LU84058A1 - IMPROVED PROCESS FOR MEASURING THE DUST CONTENT OF SMOKE AND DEVICE FOR CARRYING OUT SAID METHOD - Google Patents

Description

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METALLURGICAL RESEARCH CENTER -CENTRUM VOOR RESEARCH IN DE METALLURGIE,

Non-profit association -Vereniging zonder winstoogmerk I in BRUXELLES, (Belgium).

Improved method for measuring the dust content of the fumes and device for implementing this method.

The present invention relates to an improved method for measuring the dust content of smoke.

In certain numbers of industrial processes, and especially in multiple metallurgical or iron and steel operations, for example in the case of the production of cast iron or steel, it is of great interest to know, continuously, the composition also as accurate as possible, the fumes produced by the operations considered and in particular their solids content, commonly referred to as dust. / /> - 2 -

To this end, various methods have already been envisaged making it possible to take a sample of smoke, then to pass this smoke through a filter sufficiently fine to retain the dust, which can be weighed according to a process determined, known per se.

However, it turns out that such a procedure is generally not considered satisfactory in the case of continuous sampling, because the problem posed, and which must be resolved before the result can be considered valid and usable, involves compliance with the following two conditions: - the isokinetics of taking samples, - the determination of the dust dust content, calculated „.. 3 in grams of dust per Nm. dry.

To achieve the isokinetic nature of taking samples, it has already been imagined to bring the dedusted fumes to a temperature higher than that which they had at the place of their sampling, for example by passing them through a heating element, then pass them through a pressure-reducing element (Venturi or diaphragm) where their differential pressure (AP), their pressure P and their temperature T can be measured, quantities below. repeated under the signs ^ & 2 'P2 ^ 2 * ^ e ^ on this known Process, all the water contained in the sample is at this moment in the vapor state and the speed of the dusted fumes can, in the sampling circuit, be adjusted using an appropriate valve located downstream of said heating element and making it possible to obtain isokineticism from the measurements made on the fumes at the place of taking the samples (for example by the well-known Pitot tube and Prandtl tube method), supplying the local values ΔP ^, and fumes (in practice we use an electronic calculation unit to directly obtain the values of the quantities sought ). In this way, we have already succeeded in obtaining the isokinetics of /, / • s / - 3 - smoke, which is the first condition imposed.

To observe the second condition, namely knowledge of the dry gas flow rate, we have already used certain methods which are well known in themselves. For example, it has been imagined to pass the dedusted fumes through a condenser at low temperature. The weighing of the condensed water makes it possible to deduce from the measurements P2, Δ P2 and T2 ° ® dry gas kit. However, such a process does not lend itself to continuous measurement. We also thought of calculating the dry gas flow rate, based on an assumed average water content, of the sampled fumes. This method is imprecise and inapplicable if the process studied is variable over time.

The use of a continuous hygrometer has also been envisaged, but, in addition to its high cost, such a device appears to require significant maintenance costs.

The present invention relates to a process by which, while observing the two conditions mentioned above, one * can avoid the disadvantages of the known methods mentioned above.

The process, object of the present invention, in which a continuous sampling of fumes is made, in a pipe traversed by these fumes, then this dust is dusted, is essentially characterized in that the dusted fumes successively pass through a first member pressure reducing valve, then a valve which is adjusted so as to obtain the isokinetism of the sampled fumes, in that said fumes are then introduced into a contact condenser, where almost all of their water vapor content condenses and is thus eliminated from the fumes, in that downstream of the condenser, the dry fumes pass through a second depressogenic organ (for example a Venturi) / * / Λ - 4 -

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where their differential pressure P ^, their pressure P2 and their temperature are measured and in that the gas flow is deduced therefrom; dry and therefore the rate of dust (for example in grams / Nm. dry).

In practice, at the outlet of the condenser, the flue gases are at a temperature of the order of 20 ° C. easily measurable (T ^) to which corresponds a value of the saturated vapor pressure well known, stable and very low (4 %), which can easily be taken into account when calculating the dust content of the fumes considered dry at the outlet of the condenser.

The diagram below, given by way of nonlimiting example, and not to scale, makes it possible to realize how one can design a device authorizing the implementation of the method of the invention.

A pipe 1, for example of cylindrical shape and axis 2, is assumed to be traversed in the direction of arrow 3, by fumes containing dust and water vapor.

In 4, a smoke sample is taken, which is dusted in 5. A pitot tube measurement sample is taken in 6 and sent to a measuring device 7, for example electronic, which provides the information below , temperature T ^, pressure P ^, differential pressure P ^. Before and after dedusting 5, a heating system 8 brings the fumes to a temperature higher than that which they had in the pipe at the place of sampling. The fumes then pass successively through a heated pressure-reducing element 9, where T2, P ^, Δ P2 are measured / a contact condenser 11 collecting the condensed water at 12 at the temperature / temperature T ^, a control valve 10 pressure, which is isokinetic, a sampling pump 14 dd / ί - 5 -

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finally, a second depressogenic organ where T ^ / P ^ I and L · P ^ are measured, which makes it possible to carry out the requested calculation, namely the dust content of dry smoke. "- / (i", w

Claims (2)

1. Improved method for measuring the dust content of the fumes, in which a continuous sampling of fumes is made, in a pipe traversed by these fumes, then the fumes are dusted, characterized in that the dusted fumes pass through a first pressure-reducing element, then a contact condenser where almost all of their water vapor content condenses and is thus eliminated from the fumes, in that downstream of the condenser, the dry fumes i pass through a valve that the on the basis of the results of the measurements carried out in this first pressure-reducing member, one adjusts, so as to obtain the isokinetism of the fumes sampled, then a second pressure-reducing member (for example a Venturi) where their differential pressure k P, their pressure P and their temperature T, and in that one deduces therefrom the flow of dry gas and therefore the rate of dust (for example in grams / Nm3. Dry). 2. Device as described above. # ^ I 1 - I. Drawings: —d— ptenche ^ »£ - panes dor-t ........... r-r- ~? . . S \ - 'T -v. s, ^ (. · Γτ.cTicicâiions ______ ^ ..... tLuyé descriptif Luxembourg, le 3 1 u.o · -Le f ^ * f'iy v— Charles München