-By

Sai Krishna Mahidhar Devulapalli

A thermal power station is a power plant in which

the prime mover is steam driven. Water is heated,

turns into steam and spins a steam turbine which

drives an electrical generator. After it passes

through the turbine, the steam is condensed in a

condenser and recycled to where it was heated; this

is known as a Rankine cycle.

TPP/BH of V.S.P. caters to the power and cold

blast air requirement of 3 million ton capacity

integrated steel plant. It supplies process steam at

13 and 4 kg/cm2 and demineralised water required

by other departments.

TPP/BH comprises of three turbo generators of

60MW each and a fourth generator of 67.5MW to

generate a total of 247.5 MW of power.

These blowers deliver 6067 Nm3/min of air for

supplying compressed air for BF cold blast

requirements.

Thermal Power Plant of VSP has 4 working and 1

standby TG catering to a demand of 240 MW.

Special features of turbo generators used are

• Electro hydraulic turbine governing system

• Central admission of steam to reduce axial thrust

To meet blast air requirements, 3 turbo blowers are

installed. Normally two blowers will be in service.

These blowers are of axial flow type and are the

largest blowers installed in India to meet varying

need of blast furnaces.

Blowers are provided with suction filter, pre cooler

and inter cooler.

The boilers are of Single drum, natural circulation,

balanced drift and fused welled dry bottom

furnace. Tangential burners are provided for fuel

firing and are located at the four corners of the

furnace.

Coal is pulverised and supplied to boiler

Boilers are designed to fire COG at four elevations

Secondary air is supplied by two number of axial

impulse fans and primary air is supplied by two

number of radial fans.

Two number of radial bubble function ID fans are

provided to handle the production of combustion.

A boiler is a complicated machine which handles

huge volumes of water, steam and air at high

pressures and high temperatures.

Pressures up to 200 ATA and temperatures up to

1500 K need to be carefully administered.

To do this task a complicated, efficient and reliable

and automated Distributive Control System is

used.

The major activities of the DCS system includes

Annunciation systems

It’s main objective is to provide the Field Operator

with timely warnings and reminders of the

fluctuations in the control parameters through

alarms and display panels.

Automatic control has played a vital role in the

advancement of engineering and science.

Process automation systems are classified into:

1.Analog control system

2.Digital control systems

Digital control systems are further classified into:

1.Centralized control system

2.Distributed control system

In the early days of introduction of the computers

for process automation, a single big mainframe

was used to control whole plant.

This single mainframe computer was alone made

responsible to carry out all the functions such as

communicating with the field instruments,

performing calculations and control operations.

That means computer itself can perform the

control algorithm. This is known as Direct Digital

Control [DDC].

The main problem with this type of

configuration is that if any problem occurs in

the mainframe computer, the operation of the

whole plant is disturbed.

A distributed control system (DCS) refers to a

control system usually of a manufacturing system,

process or any kind of dynamic system, in which

the controller elements are not central but are

distributed throughout the system with each

component sub-system controlled by one or more

controllers.

The entire system of controllers is connected by

networks for communication and monitoring.

To overcome these difficulties the concept of DCS

came out.

The basic concept of DCS is to distribute the

control system both functionally and

geographically.

The Automation system is used to implement

closed loop control, open loop control, interlock &

protection and monitoring.

The Automation system is used to implement

closed loop control, open loop control, interlock &

protection and monitoring.

The intelligence of the system is distributed among

several modules, each working independently, with

its own inputs and outputs.

The following features are to be satisfied by plant

in order to implement maxDNA DCS System.

• Open environment for optimizing the whole

enterprise.

• Optimal operation environment, hardware up

gradable to the latest technology.

• Flexible, durable system that can be optimized

for plant operation.

• Minimize total cost of ownership.

• Powerful engineering functions.

Distributed Control System offer number of

advantage over conventional hardwired system.

It is considered that these systems are technically

much superior to conventional system and are also

considered to be more reliable due to their self-

diagnostic features.

The application of DCS in automation is a

contribution to a better implementation of

networks to reduce system downtime and improve

operator’s satisfaction.