Sorg recently installed the largest container furnace in the world at Encirc’s Elton, UK glass manufacturing facility. Sorg’s Hartmut Hegeler (HH) discusses how the installation was planned and how they overcame any challenges.

GI: Encirc’s 900 tonnes per day furnace is the largest container glass furnace in the world in terms of tonnage. When Encirc discussed the project with you, what were your initial thoughts?

HH: The Sorg subsidiaries SKS and Fusetech have been successfully performing service and repair work on the Encirc systems for years. In addition, Nikolaus Sorg has already technically optimised the Encirc furnaces in Derrylin (furnace F) and Elton (furnace B) fundamentally and also increased the melting capacity. Over the years, a close cooperation and relationship of trust has developed between the companies. Thanks to this collaboration, Encirc is familiar with the services of the Sorg Group in terms of technology, furnace design, system performance, as well as the level of service and support. Of course, building such large systems is always a challenge that needs to be approached with the necessary respect. But Sorg has experience with such systems, the specialists, and the knowledge to successfully master such tasks.

GI: What was the largest furnace (in tonnage) that Sorg had constructed before this?

HH: For example, at Encirc the performance of furnace Elton B has already been increased to 800 tpd. Sorg has also successfully implemented larger cross-fired furnaces in the flat glass area.

GI: Did you have to take into account any special considerations when planning the construction?

HH: The challenge was to implement the required enlargement of the melting surface to increase performance while maximising reuse of the furnace steel and the peripherals, such as platforms and furnace cooling. A detailed inventory was necessary. This resulted in special solutions for the subsequent use of the buckstays, the widening of the furnace grating, etc. The additional weights had to be calculated and the load capacity of all components had to be checked. This applied especially to the furnace crown. Some components had to be strengthened. Statics for the foundations and the steel structure were created. Of course, the entire furnace design has also been brought up to date with the latest refractory design as well as melting technology. Therefore, the number of electrodes was increased, there is no bubbling anymore and the throat was lengthened - to name just a few points. In the refractory area, the insulation has been improved in many zones and the run time has been increased due to material changes.

During all planning, the estimated construction time also had to be taken into account. In order to comply with these, as much work as possible had to be carried out in advance of the repair while the furnace was still in operation. To be able to do this, the structural design of many components had to be adapted so that the installations and work can be carried out even with restricted accessibility and without influencing the operation.

GI: Did the furnace have any special environmental standards?

HH: For technological reasons, cross-fired furnaces have higher NOx emissions than end-fired furnaces. Thus, a DeNOx filter system was already installed in the previous furnace to comply with the legally prescribed emissions. Therefore, the demand on Sorg was not to meet the requirements by means of primary measures, since this is also very difficult and may not be possible with this type of furnace, depending on the limit values. The requirement was to bring the NOx value to a very low level of 1000 mg NOx so that the DeNOx plant could be operated more economically by reducing the amount of urea required.

GI: What is the advantage of such a large-scale furnace?

HH: Large melting systems with high tonnages have lower specific melting and operating costs. This is the customer’s market strategy and also his company philosophy. As a result, the prime costs for the glass are cheaper compared to smaller systems. On the other hand, the systems have less flexibility regarding colour changes etc.

This does not have to be a disadvantage for the operator if he has a corresponding product portfolio and is not geared towards small series, which require a high degree of flexibility.

GI: Were there any challenges during construction?

HH: To accommodate the increased loads caused by the furnace enlargement, 10 additional steel supports had to be built under the furnace, taking into account the electrodes, the existing steel and the periphery. This was done as a preparatory measure for the furnace construction while the system was already in full operation. During the construction of the furnace, the furnace supports were moved outwards in the existing building under very cramped conditions. After the calculations, many steel components had to be reinforced, especially the crown skew backs. In addition, Sorg components such as the furnace pressure control flap, gas supply and single port control with 22 burners have been adapted and fitted into the existing structures. Sorg delivered the complete SSPS safety control and integrated it into the customer’s SCADA system and the subsequently used modules.

Altogether up to 180 Sorg group employees were on the construction site at times. This was a challenge for the coordination, especially in compliance with the Coronavirus regulations. With 60 days the construction time from glass to glass was a challenge, even without Coronavirus. Nevertheless, even under corona conditions, the entire Sorg team managed to have the glass flow two days earlier than planned. An additional line was also implemented during this construction period.

GI: Do you anticipate more such large-scale furnaces being installed by the glass industry in future?

HH: It’s hard to predict. As mentioned above, such large systems have great advantages compared to smaller ones in terms of efficiency, but they also have clear deficits. The energetic advantages are there, but not so great that they represent a significant and required GHG reduction. The use of green heating media, such as hydrogen from regenerative production, is certainly of great importance.

In line with the GHG discussion, Nikolaus Sorg believes that the proportion of electrically melted glass will increase significantly in the future. And the melting capacities from completely or predominantly electrically operated systems are limited.

With the hybrid furnace CLEAN Melter hybrid furnace, Sorg has taken a significant step towards higher melting rates. Here we see the future. But still: even systems with the size of Encirc‘s Elton A will have a future.