Exploring future flue gas conditions from silicon production through stochastic process simulation

Many industrial producers of metallurgical grade silicon (MG-Si) have a strategy for emission reduction involving biocarbon reductants in the near future, followed by carbon capture on the medium term. Technical and economic challenges in implementing carbon capture are related to flue gas conditions from the submerged arc furnace. This work takes a modelling approach to explore how these conditions will be affected by the upcoming transition to biocarbon. Two different scenarios are studied, one investigating mixed fossil/bio-reductant charges with increasing use of charcoal, and one investigating selected charge parameters with biocarbon as the only reductant. Six different charcoals, treated at different temperatures and from various wood sources are used in the model. A Monte Carlo approach is taken for simulations, capturing variability and uncertainty in process and furnace parameters. Results show the significance of volatiles on flue gas conditions. The charcoals contain less volatiles than coal, and thus produce flue gases with significantly lower heat content and temperatures, and with less water and CO₂. There is also a drastic reduction observed on the flue gas sulfur content, although this relies on a mechanism that requires verification. In general, the results indicate that conditions could become more favourable for carbon capture implementation when biocarbon is replacing fossil carbon sources in silicon production.