GREENER SOLVENT SELECTION

AND SOLVENT RECYCLING

FOR CAPTURE

NSF Research Experience for Undergraduates

August 04, 2011

Ghinwah Hachem

OUTLINE

Project Motivation & Description

Accomplished Work

Future Work

COAL-FIRED ELECTRICITY GENERATION

Coal-fired power plants provide

44.9 % of the electricity consumed

in the USA.

847 billion tons of coal reserves

worldwide will last around 119 years

at current rates of production.

Coal generates 25 % of global

greenhouse gas emissions.

CO2 makes up 77 % of global

greenhouse gas emissions.http://www.worldcoal.org/coal , http://en.wikipedia.org/wiki/Coal_power_in_the_United_States

CO2 CAPTURE SOLUTIONS

http://www.geos.ed.ac.uk/sccs/capture/ , Integrated Framework for Solvent Selection and Solvent Recycling for CO2 Capture: August 09 Monthly Report. EPRI, Palo Alto, CA. Product ID # 069040

Carbon Capture Systems:1. Post-Combustion

2. Pre-Combustion

3. Oxy-Fuel Combustion

Separation Techniques:1. Physical Absorption

2. Chemical Absorption

3. Adsorption

4. Membrane Separation

5. Cryogenic Separation

POST – COMBUSTION CARBON CAPTURE

Physical and chemical absorption, using amine solvents, for gases with low concentrations of CO2. CO2 stripping and solvent regeneration. High energy penalty: 20-40% of plant’s power output

Folger, P. (2010). Carbon Capture: A Technology Assessment . Congressional Research Service, (p. 99)

REDUCTION OF ENERGY PENALTY BY: Using different solvents:

Monoethanolamine (MEA)Diethanolamine (DEA)Amino Methyl Propanol (AMP)Solvents with solubility parameters similar to that of CO2

Varying design conditionsHeights of columnsFeed location

Varying operating conditionsOperating temperatureOperating pressureSolvent flowrate

http://michelledagninosblog.blogspot.com/

Use a numerical optimization technique, Simulated Annealing (SA), to minimize the energy consumed by the carbon capture process.

OPTIMIZATION

Diwekar, U. Introduction to Applied Optimization 2nd Edition. Clarendon Hills: Springer.

Model: Simulation developed in Aspen Plus Decision Variables: Model Parameters Objective Function: Energy Constraints: mass and energy balance, reaction kinetics

FIRST ASSIGNMENT

Solvent = 30 weight percent MEA solution Rate-based model NOT Equilibrium Model

Perform Parametric Studies

% CO2 CAPTURED & STRIPPER REBOILER DUTY

% CO2 CAPTURED & STRIPPER REBOILER DUTY

% CO2 CAPTURED & STRIPPER REBOILER DUTY

Possible combinations:

Where:

1005 = 100 samples of each of the 5 continuous variables

Na = Maximum number of trays in absorber

Ns = Maximum number of trays in stripper Na ! = Possible absorber feed tray locations Ns ! = Possible stripper feed tray locations

Use simulated annealing, a numerical optimization method, to minimize the energy penalty.

IMPORTANCE OF SA

SECOND ASSIGNMENT

Read “Introduction to Applied Optimization” Use SA to solve an example problem in Aspen Plus

1. Understand what Simulated Annealing (SA) is

2. Become Familiar with the CAPE-OPEN SA Capability in Aspen Plus

Global optimization technique that: Mimics physical annealing: Heating and controlled cooling of a material which allows atoms to find configurations with lower internal energy compared to their initial configurations.

WHAT IS SA?

High Temperature Low Temperature

http://on.wikipedia.org/wiki/Simulated-Annealing , Diwekar, U. Introduction to Applied Optimization 2nd Edition. Clarendon Hills: Springer.

Goal: Minimize Objective Function

Multiply by (-) to maximize

Specify: Binary variables AND discrete variables

Discretize continuous variables

Equality constraints AND inequality constraints

Initial temperature

Freezing temperature

Temperature decrement

Simple rule: Tnew = α Told where 0.8≤ α ≤0.99

HOW IS SA APPLIED?

Temperature is a parameter

EXAMPLE PROBLEM

Maintain constant temperature by: Varying oxygen flow-rate between 5000

and 10000 kmol / hr Maximizing water flow-rate

(-water flow-rate = cost)

Oxy

gen

km

ol /

hr

Wa

ter

kmo

l / h

r

OXYGEN FLOW-RATE: 5800 kmol / hr

Continuous Variables Stripper reflux ratio : optimum at 0.017 LEAN-IN Pressure : optimum at 1.05 atm RICH-IN Pressure : optimum at 1.07 atm LEAN-IN Temperature: optimum at 42.28 ⁰ C Moles CO2 / Mole MEA: optimum at 0.25

Integer Variables Stripper feed stage: optimum at stage 6

SA FOR CARBON CAPTURE SYSTEM

Understood performance of MEA rate based system1. Parametric studies2. Simulated annealing

Perform parametric studies and simulated annealing on:1. DEA system

2. MEA+DEA system

3. New Solvent

SUMMARY & FUTURE WORK

http://4photos.net/en/image:111-195616-save_energy_pictures_images

ACKNOWLEDGMENTS

National Science Foundation

EEC-NSF Grant # 1062943

Dr. Urmila Diwekar

Dr. Juan Salazar

Dr. Christos Takoudis

Dr. Greg Jursich