Emissions Catalyst Design using GT-SUITE. Dr. Chaitanya Sampara Viridis Chemicals Private Limited

Transcription

1 Emissions Catalyst Design using GT-SUITE Dr. Chaitanya Sampara Viridis Chemicals Private Limited

2 Viridis Chemicals Background Originated at KSRM College of Engineering (212) Research Focus Develop tailored reaction kinetics for exhaust aftertreatment catalysts» Urea-SCR catalyst kinetics for MAN (Germany) Develop non-pgm based catalysts for Automotive and Petroleum» Light Naphtha Isomerization Catalyst (Indian Oil Corporation)

3 Exhaust Aftertreatment - Motivation Bharat IV standards Euro IV 1 year lag Why is aftertreatreatment modeling required? Minimize Platinum group metals (PGM) Implications of catalyst positioning Cost Saving! Effect of fuel/additives on catalyst Create IP new materials and systems Rigorous architecture by GTI User friendly GUI Robust mathematical architecture» Wide range of physics and chemistry

4 In-Cylinder Pressure Diesel Aftertreatment Perennial soot-no x trade-off Reductant dosing DOC SCR Diesel Engine Hydrocarbon Injection` DOC DPF Exotherm Hydrocarbon Injection` PCI combustion DOC Exotherm LNT HCs & CO DOC Clean-up HCs and CO Crank Angle

5 DOC Reactor Modeling Physics Heat loss Active metal - Platinum Washcoat - Alumina Chemistry Substrate - Cordierite Hot Bulk Transport Gas Harmless species & products heat Conduction HC CO O 2 CO 2 H 2 O CO 2 H 2 O ~ > o C o C Noble metal Zeolite Transport (Physics) common for aftertreatment components (except DPF) Heat & Mass Transfer Devices different only w.r.t their Chemistry Device can have different catalyst compositions (Pt, Pd, Rh etc.)» Different reaction kinetics required

6 DOC Chemistry Model set-up Reaction kinetics (Catalyst specific) CO, NO, H 2 THC How much Pt is available for reaction? Site-density (mol Pt /m 3 ) Site density = Pt * Dispersion» Fast oxidizing hydrocarbons C 3 H 6» High mol.wt HC chains C 12 H 26» High mol.wt HC rings C 7 H 8 Global Rate Expressions (Pt) Accessible Inaccessible r CO (1 K CO k c CO CO c ) CO 2 c 1 O2 K NO c NO Dispersion» Experimental Measurements» Lowered by high temperature exposure (closer to exhaust port)

7 Representative DOC Property Value V 3.2L Cpsi 4 w 2 g/s Platinum loading 8 g/ft 3 22% Dispersion Conventional vs. PCI combustion Inlet Temperature [ o C] o C/min Typical ramp rate Species Conventional (ppm) PCI (ppm) CO 7 3 C 3 H DF1 1 8 DF2 1 8 NO 15 4 O 2 13% 5% Time [s]

8 DOC Conventional Exhaust r oxn, HC K c 1 K c CO k CO c s, CO s, HC c s, O NO s, NO CO reaction starts in the rear end of the catalyst Reduced inhibition DF1 adsorbed HCs on zeolite Minimize cold-start HCs

9 DOC Conventional vs. PCI Exhaust 1 1 CO conversion [%] T 5 shifted by 5 o C CO conv in = 7 ppm O 2 conv = 13% CO in PCI = 3 ppm O 2 PCI = 5% THC conversion [%] Higher cold start HC emissions THC conv = 4 ppm in O 2 conv = 13% THC in PCI =26 ppm O 2 PCI = 5% T 5 shifted by 45 o C NO conversion [%] Temperature [ o C] NO conv in = 15 ppm O 2 conv = 13% NO in PCI = 4 ppm O 2 PCI = 5% Temperature [ o C] Catalyst Design 8 g/ft 3 of Pt Temperature [ o C] 22% Dispersion Loss of catalyst efficacy T 5 shifted by ~ 5 o C High cold-start HC emissions

10 Catalyst Loading Cost Advantage Catalyst performance with PCI exhaust matched with T 5 of conventional exhaust 8 g/ft 3 vs. 5 g/ft Pt Equivalent catalyst performance with increased dispersion Better dispersion possible by modifying support material Cost saving with better understanding of parameters CO Conversion [%] CO Conversion [%] Increased disperion from 22% to 47% Temperature [ o C] Conventional PCI PCI Increased Pt loading from 8 g/ft 3 to 5 g/ft 3 Conventional PCI PCI Increased Pt loading from 8 g/ft 3 to 25 g/ft Temperature [ o C]

11 Zoned DOC design Varying Pt loading Proposed zoned catalyst design Possible during catalyst coating 2% of front end 5% lower loading Overall cost saving 1-15% Pt saving New IP generation High surface area Alumina Higher Pt-Alumina interaction» Higher dispersion g/ft 3 25 g/ft^3 Zone DOC Design Conventional PCI-DOC 5g/ft 3 PCI-DOC Zoned Zone g/ft 3 and 4% Dispersion Zone 2 25 g/ft 3 and 45% Dispersion

12 Optimizing Cold-Start HC Emissions (?) Baseline Case 8 g/ft^3 Pt + Zeolite 4 ppm THC (C 3 basis) Increased Zeolite 3x increase 25% lower THC emissions Mass transfer implications Increase Ramp-rate 1.5x increase 1 o C/min 2 o C/min 55% lower THC emissions THC Conversion [%] THC Conversion [%] THC conversion [%] Zeolite Loading = Baseline Conventional - Baseline Conventional - 3x higher Zeolite Ramp = 1 o C/min 25% lower THC Emissions Temperature [ o C] Inlet Temperature [ o C] Baseline 3x higher Zeolite 1.5x high Zeolite - 2 o C/min 55% lower THC Emissions Inlet Temperature [ o C]

13 Sulfur Effects Bharat IV regulation Sulfur ~ 5 ppm (max) Sulfur in fuel as SO 2 in exhaust SO 2 SO 3 H 2 SO 4 Damages support and Platinum SO 4 + Pt Pt SO 4 * Strong bond with Pt Decomposition at 6 o C Kinetics for SO 2 /SO 3 developed for Pt and Support» Collaboration with University of Houston, Cummins R&D (US) Need detailed kinetics (micro-kinetics) to capture effects accurately Global kinetics not viable

14 Model Set-up Parametric Studies Challenge Incorporate global and micro-kinetics in same model Strategy: Incorporate kinetics for CO, THC and NO as before (Global) SO 2 (g) + Pt Pt SO 2 Incorporate micro-kinetic network for SO2 adsorption on Pt Multiply vacant sites (Pt) with global rates to get actual rates All other parameters remain the same

15 Effect of SO 2 Concentration on DOC 1 Profile shows the vacant Pt site available for reaction at various times Only 7% sites available in SS T 5 shift ~ 39 o C Coverage of SO 2 nearly constant for typical concentration ranges Vacant site [%] s 5s 8s 1s 14s Axial Location [z/l] CO - Base Case CO - 25ppm SO 2 CO - 5ppm SO 2 Other species show similar trend Conversion [%] T 5 shifted by 39 o C with 25,5 ppm SO Temperature [ o C]

16 Conclusions GT-SUITE a powerful tool for aftertreatment modeling System Design Cost Saving! Minimize PGM Develop new IP for aftertreatment materials Chemistry is catalyst specific needs adaptation for new system DOC Pt, Pt/Pd (2:1), Pt/Pd (1:2) etc. For the same catalyst loading and dispersion can vary Ask your catalyst supplier for these numbers

17 Customer Specific Chemistry Development Viridis bench scale reactor to develop customer specific catalyst models (reaction kinetics) Consultation for aftertreatment system design Developed NH 3 -SCR catalyst kinetics for MAN Turbo & Diesel 213/14

18 Questions?

19 Varying heat-up rates Cold-start HC Emissions 1C/min 2C/min 4C/min 9C/min

20 Back-up Slides Swedish Low Sulfur Diesel Fuel Speciation Data Speciation Data - Han et al. (27)