HAB indirect-fired air heater

In the HAB, clean air flows continuously at 5–6 m/s around the combustion chamber and the flue tubes, in turbulent flow with no dead zones. It takes up the heat of the flame and flue gases through the tube and chamber walls and never mixes with the combustion products. The heater is non-pressurised and can be built horizontally or vertically. TSB supplies the HAB for diesel, fuel oil, natural gas, LPG, LNG or biogas, with a heat output of up to 7000 kW (6 000 000 kcal/h) and clean air temperatures of up to 380 °C.

Burner and driven clean-air fan run together under PID control; modulation sets the heat input over a range of up to 20:1 and keeps the process air outlet temperature fully under control. Heating begins 10–15 seconds after start-up. Compared with steam heating, the HAB avoids condensate, flash steam and blowdown losses, needs no make-up water and discharges no waste water. It can sit upstream or downstream of the process air fan under positive or negative pressure. With clean combustion, NOx stays below 70 mg/Nm³ on gas and below 150 mg/Nm³ on liquid fuel; with a suitable burner it can fire up to 100 % hydrogen.

Three insulation layers on the front door and the rear chamber door — Hycast SS alumina-enriched refractory concrete, ceramic fibre blanket and ceramic paper — keep the doors safe to touch, and the outer wall has 100 mm of high-density insulation. Shell and covers are P355GH boiler plate or, for hygienic applications, AISI304 stainless sheet; flue tubes are AISI304 or AISI321, and tube plates and combustion chamber AISI310S and AISI253 high-temperature stainless steel. The PLC monitors the air flow pressure switch, outlet temperature protection, flue and surface temperatures; data go out via Modbus, Modbus TCP/IP or Profinet. Design follows EN 13445 and ASME Section VIII Div. 1.