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The University of Texas at Austin

Amine Solvent Reclaiming Options from Post-Combustion CO2 Capture Processes

Andrew J. Sexton, Anne I. Ryan Trimeric Corporation

Gary T. Rochelle, Paul Nielsen, Eric Chen


Katherine Dombrowski and Jean Youngerman URS Corporation

Prachi Singh

IEA Greenhouse Gas R&D Programme (IEAGHG)

2013 AIChE Annual Meeting: San Francisco, CA November 8, 2013


Disclaimer • Most results in this presentation are based

largely upon existing project supported by IEA Greenhouse Gas R&D Programme (IEAGHG)

• These results are interim results from a work-in-progress and subject to change

• Final results will be published in greater detail next year by IEAGHG


Project Objectives • Establish CO2 capture process reference cases

• Identify and perform sensitivity analyses on solvent loss and formation of degradation components

• Perform a techno-economic evaluation on multiple solvent reclaiming technologies

• Evaluate and characterize reclaimer waste streams

• Evaluate reclaimer waste handling and disposal costs


Why is Amine Solvent Reclaiming Important?

• Reclaiming concentrates impurities to facilitate environmentally acceptable disposal

• Reclaiming recycles useful solvent

• Reclaiming reduces cost of solvent disposition • Less material to dispose of

• Less makeup of fresh amine


Outline

• Basis for Study

• Impurities to be Removed

• Economic Evaluation of Reclaiming

• Classification of Reclaimer Wastes

• Conclusions


Reference Cases • Two power plant reference cases with 90%

CO2 Capture1

– Pulverized Coal: 900 MW – Natural Gas: 810 MW – Gross electrical generating capacity

• Three reference capture solvents – 7 m MEA (monoethanolamine) – 8 m PZ (piperazine) – 7 m MDEA (methyldiethanolamine) / 2 m PZ

1IEAGHG, “Post-Combustion Capture Scale-up Study”, 2013/05, February 2013


Classes of Impurities • Volatile Products

– Oxidation: Ammonia, Amines

– NOX reaction: Nitrosamines

• Non-Volatile Products – Oxidation: Heat stable salts (formate, oxalate)

– Thermal Degradation/Carbamate Polymerization: Higher-MW products

– Reaction with Flue Gas Impurities (NOX/SOX/HCl): Heat stable salts (HSS)

– Dissolved metals


Economic Evaluation (1 of 2)

8

• Eighteen cases evaluated – Three solvent systems: MEA, PZ, MDEA/PZ – Three reclaiming technologies: thermal, ion exchange,

electrodialysis

• Slipstream ratio of 0.1% (or less) – Defined as ratio of reclaimer feed to total solvent

circulation rate

• CO2 pretreatment required for all reclaiming technologies

• Caustic required for HSS neutralization (1 mol NaOH:1 mol HSS)


Economic Evaluation (2 of 2)

9

• Conducted literature review on amine reclaiming technologies – Key information: rates of amine degradation, amine recovery, energy

requirements, chemical requirements, cost information, rates of HSS removal, waste generation

• Correspondence with amine reclaiming vendors

• Correspondence with representatives of oil and gas companies who are involved with operation of amine units for removal of acid gases


Material Balance Assumptions

10

Reclaiming Technology

Amine Recovery,

wt%

HSS to waste, wt%

Transition Metals/Non-ionic

products to waste, wt%

Thermal Reclaiming 95 100 100

Ion Exchange 99 90 0 Electrodialysis 97 91.5 0

Reclaimer slipstream ratio adjusted to get 1.5 wt% HSS in solvent into the reclaiming unit


Steady-State Material Balance

11

Goal: Rate of Impurity/Degradation Product Removal in Reclaimer Waste (lb/hr) = Rate of Impurity/Degradation Product Accumulation in CO2 Removal System (lb/hr)

Reclaiming Unit

Water

Recovered Amine

Reclaimer Waste

Sodium Hydroxide

Lean Amine Bypass

Reclaimer FeedLean Amine from

Regenerator

Lean Amine to Absorber

Impurities, Degradation Product

Accumulation

1

2

3

4

5

6 7


Thermal Reclaiming

Bleed to Reclaimer

Purified Amine(95% recovery)

1 mol NaOH/1 mol HSS Impurities

(5% Amine loss)

Reboiler

Stripping Still

Condenser

CO2 to stripper

Hot lean solvent

Lean solvent to exchanger


Ion Exchange Reclaiming

Lean Amine Reclaimer

Feed

Anion Exchange

Resin

Caustic for Regeneration (Distilled, deionized water)

Aqueous Brine to Wastewater

Treatment Plant

Purified Amine(99% recovered)

Cation Exchange

ResinCaustic

Pretreatment

Sulfuric Acid for Regeneration

(Distilled, deionized water)

1 mol NaOH/1 mol HSS


Treatment Plant

ParticulateFilter

CO2 Pretreatment

(Heating)

Cation Exchange: Designed to remove Na+ from reclaimed amine; sulfuric acid used to regenerate bed with H+ Anion Exchange: Designed to remove heat stable salt anions from reclaimed amine; sodium hydroxide used to regenerate bed with OH-


Electrodialysis Reclaiming

Lean Amine Reclaimer Feed

ElectrodialysisCell

Makeup Water (Distilled, deionized)

Purified Amine(97% recovered)

Caustic Pretreatment

1 mol NaOH/1 mol HSS

ParticulateFilter

Applied Current

Applied Current


Treatment Plant

Makeup Water (Distilled, deionized)


Treatment Plant

CO2 Pretreatment


Major Cost Centers • Capital Costs (PEC)

– Reference capital costs provided by thermal reclaiming vendor evaluation for thermal reclaiming unit

– Reference ion exchange, electrodialysis costs provided from literature (MDEA)

• Major Operating Costs – Thermal Reclaiming: solvent losses

– Ion Exchange: consumables (NaOH, H2SO4) for resin bed regeneration, resin bed replacement

– Electrodialysis: solvent losses, membrane replacement

• Major Sources of Energy Consumption – Thermal Reclaiming: reboiler (thermal energy)

– Ion Exchange: N/A

– Electrodialysis: applied current


Qualitative Analysis of Reclaiming Options (1 of 2)

• Thermal Reclaiming – Removes all species (HSS, transition metals and high-MW products)

– Corrosion is an operational concern

– Solvent losses are a concern for novel, expensive solvents

• Ion Exchange – Does not remove non-ionic species; may need to batch reclaim solution

periodically to remove these species

– Not practical for removal of transition metals

– Large volumes of wastewater

– Minimal solvent losses

– Requires minimal operator attention and maintenance

• Electrodialysis – Similar when compared to ion exchange, but requires continuous operator

attention

– Greater solvent losses than ion exchange


Qualitative Analysis of Reclaiming Options (2 of 2)

• Correspondence with amine reclaiming vendors – Technology selection may be based upon operating costs,

waste management preferences (capital costs should be similar)

– Important to integrate and design reclaiming unit in conjunction with capture plant

– Incursion rate of HSS is major driver for reclaimer design basis


Economic Evaluation – Summary (1 of 2) • Estimated cost of electricity2

– 0.08 to 0.16 ¢/kWh (0.0006 to 0.0012 €/kWh) for the coal combustion cases

– 0.03 to 0.05 ¢/kWh (0.0002 to 0.0004 €/kWh) for the natural gas combustion cases.

• Estimated cost of CO2 capture – $1.11 to $2.18/MT CO2 captured (€0.84 to €1.64/ MT CO2

captured) – 0.82 to $1.69/MT CO2 captured (€0.61 to €1.27/ MT CO2

captured) • Reclaiming accounts for approximately 1% (or less) of total

cost of electricity for a power plant with CO2 capture2

2Department of Energy (DOE) National Energy Technology Laboratory (NETL). “Cost and Performance Baseline for Fossil Energy Plants Volume 1: Bituminous Coal and Natural Gas to Electricity”, Revision 2, November 2010, DOE/NETL 2010/1397.


Economic Evaluation – Summary (2 of 2) • There is a lack of documented cost information

• Economics are a strong function of – Concentration and uptake of flue gas contaminants (NOX, SO2,

halogens)

– Assumed solvent losses (which is a function of the slipstream ratio)

• For more expensive amines, preferred to design thermal reclaimer with lower amine slip

– Assumed concentration of HSS at steady-state conditions

• Operating costs, level of operator attention, operating preferences, and/or waste disposal preferences may influence reclaiming technology selection


Classification of Reclaimer Wastes

• Hazardous classifications relied on modeled calculations of waste composition – Solvent characteristics

– Metals content

– Nitrosamine content

• No wastes tested; therefore, classifications are not definitive


US Hazardous Waste Classification Thermal Reclaiming Waste (Coal)

Thermal Reclaiming Waste (NGCC)

Ion Exchange and Electrodialysis (Coal, NGCC)

Listed No No No

Ignitable No No No

Reactive No No No

Toxic Maybe No No

Corrosive Unlikely Unlikely No

Waste is toxic if extract from TCLP* contains a toxic constituent at a concentration above the regulatory level

Coal waste will contain metals • Potentially hazardous • Cr, Se, Hg NGCC waste will not contain metals • Non-hazardous IE/ED is likely non-hazardous waste • Stream mostly water • Processes do not transfer metals to waste

*TCLP = toxicity characteristic leaching procedure


Estimated Steady-state toxic impurities (ppmw) - Reclaimed to 1.5 wt% HSS

Component 7 m MEA 8 m PZ (ppmw) Coal NGCC Coal NGCC

Mercury 0.36 0 0.32 0 Selenium 0.46 0 0.42 0

Chromium 0.91 3.3 0.82 3.8

Nitrosamines 60 60 118 104


EU Hazardous Waste Classification

• EU system uses 12 characteristics + listing of specific wastes • All Coal and NGCC thermal reclaimer wastes likely hazardous • Solvents in the reclaimer waste are hazardous and meet criteria for

– Irritant – Harmful – Corrosive (much lower threshold for corrosivity in EU vs. US)

• Metals in reclaimer waste are hazardous and meet criteria for – Ecotoxic – Listed waste

• PZ containing wastes hazardous due to – Carcinogen (nitrosamines) – Sensitizing – Toxic for reproduction


EU Hazardous Waste Classification

• Ion Exchange and electrodialysis wastes might be non-hazardous – Low concentrations of solvents do not exceed

thresholds for irritant, harmful, toxic, etc. – No minimum threshold for sensitizing

components, so PZ-containing IE/ED wastes may be hazardous

– Assumed no metals removal by these processes; in reality if even some metals are removed, then streams could be listed wastes and thus hazardous


Sludge from Thermal Reclaimer

TransportationTransportation/

Processing

Off-site hazardous waste landfill; processing by landfill facility

Off-site hazardous waste commercial

incinerator, including cement

kilnOn-Site Power

Plant Boiler

Additional Processing as Needed (e.g., homogenize,

liquefy)

On-site Transportation

Hazardous Waste Disposition Options


Sludge from Thermal Reclaimer

Aqueous Stream from Ion Exchange/Electrodialysis

Stabilize with cement or fly ash

On-site Transportation

Non-hazardous landfill

(on or off-site)

On-site Power Plant Boiler

Off-site Cement Kiln

On Site WWTP

Transportation

Homogenization StepTransportation

Additional Processing as Needed (e.g., homogenize,

liquefy)

Non-Hazardous Waste Disposition Options


Costs of Disposal • Selection of reclaiming method must consider

implications of waste classification on disposal costs • Thermal reclaimer disposal costs

• Additional wastewater treatment processes needed at power plants to handle ion exchange and electrodialysis streams – Advanced oxidation, bioreactors

Disposition Option Reclaiming Case Cost Added to Annualized Reclaimer Operations (US)

Non-hazardous landfill

NGCC thermal reclaimer waste (US)

15 - 30%

Hazardous landfill or incineration

Coal thermal reclaimer waste (US)

~ 100%


Conclusions • Cost of reclaiming and solvent makeup will be less than

$2/MT CO2, but disposal could make it $4/MT CO2.

• When reclaimer design is set by flue gas contaminants, expensive solvents will be less attractive.

• Thermal reclaimer waste may be “hazardous” depending upon the geographic location – U.S.: metals

– Europe: amine, nitrosamine, metals

– Regulations may differ in other countries

• The waste generator’s preferences for waste management and operability may dominate the decision-making process

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