A Combined Cycle Indirect Air Cooling System

Abstract

The invention discloses a combined-cycle indirect air cooling system. The combined-cycle indirect air cooling system comprises an air cooling island and a condenser. An outlet end of the air cooling island is connected with a working medium inlet end of the condenser by a working medium pump, a working medium outlet end of the condenser is connected with a working medium turbine and the outlet end of the working medium turbine is connected with an inlet end of the air cooling island. A steam inlet end of the condenser is connected with a main steam turbine. The inlet end of the main steam turbine is connected with a main steam pipeline and a power output shaft of the main steam turbine is connected with a main electric generator. The power output shaft of the working medium turbine is connected with an auxiliary electric generator and a condensed water outlet end of the condenser is connected with a condensed water pipeline by a condensed water pump. A working medium tank is arranged between the outlet end of the working medium turbine and the inlet end of the air cooling island. According to the system, the advantages of the cold sources in the cold areas can be used for lowering the coal consumption rate of an air cooling machine set more efficiently, more environmentally and more reliably.

Description

technical field [0001] The invention belongs to the fields of mechanical engineering and low-temperature waste heat recovery, and relates to a novel high-efficiency air-cooled coal-fired power generation system, in particular to a combined cycle indirect air-cooling system. Background technique [0002] The energy characteristics of "rich coal, poor oil, and little gas" determine that China's coal-based primary energy production and consumption pattern will not change for a long time. In recent years, although the proportion of nuclear power, wind power, and solar power has been increasing, coal-fired power generation is still the absolute main force of my country's electricity production. As of the end of 2015, its installed capacity reached 990 million kilowatts, and its power generation accounted for 73.1% of the total power generation in 2015. However, due to the extremely unbalanced distribution of coal resources and water resources in my country, water resources are e...

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Problems solved by technology

[0004] The direct air cooling system refers to the power station system that directly uses mechanical ventilation to condense the exhaust steam of the steam turbine in the surface heat exchanger. figure 1 As shown, it has the advantages of less equipment, simple system, less floor space, flexible system adjustment, etc., but there are also many problems: First, the back pressure of the direct air cooling unit is greatly affected by the ambient temperature, which is in the range of about 7kPa to 50kPa Second, in order to avoid partial freezing of condensed water in winter, some severe cold regions even require the back pressure of the unit to be above 20kPa in winter; third, the performance of the air-cooled condenser is greatly affected by the ambient wind, especially the return flow of hot air. The vacuum can be reduced by 5-20kPa; fourth, the heat transfer effect of the air-cooled island is poor, so that the operating back pressure of the direct air-cooled unit is more than 3 times higher than that of the wet-cooled unit; fifth, the performance of the final stage of the steam turbine is poor, far away from the design point Low back pressure operation does not reduce unit coal consumption rate

Therefore, although most large-scale air-cooled coal-fired generating units work in alpine regions with less precipitation, due to the combined effects of the above factors, even in cold winters, air-cooled units still need high back pressure to operate, and cannot make full use of the low temperature environment to improve The cycle efficiency of the unit causes its coal consumption rate to be 15-25g / kWh higher than that of a wet-cooled unit with the same parameters and capacity

[0005] Compared with the direct air cooling system, the indirect air cooling system has the advantages of small pressure loss in the steam turbine exhaust pipe, small heat exchange end difference of the condenser, no hot air backflow and no fouling of the condenser tube bundle, etc., so that the annual average back pressure ratio of the unit is directly The air-cooled unit is more than 2kPa lower, and the coal consumption rate is reduced by about 4g / kWh. However, the coal consumption rate is still far away due to the failure to fundamentally solve the key problems such as the unit’s back pressure fluctuating with the ambient temperature and increasing the unit’s back pressure to avoid cooling water freezing. It is higher than the wet cooling unit, and does not get rid of the physical essence of "exchanging coal for water" of the air cooling unit

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