a two-stage membrane system with air sweep for post ......integrated environmental control model -...

IECM Technical Documentation:

A Two-Stage Membrane System with Air Sweep for

Post-Combustion Carbon Capture and Storage

January 2019

IECM Technical Documentation:

A Two-Stage Membrane System with Air

Sweep for Post-Combustion Carbon Capture

and Storage

Prepared by:

Haibo Zhai

Edward S. Rubin

The Integrated Environmental Control Model Team

Department of Engineering and Public Policy

Carnegie Mellon University

Pittsburgh, PA 15213

www.iecm-online.com

For

U.S. Department of Energy

National Energy Technology Laboratory

P.O. Box 880

Compiled in January 2019

Integrated Environmental Control Model - Technical Documentation Table of Contents • iii

Table of Contents Membrane-Based Carbon Capture 1

Objective ............................................................................................................1 Overview of Design Approach and Basis ..........................................................2 Counter-Current Flow Separation Model ..........................................................2 Cross-Flow Separation Model ...........................................................................4 Reduced-Order Models of Membrane Capture System .....................................6

Two-Stage Membrane Separation Process ............................................6 Vacuum Pump ........................................................................................9 CO2 Cryogenic Purification Unit ...........................................................9

Engineering-Economics of a Membrane Capture System .................................9 Case Study .......................................................................................................11

References ........................................................................................................13

Integrated Environmental Control Model - Technical Documentation List of Figures • iv

List of Figures

Figure 1. Schematic of a Two-Stage Membrane-Based Capture System ............................................. 1

Figure 2. Schematic of Counter-Current Flow Membrane Module ...................................................... 2

Figure 3. Schematic of Cross-Flow Membrane Module ....................................................................... 4

Figure 4. Set Membrane Properties in IECM ..................................................................................... 11

Integrated Environmental Control Model - Technical Documentation List of Tables • v

List of Tables

Table 1. Reduced-Order Performance Models of a Two-Stage Membrane-Based Capture System

with Air Sweep for CO2 Removal of 50% @Cross-Flow+90% @Counter-Current ..................... 7

Table 2. Reduced-Order Performance Models of a Two-Stage Membrane-Based Capture System

with Air Sweep for CO2 Removal of 50% @Cross-Flow+50% @Counter-Current ..................... 8

Table 3. Capital Cost Estimation ........................................................................................................ 10

Table 4. Operating and Maintenance Cost Estimation ....................................................................... 10

Table 5. Performance and Cost Results of Plants with and without CO2 Capture ............................. 12

Integrated Environmental Control Model - Technical Documentation Acknowledgements • vi

Acknowledgements

This work was supported by the National Energy Technology Laboratory. The authors also

acknowledge Bingyin Hu for the assistance in coding the counter-current flow model and Dr. Hari

Mantripragada for sharing his reduced-order vacuum pump model. Any opinions, findings, and

conclusions or recommendations expressed in this material are those of the authors alone and do not

reflect the views of any agency.

Integrated Environmental Control Model - Technical Documentation Membrane-Based Carbon Capture • 1

Membrane-Based Carbon Capture

Objective

This documentation reports the performance and cost models of a two-stage membrane system with

air sweep for post-combustion carbon capture and storage (CCS) at coal-fired power plants.

Figure 1. Schematic of a Two-Stage Membrane-Based Capture System

As shown in Figure 1, the two-stage membrane separation process originally designed by Membrane

Technology & Research, Inc. (MTR) consists of two membrane modules (NETL 2012). The first

module is a cross-flow module that removes part of the carbon dioxide (CO2) from its inlet flue gas

to produce a concentrated CO2 stream. The concentrated CO2 stream is further purified and

compressed in a cryogenic purification unit. The second membrane module is a counter-flow module

that uses boiler combustion air as membrane sweep gas to recover the permeated CO2. The

permeated gas from the counter-flow membrane module is recycled to the boiler, which in turn

increases the CO2 concentration in the flue gas stream entering the capture system.


Overview of Design Approach and Basis

This study utilizes previous techno-economic modeling studies of polymeric membrane systems

(NETL 2012; Zhai and Rubin 2013). Generalized mathematical models are first developed for multi-

component flue gas separation employing membrane systems under cross- and counter-current flow

patterns based on peer-reviewed journal papers. Then, the gas separation models are employed in the

design of an advanced two-stage membrane-based capture system with air sweep gas, similar to the

system design employed in recent National Energy Technology Laboratory (NETL) studies (NETL

2012). Reduced-order regression models are further derived for the two-stage membrane-based

capture system based on the system simulation results, which are incorporated into the Integrated

Environmental Control Model (IECM). The previously developed engineering-economic model for

membrane-based capture systems is employed to evaluate this advanced membrane-based capture

system (Zhai and Rubin 2013). The engineering-economic model is updated with latest membrane

cost studies available from NETL to estimate capital and operating and maintenance (O&M) costs

based on performance model results (NETL 2012).

Counter-Current Flow Separation Model

This study employs the multi-component gas separation model developed by Coker et al. (1998) for

membrane modules under the counter-current flow pattern. The mathematical model was formulated

based on numerous assumptions: the membrane module is operated at steady state; the representative

hollow fiber is divided into a series of N perfectly mixed segments in the axial direction and mass

balances are enforced in each section; there is no axial mixing of shell or lumen side gases in the

direction of bulk gas flow; the gas on the shell side of the hollow fibers and in the lumen is in plug

flow; shell side pressure change is negligible, and bore side pressure change can be described by the

Hagen-Poiseuille equation; the hollow fibers consist of a very thin membrane separation layer on a

porous support; the performance of a single hollow fiber is calculated in the simulation and these

results are scaled in proportion to the number of fibers in the module to account for total gas flow

and membrane area; all fibers have uniform inner and outer radius as well as a uniform thickness

separation membrane; and the deformation of the hollow fiber under pressure is negligible (Coker et

al., 1998).

Figure 2. Schematic of Counter-Current Flow Membrane Module

The governing equations are described as follows (Coker et al., 1998):

• Membrane area at segment k

Sweep Gas (air)

Feed Gas

Permeate(to boiler)

Flue Gas (to stack)

N k 1


∆𝐴𝑘 =2𝜋𝑅𝑜𝐿𝑁𝑓

𝑁

(1)

• Flue gas component j and total stream flow rates at segment k

𝑙𝑗,𝑘 = 𝑥𝑗,𝑘𝐿𝑘 (2)

𝑣𝑗,𝑘 = 𝑦𝑗,𝑘𝑉𝑘 (3)

𝐿𝑘 = ∑𝑙𝑗,𝑘

𝑅

𝑗=1

(4)

𝑉𝑘 = ∑𝑣𝑗,𝑘

𝑅

𝑗=1

(5)

• Mass balance of component j at segment k

𝑙𝑗,𝑘+1 − 𝑙𝑗,𝑘 + 𝑣𝑗,𝑘−1 − 𝑣𝑗,𝑘 = 0 (6)

• Mass balance of total stream flow rates at segment k

𝐿𝑘+1 − 𝐿𝑘 + 𝑉𝑘−1 − 𝑉𝑘 = 0 (7)

• Permeation of component j at segment

�̇�𝑗,𝑘 = 𝑙𝑗,𝑘+1 − 𝑙𝑗,𝑘 = 𝑄𝑗∆𝐴𝑘(𝑥𝑗,𝑘𝑃𝐿𝑘− 𝑦𝑗,𝑘𝑃𝑉𝑘

) (8)

The governing equations above are combined and reformulated to yield the following equation:

𝐵𝑗,𝑘𝑙𝑗,𝑘−1 + 𝐶𝑗,𝑘𝑙𝑗,𝑘 + 𝐷𝑗,𝑘𝑙𝑙,𝑘+1 = 0 (9)

Where the coefficients in Equation (9) are:

𝐵𝑗,𝑘 =−𝑉𝑘−1

𝑃𝑉𝑘−1∆𝐴𝑘−1𝑄𝑗

(1 +𝑄𝑗∆𝐴𝑘−1𝑃𝐿𝑘−1

𝐿𝑘−1)

(10)

𝐶𝑗,𝑘 = 1 +𝑉𝑘−1

𝑃𝑉𝑘−1∆𝐴𝑘−1𝑄𝑗

+𝑉𝑘

𝑃𝑉𝑘∆𝐴𝑘𝑄𝑗

(1 +𝑄𝑗∆𝐴𝑘𝑃𝐿𝑘

𝐿𝑘)

(11)

𝐷𝑗,𝑘 =−𝑉𝑘

𝑃𝑉𝑘∆𝐴𝑘𝑄𝑗

− 1 (12)

A set of simultaneous equations are yielded for N segments to form a tridiagonal matrix as follows:

[ 𝐶𝑗,1 𝐷𝑗,1

𝐵𝑗,2 𝐶𝑗,2 𝐷𝑗,2

… … … … …

𝐵𝑗,𝑘 𝐶𝑗,𝑘… … …

𝐵𝑗,𝑁−1

𝐷𝑗,𝑘

⋯𝐶𝑗,𝑁−1

𝐵𝑗,𝑁

⋯𝐷𝑗,𝑁−1

𝐶𝑗,𝑁 ]

[

𝑙𝑗,1𝑙𝑗,2…𝑙𝑗,𝑘…

𝑙𝑗,𝑁−1

𝑙𝑗,𝑁 ]

=

[

−𝑣𝑗,0

0⋯0…0

−𝐷𝑗,𝑘𝑙𝑘+1]

(13)

To solve the matrix using the Thomas algorithm, an initial guess has to be provided for the

component flow rates at each segment since the coefficients 𝐵𝑗,𝑘, 𝐶𝑗,𝑘, and 𝐷𝑗,𝑘 need them. A cross-


flow separation simulator can provide the initial estimates. The matrix solution yields the feed-side

component flow rates at each segment, which are used later to estimate the permeate-side flow rates

based on the mass balance at each stage.

Where:

∆𝐴𝑘: membrane area available for mass transfer on segment k

𝐿: permeating length of the membrane fiber

𝑁𝑓: number of fibers in the module

𝑅𝑜: outer radius of the membrane fiber

𝑥𝑗,𝑘, 𝑦𝑗,𝑘: mole fractions of component j leaving the feed and permeate sides at segment k

𝑙𝑗,𝑘, 𝑣𝑗,𝑘: feed and permeate flow rates of component j leaving segment k

𝑣𝑗,𝑜: sweep gas flow rates of component j

𝐿𝑘, 𝑉𝑘: total feed and permeate flow rates leaving segment k

�̇�𝑗,𝑘: mass flow rate of component j that permeates through membrane at segment k

𝑄𝑗: permeance of component j

𝑃𝐿𝑘, 𝑃𝑉𝑘

: feed and permeate pressures on segment k

Subscript j: component indication

Subscript k: segment indication

Cross-Flow Separation Model

This study employs the multi-component gas separation model developed by Shindo et al. (1985) for

membrane modules under the cross-flow pattern, where the permeate stream is vertical to the feed

stream. The mathematical model was formulated based on numerous assumptions: the permeation

rates obey Fick's law; the gas permeability is the same as that of the pure gas; the effective

membrane thickness is constant along the module length; concentration gradients in the permeation

direction are negligible; and pressure drops on both the feed and permeate sides are negligible

(Shindo et al., 1985).

Figure 3. Schematic of Cross-Flow Membrane Module

Retentate Flue Gas

Permeate


A number of dimensionless variables are defined, which are used in the governing equations.

𝑠 = 𝐴𝑄𝑚𝑃ℎ

𝐹𝑓𝛿, 𝑠𝑡 = 𝐴𝑡

𝑄𝑚𝑃ℎ

𝐹𝑓𝛿 ; 𝑓 = 𝐹 𝐹𝑓⁄ , 𝑓𝑜 = 𝐹𝑜 𝐹𝑓⁄ ; 𝜃 = 1 − 𝑓𝑜; 𝑔 = 𝐺 𝐹𝑓⁄

𝛾 = 𝑃𝑙 𝑃ℎ⁄ ; 𝑞𝑖 = 𝑄𝑖 𝑄𝑚⁄

Where: 𝑄𝑚 is the permeability of the most permeable component.

The governing equations are described as follows (Shindo et al., 1985):

𝑑𝑥𝑖

𝑑𝑓=

𝑞𝑖(𝑥𝑖 − 𝛾𝑦𝑖) − 𝑥𝑖 ∑ 𝑞𝑘(𝑥𝑘 − 𝛾𝑦𝑘)𝑛𝑘=1

𝑓 ∑ 𝑞𝑘(𝑥𝑘 − 𝛾𝑦𝑘)𝑛𝑘=1

(i=1, 2, …, n-1)

(14)

𝑑𝑠

𝑑𝑓 =

−1

∑ 𝑞𝑘(𝑥𝑘−𝛾𝑦𝑘)𝑛𝑘=1

(15)

𝑥𝑛 = 1 − ∑ 𝑥𝑘

𝑛−1

𝑘=1

(16)

∑𝑥𝑘 𝑞𝑘 𝑞𝑖⁄

𝛾{(𝑞𝑘 𝑞𝑖⁄ ) − 1} + (𝑥𝑖 𝑦𝑖⁄ )= 1

𝑛

𝑘=1

(just for 𝑦𝑖)

(17)

𝑦𝑗 =𝑥𝑗 𝑞𝑗 𝑞𝑖⁄

𝛾{(𝑞𝑗 𝑞𝑖⁄ ) − 1} + (𝑥𝑖 𝑦𝑖⁄ )

(𝑗 ≠ 𝑖, 𝑛)

(18)

𝑦𝑛 = 1 − ∑ 𝑦𝑘

𝑛−1

𝑘=1

(19)

The Runge-Kutta-Gill algorithm is used to solve differential equations, while the Newton’s iterative

algorithm is used to solve 𝑦𝑖 at the permeate stream. The overall mass balance of component i for

the outlet mole fractions of the permeate stream is:

𝑥𝑓𝑖 = 𝑥𝑜𝑖(1 − 𝜃) + 𝑦𝑝𝑖𝜃 (20)

Where:

𝐴: membrane area

𝐴𝑡: total membrane area

𝐹: feed-side flow rate

𝐹𝑓:feed flow rate

𝐹𝑜: reject flow rate

𝑓: dimensionless flow rate on the feed stream

𝑓𝑜: dimensionless flow rate on the feed stream at the outlet

𝐺 : flow rate on the permeate stream parallel to the feed stream

𝑔 : dimensionless flow rate on the permeate stream

𝑛 : number of components

𝑃ℎ: pressure of the feed stream

𝑃𝑙: pressure of the permeate stream


𝑄: permeability

𝑞: ratio of permeability

𝑠: dimensionless membrane area

𝑠𝑡: dimensionless total membrane area

𝑥: mole fraction of the feed-side gas component

𝑥𝑓: mole fraction of the feed-side gas component at the inlet

𝑥𝑜: mole fraction of the feed-side gas component at the outlet

𝑦: mole fraction of the permeate-side gas component

𝑦𝑝: mole fraction of the permeate-side gas component at the outlet

𝛾: pressure ratio

𝛿: membrane thickness

𝜃: stage cut

Subscripts i, j, k: component indication

Subscript m: base component

Reduced-Order Models of Membrane Capture System

Two-Stage Membrane Separation Process The gas separation models discussed above are applied to design and evaluate the two-stage

membrane separation process shown in Figure 1. Reduced-order performance models are derived

based on the results of a range of simulation scenarios for the membrane separation process. The

procedure for developing reduced-order performance models is illustrated as follows:

• Conduct simulations for the capture system using membranes with different properties and

operating conditions.

• Use the flue gas composition from the reference plant without capture (Case 1A) from the

NETL study “Current and Future Technologies for Power Generation with Post-Combustion

Carbon Capture” (NETL 2012).

• Derive reduced-order input-output regression equations based on the system simulation

results.

This effort makes a number of assumptions in common for all the simulation scenarios: nitrogen

(N2), oxygen (O2), and argon (Ar) have identical permeance, whereas the water (H2O)/CO2

selectivity is fixed at 0.7 (NETL 2012); the molar ratio of sweep air versus inlet flue gas flow rates is

0.673; the system operating temperature is fixed at 50°C; the designated CO2 recovery rate of the

first-stage cross-flow module is 50 percent, while that of the 2nd-stage counter-current flow module

is either 90 percent or 50 percent; the pressure ratio of the feed versus permeate sides is kept at 6 for

the cross-flow module, while the designated vacuum pressure at the permeate side remains constant

at 0.20 bar; and there is no pressure drop in the membrane module. The scenarios cover a range of

membrane properties with the CO2 permeance from 1,000 to 4,000 graphics processing unit (gpu)

and the CO2/N2 selectivity from 30 to 50. Tables 1 and 2 summarize the developed reduced-order

models for two levels of CO2 removal.


Table 1. Reduced-Order Performance Models of a Two-Stage Membrane-Based Capture

System with Air Sweep for CO2 Removal of 50% @Cross-Flow+90% @Counter-Current

Independent

Variable

Dependent

Variable

Regression R2

x: CO2/N2 selectivity Cross-Flow Module

Component Removal Efficiency (fraction)

CO2 0.5 (Design)

N2 2.420E-05x2 - 2.829E-

03x + 1.164E-01 97.1%

H2O -2.469E-06x2 + 9.838E-

04x + 6.772E-01 86.9%

O2 2.899E-05x2 - 3.233E-

03x + 1.285E-01 90.4%

Ar 2.418E-05x2 - 2.827E-

03x + 1.164E-01 97.1%

Stage Cut (fraction) 1.429E-05x2 - 1.443E-

03x + 2.161E-01

81.0%

y: CO2 Permeance Counter-Current Flow Module

(gpu) Component Removal Efficiency (fraction)

CO2 0.90 (Design)

N2 6.934E-05x2 - 9.582E-

03x + 4.998E-01 99.9%

H2O 1.00 100.0%

O2 6.995E-05x2 - 1.162E-

02x + 8.911E-01 100.0%

Ar 6.922E-05x2 - 9.561E-

03x + 4.983E-01 99.9%


03x + 5.705E-01

99.5%

Molar Ratio of Permeated Component Relative to Permeated CO2

N2/CO2 8.917E-04x2 - 1.087E-

01x + 4.649E+00

99.8%

H2O/CO2 6.038E-05x2 - 6.652E-

03x + 7.418E-01

97.5%

O2/CO2 1.171E-04x2 - 1.432E-

02x + 6.161E-01

99.8%

Ar/CO2 1.069E-05x2 - 1.303E-

03x + 5.571E-02

99.8%

Total Membrane Area

(m2/ tCO2 /hr removed in

membrane process alone)

1.712E+04 +

7.680E+00x - 8.087y +

1.123E-03y2

98.0%


Table 2. Reduced-Order Performance Models of a Two-Stage Membrane-Based Capture

System with Air Sweep for CO2 Removal of 50% @Cross-Flow+50% @Counter-Current

Independent Variable Dependent Variable Regression R2

x: CO2/N2 selectivity Cross-Flow Module

Component Removal Efficiency (fraction)

CO2 0.5 (Design)

N2 2.885E-05x2 - 3.143E-

03x + 1.212E-01

99.5%

H2O 3.719E-05x2 - 2.915E-

03x + 7.907E-01

68.4%

O2 2.780E-05x2 - 3.144E-

03x + 1.236E-01

99.2%

Ar 2.883E-05x2 - 3.142E-

03x + 1.212E-01

99.5%


03x + 2.644E-01

98.2%

y: CO2 Permeance Counter-Current Flow Module

(gpu) Component Removal Efficiency (fraction)

CO2 0.50 (Design)

N2 2.497E-05x2 - 3.041E-

03x + 1.237E-01

100.0%

H2O 1.593E-05x2 - 1.256E-

03x + 6.833E-01

94.3%

O2 6.990E-05x2 - 8.867E-

03x + 3.905E-01

100.0%

Ar 2.485E-05x2 - 3.027E-

03x + 1.231E-01

100.0%


03x + 1.870E-01

99.4%

Molar Ratio of Permeated Component Relative to Permeated CO2

N2/CO2 4.920E-04x2 - 5.589E-

02x + 2.089E+00

99.8%

H2O/CO2 6.973E-06x2 - 1.075E-

03x + 7.562E-01

59.7%

O2/CO2 6.753E-05x2 - 7.687E-

03x + 2.881E-01

99.8%

Ar/CO2 5.894E-06x2 - 6.696E-

04x + 2.503E-02

99.8%

Total Membrane Area

(m2/ tCO2 /hr removed in

membrane process alone)

6842 - 3.301y

+ 0.000457y2 + 7.21x

97.6%


Vacuum Pump A three-stage vacuum pump with inter-cooling is modeled using Aspen Plus. The inlet flue gas

temperature is fixed at 50°C. The intercooling temperature is 38°C for two stages and 43°C for

outlet. The inlet pressure ranges from 0.1 to 0.2 bar, while the inlet H2O concentration ranges from

0.125 to 0.6. The outlet pressure is fixed at 1 bar. Reduced-order performance models are also

derived based on the Aspen simulation results and are regressed as a function of the inlet water

concentration (xH2O_in) and flue gas pressure (p_in).

The water removal efficiency is calculated as:

Eff_H2O_condensed (fraction) = 0.16401 + 2.9630*xH2O_in – 2.7408*(xH2O_in)^2

(R2=96.8)

(21)

The cooling duty is calculated as:

Qcool (MJ/kmol inlet gas) = 8.811 – 30.22 *p_in (bar) + 41.306*xH2O_in

(R2=96.6)

(22)

The vacuum power use is calculated as:

W_vacuum (kWh/kmol inlet gas) = 2.93735 - 6.6168*p_in (bar) - 1.3136*xH2O_in

(R2=98.7)

(23)

CO2 Cryogenic Purification Unit The detailed models of CO2 cryogenic purification unit are available in another report

(Mantripragada and Rubin 2017).

Engineering-Economics of a Membrane Capture System

This study employs the previously developed costing framework to estimate capital and O&M costs

for the two-stage membrane-based capture system with air sweep (Zhai and Rubin 2013). Table 2

summarizes major capital cost components and their estimation methods. The total capital

requirement takes into account the direct costs plus a number of indirect costs, such as the general

facilities cost, engineering and home office fees, contingency costs, financing cost, and owner’s

costs. The major direct cost components include membrane separation module, membrane frame

structure, vacuum pump, and CO2 cryogenic purification unit. Table 3 summarizes major fixed and

variable O&M cost components and their estimation methods. Fixed O&M costs include operating

labor, maintenance costs, administrative and support labor costs, and taxes and insurance. Variable

O&M costs include membrane replacement, power use, and CO2 transport and storage.


Table 3. Capital Cost Estimation

Process Area4 Methoda Plant Costs Method

Membrane module (1) 𝐴𝑚 ∙ 𝑐𝑚 Process facilities capital (5)

Membrane frame (2) (𝐴𝑚

2000)0.7

∙ 𝑐𝑚𝑓 General facilities capital (6) 5.8% of PFC

Vacuum pumps (3) 𝑒𝑣𝑝 ∙ 𝑐𝑣𝑝 Eng. & home office fees (7) 9.6% of PFC

CO2 cryogenic purification

unit (4)

Mantripragada

and Rubin, 2017 Project contingency cost (8) 20% of PFC

Process contingency cost (9) 20% of PFC

Interest Charges (10)

Royalty fees (11) 0.0% of PFC

Preproduction cost (12)

Inventory capital (13) 1.7% of TPCb

Financing Cost (14) 2.7% of TPCb

Other owner's costs (15) 15% of TPCb

Process facilities capital

(PFC) (5) (1) +(2)+(3)+ (4)

Total capital requirement

(TCR)

(5) + (6) +…. +

(15) a Notation: 𝐴𝑚: membrane area (m2); 𝑐𝑚: unit cost of membrane module ($/m2); 𝑐𝑚𝑓: referred frame cost

(M$ 0.238); 𝑒𝑐𝑝𝑟: compressor power use (kW); 𝑐𝑐𝑝𝑟: installed unit cost ($/kW); 𝑒𝑒𝑥𝑝: expander power use

(kW); 𝑘𝑒𝑥𝑝: unit cost ($/kW); 𝐹ℎ: equipment cost factor for housing, installation, etc (1.8); 𝑒𝑣𝑝: vacuum

pump power use (kW); 𝑐𝑣𝑝: installed unit cost of vacuum pump ($/kW). b TPC= total plant cost, which is the sum of (5)+(6)+(7)+(8)+(9).

Table 4. Operating and Maintenance Cost Estimation

Variable

Cost Component Methoda Fixed Cost Component Method

Material replacement (1) (𝐴𝑚 ∙ 𝜗) ∙ 𝑐𝑟𝑚 Operating labor (4) Electricity (2) MWh ∙ 𝐶𝑂𝐸 Maintenance labor (5) 40 % of TMC

CO2 transport & storage

(when considered) (3) 𝑚𝐶𝑂2 ∙ 𝑐𝑇&𝑆 Maintenance material (6) 60 % of TMC

Admin. & support labor (7) 30 % of Total labor

Taxes & insurance (8) 2% of TPC

Variable O&M Costs (1)+(2)+(3) Fixed O&M Costs (4)+(5)+(6)+(7)+ (8) a Notation: 𝐴𝑚: membrane area (m2);𝑐𝑟𝑚: material replacement cost ($/m2); 𝜗: annual material replacement

rate (%); MWh: annual system power use (MWh); 𝐶𝑂𝐸: cost of electricity ($/MWh); 𝑚𝐶𝑂2: annual CO2

captured (mt/yr); 𝑐𝑇&𝑆: CO2 product transport and storage cost ($/mt CO2).


Case Study

The aforementioned performance and cost models of the two-stage membrane system with air sweep

are incorporated in IECM (IECM 2017). A case study is performed using IECM v9.6 to evaluate this

advanced membrane-based capture system. “NETL Case 11 (Rev2a)” in the IECM Session

Databases Library is uploaded and chosen as a reference plant that is a supercritical coal-fired power

plant without CO2 capture. Then, the two-stage membrane system with air sweep is added to the

reference plant to yield a capture plant. To make comparisons between the cases with and without

carbon capture, the resulting capture plant is further adjusted to ensure that both the reference and

capture plants have the same power output on the net basis. Figure 4 shows the membrane properties

chosen for IECM modeling and evaluation.

Figure 4. Set Membrane Properties in IECM

Table 5 summarizes the major performance and cost results of the plants with and without CO2

capture. The addition of this advanced membrane-based capture system with good material

properties would decrease the overall plant efficiency by about five percent points and the plant cost

of electricity (COE) by 63 percent.


Table 5. Performance and Cost Results of Plants with and without CO2 Capture

Parameter Plant

w/o CCS

Plant

w/CCS

Gross Power Output (MW) 580 672

Net Power Output (MW) 550 550

Capacity Factor (%) 85 85

Fixed Charge Factor (fraction) 0.103 0.103

Net Plant Efficiency (HHV, %) 39.3 34.0

CO2 Capture System

CO2 Removed in Membrane System (%) 90.9

Overall Plant CO2 Removal Efficiency (%) 81.3

Vacuum Pump Power Use (MW) 26.8

CPU Power Use (MW) 59.7

Total Power Use (MW) 86.5

Membrane Area (x 106 m2) 1.3

Total Capital Requirement (2007$/kW) 934

Plant COE, excluding CO2 T&S Costs* (constant 2007$/MWh) 86.7

Plant COE, including CO2 T&S Costs* (constant 2007$/MWh) 57.7 94.1

* T&S = $10/t transport and storage (via pipeline and geological sequestration)


References

Coker et al (1998). Modeling multi-component gas separation using hollow‐fiber membrane

contactors. AIChE Journal, 44(6), 1289-1302.

National Energy Technology Laboratory (2012). Current and Future Technologies for Power

Generation with Post-Combustion Carbon Capture, Final Report, DOE/NETL-2012/1557,

March, Pittsburgh, PA.

Integrated Environmental Control Model (IECM), v9.6. Carnegie Mellon University, Available at

www.iecm-online.com, Accessed in June 2017.

Shindo et al (1985). Calculation methods for multi-component gas separation by permeation.

Separation Science and Technology, 20(5-6), 445-459.

Zhai, H., and Rubin, E.S. (2013). Techno-economic assessment of polymer membrane systems for

postcombustion carbon capture at coal-fired power plants. Environmental Science &

Technology, 47(6), 3006-3014.

Mantripragada, H., and Rubin, E.S. (2017). IECM Technical Documentation: CO2 Purification Unit

– Performance and Cost Models. Carnegie Mellon University, Pittsburgh, PA.

http://www.iecm-online.com/

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