Industrial Wastes and By‐products as Alternative Fuels in Cement Plants: Evaluation of an Industrial Symbiosis Option

Abstract

SummaryA ravenous fuel consumer, the cement industry may substitute fossil fuels by industrial wastes and by‐products, identifying the industry as a key example of industrial symbiosis (IS). Benefits from industrial waste alternative fuels (IWAFs) include safe disposal, fossil fuel cost savings, gate fees, and greenhouse gas credits. Poor IWAFs, (high moisture, ash and halogen content) bring higher gate fees, but lessen clinker production. Thermal rating and blower capacity constraints should be satisfied in such a case study of IS. Cement plants must comply with potentially tighter emission limits, compared to fossil fuel utilization, despite higher pollutant precursors in IWAFs. Emissions’ compliance, operational, and production implications are a few among several challenges when assessing multiple IWAF valorization as a symbiotic option from a systems’ perspective. A novel method is proposed to quantitatively assess critical trade‐offs. Species and energy transformations convey a rigorous picture of clinker level, kiln flue gas, and offgas volumes and lay the groundwork for screening, a priori selection, and process tuning. Necessary and sufficient compliance conditions and safety margins are presented in terms of process parameters and actual emissions’ data. Main challenges posed by high flue gas, high offgas volumes, high moisture, low heating value, increased nitrogen oxides emissions, and high halogen and metal content are quantified. As demonstrated in a case study of an actual 1.5 × 106 tonnes per annum clinker plant in this paper, concurrent use of several IWAFs may increase clinker production, while satisfying operational constraints and maintaining compliance. The method may serve for devising IWAF preparation, or tuning mechanisms expanding IWAF valorization.