RU2081818C1 - Method for controlling phosphorus production process in electrothermic furnace - Google Patents

Abstract

FIELD: electrothermics. SUBSTANCE: electrical and process parameters of operating furnace are maintained by introducing adjustments into reductant doses with due consideration for relationship existing between P₂O₅ content in slag and electrical parameters. Proposed method also takes into account errors in metering-out other components, i.e. phosphorite and quartzite, and eliminates effect of transition process taking place along "feedstock-slag" path. EFFECT: method offers greater flexibility in controlling phosphorus production process. 1 tbl, 1 dwg

Description

 The present invention relates to the field of electrothermia, in particular to methods for controlling the process of producing phosphorus in an electric furnace.

 Known methods of controlling the operating mode of a phosphoric electric furnace, which are based on various methods of regulating the electrical mode.

 The main factors disturbing the electric mode are the inconsistency of the resistance of the sub-electrode space, determined by the different conditions of the charge gathering and its composition, as well as fluctuations in the supply voltage.

 Compensation of these disturbances is carried out by moving the electrodes or switching the voltage steps of the furnace transformer (Automatic control system for the electric regime of ore-thermal electric furnaces. M. NIITEKHIM, 1978).

 A common disadvantage of the known methods for controlling the electric mode is the low accuracy of control due to the presence of statism, since the different position of the electrode control element can correspond to the same value of the adjustable parameter. This leads to a deviation of the technological mode from the optimum.

 In addition, this control does not take into account the influence of technological factors (composition of the charge, granulometry of the reducing agent, electrode position, carbon mode of the bath, etc.) on the phosphorus production process.

 In electrothermal processes, multicomponent mixtures containing various impurities are usually used. Therefore, in addition to the target reaction, side-effects corresponding to the target process are inevitable.

So, in the production of phosphorus, the target reaction
Ca ₃ P ₂ O ₈ + 5C + nSiO ₂ _ → 3CoO + nSiO ₂ + P ₂ +500 (1)
inevitably accompanied by reduction of O ₂ . The result is a by-product of the electric sublimation of phosphorus ferrophosphorus, enriched in silicon, which is used in ferrous metallurgy as a component in the production of various alloys.

A known method for producing yellow phosphorus, including the dosage of the components of the initial charge (phosphorite, quartzite, coke), loaded into the furnace, and monitoring the content of P ₂ O ₅ in the slag. At the same time, the ratio of phosphate-silicon raw materials and carbonaceous material (reducing agent) is selected only for such reduced oxides as P ₂ O ₅ , Fe ₂ O ₅ , N ₂ O, CO ₂ , and an additive of 1 or more is taken for the remaining unaccounted reactions up to 5 from the calculated stoichiometric amount of carbon material. The adjustment of the mixture is carried out taking into account the content of P ₂ O ₅ in the slag ("Technology of phosphorus", under the editorship of VA Ershov and VN Belova Chemistry, 1979, S. 144-146).

The accuracy of the dosage and adjustment of the charge by this method is low, therefore, the content of P ₂ O ₅ in the slag ranges from 0.4 to 5%. As a result, either the reductant is not enough in the furnace bath or excess carbon accumulates, which makes it difficult to discharge slag, and slows down charge, complicates the operation of the furnace, because additional washing of the bath is required due to its carbonization, resulting in significant losses of phosphorus with slag, and, as a result, the release of phosphorus is reduced. In addition, there is no account of the relationship between the furnace power and the content of P ₂ O ₅ in the slag, which does not allow to maintain the content of P ₂ O ₅ in the slag depending on the operating power of the furnace.

The absence of a relationship between the residual content of P ₂ O ₅ in the slag and the electrical parameters of the melting process reduces the quality of regulation and reduces the technical and economic performance of the furnace due to the increased energy consumption.

A known method of controlling the process of producing phosphorus (ed. Certificate N 922066, BI N 15, 1982), including monitoring the dosage and loading of the initial charge, regulating the electric mode of the electric furnace by moving the electrodes and / or switching voltage levels, measuring the energy consumption and temperature under furnace lid, monitoring the content of P ₂ O ₅ in the slag and the level of raw phosphorus in the condensation baths, determining the actual phosphorus produced over a certain period of time, comparing the obtained actual parameters with data, and in case of deviation, they change the electric mode and adjust the composition of the initial charge to restore the optimal parameters.

 The aim of the invention according to ed. testimonial. N 922066 is increasing the yield of the finished product and saving energy.

 This goal is achieved due to the fact that the productivity of the electric furnace by phosphorus is determined not by indirect parameters, but by direct means: by the amount of phosphorus formed in the condensation baths. This allows you to quickly determine the actual specific energy consumption and control the operation of electrostatic precipitators, i.e. sludge formation process. The output of phosphorus is increased by reducing losses of phosphorus with sludge, and energy savings by maintaining the optimal specific energy consumption.

The adjustment of the charge is carried out in a known manner by deviating the value of P ₂ O ₅ in the slag compared to the regulatory value, which is 1.5-2.0%. Such adjustment is not accurate and does not exclude the violation of the carbon mode of the electric furnace.

 The position of the electrode, i.e. the distance under the electrode is not controlled, but change it only depending on the deviation of the specific energy consumption from the optimum. However, the position of the electrode depends on many factors: the electric and carbon conditions of the bath, the state of the electrodes, the amount of melt in the bath, etc.

 In addition, the disadvantages include the fact that the zone structure of the furnace bath is not taken into account, according to which the end of the electrode should be in the carbon zone.

где r средний размер кусков углеродистого материала, см;
C_к концентрация пятиокиси фосфора в шлаке,
d диаметр электрода, см;
P_a активная мощность электропечи, МВт.A known method of controlling the operation of an electric furnace for the production of phosphorus by ed. St. N 769268, BI N 37.1980. In accordance with this method, the dosage of the initial charge is carried out similarly to that described, but taking into account the granulometric composition of the reducing agent, and the average size of the pieces of carbon material is determined by the empirical formula:

where r is the average size of the pieces of carbon material, cm;
C _{to the} concentration of phosphorus pentoxide in the slag,
d electrode diameter, cm;
P _{a the} active power of the electric furnace, MW.

Maintaining the electrical mode and monitoring electrical parameters (electrode current, voltage and phase resistance, etc.) are carried out by moving the electrodes and / or switching the voltage steps of the furnace transformer, and the movement of the electrode is limited so that the ratio of the height of the sub-electrode space to the diameter of the electrode It was maintained in the range of 0.65-0.90. The adjustment of the charge loaded by the value of the content of P ₂ O ₅ in the slag is carried out by changing the electrical resistivity of the material, i.e., the amount and granulometry of the reducing agent.

 The essence of the known control method is to regulate the electric mode in combination with technological parameters, taking into account the zone structure of the furnace bath.

 Due to the control of the carbon regime, phosphorus losses with sludge are reduced, however, the accuracy of the charge adjustment is insufficient.

A common disadvantage for all known methods for producing phosphorus is that the dosing of charge materials, in particular the weight ratio of the reducing agent and phosphorite in the charge, is carried out regardless of the capacity of the furnaces. The power of the furnaces quite often and for a long time varies from maximum to minimum for a given unit, based on the state of the entire production line, the number of working electrostatic precipitators, the state of condensation systems, restrictions on the supply of electricity, charge, etc. Authors' studies conducted on existing furnaces , allowed us to establish that if, at the maximum (certified) power of the furnace, for normal process control, the residual content of P ₂ O ₅ (P ₂ O _5ost ) in the slag needs to be maintained more than 1 P ₂ O ₅ ( 1-2% according to the regulations), while reducing the power of the furnaces, the normal technological mode can be maintained at 0.3-1.0 P ₂ O ₅ . Consequently, if the furnace power decreases against the maximum, then the preservation of residual P ₂ O ₅ contents in the slag of more than 1% leads to unnecessary phosphorus losses.

 The closest in technical essence and the achieved result to the alleged invention is a method of controlling the process of producing phosphorus in an electrothermal furnace according to ed. St. N 1288155, published 07.02.87, BI N 5.

 The essence of the method is as follows.

 During the operation of the electric furnace, the mixture is analyzed and dosed, the specified electrical mode is maintained by changing the position of the electrodes and switching the voltage levels of the furnace transformer.

Periodically adjust the amount of reducing agent in the mixture according to the formula
Y = Y _o + 4,22 • 10 ^-3 W (C _f -C ₃ ) + (α _pr -α _f ) Q _Fe (3)
where Y _{o the} amount of reducing agent, as determined in the previous period;
Ш amount of slag;
With _{f the} content of P ₂ O ₅ in the slag;
C _s optimal content of P ₂ O ₅ in the slag, determined by the formula C ₃ = to • P $\genfrac{}{}{0ex}{}{\text{P}}{\text{a}}$ where P _{a is the} actual average furnace power; k and p coefficients, depending on the size of the furnace;
α _CR , α _{f the} coefficients corresponding to the predicted and actual silicon content in the ferrophosphorus;
Q _{Fe is} the iron content in the initial charge.

 All parameters included in the formula are averaged over a given period of time.

где п₁ коэффициент, зависящий от номинальной мощности печи МВа;
I_эр- рабочий ток электрода, КА.One of the limiting factors in the implementation of the method is the maximum permissible value of the electrode current, which is determined by the formula

where n is ₁ coefficient depending on the rated power of the furnace MVA;
I _er - working current of the electrode, KA.

This invention takes into account the relationship of electrical (current, power) with technological parameters (content of P ₂ O ₅ in slag and P ₄ in ferrophosphorus), which allows to increase the extraction of phosphorus, but does not take into account the complexity of the object, which is an ore-thermal furnace, therefore it does not provide optimal quality regulation.

 In addition, the graphical dependences of the phosphorus content in ferrophosphorus on the silicon content in it do not have sufficient reliability, since it is impossible to accurately determine the amount of iron in the initial charge, because it is contained in each component.

 In the developed approach to the synthesis of the control algorithm, the following features of the furnace as a controlled object by technological parameters should be taken into account: instability of the chemical composition of the charge and inaccuracy of the chemical. analyzes; transport delay of the furnace as a capacitive link.

где Т постоянная времени, характеризующая экспоненциальное запаздывание процесса возгонки;
A₀, A₁, B постоянные коэффициенты, принятые по данным материального баланса и отражающие влияние параметров X, Y, u на переходный процесс;
τ постоянная времени, характеризующая транспортное запаздывание по каналу шихта шлак;
x(t) P₂O₅ шл (t) содержание P₂O₅ в шлаке регулируемый параметр;
u Q_c/Q_ф управляющее воздействие;
y(t-t) содержание P₂O₅ в шихте возмущение.Given the above features of the furnace as a managed facility in terms of technological parameters, its model can be represented as

where T is the time constant characterizing the exponential delay of the sublimation process;
A ₀ , A ₁ , B are constant coefficients, taken according to the material balance and reflecting the influence of the parameters X, Y, u on the transition process;
τ is the time constant characterizing the transport delay along the channel of the slag mixture;
x (t) P ₂ O ₅ sl (t) content of P ₂ O ₅ in the slag adjustable parameter;
u Q _c / Q _f control action;
y (tt) the content of P ₂ O ₅ in the charge perturbation.

 The need to take into account the data on the composition of the charge in the control algorithm is determined by the following considerations.

It has been experimentally established that in the bath of a phosphoric furnace a non-expendable coke layer is formed, which is in direct contact with the liquid phase. The completeness of phosphorus reduction depends on its height. Ceteris paribus, each value of the layer height corresponds to a certain content of P ₂ O ₅ in the slag. The height of the layer remains constant as long as there is a balance in the sub-electrode space between the arrival of coke from the charge and its consumption for the main and secondary processes.

 Imbalance leads to a transitional regime in which self-regulation of the height of the coke layer occurs.

A change in the content of P ₂ O ₅ in phosphorite by 1 or a change in the consumption of phosphate or coke by 4.5% leads to a change in the height of the coke layer by about 0.3 m per day, which is comparable with the permissible zone of movement of the electrode holder (0.6 0.8 m).

 Errors in the preparation of the charge can bring the furnace out of operation within one to two days.

The technical task of the proposed invention is to better control the process of sublimation of phosphorus due to more accurate management of the carbon mode, taking into account the relationship of the controlled parameter of the content of P ₂ O ₅ in the slag with the electrical parameters and features of the phosphorus furnace as a pronounced capacitive-inertial control object.

The technical result is achieved due to the fact that by the method of controlling the production of phosphorus in an electrothermal furnace, which includes analysis and dosage of the charge components, adjusting the electrical mode by maintaining the specified values of the electrode current and operating power of the furnace, moving the electrode and switching voltage levels of the furnace transformer, determining P ₂ O ₅ in the slag, averaging these parameters over a specified interval of time, comparing the obtained values with preset correction amount and restores To a batch, a predetermined amount of the electrode current value determined in consideration of the operating power of the furnace and the content of P ₂ O ₅ in the slag, averaging P ₂ O ₅ in the slag is carried out considering the delay time on the channel charge slag control electrode position in the carbon area, and the number reducing agent in the mixture is adjusted according to the formula
v _k = Φ _kz + ΔΦ _k + ΔΦ _days (6)
where Φ _{KZ the} originally specified amount of coke in the charge;
ΔΦ _{to the} correction value of coke by the deviation of P ₂ O ₅ in the slag;
ΔΦ _day the daily value of the change in the dosage of coke according to the analysis of raw materials

Studies of the dynamic characteristics of the phosphorus furnace, in particular the transition regime in the carbon zone with a stepwise change in the dosage of the reducing agent and the constant weight composition of the remaining components of the charge, showed that the content of P ₂ O ₅ in the slag varies exponentially.

где P_cτ средняя активная мощность за время транспортного запаздывания, т/м³;
q удельный расход шихты, т/т;
W_у удельный расход электроэнергии, мВтч/т;
V_б объем бункеров, м³;
V_t объем течек, м³;
a угол естественного откоса шихты;
n число труботечек;
d_к диаметр конуса шихты, м;
d_т диаметр течки, м;
H высота ванны печи, м;
H_р.з. высота углеродистой зоны, м;
H_т заглубление течки под сводом печи, м;
H_шл высота уровня шлака от пода, м;
D_в диаметр ванны печи, м;
n₁ число электродов;
d_э диаметр электродов, м.The gain (K _y ) of the influence of the input parameter on the output parameter was determined by the methods of mathematical statistics and K _y = 18.7, and dynamic characteristics of the process were obtained based on the regulated content of P ₂ O ₅ = 1.5-1.7%
To control the feedback process, where the content of P ₂ O ₅ in the slag is used as the feedback parameter, it is necessary to know the inertia of the furnace unit, i.e. the passage of the charge from the weight batchers to the carbon zone, where there is a process of phosphorus reduction. The time of transport delay was determined by the results of active experiments and compared with the mathematical description of the process of transport delay:

where P _{cτ is the} average active power during the transport delay, t / m ³ ;
q specific charge consumption, t / t;
W _u specific power consumption, mWh / t;
V _{b the} volume of bins, m ³ ;
V _{t the} volume of leaks, m ³ ;
a angle of repose of the charge;
n number of tubules;
d _{to the} diameter of the cone of the charge, m;
d _t diameter estrus, m;
H furnace bath height, m;
H _rz carbon zone height, m;
H _t deepening estrus under the arch of the furnace, m;
H _{shl the} height of the slag level from the hearth, m;
D _{in the} diameter of the furnace bath, m;
n _{1 is the} number of electrodes;
d _{e the} diameter of the electrodes, m

где ΣW_п суммарное количество электроэнергии, потребленное печью за равные промежутки времени от предыдущего изменения дозировки шихты, МВтч;
ΣQ_ш суммарный расход шихты за те же промежутки времени от предыдущего изменения дозировки шихты, т;
A эмпирический коэффициент, определенный для конкретной фосфорной печи, причем для печей РКЗ-72Ф и РКЗ-80Ф A 520 70 Н_р.з., а для печей ФКЗ-48Ф A 340 50 H_р.з..For each specific furnace size and type of raw material (piece, sinter), after a series of transformations and substitution of geometric dimensions, the expression of the transport delay time will take the form

where ΣW _{p is the} total amount of electricity consumed by the furnace for equal periods of time from the previous change in the dosage of the charge, MWh;
ΣQ _{W the} total charge consumption for the same time intervals from the previous change in the dosage of the charge, t;
A empirical coefficient determined for a particular phosphoric furnace, and for RKZ-72F and RKZ-80F furnaces A 520 70 N _r.z. , and for furnaces FKZ-48F A 340 50 H _r.z. .

As studies have shown, measurements when the furnace stops, the fluctuations in the height of the carbon zone (H _rz ) are 0.5-1.5 m (average 1 m), which corresponds to the fluctuation of P ₂ O ₅ in the slag within 0.5-1, 7.

The mismatch value of P ₂ O ₅ in the slag corresponds to the range of values of K ₁ 0,92 1,8.

The transport delay time is usually expressed by the amount of electricity, i.e. P _cτ τ _s
On the other hand, it is required to ensure sufficient accuracy of dosage adjustment over time, i.e. to know the moment when the charge from the previous change in the dosage of the reducing agent reached the carbon zone, and the change in the content of P ₂ O ₅ in the slag is associated with this effect, and is not the result of a change in the state of the bath.

The charge consumption mainly depends on the amount of electric energy introduced into the furnace, which is confirmed by a high pair correlation coefficient (0.89), obtained by daily indices and characterizing the reliability of these bonds. This dependence is described by the equation
Q _w 1.208 W _n 229.5, (9)
Where
Q _W charge charge, t / h;
W _p power consumption, kWh.

где n число бункеров;
γ насыпная плотность шихты (1 т/м³), состоящей из агломерата, кварцита и кокса с массовым соотношением 86:6:8;
S площадь бункера (3,3 x 1,5 4,95 м²).With a furnace capacity of the RKZ-80F type equal to 72 MW, the charge consumption (when using an agglomerate) is 72 t / h, the linear average rate of charge displacement v into the furnace bath from one hopper is (mm):

where n is the number of bins;
γ bulk density of the mixture (1 t / m ³ ), consisting of agglomerate, quartzite and coke with a mass ratio of 86: 6: 8;
S hopper area (3.3 x 1.5 4.95 m ² ).

где α отношение скорости схода шихты по центральной течке к линейной средней скорости равно 1,65.At such a speed and a distance from the upper to lower level H equal to 4000 mm, the charge descent time t (h) from the most rapidly emptying bins in the absence of charge supply is determined

where α the ratio of the speed of the mixture in the central estrus to the linear average speed is 1.65.

 Therefore, the exponential delay along the channel of the slag charge will be 150 MWh for the RKZ-72F and RKZ-80F furnaces, and 100 MWh for the RKZ-48FM kiln, respectively.

Based on studies conducted on industrial furnaces during testing and analysis of their operation data with an optimal range of active resistance of the phases of the furnace bath R _af = 3.0-3.5 MΩ, the dependence of the electrode current on the operating power of the furnace and the content P ₂ O ₅ in the slag, which has the form
I _e a C _k + b P _a , (11)
where P _{a is the} current value of the active power of the furnace, MW;
C _{to the} current value of the content of P ₂ O ₅ in the slag,
I _{e the} average working current of the electrode, kA.

Given the zone structure of the furnace bath when regulating the carbon regime, it is necessary that the electrode is in it. For this purpose, it is recommended to maintain the electrode distance under in the range of H _ep = 0.65-0.90 d _e (electrode diameter), but since the height of the working (carbon) zone varies over a wide range (0.5-1.5 m), therefore, in the proposed control method, the electrode position in this zone is controlled by comparing the actual electrode distance under (H _ep ) with a predetermined one, which is determined from the following premises.

Based on the operation of phosphorus furnaces, it is known that the height of the slag zone (H _sl ) is in the range of 40-60 cm (average 0.5 m). The set value of H _ep = H _R. + 0.5 (m).

Significant differences of the proposed control method from the prototype are
determination of transport and exponential delays of a phosphoric furnace through a slag charge channel;
averaging the content of P ₂ O ₅ in the slag, taking into account the result;
determination of the working current of the electrode according to an empirical formula that takes into account its dependence on the working power and the content of P ₂ O ₅ in the slag;
the adjustment of the amount of reducing agent in the mixture according to the deviation of the average content of P ₂ O ₅ from the given taking into account the dosage error of phosphorite due to fluctuations in the content of P ₂ O ₅ .

 From the analysis of the prior art, a similar set of features has not been established for controlling the process of producing phosphorus, in particular for controlling the carbon mode of the furnace, therefore it can be concluded that the proposed technical solution meets the criteria of patentability "novelty" and "inventive step".

The compliance with the "applicability" criterion can be judged by the example of the implementation of the proposed control method on a phosphor furnace RKZ-48F or RKZ-80F, since they are most widely used in the phosphorus industry and work on a piece and sinter. Their maximum operating power is respectively 45 and 65 MW. The geometric dimensions of the RKZ-72F or RKZ-80F phosphor furnace are as follows: electrode diameter d _e 170 cm; the diameter of the decay of the electrodes D _p 480 cm; bath diameter D _of 1020 cm; .. H bath height ₅₆₅ cm Structural parameter Z 73 cm Geometrical parameters phosphoric furnace RHM-48FM, respectively, the following: d _e is 140 cm, D _p 400 cm, D ₈₅₀ cm, H _at 420-475 cm.

 The drawing shows a block diagram of a device for implementing the proposed control method.

The device (the electrical part is shown for one phase, it is similar for the other two) contains a bath of a phosphor furnace 1, estrus 2 (one is shown, in fact there are nine, and three are connected in the central estrus), electrode 3, current transformers 4, which are current sensors of the electrode , 5 voltage selector switch for furnace transformer 6, electric mode regulator 7, electrode moving unit 8, block 9 (active energy meter), slag sampler 10, P ₂ O ₅ content meter in slag 11, average and setpoint comparison unit 14 P ₂ O ₅ in the slag, block 15 for adjusting the amount of coke, batchers 16 components of the charge, block 17 for determining the working power of the furnace, a computing device 18 for determining the height of the working (carbon) zone, block 19 for determining the distance of the electrode under, block 20 comparing the actual and target distance electrode under, block 21 sets the distance electrode under. The electric mode controller 7 is a well-known control system of self-propelled guns "Foscar", used on all phosphor furnaces. As a meter 11 of the content of P ₂ O ₅ in the slag, you can use a quantometer or blocks for determining this parameter by viscosity and conductivity, used in the prototype.

The height of the working area (H _rz ), the length of the electrode (d _e ) and the distance of the electrode under (H _ep ) are determined in accordance with the "Methodological recommendations for determining the electrotechnological parameters of phosphoric furnaces". Compiled by Arlievsky M.P. Valkova Z.A. Zhilov G.M. et al. L. LenNIIGiprokhim, 1986 or in accordance with the description of the patent of the Russian Federation N 2007055, registered 01.30.94, op. BI N 2, 1994. Some blocks can be implemented using computers. Computer programs are used in some factories.

 The operation of the device is as follows.

The mixture, consisting of phosphorite, quartzite and coke in the indicated proportions, is prepared in the dosing unit (for RKZ-80F furnaces, the mixture consists of agglomerate, quartzite and coke, but the ratio of the components of the mixture in terms of phosphorite is almost the same). When processing lump phosphorite, the ratio of components: 80-85% phosphorite, 4-6% quartzite and 10-14% coke; bulk density of the mixture of 1.4-1.5 t / m ³ ; Based on the experiment, the transport delay time expressed by the amount of electric power (P _cτ • τ _s ) was assumed to be 650 MWh, and in the processing of sinter, the charge has a bulk density of 0.9-1.0 t / m ³ and P _cτ • τ _s = 350 MW .
The initial dosage of the initial charge was carried out according to the known method described in the book "Technology of phosphorus", ed. Ershova V.A. and Belova V.N. L. Chemistry, 1979, p. 144-146.

 The chemical composition of the charge components (average sample) is given in the table.

The total carbon consumption per 100 kg of phosphorite with some excess from stoichiometry was 12.55 kg, or in terms of coke 12.55 / 0.863 = 14.54 kg. The silicon content in quartzite is 94% i.e. 5 / 0.94 = 5.3 kg of quartzite. Thus, per 100 kg of phosphorite accounts for 14.54 kg of coke and 5.3 kg of quartzite; bulk density of the mixture of 1.5 t / m ³ .

 The set ratios are established on the weighing batchers 16, then on the assembly line the components are mixed, and the mixture is loaded through the furnace bins into the bath of the furnace 1 through estrus 2.

 The initial electric mode of electric sublimation is set in accordance with the "Methodological recommendations" mentioned above.

Let the following parameters be selected: operating power P _a 47.5 MW, power consumption (mains) S 51 MVA, cos Φ 0.915, rms current across three electrodes I _e 66.1 kA, then the line voltage U _{l is} 453 V, i.e. . 34th voltage level. The active resistance of the individual phases was 3.4-3.6 mOhm.

Signals proportional to the indicated parameters, through current sensors (4) and voltage (5), enter the regulator 7, which maintains the specified electrical mode by moving the electrodes (block 8) and / or switching stages (block 5), respectively, with signals F ₁ and F ₂ . After the consumption of a certain amount of electricity, which is recorded by the energy meter (block 9), the slag is released (continuous release is possible). Once a day, ferrophosphorus is produced (with an energy consumption of 1000-1100 MWh). When slag is released once per hour (or less often), its sample is taken by sampler 10, and the content of P ₂ O ₅ in the slag is determined in it by a quantimeter 11 or other express method. The obtained values of the content of P ₂ O ₅ in the slag per shift (6 hours): 1.54; 1.9; 1.78 on the integrator are not averaged, because at the second input of block 12 there is an averaging inhibit signal f ₁ , since the electric energy consumed by the furnace is less than the transport delay, and the furnace operates in transition mode.

In block 14, the actual content of P ₂ O ₅ in the slag is compared with the specified one, which is determined in block 13 by the formula of the prototype, i.e.

Kp = _ks C $\genfrac{}{}{0ex}{}{\text{P}}{\text{a}}$ , (12)
where k 0.3 for furnaces RKZ-72F and RKZ-80F; to 0.07 for RKZ-48F furnaces; respectively, p 0.69 for RKZ-48F and 0.39 for RKZ-72F.

In our example, the set values of C _KZ 0.3 • 4.57 ^0.39 1.1.

If at the output of the comparison unit 14 there is a deviation signal (ΔC _k ), the dosage of the coke is not changed, because at the second input of block 15 there is a ban signal f ₂ , similar to f ₁ for the same reason - the transition mode has not ended.

где A_п постоянная, зависящая от отношения усредненной рабочей мощности к максимальной для каждого вида печи: для фосфорных печей для P_ср ≅ 0,67 P_max A_п 161•10⁴, для диапазона 0,475 P_max ≅ P_ср ≅ 0,67 P_max A_п 187•10⁴, для диапазона 0,41 P_max ≅ P_ср ≅ 0,475 P_max A_п 220•10⁴;
r средневзвешенный размер куска восстановителя, 1,516 см;
P_a усредненная за период рабочая мощность печи, МВт;
С_к остаточное содержание P₂O₅ в шлаке,
D_р диаметр распада электродов, см;
п, п₁ эмпирические коэффициенты, определяемые для каждого типа руднотермических печей и от вида полученного продукта (для фосфорных печей п 0,74, п₁ 0,97).At the same time, in block 18, the height of the working area (H _rz ) is determined according to one of the formulas indicated by the “Methodological recommendations”, for example, according to the adjusted formula

where A _{p is} constant, depending on the ratio of the average operating power to the maximum for each type of furnace: for phosphor furnaces for P _cf ≅ 0.67 P _max A _p 161 • 10 ⁴ , for the range 0.475 P _max ≅ P _cf ≅ 0.67 P _max A _p 187 • 10 ⁴ , for the range 0.41 P _max ≅ P _cf ≅ 0.475 P _max A _p 220 • 10 ⁴ ;
r weighted average size of a piece of reducing agent, 1.516 cm;
P _a averaged over the period the operating power of the furnace, MW;
C _{to the} residual content of P ₂ O ₅ in the slag,
D _{p the} diameter of the decay of the electrodes, cm;
p, p ₁ empirical coefficients determined for each type of ore-thermal furnaces and on the type of product obtained (for phosphor furnaces p 0.74, p ₁ 0.97).

Значения A_п находят из условия

В блоке 19 вычисляется расстояние H_эп (электрод под) по формуле патента РФ N 2007055, а именно
H_эп≠ Brⁿ³H $\genfrac{}{}{0ex}{}{\text{n4}}{\text{рз}}$ R $\genfrac{}{}{0ex}{}{\text{n5}}{\text{a}}$ •d $\genfrac{}{}{0ex}{}{\text{n6}}{\text{э}}$ (14),
где R_Q- активное сопротивление ванны печи на один электрод, nОм;
B эмпирическая постоянная, зависящая от типоразмера печи и получаемого продукта;
п₃, п₄, п₅, п₆ эмпирические коэффициенты.Substituting the corresponding values in the calculation formula, we obtain

The values of A _{p are} found from the condition

In block 19, the distance H _ep (electrode under) is calculated according to the formula of RF patent N 2007055, namely
H _ep ≠ Br ⁿ³ H $\genfrac{}{}{0ex}{}{\text{n4}}{\text{rz}}$ R $\genfrac{}{}{0ex}{}{\text{n5}}{\text{a}}$ • d $\genfrac{}{}{0ex}{}{\text{n6}}{\text{uh}}$ (fourteen),
where R _Q is the resistance of the furnace bath to one electrode, nOhm;
B empirical constant, depending on the size of the furnace and the resulting product;
n ₃ , n ₄ , n ₅ , n ₆ empirical coefficients.

For phosphor furnaces, B = 2.98, n ₃ = 0.38, n ₄ = 0.88, n ₅ = 1.22, n ₆ = 1.35. The remaining parameters in our case are equal: r = 1.516 cm, R _a = 3.6 mOhm, then N _ep 2.98 • 1.516 ^0.38 • 137 ^0.88 • 3.6 ^1.22 • 1.70 ^1.35 130 cm.

The obtained value of H _{ep is} compared in block 20 with the specified value defined in block 21 and equal to H _ep = 137 + 50 = 187 cm.

.Therefore, the electrode is in the working area and is buried in it:

.

т. е. в пределах оптимального значения, поэтому на выходе блока 20 нет сигнала в регулятор 7 на корректировку электрического режима.We check the condition:

i.e., within the optimal value, therefore, at the output of block 20 there is no signal to regulator 7 to adjust the electrical mode.

т.е. меньше 10% поэтому ток электрода остается без изменения.We check the correctness of the choice of the electrode current according to dependence (11), which for the furnace RKZ-72F and RKZ-80F has the form
I _e 111.4-60.4 C _k + 0.99 P 111.4-60.4 • 1.58 + 0.99 • 47.5 63 kA;

those. less than 10%, therefore, the electrode current remains unchanged.

, т. к. расход электроэнергии шихты для печей РКЗ-72Ф и РКЗ-80Ф прямо пропорционален.We determine the actual transport delay of the phosphorus furnace by the formula (8), we obtain

, since the charge energy consumption for furnaces RKZ-72F and RKZ-80F is directly proportional.

Based on the obtained transport delay time, the ban on averaging P ₂ O ₅ in the slag will be lifted only after the furnace consumes 606 MWh of electricity, i.e. 12-13 hours after turning on the furnace, and the first value of the content of P ₂ O ₅ in slag, which will be averaged taking into account the exponential delay, after 3 hours, i.e. finally the transition process from entrance to exit along the slag charge path will end in 16 hours.

Let the furnace continue to work in the same mode, as there are no deviations in electrical parameters. At time t 22 hours after the start-up of the furnace, we obtain the following indicators: power consumption W _ht = 310 MWh, i.e. P _asr = 51.7 MW; measurements of P ₂ O ₅ in the slag (five measurements): 1.3; 1.8; 1.9; 1.78; 1.8, i.e. C _ksr = 1.72% C _short = 1.2% ΔC _k = 0.52%, i.e. exceeds the permissible value of 0.4, therefore, at the input of block 15 adjusting the amount of coke, a signal C _k will appear. The inhibit signal f _{2 is} removed, because total electricity consumption is 1080 MWh.

(в пределах заданного диапазона).Define the height of the working area

(within the specified range).

.The electrode is buried in the working area:

.

где ΔC $\genfrac{}{}{0ex}{}{\text{*}}{\text{к}}$ приведенное отклонение P₂O₅ в шлаке, определяемое как

;
W_hi 3W_э 150•3 450 МВтч;
W_hт текущий расход электроэнергии, равный 310 МВтч.We determine the amount of coke adjustment by the deviation of P ₂ O ₅ in the slag, because C _k = 0.52%, taking into account the gain along the mine-slag channel, according to the formula

where ΔC $\genfrac{}{}{0ex}{}{\text{*}}{\text{to}}$ reduced deviation of P ₂ O ₅ in the slag, defined as

;
W _hi 3W _e 150 • 3 450 MWh;
W _ht current power consumption equal to 310 MWh.

по углероду или по коксу;

, т. е. отклонение P₂O₅ в шлаке фактического от заданного указывает на недостаток углерода, а увеличение высоты рабочей зоны на накопление кокса в печи.

carbon or coke;

, i.e., the deviation of P ₂ O ₅ in the actual slag from the target indicates a lack of carbon, and an increase in the height of the working zone results in the accumulation of coke in the furnace.

Analysis of the daily content of P ₂ O ₅ in phosphorite showed that its average daily content was 22.5 P ₂ O ₅ and the dosage was 23.9% P ₂ O ₅ , so the dosage of coke (carbon) to the target reaction should be reduced.

по углероду, а по коксу 0,73 кг.The initial dosage of coke (carbon) for the reduction of P ₂ O ₅ phosphorite was 10.7 kg of carbon. Therefore, the daily correction for the analysis of the charge will be

for carbon, and for coke 0.73 kg.

The new dosage of coke per 100 kg of phosphorite will be
Φ _k = Φ _kz + ΔΦ _k + ΔΦ _days = 14.54 + 0.36-0.73 = 14.11 kg.

However, given the fact that, despite the actual excess of coke in the furnace bath, the content of P ₂ O ₅ in the slag exceeds the optimal value, this indicates the need to change the electric mode. We check the optimality of the set value of the electrode current similar to the above:
I _e = 111.4-60.4 • 1.7 + 51.7-0.99 59 kA;
I _e = I _ezad -I _e = 66.1-59 = 7.1 kA, i.e. Δ11
Based on this, I _e = 60 kA was adopted as the given one.

To maintain a given power of 50 MW, regulator 7 switched the transformer from 34 steps to 33 steps (signal F ₂ ) and U _l = 474 V. As a result of adjustments to the electric mode and the amount of reducing agent, the average furnace performance for the next shift was C _k = 1.4 % H _rz = 135 cm, H _ep = 140 cm, I _esr = 62 kA, P _asr = 52 MW, R _af = 3.62 mOhm, cosΦ = 0.926.

 Thus, there is a tendency to improve the electrotechnological parameters of the furnace.

Using the proposed control method allows you to more accurately adjust the carbon mode of the electric sublimation process, because exclude during the transition mode the adjustment of the components of the charge, and the averaging of the main adjustable technological parameter in the steady state increases the reliability of the determination of P ₂ O ₅ in the slag.

The quality of adjustment is also facilitated by taking into account fluctuations in the content of P ₂ O ₅ in the initial charge, moreover, as the above example shows, the deviation in the amount of coke is the opposite, therefore, if the adjustment was carried out only on the deviation of P ₂ O ₅ in the slag, the control quality would deteriorate would. The change in the electric regime as a result of more precise regulation made it possible to reduce the specific energy consumption for the furnace process by 1.5% and to optimize the ratio between the voltage and current of the electrode.

 The use of the invention is expected at JSC Kuibyshevphosphorus in 1995.

Claims (1)

A method for controlling the process of producing phosphorus in an electrothermal furnace, including analysis and dosage of charge components, regulating the electric melting mode by maintaining a given electrode current and furnace working power by moving the electrodes and / or switching voltage levels of the furnace transformer, determining the content of phosphorus pentoxide in slag, averaging the actual active furnace capacity and the content of phosphorus pentoxide in the slag for a given period of time and comparing the results with the given ones, and the deviation of the value of phosphorus pentoxide in the slag from the set value corrects the amount of reducing agent in the charge, characterized in that the set value of the electrode current is determined taking into account the optimal content of phosphorus pentoxide in the slag and the specified furnace power, the averaging of the values of phosphorus pentoxide in the slag is carried out taking into account the delay of the effect the composition of the charge on the composition of the slag, control the position of the electrode in the carbon zone, and the amount of reducing agent in the charge is adjusted according to the formula
Φ _k = Φ _k3 + ΔΦ _k + ΔΦ _days
where Φ _{to the} amount of coke needed to restore phosphorus pentoxide in the mixture per 100 kg of phosphorite, kg;
Φ _K3 initial dosage of coke in the charge per 100 kg of phosphorite, kg;
ΔΦ _to change the dosage of coke by the deviation of phosphorus pentoxide in the slag from the set, kg;
ΔΦ _{days the} daily value of the change in the dosage of coke according to the analysis of raw materials, kg

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