JPS6154451B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for controlling the suction air volume of dust collection equipment in, for example, steel works and sintering equipment. In order to prevent the generation of dust and smoke, it is desirable to install airtight hoods to collect dust and smoke, but even if hoods are installed, it is often impossible to seal them due to space, structure, and work considerations. Furthermore, the equipment itself is not a sealed structure and often has gaps. When there are gaps in equipment or hoods, it is necessary to suction air at a sufficiently high flow rate to prevent dust from escaping to the outside. The flow rate at the hood opening is as follows in one example in a sintering facility.

[Table] Figure 1 shows an example of conventional dust collection equipment. In the figure, 1 is equipment that generates dust;
A hood 2 for suctioning dust is provided on the top of the hood. The hood 2 has an opening larger than the width of the equipment 1, and the hood 2 has an opening larger than the width of the equipment 1.
The hood 2 functions to suck atmospheric air through the gap 3 at a predetermined flow rate. The outside air sucked in by the hood 2 is introduced into the dust collector 5 through the dust collection duct 4 along with the generated dust, and after the dust is removed by the dust collector 5, it passes through the dust collection fan inlet damper 6 and the exhaust fan 7, and enters the atmosphere from the chimney 8. It is configured to be released. In dust collection equipment with such a configuration, the equipment 1 usually causes various reactions or handles high-temperature materials, but these changes over time.
The temperature of the collected gas also changes over time.
How the amount of suction gas changes when the suction gas conditions change in this way will be explained using FIG. 2. In Figure 2, curves A and A' are the exhaust fan 7.
This is a characteristic curve showing the relationship between actual air volume and pressure.
A is for the gas temperature t ₁ and A' is for the gas temperature t ₂ , where t ₁ >t ₂ . Similarly, curves C and C' show the relationship between the actual air volume of the exhaust fan 7 and the power when the gas temperatures are t ₁ and t ₂ . On the other hand, the resistance of equipment is generally expressed by the following formula. ΔP=k ₁・γ・v ² …(1) where ΔP: resistance k: coefficient γ: gas specific gravity v: gas flow velocity Now, when the gas temperature is t°C, the gas specific gravity γ is expressed by the following formula. It can be done. γ= _k2・273/273+t...(2) From equations (1) and (2), the following equation holds true. ΔP=k ₁・k ₂・273/273+t・v ² ……(3) In other words, in the case of a constant cross section, the gas flow velocity is proportional to the actual air volume, so if the gas temperature rises, the resistance will increase if the actual air volume is the same. becomes smaller. Here, the curves indicated by B and B' in the figure are resistance curves at gas temperatures _t1 and _t2 . As is clear from the figure, even if the gas temperature changes, the actual air volume passing through the exhaust fan hardly changes at the intersections (operating points) P and Q between the resistance curves B and B' and the exhaust fan performance curves A and A'. . Further, the power increases as the temperature decreases, as shown at the RS point in the figure, for temperatures t ₁ and t ₂ . By the way, regarding dust collection, since the dust collection air volume is determined by the flow velocity at the opening of the hood 2 mentioned above, if the outside air temperature is t ₀ °C, then t ₀
The optimal air volume Q ₀ at °C has been determined, and it is necessary to draw in this air volume despite the temperature rise mentioned above.
Conversely, there is no need to draw more than this amount of air. Now, if the actual air volume sucked by the exhaust fan 7 at the temperature t ₁ °C is Q ₁ , then convert it to the air volume Q ₀ ' at the temperature t ₀ °C.
Q ₀ ′ becomes the following formula. Q ₀ ′=Q ₁・273+t ₀ /273+t ₁ ……(4) The air volume Q ₀ ′ should be Q ₀ as the optimal air volume as described above. Therefore, if Q ₀ =Q ₀ ′, then according to equation (4), the temperature If the temperature rises, the actual suction air volume will be increased, and if the temperature decreases, the suction actual air volume will be decreased. As described above, according to conventional dust collection equipment, although the gas temperature fluctuates depending on the process situation, the exhaust fan 7 is operated at a constant rotation based on the air volume corresponding to the expected maximum temperature. , there was no control whatsoever. In other words, as mentioned above,
If the gas temperature decreases, the actual suction air volume can be reduced, but since the actual suction air volume is not changed, there is a large difference as shown at points R and S in Figure 2, and the power consumption at low temperatures is reduced. Since the exhaust fan 7 is large in size and the design value of the exhaust fan 7 is usually set with a margin, the equipment actually consumes more power than necessary. The reason why the suction air volume of the dust collection equipment is not controlled is that it is difficult to accurately grasp the suction air volume at the gap 3 between the equipment 1 and the hood 2, that is, at the outside air suction point. In this case, it is possible to calculate the amount of atmospheric suction by measuring the air volume and temperature of the exhaust air after the dust collector 5, but it is difficult to obtain an accurate value due to the influence of dust in the exhaust and fluctuations in temperature, and the suction point is If there are many, the amount of air sucked at each suction point must be measured in the duct 4 near the suction point, but in that case, the amount of dust will be even larger, and the straight pipe section of the duct 4 may be insufficient. This is because the larger the measurement difference, the more difficult it is to obtain an accurate value. Also, food 2
There is also a method of determining the amount of suction in the hood 2 by measuring internal pressure and other pressures, but this also results in extremely inaccurate and unstable measurements due to dust problems, drafts due to temperature rise due to suction, and temperature fluctuations. I had no choice but to do so. The purpose of the present invention is to solve such problems, and in dust collection equipment equipped with a suction part such as a hood equipment in order to prevent the generation of dust and smoke from the equipment, a vacuum cleaner is installed near the outside air suction part of the suction part. A measurement pipe communicating with the outside air is provided, the flow rate or flow velocity of the air passing through this measurement pipe is measured, and the value is taken as a representative value of the dust collection air volume at the suction point, and this representative value is set as a predetermined set value. This objective is achieved by providing a suction air volume control method for dust collection equipment that automatically adjusts the exhaust air volume of dust collection equipment.
This makes it possible to accurately measure the flow rate or flow velocity of the atmosphere at the outside air suction point of the suction section, making it possible to use dust collection equipment to keep up with gas temperature fluctuations and to ensure sufficient exhaust air volume, while also minimizing power consumption. It is possible to save energy by keeping the amount of energy to a minimum. Hereinafter, the method of the present invention will be explained in detail based on the drawings showing one embodiment thereof. In FIG. 3, the same equipment as in FIG. 1 is designated by the same number. In the figure, reference numeral 9 denotes a small-diameter pipe-shaped measurement tube that communicates with the outside air and is installed in the gap 3 of the hood 2, that is, near the outside air suction point. A device 10 for measuring air volume or speed is provided. The measuring device 10 is electrically connected to a speed adjusting device 12 that adjusts the speed of the exhaust fan driving electric motor 11 so that the measured air volume matches the set air volume. The rotation speed can be controlled. Next, gap 3 of hood 2
The reason why the measurement tube 9 was provided nearby will be explained. As mentioned above, the suction air is suctioned from the equipment 1 and the gap 3, and the suction air volume is determined by the pressure difference between the internal pressure and the outside air pressure. Therefore, if the differential pressure is known, the flow rate passing through the three gaps can be calculated, and the flow rate as the product of the flow rate and the area of the three gaps can be calculated. Moreover, this allows the differential pressure to be used as a representative value of the suction amount. However, as described above, it is difficult to measure the pressure inside the hood 2 accurately, and it is also difficult to directly measure the flow rate passing through the three gaps. Therefore, gap 3 of hood 2
By providing a small-diameter measuring tube 9 nearby as a new gap, the flow velocity or flow rate inside the measuring tube 9 can be used as a representative value of the suction amount. For this reason, since the fluid passing through the measuring tube 9 is the atmosphere and the temperature is the atmospheric temperature, extremely accurate measurements can be made. Although not shown, if measurements are to be made intermittently, a valve may be provided at the inlet of the measurement tube 9 and normally closed to reduce the amount of leakage. With such a configuration, during actual operation, the rotational speed of the exhaust fan 7 is varied, and the numerical value of the measuring closed device 10 is read when the necessary and sufficient dust collection situation is achieved. Then, by controlling the rotational speed of the exhaust fan driving electric motor 11 using this numerical value as a set value, loss of effectiveness due to excessive exhaust air can be prevented. In the above embodiment, the rotation speed of the electric motor 11 of the exhaust fan 7 is controlled, but any air volume control means that can reduce power, such as a fluid coupling or control of the inlet damper 6, may be used. As described above, according to the method of the present invention, it is possible to accurately measure the flow rate or flow velocity of the atmosphere at the outside air suction point of the suction part of the hood equipment, etc., and to make it possible to ensure a sufficient exhaust air volume even when the dust collection equipment is necessary for fluctuations in gas temperature. I can,
As a result, power consumption can be kept to a necessary minimum and energy savings can be achieved. In addition, by adopting this method, for example, if a hole occurs due to dust in the dust collection duct, the value in the measurement pipe will not reach the predetermined value. It is possible to know the occurrence of a hole without having to check the hole, which can be of great help in saving labor.

[Brief explanation of the drawing]

Figure 1 is a schematic configuration diagram of a conventional dust collection equipment, Figure 2 is a diagram showing the relationship between the actual air volume and pressure of the exhaust fan and the relationship between the actual air volume and power of the exhaust fan in the dust collection equipment shown in Figure 1. FIG. 3 is a schematic diagram of the dust collection equipment according to the present invention. 1... Equipment, 2... Hood, 3... Gap (outside air suction point), 9... Measuring pipe, 10... Equipment for measuring air volume or wind speed.

Claims (1)

[Claims] 1 In dust collection equipment equipped with a suction part such as a hood equipment in order to prevent the generation of dust and smoke from the equipment, a measurement pipe communicating with the outside air is installed near the outside air suction point of the suction part, and the air passing through this measurement pipe is installed near the outside air suction point of the suction part. The method is to measure the flow rate or flow velocity of the atmospheric air, use that value as a representative value of the dust collection air volume at the suction point, and automatically adjust the exhaust air volume of the dust collection equipment so that this representative value becomes a predetermined set value. Features: A suction air volume control method for dust collection equipment.