Emission Control Technology for Stationary Diesel Engines Rasto Brezny September 13, 2013 Manufacturers of Emission Controls Association www.meca.org www.dieselretrofit.org
Outline Compliance Challenges Catalysts for RICE NESHAP Diesel oxidation strategies NOx reduction strategies Diesel particulate filters (DPF) Summary and recommendations
MECA Background Founded in 1976 to be the Technical Spokesperson for the emission control industry Manufacturers of emission controls primarily for sale to others Currently, 44 members Member companies have over 40 years of experience and a proven track record of success in developing and manufacturing emission control technology Members cover diverse range of emission control technologies for both new and existing engines/vehicles: Catalytic Converters (All Fuels) Diesel Particulate Filters System integration Sensor Technologies
Compliance Challenges Many legacy engines affected by NESHAP rule May require retrofit of equipment, and maintenance practices Some operators may not have expertise with emission control systems or maintenance practices EPA has no product certification or verification standards for RICE NESHAP catalysts Compliance is determined by a stack emissions test Ensure that equipment vendor and installer provides a suitable warranty
Stationary Engine Profile Drives Oxidation Technology Selection Fuel: Natural Gas Combustion: Fuel-Rich Emissions: CO, HC, VOC Technology: NSCR Fuel: Natural Gas Combustion: Fuel-Lean Emissions: CO, HC, VOC Technology: Ox Cat Fuel: Diesel (500 ppm S max) Emissions: CO, HC, VOC, PM Technology: DOC
DOCs Form the Technology Base for Reducing HAP Emissions from New and In-Use Diesel Engines Diesel Oxidation Catalysts CO Aldehydes HC PAH SO 2 NO Flow through monolith with catalytic coating CO 2 H 2 O SO 2 /SO 3 NO 2 Catalytic Surface (Precious Metal) Substrate (Metal foil) Simplest most cost effective solution to reducing CO and Toxics Typically 95% CO, 80-85% HC and 20-50% PM >70% aldehydes, 80-95% HAPs Applicable to nearly all diesel engines; significant retrofit & OE experience base Fuel sulfur below 500 ppm S
Oxidation Catalyst - Maintenance and Lifespan If applied properly, an oxidation catalyst technology is relatively maintenance free However, certain engine upset conditions can affect the performance and lifespan of oxidation catalyst technology Thermal deactivation: temperatures > 700 C (1300 F) Bad injectors 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) Turbo failure Failure due to improper engine maintenance may void catalyst warranty
Oxidation Catalysts and Converters Converters can be mounted in-line, before the silencer (cheapest solution) OE Silencer can be replaced with combination catalytic silencer
Custom HAP converters can be designed to match engine and site limitations
Exhaust Monitors are Essential Hardware Monitors your system so that the pressure drop across the catalyst is below engine specifications. Monitors the exhaust temperature and calculates a four hour rolling average to protect against overheating. Alarm signal if the catalyst inlet temperature and/or catalyst differential pressure are out of the required ranges Stores data for reporting purposes
In-Line Converter Installations
Selective Catalytic Reduction (SCR) Reduce NOx with SCR catalyst using reducing agents: aqueous NH 3 anhydrous NH 3 Urea (decomposes to ammonia above 200 o C) Best Available Control Technology (BACT) (>95%) First use on stationary engines in the 1980 s Stationary engines with SCR: from 100 s of KW to 20+ MW Tolerant to a variety of fuels Two different catalyst options Vanadia or Zeolite Reactor designed to house a number of catalyst blocks to satisfy performance requirements.
Many different formats of SCR catalysts Coated ceramic or corrugated metallic honeycomb (low dust applications, low backpressure, compact) Coated expanded metal plate (high dust applications, low backpressure, variable pitch) Extruded honeycomb
SCR System Layout
Ammonia dosage control is critical Catalyst has optimal NOx/ammonia operating range. Urea dosing depends on engine out NOx to minimize ammonia slip (< 10 ppm) Ammonia clean-up catalyst may be used
SCR Installations Cat 3516 diesel engines Dynamic load following 90% NOx reduction Skid-mounted, portable Remote locations Turnkey application ULSD Cummins QSK78 (3500 Hp) Emissions reductions achieved: 94.6% Nox 98% PM 96% CO 92% VOC <10 ppm NH3 slip
Wall-Flow Diesel Particulate Filters Offer the Highest PM Filtration Efficiency >85% PM reduction Large reduction in toxics from catalyzed DPFs Over 1000 DPFs on stationary engines in US >250,000 truck retrofits worldwide Same technology as on all new MY 2007 and newer OE trucks DOC Catalyst Ceramic Soot Filter Passively regenerated DPFs employ catalysts and available exhaust heat to burn captured soot specified exhaust temperature requirements Actively regenerated DPFs use external heat such as burner or electric to burn soot on filter
Ball Park Converter Costs Technology Approximate Reduction Approx. Cost Range/hp (uninstalled) Oxidation Converter >70%CO, >80% HC $8-$10/hp (HAP) Converter 30% PM SCR 90% NOx $110-$30/hp (500-3000 hp) Diesel Particulate >85%PM $35-$25/hp Filter >70%CO, >80%HC (500-3000 hp)
Summary SCR, DOCs and DPFs are mature and effective means to control emissions from stationary diesel engines Diesel oxidation catalysts represent the lowest cost solutions to reduce hazardous air pollutants. Catalyst designs can be tailored to develop the most cost effective solution for the application. Proper engine maintenance is essential for catalyst performance and durability
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