Optimization of low-pressure flow part of high back-pressureheating steam turbine

doi:10.16085/j.issn.1000-6613.2019-0428

Abstract

Abstract:

High back-pressure(HBP)heating method can expand the heating capacity of the unit by recovering the exhaust heat and reducing the available energy losses of the extract steam, which is of high energy conversion efficiency. The low-pressure rotor adopts the double-rotor interchange technology and the back-pressure is high during the heating season, the low-pressure cylinder’s thermal characteristics are changed. Therefore, a thermodynamic system model for a 300MW high back-pressure heating unit was established, the effect of the extraction parameter change on the additional unit consumption of the low-pressure heater was calculated and analyzed, and the additional unit consumption during the heating season through parameter optimization was reduced. The optimal optimization effect was obtained when the extraction pressures of the five sections and six sections were 0.3591MPa and 0.1559MPa, and the temperature rise of the low-pressure heaters at all levels was reasonable because of the lower heat transfer end difference. After optimization, the power generation of the unit was increased by 507kW, the exergy loss was reduced by 575.5kW, and the additional unit consumption was reduced by 0.3121g/(kW·h). Based on this, the low-pressure cylinder’s flow section of the high-pressure heating unit was subjected to thermal calculation, the pressure drop of each low-pressure cylinder’ blades was re-allocated to increase the flow efficiency of the low-pressure cylinder. The results showed that by optimizing the low-pressure heat recovery system and the through-flow part, the efficiency of the low-pressure cylinder increases to 0.9250, and the unit output increases by 3068.49kW.

Key words: high back-pressure heating, regenerative feed system, specific consumption analysis, flow part, exergy, model, optimization

摘要：

汽轮机高背压供热方式可回收低压缸排汽余热，扩大机组的供热能力，减少高品位抽汽造成的可用能损失，能源转换效率高。供热季运行背压高，低压转子采用了双转子互换技术，低压转子结构的变化使低压部分热力特性发生变化。本文建立了300MW等级高背压供热机组热力系统模型，计算并分析抽汽参数变化对低压加热器附加单耗的影响，并通过参数优化降低供热季低压加热器附加单耗。获得五段和六段抽汽压力优化结果，降低了传热端差，使各级低压加热器温升分配合理，优化后机组发电功率增加507kW，?损减小575.5kW，整体附加单耗下降0.3121g/(kW·h)。以此为基础，进行高背压供热机低压通流部分热力计算，重新分配低压缸各压力级焓降，提高低压缸的通流效率。结果表明：通过对低压回热系统和通流部分优化，低压缸内效率提高至0.9250，机组发电功率增加3068.49kW。

关键词: 高背压供热, 回热系统, 单耗分析, 通流部分, ?, 模型, 优化

CLC Number:

TM621

Zhihua GE,Youjun ZHANG,Nian XIONG,Shifei ZHAO. Optimization of low-pressure flow part of high back-pressureheating steam turbine[J]. Chemical Industry and Engineering Progress, 2019, 38(12): 5264-5270.

戈志华,张尤俊,熊念,赵世飞. 高背压供热汽轮机低压部分性能优化[J]. 化工进展, 2019, 38(12): 5264-5270.

Figures/Tables 13

References 23

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项目	数值	项目	数值
发电功率/kW	238928	再热蒸汽流量/kg·h^-1	745105
主蒸汽压力/MPa	16.67	抽汽压力/MPa	0.791
再热蒸汽压力/MPa	3.191	抽汽量/kg·h^-1	190000
主蒸汽温度/℃	538	排汽压力/kPa	54
再热蒸汽温度/℃	538	排汽流量/kg·h^-1	444240
主蒸汽流量/kg·h^-1	970004	末级高加出口给水温度/℃	276.3

项目	数值	项目	数值
发电功率/kW	238928	再热蒸汽流量/kg·h^-1	745105
主蒸汽压力/MPa	16.67	抽汽压力/MPa	0.791
再热蒸汽压力/MPa	3.191	抽汽量/kg·h^-1	190000
主蒸汽温度/℃	538	排汽压力/kPa	54
再热蒸汽温度/℃	538	排汽流量/kg·h^-1	444240
主蒸汽流量/kg·h^-1	970004	末级高加出口给水温度/℃	276.3

工况	设计功率/kW	模拟功率/kW	相对误差/%
额定供热工况	238928	238900	0.01
最大供热工况	261781	261551	0.09
最小供热工况	196493	196236	0.13

工况	设计功率/kW	模拟功率/kW	相对误差/%
额定供热工况	238928	238900	0.01
最大供热工况	261781	261551	0.09
最小供热工况	196493	196236	0.13

项目	1^#高加	2^#高加	3^#高加	4^#除氧器	5^#低加	6^#低加	合计
?损/kW	990.062	1277.862	1348.868	3768.21	1267.125	129.27	8781.397
附加单耗/g·kW^-1·h^-1	0.4572	0.5901	0.6628	1.74	0.5851	0.0587	4.0939