Heat Recovery Steam Generators — HRSG
Petro Energy Man engineers Heat Recovery Steam Generators (HRSGs) for conversion of high-temperature exhaust-gas energy into useful steam.
HRSGs can be applied downstream of gas turbines and other industrial processes where significant thermal energy remains available in the exhaust stream.
The objective is to maximize recoverable energy while controlling gas-side pressure drop, steam conditions, material temperatures, equipment dimensions and operational reliability.
Heat-Recovery Principle
Hot exhaust gas enters the HRSG and transfers thermal energy progressively through selected heat-transfer sections.
Depending on configuration, these may include:
Superheaters
Evaporators
Economizers
Steam Drums
Reheaters
Feedwater Preheaters
Gas temperature decreases progressively through the unit before the exhaust gas is discharged through the stack or routed to downstream treatment equipment.
HRSG Configurations
Petro Energy Man can engineer different configurations based on plant requirements:
Horizontal Gas Flow
Vertical Gas Flow
Natural Circulation
Forced Circulation
Single-Pressure Systems
Dual-Pressure Systems
Multi-Pressure Systems
Fired HRSG
Unfired HRSG
Supplementary-Fired HRSG
Process Waste Heat Boilers
High-Pressure and Low-Pressure Sections
For multi-pressure arrangements, independent HP and LP circuits may be incorporated.
Typical sections may include:
High-Pressure Circuit
HP Economizer
HP Evaporator
HP Steam Drum
HP Superheater
Low-Pressure Circuit
LP Economizer
LP Evaporator
LP Steam Drum
This arrangement enables more effective utilization of the available exhaust-gas temperature profile.
Economizer
The economizer recovers lower-grade heat from the flue gas and transfers it to boiler feedwater before the water enters the evaporation circuit.
Engineering considers:
Feedwater inlet temperature
Gas outlet temperature
Approach temperature
Tube geometry
Gas velocity
Fouling
Corrosion risk
Pressure drop
Evaporator
The evaporator provides the primary steam-generation duty.
Its design requires careful evaluation of:
Heat-transfer rate
Circulation ratio
Steam quality
Tube arrangement
Gas-side temperature profile
Tube-metal temperature
Fouling tendency
Steam Drum
The steam drum provides steam-water separation and serves as a key component in maintaining stable circulation.
Drum engineering includes:
Separation requirements
Drum internals
Normal water level
Low and high water levels
Steam disengagement
Blowdown connections
Chemical dosing
Instrument connections
Superheater
The superheater raises saturated steam to the required final steam temperature.
Particular attention is given to:
Tube-metal temperature
Steam-flow distribution
Gas temperature
Overheating risk
Material selection
Thermal expansion
Startup and transient operation
Supplementary Firing
Where additional steam production is required, an HRSG can incorporate supplementary firing.
The firing system may be engineered for:
Natural Gas
Refinery Fuel Gas
Hydrogen-Blended Gas
Other Suitable Gaseous Fuels
Supplementary firing is integrated with the gas turbine or upstream process conditions to maintain stable thermal performance.
CFD-Based Gas Flow Optimization
Uniform exhaust-gas distribution across the HRSG tube banks is essential for reliable performance.
Petro Energy Man can employ 3D CFD simulations to evaluate:
Gas inlet distribution
Flow maldistribution
Recirculation
Local high-velocity zones
Tube-bank velocity profile
Pressure drop
Temperature distribution
Flow through transition ducts
Stack flow behavior
Optimization of the gas path improves heat-transfer uniformity and helps reduce local overheating and erosion.
Materials Engineering
Material selection depends on:
Steam pressure
Steam temperature
Gas temperature
Gas chemistry
Corrosion mechanisms
Design life
Potential materials include appropriate carbon steels, Cr-Mo low-alloy steels, stainless steels and corrosion-resistant alloys or overlays where necessary.
Emission-Control Integration
HRSG systems can be configured for integration with:
Selective Catalytic Reduction — SCR
CO Oxidation Catalyst
Flue Gas Monitoring
Downstream Emission-Control Equipment
Applications
Combined Cycle Power Plants
Cogeneration Plants
Oil Refineries
Petrochemical Complexes
Process Furnaces
Steel Plants
Cement Plants
Metallurgical Industries
Industrial Waste-Heat Recovery