A Novel Gas Pressurized Stripping (GPS) Technology for CO2 Separation

Fei Yi, Ph.D. Senior Chemical Engineer

Carbon Capture Scientific, LLC.

June 9, 2015

Company Background

A start-up company located in Pittsburgh, PA Two granted patents (US 8425655 B2, US 8512445 B2) Bench-scale development funded by the Department of

Energy / National Energy Technology Laboratory Chemical engineers/scientists with strong expertise in

process design, simulation and optimization Technology development pathway -- from thermodynamic

analysis, to process simulation, to bench scale prototyping

2

An Generic Process for CO2 Separation

M+CO2! N

Ignore all the driving force for heat and mass transfer 3

N!M+CO2

40C

-H

120C

H

P1a=0.14 atm

P2=80 atmP1b=0.014 atm

2CO2

RTH-

dTdlnP-

dTdlnK

=

HNCOM 2 +CO2 Capture/ Regeneration:

Vant Hoff Equation:

Equilibrium constant expression:

Thermodynamics of the Generic Process

2COMM

NN

P1

xxK

=

4

5

222

2

lnlnlnln

lnlnlnlnlnln

RTH

TP

TP

TPxx

dTKd

COCOMN

COMMNN

=

=

+=

For liquid solvent, equilibrium constant:

)11()ln()ln(12

12 TTRHPP =

Assuming constant H and integrate:

Integrated vant Hoff Equation

6

According to the integrated vant Hoff Equation and ignore activity coefficient change with temperature:

)11()ln()ln(12

12 TTRHPP =

Minimum Heat of the Generic Process

And minimum heat requirement can be calculated for different temperature ranges.

12

2112 )]ln()[ln( TT

TTPPRH

=

We have:

1

10

100

1000

10000

100000

40 60 80 100 120 140 160 180 200

P 2/P

1

T2 oC (T1=40 oC)

130

120

110

100

90

80

70

60

50

40

30

20

H=kJ/mol

7

)11()ln()ln(12

12 TTRHPP =

Required pressure ratio

)11()ln()ln(12

12 TTRHPP =

P2

Graphic Display of Integrated vant Hoff Equation

( )

)kgCO/kJ(2060)molCO/kJ(655.90637.34018.56

)PP(P)Pln(P)Pln(PP1)Pln(

TTTTRH

22

a1b1a1a1b1b1a1b1

212

21average

==+=

=

Minimum Heat Requirement PC CO2 Capture

8

For coal fired power plant: Initial P: P1a= 0. 014, P1b = 0.14atm Product P: P2=80 atm

(90% of CO2 removal) Absorption T: T1=313K Stripping T: T2=393K

And the heat of reaction required:

9

Strip

ping

C

olum

n

Raw Flue Gas

Clean Flue Gas Pure CO2

Steam

Cross Heat Exchanger

ReboilerRich Solution

Lean Solution

Hot Lean Solution

Hot Rich Solution

Abs

orpt

ion

Col

umn

Makeup MEA

Cooling

Qtotal

Hrich

Hlean

PH2O/PCO2 = ~0.8/1.1=0.8

P=~2 atm

T~120 C

T~95 C

Conventional Amine-Based Absorption/Stripping Processes

strippingreactionsensibletotal QQQQ ++=

Heat Components of the Conventional Process

reactionreaction HQ =

OH

stripperthe

ofTopCO

OHstripping HP

PQ

2

2

2

=

LoadingTTC

Q hotrichhotleanpsensible

=)(

Little contribution to the process

All contributes to the process

Should be minimized

Should be minimized

Maximize its potential

No contribution to the process

10

11

Issues with Conventional Stripper

Stripping Column

CO2 Product

Steam

Reboiler

Qtotal

P=~2 atmT=120 C

T=~95 C

Lean Solution

Rich Solution

q Water vapor is used as stripping gas, thus operating pressure is limited by the vapor pressure of the lean solution at the reboiler temperature

T=~95 C

T=120 C

P=~2 atm

PH2O/PCO2 = ~0.8/1.0=0.8

q Water vapor is also used as a heat carrier which leads to a temperature gradient along the column

q Low operating pressure results in a high ratio of PH2O /PCO2 at the top of the stripper

Consequences: Low thermal eciency High compression work

The Novel Gas Pressurized Stripping (GPS) Column

12

q Adding a high pressure stripping gas stream into the column Eliminating water as stripping gas Enables high operating pressure

q Adding side heaters to provide heat Eliminates the necessity of using water

vapor as heat carrier Reduces temperature gradient in the

stripper

q Product gas is a mixture of stripping gas and CO2 along with water vapor Increased CO2 partial pressure

GPS Based Absorption/Stripping Process

13

Advantages of the GPS Based Processes

14 14 14

qUses commercial off-the-shelf technology Proven unit operations

Suitable for large scale applications such as power plants

qHigh stripping pressure Low stripping heat

qHigh thermal efficiency Reduced mechanical CO2 compression work

qFlexible Applicable to solvents with different heat of reaction

GPS and Conventional Column Efficiencies

Items Conventional Stripper GPS Column

Reaction Heat kJ/kgCO2 1870 1400

Stripping Heat kJ/kgCO2 690 170

Stripping Column Total Heat kJ/kgCO2 2560 1570

Minimum Heat Required kJ/kgCO2 1047 1377

Average Pressure in Absorption Column (atm) 0.049 0.049

Average Pressure in Stripping Column (atm) 1.8 5.60

Stripping Column Efficiency (%) 41* 87*

15

* does not include sensible heat

Current and Future Performance of GPS Processes

Process Baseline MEA Current

GPS Process Future

GPS Process

Operating Pressure (atm) 1.8 ~10 ~10 Reaction Heat (kJ/kgCO2) 1870 1680 1350

Sensible Heat (kJ/kgCO2) 990 220 200

Stripping Heat (kJ/kgCO2) 690 182 150 Total Heat (kJ/kgCO2) 3550 2082 1700 Electricity Equivalent (kWh/kgCO2) 0.29* 0.13 0.08 Other load (kWh/kgCO2) 0.04 0.04 0.03

Compression Work (kWh/kgCO2) 0.09 0.05 0.07

Electricity Equivalent (kWh/kgCO2) 0.42 0.22 0.18

Energy Penalty to SPC Plant (%) 30 16 15

16

*No back pressure turbine was used

Test at NCCC

17

6 atm in stripper 90% removal in absorber 95% purity CO2 from stripper