JPS63205392A - Combustion control in asphalt plant - Google Patents

Abstract

PURPOSE:To prepare a piled material of asphalt without excess aggregate heating, by detecting waste gas temp. at the start of aggregate feeding and conducting initial combustion at this temp. in a predetermined combustion amt. for a predetermined combustion time. CONSTITUTION:In an asphalt plant for manufacturing a piled material of asphalt for use in road pavement, low-combustion start is conducted, and aggregate feeding is initiated from an aggregate hopper 2. When the aggregate reaches an aggregate sensor 10, the waste gas temp. is imputted into a central operating control unit 14 by means of the temp. sensor 12 installed in an exhaust chimney 6. An output signal is given to a combustion control circuit 18 so that a predetermined combustion amt. is attained at this temp. The combustion amt. is maintained for a predetermined combustion time. Thus, initial combustion is conducted. The initial combustion is conducted, until the aggregate is passed through the inside of a dryer 1 and reaches an aggregate sensor 11 and the aggregate sensor 11 detects the true temp. of the aggregate. Thereafter, normal operation is conducted.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an asphalt plant for manufacturing asphalt mixture, which is a road paving material, and in particular, to a method for controlling combustion of a burner that supplies hot air to a dryer, which is an aggregate heating device. It is about the method.

(Prior art) Combustion control in conventional asphalt plants/I
), as shown in the schematic flowchart in Figure 1, starts with low combustion and starts supplying aggregate, and then reaches high combustion when aggregate is detected by an aggregate sensor installed near the inlet of the dryer. Automatic combustion control is performed by switching. This automatic combustion control detects the temperature of heated aggregate discharged from the dryer, compares it with a preset aggregate temperature, and adjusts the combustion amount of the burner and the amount of combustion air using control signals corresponding to the comparison. Combustion is controlled by driving the motor.

(Problem to be solved by the invention) However, as mentioned above, automatic combustion control controls the combustion of the burner in response to the temperature of the heated aggregate discharged from the dryer. When the control is performed, the aggregate has not reached the dryer outlet, and the combustion is controlled at a low virtual aggregate temperature, and the combustion amount reaches the maximum and the aggregate is used more than necessary until the aggregate reaches the dryer outlet. There was a problem with the quality of the asphalt mixture, which is manufactured by heating and raising the temperature.

(Means for Solving the Problems) The present invention has been made in view of the above-mentioned points, and is designed to heat the aggregates more than necessary by performing initial combustion at a preset combustion rate until the aggregates reach the dryer outlet. I tried not to do that.

That is, the present invention provides a temperature sensor in the exhaust flue that guides the gas flow passing through the dryer, which is a heating device, detects the exhaust gas temperature at the start of aggregate supply with the temperature sensor, and sets the temperature in advance based on the exhaust gas temperature. Combustion control in an asphalt plant, characterized in that the combustion amount of the burner is controlled in response to the temperature of heated aggregate discharged from a dryer after the initial combustion of the burner is performed using the combustion amount and combustion time specified. We are here to provide you with a method.

(Function) According to the present invention, the exhaust gas temperature at the start of aggregate supply is detected, and the initial combustion of the burner is performed with the combustion amount and combustion time preset according to the exhaust gas temperature, so that the aggregate is supplied at the beginning of the operation. C3) It is possible to produce high-quality asphalt mixture without heating more than necessary.

(Example) Hereinafter, the present invention will be explained based on examples.

FIG. 2 is a system diagram of combustion control of a dryer in an asphalt plant.

In the figure, reference numeral 1 denotes a dryer in which a cylindrical body with a large number of scraping blades arranged around its inner periphery is rotatably supported at an angle. The aggregate is fed into the dryer 1 through a pipe 3.4, and the aggregate is raked up by the raking blades provided around the inner periphery, while being transferred and flowed down. Reference numeral 5 denotes a liquid fuel spray burner, which sends combustion gas into the dryer 1, and sucks the combustion gas into the dryer 1 by using an exhaust fan 7 disposed at the end of an exhaust flue 6 connected to the dryer 1. A high-temperature gas flow is maintained inside the tank, and the aggregate flowing down is heated and dried. Since the exhaust gas discharged through the exhaust flue 6 contains a large amount of dust, coarse particles of dust are removed using a dry cyclone dust collector (not shown), and finer dust is removed using a bag filter 8. and is released into the atmosphere from chimney 9. 10 is an aggregate sensor that detects the aggregate conveyed by the belt conveyor 4, and 11 is a temperature sensor that detects the temperature of the heated aggregate discharged from the dryer 1. A temperature sensor 12 detects the temperature of the exhaust gas passing through the exhaust flue 6, and is provided at the entrance of the bag filter 8 in the embodiment.

Reference numeral 13 denotes a process input/output device for exchanging analog and digital contact signals with external equipment, and the signals detected by the sensors are transmitted to the central processing control unit 14 via this process input/output device 13. Central processing control unit 14
It processes signals input from external equipment, has a storage device that stores necessary operation blocks, displays, recorded signals, etc., and controls the entire plant. Reference numeral 15 denotes a CRT display device that displays the output results of the central processing control unit 14 in the form of messages or graphics on a cathode ray tube. is attached. Reference numeral 17 denotes an operator's console comprised of pushbutton switches and the like for operators to operate the plant.

Reference numeral 18 denotes a combustion control circuit that controls the amount of combustion in accordance with a control signal sent from the central processing controller 14.
A control motor 19 is driven and controlled to intake fuel and fuel air.

Next, a combustion control method will be explained.

FIG. 3 is a schematic flowchart of combustion control. First, low combustion is started and supply of aggregate from the aggregate hopper 2 is started. When the aggregate sensor 10 detects that the aggregate has reached the position of the aggregate sensor 10, the temperature sensor 12 provided in the exhaust flue 6 inputs the exhaust gas temperature into the central processing controller 14, and the temperature is set in advance according to the exhaust gas temperature. An output signal is given to the combustion control circuit 18 so as to achieve the combustion amount, and initial combustion is performed in which the combustion amount is maintained for the set combustion time.

This initial combustion is performed until the aggregate passes through the dryer 1 and reaches the aggregate sensor 11, and the aggregate sensor 11 can detect the true aggregate temperature. The time etc. can be entered on the keyboard 16 along with various setting values before operation.
It is typed by. FIG. 4 shows a CRT display device 15.
This is the initial combustion setting screen displayed on the screen, on which the exhaust gas temperature range, the combustion time within that temperature range, and the combustion opening degree of the burner 5 are set and input in advance. In Fig. 4, the exhaust gas temperature range is set in three patterns: 60°C or less, 60-80°C, and 180°C or more, but this is not limited to three patterns. In the initial combustion, when the detected exhaust gas temperature is low, the combustion amount of the burner 5 is increased, and when the exhaust gas temperature is high, the burner 5 is increased because the dryer 1 and the exhaust flue 12 have already been heated in the previous operation.
By reducing the amount of combustion of the aggregate, the aggregate is not heated more than necessary, and the exhaust gas temperature is also prevented from rising too much and burning out the filter cloth of the bag filter 8.

Since the set value is influenced by, for example, the amount of aggregate supplied, the moisture content of sand, etc., it is preferable to determine and set the set value by taking these operating conditions into consideration through trial runs or the like.

After the initial combustion is completed, the system switches to the same automatic combustion control as before, but this automatic combustion control, as described above,
The temperature of the heated aggregate discharged from the burner 5 is detected by the temperature sensor 11, and compared with the aggregate temperature set in advance by the central processing controller 14, and a control signal corresponding to the comparison is sent to the combustion control circuit 18 to control the burner 5. The combustion is controlled by driving and controlling a control motor 19 that adjusts the amount of combustion and the amount of combustion air.

(Effects of the Invention) As described above, in the present invention, the exhaust gas temperature at the start of aggregate supply is detected, and the combustion rate is set in advance based on the exhaust gas temperature to prevent the aggregate from being overheated. Unlike conventional methods, the low imaginary temperature of the aggregate that has not reached the dryer outlet is detected, and automatic combustion control allows the aggregate to be burned at the maximum amount without heating the aggregate more than necessary. The quality of the composite material can be improved. Furthermore, since the exhaust gas does not reach an extremely high temperature, it is possible to prevent the filter cloth of the bag filter from burning out.

(l)

[Brief explanation of the drawing]

Figure 1 is a schematic flowchart of a conventional combustion control method;
FIG. 2 is a system diagram of combustion control of a dryer in an asphalt plant, FIG. 3 is a schematic flowchart of the combustion control method of the present invention, and FIG. 4 is an initial combustion setting screen of a CRT display device. 1... Dryer 2... Aggregate hopper 5... Burner 6... Exhaust flue 8... Bag filter-lO・
・・Aggregate sensor 11.12・・Temperature sensor 13・
...Process input/output device 14...Central processing control unit 15...CRT display device 16...Keyboard
17... Operator's console 18... Combustion control circuit 19... Control motor

Claims (1)

[Claims] A temperature sensor is installed in the exhaust flue that guides the gas flow through the dryer, which is a heating device, and the temperature sensor detects the exhaust gas temperature at the start of aggregate supply, and the combustion amount and combustion time are set in advance based on the exhaust gas temperature. 1. A method for controlling combustion in an asphalt plant, characterized in that the amount of combustion in a burner is controlled in response to the temperature of heated aggregate discharged from a dryer after initial combustion in a burner is performed.