A PRESENTATION

ON STEAM GENERATORS

SUMITTED TO: SUBMITTED BY:Prof. (Dr.) K. V. S. Rao Shiv ShankerProf. & Head 15/947

DEPARTMENT OF RENEWABLE ENERGY RAJASTHAN TECHNICAL UNIVERSITY, KOTA

Outlines Introduction Types Fire-Tube boilers Water-Tube boilers Diff b/w fire-tube boiler &water-tube boiler

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A Steam Generator generate steam at desired rate at the desired pressure and

temperature.

The steam generation is done by burning fuel in the furnace .

A steam generator is a complex integration of furnance, superheater, reheater, boiler

or evaporator, economiser and air preheater along with various auxiliaries such as

pulverizers, burners, fans, stokers, dust collectors and precipitators, ash-handing

equipment, and chimney or stack.

INTRODUCTION

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1. On the basis of flows of fuel gases and water: Fire-Tube Boilers(P=18bar) Water-Tube Boilers(P=180bar)

2. From the point of view of applications: Utility steam generators (P=130-180bar) Industrial steam generators (P=5-105bar) Marine steam generators(P=60-65bar)

TYPES OF STREAM GENERATOR

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In this boiler, the product of combustion pass through its tubes, which are surrounded by water.

Fire tube boiler is one of the most basic types of boiler and the

design is also very old. It was popular in 18th century. It was mainly used for steam locomotive engines.

It produce saturated steam at the upper limit of about 18 bar pressure and 6.2 kg/s steaming capacity.

FIRE-TUBE BOILER

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External Fired:TYPES OF FIRE TUBE

Fig.1: A typical fire-tube boiler

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Working In fire tube boiler, the coal is burnt inside a furnace. The hot gases

produced in the furnace then passes through the fire tubes. The fire tubes are immersed in water inside the main vessel of the boiler.

As the hot gases are passed through these tubes, the heat energy of the gasses is transferred to the water surrounds them.

As a result steam is generated in the water and naturally comes up and is stored upon the water in the same vessel of fire tube boiler. This steam is then taken out from the steam outlet for utilizing for required purpose. The water is fed into the boiler through the feed water inlet.

to be continue…………….

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Internal Fire Tube:

To be Continue………

Fig.2:An oil-fired package boiler

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Working An oil-fired package boiler is an internally fired fire-tube boiler, since the furnace is

within the cylindrical shell. Oil is filtered, sufficiently heated either by electricity or steam, and is then fed through the burner.

Air is supplied by an FD fan. Excess oil is returned to the main fed line Combustion occurs in a horizontal corrugated flue, and the combustion gases flow

through the tubes in two passes till they are let out through a chimney to atmosphere. The corrugations of the flue increase strength and help in allowing thermal expansion

and contraction, also in cracking and removing the carbon deposited. The gases get cooled as they flow through the tubes and water is heated to form steam.

To be Continue……

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Advantages: Low installation cost Reliability in operation Need of only unskilled labour Quick response to load changes

Disadvantages As the water required for operation of the boiler is quite large, it requires long time for

rising steam at desired pressure. As the water and steam are in same vessel the very high pressure of steam is not

possible. The steam received from fire tube boiler is not very dry.

ADVANTAGES and DISADVANTAGES

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Water-tube boilers were developed to permit increases in boiler pressure and capacity with reasonable metal stresses.

In water tube boilers, water flows through the tubes and flue gases flow outside them. Puts the pressure in the tubes and the relatively small diameter drums, which are capable of withstanding extreme pressures of the modern steam generator.

WATER- TUBE BOILER

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STRAIGHT- TUBE BOILER

Fig.3: Early water-tube boiler

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Straight-TUBE Boiler can be made, installed and replaced easily. The tubes were of 75-100 mm O.D., inclined upward of about 15 degree to the horizontal.

Nearly Saturated water leaving the drum flowed through downcomer, into the tubes. While flowing upward in the tubes some the water on being heated by flue gases flowing outside gate transformed to vapour. Water-Steam mixture went back to the drum through riser.

Because of density difference, natural convection takes place. The drum was arranged either parallel or perpendicular to the tubes

STRAIGHT-TUBE BOILER

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BENT-TUBE BOILERS

Fig.4:A four-drum bent tube boiler

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Bent-Tube Boilers is being greater accessibility for inspection , cleaning and maintenance and ability to operate at higher streaming rates and to deliver drier steam.

In a bent-tube boiler, the tube where so bent that they entered and left the drum rapidly.

The combustion gases flowed upward from the furnace through the first bank of tubes connecting the front steam drum and the mud drum and then second and third tubes banks coonecting to the second and rear steam drum.

BENT-TUBE BOILERS

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Table 1 : Difference B/W Fire-tube Boiler & Water-tube Boiler

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THANK YOU