Process drying hot air generators are not space heaters
If you arrived here looking to heat a building, this page will save you time.
Two different machines are sold under the name hot air generator. One is process equipment: it holds air at a 50–150 °C setpoint and moves it over a product until the moisture reaches a target. The other warms an occupied space to a comfort band. Confusing them wastes an enquiry.
The six differences that decide it
The confusion is reasonable: both machines burn a fuel, heat air and blow it down a duct. Everything after that differs, and every line below changes the specification.
| Process drying hot air generator | HVAC / space-heating hot air generator | |
|---|---|---|
| Purpose | Drying a product to a target moisture content | Heating an occupied space |
| Heat transfer | Indirect, through a heat exchanger | Often direct-fired |
| Air contact | Air touches food or product — must stay clean | Air touches people |
| Temperature control | Held to a process setpoint | Comfort band |
| Typical fuel | Biomass: pellets, briquettes, crop residue | Gas, oil, electricity |
| Typical buyer | Food processor, agro-processor, dryer operator | Building services, sports facility, workshop |
The heat-transfer row is the one that decides it. A direct-fired generator puts combustion products into the delivered air, which does not matter when you are warming a warehouse and disqualifies the machine outright when that same air touches food.
If you are heating a building
We do not supply that equipment, and saying so now beats an exchange of emails. If what you need to heat is a warehouse, a workshop, a hangar, a sports hall, an air-supported or pressostatic structure, a spray booth or any other occupied volume, the equipment is a unit heater or a space-heating hot air generator — a building-services product.
The terms worth searching are “gas unit heater”, “space heating hot air generator”, “industrial warm air heater” and, for inflatable domes, “pressostatic structure heating”. The suppliers of those machines are HVAC specialists, and they are not us.
One distinction worth carrying into the comparison: a heater is judged on combustion efficiency and the comfort it delivers, while drying equipment is judged on water evaporated per unit of fuel. Those are different calculations, and a supplier who quotes you the first when you need the second has not understood the duty.
If you are drying a product
Then you are in the right place. These are the numbers that describe the machine on the left-hand column of the table above — if they match the duty you have in mind, this is the equipment class you want.
| Parameter | Value |
|---|---|
| Delivered air temperature | 50–150 °C, held to a process setpoint |
| Airflow | 2,500–3,000 m³/h per generator |
| Heat transfer | Indirect — double chamber, three-pass exchanger |
| Matched burner | 200,000–900,000 kcal/h |
| Fuel | Biomass: pellets, 90 × 90 mm briquettes, loose crop residue |
See the biomass hot air generator for the equipment itself, industrial drying duty for what it is asked to do, industrial tunnel dryers for the chambers it feeds, and the biomass fuel envelope for what can be burned in it.
Frequently asked questions
Can I use a process drying hot air generator to heat my workshop?
Technically yes, and it would be a poor purchase. The machine is built to hold a process setpoint between 50 and 150 °C through an indirect heat exchanger, which is expensive in exactly the place space heating does not need it. A direct-fired unit heater does the same thermal work for a fraction of the cost.
Why does process drying require indirect heat transfer?
Because the air touches the product. Direct firing puts smoke, ash and CNSL-derived compounds into the air stream, and they arrive on the food as odour or surface deposit. The exchanger keeps the two streams apart, and that is what makes 50–150 °C air usable in a food process at all.
Can both machines run on biomass?
Yes, but they are optimised for different things. A biomass heater is judged on delivered cost per kWh; a biomass dryer is judged on water evaporated per kilo of fuel, across a 3,200–5,100 kcal/kg envelope depending on the residue. The two sizing calculations do not overlap.