Horn has repaired a 260tpd end-fired furnace at Vetropack’s Straža site in Croatia.

Horn originally built the furnace back in 2004, and at the beginning of 2015 it was due for repair.

The furnace produces three different glass colours: olive, green and amber.

Vetropack Group is one of Europe's leading manufacturers of glass packaging for beverages and food.

In Straža the company is not only a supplier to the Croatian domestic market, but also a key exporter to neighbouring markets in Slovenia, Italy, Hungary, Bosnia, Serbia and other countries in south-eastern Europe.

The complete combustion system has been changed over to the latest technology, as Horn supplied the individual burner control combustion system with the latest DualFlame AC burners.

In addition, all the gas stations and burners at the distributor and forehearth have been changed to a modern combustion system, using independent left and right control of the temperature in each cooling section of the forehearths.

The furnace now has a natural gas chromatograph (Siemens Sitrans CV), to analyse the gas composition.

Moreover, the Sitrans CV can calculate the upper and lower heat value, gas density, Wobbe Index and specific gravity.

A new sensor at the forehearth had been installed for the continuous measurement of the glass redox potential.

The water-cooled sensor contains a thermocouple and an oxygen cell.

Both provide a mV-signal to an IOSI-01 oxygen interface, which converts these two mV-signals to three, programmable, loop powered 4.20 mA analog outputs.

In the standard configuration, the three 4-20 mA output channels represent glass melt temperature, oxygen cell emf and oxygen partial pressure.

This information allows Vetropack to observe the glass melt and to modify the glass composition in order to avoid glass quality problems.

To adjust the ratio of air and natural gas automatically at the forehearth combustion systems, Horn installed an extractive and heated oxygen sensor MPLS from its daughter company Eurox at each forehearth.

With this unit the oxygen content of the premixed natural gas/air, and thus the atmosphere of the combustion space of the forehearth, can be controlled at a constant level.

The MPLS contains a zirconia measuring cell which is heated to an exceptionally high temperature of 900°C.

A slight portion of the gas/air mixture is fed to the heated sensor, where a complete catalytic transformation takes place.

The unique design of the measuring cell and its heating facility determines the real residual oxygen content according to an ideal, complemented combustion.

Along with control equipment, the ratio of the gas/air mixture can be fine-tuned in order to keep a constant oxygen value in the forehearth’s atmosphere.

The very short reaction time of the sensor allows for switch-over times of only two minutes, and thus the multiple collecting of up to 10 sampling points by each measuring unit.

For this purpose, the unit is equipped with a solenoid valve block to collect samples from the different forehearth control sections.

As well as the above mentioned equipment, Horn also supplied the complete refractory and steel drawings; forehearth superstructure cooling; steel parts; tank and throat cooling; reversal system; waste gas ducting; electrical control system; computer supervisory system PCS7 V8; electric boosting equipment; cooling water; TV camera and stirrers for all three lines.

As a well-known supplier, Horn carried out the complete project with all services for steel, refractory, heating-up and successful commissioning.