RU2241764C1 - Method for regulating of fuel consuming rate for dispensing of fuel into blast furnace tuyeres - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method involves measuring total consumption of fuel additive for blasting process and fuel consumption for each tuyere and providing regulation thereof; additionally measuring cooling water flow rates and temperature differences in water supplying and water discharge pipelines in each tuyere; calculating heating load required for cooling of each tuyere upon interruption of air supplying process and during air supplying process; setting fuel consumption rate for each tuyere in accordance with predetermined dependence.

EFFECT: increased efficiency and reduced consumption of coke.

1 dwg, 1 tbl, 1 ex

Description

The invention relates to ferrous metallurgy, in particular to blast furnace production, and specifically to the regulation of fuel consumption by tuyeres of a blast furnace.

Known methods for controlling the flow of gaseous fuel by the tuyeres of a blast furnace, including measuring the pressure of the blast on the inlet to each tuyere, determining the flow rate of hot blast on each tuyere by the absolute value [RU No. 21115741, IPC С 21 В 7/24, 1998] or differential pressure [SU No. 1010135, IPC С 21 В 7/24, 1983], measured between two sections of a specific tuyere device, and the corresponding regulation of the flow of gaseous fuel.

None of these methods takes into account differences in the distribution of resistances and other important gas-dynamic characteristics, for example, in the nozzle of a tuyere device, in an annular air duct, in the circuit of wiring and supplying enriched blast to the lance cavity.

A disadvantage of the known methods is that the different pulse paths and the distances to the input unit do not allow for correct calibration of the sensor readings on the working furnace, and the pressure in the knee of the tuyere device depends not only on the flow rate of the blast, but also on the temperature, oxygen content in the blast and a number of geometric parameters of the gas path. The industrial implementation of these methods is necessarily accompanied by a periodic shutdown of the pulse paths for their prevention or replacement, which leads to a complete shutdown of the corresponding control systems. With significant operating costs for instrumentation and control circuitry, the reliability and accuracy of these methods for determining the distribution of blast by tuyeres is low.

The disadvantage of the uniform distribution of the fuel additive over the tuyeres of the blast furnace is that the virtually uneven distribution of blast over the tuyeres entails significant deviations in the combustion of the injected fuel and coke around the circumference of the furnace, as well as in the thermal state of the tuyere foci.

Closest to the claimed method in terms of technical nature and the achieved effect is a method of controlling fuel consumption by tuyeres of a blast furnace depending on temperature differences of cooling water at the nozzle heads [SU No. 1765177, IPC С 21 В 7/24, 1992]. The method necessarily involves aligning the hydraulic resistance of the pipelines for supplying cooling water.

The disadvantage of this method is that it does not take into account heat transfer from the tuyere to the nozzle head, which affects the temperature difference of the cooling water, and the requirement to equalize the hydraulic resistance of the pipelines is almost impossible to fulfill.

The technical result of the invention is to reduce the consumption of coke by reducing the difference in the burning rate of adjacent tuyeres, reducing the circumferential unevenness of the thermal state of the tuyere foci.

The specified technical result is achieved by the fact that in the method of controlling fuel consumption by tuyeres of a blast furnace, including measuring the total consumption of fuel additive to the blast, fuel consumption on each tuyere and its regulation, additionally measure the flow rates and temperature differences of cooling water in the supply and exhaust pipelines of each tuyere calculate the thermal load on the cooling of each lance Q _n (i) during periods of the cessation of the supply of blast and Q _o (i) in the periods of the presence of blast in them and set the fuel consumption for each lance in accordance with the dependence:

where i is the tuyere number;

n is the number of open tuyeres;

V _TD (i) - fuel additive consumption for the i-th lance, kg / min;

Q ₀ (i) is the thermal load on the cooling of the i-th lance in the presence of blast in it, kW;

Q _n (i) is the thermal load on the cooling of the i-th lance in the absence of blast in it, kW;

V _TD - total fuel additive consumption for all tuyeres, kg / min.

The regulation of fuel consumption for each tuyere of a blast furnace is carried out according to the proposed method as follows.

A mixture of atmospheric blast and process oxygen, heated to a high temperature, enters the tuyere devices. To cool the tuyeres, water is used, which is pumped through the inlet pipe into the cavity between the inner and outer “glasses”. At the inlet and outlet pipelines, flow and temperature difference meters of the cooling water are installed. A diagram of the tuyere of a blast furnace, its surroundings, and the structure of heat fluxes is given below. The lance serves as a calorimeter as shown in the diagram (Figure 1) as follows: heat load Q ₀ determined with an accuracy of measurement costs _VC V = V _OUT and the temperature difference ΔT _B = T _OUT -T _BX cooling water heat transfer due to energy Q _P to the outer “cup” of the tuyere from the lining of the furnace, charge and tuyere source Q _Ф , as well as the energy Q _D transmitted by high-temperature blast to the inner “cup” of the tuyere.

where ƒ (Q _Д , Q _П , Q _Ф ) - heat transfer function, kW;

Q _O - thermal load, kW;

c _B is the heat capacity of water, kJ / kg · K;

ρ _B is the density of water, kg / m ³ ;

V _B - water flow, m ³ / s;

ΔT _B - water temperature difference, K.

Initially, it is necessary to determine the component Q _P - the heat load due to heat transfer due to the contact of the tuyere with the lining and with heated materials in the furnace, provided that there is no heat transfer per tuyere from the blast and the tuyere source, i.e. О _Д = 0 and Q _Ф = 0. There are two possibilities for this in an industrial environment. The first, at the initial moment of stopping the furnace after a full stroke for all tuyeres, the blast is removed (Q _D = 0, Q _Ф = 0) and the heat flux Q _P (i) Q _O (i) is the Second, for the closed one i-th tuyere at full speed of the furnace, its heat load Q _P (i) = Q _O (i). Experimental studies have shown that the difference in the readings of the integral value Q _P for these two options fits into 1%.

Next, the difference Q _O (i) -Q _P (i) is determined, which characterizes the amount of heat transferred by the gas to the inner “glass” of each i-th lance. Its value is determined at full speed, as a component of the heat flux proportional to the product of the blast flow rate by its temperature. Since the total heating of the blast is carried out in air heaters, it was experimentally established that the temperature difference of the blast on adjacent tuyeres is insignificant, while the difference in its tuyere expenditures is very significant. On individual blast furnaces, the uneven distribution of blast by tuyeres can reach 30–40%. Assuming that all lances have the same structural characteristics and material, the proportion follows from the above:

Where

i is the tuyere number;

n is the number of open tuyeres;

Q _O (i) is the thermal load on the cooling of the i-th lance in the presence of blast in it, kW;

Q _P (i) is the thermal load on the cooling of the i-th lance in the absence of blast in it, kW;

V _D (i) is the flow rate of the blast on the i-th lance, m ³ / min.

From equation (3) it is possible to determine the flow rate of the blast V _D (i) for the known other quantities.

In practice, in order to maintain the carbon burning rate at the tuyeres С _Ф and the theoretical combustion temperature Т _Ф at a certain level of values, the ratio of the total fuel additive (V _ТД ) and blast (V _Д ) consumption for a blast furnace is fixed:

where α is the specific fuel consumption, kg / m ³ blast.

In the proposed method, condition (4) is established for each of the tuyeres in order to align the values of C _f (i) and T _f (i) around the circumference:

where V _TD (i) is the consumption of fuel additives to the blast on the i-th lance, kg / min

As a fuel additive can be used pulverized coal, fuel oil, natural gas, coke oven gas, water-oil mixture. In practice, it is more convenient to indicate the consumption of pulverized coal fuel oil and fuel oil in kg / min, and gaseous fuel in m ³ / min. The volumetric gas flow rate - m ³ / min - can be converted into mass flow rate - kg / min - through a known gas density. For example, for natural gas with a density ρ _GHG .

where V _TD , V _G - natural gas consumption, respectively, in dimension, kg / min, m ³ / min;

ρ _GHG - the density of natural gas is 0.76 kg / m ³ .

An example of the practical implementation of the method of controlling the flow of natural gas.

The table shows an example of determining heat loads and regulating the flow of natural gas for each of the 16 tuyeres at DP No. 1 of OJSC Severstal by the proposed method.

On the inlet and outlet pipelines of the tuyere cooling system of DP No. 1, cooling water flow meters and sensors for measuring its temperature difference at each tuyere were installed.

Let us consider one of the periods of operation of DP No. 1, which was characterized by an even course with a blast flow rate of 2025 m ³ / min, natural gas flow rate - 14560 m ³ / h, blast temperature - 1196 ° С, oxygen content in the blast - 23.5%. For the specified period of operation, the thermal loads Q _O (i) amounted to the values given in the first row of the table.

When transferring the furnace from full speed to shutdown, the heat loads Q _P (i) were determined for each lance at the completely removed flow rates of blast, natural gas and process oxygen (see row 2 of the table). Subsequently, if the supply of blast and additives to a separate lance was cut off, the values of Q _P (i) were refined for the closed lance at full speed. The heat load on a specific tuyere closed at full speed did not practically differ from the heat load on it at the initial moment of a complete stop and closure of all tuyeres.

The difference in thermal loads due to the influence of the distribution of blast consumption by tuyeres is presented in row 3, and its relative value is in row 4 of the table.

Recommended by the proposed method, the flow rate of natural gas for each lance is shown in row 5 of the table.

As a result of establishing the consumption of natural gas for each tuyere according to the proposed method, the differences in the coke burning rates and theoretical combustion temperatures for adjacent tuyeres were reduced by 10%, which ultimately reduced the specific consumption of dry coke by 0.9 kg / t of pig iron.

Claims (1)

A method for controlling fuel consumption by tuyeres of a blast furnace, including measuring the total consumption of fuel additive for blasting, fuel consumption on each tuyere and its regulation, characterized in that they additionally measure the costs and temperature drops of cooling water in the supply and exhaust pipelines of each tuyere, calculate thermal loads for cooling each lance Q _n (i) - during periods of stopping the supply of blast in them and Q _o (i) - during periods of the presence of blast in them and set the fuel consumption for each lance in accordance with the dependence tew

where i is the tuyere number; n is the number of open tuyeres; V _TD (i) - fuel additive consumption for the i-th lance, kg / min; Q _o (i) is the thermal load on the cooling of the i-th lance in the presence of blast in it, kW; Q _n (i) is the thermal load on the cooling of the i-th lance in the absence of blast in it, kW; V _TD - total fuel additive consumption for all tuyeres, kg / min.