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Home , Catalytic converter

Knowledge to go Basic

Application description Emissions.

Theoretical background 1 Development of emissions based on Lambda (λ) values 12000 Rich burn (λ ≤ 1)

Characteristics: Advantage and disadvantage CXHY or HC (hydrocarbon, e.g. 10000 - Engines with air deficiency for rich engine: methane): (Lambda = 1): Fuel is therefore + High performance density Due to the lack of , not all lean engine not used efficiently fuel (HC) is combusted 8000 + Initial cost is lower than lean –> high C H value stoichiometric - Typical applications: burn engine X Y [mg/Nm³] Y engine Compressor stations CO ():

H + Secure operation X 6000 (comparable to engine Oxygen deficiency in the in ) + Low emissions with controls process to , C X CO NOX – High fuel consumption the inability of all CO molecules - Typical working range: to be converted into CO . As 4000 – High emissions (if not controlled) 2 C H λ~0.85 to 0.95 a result, fuel leaves the engine X Y O 2 – Not suitable for use with bio-gas incompletely burned or unburned. CO, NO CO, 2000 10% –> leads to high fuel consumption (HC slip) NOX ( oxides): O 2 NO ≤ NO max.: 0 X X low NOX component due to 0,9 1,1 1,3 1,5 1,7 1,9 incompletely burned or unburned fuel (HC) A/F-ratio (λ) –> no max. temperature development (so less thermal

NOX is generated)

In general: NOX: CxHy: Lean burn engines (λ > 1) The curve on the combustion NO = NO + NO –> measure C H + O –> CO + H O X 2 X Y 2 2 2 Characteristics: Advantage and disadvantage CxHy or HC (hydrocarbon, e.g. chart shifts, depending on the NO separately (combustion equation) X - Engines with excess air (lean for lean engine: methane): relation between air and fuel - NO components can fluctuate If excess oxygen levels are too 2 engines) + Suitable for use with bio-gas ratio widely high, the combustion temperature –> Fuel is used efficiently + High fuel efficiency - Consisting of fuel NO and is lowered such that the flame X - Typical applications: Gas thermal NO + Low in emissions temperature is no longer X compression, power supply for sufficient to burn up all of the - Highest NOx value = highest – May require oxidation catalyst hospitals, government buildings, fuel (HC) mechanical efficiency server buildings, sewage plants, – Higher initial cost –> Increased CXHY value mining NO (nitrogen oxides): X CO (carbon monoxide): - Typical working range: Excess oxygen in the combustion NOX > NOX max.: An elevated λ~1.05 to 1.3 process leads to the ability of the O2 level leads to a lowering of the CO molecules to combine with O to CO temperature, therefore low NOX 2 2 percentage (lower levels of –> Oxygen is left over

thermal NOX)

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Application description Engine Emissions.

Theoretical background 2

Correctly configuring the engineto prevent “knocking” and “spark failures” of the engine.

Setting options for rich engines Lambda Incorrect configuration of the –> Measurement before/after High NOx or HC values before

fuel/air mixture: TWC, see high NOX values TWC: Lean Burn Engine 100 % Load lean misfire Depending on the load point and before TWC –>  error caused on the specifications provided by by misfire: burnable gas Lambda X High NOx levels before TWC: 1,6 the engine manufacturers or the –> High temperatures in the composition, ambient Too much O 2 national emission regulations combustion chamber: Set temperature and humidity, –> No ignition takes place temperature and pressure lean High HC and/or NO values ignition in “earlier” direction X of the burnable gas, inlet 12:1 after TWC (3-way catalytic and check Lambda probe 8:1 air temperature after the Load Curve Lean Burn converter): Detonation etc. Uncontrolled combustion, or Lambda Lambda 1 Load Curve X self-ignition of the fuel 1 Setting options for lean engines ! Lambda 1 Engine 100 % Load High NOx levels before Selecitve Setting options CAUTION: rich Catalytic Reduction (SCR): for knocking: "Ignition point too early" leads Methan Number 65 85 100 –> Measurement before/after SCR, –> incandescent burnup to knocking, "ignition point too Too little O 2 see high NOX values before (combustion and oil residue) on late" leads to spark failures –> –> No ignition takes place SCR burner walls precise adjustment only possi- –> premature ignition ble with measuring instrumen- High NOx levels before SCR: rich misfire too much heat –> Ignition point too early –> new engines have knocking tation. "Guideline values" can –> Shift ignition point towards late sensors also have an effect on other parameters (e.g. lubricants, Too low methane count (often –> Stone impact, rattling chains Lambda principle representation temperatures etc.), which can Load fluctuation with bio-gas): etc. can to error signals lead to increased wear. –> low ignition temperature from the knocking sensor –> premature ignition (=acoustic)

Rich engine Lean engine Why a catalytic converter?

Secure engine operation Efficient operation General Rich engine Lean engine • Large engine adjustment corridor • Exact adjustment of the engine using measuring Principle: 3-way catalytic converter Oxidising catalytic "Lean misfire" or "rich misfire" instrument (testo 350) necessary (TWC): converter: • Small engine adjustment corridor Catalytic • In rich combustion engines, this is unusual converters - Controlled catalytic converter: Reduces CO and HC If engine incorrectly adjusted: • Exact adjustment of the engine using measuring increase the is controlled by a λ probe emissions; NOX emissions, instrument (testo 350) necessary to optimize • "Lean misfire" or "knocking risk" speed of a chem. reaction by (sensor which analyses the air/ however, are not reduced. catalyst life lowering the activation energy. fuel ratio in the flue gas of a Catalytic converters are not combustion process) SCR (Selective Catalytic used up themselves. - Reduces by up to Reduction) = DeNOx: 90%: CO and NOx and HC NOx reduction in exhaust * Counts in general for all engine applications - Optimum working range: gases λ~0.98 to 0.998

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Application description Engine Emissions.

Emissions Measurements Measurement point 1 efficiency test measurement Measurement point 2 emission test measurement Measurement ports Measurement point before the catalytic converter Measurement point after the catalytic converter - Drilled hole or short, welded-on piece with external thread (after the turbocharger) (at the end of the exhaust pipe) -  hole with internal thread, directly integrated into the Why are measurements Typical Why are measurements Typical exhaust gas exhaust pipe taken? properties: taken? properties: - Various flange solutions - Checking and inspecting - Temperature: approx. - Testing catalytic converter - Temperature: approx. engine efficiency +1,200 °F efficiency 490 °F - Error detection/analysis of the - Overpressure: up to approx. - Checking emission limits - Overpressure: no high engine’s operating conditions, 100 mbar (dependent on (dependent on national overpressure in the flue gas including engine control system turbocharger and catalytic emission standards) - NO X value: Values range - Optimum adjustment of the converter) according to local regulations engine in order to save fuel from 10-20 ppm to many 100s —> better efficiency ppm - Correct adjustment of the relations between ignition timing, excess air etc. of the engine

Typical measurement values with testo 350**: Typical measurement values with testo 350:

Meas. Meas. parameter Landfill gas Oil parameter Type of engine Limit values* O 8 % 5 to 6 % 8 to 10 % CO Natural gas 50-1,500 ppm 2 Alternative: Drop line from higher elevation to ground. Line can be heated or non-heated. NO 100 - 300 ppm 100 - 500 ppm 800 - 1000 ppm NO + NO2 Compression ignition (Diesel) 50-750 ppm Caution: Blow out line prior to sampling to remove moisture build up. NO2 30 - 60 ppm 90 - 110 ppm 10 - 20 ppm NO + NO2 Other 4- (gas engines) 50-750 ppm

CO 20 - 40 ppm 350 - 450 ppm 450 - 550 ppm NO + NO2 Other 2-stroke (gas engines) 50-750 ppm

CO2 10 % 13 % 7 to 8 % O2 Reference value 15% *dependant upon local regulations SO2 30 ppm 30 to 50 ppm ** lean burn engine

Practical information: i Information: i Excess air, fuel pressure, the timing of the engine or the Many measurement locations can often only be reached ambient temperature or humidity can have significant impact on the using a ladder, platform or similar. emission. Must consider all when tuning or adjusting engines.

* Counts in general for all engine applications

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Application description Engine Emissions.

Schematic of Engine Application

Emission measurement with testo 350 EMISSIONS 1 5 9 Current output 2 6 Turbocharger 10 Catalytic con- FUEL 3 7 Inlet valve verter (GAS) COMPRESSION INDUSTRY 4 8 Outlet valve OR HEAT Measurement point for Fresh air 2 emission test Engine Compressor measurement 5 or Heat 6 exchanger Catalytic converter OIL AIR 1 10 + 4 7 8 Measurement point for efficiency Cold test measurement POWER PUBLIC FUEL (DIESEL) 1 POWER GRID

Generator D 3

2 9

Typical combustion process in a CHP engine

I. The fuel/air mixture is drawn in by way of the IV. This causes a rotary motion of the crankshaft. VI. The turbocharger, driven by the exhaust gas, VII. The compressor or heat exchanger utilizes inlet valve. The rotary motion is converted into electricity by compresses the combustion air that is supplied the pressure or heat stored in the exhaust gas to the generator. to the engine. As a result, engine output is operate the system. II. The mixture is compressed and heated. increased while fuel consumption is reduced and V. Burnt up exhaust gas is ejected through the open III. Ignition of the fuel-air mixture (by a spark plug in emission levels are improved. outlet valve. richburn engines, by compression via self-ignition in diesel engines).

* Counts in general for all engine applications

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