RU2013453C1 - Method of heating ingots in heating well - Google Patents

Abstract

FIELD: heating of ingots. SUBSTANCE: method involves elevating temperature in heating well, with heat power being constant, and holding at blistering temperature with reduced supply of fuel. During heating of metal ratio of gas flow rate and two-component gas mixture flow rate is maintained in accordance with dependence recited in specifications. EFFECT: increased efficiency of heating. 2 dwg, 1 tbl

Description

 The invention relates to metallurgical heat engineering and can be used in heating wells when heating ingots before pressure treatment at metallurgical plants.

 A known method of heating metal in heating wells [1], including continuous measurement of the temperature of the working space of the well, determining the estimated temperature of metal heating by means of a computing device, controlling the temperature of the working space by changing the fuel consumption and the fuel-air ratio by changing the air flow. In this case, the difference between the temperature of the working space and the calculated temperature of the metal heating is determined, as well as the average integral temperature of the metal section and taken as a parameter for controlling the temperature of the working space of the well and the fuel-air ratio.

 The disadvantage of this method is the low quality of metal heating, the melting of part of the ingots and underheating of the metal due to insufficiently reliable determination of the average integral temperature of the metal during the heating period.

 A known method of heating metal, implemented when regulating the operation of the furnace for heating steel ingots. The method includes supplying fuel and air to the heating well, measuring the surface temperature of the ingots and the thermal performance of the furnace. Based on the heat balance, the temperatures of the surface and center of the fusion are calculated, and the calculated temperature of the core of the ingot and the measured surface temperature are compared with the desired temperature of the center and surface. Depending on the comparison results, the fuel supply to the furnace is regulated.

 It is difficult to measure the surface temperature of a metal during heating. The pyrometer readings significantly depend on the relative location of the surface of the ingot and the sensor, the presence of scale and its structure, and the composition of the gas atmosphere of the furnace. Along with the errors in calculating the core temperature, this leads to a low quality of metal heating and the uneconomical operation of the well.

 A known method of heating ingots in a heating well, including preheating the well, planting ingots and holding them until they reach the well warming temperature, then stepwise heating the ingots to a languid temperature and languishing with decreasing fuel consumption. Step heating to the temperature of languishing is carried out cyclically, the duration of each heating step in each cycle is set within 1 / 3-1 / 2 of the ingot holding time. At the first stage of the first cycle fuel is supplied in an amount of 0.85-1.0 of the minimum fuel consumption during the languishing mode. Next, each subsequent step after the first begins with a fuel consumption equal to the fuel consumption in the previous cycle in the second stage, and in each cycle, when switching from a stage to a heating stage, fuel consumption is increased 1.6-2 times.

 The method is specific to the scope, its implementation provides a significant increase in yield when heating ingots of structural steel. When heating other steels, an increase in the quality of rolled products is not achieved, and lengthening the period of temperature rise only leads to a decrease in the productivity of wells and excessive consumption of fuel.

A known method of heating ingots in a heating well, implemented when controlling the heating rate of the charge. The method includes raising the temperature in the well at a constant flow rate and the calorific value of the mixed gas and holding at the temperature of languishing with a decrease in the calorific value of the fuel. At the same time, during the temperature rise, the well is heated by a mixture of coke oven and blast furnace gases with a calorific value of 2500 × 4.18 kJ / m ³ . Upon reaching the furnace temperature ^of 1320 C in the mixture is increased content of blast furnace gas having a low calorific value of (800 × 4,18 kJ / m ^3). In the future, the heat of combustion of the fuel during the exposure period is changed in the range (1500-2300) × 4.18 kJ / m ³ with the same gas volume.

 The disadvantage of this method is the low quality of metal heating and increased fuel consumption. This is due to the lengthening of the torch during the holding period by increasing the unevenness of the heating of the charge.

 A known method of heating ingots in a heating well, implemented in a method of heating heating furnaces and comprising maintaining a predetermined pressure in the pipeline of the gas mixture by introducing a mixture of technical nitrogen and natural gas in a ratio of 7: 1 when the pressure of the blast furnace gas drops. When the pressure of coke oven gas drops, a mixture of industrial nitrogen and natural gas is introduced in a ratio of 1: 1.

 The disadvantage of this method is the increased specific fuel consumption for heating ingots due to the introduction of ballast (nitrogen) fuel into the working space of the furnace, which leads to an increase in heat loss with smoke leaving the furnace.

 A similar disadvantage has the method of heating ingots in heating furnaces, implemented in the heating method and including a change in the ratio of the ratio of nitrogen to natural gas inversely proportional to the calorific value of the total gas mixture.

 The closest in technical essence and the achieved effect to the claimed method is a method of heating ingots in a heating well, implemented when heating heating wells. The method includes raising the temperature in the well at constant heat output and holding at the temperature of languishing with a decrease in fuel supply. At the same time, when the temperature rises, when the flow rate of blast furnace gas changes, the flow rate of natural gas is inversely proportional to 8: 1, and when supplying blast furnace and coke oven gas, it is 4: 1.

 The disadvantage of this method is the low quality of the ingots and the increased specific fuel consumption.

 This is explained by the following. An inversely proportional change in the increment of blast-furnace and natural gas costs in a ratio of 8: 1 when changing the base flow of blast-furnace gas makes it possible to balance the combustible components of the fuel and oxidizer with a changed air flow. However, the absolute value of the ratio of the costs of blast furnace and natural gases with such regulation during the temperature rise varies arbitrarily and does not take into account specific heating conditions. From a technological point of view, the most important factor determining the choice of the basic ratio of blast-furnace and natural gas costs is the heat deficit introduced by the cage into the workspace. In the prototype there is no relationship between the temperature of the metal on the landing and the value of the basic ratio of the costs of blast furnace and natural gases. This leads to situations where the rise in temperature of ingots with a high initial temperature occurs when large quantities of natural gas are supplied and the consumption of blast furnace gas is reduced. A hard torch forms, the effect of which on the high-temperature surface of the cage leads to overheating and melting of the ingots.

 Maintaining an unreasonably high basic ratio of blast furnace and natural gas costs when heating ingots with a low initial temperature causes a decrease in thermal power and a decrease in heat transfer to the metal. The duration of the temperature increase increases, which leads to a decrease in productivity and excessive consumption of fuel.

 The aim of the invention is to improve the quality of heating and reduce specific fuel consumption.

1-

где Т_п - температура слитков на посаде, ^оС;
Т_м - требуемая температура нагрева слитков, ^оС.The goal is achieved in that in the well-known technical solution, which includes raising the temperature in the well at constant heat output and holding at the temperature of languishing with decreasing fuel supply, the ratio of the costs of natural and blast furnace gases when the temperature rises depends on the heat content of the planted ingots and is established from the dependence:
Q = (0.3-0.4)

1-

where T _p - the temperature of the ingots in the village, ^about C;
T _m - the required temperature of the ingots, ^about C.

 The presence of these distinctive features from the prototype of the signs indicates the conformity of the proposed technical solution to the criterion of "Novelty."

 Since the claimed combination of essential features allows us to achieve the goal due to distinctive features, the present invention meets the criterion of "Positive effect" by the presence of a difference in the results when using it and the prototype.

 To determine the conformity of the claimed technical solution to the criterion of "Inventive step", a search was conducted on the scientific and technical literature and patent documentation. Since there are no known technical solutions with similar features that perform the claimed function, the claimed technical solution meets the criterion of "Inventive step".

 Improving the quality of heating and reducing specific fuel consumption is due to the differentiated choice of the basic ratio of the consumption of natural and blast furnace gases, depending on the initial thermal state of the ingots.

 Raising the temperature of hot posad ingots in a gentle mode with a reduced consumption of natural gas prevents melting of the metal overheating, helps to equalize the temperature field in the working space and ensure the required temperature of all ingots at the output.

 The supply of an increased amount of natural gas when landing ingots with a low initial temperature in the well provides a forced rise in temperature in the working space to the control, a reduction in the total duration of heating, an increase in productivity, and a decrease in specific fuel consumption.

 The method is as follows.

1-

После посада и закрытия крышки колодца осуществляют подачу постоянного количества доменного и природного газов из расчета а м³природного газа на 1 м³ доменного. По достижении контрольной температуры постепенно снижают подачу топлива, осуществляя выдержку в течение заданного времени при температуре томления. По ее окончании производят выдачу нагретых слитков в прокат.When ingots of arrived melting are planted in a well, depending on the time elapsed from casting to stripping and from stripping to planting, the temperature of the metal at the planting T _{p is} determined from graphs or tables. The measurement of T _p, if necessary, can also be performed using a pyrometer. According to the technological design, depending on the steel grade, the required ingot heating temperature T _{m is set} and the required (base) ratio of the costs of natural and blast-furnace gases is calculated according to:
Q = (0.3-0.4)

1-

After planting and closing the lid of the well, a constant amount of blast furnace and natural gases is supplied at the rate of a m ^{3 of} natural gas per 1 m ^{3 of} blast furnace. Upon reaching the control temperature, the fuel supply is gradually reduced, holding for a predetermined time at the temperature of languishing. At its end produce the issuance of heated ingots for hire.

1-

наблюдается оплавление и перегрев части садки при нагреве слитков горячего посада.With a ratio of greater than 0.4

1-

melting and overheating of part of the cage is observed when heating ingots of hot posad.

1-

из-за неоправданного снижения тепловой мощности и увеличения длительности подъема температуры резко снижается производительность колодца, что ведет к повышению удельных расходов топлива.With a ratio of less than 0.3

1-

due to an unjustified decrease in thermal power and an increase in the duration of temperature rise, the well productivity sharply decreases, which leads to an increase in specific fuel consumption.

In FIG. 1 shows a block diagram of the proposed device; in FIG. 2 is a graph of the temperature of the ingots in the Posad Т _n ^о С to the ratio of the costs of natural and blast-furnace gases.

 The device includes flow sensors 1 - blast furnace gas, 2 - natural gas, 3 - air; secondary consumption devices 4 - blast furnace gas, 5 - natural gas, 6 - air; flow rate adjusters 7 - natural gas - blast furnace gas, 8 - fuel - air; multiplication blocks 9, 10, 11, adder 12, regulators 13, 14, actuators 15, 16, actuators 17 — natural gas flow rate and 18 — air flow rate.

 Blocks (1, 4, 10, 13, 15, 17) are connected in series. The setter 7 is connected to the block 10, and the sensor 2 through the secondary device 5 to the input of the regulator 13. Blocks (5, 9, 12, 11, 14, 16 and 18) are connected in series. The setter 8 is connected to the input of block 11, and the sensor 3 through the secondary device 6 is connected to the input of the controller 14. The output of the secondary device 4 is connected to the input of the adder 12.

 The device operates as follows.

1-

и устанавливают его задатчиком 7. Задатчиком 8 устанавливают требуемый коэффициент расхода воздуха. В блоке 9 умножения устанавливают коэффициент, равный соотношению стехиометрических расходов воздуха на снижение 1 м³ доменного и природного газов.When ingots are planted in a well, the value a = (0.3-0.4) is determined by the temperature of the metal at the site T _p and the required temperature of its heating T _m

1-

and set it by the adjuster 7. The adjuster 8 sets the required coefficient of air flow. In block 9 of the multiplication set the coefficient equal to the ratio of stoichiometric air flow rates to reduce 1 m ³ blast furnace and natural gases.

 After ingots are planted and the lid of the well is closed, the local temperature stabilization system in the working space sets the desired temperature of languishing. In this case, the temperature controller fully opens the control throttle of the blast furnace gas supply.

 The signal from the sensor 1 flow of blast furnace gas through the secondary device 4 enters the multiplication unit 10, where it is multiplied with the signal from the setter 7. At the input of the regulator 13, signals from the sensor 2 of the flow of natural gas through the secondary device 5 and from the multiplication unit 10, where they are compared. The regulator 13 fulfills the control action through the actuator 15 to the actuator 17 for supplying natural gas and adjusts the actual consumption of natural gas with the required ratio established on the master 7.

At the same time, the adder 12 receives signals from the secondary device 4 for the consumption of blast furnace gas and the secondary device 5 after multiplying in block 9 by a proportionality coefficient equal to the ratio of stoichiometric air consumption for burning 1 m ^{3 of} natural and blast furnace gases. The total signal enters block 11, where it is multiplied with a signal from the master 8 of the fuel-air ratio. The controller 14 receives the signal of the required air flow from block 11 and the signal of the actual air flow from the sensor 3 through the secondary device 6. Depending on the size and sign of the difference of these signals, the controller 14 through the actuator 16 controls the actuator of the air supply until the difference signal at the input is eliminated controller 14.

 Upon reaching the languishing temperature, the local control system reduces the flow of blast furnace gas. This decreases the signal from the sensor 1, which through the secondary device 4 is supplied to the input of the multiplication unit 10. In proportion to the decrease in the flow of blast furnace gas, the signal of the set flow rate of natural gas from the output of the unit 10 decreases. The regulator 13, through the actuator 15, covers the regulator 17 for supplying natural gas. The regulation stops when the balance of the signals from the block 10 and the sensor 2 passing through the secondary device 5 is reached at the input of the regulator 13, i.e., when the consumption of natural gas is reduced to a value corresponding to the reduced consumption of blast furnace gas.

 At the same time, the signals from the secondary device 4 and the secondary device 5 are reduced through block 9 at the inputs of the adder 12, which leads to a decrease in the total signal at the input of the multiplication unit 11. The signal to reduce the air supply comes from block 11 to the regulator 14, which, using the actuator 16 and the actuator 18, reduces the air supply for combustion.

PRI me R. Pilot tests of the method were carried out on heating wells NN 15 and 16 with the upper burner of the Blooming-3 workshop of the Krivorozhstal metallurgical plant. Well heating with blast furnace and natural gas. The consumption of blast furnace gas with a fully open control choke 3600 m ³ / h, the calorific value of 3.6-3.9 kJ / m ³ . The minimum consumption of natural gas is 1044 m ³ / h, the calorific value of 33.7-33.9 kJ / m ³ .

1 -

= 0,22 . После окончания посада и закрытия крышки колодца осуществляли подачу 3600 м³/ч доменного газа и 3600 x 0,22 = 792 м³/ч природного газа, стабилизируя эти расходы до окончания периода подъема температуры в течение 4,5 ч. По достижении температуры томления (1300^оС) стабилизировали температуру в колодце в течение 2 ч 15 мин при постоянном уменьшении подачи топлива.10 ingots of semi-quiet steel weighing 12.5 tons each were planted in the well. The graphs promoting compositions was determined in the suburb ingots temperature T _n = 470 ^{° C} and technological instructions required heating metal temperature T _m = 1250 ° ^C was calculated basic value for natural gas and blast spending a = 0,3

1 -

= 0.22. After planting and closing the lid of the well, 3600 m ³ / h of blast furnace gas and 3600 x 0.22 = 792 m ³ / h of natural gas were supplied, stabilizing these costs until the end of the temperature rise for 4.5 hours. (1300 ^о С) stabilized the temperature in the well for 2 h 15 min with a constant decrease in fuel supply.

The temperature of the ingots at the output was 1250-1260 ^о С, there was no melting of the metal surface, the well productivity was 14.8 t / h, specific fuel consumption was 83.3 kg. at. t / t

 The heating parameters of similar cages at various ratios of the costs of natural and blast furnace gases by the proposed method and the known method are shown in the table.

 In FIG. 2, the region of the working ratios of natural and blast-furnace gas flow rates is shaded, obtained by heating the melts of semi-quiet steel (ingot mass 12.5 t) and boiling steel (ingot mass 10.5 t) with different ingot temperatures at the landing.

 A comparative analysis of the data shows that the use of the proposed method in comparison with the prototype allows for the conditional heating of the metal at different temperatures of ingots, prevent melting and return of the ingots due to underheating of the metal, and reduce specific fuel consumption by 4-5%.

Claims (1)

 METHOD FOR HEATING INGOTS IN A HEATING WELL, including raising the temperature in a well at constant heat output and holding at a temperature of languishing with a decrease in fuel supply, characterized in that during the heating of the metal, the gas flow ratios in a two-component gas mixture are determined in accordance with the temperature of the ingots and change according to. a = (0.3 - 0.4) (1 - T _p / T _m ),
where T _p - the temperature of the ingots in the village, ^o C;
T _m - the required temperature of the ingots, ^o C.

Images