基于当量抽汽压力的大型热电联产供热模式研究

Study on Heating Mode of a Large Heat and Power Cogeneration Unit Based on Equivalent Extraction Pressure

建立了大型热电联产机组变工况分析模型,揭示出不同热网回水温度和热网回水温升条件下,单效溴化锂吸收式热泵驱动热源饱和蒸汽压力和热力系数的变化规律.提出2种不同供热模式选取的判据,即当量抽汽压力.以某300MW直接空冷抽凝供热机组为例,进行了变工况计算及分析.结果表明:随热网回水温升的增大以及热网回水温度的升高,驱动热源饱和蒸汽压力升高,而吸收式热泵热力系数则减小;对于300MW等级及以上供热改造机组,由于汽轮机中低压缸抽汽压力高于对应的当量抽汽压力,采用吸收式热泵供热模式更节能.

An analysis model was established for a large heat and power cogeneration unit with single-effect lithium bromide absorption heat pump(AHP)under variable working conditions,which reveals the change rules of AHP thermodynamic coefficient with the saturation steam pressure of AHP driving heat source,under different backwater temperature and temperature rise conditions.The concept of equivalent extraction pressure(EEP)was proposed for selection of heating mode from two options.Taking a 300 MW direct air-cooling unit as an example,calculation and analysis were carried out under variable working conditions.Results show that with the increase of backwater temperature and temperature rise in the heatsupply network,the AHP thermodynamic coefficient reduces;for heating units of 300 MW and above to be retrofitted,the AHP heating mode is more energy saving,as the extraction pressure of turbine's medium-and low-pressure cylinder is higher than corresponding equivalent extraction pressure.