Dynoptic Opacity Monitors
Dynoptic opacity monitors use the light transmission technique to measure the visible opacity of exhaust gas in a duct, stack or flue, in which a high intensity light beam is projected across the stack. Any dust, smoke or particulate present will attenuate the transmitted light and the decrease in light intensity, due to absorption and scattering, is measured.
One advantage of opacity systems is that they are insensitive to interference from other flue gas components since the beam spectrum is within the photopic region (400-700 nm) and most other flue gas constituents do not absorb in this spectral region.
There are two types of opacity monitors; Single Pass and Double Pass.
Single pass opacity monitors have a Transmitter/Receiver arrangement with the light beam emitted from the Transmitter passing across the stack to a Receiver. Double pass opacity monitors have a folded beam Transceiver/Reflector arrangement with the light beam emitted from the Transceiver (TRX) passing across the duct to a Reflector, which then returns the light to the Transceiver.
Single pass opacity monitors are the simplest type of instrument and offer a very cost effective solution to meet monitoring requirements. One advantage to single pass systems is that they are suitable for applications with long path lengths, i.e. large stack diameters and DynOptic single pass opacity monitors can be used for path lengths of up to 20m.
Double pass systems are more suited to continuous emission monitoring as they have a number of advantages over single pass systems in that:
- Double pass opacity monitors have better sensitivity at smaller duct diameters
- Double pass opacity monitors are simpler to install as electrical services are only required to one side of the stack
- Double pass opacity monitors allow for an in-situ zero and calibration facility
DynOptic currently offers three different opacity monitors.
Dynoptic Particulate Monitors
With the advent of specific process emission limits being defined, continuous particulate monitoring has become a regulatory requirement for many industries.Particulate monitoring requires the measurement of the mass concentration of particulate matter in stack emissions to atmosphere. There is no known method of continuously measuring particulate concentration by direct measurement and therefore, all continuous particulate measurement methods are inferential.
Each method involves the measurement of a parameter related to particulate concentration and then requires a calibration to be determined to convert the measured value into one of particulate mass concentration.
DynOptic currently offers three different particulate monitors which each use the open path light transmission technique.
- DSL-230 MkIII Single Pass Particulate Monitor
- DSL-330 MkIII Double Pass Particulate Monitor
- DSL-460 MkII Double Pass Opacity and Particulate Monitor
In order to output particulate concentration in mg/m3, a Density Scale Factor (DSF) must be determined. The Density Scale Factor for any given installation will vary based on the type, shape, size and colour of the particles in the gas stream and therefore, the Density Scale Factor must be determined on site, through comparison of the instrument readings with an independent reference measurement*.
During normal operation:
Particulate concentration (mg/m3) = measured parameter x DSF
Dynoptic DDP Dust Monitors
DynOptic dust monitors use the innovative Dynamic Detection Principle (DDP) to measure dust and particulate within exhaust gases from various manufacturing processes.DDP, or optical scintillation as it sometimes referred to, measures the dynamic fluctuation in light transmission as dust particles move through a light beam. This dynamic fluctuation derives from temporal distributions of the dust particles which attenuate the light beam. The more dust present in the exhaust, the greater the amplitude of these fluctuations.
DDP instruments calculate the dynamic response, or the ratio of light variation to light intensity, which for particular applications, is proportional to dust concentration and when calibrated against standard reference measurements, this can be presented as a reading in mg/m³.
Unlike the standard transmission technique, DDP has immunity to gradual reductions in the absolute intensity of the light signal. Therefore, DDP instruments have the advantage that they are significantly less susceptible to drift with time, temperature or dirtying optics, than traditional opacity monitors and less sensitive to misalignment. In practice, this means that the instruments require less maintenance.
DynOptic currently offers two dust monitors using the DDP technique:
In order to determine whether DDP is suited to your application, it is necessary to consider a number of factors such as the typical size distribution of the particulates to be measured, whether they have constant or variable physical properties and the ease of which the heads can be accessed for routine cleaning of the optical surfaces. The following table summarises the key requirements for using DDP as compared to the more traditional opacity monitors.
|Optimum particle diameter (mean of the particle diameter mass distribution)||>10μm||<1μm|
|Dependence on optical properties of the particles||Low||High|
|Dependence on optical surface contamination||Low||High|
|Dependence on noise pick-up (optical or electrical)||High||Low|
|Dependence on gas flow velocity||High (<3m/s)
Dynoptic Marine Monitors
In recent years, new regulations have been introduced governing emissions from ships. With the International Maritime Organization (IMO) adopting Annex VI of MARPOL designed to limit sulfur oxides (SOx), nitrous oxides (NOx) and particulate matter emissions, as well as introducing emission control areas (ECAs) to reduce emissions of those air pollutants further in designated sea areas, ship owners/operators can face hefty fines for failing to meet these new requirements on the “polluter pays” principle.
Ships emit more particulate matter (PM) per unit of fuel consumed than other fossil fuel combustion sources due to the quality of fuel used. Stringent rules against ships exhausting black smoke within sight of shore – notably in regions such as Alaska and Hawaii, where cruise ships and tankers are particularly vulnerable – have been introduced and are backed up by ‘spotters’ employed by authorities to report any infringements. Penalties extend from warnings and fines to future banishment of guilty tonnage from the area.
Therefore, effective smoke monitoring is becoming increasingly important and installing a smoke opacity monitor is one way of providing a warning if the combustion of a boiler, incinerator or engine is poorly adjusted thus leading to the emission of black smoke. This will also help to protect ship-owners against heavy fines as well as potential damage to the ship’s and company’s image.
DynOptic smoke monitors measure the density of the smoke using the light transmission technique to measure the visible opacity of exhaust gas in a duct, stack or flue, in which a high intensity light beam is projected across the stack. Any smoke or particulate present will attenuate the transmitted light and the decrease in light intensity, due to absorption and scattering, is measured. The higher the level of smoke present, the more light lost and therefore, the greater the opacity.
DynOptic currently offers three different smoke monitors for measuring marine emissions.
- DSL-220M Lloyds Type Approved Smoke Opacity Monitor for measuring visible opacity (0 – 100%)
- DSL-230M Lloyds Type Approved Smoke Density Monitor for measuring smoke and particulate emissions (mg/m³)
- SM-202M Smoke Opacity Monitor for measuring visible opacity and smoke emissions (non-Type Approved)