Energy Balance

Glass manufacturers are constantly under pressure to enhance production, improve quality, meet increasingly strict emission regulations and reduce costs and investments. Glass Melting is a key element within the glass production process from batch preparation to product packaging and the main goal is to cost optimize glass melting processes. In the last 40 years there have been various trends to achieve this cost optimization and the main drivers can be highlighted as follows:

• Higher melting efficiencies
• Longer durability of the melting furnaces o Better fuel utilization or fuel reduction
• Glass quality improvements
• Emissions reduction (NOx, SOx and particulates)

The Energy Balance Modul provides a comparison of all the energy flows supplied and removed in a thermotechnical process. The thermal balance allows conclusions to be drawn regarding energy efficiency and the nature and scale of energy losses.

The more detailed the recording of the balance parameters, the easier it is to find starting points for technical and technological improvements. One of the major features of the thermal balance of melting furnaces is the link between the upper furnace and heat recovery.

For detecting energy losses in a melting furnace, this module is also able to compare various parameters for a bath with the current setup. In this way, for example, the effect of using a booster can be calculated beforehand before the furnace is rebuilt at considerable expense.

Heat & Mass balances

With the experience on a large variety of furnaces it is possible to forecast possible variations mainly focusing on the fuel consumption, such as:

• Electricity vs. Fuel as well as fuel changes
• Batch and/or glass changes o Heat recovery modifications
• Production increase (with additional electricity or oxygen)
• Conversion from air fuel to oxy fuel combustion (or vice versa)
• Recuperator or regenerator repairs

All these forecasts are based on heat and mass balances according to the most common enunciation of the first law of thermodynamics, that the increase in the internal energy of a thermodynamic system is equal to the amount of heat energy added to the system minus the work done by the system on the surroundings. The overall heat and mass balance of any glass melting furnace can be described as

The accuracy of the forecast is much depending on the base case and the type of variation or forecast respectively, where the base case can be an existing furnace with given data or even a new furnace design with only assumptions.

Based on an existing furnace, knowing all input variables, a forecast is very accurate. The fundamental idea behind is that with the given parameters the overall losses, as described above, can be calculated very quickly without evaluating the furnace refractory conditions etc. in detail. Within a specific forecast these losses will not change significantly. Even when the given parameters are not 100% correct, the forecast or trend respectively will be very accurate anyhow.

All Oxy-Fuel

One of the most popular oxygen applications, all oxy-fuel-fired melting eliminates the need for a combustion air or heat-recovery device. This process is one of the most efficient ways of reducing nitrogen oxides (NOx) and particulate emissions from glass furnaces.

Chart: Energy consumption of air fuel and oxy fuel installations as a function of the flue gas and air preheating temperatures

The chart shows the energy consumption of different air fuel and oxy fuel installations as a function of the flue gas and air preheating temperatures i.e. a furnace with a flue gas temperature of 1480 °C and an air preheating temperature of 1000 °C saves 65% (100- 35) of the energy compared to a furnace with no air preheating. When this furnace would be converted to AOF we can count with another 9% (35-26) compared to the furnace with no air preheating or 26% compared to the case of air preheating of 1000 °C.

Variants

This function can be used to compare any number of energy balances. This provides you with a direct overview of what effect the individual changes are having. To create variants, you must first determine the wall losses. Then use the tabs to move to the entry pages and change the entry parameters.

To compare all the values in a table with the original values, click on the left button "calculate". If you want to have the results of the comparison of the individual energy balances displayed, click on the Text link below. The data will be displayed in a new window, for greater clarity.

Oxy-Fuel Boosting

This program item is one of the most interesting in the calculation of energy balances. On the basis of the original balance (original data), the wizard creates a new variant with the simulated incorporation of additional oxygen burners (Oxy-Boosting).

O2 Conversion

This function creates a new balance variant. In this variant, the firing of your furnace will be converted from gas/oil to pure oxygen. In this process, the parameters exhaust gas temperature, temperature of air preheating, type of combustion air, and lambda value and wall losses will be automatically adjusted.