HEAT RECOVERY STEAM GENERATOR(HRSG )

Heat Recovery Steam Generator is a horizontal, natural circulation, single drum, dual pressure, unfired, water boiler. It is designed to generate steam quantities as furnished in operating parameters at main steam stop value, under specified modes of operation. Water temperature is 151.3 degree Celsius for HP and 150.2 c for LP.
The HRSG unit having following sections. HP section, LP section, condensate pre heater section.
HP section input steam temperature is 520 degree Celsius; feed water temperature is 151 degree Celsius. In LP section input steam temperature is 200 degree Celsius; feed water temperature is 150.2 degree Celsius.

HRSG consists of following components

a) HP, LP, super heater and components
b) HP, LP, evaporator and components
c) HP economizer and components
d) Condensate pre-heater and components
e) Attemperator
f) Expansion joints
g) Steel chimney
h) Stack closer damper

A. 1) HP super-heater and component
HP super-heater is the first heat transfer surface arranged in the direction of gas flow. HP super-heater is constructed of modules consisting of fin tubes. The HP super-heater is designed for single pass flow on the gas side and multi-pass flow on the tube side. Interconnection of the modules will be multiple 180 degree Celsius bent tubes of similar material as header.
A.2) LP super-heater and components
It is the fourth heat transfer surface arranged in the direction of gas flow. LP super-heater is constructed of modules consisting of finned tubes, welded to top and bottom headers, two rows per module. It is designed for a single pass flow on the gas side and multiple flow on the tube side.
B.1) HP evaporator and component circulation system.
HP evaporator is the second that transfer surface arranged in the direction of gas flow. In the direction system the heated feed water from the economizer goes to the steam drum. The boiler water from the steam drum flows to the common feed headers.
B.2) LP evaporator and component circulation system
LP evaporator is the fifth heat transfer surface arranged in the direction of gas flow. In the circulation system the heated feed water system from LP economizer goes to the economizer.
C.1) HP economizer and components
HP economizer-2 is the third and HP economizer-1 is the sixth heat transfer surface arranged in the direction of gas flow. The HP economizer is constructed of modules consisting of spiral finned tubes welded to the top and bottom headers, two rows per module.
D) Condensate pre-heater
Condensate pre-heater (CPH) is the eighth and final heat transfer surface arranged in the direction of the gas flow. CPH is constructed of modules, consisting of spiral finned tubes welded to the top and bottom headers, two rows per module.
E) Attemperator
Spray at temperature is utilized to control the HP steam temperature to 520 degree Celsius. For this application inter stage attemperator is used after the HP super-heater. The attemption piping is furnished and will be designed with an internal sleeve for the first 3mts.
F) Expansion joints
One expansion joint at HRSG inlet and one more at chimney are provided to take care of expansions.
G) Chimneys
The Gas turbine exhaust gases, after passing through all the heat transfer surfaces are discharged into the atmosphere at the safe height through a 70 mt high steel chamber.

FEED WATER

In boiler water is continually circulated and drawn out as super heated steam. This water circulation is done through feed water system.
HPBFP
High pressure boiler feed pump is for feed water to the HP section.
b) LPBFP
Low pressure boiler feed pump is for feed water to the LP section.
c) CPHRP
Condensate preheater and recirculation pump, condensate preheater is the final heat transfer surface arranged in the direction of heat flow. CPH is constructed of modules consisting of spiral finned tubes welded to the top and bottom headers, two rows (max) per module.
Recirculation pump is for recirculating the feed water. Steam water mixture generated in the evaporated tubes, due to the heat transfer from the gas turbine exhaust, flow back to the drum to the riser tubes, the saturated steam is separated by the centrifugal separator and final scrubbers placed inside the drum. The separated boiler water is recirculated through the down comers, common feeders, individual feeders, evaporator tubes and risers. The saturated steam is flow to the LP super heater where necessary super heat is added.

STEAM TURBO GENERATOR

Steam turbines are devices which convert the energy stored in steam into rotational mechanical energy. These machines are widely used for the generation of electricity in a number of different cycles
CONDENSER
The condenser is used in both reflux and distillation procedures as to cool and condense vapors. The condenser action is such that the steam passing through the pipes is cooled using a number of fans and sprays of water for steam recovery.
DEAERATOR
Deaerator is the apparatus used for removal of air from condensed steam coming from condenser. This process is for avoiding corrosion of the boiler.
CHEMICAL DOSING
The process of adding chemicals to the water pumped from the reservoir. this process is done for making the pH value of the water 7.
DEMINERALISATION WATER SYSTEM.
Demineralization of the feed water is done for removing minerals present in the water. This avoids corrosion of the boiler due to dissolved minerals present in the feed water.
COOLING WATER SYSTEM
Due to prolonged usage the moving parts of the plant tend to heat up. This can sabotage the working of the plant. Therefore a cooling water system is used to maintain the temperature of the plant at an acceptable level.
EFFLUENT TREATMENT PLANT (ETP)
Effluent maybe present in water after power generation. This contaminated water cannot be released into environment without proper treatment. So an ETP is used to remove effluents that are harmful.
WS POSE
Work station based processors operated supervisory environment
1) Introduction
In distributed digital control system environment, it is all the more important that operator has all the processor information at a single point’s POSE FULL fills this requirement.
Work station based man machine interface is system of computers with real; time software with associated specials and general hardware components. This system of computers is integrated with date high way down stream (the procontrol P bus or IP BUS) through special interface. This permits the realization or an integrated control and monitoring system. This environment provide the following function-
a) Supervision of plant process
b) Processing of plant information
c) Representation/presentation of plant information
d) Analysis’s of plant event
e) Operator dialogue
f) CRT/keyboard based control of the plant
g) Long time storage of data for analysis of plant performance
h) Monitoring of plant performance by periodic calculation
These functions are realized through a variety of displaced and logs which works around a process data base and historical data. The operated is guided through a hierarchal menu display set, to select the required function/ picture. Additionally, the operator has access to a series of help display.
2. System characteristics
The main characteristics of the system are:
a) High speed 64 bit computer system is at the heart or the system.
b) Standard computer systems are used to control planes of varying size and complexity.
c) Windows NT as operating system.
d) A set or structured software products, combination of which means customer requirements.
e) Function keyboards of operation or the plant.
f) Windows for four windows and simultaneous view of process using pictures, trends, X-Y plots, bars on all these windows.
g) Network wide printing
3) Redundancy Features
Following are redundancy features:
a) All control and monitoring function are available on all the six operator work stations mounted on the control desk. Therefore in the event or failure of any workstation another workstation on the control desk control be used to perform the same functions.
b) Failure or anyone workstation will not affect the other workstations.
c) Two server stations are provided. In case of failure of one server, all the workstations will continue to work through the others.
d) Failure or any workstation will result in only one CRT being disabled.
e) Each printer can be associated with any workstation. Logs can be directed to any printer by the operator.
4) System constitution
System configuration
The workstation based MMI system for kayamkulam CCPP project is made of two server stations, residing on P42v bus. The two server stations are connected through an Ethernet to six workstation.
Thus we have a distributed configuration of computer system to cater the modular growth, logical distribution or tasks, increased reliability and more choice in configuring the individual operator workstations.
Turbine Control System
-General description
-Start up procedure
-Speed control
-Remote speed indication
-Proactive devices
-Over speed trip test
-Testing of stop values
-Bypass control
-Automatic turbine tester
-Main stop & control values
-Lubrication system
1) General description
The combined cycle plant comprises two gas turbine generators each with a dedicated dual-pressure heat recovery steam turbine generator. A dedicated main system bypass control a dedicated induction steam bypass control is provided for each steam generator.
These permits operation of a single gas turbine generator in a conjunction with a single
HRSG.
The first cylinder is supplied with steam from the HRSG via two combined main stop and control values. Steam from the LP reheat recovery steam generators passes to cross around pipes between the two cylinders via two combined induction steam stop and control values.

HARDWARE

The hardware components can be classified into the following functional groups.

1. Server work station / Engineering station.

The station consists of a DEC ALPHA 1000A 5/333 server. This computer has 21064A 64 bit RISC (Reduced Instruction Set Computing) processor working at 333MHZ speed and 192 Mb memories, with Windows NT server operating system. The server is connected to operator work stations though an Ethernet. On the other side it connects to the protocol bus through a VME cage. The VME cage consist an CPU, and interface cards to protocol bus and to the server computer.
One of the functions of this station is signal conditioning and preprocessing. It picks signal from the process filters out only those signals are required, and checks from validity of these signals. If the signals are valid formation is passed on to the operator work stations.
It also does long term storage and retrieval, long term logs and supervisory functions using optical disc media. The server stores all database configurations and log formats in its hard disc.
The server work station is also called as Engineers station. The engineers station comprises of a color display terminal, an ASCII key board and mouse. The various functions of an engineer can perform from this terminal include creation of new pictures, editing old ones, changing the characteristics of the database elements etc. the key board along with mouse is used by the engineer to configure parameters of the data base and other parameters of the system like composition of logs, displays etc. he can continuously monitor the functions of the plant like an operator.

2. Operator work station.

The operator work station is a DEC ALPHA XL433 with a 21064A, 64 bit processor, running at 433MHZ speed, 64 MB memory and windows NT operating system.
The work station performs all of the tasks associated with the operator’s dialog with the control system. All the software components for the storage, presentation, processing and control of the process are executed on this.
The computer system also includes the various storage devices like hard disc, floppy disc. Many operator work stations may be residing on same Ethernet. In the multiple operating work stations participating in the system, the process data base in all the individual operator work stations and the sever is in format and content, and are updated constantly using the information received from the P42 bus. The various operator communication devices are connected to the different operator work stations, according to the needs of the process and the control strategy. Any changes made from one of the operator work stations are transmitted through the Ethernet to the other nodes.

3. Information output devices.

These are the devices which are used for presenting the various logs, displays, alarms etc, and include CRTs and printers

4. Operator interface devices.

These devices are used by the operator for communicating with the computer or control systems. These consist of color display monitors, an ASCII keyboard, a functional keyboard and mouse. The color display monitors are the basic display devices for the various process related displays. The functional key board is used by the operator to issue control commands and commands to change display, control the plant processes (VPC) etc. ASCII keyboard is used only at the time of booting the system.
The mouse is used for selecting and item, menu etc.

5. MMI software.

A number of software components are executed on the computer system for realizing the various functions of this subsystem. The operating system for the system executes the task necessary for scheduling of the tasks in the computer, management of resource of the computer, processing inputs from the operator and monitoring of the computer system components working. The features of windows NT operating system has been exploited to give user friendly environment to the operator and for simultaneous viewing of various pictures, trends bars etc on different windows. The windows sizes are flexible and four windows are allowed at a time on the screen.
Some of powerful features of windows NT operating system are
a) It offers strong capabilities in the areas of both interrupt management and input/output management.
b) It runs many programs at the same time, switching rapidly between them to perform multi tasking.
c) Further more a single program can perform tasks simultaneously by dividing itself into threads. Threads execute independently, like other programs, but several threads can share the resources and global data of a program.
d) It uses sophisticated memory management of virtual addresses.
e) Built in support for sharing printers, files across networks.
System software is a set of programs which provides the basics services of the system like data acquisition, storage and retrieval of data from the data base, software control of printers and other resources etc. these software are developed using MS VC++
6. Standard application software
These are programs designed to execute along with the system software. These includes plant schematic picture, VPC pictures, assignment of logs, data base lists etc.
The other software components can be broadly classified
1. Display functions.
The software modules under this group are concerned with the display and output information on the color monitors used by operator. Various displays are
a). Alarm display-provides the facility for alarming those messages which have been allocated to the alarm display function. Each message is allocated a color, according to its priority level, and a flashing symbol for the operator to acknowledge.
b). Group display-The group display function allows grouping of analog and binary values for display in alpha numeric form. Grouping may represent some plant function areas, with each message occupying a single line.
c). Bar chart display- Provides an overview of a group of eight analog values in form of horizontal bar. The bar allows quick comparison between various values, or each value to its individual set limits.
d). Trend curve display- shows the behavior of six analog variables in relation to time. The dynamic behavior of values can be used to optimize the plant operation or to recognize plant disturbances.
e). Profile display- Shows several process values of the same measuring range in form of vertical bars. Process values limits are additionally superimposed on the bars of horizontal lines to indicate deviations from alarm levels.
f). Plant schematic display- Shows the part of a plant or process in graphic form together with the related process control system analog and binary values. The binary values are generally represented as dynamic symbols and analog values are generally represented as dynamic values in alpha numeric form.
2. Print or log functions.
These functions are for recording the process data and any information derived from them analysis and reference. These functions are also alternatively called logging functions. Logs can also be viewed on the screen. So of the automatic logs like post trip logs get printed on printers assigned for them. The various logs possible in the MMI computers are
Alarm log- Continuously register event of the plant in chronological order. Events are reported from status charges, alarms, analog limits, signal malfunction and operator actions. Special symbols indicate priority levels.
Post trip log- Allows the grouping of binary values which relate to a particular plant component. When a disturbance occurs in the component area the log is automatically triggered. It shows in tabular form the course of changes in the values for a pre defined time before and after the trip.
Trend log- The trend log is configured to a group of a number of analog points which are pointed out critically in tabular form. The point cycle time and number of cycles are configurable. The log can be automatically or manually triggered.
The plant status log-The plant status log is a kind of group log meant for current or calculated binary or analog values. Two variations are possible, one with current value and other with values in predetermined times steps.
Log of current alarms-The log of current alarms produces a list of all analog and binary alarms on the system at the time of log request.
Log of distributed signals- The log of distributed analog and binary signals produces a list of all analog signals which are distributed in the system at the time of log request.
Points out of scan log- The points out of scan log records, on demand all analog and binary values which are specified by an input or output address but which are not included in the data acquisition process.
Log of stimulated signals- The log of simulated signals produces a list of all binary and binary simulated for the system at the time of log request.
Operator action log- This log gives information about the drives operated by the operator during the last shift.

Control function (Video Process Control)

The Video Process Control (VPC) function through the CRT display involves the display of various pictures, identification of control elements and issue of the control commands.
The commands are issued with dedicated keys on the operators function key board. All the functions can be performed from either the plant schematic displays, process pictures or the control displays which are representative of the conventional operator’s push button panels. Selection of control elements can be done based on physical positioning in case of VPC group pictures or by pointing in case of plant schematic. Actual operation is done by using FKB keys. The operation can also be initiated by using mouse, by clicking the mouse button after placing the cursor on the rise or lower buttons.
Supervisory functions
The supervisory calculation and reporting functions required for effective maintenance and operation by the plant supervisor are implemented in the server. The logs available are maintenance logs, hourly logs, daily logs, monthly logs, shift logs etc. These logs can be printed on any of the printers.
Hourly / Daily logs- These logs consist of accumulated, average, calculated values and minimum or maximum values which are recorded over defined time periods. These logs are triggered automatically at the end of the day and at the end of the month respectively.
Shift log- The shift log consists of hourly values for some calculated or accumulated values and instantaneous values as at the end of the shift. This log is triggered automatically at the end of the shift.
Historical trend log- Historical trend log prints out select long term historical data in tabular form. These data can be directly scanned analog values which can be stored by long term storage function.
System scope
Scope of supply
This section gives an overview of the equipment and services proposed for man-machine interface. The proposed equipment is ideally configured to meet the plant requirements. The scope of supply of the process computer system hardware for the plant can be subdivided into the following parts.
Alpha client-server computer systems.
Computer peripherals.
Operator / Engineer Interface Devices.
This included in the scope of supply in the interval power distribution between computer and peripherals as well as the cables for all data connection between the central computer and the peripherals.
Hardware components
Six operator work stations each comprising of the following:- 64 bit, DEC ALPHA with 64 MB memory and windows NT operating system.
Computer peripheral on work stations consists of:-
One floppy drive 1.44 MB 3.5’
One hard disc 1.05 GB
One CD – ROM drive
One 21’ color monitor
One operator function keyboard
One mouse
Two server work stations each comprising of the following:-
64 bit, DEC ALPHA server with 192 MB memory and windows NT operating system and SQL server support.
Computer peripheral and engineer’s interface on server:-
- One floppy drive 1.44 MB 3.5’
One hard disc 6 GB
One CD – ROM drive
One read or write optical disc drive
One 21’ color monitor
One operator function keyboard
One mouse
Interface devices are common for all work stations and engineers’ stations. it comprising of
four logging printers (dot matrix)
two ink jet printers (color)
System functions
The following functions are envisaged and will be performed in the system.
Data acquisition and processing
Analog input
Binary input
Analog output
Binary output
Displays
Plant schematics
VPC group pictures
Unfulfilled criteria
Warm displays
Group displays
Bar charts
Trend curves
Profile displays
The actual number of pictures will be as per approved.
Video Process Control
Video process control function for control of groups /drives is similar to conventional console configuration.
Functions can be performed by means of dedicated push buttons on the function keyboard. For certain functions, the numeric keypad on the function keyboard will be used in conjunction with other push buttons.
Engineer’s Functions
Maintenance of data base is performed through a keyboard and a mouse in conjunction with the color monitor, as and when used for editing purposes.
Online assignment of parameters to system functions (parameters of logs and display pictures).
The ALPHA server has its process data base organized as relational database management (RDBMS) with SQL server residing on it. Queries can be done on database by the user using simple SQL.
Creation of new plant schematic pictures editing of standard pictures etc. can be done using an offline package called picture editor. All pictures in WSPOSE system are created using this editor.
Database modifications can be done using an online package called database editor. The engineer can edit /configure the plant database using this package.
Project Engineering
The following are the steps in the Engineering of work station based MMI system.
Specification of I /O lists with the associated parameters. This is generated as per a procontrol-P system Engineering.
Configuration of sketches for plant schematics /video process control.
Configuration of data for individual display and video process control functions.
Operator Interface-Overview
Operator screen
When the operator work station is switched on, after the initialization routines are completed, the operator’s screen is presented on the screen. This screen has a title, a menu bar, a tool bar and the picture area. With the help of these menu and tool options, the operator can call-up pictures on this display. The pictures are presented in the picture area. The operator can access the menu and tool options using the mouse and ASCII keyboard. The operator continues his dialog with the MMI system through a set of commands with information from the system being presented on different types of pictures.
Menu
The menu gives the MMI application a windows look and feel. The grouping of functions, placement of the menu elements are like any other standard windows application.
File
This element is like ‘file’ menu in any windows application. It has commands for printing, previewing before a print for opening a pictures and for log-out /exit from the program.
Close
This element closes the picture being currently displayed.
View
The view menu is like the view menu in any windows application. It has commands to zoom-out or out of pictures and also to return to the just previous picture.
Display
This menu provides for an exhaustive list of all kinds of displays from which the operator can choose. The actual method of calling up the required picture is discussed in a later paragraph.
Logs
This menu item provides an exhaustive list of logs from which the operator can choose. Ex: post-trip logs, trend logs etc.
Definition
It provides a connection to the database editor for viewing /changing configuration in the database.
Keyboard
It provides a picture of the function keyboard on the screen so that the operator can, with the help of the mouse, operate it like a physical keyboard. Control functions will not be available in this case.
Users
Add new users, change passwords etc. Available only when user has logged in as administrator.
Window
Like window commands of any window application. Allows to tile up pictures and lists of all pictures currently open in different windows.
Help
It provides help to operator.
Tools
Tools further enhance the user-friendliness. Many often used commands are configured as tool bar buttons. This eliminates the need of having to navigate through menus and sub-menus. Pictures and too tips are present on the tool bar buttons which give an intuitive feel for the operator to operate them. Many of them are again an element of commonality with other windows applications.
Features
Pictures are the basic mechanism through which the operator gets information from the system. This information includes feedbacks for the control commands issued by the operator. The graphical nature of the picture elements enables information to be presented in a variety of formats like bars, numbers, shapes, colored text lines etc.
Pictures are freely configurable by the user. However, some pictures are standard while others are fully user configurable. So pictures like a bar chart display are configurable. So pictures like a bar chart display are usually invariant across projects. Such pictures are designed once and stored for use across projects. These are called ‘standard pictures’ and are stored in a directory named ‘user/ standard’. Some standard pictures are also generated online through program. A VPC group picture will not exist as a picture, but is synthesized from the group configuration on being called upon the screen. Log formats are also basically standard pictures.
The other pictures which are particular to a project are stored in the directory PLNTSCH under the project directory.
However, all pictures are created using the same editor program and are generically the same.
Any picture consists of three parts- the static part, the dynamic part and targets.
Static part is the part of the picture which does not change after the pictures has been called upon the screen in relation to the actual /process condition, where as those elements or parts which change depending upon the current plant condition are called dynamic parts. For example, a string like ID FAN-A may be written beside a symbol for a fan to give it a designation. This is a static part. The fan symbol itself maybe green in color when the ID FAN is standstill and red in color when the ID FAN is running. That is dynamic part.
Some elements of a picture which though not changing dynamically, may refer to variables being picked from the plant database and are unknown while being placed in the picture are also treated as dynamic elements. Typical examples are address, description, KKS, limit values, engineering unit etc, of a process variable. Dynamic elements can be defined in a picture to represent integer values, real values, Boolean values, text or an equipment or controllable element such as pump etc. An element may be defined to display different shapes depending on the status of the process object it represents. For example,
A shape for pump ON in a certain color
Another shape for pump in OFF condition in another color.
Analog and binary values can be represented in a variety of colors to indicate their current states and quality of the signals. These color combinations are configurable by the user
The foreground and background color for any element in a picture can be specified. Shapes can also be programmed to flash when the object they represent is in a certain state. Values to be included in the bar curve and group displays can be defined online quickly and conveniently. To display these signals, the base picture is used while applying these specified signals on that base picture.
Targets are active areas in a picture. By clicking on these pictures certain actions can be invoked. These actions can be:
Display another picture
Start /stop a log
Select an element for control
Targets are also defined using the picture editor.
Description
General layout of a picture:
Header:- Each picture has eight target at the top which common for all picture of that project. They are represented as eight buttons in the toolbar area. There are eight other picture dependent targets at the bottom. There are a minimum users can further configure targets of their choice freely at convenient locations on the pictures.
Picture area:- The actual picture to be displayed is presented in this area. This represents 774*442 panels on display of 800*600 resolutions. Latest three alarms are always available at the bottom position of the screen.
Login
On the operator work stations the operator task will be automatically started up and the initial welcome screen will be displayed. The dialog for logging in to the system will also be displayed. The operator logs in with his name and password. He can also log into the system with the administrator pass word if he wants to do administrator level tasks. The operator can then display different pictures control the plant, print out logs etc.
A user can log out from the operator task by choosing the command ‘log out’ from the file menu. The initial screen will again be presented.
Picture call up
There are many ways to call up pictures. It is possible for operator to use an FKB or a mouse. It is possible that the picture call up from both FKB and mouse.
Call up using FKB:- There are 65 direct call up buttons on the FKB. Each button can be assigned to a particular picture of any type. Pressing any direct call up button, the assigned picture will be displayed.
Pictures of a particular type can be called up by pressing the generic display buttons. They are grouped under the ‘DISPLAY’ category. In this, after the generic button is pressed, a number has to be entered. Then the picture with that number is presented on the display. For example, after ‘Plant group’ is pressed followed by ‘3’ and ‘E’ on numeric group, the third plant status group will be displayed.
For every picture, we can have four linked pictures. These are ‘Previous Picture’, ‘Next Picture’, ‘First Picture’ and ‘Last Picture’. In case of standard pictures like bar chart displays, the first picture will be group1; last group will be the maximum possible group number. Next picture will be numerically the next group (not exceeding the maximum) and the previous picture will be the numerically previous group. In case of plant schematic, they will be configured on the editor. It is to be noted that these four links are always to pictures of the same type. By pressing the four keys corresponding to the above links, that picture can be called.