JPS5933825B2 - Combustion control method in asphalt plants - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of increasing drying efficiency in an asphalt plant by controlling the gas flow in an aggregate heating drum.

Asphalt mixtures are obtained by putting the raw materials, aggregates of various particle sizes, into a drum and heating them to a desired temperature, and then mixing and stirring the heated aggregates of various particle sizes with molten asphalt in a fixed proportion. It will be done.

The drum is a rotatable inclined cylindrical body, and the raking blades disposed inside the cylindrical body move the aggregate while raking it up while transferring it down, while a burner provided at one end of the cylindrical body sends combustion gas. At the same time, the combustion gas is sucked and exhausted by an exhaust fan installed at the end of an exhaust flue connected to the other end of the cylinder, thereby heating and drying the aggregate while maintaining a high-temperature gas flow passing through the cylinder.

In conventional asphalt plants, a control motor detects the temperature of the heated aggregate discharged from the drum, compares it with a preset aggregate temperature, and adjusts the intake of fuel and air to the burner using control signals based on the comparison. , the combustion amount is controlled by drive control.

In other words, the amount of combustion gas fed by the burner changes in accordance with various conditions such as the amount of aggregate fed into the drum and its moisture content.

However, the amount of gas sucked in by the exhaust fan disposed at the end of the exhaust flue connected to the drum remains unchanged during plant operation.

Therefore, it is good when the amount of combustion gas sent into the drum and the amount of gas sucked in by the exhaust fan are balanced, but if the balance is lost, the amount of gas sucked in by the exhaust fan is less than the amount of combustion gas sent in. If there is too much cooling air, excess cooling air (outside air) will be sucked through the gap in the drum, which will affect the gas flow and gas temperature inside the drum.
This results in a decrease in drying efficiency.

On the other hand, if the amount of gas sucked in by the exhaust fan is insufficient compared to the amount of combustion gas sent in, excess gas will be present in the drum, which will prevent good combustion and also reduce drying efficiency. Invite.

In addition, in recent years, as the amount of construction work has increased, it has become increasingly difficult to stably obtain high-quality aggregates, making it difficult to obtain aggregates with a constant moisture content.

Therefore, it is not possible to improve the drying efficiency unless the amount of water vapor generated when heating and drying such aggregates is taken into account and the amount of water vapor is sucked and exhausted in just the right amount.

The present invention has been proposed in view of the above points, and an object of the present invention is to suction and exhaust the amount of combustion gas sent into the drum using an exhaust fan in just the right amount and exhaust, so as to prevent excess gas from being present in the drum. This improves drying efficiency by avoiding excessive cooling air intake and maintaining constant gas flow through the drum, thereby saving fuel.

Furthermore, it is an object of the present invention to exhaust the inside of the drum by suctioning and exhausting the sum of the amount of combustion gas sent into the drum and the amount of water vapor evaporated from aggregates in the drum using an exhaust fan. Always maintain an optimal thermal atmosphere,
This improves drying efficiency.

The embodiment will be described in detail below. Reference numeral 1 denotes a drum made of an inclined cylindrical body, which is rotatably supported around its long axis.

A suitable number of raking blades are disposed inside the drum 1, and the aggregates supplied by a conveying means 2 such as a belt conveyor are raked up by the raking blades while being transferred down the drum 1.

Reference numeral 3 denotes a liquid fuel spray burner, which sends combustion gas into the drum 1, and sucks the combustion gas into the drum 1 using an exhaust fan 5 disposed at the end of an exhaust flue 4 connected to the drum 1. Maintain a high temperature gas flow through and heat dry the aggregate flowing down the transfer.

The heated aggregate is sent to the main tower (not shown) of the plant following the outlet 6.

Since the gas discharged through the exhaust flue 4 contains a large amount of dust, a dry cyclone dust collector 7 is used to remove the coarse part of the dust, and a filter cloth dust collector (not shown) is used to remove finer dust. I have to.

8 is a valve device provided in the exhaust flue 4 to adjust the gas flow rate.

Next, the control relationship of this device will be explained.

Reference numeral 9 denotes a temperature sensor facing the discharge port 6 of the drum 1, which continuously detects the temperature of the heated aggregate.

This detected value is converted into an electrical signal by a converter 10 and applied as an input to a controller 11.

Comparing the input value and the preset value in the controller 11,
An output depending on the comparison is applied as a control input to the control motor 12 which regulates the fuel and air intake of the burner 3.

That is, if the temperature of the heated aggregate discharged from the drum 1 differs from a preset value, the control motor 12 that adjusts the intake of fuel and air of the burner 3 is operated in response to the amount of the difference. , the amount of combustion by the burner 3 is increased or decreased to bring the aggregate closer to the desired temperature.

Further, a control motor 13 for adjusting the opening/closing degree of the valve device 8 is operated in conjunction with the control motor 12 of the bar t-3.
The controller 11 sends a signal to operate the combustion gas, and the exhaust fan 5 sucks in the amount of gas that follows the fluctuations in the combustion gas.

14.15 is a sensor for detecting the moisture content of the aggregate supplied to the drum 1 and the feed rate per unit time, and is equipped with a converter 16.17 for converting the moisture content response into an electric signal, and the electric A signal is input to controller 11.

The calculation section of the controller 11 calculates and extracts the amount of water vapor generated per unit time when the aggregate is heated and dried based on the input signal, and the control motor adjusts the opening/closing degree of the valve device 8 based on the output signal. 13 is corrected and controlled.

In other words, when heating and drying aggregates with varying moisture content,
The valve device 8 is loaded with opening/closing degree adjustment that follows the fluctuations in combustion gas and the fluctuations in the generated water vapor, and the exhaust fan 5 sucks in just the right amount depending on the amount of combustion gas sent into the drum 1 and the amount of water vapor generated. Exhaust.

As described in the paper, the present invention adjusts the valve device installed in the exhaust flue in response to the amount of gas generated in the drum, and suctions and exhausts the gas with the exhaust fan without excess or deficiency. It is possible to avoid the presence of excessive gas in the drum, which would cause a deterioration of the combustion state, or the introduction of excessive cooling air into the drum, which would cause a drop in gas temperature, due to excessive suction.

The present invention controls the gas flow passing through the drum in response to fluctuations in the amount of combustion gas and water vapor within the drum, so that the inside of the drum can always be maintained under optimal conditions, so it can be expected to improve drying efficiency.

Of course, the method of the present invention is not limited to the case where only aggregate is heated and dried, and similar benefits can be enjoyed when, for example, asphalt concrete waste is heated and dried.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of the present invention. The symbols in the figure are explained as follows. 1...Drum, 3...Burner, 4.
...Exhaust flue, 5...Exhaust fan, 8...
...Valve device, 9...Temperature sensor, 11...
...Nutrition controller, 12, 13...Control motor, 14...Moisture sensor, 15...
...Feed amount detection sensor.

Claims (1)

[Scope of Claims] 1. A valve device for controlling the gas flow rate is provided in the exhaust flue that guides the gas flow through the drum, which is a heating device, and a control motor that adjusts the degree of opening and closing of the valve device, and A control motor that adjusts the intake of fuel and air into the burner in response to the temperature of the heated aggregate is controlled in conjunction with the control motor, and the amount of gas commensurate with the amount of combustion gas sent into the drum by the burner is delivered to the end of the exhaust flue. A method for controlling combustion in an asphalt plant, characterized in that the degree of opening and closing of the valve device for controlling the gas flow rate is adjusted so that the provided exhaust fan can suck and exhaust the gas in just the right amount. 2. A valve device for controlling the gas flow rate is provided in the exhaust flue that guides the gas flow through the drum, which is a heating device, and a control motor that adjusts the opening/closing degree of the valve device and the temperature of the heated aggregate discharged from the drum are installed. In response to this, the control motor adjusts the intake of fuel and air into the burner in conjunction with the control motor, and by measuring the moisture content of the aggregate fed into the drum, the valve device sends a correction signal according to the moisture content. The amount of combustion gas sent into the drum by the burner and the amount of water vapor evaporated from the aggregate in the drum are applied to the control motor that controls 1. A method for controlling combustion in an asphalt plant, characterized in that the degree of opening and closing of the valve device for controlling the gas flow rate is adjusted so that the gas is sucked and exhausted without any problem.