Oxidation Technologies for Stationary Rich and Lean Burn Engines

Transcription

1 Oxidation Technologies for Stationary Rich and Lean Burn Engines ICAC MARAMA Advances in Air Pollution Control Technologies May 18-19, 2011 Baltimore, MD 1

2 Overview Oxidation catalyst technologies Oxidation catalyst Diesel oxidation catalyst (DOC) NSCR (Three-way catalyst) Maintenance Advances in emission control Substrates Systems Selections of catalyst for challenging applications Applications on stationary engines Case study Summary 2

3 Oxidation catalyst: General characteristics CO HC VOCs HAPs SO 2 NO Activity 100% 80% CO CH 2 O Passive technology will oxidize everything that it contacts, but not necessarily to the same degree. CONVERSION, % 60% 40% NMNEHC 50% UNSATURATED SO 2 TO SO 3 NO TO NO 2 The catalyst performance for each compound typically determined by residence time (i.e. catalyst volume) & operating temperature. 20% Selectivity 0% TEMPERATURE, O F Generic 90% CO conversion case shown Catalyst formulation may be customized to enhance or inhibit certain reaction pathways. 99% CO conversion possible with additional catalyst volume 3

4 Diesel oxidation catalyst Diesel particulate matter What is it? Carbon soot Soluble organic fraction Sulfate and water Ash D O C Applicable for diesel fuel < 500 ppm S Soluble organic fraction CO & hydrocarbons 20% - 50% PM reduction > 90% Ash, carbon soot, sulfate & water Aldehydes > 70% SO 2 Some oxidation to SO 3 No impact 4

5 NSCR on rich burn engines (NSCR = Non-Selective Catalytic Reduction) Generic engine emissions profile inlet to NSCR catalyst Fuel Rich Fuel Lean Engine operates slightly fuel rich Air-fuel ratio controller required to maintain balanced engine emissions (NO X, CO, HC) for stable catalyst performance Catalyst depletes O 2 via oxidation reactions then reduces NO X using remaining CO, H 2, and HC as reagents. Typical reductions: 90% - 99% NO X 90% - 99% CO 50% - 90% HC 80% - 95% CH 2 O 80% - 95% HAPs 5

6 Oxidation catalyst: Maintenance and lifespan If applied properly, an oxidation catalyst technology NSCR DOC oxidation catalyst ammonia destruction catalyst does not need regular maintenance No moving parts No chemical reagents However, certain engine upset conditions can affect the performance and lifespan of oxidation catalyst technology Thermal deactivation Very high temperatures > 700 C (1300 F) (varies by formulation) Catalyst poisoning from Use of high sulfur diesel fuel (e.g. 2,000 ppm S) Certain lube oil and lube oil additives (e.g. Zn, P) In some cases, catalyst may be regenerated with proper cleaning to extend its useful life 6

7 Overview Oxidation catalyst technologies Oxidation catalyst Diesel oxidation catalyst (DOC) NSCR (Three-way catalyst) Maintenance Advances in emission control Substrates Systems Selections of catalyst for challenging applications Applications on stationary engines Case study Summary 7

8 Substrates offer versatility in technology applications Metal substrate Low pressure drop High surface area Design flexibility to address application specific constraints on space Ceramic substrate Well-suited for washing to extend useful life Resistant to acid gas environments 8

9 System packaging of multiple technologies allows for optimization Each component in an integrated catalyst technology system is considered for: Its contributions toward the overall required performance Its impact on other installed technologies urea DOC DPF or CSF SCR AMOX A DOC installed upstream of the particulate collection element may be optimized for activity: high VOC conversion at higher temperatures. An ammonia destruction (AMOx) catalyst installed downstream of the SCR may be optimized for selectivity: high NH 3 slip conversion to N 2 rather than NO X, at lower temperatures. 9

10 Selection challenges: Ammonia Destruction Catalyst (AD) Ammonia Destruction Catalyst (AD) installed downstream on an SCR system: Minimizes NH 3 slip emissions Extends working life of SCR systems Promotes reliable operation of load-mapped urea/ammonia injection control systems N 2 NO X NH 3 CONVERSION, % NH 3 N TEMPERATURE, C NH 3 NO X NH 3 10

11 Selection challenges: Biofuels for stationary engines Catalyst issues posed by biofueled stationary engines: Biodiesel is an effective solvent, can dissolve engine/component deposits. Ethanol corrosive to pipelines and older fuel systems components. Trace contaminants in exhaust stream originating in biofuel: Processing catalysts: Na, K, Cu, Ni Alkali metals and alkaline earth metals: Mg, Ca, Na, K Siloxanes typical contaminant in landfill gas. When biofuels are blended into the main fuel, what is the real fuel specification? Early adopters of oxidation catalyst technologies on biofueled stationary engines have been successful in EU (~ 200 engines) 11

12 Biofuels pose complex challenges for oxidation catalyst technology May impact catalyst performance as poisons and/or masking agents Trace contaminants from production processes + Trace elements in soil & water Graphic source: Vermont Sustainable Jobs Fund ( 12

13 Each biofuel may exhibit a unique catalyst contaminant profile Oxidation catalyst profile after 24 hour trial of soy-based biofuel blended into natural gas feedstock 13

14 Selection challenges: Perspectives on VOCs The term VOCs represents a class of compounds (~ 200+ unique VOCs ) There is no one compound that may characterize the reaction of all VOCs across a given oxidation catalyst technology Propane H H H H C C C H H H H Propylene H H H C C H C H H C3 - saturated compound Single bonds only Ignition temp ~ 770F Difficult to react across catalyst C3 - unsaturated compound Double bond present Ignition temp ~ 500F Easy to react across catalyst Control of specific VOCs may require customized catalyst formulations to offset operating condition limitations (e.g. operating temperature) 14

15 Overview Oxidation catalyst technologies Oxidation catalyst Diesel oxidation catalyst (DOC) NSCR (Three-way catalyst) Maintenance Advances in emission control Substrates Systems Selections of catalyst for challenging applications Applications on stationary engines Case study Summary 15

16 Case Study: 2-stroke engines in California In , an owner/operator of several 2-stroke diesel engines in California follows a Compliance Plan approved by SCAQMD and EPA and operates under variance to collect data necessary to determine: If a controlled emission of 30 ppmvd VOC is sustainable on the 2- stroke engines in question If not, to determine an appropriate alternative limit as allowed by SCAQMD Rule A standard oxidation catalyst formulation for stationary diesel engines is used and preferred as an economically feasible solution. 16

17 Case Study: CA Rule VOC Emissions California - Rule (Amended 7/9/10) Purpose Reduce Oxides of Nitrogen (NOx), Volatile Organic Compounds (VOCs), and Carbon Monoxide from engines (CO). Applicability All stationary and portable engines over 50 rated brake horsepower (bhp) VOC as defined in Rule 102 Rule 102: Any volatile compound of carbon, excluding methane, carbon monoxide, carbon dioxide, carbonic acid, metallic carbides or carbonates, ammonium carbonate, and exempt compounds SCAQMD Method 25.3, used for compliance testing, identifies ethane as an exempt compound 17

18 Case Study: CA Rule VOC Emissions VOC concentration limit 30 ppmvd Effective 7/1/10 stationary engines > 500 hp Effective 7/1/11 all stationary engines Rule (d) (1) (B) If the operator of a two-stroke engine equipped with an oxidation catalyst and insulated exhaust ducts and catalyst housing demonstrates that the CO and VOC limits effective on and after July 1, 2010 are not achievable, then the Executive Officer may, with United States Environmental Protection Agency (EPA) approval, establish technologically achievable, case-by-case CO and VOC limits in place of the concentration limits effective on and after July 1, The case-by-case limits shall not exceed 250 ppmvd VOC and 2000 ppmvd CO. 18

19 Case Study: Mega-trends in 2-stroke engine data 1.00 Temperature drives catalyst performance 0.90 TEMP/1000; VOC DESTRUCTION EFFICIENCY Field measurements are always a challenge 0.00 Temp (F) TNMNE Methane Ethane Ethene Propane Butane COMPOUND Engine 1 Engine 2 Engine 3 Data collected in 2010 by Method 18 Measurement of Gaseous Organic Compound Emissions by Gas Chromatography 19

20 Case Study: Mega-trends in 2-stroke engine data Changes in the engine combustion profile with engine load may affect compliance VOC speciation and exhaust temperature 20

21 Case Study: 2-Stroke engines in California Control of VOC emissions on a 2-stroke stationary engine poses intrinsic challenges to oxidation catalyst technology: Catalyst performance is driven by operating temperature of engine VOC speciation profile may change with engine load (combustion characteristics) Compliance may be driven by both catalyst and engine Engine owner/operator continues to work with catalyst supplier and State of California pursuant to Rule (d) (1) (B) to determine what is technologically achievable and measureable on a consistent and reliable basis. 21

22 Overview Oxidation catalyst technologies Oxidation catalyst Diesel oxidation catalyst (DOC) NSCR (Three-way catalyst) Maintenance Advances in emission control Substrates Systems Selections of catalyst for challenging applications Applications on stationary engines Case study Summary 22

23 Summary Oxidation catalyst technologies offer: Historically proven success of controlling emissions from a wide variety of combustion sources, including stationary engines 23

24 Summary Oxidation catalyst technologies offer: Robust and mature technology whose cost is directly related to the level of performance required and the identity of those compounds (CO, HCs, VOCs, HAPs, NO X for rich burn engines) whose emissions are to be controlled RELATIVE CATALYST VOLUME FOR FIXED CONVERSION CO C7H8 C6H14 C5H12 C4H10 C3H8 C2H6 24

25 Summary Oxidation catalyst technologies offer: A future of continued innovation into new applications and price/performance optimization of existing applications to ensure sustainable development 25

26 Questions? Catalytic Surface (Precious Metal) Substrate Schematic of honeycomb oxidation catalyst STAN MACK BUSINESS MANAGER STATIONARY SOURCE WILLIAM HIZNY TECH. PROJECTS MGR STATIONARY SOURCE BASF CORPORATION 2655 ROUTE 22 WEST UNION, NJ