JPH0517910A - Dust-collector for asphalt plant - Google Patents

Abstract

PURPOSE:To make the grain size of collected dust even by simultaneously keeping pressure difference between a drier and the atmospheric pressure and the flow speed of exhaust gas constant. CONSTITUTION:A drier 1 is provided with a dust catcher 2 in series. An exhaust fan 4 is provided on the side of the exhaust duct 11 of the dust catcher 2. A return duct 20 is provided between the exhaust duct 11 and the drier 1, and with a return fan 21. As the exhaust fan 4 is operated to discharge exhaust gas outside, the return fan 21 is actuated, as an occasion calls, to partially return the exhaust gas passing through the exhaust duct 11 to the drier 1. The above operation can make pressure difference between the drier 1 and the atmospheric pressure and the flow speed of the exhaust gas constant and the grain size of collected dust even.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dust collector for removing dust contained in exhaust gas generated by a dryer of an asphalt plant.

[0002]

2. Description of the Related Art As a dust collector for an asphalt plant, one shown in FIG. 2 is known. This dust collector mainly includes a dryer 1, a primary dust collector 2, a secondary dust collector 3, and an exhaust fan 4.

The dryer 1 is provided with a burner 6 at the lower end of a dryer drum 5 which is rotated in the circumferential direction in an inclined state, and heats and dries the aggregate and the like introduced from the upper end by a conveyor 7 and then from the lower end. Let it drain.

The primary dust collector 2 is of a cyclone type, and the exhaust gas generated in the dryer 1 is sucked by the suction duct 8 to remove the dust component having a relatively large particle diameter contained in the exhaust gas. The primary dust collector 2 is connected to a screen device (not shown) or the like for sieving the aggregate heated and dried by the dryer 1 by suction ducts 9 and 10, and also removes dust generated in those connecting portions. ..

The secondary dust collector 3 is equipped with a bag filter 3a, and is provided with its suction side connected to the exhaust duct 11 of the primary dust collector 2. The exhaust fan 4 is connected to the exhaust duct 12 of the secondary dust collector 3, and the exhaust gas of the dryer 1 is sucked into the suction duct 8, the primary dust collector 2, and the exhaust duct 1.
First, the secondary dust collector 3 and the exhaust duct 12 are suctioned in this order and discharged from the chimney 13 to the atmosphere.

The dryer 1 is provided with a pressure gauge (differential pressure gauge) 14 for detecting the pressure in the dryer drum 5, and the exhaust duct 12 is provided with an opening / closing damper 15. The pressure gauge 14 and the opening / closing damper 15 are connected to the control device 16. Based on the detection signal output from the pressure gauge 14, the control device 16 increases the opening degree of the opening / closing damper 15 when the pressure in the dryer drum 5 increases and the difference from the atmospheric pressure decreases, and also the atmospheric pressure. When the difference between the opening and closing damper 15 becomes large, the opening of the opening and closing damper 15 becomes small.
To control.

In this structure, the opening / closing of the opening / closing damper 15 is controlled based on the pressure difference between the dryer drum 5 and the atmospheric pressure. As a result, for example, the amount of gas generated in the dryer 1 is changed due to the difference in the water content of the aggregate. Even if there is a change, the differential pressure between the dryer drum 5 and the atmospheric pressure is kept constant, and dust is prevented from leaking from the dryer drum 5 to the outside.

[0008]

However, with the above configuration, when the amount of gas generated by the dryer 1 changes, the flow velocity of the exhaust gas passing through the cyclone type dust collector 2 changes accordingly. Therefore, the particle size of the dust collected by the dust collector 2 varies. The collected dust is recovered and used as a part of the mixture, but if the particle size varies as described above, the quality of the mixture is not constant, which is not preferable.

An object of the present invention is to provide a dust collecting apparatus such as an asphalt plant capable of collecting dust while keeping the differential pressure between the atmospheric pressure and the atmospheric pressure in the dryer and the flow velocity of the exhaust gas constant.

[0010]

In order to achieve the above object, the present invention provides a dust collector connected to a dryer for heating and drying aggregates, and the exhaust gas generated by the dryer is passed through the dust collector to the dust collector. In a dust collector such as an asphalt plant provided with an exhaust fan that is discharged to the outside through the exhaust duct, a return duct is provided between the exhaust duct of the dust collector and the dryer, and one of exhaust gas in the exhaust duct is provided in the return duct. A return fan that returns the part to the dryer through a return duct is provided.

[0011]

[Function] When the generated gas amount in the dryer is large, the return gas amount by the return fan to the dryer is reduced, and when the generated gas amount is small, the return gas amount is increased to keep the exhaust gas flow rate constant. By adjusting the amount of exhaust gas discharged to the outside by the exhaust fan, the pressure difference between the internal pressure of the dryer and the atmospheric pressure is kept constant.

[0012]

FIG. 1 shows an embodiment of the present invention. 1, the same members as those in FIG. 2 are designated by the same reference numerals, and detailed description thereof will be omitted.

Reference numeral 20 is a return duct. The return duct 20 has one end connected to the middle of the exhaust duct 11 of the primary dust collector 2 and the other end connected to the dryer drum 5. The return duct 20 is provided with a return fan 21 and an opening / closing damper 22. The return fan 21 returns a part of the exhaust gas flowing through the exhaust duct 11 to the dryer drum 5, and the opening / closing damper 22 serves as the return duct 2.
Adjust the opening of 0.

The suction duct 8 is provided with a velocity meter 23. The velocity meter 23 detects the velocity of the exhaust gas flowing through the suction duct 8. The opening / closing damper 22 and the velocity meter 23 are connected to the control device 16. The control device 16 controls the opening / closing of the opening / closing valve 15 based on the detection signal of the pressure gauge 14 as described above, and controls the opening / closing of the opening / closing damper 22 based on the detection signal of the flow velocity meter 23.

Next, the operation of the dust collecting apparatus for an asphalt plant or the like according to the present invention constructed as described above will be described.
While operating the dryer 1 to heat and dry the aggregate, the exhaust fan 4 is operated to allow the exhaust gas generated by the dryer 1 to pass through the dust collectors 2 and 3 and be discharged from the chimney 13 to the atmosphere.
At this time, the dust collectors 2 and 3 capture the dust in the exhaust gas.
If necessary, the return fan 21 is operated to return a part of the exhaust gas flowing through the exhaust duct 11 to the dryer 1 through the return duct 20.

The control device 16 includes a pressure gauge 14 and a velocity meter 23.
The opening degree of the opening / closing dampers 15 and 22 is controlled based on the detection signal of 1) to keep the differential pressure between the dryer 1 and the atmospheric pressure and the flow velocity of the exhaust gas flowing through the suction duct 8 constant.

That is, for example, the suction gas amount per unit time from the dryer 1 required for setting the differential pressure between the internal pressure of the dryer 1 and the atmospheric pressure to a predetermined value is "1", and the suction duct 8 is When the required flow rate of the exhaust gas flowing per unit time is "8" and the generated gas amount per unit time in the dryer 1 is "5", the control device 16
The amount of exhaust gas returned to the dryer 1 through the return duct 20 per unit time is "2"("2" = "8"-
The opening / closing damper 22 is controlled so as to be “5”-“1”), and the discharge amount of the exhaust gas discharged from the chimney 13 to the atmosphere per unit time is “6” (“6” = “8” −). "2")
The opening / closing damper 15 is controlled so that When the amount of gas generated in the dryer 1 is changed to "4", the opening / closing damper 2 is adjusted so that the amount of exhaust gas returned is "3" and the amount of discharge is "5".
2, 15 are controlled.

In the above embodiment, the control device 16 controls the opening degrees of the open / close dampers 15 and 22, but the same effects can be obtained by controlling the rotation speeds of the exhaust fan 4 and the return fan 21. In addition, when the amount of gas generated in the dryer 1 can be predicted, the opening / closing control of the opening / closing dampers 15 and 22 and the rotation speed control of the fans 4 and 21 are not automatically controlled by the control device 16, but manually by an operator. It can be controlled. Pressure gauge 14, velocity meter 23, and opening / closing damper 1
The mounting positions of 5, 22, etc. are not limited to the figures, and the types of the pressure gauge 14 and the velocity meter 23 are also arbitrary. Furthermore, the present invention can be implemented in dust collectors other than asphalt plants.

[0019]

As described above, according to the present invention, a dust collector is connected to a dryer for heating and drying aggregates and the like, and the exhaust gas generated by the dryer is passed through the dust collector to the outside through an exhaust duct. In a dust collector such as an asphalt plant to which an exhaust fan for discharging is attached, a return duct is provided between the exhaust duct of the dust collector and the dryer, and a part of the exhaust gas in the exhaust duct is passed through the return duct through the return duct. Since a return fan that returns to the dryer is provided, the flow rate of the exhaust gas sent to the dust collector is kept constant while keeping the differential pressure between the dryer and atmospheric pressure constant, preventing the exhaust gas from leaking from the dryer. At the same time, the particle size of the collected dust can be made uniform.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a dust collector for an asphalt plant or the like according to the present invention.

FIG. 2 is a block diagram of a conventional dust collector for an asphalt plant.

[Explanation of symbols]

 1 Dryer 2 Dust collector 4 Exhaust fan 11 Exhaust duct 20 Return duct 21 Return fan

Claims (1)

Claims: 1. A dust collector is connected to a dryer for heating and drying aggregates and the like, and an exhaust fan for discharging exhaust gas generated by the dryer to the dust collector and discharging the exhaust gas to the outside through an exhaust duct. In a dust collector such as an asphalt plant attached with, a return duct is provided between the exhaust duct of the dust collector and the dryer, and the return duct returns a part of the exhaust gas in the exhaust duct to the dryer through the return duct. A dust collector for an asphalt plant, etc., which is equipped with a fan.