Full-load efficient backheating and fire coal drying system

Abstract

The invention provides a full-load efficient backheating and fire coal drying system which comprises a plurality of heaters, at least one high-load steam source, at least one low-load steam source and fire coal drying devices. The heaters are in cascade connection; each high-load steam source is selectively communicated with one of the heaters; each low-load steam source is selectively communicated with one of the heaters; and each fire coal drying device is arranged between the corresponding low-load steam source and the heater connected with the low-load steam source or between the corresponding high-load steam source and the heater connected with the high-load steam source, and the pressure of the low-load steam sources is higher than that of the high-load steam sources. The full-load efficient backheating and fire coal drying system can increase efficiency of a generator set under particle load, and the temperature of air of an inlet of a coal mill is increased so as to increase pulverized coal drying capacity of the coal mill.

Description

technical field [0001] The invention relates to the technical field of power generation, in particular to a full-load high-efficiency heat recovery and coal-fired drying system suitable for power plants. Background technique [0002] In power plants, a heat recovery system is a system that uses steam to heat condensate and feed water. The system can recover all the heat of the steam to the working medium water to improve the efficiency of the thermal cycle. The heaters of the regenerative system mainly include condensate heaters, deaerators and feed water heaters. In the application, the heat recovery system usually configured uses the heat of multi-stage steam extraction of the steam turbine to heat the condensed water and feed water through multi-stage heaters, so that all the heat of the steam is recovered to the working medium water, and the temperature of the feed water is increased. The current system design of power plants focuses on the efficiency of the generator ...

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Problems solved by technology

[0010] However, the simple full-load high-efficiency recuperation system still has the following shortcomings: (1) Due to the sliding pressure operation of the unit at part load, the extraction steam pressure is reduced, but the extraction steam temperature does not drop or drops very little, so at part load Switching the extraction steam of the lower heater to a high-pressure steam source may lead to an increase in the extraction steam temperature, so it is necessary to increase the material grade of the heater to meet the increase in the extraction steam temperature, which increases the cost of the heater; or take measures to reduce the extraction steam (such as spraying water to reduce temperature), wasting the heat of steam extraction; (2) due to the limitation of boiler structure and hydrodynamic conditions, there is an upper limit for the increase of feed water temperature

When the moisture content of the coal is much higher than the design coal type, it will happen that the pulverized coal cannot be completely dried even if the inlet air temperature of the pulverizer reaches the upper limit, that is, the pulverized coal temperature at the outlet of the pulverizer cannot reach the design value

This situation will lead to poor boiler combustion and reduced boiler efficiency

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