Multi-objective optimization and off-design performance based on thermodynamic -economic-environmental analysis of organic Rankine & Kalina cycles for roller kiln waste heat recovery

ABSTRACT

Heat recovery from roller kiln’s flue gas and cooling gas is interest topic to make ceramic tile production cleaner and more sustainable. Comparatively, the parallel double-evaporator regenerative organic Rankine cycle (PD-RORC) & Kalina cycle (PD-KC34 (Kalina cycle 34)) provide a good solution for a roller kiln’s low-temperature double heat sources utilization. In this research, the off-design performance of the multiobjective optimized PD-RORC & PD-KC34 based on thermodynamic-economic-environmental model is investigated to provide dependable assessment for the roller kiln’s waste heat recovery. Firstly, the multiobjective optimization of PD-RORC & PD-KC34 is carried out considering thermodynamic, economic and environmental factors, and TOPSIS method is used to select the optimal Pareto solution. Then, the influences of the roller kiln’s operating conditions and heat sink on the off-design performances of PD-RORC & PD-KC34 are further explored. The results show that, under the optimal condition, PD-RORC has superior exergy efficiency (${\eta }_{ex}$) and environmental performance with ${\eta }_{ex}$ of 49.76% and environment impact load ($EIL$) of 0.096 mPE_China,90/kWh while PD-KC34 has better net power output (${\stackrel{\bullet }{W}}_{net}$) and economic behavior with ${\stackrel{\bullet }{W}}_{net}$ of 250.72 kW and electricity production cost ($EPC$) of 0.090 $/kWh. In addition, excess air coefficient has the greatest impact on ${\stackrel{\bullet }{W}}_{net}$, ${\eta }_{ex}$, $EPC$ and $EIL$ for PD-RORC and PD-KC34. On the whole, PD-KC34 has higher sensitivity on ${\stackrel{\bullet }{W}}_{net}$ and ${\eta }_{ex}$ while PD-RORC shows greater sensitivity on $EPC$ and $EIL$.

KEYWORDS:

• Roller kiln
• organic rankine cycle
• Kalina cycle
• multi-objective optimization
• off-design performance
• thermodynamic-economic-environmental analysis

Nomenclature

$a$ heat transfer coefficient (W/(m²·K)

$A$ heat transfer area (m²)

$c_p$ specific heat (kJ/(kg·K))

$C_{bm}$ bare cost of component ($)

$D$ hydraulic diameter (m)

$\stackrel{\bullet }{Ex}$ exergy (kJ)

$f_k$ maintenance cost factor

$F_{bm}$ bare cost factor

$h$ enthalpy (kJ)

$h_{full-load}$ operation hour (h)

$i$ interest rate

$•$ mass flow (kg/s)

$P$ pressure (kPa)

$Q$ emission quantity (kg)

$\stackrel{\bullet }{Q}$ energy (kJ)

$r_H$ enthalpy drop ratio

$r_V$ volumetric flow rate ratio

$R_v$ inlet volume flow to design point ratio

$s$ sensitivity

$t$ thickness (m)

$T$ temperature (K)

$U$ total heat transfer

coefficient (W/(m²·K))

$\stackrel{\bullet }{W}$ power (kW)

Greek letters

$\alpha$ excess air coefficient

$\eta$ efficiency (%)

Subscripts

ca cooling air

cg cooling gas

coma combustion air

con condenser

cw cooling water

des design

en environment

evap evaporator

evu evaporation unit

fg flue gas

in inlet

mix mixer

net net

sup superheater

total total

turb turbine

uft unfired tile

wf working fluid

out outlet

pump pump

sep separator

Acknowledgments

The authors would like to acknowledge the National Natural Science Foundation of China (Grant No: U1501248, 51905109).

Disclosure statement

The authors declare that they have no known potential conflict of interest.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China [51905109]; the Joint Funds of the National Natural Science Foundation of China [U1501248].