NSPS & Tier 4 Catalyst Solutions


When it comes to Power Generation via Spark Ignited or Compression Ignition engines, trying to figure out the various EPA rules to maintain compliance can be very complicated.  Also the types of devices used to meet these regulations can be different depending on the engine tuning, type of fuel and strategy of the end user.  NESHAP, NSPS, RICE, Tier 4 Interim versus Tier 4 Final, what do all these acronyms mean?

A great deal of information can be found here:  https://www.epa.gov/stationary-engines
RICE – Reciprocating Internal Combustion Engine
NESHAP – National Emission Standard for Hazardous Air Pollutants
CFR Title 40> Chapter 1 > Subchapter C > Part 63 > Subpart ZZZZ
NSPS – New Source Performance Standards. There are two rules for this, one for Spark Ignited and one for Compression Ignition engines.
CFR Title 40 > Part 60 > Subpart JJJJ

What is Tier 4?

Tier 4 is an EPA rule designed to reduce harmful exhaust gases for diesel powered equipment. Tier 4 standards require significant emission reductions of particulate matter (PM) and Nitrogen Oxides (NOx). PM is defined as the black smoke/soot found in engine diesel engine exhaust, and NOx is defined as nitrogen monoxide and nitrogen dioxide.  The table below shows the Tier 4 Final emission limits by pollutant type.

Tier 4 Final Emission Limits by Pollutant
Pollutant Tier 4 Final (g/bhp-hr
Hydrocarbons (HC) 0.14
Nitrogen Oxides (NOx) 0.3
Carbon Monoxide (CO) 2.2
Particulate Matter (PM) 0.015

What do all these EPA rules mean?  Depending on the engine size, the duty cycle, the fuel type and the targeted regulation, the solution may be a lean burn oxidation catalyst, an NSCR (non-selective catalytic reduction or 3-way) catalyst, a Diesel Oxidation Catalyst, a Diesel Particulate Filter, and SCR Catalysts (selective catalytic reduction via use of urea as reductant).

Product types

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