Thermal Applications


The first LOESCHE hot gas generators were developed, built and delivered in 1960, and were available both with and without refractory linings. Which hot gas generator is used depends on the desired outlet temperature for the downstream processes and on the dust content of the process gas to be heated. Up till today far more than 640 LOESCHE hot gas generators were delivered and commissioned worldwide.

For decades Loesche hot gas generators have been used around the world in a wide range of thermal processes in order to provide an optimum thermal configuration of the process.

It is used to heat:

  • fresh air
  • return gases
  • cleaned exhaust gases
  • hot blast furnace gases
  • process gas with low dust content

LOESCHE hot gas generators are ideally suitable for direct drying processes and are used for example in conjunction with:

  • grinding plants
  • drum-type driers
  • fluidised-bed furnaces/driers
  • flash driers
  • spheroidisers

How it works

The flow of process gas entering via the spiral housing (3) cools the protective jacket (5), the burner muffle (2) and the perforated jackets (6) as a result of flow control.

The process gas passes through the ring slots (4) and holes in the perforated jacket into the interior of the combustion chamber, where it mixes with the hot smoke gases from combustion.

The combustion chamber geometry and flow control protect the perforated jacket against the flame and the hot smoke gases. The combustion chamber has an overall pressure loss of 2 – 3 mbar.



How it works

The process gas is drawn or forced through the spiral housing (3) into the combustion chamber and flows through the ring slot (4) between the burning chamber (5) and muffle housing (2) into the combustion chamber.

Here the process gas mixes with flue gas from the combustion process of the burner (1). The mixing of these two gas flows results in the desired outlet temperature at the hot gas outlet (6).

For burning lean gases

The multiple-lance burner comprises a number of individual nozzles for lean gas and combustion air, thereby enabling lean gas to be fully combusted without a supporting flame. Both media strike one another within the nozzle system at high velocity. This provides for an intensive mixing of the media, and thereby ensures that the basic requirement for efficient combustion is achieved. The main burner has a control range of 1:10, the start burner has a control range of 1:5 to 1:8.

Every necessary operating point within the control range of 1:40 to 1:70 can therefore be easily achieved.

Our Portfolio comprises the burner, the gas regulating station, the complete burner control (LOMA Control, service for the installation, commissioning and After-Sales Service). 


The use of hot gas generators in industrial plants is characterised by the different ways in which they are integrated in the process.
Three variants are shown using dry-grinding plants with a Loesche mill as the example.

Integration in the return gas line 

In this arrangement the entire process air for the dry-grinding process is routed through the hot gas generator.

This arrangement provides for maximum energy recovery and is necessary for example when process air that is low in oxygen (inert operation) is stipulated for safety reasons during the comminution of combustible grinding stock.

Installation in a bypass to the return gas line

Here only some of the process air is routed through the hot gas generator.

This variant is chosen if, on account of large plants, the volumetric flow of process gas would necessitate very large combustion chambers and high investment costs would be incurred. The use of only a small proportion of the process gas means that the combustionchamber has significantly smaller dimensions.

Flanged to a return gas line

In this arrangement, fresh air (and not process air) is routed through the hot gas generator.

This variant is chosen primarily when the hot gas generator is only required for starting the overall system and is then shut down.