FR2519950A2 - Anti blow back valve for powdered pneumatic furnace feed - uses top hung one way flap valve sited between end of screw and diffuser - Google Patents

Abstract

The one-way top-hung safety flap valve (13) may be incorporated in a pneumatic carbon powder feed to a furnace, to prevent a blow back. The feed uses a screw (2,3) to move the powder to a diffuser, and the valve in the form of a rectangular flap is rigidly connected to an axle rod (14). It is sited between the screw and the diffuser. It may be sited in a valve box comprised of two interhousing cylindrical pieces (5,6), the first piece contg. a half round end (2') of the screw shaft whilst the valve fits between the two pieces. The first piece may use converging vertical internal side walls to effect the transition from the end of the screw case (1) to the valve opening (11). The cross sectional area of the screw is less that of the shaft and not more than the area of the opening.

Description

Pneumatic conveying device for powdery material.

 The present invention constitutes an addition to French patent application No. 81 00100 of January 6, 1981, relating to the suspension at high concentration of a pulverulent material in a carrier gas, for the purpose of pneumatic transport in a pipe of the mixture thus obtained. .

 The invention, according to the main patent, relates to a pneumatic transport device for pulverulent material, comprising a powder distributor supplying a worm, followed by suspending the pulverulent material in a carrier gas, characterized in that that the pulverulent material, at its exit from the worm, enters a closed diffuser, in the external form of a hollow disc laterally receiving at least one supply of carrier gas, and opening into a convergent connected to the pipe to be supplied, this diffuser internally comprising a fixed part, of revolution, the hollow central part of which continuously receives the pulverulent material coming from the worm, the downstream profile of which forms, with the hollow disc, an annular chamber supplied with carrier gas and opening into said convergent, and which has several slots blowing carrier gas into said hollow central part, in order to disaggregate the compressed powdery material ée at its exit from the worm, before it is entrained in the convergent by the main flow of carrier gas from said annular chamber.

 This invention according to the main patent gives all satisfaction in normal operation, with a low or moderate back pressure downstream of the device.

 On the other hand, in exceptional or accidental cases either of lack of pulverulent material in the worm, or of abnormally high back pressure, it is necessary to avoid the possible risks, for example of explosion of thundering mixture if it is pulverized coal and air (or enriched air), ensuring a perfect seal between the worm and the entire circuit downstream of it.

 The purpose of this a d d i t i o n is to achieve this perfect seal between the worm and the diffuser, if necessary, automatically, by means of an appropriate safety device.

 To this end, the present addition first relates to a device according to the main patent, characterized in that there is interposed, between the worm and the diffuser, a non-return valve of oblong shape in the vertical direction , and secured to a rod movable in rotation about a horizontal axis.

 This oblong shape can advantageously consist of a rectangular shape terminated by two rounded at its upper and lower ends.

 This check valve is movable around a horizontal axis disposed at the top of the opening to be closed.

 The rod arranged along this horizontal axis and passing through the wall may be provided with a counterweight, adjustable or not.

 One of its outer ends can advantageously be provided with a lever whose position indicates the opening or closing of the valve.

 The present addition also has the object of disposing said non-return valve in a valve box, interposed between the housing of the worm and the diffuser, and characterized in that it consists of two tubular parts of revolution, which nest one into the other, in that the hollow central part of the first of these two parts constitutes a first chamber placed upstream of said valve and which surrounds the end of the rod of the worm, and in that the hollow central part of the second of these two parts constitutes a second, cylindrical chamber, placed downstream of said valve, of length at least equal to the length of the valve, and of the same diameter as the hollow central part of the diffuser.

 According to a particular characteristic of the valve box according to this addition, the first chamber has, from upstream to downstream of the material flow, a horizontal narrowing produced by two vertical walls of connection with the width of the opening closable by the non-return valve, without any vertical narrowing.

 According to another particular characteristic of the valve boot according to the present addition, the closure opening by the valve has an area at least equal to the difference between the internal cross section of the housing containing the worm and the cross section of the rod of said worm.

 According to another particular characteristic of the valve box according to this addition, the cross section of the second chamber is larger than the internal cross section of the housing of the worm, which is also equal to the inlet section from the first bedroom.

 More advantageously still, according to another particular characteristic of the safety device according to the present addition, the cross section of the second chamber of the valve boot is slightly greater than the sum of the opening closable by the non-return valve and of the cross section of the worm shaft.

 Finally, according to another particular characteristic of the invention according to the present addition, the useful end of the rod of the worm is rounded according to a half-sphere of the same diameter as the rod.

 Thus, the safety device according to the present addition has both the advantage of closing automatically in the event of excessive inadvertent back pressure, while completely disappearing in the horizontal position in normal operation of the entire device. pneumatic transport, while the design of the valve boot makes it possible to retain all the advantages of good flow and disintegration of the lumps of pulverulent material described in the main patent.

 It can also be advantageous for the closure of the non-return valve to automatically stop the installation, that is to say stop the rotation of the worm. This may be the case when the supply of the auger is accidentally interrupted.

 You can also equip the valve closure with an audible or light signal.

 In order to clearly understand the invention, an embodiment of a safety device according to the present invention will be described below, by way of nonlimiting example, to be inserted between the worm and the diffuser. the example described in the main patent. It should be remembered that, in this example, it involves suspending pulverized coal in a stream of compressed air in order to supply a blast furnace nozzle.

 The pulverized coal supply pipe for the blast furnace nozzle has a diameter of 25.4 millimeters (or one inch) and its length between the pneumatic transport device according to the invention and the blast furnace nozzle, in which it penetrates, is 80 meters. The back pressure, measured just downstream of the convergent at the head of the pipe, is 1.8 bar.

The difference in level between the device according to the invention and the nozzle to be supplied is 9 meters.

 The safety device, constituted by the non-return valve and the valve box according to the present addition, is interposed between the worm and the diffuser described in the main patent.

- Figure 1 is a longitudinal vertical section of this safety device;
- Figure 2 is a vertical cross section
II-II of this device with a view of a fixing flange.

- Figure 3 is the same section as Figure 2, the valve being removed-
- Figure 4 is a horizontal cross section along IV-IV of this device.

 In FIG. 1, we see, on the left, the end of the casing 1 containing the end of the worm, consisting of a rod 2 and a thread 3.

 The internal diameter of the casing 1 is 96 millimeters. The screw shank has a diameter of 48 millimeters, while the thread pitch is 68 millimeters.

 It follows from the above that the internal section of the casing is 7240 square millimeters, and that the cross section of the screw rod is 1810 square millimeters.

 The end 2 ′ of this rod is a half-sphere, of the same diameter as the rod, that is to say 48 millimeters.

 The length of the screw rod, which is not entirely shown in Figure 1, is actually 800 millimeters, which is abnormally long compared to the usual worms, given the diameter. But this characteristic is deliberately desired, in order to ensure excellent compression of the pulverulent material conveyed, which, on the one hand, gives a favorable relationship between the speed of rotation of the screw and the flow rate of material transported, and on the other hand, provides a good seal and gives a safety margin in exceptional cases of lack of material at the entry of the screw, coming from the distributor or even simply in the event of a slowdown of this supply.

 Downstream, the housing is made integral with a flange 4.

 The valve box according to the present invention is made up of two tubular parts 5 and 6 which fit into one another as shown in FIG. 1.

 The first part 5 is fixed to the flange 4 of the casing by means of its flange 7.

 The second part 6 is fixed, downstream, to the diffuser according to the main patent (not shown in FIG. 1) by means of a flange 8.

 The interior of part 5 constitutes a first chamber 9, and the interior of part 6 a second chamber 10.

 The first chamber 9 contains the end 2 'of the rod 2 of the worm. Its inlet section 11 is constituted by a circle equal to the inner cross section of the casing 1, with an area equal to 7240 mm 2.

 Its outlet section 12, visible in FIGS. 1 to 3, constitutes the opening to be closed by the non-return valve 13.

It is an oblong opening comprising a rectangular main part 60 mm wide, terminated by two rounded edges, the total length of the opening being 96 millimeters, equal to the inside diameter of the casing 1. The first chamber 9 is, in Consequently, delimited by two vertical walls 18 and 19, the horizontal section of which is visible in FIG. 4. The area of the section 12 is equal to 5.500 mm2.

 The non-return valve 13 is integral with a cylindrical rod 14 which rotates around a horizontal axis 15, visible in FIG. 2.

 The position of this axis 15 and the diameter of the rod 14 must be such that the valve, with a width of 64 mm, can be placed in a horizontal position at the top of the chamber 10 during the normal operation of the entire device. .

 This is one of the reasons - it is not the only one for which the second chamber 10 has a diameter greater than 96 mm. This diameter is in fact 106 mm in the present example, hence a section of 8840 mm2. The part 6 is internally cylindrical, and its length is just a little longer than the length of the valve; it is worth 110 mm.

 A second reason for the second chamber 10 to have a diameter slightly greater than the diameter of the inlet section 11 of the first chamber 9 is that it is necessary that the pulverulent material, on leaving the worm, is no longer also compressed and can begin to dislocate, thanks to the enlargement of the chamber 10, after the narrowed passage of the opening 12 closable by the valve 13.

 If necessary, the non-return valve 13 folds down by completely closing the opening 12. This folding can be effected by gravity, either under the effect of the own weight of the valve, or, in addition, under the effect of a counterweight fixed to the rod 14 and not shown in the figures.

 The external end 16 of the rod 14 is provided with a lever 17, the position of which indicates in a very visible manner the opening or closing of the valve 13. The closure of the valve can be equipped with an audible or light signal .

 It is also possible to install, if this valve 13 is closed, an automatic system for stopping the installation, that is to say for automatically stopping the worm.

 To complete the description of the present example, it is useful to note the correct application of the rules according to the invention, concerning the surfaces present.

 First of all, the opening closable by the valve has a surface (5.500 mm2) greater than the difference (5.430 mm2) between the internal cross section (7.240 mm2) of the housing containing the worm and the cross section (1.810 mm2) of the rod of said worm.

 Then, the cross section (8.840 mm2) of the second chamber 10 is larger than the internal cross section (7.240 mm2) of the worm gear housing.

 Finally, the cross section (8.840 mm2) of the second chamber 10 is much greater than the sum (7.310 mm2) of the opening (5.500 mm2) closable by the valve 13 and the cross section (1810 mm2) of the worm screw rod.

 The observation of all these rules is necessary for the proper flow of the pulverulent material in the valve box, before it is suspended by the diffuser according to the main patent.

 In summary, the cooperation of a long length of the worm with the valve box which has just been described ensures the pneumatic transport device of powdery material according to the main patent an absolutely total operating safety at the same time as a perfect seal, while achieving an excellent flow of the pulverulent material.

 Without departing from the scope of the invention, it is possible to add supplements or imagine variants or equivalent means.

Claims (10)

1. Safety device to be added to a pneumatic conveying device for pulverulent material according to any one of claims 1 to 4 of main patent No. 81 OOlOO, comprising a powder distributor feeding a worm (2) followed by a diffuser ensuring the suspension of the pulverulent material in a carrier gas, this safety device being characterized in that, between the worm (2) and the diffuser, a non-return valve (13) is inserted oblong and integral with a rod (14) movable in rotation about a horizontal axis (15) disposed at the top of the opening to be closed (12). 2. Safety device according to claim 1, characterized in that said non-return valve (13) is disposed in a valve box, itself interposed between the housing (1) of the worm (2) and the diffuser, and made up of two tubular parts of revolution (5) (6) which fit into one another, the hollow central part of the first (5) of these two parts constituting a first chamber (9) placed upstream of said valve (13) and which surrounds the end (2 ') of the rod (2) of the worm, while the hollow central part of the second (6) of these two parts constitutes a second chamber ( 10), cylindrical placed downstream of said valve (13), of length at least equal to the length of the valve, and of the same diameter as the hollow central part of the diffuser. 3. Safety device according to claim 2, charac terized in that the first chamber (9) of the valve box has, from upstream to downstream of the material flow, a horizontal narrowing produced by two vertical walls (18 / 19) of connection with the width of the opening (12) closable by the valve (13), without any vertical narrowing. 4. Safety device according to claim 3, characterized in that the opening (12) closable by the valve (13) has an area at least equal to the difference between the internal cross section of the housing (1) of the screw without end and the cross section of the rod (2) of said worm. 5. Safety device according to any one of claims 2 to 4, characterized in that the cross section of the second chamber (10) of the valve box is larger than the internal cross section of the housing (1) of the endless screw. 6. Safety device according to any one of claims 2 to 5, characterized in that the cross section of the second chamber (10) of the valve box is slightly greater than the sum of the opening (12). closable by the valve (13) and the cross section of the rod (2) of the worm. 7. Safety device according to any one of claims 1 to 6, characterized in that the end (2 ') of the rod (2) of the worm is rounded according to a semisphere of seme diameter that the rod (2). 8. Safety device according to any one of claims 1 to 7, characterized in that one (16) of the ends of the rod (14) integral with the valve (13) and movable in rotation about the horizontal axis (15) is provided with a lever (17) whose position visibly indicates the opening or closing of the valve (13). 9. Safety device according to any one of claims 1 to 8, characterized in that the closing of the valve (13) automatically stops the rotation of the worm. 10. Safety device according to any one of claims 1 to 9, characterized in that the closing of the valve (13) is equipped with an audible or light signal.