Given the raw fuel conditions and smelting parameters, the consumption and proportion calculation of coke, ore and flux per unit pig iron in blast furnace ironmaking process are determined. Through calculation, we can also determine the amount of blast consumed, the amount and composition of slag produced, and the amount and composition of gas. The calculation results are an important basis for blast furnace design and production operation. According to the purpose, it can be divided into three types: normal charge calculation, furnace opening charge calculation and daily variable charge calculation. The data obtained from normal batching calculation and its application are: (1) unit raw pig iron fuel consumption, which provides a basis for the design and equipment selection of feeding equipment, material conveying system and adjacent workshops; (2) Air volume, which provides a basis for the selection of fans and the design of air supply system (including hot blast stove, air supply pipeline, valves, etc.). ); (3) The composition and quantity of pig iron and slag obtained by smelting provide a basis for the design of slag iron treatment system, and check whether the performance of the obtained slag meets the smelting requirements; (4) The generated gas quantity and components provide a basis for the design of gas dust removal system and the gas balance of the whole plant; (5) The consumption of ore, coke and flux. It provides a basis for their proportion in the batch when the blast furnace is put into production. The calculation of charge is used for charging before the blast furnace is turned on. Because the furnace lining is cold when the furnace is turned on, and there is no slag iron in the lower part of the furnace, the coke ratio of the charge is higher than that of the normal charge. >1000 m3 blast furnace is 2.0~3.5t coke /t pig iron; 500 ~ 1000m3 blast furnace is 2.5~4.0t coke /t pig iron; Blast furnace ≤350m3 is 3.0~6.0t coke /t pig iron. Generally, on the basis of normal batching, the coke ratio is improved by adding clean coke and empty coke; Clean coke is charged into the furnace, empty coke (with the melting amount required for coke slagging, but excluding iron-containing burden) is charged above the furnace waist, and a part of normal material is charged with empty coke at regular intervals, and the proportion of normal material is gradually increased until the upper part of the furnace body is completely charged with normal material (see blast furnace opening). Variable material calculation is the calculation of local change of one or more kinds of burden caused by the change of smelting parameters such as burden and iron species in the process of blast furnace production (see blast furnace operation).

There are two calculation methods of blast furnace burden: joint calculation and simple calculation.

The combination calculation method was founded by Professor A.H.PaMM of the former Soviet Union in the mid-1930s, and has been improved many times with the technical progress of blast furnace smelting in the following 30 years. In this method, the consumption of coke, ore, flux, etc. The unit pig iron smelting quantity is regarded as an unknown quantity, which is calculated by the equilibrium equation of combined iron and a small amount of manganese, the equilibrium equation of slagging oxide and the thermal balance equation. The general form of these equilibrium equations is: iron equilibrium equation according to iron output:

Or abbreviated as

According to slag basicity, slagging oxide equilibrium equation:

According to the equilibrium equation of one element content in pig iron:

According to the equilibrium equation of a certain oxide content in slag:

According to the heat balance equation of heat equivalence:

In the above equilibrium equation, e is the theoretical iron output of various charges, kg/kg (that is, the theoretical pig iron output of a charge1kg); It is a free alkaline oxide, and the excess or insufficient alkaline oxide in the charge is kg/kg under the required slag alkalinity; When the elements in raw iron reach the specified content, they are redundant or uncertain in various burden materials, k/kg; General, and so on; Refers to the excess or deficiency of oxides in various furnace charges when the required content of oxides in slag reaches the specified level, kg/kg; In general, etc. ; Is heat equivalent or heat equivalent, which means the "converted" heat consumption required for 1kg burden to undergo all physical and chemical changes in the blast furnace, kj/kg; For coke and injected fuel, their conversion heat consumption is less than the heat released during combustion, so this means their conversion heat in blast furnace.

Calculation of material characteristics The material characteristics () and heat equivalent () in the above equilibrium equations can be calculated according to the chemical composition of the material and the known or selected smelting parameters.

(1) theoretical iron output

In the formula, Fe, Mn, P and V are the contents of the corresponding elements in the material. If the content is small, it can be ignored in order to simplify the calculation. For example, Mn, P and V are the recovery rates of corresponding elements, which are generally the specified contents of corresponding elements in pig iron.

(2) Theoretical slag discharge, including SiO2, Al2O3, etc. Is the content of corresponding oxides and elements in the charge, kg/kg; μ n and μFe are the amounts of corresponding elements entering the slag, and the output μ n is about 0.2 and the threat μ Fe is 0.003 ~ 0.005. φ is the volatilization rate of sulfur 0.1~ 0.15; Coefficient; 0.5 means that when CaO forms CaS, the amount of oxygen entering the gas is equal to half the mass of sulfur.

(3) Free basic oxides. With the different expressions of slag basicity in charge calculation, the calculation methods are also different. According to the regulations: binary alkalinity; Ternary alkalinity,; Content of (CaO)+(MgO) in slag.

(4) Excess or deficiency of corresponding elements. .

(5) Excess or deficiency of corresponding oxides. . .

The calculation of heat equivalent comes from the general equation of the first heat balance in blast furnace smelting process:

Among them, qC is the effective heat released by carbon combustion in front of tuyere, and it is the effective heat released by CO oxidation into CO2 in the process of indirect reduction. QCi is the effective heat released from the oxidation of C to CO in the direct reduction process, and the effective heat released from the oxidation of H2 to H2O in the reduction of iron oxide is the calorific value of carbon dissolved in molten iron of 33410kj/kgc; C, Ci, Cd and C are the fixed carbon content of the charge, the carbon consumption of indirect reduction and direct reduction and the carbon consumption of pig iron carburization, respectively, kg/kg, H2i is the indirect reduction consumption of H2, m3/kg; Z is the heat loss, and the total heat loss is equivalent to the fraction of 1kg carbon, generally 0.10 ~ 0.15; Q0 is the effective heat consumption per unit of pig iron smelting, which is composed of oxide decomposition, desulfurization, carbonate decomposition, slag and hot metal enthalpy. , kj/kg substance; V- wind, V- coal, air consumed and gas produced by burning lkg carbon before tuyere, m3/kgc；; C, CCO, CCO2 CH2 and CH2O are the specific heat capacities of wind, CO, CO2, H2 and H2O, respectively, in KJ/m3; The test air and test gas are the temperatures of hot air and top gas respectively, which are℃. After calculating various ingredients, the consumption of coke, ore and flux can be obtained by solving simultaneous equations.

The joint calculation method is scientific and rigorous, but the calculation is complicated. In the early days, Professor Ram designed a special calculation table for this purpose. In recent years, with the development of computer technology, this method has been compiled into a joint computing software, which can quickly complete the calculation on the computer and solve the tedious pain.

Calculation of Slag Quantity and Slag Composition Slag is composed of various reduced residual and unreduced oxides and a small amount of sulfides in the furnace charge, and it also contains CaF2 in the smelting of special ores. You can also use μ=∑nμn for checking calculation. Where "is the unit consumption of various charges for producing 1t pig iron, kg/t; CaOn, MgOn, Al2O3, etc. It is the content of calcium oxide, magnesium oxide, alumina, etc. In each allegation; S material is the total sulfur content brought into the blast furnace by the burden, kg/t; ψ is the volatile matter of sulfur; [S] is the amount of sulfur entering pig iron; I0 is the conversion factor for converting "tons" into "kilograms", expressed as a percentage. It is the theoretical slag output of various burden materials. After calculating the amount and composition of slag, the method of testing the desulfurization ability of slag (see blast furnace desulfurization) is selected to test whether the obtained slag can meet the desulfurization requirements.

The calculation of pig iron composition is the distribution rate of elements selected according to smelting process parameters, such as [Fe], [-Mn], [P], [V] and so on. , then the sum of [Si], [S] and [C] initially selected should be 1000kg.

The calculation of air volume is to find out the amount of carbon C wind burned before the air outlet according to the carbon balance, and then calculate the air volume V wind needed for burning 1kg carbon before the air outlet. The product of the two is air volume V wind =C wind V wind per unit pig iron smelting, m3/t.

Where k is the focal length ratio; M is the coal injection quantity; C solid, Cm is the fixed carbon content in coke and pulverized coal; C dSi, Mn, P and S are the carbon consumed by the reduction and desulfurization of a few elements; CdFe is the carbon consumed by direct reduction of iron; CdCO2 _ 2 is the amount of carbon consumed by CO2 decomposed from limestone for dissolution reaction; 10[C] is the amount of carbon consumed by carburizing; W is the oxygen content in the wind, and when it is not oxygen-enriched, it is the blast humidity.

The amount and composition of top gas are calculated according to the amount and composition of gas formed by carbon combustion in front of tuyere plus the amount of CO, CO2 and H2O formed by chemical and decomposition reactions in the rising process. Calculate one by one according to each component:

Divide each component by Y coal to get the gas component. It should be clear that CH4 is not formed in the blast furnace, but injected into the blast furnace. Either burning to form carbon monoxide and H2, or cracking to carbon black and H2. There is CH4 in the top gas of some factories, which is purely the result of the test error of austenite analyzer. K in the above gas quantity calculation formula is coke ratio; M is the coal injection quantity; Organic hydrogen and organic nitrogen contained in coke (about 0.5% each) and CO2, hydrogen and nitrogen contained in volatile matter of coke and pulverized coal; Ф is limestone consumption; Ψ CO2 is the CO2 content in limestone; ψCO is the CO decomposed from limestone: the degree of participation in carbon dissolution reaction; Fe2O3 is the direct reduction degree of iron and the indirect reduction degree of iron oxide by H2.

Simple calculation method is a simplified calculation method by solving complex simultaneous equations according to modern blast furnace smelting conditions. The raw materials used in modern blast furnace production are relatively refined, with few varieties, and the iron-containing materials are self-fluxing sinter or acid pellet high alkalinity sinter, so the single composition of mixed ore can be calculated in advance according to the optimized burden structure; Generally speaking, no flux is added to the blast furnace burden, or a little flux is added to adjust the alkalinity in production; The amount of fuel to be injected is predetermined. In this case, the "reasonable" coke ratio is often selected according to the production experience of similar blast furnaces and similar burden, and the burden calculation can be simplified as calculating the consumption of iron-containing materials by iron balance equation, and then checking whether limestone needs to be added by slag alkalinity balance:

Because the iron content in coke and limestone is rarely negligible, the consumption of ore at this time.

Check whether limestone is added. After the consumption of ore and flux is determined, the slag quantity and slag composition, air quantity and gas quantity can be calculated according to the slag quantity, air quantity and gas quantity in the joint calculation method. When using the simple calculation method, the material balance table and heat balance table need to be compiled after the above calculation. Check whether the selected coke ratio is reasonable from the income and expenditure of thermal balance, especially whether the final heat loss of expenditure items is within a reasonable range. Too large or too small, you need to re-select the focal ratio and recalculate.

References:

Ferroalloy online, China.