Petroleum coke blending dust suppression and recovery equipment

Abstract

The invention relates to the technical field of dust suppression, and discloses petroleum coke blending dust suppression and recovery equipment which comprises a machine shell and a plurality of pulse guns, a partition plate is fixedly arranged in the machine shell, and an inner cavity of the machine shell is divided into a dust collection cavity and a clean cavity by the partition plate; the driving piece is used for controlling the turning plate to close the square groove in the pulse dust cleaning stage, so that dust falling from the outer wall of the filter cartridge is guided to the dust collection cavity along the inclined plate; and the turning plate is controlled to open the square groove in a non-deashing filtering stage, so that dust-containing gas enters the external space of the filter cartridge through the square groove. An inclined plate is arranged below each layer of filter cartridge, and a turning plate controlled by a driving piece is arranged on each inclined plate. The equipment opens the turning plate in the filtering stage to enable airflow to pass through, and closes the turning plate below the ash removal layer in the pulse ash removal stage to form physical isolation. And dust falling from upper-layer dust removal is thoroughly prevented from falling onto the surface of the lower-layer filter cartridge. The service life of the filter cartridge is obviously prolonged and the maintenance frequency and energy consumption are reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of dust suppression, in particular to a petroleum coke blending dust suppression and recovery equipment. BACKGROUND

[0002] In the process of petroleum coke blending, conveying and processing, due to the characteristics of high fineness, low density and easy flying of the material, a large amount of dust is easily produced, which not only causes waste of raw materials, but also seriously affects the working environment and the health of operators. In order to control dust pollution, bag or filter cartridge type dust removal equipment is generally used in industry to purify and treat dust-containing gas. For example, patent publication (announcement) No. CN222956115U-China Utility Model Industrial Grade Filter Cartridge Dust Collector, which adopts a multi-layer horizontally arranged filter cartridge structure to improve the filtration area per unit volume. The dust cleaning method is mainly pulse blowing technology, that is, high-pressure airflow is instantaneously sprayed into the inside of the filter cartridge to make the dust layer attached to the outer surface of the filter cartridge fall off and fall into the lower dust collection area. However, in actual operation, it is found that when the upper filter cartridge is pulsed for dust cleaning, a large amount of falling dust directly falls due to gravity and is easily deposited on the outer surface of the filter cartridge located directly below. This not only causes the lower filter cartridge to be blocked, the resistance to rise and the filtration efficiency to decrease, but also affects the overall dust removal effect due to secondary adsorption of dust, reducing the continuous operation capacity of the equipment. Therefore, there is an urgent need for a dust suppression and recovery equipment that can effectively isolate the influence of falling dust on the lower filter cartridge during the dust cleaning stage. SUMMARY

[0003] The main purpose of the present application is to provide a petroleum coke blending dust suppression and recovery equipment to solve the problem that in the prior art industrial grade filter cartridge dust collector, when the upper filter cartridge is pulsed for dust cleaning, a large amount of falling dust directly falls due to gravity and is easily deposited on the outer surface of the filter cartridge located directly below. This not only causes the lower filter cartridge to be blocked, the resistance to rise and the filtration efficiency to decrease.

[0004] In order to achieve the above purpose, the present application provides a petroleum coke blending dust suppression and recovery equipment, which comprises a shell and a plurality of pulse guns, a partition plate is fixedly arranged in the shell, and the partition plate divides the inner cavity of the shell into a dust collection cavity and a clean cavity; The dust collection cavity is communicated with an air inlet pipe, and the clean cavity is communicated with an air outlet pipe; A plurality of support plates are uniformly distributed along the height direction of the dust collection cavity, and the two ends of each support plate are fixedly connected with the two inner side walls of the shell; At least one filter cartridge is detachably arranged on each support plate, one end of the filter cartridge abuts against the partition plate, and the inner cavity is communicated with the clean cavity; A inclined plate is obliquely arranged below the filter cartridge on each support plate, a dust flow channel is formed between the inclined plate and the adjacent upper support plate, and the inclined plate is fixedly connected with the partition plate; At least one square slot is formed on each inclined plate, and a flap is arranged at the square slot; The pulse guns are fixed on the casing and correspond to the filter cartridges one by one. The air outlet of each pulse gun is located in the clean cavity and faces the inner cavity of the corresponding filter cartridge.

[0005] Preferably, a support frame is sleeved in each filter cartridge, one end of the support frame is fixedly connected with the partition plate, and the other end is fixedly provided with a screw rod. At least one mounting hole is formed on the cover plate, the cover plate is sleeved on the screw rod and covers the mounting hole, and the cover plate and the end of the filter cartridge are detachably fixed by a nut screwed on the screw rod.

[0006] Preferably, the plurality of pulse guns are communicated with a pulse generator through a plurality of connecting pipes.

[0007] Preferably, a sealing door is arranged on the side wall of the dust collecting cavity, and the sealing door is located on one side of the cover plate.

[0008] Preferably, a hopper is communicated with the bottom of the dust collecting cavity, a straight pipe is connected below the hopper, two rectangular slots are formed in the side wall of the straight pipe along the axial direction of the straight pipe, and a baffle capable of completely shielding the inner cavity of the straight pipe is slidably arranged in each rectangular slot.

[0009] Preferably, the driving member comprises a receiving plate and a cylinder. A rotating shaft is fixedly arranged on each flap, the rotating shaft is rotatably arranged on the inclined plate, and a spur gear is fixedly sleeved on the end of the rotating shaft. The spur gears arranged on one inclined plate are in meshing transmission through a rack. The racks are fixedly connected with the receiving plate. The cylinder base of the cylinder is fixed to the outer wall of the casing, the piston rod of the cylinder extends into the dust collecting cavity and is fixedly connected with the receiving plate.

[0010] Preferably, a flow guide block is arranged on each inclined plate at the downstream end of the inclined plate and above the side of the spur gear. A horizontal slot is formed on the flow guide block, a sliding block is slidably arranged in the horizontal slot, and the sliding block is fixedly connected with the rack through a connecting plate.

[0011] Preferably, a plurality of pipe shifting rods are fixedly arranged on each rack along the length direction of the rack, and the pipe shifting rods pass through the dust flow channel.

[0012] Preferably, a dust collecting cover is communicated with the end of the air inlet pipe away from the casing.

[0013] Preferably, a fan is arranged on the air outlet pipe.

[0014] The above-mentioned scheme has the following beneficial effects: Dusty petroleum coke mixed with exhaust gas enters the dust collection chamber of the device through the air inlet pipe. At this time, the driving member controls all the flaps to be in the open state, that is, the flaps do not cover the square grooves on the inclined plates. Dusty gas passes through the opened square grooves and diffuses downward to the area where the filter cartridges are located. The dusty gas passes through the filter material of the filter cartridges from the outside to the inside. The dust is intercepted and adsorbed on the outer surface of the filter cartridges, and the cleaned gas enters the inner cavity of the filter cartridges. The cleaned gas in the inner cavities of all filter cartridges is collected in the clean chamber, and finally discharged through the air outlet pipe, completing a filtration cycle. As the filtration proceeds, the dust layer attached to the outer surface of the filter cartridges thickens, and the operating resistance (pressure difference) of the device gradually increases. Before pulse blowing, the driving member works to close the flaps on all the inclined plates in the layer where the filter cartridges being cleaned and below. The flaps tightly cover the square grooves, and the inclined plates are converted into complete flow guide slopes. The pulse gun corresponding to the filter cartridges is instantaneously opened to inject a high-pressure reverse airflow into the clean chamber. The airflow rushes into the inner cavity of the filter cartridges at high speed, causing the filter cartridges to produce high-frequency expansion vibration and form a strong reverse airflow. Under the action of the pulse force, the dust layer firmly attached to the outer surface of the filter cartridges is peeled off and falls off in pieces. Since the flaps directly below have been closed, the falling dust will not fall through the square grooves into the lower layer, but will fall on the closed inclined plates. The dust falling on the inclined plates slides down along the inclined plate surface under the action of gravity and is directly guided into the dust collection chamber at the bottom through the dust flow channel without contacting the outer surface of the lower filter cartridges.

[0015] The driving member is used to control the flaps to close the square grooves during the pulse cleaning stage, so that the dust falling from the outer wall of the filter cartridges is guided along the inclined plates to the dust collection chamber; and control the flaps to open the square grooves during the non-cleaning filtration stage, so that the dusty gas enters the outer space of the filter cartridges through the square grooves. Inclined plates are arranged below each layer of filter cartridges, and flaps controlled by the driving member are arranged on the inclined plates. The device opens the flaps to make the airflow pass through during the filtration stage, and closes the flaps below the cleaning layer to form physical isolation during the pulse cleaning stage. It prevents the dust falling from the upper layer cleaning from falling onto the surface of the lower filter cartridges. The service life of the filter cartridges is significantly prolonged, and the maintenance frequency and energy consumption are reduced. BRIEF DESCRIPTION OF DRAWINGS

[0016] The application will be further described in detail below in combination with the drawings and specific embodiments.

[0017] Figure 1 is a perspective structural schematic diagram of the application; Figure 2 is an enlarged structural schematic diagram of the A area in Figure 1 Figure 3 is another perspective structural schematic diagram of the application; Figure 4 is a sectional view structural schematic diagram of the application without a closed door and a filter cartridge; Figure 5 is a sectional view structural schematic diagram of the application without a closed door and a filter cartridge; Figure 4 ​Enlarged structural schematic view of middle B area; Figure 6 is Figure 4 Enlarged structural schematic view of middle C area; Figure 7 is Figure 4 Front structural schematic view of Figure 8 is Figure 7 Enlarged structural schematic view of middle D area; Figure 9 is a part of the schematic view of the three-dimensional structure of the present application.

[0018] Explanation of reference numerals 11, casing; 12, partition; 13, dust collecting cavity; 14, clean cavity; 15, air inlet pipe; 16, air outlet pipe; 21, mounting plate; 22, mounting hole; 23, cover plate; 24, nut; 31, filter cartridge; 32, support frame; 33, screw rod; 41, inclined plate; 42, dust flow channel; 43, square groove; 44, turning plate; 45, flow guide block; 46, horizontal groove; 47, sliding block; 48, connecting plate; 51, pulse gun; 52, connecting pipe; 53, pulse generator; 61, driving member; 62, receiving plate; 63, air cylinder; 64, rotating shaft; 65, spur gear; 66, rack; 67, pipe pushing member; 71, sealing door; 72, funnel; 73, straight pipe; 74, rectangular groove; 75, baffle. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. In the following description, a lot of specific details are set forth in order to give a full and thorough understanding of the present application, but the present application can also be implemented in other ways different from those described herein, and those skilled in the art can make similar generalizations without departing from the connotation of the present application, therefore the present application is not limited by the specific embodiments disclosed below. EMBODIMENTS

[0020] Please refer to Figures 1 to 9This embodiment provides a petroleum coke blending dust suppression and recovery device. This device effectively solves the technical problem of dust falling from the upper filter cartridges during cleaning and contaminating the lower filter cartridges in a multi-layer cartridge dust collector, thereby improving the stability, filtration efficiency, and reliability of the equipment. The petroleum coke blending dust suppression and recovery device mainly includes a housing 11 and multiple pulse guns 51. A partition 12 is fixedly installed inside the housing 11, dividing the inner cavity of the housing 11 into left and right parts: a dust collection chamber 13 on the left and a clean chamber 14 on the right. An inlet pipe 15 is connected to the side wall of the dust collection chamber 13 for introducing dust-laden petroleum coke blending waste gas. An outlet pipe 16 is connected to the side of the clean chamber 14 for discharging filtered clean gas. To allow the dust-laden gas to be drawn into the device, a fan (not shown in the figure) is typically installed along the outlet pipe 16. A dust collection hood (not shown in the figure) can be connected to the inlet end of the air intake pipe 15. The dust collection hood is used to collect dust at the dust generation point. Figure 4 As shown, multiple inclined mounting plates 21 are evenly fixedly installed at intervals along the height direction (i.e., the height direction of the housing, which is also considered as the vertical direction) inside the dust collection chamber 13. The two ends of each mounting plate 21 are fixedly connected to the two inner side walls of the housing 11, respectively.

[0021] like Figure 4 As shown, each mounting plate 21 has one or more mounting holes 22. A filter cartridge 31 is detachably mounted at each mounting hole 22. The filter cartridge 31 is generally cylindrical, and its filter material allows gas to pass through but intercepts dust. The filter cartridge 31 is based on existing technology and will not be described in detail. The upper end of the inclined filter cartridge 31 (i.e., the end near the partition plate 12) abuts against the surface of the partition plate 12, and its inner cavity communicates with the upper clean cavity 14 through an opening in the partition plate 12. To achieve stable installation and convenient replacement of the filter cartridge 31, the following structure is adopted, as follows: Figure 6 As shown, a support frame 32 is fitted inside each filter cartridge 31. One end (upper end) of the support frame 32 is fixedly connected to the partition plate 12, and the other end (lower end) is fixedly connected to a screw 33. During installation, the filter cartridge 31 is fitted over the support frame 32, with its upper end abutting against the partition plate 12. Then, a cover plate 23 is fitted over the screw 33, covering the mounting hole 22 on the mounting plate 21. Finally, by tightening the nut 24 on the screw 33, the cover plate 23, the end of the filter cartridge 31 (usually the lower flange), and the mounting plate 21 are pressed and fixed, thus achieving a detachable connection.

[0022] Directly below each filter cartridge 31 mounted on the mounting plate 21, an inclined plate 41 is disposed at an angle. The higher end of the inclined plate 41 is fixedly connected to the partition plate 12, and its lower end extends downward. A certain gap is maintained between the inclined plate 41 and the adjacent mounting plate 21 directly above it, forming a dust flow channel 42 for dust to fall.Figure 9 As shown, one or more square slots 43 are formed in each of the inclined plates 41. A flap 44 is rotatably arranged at each square slot 43 by a rotating shaft 64. The shape of the flap 44 matches that of the square slot 43, and the flap 44 can be rotated under the drive of the driving member 61, so as to realize the "opening" (the flap 44 stands up or forms a certain angle with the plane of the inclined plate 41 to open the passage) or "closing" (the flap 44 is laid flat to tightly cover the square slot 43) of the square slot 43.

[0023] All the flaps 44 are driven by a unified driving member 61 to realize synchronous action. The rotating shaft 64 is fixed on each flap 44, and both ends of the rotating shaft 64 are rotatably arranged on the inclined plate 41 by bearing seats (not shown in the figure). A spur gear 65 is fixedly sleeved on the end of the rotating shaft 64. All the spur gears 65 located on the same inclined plate 41 are linked by meshing with a common long rack 66. All the racks 66 are finally fixedly connected to a common receiving plate 62. The cylinder block of a pneumatic cylinder 63 is fixed on the outer wall of the casing 11, and the piston rod thereof extends into the dust collecting cavity 13 and is fixedly connected with the receiving plate 62. By controlling the extension and retraction of the piston rod of the pneumatic cylinder 63, the receiving plate 62 and the rack 66 can be driven to move, thereby driving all the spur gears 65 and the rotating shafts 64 to rotate synchronously, and realizing the synchronous opening and closing of all the flaps 44. This design ensures that all the flaps 44 on each inclined plate 41 move in unison.

[0024] For further optimization, a flow guide block 45 (see Figure 5 ) can be arranged above the side of the spur gear 65 at the lower end (downstream end) of each inclined plate 41. A transverse transverse slot 46 is formed in the flow guide block 45, and a sliding block 47 can slide in the transverse slot 46. The sliding block 47 is fixedly connected with the rack 66 that drives the flaps of the layer by a connecting plate 48. In this way, when the rack 66 moves, the sliding block 47 will be driven by the connecting plate 48 to slide in the transverse slot 46, which plays a certain guiding and limiting role for the movement of the rack 66, and ensures stable transmission. In addition, a plurality of stirring tubes 67 (see Figure 5 、 Figure 8 ) can be fixedly arranged on each rack 66 along the length direction thereof. These stirring tubes 67 pass through the dust flow channel 42 between the inclined plate 41 where the stirring tube 67 is located and the upper plate 21. When the rack 66 moves with the driving member, the stirring tubes 67 will stir in the dust flow channel 42, which helps to prevent dust from accumulating or bridging in the channel, and ensures smooth falling.

[0025] The dust cleaning system is composed of a plurality of pulse guns 51, connecting pipes 52 and a pulse generator 53. The pulse generator 53 is of prior art, and thus will not be described in detail. The pulse guns 51 are fixed on the casing 11, and specifically extend into the clean chamber 14 through the casing 11. The gas outlet of each pulse gun 51 is accurately aligned with the inner cavity of a filter cartridge 31. All the pulse guns 51 are connected to a common pulse generator 53 (such as a gas pocket controlled by an electromagnetic pulse valve) through a plurality of connecting pipes 52. The pulse generator 53 releases high-pressure gas instantaneously, which is sprayed into the corresponding filter cartridge 31 through the pulse gun 51 to clean the dust.

[0026] In order to facilitate the internal maintenance of the equipment and the replacement of the filter cartridges, a sealed door 71 is provided on the sidewall of the dust collecting chamber 13, which is opposite to the area where the support plate 21 is located.

[0027] As shown in Figure 2 , the bottom of the dust collecting chamber 13 is designed in the shape of a hopper 72 for collecting all the dust falling thereon. A vertical straight pipe 73 is connected to the lower part of the hopper 72 as a dust discharge port. Two rectangular grooves 74 are formed in the sidewall of the straight pipe 73 along the axial direction, and each rectangular groove 74 is slidably provided with a baffle 75. The two baffles 75 can completely cover the inner cavity of the straight pipe 73. By alternately pulling the two baffles 75, intermittent dust discharge can be achieved without interrupting the operation of the equipment, thereby avoiding the influence of air leakage on the dust removal effect.

[0028] The dust-containing exhaust gas enters the dust collecting chamber 13 from the inlet pipe 15. At this time, the driving member 61 controls all the flaps 44 on the inclined plates 41 to be in the "open" state. The dust-containing gas can uniformly diffuse to the area where the filter cartridges 31 are located through the open square grooves 43. Under the action of the negative pressure generated by the fan, the gas passes through the filter material of the filter cartridges 31 from the outside to the inside, and the dust is trapped on the outer surface of the filter cartridges 31. The clean gas enters the inner cavity of the filter cartridges 31, and then flows into the clean chamber 14, and finally is discharged from the outlet pipe 16. When the dust on the outer surface of the filter cartridges 31 increases, dust cleaning is needed. Before the pulse spraying action is triggered, the cylinder 63 pulls or pushes the receiving plate 62, so that all the racks 66 move to drive all the flaps 44 to rotate synchronously to the "closed" state, which tightly covers the square grooves 43 on all the inclined plates 41. In particular, the flaps 44 on all the inclined plates above and below the layer of filter cartridges to be cleaned are closed to form physical isolation.

[0029] After the flap 44 is closed, the pulse gun 51 corresponding to the filter cartridge 31 that needs to be cleaned is started instantaneously to spray a high-pressure reverse airflow into the inner cavity of the filter cartridge 31. The airflow makes the filter cartridge 31 expand and vibrate instantaneously, and the dust layer attached to the outer surface of the filter cartridge 31 is peeled off in pieces. The peeled-off dust falls under the action of gravity. Since the flap 44 on the inclined plate 41 directly below has been closed, the dust cannot fall through the square groove 43 into the lower layer. The dust falls on the inclined plate 41 that has been closed as a complete flow guide surface and slides downward along the inclined plate surface, and is directly guided to the hopper 72 at the bottom of the device through the dust flow channel 42. The tube 67 on the rack 66 moves with the driving member before and after the dust cleaning, which helps the dust flow channel 42 prevent blockage. After the dust cleaning action is completed, the driving member 61 is actuated again to restore the flap 44 to the "open" state, and the device reenters the normal filtering cycle. The dust collected in the hopper 72 can be regularly discharged from the straight pipe 73 by operating the baffle 75.

[0030] Other embodiments: A soft tube (not shown) is arranged in communication with each tube 67, and the soft tubes are in communication with the pulse generator 53. The high-pressure gas generated by the pulse generator 53 can be distributed to each tube 67 through the soft tubes, which effectively disperses the dust accumulation and bridging. When the upper filter cartridge 31 is subjected to pulse cleaning and a large amount of dust falls off, the tubes 67 in all the dust flow channels 42 below are simultaneously subjected to pneumatic blowing, and the high-speed airflow sprayed laterally from the tubes 67 helps guide the falling dust to the inclined surface of the inclined plate 41.

[0031] Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

Claims

1. A device for suppressing and recovering dust from petroleum coke blending, characterized in that, Includes a housing (11) and multiple pulse guns (51); A partition (12) is fixed inside the housing (11), and the partition (12) divides the inner cavity of the housing (11) into a dust collection chamber (13) and a clean chamber (14). The dust collection chamber (13) is connected to an air inlet pipe (15), and the clean chamber (14) is connected to an air outlet pipe (16). Multiple safety plates (21) are evenly distributed along the height direction inside the dust collection chamber (13), and each safety plate (21) is fixed inside the housing (11); At least one filter cartridge (31) is detachably provided on each safety plate (21), one end of the filter cartridge (31) abuts against the partition plate (12), and the inner cavity is connected to the clean cavity (14); An inclined plate (41) is inclinedly disposed directly below the filter cartridge (31) on each of the safety plates (21). The inclined plate (41) forms a dust flow channel (42) with the adjacent upper safety plate (21) and is fixedly connected to the partition plate (12). At least one square groove (43) is provided through each of the inclined plates (41), and a flap (44) is provided at the square groove (43). These flaps (44) are connected to a driving member (61). These pulse guns (51) are all fixed on the housing (11) and face the inner cavity of each filter cartridge (31).

2. The petroleum coke blending dust suppression and recovery equipment according to claim 1, characterized in that, Each of the filter cartridges (31) is fitted with a support frame (32), one end of which is fixedly connected to the partition plate (12), and the other end is fixed with a screw (33). At least one mounting hole (22) is provided on the mounting plate (21), a cover plate (23) is sleeved on the screw (33) and covers the mounting hole (22), the screw (33) is screwed to the nut (24), and one end of the filter cylinder (31) abuts against the cover plate (23).

3. The petroleum coke blending dust suppression and recovery equipment according to claim 1, characterized in that, Multiple pulse guns (51) are connected to a pulse generator (53) via multiple connecting pipes (52).

4. The petroleum coke blending dust suppression and recovery equipment according to claim 1, characterized in that, A sealing door (71) is provided on the side wall of the dust collection chamber (13), and the sealing door (71) is located on one side of the safety plate (21).

5. The petroleum coke blending dust suppression and recovery equipment according to claim 1, characterized in that, The bottom of the dust collection chamber (13) is connected to a funnel (72), and a straight tube (73) is connected below the funnel (72). Two rectangular grooves (74) are opened on the side wall of the straight tube (73), and a baffle (75) that can cover the inner cavity of the straight tube (73) is slidably arranged in each rectangular groove (74).

6. The petroleum coke blending dust suppression and recovery equipment according to any one of claims 1-5, characterized in that, The drive unit (61) includes a receiving plate (62) and a cylinder (63). A rotating shaft (64) is fixed on each of the flaps (44), the rotating shaft (64) is rotatably mounted on the inclined plate (41), and a spur gear (65) is fixedly sleeved on one end of the rotating shaft (64). These spur gears (65) located on one of the inclined plates (41) are driven by a rack (66); These racks (66) are all fixedly connected to the receiving plate (62); The cylinder seat of the cylinder (63) is fixed to the outer wall of the housing (11), and the piston rod extends into the dust collection chamber (13) and is fixedly connected to the receiving plate (62).

7. The petroleum coke blending dust suppression and recovery equipment according to claim 6, characterized in that, A guide block (45) is provided at the downstream end of each inclined plate (41) and above the side of the spur gear (65). A transverse groove (46) is provided on the guide block (45), and a slider (47) is slidably disposed in the transverse groove (46). The slider (47) is fixedly connected to the rack (66) through a connecting plate (48).

8. The petroleum coke blending dust suppression and recovery equipment according to claim 6, characterized in that, Each of the racks (66) has a plurality of pinions (67) fixed at intervals along its length, the pinions (67) passing through the dust flow channel (42).

9. The petroleum coke blending dust suppression and recovery equipment according to claim 1, characterized in that, The end of the air intake pipe (15) away from the housing (11) is connected to a dust collection hood.

10. The petroleum coke blending dust suppression and recovery equipment according to claim 1, characterized in that, A fan is installed on the air outlet pipe (16).

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