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Required Information
To adequately size the appropriate catalyst for your application, the following information is needed:
Engine Classification
Is the engine an area or major source of HAP emissions? A major source of HAP emissions is defined as having the potential to emit 10 tons per year of a single HAP or 25 total tons per year of multiple HAPs. An area source is any source which is not classified as a major source.
Engine Specifications
Brake Horsepower
Exhaust Flow Rate
Displacement
Maximum Allowable Backpressure
Fuel Type
Emission Requirements
What amount of pollutant is present in the exhaust stream and how much reduction is required?
Exhaust Temperature at Catalyst Location
The temperature of the exhaust at the location where the catalyst is to be placed is essential to the catalyst performance. The exhaust temperature at the catalyst must remain between 450F and 1350F. Generally, higher temperatures yield more efficient emission reduction.
Installation/Maintenance Space
Is there adequate space to install the catalyst unit or combination catalyst/silencer unit? Space and accessibility for periodic maintenance must also be considered.
Considerations
In addition to determining compliance, some additional considerations must be taken into account for each application.
Low Sulfur Diesel Fuel
Use of high sulfur fuel (>15 ppm) is prohibited by the new regulations. If unsure about the current fuel being used, a diesel sulfur test kit can be purchased.
Required Engine Backpressure
What is the maximum allowable backpressure of the specific engine? How much backpressure is being applied to the engine with the current exhaust system? Incorporating a catalyst into the current exhaust system may add an additional 5 to 10 in-H2O of backpressure to the engine and could exceed the backpressure limits of the engine. Appropriate sizing and calculations will need to be performed to ensure proper backpressure.
Catalyst Placement
Placement of the catalyst within the exhaust system is pivotal in the effectiveness of the catalyst in reducing emissions from the engine as most catalysts require temperatures in excess of 450°F to operate efficiently. In cases where the catalyst must be located further down the exhaust stream, insulation around the exhaust system may be required to maintain a temperature suitable for an effective catalytic reaction. Colder climates may also require insulation of the exhaust system to maintain performance. To assure system performance the catalyst must be mounted upstream of any silencer within the system.
Exhaust/Catalyst Support Structure
Before installation of the catalyst system, the support system needs to be evaluated. Larger systems require additional supports as the connecting pipe will not be able to support the weight of the catalyst. A steel ladder support system may be required.
Service Requirements
Habitually catalysts require servicing every 8,700 hours of operation. To facilitate service requirements the catalyst system needs to be place where it is easily accessible. This will allow for easy access and removal of the catalyst without special equipment.
Compliance Testing and Monitoring
The new regulations require compliance testing of all engines requiring additional catalyst systems. Emissions are tested before and after the addition of a catalyst system to ensure the required emission reduction is met. Additional monitoring of the catalyst system must also be performed. Catalyst temperature recorded at the inlet of the catalyst must be continuously monitored and the pressure drop across the catalyst must be measured monthly to maintain compliance.
