Study on Cold End Temperature Optimization of Supercritical CO2 Cycle

doi:10.12096/j.2096-4528.pgt.19149

Abstract

Abstract:

Supercritical CO₂ cycle has a high cold end temperature. Optimizing the cold end temperature plays an important role in improving the cycle efficiency. In order to obtain the best annual average efficiency, it is necessary to introduce artificial refrigeration to make the supercritical CO₂ cycle run at a more optimized cold end temperature. For the supercritical CO₂ recompression cycle with parameters of 550℃/20MPa, the annual average cycle efficiency under different cold end temperature of 5 to 35℃, with the combination of natural cooling and artificial refrigeration was analyzed by thermodynamic method, and the feasibility and economic analysis of the cold end temperature optimization method were studied as well. The annual average efficiency of the unit can be improved by choosing the optimal cold end temperature and combining natural cooling with artificial refrigeration. For northern China, the cold end temperature optimization method has better feasibility. The artificial refrigeration increases the investment of unit equipment, but the improvement of operation efficiency brings more power generation revenue and moreover increases the net income of the unit during its life cycle.

Key words: supercritical CO₂ cycle, cold end optimization, cycle efficiency, economy

CLC Number:

TK02
TM61

Kaiyun ZHENG. Study on Cold End Temperature Optimization of Supercritical CO₂ Cycle[J]. Power Generation Technology, 2021, 42(2): 261-266.

Figures/Tables 5

References 18

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参数	取值
净输出功率/MW	100
透平入口温度/℃	550
透平入口压力/MPa	20
压缩机等熵效率/%	85
透平等熵效率/%	90
回热器最小温差/℃	10

参数	取值
净输出功率/MW	100
透平入口温度/℃	550
透平入口压力/MPa	20
压缩机等熵效率/%	85
透平等熵效率/%	90
回热器最小温差/℃	10

冷端温度/℃	冷端压力/MPa	分流比	制冷温度区间/℃	循环效率/%	净效率/%
5	4.0	0.47	5~29.2	50.8	38.5
8	4.3	0.465	8~33.0	50.4	38.0
11	4.7	0.46	11~35	49.9	37.5
14	5.0	0.456	14~35	49.4	37.3
17	5.4	0.45	17~35	48.9	37.0
20	5.9	0.44	20~35	48.2	36.7
23	6.2	0.435	23~35	47.8	36.8
26	6.6	0.403	26~35	46.6	38.6
29	7.1	0.415	29~35	46.4	37.8
32	7.7	0.398	32~35	45.4	39.7
35	8.0	0.356	—	44.2	—

冷端温度/℃	冷端压力/MPa	分流比	制冷温度区间/℃	循环效率/%	净效率/%
5	4.0	0.47	5~29.2	50.8	38.5
8	4.3	0.465	8~33.0	50.4	38.0
11	4.7	0.46	11~35	49.9	37.5
14	5.0	0.456	14~35	49.4	37.3
17	5.4	0.45	17~35	48.9	37.0
20	5.9	0.44	20~35	48.2	36.7
23	6.2	0.435	23~35	47.8	36.8
26	6.6	0.403	26~35	46.6	38.6
29	7.1	0.415	29~35	46.4	37.8
32	7.7	0.398	32~35	45.4	39.7
35	8.0	0.356	—	44.2	—

冷端温度/℃	最高自然冷却环境温度/℃	自然冷却时间比例门槛值/%
5	2	46.2
8	5	50.1
11	8	54.4
14	11	57.1
17	14	60.7
20	17	65.3
23	20	67.7
26	23	70.8
29	26	74.9
32	29	78.8

Study on Cold End Temperature Optimization of Supercritical CO₂ Cycle

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Figures/Tables 5

References 18

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冷端温度/℃	制冷量/MW	制冷机投资/万元	高温回热器功率/MW	低温回热器功率/MW	回热器投资变化/万元	设备投资变化/万元
5	96.7	5 803.0	137.2	127.9	-7 297.2	-1 494.2
8	98.4	5 901.7	151.1	128.8	-6 852.6	-950.9
11	99.5	5 968.2	170.6	129.9	-6 234.0	-265.8
14	98.5	5 908.3	184.8	131.3	-5 765.1	143.2
17	97.3	5 838.3	205.0	132.8	-5 113.0	725.3
20	95.5	5 727.7	232.0	134.7	-4 246.6	1 481.1
23	91.5	5 488.0	247.1	137.0	-3 722.5	1 765.5
26	68.6	4 115.6	256.9	147.9	-3 106.0	1 009.6
29	74.4	4 461.0	298.4	143.3	-1 997.0	2 464.0
32	50.7	3 042.2	337.3	147.7	-694.9	2 347.3
35	0	0	350.9	157.4	0	0

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