What’s the difference between Laser emissions sensors and the other technologies such as NDIR and CLD?
Emsys utilises a Quantum Cascade laser (QCL) sensor to measure emissions concentrations. The sensor is multi-channeled and can measure multiple gases including NO, NO2, (NOX), SO2, CO2, CO, CH4 and H2O. The unique principle of operation provides industry-leading accuracy in a sensor, which is calibration-free. Measuring the gas in its ‘hot & wet’ state, allows Emsys to provide highly reliable and accurate measurements.
Calibration Gas for Marine Emissions Monitoring Systems – The Facts
Why do I need calibration gas? Two reasons;
To keep traditional analysers in calibration; the CLD, NDIR and Zirconium sensors drift out of specification with changes in temperature and pressure. Also vibration usually experienced on board ships causes significant drift. This uses a huge amount of gas over the vessels lifetime. Costs of $6K per annum are regular.
To satisfy MARPOL, Class Society and Port State requirements that the system is measuring accurately. This requirement only uses a small amount of gas at irregular intervals.
Why does some suppliers’ gas have verification barcodes?
The maker claims for compliance and to verify the gas is ‘in-date’ as the gas has a finite shelf life. This is not the case; it is only to obligate the operator into buying their gas and having it shipped by airfreight around the globe. This gas is supplied in small 55 litre disposable canisters to increase cost. The supplier charges up to 8 times more per canister than gas available locally and marks up airfreight charges by 3 times the cost.
The NOx Technical Code allows use of any certified gas provided it meets the specification of the EMS maker and the accuracy defined in the NOX Technical Code.
Emsys uses 2 x 800 litre tanks for Span checks only. The laser sensor is calibration free saving huge amounts of gas over the vessels lifetime.
So, why is the other EMS Company telling me I must have these charge air sensors and RPM sensors?
It’s how their system works, it is not designed to use simple communications to the engine automation system over MODBUS.
A WR Systems engineer can guide you through by detailing the relevant sections in the NOX Technical Code and liaise with the engine builder and Class Society.
Emsys is designed for the simplest installation and lowest maintenance.
Why do I have to install my EMS system in an air-conditioned space?
Most analysers (NDIR, CLD AND Zirconia) do not operate properly at ships engine room temperatures (30° C +), therefore the EMS makers specify siting the analysers in the ECR or engineers workshop. However, owners do not want equipment containing potentially hazardous gas in personnel areas so the ECR is usually not an allowable siting area for these systems.
Your competitors state they can install in the engine room with a self-contained air conditioning package if they can’t site it in a suitable environment?
This may be the case but these A/C units do not operate effectively at 40° C and above, they also consume a lot of power to operate continuously and have refrigerant gas (not preferred by owners), which needs regular maintenance.
Emsys is designed to install in the engine room or stack fiddly area without any air conditioning package. It’s certified to operate up to 55° C and has been tested to the strictest vibration and environmental standards. Siting in the upper funnel space means the sample lines are very short giving low power requirements and fast cycle times between exhaust ducts.
Emsys sample flow rate is up to 20 times faster than other marine EMS systems, primarily for fast sampling but additionally to ensure the Particulate Matter remains in suspension.
Why is measuring the gas ‘hot and wet’ better?
Emsys measures the gas in the state it leaves the exhaust duct. This is hot and wet (the exhaust gas has quite a high moisture content).
Most other systems measure cold and dry, requiring to either cool and dry the gas, or dilute it with instrument air.
So what’s the problem with cold dry?
It requires a gas chiller, multiple filters and gas conditioning equipment to prepare the gas, these are complex, high maintenance items which require regular consumable parts and operator intervention.
What’s a NOX Converter?
It converts NO2 into NO. Why?
Cold dry and dilution systems analysers only measure the NO species, they need to convert the NO2 to NO (MARPOL specifies NOX as NO + NO2 ) NOX converters are expensive consumable catalysts requiring changing on a regular basis (usually annually). They can cost up to $2,500.
Emsys measures NO and NO2 individually in the multi-channel laser, there is no gas conditioning equipment, coolers or NOX converters in the system.
I am being told by your competitor that I need Engine Performance Sensors?
Why do on-board Emissions Monitoring Systems require these?
Calculating IMO specific NOX in g/kWh requires both emissions concentrations and engine performance measurements.
So, if I have these signals existing in my engine automation system, do I need to purchase separate Type Approved sensors?
No, subject to the fact these existing signals meet the calibration and accuracy requirements as detailed in the NOX Technical Code. This simplifies the EMS installation, less sensors, less installation, less maintenance, less COST. The calculations do require an ambient temperature/ humidity signal from each engine room space, this is not usually standard in most vessels. The addition of a simple sensor connected over Ethernet fulfils this need.
Measurement of Particulate Matter (PM) – The Facts
PM is difficult to measure; traditionally one PM sensor is situated in each exhaust duct. These sensors are usually cross duct and feature a transmit and receive sensor.
These sensors usually require a blower or compressed air system to keep the optics clean, this uses lots of energy and requires regular maintenance to clean the optics.
Multiple PM sensors require a significant installation effort; additionally more equipment means more to go wrong.
Emsys utilizes a single patented ‘outside the stack’ sensor, which is fed by the same sample line that draws the emissions gas to the laser. This means a significantly simpler installation and a single PM sensor for all exhaust ducts.
Emsys uses the EPA standard of Green LED to determine PM concentration. This concentration is combined with the engine/boiler exhaust gas mass flow measurements in the Emsys software to provide the more common PM outputs, specific (g/kWh) and volumetric (mg/m3).
It is currently not possible to differentiate PM by particle size (2.5, 10 or 40) as these laboratory type instruments are extremely sensitive and very difficult to operate reliably and calibrate in the marine environment.
Emsys also measures Opacity (%), this is useful for managing visible smoke emissions regulations and monitoring of boilers during cargo operations on Tankships.