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: vmohan@jspl.com

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