1、 Composition of blast furnace gas:

Blast furnace gas is a byproduct produced during the ironmaking process, mainly composed of CO, CO2, N2, H2, CH4, etc. The combustible component CO accounts for about 25%, while the content of H2 and CH4 is very low. The content of CO2 and N2 accounts for 15% and 55% respectively, with a calorific value of only 3500KJ/m ³ About 750-800 kcal. Increased difficulty in utilization. The CO2 and N2 in blast furnace gas neither participate in combustion to generate heat nor support combustion. On the contrary, they also absorb a large amount of heat generated during the combustion process, resulting in a low theoretical combustion temperature of blast furnace gas. The ignition point of blast furnace gas is not high, but in the actual combustion process, due to various factors, the temperature of the mixed gas must be much higher than the ignition point to ensure combustion stability. The theoretical combustion temperature of blast furnace gas is low, and the amount of blast furnace gas involved in combustion is large, resulting in a slow heating rate of the mixed gas, low temperature, and poor combustion stability.

Another condition for combustion reactions to occur is that effective collisions can occur between gas molecules, that is, collisions between molecules with sufficient energy that can undergo oxidation reactions with each other. The presence of a large amount of CO2 and N2 reduces the probability of effective collisions between molecules, resulting in slow combustion speed and unstable combustion at a macro level.

There is a large amount of CO2 and N2 in blast furnace gas that do not participate in chemical reactions during combustion and are almost equally transferred to the flue gas generated by combustion.

2、 Characteristics of blast furnace gas:

(1) Blast furnace gas has a high non combustible content and a low combustible content (about 30%), with a low calorific value, generally ranging from 3344 to 4180 kilojoules per standard meter (approximately 750 to 800 kcal).

(2) Blast furnace gas is a colorless, odorless, and odorless gas, with high CO content and high toxicity;

(3) Slow combustion speed, long flame, and small temperature difference between upper and lower parts:

(4) When heating with blast furnace gas, the gas contains a large amount of dust.

(5) The safety specification is set at 1 meter; The CO content in the air should not exceed 30mg;

(6) The ignition temperature is greater than 700 ° C.

(7) Blast furnace gas contains H2 (1.5-3.0%), Ch4 (0.2-0.5%), CO (25-30%), CO2 (9-12%), N2 (55-60%), and O2 (0.2-0.4%); Density is 1.29-1.30Kg/Nm ³。

3、 Precautions for using blast furnace gas:

1. Blast furnace gas needs preheating:

The heating capacity of blast furnace gas with the same volume is much lower than that of coke oven gas, generally 3300-4200KJ/m ³。 Blast furnace gas with low calorific value is not easy to burn. In order to improve the thermal effect of combustion, in addition to preheating the air, blast furnace gas must also be preheated.

2. The resistance of the combustion system is high:

When heating with a blast furnace gas burner, the heat consumption is high (usually about 15% higher than that of coke oven gas), resulting in more skin gas and high density, resulting in greater resistance.

3. The combustion flame of blast furnace coal is relatively long:

The emotional gas in blast furnace gas accounts for over 60%.

4. Blast furnace gas has high toxicity:

The CO content in blast furnace gas is generally 25% -30%. In order to prevent the CO content in the air from exceeding the standard, the blast furnace gas burner equipment should strictly meet the pressure testing standards during installation. If it is idle for a long time and then reused, a pressure test must be conducted again to confirm that the pipeline and equipment are tight before switching to blast furnace gas heating.

5. High dust content in blast furnace gas:

The maximum dust content of blast furnace gas used for blast furnace coal burners is required to not exceed 15mg/m ³。 In recent years, due to the improvement of high-pressure furnace top and washing process, the dust content of blast furnace gas can be reduced to 5mg/m ³ However, after long-term use of blast furnace gas, dust in the gas will also deposit in the coal channel, increasing resistance and affecting the normal adjustment of heating. Therefore, cleaning measures need to be taken.

The higher the temperature of blast furnace gas, the more moisture it contains, which will lower the calorific value of the gas. From the calculation, it can be seen that when the gas temperature increases from 20 ° C to 40 ° C, to maintain the same heating amount, the surface flow rate of the gas increases by about 12%.

4、 Characteristics and applications of blast furnace gas burners:

1. The burner adopts a stable flame disc structure, and the mixture of blast furnace gas and air is uniform and precise, achieving full combustion and significant solar terms.

2. The control of blast furnace gas burners is safer. Equipped with automatic ignition, liquefied gas or other high calorific value gas must be used as the ignition guide, and the shutdown function must be maintained for more convenient and safe maintenance.

3. During the design of blast furnace coal burner, safety protection measures such as flame arrester must be added, and explosion-proof pneumatic valves must be used for gas pipeline safety protection.

4. Innovative blast furnace gas regenerative burner is mainly used in: regenerative steel rolling heating furnace, regenerative forging heating furnace, regenerative ladle baking device, regenerative aluminum melting furnace, regenerative head heating furnace, as well as blast furnace gas dryer, blast furnace coal rotary kiln burner and other equipment.