What Are High-Pressure and Low-Pressure Heaters?

High-Pressure Heaters (HP Heaters) and Low-Pressure Heaters (LP Heaters) are critical components in power plant feedwater heating systems. These heaters utilize extraction steam from the turbine to gradually heat condensate or feedwater before it enters the boiler. The main purpose is to:

• Increase thermal efficiency of the Rankine cycle

• Reduce fuel consumption and operational costs

• Prevent thermal stress in boiler components

This regenerative heating process significantly improves overall plant performance, making HP and LP heaters indispensable for modern thermal power plants.

How Do They Work?

Low-Pressure Heater (LP Heater)

• Location: Between the condenser and boiler feed pump

• Function: Heats condensate from around 30–40°C up to 80–120°C

• Steam Source: Low-pressure extraction steam from the turbine

• Purpose: Preheats condensate, reducing thermal shock to the boiler

High-Pressure Heater (HP Heater)

• Location: After the feed pump, before the boiler

• Function: Heats feedwater to 180–260°C

• Steam Source: High-pressure or intermediate-pressure extraction steam

• Purpose: Deep heating of feedwater to reduce the boiler’s heat absorption requirement

Working Principle: Steam enters the shell side of the heater, while feedwater flows through the tube bundle. Heat transfer occurs as the steam condenses, and the condensate is drained back through the system.

Key Technical Differences

Benefits of HP and LP Heaters

• Higher Plant Efficiency: Regenerative heating can improve cycle efficiency by 2–5%.

• Fuel Savings: Reduced fuel consumption leads to lower operating costs.

• Equipment Protection: Gradual heating minimizes thermal stress on boiler components.

• Environmental Benefits: Lower coal consumption reduces CO₂ emissions.

Applications

• Thermal Power Plants: Supercritical and subcritical units

• Nuclear Power Stations: Feedwater preheating systems

• Industrial Steam Systems: Chemical, petrochemical, and metallurgical sectors

Why Are HP and LP Heaters Important for Power Plants?

By integrating high-pressure and low-pressure heaters, power plants achieve:

• Improved Rankine cycle efficiency

• Extended boiler life

• Lower energy costs and reduced emissions