JPS62147286A - Method of controlling temperature of blast furnace gas - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is directed to B gas (blast furnace gas, approximately 900 gcal/
The present invention relates to a blast furnace gas temperature control method applied to a blast furnace gas fired boiler that uses a large amount of NrH (low calorie gas) as fuel.

C gas (coke oven gas approximately 5200 Kcal/Nr
rl') and B gas (blast furnace gas approximately 920 Kcal
/ Nm”) in a gas-fired boiler,
B gas (blast furnace gas), a low-calorie gas that is inexpensive and available in large quantities, is often used. If using B gas, use C gas,
Since a large amount of B gas is required compared to heavy oil, the amount of exhaust gas also increases, and the exhaust gas temperature cannot be lowered by the air heater alone, so the exhaust gas loss, which is the largest among boiler heat losses, increases and boiler efficiency decreases. . For this reason, in the past, in order to increase this boiler efficiency, water was used to recover exhaust gas heat. S4, this lowers the exhaust gas temperature, increases boiler efficiency, and increases the amount of B gas, and furthermore, the hot water obtained by heat exchange is used to convert B gas (blast furnace gas).
A good combustion temperature is obtained by increasing the temperature.

This system is shown in Figure 3. In the figure, code 1 is an air heater;
2 is an air heater inlet exhaust gas damper, 3 is an exhaust gas cooler inlet damper, 4 is an exhaust gas cooler, 5 is a circulation pump, 6 is B
A gas heater, 7 a forced air blower, and 8 an induced fan.

A portion of the exhaust gas from the furnace is extracted from the upstream side of the air heater 1 and enters the exhaust gas cooler 4. In the exhaust gas cooler 4, circulating water, which is a circulating medium, undergoes heat exchange and is heated. The heated circulating water is sent to the B gas heater 6 by the circulating water pump 5, where it exchanges heat with the B gas, and then is sent to the exhaust gas cooler 4 again.
It is circulated to.

A control system for the system shown in FIG. 3 is shown in FIG.

In FIG. 4, reference numeral 9 indicates a temperature controller, where B
The B gas temperature at the outlet of the gas heater is set, and a constant temperature control signal is output based on the B gas temperature at the outlet of the B gas heater. 1
0 is an adder, and since single-loop control using only the B gas heater output and B gas temperature has poor controllability, it inputs the B gas flow rate (temperature corrected) as a preceding signal and outputs the calculated control signal. It is something. 11 is a signal upper limit limiter;
This is to prevent the air heater exhaust gas damper 2 from being fully closed and the pressure inside the furnace from rising. Reference numerals 12 and 13 indicate automatic/manual operating devices for the air heater inlet exhaust gas damper 2 and the exhaust gas cooler inlet damper 3. The two control signals output by the adder 10 control the air heater inlet exhaust gas damper 2 and the exhaust gas cooler inlet damper 3 as shown in FIG. 5, thereby controlling the amount of exhaust gas (heat amount).

Problems to be Solved by the Invention According to the conventional method, even if the amount of exhaust gas is controlled by an exhaust gas damper based on the B gas temperature at the B gas heater outlet and the B gas flow rate, the hot water that has recovered heat does not reach the B gas heater. Depending on the distance reached and the flow rate of hot water, it takes time for the temperature to stabilize, and it is difficult to stabilize the temperature due to load fluctuations and B gas flow rate fluctuations.Furthermore, the temperature may change because hot water flow rate is not controlled. There was a risk of severe low-temperature corrosion of the exhaust gas cooler heat exchange tube.

Therefore, the present invention provides a boiler such as a B gas-fired boiler that digests a large amount of B gas (low calorie gas), which is inexpensive and has a large amount of supply, to maintain a stable temperature against load fluctuations and B gas flow rate fluctuations. The object of the present invention is to provide a blast furnace gas temperature control method that can be controlled, protect the circulation pump, and prevent low-temperature corrosion of the exhaust gas cooler heat exchange tube.

Means for Solving the Problems According to the present invention, a part of the exhaust gas on the upstream side of the air heater is extracted, the extracted exhaust gas and the circulating medium are heated by exchanging heat, and the heated circulating medium and the circulating medium are heated. A blast furnace gas-fired boiler that heats the blast furnace gas by exchanging heat with the blast furnace gas before being supplied to the furnace, and the circulating medium that has been cooled by the heat exchange with the blast furnace gas is sent again for heat exchange with the exhaust gas. In the blast furnace gas temperature control method, the amount of exhaust gas to be extracted is determined from the boiler load and the amount of blast furnace gas combustion, and the amount of exhaust gas is controlled, and the temperature of the circulating medium after heat exchange with the blast furnace gas is adjusted to the set temperature. To provide a blast furnace gas temperature control method that controls the flow rate of a circulating medium before heat exchange with the blast furnace and forcibly increases or decreases the amount of extracted exhaust gas when the flow rate of the circulating medium exceeds a predetermined control range. .

Embodiment FIG. 1 shows a system diagram of a blast furnace gas-fired boiler according to the present invention. In FIG. 1, numeral 1 is an air heater, 2 is an air heater inlet exhaust gas damper, 3 is an exhaust gas cooler inlet damper,
4 is an exhaust gas cooler, 5 is a circulation pump, 6 is a B gas heater, 14 is a circulating water temperature control valve, and 15 is a circulating water temperature detection end (thermocouple) at the outlet of the B gas heater.

As illustrated, in the method according to the present invention, a circulating water temperature control valve 14 controlled by a B gas heater outlet circulating water temperature detection end 15 is added to the circulating water system. FIG. 2 shows a B gas temperature control system diagram for carrying out the method of the present invention. In the figure, reference numeral 1G is a temperature controller that receives a temperature signal from the B gas heater outlet circulating water temperature detection terminal 15, and by setting the B gas heater outlet circulating water temperature, the circulating water temperature is controlled to be kept constant against temperature changes. A signal 11 for controlling the valve 14 is output. Reference numeral 17 denotes a signal upper limit setting device for preventing the circulating water temperature control valve 14 from being completely closed to protect the circulating pump during operation. 18 is an automatic/manual operator for the circulating water temperature control valve 14. Reference numeral 19 denotes a multiplier that calculates and outputs a signal that changes depending on load fluctuations and the amount of B gas burned. Reference numeral 20 denotes a polygonal function unit which programmatically controls the signal output from the multiplier 4 using a function curve to output an exhaust gas side damper opening signal. Reference numeral 21 denotes an adder, which normally controls the exhaust gas damper using only the output signal from the linear function unit 20. 22
is a no.i/low monitor that constantly monitors the control output from the automatic/manual operating device 18. 23 shows the rate of change setting device.

When the circulating water temperature control valve 14 exceeds the control range, the I/L monitor 22 detects this and outputs a command signal to the signal generators 23 and 24. If the temperature of the circulating water becomes too high, the signal generator 23 is activated and the (-) side signal is input to the adder 21 via the change rate setting device 26, and the exhaust gas cooler inlet damper: (It' The exhaust gas damper 2 operates in the l-closing direction and the air heater inlet exhaust gas damper 2 operates in the open direction, respectively, to control the amount of exhaust gas to be reduced.In addition, when the temperature of the reverse busy circulating water is low, the signal generator 24 operates, and (+ ) side signal is input to the adder 21, the exhaust gas artificial damper 3 is operated in the opening direction, and the air heater inlet exhaust gas damper 2 is operated in the closing direction, thereby controlling the amount of exhaust gas to be increased.

27 and 28 are bias setting devices for finely adjusting the output signal of the adder 21 to improve temperature controllability; 11 is a signal upper limit limiter for preventing the air heater inlet exhaust gas damper 2 from being completely closed during operation; 12 and 13 is an automatic/manual operator (
(for each damper opening/closing), 2 is the air heater inlet exhaust gas damper,
3 is an exhaust gas cooler inlet damper.

With the above control system, the amount of exhaust gas extracted from the boiler load and blast furnace gas combustion amount is determined, and the amount of exhaust gas is controlled.
The flow rate of the circulating medium before heat exchange with the blast furnace gas is controlled so that the temperature of the circulating medium after heat exchange with the blast furnace gas is the set temperature, and when the flow rate of the circulating medium exceeds a predetermined control range. By forcibly increasing or decreasing the amount of extracted exhaust gas, it is possible to control the B gas (blast furnace gas) temperature, protect the circulation pump, and furthermore prevent low-temperature corrosion of the exhaust gas cooler heat exchange tube.

[Brief explanation of drawings]

FIG. 1 is a system diagram of a blast furnace gas-fired boiler to which the present invention is applied, FIG. 2 is a system diagram of a blast furnace gas temperature control system according to the present invention, and FIG. 3 is a system diagram of a conventional blast furnace gas-fired boiler. Fourth
The figure is a conventional control system diagram, and FIG. 5 is a diagram showing the relationship between damper opening degrees. 1. Air heater, 2. Air heater inlet exhaust gas damper, 3. Exhaust gas cooler inlet damper, 4. Exhaust gas cooler, 5. Circulation pump, 6. B gas heater, 14. Circulating water temperature control valve, 15.・B gas heater outlet circulating water temperature detection end, 16. Temperature controller, 17. Signal upper limit setting device, 18. Automatic/manual operation device, 19. Multiplier, 20.
- Linear function unit, 21... Adder, 22... I/Low monitor, 23.24... Signal generator, 25... Switcher,
26... Rate of change setter, 27.28... Bias setter. ,')・Fourth Flash

Claims (1)

[Claims] Part of the exhaust gas on the upstream side of the air heater is extracted, the extracted exhaust gas and the circulating medium are heated by exchanging heat, and the heated circulating medium and the blast furnace are heated before being supplied to the furnace. In a blast furnace gas temperature control method for a blast furnace gas-fired boiler, the circulating medium that has been cooled by heat exchange with the blast furnace gas is sent again for heat exchange with the exhaust gas, The amount of exhaust gas extracted from the boiler load and blast furnace gas combustion amount is determined to control the amount of exhaust gas, and the temperature of the circulating medium after heat exchange with blast furnace gas is adjusted to the set temperature. A blast furnace gas temperature control method that controls the flow rate of the circulating medium and forcibly increases or decreases the amount of extracted exhaust gas when the flow rate of the circulating medium exceeds a predetermined control range.