GAS MONITORING IN AUTOMOTIVE INDUSTRY
The automotive industry is a major air pollution contributor and thus one of the most regulated industries in the world.
Several gas monitoring techniques are widely used in the automotive industry for measuring vehicle emissions. Typical applications include live on-board exhaust monitoring (CO, CO2, N2O, NOx, formaldehyde, acetaldehyde, oxygen and moisture), analysis of raw and dilute exhaust gas from the engine and tailpipe with gas-bags (CO2, N2O, NOx, CH4, EtOH, THC, H2S, SO2, NH3, formaldehyde and acetaldehyde), diesel Selective Catalytic Reduction (SCR) after-treatment monitoring (NH3) and the Sealed Housing for Evaporative Determination (SHED).
WHAT IS THE SHED (SEALED HOUSING FOR EVAPORATIVE DETERMINATION)?
In the automotive industry, regulatory requirements applying to qualification type testing procedures have been upgraded since the introduction of new gasoline mixes on the market. According to several industry codes and standards, evaporative losses from gas handling and storage system have to be tested and quantified for vehicle certification. Sealed Housing for Evaporative Determination (SHED) is used to measure evaporative emissions and it is used by the US Environmental Protection Agency (EPA). Photoacoustic spectroscopy (PAS) is approved technology by the US EPA as a measurement method for the SHED (regulation 40 CFR Part 1065.269). Vehicle, engine, and fuel testing is an important way for EPA to verify that emission standards are met.
WHAT TO MEASURE?
In the SHED testing, components of interest are ethanol, methanol and refrigerants (R-134a and HFO-1234yf). For example, when E10 gasoline (10% ethanol) is used, ethanol vapors escape from the tank and permeate through plastic materials (e.g., fuel tanks and fuel hoses). The US EPA prescribes a conservative 1.08 correction factor on conventional FID measurements to account for ethanol emissions. This is unless its vapor fraction is directly measured by advanced instruments. Various methods are approved for the ethanol measurement (e.g. GC-FID or PTR-MS) but PAS is currently the most practical one.
Refrigerants and methanol are measured for additional information. Methanol is leaking from windshield washing liquid container and frigerants from the refrigeration system. Performance of the conventionally used PAS analyzer only marginally meets the requirements. As emission levels drop, higher performance will be required from the PAS analyzer in the future.
The GASERA ONE SHED multi-gas analyzer unit was characterized against requirements for the SHED application in laboratory. The GASERA ONE SHED is an automatic and standalone measurement system that uses an external cavity quantum cascade laser (EC-QCL) as the light source. It meets the current EPA measurement specifications of ethanol and its detection limits are superior to previously used instrumentation:
- EtOH GASERA ONE SHED 23 ppb
- EtOH earlier limits 60 ppb
- The EPA required limit is 36 ppb
Ethanol and methanol can be measured simultaneously and distinguished from each other. The GASERA ONE SHED provides stable and reliable measurement results that are fully pressure and temperature compensated.