RU2486716C2 - Method for regulation of power consumed by group of alternating-current electric arc furnaces - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: subject-matter of the method involves switching on of each furnace in the group with a certain delay in time, and namely, start-up of the ready to launch electric arc furnace when melting period of the previous furnace is over in start-up sequence.

EFFECT: reduction of specific energy consumption, increase in efficiency of the group of electric arc furnaces and minimisation of their negative impact on supply mains.

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Description

The invention relates to electrical engineering, in particular to electrometallurgy, as well as to methods for regulating the power consumed by a group of AC steelmaking furnaces (ACD).

A known control system for the electric mode of electric arc furnaces during group work during hours of maximum energy consumption [A. No. 1162063 USSR, MKI H05B 7/148, F27D 11/10, G05F 1/66, declared 01/04/1980]. It contains the setters-programmers of the active power of the electric arc furnaces, connected by the first outputs to the adder of the electric furnace powers included in the work, the second outputs - with the unit for setting and coding time shifts of adding the values of the active power of the electric furnaces, the first output of which is connected to the first input of the register of addition blocks, and the second output is through a temporary setpoint timer with an additional input of the adder power electric furnaces included in the work, the output of which is connected to the second input of the register block addition, associated with the output through the register of signal generation blocks proportional to the maximum values of a given duration, with the input of the register of comparison blocks and determining the minimum value of the maximum values of a given duration, the output of which is connected to the first input of the next-furnace turn-on time measurement unit, to the second input of which a third the output of the unit of assignment and coding of temporary shifts of addition, and the output of the unit for measuring the turn-on time of another furnace is connected to the input a specific mechanism for switching on electric furnaces, the electric furnace panels are connected to the first output, and the first input of the discriminator is connected to the second output through the initiative block, which is connected to the second input with the time generator for maximum energy consumption, the third input is connected to the electric furnace panels, and the discriminator outputs are connected to the inputs of the sets -programmers of active power of electric furnaces. The system is designed to provide the required technology and uninterrupted supply of electric energy for heating, melting the charge loaded into the furnace and refining the melt to a predetermined composition. The described system has some disadvantages. The load regulation of a group of electric furnaces is carried out by changing the start-up time of one of them, while in the electric furnace shop it is possible to control the start-up time of all furnaces. The depth of regulation based on a change in the ON time of one furnace-regulator may not be sufficient to maintain the maximum load set by the power system, which may lead to penalties from the power system. Those. opportunities to reduce maximum power are not fully utilized.

These disadvantages are eliminated by the control system of the regime of electric arc steelmaking, containing a group of programmers, the first inputs of which are connected to the first outputs of the electric furnaces, the second inputs are connected to the first output of the discriminator, the first input of which is connected to the second output of the basic electric furnace, and also the maximum duration power systems, timer, actuator connected by a group of outputs to inputs of electric furnace panels, start-stop system, memory register the time of turning on the electric furnace, a computing device, a setter for the duration of the melting cycle, a block of 2I elements, a block of time delay elements, the group of outputs of which is connected to a group of inputs of an actuator, the first group of inputs of a block of time delay elements is connected to a group of outputs of a block of 2I elements, the second group of inputs to the timer output, the output of the start-stop block is connected to the second input of the discriminator and to the first group of inputs of the block of elements 2I, the second group of inputs of which is connected to the group of outputs s of the computing device, the first group of information inputs of which are connected to the outputs of the electric furnace consoles, the second group of information inputs - with the outputs of the set-programmers of the group, the first input of the job of the computing device is connected to the output of the setter for the duration of the melting cycle, the second input of the task - with the output of the setter of the maximum duration of the power system , and the third input of the task with the output of the memory register of the time for switching on the electric furnace, the information input of which is connected to the timer output, and the input d start - with the second output of the discriminator [Pat. No. 2066939 RF IPC ⁷ H05B 7/148, G05F 1/66, declared 01/30/1991].

For the presented systems, a general drawback can be distinguished. The possibility of superimposing the durations of the melt periods of two or more chipboards connected to one bus section is not taken into account. This variant of coincidence of load schedules is the most difficult, and its duration determines the degree of negative impact of a group of electric furnaces on the functioning of the supply network and its elements. At the same time, there is a sharp increase in the consumption of active and especially reactive power by a group of chipboards, and the level of voltage fluctuations in the power supply system also increases. According to [3], to fulfill the requirements for limiting voltage fluctuations in the electric network supplying arc electric furnaces, the condition

$$\frac{\sqrt{{\displaystyle \sum _{i=\mathrm{one}}^n{S}_{PTi}^2}}}{S_{\mathrm{TO}3}}\le 0.01\cdot D,\left(\mathrm{one}\right)$$

where S _PTi is the rated power of the i-th furnace step-down or converter transformer, MVA;

S _KZ - short circuit power at the point of connection of the arc furnace to a general-purpose electric network, MVA;

n is the number of connected electric furnaces;

D - coefficient (D = 1 for arc furnaces of alternating current, D = 2 for arc furnaces of direct current).

The coincidence in time of the melt periods of two or more electric furnaces connected to one bus section can lead to non-fulfillment of condition (1). As a result, the technical and economic indicators of the supply network are reduced, the duration of the melting cycle is increased, and the specific energy consumption is increased.

Of the known inventions, the closest to the claimed method according to the principle of regulation of the chipboard modes operating in the group is the invention described in [Pat. No. 2338338 of the Russian Federation, IPC ⁷ H05B 7/148, F27B 3/28, declared 04/02/2007]. It eliminates the inherent disadvantages of the two systems discussed earlier. A method for controlling the reactive power consumed by a group of electric arc furnaces involves switching on each arc furnace with a certain time delay. For each arc furnace, the groups determine the average melt duration, the average melting time, the average lapping time, the average deviation of the melting time, and the average downtime and calculate the time delay according to the expression

$$\Delta t_{D\mathrm{FROM}P}=\frac{{\displaystyle \sum _{i=\mathrm{one}}^n\left[\left(n-i+\mathrm{one}\right)\left(t_{p\left(i\right)}+t_{P\left(i\right)}+t_{d\left(i\right)}+\Delta t_{\left(i\right)}\right)+t_{PR\left(i\right)}\right]+\left(t_{p\left(n\right)}+t_{P\left(n\right)}+t_{d\left(n\right)}+\Delta t_{\left(n\right)}\right)+t_{PR\left(n\right)}}}{{\displaystyle \sum _{i=\mathrm{one}}^{n}i}},\left(2\right)$$

where Δt _chipboard - time delay, min;

n is the number of electric arc furnaces in the group;

i is the number of the electric arc furnace;

t _p is the average duration of the melt, min .;

t _p - average duration of melting, min .;

t _d - the average duration of refinement, min .;

Δt is the average deviation of the duration of the heat, min .;

t _CR - the average idle time of an electric arc furnace, min.

With the simultaneous operation of two or more electric furnaces, it is proposed to start each of them sequentially one after another after starting the previous one with a time delay Δt of _chipboard . The described method has the following disadvantages. Firstly, the authors did not provide for the possibility of its use in automatic mode. Secondly, when coordinating the modes, the average values of the durations of the periods of functioning of the electric arc furnaces and their deviations are used, the real values of which can vary significantly, and the time interval of the sequential start-up has one value for all chipboards of the group, despite the fact that in practice it is possible to individually determine this parameter. This does not allow for rational regulation of the power of a group of electric furnaces due to the separation of the periods of the melt in time, taking into account the fulfillment of the main production task, which consists in maintaining their maximum productivity. The solution to this problem is to minimize the duration of inter-melting downtime of each electric furnace, which, if possible, should not exceed the time interval necessary for carrying out technological operations, which is not provided for in the considered method. For example, in the case of functioning in a group of two electric furnaces, the second one is initially started after a delay in time from the moment the first furnace was started, and the next start of the first is made after a time delay relative to the moment the second furnace was started. In this case, the pause between the melts significantly exceeds the time required for technological operations. The introduction of such prolonged additional downtime is unjustified. As a result, the total productivity of the group of electric furnaces decreases and the specific energy consumption increases. Thirdly, the launch of furnaces is irrational. The second and subsequent electric furnaces are in idle mode for a long time before the first start-up. For the second chipboard to start, the idle time duration is equal to the time delay determined by expression (2), for the third, to the doubled time delay value, etc. This reduces the overall performance of the group of electric furnaces.

The objective of the invention is to reduce the specific energy consumption and increase the performance of the chipboard group by adjusting their power by putting each of them into operation with a certain delay in time, namely by starting the ready-to-start arc steel-smelting furnace in automatic mode at the end of the melt period of the steel-arc the oven previous to the launch.

The essence of the proposed method of regulating the power consumed by a group of arc steelmaking furnaces of alternating current is to turn on each of them with a certain delay in time, namely, to start the arc-steelmaking ready to start up in automatic mode at the end of the melt period of the arc steelmaking previous to launch. The idea is to minimize the duration of inter-melting downtime by dividing in time the melt periods of two or more chipboards based on the actual (real) values of their durations. The personnel responsible for carrying out steel melting on a chipboard, based on the technological indicators of the melting and their compliance with the technological map of the steel melting of a certain brand, in which for each of the melting periods and their stages the steps of the secondary voltage of the furnace transformer and the current settings of the power regulator are set, identifies the beginning and the end of each of the melting periods, which allows you to determine the actual (real) values of the durations of the melting periods, including the duration of the melt period. In this case, the time interval between the end of the melt period of the previous chipboard starting and the beginning of the melt period of the next chipboard starting is of the least importance. It is equal to the time of technological operations to start the electric furnace by responsible personnel. Each electric furnace is equipped with a start regulator (RPP), a setter-programmer of the period of operation (ZPP) and a setter-programmer of readiness for start-up (ZPG). This allows you to create a power control system consumed by a group of chipboards connected to one bus system. To control the operation of the system, an on / off switch-programmer (ZPV) is provided. Each arc furnace acts as an object of regulation. The following states of the regulatory object can be distinguished: 1 - the beginning of the melt period; 2 - the end of the melt period (the beginning of the melting period); 3 - the end of the lapping period (the beginning of the downtime of the furnace). The time interval 1-2 is equal to the length of the melt period, 2-3 is the duration of the melting and lapping periods, 3-1 is the downtime. Responsible personnel sends information signals to the control panel on switching on or off the power control system of the N-number of chipboards. The PZV forms an on-state signal 0 or an off-state signal 6. These signals are fed to the start-up regulator of the furnace. RPP is designed to signal the responsible personnel to start the furnace into operation, as well as to analyze the information received from its furnace, the air conditioner and the air conditioner of the previous electric furnace start-up. The personnel responsible for carrying out steel melting at the chipboard, sends information signals to the ZPP about the state of the regulatory object, i.e. information about starting the furnace, the end of the melt period, the end of the lapping period. Based on the information received from the chipboard, the RFP generates certain signals corresponding to states 1, 2 or 3. At the same time, during the 1-2 time interval, it generates a state signal 1; 2-3 - status signal 2; 3-1 - status signal 3. Responsible personnel sends information signals to the ZPG on readiness or not ready to start chipboard. Based on the information received from the electric furnace, the ZPG generates state signals 4 or 5, which correspond to the unavailability to start and readiness to start the installation. RPP verifies the fulfillment of two conditions. The first condition is fulfilled in the case when the signal of state 2 comes from the PSC of the previous chipboard start-up, or status signal 0 or 6 comes from the PES, and is not satisfied when the signal of state 1 or 3 comes from the PSC of the previous chip start-up. If the first condition is fulfilled verification of the second. It is fulfilled when the status signal 5 comes from the ZPG and the status signal 2 is the previous signal from the start-up of the furnace, or the status signal 0 comes from the ZPV. The second condition is not fulfilled in two cases: when the status signal 4 comes from the ZPG and the status signal goes back from the ZPG 2; upon receipt of the status signal 6 from the PEL. To turn off the system, an additional condition check is introduced. It is carried out in case of failure to fulfill the second condition. An additional condition is not fulfilled when status signal 4 is received from the CCP and the signal of state 2 precedes the start of the furnace. As a result, state 2 signal received from the preceding signal from the previous start of the chipboard is transferred to the start controller of the next furnace. An additional condition is fulfilled when the state signal 6 arrives from the PZV, which leads to system shutdown. It is enough to check this condition only on the start regulator of the first electric furnace.

Example 1. The functioning of the group consisting of the N-number of particleboard. The figure 1 shows a structural diagram of a power control system N-number chipboard. Digits corresponding to the numbers of electric furnaces have been added to previously accepted designations. Initially, the system, like all electric furnaces included in the group, is in standby mode. The system is launched by supplying a status signal 0 from the PES to RPP-1. RPP-1 sends a signal to the responsible personnel to launch DSP-1, because it is in state 5. Responsible personnel starts the electric furnace and gives an information signal about starting DSP-1 to ZPP-1, which generates a status signal 1 and sends it to RPP-2. Even when the DSP-2 is ready, the signal to start the furnace does not come from the RPP-2 to the responsible personnel, as the first condition is not satisfied. As a result, the launch of DSP-2 is not performed. This creates a time delay equal to the duration of the melt period of the first electric furnace. As soon as the DSP-1 melt period ends, the responsible personnel transmits the corresponding information signal to ZPP-1, which generates a state 2 signal, which is fed to RPP-2. If at the same time a status signal 5 is supplied from ZPG-2, then RPP-2 gives a signal to the responsible personnel to start DSP-2, because the first and second conditions are satisfied. In the opposite case, when state signal 4 is supplied from ZPG-2, no signal is sent from RPP-2 to responsible personnel and the DSP-2 is not started, and status signal 2, generated by ZPP-1 and received initially at RPP-2, is transferred to RPP-N. This allows you to start the next in operation electric furnace, transitioning to state 5 faster than the previous one. Such a situation may arise due to prolonged pauses of a technological nature or in the case of repair work on chipboard-2. RPP-N performs the analysis of incoming signals, based on the results of which it gives or does not give a signal to the responsible personnel to start the chipboard-N. In the process of regulating the power of a group of electric furnaces, such operations are repeated many times. To turn off the system with the PES, a status signal 6 is supplied, which corresponds to the fulfillment of the additional condition checked at RPP-1.

Example 2. The functioning of the group consisting of two electric furnaces. We use the temporary characteristics of the electric furnaces No. 1 and No. 2, presented in [Pat. No. 2338338 of the Russian Federation, IPC ⁷ Н05В 7/148, F27B 3/28, declared 04/02/2007]. They are summarized in table.

Table The temporal characteristics of the functioning of two chipboard Chipboard number t _p min t _p min t _d min Δt, min t _ol , min one fourteen 48 5 7 28 2 fifteen fifty four 6 25

We assume that the actual (real) values of the durations of the periods of functioning of these electric furnaces are equal to the averaged values given. We will regulate the functioning of electric furnaces according to the above description. The operation of two AC chipboards arranged in such a way in time is shown in Figure 2. The thick line indicates the graph of active power, and the thin line shows the graph of reactive power.

Define the time delay according to the expression (2)

$$\Delta t_{D\mathrm{FROM}P}=\frac{\left(2-\mathrm{one}+\mathrm{one}\right)\left(\mathrm{fourteen}+48+5+7\right)+28+\left(\mathrm{fifteen}+\mathrm{fifty}+\mathrm{four}+6\right)+25}{\mathrm{one}+2}=\mathrm{92,}m\mathrm{and}n.$$

Based on a comparison of the results obtained, the following conclusions can be drawn. In the case of application of the proposed method, DSP-2 is in idle mode for 14 minutes before the first start, and the second start of DSP-1 is carried out without introducing additional downtime, i.e. 28 minutes after the end of the first heat. When using the method selected as a prototype, the DSP-2 is idle for 92 minutes before the first launch, and the DSP-1 is launched the second time after 92 minutes after starting the DSP-2, i.e. the downtime significantly exceeds the time allotted for inter-melting technological operations. This eliminates the overlap in time of the durations of the melt periods and smooths the total load schedule, however, the group performance is significantly reduced. The application of the proposed method can reduce the specific energy consumption and improve the performance of the chipboard group.

Example 3. The functioning of the group consisting of four electric furnaces. We use the time characteristics of the four chipboard, given in [Pat. No. 2338338 of the Russian Federation, IPC ⁷ Н05В 7/148, F27B 3/28, declared 04/02/2007]. We assume that the actual (real) values of the durations of the periods of functioning of these electric furnaces are equal to the averaged values. We will regulate the functioning of electric furnaces according to the above description. The work of the group consisting of four AC chipboards arranged in such a way in time is shown in Figure 3. The thick line indicates the graph of active power, and the thin line shows the graph of reactive power. The application of the method specified as a prototype, involves starting an electric furnace through a time delay equal to according to the calculations performed in [Pat. No. 2338338 of the Russian Federation, IPC ⁷ Н05В 7/148, F27B 3/28, declared 04/02/2007], 86.1 min. We analyze the results. When using the proposed method, the chipboard-2, chipboard-3 and chipboard-4 before the first launch are in idle mode 14, 29 and 44 minutes, respectively. From the graphical constructions presented in figure 3, it is seen that the periods of the melt of the electric furnaces of the group go in a certain order one after another. The melt period on DSP-4 ends after 58 minutes from the launch of DSP-1. The second launch of DSP-1 due to a forced pause due to its unavailability to start is carried out after 102 minutes from the first start, i.e. during regulation, there is a reserve lasting 44 minutes, during which none of the electric furnaces of the group operates in the melt mode. Analysis of the passports of chipboard melts showed that the duration of the melt period can reach 48 minutes. Therefore, with increasing durations of the periods of the melt of the electric furnaces of the group, the available reserve can be effectively used, minimizing the need for additional inter-melting downtime. When adjusting the power of the chipboard group based on the method claimed as a prototype, a simple chipboard-2, chipboard-3, chipboard-4 before the first launch is 86.1, 172.2 and 258.3 min, respectively. In the case of increasing durations of the melt periods, their averaged values also increase, and, consequently, the time delay value determined by expression (2). This is expressed in an increase in the downtime of the electric furnaces of the group. Using the proposed method allows to increase productivity and reduce specific consumption of electric energy.

The implementation of the proposed method in the production process does not require significant economic costs, because programmable controllers can be used as programmers and controllers, for the supply of information signals by the responsible personnel to start the power control system of the chipboard group and the status of the control object, the use of simple data input devices is provided, and the signal to start the furnace to work for responsible personnel with the analogue control is proposed transmit using light signaling equipment. The technical result is to reduce the specific energy consumption and increase the productivity of the chipboard group, as well as minimizing the negative impact on the supply network. The advantage of the method lies in the automation of the implementation of certain actions, minimizing the duration of inter-melting downtimes of electric furnaces, reducing the downtime of the second and subsequent groups after starting up the electric furnaces before the first launch.

Information sources

1. A.S. No. 1162063 USSR, MKI N05V 7/148, F27D 11/10, G05F 1/66. The control system for the electric mode of electric arc furnaces during group work during hours of maximum energy consumption [Text] / N.M. Voroshilov, R.V. Mineev, O.V. Ulzituev, A.P. Mikheev, I.F. Antonov, N.B. Mineeva, O.I. King (USSR). - No. 2864264 / 27-07; declared 01/04/1980; publ. 06/15/1985. Bull. Number 22. - 8 p.: Ill.

2. Pat. No. 2066939 Russian Federation, IPC ⁷ Н05В 7/148, G05F 1/66. The control system of the regime of arc steel-smelting electric furnaces [Text] / Demov A.D., Rogalsky B.S., Slavenko E.I., Ivankov V.O., Dmitrash A.V., Sviridov N.P .; applicant and patent holder Vinnitsa Polytechnic Institute. - 4906522/09; declared 01/30/1991; publ. 09/20/1996. - 8 p.: Ill.

3. Rules for the installation of electrical installations [Text] / Ministry of Energy of the Russian Federation. - St. Petersburg: DEAN, 2004 .-- 464 p.

4. Pat. No. 2338338 Russian Federation, IPC ⁷ Н05В 7/148, F27B 3/28. A method for controlling the reactive power consumed by a group of electric arc furnaces [Text] / Shpiganovich AN, Shpiganovich AA, Zakharov KD, Zatsepina VI, Zatsepin EP, Shilov IG; Applicant and patent holder Lipetsk State Technical University. - 2007112074/02; declared 04/02/2007; publ. 11/10/2008. Bull. No. 31. - 6 p.: Ill.

Claims (1)

A method for controlling the power consumed by a group of AC electric arc steelmaking furnaces, based on the inclusion of each of the electric furnaces in the group with a certain time delay, characterized in that the ready-to-start arc steelmaking furnace is launched at the end of the previous start-up period of the molten arc furnace.

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