Abstract
This paper attempts to present a fundamental system analysis for the performances of currently operating waste-to-energy incinerators in Tokyo special ward district. Firstly, it is stated that the gross thermal efficiency η G of any steam turbine generation system could be expressed as a product of four parameters: the boiler efficiency η b, turbine steam utilization fraction R t, heat cycle constant R h, and turbine generator chamber efficiency η tg. Secondly, reliable heat inputs to waste-to-energy systems were established by the ideal boiler efficiencies η b,ids which are based on the versatility of the standardized combustion gas properties, to avoid totally depending on the conventional low calorific value measurements of the fed-waste which occasionally include dubious results. Thirdly, the achievement of technological progress of power generation in waste-to-energy systems over the past 3 decades was reviewed. The advantage of 4 MPa class incinerators (installed after 2001) over 3 MPa class incinerators (installed before 1999) in η G by 33.1% on average was clarified. Fourthly, the difference in operational modes which affects the η G was studied to seek for the optimum operation in terms of energy recovery. In conclusion, this paper evaluated that the overall η G of the 20 incinerators in FY2015 proved to be 15.0%.
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Abbreviations
- Comp i :
-
Weighted average of n mass percentages of i constituent of fed-waste (%kg/kg−w) Eq. (9)
- C ji :
-
Mass percentage of i constituent of fed-waste at j incinerator (%kg/kg−w)
- c :
-
Energy unit conversion factor (c ≡ 3.6 × 106 J/kWh)
- cE :
-
Heat equivalent of power generation (J)
- c p :
-
Constant-pressure specific heat of combustion gas \(({\text{kJ}}/({\text{m}}_{\text{N}}^{3} \;{\text{K}}))\)
- \(\bar{c}_{\text{p}}\) :
-
Mean constant-pressure specific heat of the standardized combustion gas \(({\text{kJ}}/({\text{m}}_{\text{N}}^{3} \;{\text{K}}))\)
- E :
-
Power generation (kWh)
- E u :
-
Power generation per ton of waste (kWh/t−w)
- G 0 :
-
Amount of theoretical combustion gas per unit mass of waste (\({\text{m}}_{\text{N}}^{3} /{\text{kg}}_{{ - {\text{w}}}}\))
- G(λ):
-
Amount of SCG per unit mass of waste (\({\text{m}}_{\text{N}}^{3} /{\text{kg}}_{{ - {\text{w}}}}\)) Eq. (11)
- \(\bar{H}\) :
-
The mean LCV of fed-waste (J/kg−w) (\(\bar{H}\) ≡ Q w/W)
- H j :
-
Annual LCV measurement at j incinerator (J/kg−w)
- H j *:
-
Estimated annual mean LCV of fed-waste at j incinerator (J/kg−w) Eq. (15)
- H ω :
-
The LCV of the waste of representative composition (J/kg−w) Eq. (10)
- H ω *:
-
Estimated annual overall mean LCV of fed-waste (J/kg−w) Eq. (16)
- h X :
-
Specific enthalpy at condensate return tank outlet (J/kg)
- h Y :
-
Specific enthalpy at boiler feeding pump outlet (J/kg)
- h Z :
-
Specific enthalpy at superheater outlet (J/kg)
- L 0 :
-
Amount of theoretical air per unit mass of waste (\({\text{m}}_{\text{N}}^{3} /{\text{kg}}_{{ - {\text{w}}}}\))
- l boiler :
-
Boiler heat losses (J)
- l other :
-
Heat losses except boiler heat losses (J)
- M :
-
Amount of turbine entering steam over a period for examination (kg)
- M 0 :
-
Amount of steam evaporation over a period for examination (kg)
- \(\dot{m}\) :
-
Mass flow rate of turbine entering steam (kg/s)
- \(\dot{m}_{0}\) :
-
Evaporation rate (kg/s)
- n :
-
Number of operating incinerators in a period for examination
- \(\dot{n}\) :
-
Mass flow rate of extracted steam (kg/s)
- P :
-
Power output (kW)
- P r :
-
Rated power output (kW)
- Q b :
-
Heat absorbed by boiler (J) (Q b ≡ M 0 (h Z-h Y))
- Q C :
-
Circulating heat (J)
- Q E :
-
External heat supply quantity (J)
- Q g :
-
Combustion heat of auxiliary fuel (city gas) (J)
- Q I :
-
Heat input to the WtE system (J) Eq. (1)
- Q S :
-
Vaporization heat (J)
- Q t :
-
Heat supplied to steam turbine (J) (Q t ≡ M (h Z-h X))
- Q w :
-
Combustion heat of fed-waste (J)
- q :
-
Volumetric fraction of water vapor over unit dry combustion air when absolute humidity of air is taken into account
- R E :
-
External heat supply fraction Eq. (5)
- R h :
-
Heat cycle constant Eq. (7)
- R t :
-
Turbine steam utilization fraction Eq. (6)
- r :
-
Correction factor representing minor heat losses between ideal and actual boiler heat absorptions
- W :
-
Amount of waste incineration (kg−w)
- η b :
-
Boiler efficiency Eq. (2)
- η b,id :
-
Ideal boiler efficiency Eq. (14)
- η G :
- η tg :
-
Turbine generator chamber efficiency Eq. (4)
- θ :
-
Temperature of combustion gas (°C)
- θ a :
-
Adiabatic theoretical temperature of combustion gas (°C) Eqs. (12) and (13)
- θ b,o :
-
Flue gas temperature at the boiler outlet (°C)
- θ 0 :
-
Standard reference temperature (°C) (θ 0 = 25 °C)
- θ ∞ :
-
Surrounding temperature (°C)
- λ :
-
Excess air ratio
- ρ j *:
-
Fraction of auxiliary fuel heat over waste heat at j incinerator ρ j * ≡ Q g,j /(H j *W J )
- τ :
-
Period for examination (s), (D)
- ψ :
-
Generator load factor (ψ ≡ P/P r)
- ω j :
-
Waste incineration fraction of j incinerator over the total amount of annual waste incineration (ω j ≡ W j /ΣW j ) (j = 1,2,…,n)
- Subscript j :
-
When added, subscript j denotes that the symbol is related to j incinerator
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Shino, Y. Analytical study of power generation efficiency of WtE systems operating in Tokyo special ward district. J Mater Cycles Waste Manag 20, 632–644 (2018). https://doi.org/10.1007/s10163-017-0632-2
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DOI: https://doi.org/10.1007/s10163-017-0632-2