To identify the information flow, and to manipulate the material and energy flow of the given process in a desired optimal way.

Response time, computing power, flexibility and fault tolerance-crucial –ON LINE

Requirements

Objective of CCP

Digital computer control in Process Industries

Active Applications

Manipulation of process and Optimisation

Passive ApplicationsAcquisition and manipulation of

process data.

Monitoring ,alarming

•Smart sensors, smart transmitters and smart actuators(final control elements) has inbuilt microcomputer.

•To get real time process measurement information and automatic transmission in required form.

•To ensure that the actuator ,transmitter or sensor function according to the design.

Smart Instruments

•Video display terminals to supervise the whole plant from control room.

•A few keyboards and screens replace large panel of instruments, switches and knobs.

•Control rooms are much smaller and few people are required to monitor the plant.

•Sophisticated mathematical models can be implemented.

Modernisation

Modernisation

•Plant managers and engineers can be provided with comprehensive information concerning the status of plant operations to aid effective operation.

•Automatic tuning of controller parameters for the best performance.

•Model based Predictive technique-optimisation of process operation

PULP AND PAPER INDUSTRY-CONTROL ROOM

NATURAL GAS INDUSTRY-CONTROL ROOM

BASIC FUNCTIONS OF COMPUTER AIDED PROCESS

•Measurements and data acquisition•Data conversion with scaling and checking•Data accumulation and formatting•Visual display•Comparing with limits and alarm raising•Recording and monitoring of events, sequences and trends•Data logging•Control Actions

SCHEMATIC DIAGRAM OF COMPUTER AIDED PROCESS CONTROL

The control strategy is repeated at some predetermined frequency to achieve closed loop computer control system.

Computer Controlled Process-Mode of Operations

•Batch or Sequential control•Continuous Control•Supervisory Control•Direct digital control

BATCH PROCESS

CONTINUOUS PROCESS

Supervisory Control

•Comprehensive picture of the status of the plant operations.•To optimize the plant operations by maximizing the plant yield, production rates,minimising energy consumption, etc.•Computing set points-reorganise the control algorithm•Review the operating conditions periodically.

Direct digital control

•Computer directly controlled the process.•Loop control-Functions of Comparator, controller, safe guarding operations•Large computer-to implement hundreds of control loops•Control equation is chosen to suit dynamic characteristic of the process.•Not only limited to the 3 term PID control action.Drawback – One processor used.A single failure affect a large no.of controlled variables and disable the entire process

Architecture of Computer Aided Process Control

•Centralized controlled system-Large computer system –both Supervisory and DDC

•Distributed controlled system (DCS) -Total work is divided and spread across several computers.