Unit Operations in Process Plants
Distillation / Evaporation
Heat Transfer
Pumping and Compression
Filtration / Crystallisation
Chemical reaction processes
Energy Minimisation in Distillation
Typically distillation is a maximum energy consuming unit operation deployed in Refineries and Petrochemicals
Energy Requirement : 40 – 60 % of the total Energy
Energy Minimisation in Distillation
Distillation at low pressure
Maximizing Pump Arounds in Petroleum type distillation
Compensating seperation with increased no of stages as Pump Arounds will reduce internal reflux
Drawing products/Pump Arounds at maximum temperature for preheating feed/utilities.
Optimisation of Stripping steam / overflash
Energy Minimisation in Distillation
Overhead Heat Integration
GAS
FEED
Preferred for super fractionators and also in crude distillation
Conventional Process
GAS
FEED
Example:-1 Butene Separation process
Energy Minimisation in Distillation
Heat Coupled Process
Example:-1 Butene Separation through Heat Coupled Process
Energy Minimisation in Distillation
FEED
Heat Coupling in Distillation
GAS
FEED
Example:-In super fractionator or distillation column operating with high R/R, above type of Heat coupling is beneficial
Energy Minimisation in Distillation
Multiple Heat Coupling
GAS
Example:- Xylene Column of Px Plant
REB-1
REB-3
REB-2
Energy Minimisation in Distillation
Low Temp heat integration in Distillation column
Conventional
FEED
Energy Minimisation in Distillation
Steam reboiler
190 C
Low Temp heat integration in Distillation column
FEED
Energy Minimisation in Distillation
To Crude Preheat Train
Energy Minimisation in Crude/Vacuum Distillation
Overhead Integration
Maximisation Pump Arounds
Introduction of top PA
Use of Pretopper
Low column pressure
Avoid successive distillation and try to draw product from same distillation column.
Top Pump Around crude integration
FEED
Energy Minimisation Crude/Vacuum Distillation
Crude
PA’s are maximised to reduce R/R and seperation is compensated by higher nos of stages
Conventional stripping of CLPS Stream
CLPS LIQ
Energy Minimisation in Hydrotreaters/ Hydrocrackers
FRACTIONATOR
GAS to LE Section
STABILISER
Adding Stripper ahead of Main Fractionators
CLPS LIQ
Energy Minimisation in Hydrotreaters/ Hydrocrackers
STEAM
MP STRIPPER
FRACTIONATOR
Eliminate WGC
Reduce reboil requirement for stabiliser/de-ethaneiser
GAS
Addition of heat exchangers /steam generators in between successive reactors
FRACTIONATOR
Energy Minimisation in Hydrotreaters/ Hydrocrackers
HPS
CLPS LIQ
FEED RG
Energy Minimisation in Hydrotreaters/ Hydrocrackers
Even Steam Generators can be installed to recover heat of individual reactors
Utility generation in HP heater convection to increase efficiency of HP furnaces
CHPS/HHPS CLPS/HLPS 160 Kg/cm2g
Pressure RT Cascaded with drives of feed pump to provide around 30% pump power drive
Energy Minimisation in Hydrotreaters/ Hydrocrackers
PRT
HHPS/CHPS HLPS/CLPS
25 kg/cm2g
WASH WATER
GAS
CONVENTIONAL DESIGN
CHPS
55 – 60 C
RxEFFLUENT
AIR COOLER
RGC
Energy Minimisation in Hydrotreaters/ Hydrocrackers
HEATER
FRACTIONATOR
CLPS
Use of HHPS to conserve heat instead of CHPS
WASH WATER
R GAS
CHPS
55 – 60 CRxEFFLUENT
AIR COOLER
RGC
MODIFIED ENERGY EFFICIENT DESIGN
Energy Minimisation in Hydrotreaters/ Hydrocrackers
~180 C HHPS
HLPS
~180 C
FRACTIONATOR
CLPS
Very Low Temp heat integration
Hot products are cooled by tempered water coolers and the tempered water is cooling with heating of DM Water before feeding to Deaerators
Overall pinch to improve plant efficiency / Grand composite
Energy Minimisation Refinery
Energy Minimisation in Coker
Efficient integration of feed preheat circuit
Maximisation of Hot feed streams
Recovery of Blowdown tower off gases
Energy Minimisation in FCCU
Maximize Main Column Bottom Pump Around to heat feed /raise BFW
PRT for air blower---Regen. Flue Gas PRT provides part of power to drive main air blower
Two stage regeneration --- First stage: 2C+O2=2CO CO incinerator --- Second stage:2CO+O2=2CO2
Feed Preheat improvement
Energy Minimisation in other processes
Separation done through Molecular Sieve or Membrane separation technology as a substitute of distillation/extraction
-- ISOSIV for separation of iso-paraffins from normals -- PSA for H2 separation from Syn Gas -- Molex Process- for ext of n-paraffin for LAB prodn -- Parex Process- for ext of p-xylene for PX prodn
Supercritical extraction of Asphalts with propane
Introduction of Low Pressure Technologies
Energy Minimisation in Refinery
Furnace Flue Gas temp lowering either with APH or outside/inside mounted steam generator
Excess Air Control
Steam Generation in HP Furnaces
General for Furnace Efficiency Improvement
Energy Minimisation in Refinery
Use of packinox to low approach Heat Exchangers
Cleaning of Heat Exchangers periodically
Better thermal design with optimum velocities
General for Heat Exchanger Efficiency Improvement
Energy Minimisation in Refinery
Minimise Recirculation / Spillback flows
Operate at the best efficiency point to the extent possible
Better specification of pumps / compressors during design stage for operation around best efficiency point.
Pressure cascading to avoid successive pumping and compression.
General Pumps & Compressors Efficiency Improvement