Method for determining a dephosphorization treatment

Abstract

Any one dephosphorization treatment is determined from a plurality of dephosphorization treatments.SOLUTION: Under the condition that the phosphorus concentration in the iron ore after the dephosphorization treatment is reduced to the target phosphorus concentration, a treated ore ratio showing the ratio of the amount of the iron ore to be subjected to the dephosphorization treatment to the total amount of the iron ore is calculated based on the dephosphorization ratio by the dephosphorization treatment. Based on the treated ore ratio, an energy saving amount, which is an energy amount that can be reduced in the iron mill by the dephosphorization treatment, is calculated. On the basis of the total treatment capacity requiring dephosphorization treatment and the treatment capacity of a treatment facility for performing dephosphorization treatment, the required number of treatment facilities which is the total number of treatment facilities for securing the total treatment capacity is calculated. An evaluation index is calculated by dividing the energy saving amount by the required number of bases. Based on the evaluation index calculated in each of the plurality of dephosphorization treatments, any one dephosphorization treatment is determined.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for determining one dephosphorization treatment from among a plurality of dephosphorization treatments for removing phosphorus contained in iron ore. [Background technology]

[0002] Phosphorus contained in iron ore is known to reduce the quality of steel products, and therefore it is necessary to remove phosphorus from iron ore. Methods for dephosphorizing iron ore include a method of reducing and vaporizing phosphorus compounds contained in iron ore (Patent Document 1), an acid leaching method using sulfuric acid (Patent Document 2), and a method of contacting iron ore with microorganisms (Patent Document 3).

[0003] In Patent Document 4, phosphorus bound to iron in iron ore is transferred to a slag phase (a phase of components other than iron, an impurity phase) formed by roasting (oxidizing roasting) a flux, thereby chemically separating the phosphorus and iron phases. In Patent Document 5, phosphorus-containing iron ore is reacted with a nitrogen-containing gas at a processing temperature (below the melting temperature) to remove phosphorus in the form of phosphorus nitride (PN). In Patent Document 6, gangue and phosphorus are removed from iron ore by adding a predetermined concentration of NaOH aqueous solution to the iron ore and heating it in a sealed container at 200°C to 300°C for 10 minutes or more. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-020010 [Patent Document 2] Special Publication No. 45-21174 [Patent Document 3] Japanese Patent Application Laid-Open No. 2000-119759 [Patent Document 4] Japanese Patent Publication No. 2023-126085 [Patent Document 5] International Publication No. 2019 / 131128 [Patent Document 6] Japanese Patent Publication No. 2024-030025 Summary of the Invention [Problem to be solved by the invention]

[0005] As described above, various types of dephosphorization processes have been proposed as processes for removing phosphorus from iron ore, but no criteria have been established for determining which dephosphorization process to adopt. Therefore, an object of the present invention is to provide a method for determining a dephosphorization process using unified criteria for determining the dephosphorization process. [Means for solving the problem]

[0006] The present invention provides a method for determining one dephosphorization process from among multiple dephosphorization processes for removing phosphorus from iron ore. First, a processing ore rate, which indicates the ratio of the amount of iron ore to be dephosphorized to the total amount of iron ore, is calculated based on the dephosphorization rate of the dephosphorization process under conditions that reduce the phosphorus concentration in the iron ore after the dephosphorization process to a target phosphorus concentration. Next, an energy saving amount, which is the amount of energy that can be reduced at a steelworks by the dephosphorization process, is calculated based on the processing ore rate. Next, a required number of bases, which is the total number of treatment facilities that ensure the total treatment capacity, is calculated based on the total treatment capacity required for the dephosphorization process and the individual treatment capacity of the treatment equipment that performs the dephosphorization process. Next, an evaluation index is calculated by dividing the energy saving amount by the required number of bases. One of the dephosphorization processes is determined based on the evaluation indexes calculated for each of the multiple dephosphorization processes.

[0007] The dephosphorization treatment with the highest evaluation index can be determined. When the energy saving amount is a negative value, the target phosphorus concentration can be increased and the energy saving amount can be recalculated. The correlation between the dephosphorization rate and the treated ore rate can be calculated from the dephosphorization rate using the correlation.

[0008] The energy savings include the following: The amount of energy that can be reduced in the blast furnace process by removing gangue during dephosphorization. The amount of energy that can be reduced in the steelmaking process by removing phosphorus through dephosphorization treatment. The amount of energy that can be reduced by reusing the phosphorus obtained through dephosphorization. The amount of energy consumed to perform dephosphorization treatment. The amount of energy consumed to replenish the iron removed during dephosphorization.

[0009] The amount of energy saved can further include the amount of energy saved in the sintering process due to the removal of water of crystallization associated with the dephosphorization treatment. The total processing capacity can be calculated based on the total amount of iron ore and the processing ore rate. [Effects of the Invention]

[0010] According to the present invention, it is possible to select one dephosphorization treatment from among a plurality of dephosphorization treatments using an evaluation index that is a unified criterion for judgment. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a flowchart illustrating a method for determining a dephosphorization treatment. [Figure 2] FIG. 1 is a diagram showing the correlation between the dephosphorization rate DP and the treated ore rate DPR to achieve a target phosphorus concentration. DETAILED DESCRIPTION OF THE INVENTION

[0012] In an embodiment of the present invention, one dephosphorization treatment is selected from among a plurality of dephosphorization treatments based on an evaluation index KPI, which is a unified criterion for judgment. Specifically, an evaluation index KPI is calculated for each of the plurality of dephosphorization treatments, and one dephosphorization treatment is selected by comparing the calculated evaluation index KPIs.

[0013] The multiple dephosphorization processes include multiple dephosphorization processes of different types. Dephosphorization processes are broadly classified into dry dephosphorization processes and wet dephosphorization processes. An example of a dry dephosphorization process is the reduction vaporization method. An example of a wet dephosphorization process is the acid leaching method, the alkali roasting method, and the alkali hydrothermal method. Both dry dephosphorization processes and wet dephosphorization processes have their advantages and disadvantages. In general, wet dephosphorization processes have a high dephosphorization rate and can reduce energy consumption, but the amount that can be processed industrially is limited. On the other hand, dry dephosphorization processes can process a larger amount industrially than wet dephosphorization processes, but the dephosphorization rate is likely to be limited and energy consumption is likely to be high.

[0014] (Evaluation Index KPI) The evaluation index KPI is an index calculated based on the amount of energy saved ES and the required base number N, which will be described later, and is expressed by the following formula (1).

[0015]

number

[0016] The energy savings ES is the amount of energy that can be reduced at a steelworks through dephosphorization, in other words, the overall amount of energy that can be reduced taking into account all processes affected by the dephosphorization process. The required base number N is the minimum number of processing equipment (equipment that performs dephosphorization) required to perform dephosphorization on a desired amount of iron ore. As can be seen from the above formula (1), the evaluation index KPI is the amount of energy saved per processing equipment. The greater the energy savings ES, the greater the reduction in CO2 emissions and operating costs.

[0017] In general evaluations of specific processing processes, the return on investment (i.e., the value obtained by dividing the profit amount by the capital investment amount) may be taken into consideration, but in this embodiment, an evaluation index KPI that focuses on the amount of energy saved ES is taken into consideration, and there is no need to take into consideration various economic factors for understanding the return on investment as in the general evaluations described above.

[0018] (Calculation method of evaluation index KPI) Next, the calculation method of the evaluation index KPI will be explained using the flowchart shown in Figure 1. The evaluation index KPI is calculated for each of multiple types of dephosphorization treatments. Here, the multiple types of dephosphorization treatments may include all possible dephosphorization treatments, or may be limited to feasible dephosphorization treatments.

[0019] In step S101, the dephosphorization rate DP represented by the following formula (2) is determined.

[0020]

number

[0021] In the above formula (2), DP is the dephosphorization rate [%], Pa is the phosphorus concentration [mass%] in the iron ore after dephosphorization, Fa is the iron concentration [mass%] in the iron ore after dephosphorization, Pb is the phosphorus concentration [mass%] in the iron ore before dephosphorization, and Fb is the iron concentration [mass%] in the iron ore before dephosphorization. The phosphorus concentration can be measured in accordance with JIS M8216, and the iron concentration can be measured in accordance with JIS M8212.

[0022] The dephosphorization rate DP is determined for each dephosphorization treatment that is the subject of calculation of the evaluation index KPI. Here, the dephosphorization rate DP for each dephosphorization treatment can be determined experimentally, or values ​​published in literature can be used.

[0023] In step S102, a processed ore rate DPR [%] is determined based on the dephosphorization rate DP determined in the process of step S101. The processed ore rate DPR is the ratio (100 × Mp / Mt) of the amount of iron ore to be dephosphorized (Mp) to the total amount of iron ore (Mt). Specifically, the processed ore rate DPR is determined so that the phosphorus concentration in the entire iron ore after dephosphorization is reduced to the target phosphorus concentration. Here, one type of iron ore or multiple types of iron ore can be used.

[0024] The target phosphorus concentration can be set as appropriate. For example, depending on the iron ore producing region, it is predicted that the phosphorus concentration in iron ore will increase in the future, so the target phosphorus concentration can be set so as to reduce this increase in the phosphorus concentration.

[0025] When one type of iron ore is used, the phosphorus concentration of the iron ore after dephosphorization can be determined based on the phosphorus concentration of the iron ore before dephosphorization and the dephosphorization rate DP. Then, the amount of iron ore to be dephosphorized (i.e., the processed ore rate DPR) can be determined so that the phosphorus concentration after dephosphorization reaches the target phosphorus concentration. Here, the amount of iron ore to be dephosphorized may be the entire amount of iron ore (one type), or may be a portion of the iron ore (one type). When dephosphorizing a portion of iron ore (one type), the target phosphorus concentration can be determined by averaging the phosphorus concentration of the iron ore that has been dephosphorized and the phosphorus concentration of the iron ore that has not been dephosphorized.

[0026] When multiple types of iron ore are used, the phosphorus concentration of each iron ore after dephosphorization can be determined based on the dephosphorization rate DP of each iron ore.The amount of iron ore to be dephosphorized (i.e., the processed ore rate DPR) can then be determined so that the phosphorus concentration (average value) of the multiple types of iron ore after dephosphorization reaches the target phosphorus concentration.Here, the iron ore to be dephosphorized may be one type of iron ore out of the multiple types of iron ore, or may be two or more types of iron ore.

[0027] For example, a specific description will be given of a case where two types of iron ore A and B are used. Cases in which the phosphorus concentrations (average values) of iron ore A and B after dephosphorization treatment reach the target phosphorus concentration can be roughly divided into the following (1) to (5).

[0028] (1) A case in which the phosphorus concentration reaches the target phosphorus concentration by performing dephosphorization treatment on only iron ore A (partial or total amount). (2) A case in which the phosphorus concentration reaches the target phosphorus concentration by performing dephosphorization treatment on only iron ore B (partial or total amount). (3) A case in which the phosphorus concentration (average value) reaches the target phosphorus concentration by performing dephosphorization treatment on iron ore A (all) and iron ore B (part). (4) A case in which the phosphorus concentration (average value) reaches the target phosphorus concentration by performing dephosphorization treatment on iron ore A (part) and iron ore B (all). (5) A case in which the phosphorus concentration (average value) reaches the target phosphorus concentration by performing dephosphorization treatment on iron ore A (part) and iron ore B (part).

[0029] For the above (1) to (5), a case is identified that satisfies the condition that the phosphorus concentration becomes the target phosphorus concentration. Here, if only one case applies, the processing ore rate DPR for this case is determined. On the other hand, if multiple cases apply, the lowest processing ore rate DPR among the processing ore rates DPR for the multiple cases is determined.

[0030] Even when three or more types of iron ore are used, the processing ore rate DPR can be determined based on the same concept as in the case where two types of iron ore are used as described above.

[0031] On the other hand, the correlation between the dephosphorization rate DP and the processed ore rate DPR can be determined in advance under the condition that the phosphorus concentration of the iron ore after the dephosphorization treatment satisfies the target phosphorus concentration. Here, when using multiple types of iron ore, if the dephosphorization rates DP of the multiple types of iron ore are equal to each other, the above correlation can be determined in advance. By using this correlation, the processed ore rate DPR corresponding to the dephosphorization rate DP determined in the process of step S101 can be determined.

[0032] The above correlation can be expressed as a map showing the correlation between the dephosphorization rate (DP) and the treated ore rate (DPR), or the treated ore rate (DPR) can be expressed as a function of the dephosphorization rate (DP). When three or more types of iron ore are used, the treated ore rate (DPR) can be easily determined by using the above correlation.

[0033] In step S103, the amount of energy saved ES is calculated using the following formula (3).

[0034]

number

[0035] In the above formula (3), ES is the energy saved [kL / t-pig], ESB is the energy saved in the blast furnace process [kL / t-pig], ESC is the energy saved in the steelmaking process [kL / t-pig], ESS is the energy saved in the sintering process [kL / t-pig], ESU is the energy saved by recycling phosphorus [kL / t-pig], EDP is the energy consumption required for dephosphorization [kL / t-pig], and EIL is the energy consumption to compensate for the iron removed during dephosphorization [kL / t-pig]. Here, each energy amount is expressed as a heavy oil equivalent value [kL / t-pig], but it can also be expressed as other equivalent values.

[0036] (Energy savings in the blast furnace process ESB) The energy saving amount ESB is the amount of energy that can be reduced in the blast furnace process by removing gangue during the dephosphorization of iron ore. The more gangue contained in the iron ore, the more energy is consumed in the blast furnace process. Here, the energy increase ΔEf in the blast furnace process due to an increase in gangue is 9.4 × 10 -3 Since the amount of gangue removed is estimated as [kL / t-pig], the amount of energy saved (ESB) can be calculated based on the rate at which gangue is removed. If gangue is not removed, the amount of energy saved (ESB) will be 0 [kL / t-pig].

[0037] The energy increase ΔEf in the blast furnace process due to the increase in gangue is 9.4×10 -3 The reason for estimating it to be [kL / t-pig] will be explained below. The energy increase amount ΔEf is calculated from the energy increases ΔEf1, ΔEf2, ΔEf4 and the energy decrease amount ΔEf3, which will be described later.

[0038] (Energy increase ΔEf1) Due to an increase in impurities in iron ore, the amount of blast furnace slag per ton of molten pig iron increases by 32 kg. In this case, the RAR (total amount of coke and pulverized coal used) deteriorates by 12.8 kg per ton of molten pig iron. If the deterioration in RAR is compensated for by increasing the amount of coke used, the heat required for carbonization in the coke oven becomes 3.4 MJ per kg of coke. Therefore, the increase in energy required to produce coke per ton of molten pig iron due to an increase in RAR, ΔEf1, is 43.5 [MJ / t-pig] (= 3.4 [MJ / t-pig] × 12.8 [kg / t-pig]).

[0039] (Energy increase ΔEf2) Since the calorific value of coke is 29.18 MJ per kg of coke, the energy increase ΔEf2 in the blast furnace per ton of molten iron due to an increase in the reducing agent ratio is 373.5 [MJ / t-pig] (= 29.18 [MJ / kg] × 12.8 [kg / t-pig]).

[0040] (Energy reduction ΔEf3) Because exhaust gas from blast furnaces contains CO components, it is reused as an energy source within steelworks. As the reducing agent ratio increases, the amount of reusable energy increases, and this increase is deducted. Here, the carbon content of coke is 86.3%, and 50% of CO gas is generated from the carbon in the coke. The remaining carbon is emitted as CO2 gas. The heat value of combustion of CO gas is 10.1 MJ per kg of CO gas. Therefore, the energy reduction ΔEf3 resulting from the reuse of exhaust gas is 130.2 [MJ / t-pig] (= 10.1 [MJ / kg] × 12.8 [kg / t-pig] × 0.863 × 0.5 × 28 / 12).

[0041] (Energy increase ΔEf4) The sensible heat of the hot air required to burn coke down to CO gas is the energy increase. Since the specific heat of air is 1.006 kJ / kg·°C and its molar weight is 28.84 kg / kmоl, the energy increase ΔEf4 due to the sensible heat of the hot air is 76.3 [MJ / t-pig] (= 1.006 kJ / kg·°C × 1200°C × 12.8 [kg / t-pig] × 0.863 ÷ 12 ÷ 2 ÷ 0.21 × 28.84 kg / kmоl ÷ 1000).

[0042] Considering the above-mentioned energy increases ΔEf1, ΔEf2, ΔEf4 and energy decrease ΔEf3, the energy increase ΔEf per ton of hot metal due to the increase in impurities in iron ore is 363.1 [MJ / t-pig] (= ΔEf1 + ΔEf2 - ΔEf3 + ΔEf4). This is equivalent to 9.4 × 10 -3 [kL / t-pig](=363.1[MJ / t-pig]×2.58×10 -5 [kL / MJ]).

[0043] (Energy savings in steelmaking process ESC) The energy saving amount ESC is the amount of energy that can be reduced in the steelmaking process due to the decrease in phosphorus concentration caused by the dephosphorization treatment of iron ore. The higher the phosphorus concentration in iron ore, the more energy is consumed in the steelmaking process. Here, the energy increase ΔEsm in the steelmaking process due to the increase in phosphorus concentration is 5.4×10 -3 Since the phosphorus concentration is estimated as [kL / t-pig], the amount of energy saved ESC can be calculated based on the rate at which the phosphorus concentration is reduced.

[0044] Here, the energy increase ΔEsm is 5.4×10 -3 The reason for the estimation of [kL / t-pig] is explained below.

[0045] If the phosphorus concentration in hot metal is reduced from 0.172% to 0.135% by dephosphorization of iron ore, the suppression of the increase in phosphorus concentration in steelmaking slag is 21.2 kg-slag / t-pig (=(0.00172-0.00135) × 1000 kg-P / t-pig ÷ (0.04 ÷ 142 × 62) kg-P / kg-slag) assuming a P2O5 concentration of 4% in the steelmaking slag. Furthermore, the iron removal and steam aging costs per kg of steelmaking slag are 6.479 MJ / kg slag and 0.231 MJ / kg slag, respectively.

[0046] The sensible heat loss of steelmaking slag is 1.659 [MJ / kg slag] (= 0.24 (specific heat) [kcal / kg] × 1650 [℃] × 0.00419 [MJ / kcal]), and the limestone calcination energy used in the dephosphorization process is 1.544 [MJ / kg-slag] (= 3.86 [MJ / kg-CaO] × 0.4 [kg-CaO / kg-slag]).

[0047] Therefore, the energy saving amount ESC is 210.2 [MJ / t-pig] (= (6.479 + 0.231 + 1.659 + 1.544) [MJ / kg slag] x 21.2 [kg slag / t-pig]). And, when converted to heavy oil, it is 5.4 x 10 -3 [kL / t-pig](=210.2[MJ / t-pig]×2.58×10 -5 [kL / MJ]).

[0048] (Energy savings during the sintering process) The energy saving amount ESS is the amount of energy that can be reduced in the sintering process by removing the water of crystallization that accompanies the dephosphorization of iron ore. By removing the water of crystallization contained in the iron ore through the dephosphorization of iron ore, the amount of energy required to remove the water of crystallization can be reduced in the sintering process. On the other hand, since the iron ore is refined by removing the water of crystallization, the ignition intensity of the ignition furnace must be increased (i.e., energy consumption must be increased) to compensate for the loss in product strength due to the refinement. The energy saving amount ESS can be calculated taking these points into consideration. The energy saving amount ESS may or may not be taken into consideration when calculating the energy saving amount ES.

[0049] (Energy savings from phosphorus resource ESU) The energy savings ESU is the amount of energy required to recycle (reuse) dephosphorized phosphorus, and one example of recycling is to produce yellow phosphorus. When producing yellow phosphorus, the energy savings ESU can be calculated by taking into account the amount of energy consumed during production (energy consumption Ep1) and the amount of energy that can be reduced during production (energy reduction Ep2). Generally, the energy reduction Ep2 is greater than the energy consumption Ep1, so the amount of energy can be reduced by recycling phosphorus.

[0050] In the case of producing yellow phosphorus, the energy consumption Ep1 includes the energy consumption involved in the production of yellow phosphorus and the energy consumption required for the pretreatment for producing yellow phosphorus. The energy consumption in the pretreatment includes the energy consumption involved in the high-temperature reduction and the energy consumption involved in the conversion of slag into dense aggregate.

[0051] In the case of producing yellow phosphorus, the energy reduction amount Ep2 includes the amount of energy that can be reduced by recycling phosphorus in the production of yellow phosphorus and the amount of energy that can be reduced by recycling phosphorus in the pretreatment for producing yellow phosphorus.

[0052] The recycling (reuse) of phosphorus is not limited to the production of yellow phosphorus, but may be any method that can recycle (reuse) phosphorus. In other recycling methods, the energy savings ESU can be calculated by taking into account the amount of energy consumed in the recycling and the amount of energy that can be reduced in the recycling, as described above.

[0053] (Energy consumption required for dephosphorization treatment EDP) The energy consumption EDP is the amount of energy consumed to perform the dephosphorization treatment, and includes the amount of energy for reducing phosphorus, the amount of energy for heat generation, and the amount of energy for dehydration. Here, the amount of energy for reducing phosphorus and the amount of energy for heat generation can be calculated based on the amount of energy consumed when roasting Mn ore.

[0054] The energy consumption during the roasting process of Mn ore can be measured in advance. This energy consumption includes the reduction energy amount of MnO2 and the heat-up energy amount, and the ratio of the reduction energy amount to the heat-up energy amount can be specified.

[0055] If the correlation between the reduction energy of MnO2 and the reduction energy of phosphorus is determined in advance, the reduction energy of phosphorus can be calculated from the reduction energy of MnO2. Here, the reduction energy of phosphorus is 2.1 times the reduction energy of MnO2. Furthermore, if the correlation between the heat rise energy of Mn ore and the heat rise energy of the dephosphorization treatment is determined in advance, the heat rise energy of the dephosphorization treatment can be calculated from the heat rise energy of the Mn ore. Here, the heat rise energy of the dephosphorization treatment is 19.1 times the heat rise energy of the Mn ore.

[0056] As described above, if the reduction energy amount and heat rise energy amount in the dephosphorization treatment are calculated and the dehydration energy amount is measured in advance, the energy consumption EDP required for the dephosphorization treatment can be calculated.

[0057] (Energy increase to compensate for iron removal) The energy increase amount EIL is the amount of energy newly consumed to compensate for the iron removed by the dephosphorization process, and can be calculated based on the above-mentioned processed ore rate DPR and iron recovery rate Rr. Here, the higher the iron recovery rate Rr, the smaller the energy increase amount EIL. When the iron recovery rate Rr is 100%, the energy increase amount EIL is 0 [kL / t-pig]. In other words, the lower the iron recovery rate Rr, the greater the energy increase amount EIL.

[0058] In Fig. 1, in step S104, it is determined whether the amount of energy saving ES calculated in the processing of step S103 is a negative value. Here, when the amount of energy saving ES is a positive value, the amount of energy can be reduced, but when the amount of energy saving ES is a negative value, the amount of energy increases. Therefore, in the processing of step S104, it is confirmed that the amount of energy saving ES calculated in the processing of step S103 is not a negative value.

[0059] If the energy saving amount ES is a negative value, the process proceeds to step S105. On the other hand, if the energy saving amount ES is not a negative value, in other words, if the energy saving amount ES is 0 or a positive value, the process proceeds to step S106.

[0060] In step S105, the target phosphorus concentration set in the process of step S102 described above is increased. After the target phosphorus concentration is increased, the processing ore rate DPR is determined again in the process of step S102, and the energy saving amount ES is calculated again in the process of step S103. Here, the amount of increase in the target phosphorus concentration can be determined appropriately, but if the increase amount is too large, the effect of the dephosphorization process will be reduced. For this reason, it is preferable to gradually increase the increase amount and check whether the energy saving amount ES becomes a negative value.

[0061] In step S106, the necessary cardinal number N expressed by the following formula (4) is calculated.

[0062]

number

[0063] In the above formula (4), N is the required number of dephosphorization treatment facilities [units], Mo is the total amount of iron ore (iron ore with or without dephosphorization treatment) [t / d], DPR is the ore treatment rate [%], and PC is the dephosphorization treatment capacity of one treatment facility (hereinafter referred to as "single treatment capacity"). The value of "Mo x DPR" is the amount of iron ore that will be dephosphorized out of the total amount of iron ore Mo. The single treatment capacity PC varies depending on the type of dephosphorization treatment. For example, the single treatment capacity PC is higher in dry dephosphorization treatment than in wet dephosphorization treatment.

[0064] In step S107, the evaluation index KPI is calculated based on the energy saving amount ES calculated in the process of step S103 and the required base number N calculated in the process of step S106. The method for calculating the evaluation index KPI is as shown in the above formula (1).

[0065] In step S108, it is determined whether or not the evaluation index KPI has been calculated for all dephosphorization treatments (candidates) to be evaluated. If there are any remaining dephosphorization treatments for which the evaluation index KPI has not been calculated, the process returns to step S101, and the evaluation index KPI is calculated through steps S101 to S107. If the evaluation index KPI has been calculated for all dephosphorization treatments, the process proceeds to step S109.

[0066] In step S109, the dephosphorization treatment to be actually performed is determined based on the evaluation index KPI calculated for each of all the dephosphorization treatments to be evaluated. For example, the dephosphorization treatment with the largest evaluation index KPI can be determined.

[0067] In this embodiment, the evaluation index KPI is calculated for multiple dephosphorization treatments of different types, but this is not limited to this. Specifically, for the same type of dephosphorization treatment, the evaluation index KPI can be calculated for multiple dephosphorization treatments with different treatment conditions. In this case, the dephosphorization treatment under one of the treatment conditions can be determined based on the evaluation index KPI.

[0068] The process described in Fig. 1 can be realized by a program. Here, it is sufficient to input the information required to perform each process shown in Fig. 1. Alternatively, the processes from steps S101 to S108 shown in Fig. 1 may be executed by a program, and for the process in step S109, an operator may check the evaluation index KPIs of all dephosphorization processes to be evaluated and decide on a dephosphorization process.

[0069] A computer program prepared in advance to realize each process (function) shown in Fig. 1 is stored in an auxiliary storage device, and a control unit such as a CPU reads the program stored in the auxiliary storage device into a main storage device, and the control unit executes the program read into the main storage device, thereby operating each function. Each function can be operated by one control device, or by multiple control devices connected to each other.

[0070] The above program can also be provided to a computer in a state in which it is recorded on a computer-readable recording medium. Examples of recording media include optical disks such as CD-ROMs, phase-change optical disks such as DVD-ROMs, magneto-optical disks such as MOs (Magnet Optical) and MDs (Mini Disks), magnetic disks such as floppy disks and removable hard disks, and memory cards such as CompactFlash (registered trademark), SmartMedia, SD memory cards, and memory sticks. Also included as recording media are hardware devices such as integrated circuits (e.g., IC chips) specially designed and configured for the purposes of the present invention. [Example]

[0071] In this example, two types of iron ore, A and B, were considered as the iron ores to be dephosphorized, with the blending ratio of iron ore A being 8% by mass and the blending ratio of iron ore B being 13% by mass. The dephosphorization processes selected were a reduction vaporization method (dry dephosphorization), an alkali drying method (wet dephosphorization), and an alkali hydrothermal method (wet dephosphorization), and the evaluation index KPI was calculated for each dephosphorization process. The calculation of the evaluation index KPI for each dephosphorization process is described below.

[0072] (reduction vaporization method) The evaluation index KPI was calculated for the reduction vaporization method. The calculation method for the evaluation index KPI is explained in detail below.

[0073] (Dephosphorization rate DP) The dephosphorization rates DP of iron ores A and B were measured using a small rotary kiln under the conditions shown in Table 1 below, and both were found to be 42%.

[0074] [Table 1]

[0075] (Processed ore rate DPR) The target phosphorus concentration was set to 0.082 [mass%], and the correlation between the processing rate DPR and the dephosphorization rate DP that satisfied the target phosphorus concentration was calculated for iron ores A and B. It was possible to express this as a quadratic function shown in the following equation (5). The correlation between the processing rate DPR and the dephosphorization rate DP is also shown in Figure 2.

[0076]

number

[0077] The dephosphorization rate DP of iron ores A and B was 42%. The calculated DPR was calculated based on the formula (5) and found to be 15%. Since the blending rate of iron ore A was 8% by mass, it was decided to dephosphorize the entire amount of iron ore A. Even if the entire amount of iron ore A (8% by mass) were dephosphorized, the DPR would still be 7% short of the required DPR of 15%. Therefore, it was decided to dephosphorize a portion of iron ore B (7% by mass).

[0078] (Energy savings ES) To calculate the energy saving amount ES, the energy saving amounts ESB, ESC, ESS, ESU, the energy consumption amount EDP, and the energy increase amount EIL were calculated. When the energy saving amount ES was calculated based on the above formula (3), the energy saving amount ES was 6.5 × 10 -3 [kL / t-pig]. Below, we will explain the specific calculation results of the energy savings ESB, ESC, ESS, ESU, energy consumption EDP, and energy increase EIL.

[0079] (Energy saving amount ESB, ESC, ESS) In the reduction vaporization method, the gangue removal rate is 0% and the energy saving amount ESB is 0 kL / t-pig. As mentioned above, the energy saving amount ESC is 5.4 × 10 -3 [kL / t-pig], and the energy saving amount ESS is 0.2×10 -3 The energy savings (ESS) was calculated using the method described below.

[0080] (Energy saving ESS) As described above, the energy saving amount ESS includes the energy amount Ee1 required to remove the water of crystallization contained in the iron ore and the energy amount Ee2 required to increase the ignition strength of the ignition furnace. The energy amount Ee1 was calculated based on the conditions shown in Table 2 below and was found to be 1.3 × 10 -3 The energy amount Ee2 was calculated based on the conditions shown in Table 3 below, and was found to be 1.1 x 10-3 The amount of energy saved ESS is the amount of energy saved Ee1 minus the amount of energy saved Ee2, and as mentioned above, it is 0.2 × 10 -3 [kL / t-pig].

[0081] [Table 2]

[0082] [Table 3]

[0083] (Energy Savings Unit) As mentioned above, when calculating the energy savings ESU, it is necessary to consider the energy consumption Ep1 and energy reduction Ep2 for each of high-temperature reduction, slag densification, and phosphorus recycling. Energy consumption Ep1 is the total energy consumption for the three elements shown in Table 4 below, and was 1,538 [MJ / t-pig]. Energy reduction Ep2 is the total energy reduction for the three elements shown in Table 5 below, and was 1,731 [MJ / t-pig]. Energy savings ESU is the amount obtained by subtracting energy consumption Ep1 from energy reduction Ep2, and is 193 [MJ / t-pig] (= 4.8 x 10 -3 [kL / t-pig]).

[0084] [Table 4]

[0085] [Table 5]

[0086] (Energy consumption EDP) As mentioned above, the energy consumption EDP was calculated based on the energy consumption when roasting Mn ore, and was found to be 3.9 × 10 -3[kL / t-pig]. Table 6 below shows the conditions for calculating the energy consumption EDP.

[0087] [Table 6]

[0088] (Energy Increase EIL) The energy increase amount EIL was calculated based on the treated ore rate DPR and the iron recovery rate Rr. In this example, considering the conditions shown in Table 7 below, the energy increase amount EIL was 0.0 [kL / t-pig].

[0089] [Table 7]

[0090] (Required base N) In a case where pig iron production is limited to 2 million tons per year, and 15% of the total iron ore (DPR) is dephosphorized, the amount of iron ore to be dephosphorized will be 400,000 tons per year. If the operating rate of the processing equipment (here, a rotary kiln) that performs dephosphorization using the reduction vaporization method is 0.9, the total processing capacity will be 1,220 t / d (= 400,000 / 365 / 0.9). Since the processing capacity of one processing equipment (rotary kiln) is 305 t / d, in order to ensure the above total processing capacity, four processing equipment (rotary kilns) must be operated, and the required number N is four.

[0091] (Evaluation Index KPI) Using the above-mentioned energy saving amount ES and the required number of bases N, the evaluation index KPI was calculated based on the above formula (1), and the evaluation index KPI was 1.6 × 10 -3 It was.

[0092] (Alkaline drying method) Next, we calculated the evaluation index KPI for the alkali drying method. In the alkali drying method, iron ores A and B, from which ultra-fine particles (particle size less than 20 μm) have been removed in advance, are subjected to silica flotation, alkali drying, and washing. The calculation method for the evaluation index KPI is explained in detail below.

[0093] (Dephosphorization rate DP) The dephosphorization rates (DP) of iron ores A and B were measured using a small test device under the conditions shown in Table 8 below. Both were 40%. The alkaline drying method removed 80% of gangue by mass along with the removal of phosphorus. The iron recovery rate was 90%.

[0094] [Table 8]

[0095] (Processed ore rate DPR) The calculated ore treatment rate (DPR) was 16% based on the above formula (5). Here, we decided to perform dephosphorization treatment on the entire amount of iron ore A (blending rate: 8% by mass) and a portion (8% by mass) of iron ore B (blending rate: 13% by mass).

[0096] (Energy savings ES) To calculate the energy saving amount ES, the energy saving amounts ESB, ESC, ESS, ESU, the energy consumption amount EDP, and the energy increase amount EIL were calculated. Then, when the energy saving amount ES was calculated based on the above formula (3), it was found to be 10.5 × 10 -3 [kL / t-pig].

[0097] Energy saving ESB is 1.2 x 10 -3 (=9.4×10 -3 × 0.16 × 0.8) [kL / t-pig], and the energy saving amount ESC is 5.4 × 10 -3 [kL / t-pig], and the energy saving amount ESS is 0.2×10 -3 [kL / t-pig], and the energy saving ESU is 4.8×10 -3[kL / t-pig].

[0098] Energy consumption EDP is 0.8 x 10 -3 (=165×1.16×0.16×2.85×10 -5 ) [kL / t-pig]. Regarding the calculation formula in parentheses, "165" is the amount of energy [MJ / t-ore] when the heat amount at 100°C (processing temperature) is compensated for by exhaust heat recovery, etc., "1.16" is the amount of iron ore required per ton of hot metal [t-ore / t-pig] (see Table 7 above), "0.16" is the processing ore ratio DPR, and "2.85 x 10 -5 " is the unit conversion value [kL / MJ].

[0099] (Energy Increase EIL) The energy increase amount EIL was calculated using the formula shown in Table 7. Here, the iron recovery rate Rr is 90% and the processed ore rate DPR is 15%, so the energy increase amount EIL is 0.1 × 10 -3 (=5.84×10 -3 ×1.16×0.55×0.16×0.1).

[0100] (Required base N) When dephosphorization treatment is performed on 16% of the total iron ore (processing rate DPR), the total processing capacity is 1,298 t / d. Since the processing capacity of one processing facility (alkaline drying oven) is approximately 50 t / d, in order to ensure the above total processing capacity, 26 processing facilities (alkaline drying ovens) must be operated, and the required number N is 26.

[0101] (Evaluation Index KPI) Using the above-mentioned energy saving amount ES and the required number of bases N, the evaluation index KPI was calculated based on the above formula (1). The evaluation index KPI was 0.4 × 10 -3 It was.

[0102] (Alkaline hydrothermal method) Next, the evaluation index KPI was calculated for the alkaline hydrothermal process. In the alkaline hydrothermal process, iron ores A and B with particle sizes of 1 mm or less were charged into a sealed container through which a medium was circulated, and hydrothermal treatment was carried out at 250°C using NaOH (5M). The alkaline hydrothermal process can remove gangue (SiO2, Al2O3, etc.) in addition to phosphorus. The calculation method for the evaluation index KPI is explained in detail below.

[0103] (Dephosphorization rate DP) The dephosphorization rates (DP) of iron ores A and B were measured using a small test device, and both were found to be 80%. In the alkaline hydrothermal process, 80% of gangue was removed along with the phosphorus removal. The iron recovery rate was 90%.

[0104] (Processed ore rate DPR) The calculated ore treatment rate DPR based on the above formula (5) was 8%. Here, the entire amount of iron ore A (blending rate: 8% by mass) was subjected to dephosphorization treatment. However, iron ore B (blending rate: 13% by mass) was not subjected to dephosphorization treatment.

[0105] (Energy savings ES) To calculate the energy saving amount ES, the energy saving amounts ESB, ESC, ESS, ESU, the energy consumption amount EDP, and the energy increase amount EIL were calculated. Then, when the energy saving amount ES was calculated based on the above formula (3), it was found to be 10.2 × 10 -3 [kL / t-pig].

[0106] Energy saving amount ESB is 0.6 x 10 -3 (=9.4×10 -3 × 0.08 × 0.8) [kL / t-pig], and the energy saving amount ESC is 5.4 × 10 -3 [kL / t-pig], and the energy saving amount ESS is 0.2×10 -3 [kL / t-pig], and the energy saving ESU is 4.8×10 -3 [kL / t-pig].

[0107] Regarding the energy consumption EDP, compared to the alkaline drying method described above, the alkaline hydrothermal method is a batch operation using a sealed container, so it is expected to consume twice as much energy as the alkaline drying method. Also, considering that it has a high dephosphorization rate and only requires about half the processing volume of the alkaline drying method, it is assumed to consume the same amount of energy as the alkaline drying method (0.8 × 10 -3 [kL / t-pig]).

[0108] (Energy Increase EIL) The energy increase amount EIL was calculated using the formula shown in Table 7. Here, the iron recovery rate Rr is 90% and the processed ore rate DPR is 8%, so the energy increase amount EIL is 0.0 (= 5.84 × 10 -3 × 1.16 × 0.55 × 0.08 × 0.1) [kL / t-pig].

[0109] (Required base N) When dephosphorization treatment is performed on 8% of the total iron ore (processing rate DPR), the total processing capacity is 613 t / d. Since the processing capacity of one processing facility is approximately 30 t / d, in order to ensure the above total processing capacity, 20 processing facilities (alkali drying furnaces) must be operated, and the required number of units, N, is 20.

[0110] (Evaluation Index KPI) Using the above-mentioned energy saving amount ES and the required number of bases N, the evaluation index KPI was calculated based on the above formula (1). The evaluation index KPI was 0.5 × 10 -3 It was.

[0111] Table 9 below shows various parameters for each of the reduction vaporization method, the alkali drying method, and the alkali hydrothermal method.

[0112] [Table 9]

[0113] When comparing the evaluation index KPIs of the reduction vaporization method, the alkali drying method, and the alkali hydrothermal method, the reduction vaporization method had the largest evaluation index KPI, so the reduction vaporization method can be selected as the dephosphorization method. Note that if the treatment capacity of the treatment equipment increases through improvements to the treatment equipment, the required number of bases N will change, and the evaluation index KPI will also change. In this case, the dephosphorization method with the largest evaluation index KPI may be different from the reduction vaporization method.

Claims

1. A method for determining one dephosphorization treatment from among a plurality of dephosphorization treatments for removing phosphorus contained in iron ore, comprising: calculating a treatment ore rate indicating the ratio of the amount of iron ore to be dephosphorized to the total amount of iron ore based on the dephosphorization rate by the dephosphorization treatment under conditions that reduce the phosphorus concentration in the iron ore after the dephosphorization treatment to a target phosphorus concentration; Calculating an energy saving amount, which is the amount of energy that can be reduced in the steelworks by the dephosphorization treatment, based on the treatment ore rate; Calculating the required number of units, which is the total number of treatment facilities that will ensure the total treatment capacity, based on the total treatment capacity that requires the dephosphorization treatment and the individual treatment capacity of the treatment facilities that will perform the dephosphorization treatment; Calculating an evaluation index by dividing the amount of energy saved by the required base number; A method for determining a dephosphorization treatment, comprising determining one of the plurality of dephosphorization treatments based on the evaluation index calculated for each of the plurality of dephosphorization treatments.

2. 2. The method for determining a dephosphorization treatment according to claim 1, wherein the dephosphorization treatment with the maximum evaluation index is determined.

3. 2. The method for determining a dephosphorization treatment according to claim 1, wherein when the amount of energy saved is a negative value, the target phosphorus concentration is increased and the amount of energy saved is recalculated.

4. A correlation between the dephosphorization rate and the treated ore rate is determined in advance, 2. The method for determining a dephosphorization treatment according to claim 1, wherein the correlation is used to calculate the treated ore rate from the dephosphorization rate.

5. The amount of energy saved is The amount of energy that can be reduced in the blast furnace process by removing gangue associated with the dephosphorization treatment; the amount of energy that can be reduced in the steelmaking process by removing phosphorus through the dephosphorization treatment; and the amount of energy that can be reduced by reusing the phosphorus obtained by the dephosphorization treatment; and The amount of energy consumed to perform the dephosphorization treatment; and the amount of energy consumed to replenish the iron removed during the dephosphorization treatment; and The method for determining a dephosphorization treatment according to claim 1, further comprising:

6. 6. The method for determining a dephosphorization treatment according to claim 5, wherein the amount of energy saved further includes the amount of energy that can be reduced in the sintering step by removing water of crystallization associated with the dephosphorization treatment.

7. 2. The method for determining a dephosphorization treatment according to claim 1, wherein the total treatment capacity is calculated based on the total amount of iron ore and the treatment ore rate.

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