Measuring and testing – Gas analysis – Solid content of gas
Patent
1993-10-12
1994-12-06
Williams, Hezron E.
Measuring and testing
Gas analysis
Solid content of gas
73 2333, 7386323, G01N 1506, G01N 124
Patent
active
053699815
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a process for the continuous determination of the dust content of flowing media with the isokinetic partial flow removal for sampling by separation of the dust or aerosols via cake filtration on a filter.
Known processes for the continuous emission surveillance employ absorption of light waves or other radiation sources. It is also known to monitor the pressure losses in filters for a threshold value at which it is pressurized that the filter needs to be exchanged. Only afterward the integral amount of the particles deposited on the filter can be determined by weight measurements. A continuous surveillance of the amounts deposited over predetermined time steps is not possible with this method.
It is the object of the present invention to provide a process by which the continuous surveillance of dust emissions with subsequent record keeping capability of the sample material regarding the analytical determination of dust content materials such as heavy metals, dioxines, etc. is made possible.
SUMMARY OF THE INVENTION
The invention relates to a process for the continuous determination of the dust content of flowing media with the isokinetic flow sampling with the separation of the dust or aerosols by cake filtration on a filter and the measurement of the pressure drop at the filter to determine its degree of clogging. To this end the time cycle of the quantity of dust separated on the filter is determined by the measurement of the pressure loss at the filter of an isokinetically operating sampling system. To find the dust load, this quantity of dust is related to the partial quantity of gas extracted isokinetically during the period concerned.
The process according to the invention takes into consideration that the pressure loss during filtration depends on the height of the filter cake, the filtration speed, the viscosity of the gases and the properties, such as particle size, particle shape, void volume, etc. of the deposited dust. It further assumes that, during the filtration process, the properties of the deposited materials do not change substantially. Then the increase of the deposited layer and consequently the amount of deposited material can be determined by measuring the pressure loss taking into consideration filter gas speed and viscosity.
Further details of the process according to the invention will be explained below on the basis of a figure.
BRIEF DESCRIPTION OF THE DRAWING
The sole FIGURE is a schematic representation of a measuring arrangement by which the new process can be performed. The process facilitates the continuous determination of dust contents in flowing media with isokinetic partial flow removal for sampling and separation of the dusts or aerosols via cake filtration on a filter and measuring the pressure drop across the filter for determining the degree of filter loading.
In the discharge duct 1 of an environmentally unsafe material emitter there is provided a sampling device, that is, a suction nozzle 2 via which a representative partial stream is removed from the main gas flow 3. The partial stream is removed isokinetically, that is, at the same speed as the main flow, the required vacuum in the suction pipe 4 being generated by a suction pump 5. Isokinetic adjustment of the removal speed of the partial stream at the nozzle opening 6 is done by RPM control of the HF-drive motor of the suction pump 5 via frequency control. An isokinetic control of suction at the nozzle opening 6 requires triple pressure measurements P.sub.G total pressure 7, ps.sub.T static pressure of the partial gas stream 8, pst.sub.H static pressure of the main gas flow 9 and temperature measurement 10 at the nozzle, in order to determine the momentary condition in close proximity of the nozzle opening 6. The pressures are transmitted through slots or passages in the nozzle wall. From these measurement data a measuring and control unit 11 with an operating unit 12 provides the frequency needed for operating the drive motor of the suction p
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patent: 4442699 (1984-04-01), Ramelot
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patent: 4856352 (1989-08-01), Daum et al.
patent: 5090257 (1992-02-01), Bruce
Becker Ernst
Brielmaier Thomas
Merz Albert
Walter Roland
Bach Klaus J.
Kernforschungszentrum Karlsruhe GmbH
Roskos Joseph W.
Williams Hezron E.
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