Evaluation of Overall Environmental Impacts of Alternatives for Emission Control Systems applied for Waste to Energy Process

Sammanfattning: Vattenfall operates a cogeneration plant where household and industrial waste is incinerated to generate electricity and district heating. The waste incineration generates flue gases, and the energy in the hot flue gases is recovered by condensation. Both flue gases and the flue gas condensate are treated by emission control systems before being released into nature. The emission control system is planned to be updated with better technologies currently applied in Sweden. In this study, a comparison of the overall environmental impact of the current emission control system and the new system for emission control is performed. Vattenfall will perform a comparative life cycle assessment, LCA, of the two emission control systems. A part of the LCA is an inventory analysis. In this study, data required for the inventory analysis will be collected and quantified. The parameters considered are emissions to air and water, consumption of chemicals, produced solid residue, and water utilization. The objectives with the planned upgrade of the emission control system, which are evaluated in this study, are to obtain a cleaner condensate stream that can be reused in the system, to reach a higher tolerance of sulphur content in the fuel, and to reach a better reduction of emissions, for future stricter regulation. From the perspective of this study, the new system for emission control system seems to be the choice for emission control system with the least environmental impact. The results show that the reasons for upgrading the emission control system are met with the new system. The condensate is significantly cleaner with the new alternative emission control system than in the current one, the total amount of emissions decreases by 99,98 w%. The significantly smaller amount of emissions results in a condensate flow that can be reused in the system, which could save a considerable amount of raw water each year. The SO2 emissions are reduced by 99,5 w%, which show that a higher sulphur content in the fuel could be tolerated with the new emission control system. Furthermore, the total amount of emission content in the flue gas decreases with 61,9 w% with the new emission control system. The emission parameters that are deemed likely to be more strictly regulated in coming regulations, NOx and Hg, are both significantly reduced with the new emission control system. On the other hand, both the consumption of chemicals and the production of solid residue increases in the new emission control system, compared to the current one. These aspects are important drawbacks with the new system, and the environmental impact of these aspects needs to be further investigated in the planned LCA.