Multi-Objective Optimization Analysis of Gas-Steam Combined Cycle Power Generation Systems

doi:10.12096/j.2096-4528.pgt.24033

Abstract

Abstract:

Objectives To improve the efficiency of gas-steam combined cycle power generation units, an optimized design of thermodynamic systems is required. Therefore, a multi-objective optimization modeling method for combined cycle power generation systems, simultaneously considering thermal efficiency, operating cost, and carbon emission is proposed. Methods The gas cycle is modeled incorporating blade cooling, while the steam cycle is modeled based on a triple-pressure reheat heat recovery steam generator. The constructed mixed-integer nonlinear mathematical programming model is solved using GAMS software to optimize the generation units, explore optimal design parameters of the combined cycle power generation system including cycle pressure ratio, turbine inlet temperature, and bottom-cycle steam parameters, and analyze trade-off relationships among multiple objectives. Results Turbine inlet temperature has the most significant effect on cycle efficiency, total cost, and carbon emissions. When conducting multi-objective optimization that balances combined cycle efficiency, total system cost, and carbon emissions, the combined cycle efficiency should be 65%. Conclusions The proposed method can more effectively optimize the thermodynamic parameters of large-scale generation units to achieve energy saving, emission reduction, and improved energy efficiency.

Key words: combined cycle generator sets, multi-objective optimization, carbon emission, thermodynamic calculation, waste heat boiler, cycle pressure ratio, simulated analysis

CLC Number:

TK 121

Wenjing WANG, Yixuan HAN, Jibin LI, Xiaoxu SHEN, Zhaoyi HUO, Lianghua FENG. Multi-Objective Optimization Analysis of Gas-Steam Combined Cycle Power Generation Systems[J]. Power Generation Technology, 2025, 46(4): 839-848.

Figures/Tables 16

Fig. 1 Flowchart of gas-steam combined cycle system

Fig. 2 Temperature-enthalpy diagram of triple-pressure reheat heat recovery steam generator

Tab. 1 Calculation parameters

名称	参数	数值
燃气轮机	空气绝热指数γ_a	1.4
	燃气绝热指数γ_k	1.33
	空压机效率η_ac/%	87
	燃烧室效率η_cc/%	99.5
	透平效率η_t/%	90
	叶片温度T_b/℃	860
	燃料流量v_f/(m³/s)	20.44
	燃料热值h_u/(kJ/m³)	37 355
	甲烷体积分数/%	91.73
	乙烷体积分数/%	6.17
	氮气体积分数/%	1.44
	二氧化碳体积分数/%	0.66
余热锅炉	给水温度t_c/℃	28.96
	接近点温差ΔT/℃	8
	夹点温差Δt/℃	8
	省煤器传热系数u_ec/[W/(m²⋅℃)]	42.6
	蒸发器传热系数u_ev/[W/(m²⋅℃)]	43.7
	过热器传热系数u_sh/[W/(m²⋅℃)]	50
汽轮机	低压汽轮机效率η_lst/%	92
	中压汽轮机效率η_mst/%	91
	高压汽轮机效率η_hst/%	90
冷凝器	工作压力p	0.004
价格系数	省煤器c^ec/(美元/m²)	45.7
	蒸发器c^ev/(美元/m²)	34.9
	过热器c^sh/(美元/m²)	96.2
	电力c^power/[美元/(kW⋅h)]	0.076
	冷却水c^cw/(美元/m³)	0.02

Fig. 3 Effect of pressure ratio on cycle efficiency

Fig. 4 Effect of turbine initial temperature on cycle efficiency

Fig. 5 Effect of pinch point temperature difference on cycle efficiency

Fig. 6 Effect of approach point temperature difference on cycle efficiency

Fig. 7 Effect of pressure ratio on total system investment cost and carbon emission

Fig. 8 Effect of turbine initial temperature on total system investment cost and carbon emission

Fig. 9 Effect of pinch point temperature difference on total system investment cost and carbon emission

Fig. 10 Effect of approach point temperature difference on total system investment cost and carbon emission

Fig. 11 Evaluation of effects of different parameters on main indicators for cycle efficiency

Fig. 12 Evaluation of effects of different parameters on total system cost and carbon emission

Fig. 13 Pareto frontier for multi-objective optimization

Fig. 14 Pareto frontier solution for total cost and cycle efficiency

Fig. 15 Pareto frontier solution for total cost and CO2 emission

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