The hottest view on the energy saving direction of

From the analysis of blast furnace heat balance, this paper starts with the analysis of blast furnace heat balance, tracks the distribution of heat energy in the smelting process of blast furnace, finds out the energy-saving direction and realization way of blast furnace process, improves the utilization rate of blast furnace heat energy, and has important practical significance for the research and development of energy saving and consumption reduction of blast furnace in the future

blast furnace heat balance analysis

take a new 3200m3 blast furnace in a steel plant as an example (the heat balance calculation data of other blast furnaces may be different from this calculation due to different furnace capacity, raw fuel conditions and other reasons). The calculation conditions of the heat balance calculation of this furnace are as follows:

Table 1 blast furnace heat balance calculation conditions

based on the gas law, the reaction process in the furnace is not considered, and the starting point is the state of material entering the furnace, The output state is the end point, and the heat balance of the blast furnace is calculated. Heat revenue items include carbon combustion heat release in front of the tuyere, direct reduction heat release (C oxidizes to co), indirect reduction heat release (co oxidizes to CO2, H2 oxidizes to H2O), heat brought in by hot air, a small amount of slag forming heat and heat brought in by furnace charge (this item is ignored in this calculation); Heat expenditure items include oxide decomposition, desulfurization, solvent decomposition, slag enthalpy, molten iron enthalpy, furnace top gas enthalpy, cooling water removal and heat dissipation loss

the calculation results of the heat balance of the whole furnace are as follows:

Table 2 heat balance of the whole furnace

it can be seen from table 2 that among the heat income items of the blast furnace, the heat of carbon oxidation (Q1, Q2, Q3) accounts for 77.58% of the total heat income (q), mainly from the coke and pulverized coal into the furnace, which is the focus of energy conservation of the blast furnace. From the above heat income structure and data, the main energy-saving direction of blast furnace is to reduce fuel consumption, that is, to reduce coke ratio and fuel ratio

2. Implementation approach

2.1 Ways to reduce fuel consumption

2.1.1 An effective process to improve the level of fine feed into the furnace

feed screening and granulation process under the trough: for every 1% reduction in the powder of the feed, the utilization coefficient of the blast furnace can be increased by 0.4% to 1.0%, and the feed coke ratio can be reduced by 0.5%

sinter classification and feeding process: after sinter classification and feeding, the pulverization rate of sinter in ore bin decreases by 1 Therefore, it is also very simple to wear 8%, the fuel ratio is reduced by 4.3kg/tfe, and the silicon content of pig iron is reduced by 0.05%

coke Ding recovery process: according to the production experience of adopting high nickel 811 material for 50% batteries in the whole production year, the replacement ratio of coke Ding to coke is greater than 1.05. Under certain smelting conditions, it improves the permeability in the furnace, improves the utilization rate of gas, increases production and saves coke, and reduces the cost per ton of iron

2.1.2. The hot blast temperature of the blast furnace can increase the heat brought into the blast furnace, reduce the proportion of carbon combustion heat release (carbon oxidation heat) in the heat revenue item, and reduce the fuel consumption of the blast furnace. At the same time, it can speed up the temperature rise of pulverized coal, improve the combustion conditions and improve the combustion rate of pulverized coal

2.1.3. Adopt oxygen enriched coal injection technology. Generally speaking, in the oxygen enriched coal injection smelting operation, the oxygen enriched rate is increased by 1%, the increased coal injection amount is 12~13kg/t, and the increased coal injection amount is 17~23kg/t when injecting bituminous coal, which can effectively reduce the coke ratio

2.1.4. The blast furnace adopts coke production of dry quenching (which can reduce the water content of coke into the furnace), and its coke ratio can be reduced by 2%. Taking the blast furnace described in this paper as an example, about 18000 tons of coke can be saved in the whole year. Based on 1800 yuan per ton of coke, the economic benefit of saving coke in the whole year is 32.4 million yuan

2.1.5. At present, the technology of oxygen enriched pulverized coal injection is widely used in blast furnaces, but there are many problems. Therefore, it is difficult for blast furnaces to achieve the minimum coke ratio by injecting coal. Injecting gas (or coke oven gas) can reduce the proportion of carbon combustion heat release (carbon oxidation heat) in the heat income item, and increasing the work of injecting gas heat release can reduce the coke ratio and fuel ratio

2.2. Ways to reduce enthalpy loss of molten iron

2.2.1 The so-called hot metal tank "one tank to the end" means that the hot metal tank of the blast furnace and the hot metal tank of the converter are unified tank cars. This process has less temperature drop and low temperature fluctuation. When the production pace is fast, the temperature of the lining and bottom of the hot metal tank when it reaches the blast furnace is still high, which makes the temperature drop of hot metal flowing into the hot metal tank of the blast furnace relatively small, which is conducive to reducing hot metal loss

2.2.2. In recent years, a torpedo tank car with dense and high-strength heat insulation board behind the safety lining has been developed. The specific installation method is to install the heat insulation layer in the whole tank car as the first lining, then install the safety lining, and finally install the wear-resistant lining. The temperature of molten iron in the insulated torpedo tank car can be increased by 20 ℃ on average compared with that in the non insulated tank car

2.2.3. Ways to fully recover slag enthalpy

in recent years, various iron and steel enterprises have also strengthened the research on slag heat energy recovery. At present, the effective ways to achieve this are:

2.2.3.1 Recover the sensible heat of slag to produce steam, which is used for power generation or heating

2.2.3.2. The slag flushing water is used for heating. The hot water in the slag pool is heated after sedimentation, filtration and pressurization, and then returned to the slag pool for recycling. Shougang and Angang have adopted this method, which can save a lot of energy, manpower and material resources

2.2.3.3. Dry granulation treatment of blast furnace slag: at present, the research on this treatment method at home and abroad has entered the pilot stage, which is divided into ordinary type and fluidized bed type

through the thermal balance analysis of blast furnace, this paper finds out that the main energy-saving direction of blast furnace is to reduce fuel consumption. Since the implementation of the national standard of polyurethane waterproof coating revised in 2003, reduce the enthalpy loss of molten iron, fully recover the enthalpy of slag and gas, and reduce the heat loss of blast furnace. The realization ways and energy-saving effects of the above energy-saving directions are discussed, It is of great practical significance to carry out the research on energy saving and consumption reduction of blast furnace in the future