚 + 1𝑘𝑚𝑛5 𝐵5

𝑛𝑐𝑁𝑂𝑖𝑚−1 +

2𝑝 + 1

𝑘𝑝𝑞6 𝐵6

𝑞𝑐𝑁𝑂𝑖𝑝−1

)−1𝑐𝑁𝑂𝑖 (4-3)

Y

2013-03-16

APRIL Group

29

Determination of Reaction Orders with regard to Penta- and

Hexa-amminecobalt(II) Solutions

The value of reaction rate decreases

with temperature

2013-03-16

APRIL Group

30

(a) (b)

Analysis of Reaction Orders with respect to Penta- and Hexa-

amminecobalt(II) Solutions


−1

𝐻𝑘𝐺

−2

𝐷𝑁𝑂−𝑘2

6𝐵6 = 𝑘25𝐵5(4−5)


−1

𝐻𝑘𝐺

−2

𝐷𝑁𝑂−𝑘2

5𝐵5 = 𝑘26𝐵6(4−6)

Y

2013-03-16

APRIL Group

31

5. Effect of Oxygen and

Regeneration

2013-03-16

APRIL Group

32

Laboratory Setup

2013-03-16

APRIL Group

33

Effect of Oxygen on NO Absorption into Ammonical

Cobaltous Solutions

0%

5.6%

2.1%

8.7%

2013-03-16

APRIL Group

34

Proposed Scheme for NO Absorption with Presence of Oxygen

Hentaaminecobalt(II)

Pexaaminecobalt(II)

Nitrosylpentaamminecobalt(III)

(1b)

μ-peroxo-bis[pentaamminecobalt(III)]

(2b)

O2

O2

NO

NO

Cobalt peroxynitrite

intermediate

2b

Cobalt peroxynitrito

Nitrate

and/or

Nitrite

O2

2013-03-16

APRIL Group

35



4+ + 2𝑁𝐻3 (5-1)


4+ (5-2)

Conclusion:

For continuous feed of flue gas into ammoniacal cobalt(II) system, Reactions 5-1 and 5-

2 are in fact irreversible with the existence of oxygen. The presence of oxygen

significantly improves the NO absorption into ammoniacal cobaltous complexes. The

final NO absorption amount into the ammoniacal absorbent is entirely dependent upon

the original absorbent concentration regardless of nitric oxide and oxygen

concentration. This finding corresponds with our experimental results.

2013-03-16

APRIL Group

36

Regeneration Tests of Different Additives at Various

Temperatures

Without KI at RT

With KI at RT

2013-03-16

APRIL Group

37

Regeneration Tests of Different Additives at Various

Temperatures

Without KI at 52 oC

With KI at 52 oC

2013-03-16

APRIL Group

38

Performance of Combination of AC and Na2S5O8

2013-03-16

APRIL Group

39

Performance of Combination of AC and KI

2013-03-16

APRIL Group

40

6. Mass Transfer in Industrial

Gas-Liquid Contactors

2013-03-16

APRIL Group

41

Experimental Setup of the Gas-Liquid Contactor System

2013-03-16

APRIL Group

42

Effect of Impeller Speed on Degassing Efficiency in GIAT and

CSTR

CSTR: conventional

stirred tank reactor

GIAT: gas-inducing

agitated tank

2013-03-16

APRIL Group

43

Effect of Purge Nitrogen Flow Rate on Degassing Efficiency in

CSTR and BC

CSTR: conventional

stirred tank reactor

BC: bubble column

(Porous media)

(Multiorifice)

2013-03-16

APRIL Group

44

Degassing Efficiency of the Semi-batch Degasser at Different

Conditions

2013-03-16

APRIL Group

45

7. Conclusions

2013-03-16

APRIL Group

46

Conclusions:


4+ + 2𝑁𝐻3 (3-1)


4+ (3-2)

𝑙𝑛𝐾𝑁𝑂5 = 3598.5 ∙

1

𝑇+ 16.759 (R2=0.994) (3-3)

𝑙𝑛𝐾𝑁𝑂6 = 1476.4 ∙

1

𝑇+ 26.597 (R2=0.970) (3-4)

The reaction rate constants of Reactions 3-1 and 3-2 are calculated based on the

enhancement factor derived for gas absorption accompanied by parallel chemical reactions.

Both reactions are first order with respect to NO and first order with respect to liquid

absorbent. The forward reaction rate constants of Reactions 3-1 and 3-2 are 6.43×106

and 1.00×107 L∙mol-1∙s-1, respectively at 298.15 K, and increase to 7.57×106 and

1.12×107 L∙mol-1∙s-1, respectively at 303.15 K.

2013-03-16

APRIL Group

47


Hentaaminecobalt(II)

Pexaaminecobalt(II)

Nitrosylpentaamminecobalt(III)

(1b)

μ-peroxo-bis[pentaamminecobalt(III)]

(2b)

O2

O2

NO

NO

Cobalt peroxynitrite

intermediate

2b

Cobalt peroxynitrito

Nitrate

and/or

Nitrite

O2

Conclusions:

2013-03-16

APRIL Group

48

Conclusions:

Liquid-phase mass transfer coefficient for different reactors

Conventional stirred tank reactor 𝑘𝐿𝑎𝐶 = 1.59𝑁𝐼𝑁𝑐𝑑

1.342

𝑈𝐺0.93(

𝑑𝑇𝑑𝐼)0.415

Gas-inducing agitated tank 𝑘𝐿𝑎𝐺𝐼 = 1.212𝑃𝑐𝑉𝐿

0.0816

(𝑄𝐼

𝑑𝑇2)

0.692(𝑠

𝑑𝑇)−0.390

Bubble column with efficient gas sparger 𝑘𝐿𝑎𝐵 = 1.091𝑈𝐺0.8

Bubble column with simple gas sparger 𝑘𝐿𝑎𝐵𝑑𝑇

2

𝐷𝐿= 0.6(

𝜈𝐿𝐷𝐿)0.5(

𝑔𝑑𝑇2𝜌𝐿𝜎𝐿

)0.62(𝑔𝑑𝑇

3

𝜈𝐿2 )0.31𝜀𝐺

1.1

2013-03-16

APRIL GROUP MECHANICAL

ENGINEERING 49

Acknowledgement

Dr. Zhongchao Tan

Dr. Mark J.Rood

Dr. Xianguo Li

Dr. John Z. Wen

Dr. Eric Croiset

Dr. Qunyi Zhu

Dr. Guangyuan Xie

Dr. Sudong Yin

Grace Pan

Chao Yan

Harry Lei

Ke Zhang

Zhe Li

Stephen Kuan

Raheleh

Fang Liu

2013-03-16

APRIL GROUP MECHANICAL

ENGINEERING 50

Documents

Absorption of Nitric Oxide from Flue Gas using Ammoniacal ...mecheng1.uwaterloo.ca/~tanz/research/NOx.pdf · Absorption of Nitric Oxide from Flue Gas using Ammoniacal Cobalt(II) Solutions