Collective Protection 2005

Design of Catalytic Process for the Removal of CW Agents and TIC’s

Cheryl Borruso1, Christopher J. Karwacki1, Michael J. Knapke2, Michael Parham1 and Joseph A. Rossin2

1Edgewood Chemical Biological Center 2Guild Associates, Inc. Research and Technology Directorate 5750 Shier-Rings Road

APG, Maryland 21010-5423 Dublin, Ohio 43016

IntroductionCatalytic Oxidation Technology is Well Suited for Military Air Purification Applications

1. Technology Non-selective: Agents and TIC’s reduced toCO2, H2O and haloacids

2. Elevated Temperatures may Offer Biological Decontamination

3. Unlimited Capacity for Agents and TIC’s: Catalytic sites not consumed during reaction

4. Technology lends itself well towards integration with many hostapplications

Introduction

Catalytic Process versus Chemical Threat1. Chemical threat; how catalytic process will be exposed to chemical

agent, differs greatly with how gas-mask and CP filters are tested.

2. During a chemical attack, a filtration device can be exposed to a rapidly increasing, high concentration of chemical agent that willdecay over time.

0

2 0 0 0

4 0 0 0

6 0 0 0

8 0 0 0

1 0 0 0 0

0 5 1 0 1 5 2 0T i m e , m i n

Con

cent

ratio

n, p

pm

Introduction: Catalytic Response1. Catalytic reaction rates can be highly non-linear in concentration.

Catalyst must be operated at conditions sufficient to achieve highdestruction efficiencies when challenged with high concentration of agent.

2. When exposed to high concentration of chemical agent, thetemperature within the catalyst will increase significantly in a shortperiod of time.

o Conversion will increase, as catalyst performance increasesexponentially with increasing temperature.

o For nitrogen-containing compounds (e.g HCN, NH3), product selectivity will shift from N2 to NOx with increasing temperature.

3. NOx (NO and NO2) is difficult to filter within the constraints of regeneration system. Therefore, catalytic process must be designed tominimize NOx formation during the destruction of nitrogen-containingcompounds.

Catalytic Destruction of Nitrogen-Containing Compounds

HCN + yO2 CO2 + ½N2 + ½H2O

Requirements:NO: Less than 30 mg/m3

NO2: Less than 5 mg/m3

N2O: Less than 60 mg/m3

CO2 + NOx + ½H2O

CO2 + ½N2O + ½H2O

Effects of Concentration of Reaction Rate

Rossin, 1995

0

20

40

60

80

100

0.001 0.01 0.1 1Residence Time, s

Con

vers

ion,

%

[HCN] = 1,650 ppm

Destruction of HCN at 310oC over Monolithic Oxidation Catalyst

[HCN] = 5,000 ppm

[HCN] = 10,000 ppm

Catalyst Thermal Response during Pulse of HCN

0

50

100

150

200

250

-2 0 2 4 6 8 10 12Catalyst Length, cm

Del

ta T

empe

ratu

re, o C

Time = 0 minTime = 30 secondsTime = 60 secondsTime = 120 seconds

Tin = 330oC[HCN] = 10,000 ppmTau = 0.33 sec

Rossin, 1995

Objective

Evaluate the use of an adsorption bed up-stream of the catalytic reactor to minimize NOx formation

o Adsorption bed expected to dampen high concentration spikesin chemical

o Chemical will be delivered to the catalyst at lower concentrations over longer time.

- Favorable reaction kinetics- Greater thermal management

o NOx formation will be reduced via lower catalyst temperatureand lower chemical concentration.

Catalytic Oxidation Process

1. Expose catalytic process to pulse of chemical

2. Record catalyst temperature in real time

3. Monitor NOx in real time using NO-NOx analyzer

4. Monitor concentration of N2O, CO2 and chemical in effluent stream using grab bags and discrete on-line analysis.

Catalytic Reactor Pre-Adsorption Bed

0

20

40

60

80

100

0 1 2 3 4 5Time, minutes

[NO

x] o

r [N

2O],

ppm

[NOx], ppm

[N2O], ppm [HCN] = 1,000 ppm for 4 minutes Tau: 0.40 sCatalyst: No-NOx

Tinlet = 320oC[H2O] = 2.5%

No Pre-Adsorber, Low Concentration

0

10

20

30

40

0 5 10Time, minutes

Del

ta T

empe

ratu

re, o C Inlet

Middle

Outlet

[HCN] = 1,000 ppm for 4 minutes Tau: 0.40 sCatalyst: No-NO x

Tinlet = 320oC[H2O] = 2.5%Pre-adsorber: None

No Pre-Adsorber, Low Concentration

No Pre-Adsorber, Insufficient Temperature

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

0 50 100 150 200Time, Seconds

[AC

] or

[CO

2], p

pm

[CO2][AC]

[HCN] = 5,000 ppm for 3 minutes Tau: 0.40 sCatalyst: No-NOx

Tinlet = 330oC[H2O] = 2.5%

No Pre-adsorber, Increased Temperature

0

100

200

300

400

500

600

700

800

900

1000

0 1 2 3 4 5T im e, m inu te s

[NO

x] o

r [N

2O],

ppm

[NO x], ppm

[N2O ], ppm

[H CN] = 5,000 ppm for 3 minutes Tau: 0.40 sCatalyst: No-NO x

Tinlet = 350oC[H 2O] = 2.5%

No Pre-adsorber, Increased Temperature

0

20

40

60

80

100

0 5 10Time, minutes

Del

ta T

empe

ratu

re, o C Inlet

Middle

Outlet

[HCN] = 5,000 ppm for 3 minutes Tau: 0.40 sCatalyst: No-NOx

Tinlet = 350oC[H 2O] = 2.5%Pre-adsorber: None

Use of Pre-adsorber for Destruction of HCN

0

200

400

600

800

1,000

0 5 10 15 20 25 30Time, minutes

[NO

x], p

pm

Pre-adsorber, 6,500 ppm HCN

No Pre-adsorber, 5,000 ppm HCN

3-Minute HCN PulseTau: 0.40 sCatalyst: No-NOx

Tinlet = 318oC[H2O] = 2.5%

52 ppm Maximum [NOx]

Use of Pre-adsorber for Destruction of HCN

0

20

40

60

80

100

0 5 10 15 20 25Time, minutes

Del

ta T

empe

ratu

re, o C

With Pre-adsorber, 6,500 ppm HCN

No Pre-adsorber, 5,000 ppm HCN

Catalyst Inlet Temperature During 3 Minute Pulse of HCNTau: 0.40 sCatalyst: No-NOx

[H2O] = 2.5%

Tin = 350oC

Tin = 320oC

0

20

40

60

80

100

120

140

0 5 10 15 20 25Time, minutes

[NO

x], p

pm

T = 318 CT = 331 CT = 345 C

[HCN] = 6,500ppm for 3 minutes 23,500 mg-min-m3

Tau: 0.40 sCatalyst: No-NOx

[H2O] = 2.5%

Use of Pre-adsorber for Destruction of HCN

Results: Destruction of Acetonitrile using pre-adsorption

0

10

20

30

40

50

0 10 20 30 40 50 60 70

Time, min

[NO

x], p

pm

T = 280 CT = 300 CT = 320 CT = 340 C

Catalyst: No-NOx

GHSV: 20,000[CH3CN]: 1,100 ppm (2,000 mg/m3 ) Duration: 10 minutesChallenge: 20,000 mg-min/m3

[H2O]: 4.3%

Results: Destruction of NH3 using pre-adsorption

0

20

40

60

80

100

0 20 40 60 80 100Time, min

[NO

x], m

g/m

3

300°C

312°C

325°C

338°C

[NH3] = 8,300 mg/m3 for 3 minutesCT = 25,000 mg-min/m3

2.5% H2O

Conclusions

1. NOx generation during destruction of nitrogen-containing compounds can be greatly minimized using a pre-adsorber.

2. Use of a pre-adsorption bed to minimize concentration excursions greatly improves catalyst performanceso Greatly reduced NOx formationo Improved thermal management

3. In the case of HCN, not able to meet low NOx requirements. Identification of improved adsorption materials should allow formeeting this objective.