Hot primary air heating system for dry coal pulverizing system

Abstract

The invention provides a hot primary air heating system for a dry coal pulverizing system. The hot primary air heating system comprises a steam extraction pipeline, wherein the steam extraction pipeline is connected to the steam extraction end of a steam turbine, and the steam extraction pipeline communicates with a high-pressure heater. The hot primary air heating system is characterized in that a stop valve I is arranged on a pipeline between the steam extraction pipeline and the high-pressure heater, the hot primary air heating system further comprises a primary air heater I, a primary air heater II and a reheat steam pipeline, the steam extraction pipeline is connected to the inlet ends of the primary air heater I and the primary air heater II by virtue of a stop valve II at the same time, the outlet ends of the primary air heater I and the primary air heater II communicate with the high-pressure heater, the reheat steam pipeline communicates with a reheater, and the reheat steam pipeline is connected to the inlet ends of the primary air heater I and the primary air heater II by virtue of a stop valve III at the same time. According to the hot primary air heating system, the degree of superheat of high-temperature steam is fully used, so that the effect of energy conservation of a whole thermal cycle unit is achieved, the drying capacity of the coal pulverizing system is increased, and the operating cost of the unit is reduced.

Description

technical field [0001] The invention relates to a system that uses reheated steam and steam extraction from a steam turbine to increase the temperature of the hot primary air so as to increase the drying output of the pulverizing system. It is used for secondary reheating of the hot primary air to realize a large proportion of boiler units mixed with low-quality coal , belongs to the technical field of boilers. Background technique [0002] The fuel sources of my country's coal-fired units are mainly lignite, bituminous coal, anthracite, etc., of which bituminous coal accounts for three quarters of the total, and the excessive mining and burning of bituminous coal has reduced its reserves to less than 7% of the total coal reserves. Ten, it cannot meet the strong demand for power supply, which requires us to actively develop the utilization of low-quality coal, expand the adaptability of coal types, and increase the proportion of lignite, peat and other coal resources in coal ...

AI Technical Summary

Problems solved by technology

Faced with the abundant reserves and low cost of lignite, many power generation groups currently require bituminous coal-burning units to start blending a large proportion of lignite, and lignite has the characteristics of high volatile content, high moisture, and low calorific value, which causes boiler units to blend lignite Sometimes the output of the coal mill is insufficient, so it can only operate at reduced load or reduce the blending ratio of low-quality coal, which seriously affects the economy of the unit

[0003] The primary air temperature of the air preheater outlet of the bituminous coal-fired boiler unit is generally designed at 310°C to 320°C, and the outlet temperature of the coal mill is at 65°C. When a large proportion of lignite is blended, due to the high moisture and high volatile characteristics of lignite, As a result, when the cold primary air entering the coal mill is fully closed, the drying capacity of the hot primary air is still insufficient. There are two main conventional means of adjustment: one is to increase the primary air rate, which will increase the power consumption of the primary fan, And it reduces the secondary air rate, affects the rigidity of the secondary air, and affects the overall aerodynamic field of the boiler, resulting in poor combustion effect and increased incomplete combustion heat loss

The other is to reduce the amount of coal grinding, which will cause insufficient combustion heat of the boiler and the load of the unit cannot be increased.

The Chinese patent No. 201320504090.9 discloses a heat recovery system to improve the drying output of the pulverizing system. The temperature of the air-powder mixture is increased by adding a drying system at the outlet of the coal mill. The wear and tear is relatively large, and there are too many extraction systems involved, and the pipeline design is complicated

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