Control and regulation of boiler operation

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Control and regulation of boiler operation

• Heat Engines Boilers

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Contents

• Hot- and warm water boiler operation controland
  safety limits
• Domestic heating and hot water generation control
  
• Hot- and warm water boiler operation controland
  safety limits- Spray type superheat control-
  Water level control
• Boiler controls for operation without permanent
  supervision
• Steam supply system principals
• Steam traps

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Hot- and warm water boiler operation control
Thermal oil boiler control is similar

• In these type of systems there is not phase
  change only heating up of heat transfer medium
  happens. Useful heat can be expressed according
  to following expression.
• Quseful mwater ? c ?( tout tin )
• Heat supply is controlled mainly by two ways-
  In case of quantity control inlet and outlet
  temperature level constant and mass flow rate of
  heat transfer medium is modified - In case of
  quality control inlet and outlet temperature
  level modified and mass flow rate of heat
  transfer medium is constant
• Power level control happens generally from outlet
  temperature of the boiler(Power level control
  means burning fuel control done generally by
  fuel inlet quantity control)

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Safety limits

• Maximal outlet temperature
• Minimal inlet temperature(in case of non
  condensing boilers)
• Overpressure limitation
• Heat transfer medium absence limitation
• Minimal flow limitation

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Domestic heating system control
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Heating water temperature variation
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Domestic heating and hot water generation control
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Steam generator operation control

• In case of steam generator useful heat can be
  calculated according to following expression
• Quseful msteam ? ( hout hin )
• Heat demand variation results variation of steam
  mass flow rate. Mass flow rate variation at
  constant power level and at constant feed water
  parameters results outlet enthalpy and outlet
  pressure variation.
• Power level control happens generally by means of
  outlet pressure control, because of previously
  detailed phenomena.(Power level control means
  burning fuel control done generally by fuel
  inlet quantity control)

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Outlet temperature control

• In case of saturated steam outlet temperature is
  not needs to be controlled, because outlet
  temperature is determined by saturation
  condition.
• But in case of superheated steam generation
  superheat temperature is affected by load
  conditions, and several operation parameters, so
  it needs to be controlled.
• Earlier several methods were used for superheat
  temperature control,
• but nowadays only spray type superheat control is
  used.

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Spray type superheat control

• Of all the direct contact types, the spray
  attemperator has proved most satisfactory.
• Water of high purity is injected directed into
  the superheated steam main or into a mingling
  chamber.
• The water is sprayed in through a series of
  nozzles at the throat of a venturi section,
  forming a fine mist.
• It is quickly vaporized and first mixes with and
  then cools the superheated steam. The design must
  include a thermal sleeve to protect the piping
  from thermal shock caused by water droplets
  striking the hot surface.

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Spray at different locationsfor outlet steam
temperature controlat the boiler outlet in
between two superheater
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Installation of a spray type attemperator
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Installation of a spray type attemperator
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Typical injector construction of spray type
attemperators
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Feed water quantity control

• According to actual evaporated water quantity the
  same amount of feed water needs to be fed into
  the boiler.
• Generally water level in the drum is used for
  this task.
• In case of once-through type boilers it has to be
  connected with power level control.

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Water level sensors
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Water quality control

• At any type of water treatment a certain amount
  of salt is delivered to the boiler with feed
  water.
• But the steam delivers nearly any salt out from
  the boiler.
• So salt is accumulated in boiler water. Over a
  certain concentration it can cause operation
  troubles e.g. foaming of water, etc.
• So salt concentration needs to be held below a
  certain concentration level.
• This is solved by letting out some boiler water
  quantity, which is called slugging or
  desalination. Fresh feed water will reduce salt
  concentration

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General safety limitations

• Maximal outlet pressure is generally limited by
  both- electronic and - mechanical way with
  safety valves
• Maximal outlet temperature
• Water level limitation- minimal more important-
  maximal less important
• Boiler water quality limitation- salt
  concentration by means of water conductivity

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Boiler operation supervision

• In general case boiler operation is potential
  danger, so it needs continuous attendance to
  supervise.
• With fulfilling special requirements boiler can
  be operated without permanent attendance. But it
  does not mean without attendance, it means only
  that supervisor visit needs to be held regularly,
  and not continuously.
• Special requirement means that boiler has to be
  protected automatically from all the possible
  dangerous operation condition

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Boiler controls
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Shell boilers controls
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Condensate monitoring for salt and oil pollution
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Boiler and auxiliary controls
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Steam supply system principals
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Flash steam formation
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Flash steam formation
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Example for steam trap installation
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Float steam trap
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Operation of a thermodynamic steam trap
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Operation of a bimetal steam trap
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Termic steam trap
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Summary

• You are already familiar with
• Hot- and warm water boiler operation controland
  safety limits
• Domestic heating and hot water generation control
  
• Hot- and warm water boiler operation controland
  safety limits- Spray type superheat control-
  Water level control
• Boiler controls for operation without permanent
  supervision
• Steam supply system principals
• Steam traps

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Thank You for Your Attention !