Collective Protection 2005

Transcription

1 Collective Protection 25 Design of Catalytic Process for the Removal of CW Agents and TIC s Cheryl Borruso 1, Christopher J. Karwacki 1, Michael J. Knapke 2, Michael Parham 1 and Joseph A. Rossin 2 1 Edgewood Chemical Biological Center 2 Guild Associates, Inc. Research and Technology Directorate 575 Shier-Rings Road APG, Maryland Dublin, Ohio 4316

2 Introduction Catalytic Oxidation Technology is Well Suited for Military Air Purification Applications 1. Technology Non-selective: Agents and TIC s reduced to CO 2, H 2 O 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 host applications

3 Introduction Catalytic Process versus Chemical Threat 1. 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 will decay over time. Concentration, ppm T i m e, m i n

4 Introduction: Catalytic Response 1. Catalytic reaction rates can be highly non-linear in concentration. Catalyst must be operated at conditions sufficient to achieve high destruction efficiencies when challenged with high concentration of agent. 2. When exposed to high concentration of chemical agent, the temperature within the catalyst will increase significantly in a short period of time. o Conversion will increase, as catalyst performance increases exponentially with increasing temperature. o For nitrogen-containing compounds (e.g HCN, NH 3 ), product selectivity will shift from N 2 to NO x with increasing temperature. 3. NO x (NO and NO 2 ) is difficult to filter within the constraints of regeneration system. Therefore, catalytic process must be designed to minimize NO x formation during the destruction of nitrogen-containing compounds.

5 Catalytic Destruction of Nitrogen-Containing Compounds CO 2 + NO x + ½H 2 O HCN + yo 2 CO 2 + ½N 2 + ½H 2 O CO 2 + ½N 2 O + ½H 2 O Requirements: NO: Less than 3 mg/m 3 NO 2 : Less than 5 mg/m 3 N 2 O: Less than 6 mg/m 3

6 Effects of Concentration of Reaction Rate 1 Destruction of HCN at 31 o C over Monolithic Oxidation Catalyst 8 [HCN] = 1,65 ppm Conversion, % 6 4 [HCN] = 5, ppm 2 [HCN] = 1, ppm Residence Time, s Rossin, 1995

7 Catalyst Thermal Response during Pulse of HCN 25 2 T in = 33 o C [HCN] = 1, ppm Tau =.33 sec Delta Temperature, o C 15 1 Time = min Time = 3 seconds Time = 6 seconds Time = 12 seconds Catalyst Length, cm Rossin, 1995

8 Objective Evaluate the use of an adsorption bed up-stream of the catalytic reactor to minimize NO x formation o Adsorption bed expected to dampen high concentration spikes in chemical o Chemical will be delivered to the catalyst at lower concentrations over longer time. - Favorable reaction kinetics - Greater thermal management o NO x formation will be reduced via lower catalyst temperature and lower chemical concentration.

9 Catalytic Oxidation Process Catalytic Reactor Pre-Adsorption Bed 1. Expose catalytic process to pulse of chemical 2. Record catalyst temperature in real time 3. Monitor NO x in real time using NO-NO x analyzer 4. Monitor concentration of N 2 O, CO 2 and chemical in effluent stream using grab bags and discrete on-line analysis.

10 No Pre-Adsorber, Low Concentration [NO x ] or [N 2 O], ppm [NOx], ppm [N2O], ppm [HCN] = 1, ppm for 4 minutes Tau:.4 s Catalyst: No-NO x T inlet = 32 o C [H 2 O] = 2.5% Time, minutes

11 No Pre-Adsorber, Low Concentration Delta Temperature, o C Inlet Middle Outlet [HCN] = 1, ppm for 4 minutes Tau:.4 s Catalyst: No-NO x T inlet = 32 o C [H 2 O] = 2.5% Pre-adsorber: None 5 1 Time, minutes

12 No Pre-Adsorber, Insufficient Temperature 4, 3,5 3, [HCN] = 5, ppm for 3 minutes Tau:.4 s Catalyst: No-NO x T inlet = 33 o C [H 2 O] = 2.5% [AC] or [CO 2 ], ppm 2,5 2, 1,5 1, 5 [CO2] [AC] Time, Seconds

13 No Pre-adsorber, Increased Temperature [NOx], ppm [N2O], ppm [NO x ] or [N 2 O], ppm [HCN] = 5, ppm for 3 minutes Tau:.4 s Catalyst: No-NO x T inlet = 35 o C [H 2 O] = 2.5% Time, minutes

14 No Pre-adsorber, Increased Temperature 1 Delta Temperature, o C Inlet Middle Outlet [HCN] = 5, ppm for 3 minutes Tau:.4 s Catalyst: No-NO x T inlet = 35 o C [H 2 O] = 2.5% Pre-adsorber: None Time, minutes

15 Use of Pre-adsorber for Destruction of HCN 1, Pre-adsorber, 6,5 ppm HCN 8 No Pre-adsorber, 5, ppm HCN [NO x ], ppm Minute HCN Pulse Tau:.4 s Catalyst: No-NO x T inlet = 318 o C [H 2 O] = 2.5% 2 52 ppm Maximum [NO x ] Time, minutes

16 Use of Pre-adsorber for Destruction of HCN 1 8 Catalyst Inlet Temperature During 3 Minute Pulse of HCN Tau:.4 s Catalyst: No-NO x [H 2 O] = 2.5% Delta Temperature, o C 6 4 T in = 35 o C With Pre-adsorber, 6,5 ppm HCN No Pre-adsorber, 5, ppm HCN T in = 32 o C Time, minutes

17 Use of Pre-adsorber for Destruction of HCN T = 318 C T = 331 C T = 345 C [HCN] = 6,5ppm for 3 minutes 23,5 mg-min-m 3 Tau:.4 s Catalyst: No-NO x [H 2 O] = 2.5% [NO x ], ppm Time, minutes

18 Results: Destruction of Acetonitrile using pre-adsorption 5 4 Catalyst: No-NO x GHSV: 2, [CH 3 CN]: 1,1 ppm (2, mg/m 3 ) Duration: 1 minutes Challenge: 2, mg-min/m 3 [H 2 O]: 4.3% T = 28 C T = 3 C T = 32 C T = 34 C [NO x ], ppm Time, min

19 Results: Destruction of NH 3 using pre-adsorption C 312 C 325 C [NH 3 ] = 8,3 mg/m 3 for 3 minutes CT = 25, mg-min/m 3 2.5% H 2 O [NO x ], mg/m C Time, min

20 Conclusions 1. NO x 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 performances o Greatly reduced NO x formation o Improved thermal management 3. In the case of HCN, not able to meet low NO x requirements. Identification of improved adsorption materials should allow for meeting this objective.