SUPPORTING INFORMATION

300 MW Boiler Design Study for Coal-fired

Supercritical CO2 Brayton Cycle

Wengang Bai, Yifan Zhang, Yu Yang, Hongzhi Li , Mingyu Yao

National Energy R&D Center of Clean and High-efficiency Fossil-fired Power Generation Technology,

Xi'an Thermal Power Research Institute Co. Ltd , Xi'an, 710054, People’s Republic of China

To whom correspondence should be addressed. Tel: +86-029-82001207; Fax: +86-029-82001204.E-mail address: lihongzhi@tpri.com.cn

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Table S1 Main parameters of the experiments conducted by Iverson, et al. Ref. [1]

Table S2 Comparison of the calculation results and the experimental data

Table S3 Structure parameter and area calculation of HSH

Table S4 Structure parameter and area calculation of HRH

Table S5 Structure parameter and area calculation of LRH

Table S6 Structure parameter and area calculation of LSH

Table S7 Structure parameter and area calculation of SH

Table S8 Calculation of coal combustion (Unit: Nm3/kg)

Table S9 Calculation of the flue gas parameter

Table S10 Key design parameters of HTR and LTR

Table S11 Tubes used in the boiler

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Fig. S1. Structure size of the furnace of the S-CO2 boiler (Unit: m)

Fig. S2. Subsection model based on the quantity of heat

Fig. S3. Thermal-hydrodynamic calculation model of the S-CO2 boiler

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Model validation for S-CO2 cycleIt is found that there is almost no published experimental data with regard to the

coal-fired S-CO2 Brayton cycle. As a compromise, experimental results from the literature of Iverson, et al. Ref. [1] are employed for the validation of the present model, because the core power conversion processes in this manuscript and in Iverson’s are similar, which are used for different heat sources. The experiment test loop in SNL is a standard recompression S-CO2 Brayton cycle. The main working condition parameters are shown in Table S1.

Table S1 Main parameters of the experiments conducted by Iverson, et al. Ref. [1]

Main parameters Measured values

Split ratio to RC 0.288Mass flow rate (kg/s) 3.483Inlet pressure of MC (MPa) 7.485Inlet temperature of MC ( )℃ 31.8Inlet pressure of RC (MPa) 7.574Inlet temperature of RC ( )℃ 45.1Inlet pressure of turbine A (MPa) 9.894Inlet temperature of turbine A ( )℃ 390Mass flow rate of turbine A (kg/s) 1.741Inlet pressure of turbine B (MPa) 9.853Inlet temperature of turbine B ( )℃ 390.6Mass flow rate of turbine B (kg/s) 1.741Inlet pressure of solar source (MPa) 10.045Inlet temperature of solar resource ( )℃ 316.1Efficiency of MC (%) 36.3Efficiency of RC (%) 61.9Efficiency of turbine A (%) 79.1Efficiency of turbine B (%) 84.6

The calculation results are compared with the experimental results in Table S2. Since there is no detailed geometric parameters shown in the Ref. [1], frictional pressure drops are neglect. The turbine heat loss is a test parameter in Iverson’s experiments, thus, it is assumed with the same value in the present calculation. In general, the errors between calculation results and experiment results are all in a reasonable range, indicating that the present model can accurately reproduce the experimental results of the S-CO2 Brayton cycle. Although the calculation of the net electricity and cycle efficiency are a little bit larger than the experiments, it is still within the error range of the tests and it is mainly because the frictional pressure

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drop are ignored in the calculation.

Table S2 Comparison of the calculation results and the experimental data

Output parameters Experimental data[1]

Calculation results

error

Heat duty of the heater (kW) 341.7 341.1 -0.18%Heat duty of PC (kW) 239.2 239.0 -0.08%Power consumption of MC (kW)

39.2 38.3 -2.30%

Power consumption of RC (kW)

16.7 18.2 8.98%

Turbine power (total) (kW) 74.2 76.0 2.43%Turbine heat loss (total) (kW)

16.2 16.2(assumed) /

Net electricity (kW) 16.6 19.5 17.47%Cycle efficiency (%) 4.9 5.7 16.33%

[1] Iverson BD, Conboy TM, Pasch JJ, Kruizenga AM. Supercritical CO2 Brayton cycles for solar-thermal energy. Applied Energy. 2013;111:957-70.

Area calculation of the S-CO2 boiler(1) Area of the furnace

The structure size of the furnace of the designed S-CO2 boiler is shown in Fig. S1. According to the structure parameters in the Fig. S1, it is easy to obtain the area of the furnace. Area of the front wall (Af):Af =12.5×50+(5.06+7.0145/2)×12.5=732.1 m2

Area of the rear wall (Ar): Ar =12.5×35.65+(5.06+7.0145/2)×12.5+12.5×2.7=586.5 m2

Area of the side wall (As):As =(7.0145+12.5)×4.15+12.5×35.65+(3.3+6.86+12.5)×1.35/2+13×3.3=544.3 m2

Total area of the furnace (AT):AT = Af + Ar +2×As +(13+6.86)×12.5+12.5×3.3=2697 m2

Area of the WRH (AWRH): AWRH =1150 m2

Area of the SWH (ASWH): ASWH = AT - AWRH =2697-1150=1547 m2

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Fig. S1 Structure size of the furnace of the S-CO2 boiler (Unit: m)

(2) Area of HSHDetails of the area calculation of the HSH of the designed S-CO2 boiler is shown

in Table S3.Table S3 Structure parameter and area calculation of HSH

HSHStructure parameter Symbol Unit ValueOuter diameter of tube OD mm 51.00Wall thickness of tube t mm 8.00Transverse rows z1 - 9Longitudinal rows z2 - 64Transverse average spacing

s1 mm 1371.60

Longitudinal average spacing

s2 mm 61.00

Heating surface height h m 13.00Heating surface area A m2 (A=h×z1×z2×3.14×OD/1000) 1199.13

(3) Area of HRHDetails of the area calculation of the HRH of the designed S-CO2 boiler is shown

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in Table S4.Table S4 Structure parameter and area calculation of HRH

HRHStructure parameter Symbol Unit ValueOuter diameter of tube OD mm 51.00Wall thickness of tube t mm 6.00Transverse rows z1 - 62Longitudinal rows z2 - 68Transverse average spacing

s1 mm 200.00

Longitudinal average spacing

s2 mm 100.00

Heating surface height h m 11.00Heating surface area A m2 (A=h×z1×z2×3.14×OD/1000) 7426.66

(4) Area of LRHDetails of the area calculation of the LRH of the designed S-CO2 boiler is shown

in Table S5.Table S5 Structure parameter and area calculation of LRH

LRHStructure parameter Symbol Unit ValueOuter diameter of tube OD mm 57.00Wall thickness of tube t mm 4.50Transverse rows z1 - 113Longitudinal rows z2 - 54Transverse average spacing

s1 mm 110.00

Longitudinal average spacing

s2 mm 70.00

Heating surface height h m 5.50Heating surface area A m2 (A=h×z1×z2×3.14×OD/1000) 6006.75

(5) Area of LSHDetails of the area calculation of the LSH of the designed S-CO2 boiler is shown

in Table S6.Table S6 Structure parameter and area calculation of LSH

LSHStructure parameter Symbol Unit ValueOuter diameter of tube OD mm 45.00Wall thickness of tube t mm 4.50Transverse rows z1 - 114Longitudinal rows z2 - 51Transverse average s1 mm 110.00

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spacingLongitudinal average spacing

s2 mm 70.00

Heating surface height h m 5.50Heating surface area A m2 (A=h×z1×z2×3.14×OD/1000) 4518.35

(6) Area of SHDetails of the area calculation of the SH of the designed S-CO2 boiler is shown in

Table S7.Table S7 Structure parameter and area calculation of SH

SHStructure parameter Symbol Unit ValueOuter diameter of tube OD mm 57.00Wall thickness of tube t mm 4.50Transverse rows z1 - 114Longitudinal rows z2 - 67Transverse average spacing

s1 mm 110.00

Longitudinal average spacing

s2 mm 70.00

Heating surface height h m 11.00Heating surface area A m2 (A=h×z1×z2×3.14×OD/1000) 15037.54

Calculations of coal combustion and flue gas parametersThe calculations of coal combustion and the flue gas parameters have been shown

in Table S8 and S9.Table S8 Calculation of coal combustion (Unit: Nm3/kg)

No. Name Symbol Calculation formula Value1 Theoretical

air quantityV0 0.089×(Car+0.375×Sar)+0.265×Har-0.0333×Oar 6.055

2 Theoretical N2 volume

V0N2 0.79×V0+0.008×Nar 4.789

3 Total volume of CO2 and SO2

VRO2 0.01866×(Car+0.375×Sar) 1.145

4 Theoretical volume of water vapor

V0H2O 0.111×Har+0.0124×Mar+0.0161×V0 0.657

5 Theoretical flue gas volume

V0g V0

N2+ V0H2O + VRO2 6.591

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Table S9 Calculation of the flue gas parameterParamete

rSymbol Unit Furnace HRH Flue

gas dampe

r

SH APH

Excess air ratio at the exit

αav - 1.2 1.21 1.22 1.23 1.32

Flue gas volume

Vg

(Vg=V0g+1.0161(αav -1)V0)

Nm3/kg 7.82 7.88 7.94 8.01 8.56

Flue gas mass

Gg

(Gg=1-Aar/100+1.306αavV0)kg/kg 10.36 10.44 10.52 10.60 11.31

Fly ash mass

μash

(μash=0.95Aar/100/Gg)kg/kg 0.0115 0.0114 0.0113 0.0112 0.0105

Pressure drop calculation of heat exchangersIt is widely acknowledged that Printed Circuit Heat Exchanger (PCHE) can be

employed as the recuperators and the pre-cooler. Hence, to keep a same standard in the following calculations, counterflow PCHEs were employed as the recuperators. A subsection method based on quantity of heat was employed to build the calculation model for PCHE, shown in Fig. S2. The subsection number of this model was selected as 10, and it was proved to have enough calculation accuracy with less computation time.

Fig. S2 Subsection model based on the quantity of heatAccording to the calculations of High Temperature Recuperator (HTR) and Low

Temperature Recuperator (LTR), key design parameters of HTR and LTR are obtained, shown in Table S10. Pressure drops of HTR and LTR are 0.052 MPa and 0.047 MPa. These results are employed to obtain the boundary conditions of the present S-CO2 boiler.

Table S10 Key design parameters of HTR and LTR

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PCHE HTR LTRcore length (flow direction)/m 3.53 4.74core width/m 6 4core height/m 4 3channel shape semicircle semicirclediameter/mm 2 2channel numbers 24972666 16641998heat transfer area/m2 60373.5 40485.6heat transfer coefficient/Wm-2K-1 845.5 1308.8pressure drop/MPa 0.052 0.047

Pressure drop calculation of boilerThe pressure drop in the boiler was assumed firstly, to determine the boundary

conditions for the S-CO2 boiler design. Then, the elementary design of the boiler was made. After knowing the geometric constructions of all the boiler heating surfaces, thermal-hydrodynamic calculations of the boiler were made, and the new pressure drop in the boiler was calculated. The thermal-hydrodynamic calculation model shown in Fig. S3 was used, and detailed tube size is shown in Table S11.

According to the thermal-hydrodynamic calculations, pressure drops of the spiral wall heater and the superheater are about 1.1 MPa and 0.9 MPa , and pressure drop of the wall re-heater and the reheaters are 0.1 MPa and 0.2 MPa, respectively. The thermal-hydrodynamic calculations presented here are simplified, and inhomogeneous distribution of heat flux and flow deviation are all neglected. Because the thermal-hydrodynamic analysis is out of the scope of this paper, it will not be further discussed in this paper, although it is an interesting topic. It would be carried out in our future work.

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Fig. S3 Thermal–hydrodynamic calculation model of the S-CO2 boiler

Table S11 Tubes used in the boilerSWH WRH LSH HSH LRH HRH

Tube outside diameter /mm

34 50 45 51 57 51

Tube thickness /mm 5 4.5 4.5 6 4.5 6Tube pitch /mm 43 60.8 113 1370 110 200

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