Muthanna Journal of Engineering and Technology
Volume (14), Issue (4), Year (2026), Pages (103-117)
DOI:10.52113/3/eng/mjet/2026-14-04-/103-117
Research Article By:
Ismael Badawi Dahash
Corresponding author E-mail: ismael@gmail.com
ABSTRACT
Cement manufacture is among the most energy- and carbon-intensive industrial activities, yet much of its energy input leaves the kiln line as medium- and low-grade waste heat. This paper reports a plant-scale techno-environmental case study of a water-free, air-cooled cascaded dual-loop organic Rankine cycle (ORC) for a cement plant in Mazandaran, Iran, in which a pure-toluene topping loop recovers the suspension-preheater exhaust and an ultra-low-GWP R1233zd(E)/R1234ze(Z) bottoming loop (0.633/0.367 by mass) recovers the clinker-cooler air together with the topping-loop condensation duty. Fifteen candidate fluids are filtered against explicit numerical criteria and the survivors evaluated on the full cascade model under identical boundary conditions; the design is obtained by surrogate-assisted NSGA-II optimisation with entropy-weighted TOPSIS selection and assessed through five lenses — energy, exergy with avoidable/unavoidable and endogenous/exogenous decomposition, economic, environmental and exergoenvironmental — supported by a digital-twin-oriented operational layer. The cascade absorbs 28.60 MW and delivers 4.851 MW of net shaft power (17.0 % thermal, 33.3 % exergy efficiency) at a levelised cost of 0.0434 $ kWh⁻¹, a 3.6-year discounted payback at an avoided-outage valuation and 22.0 kt yr⁻¹ of avoided grid CO₂. Monte-Carlo propagation places the levelised cost at 0.031–0.071 $ kWh⁻¹ (P10–P90) and returns a 99.7 % probability of a positive net present value at that valuation against 0.05 % at the subsidised tariff, so bankability is governed by tariff treatment rather than by engineering. The direct refrigerant impact is 0.0011 % of the avoided emission and the 0.61 K zeotropic glide is worth under 1 %; replacing the optimistic loss assumptions lowers net power by 19.0 % without altering any conclusion.
Keywords:organic Rankine cycle; cement waste-heat recovery; cascaded dual-loop; ultra-low-GWP working fluids; exergoenvironmental analysis; digital twin