Preheater is a general term to describe any device designed to preheat the combustion air used in a fuel-burning furnace for the purpose of increasing the thermal efficiency of the furnace. The combustion air preheaters are used for the large fuel-burning furnaces used to generate steam in thermal power plants. The air preheater increases the steam generator's thermal efficiency by preheating the combustion air with heat recovered from the hot combustion flue gases.
The two most often used categories of preheaters in thermal power plants are regenerative air preheaters and tubular air preheaters.
Regenerative air preheaters
Regenerative air preheaters are special types of heat exchangers designed to recover or reclaim heat in order to reuse or recycle it.
Rotating-plate regenerative air preheater
The rotating-plate air preheater (RAPH) consists of a central rotating-plate element installed within a casing that is divided into sectors.
- Preheating of both lube oil and coolant for engines of all sizes
- External and internal immersion coolant heaters
- Convection circulation and pump circulation
- Heating of coolant, lube oil, and diesel fuel for layover periods to ensure easy start
- Heating of fuel oil for standby units such as generator sets to ensure reliable start
- Industrial, marine, railroad, and on-road applications
- Heating of hydraulic, transmission, and industrial oils
- Controls and accessories
- Hazardous locations (Class I Group D) and weather tight
- Battery warmers and thermal pads
Preheater process has got many advantages such as: Good preheat effect, suitable for any cement raw materials, not easy to be damaged and blocked up, materials fed into the kiln easily to be separated, and the system is well sealed up.