Glass - Back to the Future!

Presenting Author:
Oscar Verheijen

article posted 08 April 2016

Oscar Verheijen received his master degree in Chemical Engineering in 1995 at the Eindhoven University of Technology in the Netherlands. Following this, he started as glass technologist at the Dutch research institute TNO. In 2003, Oscar finalized his PhD-study entitled ‘Thermal and chemical behavior of glass forming batches‘. After being active for 12 years in the field of glass melting technology, glass tank modeling and process control, Oscar became responsible within TNO for business development of sustainable technologies with emphasis in the last years on thin film solar technologies. In September 2013, Oscar rejoined the former TNO Glass Group and is now active as consultant for CelSian Glass & Solar. His main focus areas comprise energy and emission reduction at glass furnaces and securing glass furnace lifetime by means of applying a unique set of tools including dedicated industrial furnace measurements and advanced glass furnace simulation models.

Practical measures to reduce emissions and to align with environmental legislation.

Oscar Verheijen*, Marco van Kersbergen, Anne Jans Faber, Steff Lessmann
CelSian Glass & Solar

More stringent environmental legislation, together with the permanent need to reduce glass melting costs, requires optimal implementation of primary measures to reduce glass furnace emissions. These glass furnace emissions include combustion species (e.g. NOx), evaporated volatile batch and glass melt species (e.g. alkaline compounds), and carry-over of batch components. Reducing glass furnace energy consumption directs, amongst others, to more near-stoichiometric and staged firing, thereby lowering the excess of air and/or oxygen in the combustion space and improving the heat transfer from the flames into the glass melt. Generally, changing to near-stoichiometric and staged firing reduces the NOx concentrations on one hand but might, on the other hand, lead to undesirable formation of (extra) CO in the combustion space. Reduced firing conditions support the evaporation of volatile species, especially at the surface of the glass melt and batch blanket. Therefore, changing to near-stoichiometric and staged firing conditions should concur with optimization of the combustion settings preventing local reducing conditions and high gas velocities at the surface of batch and glass melt. In addition, advanced sensors to monitor CO-concentrations are inevitable to secure safe production at lowest energy and emission footprint. Besides avoidance of local reducing conditions, high gas velocities, entrainment of batch particles and local high glass melt surface temperatures, emissions can also be influenced by proper choice of raw materials that are less sensitive to flue gas entrainment. This paper presents a combined approach of glass furnace modeling, industrial process measurements and laboratory tests to optimize the glass melting process in view of emission reductions by means of practical measures. Examples are provided of glass furnace simulation studies to optimize combustion / process settings ensuring lower emissions (NOx and glass melt species) and advanced laboratory tests to assess the potential for carry-over of complete batch and/or individual batch components.