ENERGY AUDIT

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ENERGY AUDIT

• Pinpoint Areas where Energy Efficiency can be
  Improved

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DISTILLATION COLUMN

• Conventional Distillation Column vs Heat
  Integrated Distillation Column
• In conventional column, rectification and
  stripping section are at same pressure
• In HIDC, rectification section is at higher
  pressure than stripping section steam requirement
  decreases and hence energy efficiency is improved
• Rectification and Stripping section are connected
  by compressor and throttle valve

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HIDC Conventional
column
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Heat Integration of Reactor and Distillation
Column

• Energy of Organic vapors can be used to preheat
  the feed
• Vapors are compressed firstly to increase their
  bubble point
• These vapors are feed of distillation column

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Process Description

• The reaction is between pivalic acid and
  benzotrichloride. The reaction is exothermic
• Vapors which leave the reactor have to be
  condensed to remove the HCl which is formed in
  the reactor before feeding to Distillation
  Column.
• One of the ways for heat integration is to use
  heat released by condensation of organic vapours
  for heating of reactants and as a heating medium
  in reboiler. But the problem is that the
  temperature required for heat transfer fluid in
  reboiler and feed preheater should be in the
  range of 210 0C 240 0C while the organic vapour
  condenses at 190 0C.

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Heat Integration

• Organic vapours are pressurized so that its
  bubble point rises to 2400C. The corresponding
  pressure is found out to be 3 atm. Energy
  requirement to compress vapours to 3 atm pressure
  is 20 kJ/s.
• This forms vapors of temperature 3590C. It has to
  be brought down to its bubble point. It is done
  so by pre-heating the feed of the reactor using
  finned tube heat exchanger. The saturated vapours
  are then fed to the reboiler of the distillation
  column

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Energy Saving

• Steam requirement becomes zero after heat
  integration
• Steam requirement before heat integration 5000
  tons i.e. Rs 50 lakhs per year
• Also there is saving of pumping 28.5m3/hr. Pump
  Power 4kW i.e. approx 2.6lakh.
• Compressor Duty (assuming 50 compressor
  efficiency) 40kW i.e. approx. 26 lakhs per
  year.

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Increasing Efficiency in Heat Exchanger

• Air Cooled Heat Exchangers Low HTC so large area
  and consume a lot of metal
• First Generation Equilateral Pitch 63.5-67mm.
• Second Generation Equilateral Pitch 58mm. Gives
  Energy Saving of 8-10
• Further instead of using equilateral pitch
  increase the Longitudinal pitch and keep
  Transverse pitch constant increases the energy
  efficiency by a further 10.
• Also, addition of fins and ribs increases the
  surface area which increases the energy efficiency

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Pump Selection

• Centrifugal
• Positive Displacement
• Advantages of centrifugal pumps
• Very efficient
• Produce smooth and even flow
• Reliable with good service life

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Systems requirement
Flow ?
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Pump sizing

• Pump must be operated within 20 of the maximum
  efficiency value.
• Understanding of the system requirement is
  important parameter.

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Case study

• Flow rate of liquid 1 m3/sec.
• Head required 46 m
• Pump 1 operating efficiency 81
• Pump 2 operating efficiency 72
• Cost difference Rs. 2.5 L
• Reduction in power 20 kW
• Reduction in energy 16000 kWh/yr.
• Savings Rs. 11.2 L

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Thank You