CN107504512A - A kind of hot primary wind heating system for being used to dry pulverized coal preparation system - Google Patents

Abstract

The invention provides a hot primary air heating system for a dry pulverizing system, which includes a steam extraction pipeline connected to the steam extraction end of a steam turbine, and the steam extraction pipeline is connected with a high-pressure heater. The pipeline between the steam pipeline and the high-pressure heater is provided with a shut-off valve 1, which also includes primary air heater 1 and primary air heater 2. The inlet port of heater 2 is connected, the outlet port of primary air heater 1 and primary air heater 2 is connected with high-pressure heater, and also includes the reheat steam pipeline connected to the reheater, and the reheat steam pipeline passes through the stop valve Three are connected with the inlet ends of primary air heater one and primary air heater two at the same time. The invention makes full use of the superheat degree of high-temperature steam, achieves the energy-saving effect of the overall thermal cycle unit, increases the drying output of the pulverizing system, and reduces the operating cost of the unit.

Description

A hot primary air heating system for dry powder making system

technical field

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

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 combustion, so as to alleviate the current situation of bituminous coal shortage . The latest data show that the proven lignite reserves have reached 100 billion tons, accounting for about 16% of the country's total coal reserves. 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.

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 heat loss from incomplete combustion. 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 steam extraction systems involved, and the pipeline design is complicated.

Contents of the invention

The purpose of the present invention is to increase the drying output of the pulverizing system and realize the mixed burning of low-quality coal in a large proportion or a full proportion of the bituminous coal burning unit.

In order to achieve the above object, the technical solution of the present invention is to provide a hot primary air heating system for the dry pulverizing system, including a steam extraction pipeline connected to the steam extraction end of the steam turbine, the steam extraction pipeline and the high-pressure heater It is characterized in that a shut-off valve 1 is set on the pipeline between the extraction pipeline and the high-pressure heater, and it also includes a primary air heater 1 and a primary air heater 2, and the extraction pipeline passes through the shut-off valve 2 at the same time. It is connected to the inlet port of primary air heater 1 and primary air heater 2, and the outlet port of primary air heater 1 and primary air heater 2 is connected to the high-pressure heater, and also includes the reheat steam pipeline connected to the reheater , the reheat steam pipeline is connected to the inlet ports of the primary air heater 1 and the primary air heater 2 via the stop valve 3 at the same time.

Preferably, a temperature and pressure reducing valve is provided on the pipeline between the outlet ends of the primary air heater 1 and the primary air heater 2 and the high pressure heater.

Preferably, the inlet port of the primary air heater 1 communicates with the steam extraction pipeline or the reheat steam pipeline via a flow regulating valve 1, and the inlet port of the primary air heater 2 passes through a flow regulating valve The second is in communication with the steam extraction pipeline or the reheat steam pipeline.

Preferably, a flow regulating valve 3 is provided on the pipeline between the shut-off valve 3 and the inlet ends of the primary air heater 1 and the primary air heater 2.

Preferably, a cut-off valve 4 is provided on the inlet end of the extraction pipeline and the inlet end of the high-pressure heater.

The invention uses a high-temperature steam heat exchanger to heat the hot primary air for the second time, fully utilizes the superheat degree of the high-temperature steam, achieves the energy-saving effect of the overall thermal cycle unit, improves the drying output of the pulverizing system, and reduces the operating cost of the unit.

Description of drawings

Fig. 1 is a system diagram of the present invention;

Fig. 2 is a schematic diagram of the present invention.

detailed description

Below in conjunction with specific embodiment, further illustrate the present invention. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the teachings of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

In order to solve the problems pointed out in the background technology, the present invention proposes to add a heat exchanger in the hot primary air duct in front of the coal mill to reheat the hot primary air twice, and after the air duct is reformed, the hot primary air rate returns to the original Design parameters to ensure the drying capacity of the coal mill, and at the same time, the side outlet temperature of the coal mill is 65°C to ensure the output capacity of the coal mill.

With reference to Fig. 1 and Fig. 2, specifically, the structure of a hot primary air heating system used in the drying and pulverizing system provided by the present invention is as follows:

The 538°C reheat steam from the reheat steam pipeline connected to the reheater enters the primary air heaters A and B, and the primary air heaters A and B raise the temperature of the 319°C hot primary air to 360°C and are heated The final hot primary air enters the coal mill, and the heated reheated steam enters the existing #3 high-pressure heater through the temperature and pressure reducing valve 1. The #3 high-pressure heater is connected to the #3 extraction steam pipeline through the shut-off valve 4, and the #3 extraction steam pipeline is connected to the #3 steam extraction end of the steam turbine.

In the same way, the 440°C steam from #3 steam extraction pipeline enters the primary air heaters A and B, and the primary air heater raises the temperature of the 319°C hot primary air to 340°C, and the heated primary air enters the mill Coal machine, the heated reheated steam enters #3 high-pressure heater through temperature and pressure reducing valve 1.

The reheating steam pipeline and #3 extraction steam pipeline are respectively equipped with stop valve 3 7 and stop valve 2 3, which can realize the switching of the two-way steam to heat the primary air heaters A and B. Due to the different calorific value of the two steams, under high load conditions, switch to #3 extraction steam pipeline for heating, and under low load conditions, switch to reheat steam pipeline for heating.

Before primary air heater A and primary air heater B, flow regulating valve 1 5 and flow regulating valve 2 6 are set to adjust the flow of steam to meet the control requirements of the system.

Claims (4)

1. A hot primary air heating system for a dry pulverizing system, comprising a steam extraction pipeline connected to the steam extraction end of the steam turbine, the steam extraction pipeline is connected with a high-pressure heater, and it is characterized in that the steam extraction pipeline There is a cut-off valve 1 (4) on the pipeline between the high-pressure heater and the high-pressure heater, and it also includes primary air heater 1 and primary air heater 2. The extraction pipeline is connected to the primary air heater The inlet ports of primary air heater 1 and primary air heater 2 are connected, the outlet ports of primary air heater 1 and primary air heater 2 are connected with high-pressure heater, and the reheat steam pipeline connected to reheater, reheat steam pipe The path is connected to the inlet ports of the primary air heater 1 and the primary air heater 2 via the stop valve 3 (7). 2. A kind of hot primary air heating system for dry pulverization system as claimed in claim 1, it is characterized in that, the outlet end of described primary air heater one and described primary air heater two is connected with the high pressure A temperature and pressure reducing valve (1) is provided on the pipeline between the heaters. 3. A kind of hot primary air heating system for drying powder making system as claimed in claim 1, characterized in that, the inlet end of said primary air heater 1 is connected to said suction port via flow regulating valve 1 (5). The steam pipeline or the reheat steam pipeline is connected, and the inlet end of the primary air heater 2 is connected with the steam extraction pipeline or the reheat steam pipeline through a flow regulating valve 2 (6). 4. A kind of hot primary air heating system for dry powder making system as claimed in claim 1, characterized in that, said stop valve three (7) is connected with said primary air heater one and said primary air heating A flow regulating valve three (2) is provided on the pipeline between the inlet ends of the device two.