Òåõíè÷åñêèå íàóêè/12.
Àâòîìàòèçèðîâàííûå ñèñòåìû óïðàâëåíèÿ íà ïðîèçâîäñòâå
Mohammad Dgavad
Sharbatian, candidate
Technical of Science,
Vladimir Svyatoslavovich
Bogushevsky, Doctor Technical of Science,
Victoria Suhenko,
post-graduate student
National Technical University of
Ukraine "Kyiv Polytechnic Institute"
AUTOMATIC CONTROL
OF CONVERTER PROCESS
Abstract
The main problems, that are solved by
control system of converters of 350-tonnes capacity. The
two-stage process of preparing input data and the procedure of solving the
management problem are discussed. The structure of computer system for control
system is stated.
Keywords: oxygen-converter,
control system, sample melting, model, static control.
Recently in the range of steel grades melted in the converter plants
there are quality and high-quality ones with sulfur content of 0,004…0,020 %
only. At that the requirements to the technology process performance are
raised, and it is impossible to meet them without automatic control.
In the National Technical University of
Ukraine "Kyiv Polytechnic Institute", Research and Production
Corporation, a control system for oxygen-converter process for 350 t-converters
has been developed, which is intended for functioning in the
information-and-advising mode when technical means produce and give to the
operating personnel the information including control parameters of the
process. The system provides for a possibility to affect on the drives of
oxygen lances, blowing consumption valves and to form a task for program
controlling of dosing friable materials and ferroalloys by means of giving
settings into the local systems of control and regulation of lance position,
consumption of oxygen, friable materials and ferroalloys. The system allows to
control melt blowing by parameters of exit gases including last minutes of
blowing (to 2,5 min) using information about temperature and carbon content of
the melt or by temperature only without blowing interrupt (from the Quik-Tap system).
Control by "sample" melting is the base of a mathematical
description of the oxygen-converter process. It provides for that under the
same initial (chemical composition and temperature of cast iron, cast iron
mass, mass and type of scrap, duration of converter idle time, number N of
melting on lining) and final conditions (preset chemical composition and
temperature of metal and slag defined by the grade of steel to be melted and
blowing regime) the control parameters (blowing supply intensity, distance
between the lance nozzle and killed metal level, mass and time of friable
materials supply) would be the same as at the "sample" melting [1].
Melting is referred to as "sample" one when there was no disturbance
in the process regime and the first turndown gives positive result.
For this purpose at the first stage the melting filtration is performed
in the respect with the following criteria of data adequacy:
Cast iron temperature, 0Ñ
…….................................................. 1200 -
1400;
Mass of scrap, t
………............................................................... 40 -
100;
Total oxygen rate, m3
.......…...............…………..................
14000 - 20000;
Mass of cast iron, t
..................................................................... 270 -
320;
Blowing time, min
………............................................................... 12 -
16;
Discontinuing of blowing
.....................................................………. absent;
Melt tapping, min
..…………............................................................... 4 -
8;
Total lime rate, t
…………..................................………….............. 13 -
40;
Total limestone rate, t
……………..…....................………….........
0 - 5;
Total fluorite rate, t
……..………………….......………….......... 0 - 1,5;
Final
blowing...............................................................….........…….. absent.
Then the meltings are divided into classes in
the respect with the criteria of closeness.
To reduce a number of classes the criteria of melting closeness are
chosen sufficiently large, for example content of silicon and manganese in the
cast iron is 0,3 %, mass of cast iron
and scrap - 5 t, cast iron temperature - 25 ÎÑ, steel temperature - 10 ÎÑ.
To refine the prediction model for meltings
relating by criterion of closeness to the same class a divergence of concrete
melting parameters from chosen "sample" melting in the class is taken
into account and then recalculation is executed [2].
The model includes calculation of melt blending - recommended mass of
cast iron and scrap on the melting (by thermal balance), static control, final
melting after intermediate measuring of carbon content and bath temperature
without blowing interrupt and calculation of deoxidizers.
Static control provides for the calculation of blowing volume, total
mass of lime, fluorite and coolant (if need) on the melting with dopant distribution. To provide for the identical
conditions of blowing the preset blowing regime is calculated which is
determined by ratio of blowing supply intensity to the distance of lance nozzle
to level of killed metal. Criterion of closeness for blowing supply intensity
makes 50 m3/min and for lance position - 50 mm.
Dopant
distribution in friable materials is carried out depending on the initial
conditions. Temperature regime at the blowing beginning is determined by amount
of heat accumulated by the converter lining and used on scrap melting. At
N>15 and scrap of high or middle volume weight 40 % of the total lime mass
on melting determined at static calculation is given for scrap, the rest by
means of equal additions is introduced at (t* +
1)- and (t* +
4)-th minutes of blowing, where t* - time from the beginning to the first change of
the lance position (finish of slag forming period), min. Limestone is
introduced by means of additions of 0.5 t at (t* +
5)-, (t* +
6)-,¼, (t* +
4 + ïls)-th minutes. Here ïls - is number of limestone additions determined with
rounding to the nearest integral number by formula:
ïls =
(òls - 0,5)/0,5.. (1)
At N >15 and scrap of low weight during
blowing lime is introduced by means of three equal additions at the first, (t* +
4)- and (t* +
6)-th minutes of blowing, limestone is introduced by
equal additions of 0,5 t at each minute starting from (t* +
7)-th. At that if the number of limestone additions
exceeds maximal value
ïls.max =
15 - (t* + 7) - 1, (2)
it
is introduced by equal additions which volume is determined by the ratio
òls.add.=
(òls - 0,5)/ ïls.max, (3)
where òls.add - mass of limestone in addition, t.
At N£15
and scrap of any weight during blowing lime is introduced by three equal
additions at the first, (t* +
6)- and (t* +
8)-th minutes, and limestone is introduced by two
equal additions at the (t* +
9)- and (t* +
10)-th minutes of blowing.
In the case when melting does not relate to some class (for example at
the melting of new grade of steel) the calculation is carried out as for the
last carried melting.
In the blowing process carbon content and bath temperature are
continuously calculated on the base of information about composition of exit
gases, blowing rate, distance between the lance nozzle and killed metal level,
mass of slag-forming and cooling materials.
Calculated values of the parameters are used to determine the moment of
intermediate measuring of carbon content and bath temperature without blowing
interrupt (Quik-Tap).
The final melting is calculated in two stages. At the first stage the
qualitative characteristics of control actions for the final melting regime are
determined in the respect with the "sample" melting which are
necessity of final blowing performance, lance position (final blowing with
raised lance or with lance in normal position), introduction of coolants. At
the second stage of the final melting control organization the quantitative
characteristics are calculated such as volume of oxygen, coolant rate.
The automatic
control system comprises:
- network
concentrator;
- automated
work places (AWP) -
converter work stations located in the main control posts;
- AWP of converter division foreman - work station of platform.
At the converter AWP it is calculated the recommended total blowing
volume, mass of lime, limestone and fluorite on the melting, preset blowing
regime, determination of mass and introduction time of separate additions of
friable materials, changing of blowing rate and lance position with transfer of
corresponding settings into local systems including calculation on the base of
results of intermediate measuring of bath parameters without blowing interrupt.
At the foreman AWP melting blending for each converter is carried out,
these are - recommended mass of cast iron and scrap on the melting according to
the steel grade, determination of mass and sequence of ferroalloys introduction
with transfer of corresponding settings in the local system of ferroalloys
supply.
The network concentrator provides for interaction of separate system
AWPs, their connection with plant AWP of the charge division, express-laboratory,
subsystem of information collection and local systems for control of lance
position, oxygen rate, friable materials and deoxidizers supply.
1. Â.Ñ.Áîãóøåâñêèé,
Ã.Ã..Ãðàáîâñêèé, Í.Ñ.Öåðêîâíèöêèé, Ì.Ä.Øàðáàòèàí Óïðàâëåíèå ïðîöåññîì øëàêîîáðàçîâàíèÿ â
âàííå êîíâåðòåðà // Ìåòàëë è ëèòüå Óêðàèíû, 2005. – ¹ 3, 4. – Ñ. 36 – 37.
2. Â.Ñ.Áîãóøåâñêèé,
Ã.Ã.Ãðàáîâñêèé, Í.Ñ.Öåðêîâíèöêèé, Ì.Ä.Øàðáàòèàí
Êîìïüþòåðíàÿ ìîäåëü ðàñ÷åòà øèõòîâêè è ïðîäóâêè êîíâåðòåðíîé ïëàâêè // Ñòàëü,
2006. – ¹ 1. – Ñ. 18 – 21.