A deep knowledge of the glass production process enables us to design and manufacture raw materials handling and storage, weighing and mixing lines and batch conveyance for any kind of glass and for any capacity, for both single and multi furnaces supply and glass colour.

G.T. Conditioning Concept for W-end & Forehearths

The Working End and forehearth concept developed by G.T. is based on the assumption, well proved and generally accepted, that the conditioning of the glass begins just at the furnace exit. The forming process requires to be fed with glass on a viscosity range that is normally much different from the one we find at the furnace exit. In the container plants the Working End and the forehearths must cool the glass, being the exit furnace temperature much higher than what required to grant the necessary glass viscosity for the forming process.
The glass is a material that can not be strongly cooled, therefore the cooling process to be applied must be designed taking into account a number of variables such as the thermal balance, the glass colour, the path, the "head loss". We also cannot forget the chemical aspect, as sometimes the glass quality may be affected by the characteristic of the atmosphere which it is in contact with.

Bearing in mind all the above aspect, G.T. approach is first of all, to calculate the Working End and Forehearth features on the basis of the lay out, which imposes the glass path, together with the different scenarios that are determined by the pull and gob temperature in different situations that can be expected. A specific software has been developed to simulate the operation condition in order to identify the most suitable technical solution.

G.T. cooling concept

Very often the energy to be removed from the glass to deliver the required gob temperature is much higher than what is possible to achieve by the dispersion from the refractory and it is necessary, in this case, to implement some additional cooling.

The forced convection cooling system is based on introducing cooling air through the forehearth superstructure.
Longitudinal centre line cooling, efficiently removes heat from the hot centre glass without adversely affecting side glass temperatures, and using relatively small volumes of cooling air.

The cover roof design has been developed in order to maximize the refractory surface exposed to the glass in the forehearth centre.

This shape allows increasing the heat exchange between the glass and the cover roof since the glass is exposed to a colder large refractory surface.

The application of this system basically involves the application of openings in the superstructure roof blocks, also used for the combustion waste gases exhaust.

The area to be cooled is covered by a refractory tile, made of material with a very good thermal conductivity.

A small refractory channel is installed over the superstructure, so that the channel runs parallel to the forehearth axis.

When cooling air is blown along this channel, the upper surface of the roof block is cooled.
This reduces the temperature of the lower surface of the tile and energy is removed from the glass bath by radiative heat transfer to the cooled tile.
The cooling air travels in the direction of the glass flow and is exhausted, together with the combustion gases, through the centrally located cooling air exhaust.
The volume of the cooling air blown along the channel is adjusted to vary the cooling effect.
The cooling effect is controlled by the flow regulation of the cooling air stream.
The automatic control system will control heating and cooling functions within each independent zone.

The air damper is made of a series of internal concentric air jets creating an air curtain which is controlled to allow either cooling air enter into the superstructure or products of combustion to exhaust from the forehearth, depending on whether they act as a cooling air inlet or flue.

HEATING VALVE TRAIN

Air dampers represent an effective means of controlling forehearth pressure without the use on any moving parts, hence minimising maintenance requirements.

The amount of cooling air entering the cooling channel and the position of the dampers are automatically regulated according to the cooling requirement of the forehearth.

At 100% cooling mode, the dampers are fully opened, the cooling air flow rate is at the maximum and the combustion is at the minimum fire.

Combustion and cooling units

To control the heating and the cooling G.T. provides a unit which is normally supplied preassembled and ready to be installed.

The same ventilators are used for the combustion and for the cooling. The air is fed into a main box to which the heating - cooling section are connected.

The air - gas mix to be sent to the burners is generated independently per each section.

GT can provide "tailored made" solutions according to our customers' needs. GT's combustion-control unit can be supplied according to different "philosophies" of control: one of our typical designs includes a linear characteristic regulating valve with electric actuator, driven by the temperature control system to control the air flow which is passing trough a mixer. The air pressure is detected after the air regulating valve and it is used to control the gas flow by a gas regulator. The gas is fed into the mixer to achieve a proper air - gas mix to be sent to the burners.
The system is designed to assure a constant air - gas ratio in a range of 1 to 10 in terms of supplied energy, with an average error of 1%, (maximum 2%) on the regulation of air - gas ratio (as for observational data).

An alternative solution that GT can provide to customers includes a linear characteristic regulating valve with electric servomotor which is driven by the temperature control system; the air flow is passing through an orifice plate; this device creates an air pressure difference, proportional to the air flow; The delta p is sent to a proportionating valve and it compares the air signal to the gas flow. The gas flow is measured through an analogous detecting system with a pressure delta p regulating valve. The comparison between the two signals permits to have a proportional regulation with the advantage of having a very precise regulation of the gas flow, reducing all the noises related to the fluctuation of the gas pressure.

The cooling air flow is controlled independently per each section by a butterfly valve with electric actuator driven by the temperature control system.
The same actuator drives the air to be sent to the air damper to control the pressure into the forehearth superstructure in order to avoid fresh air infiltration through the chimney when the cooling is working at low capacity.

The heat mass dispersion zone

Sometimes the air cooling and the refractory dispersion is not enough to cool the glass properly. In this case it s possible to increase the heat loss by exposing part of the glass surface to the environment.
The heat mass dispersion zone is normally installed at the forehearth entry, where the glass temperature is higher and the heat loss is more efficient. Furthermore the rest of the path to reach the bowl allows to recover the temperature homogeneity that may be deteriorated by the surface cooling.

The same concept is applied on the riser cover roof just at the throat entry to decrease the glass temperature at the Working End entry.
The number of movable cover tails depends on the throat size and on the Working End type.

Furnace Types
- U-Flame Regenerative Furnace from 15 to 150 m2
- Cross Fired Regenerative Furnace
- Recuperative Furnace
- Oxy/fuel Furnace

Heating systems
- Light and heavy Oil, Gas with or without boosting

The control system is necessary in order to achieve the best performances for what efficiency and reliability are concerned.

The control system can be conventionally supplied but the best performances can be achieved through hi-tech computer supervision system.

The execution of every project comes after a phase in which the idea turns into documents and information that consitute the concrete basis of future activities. Every detail is considered and analysed from the project of reinforced concrete and steel structures to the use and the refractory materials design. The most updated calculation and design programms (CAD) are the fundamental instruments to be able to guarantee the highest precision and reliability of the works as shortly as possible. The complete and deep knowledge of the glass technology , thanks to our technician's several years of experience, gives to Glass Technologies the possibility of facing every theme in this specific sector and also the capability of giving to the customer,not only the materials and the equipment, but also the most up-dated know how.