JP2002266012A - Waste heat recovering equipment for hot air stove for blast furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hot air stove waste heat recovering equipment for a blast furnace, which is capable of raising the temperature of feed air to the blast furnace by raising the temperature of a heating medium after the heat recovery by using a blast furnace gas, which has low availability and is conventionally released as a residual gas, to elevate the pre-heating temperature of each of combustion air and a fuel gas without using fuel such as COG having high availability or LPG or LNG as an expensive purchased gas. SOLUTION: In the hot are stove waste heat recovering equipment for the blast furnace, in which the heat of the waste combustion gas of the hot air stove is recovered and the combustion air and the combustion gas in the hot air stove is preheated with the recovered heat, a heater 13 using the blast furnace gas, which has low availability and is conventionally released as the residual gas, as fuel is arranged between a waste combustion gas heat exchanger 7 in heat receiving side, and a combustion air heat exchanger 9 and a fuel gas heat exchange 11 in the heat releasing side, and the heating medium after receiving the heat in the waste combustion gas heat exchanger 7 is introduced into the heater 13 to be heated, and after that, introduced into the combustion air heat exchanger 9 and the fuel gas heat exchanger 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blast furnace hot air exhaust heat recovery system for recovering the sensible heat of combustion exhaust gas from a hot air furnace and raising the temperature of combustion air and fuel gas.

[0002]

2. Description of the Related Art For example, Japanese Unexamined Patent Publication No. Sho 55-11152 and Japanese Utility Model Publication No. Sho 57-1843 disclose a hot air stove exhaust heat recovery facility for a blast furnace.
As described in Japanese Patent Application Laid-open No. 1 and JP-A-9-287013, combustion exhaust gas from a hot-blast stove is used to raise the temperature of combustion air and fuel gas in the hot-blast stove.
By recovering the sensible heat of the combustion exhaust gas and raising the temperature of the combustion air and fuel gas, the amount of high-calorie gas such as LPG, LNG, and COG mixed with the fuel gas as auxiliary fuel can be reduced or the blast furnace temperature. Can be raised.

FIG. 3 is a flow chart of a hot-blast stove exhaust heat recovery facility for a blast furnace, in which fuel gas and combustion air are supplied to a combustion chamber 1 of the hot-blast stove and a combustion gas burned by a combustor built in the combustion chamber 1 is supplied. The heat is stored in the heat storage chamber 3 via the connecting pipe 2 and the heat storage body incorporated in the heat storage chamber 3 is heated. Then, after that, it passes through the flue 4, passes through the chimney 5, and is emitted to the atmosphere as combustion exhaust gas. Air is sent to the heat storage chamber 3 by the blower 6, the temperature rises through the heat storage body in the heat storage chamber 3, and is sent to the blast furnace via the connecting pipe 2 and the combustion chamber 1.

A flue gas heat exchanger 7 is provided in the middle of the flue 4 of the hot stove, a combustion air heat exchanger 9 is provided in the
A fuel gas heat exchanger 11 is disposed in the middle of the fuel gas pipe 10, and a closed circuit is provided in which a heat medium can be circulated between the heat exchangers by a heat medium circulation pump 12. In this closed circuit, the heat medium first passes through the flue gas heat exchanger 7 in the flue 4.
And the temperature is increased by the sensible heat of the combustion exhaust gas, and the high-temperature heat medium passes through the closed circuit and enters the combustion air heat exchanger 9 and the fuel gas heat exchanger 11 to heat and raise the combustion air and the fuel gas, respectively. . By heating the combustion air and the fuel gas, the temperature of the heat medium drops, and the heat medium circulating pump 12 passes through the closed circuit again to cause the combustion exhaust gas heat exchanger 7
And is heated.

[0005]

SUMMARY OF THE INVENTION Reducing the fuel ratio of a blast furnace;
In order to raise the blowing temperature to the blast furnace more than ever with the aim of improving the tapping ratio, it is necessary to raise the preheating temperature of the combustion air and fuel gas and to increase the auxiliary fuel mixed with the fuel gas. A method of increasing the amount of high-calorie gas such as LPG, LNG, and COG can be considered.

However, the method of raising the preheating temperature of the combustion air and the fuel gas to a higher temperature has a limit in the conventional exhaust heat recovery equipment. FIG. 4 is a diagram showing the temperature of each gas and heat medium, showing the temperatures at the inlet and outlet of each heat exchanger 7, 9, 11 for each gas and heat medium. According to this, the exhaust gas temperature of the flue 4 is 250 ° C., the temperature of the heat medium that has recovered its sensible heat is 200 ° C., and the temperature of the combustion air and fuel gas preheated by the heat medium is 140 ° C.
° C and 120 ° C, and it was not possible to raise the temperature further than this due to restrictions on the exhaust gas temperature.

A method for increasing the amount of high-calorie gas such as LPG, LNG or COG as an auxiliary fuel mixed with fuel gas is that LPG and LNG are expensive purchased fuels, and COG is a coke oven Because of the limited use of these supplementary fuels in the steelworks and their lack of value, the use of these supplementary fuels was limited both economically and in terms of the gas balance of the steelworks.

The present invention utilizes blast furnace gas, which has low utility value and is released as surplus gas, without using fuel such as COG having high utility value and LPG and LNG which are expensive purchase gases. The purpose of the present invention is to provide a hot blast stove exhaust heat recovery facility for a blast furnace that can raise the temperature of the heat medium after the recovery heat, raise the preheating temperature of each of the combustion air and the fuel gas to a higher temperature, and raise the blowing temperature to the blast furnace. is there.

[0009]

SUMMARY OF THE INVENTION The present invention recovers the sensible heat of flue gas from a hot blast stove by circulating a heat medium,
In a blast furnace hot air stove exhaust system that preheats the combustion air and fuel gas of the hot stove with the recovered heat, the heat exhaust gas heat exchanger on the heat receiving side, the combustion air heat exchanger on the heat radiating side, and the fuel gas heat exchanger A heater using blast furnace gas as a fuel is arranged in between, and the heat medium received by the flue gas heat exchanger is introduced into the heater and heated, and then the heat medium is used as the combustion air heat exchanger and the fuel. It is characterized in that it is introduced into a gas heat exchanger.

[0010]

FIG. 1 is a flow chart of a blast furnace hot-air stove exhaust heat recovery facility in which a heater according to the present invention is arranged. The present invention
As shown in FIG. 1, a heater 13 and a booster pump 14 are newly arranged between the conventional combustion exhaust gas heat exchanger 7, the combustion air heat exchanger 9 and the fuel gas heat exchanger 11, and the heater 1
3. A closed circuit in which the heat medium can be circulated by the heat medium circulation pump 12 between the booster pump 14 and each heat exchanger.

The heater 13 comprises a combustion burner 16 using blast furnace gas 15 as fuel, and a heat exchange section 17 into which a fin tube is inserted for raising the temperature of the heat medium.
The pressurizing pump 14 pressurizes the heat medium to compensate for the pressure loss of the heater 13.
If there is enough capacity, the boosting pump 14 can be omitted.

In this closed circuit, the heat medium first enters the combustion exhaust gas heat exchanger 7 by the heat medium circulation pump 12 and is heated by the sensible heat of the combustion exhaust gas. The temperature of the heated heat medium is increased by the pressure increasing pump 14 through the closed circuit, and enters the heater 13. The blast furnace gas is burned in the heater 13, and the heat medium becomes higher in temperature by receiving the sensible heat of the combustion gas in the heat exchange unit 17.

The heating medium that has exited the heater 13 due to the high temperature is:
As in the conventional case described with reference to FIG. 3, the combustion air and the fuel gas enter the combustion air heat exchanger 9 and the fuel gas heat exchanger 11 through a closed circuit, and the combustion air and the fuel gas are heated and heated, respectively. By heating the combustion air and the fuel gas, the temperature of the heat medium is reduced, and the heat medium is again passed through the closed circuit to enter the combustion exhaust gas heat exchanger 7 by the heat medium circulation pump 12 and is heated.

FIG. 2 is a diagram showing respective gas and heating medium temperatures when the heater of the present invention is arranged.
The temperature at the inlet and the outlet of each heat exchanger is shown for each gas and heat medium of the exhaust heat recovery facility where is disposed. According to this, the flue gas temperature of the flue 4 is 250 ° C., and the temperature of the heat medium that has recovered the sensible heat and exited the flue gas heat exchanger 7 is 2 ° C.
At 00 ° C., this is the same as before. In the present invention,
The heating medium at a temperature of 200 ° C. enters the newly installed heater 13 where it is heated to 300 ° C. The heating temperature of 300 ° C. is determined by the specification of the heat medium capable of maintaining high-temperature stability. The heating medium at 300 ° C. that has exited the heater 13 is
It enters the combustion air heat exchanger 9 and the fuel gas heat exchanger 11, where the temperature of the combustion air and fuel gas received is:
20 ° C to 230 ° C and 40 ° C to 210 ° C respectively
Temperature. When these temperatures are compared with the conventional combustion air and fuel gas, it can be seen that the temperatures are as high as 90 ° C.

Further, since the heater 13 can be constructed independently by laying a heating medium pipe, it can be installed not only in a new exhaust heat recovery facility but also in an existing exhaust heat recovery facility. It is easily possible.

[0016]

According to the present invention, a heater can be added to a new or existing waste heat recovery facility, and its useful value can be reduced without using expensive fuel gas such as COG, LPG, and LNG which are highly useful as fuel. The blast furnace gas, which has been released as a surplus gas, is effectively used to increase the preheating temperature of the combustion air and fuel gas, resulting in a high combustion temperature.
High-temperature blowing to the blast furnace is economically possible, and it is expected that the fuel ratio of the blast furnace will be reduced and the tapping ratio will be improved.

[Brief description of the drawings]

FIG. 1 is a flow chart of a blast furnace hot stove exhaust heat recovery facility provided with a heater of the present invention.

FIG. 2 is a diagram showing respective gas and heat medium temperatures when the heater of the present invention is arranged.

FIG. 3 is a flowchart of a conventional hot blast stove exhaust heat recovery facility for a blast furnace.

FIG. 4 is a diagram showing respective gas and heat medium temperatures in the related art.

[Explanation of symbols]

1: Combustion chamber 2: Connecting pipe 3: Thermal storage chamber 4: Flue 5:
Chimney 6: Blower 7: Combustion exhaust gas heat exchanger 8: Combustion air tube 9: Combustion air heat exchanger 10: Fuel gas tube 11: Fuel gas heat exchanger 12: Heat medium circulation pump 13: Heater 14: Pressurization Pump 15: Blast furnace gas 1
6: Combustion burner 17: Heat exchange section

Claims (1)

[Claims] 1. A blast furnace heat exhaust device for a blast furnace for recovering sensible heat of combustion exhaust gas of a hot stove by circulating a heat medium and preheating combustion air and fuel gas of the hot stove with the recovered heat. A heater using blast furnace gas (BFG) as fuel was added between the combustion exhaust gas heat exchanger on the side and the combustion air heat exchanger on the heat radiation side and the fuel gas heat exchanger, and heat was received by the combustion exhaust gas heat exchanger. A hot blast stove exhaust heat recovery facility for a blast furnace, wherein a heat medium is introduced into the heater and heated, and then the heat medium is introduced into a combustion air heat exchanger and a fuel gas heat exchanger.