A preheating method for the transformation of a hot blast stove preheating system

Abstract

The present invention relates to the technical field of ironmaking, and particularly to a preheating method for the transformation of a hot blast stove preheating system. Specifically, it includes the following steps: Step 1: Calculate the entire preheater transformation system, which includes three types of calculations: the calculation of the blast temperature of the blast furnace after transformation, the calculation of the heat exchange capacity of the preheater, and the calculation of the pressure loss of the hot blast stove system. Step 2: The specific dimensions of the preheater are determined based on the on-site investigation and the characteristics of the original preheater structure layout; based on the on-site investigation and the characteristics of the original preheater structure layout, the entire preheating system is selected as the research object to minimize the project volume and save time. Step 3: Design multiple schemes based on the above results, compare these schemes, and select the optimal final scheme. It can not only provide suggestions for the selection of heat exchanger replacement through a series of calculations before the start of the project, but also determine the minimum project volume according to the results of on-site research.

Description

Technical Field

[0001] The present invention relates to the technical field of ironmaking, and in particular to a preheating method for the transformation of a hot blast stove preheating system. Background Art

[0002] At the beginning of this century, heat pipe heat exchangers were widely used, and good results were achieved in increasing the hot blast temperature of blast furnaces and reducing the coke ratio in ironmaking. The core heat exchange element of the heat pipe heat exchanger is the gravity heat pipe. In the long-term application of hot blast stoves in blast furnaces, with the increasingly harsh working conditions of the used medium, problems such as ash accumulation and failure have generally occurred in heat pipe heat exchangers.

[0003] Facing this situation, there is an urgent need for such a transformation method. Through the implementation of this method, it can not only meet the transformation of the old heat exchange system by the manufacturer, but also minimize the impact on production to the lowest extent. Summary of the Invention

[0004] In order to overcome the deficiencies of the prior art, the present invention provides a preheating method for the transformation of a hot blast stove preheating system, which can not only provide suggestions for the selection of heat exchanger replacement through a series of calculations before the start of the project, but also determine the minimum project quantity according to the results of on-site investigations.

[0005] To achieve the above object, the present invention is implemented by adopting the following technical solutions:

[0006] A preheating method for the transformation of a hot blast stove preheating system specifically includes the following steps:

[0007] Step 1: Calculate the entire preheater transformation system, which includes 3 types of calculations: calculation of the hot blast temperature of the blast furnace after transformation, calculation of the heat exchange capacity of the preheater, and calculation of the pressure loss of the hot blast stove system.

[0008] 1) Calculate the hot blast temperature of the blast furnace after transformation

[0009] Substitute the preheated temperatures of the gas and combustion-supporting air and the known flue gas temperature into the calculation formula respectively, and calculate the hot blast temperature by first calculating the theoretical combustion temperature and then determining the combustion temperature. The specific method is as follows:

[0010] ① Calculate the flue gas volume V generated by burning 1 standard cubic meter of gas y.m

[0011] Vy.m = VCO2 + VH2O + VN2 + VO2 + VSO2;

[0012] Wherein: VCO2, VH2O, VN2, VO2, and VSO2 are the volume contents of each component in the wet gas, %.

[0013] ② Flue gas composition:

[0014] CO2 = VCO2 / Vy.m × 100%

[0015] H2O = VH2O / Vy.m × 100%

[0016] Total = 100%

[0017] ③ Calculate the lower heating value of the fuel

[0018] kcal / Nm 3 ;

[0019] CO, H2, CH4, C2H4, H2S are the volume contents of each component in the fuel, %;

[0020] ④ Calculate the theoretical combustion temperature

[0021] Heat content of flue gas kcal / Nm 3 ;

[0022] is the lower heating value of blast furnace gas, kcal / Nm 3 ;

[0023] t m is the temperature of the preheated gas, °C

[0024] c m is the average heat capacity of the gas at temperature t m kcal / Nm 3 .°C;

[0025] th is the temperature of the preheated combustion-supporting air, °C;

[0026] c k is the average heat capacity of the combustion-supporting air at temperature th, kcal / Nm 3 .°C;

[0027] Vy.m is the flue gas volume, Nm 3 / Nm 3 gas;

[0028] The theoretical combustion temperature t0 = t x × (iy0 / ix) = 1269.8°C;

[0029] Where: tx is the assumed theoretical combustion temperature before calculation, °C;

[0030] Ix is the actual heat content of the flue gas at the preheating temperature;

[0031] According to the hot air temperature t f2=(0.84 - 0.86)×{theoretical combustion temperature - (70 + 80) / 2}, then the preheated hot air temperature can be calculated;

[0032] 2) For the design of the specific dimensions of the preheater, requirements are put forward according to the on-site situation, and the equipment manufacturer completes the calculation by converting the design according to the requirements;

[0033] 3) Calculation of the pressure loss of the preheater

[0034] The pressure loss of the original system is Σh = Δhf + ΔhE;

[0035] In the formula: Σh is the total pressure loss of the hot blast stove system, Pa;

[0036] Δhf is the frictional resistance loss, Pa;

[0037] ΔhE is the local resistance loss, Pa;

[0038] The increased pressure loss after the transformation of the preheater:

[0039] The pressure loss of the original system + the increased pressure loss Σh + h' of replacing the preheater < h of the fan or h of the gas;

[0040] In the formula: h' is the increased pressure loss of replacing the preheater, Pa;

[0041] H is the increased pressure loss of replacing the preheater, Pa;

[0042] Hw is the effective draft of the existing chimney, Pa;

[0043] h of the fan is the outlet air pressure of the burner fan, Pa;

[0044] h of the gas is the gas pressure, unit: Pa.

[0045] Step 2: The specific dimensions of the preheater are determined according to the on-site investigation and the characteristics of the original preheater structure layout; based on the on-site investigation and the characteristics of the original preheater structure layout, the entire preheating system is selected as the research object to minimize the project volume and save time.

[0046] Step 3: Select the optimal solution as the final transformation solution in the solution comparison; based on the above results, design multiple solutions, compare these solutions, and select the optimal final solution.

[0047] Compared with the existing technology, the beneficial effects of the present invention are:

[0048] In view of the actual situation that the old preheating system needs to be reformed and optimized, the present invention provides a scientific, reasonable, simple and effective method for reforming and optimizing. Based on on-site investigation, the core equipment of the preheating system, i.e., the heat exchanger, is determined by calculating the resistance loss and preheating capacity. On this basis, by comparing the increased resistance loss after transformation with the original chimney and combustion air blower or with the pressure of the original chimney and gas, it provides a reference for finally selecting the structural form of the heat exchanger. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 is the process flow chart of the present invention;

[0050] Figure 2 is the schematic diagram of the first solution of the present invention;

[0051] Figure 3 is the schematic diagram of the second solution of the present invention;

[0052] Figure 4 is the schematic diagram of the third solution of the present invention;

[0053] Figure 5 is the schematic diagram of the fourth solution of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0054] The present invention discloses a preheating method for reforming a hot blast stove preheating system. Those skilled in the art can draw on the content of this article and appropriately modify the process parameters to achieve it. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art, and they are all regarded as included in the present invention. The method and application of the present invention have been described through preferred embodiments, and those related can obviously make changes or appropriate alterations and combinations to the methods and applications described herein without departing from the content, spirit and scope of the present invention to implement and apply the technology of the present invention.

[0055] The following further describes the specific embodiments of the present invention in conjunction with the drawings:

[0056] As Figures 1 to 5 shown, a preheating method for reforming a hot blast stove preheating system specifically includes the following steps:

[0057] Step 1: Calculate the entire preheater reforming system, which includes three types of calculations: calculating the blast furnace air temperature after reforming, calculating the heat exchange capacity of the preheater, and calculating the resistance loss of the hot blast stove system;

[0058] 1) Calculate the blast furnace air temperature after reforming

[0059] Substitute the temperatures of the preheated gas, combustion air and the known flue gas temperature into the calculation formula respectively, and calculate the hot blast temperature by first calculating the theoretical combustion temperature and then determining the combustion temperature. The specific method is as follows:

[0060] ① Calculate the flue gas volume V generated by burning 1 standard cubic meter of gas y.m

[0061] Vy.m = VCO2 + VH2O + VN2 + VO2 + VSO2;

[0062] Where: VCO2, VH2O, VN2, VO2, VSO2 are the volume contents of each component in wet gas, %;

[0063] ② Flue gas composition:

[0064] CO2 = VCO2 / Vy.m × 100%

[0065] H2O = VH2O / Vy.m × 100%

[0066] Total = 100%

[0067] ③ Calculate the lower calorific value of the fuel

[0068] kcal / Nm 3 ;

[0069] CO, H2, CH4, C2H4, H2S are the volume contents of each component in the fuel, %;

[0070] ④ Calculate the theoretical combustion temperature

[0071] Heat content of flue gas kcal / Nm 3 ;

[0072] is the lower calorific value of blast furnace gas, kcal / Nm 3 ;

[0073] t m is the temperature of the preheated gas, °C

[0074] c m is the average heat capacity of the gas at temperature t m kcal / Nm 3 .°C;

[0075] th is the temperature of the preheated combustion-supporting air, °C;

[0076] c k is the average heat capacity of the combustion-supporting air at temperature th, kcal / Nm 3 .°C;

[0077] Vy.m is the flue gas volume, Nm 3 / Nm 3 gas;

[0078] The theoretical combustion temperature t0 = t x ×(iy0 / ix) = 1269.8 °C;

[0079] Where: tx is the theoretical combustion temperature assumed before calculation, °C;

[0080] Ix is the actual heat content of the flue gas at the preheating temperature;

[0081] According to the hot air temperature t f2 =(0.84 - 0.86)×{theoretical combustion temperature - (70 + 80) / 2}, then the hot air temperature after preheating can be calculated.

[0082] 2) The design of the specific dimensions of the preheater is completed by putting forward requirements according to the on-site situation and the equipment manufacturer converting the design according to the requirements.

[0083] 3) Calculation of the pressure loss of the preheater

[0084] The pressure loss of the original system is Σh = Δhf + ΔhE;

[0085] Where: Σh is the total pressure loss of the hot blast stove system, Pa;

[0086] Δhf is the frictional resistance loss, Pa;

[0087] ΔhE is the local resistance loss, Pa;

[0088] The increased pressure loss after the transformation of the preheater:

[0089] The pressure loss of the original system + the increased pressure loss Σh + h' of replacing the preheater < h fan or h gas;

[0090] Where: h' is the increased pressure loss of replacing the preheater, Pa;

[0091] H is the increased pressure loss of replacing the preheater, Pa;

[0092] Hw is the effective draft of the existing chimney, Pa;

[0093] h fan is the outlet air pressure of the burner fan, Pa;

[0094] h gas is the gas pressure, unit: Pa.

[0095] Step 2: The specific dimensions of the preheater are determined according to the on-site investigation and the characteristics of the original preheater structure layout.

[0096] Step 3: Compare the plans

[0097] Plan 1) Transform in the area of the original preheater, replace it with two horizontal plate preheaters, remove the upper frame and transform the lower frame;

[0098] Plan 2): Add a set of plate-type vertical preheaters for gas and air beside the original preheater area, and make new frames and pipelines.

[0099] Plan 3): Adopt split installation. Install a horizontal plate-type gas preheater in the original area, remove the upper frame, and newly build a horizontal air preheater and its auxiliary pipelines beside it.

[0100] Plan 4): Install vertical plate-type air and gas preheaters in the original area and transform the existing upper frame.

[0101] Compare the four plans: Plan 1 uses two horizontal plate-type preheaters to replace the existing heat pipe preheaters. Since they are horizontal preheaters, the pipelines and frames need to be rearranged. Plan 2 uses two horizontal plate-type preheaters in a group to complete the preheating of air and gas. Although the amount of modification is small, it is difficult to guarantee the preheating effect of the preheaters, and the difficulty of separate maintenance of the preheaters increases. In Plan 3, the gas preheater is in the original position, but the air preheater needs to be newly built in a different location, which will inevitably result in a huge on-site construction workload and a relatively high overall project investment. Plan 4 uses two vertical plate-type preheaters as gas and air preheaters, with relatively simple overall construction and a small one-time investment.

[0102] On the basis of comparison, multiple design plans are selected. The ranking of various plans is Plan 4 > Plan 1 > Plan 2 > Plan 3. Judging from the comparison results, Plan 4 is a very good plan.

[0103] In view of the actual situation that the old preheating system needs to be reformed and optimized, the present invention provides a scientific, reasonable, concise and effective reforming and optimizing method. Based on on-site investigation, it determines the core equipment of the preheating system, i.e., the heat exchanger, by calculating the resistance loss and preheating capacity. On this basis, by comparing the increased resistance loss after transformation with the original chimney and combustion-supporting fan or with the pressure of the original chimney and gas, it provides a reference for finally selecting the structural form of the heat exchanger.

[0104] The present invention can not only provide suggestions for the selection of heat exchanger replacement through a series of calculations before the start of the project, but also determine the minimum amount of work according to the results of on-site investigation.

[0105] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and all should be covered within the protection scope of the present invention.

Claims

1. A preheating method for the transformation of a hot blast stove preheating system, characterized in that, Specifically, it includes the following steps: Step 1: Calculate the entire preheater renovation system, which includes three types of calculations: the calculation of the blast furnace air temperature after renovation, the heat transfer capacity calculation of the preheater, and the resistance loss calculation of the hot blast stove system; 1) Calculate the blast furnace air temperature after renovation Substitute the temperatures of the preheated gas, combustion-supporting air, and the known flue gas temperature into the calculation formula respectively, and calculate the hot blast temperature by first calculating the theoretical combustion temperature and then determining the combustion temperature. The specific method is as follows: ① Calculate the flue gas volume V generated by burning 1 standard cubic meter of gas y.m V y.m = VCO2 + VH2O + VN2 + VO2 + VSO2; Where: VCO2, VH2O, VN2, VO2, VSO2 are the volume contents of each component in the wet gas, %. ② Flue gas composition: CO2 = VCO2 / V y.m × 100% H2O = VH2O / V y.m × 100% Total = 100% ③ Calculate the lower heating value of the fuel CO, H2, CH4, C2H4, H2S are the volume contents of each component in the fuel, %. ④ Calculate the theoretical combustion temperature Heat content of flue gas Wherein: is the lower calorific value of blast furnace gas, kcal / Nm 3 ; t m is the temperature of the preheated gas, in °C c m is the average heat capacity of the gas at temperature t m in kcal / Nm 3 .℃; t k is the temperature of the combustion-supporting air after preheating, °C; c k is the average heat capacity of the combustion-supporting air at temperature th, kcal / Nm 3 .℃; V y.m is the flue gas volume, Nm 3 / Nm 3 coal gas; The theoretical combustion temperature t0 = t x ×(i y0 / ix) = 1269.8 °C; where: t x is the theoretical combustion temperature assumed before calculation, in °C; ix is the actual heat content of the flue gas at the preheating temperature; According to the hot air temperature t f2 =(0.84 - 0.86)×{theoretical combustion temperature - (70 + 80) / 2}, the preheated hot air temperature can be calculated; 2) The design of the specific dimensions of the preheater is completed by putting forward requirements according to the on-site situation and the equipment manufacturer converting the design according to the requirements; 3) Calculate the resistance loss of the preheater The resistance loss of the original system is Σh = Δhf + ΔhE; In the formula: Σh is the total resistance loss of the hot blast stove system, Pa; Δhf is the frictional resistance loss, Pa; ΔhE is the local resistance loss, Pa; The increased resistance loss after the preheater renovation: The resistance loss of the original system + the increased resistance loss Σh + h' of replacing the preheater < h fan or h gas; In the formula: h' is the increased resistance loss of replacing the preheater, Pa; H is the increased resistance loss of replacing the preheater, Pa; h fan is the outlet air pressure of the burner fan, Pa; h gas is the gas pressure, unit: Pa; Step 2: Determine the specific dimensions of the preheater according to the on-site investigation and the characteristics of the original preheater structure layout; on the basis of the on-site investigation, select the entire preheating system as the research object according to the characteristics of the original preheater structure layout to minimize the project volume and save time; Step 3: Design multiple schemes based on the above results. Scheme 1) Renovate in the original preheater area, replace it with two horizontal plate preheaters, remove the upper frame, and renovate the lower frame; Scheme 2) Add a set of vertical plate preheaters for gas and air beside the original preheater area, and build new frames and pipelines; Scheme 3) Adopt split installation, install a horizontal plate preheater for gas in the original area, remove the upper frame, and build a new horizontal preheater for air and its accessory pipelines beside it; Scheme 4) Install vertical plate preheaters for air and gas in the original area, and renovate the existing upper frame; Compare these schemes and select the optimal final scheme. Select the optimal scheme as the final renovation scheme in the scheme comparison.

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