燃煤机组超高供热负荷改造方案研究

Research on Retrofit Scheme of Ultra-high Heating Load of Coal-fired Units

随着“30/60双碳”目标的深入推进,国家对燃煤机组的碳减排工作提出了更高的要求,因此,今后会有更多的燃煤机组进行供热改造。为满足燃煤机组改供热机组的技术需求,通过对某电厂4台超临界燃煤机组特性及超高供热负荷需求的分析,提出了2种改造方案:改造方案一为拆除机组原有的汽轮机,安装一台小汽轮机用于给电厂辅助设备供电,利用减温减压器调整蒸汽参数以满足用户需求;改造方案二则是新建一台相同参数的发电机组,拆除原有机组的汽轮机中低压缸,保留原有机组的汽轮机高压缸、高低价回热系统,这样原有机组的低压加热器、除氧器和3^(#)高压加热器的抽汽来自于新建机组汽轮机中低压缸,另外,为了降低新建机组的燃煤消耗,原有机组的再热蒸汽可用于加热新建机组的给水、主蒸汽或再热蒸汽。通过对2种改造方案的供热能力及系统[火用]效率做计算,结果表明,改造方案一尽管改造简单,投资较小,但是改造后机组基本上转变为蒸汽锅炉,所以系统[火用]效率较低,不足35%;改造方案二虽然系统相对复杂,投资成本高,对机组的可靠性要求也较高,但是系统的?效率高,且供电量大,改造后系统[火用]效率能够达到45.3%,供电量能够达到1704.56 MW。因此该研究成果能够为该电厂的供热技改提供很好的选择方案,也能够为今后类似的改造提供技术参考。

With the deepening of the national“30/60 dual-carbon”goal,the country has put forward higher requirements for carbon emission reduction of coal-fired units,therefore,more coal-fired units will be retrofitted for heating in the future.In order to meet the technical needs of converting coal-fired units to heating units,based on the analysis of the characteristics of 4 supercritical coal-fired units in a power plant and the demand for ultra-high heating load,two transformation schemes are proposed.The first transformation scheme is to dismantle the original steam turbine of the unit and install a small steam turbine for the power plant.The auxiliary equipment is powered,and the steam parameters are adjusted by the desuperheater and pressure reducer to meet the user’s needs.The second transformation plan is to build a new generator unit with the same parameters,remove medium and low pressure cylinder of the steam turbine,and retain high pressure cylinder of the steam turbine and high-pressure heater and low-pressure heater of recovery system of the original unit.The low-pressure heater,deaerator and No.3 high-pressure heater steam extraction of the original unit come from the medium and low pressure cylinders of the new unit;on the other hand,in order to reduce the coal consumption of the new unit,the reheated steam of the original unit is used to heating feed water,main steam or reheat steam for the new units.The heating capacity and system exergy efficiency of the two transformation schemes are calculated,the calculation results show that although the 1st scheme is simple to transform and has a small investment,the unit is basically transformed into a steam boiler after the transformation,so the system exergy efficiency is less than 35%;although the system of the 2nd scheme is relatively complex,the investment cost is high,and the reliability requirements of the unit are also high,however,the exergy efficiency of the system is high and the power supply is large.After the transformation,the exergy efficiency of the system of the 2nd scheme can reach45.3%,and the power supply can reach 1704.56 MW.Therefore,the research results can provide a good choice for the heating technical transformation of the power plant,and can also provide a technical reference for similar technical transformations in the future.