ada carbon solutions esp optimized

Expertise. Reliability. Compliance.1

Tuning Electronic Properties of PAC for Enhanced Electrostatic Precipitator Performance

EUEC – San Diego, CAFebruary 18, 2015

C8.1 HG Control & ESP

Herek L. Clack1, Eric M. Lee2,

Chris Vizcaino3, Roger H. Cayton3 and Joe Wong3 1University of Michigan, Ann Arbor, MI

2Illinois Institute of Technology, Chicago, IL3ADA-Carbon Solutions, Littleton, CO


Challenges of Sorbent Injection for ESPs (1/2)

Retrofitting Coal Fired Power Plants using Activated Carbon Injection (ACI) upstream of ESPs is cost effective.

Maximizing mercury adsorption capacity and maintaining ESP PM collection efficiency are both important.

Full-scale PAC injection testing at the Brayton, Meramec, Monroe, and Pleasant Prairie sites did not negatively impact stack opacity1.

However, at Conesville, testing of 18 different sorbents resulted in increased ESP sparking, decreased ESP power, or increased opacity in most cases1.

____________________

1Clack, H.L. “Estimates of Increased Black Carbon Emissions from Electrostatic Precipitators during Powdered Activated Carbon Injection for Mercury Emissions Control”. Environmental Science & Technology 46 (2012), pp. 7327–7333.


Challenges of Sorbent Injection for ESPs (2/2)

Stanton Unit 1: gas sampling particulate filters at ESP outlet darkened (may have reflected load changes)1.

Limestone Unit 1: roughly half of the particulate loading measurements (EPA Method 17) taken during PAC injection exceeded baseline measurements taken without PAC injection1.

Lausche: observed opacity increases were highly dependent on particle size and injection rate1.

• 20 μm MMD: 5% constant opacity for injection rates up to 8 lb/MMacf.• 5 μm MMD: 9% opacity (nearly doubled) at 2.5 lb/MMacf.• 1 μm MMD: 15-16% opacity (more than tripled) at 1.5 lb/MMacf.

____________________

1Clack, H.L. “Estimates of Increased Black Carbon Emissions from Electrostatic Precipitators during Powdered Activated Carbon Injection for Mercury Emissions Control”. Environmental Science & Technology 46 (2012), pp. 7327–7333.


Preferential PM Collection on ESP Discharge Electrode Our previous studies1,2 using a lab-scale ESP revealed effects of PAC on PM

collection:• PAC alone collected on both collection and discharge electrodes.• Fly ash (FA) alone (lignite and IL bit.) collected primarily on collection

electrode.• FA + PAC admixtures collected 4-10% on discharge electrode, where PAC

concentration was enriched by up to 50% from inlet values. Question #1: How do PAC electrical properties affect FA + PAC collection? Question #2: How can PAC electrical properties be tuned for improved

collection of FA + PAC admixtures within ESPs.____________________

1Prabhu, V. et al. “Evidence of powdered activated carbon preferential collection and enrichment on electrostatic precipitator discharge electrodes during sorbent injection for mercury emissions control”. Fuel Processing Technology 93 (2012), pp. 8-12.2Prabhu, V., S. Lee, H.L. Clack. “Electrostatic Precipitation of Powdered Activated Carbon and Implications for Secondary Mercury Adsorption within Electrostatic Precipitators”. Energy & Fuels 25 (2011), pp. 1010-1016.


Volume Resistivity Testing, Inferred Differential Collection

Volume resistivity of PM is important to ESP performance.• Optimum PM collection and ESP rapping efficiency: 108 - 1013 ohm-cm.• Fly ash: 1011 to 1013 ohm-cm, depending on composition, LOI.• Conventional PAC: 104 ohm-cm.• Using ACI, collected PM resistivity varies as particle size decreases and

as PAC concentration increases, and has different implications from front to rear field.

Volume resistivity conventionally measured after passive exposure & conditioning of PM samples in controlled T/RH environmental chamber.

For faster evaluation, developed a novel test fixture combining T & RH conditioning with volume resistivity measurement.


Volume Resistivity Test Set-up

• T = 102.5 ± 0.5 [oC]• RH = 10.8 ± 0.6 [%]

(Downstream Sensor)

Desiccant Air Dryer

Heat Ropes

Distilled Water Impinger

Ceramic Air Heater

Resistivity Test Cell

T, RH

T, RH

Gravitational Water Leveler

Powder Sample


Novel Flow Through Resistivity Test Fixture

Low sheath flow (3 SCFH) to prevent particle loss.

Heated and moisturized air diffused through powder samples by a sintered filter (0.5 μm).

Powder sample compression to minimize systematic measurement error.

E = 0.05 [kV/cm].


Volume Resistivity Test Parameters

PRB FA enriched with 1% (by weight) PAC samples• Baseline PAC - ε• Treated PACs - α, β, γ, and δ

Resistivity data serves as baseline data for evaluating:• Content of PAC within dustcake collected from an ESP.• Potential for PAC and fly ash penetration through an ESP.


Volume Resistivity: PAC Formulations a through e Volume resistivity measurements show differentiation between five PAC

formulations.• Charge dissipation causes slow measurement creep• Reported values at t = 60s (ref. IEEE 548 test method).

100% α 100% β 100% γ 100% δ 100% Ɛ0.0E+00

1.0E+04

2.0E+04

3.0E+04

4.0E+04

5.0E+04

6.0E+04

7.0E+04

8.0E+04

9.0E+04

1.0E+05

34500

87125

41000

55250 55250

Volu

me

Resis

tivity

[ohm

-cm

]

0 10 20 30 40 50 60 70 800.0E+00

1.0E+04

2.0E+04

3.0E+04

4.0E+04

5.0E+04

6.0E+04

7.0E+04

8.0E+04

9.0E+04

1.0E+05

100% α

100% β

100% γ

100% δ

100% Ɛ

Time [s]

Volu

me

Resis

tivity

[ohm

-cm

]


Volume Resistivity: 100% PAC vs. 1% PAC FA Admixture

α β γ δ Ɛ 100% PRB1.00E+00

1.00E+02

1.00E+04

1.00E+06

1.00E+08

1.00E+10

1.00E+12

1.00E+14

100% PAC 1% PAC + 99% FA

Volu

me

Resis

tivity

[ohm

-cm

]

PAC formulation ε added to PRB yields resistivity similar to PRB alone.

PAC formulations α, β, γ, δ added to PRB variously increase or decrease resistivity.

Suggest PAC formulations selected to tune fly ash resistivity for optimized mercury capture and PM collection.


Lab-Scale Cylindrical ESP Test Set-up

Upper Extension

Venting gap

Voltage range: 0 to -25 kV. Upper extension acts as grounded

perf. plate, preventing particle loss from EHD-induced reverse flow.

Increased PM loading compensated by increased current.

Gravity fed. Max. collection efficiency ~ 93%. Unavoidable fine particle loss

through ½” venting gap.


Lab-Scale ESP Test Results: PRB FA+1% PAC (1/2)

Collection bin contents: coarse particles with high terminal velocities.

Discharge electrode: fine particles (~ 0.06%).

Collection electrode: majority of collected PM.

Calculated loss: remainder needed to close mass balance, mostly particle loss due to EHD flows at inlet.

1% α 1% β 1% γ 1% δ 1% ε PRB0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

80.00

90.00

100.00

Calculated LossCollection BinCollection ElectrodeDischarge Electrode

Mas

s Rati

o {%

]


Lab-Scale ESP Test Results: PRB FA+1% PAC (2/2)

Admixtures with γ-formulation: improved collection by 1% and reduced mass out by 50%, compared to 100% PRB.

Admixtures with α-, β-, δ-, and ε-formulations: decreased particle collection and increased penetration compared to 100% PRB.

1% α 1% β 1% γ 1% δ 1% ε PRB0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

80.00

90.00

100.00

85 86 90 86 8489

9 83

9 9 6

6 67

5 65

Calculated LossCollection BinCollection ElectrodeDischarge Electrode

Mas

s Rati

o {%

]


Pre-/Post-Test Volume Resistivity Comparisons (1/2)

Compares volume resistivities of initial feed and collection electrode dustcake.

Decreases imply PAC-enrichment.

Increases imply FA-enrichment.

1% α 1% β 1% γ 1% δ 1% ε PRB1E+09

1E+12

1E+15Initial Collected

Volu

me

Resis

tivity

[ohm

-cm

]


Pre-/Post-Test Volume Resistivity Comparisons (2/2)

100% PRB increase implies other effects, e.g., exclusion of coarsest particles.

γ-, β-, δ-, and ε-admixtures suggest PAC-enriched dustcake.

α-admixture suggests FA-enriched dustcake.

1% α 1% β 1% γ 1% δ 1% ε PRB1E+09

1E+12

1E+15Initial Collected

Volu

me

Resis

tivity

[ohm

-cm

]

+1471%-7%

-7%

-94%

-50%

+350%


Conclusions

Volume resistivity used as experimental parameter in PAC formulations to evaluate the impact of ACI on ESP performance.

Used novel flow-through volume resistivity test fixture to measure PAC formulations and their PRB FA admixtures under elevated temperature and humidity.

ESP differential collection test indicates different collection behaviors as a function of different PAC formulations.

Comparison of volume resistivities of initial feed and collected dustcake provides insight into preferential collection behaviors.

PAC development can incorporate tuning electrical properties to achieve optimum mercury capture and PM collection in ESPs.

γ-PAC: 1% improvement of collection efficiency and 50% reduction of mass out, compared with PRB FA.


Questions?

Herek L. ClackUniversity of Michigan

[email protected]

Eric Monsu LeeIllinois Institute of Technology

[email protected]

Chris VizcainoADA-Carbon Solutions

[email protected]

Roger H. CaytonADA-Carbon Solutions

[email protected]

Joe WongADA-Carbon [email protected]

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