Fourier Trans Infrared spectrometry傅里叶变换红外光法

1、. aim:to evaluate the analytical methods for determining emissions.what is the best approach for gksb?the biogeochemical cycles in our biosphere ecosystems respond to climate systems through physical, biological & chemical feedback systems. anthropogenic emissions of so2 alter the balance of the

2、 sulfur cycle in our biosphere. this has adverse effects on human health and alters the balance of the earth-atmosphere system;acid airchange in earths energy budget. to the atmosphere are significant and can be larger in magnitude than those from natural sources in urban regions in the industrialis

3、ed developed world. atmospheric sulfur compounds exists in aerosols condensed phase particles in stable suspension with gases e.g. . acidic aerosols contain sulfate particles. such aerosols adversely impact on human health. sulfate particles are derived from so2 gas in air scatter light and reduce a

4、mount of solar heat reaching the earths surface add to phenomenon. monitoring of so2 emissions is a fundamental aspect of an environmental authorities air control policy.primary inorganic pollutant gases play an important role in atmospheric acidity. sulfur dioxide is a primary inorganic gas polluta

5、nt. it takes part in chemical reactions in the atmosphere and produces secondary pollutants such as sulfate compounds in particulate. these secondary pollutants formed in the atmosphere include acidic sulfate aerosols. glaxosmithkline (gsk)gsk is the second largest pharmaceutical company in the worl

6、d.the company is a global leader and a pioneer in all elements of healthcare from r&d and vaccines to all the main therapeutic areas. the cork facility was established in carrigaline in 1974 and employs over 400 people.the facility generates solid waste from its production processes which it dea

7、ls with on site. incineration at gskthere are three high temperature toxic waste incinerators at the site.the three units are designed to burn solids,liquids and vapours from chemical processes.the units operate at a temperature of 1100 0c and there is 99.99% removal of the toxic waste.by products o

8、f the incineration include so2.each incinerator has a continuous emission monitoring system installed. a schematic of the operations of a typical incinerator showing gaseous pollutant formation.reasons for continuous monitoringcontinuous emissions monitoring equipment is installed for a number of re

9、asons.regulatory compliance.monitoring of plant performance.calculation of emissions inventories.compilation of environmental impact assessments legislationthe primary environmental legislation driving continuous emission monitoring is the integrated pollution prevention and control (ippc) which is

10、embodied in the ippc directive of 1996.this requires all industrial operations covered by the directive to obtain a permit from authorities within the country.the permit is based on the concept of best available techniques (bat) which is sometimes costly for plants to adapt to bat.the directive allo

11、ws installations an eleven-year transition period to achieve compliance beginning on the day that the directive entered into force. the epas rolegsk send the epa quarterly reports of all continuous monitoring data.an alternate to this is real time data gathering from industries by direct computer li

12、nk up.this is used in germany however, the epa feel that this would be expensive and technically challenging to install for industries in ireland such as gsk.the epa has a team that carry out spot checks on flue gas monitoring, occasionally throughout the year to validate results.to date gsk have be

13、en in full compliance with epa regulations regarding so2 emissions from the plant.the epa consider their role in the future is unlikely to change unless legislation is strengthened. epa method of analysis for so2 the epa use a horiba pg-250 portable multi-gas analyzer when spot checks are carried ou

14、t at gskthe pg-250 is a portable stack gas analyzer that can simultaneously measure up to five separate gas components. the pg-250 uses non-dispersive ir detection for co, so2, and co2.the performance of the pg-250 has been tested and verified under a number of programs.pg-250 portable stack gas ana

15、lyzercontinuous emission monitoring technologies continuous emission monitoring or automated measuring systems can be categorised into two types: type 1: extractive systems type 2: in situ systems extractive systems withdraw flue gas continuously from stack and transport it to the analyser.in situ s

16、ystems carry out most of their operations in the stack.point in situ carry out analysis at a single point in the stack.path monitors carry out analysis usually over the entire stack.extractive monitoring systemin situ monitoring system.comparison of so2 analysis techniques.simple non-dispersive infr

17、ared (ndir)based on beer lambert law.low cost.reliable.suffers interferences from co2 and h2oluft detector (ndir)works on same basis as ndir. reduces interference associated with ndir. susceptible to problems associated with vibration.fourier transform ir (ftir)heart of the system is the interferome

18、ter.fast response time.fewer interferences than ir.generates large amounts of data.ultraviolet fluorescence (uv)based on the absorption of uv light.specific to so2.high sensitivity & selectivityquenching effect by other molecules in the sample gas. differential optical absorption spectroscopy. (

19、doas)based on beer lambert law.highly selective. extractive and in situexpensive to install & high training demands.technique presently in use at gskgsk are presently using a perkin elmer mcs 100 multi component non dispersive infrared (ndir) system for so2 analysis. this is an extractive system

20、.the principle of the method is based on beer lamberts law. (a= x c x l).many heteroatomic ( e.g. so2,co2) gaseous molecules absorb light in the ir region.in ndir light is emitted from a heated coil through a reference cell and the sample cell.mcs 100 multi component non dispersive infrared (ndir) s

21、ystem for so2 analysis. technique presently in use at gskas the beam passes through the sample cell the pollutant molecule absorbs some light.the light energy entering the cell will now have less energy.the energy difference is detected by a solid state detector.the ratio of the detector signals fro

22、m the cells gives the light transmittance. this ratio can be related to the pollutant gas concentration. courtesy of cascade-technologies, uk.typical ir spectrumlimitations of ndira limitation of this method is that gases that absorb light in the same spectral region will cause a positive affect.wat

23、er vapour and co2 strongly absorb in the ir region.at gsk these molecules are removed by a scrubber, decreasing interferences. also, another solution to this problem by using absorption cells arranged in series.this is incorporated into systems to enable accurate detection of emission gases. a typic

24、al scrubber systemscrubberluft detector ndirthe luft detector works on the same basis as the simple ndir.the reference cell and a sample cell are arranged in series.the light energy is absorbed by the so2 causing the gas to heat up.differential heating caused by the difference in ir light causes a d

25、ifferential pressure between the two cells.the pressure difference between the two cells is detected by a flow sensor.luft detector with cells in parallel.luft detector ndirthis dual beam analyser is a standard method for analysis of so2 across europe.it has received regulatory approval in germany.h

26、owever, these detectors are more susceptible problems associated with vibration than other detectors.the development of microflow sensors has helped to overcome this problem. luft detector unit.fourier transform infrared (ftir) spectroscopynft-ir is the preferred method of infrared spectroscopy and

27、is growing in popularity for the multi component analysis of stack gases. nit produces a infrared spectrum with a unique combination of bands corresponding to an individual species, creating a distinct fingerprint for the sample. courtesy of maine tech. uk.what is ftir?the heart of the system is the

28、 interferometer in which the light from the source is divided into two beams. beams pass through the sample cell and then recombine resulting in a signal.all information required to identify and quantify the gases in the sample is present in the interferogram.interferogram signal is converted to a f

29、requency spectrum by a mathematical technique called fourier transformation.a typical interferogram.advantages and disadvantages of ftiradvantagesanalysers capable of measuring 50 determinants.fewer interferences than irdoes not require frequent calibration.typically have a range of 2.5 to 25 m. dis

30、advantagesdifficulty in obtaining a representative backgroundgeneration of large amounts of data from inferograms when continuous emission monitoringreal time ftir analyzer: supplied by applitek, venecoweg, 199810 nazareth, belguim. fluorescence spectroscopy is a powerful tool for the study of chemi

31、cal & photochemical species.absorption of uv radiation is followed by at longer wavelengths. intensity of fluorescence is used to determine the concentration of analyte. changes in concentration can be detected rapidly, changes in fluorescence intensity within picoseconds can be detected. fluore

32、scence signal is proportional to concentration and therefore high sensitivity can be achieved.sulfur dioxide molecules absorb light at a specific wavelength (214 nm) & emit light at a longer wavelength. fluorescence occurs as the molecules emit excess energy and return to ground state. the distr

33、ibution of wavelength is dependent on intensity of emitted energy. this is shown in a fluorescence emission spectrum.uv fluorescence detectors can be used in on-line monitoring systems.fluorescence is detected using a photomultiplier tube.a hydrocarbon scrubbing system removes interfering molecules

34、prior to measurement.air sample intakedifferential optical absorption spectroscopy - doasnapplicable to extractive & in situ systemsnmethod principle is beer-lambert law.nlight of different length is transmitted across emission stack.nlight wavelength are selected using diode laser, photodiode arrays or moving slits.ndetectors signal at wavelength where no absorption occurs is reference measurement.doas how it workscourtesy of enviro tech. ukdoas - extractive system featuresnmeasurement cell & heated oven for the sample cellnheated sample line including temperatu