Performance and Economic Improvement in Vapor Adsorbers ... · Performance and Economic Improvement...

Performance and Economic Improvement in Vapor Adsorbers Using Structured Activated Carbon Media

Paula S. Walmet, Ph. D., John D. Perry, Ph.D., and David A. Schaaf MeadWestvaco Corporation

2012 OWEA Annual Conference

June 20, 2012

2 Structured Activated Carbon

Agenda

1. Introduction to Atmospheric Corrosion

2. Strategies for Corrosion Prevention

3. Structured Activated Carbon Technology

4. Honeycomb vs. Pellet: Performance

5. Honeycomb vs. Pellet: Economics

Introduction to Atmospheric Corrosion

Atmospheric Corrosion 1

• Corrosion – the disintegration of an engineered material due to chemical reactions with its surroundings

• Electrolyte – Fundamental requirement for electrochemical corrosion

◦ Substance with free ions that allow electrical

conductivity

◦ Most commonly a thin film of water that forms at

critical humidity

• Critical Humidity ◦ Not a constant

◦ Depends on corroding material, tendency to

adsorb moisture, and presence of

atmospheric pollutants.



• Atmospheric corrosion proceeds by balancing anodic and cathodic reactions.

• During the reaction, metal is dissolved into the electrolyte, and oxygen from the atmosphere is reduced in the solution.

• This reaction is often accelerated by the presence of contaminants in the air (e.g. H2S, SO2, Cl2)

Corroding Metal

Anodic Reaction

Cathodic Reaction

M+ M+ M+

M M+ + e-

O2 + 2H2O + 4e- 4 OH-

Electron Transfer

Oxygen from the atmosphere dissolves into the electrolyte



• The miniaturization of electronic components and the increase in availability continues to make the corrosion of electronics a matter of increasing concern.

• Another challenge faced with the increasing component density and decreasing size is the measurable impact of smaller and smaller defects.

Corrosion creates bridges between the electronic connections,

destroying the computer card.


Strategies for Corrosion Prevention

Corrosion Prevention 1

• Eliminate the root cause of the corrosive gas ◦ May require large capital expense or be invasive to the process

◦ Sometimes the result of excursions or other uncontrolled releases

◦ Potentially from widespread source or external source

• Isolate the sensitive equipment ◦ Coat all vulnerable components with barrier material

◦ Enclose all equipment in impermeable housing

◦ Relocate process to cleaner environment

• Create a protected environment ◦ Purify air in a space to reduce contaminants

◦ Pressurize a space with clean air from alternative source

◦ Pressurize a space with purified air


Corrosion Prevention 2

A vapor adsorber may be used to purify the air that is used to pressurize a protected space.

Contaminated

Air

Purified Air

Vapor

Adsorber

HVAC Contained in Protected Room

Pressurized by Purified Air


Structured Activated Carbon Technology

What is Activated Carbon?

Range of Products

Raw Materials

• Wood, Coal, Coconut, etc.

Activation Process

• Chemical, Thermal

Pore size depends on both raw

material + process

micropore (pore width < 20 Å)

mesopore (20 – 500 Å)

macropore (> 500 Å)

What is Activated Carbon?

Adsorption for Corrosion and Odor Control

• is the binding of molecules to a surface

• Physisorption occurs due to weak attractive interactions known as van der Waals forces

• Chemisorption is driven by a chemical reaction at the exposed surface and typically involves addition of an active chemical (e.g. carbonate, KI, oxides)

Adsorption….

Structured Carbon 1

Activated carbon can be produced in a variety of forms depending on the desired final application.

Granular carbon is the initial form derived from the activation process.

Powdered carbon is typically produced by grinding granular carbon into smaller particles.


Structured Carbon 2

Powdered carbon can be extruded into alternative configurations to provide enhanced performance.

Pellets can provide excellent performance with lower pressure

drop than granular carbon.

Honeycombs provide a fully structured media bed.


Structured Carbon 3

The structured activated carbon media is composed of a homogeneous structure. The composition is consistent throughout the entire structure.

The entire wall of each cell is composed of a combination of

activated carbon and ceramic binder.

The open structure in the media is critical to good mass transfer (and

performance).

2000X Magnification

Carbon

Binder


Honeycomb vs. Pellet: Performance

Activated Carbon Product Types

Granular Powder Pellets Honeycomb

Adsorption Kinetics

Pressure Drop

Slower

Lower

Faster

Higher

Traditional Revolutionary

Fast Kinetics

Low Pressure Drop

Ease of Use

Honeycomb vs. Pellet: Performance 1

Kinetic Performance and Mass Transfer Advantage

100%

84%

50%

12%

0%

100%

23%

0%0%

20%

40%

60%

80%

100%

120%

0 3 6 9 12

Depth in Bed, inches

Co

ncen

trati

on

in

Bed

, %

of

inle

t

Pellets - 100 ft/min

HM® Media - 500 ft/min



0.1

1

10

10 100 1000

Superficial Air Velocity, ft/min

Pre

ssu

re D

rop

, in

_H

2O

/ft_

bed

__

HM® Media

Pellet

Standard

Operating

Conditions

100 ft/min

3 in_H2O/ft_bed

500 ft/min

2 in_H2O/ft_bed

Improved Energy Efficiency – Reduced Pressure Drop

Pressure drop in honeycomb media is much lower than in traditional pellet media.


4

1

2

3

AIR IN

AIR OUT

New module(s)

added to Stage 4

Old module(s)

discarded from Stage 1

Modules in Stages 4,

3, and 2 each move

down one stage


0%

20%

40%

60%

80%

100%

0 1 2 3 4

1 3 42

0%

20%

40%

60%

80%

100%

0 1 2 3 4

1 3 42

0%

20%

40%

60%

80%

100%

0 1 2 3 4

STAGE 1 CONSUMED -

ROTATE HONEYCOMBS

1 3 42

Mass Transfer and Cube Rotation



Mass Transfer Advantage

The mass transfer of contaminants into the carbon

is faster and more efficient in the honeycomb media.

• Easier access to carbon

0.2 mm (honeycomb) vs. 2 mm (pellets)

• Shorter mass transfer zone at higher velocity

• Equivalent performance with 5X air flow

• Full removal of contaminants from air stream


Honeycomb vs. Pellet: Economics

Honeycomb vs. Pellet: Economics 1

Better Energy Efficiency

The pressure drop in honeycomb media is much lower

than in traditional, loose fill media.

• Lower energy consumption at higher velocities

• Smaller beds needed for same air volume

• Lower capital cost to provide equivalent performance

• Lower energy cost to move the air.


1000 CFM Vapor Adsorber

Pellet Versacomb™

Vapor Adsorber Cost Higher Lower

4 Year Cost Analysis

HEPA Final Filter Required Not Required

Carbon Replacement Every 3-4 years One fourth per year

Vacuum Truck Rental Required Not Required

Energy ($/kW-hr) Higher Lower

Total Cost @ yr 4 $1.5X $X

Honeycomb vs. Pellet: Economics 2


Questions?


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