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Content archived on 2022-12-27

CULLET PREHEATING

Objective

To achieve considerable energy savings through use of preheated cullet in the glass melt. The waste gases, which up until now have been lost to the atmosphere, are taken as heating medium from the waste gas channel of the melting end. The procedure requires a considerably lower use of combustibles.
For a 200 t/day production rate, an energy saving of 67 TOE/year is expected at project level (12% of the total energy consumption). Payback time is estimated at 4 years.

Principally glass is melted out of a composition of different raw materials, e.g. silica sand, lime, soda and glass cullet. Oil, gas or electrical energy can be used as heating media. The individual raw materials are mixed in the processing installation and are fed to a storage silo situated in front of the melting process by means of batch chargers. The initial temperature of the batch is 20 deg. C, whereas the melting temperature ranges between 1400-1500 deg. C. The waste gases are primarily fed again into the melting process by means of heat exchangers (regenerators) or recuperator, thus reducing the waste gas temperature to approx. 500 deg. C by preheating the combustion air. The novelty of this project consists in preheating the glass cullet prior to the mixing with other raw materials, by covering the waste gases energy at a level of approx. 500 deg. C.
The glass cullet is firstly led to a preheating aggregate. The humidity of the cullet can be reduced by this preheating, which results in improved conditions for the melting process.
The main characteristic of this system is the direct contact between cullet and waste gases. Up until now the gases from the melting durnace have been cooled down to approx. 400-500 deg. C in recuperators or regenerator heat exchangers, and then released into the atmosphere, in most cases without any further waste gas treatment. With the new system the residual heat content of the waste gas is used to pre-heat the cullet. If the system is correctly designed, then not only is the cullet heated, but the dust content of the waste gas is reduced by approximately 30-40 %.
The cullet is contained by louvred segments. The openings for the waste gases are designed so that the gas velocities are very low, which helps to reduce the dust emission.
The waste gases, which must have a maximum temperature of no more than 550 deg. C, move in cross counter flow up through the cullet. In this way a large amount of the heat content of the waste gases is transferred to the cullet as it flows slowly from the top to the bottom. The cullet stream moves continuously, so the contact area is continuously renewed, which guarantees a very good heat exchange. The cullet is heated to a maximum of 450 deg. C, whilst the waste gas leaves the system with a temperature of 250-300 deg. C.
In addition to the energy savings, the project will also achieve improved glass qualitites, and reduced reject rates due to the better furnace temperature.
as well as reduced dust and halogen emissions, a fact that contributes both in environment protection and profitability. Additional advantage of this system is the very short amortization period.

Call for proposal

Data not available

Coordinator

NIKOLAUS SORG GMBH AND CO
EU contribution
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Address
STOLTESTR 23
8770 LOHR
Germany

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Total cost
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