FR2515061A1 - Air purifier comprising cyclone and bag filter - has rotatable central shaft to sequentially block bag inlets and extract accumulated dirt - Google Patents

Abstract

An air filter consists of a conventional cyclone in which air is given a pretreatment to remove the bulk of the dust; this is followed by a downflow bag filter, within the same enclosing vessel, in which air flows from inside to outside of the bags. A central rotating shaft permits sequential removal of accumulated dust from the bags by stopping the air inflow to a pair of bags, while simultaneously connecting the outlets to a separate aspirated dust discharge. Used for the cleaning of dusty air and gases the device combines the features of a cyclone and a bag filter.

Description

 The present invention relates to machines of the type "air purifier" or "air filter" or "cyclone dusting". The purpose of these machines is to separate the air from the dust from which it can be loaded.

In cyclones the yield is about 95%. It is possible to consider several cyclones in serin, or at full dusting. But the pressure losses of each cyclone are reduced and the necessary driving force becomes exaggerated. In addition, a battery of cyclones is never 100% sire. When there is more dust, there is "stuffing". And dust can escape through the exit chimney. In addition to the environmental pollution, this exhaust can have another drawback: dust
May have a market value, hence a financial loss. This is the case for example with air loaded with flour dust.

 Every time, therefore, that we are looking for an absolute purification, and this is the case in the flour mill, we use filters. The filters used consist of generally cylindrical sleeves filtering fabrics, wool, cotton, or synthetic. The air can be sent either inside the sleeves, and these are then air filters "repressed" around the sleeves, and these are n aspirated air filters. "In both cases the degumming is necessary. It consists in cleaning the sleeves in a periodic way, because the dust retained by the filtering fabric closes the drier as quickly as the air is more dusty.

 There are several methods of degumming. The sleeves can be shaken mechanically. It is a noisy old process, which mistreats the sleeves, shortening their service life.

The sleeves can be degummed by high-pressure air blowing against the current.-This air is distributed continuously, in all the sleeves simultaneously, by a rake that is oromed from top to bottom. The sleeves can also be torn off. compressed air injected against the current, and distributed alternately in each sleeve. These last two methods are currently the most used. They give technical satisfaction. But the filters using these processes content expensive. In the first case the rider's ballast mechanism and the high pressure fan are expensive. In the second case, the air compressor and the distribution system by programmer and electro-valves are still more expensive. This explains why small mills which are still a majority in France, can not equip such filters. They sometimes use filters called "static" or "filter grids". It is simply sleeves without degumming and without recovery of flours. In this case it is necessary to Predict a number of sleeves The loss of load of such filters, quickly clogged, is very important, thus increasing the necessary driving force. And the miller often has to come shake the sleeves and pick up the flours. His filter remains one of the few machines, if not the only one, that does not operate automatically in his factory.

The purification of air according to this invention is intended to avoid the technical disadvantages of cyclones and filtering groups, and to obtain the same technical performance as those of the filters. This for a much lower manufacturing cost, allowing its acquisition by all the millers. This air purifier has only one motor, low power - 1 KW
The degumming of the sleeves is ensured by the main fan of the installation and it also ensures the recovery of flours continuously.

 This air purifier consists of a cyclone associated with a filter. It is intended for the purification of air used for the trans-port tire milling products for ooulin with a capacity of 100 tons 7ar 24 hours. Its purpose is to use a maximum of 1 cyclonic effect, because the centrifugal force is the most economical hub for air and flour. The cyclonic effect is supplemented by the filtering winches degummed by a suction of the ventilator used for pneumatic transport. This degumming is effective despite a moleste nression of this ventilator - about 1000 mm C3 - because contrary to existing filters, they do not has not injection of air against the current. The aspiration of degumming is done by inside the sleeves, like the air intake. This one is momentarily interrupted in the sleeve in degumming. Finally it should be noted that the air entering the sleeves has already been cleaned in the cyclone, resulting in less clogging of the sleeves.

In addition to these particular features, this scrubber has been
designed to meet some more general criteria: a) tangential entry To ensure maximum cyclonic effect.

b) Calculate diameter and height as a function of airflow
chosen, and have a central fireplace, essential organ
to obtain the cyclonic effect.

c) To avoid the air going directly into the sleeves without suffering
the cyclonic effect. To do this, feed the sleeves with their
upper part, thanks to the central chimney and a
distribution cap d) Reduce as much as possible the pressure losses due to the machine and
to ensure that it is within the limits of
currently existing filters, between 100 and 150 mm wc.

e) Build a fully automatic machine, both for the
degumming that blur the recovery of flours. In case of jam
accident machine that can still occur, especially
When the installation is started, there will be no intervention inside the machine.
"débourrage" will allow the operator to empty the flour
accumulated in the bottom of the cyclone part, this flour
-cendant of the upper part by gravity, assisted descent
by a rotary scraper.

THEORETICAL AND PRACTICAL CALCULATIONS
≈A- Determination of the air flow
The machine is intended for filtering air service Dneu -matic products I grind, for medium mill soft wheat capacity of IOO TB / 24 h. Assume a conventional diagram with 5 grinders, 4 slicers, 6 converters, blutage further comprising 2 dividers-driers and 2 vibro-centrifuges. In total I9 cir -cuits. The flow at 31 is 4200 Kg.n. The air velocity is 20 mm / sec at 3I, and I8 and I6 mXsec for other breaks. the depression is of the order of 1000 mm CE. Tube diameters range from I20 to 55 min
The total air flow gives us 96.2 M3 / min. + 5% for micro-cyclone air locks, ie 101 N3 / min.

 The figures are increased by 20% to take into account the possible differences in diagrams, taps, possible meal refills. Oit I20 M3 / min. retained.

b) Détermination du diamètre du cyclone
be diamètre de la cheminée centrale doit être ch > e ceci afin de diminuer la vitesse d'air. On peut admettre dans la cheminée centrale ssP = 0,2 avec V = 10 m/sec soit P h = 500 env.B- Search for the dimensions of the cyclone part
a) Determination of the input diameter
The speed of entry is V = 20 m / sec. admitting a loss
e
load of ## = I, 5 min / M CE, which is reasonable. The diameter
entry will be #e = 355 min and the entry section:

b) Determination of the diameter of the cyclone
The diameter of the central chimney must be used to reduce the air velocity. It is possible to admit in the central chimney ssP = 0,2 with V = 10 m / sec or P h = 500 approx.

Excluding the classic raDport considered optimal in the cyclone theory is: # cy / # ch = 2,5
Let here #cy = 2,5 x 0,500 = 1,250
On the other hand if Ve / 15 <Vcy <Ve / 12 with Ve = 20 M / s.

So Vcy is between 1.333 and 1.666 m / sec.

We will have: Scy, = Se x 12 = 1,18776 M2
Scy "= Se x 15 = 1.4848 M2 Taking #cy = 1.250 we have Scy = 1.227 and Scy / Se = 1.227 / 0.09898 = 12.1 which is appropriate
e
The speed Vcy pera: Vcy = @ / 12.4 = 1.613 m / sec.

c) Control of the effectiveness of settling
We can apply the law of Stockes because the diameters of
particles to be decanted are between 1/10 and 1/1000 of MM. We
can calculate ruel will be the theoretical diameter of the finest party
-culp decanted on I kineter of fall:
g D
either v =
with: I 8 #
g = acceleration of gravity.

en ayant ris # = IOOO Kg/M3, chiffre admissible pour Poussières de farine.q = Density of dust at the constant rate of fall: v
= viscosity of the air = 0.0000I7
D = # of the particle
And if v = I, 6I3 m / sec. the fornule becomes:

having ris # = 1000 Kg / M3, permissible number for Flour dusts.

 In fact, the case will not be so favorable because if in a cyclone we benefit from the centrifugal force, we must take into account the central ascent of the air, which tends to move the particle away from the convex surface. However one can consider the speed Vcy = I, 613 m / sec. as satisfactory, but it will then be necessary to be satisfied with a larger diameter for the particle, for example: Dmax = I5 #. This Dmax corresponds in fact to approximately 90% of the mass of dusts in suspension. D) Determination of the resistance of the cyclone.

This resistance, or loss of load, is related to the diameter of the cyclone, #cy and the diameter of the central chimney, #ch.

have rows of # 160 sleeves.

that's good.

e) Diameter of the largest particle likely to escape:
Its density is assumed to be # = 1000 Kg / M3 a ci of Stockes said; e tar the effect of centrifugal force mV2
F = e becomes
c R

f) Hauteur de la partie cyclone:
- Partie verticale minimum pour entrée è section rectang- -laire équivalente à section cylindrique #e = 355 mm soit
Se = 0,09898 : d'où 0,200 x 0,500 = OIOO @ 0,09898 - Il faut une hauteur cylindrique suffisante pour profiter de l'effet centrifuge et faire en sorte que l'air ne s'échappe uas trop vite.Et la hauteur totale doit permettre à une particule de D = II,5 # de se décanter.

f) Height of the cyclone part:
- Minimum vertical part for entry of equivalent rectangular section with cylindrical cross-section #e = 355 mm
Se = 0.09898: where 0.200 x 0.500 = OIOO @ 0.09898 - A sufficient cylindrical height is required to take advantage of the centrifugal effect and to ensure that air does not escape too quickly. total height should allow a particle of D = II, 5 # to decant.

cyclone circumference # I250: Ccy = ## cy = I250 x 3, I4 = 3.927 m given the inlet section, each airstream will have a height h = 0.5. Two nets per meter in height
Settling length over I meter height: 2 x 3,927 1 7,855 which are traveled in V = 20 m / sec or in 2,546 seconds.

Falling velocity of a particle D = max
9.81 x I000 x II, 5
= 4.23978 m / sec.

I8 x O, ooo 0I7
The height of fall required will be: 2.54 x 4.24 = I0.77 m.

The necessary vertical height will therefore be: hv = ##### = I, 37
To take account of the drag due to the centrifugal force, we take a coefficient the safety k = I, 5 where:
Hv = I, 37 x I, 5 = about 2 meters.

The height of the cylindrical portion will be sufficient to prevent the arm of the degumming dispenser is in the conical area where it may disrupt the flat propellers carrying air streams in the center. If Hcyl = #cy = I200, the conical part will be: Hcon = Hv - Hcyl = 800 mm
C - Dimensions of the filter part
This filter cloth is supposed to be determined. The sleeves have a
diameter of I60 mm, commercially available.

a) Determination of the minimum distance between two runs:
It can be expressed in angle, the sleeves being on a cir
-conference. That is 3 mm thickness of the fabric and ring of 4 min on the
sleeve support. The outside diameter needed for each man
-che will be: 160 + 8 + 6 = 174 mm = of either re = 87 mm
For the pencils arranged on # 670, the most delicate case, the
minimum will be the two tangent heats either ce = re = 87 mm.

c 0.087
if Co = 0.087 on Ro = 0.335 for R1 = 1, o1 = o / Ro @ 0.335
0.2598 and for C1 = 0.2597, are A1 = 0.2604 or 2Ao = 0.5208
And for Ro = 0.335 2Ao = 2A1 / o = 0.1745 m.

o
2A1 = approx. 0.5239 are de &alpha; = 30 which is the minimum distance
b) Determination of the number of heats: N
Several solutions have been considered:
I2 innings on # I020 + I2 on # 670 = 24 innings
18 "" 12 = 30 "
18 "" 9 "= 27"
16 "" 8 "= 24"
The appropriate solution is N + = 25:
15 boards on # 1020 + 10 on # 670 on # 1020 with c = 3,204,432 we have &alpha; 1 = 24
on # 670 with c = 2,104,872 we have &alpha; 2 = 36
On # 1020 no problem because long. are Be> 0.220 On # 670 for &alpha; 1 = 36 # are 0.6283 for R1 = I
for R = 0.335 are Ae = 0.21048 which is convenient relative
at least 0,1754.

You do not need to divide # 670 evenly. It is worth
better to shake sleeves two by two to avoid the eemes
- too close to those on # 1020. We can admit:
&alpha; @ = 310 instead of DE = 300 minimum
For = 310 and R = 1, chord = 0.5345, arc = 0.54II
for R = 0.335 "= 0, I78 arc = I8I27
It remains Passages between the sleeves for assembly, checking sleeves, passage of the grease tubes, ...

c) Determination of the height of the sleeves:
Nt = 25, but there is always a handle in degumming; the useful number of sleeves will therefore be: N r Nt-I = 24 filter area per meter of filter height:
Sfl = 24 (# Dh) = I2.0637 M2
For static filters, there are 2.5 M3 / M2 and for air deflashing filters, 6 M3 / N2. Here we can take 5 M3 / M2, double the size of a static filter. Indeed the air is already purified in the cyclone, and we have a degumming quite effective .The necessary height will therefore be:
Q m / min Hf f = I, 989 ie 2 meters
5 xd) Calculation of the resistance due to the filter:
Passage through the filter fabric can be likened to a sudden narrowing of section, according to Carnot's theorem:
P (U1 U2) 2 hence the formula
2 ## = # U22 (## - 1) with S2 = passage section
Sm = shrink section (laminar flow)
o = specific mass of the air = I, 293 kg / M3 to OOC, and 76N Hg.

but here we have about T 300 and P = 1000 min SE
be # = I, 5
Filtering surface: 24 HR # = 24, I274 M2
The filter must retain the particles of D <II, those of D> II, 5 are already retained by the cyclone.

The lower limit can be considered at D = I
The filtering will therefore be done on the particles of
<df <11.5 @ which leads us to suppose a weave where the mesh openings are: S @ = 1/4 S = 6.032
The section in laminar flow will be 0.8 S / 4 =
U2 = Passage speed in S2 corresponds to

The abacus gives 50 mm / sec
We have:
#p = 115 / 2.50 (6032 / 4.825 - I) = 89.85 = 90 mm / M approx.

e) Total load loss of the machine:
central stacking chimney #ch = 480 mm length 3 m.

gives a loss of load of: 3 x 0.25 = 0.75 is approx. I min CE
to account for the distribution cap. Resistance
total of the machine will be: (## cyclone + ## chimney) + ## filter = 55 + 90 = 145 mm CE which is a lot but still reasonable because included in the limits allowed for this kind of machine (between 100 and 160 mm CE).

PRINCIPLE OF OPERATION
The entrance of the dusty air is tangential to the nozzle (I). See attached drawings. The air undergoes a cyclonic effect in Part (2). The dust settles at the bottom of the cane (3). They are transported by the scrapers (4) and (5) to the inlet of the air lock with vertical axis (6). This type 1 lock, cast iron star, is controlled by a geared motor (7) which is not visible on the drawings, by means of an angle box (8) with a wheel and worm. the sluice carries the dust into the outlet box (9) from where it is taken up by the suction of the main fan of the installation This recovery is done by an elbow (10) at 453 and radius r 500 min To facilitate the launch of the product, the air from the pneumatic rework tire is always taken from the upper part of the machine via the handle, which is then degummed in. The lock must be tight because it must not be sucked into the machine. cyclone bottom through pneumatic recovery.

 The air having been purified in the cyclone part and arriving at the bottom of the cone (3), goes up in the center and reaches the central chimney (II). The latter brings it into the distribution cap (I2).

The purified air thus enters the sleeves (I3) of the filter, by the sumerieure part. It passes through the filter cloth, and it is a clean air that is on the outside of the sleeves. This air rises to the hood (I4) and reaches the exhaust stack (15). Inside the latter a helical electro-fan provides a decompression -Pression 11 outside the sleeves, facilitating filtering and decreasing the pressure drop dde a resistance of the filter. Its installation is therefore recommended, but not essential.

 The vertical shaft (I7) of the lock carries an eccentric (I8) which itself carries a pallet (19). This rotates a toothed wheel (20) mounted on a vertical shaft (21) in the axis of the machine. The shaft (2I) is hollow. He carries the scrapers (4) and (5).

It has a first panties (22) and a second panties (23)
All of these panties and trunks (24) terminating the conduits, and their support (25) will be called "distributor".

The dispenser is driven by a jerky rotational movement due to the pallet (19) meshing with the wheel (20). At each saccade distributor one of the two chutes (24) is placed under a sleeve which is then put in suction by the hollow shaft (21) and the output box (9). The troughs are applied to the lower support flange of the sleeves, by two strong compression springs (26) bearing on the support (25), and held by sliding guides i'un'in the other.

 It is necessary to avoid that the suction in the sleeve by degumming cup by part upwards. The hollow shaft (2I) is thus extended by a solid shaft (27) held by a plain bearing (28j resting on the cap) This shaft (27) carries a support (29) rotating inside the cap distribution and coming place two closing plates (30) and (31) 3 the entrance of the sleeves.

oimultaneously when a chute (2iy is placed in asmira- tion -tion under a sleeve, a closing plate (30j or (31) just close the air inlet in the corresponding sleeve.The dégommage neut so be done. degummed descend through the hollow shaft (21) and live without the outlet box (9) where they find the dust from the lock and are taken together.The sleeves are held tensioned by clamping circlips on upper supports and lower rushes (31) o
Stuffing is an accident that can occur during start-up on any machine of this type. A rotary level probe (32) is installed on a wall. It slaves the DrinciDal fan motor of the pneumatic transport of the installation.

 It will stop the fan and all the factory By a timed-adjustable relay, after sound and light alarm syncotic table. Debouring will be done by manually opening the pull valve (33). The scrapers (4) and (5) will bring the flours to the lock (6) and the rotor thereof will drop them into the output box (9).

 The machine still has 4 visiting tortoises (34) to monitor the sleeves and change them then wear. It also includes a control window (35) in the conical part. She finally has feet of variable height for support on floor, but which are not shown on the drawings.

 This machine has been designed mainly to purify the air of small and medium oulins.Elle can also be used to purify the air from fson of the sasseurs or the air of aspiration on any machine. It is suitable for the semolina to the matrerie, and any industry of cereals. Its job is to be envied in any industry where the need arises to purify dust-laden air: sawmills, factories of pan-nails, silos, oil mills, feed mills, ect. may be useful in all services or handling in bags or bulk orod-bed of dust, tar example sorting of mailbags, mines, quarries, crushing facilities. it is used to reduce investment costs and codes function.

Claims (3)

 I - Air purifier constitutes a cyclone surmounted by a repressed air filter. The filter consists of cylindrical-sleeve filter cloth.  2 - air purifier according to claim I characterized in that a central chimney in the cyclone portion ensures a true and effective cyclonic effect, and allows to supply the filter nar its upper part.  3 - Air purifier according to claim 2 characterized in that the degumming of the sleeves is provided by a suction inside the sleeves, this suction also serving to the ascent of the underesières. The same rotating central axis distributes the suction under the sleeves and closes the corresponding upper air inlet.