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英国环境保护技术文献
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Continuous Emissions Monitoring
requires the use of Continuous Emissions Monitoring Systems
(often referred to as CEMS). CEMS are generally made up
of four main parts, sampling system (or the lack of in
cross-duct systems), analysers, calibration system and
data logging / signals handling systems.
There are many types of systems available for CEM. Below
are listed the more common:
Extraction (Heated Line).
This is one of the oldest technologies for CEM and involves
taking a sample from the stack with a probe and transporting
the sample (in its supposed original state) to gas analysers
via a length of heated sample line. Although still widely
used and promoted, there are inherent problems with this
technique, mainly to do with the fact that it is very
difficult if not impossible to maintain the sample of
gas in its original state from the stack to the analysers,
especially with soluble acid gases such as HCl, SO2 or
NO2. Enviro Technology does NOT offer this technology.
Extraction (Dilution Probe).
Extraction via dilution probe goes one stage further than
heated extraction in ensuring that the composition of
the sample gas is transported to the analysers via the
sample line in its original state. This is achieved by
a number of means including diluting the stack gas with
zero air (by a factor of 20:1 for example) and utilising
two heated orifices in the probe tip to create a pressure
drop from one side to the other. This results in the dew-point
of the gas being lowered thereby removing the problems
of transporting the gas to the analysers. Enviro Technology
has a range of stand-alone analysers dilution analysers
for NOx, SO2 and CO/CO2
Cross Duct (or Cross-Stack) Monitoring.
This is the most modern method of
CEM and by far the most representative and accurate.
（这是连续监测最现代化的方法，目前最准确和最具代表性）Cross Duct gas and particulate
analysers measure stack gas emissions by a number of different
technologies (i.e. IR/UV/DOAS/Laser) as the name suggests,
across the duct thereby eliminating the need for any probes
or sample systems. These systems are often favoured by
operators and regulators alike as they are generally provide
more reliable, accurate and representative measurements
of gases and dust concentrations along the whole of the
measurement path (from one side of the stack to the other).
Enviro Technology offers a wide range of Cross Duct CEMS
for multiple gas and particulate measurement. |
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