Automation and IT Initiative for Operational Excellence in...
Transcript of Automation and IT Initiative for Operational Excellence in...
Automation and IT Initiative for Operational Excellence in Blast
Furnace
Vikas Mohan, Mandeep Singh Rajput, SandeepDeshwal
Jindal Steel and Power Ltd, Raigarh, Chhattisgarh
Tel: +91-9827477161
Email: [email protected]
JSPL has always focused on in-house developments and innovative practices for process
improvements. Working on this theme, the Blast Furnace team at JSPL, Raigarh has taken
following initiatives:
Development of Process models namely RIST Diagram, Hearth Liquid Level and Furnace
Burden Tracking which help the operators to make decisions for optimizing the process.
Same have been developed using the technical knowhow of Process team & available
Automation and IT support at JSPL.
Small modifications in the PLC SCADA and logic for process improvement and ease of
operators for better process monitoring and operation
Key words: Online Process Models and Modifications in PLC Logics.
INTRODUCTION
The iron-making blast furnace (BF) is a giant countercurrent heat exchanger and chemical reactor
used for reduction of iron ore to molten iron. It is the most important commercial reactor for
producing the majority of the world’s primary steel. To improve blast furnace productivity, iron
and steel industries are constructing larger furnace having more than 4000 m3 internal capacity.
Even though the Level-1 automation shows all required parameter to operate the furnace but still
some very important estimates as hot liquid metal level in hearth, position of the charged burden
ABSTRACT
in furnace belly and overall performance at a glance are required for the optimization of process
and better understanding of operators.
Estimation of drain rate and liquid level in hearth needs to be simulated based on the operating
parameters available as carrying out any direct measurement is extremely difficult due to the
hostile conditions. Same way it is impossible to find out the exact position of charged material
inside the furnace through any direct parameter feedback or any visuals inside the furnace
Here, mathematical models have been developed to simulate real-time liquid level and drainage
behavior of the furnace hearth. Based on the computed drainage rate, production rate, and mass
balance, other models have been also developed for charged material burden tracking and the
furnace performance at a glance. Although the above models provide reasonable estimates with
level -1 automation parameters, they have some deficiencies. They either require a huge
infrastructure or involve a lot of variables, whose values are not readily available, and they change
significantly with process parameters. In order to solve this problem and provide the furnace
operator with a tool to examine and control the process, a mathematical model is prepared to
simulate the process.
These online process models have been provided to the operators through a required IT and
Automation system architecture.
HEARTH LIQUID LEVEL MODEL
Proper drainage of blast furnace (BF) hearth is very important in order to maintain smooth hot
metal production and stable burden descent. The condition of the hearth plays an important role,
since it affects the reduction of the leftover FeO in slag, the dissolution of carbon in liquid iron,
the distribution of various solutes between iron and slag, and the fresh hot metal flow from the
dripping zone. Inadequate drainage can make the blast furnace operation problematic when liquid
levels exceed a critical limit characterized by very short distance between slag surface and
raceways. Furthermore, at an elevated liquid level, the buoyancy force acting upon the coke
column increases, and the deadman starts to float, causing sluggish or irregular descent of burden
material. Therefore, it is very important for furnace operators to understand the mechanisms
governing hearth drainage and access internal state of the liquids in the hearth.
Fig 1.0: Cross-sectional view of blast furnace hearth.
Fig 2.0: Metal & Slag Drainage Mechanism
Modeling Methodology:
Velocity of liquid
Production rate
Liquid Slag
Liquid Metal
Salamander
Taphole
Liquid Out
Slag Line
hg
PPv
outin..2
p
m
pQ
PR
dt
dQ
.3600
1000.
Drain rate
Volume change rate
Remaining liquid volume
Liquid level change rate
Effective tap hole diameter
Initial liquid quantity
The inner height of the BF hearth is generally considered to be from the top of the refractory lining
to the tuyere center line, but for drainage calculation, the effective height is considered to be from
the tap hole center line to the tuyere center line. In order to avoid any mishap due to the rising
liquid levels, there must be a defined safety level beyond which the liquid level should not rise.
According to the general understanding, the slag being lighter remains on top of the metal layer,
and it should come out only after the complete drainage of metal from the hearth.
dd
Qfavdt
dQ .. 2
mdpm
Qdt
dQ
dt
dQ
dt
dQ
t
t
mmm
h
dtQQQ 0
mmm
ha
Q
dt
dh
1.
t
t
ththth
h
dtKDD .0
m
hm PR
tQ
1000..
36000
Fig 3.0: Metal & Slag Level in Model
RIST DIAGRAM
RIST diagram is an analytical expression which is developed for calculating the specific fuel
rate and the direct reduction rate for the iron blast furnace process as a function of blast
conditions as well as other control parameters for the process. These are relevant for
carbonaceous as well as hydrogenaceous gases in the system. The equations are based on an
oxygen balance and a heat balance for the bottom half of the furnace, separated from the upper
half at the location where equilibrium of the gas phase with wustite and iron is assumed to occur
and where the temperatures of the gas and solid streams are approximately equal. The mass and
heat balances employed are those which are the basis for the classical Rist diagram.
Ultimately RIST diagram shows that in certain conditions of inputs how far we have optimized the
furnace process and results.
Liquid Slag
Liquid Metal
Coke Grid
Salamander Metal
Tapping opened no Slag (T=35 min) Tapping opened Slag coming out (T=70 min)
Tapping closed (T=20 min) Previous Tapping closed (T=0 min)
Fig 4.0: RIST Diagram- Blast Furnace
BURDEN TRACKING MODEL
A mathematical model has been developed to estimate the charged material burden location and
position inside the furnace at any instant of time along with the information of burden mass
change.
The methodology behind this model is based on certain calculation of furnace inside working
volume, density of the charged material, burden charge rate, burden level and the selected mass of
material to be charged.
Fig 5.0: Burden Tracking Model- Blast Furnace
SYSTEM ARCHITECT AND DATA FLOW FOR ONLINE MODELS
Methodology and calculation for these process models have been prepared by operation experts,
now the job was to present and display these models with online parameters of furnace and
controls for process simulations. For this we needed a proper infrastructure and architect of
computer, communication and dataflow.
For the model database, process parameters and data are retrieved from the Level-1 system
through the OPC (OLE for) collector and database is prepared with the Relational Database
Management. The GUI (Graphics User Interface) page of these models has been designed through
the VB code (Visual Basics) programming.
Fig.6.0: Data Flow Architecture for online process models
For online process models it is required to retrieve the online furnace process parameters to these
models, for this purpose a dedicated processor unit and data communication architect has been
established. In figure 6 it has been shown how furnace process parameters come to the server for
online process models. From the BF data server data it comes to SQL server through an OPC
collector server. As SQL server is on common IT intranet so there was always threat to BF process
server of malwares hence BF process data is being transfer to SQL server through a firewall
network security. This firewall manages the BF PLC network intake to the common IT intranet.
For the models as liquid level in hearth, furnace burden tracking and RIST diagram models we
needed parameters such as furnace working volume, burden charge rate, furnace temperature,
pressure, hot blast volume, metal drain rate, tap diameter etc. Some of these parameters come from
BF data server and some of the inputs required to be fed manually. So online parameters are
provided to SQL database directly through OPC server and for manual database operator data
entry facility is provided in VB framework of models. Models calculation and modeling
methodology has been done in Visual Basic programming language. As this database server is in
common IT intranet, hence anybody in common IT intranet can view these online models VB
forms anywhere in common IT LAN network.
FURNACE MATERIAL CHARGING PROCESS OPTIMIZATION
THROUGH MODIFIED PLC LOGICS
Any process optimization and betterment comes with innovative ideas and these can be achieved
through the small and remarkable modifications in process methodology or with changes in
process variables. In Blast Furnace, raw material charging methodology is a vital process which
directly affects the production process as efficient charging of raw material results in desired Hot
metal production. Through some modification in PLC logics and SCADA pages we have
improved our material feeding process for Blast Furnace along with ease and understanding of
operator for the material charging.
Individual material batch weight selection in charging pattern:
In furnace, iron ore, coke and sinter is used as raw material to produce hot liquid molten metal.
Material charging is done in a cyclic process of set weight of fix numbers of material batches. In
earlier PLC logic provision was provided that when operator selects the weight for a batch then
this weight will be set for all batches numbers which has been given by operator until he will
change the different weight again. So if operator selects 8 numbers of batch cycles then he was not
able to set the different weight for individual batch.
Through the modification in PLC logics and design in SCADA page this facility has been
provided for better process operation.
Ring Wise Material Distribution inside furnace:
Furnace inside circumference is divided into virtual rings and material is charged in these different
rings according to process requirements. In our earlier PLC logics of material charging total
weight of a batch was being dump to particular set ring area, but this process had a restriction for a
facility of material feeding of an individual batch weight in different rings. So required
modification in logics and SCADA pages have been done and fulfilled the process requirement.
Fig.7.0: Furnace inside material charging ring area
CONCLUSION
The developed models are very much useful as these provide the operator with a tool by which
he/she can get a real-time view of the variation in the level of liquids in the hearth as well as the
drainage behavior of the hearth. Other two models of RIST and Burden Tracking help the operator
to estimate the performance of the furnace and burden position of the charged material
respectively. These data in turn helps to control the parameters before they pose any threat to
process stability and can be used for process control and to judge irregularities in the Blast
Furnace operation.
These models require only the readily available data from an operating Blast Furnace. Effects of
the unknown parameters, which vary from plant to plant, are taken into account by introducing
raw material inputs and process factors.
The modifications which have been done in charging system through PLC logics helps the
operator to achieve required charging pattern and distribution of raw material to optimize the
process and production of hot molten metal.
R
1
R
2
R
3
R
4
R
5
R
6
LIST OF SYMBOLS
• Blast Pressure (kg/m2) = Pb
• Production rate (t/hr) = PR
• Slag rate (t/hr) = SR
• Metal density (kg/m3) = ρm = 6700
• Slag density (kg/m3) = ρs = 2800
• Void fraction in hearth = ε = 0.3
• Flow factor = f
• Taphole erosion coff. (m/sec ) = Kth = 1.493e-6
• Initial drill diameter = Dtho
• Cross sectional area of tahole = a2
• Cross sectional area of hearth = a1
• Atmospheric gauge pressure (kg/m2) = Pout
• Gravitational acceleration (m/sec2) = g = 9.81
• Holding time (Seconds) = th
• SQL = S Query Language
• OPC = OLE for rocessontrol
• OLE = Object Link Enable
• BF = Blast Furnace
• PLC = Programmable Logic Controller
• SCADA = Supervisory Control And Data Acquisition
System
REFERENCES
1. A.K. Biswas:Principles of Blast Furnace Ironmaking, Cootha Publishing House, Brisbane, Australia, 1981
2. A .Rist and N. Meysson:Rev. de Met., 1965, vol. 61, pp. 121, 995.
3. Brännbacka and H. Saxén, “Modeling the liquid levels in the blast furnace hearth,” ISIJ International, vol. 41, no.
10, pp. 1131–1138, 2001
4. Published Paper on :https://www.hindawi.com/journals/isrn/2013/960210/
Vikas Mohan