Filters and granular material processing equipment

Abstract

To provide a filter which is excellent in filtration performance and can recover the filtration performance by backwash while reducing the supply amount and supply time of backwash gas, and to provide a powder / granular material treatment apparatus using the filter.SOLUTION: The filter includes: a cylindrical metal filter part 11 composed of a metal filter material; a cylindrical flexible filter part 12 composed of a flexible filter material and arranged on the side of an outer peripheral surface 11a of the metal filter part 11; and a retainer 13 for supporting the filter materials 11 and 12, in which powder / granular particles mixed in to-be-treated gas G are separated when passing through the filter parts. At the time of backwashing, the supplied pulse air P passes through the inside of the filter material from the side of the inner peripheral surface 11b of the metal filter part 11 and is jetted to the side of the outer peripheral surface 11a. The flexible filter part 12 is deformed to expand in a radial direction by receiving the pulse air P jetted from the side of the outer peripheral surface 11a, and the powder / granular particles stuck to the flexible filter part 12 are dusted off by the deforming operation.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a filter for separating solid particles from a solid-gas mixed gas and a powder and granular material processing apparatus using the filter.

Background Art

[0002] For example, a fluidized bed apparatus, which is an example of a powder and granular material processing apparatus, is an apparatus that performs processes such as granulation, coating, and drying while suspending and fluidizing powder and granular materials accommodated in a fluidized bed container by a processing gas introduced from the bottom of the fluidized bed container. In this type of fluidized bed apparatus, a filter is disposed above the fluidized bed container in order to separate powder and granular particles from the exhaust gas of the processing gas mixed with powder and granular particles (fine powder, etc.). As the filter, in addition to a filter composed of a cloth filter medium called a bag filter, a cartridge filter in which a filter medium made of resin or metal is formed into a cylindrical shape and held by a retainer is used (Patent Documents 1 to 5).

[0003] Due to use, the powder and granular particles separated from the solid and gas may adhere to the inside of the filter medium or the collection surface (the surface on the inflow side with respect to the flow of the solid-gas mixed gas), resulting in a decrease in filtration performance (clogging). Therefore, it is necessary to timely remove the powder and granular particles adhering to the filter medium to restore the filtration performance. In the cartridge filters described in Patent Documents 1 to 5, a reverse washing gas such as pulse air is supplied to the side of the back surface (the surface on the outflow side with respect to the flow of the solid-gas mixed gas) opposite to the collection surface of the filter medium, passed through the inside of the filter medium, and ejected from the side of the collection surface, thereby removing the powder and granular particles adhering to the filter medium (reverse washing).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

[0005] While metal filters, composed of metal filter media, offer excellent filtration performance, they also have drawbacks. Because the filter media is highly rigid and does not deform under the pressure of backwash gas, powdery particles adhering to the media are not adequately removed by the backwash gas. This can result in a failure to restore filtration performance, or require a large supply volume and duration of backwash gas to restore performance. This tendency is particularly pronounced when processing highly adhesive and cohesive powdery particles.

[0006] The object of the present invention is to provide a filter that has excellent filtration performance and can restore filtration performance by backwashing while reducing the supply amount and supply time of backwash gas, and a powder and granular material processing apparatus using the filter. [Means for solving the problem]

[0007] To solve the above problems, the present invention provides a filter for separating solid particles from a solid-gas mixture, comprising: a metal filter section made of a metal filter material and having one side that is the inlet side and the other side that is the outlet side with respect to the flow of the solid-gas mixture; and a flexible filter section made of a flexible filter material, provided on the side of the one side of the metal filter section, which is supplied from the other side of the metal filter section during backwashing with backwash gas and deforms due to the pressure of the backwash gas ejected from the side of the one side of the metal filter section.

[0008] Furthermore, in order to solve the above problems, the present invention provides a powder and granular material processing apparatus in which the above-mentioned filter is placed in the exhaust path of the processed gas. [Effects of the Invention]

[0009] In the process of separating solid particles from a solid-gas mixture using the filter of the present invention, solid particles mixed in the solid-gas mixture are first collected in the flexible filter section, and the solid particles that pass through the flexible filter section are collected in the metal filter section. As a result, solid particles are less likely to adhere to the collection surface of the metal filter section (the side facing the inflow of the solid-gas mixture) or the inside of the filter material, thus maintaining the good filtration performance of the metal filter section. Furthermore, during backwashing with backwash gas, the backwash gas is supplied from the back side of the metal filter section (the other side facing the inflow of the solid-gas mixture), passes through the inside of the filter material, and is ejected from the other side. The pressure of the backwash gas deforms the flexible filter section, and this deformation of the flexible filter section dislodges and removes solid particles that have adhered to it. This restores the filtration performance of the filter. In addition, the amount and time of backwash gas supply required to restore the filtration performance of the filter can be reduced.

[0010] In a powder and granular material processing apparatus that incorporates the filter of the present invention into the exhaust path of the processed gas, the excellent filtration performance and recovery function of the filter effectively separate (collect) powder and granular material particles mixed in the exhaust. Therefore, it is not necessary to install a dust collector in the exhaust path, or the dust collector installed in the exhaust path can be made smaller. This makes it possible to simplify and reduce the cost of powder and granular material manufacturing equipment, including the powder and granular material processing apparatus. [Brief explanation of the drawing]

[0011] [Figure 1] This is a cross-sectional view showing one example configuration of a fluidized bed apparatus equipped with a cartridge filter according to the embodiment. [Figure 2] This is a cross-sectional view of a cartridge filter according to the first embodiment. [Figure 3] This is a cross-sectional view of a cartridge filter according to the second embodiment. [Figure 4] This is a cross-sectional view of a cartridge filter according to a third embodiment. [Figure 5] This is a cross-sectional view of a cartridge filter according to the fourth embodiment. [Figure 6A] It is a cross-sectional view (viewed from the front side) conceptually showing a configuration example of a drum-type coating apparatus equipped with a cartridge filter according to an embodiment. [Figure 6B] It is a left side view (partial cross-section) of the drum-type coating apparatus of FIG. 6A.

Mode for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0013] FIG. 1 shows a configuration example of a fluidized bed apparatus as a granular material processing apparatus.

[0014] The fluidized bed container 1 of the fluidized bed apparatus includes a processing chamber 2 for processing granular materials, for example, granulating or coating granular materials, a filter chamber 3 provided above the processing chamber 2, and an exhaust chamber 4 provided above the filter chamber 3. The filter chamber 3 and the exhaust chamber 4 are partitioned by a partition wall 5.

[0015] At the bottom of the processing chamber 2, a gas dispersion plate 2a made of a perforated plate (or wire mesh) such as punching metal is disposed. The processing gas G such as hot air supplied from the air supply duct 6 to the air supply chamber 7 is introduced into the fluidized bed container 1 through the gas dispersion plate 2a. Further, in the processing chamber 2, a spray nozzle 8 for spraying a spray liquid (film agent liquid, binder liquid, etc.) downward is installed.

[0016] In the filter chamber 3, one or more filters, for example, a plurality of cartridge filters A, are arranged. Each cartridge filter A is attached to the partition wall 5, and the filter chamber 3 and the exhaust chamber 4 communicate with each other through the cartridge filter A. The processed gas G that enters the exhaust chamber 4 from the filter chamber 3 through the cartridge filter A is exhausted to the outside of the apparatus through the exhaust duct 9. Further, inside the exhaust chamber 4, a backwashing device, for example, a backwashing nozzle 10, is arranged to supply a backwashing gas, for example, pulse air (pulse jet air) P, to the cartridge filter A to backwash (purify) the cartridge filter A.

[0017] FIG. 2 shows the cartridge filter A according to the first embodiment. In this embodiment, the cartridge filter A includes a cylindrical metal filter part 11 made of a metal filter medium, a cylindrical flexible filter part 12 made of a flexible filter medium and arranged on the outer peripheral side of the metal filter part 11, and a retainer 13 that supports the metal filter part 11 and the flexible filter part 12.

[0018] The metal filter part 11 is formed by molding a filter medium made of a metal porous material such as a metal mesh, a woven or non-woven fabric of metal fibers, or a sintered metal into a cylindrical shape.

[0019] The flexible filter part 12 is formed by molding a resin filter medium subjected to pleating into a cylindrical shape and has a pleated form in which the peaks and valleys are alternately arranged in the circumferential direction. This flexible filter part 12 has flexibility that allows it to expand and contract in the radial direction due to the combined action of the elasticity of the resin filter medium and the pleated form. Further, a bottom cap 12a is attached to the lower end of the flexible filter part 12.

[0020] The retainer 13 consists of a core 13a, a flange 13b fixed to the upper end of the core 13a, and an end cap 13c detachably attached to the lower end of the core 13a. The core 13a comprises a cylindrical portion 13a1 having numerous ventilation holes and an opening 13a11 at its upper end, a shaft portion 13a2 provided at the lower end of the cylindrical portion 13a1, and a sealing ring 13a3 fixed to the shaft portion 13a. The end cap 13c is screwed (or press-fitted) onto the shaft end of the shaft portion 13a2.

[0021] The metal filter section 11 is fitted onto the core 13a, its upper end is fixed to the flange 13b, and its lower end is attached to the sealing ring 13a. The lower end of the metal filter section 11 comes into contact with the sealing ring 13a, sealing the vent hole and creating a non-ventilated section 11c. The flexible filter section 12 is fitted onto the metal filter section 11, and its bottom cap 12a is attached to the shaft section 13a2. The bottom cap 12a is pushed towards the flange 13b by an end cap 13c that is screwed (or press-fitted) onto the shaft end of the shaft section 13a2 via an O-ring 14. As a result, the flexible filter section 12 is held in the retainer 13, sandwiched from above and below by the flange 13b and the end cap 13c.

[0022] The cartridge lifter A is installed in an opening 5a provided in the partition wall 5 and is detachably fixed by an annular expansion seal 15. More specifically, the expansion seal 15 is installed on a U-shaped mounting portion 13b1 provided on the outer circumference of the flange 13b. In addition, a seal wall surface 5a1 is provided on the edge of the opening 5a, rising downwards. When compressed gas such as compressed air is supplied to the expansion seal 15 with the cartridge lifter A inserted into the opening 5a so that the expansion seal 15 faces the seal wall surface 5a1, the expansion seal 15 expands and presses against the seal wall surface 5a1. This seals the space between the cartridge lifter A and the opening 5a, and fixes the cartridge filter A to the opening 5a. When compressed gas is discharged from the expansion seal 15, the expansion seal 15 contracts and separates from the seal wall surface 5a1. This allows the cartridge lifter A to be removed from the opening 5a.

[0023] The treated gas G, rising within the fluidized bed container 1 and entering the filter chamber 3, flows into the cartridge filter A through the flexible filter section 12 and the metal filter section 11, circulates through the cylindrical section 13a1 of the core 13a, and flows out to the exhaust chamber 4 through the opening 13a11. Powdered and granular particles mixed in the treated gas G are separated from the treated gas G as they pass through the flexible filter section 12 and the metal filter section 11. With respect to this flow of treated gas G, the outer surface 11a of the metal filter section 11 becomes the side (collection surface) on the inflow side of the treated gas G. The flexible filter section 12 is positioned to cover the outer surface 11a of the metal filter section 11. Meanwhile, the backwash nozzle 10 supplies pulsed air P to the cartridge filter A in the opposite direction to the flow direction of the treated gas G. Specifically, the backwash nozzle 10 supplies pulsed air P into the cartridge filter A through the opening 13a11 at the upper end of the cartridge filter A. Pulsed air P supplied into the cartridge filter A is ejected from the inner circumferential surface 11b of the metal filter section 11, passing through the inside of the filter material and exiting to the outer circumferential surface 11a. This ejection of pulsed air P dislodges granular particles adhering to the inside of the filter material and the outer circumferential surface 11a of the metal filter section 11. In addition, the flexible filter section 12, positioned on the outer circumferential surface 11a side of the metal filter section 11, deforms by expanding radially under the pressure of the pulsed air P ejected from the outer circumferential surface 11a side, and this deformation dislodges granular particles adhering to the flexible filter section 12. In particular, when pulsed air P is used as the backwashing gas, the flexible filter section 12 repeatedly expands and contracts radially according to the ON / OFF timing of the pulsed air P, further enhancing the effect of dislodgeing granular particles.

[0024] In Figure 1, the granular material contained in the processing chamber 2 of the fluidized bed container 1 is suspended and fluidized by the processing gas G introduced into the fluidized bed container 1 via the gas dispersion plate 2a. Then, a spray liquid (film agent liquid, binder liquid, etc.) is sprayed from the spray nozzle 8 toward this fluidized bed of granular material. The granular material particles are moistened by the spray liquid sprayed from the spray nozzle 8, for example, the mist of the film agent liquid, and at the same time, the solid components contained in the film agent liquid adhere to the surface of the granular material particles, dry and solidify, and a coating layer is formed on the surface of the granular material particles (coating). Alternatively, the granular material particles are moistened by the spray liquid sprayed from the spray nozzle 8, for example, the mist of the binder liquid, adhere and aggregate, dry, and grow into particles of a predetermined diameter (granulation).

[0025] The treated gas G, which has been suspended and flowed in the processing chamber 2, enters the filter chamber 3 as a solid-gas mixed gas containing granular particles (fine powder, etc.), flows through the inside of the cartridge filter A provided in the filter chamber 3, and enters the exhaust chamber 4. The granular particles mixed in the treated gas G are separated from the treated gas G as they pass through the flexible filter section 12 and the metal filter section 11 of the cartridge filter A. In this solid-gas separation process, the granular particles mixed in the treated gas G are first collected in the flexible filter section 12, and only the granular particles that have passed through the flexible filter section 12 are collected in the metal filter section 11. As a result, granular particles are less likely to adhere to the outer surface 11a of the metal filter section 11 or the inside of the filter material, and the good filtration performance of the metal filter section 11 is maintained.

[0026] On the other hand, if the filtration performance of the cartridge filter A deteriorates due to the elapsed operating time of the fluidized bed apparatus, backwashing is performed using the backwash nozzle 10. Backwashing of the cartridge filter A can be performed by automatically activating the backwash nozzle 10 and supplying pulsed air P to the cartridge filter A when the deterioration in filtration performance is detected by appropriate means (for example, the deterioration in filtration performance can be detected by measuring the flow rate of exhaust gas passing through the exhaust duct 9), or when a preset cycle time has elapsed. Furthermore, backwashing of the cartridge filter A can be performed while the fluidized bed apparatus is operating (processing powders and granules), or when the operation of the fluidized bed apparatus is temporarily stopped.

[0027] As described above, the pulsed air P supplied from the backwash nozzle 10 into the cartridge filter A is ejected from the inner circumferential surface 11b of the metal filter section 11, passing through the inside of the filter material and out to the outer circumferential surface 11a. This ejection of pulsed air P dislodges granular particles adhering to the inside of the filter material and the outer circumferential surface 11a of the metal filter section 11. In addition, the flexible filter section 12 repeatedly undergoes deformation by expanding and contracting radially according to the ON / OFF timing of the pulsed air P, thereby dislodgeing granular particles adhering to the flexible filter section 12. This restores the filtration performance of the cartridge filter A.

[0028] Figure 3 shows a cartridge filter A according to a second embodiment. The differences between this second embodiment of cartridge filter A and the first embodiment of cartridge filter A described above are that the flexible filter section 12 is made of a cloth filter material consisting of a woven or nonwoven fabric containing at least one of chemical fibers and natural fibers, and that the lower end of the flexible filter section 12 is fixed with an end cap 13c via an O-ring 14. The flexible filter section 12, made of cloth filter material, has flexibility that allows it to expand and contract radially due to the flexibility of the filter material. Therefore, in accordance with the ON / OFF timing of the pulse air P, the flexible filter section 12 repeatedly undergoes deformation by expanding and contracting radially, thereby effectively removing powder and granular particles adhering to the flexible filter section 12. Other matters are the same as those described for the first embodiment of cartridge filter A described above, so redundant explanations are omitted.

[0029] Figure 4 shows a cartridge filter A according to a third embodiment. The difference between this third embodiment of cartridge filter A and the first embodiment of cartridge filter A described above is that a coarse portion 12b with a larger mesh size than the filter material of the flexible filter portion 12 is provided at the lower end of the flexible filter portion 12, in this embodiment, at the bottom cap 12a of the flexible filter portion 12. The bottom cap 12a is made of an elastic material such as rubber, and the coarse portion 12b is formed by providing a number of openings with a mesh size that allows powder and granular particles to pass through in the part of the bottom cap 12a facing the non-permeable portion 11c of the metal filter portion 11. The coarse portion 12b is normally in contact with the non-permeable portion 11c of the metal filter portion 11 and is sealed by the non-permeable portion 11c. This prevents the treated gas G from passing through the coarse portion 12b and flowing into the inside of the cartridge filter A during powder and granular material processing. On the other hand, during backwashing with pulsed air P, the flexible filter section 12 expands radially due to the pulsed air P ejected from the outer peripheral surface 11a of the metal filter section 11. As the internal pressure in the space between the metal filter section 11 and the flexible filter section 12 increases, the bottom cap 12a elastically deforms in the outer diameter direction, creating a gap between the coarse section 12b and the non-permeable section 11c of the metal filter section 11. During backwashing, granular particles brushed from the metal filter section 11 into the space, and granular particles brushed from the flexible filter 12 into the space, are discharged to the outside of the cartridge filter A by passing through the coarse section 12b, due to the action of their own weight and the flow of pulsed air P flowing out from the internal space through the coarse section 12b. Other matters are the same as those described for the cartridge filter A of the first embodiment described above, so redundant explanations are omitted.

[0030] Figure 5 shows a cartridge filter A according to the fourth embodiment. The difference between this fourth embodiment of the cartridge filter A and the second embodiment of the cartridge filter A described above is that a coarse section 12c with a larger mesh size than the filter material of the flexible filter section 12 is provided at the lower end of the flexible filter section 12. The coarse section 12c is formed by making the mesh size of the part of the filter material (flexible filter section 12) facing the non-permeable section 11c of the metal filter section 11 larger than that of other parts. During powder and granular material processing, the coarse section 12c is subjected to the pressure of the flow of the processed gas G and comes into contact with the non-permeable section 11c of the metal filter section 11, and is sealed by the non-permeable section 11c. This prevents the processed gas G from passing through the coarse section 12c and flowing into the inside of the cartridge filter A during powder and granular material processing. On the other hand, during backwashing with pulsed air P, the flexible filter section 12 expands radially due to the pulsed air P ejected from the outer peripheral surface 11a of the metal filter section 11, creating a space between the metal filter section 11 and the flexible filter section 12, as well as a gap between the coarse section 12c and the non-permeable section 11c of the metal filter section 11. During backwashing, granular particles brushed from the metal filter section 11 into the space, and granular particles brushed from the flexible filter 12 into the space, are discharged to the outside of the cartridge filter A by passing through the coarse section 12b, due to the action of their own weight and the flow of backwashing gas flowing out from the internal space through the coarse section 12c. Other matters are the same as those described for the cartridge filter A of the first and second embodiments described above, so redundant explanations are omitted.

[0031] Figures 6A and 6 conceptually illustrate one example of a drum-type coating system for powder and granular material processing. This coating system includes a ventilated rotating drum 21 that is driven to rotate around an axis X parallel or approximately parallel to the horizontal line. Inside the casing 22 are a drum chamber 22a that houses the rotating drum 21 and an exhaust chamber 22c separated by a sealing plate 22b. A spray nozzle (not shown) is also positioned inside the rotating drum 21 to spray a spray liquid, such as a film material liquid, toward the powder and granular material layer.

[0032] The rotating drum 21 comprises a peripheral wall portion 21a having a polygonal (or circular) cross-sectional shape, an end wall portion 21b continuous with one end of the peripheral wall portion 21a, and an end wall portion 21c continuous with the other end of the peripheral wall portion 21a. The peripheral wall portion 21a is provided with a ventilation portion formed by a porous portion, and the treated gas G, such as hot air, is introduced into the rotating drum 21 through the ventilation portion of the peripheral wall portion 21a. In addition, a plurality of partition plates 21d are provided on the outer circumference of the peripheral wall portion 21a at predetermined intervals in the circumferential direction, and when the rotating drum 21 rotates, the partition plates 21d slide against the seal plate 22b, so that the treated gas G introduced into the rotating drum 21 passes through the powder and granular layer and is exhausted from the exhaust port 22b1 of the seal plate 22b to the exhaust chamber 22c.

[0033] One or more cartridge filters A of the above-described embodiment are arranged in the exhaust chamber 22c. The cartridge filters A are installed in openings in the ceiling wall 22c1 of the exhaust chamber 22c, and the exhaust chamber 22c communicates with the exhaust duct 23 via the cartridge filters A. A backwashing device, such as a backwashing nozzle (not shown), is arranged in the space above the ceiling wall 22c1 to supply backwashing gas, such as pulsed air, to the cartridge filters A for backwashing.

[0034] When the rotating drum 21 containing the powder or granular material, such as tablets, to be coated is driven to rotate, the powder and granular particles inside are agitated and mixed to form a powder and granular layer (rolling bed). Then, a spray liquid is sprayed from a spray nozzle onto the powder and granular layer. The spray liquid sprayed onto the powder and granular layer is spread onto the surface of each powder and granular particle by the agitation and mixing action of the powder and granular layer accompanying the rotation of the rotating drum 21. The spray liquid spread onto the surface of the powder and granular particles is then dried by the treatment gas G introduced into the rotating drum 21, forming a coating layer on the surface of the powder and granular particles. This treatment gas G passes through the powder and granular layer and is exhausted as a solid-gas mixed gas containing powder and granular particles (fine powder, etc.) from the exhaust port 22b1 of the seal plate 22b to the exhaust chamber 22c, flows through the inside of the cartridge filter A located in the exhaust chamber 22c, and is exhausted into the exhaust duct 23. The effects of the cartridge filter A during solid-gas separation and backwashing are the same as in the embodiment described above, so redundant explanations are omitted. Furthermore, a dust collection duct 24 is provided below the exhaust chamber 22c to collect granular particles that have been brushed off from the cartridge filter A by backwash gas.

[0035] In this type of drum coating equipment, it is customary to have a dust collector in the exhaust path to prevent powder and granular particles mixed in the exhaust from flowing out. However, in drum coating equipment equipped with cartridge filter A, the excellent filtration performance and recovery function of cartridge filter A effectively separate (collect) powder and granular particles mixed in the exhaust, eliminating the need to install a dust collector in the exhaust path, or allowing for the use of a smaller dust collector. This simplifies and reduces the cost of powder and granular material manufacturing equipment, including the drum coating equipment. [Explanation of symbols]

[0036] A Cartridge Filter 11 Metal filter section 11a Outer surface 11b Inner surface 11c Non-ventilated section 12 Flexible filter section 12a Bottom cap 12b Coarse part 12c Coarse part G Processed gas P Pulse air (backwash gas)

Claims

1. A filter for separating solid particles from a solid-gas mixture, A metal filter section composed of a metal filter material, having one side that faces the inlet side and the other side that faces the outlet side with respect to the flow of the solid-gas mixed gas, A flexible filter section is made of a flexible filter material, is provided on one side of the metal filter section, and deforms due to the pressure of the backwash gas supplied from the other side of the metal filter section and ejected from one side of the metal filter section during backwashing with backwash gas. A filter characterized by having the following features.

2. The filter according to claim 1, wherein the flexible filter portion is composed of a resin filter material having alternating peaks and valleys.

3. The filter according to claim 1, wherein the flexible filter portion is composed of a cloth filter material made of a woven or nonwoven fabric containing at least one of chemical fibers and natural fibers.

4. The filter according to claim 1, wherein the flexible filter is provided with a coarse section having a larger mesh size than the filter material of the flexible filter, and during backwashing with the backwash gas, solid particles that are brushed off between the metal filter section and the flexible filter section pass through the coarse section and are discharged to the outside of the filter.

5. The filter according to claim 4, wherein the metal filter portion has a non-permeable portion in the portion of the flexible filter opposite to the coarse region.

6. A powder and granular material processing apparatus that performs at least one of the following processes on powder and granular material while passing a processing gas through it, A powder and granular material processing apparatus characterized in that a filter according to any one of claims 1 to 5 is arranged in the exhaust path of the processed gas.

7. The powder and granular material processing apparatus according to claim 6, comprising a fluidized bed container for containing the powder and granular material, wherein the filter is arranged inside the fluidized bed container.

8. The powder and granular material processing apparatus according to claim 6, comprising a rotating drum for containing the powder and granular material, and a casing that houses the rotating drum and has an exhaust chamber that can communicate with the inside of the rotating drum, wherein the filter is arranged in the exhaust chamber of the casing.

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