US2281962A - Dust sampler - Google Patents

Description

May 5, 1942. H. VAN TONGEREN DUST SAMPLER Filed NOV. 26, 1940 FIGJ.

' Patented May 5, 1942 rural) STATES PATENT OFFICE DUST 7 iLER llilermannus van Tongeren, hieemstcde, Netheriandc Application November 28, 194th, hertal Ne. 361,294

. lln Germany mecernher all, 1939 4 Claims.

The determination of the dust concentration of gases flowing, for instance, through a chimney is usually effected by vmeans of a sampler or dustometer, through which the gas is drawn and pier, and a pump for drawing the gas through the plant, said pump being provided with suitable controlling devices. A plant as above described is rather complicated and requires very skilled operators.

My invention has for its object to provide a sampler, by means of which the required tests can be carried out in a much simpler and, consequently, cheaper way.

First of all, I dispense with the complete separation of the dust from the gas shunted through the sampler. This is very important, since complete separation involves the use of a paper filter or the like, i. e. a filter offering much resistance to the flow of the gas, thus necessitating the use of a powerful pump. As a matter of course, partial collection of the dust from the shunt, as contemplated by the invention, requires certain corrections, which will be considered later.

Further, according to this invention, the dust laden main flow to be analyzed is itselfutilized as a source of energy for drawing the shunt through the sampler, so that the velocity of the shunt may always have the same value as that of the .main stream. In this manner I obviate the troublesome adjustment or the velocity of the shunt during the scanning" of the cross-section of the chimney, which is indispensable when using the said known plant.

In order that my invention may be more fully understood, I shall now describe the same with reference to the annexed drawing, in which:

Fig. 1 is a vertical cross-section and Fig. 2 is a top elevation of a sampler con= structed in accordance with my invention, whereas Fig. 3 shows how said sampler is suspendedin a chimney.

Referring to Fig. 3 of the drawing, the sampler A is suspended within a chimney B by means of strings iroma bar C projecting from the chimney through an aperture D, so that the operator is capable of scanning, with the sampler, the

whole cross-section of the chimney. The inlet for the shunt is indicated by E.

The sampler represented in Figs. 1 and 2 comprises a vertical cyclone 4 of normal design, which is provided with a horizontal and tangential gas inlet conduit 5. This conduit communicates with a vertical, downwardly directed pipe 6 provided with a bottom inlet nozzle 1, through which the shunt is drawn in. At the junction between pipe 6 and conduit 5, curved, parallel vanes 8 are provided with a view to reducing the resistance to flow. At its top side the cyclone 4 has a cleaned gas outlet conduit 9.

The dust thrown out in the cyclone is discharged, through the inverted cone Ill of the cyclone, to a cylindrical dust receptacle l I having a hemispherical bottom. Said receptacle has an air-tight connection with a cylindrical jacket l3 surrounding the cyclone 4 and serving to prevent undesirably eddy currents from setting up in the main stream. The bottom'of receptacle H is located at a considerably higher level than the in-v let nozzle 1.

The outlet pipe 53 of the cyclone 4 has a flaring" mouth 9a opening into the throat of a Venturi tube l2. The jacket l3 has a tapering top portion Be, the top edge of which is connected to that of the flaring mouth 5a or the cyclone outlet pipe 9. The Venturi tube I2 is surrounded by a jacket it serving the same purpose as jacket l3. If the described device is suspended, as illus trated in Figure 3, in a chimney, part of the combustion gas is shunted through the inlet nozzle i so as to flow through pipe 6 and conduit fi into the cyclone 4, in which by far the greater portion of the dust particles-is thrown out and discharged into the receptacle H. The cleaned gas, which still contains a certain amount of fines or flour, returns into the chimney through the outlet pipefi, 9a andthe Venturi tube l2.

Owing to the fact that the bottom of receptacle M lies at a considerable distance above the inlet nozzle I, the latter is not aflected by eddy currents set up by said bottom, so that in nozzle 1 no separation of dust fractions can take place- I and the dust concentration of the shunt flowing through the sampler accurately corresponds with,

that of the surrounding gases.

Venturi tube 12 serves to overcome the resista given time interval, nor does the grading of efficiency of the cyclone depends on the passing through a tapering top portion I30, the velocity of the main stream is increased owing to the fact that both the width and the radius of the annular crosssection of said passage decreases in u ward direction, so that suction is created at the mouth 9a. The dimensions of the sampler should be so chosen that this suction just suflices to overcome the aforesaid resistances. This can be checked in the wind tunnel. Slight deviations can be compensated by means of the correction nozzle 1, which, according to Fig. 1, has a slightly smaller cross-section than pipe 6. As long as the crosssectlonal area of nozzle 1 is not essentially different from that of pipe 6, this manner of compensating is scientificall justifiable.

It is, however, to be understood that nozzle 1 should only be used to effect the very last correction. The principal means for equalizing the velocities of the shunt and of the main flow is the Venturi tube 12, in which the energy of the 'main stream itself is utilized for drawin the shunt through the sampler. This feature and the automatic equalization of the said velocities are salient features of my present invention.

Another important feature is the air-tight sealing'of the dust receptacle Hand the fact cyclone, through the dust outlet thereof. Thus, the operation of the cyclone cannot be impaired by the varying dust level in the receptacle.

As already stated, the cyclone does not effect a complete separation of the dust suspended in posed below the bottom of the dust receptacle to receive dust laden ga's'before turbulence therein is caused by the presence of the unit, nozzle means at the lower end of the shunt pipe for maintaining gas velocity in the shunt equal to the gas velocity of the gas stream enveloping the unit, a Venturi tube disposed substantially coaxially with-the cyclone, the cleaned .gas outlet of the cyclone opening into the Venturi tube substantiallyin the throat thereof, and means for portably supporting said'dust sampler.

2. A dust sampler unit adapted to be manually positioned over a selected zone of the cross sectional' area of a-chimney through which dust laden gas is flowing, comprising; a cylindrical jacket having an inwardly tapering top portion; a cyclone within the jacket having a horizontal tangential dust laden-gas inlet, a cleaned gas outlet conduit having an outwardly flaring mouth joining with the .upper edge of the inwardly tapering top portion of the jacket, and a dust'discharge cone; a dust laden gas shunt pipe ,that the latter communicates merely with the the shunt. As a consequence, the dust concen tration of the main stream cannot simply be calculated from the collection in receptacle I I and the amount of gas passed through the meter in the collection correspond with that of the dust in the main stream. However, the desired values can readilybe determined if it is known how the velocity ofthe shunt at the inlet 7 and on the size of the dust particles carried therewith. This dependenc-y can be predetermined in the laboratory. For various gas velocities and for various specific weights of the dust, the efilciency of the cyclone is plotted against the size of the grains in various fractions between 0 and say 500 t. With the aid of the resultant curves and of the easily determinable average inlet velocity, one can readily calculate, from the amount and the grading of the sample collected in'receptacle l l, the actual concentration and grading of the dust contained in the flue gases sucked through the sampler.

Although the invention has more especially been described in connection with flue gases vertical conduit, it can of course also be used for analysing other dust laden gases, or gases flowing in horizontal or inclined conduits.

What I claim is:

l. A dust sampler unit adapted to be manually positioned over a selected zone of the cross sectional area of a chimney through which dust laden gas is flowing, comprising; a cyclone having a tangential. dust laden gas inlet, a cleaned gas outlet and a dust discharge opening; a closed dust receptacle arranged substantially coaxially with the cyclone and communicating with the opening thereof, a shunt pipe dust discharge communicating at its upper end with said gas inlet of the cyclone and having its body disposed in parallel relation with the axis of the cyclone, said shunt pipe having its lower inlet end dishaving its longitudinal axis parallel of the cyclone and communicating with the axis an inlet nozzle on the bottom end of the shunt pipe for maintaining the gas velocity in the shunt equal to the velocity of the gas stream enveloping the sampler, a duct collecting receptacle having an air-tight connection with the lower end of the jacket and adapted to receive dust from said cone, the bottom of said receptacle being located above the nozzle of the shunt pipe whereby the inlet of the shunt is below the'zone.

of tubulence caused .by the presence of the sama Venturi tube having its inlet throat telescopically fitting over the end of the cleaned gas outlet conduit and in spaced relation to the inwardly tapering top portion of the jacket, thereby to create suction at the mouth of said outlet conduit to overcome resistance to gas flow in the shunt on its way from the nozzle to the mouth of the outlet conduit, and means for supporting the sampler in a selected position in the chimney.

3. A dust sampler unit according to claim 2 wherein the junction between the tangential. inlet for the cyclone and the top portion of the shunt pipe is provided with a plurality of spaced parallel substantially right-angularly curved vanes for reducing the resistance to gas flow from the shunt pipe to the cyclone.

4. In a dust sampler comprising a cyclone having a tangential dust laden gas inlet and a clean gas outlet and a dust discharge opening, a closed dust receptacle arranged substantially coaxially with the cyclone and communicating with the dust discharge opening thereof, a gas inlet pipe arranged with its long axis parallel to the axis or the cyclone and having one end in communication with said dust laden gas inlet and its other end provided with an inlet opening directly into the surrounding atmosphere below the dust receptacle, and a Venturi tube having its axis in substantially parallel relation with the axis of said gas inlet pipe and having an inlet opening, an outlet opening and a throat, the cleaned gas outlet of the cyclone opening into the Venturi tube substantially in the throat thereof, and the said inlet opening of the Venturi tube being located downstream of the inlet end of the gas inlet pipe. 7 V

HERMANNUS VAN TONGEREN.

at its upperend withthe said tangential gas laden dust inlet,

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