Furnace equipments products

Heat Recuperators

The glass industry is very energy intensive and measures to save or recover energy is a key factor in the design of glass melting furnaces.

Glass Service has developed several technologies to save energy saving including the recovery of thermal energy from the waste gases using metal recuperators. Metal recuperators are a simple and low cost investment for the recovery of waste heat and preheat the combustion air. The Glass Service technology has developed two different recuperator type:

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Double shell:

  • Low investment
  • Temperature of combustion air preheating max 600°C
  • Easy maintenance and easy installation

Tube bundle:

  • Temperature of combustion air preheating max 800°C
  • External refractory shell can be used for several campaign

Both recuperators can be installed with either bottom/top waste gas flow or top/bottom flow. The steel quality used is a function of the glass type to be melted and the fuel used (NG or heavy oil) as well as the pollutants in the fuel (e.g. Sulfur). Thanks to over 22 years experience designing and constructing metal recuperators for continuous use, the Glass Service, design plus the selection of the correct steel quality can guarantee a long recuperator life.

The fuel saving from recovering waste heat can be calculated as approximately 5% for each 100°C of combustion air preheat. Glass Service can calculate the specific fuel saving for each specific application.

Double Shell Recuperators

Type of recuperators

Double shell type heat exchanger are manufactured from stainless steel with refractory and outer insulation. These type of recuperators are made from one inner and one outer stainless steel shell with a suitably positioned axial expansion joint. The assembly is then insulated with ceramic fiber and rock-wool and clad with 0.6 mm thick aluminum sheet.

Single or double stage

Combustion air flows between the inner and outer shell while melter exhausts flow inside the inner shell. To improve the heat exchange, stainless steel fins are fitted to the inner tube. For a double shell recuperator, the maximum preheat temperature is 600°C depending on the application. The combustion air is introduced at the base of the recuperator and exits at the top (parallel flow – for combustion air and exhaust gases). Double shell recuperators can be supplied in two versions:

  • SINGLE STAGE, comprising a single recuperator.
  • DOUBLE STAGE, comprises two recuperators, installed one over the other.

In the DOUBLE STAGE configuration, after the combustion air leaves the lower recuperator, it flows into the upper recuperator from the top and exits from the bottom as shown in the picture. Each recuperator is suspended from a steel structure with 4 supporting rollers to allow lateral movement for maintenance.

Single stage data

Model REC-C-080/200
-..-S-AA		 REC-C-095/300
-..-S-AA		 REC-C-095/450
-..-S-AA		 REC-C-120/300
-..-S-AA		 REC-C-120/300
-..-S-AA
Number of stages
mm
1
1
1
1
1
Internal diameter
mm
800
950
950
1200
1200
Total height
mm
2000
3000
4500
4500
5500
Theoretical preheat temperature
°C
550
Exchange surface
m2
5,0
9,0
13,4
17
21
Natural gas max flow P.C.I.:
8500 Kcal/Nm
Nm2/h
65
110
170
220
270
Stainless steel flexible joint
diameter to burner manifold
Inch
10
12
16
16
16

Double stage data

Model REC-C-095/300
-..-S-AA		 REC-C-095/450
-..-S-AA		 REC-C-120/450
-..-S-AA		 REC-C-120/550
-..-S-AA
Number of stages
mm
2
2
2
2
Internal diameter
mm
950
950
1200
1250
Total height
mm
6000
9000
9000
11000
Theoretical preheat temperature
°C
550
Exchange surface
m2
17,9
26,9
33,9
42
Natural gas max flow P.C.I.:
8500 Kcal/Nm
Nm2/h
230
340
440
550
Stainless steel flexible joint
diameter to burner manifold
Inch
12
16
18
18

Tube Bundle Recuperator

1.

Tube bundle recuperators can be supplied in two versions:

  • SINGLE STAGE, comprising a single recuperator
  • DOUBLE STAGE, comprising two recuperators, one over the other. In this case first one is a tube bundle recuperator, the second in the top position is a double shell recuperator

2.

The tube bundle recuperator comprises:

  • An external metal cylindrical shell lined with a layer of insulating refractory with a high temperature, high resistance layer, the material selected being dependent on the nature of the glass being melted
  • The tube bundle cage, includes special finned stainless steel tubes for improved heat exchange
  • Monitoring thermocouple in several locations

3.

For a single stage tube bundle recuperator, the typical maximum preheat temperature is considered to be 650°C, a two stage recuperator, 850°C depending on the application.

The design and resulting design of a recuperator is specific to the application taking into consideration:

  • Temperature of exhaust gases
  • Exhaust gas flow
  • Preheating conditions
  • Excess air
  • Glass type, etc.