How can CRUCIFORMS® solutions help glassmakers to reduce their CO2 emissions?

Date
January 8th, 2024
Description

The glass industry is facing more and more stringent challenges related to carbon emissions. Beyond the need of extending furnace lifetime, reducing COemissions has become a critical goal of the glassmaking process.

Regenerators play an essential role in supporting the glass industry to meet this goal. Indeed, the higher the thermal efficiency they can achieve, the lower the CO2 emissions will be. The regenerator working principle consists in alternating cycles where heat is first absorbed from waste gases coming from the furnace and then released into the preheated air used in the combustion process.

The checkerwork (or checkerpack) is the key part of the regenerator, and the selection of the refractories composing it has a significant impact on the energy efficiency and durability of the solution.

 

Cruciforms® refractories are designed to increase the regenerator thermal efficiency

Cruciforms® checkerwork are fused cast products available in two different chemistries, either high alumina or alumina-zirconia-silica (AZS), with optimal properties to withstand the corrosive conditions they are subjected to. Their geometries are designed to increase heat transfer from and to the material so as to enhance the regenerator thermal efficiency and help reduce CO2 emissions. Cruciforms® shapes are specifically designed to fit the thermal and flow conditions of the various zones along the regenerator chamber.

The latest SEFPRO’s innovation, Cruciforms® Type 8, has been designed to provide a further boost in heat exchange at the very top of the regenerator checkerpack. This innovative product features a half flue-size and a rectangular geometry. As a consequence, it increases the local specific heat exchange area by more than 50% and maximizes the convective heat exchange coefficient thanks the rectangular channels shape.

 

A specific design to maximize heat transfer in each regenerator zone

The thermal and flow conditions along the regenerator chambers vary from bottom to top because of their inherent temperature distribution. Therefore, it is crucial to select Cruciforms® solutions that can offer the highest thermal efficiency at each portion of the checkerwork, especially to optimize the energy recovery during the preheating air phase cycle of the regenerator. Thanks to SEFPRO’s extensive experimental and numerical studies, it is possible to determine the best location for each product with great precision:

  • Smooth shapes (Type 3 or 6) are recommended at the bottom of the regenerator where natural convection dominates the heat exchange so as to maximize buoyancy effects.
  • As the temperature difference between the air and the refractories decreases and attenuates energy transfer, the introduction of corrugated shapes (Type 4) from the middle to the top is advised to boost turbulence effects and enhance heat exchange from forced convection.
Image
exchanged power based on experimental measurements (CLAIRE loop pilot)

 

Cruciforms® solution Q&A

How much fuel can I save using Cruciforms® solution ?

In most cases, typical CRUCIFORMS® refractory solutions can bring 2 to 5% fuel savings. For some specific conditions and with the use of Cruciforms® Type 8, savings up to 10% can be achieved when compared to checkerwork solutions based on traditional chimney blocks. Depending on local fuel prices, a payback in the range of one to four years can be obtained. At the end of a campaign, the extra savings can reach some millions of dollars based on the furnace size and pull rate.

 

How accurate are the numerical simulations of the regenerator’s thermal behavior?

Based on 20 years of intensive research and the construction of a thoroughly instrumented regenerator pilot which is unique of its kind, SEFPRO developed and rigorously validated REGEN. This numerical model simulates the regenerator’s thermal behavior and calculates the fuel savings for optimized Cruciforms®-based checkerpack configurations. REGEN’s validity was also demonstrated through the correlation to several field measurements on industrial furnaces, showing an accuracy in the range of ± 10°C for temperatures at the bottom and the top of the checkerpack.

 

Can SEFPRO help me evaluate and optimize regenerators?

Starting with the architecture, operating conditions and raw material characteristics for a specific furnace, REGEN can estimate the thermal efficiency of different regenerator designs and the corresponding fuel savings over the years. The thermal studies offered by SEFPRO can include the simulation of different checkerwork solutions, allowing customers to choose the most appropriate one based on thermal efficiency, cost, and other technical requirements. Furthermore, SEFPRO’s technical teams can also provide on site measurement services for an assessment of the regenerator performance in real conditions of use.

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