Efficient blast furnace hot blast stove burning method

Abstract

The invention relates to an efficient furnace burning method for a blast furnace hot blast stove. The method comprises the following steps that 1, the maximum gas flow Qmax accepted by furnace burning of the hot blast stove is determined according to design and on-site working conditions; determining the critical gas flow Qcriti when the hot blast stove is burnt; the method comprises the steps of (1) determining the combustion time a-b of using the maximum gas amount through calculation before each time of furnace combustion, (3) increasing the gas amount to the maximum gas flow Qmax which can be accepted by the hot-blast stove within the shortest time 0-a under the condition of ensuring stable combustion of the hot-blast stove, and (4) ending the time point b of the maximum gas flow, the gas flow is reduced to the critical gas flow Qcriti as soon as possible under the condition that stable combustion of the hot blast stove is guaranteed, 5, continuous combustion is conducted to a planned end time point d, and 6, automatic control is achieved through a computer. According to the scheme, the minimum smoke heat energy is generated, so that the hot-blast stove is always in the optimal heat efficiency interval.

Description

Technical Field

[0001] The invention relates to a furnace firing method, in particular to an efficient blast furnace hot blast furnace firing method, and belongs to the technical field of blast furnace ironmaking. Background Art

[0002] Hot blast furnace is a thermal equipment that provides hot air for blast furnace. The air temperature used in blast furnace is generally 1100-1300℃. Generally, the coal gas consumption of hot blast furnace is 55-75kgce / t, accounting for 15%-20% of the energy consumption of the whole blast furnace process. The fluctuation of consumption has a great impact on the cost of pig iron. How to improve the energy efficiency of hot blast furnace is of great significance to reduce the cost of pig iron.

[0003] There are two mainstream ways of burning furnaces: one is to manually set an initial gas flow value based on experience and burn from the beginning to the end, or adjust the exhaust gas temperature to the end of the burning process based on experience. This manual burning method depends entirely on the operator's level and sense of responsibility, and the control is relatively arbitrary, resulting in high gas consumption.

[0004] The second method is to set a gas flow value at the beginning. After the exhaust gas temperature reaches a certain management temperature, the burning begins to be reduced and the exhaust gas temperature at the end is calculated to ensure that it meets the requirements in the end. In order to balance the gas system, the hot blast furnace generally adopts a fixed time to change the furnace, and the air supply and furnace burning time are also fixed. This method is generally computer-controlled furnace burning, which is relatively accurate, but generally the exhaust gas temperature adjustment begins when the fixed exhaust gas temperature is reached. This method may cause the small amount of furnace burning in the early stage and insufficient heat storage capacity, resulting in large heat loss of flue gas in the later stage. Secondly, the flow rate in the later stage is too small, resulting in low heat exchange efficiency of the hot blast furnace and waste of flue gas heat energy. Therefore, there is an urgent need for a new solution to solve the above technical problems. Summary of the invention

[0005] The present invention aims at the problems existing in the prior art and provides an efficient blast furnace hot blast furnace firing method. Under the premise of meeting the heat storage capacity of the hot blast furnace, the technical scheme is expected to achieve the minimum flue gas thermal energy generated by the furnace, so that the hot blast furnace is always in the optimal thermal efficiency range.

[0006] The technical solution adopted by the present invention is as follows:

[0007] In accordance with the heat storage law of hot blast stoves, the burning is divided into two stages. In the first stage, at the beginning of the burning, the gas volume is increased to the maximum acceptable gas flow rate at the fastest speed and maintained for a period of time to ensure the heat storage of the hot blast stove; in the second stage, at the end of the burning, the gas volume is reduced to the critical gas flow rate at the fastest speed until the end of the burning. The calculation and control methods of the maximum flow maintenance time and the critical flow rate are also given.

[0008] In order to achieve the above object, the technical solution of the present invention is as follows: an efficient blast furnace hot blast stove burning method, the method comprising the following steps:

[0009] Step 1: Determine the maximum gas flow rate Q that this hot blast furnace can accept based on the design and on-site conditions. max ; Determine the critical gas flow rate Q when the hot blast furnace is burning criti ;

[0010] According to the definition of Reynolds number (Re = ρvL / μ, ρ, μ are fluid density and dynamic viscosity coefficient, v, L are characteristic velocity and characteristic length of flow field), we know that when the Reynolds number is less than a certain value, the flow state in the pipeline will change from turbulent state to laminar state, and the heat exchange efficiency of the hot blast furnace will decrease significantly. However, the critical flow value of the hot blast furnace is not a fixed value. Because the heat storage chamber of the hot blast furnace is composed of many multi-aperture lattice bricks placed layer by layer, the construction is different and the lattice bricks are displaced after heating, and it is difficult to ensure the perfect design aperture of the lattice bricks from top to bottom. At the same time, with the increase of heat storage, the temperature difference between the upper and lower parts of the lattice bricks in the heat storage chamber is also constantly changing, and the temperature of the flue gas from top to bottom, that is, the viscosity and density of the flue gas, is also changing.

[0011] 1.1 Benchmark critical gas flow

[0012] According to the Reynolds number calculation formula

[0013] Re=ρ*v*L / μ (1)

[0014] =4*Q 临烟 *ρ / (π*μ*D) (2)

[0015] Q 临 =Q 临烟 *k (3)

[0016] From formulas (2) and (3), we can get:

[0017] Q 临 =Re*π*μ*D / (4*ρ)*k (4)

[0018] Where:

[0019] Re——Reynolds number takes the value of 2320;

[0020] L, D - the diameter of the checker brick hole in the heat storage chamber (L is equal to D value in pipe flow), unit: m;

[0021] M——dynamic viscosity coefficient of flue gas, unit: m2 / s;

[0022] Ρ——Smoke density, unit: kg / m 3 ;

[0023] Q 临烟 ——Critical flow rate of flue gas, unit: m 3 / s

[0024] Q 临 ——Critical flow rate of gas, unit: m 3 / s;

[0025] K is the ratio coefficient of unit gas to flue gas produced by complete combustion of unit gas (which can be calculated based on the oxidation reaction of gas components), which is taken as 0.66 and has no unit.

[0026] For a single hot air furnace, the lowest exhaust gas temperature T1, the highest temperature T2 and the designed highest temperature T3 during normal production are:

[0027] When the flue gas temperature is selected as T3, the benchmark Q is calculated according to formula (4): 临 value.

[0028] 1.2 Actual critical flow

[0029] 1.2.1 Exhaust gas heat energy loss rate

[0030] q 临烟 =C*Q 临 *1 / k*(T2-T1) (5)

[0031] q 临入 =Q 临 *t 临 *q+q 临物 (6)

[0032] From formula (5) and formula (6), we can get:

[0033] η 临 =q 临烟 / q 临入 (7)

[0034] =C*Q 临 *1 / k*(T2-T1) / (Q 临 *t 临 *q+Q 临物 ) (8)

[0035] Where:

[0036] T——The time t taken for the exhaust gas temperature to rise from T1 to T2, in seconds;

[0037] C——average specific heat capacity of flue gas between T1 and T2, in kJ / m 3 ℃;

[0038] q——lower calorific value of gas, unit: kJ / m 3 ;

[0039] q 临物 ——Total physical heat of temporary gas at time t, in kJ;

[0040] q 临烟 ——Total heat generated by exhaust gas, in kJ;

[0041] q 临入 ——The total heat brought by the gas at the critical flow rate, in kJ;

[0042] η 临 ——exhaust gas heat energy loss rate, unit: none;

[0043] Q 临 ——Critical flow rate of gas, unit: m 3 / s.

[0044] 1.2.2 Selection of actual critical flow

[0045] Q 临1 =Q 临 -Q max *3% (9)

[0046] Q 临2 =Q 临1 -Q max *3% (10)

[0047] …

[0048] Q 临 n=Q 临n-1 -Q max *3% (11)

[0049] Where:

[0050] Q 临1 ——Possible critical gas flow rate1, unit: m 3 / s;

[0051] Q 临2 ——Possible critical gas flow rate2, unit: m 3 / s;

[0052] Q 临n-1 ——Iteration n-1 times possible critical gas flow n-1, unit m 3 / s;

[0053] Q 临n ——The possible critical gas flow rate n after iteration n times, in m 3 / s;

[0054] Q max ——Maximum gas flow, unit: m 3 / s;

[0055] 3% - the percentage of gas volume that needs to be removed in each iteration, unit is unknown (a value that is too large will result in a large error in the calculation of the critical flow rate, while a value that is too small will increase the amount of calculation and the time required to calculate the value).

[0056] Based on the benchmark Q 临 Based on formula (9), Q 临1 , Q 临1 Substituting into formula (8) we get η 临1 ; Similarly, according to formula (10), Q 临2 , Q 临2 Substituting into formula (8) we get η 临2 , similarly, according to formula (11), iterate to n times, that is, when η 临 There is a significant decrease, select the previous flow Q 临n-1 This is the critical flow rate of the furnace.

[0057] Step 2: Before each firing, determine the burning time ab using the maximum amount of gas by calculation.

[0058] As attached Figure 1 As shown, the furnace is divided into four stages:

[0059] 2.1 Calculate the total amount of gas required for burning the furnace

[0060] Take 4 hot blast furnaces and calculate the gas consumption of No. 1 hot blast furnace. The order of air supply is 1, 2, 2, 3, 3, 4, 4, 1. According to the heat balance, the utilization efficiency of each hot blast furnace is calculated as η1, η2, η3, η4. Since the hot blast furnace has a relatively large thermal hysteresis, the actual gas consumption of the 4 hot blast furnaces 1-4 during the recent stable burning is Q1, Q2, Q3, Q4 respectively; in the last air supply cycle, the cold air of No. 1 hot blast furnace takes away the heat q1, and the flow rate of the parallel air supply of No. 1 and No. 2 hot blast furnaces in the air supply cycle is Q1` and the time is t1. The flow rate of the parallel air supply of No. 1 and No. 4 in the air supply cycle is Q2` and the time is t2. The flow rate of the air supply of a single furnace in the air supply cycle is Q3` and the time is t3.

[0061] The total heat q1 taken away by the cold air from the No. 1 hot air furnace in the last air supply cycle can be expressed by formulas (12) and (13) respectively:

[0062] q1=q*Q0*η1 (12)

[0063] =q1`+q2`+q3` (13)

[0064] Where:

[0065] q1—The heat taken away by the cold air from the No. 1 hot air furnace in the last air supply cycle, kJ,

[0066] q——lower calorific value of gas, kJ / Nm3 ,

[0067] Q0——The total amount of gas required for this furnace burning, Nm 3 ,

[0068] η1——Thermal efficiency of No. 1 hot blast stove,

[0069] q1`——The heat removed by the cold air from the No. 1 hot blast stove during the parallel air supply of the No. 1 and No. 2 hot blast stoves, kJ,

[0070] q2`——The heat removed by the cold air from the No. 1 hot blast stove during the parallel air supply of the No. 1 and No. 4 hot blast stoves, kJ,

[0071] q3`——The heat taken away by the cold air from the No. 1 hot blast stove during the single air supply period, kJ,

[0072] Generally, not every hot blast furnace has a flow meter but only a total cold air flow meter. For 4 hot blast furnaces connected in parallel, this patent provides a method for calculating the ratio of the air volume passing through any two hot blast furnaces when supplying air by using the actual gas consumption of each hot blast furnace. According to the heat taken away by the cold air of the previous air supply and the thermal efficiency of the hot blast furnace, the total gas volume Q0 required for this furnace burning is calculated. The total heat taken away by the cold air of the No. 1 hot blast furnace in the previous air supply cycle can be expressed by formulas (15)(16)(17) respectively.

[0073] During the period of parallel air supply of hot air stove No. 1 and hot air stove No. 2, the total heat removed by the cold air can be expressed by formula (14):

[0074] C1*Q1`*t1*ΔT1=q1`+q1`*(1+Q2 / Q1) (14)

[0075]

[0076] During the period of parallel air supply of hot air stove No. 1 and hot air stove No. 4, the total heat removed by the cold air can be expressed by formula (15):

[0077] C2*Q2`*t2*ΔT2=q2`+q2` / (1+Q4 / Q1) (15)

[0078]

[0079] During the period when the No. 1 hot air furnace supplies air alone, the total heat removed by the cold air can be expressed by formula (17):

[0080] C3*Q3`*t3*ΔT3=q3` (17)

[0081]

[0082] Where:

[0083] C1, Q1, ΔT1, t1——Specific heat capacity, cold air flow rate, and hot and cold air temperature difference during the parallel air supply period of hot air stove No. 1 and hot air stove No. 2, kJ / Nm 3 ℃、Nm 3 / min,℃,min,

[0084] C2, Q2, ΔT2, t2——Specific heat capacity, cold air flow rate, hot and cold air temperature difference, time during the parallel air supply of No. 1 hot air stove and No. 4 hot air stove, kJ / Nm 3 ℃、Nm 3 / min,℃,min,

[0085] C3, Q3, ΔT3, t3——Specific heat capacity, cold air flow rate, and hot and cold air temperature difference during the single air supply period of No. 1 hot air furnace, kJ / Nm 3 ℃、Nm 3 / min,℃,min,

[0086] Q1, Q2, Q3, Q4——Actual gas consumption of No. 1-4 hot blast furnaces, Nm 3 ,

[0087] From equations (12)(13)(15)(16)(17), we can get:

[0088] Q0=(C1*Q1*t1*ΔT1 / (1+1 / Q2 / Q1)+C2*q2*t2*ΔT2 / (1+Q4 / Q1)+C3*Q3*t3*ΔT3) / (q*η1)(19)

[0089] If there is no single furnace air supply process, t3 is zero; if there is only a single furnace air supply process, t1 and t2 are both zero.

[0090] 2.2 Calculate the maximum flow duration, i.e. time point b,

[0091] As attached Figure 1 As shown, the furnace is divided into four stages. All four stages reach the highest theoretical combustion temperature. The required gas flow rate is expressed as follows:

[0092]

[0093] Where:

[0094] k——The gas increasing rate during 0-a is a constant

[0095] m——Reduce the gas rate to a constant during bc period

[0096] 0——The time when the furnace starts burning

[0097] a——The time point when the maximum gas flow is reached

[0098] b——The end time of the maximum gas flow

[0099] c——The time point when the gas is reduced to the critical flow rate

[0100] d——Planned end time

[0101] Q max ——Maximum flow rate of furnace, Nm 3 / h

[0102] q criti ——Critical flow rate of furnace burning, Nm 3 / h

[0103] Q0——The total amount of gas required for this furnace burning, Nm 3

[0104] Since the increase gas rate k constant and the decrease gas rate m constant are fixed and known under certain equipment conditions, and the planned furnace burning time d is known, the time point b can be calculated by substituting the relevant data into formulas (19) and (21).

[0105] Step 3: While ensuring the hot blast stove burns smoothly, increase the gas volume to the maximum gas flow rate Q that the hot blast stove can accept in the shortest time 0-a max ,

[0106] Step 4: At the end time point b of the maximum gas flow rate, the gas flow rate is reduced to the critical gas flow rate Q as quickly as possible while ensuring the stable combustion of the hot blast furnace. criti ,

[0107] Step 5: Continue burning until the planned end time d,

[0108] Step 6: Automatically control by computer, calculate the heat balance of the hot blast stove, dynamically obtain the hot blast stove thermal efficiency η, and correct the time point b.

[0109] Step 7: Appropriately adopt high dome temperature. According to actual statistics, under the condition of maintaining the same heat demand, the dome temperature increases by 10°C and the exhaust gas temperature decreases by 5.2°C. During the furnace burning process, when the dome temperature does not exceed the requirements, the furnace is burned with the lowest allowed flue gas oxygen content; when the dome temperature exceeds the requirements, the dome is used as the standard, and measures such as reducing the burning of high calorific value coal gas mixing are adopted. If the measures are insufficient, the flue gas oxygen content is appropriately increased to reduce the dome temperature.

[0110] Compared with the prior art, the present invention has the following advantages. The technical solution is mainly reflected in the low exhaust gas temperature and high heat exchange efficiency in the early stage, and a large amount of coal gas is used to burn the furnace to ensure sufficient heat storage. Since the exhaust gas temperature is low at this time, the heat energy loss of the flue gas is small; in the later stage, the critical flow rate is used to burn the furnace, and the lower coal gas flow also produces less flue gas, reducing the generation of high-temperature exhaust gas. At the same time, the flue gas flow state in the lattice bricks of the hot blast furnace heat storage chamber is always in a turbulent state, and the heat exchange efficiency of the lattice bricks is always in the best state, and the thermal energy utilization rate of the combustion flue gas is high. In short, the exhaust gas temperature is low in the early stage, the heat exchange efficiency is high, and more heat is stored, and the optimal heat exchange efficiency is maintained in the later stage to supplement heat. BRIEF DESCRIPTION OF THE DRAWINGS

[0111] Figure 1 Schematic diagram of furnace flow changes.

[0112] In the figure: Q - gas flow, t - furnace burning time, A - gas flow change curve of the original furnace burning method, B - gas flow change curve of the new furnace burning method, Q max－ Maximum gas flow, Q criti－ Critical gas flow, Q minii－ Minimum flow rate, 0 - the time point when the furnace starts burning, a - the time point when the maximum gas volume is reached, b - the duration point of the maximum gas volume, c - the time point when it is reduced to the critical flow rate, d - the planned end time point, q0 the initial gas flow value of the original furnace burning method, a` - the time point from the original furnace burning method to the initial gas flow rate, b` - the time point when the original furnace burning method starts exhaust gas temperature management, x - the intersection point of the flow of the original furnace burning method and the new furnace burning method. DETAILED DESCRIPTION

[0113] In order to deepen the understanding of the present invention, the present embodiment is described in detail below with reference to the accompanying drawings.

[0114] Example 1: See Figure 1 , an efficient blast furnace hot blast furnace firing method, the method comprising the following steps:

[0115] Step 1: Determine the maximum gas flow rate Q that this hot blast furnace can accept based on the design and on-site conditions. max ; Determine the critical gas flow rate Q when the hot blast furnace is burning criti ;

[0116] According to the definition of Reynolds number (Re = ρvL / μ, ρ, μ are fluid density and dynamic viscosity coefficient, v, L are characteristic velocity and characteristic length of flow field), we know that when the Reynolds number is less than a certain value, the flow state in the pipeline will change from turbulent state to laminar state, and the heat exchange efficiency of the hot blast furnace will decrease significantly. However, the critical flow value of the hot blast furnace is not a fixed value. Because the heat storage chamber of the hot blast furnace is composed of many multi-aperture lattice bricks placed layer by layer, the construction is different and the lattice bricks are displaced after heating, and it is difficult to ensure the perfect design aperture of the lattice bricks from top to bottom. At the same time, with the increase of heat storage, the temperature difference between the upper and lower parts of the lattice bricks in the heat storage chamber is also constantly changing, and the temperature of the flue gas from top to bottom, that is, the viscosity and density of the flue gas, is also changing.

[0117] 1.1 Benchmark critical gas flow

[0118] According to the Reynolds number calculation formula

[0119] Re=ρ*v*L / μ (1)

[0120] =4*Q 临烟 *ρ / (π*μ*D) (2)

[0121] Q 临 =Q 临烟 *k (3)

[0122] From formulas (2) and (3), we can get:

[0123] Q 临 =Re*π*μ*D / (4*ρ)*k (4)

[0124] Where:

[0125] Re——Reynolds number takes the value of 2320;

[0126] L, D - the diameter of the checker brick hole in the heat storage chamber (L is equal to D value in pipe flow), unit: m;

[0127] M——dynamic viscosity coefficient of flue gas, unit: m2 / s;

[0128] Ρ——Smoke density, unit: kg / m 3 ;

[0129] Q 临烟 ——Critical flow rate of flue gas, unit: m 3 / s

[0130] Q 临 ——Critical flow rate of gas, unit: m 3 / s;

[0131] K is the ratio coefficient of unit gas to flue gas produced by complete combustion of unit gas (which can be calculated based on the oxidation reaction of gas components), which is taken as 0.66 and has no unit.

[0132] For a single hot air furnace, the lowest exhaust gas temperature T1, the highest temperature T2 and the designed highest temperature T3 during normal production are:

[0133] When the flue gas temperature is selected as T3, the benchmark Q is calculated according to formula (4): 临 value.

[0134] 1.2 Actual critical flow

[0135] 1.2.1 Exhaust gas heat energy loss rate

[0136] q 临烟 =C*Q 临 *1 / k*(T2-T1) (5)

[0137] q 临入 =Q 临 *t 临 *q+q 临物 (6)

[0138] From formula (5) and formula (6), we can get:

[0139] η 临 =q 临烟 / q 临入 (7)

[0140] =C*Q 临 *1 / k*(T2-T1) / (Q 临 *t 临 *q+Q 临物 ) (8)

[0141] Where:

[0142] T——The time t taken for the exhaust gas temperature to rise from T1 to T2, in seconds;

[0143] C——average specific heat capacity of flue gas between T1 and T2, in kJ / m 3 ℃;

[0144] q——lower calorific value of gas, unit: kJ / m 3 ;

[0145] q 临物 ——Total physical heat of temporary gas at time t, in kJ;

[0146] q 临烟 ——Total heat generated by exhaust gas, in kJ;

[0147] q 临入——The total heat brought by the gas at the critical flow rate, in kJ;

[0148] η 临 ——exhaust gas heat energy loss rate, unit: none;

[0149] Q 临 ——Critical flow rate of gas, unit: m 3 / s.

[0150] 1.2.2 Selection of actual critical flow

[0151] Q 临1 =Q 临 -Q max *3% (9)

[0152] Q 临2 =Q 临1 -Q max *3% (10)

[0153] …

[0154] Q 临 n=Q 临n-1 -Q max *3% (11)

[0155] Where:

[0156] Q 临1 ——Possible critical gas flow rate1, unit: m 3 / s;

[0157] Q 临2 ——Possible critical gas flow rate2, unit: m 3 / s;

[0158] Q 临n-1 ——Iteration n-1 times possible critical gas flow n-1, unit m 3 / s;

[0159] Q 临n ——The possible critical gas flow rate n after iteration n times, in m 3 / s;

[0160] Q max ——Maximum gas flow, unit: m 3 / s;

[0161] 3% - the percentage of gas volume that needs to be removed in each iteration, unit is unknown (a value that is too large will result in a large error in the calculation of the critical flow rate, while a value that is too small will increase the amount of calculation and the time required to calculate the value).

[0162] Based on the benchmark Q 临 Based on formula (9), Q 临1 , Q临1 Substituting into formula (8) we get η 临1 ; Similarly, according to formula (10), Q 临2 , Q 临2 Substituting into formula (8) we get η 临2 , similarly, according to formula (11), iterate to n times, that is, when η 临 There is a significant decrease, select the previous flow Q 临n-1 This is the critical flow rate of the furnace.

[0163] Step 2: Before each firing, determine the burning time ab using the maximum amount of gas by calculation.

[0164] As attached Figure 1 As shown, the furnace is divided into four stages:

[0165] 2.1 Calculate the total amount of gas required for burning the furnace

[0166] Take 4 hot blast furnaces and calculate the gas consumption of No. 1 hot blast furnace. The order of air supply is 1, 2, 2, 3, 3, 4, 4, 1. According to the heat balance, the utilization efficiency of each hot blast furnace is calculated as η1, η2, η3, η4. Since the hot blast furnace has a relatively large thermal hysteresis, the actual gas consumption of the 4 hot blast furnaces 1-4 during the recent stable burning is Q1, Q2, Q3, Q4 respectively; in the last air supply cycle, the cold air of No. 1 hot blast furnace takes away the heat q1, and the flow rate of the parallel air supply of No. 1 and No. 2 hot blast furnaces in the air supply cycle is Q1` and the time is t1. The flow rate of the parallel air supply of No. 1 and No. 4 in the air supply cycle is Q2` and the time is t2. The flow rate of the air supply of a single furnace in the air supply cycle is Q3` and the time is t3.

[0167] The total heat q1 taken away by the cold air from the No. 1 hot air furnace in the last air supply cycle can be expressed by formulas (12) and (13) respectively:

[0168] q1=q*Q0*η1 (12)

[0169] =q1`+q2`+q3` (13)

[0170] Where:

[0171] q1—The heat taken away by the cold air from the No. 1 hot air furnace in the last air supply cycle, kJ,

[0172] q——lower calorific value of gas, kJ / Nm 3 ,

[0173] Q0——The total amount of gas required for this furnace burning, Nm 3 ,

[0174] η1——Thermal efficiency of No. 1 hot blast stove,

[0175] q1`——The heat removed by the cold air from the No. 1 hot blast stove during the parallel air supply of the No. 1 and No. 2 hot blast stoves, kJ,

[0176] q2`——The heat removed by the cold air from the No. 1 hot blast stove during the parallel air supply of the No. 1 and No. 4 hot blast stoves, kJ,

[0177] q3`——The heat taken away by the cold air from the No. 1 hot blast stove during the single air supply period, kJ,

[0178] Generally, not every hot blast furnace has a flow meter but only a total cold air flow meter. For 4 hot blast furnaces connected in parallel, this patent provides a method for calculating the ratio of the air volume passing through any two hot blast furnaces when supplying air by using the actual gas consumption of each hot blast furnace. According to the heat taken away by the cold air of the previous air supply and the thermal efficiency of the hot blast furnace, the total gas volume Q0 required for this furnace burning is calculated. The total heat taken away by the cold air of the No. 1 hot blast furnace in the previous air supply cycle can be expressed by formulas (15)(16)(17) respectively.

[0179] During the period of parallel air supply of hot air stove No. 1 and hot air stove No. 2, the total heat removed by the cold air can be expressed by formula (14):

[0180] C1*Q1`*t1*ΔT1=q1`+q1`*(1+Q2 / Q1) (14)

[0181]

[0182] During the period of parallel air supply of hot air stove No. 1 and hot air stove No. 4, the total heat removed by the cold air can be expressed by formula (15):

[0183] C2*Q2`*t2*ΔT2=q2`+q2` / (1+Q4 / Q1) (15)

[0184]

[0185] During the period when the No. 1 hot air furnace supplies air alone, the total heat removed by the cold air can be expressed by formula (17):

[0186] C3*Q3`*t3*ΔT3=q3` (17)

[0187]

[0188] Where:

[0189] C1, Q1, ΔT1, t1——Specific heat capacity, cold air flow rate, and hot and cold air temperature difference during the parallel air supply period of hot air stove No. 1 and hot air stove No. 2, kJ / Nm 3 ℃、Nm 3 / min,℃,min,

[0190] C2, Q2, ΔT2, t2——Specific heat capacity, cold air flow rate, hot and cold air temperature difference, time during the parallel air supply of No. 1 hot air stove and No. 4 hot air stove, kJ / Nm 3 ℃、Nm 3 / min,℃,min,

[0191] C3, Q3, ΔT3, t3——Specific heat capacity, cold air flow rate, and hot and cold air temperature difference during the single air supply period of No. 1 hot air furnace, kJ / Nm 3 ℃、Nm 3 / min,℃,min,

[0192] Q1, Q2, Q3, Q4——Actual gas consumption of No. 1-4 hot blast furnaces, Nm 3 ,

[0193] From equations (12)(13)(15)(16)(17), we can get:

[0194] Q0=(C1*Q1*t1*ΔT1 / (1+1 / Q2 / Q1)+C2*q2*t2*ΔT2 / (1+Q4 / Q1)+C3*Q3*t3*ΔT3) / (q*η1)(19)

[0195] If there is no single furnace air supply process, t3 is zero; if there is only a single furnace air supply process, t1 and t2 are both zero.

[0196] 2.2 Calculate the maximum flow duration, i.e. time point b,

[0197] As attached Figure 1 As shown, the furnace is divided into four stages. All four stages reach the highest theoretical combustion temperature. The required gas flow rate is expressed as follows:

[0198]

[0199] Where:

[0200] k——The gas increasing rate during 0-a is a constant

[0201] m——Reduce the gas rate to a constant during bc period

[0202] 0——The time when the furnace starts burning

[0203] a——The time point when the maximum gas flow is reached

[0204] b——The end time of the maximum gas flow

[0205] c——The time point when the gas is reduced to the critical flow rate

[0206] d——Planned end time

[0207] Qmax ——Maximum flow rate of furnace, Nm 3 / h

[0208] q criti ——Critical flow rate of furnace burning, Nm 3 / h

[0209] Q0——The total amount of gas required for this furnace burning, Nm 3

[0210] Since the increase gas rate k constant and the decrease gas rate m constant are fixed and known under certain equipment conditions, and the planned furnace burning time d is known, the time point b can be calculated by substituting the relevant data into formulas (19) and (21).

[0211] Step 3: While ensuring the hot blast stove burns smoothly, increase the gas volume to the maximum gas flow rate Q that the hot blast stove can accept in the shortest time 0-a max ,

[0212] Step 4: At the end time point b of the maximum gas flow rate, the gas flow rate is reduced to the critical gas flow rate Q as quickly as possible while ensuring the stable combustion of the hot blast furnace. criti ,

[0213] Step 5: Continue burning until the planned end time d,

[0214] Step 6: Automatically control by computer, calculate the heat balance of the hot blast stove, dynamically obtain the hot blast stove thermal efficiency η, and correct the time point b.

[0215] Step 7: Appropriately adopt high dome temperature. According to actual statistics, under the condition of maintaining the same heat demand, the dome temperature increases by 10°C and the exhaust gas temperature decreases by 5.2°C. During the furnace burning process, when the dome temperature does not exceed the requirements, the furnace is burned with the lowest allowed flue gas oxygen content; when the dome temperature exceeds the requirements, the dome is used as the standard, and measures such as reducing the burning of high calorific value coal gas mixing are adopted. If the measures are insufficient, the flue gas oxygen content is appropriately increased to reduce the dome temperature.

[0216] Example 2: An efficient blast furnace hot blast furnace firing method, referring to the attached drawings, actual hot blast furnace parameter modeling, ordinary firing conditions, using firing method A and firing method B respectively, with the same gas volume and time, using simulation calculation, the specific steps are as follows.

[0217] 1) Select 4070m 3 The matching hot air furnace is taken as the research object, and the parameters are shown in Table 1. A hole in the cylindrical porous heat storage body of the hot air furnace is taken as the research object, which is a hollow cylindrical column structure. The cylindrical column structure parameters are established according to the height, pore diameter and equivalent thickness of the heat storage body, see Table 2.

[0218] Table 1 Hot blast stove design parameters

[0219]

[0220]

[0221] Table 2 Parameters of heat storage body checker bricks

[0222]

[0223] 2) The outer surface of the cylinder is insulated, and the inner surface is gas-solid coupled heat exchange condition. The upper end of the cylinder is the flue gas inlet, and the lower end of the cylinder is the flue gas outlet. The flue gas inlet is under constant flow and constant temperature conditions, and the flue gas and the solid wall are coupled heat exchange, and the radiation heat exchange between the flue gas and the solid wall is considered.

[0224] 3) The temperature at the end of the normal air supply period is a known condition, and the initial temperature of the cylinder is set according to this known condition. Then, the furnace is burned according to the burning time and flow rate (Table 3) under different working conditions. Refer to the attached figure for the equivalent treatment of b'-d time and flow rate under working condition B, and the flue gas volume and flue gas temperature during production are calculated for non-steady-state heat transfer until the burning time is completed. This is the temperature field at the end of the burning period.

[0225] Table 3 Furnace burning time and flow rate under different working conditions

[0226]

[0227]

[0228] 4) Compare the changes in the initial temperature and the final temperature of the cylinder, and calculate the change in heat storage.

[0229] Method A has a total heat storage of 405,585 kJ, and method B has a total heat storage of 410,208 kJ. Method A has 1.1% less heat storage than method B, which means that method B is more economical in burning the furnace.

[0230] It can be seen from the calculation process that the greater the redundancy of the hot blast stove, the more obvious the effect, and vice versa.

[0231] Q - gas flow, t - furnace burning time, A - gas flow change curve of the original furnace burning method, B - gas flow change curve of the new furnace burning method, Q max－ Maximum gas flow, Q criti－ Critical gas flow, Q minii－Minimum flow rate, 0 - the time point when the furnace starts burning, a - the time point when the maximum gas volume is reached, b - the duration point of the maximum gas volume, c - the time point when it is reduced to the critical flow rate, d - the planned end time point, q0 the initial gas flow value of the original furnace burning method, a` - the time point from the original furnace burning method to the initial gas flow rate, b` - the time point when the original furnace burning method starts exhaust gas temperature management, x - the intersection point of the flow of the original furnace burning method and the new furnace burning method.

[0232] Meishan Iron and Steel Co., Ltd. No. 5 blast furnace uses four Nippon Steel external-fired hot blast furnaces, and the air supply modes are 1, 2, 2, 3, 3, 4, 4, 1. Take the use of No. 1 hot blast furnace as an example:

[0233] 1. Confirmation of critical gas flow rate

[0234] 1.1 Benchmark critical gas flow

[0235] The hot blast furnace of Meishan Steel's No. 5 blast furnace uses seven-hole high-efficiency checker bricks with a hole diameter of 40mm, an active area of ​​0.4, a heat storage chamber inner diameter of 8800mm, and a designed maximum temperature of 400°C. The hot blast furnace has a normal minimum temperature of 330°C and a maximum temperature of 370°C, and a designed maximum exhaust gas temperature of 400°C.

[0236] Calculated by formula (4) is 70500Nm 3 / h.

[0237] 1.2 Actual critical gas flow

[0238] Designed maximum gas flow rate 140000Nm 3 / h, according to formula (8), (9) (10), after actual measurement, the actual flow rate is 63000Nm 3 / h.

[0239] 2. Before each firing, calculate and determine the time point b when the maximum amount of gas is used for combustion.

[0240] 2.1 Maximum flow rate required for this furnace firing

[0241] According to the design and on-site conditions, the maximum gas flow rate that this hot blast furnace can accept is 140000Nm 3 / h; According to the heat balance calculation, the utilization efficiency of each hot blast furnace system of No. 1 hot blast furnace is 83%. When the furnace is burning stably recently, the actual gas consumption of the four hot blast furnaces No. 1-4 is 1240000Nm per day. 3 、1180000Nm 3 、115000Nm 3 、106000Nm 3 , wind temperature is stable at 1200℃, cold air is stable at 210℃, cold air flow is stable at 7100Nm 3 / min, the total air supply time is 120min, of which the parallel air supply time of No. 1 and No. 2 and No. 1 and No. 4 is 60min each, and the calorific value of gas is 3500kJ / m 3 According to the data, the average constant pressure specific heat capacity of air at 210-1200℃ is 1.37kJ / Nm 3 .

[0242] The total amount of gas required for this furnace burning is calculated by formula (19): 208000 Nm 3 .

[0243] 2.2 Maximum flow rate burning duration b

[0244] It is known that the furnace is burned for 103 minutes. From the beginning of the furnace burning for 3 minutes to the maximum flow rate, the gas speed increases by 2333Nm 3 / min, k is 778, and the maximum flow rate is reduced to the critical flow rate of 933Nm in 5 minutes. 3 / min, m is 187.

[0245] By using formulas (19) and (21), it can be calculated that the time point b is 84 minutes.

[0246] 3. Under the condition of ensuring the stable combustion of the hot blast stove, the gas volume is increased to the maximum gas flow rate of 140000Nm that the hot blast stove can accept in 3 minutes. 3 / h is 2333Nm 3 / min.

[0247] 4. The maximum gas flow rate is used to burn the furnace for 84 minutes, and the critical gas flow rate is reduced to 63000Nm in 5 minutes while ensuring the stable combustion of the hot blast furnace. 3 / h is 933Nm 3 / min.

[0248] 5. The critical flow rate lasts for 14 minutes, and the combustion lasts for 103 minutes to the end of the furnace.

[0249] 6. This method is automatically controlled by a computer, and the real-time dynamic solution of the hot blast furnace thermal balance is used to find out that the furnace thermal efficiency generally changes between 80-83, and the maximum furnace burning duration is corrected.

[0250] 7. According to the changes in the calorific value of coal gas, to ensure that the nitrogen oxides in the hot blast furnace exhaust meet the requirements and the dome safety conditions, more high calorific value coal gas is burned to achieve a dome temperature of 1380°C, to ensure that the exhaust gas temperature is 338°C under a wind temperature of 1200°C, and to reduce the heat energy loss of flue gas.

[0251] After 3 months of operation, good results were achieved. Before use, the heating and blowing consumed 0.522Nm3 of gas per cubic meter. 3After improving the furnace burning method, the average gas consumption per cubic meter of blast air was 0.503Nm3 in 3 months. 3 , gas consumption decreased by 3.8%, the effect is more obvious than theoretical calculation.

[0252] It should be noted that the above embodiments are not intended to limit the protection scope of the present invention, and equivalent changes or substitutions made on the basis of the above technical solutions all fall within the protection scope of the claims of the present invention.

Claims

1. An efficient blast furnace hot blast stove firing method, characterized in that: The method comprises the following steps: Step 1: Determine the maximum gas flow rate Q that this hot blast furnace can accept based on the design and on-site conditions. max ; Determine the critical gas flow rate Q when the hot blast furnace is burning criti ; Step 2: Before each burning, calculate and determine the burning time ab using the maximum amount of gas. Step 3: While ensuring the hot blast stove burns smoothly, increase the gas volume to the maximum gas flow rate Q that the hot blast stove can accept in the shortest time 0-a max , Step 4: At the end time point b of the maximum gas flow rate, the gas flow rate is reduced to the critical gas flow rate Q as quickly as possible while ensuring the stable combustion of the hot blast furnace. criti , Step 5: Continue burning until the planned end time d, Step 6: Automatically control by computer, calculate the heat balance of the hot blast stove, dynamically obtain the hot blast stove thermal efficiency η, and correct the time point b. Step 7: Appropriately adopt high dome temperature. According to actual statistics, under the condition of maintaining the same heat demand, the dome temperature increases by 10°C and the exhaust gas temperature decreases by 5.2°C. When the dome temperature does not exceed the requirements during the furnace burning process, the furnace is burned with the lowest allowed flue gas oxygen content; when the dome temperature exceeds the requirements, the dome is used as the standard, and measures such as reducing the burning of high calorific value coal gas mixing are taken. If these measures are insufficient, the flue gas oxygen content is appropriately increased to reduce the dome temperature.

2. The efficient blast furnace hot blast stove firing method according to claim 1, characterized in that: Step 1 is as follows: According to the definition of Reynolds number (Re = ρvL / μ, ρ, μ are fluid density and dynamic viscosity coefficient, v, L are characteristic velocity and characteristic length of the flow field), when the Reynolds number is less than a certain value, the flow state in the pipeline will change from turbulent state to laminar state. 1.1 Benchmark critical gas flow According to the Reynolds number calculation formula Re=ρ*v*L / μ (1) =4*Q 临烟 *p / (π*μ*D) (2) Q 临 =Q 临烟 *k (3) From formulas (2) and (3), we can get: Q 临 =Re*π*μ*D / (4*ρ)*k (4) Where: Re——Reynolds number takes the value of 2320; L, D - the diameter of the checker brick hole in the heat storage chamber (L is equal to D value in pipe flow), unit: m; M——dynamic viscosity coefficient of flue gas, unit: m2 / s; Ρ——Smoke density, unit: kg / m 3 ; Q 临烟 ——Critical flow rate of flue gas, unit: m 3 / s Q 临 ——Critical flow rate of gas, unit: m 3 / s; K——The ratio coefficient of unit gas to flue gas produced by complete combustion of unit gas; calculated based on the oxidation reaction of gas components), take 0.66, no unit; For a single hot blast furnace, the lowest exhaust gas temperature T1, the highest temperature T2 and the designed highest temperature T3 during normal production, when the exhaust gas temperature is selected as T3, the benchmark Q is calculated according to formula (4): 临 value, 1.2 Actual critical flow 1.2.1 Exhaust gas heat energy loss rate q 临烟 =C*Q 临 *1 / k*(T2-T1) (5) q 临入 =Q 临 *t 临 *q+q 临物 (6) From formula (5) and formula (6), we can get: the 临 =q 临烟 / q 临入 (7) =C*Q 临 *1 / k*(T2-T1) / (Q 临 *t 临 *q+Q 临物 ) (8) Where: T——The time t taken for the exhaust gas temperature to rise from T1 to T2, in seconds; C——average specific heat capacity of flue gas between T1 and T2, in kJ / m 3 ℃; q——lower calorific value of gas, unit: kJ / m 3 ; q 临物 ——Total physical heat of temporary gas at time t, in kJ; q 临烟 ——Total heat generated by exhaust gas, in kJ; q 临入 ——The total heat brought by the gas at the critical flow rate, in kJ; η 临 ——exhaust gas heat energy loss rate, unit: none; Q 临 ——Critical flow rate of gas, unit: m 3 / s, 1.2.2 Selection of actual critical flow Q 临1 =Q 临 -Q max *3% (9) Q 临2 =Q 临1 -Q max *3% (10) …… Q 临 n=Q 临n-1 -Q max *3% (11) Where: Q 临1 ——Possible critical gas flow rate1, unit: m 3 / s; Q 临2 ——Possible critical gas flow rate2, unit: m 3 / s; Q 临n-1 ——Iteration n-1 times possible critical gas flow n-1, unit m 3 / s; Q 临n ——The possible critical gas flow rate n after iteration n, in m 3 / s; Q max ——Maximum gas flow, unit: m 3 / s; 3% - the percentage of gas volume that needs to be removed in each iteration, unit is unknown (a value that is too large will result in a large error in the calculation of the critical flow rate, while a value that is too small will increase the amount of calculation and the time required to calculate the value). Based on the benchmark Q 临 Based on formula (9), Q 临1 , Q 临1 Substituting into formula (8) we get η 临1 ; Similarly, according to formula (10), Q 临2 , Q 临2 Substituting into formula (8) we get η 临2 , similarly, according to formula (11), iterate to n times, that is, when η 临 There is a significant decrease, select the previous flow Q 临n-1 This is the critical flow rate of the furnace.

3. The efficient blast furnace hot blast stove firing method according to claim 2, characterized in that: Step 2: The details are as follows: The firing process is divided into four stages: 2.1 Calculate the total amount of gas required for burning the furnace There are 4 hot blast furnaces. Calculate the gas consumption of No. 1 hot blast furnace. The order of air supply is 1, 2, 2, 3, 3, 4, 4, 1. Calculate the utilization efficiency of each hot blast furnace according to the heat balance η1, η2, η3, η4. Since the hot blast furnace has a relatively large thermal hysteresis, the actual gas consumption of the 4 hot blast furnaces 1-4 during the recent stable burning is Q1, Q2, Q3, Q4 respectively; In the last air supply cycle, the cold air of No. 1 hot blast furnace takes away the heat q1. During the air supply cycle, the flow rate of the parallel air supply of No. 1 and No. 2 hot blast furnaces is Q1` and the time is t1. During the air supply cycle, the flow rate of the parallel air supply of No. 1 and No. 4 is Q2` and the time is t2. The air supply flow rate of a single furnace in the air supply cycle is Q3` and the time is t3. The total heat q1 taken away by the cold air from the No. 1 hot air furnace in the last air supply cycle is expressed by formulas (12) and (13) respectively: q1=q*Q0*η1 (12) =q1`+q2`+q3` (13) Where: q1—The heat taken away by the cold air from the No. 1 hot air furnace in the last air supply cycle, kJ, q——lower calorific value of gas, kJ / Nm 3 , Q0——The total amount of gas required for this furnace burning, Nm 3 , η1——Thermal efficiency of No. 1 hot blast stove, q1`——The heat removed by the cold air from the No. 1 hot blast stove during the parallel air supply of the No. 1 and No. 2 hot blast stoves, kJ, q2`——The heat removed by the cold air from the No. 1 hot blast stove during the parallel air supply of the No. 1 and No. 4 hot blast stoves, kJ, q3`——The heat taken away by the cold air from the No. 1 hot blast stove during the single air supply period, kJ, During the period of parallel air supply of hot air stove No. 1 and hot air stove No. 2, the total heat removed by the cold air can be expressed by formula (14): During the period of parallel air supply of hot air stove No. 1 and hot air stove No. 4, the total heat removed by the cold air can be expressed by formula (15): During the period when the No. 1 hot air furnace supplies air alone, the total heat removed by the cold air can be expressed by formula (17): Where: C1, Q1, ΔT1, t1——Specific heat capacity, cold air flow rate, and hot and cold air temperature difference during the parallel air supply period of hot air stove No. 1 and hot air stove No. 2, kJ / Nm 3 ℃、Nm 3 / min,℃,min, C2, Q2, ΔT2, t2——Specific heat capacity, cold air flow rate, hot and cold air temperature difference, time during the parallel air supply of No. 1 hot air stove and No. 4 hot air stove, kJ / Nm 3 ℃、Nm 3 / min,℃,min, C3, Q3, ΔT3, t3——Specific heat capacity, cold air flow rate, and hot and cold air temperature difference during the single air supply period of No. 1 hot air furnace, kJ / Nm 3 ℃、Nm 3 / min,℃,min, Q1, Q2, Q3, Q4——Actual gas consumption of No. 1-4 hot blast furnaces, Nm 3 , From equations (12)(13)(15)(16)(17), we can get: Q0=(C1*Q1*t1*ΔT1 / (1+1 / Q2 / Q1)+C2*q2*t2*ΔT2 / (1+Q4 / Q1)+C3*Q3*t3*ΔT3) / (q*η1) (19) If there is no single furnace air supply process, t3 is zero; if there is only a single furnace air supply process, t1 and t2 are both zero. 2.2 Calculate the maximum flow duration, i.e. time point b, The furnace is divided into four stages. All four stages reach the highest theoretical combustion temperature. The required gas flow rate is expressed as follows: Where: k——The gas increasing rate during 0-a is a constant m——Reduce the gas rate to a constant during bc period 0——The time when the furnace starts burning a——The time point when the maximum gas flow is reached b——The end time of the maximum gas flow c——The time point when the gas is reduced to the critical flow rate d——Planned end time Q max ——Maximum flow rate of furnace, Nm 3 / h q criti ——Furnace critical flow rate, Nm 3 / h Q0——The total amount of gas required for this furnace burning, Nm 3 Since the increasing gas rate k constant and the decreasing gas rate m constant are fixed and known when the equipment conditions are constant, and the planned furnace burning time d is known, the time point b can be calculated by substituting the relevant data into formulas (19) and (21).

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