steam trap, steam ggeneration and boilers

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  • S.M. Taha Rehman Siddiqui

    E11-PG08

    Separation Process Lab-1

    By

  • 1

    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 o