S.M. Taha Rehman Siddiqui

E11-PG08

Separation Process Lab-1

By

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Steam Trap DEFINITION:

“It is a type of Valve which is use to Separate or Release the Condensate or non-Condensable gases from a

stream and it does not permit the steam to discharge from stream.”

WORKING PRINCIPLE:

The Condensate or Non Condensable gases is separated on the basis of temperature or density difference

USE OF STEAM TRAPS

Steam Trap is use to remove:

CONDENSATE:

The removal of condensate from steam is considered the main function of the steam trap.

NON-CONDENSABLE GASES:

In addition to Hindering steam flow and proper heat transfer, carbon dioxide can be very corrosive to parts

of system.

AIR:

This air must be removed from piping structure so that the steam can enter and eventually reach the selected

process applications.

TYPES OF STEAM TRAP:

There are three categories of Steam traps classified on the origin of their operations:

1) Thermostatic

2) Density/Mechanical

3) Thermodynamic

THERMOSTATIC STEAM TRAP:

Definition: “These steam traps permit the passing or the trapping of the fluids on the basis of their

temperature difference.”

WORKING:

Thermostatic steam trap works on the basis of Change in Temperature.

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The Principle of operation is centered on the expansion and contraction of temperature sensitive material.

The temperature sensing part can be bimetallic or sealed bellow can be used which is to some extent filled

with liquid.

TYPES OF THERMOSTATIC STEAM TRAP:

Bimetallic

Sealed Bellow

Expansion

1) Bimetallic:

In this sort of trap there are two metal strips joined together and the temperature

variation causes a deflection in one direction which set in motion the valve.

Image:

2) Sealed Bellow:

In this kind of steam trap the there is a fluid filled thermal component called the bellows.

Operation:

The operation of the thermal element is governed by the expansion and the condensation of the fluid

inside the bellows. As the air or the steam condensate enter the steam trap the fluid inside the thermal

element condenses and contracts and opens the valve and allows the air and condensate to escape. When

the steam enters the fluid vaporizes and expands and closes the valve and no steam escapes.

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Image:

3) Expansion Thermostatic Steam Trap:

The trapping part holds a filling that that contracts or expands and set in motion the valve. In this

the internal filling does not evaporate.

Image:

DENSITY STEAM TRAP:

Definition:

“These traps use the difference in the densities of the steam and the steam condensate to isolate the steam condensate.”

TYPES OF DENSITY STEAM TRAP:

1) Inverted bucket traps

2) Float and thermostatic trap

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1) Inverted bucket traps:

Working principle:

It comprises of an inverted bucket as a float device that is connected to a valve

plug. The deviation in the densities of the steam and the condensate produce a buoyancy force on the bucket

which opens or close the valve.

Operation:

When the condensate move in the trap the inverted bucket does not rise up and the condensate

releases through the open valve. When the air enters the trap it rises up the bucket and passes through a

bleed hole and is then discharged out. As the steam enters the trap the steam fills up the inverted bucket and

due to the change in the densities of the steam and the condensate the bucket rises up and closes off the

valve. In the end the steam leaves through a small orifice.

Advantages:

This trap is resistant to water hammer

it is resistant to scale in the system

Industrial Application:

Use in Sugar Industry

Material of Construction:

Stainless steel or Carbon Steel

Image:

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2) Float and thermostatic trap:

Working principle:

The float and thermostatic trap exploits both temperature and density difference to

operate. This type of trap comprises a thermostatic air vent that releases the air and a float that is coupled to

a valve plug that is used to release the condensate.

Operation:

As the air enters the trap the thermostatic air vent will open due to the shrinkage of the

thermostatic element and allow the air to release out. When the condensate level rises up it lifts the float

which opens the valve and permits the condensate to discharge out. When the steam enters the trap the

thermostatic element expands and closes off the thermostatic air vent and the steam does not discharge while

the condensate discharges out until the float drops and closes off the valve.

Advantages:

Excellent air removal capability

Used for the drainage of process heat transfer equipment

Advantageous during startup operation

Industrial Application:

Use in Sugar Industry

Material of Construction:

Cast Iron or Carbon Steel

Image:

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THERMODYNAMIC STEAM TRAP:

Definition:

These traps use the thermodynamic properties of flash steam to operate a cyclic on/off

process as the steam flows through the trap.

Working principle:

This trap uses the thermodynamic properties of flash steam to operate the cyclic on/off

process. It consists of a valve disc that opens when steam condensate enters and shuts off tightly

when the steam enters.

Operation:

As the condensate enters the trap the pressure on the disc rises and it rises off the seat and

permits the condensate to leave through the peripheral outlet. When the steam enters the condensate

leftover produces the flash steam in the chamber which moves at a high velocity from the inlet to

the outlet and produces a low pressure under the disc while some enters the top of the chamber and

produces a high pressure above the disc. This difference in pressure closes off the disc and the

steam is trapped.

Material Construction:

Stainless Steel or Cast Iron

Image:

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Industrial Application:

Thermodynamic Traps are typically used

For Tracing applications in chemical processing plants

Petroleum refineries,

Paper mills,

And other processing industries that use higher pressure steam.

Boilers DEFINITION:

A device which produces steam at a different pressure and of the quality of as dry as possible.

TYPES:

Fire tube boiler

Water tube boilers

Flash Boilers

FIRE TUBE BOILER:

It is a type of tube and shell heat exchanger in which the hot gases pass through the tubes and the

boiler feed water passes through the shell side and boils and produces steam.

CONSTRUCTION:

It Consist of a

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vessel in which water is stored,

Compressor to compress the fuel gas

Economizer to preheat the water to be boiled

Preheater to Heat the Fuel gas

Super heater to Super heat the Steam

Safety Devices

WORKING

“Water part of the way fills a boiler barrel with a little volume left above to suit the (steam space). This is

the kind of boiler utilized as a part of about all steam trains. The hotness source is inside a heater or firebox

that must be kept for all time encompassed by the water with a specific end goal to support the temperature

of the warming surface underneath the breaking point. The heater could be arranged toward one side of, a

blaze tube which extends the way of the hot gases, subsequently increasing the warming surface which

might be further expanded by making the gases reverse heading through a second parallel tube or a heap of

different tubes (two-pass or return pipe boiler); on the other hand the gases may be taken along the sides and

afterward underneath the boiler through vents (3-pass boiler). On account of a train sort boiler, a boiler

barrel reaches out from the firebox and the hot gases pass through a heap of flame tubes inside the barrel

which enormously expand the warming surface contrasted with a solitary tube and further enhance high

temperature exchange. Flame tube boilers typically have a nearly low rate of steam preparation, yet high

steam stockpiling limit. Blaze tube boilers generally smolder strong energizes, however are promptly

versatile to those of the fluid or gas mixture.”

ADVANTAGES:

It is inexpensive

It is easy to clean

It is compact

Used for low steam capacities

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DISADVANTAGES:

It is not used for high pressure applications greater than 25psig

It is not used for high capacity steam generation

TYPES OF FIRE TUBE BOILER:

i. Packaged boilers

ii. Pressurized fluid bed combustion boiler

i. Packaged boilers

Packaged boilers are already made and are ordered as a

package. As they are taken to the site they just require the electrical connections, fuel

supply and the water supply and they become fully operational.

It is a type of tube and shell heat exchanger in which the hot gases are in the tubes and the

boiler feed water is on the shell side. The number of times the hot gases pass through the

water is called the pass. After one pass the hot gases pass through another set of fire tubes

and then another. The most common type is the three pass boiler.

Advantages:

It has high thermal efficiency

ii. Fluid bed combustion boiler:

This type is a combination of a fluidized bed

combustion boiler and a gas turbine.

The gas turbine provides the combustion air at a high pressure to the

boiler. The gas containing the bed material and the ash goes to the cyclones and is

separated and the cleaned gas stream drives the gas turbine.

The steam produced in the tube bundle present in the bed is passed

to a steam turbine which produces power.

Advantages:

• It is used for large scale burning of coal

• Produces electricity efficiently

WATER TUBE BOILER:

“In this type of boiler the water is circulated in the tubes and is brought inside a boiling container. In this

boiling drum the fuel is burnt and the combustion gases rise up and heat up the boiler feed water inside the

tubes.”

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CONSTRUCTION:

It has the Same Construction as of Smoke tube boiler except in this boiler the Water is on the tube side and

hot combustion gases are on shell side.

WORKING:

“In this sort, tubes loaded with water are organized inside a heater in various conceivable arrangements:

regularly the water tubes join substantial drums, the easier ones holding water and the upper ones, steam and

water; in different cases, for example, a mono tube boiler, water is flowed by a pump through a progression

of loops. This sort by and large gives high steam creation rates, however less capacity limit than the above.

Water tube boilers could be intended to endeavor any hotness source and are for the most part favored in

high weight requisitions since the high weight water/steam is held inside little breadth funnels which can

withstand the weight with a more slender divider.”

ADVANTAGES:

o It has high thermal efficiency

o It can produce high pressure steam

o It can achieve high temperature

DISADVANTAGES:

It has high initial capital cost

It is difficult to clean

Water should be of high quality in these boilers

TYPES OF WATER TUBE BOILER

There are several types of water tube boiler.

1) Horizontal Straight Tube Boiler

2) Bent Tube Boiler.

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3) Cyclone Fired Boiler.

1) Horizontal Straight Tube Boiler

“The longitudinally located drum is fed by colder feed water at its rear feed water inlet. As the colder

water is heavier it drops down through down-comer fitted at the back part of the drum. From there the

water enters in to horizontal water tube where it converts hot and lighter. As the water converts lighter,

it passes up through these angled horizontal tubes and eventually comes back to the boiler drum through

riser. During travelling of water through angle water tubes, it absorbs heat of the hot gases, ambiances

the water tube, thus steam bubbles are formed in these tubes. These steam bubbles at that point arrive to

the steam drum through riser and naturally parted from water.”

2) Bent Tube Boiler:

The feed water first move in into right most upper drum. As a result of more density this water comes

down in the lower water drum. The water inside that water drum and the linking pipes to the other two

upper drums, are heated up and thus steam bubbles are formed.

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FLASH BOILERS

A flash boiler is a kind of water-tube boiler. The tubes are adjacent together and water is forced through

them. A flash boiler be different from the sort of water tube steam generator in which the tube is always

filled with water. In a flash boiler, the tube is held so hot that the water feed is rapidly flashed into steam and

superheated.

SAFETY FACTORS IN BOILERS

Exterior shell and/or insulation: Asses for signs of overheating.

Leaks: Stare for water on the floor. Asses for water or steam escaping from any fragment of a

Pressurized system including the boiler, valves or piping.

Flue gas leaks: Look for black dust (soot) about sheet-metal joints. Asses any portion of Boiler

enclosure and rupturing, especially in the connection to the heap, and Asses the Boiler exhaust

system reliability.

Controls: Stare for open panels, covers and signs of rewiring on floor or bottom of panels. Asses for

jumper wires and locked shutoffs.

Safety Devices: Assessment of all operating controls and safety devices for good operation.

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Electrical: Confirm that covers are installed on over-limit switches, temperature sensors and

controls.

Safety valves: Ensure that a safety valve is installed with full-sized discharge piping. Properly

supported and heading for to a point of safe discharge. Safety valve set pressure must be identical to

or less than boiler maximum permissible working pressure. Safety valve Relieving ability must be

equal to or greater than boiler output.

Fuel sources: Asses for the capability to lock off the fuel source to the vessel.

Gages: Make sure temperature and pressure gages are operational and are located for proper

observing.

Hazards: Eliminate all fire risks from the boiler room and do not use the boiler room for Storage.

Air openings: Asses’ combustion air openings for obstructions.

Proper piping: Asses for proper supports and allowance for expansion and contraction.

Steam Generation PROCESS OF STEAM GENERATION:

The Water use for Steam Generation is unionized and demineralize to avoid corrosion. This type of Water is

Called boiler Feed Water BFW.

Water is Preheated by the flue gases and fed on the top of boiler vessel where it is heated by the hot flue

gases which is produce by the combustion . The gas is on the tube or shell side according to the type of

boiler. The hot water naturally flows through the tubes down to the lower area where it is hot. Water boils

and evaporates at 100°C at atmospheric pressure. The enthalpy of vaporization is the energy necessary to

turn water into the steam. For the duration of the evaporation course, pressure and temperature are constant,

and a considerable amount of thermal energy is used for change the water from liquid to vapor phase.

When all the water is evaporated, the steam is called dry saturated. In this condition the steam contains a

large amount of latent heat. Further heating of dry saturated steam will lead to increase in temperature of the

steam. As the Water Boils it leaves the boiler and enters in the superheating coils to superheat.

TYPES OF STEAM:

SATURATED STEAM:

The steam that occurs at temperature and pressure where both the steam and the water can

coexist. It can occur when the rate of evaporation is equal to the rate of condensation.

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INDUSTRIAL APPLICATION:

It is use for the

Heat Transfer

For Humidification

For Cleaning

UNSATURATED STEAM:

The steam which contains a certain wetness due to the non-vaporized water molecules. It is

usually produced by the boilers and requires to be dis-entrained from the steam.

As the water reaches the saturation state and originates to vaporize, some water, usually in the form of mist

or droplets, is entrained in the rising steam and dispersed downstream.

It Contains Moisture Content.

INDUSTRIAL APPLICATION:

It is use in Textile Industry

It is use in Food Industry

SUPERSATURATED STEAM:

When the dry or the wet steam is heated beyond the saturation steam point then the steam

that is produced is at a higher temperature and greater density than the dry or wet steams. This is the

supersaturated steam.

This produces steam that has a higher temperature and lower density than saturated steam at the identical

pressure.

INDUSTRIAL APPLICATION:

In the Power Generation

To operate Steam engines in Rail

In Chemical Industries :

Such as

a. Fertilizer

b. Caustic Soda

METHODS OF HEATING IN STEAM GENERATION

The Steam is generated similarly but there are several methods of heating

1) Nuclear Steam generation

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The Heat of vaporization is provided by controlled fission reaction.

2) Coal Powered Plant

Coal is burnt to produce steam

3) Oil Powered Plant

Furnace oil is burnt to provide required heat

4) Solar powered Plant

The Rays of light from sun via numbers of reflecting mirrors is focuses on the boiler to heat it and

produce steam.