阅读说明：本技术 一种高效实用型热风炉烧炉操控方法 (Efficient and practical hot blast stove burning control method ) 是由 刘凯 白雪 徐春柏 贾玥彤 鲁璐 王亚腾 柏忠帅 马光宇 刘常鹏 李卫东 孙守斌 于 2020-12-28 设计创作，主要内容包括：一种高效实用型热风炉烧炉操控方法,以热风炉热平衡测试、分析、计算为基础,以热风炉前一送风期的总风量、平均风温为初始条件,建立热风炉燃烧期与送风期热平衡数学模型,合理确定下一燃烧期煤气消耗量。在高炉正常工况条件下,采用固定周期换炉制度,在高炉异常工况条件下,采用非固定周期换炉制度。以送风总热量为基准,依据当前实时热风风量、平均风温,预测当前送风热风炉的送风时间和准备送风热风炉的烧炉时间。在热风炉不同加热期采取不同的烧炉策略进行烧炉,以适应高炉生产工况变化。在满足为高炉提供所需热风风量、风温及温差的前提下,动态优化热风炉操作,提高煤气利用效率,降低热风炉煤气消耗。(A high-efficiency practical hot blast stove burning control method is based on hot blast stove heat balance test, analysis and calculation, and based on the initial conditions of total air quantity and average air temperature of the hot blast stove in the previous air supply period, a mathematical model of heat balance between the combustion period and the air supply period of the hot blast stove is established, and the gas consumption in the next combustion period is reasonably determined. Under the normal working condition of the blast furnace, a fixed period furnace changing system is adopted, and under the abnormal working condition of the blast furnace, a non-fixed period furnace changing system is adopted. And predicting the air supply time of the current air supply hot blast stove and the stove burning time of the air supply hot blast stove to be prepared according to the current real-time hot air volume and the average air temperature by taking the total air supply heat as a reference. And different burning strategies are adopted to burn the hot blast stove in different heating periods so as to adapt to the change of the production working condition of the blast furnace. On the premise of providing the required hot air quantity, air temperature and temperature difference for the blast furnace, the operation of the hot blast furnace is dynamically optimized, the utilization efficiency of coal gas is improved, and the coal gas consumption of the hot blast furnace is reduced.)

1. A burning control method of a high-efficiency practical hot blast stove is characterized by comprising the following steps:

step 1, carrying out a thermal balance test on all hot blast stoves of each blast furnace under the condition of normal production working condition to form a thermal balance test analysis report, and taking the test and analysis data as the reference of thermal balance calculation of each hot blast stove; the heat balance test is carried out once a year, and the reference value of the hot blast stove heat balance calculation is updated year by year according to new test and analysis data and is stored in a database;

step 2, collecting the air quantity, air temperature and air supply time of each hot blast stove in an air supply period in real time, and taking the parameters of the coal gas heat value, the coal gas flow, the combustion-supporting air flow, the combustion period time, the vault temperature of the hot blast stove, the exhaust gas temperature, the combustion-supporting air and the coal gas preheating temperature of each hot blast stove in a combustion period as the basis of model calculation and dynamic correction; taking the total heat brought by hot air in the thermal balance test as a reference value, taking the deviation of the reference value as a basis for judging whether the working condition of the blast furnace is normal or not and for judging a furnace change system, and when the actual value is 8-12% of the total heat of the hot air in the thermal balance test, processing according to the normal working condition and executing a fixed period furnace change system; when the actual value is more than or equal to 8-12% of the total heat of the hot air in the thermal balance test, processing according to an abnormal working condition, and executing an unfixed period furnace changing system;

step 3, establishing a hot blast stove heat balance model and a gas consumption model

3.1 Hot-blast stove heat balance model

To simplify the calculation, one working cycle of the hot blast stove is used: comprises a combustion period, a furnace change period and an air supply period³Establishing a heat balance model of total heat income and total heat expenditure by taking hot air as a unit:

Q_R＝Q₁+Q₂+Q₃+Q₄……(1)

Q_Z＝Q¹+Q²+Q³+Q⁴+Q⁵+Q⁶+Q⁷+Q⁸+Q⁹……(2)

in the formula: q_R: total heat input (kj/m)³)；Q_Z: total heat expenditure (kj/m)³)；

Q₁: chemical heat of gas combustion (KJ/m)³)，Q₁＝B×Q_D……(3)；

B, sending hot blast stove per m³Amount of gas (m) consumed by hot blast³/m³)，Q_D: low calorific value of gas (KJ/m)³)；

B＝V_m×τ_r/(V_f×τ_f)……(4)

In the formula: v_mAverage gas flow (m) for burning hot blast stove³/h)，τ_rAnd τ_fRespectively the burning period and the air supply period of the hot blast stove (h), V_fActual hot air flow (m) sent out by the hot blast stove³/h)；

Q₂: carried in by gasPhysical Heat (KJ/m)³)；Q₂＝B×(c_mt_m－c_met_e)……(5)

In the formula: t is t_m、t_eThe average temperature (DEG C) of the gas and the environment, c_m、c_meRespectively is coal gas at t_mAnd t_eAverage specific heat (KJ/m) of³℃)；

Q₃: physical heat (KJ/m) brought in by combustion air³)；Q₃＝α×B×(c_kt_k－c_ket_e)……(6)

In the formula: α: average air-fuel ratio during combustion, t_k、t_keRespectively the average preheating temperature of combustion air and the average temperature (DEG C) of the environment; c. C_kAnd c_eRespectively, air is at t_kDEG C and t_eAverage specific heat at DEG C (KJ/m)³℃)；

Q₄: physical heat (KJ/m) brought in by cold air³)；Q₄＝c_f1t_f1－c_fet_e……(7)

In the formula: t is t_f1、t_eThe average temperature (deg.C) of the cold air and the environment, respectively; c. C_f1、c_eRespectively, air is at t_f1And t_eAverage specific heat (KJ/m) of³℃)；

Q¹: heat brought out by hot air (KJ/m)³)；Q¹＝c_f2t_f2－c_fet_e……(8)

In the formula: t is t_f2、t_eThe average temperatures (deg.C) of the hot air and the environment, respectively; c. C_f2、c_feRespectively, air is at t_f2And t_eAverage specific heat at temperature (KJ/m)³℃)；

Q²: heat brought by flue gas (KJ/m)³)；Q²＝BbV_y(c_y2t_y2－c_yet_e)……(9)

In the formula: t is t_y2、t_eThe average temperatures of the flue gas and the environment are respectively; c. C_y2、c_yeRespectively at t for flue gas_y2And t_eAverage specific heat at temperature (KJ/m)³℃)；

V_y: actual amount of flue gas (m)³/m³Coal gas), if no measured data exists, the measured data can be calculated according to the components of the flue gas; b: a smoke correction coefficient when the gas is not completely combusted (b is 1 when the gas is completely combusted);

Q³: heat lost by incomplete chemical combustion, i.e. heat loss (KJ/m) of unburned combustible gas in flue gas³) If the gas is completely combusted, Q is calculated according to the smoke components³＝0；

Q⁴: heat dissipation capacity (KJ/m) of furnace body surface³)

Q⁴＝∑[k×(t_i-t_e)×A_i]×τ/(V_f×τ_f)……(10)

In the formula: k: convective heat transfer coefficient (kj/m)²C) can be selected by looking up a table according to the geometric position of the surface, t DEG C_i、t_eRespectively the surface temperature of the furnace body at the ith position and the ambient temperature (DEG C); a. the_i: surface area of furnace body at i-th position (m)²) (ii) a τ: a test cycle time (h); τ ═ τ_r+τ_f；V_f: average air volume (m) during blowing period³/h)；

Q⁵: surface heat dissipation of cold air pipeline (KJ/m)³)

Q⁵＝∑[k×(t_i-t_e)×A_i]×τ/(V_f×τ_f)……(11)

Q⁶: hot air pipe surface heat dissipation (KJ/m)³)

Q⁶＝∑[k×(t_i-t_e)×A_i]×τ/(V_f×τ_f)……(12)

Q⁷: flue surface heat dissipation (KJ/m)³)

Q⁷＝∑[k×(t_i-t_e)×A_i]×τ/(V_f×τ_f)……(13)

Q⁸: hot blast stove pressure relief belt heat output (KJ/m)³)

Q⁸＝V_L(c_f2t_f2－c_fet_e)/∑V_fτ_f……(14)

In the formula: v_LIs the volume (m) of the hot blast stove³)；t_f2、t_eThe average temperature of the hot air and the environment respectively; c. C_f2And c_feRespectively, air is at t_f2And t_eAverage specific heat (KJ/m) of³℃)；

Q⁹: cooling water endotherm (KJ/m)³)

Q⁹＝G_S(C_Ct_c-C_jt_j)×τ/∑V_fτ_f……(15)

In the formula: g_SThe flow rate of the cooling water is kg/h; c_c、C_jSpecific heat (KJ/m) of outlet water and inlet water respectively³℃)；t_c、t_jThe temperature (DEG C) of the water outlet and the water inlet are respectively;

heat efficiency eta of hot-blast stove (Q)¹-Q₄)/(Q_R-Q₄)……(16)

3.2 model of gas consumption of hot-blast stove

The following formulas (1) and (16) can be obtained: q₁＝(Q¹-Q₄)/η-(Q₂+Q₃)……(17)

Substituting into formula (3): b ═ Q¹-Q₄)/η-(Q₂+Q₃)]/Q_D……(18)

Total gas flow in the combustion period of the hot blast stove: b is_z＝B×V_f×τ_f……(19)

Substituting formula B (18) into formula (19) to obtain

B_z＝[(Q¹-Q₄)/η-(Q₂+Q₃)]/Q_D×(V_f×τ_f)……(20)

From the equation (20), the main factors influencing the total gas consumption during the combustion period of the hot blast stove are: heat (Q) brought by hot air in blowing period¹-Q₄) Thermal efficiency eta of hot-blast stove, air and gas preheating temperature (Q)₂+Q₃) Low calorific value of gas Q_DAnd total air volume (V)_f×τ_f) (ii) a In real timeIn the operation process, the total gas amount given by the formula (20) is dynamically corrected according to the data collected in real time;

(1) when the preheating temperature of the combustion air and the coal gas deviates from the heat balance test value, the following correction is carried out according to the following formula:

ΔQ₂＝B×(c_m1t_m1－c_mt_m)……(21)

ΔQ₃＝α×B×(c_k1t_k1－c_kt_k)……(22)

in the formula: delta Q₂、ΔQ₃: respectively the correction quantity (KJ/m) of the physical heat brought by the gas and the combustion air³)；

t_m、t_m1: the preheating temperature (DEG C) of the gas during the heat balance test and the actual production respectively;

c_m、c_m1: are each t_m、t_m1Average specific heat (KJ/m) of gas at temperature³℃)；

t_k、t_k1: the preheating temperature (DEG C) of combustion air during the heat balance test and the actual production is respectively;

c_k、c_k1: are each t_k、t_k1Mean specific heat (KJ/m) of combustion air at temperature³℃)；

(2) When the air supply period of the hot blast stove is changed into the combustion period, and the heat brought by hot air in the air supply period deviates from a heat balance test value, the correction is carried out according to the following formula:

ΔQ¹＝c_fst_fs－c_f2t_f2……(23)

in the formula: delta Q¹: the difference (KJ/m) between the heat quantity brought out by the hot air in the previous air supply period and the heat balance³)；

t_f2、t_fs: the average temperature (DEG C) of hot air during the heat balance test and the previous air supply period is respectively;

c_f2、c_fs: are each t_f2、t_fsAverage specific heat at temperature (KJ/m)³℃)

(3) When the calorific value of the gas deviates from the heat balance test value, correcting according to the following formula:

ΔQ_D＝Q_D1-Q_D……(24)

in the formula: delta Q_D: the difference value (KJ/m) between the current gas calorific value and the heat balance³)；

Q_D、Q_D1: respectively the low calorific value (KJ/m) of the gas during the heat balance test and at the current moment³)；

The total gas consumption B in the combustion period of the hot blast stove is combined with the above influencing factors_z(m³) The dynamic correction can be performed as follows:

B_z＝[(Q¹+ΔQ¹-Q₄)/η-(Q₂+ΔQ₂+Q₃+ΔQ₃)]/(Q_D+ΔQ_D)×V_f×τ_f……(25)

step 4, determining the air supply period and the combustion period time of the hot blast stove

The air supply period time and the combustion period time of the hot blast stove depend on the number of seats of the hot blast stove configured by the blast furnace and an air supply system, single-stove air supply comprises one-burning one-sending, two-burning one-sending, three-burning one-sending, double-stove air supply and semi-parallel cross air supply, and the specific air supply system is given by the field process technology operation rules;

4.1 determination of blowing period time

1) When the blast furnace is in normal production working condition, the hot blast stove supplies air and changes the furnace according to fixed cycle time, and the air supply time is calculated according to an air supply system:

when a single furnace is supplied with air: tau is_f＝(τ_r+τ_h)/(N-1)……(26)

When the double furnaces supply air: tau is_f＝2(τ_r+τ_h)/(N-2)……(27)

Semi-parallel cross air supply: tau is_f＝τ_r+τ_h……(28)

In the formula: tau is_f、τ_r、τ_h: respectively representing air supply, furnace burning and furnace changing time (h), wherein N is the number of hot blast stove seats configured for the blast furnace (N is 3 or 4);

2) when the blast furnace is in an abnormal production working condition, air supply and furnace replacement are carried out according to an unfixed period time, the specific time depends on the average flow and the average air temperature of hot air in an air supply period, and the air supply time can be calculated according to the following formula:

the total heat balance of hot air sent out by the air supply period of the hot blast stove can be obtained:

V_f×τ_f×Q¹＝(V_f+ΔV_f)×(τ_f+Δτ_f)×Q¹after merging, the following can be obtained:

Δτ_f＝(V_f×τ_f)/(V_f+ΔV_f)-τ_f……(29)

τ_ff＝τ_f+Δτ_f……(30)

in the formula: tau is_ff: the air supply time (h) of the hot blast stove in a non-fixed period is set; Δ V_f: the average air quantity difference (m) of the blast furnace in the air supply period under the normal working condition and the abnormal working condition of the blast furnace³/h)；Δτ_f: the difference (h) of the air supply time of the hot blast stove in the air supply period under the normal working condition and the abnormal working condition of the blast furnace is as delta V_fWhen it is negative, Δ τ_fIs positive and represents the total supply time tau_ffLengthening, otherwise shortening;

when the working condition of the blast furnace is changed from the abnormal working condition to the normal working condition, the fixed period furnace changing system is adjusted in time;

4.2 determination of burn period time

The burning period time depends on the number of the seats of the hot blast stove and the air supply system, and is respectively calculated according to the number of the seats of the hot blast stove and the air supply system:

when a single furnace is supplied with air: tau is_r＝(N-1)×τ_f-τ_h……(31)

When the double furnaces supply air: tau is_r＝τ_f×(N-2)/2-τ_h……(32)

Semi-parallel cross air supply: tau is_r＝τ_f-τ_h……(33)

In the formula: tau is_r: burning period time (h)

Step 5, determining the sectional time and the gas flow in the combustion period of the hot blast stove

5.1 determination of the time of the combustion phases

According to the burning characteristics of the hot blast stove, the burning period of the hot blast stove is subdivided into three stages of a rapid heating period, a heat preservation and storage period and a smoke exhaust temperature control period, and the heating time of each heating period can be determined according to the following formula:

τ_k＝(0.18～0.30)×τ_r……(34)；τ_w＝(0.48～0.60)×τ_r……(35)；

τ_y＝(0.07～0.10)×τ_r……(36)；τ_hc … … (37); (C: constant, about 0.17 hour)

τ_r＝τ_k+τ_w+τ_y……(38)；

In the formula: tau is_k、τ_w、τ_y、τ_h: respectively including a rapid heating period, a heat preservation and storage period, a smoke exhaust temperature control period (including furnace closing) and a furnace changing period time (h), tau_r: is the burning period time (h);

5.2 determination of the total amount of gas in each heating period

B_k＝k_k B_z/τ_k……(39)；B_w＝k_w B_z/τ_w……(40)；B_y＝k_y B_z/τ_y……(41)；

In the formula: b is_k、B_w、B_y: the gas flow (m) in the fast heating period, the heat preservation and storage period and the exhaust gas temperature control period³/h)；B_z: total gas amount (m) in combustion period³)；

k_k、k_w、k_y: the gas flow coefficients of the rapid heating period, the heat preservation and storage period and the exhaust gas temperature control period are respectively set;

wherein: k is a radical of_k＝0.20～0.35……(42)；k_w＝0.65～0.75……(43)；k_y＝0.05～0.10……(44)；

No coal gas is consumed in the furnace changing period;

step 6, optimizing air-fuel ratio of each heating period of the hot blast stove

Calculating the optimal air-fuel ratio alpha according to the gas heat value acquired on line, wherein the empirical algorithm comprises the following steps: α ═ Q_D/4180……(45)；

During the rapid heating period: alpha is alpha_k＝(1.00～1.05)×α……(46)；

And (3) during the vault temperature holding period: alpha is alpha_w＞1.05×α……(47)；

In the exhaust gas temperature control period: alpha is alpha_y＝(1.00～1.05)×α……(48)；

In the formula: alpha is alpha_k、α_w、α_y: the air-fuel ratio of the fuel gas is respectively in a rapid heating period, a heat preservation and storage period and a smoke exhaust temperature control period.

2. The method as claimed in claim 1, further comprising an air-fuel ratio control method, wherein a gas calorific value feedforward control method is adopted, a gas calorific value analyzer is installed on a gas pipeline of the hot blast stove, a gas calorific value collected in real time is uploaded to a computer system, and calculation and control are performed according to formulas (45) to (48).

3. The method according to claim 1, further comprising a temperature rise rate and a burning time coupling control;

after the rapid heating period of the hot blast stove is finished, the hot blast stove enters a heat preservation and storage period, and the marks are as follows: the vault temperature reaches the target temperature specified by the technical operating regulations; there are two control targets at this time, firstly, keep vault temperature relatively stable, secondly, the flue gas temperature rise rate is unanimous with the expected time of burning the stove, and when the time of burning the stove reaches 90% of total time of burning the stove, the exhaust gas temperature reaches target exhaust gas temperature lower limit value, and the heat preservation heat accumulation period ends this moment, begins to enter exhaust gas temperature control period, the control target during this period: firstly, the smoke exhaust temperature is slowly increased; secondly, keeping the target temperature of the vault stable; thirdly, waiting for a furnace changing instruction; when the smoke exhaust temperature reaches the upper limit of the smoke exhaust temperature and a furnace change instruction is not received, executing the furnace stewing operation to wait for furnace change;

1) in the heat preservation and storage period, the temperature rise rate and the furnace burning time coupling control method comprises the following steps:

setting the starting time of the heat preservation and heat storage period to be tau_w(i) End time is tau_w(n), the corresponding exhaust gas temperature at the beginning of the heat-preserving and heat-storing period is t (i), the exhaust gas temperature at the end of the heat-preserving and heat-storing period is t (n), and therefore the exhaust gas temperature rise rate in the heat-preserving and heat-storing period is as follows:

b＝[t(n)-t(i)]/[τ_w(n)-τ_w(i)]……(49)

from the above formula, one can obtain: tau is_wThe target control temperature of the exhaust gas at the time (i +1) is:

t(i+1)＝t(i)+b[τ_w(i+1)-τ_w(i)]……(50)

2) the control method in the exhaust gas temperature control period comprises the following steps: carrying out heat preservation operation by using a small amount of coal gas and an optimal air-fuel ratio, controlling the temperature rise rate and the target control temperature according to formulas (49) to (50), wherein the maximum smoke exhaust temperature cannot exceed the upper limit of the target smoke exhaust temperature, and if the maximum smoke exhaust temperature reaches the upper limit of the smoke exhaust temperature, carrying out annealing operation and waiting for furnace replacement; the shorter the braising time is, the better the braising time is, and the shorter the braising time is, the more energy-saving the braising time is.

Technical Field

The invention relates to the technical field of metallurgical thermal energy conservation, in particular to a high-efficiency practical hot blast stove burning control method.

Background

The blast furnace hot blast stove is a main user for blast furnace gas consumption, and accounts for more than 40 percent of the total blast furnace gas consumption. Therefore, the operation of the hot blast stove is optimized, the coal gas consumption is reduced to the maximum extent on the premise of ensuring the requirements of the temperature, the temperature difference and the air quantity of the hot blast of the blast furnace, and the method is a target always pursued by blast furnace hot blast stove workers.

At present, 3 or 4 hot blast stoves are generally configured for one blast furnace, and a furnace changing system of 'two-burning one-feeding' or 'two-burning two-feeding' is generally implemented. The hot blast stove belongs to a heat device working periodically, and can be divided into two stages, namely a combustion period and an air supply period, in a working period, and the circulation is carried out repeatedly by changing the stove. The hot blast stove consumes coal gas in the combustion period and does not consume coal gas in the air supply period. Aiming at a furnace changing system of 'two-burning one-feeding' or 'two-burning two-feeding' of a hot blast furnace, two furnace changing modes are generally adopted, wherein one mode is a fixed period (time) furnace changing mode, and the other mode is a non-fixed period (time) furnace changing mode. The fixed period furnace change is mostly suitable for semi-automatic or manual operation, and has the advantages of simple operation, relatively stable furnace burning time and easy control, and the defects of the fixed period furnace change is influenced by the air volume change of the blast furnace in the air supply period and has larger hot air temperature fluctuation; the non-fixed period furnace change is mostly suitable for automatic control, and has the advantages of no influence of air volume change in the blast furnace air supply period and small hot air temperature fluctuation, and has the defects of uncertain furnace burning time, difficult furnace burning progress control, relatively complex operation and high requirement on automation degree. The traditional hot blast stove burning operation generally adopts a two-section burning system, namely a rapid heating stage and a vault temperature heat preservation heating stage. The rapid heating stage is to perform rapid heating by maximum coal gas amount and optimal air-fuel ratio, when the vault temperature of the hot blast stove reaches the temperature (1350-1400 ℃) specified by the field technical operating rule, the vault temperature of the hot blast stove enters a heat preservation heating stage, the stage is to gradually reduce the coal gas amount and the air amount based on the target temperature stability of the vault of the hot blast stove, and stop burning the stove until the exhaust gas temperature of the hot blast stove reaches the temperature (350-400 ℃) specified by the field technical operating rule, and perform furnace closing and wait for furnace replacement. The main problems of the traditional furnace burning system are as follows: firstly, in the vault temperature heat preservation heating stage, as the best air-fuel ratio is pursued on one side, the heat convection of the checker bricks at the lower part in the hot blast stove is weakened due to the reduction of the smoke, and the heat storage capacity of the checker bricks at the middle part and the lower part is reduced. Secondly, the total air quantity and the average hot air temperature of the air supply period before the combustion period are not considered, the difference of the heat storage capacity of the checker bricks at the initial combustion stage of the hot blast stove (generally called as a hot stove or a cool stove) is ignored, and the adverse effect is that the checker bricks of the hot blast stove do not reach thermal saturation due to the fact that the total heat supply capacity is not increased for the cool stove, so that the air quantity of the next air supply period is insufficient or the average hot air temperature is reduced; the hot furnace over-burning of the checker bricks of the hot furnace is caused because the total heat supply is not reduced, the hot furnace enters a furnace closing stage in advance, and the gas consumption is increased because the furnace closing time is prolonged and the heat dissipation loss is increased. Thirdly, the operation of the hot blast stove and the operation of the blast furnace lack the cooperative optimization, when the working condition of the blast furnace changes (reducing, damping down and reblowing), the operation of the hot blast stove can not be adjusted in time, so that the hot blast stove is burnt in advance and enters a furnace-closing stage, or the hot blast stove is repeatedly heated to cause the waste of coal gas. The invention takes the three problems as the guide, and takes heat balance test, analysis and calculation as the basis, takes the total air volume, the average air temperature and the air supply time in the previous air supply period as the initial conditions, and takes the working condition change of the blast furnace as the basis to dynamically determine the high-efficiency and practical furnace burning system and the control method, thereby realizing the purpose of providing high-quality hot air for the blast furnace at any time with lower consumption of the gas of the hot blast furnace.

Disclosure of Invention

In order to solve the technical problems provided by the background technology, the invention provides a high-efficiency practical hot blast stove burning control method, which is characterized in that a hot blast stove burning system and a method are scientifically formulated to adapt to the change of the production working condition of a blast furnace, the operation of the hot blast furnace is dynamically optimized on the premise of meeting the requirements of providing the required hot blast air quantity, the required hot blast air temperature and the required temperature difference for the blast furnace, the utilization efficiency of coal gas is improved, and the coal gas consumption of the hot blast furnace is reduced.

In order to achieve the purpose, the invention adopts the following technical scheme:

a high-efficiency practical hot blast stove burning control method is summarized as follows:

(1) on the basis of hot balance test, analysis and calculation of the hot blast stove, the total air quantity and the average air temperature of the hot blast stove in the previous air supply period are used as initial conditions, a mathematical model of the hot blast stove in the combustion period and the air supply period is established, and the total gas consumption in the next combustion period is reasonably determined.

(2) Under the condition of normal production working conditions of the blast furnace, a fixed period furnace changing system is adopted, and air supply time and furnace burning time are determined according to process requirements; under the condition of the abnormal production working conditions (wind reduction, damping down and reblowing) of the blast furnace, a non-fixed period furnace changing system is adopted, the total heat of the supplied air is taken as a reference, and the air supply time of the current air supply hot blast stove and the burning time of the air supply hot blast stove are predicted according to the current real-time collected hot air quantity and average air temperature supplied to the blast furnace.

(3) The combustion period of the hot blast stove is subdivided into four stages of a rapid heating period, a heat preservation and storage period, a smoke discharge temperature control period (including furnace closing) and a furnace changing period, and the heating time and the gas flow of each heating period are subdivided.

(4) And burning the hot blast stove by adopting different burning strategies in different heating periods of the hot blast stove. Wherein:

in the rapid heating period, the furnace is fired with a large amount of coal gas and an optimal air-fuel ratio until the temperature of the vault of the hot blast furnace reaches a target temperature (1350-1400 ℃) specified by the process.

In the heat preservation and heat storage period, the target temperature of the vault is stabilized, the heat storage amount of the checker bricks at the middle part and the lower part of the heat storage chamber is quickly increased as a control target, relatively small stable gas amount is adopted for organizing combustion, but the optimal air-fuel ratio is not pursued, but the total smoke amount is ensured to be basically unchanged (after the smoke amount is reduced, all the holes of the checker bricks cannot be filled, the smoke flow velocity is reduced, the convection heat transfer of the checker bricks at the lower part in the hot blast stove can be weakened), until the smoke temperature reaches the lower limit value (350 ℃) of the smoke temperature specified by the firing process, and the operation is characterized in that the convection heat transfer of the checker bricks at the middle part and the lower part in the hot blast stove is.

In the exhaust gas temperature control period, the furnace is fired by a small amount of coal gas and an optimal air-fuel ratio so as to ensure the stable temperature of the vault of the hot blast furnace. The operation is characterized in that: considering that the control period is close to the last period of the furnace burning, the checker bricks in the hot blast furnace basically reach thermal saturation, the action of supplying more coal gas is not large, and only a small amount of coal gas is supplied for strengthening the heat preservation effect of the hot blast furnace before air supply so as to offset the heat dissipation loss of the surface of the furnace body of the hot blast furnace until the exhaust temperature of the hot blast furnace reaches the upper limit value (400 ℃) of the exhaust temperature specified by the process, and during the period, a furnace changing instruction is waited at any time to prepare for furnace changing. If the smoke discharging temperature reaches the upper limit value and the furnace changing instruction is not received, the furnace stewing operation is executed.

(5) The optimal air-fuel ratio adopts a feed-forward control method for on-line analysis of the gas calorific value, because the method is more timely for adjusting the air-fuel ratio. Compared with a flue gas residual oxygen analysis method, the method can reduce heat loss caused by air-fuel ratio regulation lag; compared with the automatic optimization method, the transient heat loss of the unstable state during the optimization can be reduced.

The method specifically comprises the following steps:

step 1, carrying out a thermal balance test on all hot blast stoves of each blast furnace under the condition of normal production working condition to form a thermal balance test analysis report, and taking the test and analysis data as the reference of thermal balance calculation of each hot blast stove; the heat balance test is carried out once a year, and the reference value of the hot blast stove heat balance calculation is updated year by year according to new test and analysis data and is stored in a database;

step 2, collecting the air quantity, air temperature and air supply time of each hot blast stove in an air supply period in real time, and taking the parameters of the coal gas heat value, the coal gas flow, the combustion-supporting air flow, the combustion period time, the vault temperature of the hot blast stove, the exhaust gas temperature, the combustion-supporting air and the coal gas preheating temperature of each hot blast stove in a combustion period as the basis of model calculation and dynamic correction; taking the total heat brought by hot air in the thermal balance test as a reference value, taking the deviation of the reference value as a basis for judging whether the working condition of the blast furnace is normal or not and for judging a furnace change system, and when the actual value deviates from the total heat of the hot air in the thermal balance test (less than 10 percent), processing according to the normal working condition and executing a fixed period furnace change system; when the actual value deviates from the total heat quantity (more than or equal to 10%) of hot air in the heat balance test, processing according to an abnormal working condition, and executing an unfixed period furnace changing system;

step 3, establishing a hot blast stove heat balance model and a gas consumption model

3.1 Hot-blast stove heat balance model

For simplifying calculation, every m of hot blast stove is sent out in one working cycle (including combustion period, furnace changing period and air supply period)³Establishing a heat balance model of total heat income and total heat expenditure by taking hot air as a unit:

Q_R＝Q₁+Q₂+Q₃+Q₄……(1)

Q_Z＝Q¹+Q²+Q³+Q⁴+Q⁵+Q⁶+Q⁷+Q⁸+Q⁹……(2)

in the formula: q_R: total heat input (kj/m)³)；Q_Z: total heat expenditure (kj/m)³)；

Q₁: chemical heat of gas combustion (KJ/m)³)，Q₁＝B×Q_D……(3)；

B, sending hot blast stove per m³Amount of gas (m) consumed by hot blast³/m³)，Q_D: low calorific value of gas (KJ/m)³)；

B＝V_m×τ_r/(V_f×τ_f)……(4)

In the formula: v_mAverage gas flow (m) for burning hot blast stove³/h)，τ_rAnd τ_fRespectively the burning period and the air supply period of the hot blast stove (h), V_fActual hot air flow (m) sent out by the hot blast stove³/h)；

Q₂: physical heat (KJ/m) brought in by gas³)；Q₂＝B×(c_mt_m－c_met_e)……(5)

In the formula: t is t_m、t_eThe average temperature (DEG C) of the gas and the environment, c_m、c_meRespectively is coal gas at t_mAnd t_eAverage specific heat (KJ/m) of³℃)；

Q₃: physical heat (KJ/m) brought in by combustion air³)；Q₃＝α×B×(c_kt_k－c_ket_e)……(6)

In the formula: α: average air-fuel ratio during combustion, t_k、t_keRespectively the average preheating temperature of combustion air and the average temperature (DEG C) of the environment; c. C_kAnd c_eRespectively, air is at t_kDEG C and t_eAverage specific heat at DEG C (KJ/m)³℃)；

Q₄: physical heat (KJ/m) from cold blast (blast furnace blast)³)；Q₄＝c_f1t_f1－c_fet_e……(7)

In the formula: t is t_f1、t_eThe average temperature (deg.C) of the cold air and the environment, respectively; c. C_f1、c_eRespectively, air is at t_f1And t_eAverage specific heat (KJ/m) of³℃)；

Q¹: heat (KJ/m) brought by hot blast (blast furnace blast)³)；Q¹＝c_f2t_f2－c_fet_e……(8)

In the formula: t is t_f2、t_eThe average temperatures (deg.C) of the hot air and the environment, respectively; c. C_f2、c_feRespectively, air is at t_f2And t_eAverage specific heat at temperature (KJ/m)³℃)；

Q²: heat brought by flue gas (KJ/m)³)；Q²＝BbV_y(c_y2t_y2－c_yet_e)……(9)

In the formula: t is t_y2、t_eThe average temperatures of the flue gas and the environment are respectively; c. C_y2、c_yeRespectively at t for flue gas_y2And t_eAverage specific heat at temperature (KJ/m)³℃)；

V_y: actual amount of flue gas (m)³/m³Coal gas), if no measured data exists, the measured data can be calculated according to the components of the flue gas; b: a smoke correction coefficient when the gas is not completely combusted (b is 1 when the gas is completely combusted);

Q³: heat lost by incomplete chemical combustion, i.e. heat loss (KJ/m) of unburned combustible gas in flue gas³) If the gas is completely combusted, Q is calculated according to the smoke components³＝0；

Q⁴: heat dissipation capacity (KJ/m) of furnace body surface³)

Q⁴＝∑[k×(t_i-t_e)×A_i]×τ/(V_f×τ_f)……(10)

In the formula: k: convective heat transfer coefficient (kj/m)²C) can be selected by looking up a table according to the geometric position of the surface, t DEG C_i、t_eRespectively the surface temperature of the furnace body at the ith position and the ambient temperature (DEG C); a. the_i: surface area of furnace body at i-th position (m)²) (ii) a τ: a test cycle time (h); τ ═ τ_r+τ_f；V_f: average air volume (m) during blowing period³/h)；

Q⁵: surface heat dissipation of cold air pipeline (KJ/m)³)

Q⁵＝∑[k×(t_i-t_e)×A_i]×τ/(V_f×τ_f)……(11)

Q⁶: hot air pipe surface heat dissipation (KJ/m)³)

Q⁶＝∑[k×(t_i-t_e)×A_i]×τ/(V_f×τ_f)……(12)

Q⁷: flue surface heat dissipation (KJ/m)³)

Q⁷＝∑[k×(t_i-t_e)×A_i]×τ/(V_f×τ_f)……(13)

Q⁸: hot blast stove pressure relief belt heat output (KJ/m)³)

Q⁸＝V_L(c_f2t_f2－c_fet_e)/∑V_fτ_f……(14)

In the formula: v_LIs the volume (m) of the hot blast stove³)；t_f2、t_eThe average temperature of the hot air and the environment respectively; c. C_f2And c_feRespectively, air is at t_f2And t_eAverage specific heat (KJ/m) of³℃)；

Q⁹: cooling water endotherm (KJ/m)³)

Q⁹＝G_S(C_Ct_c-C_jt_j)×τ/∑V_fτ_f……(15)

In the formula: g_SThe flow rate of the cooling water is kg/h; c_c、C_jSpecific heat (KJ/m) of outlet water and inlet water respectively³℃)；t_c、t_jThe temperature (DEG C) of the water outlet and the water inlet are respectively;

heat efficiency eta of hot-blast stove (Q)¹-Q₄)/(Q_R-Q₄)……(16)

3.2 model of gas consumption of hot-blast stove

The following formulas (1) and (16) can be obtained: q₁＝(Q¹-Q₄)/η-(Q₂+Q₃)……(17)

Substituting into formula (3): b ═ Q¹-Q₄)/η-(Q₂+Q₃)]/Q_D……(18)

Total gas flow in the combustion period of the hot blast stove: b is_z＝B×V_f×τ_f……(19)

Substituting formula B (18) into formula (19) to obtain

B_z＝[(Q¹-Q₄)/η-(Q₂+Q₃)]/Q_D×(V_f×τ_f)……(20)

From the equation (20), the main factors influencing the total gas consumption during the combustion period of the hot blast stove are: heat (Q) brought by hot air in blowing period¹-Q₄) Thermal efficiency eta of hot-blast stove, air and gas preheating temperature (Q)₂+Q₃) Low calorific value of gas Q_DAnd total air volume (V)_f×τ_f) (ii) a In the real-time operation process, the total gas amount given by the formula (20) is dynamically corrected according to the data acquired in real time;

(1) when the preheating temperature of the combustion air and the coal gas deviates from the heat balance test value, the following correction is carried out according to the following formula:

ΔQ₂＝B×(c_m1t_m1－c_mt_m)……(21)

ΔQ₃＝α×B×(c_k1t_k1－c_kt_k)……(22)

in the formula: delta Q₂、ΔQ₃: respectively the correction quantity (KJ/m) of the physical heat brought by the gas and the combustion air³)；

t_m、t_m1: the preheating temperature (DEG C) of the gas during the heat balance test and the actual production respectively;

c_m、c_m1: are each t_m、t_m1Average specific heat (KJ/m) of gas at temperature³℃)；

t_k、t_k1: the preheating temperature (DEG C) of combustion air during the heat balance test and the actual production is respectively;

c_k、c_k1: are each t_k、t_k1Mean specific heat (KJ/m) of combustion air at temperature³℃)；

(2) When the air supply period of the hot blast stove is changed into the combustion period, and the heat brought by hot air in the air supply period deviates from a heat balance test value, the correction is carried out according to the following formula:

ΔQ¹＝c_fst_fs－c_f2t_f2……(23)

in the formula: delta Q¹: the heat quantity and the heat level of the hot air in the previous air supply period are broughtDifference in equilibrium time (KJ/m)³)；

t_f2、t_fs: the average temperature (DEG C) of hot air during the heat balance test and the previous air supply period is respectively;

c_f2、c_fs: are each t_f2、t_fsAverage specific heat at temperature (KJ/m)³℃)

(3) When the calorific value of the gas deviates from the heat balance test value, correcting according to the following formula:

ΔQ_D＝Q_D1-Q_D……(24)

in the formula: delta Q_D: the difference value (KJ/m) between the current gas calorific value and the heat balance³)；

Q_D、Q_D1: respectively the low calorific value (KJ/m) of the gas during the heat balance test and at the current moment³)；

The total gas consumption B in the combustion period of the hot blast stove is combined with the above influencing factors_z(m³) The dynamic correction can be performed as follows:

B_z＝[(Q¹+ΔQ¹-Q₄)/η-(Q₂+ΔQ₂+Q₃+ΔQ₃)]/(Q_D+ΔQ_D)×V_f×τ_f……(25)

step 4, determining the air supply period and the burning period (burning) time of the hot blast stove

The air supply period time and the combustion period time of the hot blast stove depend on the number of seats of the hot blast stove configured by the blast furnace and an air supply system (single-stove air supply comprises one-burning one-sending, two-burning one-sending, three-burning one-sending, double-stove air supply and semi-parallel cross air supply), and the specific air supply system is given by the field process technology operation rules;

4.1 determination of blowing period time

1) When the blast furnace is in normal production working condition, the hot blast stove supplies air and changes the furnace according to fixed cycle time, and the air supply time is calculated according to an air supply system:

when a single furnace is supplied with air: tau is_f＝(τ_r+τ_h)/(N-1)……(26)

When the double furnaces supply air: tau is_f＝2(τ_r+τ_h)/(N-2)……(27)

Semi-parallel cross air supply: tau is_f＝τ_r+τ_h……(28)

In the formula: tau is_f、τ_r、τ_h: respectively representing air supply, furnace burning and furnace changing time (h), wherein N is the number of hot blast stove seats configured for the blast furnace (N is 3 or 4);

2) when the blast furnace is in abnormal production working conditions (including blast furnace air reduction, damping down and reblowing), air supply and furnace replacement are carried out according to non-fixed cycle time, the specific time depends on the average flow and the average air temperature of hot air in an air supply period, and the air supply time can be calculated according to the following formula:

the total heat balance of hot air sent out by the air supply period of the hot blast stove can be obtained:

V_f×τ_f×Q¹＝(V_f+ΔV_f)×(τ_f+Δτ_f)×Q¹after merging, the following can be obtained:

Δτ_f＝(V_f×τ_f)/(V_f+ΔV_f)-τ_f……(29)

τ_ff＝τ_f+Δτ_f……(30)

in the formula: tau is_ff: the air supply time (h) of the hot blast stove in a non-fixed period is set; Δ V_f: the average air quantity difference (m) of the blast furnace in the air supply period under the normal working condition and the abnormal working condition of the blast furnace³/h)；Δτ_f: the difference (h) of the air supply time of the hot blast stove in the air supply period under the normal working condition and the abnormal working condition of the blast furnace is as delta V_fWhen it is negative, Δ τ_fIs positive and represents the total supply time tau_ffLengthening, otherwise shortening;

when the working condition of the blast furnace is changed from the abnormal working condition to the normal working condition, the fixed period furnace changing system is adjusted in time;

4.2 determination of burn period time

The burning period time depends on the number of the seats of the hot blast stove and the air supply system, and is respectively calculated according to the number of the seats of the hot blast stove and the air supply system:

when a single furnace is supplied with air: tau is_r＝(N-1)×τ_f-τ_h……(31)

When the double furnaces supply air: tau is_r＝τ_f×(N-2)/2-τ_h……(32)

Semi-parallel cross air supply: tau is_r＝τ_f-τ_h……(33)

In the formula: tau is_r: time of combustion (with smoldering furnace) (h)

Step 5, determining the sectional time and the gas flow in the combustion period of the hot blast stove

5.1 determination of the time of the combustion phases

According to the burning characteristics of the hot blast stove, the burning period of the hot blast stove is subdivided into three stages of a rapid heating period, a heat preservation and storage period and a smoke discharge temperature control period (including furnace closing), and the heating time of each heating period can be determined according to the following formula:

τ_k＝(0.18～0.30)×τ_r……(34)；τ_w＝(0.48～0.60)×τ_r……(35)；

τ_y＝(0.07～0.10)×τ_r……(36)；τ_hc … … (37); (C: constant, about 0.17 hour)

τ_r＝τ_k+τ_w+τ_y……(38)；

In the formula: tau is_k、τ_w、τ_y、τ_h: respectively including a rapid heating period, a heat preservation and storage period, a smoke exhaust temperature control period (including furnace closing) and a furnace changing period time (h), tau_r: is the burning period time (h);

5.2 determination of the total amount of gas in each heating period

B_k＝k_k B_z/τ_k……(39)；B_w＝k_w B_z/τ_w……(40)；B_y＝k_y B_z/τ_y……(41)；

In the formula: b is_k、B_w、B_y: the gas flow (m) is respectively in a rapid heating period (initial heating period), a heat preservation and storage period (middle heating period) and a smoke exhaust temperature control period (final heating period)³/h)；B_z: total gas amount (m) in combustion period³)；

k_k、k_w、k_y: the gas flow coefficients of the rapid heating period, the heat preservation and storage period and the exhaust gas temperature control period are respectively set;

wherein: k is a radical of_k＝0.20～0.35……(42)；k_w＝0.65～0.75……(43)；k_y＝0.05～0.10……(44)；

No coal gas is consumed in the furnace changing period;

step 6, optimizing air-fuel ratio of each heating period of the hot blast stove

Calculating the optimal air-fuel ratio alpha according to the gas heat value acquired on line, wherein the empirical algorithm comprises the following steps: α ═ Q_D/4180……(45)；

During the rapid heating period (initial heating period): alpha is alpha_k＝(1.00～1.05)×α……(46)；

In the vault temperature holding period (mid-heating period): alpha is alpha_w＞1.05×α……(47)；

In the exhaust gas temperature control period (final heating stage): alpha is alpha_y＝(1.00～1.05)×α……(48)；

In the formula: alpha is alpha_k、α_w、α_y: the air-fuel ratio of the fuel gas is respectively in a rapid heating period, a heat preservation and storage period and a smoke exhaust temperature control period.

The method also comprises an air-fuel ratio control method, wherein a gas calorific value feed-forward control method is adopted, a gas calorific value analyzer is installed on a gas pipeline sent to the hot blast stove, the gas calorific value acquired in real time is uploaded to a computer system, and calculation and control are carried out according to formulas (45) to (48).

The method also comprises the coupled control of the temperature rise rate and the furnace burning time;

when the rapid heating period of the hot blast stove is finished (the mark is that the vault temperature reaches the target temperature specified by the technical operating regulation, such as 1350 ℃ or 1400 ℃), the hot blast stove enters the heat preservation and heat storage period, two control targets are provided at the time, wherein firstly, the vault temperature is kept relatively stable (the target temperature difference is +/-5 ℃), secondly, the temperature rise rate of the smoke is consistent with the predicted stove burning time, namely, when the stove burning time reaches 90% of the total stove burning time, the smoke discharge temperature reaches the lower limit value of the target smoke discharge temperature (determined according to the technical operating regulation, such as 350 ℃), at the time, the heat preservation and heat storage period is finished, the smoke discharge temperature control period is started, and the control targets in the: firstly, the smoke exhaust temperature is slowly increased (the upper limit of the smoke exhaust temperature is controlled within 400 ℃); secondly, keeping the target temperature of the vault stable; thirdly, waiting for a furnace changing instruction; when the temperature of the exhaust smoke reaches the upper limit of the temperature of the exhaust smoke (such as 400 ℃), and a furnace changing instruction is not received, executing furnace stewing operation (stopping gas and air), and waiting for furnace changing (the shorter the furnace stewing time is, the better the furnace stewing time is);

1) in the heat preservation and storage period, the temperature rise rate and the furnace burning time coupling control method comprises the following steps:

setting the starting time of the heat preservation and heat storage period to be tau_w(i) End time is tau_w(n), the corresponding exhaust gas temperature (detection value) at the beginning of the heat-preserving and heat-storing period is t (i), and the exhaust gas temperature at the end of the heat-preserving and heat-storing period is t (n), so that the exhaust gas temperature rise rate in the heat-preserving and heat-storing period can be obtained as follows:

b＝[t(n)-t(i)]/[τ_w(n)-τ_w(i)]……(49)

from the above formula, one can obtain: tau is_wThe target control temperature of the exhaust gas at the time (i +1) is:

t(i+1)＝t(i)+b[τ_w(i+1)-τ_w(i)]……(50)

2) the control method in the exhaust gas temperature control period comprises the following steps: carrying out heat preservation operation by using a small amount of coal gas and an optimal air-fuel ratio, controlling the temperature rise rate and the target control temperature according to the formulas (49) to (50), wherein the highest exhaust gas temperature cannot exceed the upper limit of the target exhaust gas temperature (400 ℃), and if the highest exhaust gas temperature reaches the upper limit of the exhaust gas temperature (400 ℃), carrying out furnace stewing operation (shutting down the coal gas and the air) to wait for furnace replacement; the shorter the braising time is, the better the braising time is, and the shorter the braising time is, the more energy-saving the braising time is.

Compared with the prior art, the invention has the beneficial effects that:

compared with the existing hot blast furnace operation (including control) method, the method has the remarkable effects of high coal gas utilization efficiency, high heat storage speed of the upper part and the lower part of the hot blast furnace, coal gas consumption reduction and the like on the premise of providing high-quality hot air for the blast furnace in time, and has strong practicability and wide popularization prospect.

Detailed Description

The following describes in detail specific embodiments of the present invention.

A high-efficiency practical hot blast stove burning control method is summarized as follows:

(1) on the basis of hot balance test, analysis and calculation of the hot blast stove, the total air quantity and the average air temperature of the hot blast stove in the previous air supply period are used as initial conditions, a mathematical model of the hot blast stove in the combustion period and the air supply period is established, and the total gas consumption in the next combustion period is reasonably determined.

(2) Under the condition of normal production working conditions of the blast furnace, a fixed period furnace changing system is adopted, and air supply time and furnace burning time are determined according to process requirements; under the condition of the abnormal production working conditions (wind reduction, damping down and reblowing) of the blast furnace, a non-fixed period furnace changing system is adopted, the total heat of the supplied air is taken as a reference, and the air supply time of the current air supply hot blast stove and the burning time of the air supply hot blast stove are predicted according to the current real-time collected hot air quantity and average air temperature supplied to the blast furnace.

(3) The combustion period of the hot blast stove is subdivided into four stages of a rapid heating period, a heat preservation and storage period, a smoke discharge temperature control period (including furnace closing) and a furnace changing period, and the heating time and the gas flow of each heating period are subdivided.

(4) And burning the hot blast stove by adopting different burning strategies in different heating periods of the hot blast stove. Wherein:

in the rapid heating period, the furnace is fired with a large amount of coal gas and an optimal air-fuel ratio until the temperature of the vault of the hot blast furnace reaches a target temperature (1350-1400 ℃) specified by the process.

In the heat preservation and heat storage period, the target temperature of the vault is stabilized, the heat storage amount of the checker bricks at the middle part and the lower part of the heat storage chamber is quickly increased as a control target, relatively small stable gas amount is adopted for organizing combustion, but the optimal air-fuel ratio is not pursued, but the total smoke amount is ensured to be basically unchanged (after the smoke amount is reduced, all the holes of the checker bricks cannot be filled, the smoke flow velocity is reduced, the convection heat transfer of the checker bricks at the lower part in the hot blast stove can be weakened), until the smoke temperature reaches the lower limit value (350 ℃) of the smoke temperature specified by the firing process, and the operation is characterized in that the convection heat transfer of the checker bricks at the middle part and the lower part in the hot blast stove is.

In the exhaust gas temperature control period, the furnace is fired by a small amount of coal gas and an optimal air-fuel ratio so as to ensure the stable temperature of the vault of the hot blast furnace. The operation is characterized in that: considering that the control period is close to the last period of the furnace burning, the checker bricks in the hot blast furnace basically reach thermal saturation, the action of supplying more coal gas is not large, and only a small amount of coal gas is supplied for strengthening the heat preservation effect of the hot blast furnace before air supply so as to offset the heat dissipation loss of the surface of the furnace body of the hot blast furnace until the exhaust temperature of the hot blast furnace reaches the upper limit value (400 ℃) of the exhaust temperature specified by the process, and during the period, a furnace changing instruction is waited at any time to prepare for furnace changing. If the smoke discharging temperature reaches the upper limit value and the furnace changing instruction is not received, the furnace stewing operation is executed.

(5) The optimal air-fuel ratio adopts a feed-forward control method for on-line analysis of the gas calorific value, because the method is more timely for adjusting the air-fuel ratio. Compared with a flue gas residual oxygen analysis method, the method can reduce heat loss caused by air-fuel ratio regulation lag; compared with the automatic optimization method, the transient heat loss of the unstable state during the optimization can be reduced.

The method specifically comprises the following steps:

1. carrying out a thermal balance test on all the hot blast stoves of each blast furnace under the condition of normal production working condition to form a thermal balance test analysis report, and taking the test and analysis data as the reference of thermal balance calculation of each hot blast stove; the heat balance test is carried out once a year, and the reference value of the hot blast stove heat balance calculation is updated year by year according to new test and analysis data and is stored in a database;

2. collecting the air quantity, air temperature and air supply time of each hot blast stove in an air supply period, and the gas heat value, gas flow, combustion air flow, combustion period time, hot blast stove vault temperature, exhaust gas temperature, combustion air and gas preheating temperature parameters in a combustion period in real time, wherein the parameters are used as the basis for model calculation and dynamic correction; taking the total heat brought by hot air in the thermal balance test as a reference value, taking the deviation of the reference value as a basis for judging whether the working condition of the blast furnace is normal or not and for judging a furnace change system, and when the actual value deviates from the total heat of the hot air in the thermal balance test (less than 10 percent), processing according to the normal working condition and executing a fixed period furnace change system; when the actual value deviates from the total heat quantity (more than or equal to 10%) of hot air in the heat balance test, processing according to an abnormal working condition, and executing an unfixed period furnace changing system;

3. establishment of hot blast stove heat balance model and gas consumption model

3.1 Hot-blast stove heat balance model

For simplifying calculation, every m of hot blast stove is sent out in one working cycle (including combustion period, furnace changing period and air supply period)³Establishing a heat balance model of total heat income and total heat expenditure by taking hot air as a unit:

Q_R＝Q₁+Q₂+Q₃+Q₄……(1)

Q_Z＝Q¹+Q²+Q³+Q⁴+Q⁵+Q⁶+Q⁷+Q⁸+Q⁹……(2)

in the formula: q_R: total heat input (kj/m)³)；Q_Z: total heat expenditure (kj/m)³)；

Q₁: chemical heat of gas combustion (KJ/m)³)，Q₁＝B×Q_D……(3)；

B, sending hot blast stove per m³Amount of gas (m) consumed by hot blast³/m³)，Q_D: low calorific value of gas (KJ/m)³)；

B＝V_m×τ_r/(V_f×τ_f)……(4)

In the formula: v_mAverage gas flow (m) for burning hot blast stove³/h)，τ_rAnd τ_fRespectively the burning period and the air supply period of the hot blast stove (h), V_fActual hot air flow (m) sent out by the hot blast stove³/h)；

Q₂: physical heat (KJ/m) brought in by gas³)；Q₂＝B×(c_mt_m－c_met_e)……(5)

In the formula: t is t_m、t_eThe average temperature (DEG C) of the gas and the environment, c_m、c_meRespectively is coal gas at t_mAnd t_eAverage specific heat (KJ/m) of³℃)；

Q₃: physical heat (KJ/m) brought in by combustion air³)；Q₃＝α×B×(c_kt_k－c_ket_e)……(6)

In the formula: α: average air-fuel ratio during combustion, t_k、t_keRespectively the average preheating temperature of combustion air and the average temperature (DEG C) of the environment; c. C_kAnd c_eRespectively, air is at t_kDEG C and t_eAverage specific heat at DEG C (KJ/m)³℃)；

Q₄: physical heat (KJ/m) from cold blast (blast furnace blast)³)；Q₄＝c_f1t_f1－c_fet_e……(7)

In the formula: t is t_f1、t_eThe average temperature (deg.C) of the cold air and the environment, respectively; c. C_f1、c_eRespectively, air is at t_f1And t_eAverage specific heat (KJ/m) of³℃)；

Q¹: heat (KJ/m) brought by hot blast (blast furnace blast)³)；Q¹＝c_f2t_f2－c_fet_e……(8)

In the formula: t is t_f2、t_eThe average temperatures (deg.C) of the hot air and the environment, respectively; c. C_f2、c_feRespectively, air is at t_f2And t_eAverage specific heat at temperature (KJ/m)³℃)；

Q²: heat brought by flue gas (KJ/m)³)；Q²＝BbV_y(c_y2t_y2－c_yet_e)……(9)

In the formula: t is t_y2、t_eThe average temperatures of the flue gas and the environment are respectively; c. C_y2、c_yeRespectively at t for flue gas_y2And t_eAverage specific heat at temperature (KJ/m)³℃)；

V_y: actual amount of flue gas (m)³/m³Coal gas), if no measured data exists, the measured data can be calculated according to the components of the flue gas; b: incomplete combustion of gasA smoke correction coefficient during burning (b is 1 when the gas is completely burnt);

Q³: heat lost by incomplete chemical combustion, i.e. heat loss (KJ/m) of unburned combustible gas in flue gas³) If the gas is completely combusted, Q is calculated according to the smoke components³＝0；

Q⁴: heat dissipation capacity (KJ/m) of furnace body surface³)

Q⁴＝∑[k×(t_i-t_e)×A_i]×τ/(V_f×τ_f)……(10)

In the formula: k: convective heat transfer coefficient (kj/m)²C) can be selected by looking up a table according to the geometric position of the surface, t DEG C_i、t_eRespectively the surface temperature of the furnace body at the ith position and the ambient temperature (DEG C); a. the_i: surface area of furnace body at i-th position (m)²) (ii) a τ: a test cycle time (h); τ ═ τ_r+τ_f；V_f: average air volume (m) during blowing period³/h)；

Q⁵: surface heat dissipation of cold air pipeline (KJ/m)³)

Q⁵＝∑[k×(t_i-t_e)×A_i]×τ/(V_f×τ_f)……(11)

Q⁶: hot air pipe surface heat dissipation (KJ/m)³)

Q⁶＝∑[k×(t_i-t_e)×A_i]×τ/(V_f×τ_f)……(12)

Q⁷: flue surface heat dissipation (KJ/m)³)

Q⁷＝∑[k×(t_i-t_e)×A_i]×τ/(V_f×τ_f)……(13)

Q⁸: hot blast stove pressure relief belt heat output (KJ/m)³)

Q⁸＝V_L(c_f2t_f2－c_fet_e)/∑V_fτ_f……(14)

In the formula: v_LIs the volume (m) of the hot blast stove³)；t_f2、t_eAre respectively heatAverage temperature of wind and environment; c. C_f2And c_feRespectively, air is at t_f2And t_eAverage specific heat (KJ/m) of³℃)；

Q⁹: cooling water endotherm (KJ/m)³)

Q⁹＝G_S(C_Ct_c-C_jt_j)×τ/∑V_fτ_f……(15)

In the formula: g_SThe flow rate of the cooling water is kg/h; c_c、C_jSpecific heat (KJ/m) of outlet water and inlet water respectively³℃)；t_c、t_jThe temperature (DEG C) of the water outlet and the water inlet are respectively;

heat efficiency eta of hot-blast stove (Q)¹-Q₄)/(Q_R-Q₄)……(16)

3.2 model of gas consumption of hot-blast stove

The following formulas (1) and (16) can be obtained: q₁＝(Q¹-Q₄)/η-(Q₂+Q₃)……(17)

Substituting into formula (3): b ═ Q¹-Q₄)/η-(Q₂+Q₃)]/Q_D……(18)

Total gas flow in the combustion period of the hot blast stove: b is_z＝B×V_f×τ_f……(19)

Substituting formula B (18) into formula (19) to obtain

B_z＝[(Q¹-Q₄)/η-(Q₂+Q₃)]/Q_D×(V_f×τ_f)……(20)

From the equation (20), the main factors influencing the total gas consumption during the combustion period of the hot blast stove are: heat (Q) brought by hot air in blowing period¹-Q₄) Thermal efficiency eta of hot-blast stove, air and gas preheating temperature (Q)₂+Q₃) Low calorific value of gas Q_DAnd total air volume (V)_f×τ_f) (ii) a In the real-time operation process, the total gas amount given by the formula (20) is dynamically corrected according to the data acquired in real time;

(1) when the preheating temperature of the combustion air and the coal gas deviates from the heat balance test value, the following correction is carried out according to the following formula:

ΔQ₂＝B×(c_m1t_m1－c_mt_m)……(21)

ΔQ₃＝α×B×(c_k1t_k1－c_kt_k)……(22)

in the formula: delta Q₂、ΔQ₃: respectively the correction quantity (KJ/m) of the physical heat brought by the gas and the combustion air³)；

t_m、t_m1: the preheating temperature (DEG C) of the gas during the heat balance test and the actual production respectively;

c_m、c_m1: are each t_m、t_m1Average specific heat (KJ/m) of gas at temperature³℃)；

t_k、t_k1: the preheating temperature (DEG C) of combustion air during the heat balance test and the actual production is respectively;

c_k、c_k1: are each t_k、t_k1Mean specific heat (KJ/m) of combustion air at temperature³℃)；

(2) When the air supply period of the hot blast stove is changed into the combustion period, and the heat brought by hot air in the air supply period deviates from a heat balance test value, the correction is carried out according to the following formula:

ΔQ¹＝c_fst_fs－c_f2t_f2……(23)

in the formula: delta Q¹: the difference (KJ/m) between the heat quantity brought out by the hot air in the previous air supply period and the heat balance³)；

t_f2、t_fs: the average temperature (DEG C) of hot air during the heat balance test and the previous air supply period is respectively;

c_f2、c_fs: are each t_f2、t_fsAverage specific heat at temperature (KJ/m)³℃)

(3) When the calorific value of the gas deviates from the heat balance test value, correcting according to the following formula:

ΔQ_D＝Q_D1-Q_D……(24)

in the formula: deltaQ_D: the difference value (KJ/m) between the current gas calorific value and the heat balance³)；

Q_D、Q_D1: respectively the low calorific value (KJ/m) of the gas during the heat balance test and at the current moment³)；

The total gas consumption B in the combustion period of the hot blast stove is combined with the above influencing factors_z(m³) The dynamic correction can be performed as follows:

B_z＝[(Q¹+ΔQ¹-Q₄)/η-(Q₂+ΔQ₂+Q₃+ΔQ₃)]/(Q_D+ΔQ_D)×V_f×τ_f……(25)

4. determining air supply period and combustion period (burning) time of hot blast stove

The air supply period time and the combustion period time of the hot blast stove depend on the number of seats of the hot blast stove configured by the blast furnace and an air supply system (single-stove air supply comprises one-burning one-sending, two-burning one-sending, three-burning one-sending, double-stove air supply and semi-parallel cross air supply), and the specific air supply system is given by the field process technology operation rules;

4.1 determination of blowing period time

1) When the blast furnace is in normal production working condition, the hot blast stove supplies air and changes the furnace according to fixed cycle time, and the air supply time is calculated according to an air supply system:

when a single furnace is supplied with air: tau is_f＝(τ_r+τ_h)/(N-1)……(26)

When the double furnaces supply air: tau is_f＝2(τ_r+τ_h)/(N-2)……(27)

Semi-parallel cross air supply: tau is_f＝τ_r+τ_h……(28)

In the formula: tau is_f、τ_r、τ_h: respectively representing air supply, furnace burning and furnace changing time (h), wherein N is the number of hot blast stove seats configured for the blast furnace (N is 3 or 4);

2) when the blast furnace is in abnormal production working conditions (including blast furnace air reduction, damping down and reblowing), air supply and furnace replacement are carried out according to non-fixed cycle time, the specific time depends on the average flow and the average air temperature of hot air in an air supply period, and the air supply time can be calculated according to the following formula:

the total heat balance of hot air sent out by the air supply period of the hot blast stove can be obtained:

V_f×τ_f×Q¹＝(V_f+ΔV_f)×(τ_f+Δτ_f)×Q¹after merging, the following can be obtained:

Δτ_f＝(V_f×τ_f)/(V_f+ΔV_f)-τ_f……(29)

τ_ff＝τ_f+Δτ_f……(30)

in the formula: tau is_ff: the air supply time (h) of the hot blast stove in a non-fixed period is set; Δ V_f: the average air quantity difference (m) of the blast furnace in the air supply period under the normal working condition and the abnormal working condition of the blast furnace³/h)；Δτ_f: the difference (h) of the air supply time of the hot blast stove in the air supply period under the normal working condition and the abnormal working condition of the blast furnace is as delta V_fWhen it is negative, Δ τ_fIs positive and represents the total supply time tau_ffLengthening, otherwise shortening;

when the working condition of the blast furnace is changed from the abnormal working condition to the normal working condition, the fixed period furnace changing system is adjusted in time;

4.2 determination of burn period time

The burning period time depends on the number of the seats of the hot blast stove and the air supply system, and is respectively calculated according to the number of the seats of the hot blast stove and the air supply system:

when a single furnace is supplied with air: tau is_r＝(N-1)×τ_f-τ_h……(31)

When the double furnaces supply air: tau is_r＝τ_f×(N-2)/2-τ_h……(32)

Semi-parallel cross air supply: tau is_r＝τ_f-τ_h……(33)

In the formula: tau is_r: time of combustion (with smoldering furnace) (h)

5. Determination of sectional time and gas flow in hot blast stove combustion period

5.1 determination of the time of the combustion phases

According to the burning characteristics of the hot blast stove, the burning period of the hot blast stove is subdivided into three stages of a rapid heating period, a heat preservation and storage period and a smoke discharge temperature control period (including furnace closing), and the heating time of each heating period can be determined according to the following formula:

τ_k＝(0.18～0.30)×τ_r……(34)；τ_w＝(0.48～0.60)×τ_r……(35)；

τ_y＝(0.07～0.10)×τ_r……(36)；τ_hc … … (37); (C: constant, about 0.17 hour)

τ_r＝τ_k+τ_w+τ_y……(38)；

In the formula: tau is_k、τ_w、τ_y、τ_h: respectively including a rapid heating period, a heat preservation and storage period, a smoke exhaust temperature control period (including furnace closing) and a furnace changing period time (h), tau_r: is the burning period time (h);

5.2 determination of the total amount of gas in each heating period

B_k＝k_k B_z/τ_k……(39)；B_w＝k_w B_z/τ_w……(40)；B_y＝k_y B_z/τ_y……(41)；

In the formula: b is_k、B_w、B_y: the gas flow (m) is respectively in a rapid heating period (initial heating period), a heat preservation and storage period (middle heating period) and a smoke exhaust temperature control period (final heating period)³/h)；B_z: total gas amount (m) in combustion period³)；

k_k、k_w、k_y: the gas flow coefficients of the rapid heating period, the heat preservation and storage period and the exhaust gas temperature control period are respectively set;

wherein: k is a radical of_k＝0.20～0.35……(42)；k_w＝0.65～0.75……(43)；k_y＝0.05～0.10……(44)；

No coal gas is consumed in the furnace changing period;

6. optimization of air-fuel ratio of hot blast stove in each heating period

Calculating the optimal air-fuel ratio alpha according to the gas heat value acquired on line, wherein the empirical algorithm comprises the following steps: α ═ Q_D/4180……(45)；

During the rapid heating period (initial heating period): alpha is alpha_k＝(1.00～1.05)×α……(46)；

In the vault temperature holding period (mid-heating period): alpha is alpha_w＞1.05×α……(47)；

In the exhaust gas temperature control period (final heating stage): alpha is alpha_y＝(1.00～1.05)×α……(48)；

In the formula: alpha is alpha_k、α_w、α_y: the air-fuel ratio of the fuel gas is respectively in a rapid heating period, a heat preservation and storage period and a smoke exhaust temperature control period.

7. The air-fuel ratio control method adopts a gas heat value feedforward control method, a gas heat value analyzer is installed on a gas pipeline sent to the hot blast stove, the gas heat value acquired in real time is uploaded to a computer system, and calculation and control are carried out according to formulas (45) to (48).

8. The temperature rise rate and the furnace burning time are controlled in a coupling way;

when the rapid heating period of the hot blast stove is finished (the mark is that the vault temperature reaches the target temperature specified by the technical operating regulation, such as 1350 ℃ or 1400 ℃), the hot blast stove enters the heat preservation and heat storage period, two control targets are provided at the time, wherein firstly, the vault temperature is kept relatively stable (the target temperature difference is +/-5 ℃), secondly, the temperature rise rate of the smoke is consistent with the predicted stove burning time, namely, when the stove burning time reaches 90% of the total stove burning time, the smoke discharge temperature reaches the lower limit value of the target smoke discharge temperature (determined according to the technical operating regulation, such as 350 ℃), at the time, the heat preservation and heat storage period is finished, the smoke discharge temperature control period is started, and the control targets in the: firstly, the smoke exhaust temperature is slowly increased (the upper limit of the smoke exhaust temperature is controlled within 400 ℃); secondly, keeping the target temperature of the vault stable; thirdly, waiting for a furnace changing instruction; when the temperature of the exhaust smoke reaches the upper limit of the temperature of the exhaust smoke (such as 400 ℃), and a furnace changing instruction is not received, executing furnace stewing operation (stopping gas and air), and waiting for furnace changing (the shorter the furnace stewing time is, the better the furnace stewing time is);

1) in the heat preservation and storage period, the temperature rise rate and the furnace burning time coupling control method comprises the following steps:

setting the starting time of the heat preservation and heat storage period to be tau_w(i) End time is tau_w(n) at the beginning of the Heat-retaining Heat-accumulating periodThe corresponding exhaust smoke temperature (detection value) is t (i), the exhaust smoke temperature at the end of the heat preservation and storage period is t (n), and therefore the exhaust smoke temperature rise rate in the heat preservation and storage period can be obtained as follows:

b＝[t(n)-t(i)]/[τ_w(n)-τ_w(i)]……(49)

from the above formula, one can obtain: tau is_wThe target control temperature of the exhaust gas at the time (i +1) is:

t(i+1)＝t(i)+b[τ_w(i+1)-τ_w(i)]……(50)

2) the control method in the exhaust gas temperature control period comprises the following steps: carrying out heat preservation operation by using a small amount of coal gas and an optimal air-fuel ratio, controlling the temperature rise rate and the target control temperature according to the formulas (49) to (50), wherein the highest exhaust gas temperature cannot exceed the upper limit of the target exhaust gas temperature (400 ℃), and if the highest exhaust gas temperature reaches the upper limit of the exhaust gas temperature (400 ℃), carrying out furnace stewing operation (shutting down the coal gas and the air) to wait for furnace replacement; the shorter the braising time is, the better the braising time is, and the shorter the braising time is, the more energy-saving the braising time is.

The above embodiments are implemented on the premise of the technical solution of the present invention, and detailed embodiments and specific operation procedures are given, but the scope of the present invention is not limited to the above embodiments. The methods used in the above examples are conventional methods unless otherwise specified.