CN1084792C - High air-temperature high furnace space gas preheating method - Google Patents

Abstract

The invention relates to a method for preheating the air and gas of a high-temperature blast furnace hot blast stove, which is to use the flue gas of the hot blast stove at 280-320°C to simultaneously preheat the combustion air and blast furnace gas of the hot blast stove to 130-150°C for the first time. The gas generator burns blast furnace gas to produce high-temperature flue gas at 900-1000°C, which preheats the air and blast furnace gas to 300-450°C for the second time. The invention makes full use of the residual heat of the flue gas of the hot blast stove, increases the preheating temperatures of the combustion air and the blast furnace gas by 50°C and 150°C respectively, and makes the air supply temperature reach 1250-1310°C under the condition of fully burning the blast furnace gas. It can save coke oven gas or coke, save electricity consumption and reduce production cost.

Description

Air and Gas Preheating Method of Hot Blast Stove in High Blast Furnace

The invention relates to a blast furnace ironmaking method, in particular to a method for preheating a blast furnace hot blast stove using air and gas.

At present, with the development of blast furnace ironmaking technology (including coal injection technology), blast furnaces require higher and higher hot blast temperatures (above 1200°C). In order to achieve high blast temperature, in addition to burning blast furnace gas with low calorific value, the hot blast stove of blast furnace must also burn a considerable proportion of coke oven gas with high calorific value. For most steel plants, coke oven gas is invaluable. Since the 1980s, many high-temperature blast furnace hot blast stoves have used flue gas waste heat recovery devices to preheat the blast furnace gas and combustion-supporting air to 130-150°C, which has achieved the effect of saving about 30% of coke oven gas. But it is also necessary to burn about 70% of high calorific value gas (coke oven gas). In order to make full use of blast furnace gas, the prior art usually adopts the method of preheating blast furnace gas and combustion-supporting air with high-temperature flue gas produced by a combustion furnace burning blast furnace gas. Preheating process", discloses the following technical scheme: use the high-temperature flue gas (about 1000°C) of burning blast furnace gas to mix a large amount of hot-blast stove low-temperature flue gas (250°C) to drop below 600°C, and reheat the hot-blast stove The blast furnace gas and combustion-supporting air are used to make the temperature reach about 300°C, so as to ensure that the air supply temperature reaches 1100-1200°C under the condition of fully burning blast furnace gas. The problems of this scheme are as follows: (1) The high-temperature flue gas (900-1000°C) produced by burning blast furnace gas in the flue gas generator is mixed with a large amount of low-temperature flue gas, and the temperature is lowered to below 600°C before being used. Low temperature is a process of increasing entropy, that is, a process of reducing "use", that is, a process of wasting energy. In addition, if the flue gas starts to heat the combustion-supporting air at 900-1000°C, then in the heat exchanger, the logarithmic average temperature difference is much greater than the logarithmic average temperature difference when the flue gas is lowered below 600°C and then used for heat exchange. The heat effect is much better. When transferring the same heat, the former has less heat transfer area, and the heat exchanger is small in size and light in weight. (2) The low-temperature flue gas is more than twice as high as the high-temperature flue gas. It must be boosted or drawn by a fan before it can be mixed with high-temperature flue gas. When it is reduced to low-temperature flue gas by the heat exchanger, it is drawn back by the induced draft fan. The high-temperature flue gas is sent in, and this part of the flue gas circulates repeatedly in this way, which causes the induced draft fan to consume a large amount of electric energy in vain. (3) The hot blast stove flue gas above 250°C is discharged into the chimney without being utilized, and the waste heat resources are not fully utilized.

The purpose of the present invention is to make full use of the waste heat of blast furnace hot blast stove flue gas, increase the temperature of blast furnace gas and combustion-supporting air fed into the hot blast stove, and ensure that the blast furnace supply air temperature is further increased under the condition of fully burning blast furnace gas.

To achieve the above object, the technical solution proposed by the present invention is:

A method for preheating the air and gas of a hot blast furnace hot blast stove with a high blast temperature. The hot blast furnace flue gas is used to preheat the air and blast furnace gas used in the hot blast furnace for the first time. Blast furnace gas and air are preheated for the second time.

The first preheating is to preheat the combustion air and blast furnace gas at the same time.

The first preheating is to heat the combustion air and blast furnace gas from normal temperature to 130-150°C with hot blast stove flue gas at a temperature of 280-320°C.

The first preheating is to use a separate heat pipe heat exchanger.

The second preheating is to preheat the air and gas successively.

The second preheating is to heat the combustion-supporting air to 400-450°C with high-temperature flue gas at 900-1000°C, and then heat the blast furnace gas to 300-350°C.

The second preheating is to use a single tube type heat pipe heat exchanger.

Fig. 1 is the process system diagram of the air and gas preheating method of the high blast furnace hot blast stove of the present invention.

The present invention will be described in further detail below in conjunction with the accompanying drawings.

The key points of the present invention are: (1) The low-temperature flue gas waste heat resources discharged from the hot blast stove are all used as heat sources for the first-stage preheating of blast furnace gas and combustion-supporting air to raise them from normal temperature to 130-150°C. (2) Use the high-temperature flue gas generated by the blast furnace gas in the flue gas generator at about 900°C as the heat source for preheating the blast furnace gas and combustion-supporting air in the second stage, and continue to heat up the two gases to 350-450°C in the heat exchanger ℃.

As shown in Figure 1, the present invention adopts two-stage preheating, and the first stage preheating adopts a separate heat pipe heat exchanger, which is composed of three heat exchangers, wherein the flue gas heat exchanger 2 is arranged in the hot blast stove 8 On the flue gas pipeline Y leading to the chimney 1, the air heat exchanger 4 is arranged on the original combustion air pipeline K of the hot blast stove 8, and the gas heat exchanger 3 is arranged on the original blast furnace gas pipeline M of the hot blast stove. The flue gas at about 300°C discharged from the hot blast stove is introduced into the flue gas heat exchanger 2 through the main flue Y. The working medium in the core tube of the heat exchanger absorbs the heat of the flue gas and vaporizes into steam, and the steam enters respectively along the multiple rows of rising pipes. In the core tubes of the air heat exchanger 4 and the gas heat exchanger 3 connected in parallel, the combustion-supporting air and blast furnace gas at normal temperature outside the tubes are respectively heated to 130-150°C. The steam after heat release condenses into liquid and flows back to the 2-core tube of the flue gas heat exchanger along the downcomer to participate in the next cycle.

The blast furnace gas that has not been preheated all the way is sent to the flue gas generator 5, and the high-temperature flue gas of about 900°C is obtained through combustion. The flue gas generator 5 is connected to the outlet pipe of the blower 9. The high-temperature flue gas first enters the lower box of flue gas/air heat exchanger 6 to heat the evaporation ends of multiple heat pipes, and then enters the lower box of flue gas/gas heat exchanger 7 to heat the evaporation ends of multiple heat pipes. That is, the evaporation ends (flue gas side) of the two heat pipe heat exchangers are connected in series, and the condensation ends (air side and gas side) are connected in parallel.

The second-stage preheating adopts two single-tube heat pipe heat exchangers. The evaporation side of the single-tube heat pipe heat exchanger is the flue gas side, which is the lower box. The flue gas/air heat exchanger 6 and the flue gas/coal gas heat exchange The flue gas sides of both devices 7 are arranged in series. The combustion-supporting air and blast furnace gas preheated to 130-150°C for the first time are respectively sent to the upper box of the second-stage preheated flue gas/air heat exchanger 6 and flue gas/gas heat exchanger 7, that is, two On the condensing side of a single-tube heat pipe heat exchanger, the two gases are heated by multiple heat pipes respectively, and the high-temperature flue gas (about 900°C) generated by burning blast furnace gas in the flue gas generator 5 first enters the flue gas/air heat exchanger 6 , heating the combustion-supporting air to 400-450°C, the flue gas drops to about 550°C, passes through the flue Y and then enters the flue gas/gas heat exchanger 7, heats the blast furnace gas to 300-350°C, and the flue gas drops to 180°C , into the atmosphere through branch flue, main flue and chimney 1. Combustion-supporting air at 400-450°C and blast furnace gas at 300-350°C respectively enter the combustion chamber of the hot blast stove 8 to participate in combustion, which can burn the vault temperature above 1450°C and ensure the air supply temperature reaches 1250-1310°C.

Compared with the prior art (CN1188808A), the present invention makes full use of the waste heat resources of the flue gas of the blast furnace hot blast stove, can preheat the combustion-supporting air to 400-450°C, and preheat the blast furnace gas to 300-350°C. 50 ℃ and 150 ℃, so that the high blast furnace hot blast stove is fully fired with blast furnace gas, the air supply temperature of the hot blast stove is increased by 50 ℃ ~ 110 ℃, reaching 1250 ~ 1310 ℃. The blast furnace ironmaking process can save coke (10-20 kg of coke per ton of iron), reduce production costs, and the facility investment payback period is about one year. And the low-temperature flue gas circulation fan that consumes more power is canceled, thereby saving power consumption (for a 4000 cubic meter blast furnace, power consumption can be saved by 180 degrees per hour). If coke is not saved, a large amount of coke oven gas can be saved (for a blast furnace of 4000 cubic meters, 10,000 cubic meters of coke oven gas can be saved per hour).

Claims (7)

1. a high-air temp hot-blast stove for blast furnace air, gas preheating method, it is characterized in that: hotblast stove combustion air, blast furnace gas are carried out the preheating first time with hot-blast stove fume, flue gas producer burning blast furnace gas, the high-temperature flue gas of generation carries out the preheating second time to blast furnace gas, air.

2. high-air temp hot-blast stove for blast furnace air according to claim 1, gas preheating method is characterized in that: the described preheating first time is simultaneously combustion air, blast furnace gas to be carried out preheating.

3. high-air temp hot-blast stove for blast furnace air according to claim 2, gas preheating method is characterized in that: the described preheating first time is to be that 280～320 ℃ hot-blast stove fume is heated to 130～150 ℃ with combustion air, blast furnace gas by normal temperature with temperature.

4. high-air temp hot-blast stove for blast furnace air according to claim 3, gas preheating method is characterized in that: the described preheating first time is to adopt the separate heat pipe interchanger.

5. high-air temp hot-blast stove for blast furnace air according to claim 1, gas preheating method is characterized in that: the described preheating second time is successively combustion air, blast furnace gas to be carried out preheating.

6. high-air temp hot-blast stove for blast furnace air according to claim 5, gas preheating method, it is characterized in that: the described preheating second time is earlier combustion air to be heated to 400～450 ℃ by 900～1000 ℃ high-temperature flue gas, again with blast furnace (BF) gas heating to 300～350 ℃.

7. high-air temp hot-blast stove for blast furnace air according to claim 6, gas preheating method is characterized in that: the described preheating second time is to use single tube type hot tube heat exchanger.

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