Supercritical CO2 and air Brayton-Joule versus ORC systems for heat recovery from glass furnaces: Performance and economic evaluation

This paper evaluates the thermodynamic and economic performance of four different heat recovery systems (HRSs) applied to two hollow glass furnaces providing 1.2 to 4 MWt of wasted heat at 450 degrees C. Organic Rankine Cycle (ORC), two configurations of supercritical CO2 Brayton-Joule cycle (sCO(2)) and an innovative regenerative air Brayton-Joule cycle generating compressed air and/or power are modeled at both design and off-design conditions. The aim is to find the most commercially attractive HRS for the considered glass furnaces, as representative of small-to-medium size ones, taking into account all physical and technological constraints. The optimized designs of all systems are first obtained by identifying "average" heat recovery conditions from real data. Off-design simulations are then conducted to predict the behavior of the HRSs considering ambient temperature variations and furnaces ageing process. Results show that the ORC systems are the most attractive HRS available in the market for small-size furnaces while the air Brayton-Joule cycle appears to be the best choice when bigger furnaces are considered. On the other hand, the sCO(2) cycle systems show the highest power output in the whole range of furnace sizes while being still penalized by the too high costs deriving by their early-stage pre-commercialization phase. (C) 2018 Elsevier Ltd. All rights reserved.