Introduction

Bruzaholms in Småland is one of Sweden's oldest foundries, with roots dating back to the 1660s. Today, Bruzaholms is one of the world’s leading manufacturers of wear-resistant and heat-resistant castings.

Foundry and metal processing are energy-intensive processes, and approximately 25% of the total energy consumption in a sand foundry is used for heating and ventilation of premises to maintain a good working environment.*

*Source: Sommarin and Arvidsson (2011) Heat Storage for Energy-Intensive SMEs with a focus on Swedish foundry industry, Report No. 2011006: Swerea SWECAST.

Despite the presence of many heat-generating processes within foundries, it has historically been challenging to utilize this heat due to high levels of steam, particles, and binders, which render traditional heat exchangers ineffective.

In spring 2025, Bruzaholms installed the Swedish-developed heat exchanger Lepido in a hot air stream from the sand cooler. The goal was to ascertain whether this solution could reliably recover waste heat from their processes, thereby reducing energy consumption and fossil CO2 emissions.

After three months of initial operation, all data indicate successful implementation.

Challenge

Various processes in the foundry produce hot air streams suitable for heating replacement air supplied to the premises. However, these streams contain substantial amounts of particles, moisture, and binders. Previous trials with traditional heat exchangers at Bruzaholms had to be abandoned due to clogging and the resulting weekly maintenance requirements.

Tradiotional HEX, needed weekly mainenance to function. (now uninstalled)

Solution

Lepido, a Swedish-developed heat exchanger, is specifically designed for polluted exhaust air. It is employed to recover waste heat from various dirty processes such as food production, industrial laundries, drying facilities, and foundries. Lepido requires no pre-filtering and uses a patented coil arrangement (without fins) that allows particles to pass through the exchanger without adhering. The recovered heat can preheat air or water, subsequently utilized for heating premises or returned to the process. Lepido by Enjay

Results

In this project, Lepido was installed in a channel from sand reclamation, with an airflow of approximately 4 m³/s and a temperature of 30°C.

The heat recovered by Lepido reduces the system’s power demand by 95 kW, covering 85% of the system's heat/energy needs. Existing heating is via an oil boiler, and each recovered kWh reduces fossil CO2 emissions by 750 grams.*

Lepido installed at Bruzaholms

*Comparing CO₂ emissions from different energy sources, 2025

The estimated annual recovery for this project is 150,000 kWh, translating to a reduction of fossil CO2 emissions by 90 tonnes annually.

Operation

While reduced emissions from recovered heat are expected, reliability remains critical, given the previous solution's maintenance interval of merely seven days.

After three months of operation (Feb – Apr 2025), several inspections have found no requirement for cleaning or other maintenance on the heat exchanger. This is supported by an essentially unchanged pressure drop in the system.

Picture taken inside the Lepiod after 12 weeks in operation. 

Air preassure drop chart (1 month data)

Conclusion

All available data indicate that Bruzaholms has successfully found a reliable method to reduce energy costs and fossil CO2 emissions by recovering waste heat from its sand cooling process.

"Enjay, with Lepido, has enabled us to recover residual heat from our sand processing. Unlike previous systems, it manages dusty and humid air over extended periods, leading to significant energy savings and substantially reduced maintenance. We have not yet operated it through the entire annual cycle, but the results so far are very promising."

Mats Ekegren, Technical Manager Bruzaholms