Sustainable water treatment in the manufacturing industry : Investigation of the water treatment system at VCE, Hallsberg

Abstract: Transitioning to circular flows is essential to economize the planet’s resources. One of the most important resources on earth is water as it is vital for all living things. However, water purification methods have proven to be very energy intensive, and increasing the circular water flows is therefore challenging. Volvo Construction Equipment (VCE) in Hallsberg is a manufacturing industry that produces cabs and tanks for VCE’s machines. The factory needs a lot of water in the pre-treatment process, and a falling film evaporator is currently used to purify most of the process water. VCE is considering investing in another evaporator to add to the existing water treatment system as a second stage to concentrate the process water further. The aim of this project was to investigate how to increase the energy efficiency of the water treatment system at VCE in Hallsberg and the planned extension of that system. The aim was also to analyze the water treatment system as it is today to get a better understanding of the current situation. The method was divided into two main parts. First, the current water treatment was investigated through measurements of electricity, temperatures and mass flows. A few mass and energy balances were also set up, and the excess steam recirculation of the current evaporator was investigated. Secondly, an investigation of potential future water treatment systems was made. The second part consisted of a comparison of different types of evaporators and combinations of these with a focus on energy performance and technical aspects. The second part also included investigating which heating and cooling sources could be used if the second-stage evaporator was to be running on waste heat. The result showed that the electricity demand of the water treatment facility at VCE Hallsbergis approximately 72.7 kWh/ m3 distillate. Measurements also showed that the falling film evaporator used today purifies approximately 0.71 m3/h. Furthermore, the results showed that only 3 % of the energy demand in the falling film evaporator could be exchanged to waste heat, and the waste heat would need temperatures of 100 °C or above. In a second-stage evaporator, the waste heat could be used to replace a larger proportion of the electricity use. There is sufficient power from the ovens to be used as waste heat in the second-stage evaporator. District heating could also be used as a heat source, but only for the low-temperature evaporator. For cooling, a new source would be needed where a compromise between energy use and water consumption of the cooling system needs to be made. This thesis is our degree project for the master of science in energy-environment-management atLinköping University. The project was carried out during the spring semester of 2023.