EMISSIONS CONTROL SOLUTIONS DOWN TO A SCIENCE
The NESHAP standards are expressed as volumetric, dry CO concentrations (ppmvd) at 15% O2 (with the exception of standards for rich-burn SI engines, expressed as volumetric concentrations of HCHO at 15% O2). The standards must be met during any operating conditions, except during periods of start-up (of maximum 30 minutes). Emissions are tested at 100% load. Alternative compliance options are available in certain engine categories, expressed as percentage CO or HCHO emission reductions. These reductions can be achieved by retrofitting engines with such controls as oxidation catalysts. The standards for stationary diesel engines are listed in the following table.
This ruling affects existing stationary diesel engines in the following categories:
The emission standards apply to engines used for non-emergency purposes.
|Subcategory||Numerical Emission Standards (Except during Start-up)|
|Non-emergency CI 100=HP=300||230 ppmvd CO at 15% O2|
|Non-emergency CI 300||49 ppmvd CO at 15% O2 or 70% CO reduction|
|Non-Emergency CI >500 HP||23 ppmvd CO at 15% O2 or 70% CO reduction|
|Subcategory Numerical Emission Standards (Except during Start-up)|
|Non-Emergency CI 300||49 ppmvd CO at 15% O2 or 70% CO reduction|
|Non-Emergency CI>500 HP||23 ppmvd CO at 15% O2 or 70% CO reduction|
Diesel oxidation catalysts (DOC) are available and recommended by the EPA to meet the emission regulations. In addition, for engines greater than 500 HP a continuous parametric monitoring system (CPMS) must be utilized to measure pressure drop across the catalyst, as the pressure drop across the catalyst must not change by more than 2 inches of water from the pressure drop across the catalyst that was measured during the initial performance test. In addition, temperature must be measured to ensure that the catalyst inlet temperature is between 450F and 1350F.
|Table 2 NESHAP Emission Requirements for Stationary Gas (SI) Engines|
|Engine Category||Emission Standard||Alternative CO/HCHO Reduction|
|4SLB, Non-Emergency > 500 hp||47 ppmvd CO||93% CO|
|4SRB, Non-Emergency > 500 hp||2.7 ppmvd HCHO||76% HCHO|
|2SLB, Non-Emergency 100 <= hp <= 500||225 ppmvd CO||-|
|4SLB, Non-Emergency 100 <= hp <= 500||47 ppmvd CO||-|
|4SRB, Non-Emergency 100 <= hp <= 500||10.3 ppmvd HCHO||-|
|Landfill/Digester Gas, Non-Emergency 100 <=?hp?<=?500||177 ppmvd CO||-|
|4SRB, Non-Emergency > 500 hp||350 ppmvd HCHO||76% HCHO|
RICE NESHAP is an acronym for Reciprocating Internal Combustion Engines National Emission Standards for Hazardous Air Pollutants. In February 2010 the EPA officially made the RICE NESHAP ruling. The rule is intended to reduce emissions of toxic air pollutants such as formaldehyde, acetaldehyde, acrolein, methanol and other air toxics from several categories of previously unregulated stationary engines.
The US Environmental Protection Agency (EPA) issued a number of rules to control emissions of toxic air pollutants from existing stationary reciprocating internal combustion engines (RICE):
The rules, titled National Emission Standards for Hazardous Air Pollutants (NESHAP) for Reciprocating Internal Combustion Engines, are intended to reduce emissions of toxic air pollutants?such as formaldehyde (HCHO), acetaldehyde, acrolein, methanol and other air toxics?from several categories of previously unregulated stationary engines. The EPA has determined that carbon monoxide (CO) can be often used as an appropriate surrogate for formaldehyde. Since testing for CO emissions has many advantages over testing for emissions of hazardous air pollutants (HAP), most of the emission standards have been finalized in terms of CO as the only regulated pollutant.
The NESHAP standards discussed below are applicable to existing engines. Separate regulations have been adopted to control emissions from new stationary engines.
The NESHAP regulations for stationary engines are published in Title 40, Part 63, Subpart ZZZZ (63.6580) of the Code of Federal Regulations (CFR).