In these recuperators, the heat transfer between the primary and secondary fluids is done by radiation..

This kind of exchange is most influenced by the temperature, so as these recuperators are suitable for the following cases:

  • When the flue-gases temperature is higher than 1.000 - 1.050 oC.
  • When the components of the flue-gases are aggressive or contain a high percent of particles.

Tubes cage radiation recuperator working at 1200 oC

Double Shell type

Constructed with two concentric cylinders where the secondary fluid circulates through the circular crown in parallel to the recuperator axe or helicoidally, at counterflow or in parallel flows.

They are suitable for working pressures up to 2.000 mm. W.G. due to the low mechanical resistance of the inside shell at these high working temperatures.

Their main advantages are as follows:

  • Decrease of the fuel consumption, which may be sometimes more than a 40% lower by preheating the combustion air.
  • No pressure drops in the gases, as a result of the geometric design of this kind of recuperators.
  • Compact design, which makes their installation in the gases stack to be easier.

This kind of recuperators is suitable for heart furnaces in the steel industry, frit melting furnaces, glass furnaces, aluminium furnaces, etc.

Double shell radiation recuperator

Tubes Cage type

In these recuperators the inside shell is substituted by a ring arranged tubes cage, where the air circulates, in order that the heat transfer follows on being done by radiation.

Among their main advantages, we can remark:

  • A better distribution of the air, resulting in a homogeneous temperature of the tubes in the cage.
  • A higher resistance to corrosion, due to a better choice of the material.
  • An easier maintenance, since the exchange element (tubes cage) is independent from the frame.
  • Higher working pressures, even up to 6.000 mm. W.G.

These recuperators are usually installed in smelting furnaces of the glass industry.

Tubes cage radiation recuperator

Combined installations

When a maximum thermal profit of gases is intended, it is advisable to use installations composed by two or more series-connected recovery units, as illustrated in the next sketch.

This system avoids the installation of only one but large recuperator, which would result in more problems in its working and maintenance as well as in higher construction costs.

There are most possibilities available and, depending on our customers' needs, different types and models of recuperators may be combined.

Installation consisting of a tubes cage recuperator and a double shell one, series-connected

FIFFI type

FIFFI type radiation recuperators are the result of a long experience both related to their study and their operation.

In these recuperators, the heat transfer between the primary and secondary fluids is done by radiation.

They consist on a chromium alloy cast body, which makes them especially suitable for those cases where the gases contain corrosive substances and then it would not be advisable, even nearly impossible, to use other kind of recuperators constructed in rolled steel sheet.

The said cast body is fitted with a set of ribs in the air side, which provides the heat exchange between primary and secondary fluids resulting in lower wall temperatures.

It makes possible to use less exigent materials for the construction of the exchange element and this implies an important reduction in the recuperator cost.

FIFFI type radiation recuperator


Generally talking, these recuperators are designed to be installed in high temperature furnaces.

In a more specific way, they are suitable for the following cases:

  • Heart furnaces.
  • Welding furnaces.
  • Melting furnaces.
  • Glass furnaces.
  • Roasting furnaces.


FIFFI type radiation recuperator works with flue-gases temperatures between 1.000 and 1.500 oC, being successful in heating the secondary fluid (the air) up to 550 oC.

FIFFI type radiation recuperator

A 400 500 600 800 800
A1 300 400 450 600 600
B 452 552 652 852 852
E 680 780 880 1080 1080
F 390 440 500 630 630
G 145 170 205 210 210
H 910 1060 1090 1180 1580
M 1200 1400 1500 1600 2000
NW 125 151 212 250 250
Dimensions / mm
Fuel Consumption
Air flow Natural Gas 9.000 Kcal/Nm3 Propane gas 22.900 Kcal/Nm3 Fuel-oil 9.600 Kcal/Kg
Type Nm3/h Nm3/h Nm3/h Kg/h
II 170-500 16,2-47,5 6,6-19,3 14,5-42,7
III 220-630 20,9-60 8,5-24,4 18,8-53,8
IV 280-750 26,6-71,3 10,8-29 24-64
V 375-1.000 35,6-95 14,5-38,7 32-85,4
VI 375-1.200 35,6-114 14,5-46,5 32-102,5
Max. gases temperature: 1500 oC
Max. air temperature: 550 oC
Pressure drops in the air side: approx. 120 mm. W.G.
Material: Ha/A2

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