Sulfur balance in biomass-fueled plants

The aim of this project has been to establish a standard deduction for sulphur retained in the ash. This is accomplished by establishing sulphur balances for biomass plants in order to document the in- and outgoing flows. The ingoing flow is the sulphur in the input fuel while the outgoing flows are different ash fractions and sulphur dioxide measured in the stack. Four balances have been established for straw fired units, three balances for wood chip fired units, and two balances for wood pellet fired units. Two previous projects provide further data on both straw and wood fired units. The main conclusions and recommendations are: For wood pellets the sulphur tax should be removed as the sulphur content in the pellets is extremely low and the emitted fraction very small. For pellets manufactured with a binder containing sulphur, the taxation should continue but with a standard deduction of 60 to 70%. Also, the rate should be reduced as the sulphur content in pellets produced with a binder containing sulphur is lower than the estimated 0,2% of the fuel. Statistics indicate that 0,1% reflects the true sulphur content in these pellets; For wood chips the tax should be removed as the sulphur content based on the fuel is considerably lower than the limit in the law (0,034% versus 0,05%). Furthermore, the emission from these plants are only between 20 and 32%. It is recommended that the plants keep the ph-value in the scrubber water above 7 as it is believed that this improves the absorption of SO2 greatly; For straw the tax should remain, but a standard deduction of 35-40% should be made. Technologies for improving the sulphur retentions should be developed. This could be scrubbers as they are very efficient towards removing especially sulphur in the form of SO2, which is by far the largest source of sulphur emission from straw fired plants. (au) 11 refs