A medium-speed mill direct-blowing pulverizing system suitable for ultra-high moisture lignite

Abstract

The invention discloses a medium-speed mill direct-blowing pulverizing system suitable for extra-high moisture lignite, and the main technical scheme adopted is: a primary fan; a rotary air preheater, which is connected to the outlet of the primary fan through a first cold primary air duct, and the smoke outlet of the rotary air preheater is connected to the smoke exhaust duct of the rotary air preheater; a tubular air preheater, the hot primary air inlet of the tubular air preheater is connected to the rotary air preheater through the hot primary air duct of the rotary air preheater, and the smoke outlet of the tubular air preheater is connected to the smoke inlet of the rotary air preheater through a first bypass duct; a medium-speed coal mill, which is connected to the primary fan through a second cold primary air duct and is connected to the hot primary air outlet of the tubular air preheater through the hot primary air duct of the tubular air preheater; a boiler, whose main smoke outlet is connected to the smoke inlet of the rotary air preheater, and the bypass smoke outlet of the boiler is connected to the smoke inlet of the tubular air preheater through a second bypass duct.

Description

Technical Field

[0001] The invention relates to the technical field of pulverized coal boiler combustion in a thermal power plant, and in particular to a medium-speed mill direct-blowing pulverizing system suitable for extra-high-moisture lignite. Background Art

[0002] Coal-fired thermal power generation technology still occupies a leading position in the field of energy utilization and power generation. With the rapid development of the world economy, global coal resources are becoming increasingly scarce, and the price of coal is also gradually increasing. In order to pursue higher economic benefits, some domestic and foreign power plants, especially those in Southeast Asia such as Indonesia, use Indonesian lignite with high moisture content and low calorific value.

[0003] For burning lignite, you can choose a circulating fluidized bed boiler or a pulverized coal boiler. Circulating fluidized bed boilers are rarely used in large thermal power generating units due to the easy tube burst, short maintenance cycle and low annual available hours. Pulverized coal boilers are mainly suitable for burning lignite in fan mill direct blowing pulverizing system and medium speed mill direct blowing pulverizing system. Among them, the fan mill direct blowing pulverizing system uses high-temperature furnace smoke as the drying medium to dry the coal, which has the disadvantages of complex system and low fan mill impeller life and frequent replacement, which is not easy to accept. The medium speed mill direct blowing pulverizing system has the advantages of simple system, convenient operation and less maintenance, which is more popular. However, the drying medium of the medium speed mill pulverizing system is hot air. Due to the influence of conditions such as the ventilation capacity of the coal mill and the allowable temperature of the outlet of the medium speed coal mill (60-70℃), the drying capacity is not as good as the fan mill pulverizing system.

[0004] In the early days, most of the power plants burning lignite in various regions of China were equipped with fan mills, and there were fewer thermal power units equipped with medium-speed mills. As the units develop towards higher parameters, the requirements for boiler thermal deviation are greatly increased, and the "missing corner" operation mode of the fan mill pulverizing system is very likely to cause flame deviation in the furnace, resulting in increased thermal deviation on the flue gas side, and cannot fully meet the requirements of high parameter deviation control. In recent years, large lignite-burning units have been exploring the solution of using medium-speed mills to grind ultra-high moisture lignite.

[0005] According to the relevant regulations and specifications of the power industry, when the total moisture content of the ground coal is ≤35%, a medium-speed mill direct-blowing pulverizing system should be used; when burning lignite with a received total moisture content of Mat>35%, a fan mill direct-blowing pulverizing system should be used. At present, the received total moisture content of local coal in Indonesia is between 39% and 48.5%, which is a very high-moisture lignite, far higher than the requirement of the regulations for a maximum total moisture content of 35% for a medium-speed mill direct-blowing pulverizing system. At this time, in order to ensure the drying output of the coal mill, the hot air temperature at the inlet of the coal mill needs to reach about 400°C. If a conventional primary air system is used, in order to meet the primary air temperature and the drying output of the pulverizing system, the traditional rotary air preheater alone is difficult to design and costly, and the boiler efficiency is low. In order to improve the drying output of the medium-speed coal mill, it is necessary to increase the temperature of the hot primary air, enhance the adaptability of the medium-speed mill direct-blowing pulverizing system to extra-high moisture lignite, and ensure the safe and economical operation of the pulverizing system. At present, a medium-speed mill direct-blowing pulverizing system suitable for extra-high moisture lignite is urgently needed to meet market demand. Summary of the invention

[0006] In view of this, the present invention provides a medium-speed mill direct-blowing pulverizing system suitable for extra-high moisture lignite, the main purpose of which is to enhance the adaptability of the medium-speed mill direct-blowing pulverizing system to extra-high moisture lignite.

[0007] In order to achieve the above object, the present invention mainly provides the following technical solutions:

[0008] An embodiment of the present invention provides a medium-speed mill direct-blowing pulverizing system suitable for extra-high moisture lignite.

[0009] It includes:

[0010] Primary fan, used to provide cold primary air;

[0011] A rotary air preheater, which is connected to the outlet of the primary fan through a first cold primary air duct, and the smoke outlet of the rotary air preheater is connected to the smoke exhaust duct of the rotary preheater;

[0012] A tubular air preheater, wherein the hot primary air inlet of the tubular air preheater is connected to the rotary air preheater through the hot primary air duct of the rotary air preheater, and the flue gas outlet of the tubular air preheater is connected to the flue gas inlet of the rotary air preheater through a first bypass flue;

[0013] A medium-speed coal mill connected to the primary air fan through a second cold primary air duct and connected to a hot primary air outlet of the tubular air preheater through a hot primary air duct of the tubular air preheater;

[0014] A boiler, wherein the main flue gas outlet of the boiler is connected to the flue gas inlet of the rotary air preheater, and the bypass flue gas outlet of the boiler is connected to the flue gas inlet of the tubular air preheater through a second bypass flue;

[0015] The cold primary air comes out of the primary fan and enters the rotary air preheater through the first cold primary air duct for primary heating, and then is introduced into the tubular air preheater from the hot primary air duct of the rotary air preheater for secondary heating to increase the temperature, and finally enters the medium-speed coal mill from the hot primary air duct of the tubular air preheater; the flue gas at the boiler outlet enters the smoke inlet of the rotary air preheater from the main smoke gas outlet on one path, and enters the tubular air preheater from the smoke gas bypass to heat the primary air twice, and then passes through the first bypass flue before entering the rotary air preheater to merge with the smoke at the main smoke gas outlet and enters the rotary air preheater from the smoke inlet of the rotary air preheater; the cold primary air comes out from the second cold primary air duct on the other path, merges with the hot primary air of the tubular air preheater coming out of the hot primary air duct of the tubular air preheater, and enters the medium-speed coal mill to adjust the temperature entering the medium-speed coal mill.

[0016] As mentioned above, the tubular air preheater comprises an upper tubular air preheater tube box, a lower tubular air preheater tube box connected to the upper tubular air preheater tube box and arranged in two layers in a vertical staggered manner, and a compensator arranged at the connection between the upper tubular air preheater tube box and the lower tubular air preheater tube box;

[0017] The upper layer tubular air preheater tube box and the lower layer tubular air preheater tube box both include a box body and a spiral grooved tube arranged in the box body. The inner channel of the spiral grooved tube is a flue gas duct, and the spiral groove outside the spiral grooved tube is an air duct.

[0018] As mentioned above, the flue gas inlet of the tubular air preheater is arranged at the top of the tube box of the upper tubular air preheater;

[0019] An adjustable shutoff damper is provided at the flue gas inlet of the tubular air preheater;

[0020] The flue gas outlet of the tubular air preheater is arranged at the bottom end of the tube box of the lower tubular air preheater.

[0021] As mentioned above, the hot primary air inlet of the tubular air preheater is arranged on one side of the tube box of the lower tubular air preheater;

[0022] The hot primary air outlet of the tubular air preheater is arranged on one side of the tube box of the upper tubular air preheater.

[0023] As mentioned above, the upper tube air preheater tube box and the lower tube air preheater tube box also include a support frame connected to the box body and used to fix the box body, and two legs installed on both sides of the bottom of the box body.

[0024] As mentioned above, the boiler comprises a boiler tail shaft and an economizer arranged below the boiler tail shaft;

[0025] The tubular air preheater is arranged behind the boiler tail shaft or on the left and right sides of the boiler tail shaft.

[0026] As mentioned above, the boiler bypass flue gas outlet is led out from the outlet of the upper economizer in the boiler rear flue.

[0027] As mentioned above, it also includes:

[0028] A flue gas bypass regulating damper is arranged on the second bypass flue, and the flue gas bypass regulating damper is used to adjust the flue gas volume entering the tubular air preheater, thereby adjusting and controlling the wind temperature entering the medium-speed coal mill.

[0029] By means of the above technical solution, the medium-speed mill direct-blowing pulverizing system applicable to extra-high moisture lignite of the present invention has at least the following advantages:

[0030] The medium-speed mill direct-blowing pulverizing system suitable for extra-high-moisture lignite of the present invention increases the temperature of hot primary air by connecting a tubular air preheater in series at the outlet of a conventional rotary air preheater, thereby ensuring the drying output of the medium-speed mill direct-blowing pulverizing system and reducing the boiler exhaust temperature, thereby improving the boiler efficiency and facilitating the safe and stable operation of the boiler. In addition, the present invention can enhance the adaptability of the medium-speed mill direct-blowing pulverizing system to extra-high-moisture lignite, and enable the boiler to efficiently burn extra-high-moisture lignite, thereby making the boiler coal source selection more extensive, reducing operating costs and obtaining better economic benefits.

[0031] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic structural diagram of a medium-speed mill direct-blowing pulverizing system suitable for extra-high moisture lignite of the present invention;

[0033] Figure 2 This is a front view of the tubular air preheater of the present invention;

[0034] Figure 3 is an AA cross-sectional view of the tubular air preheater of the present invention;

[0035] Figure 4 This is a P-direction view of the tubular air preheater of the present invention;

[0036] Figure 5 It is a schematic diagram of the structure of a single spiral grooved tube of the present invention;

[0037] Figure 6 It is a partial enlarged schematic diagram of the spiral groove of the spiral groove tube of the present invention. DETAILED DESCRIPTION

[0038] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation method, structure, characteristics and effects of the present invention application are described in detail below in combination with the accompanying drawings and preferred embodiments. The arrow direction in the accompanying drawings indicates the flow direction of the flue gas and the flow direction of the hot air of the tubular air preheater.

[0039] like Figure 1 As shown, an embodiment of the present invention proposes a medium-speed mill direct-blowing pulverizing system suitable for ultra-high moisture lignite, which includes: a primary air fan 1, a rotary air preheater 2, a tubular air preheater 3, a medium-speed coal mill 4 and a boiler 5.

[0040] like Figures 1 to 6As shown, the primary air fan 1 is used to provide cold primary air. The rotary air preheater 2 is connected to the outlet of the primary air fan 1 through the first cold primary air duct 6, and the smoke outlet of the rotary air preheater 2 is connected to the rotary preheater smoke exhaust duct 7. The hot primary air inlet 31 of the tubular air preheater 3 is connected to the rotary air preheater 2 through the rotary air preheater hot primary air duct 8, and the tubular air preheater smoke outlet 32 ​​is connected to the smoke inlet of the rotary air preheater 2 through the first bypass duct 9. The medium-speed coal mill 4 is connected to the primary air fan 1 through the second cold primary air duct 10 and is connected to the hot primary air outlet 33 of the tubular air preheater 3 through the tubular air preheater hot primary air duct 11. The main flue gas outlet 51 of the boiler 5 is connected to the flue gas inlet of the rotary air preheater 3, and the bypass flue gas outlet 52 of the boiler is connected to the flue gas inlet 34 of the tubular air preheater through the second bypass flue 12; the cold primary air comes out of the primary fan 1 and enters the rotary air preheater 2 from the first cold primary air duct 6 for primary heating, and then is introduced from the hot primary air duct 8 of the rotary air preheater into the tubular air preheater 3 for secondary heating to increase the temperature, and finally enters the medium-speed coal mill 4 from the hot primary air duct 11 of the tubular air preheater; the flue gas at the outlet of the boiler 5 One route of the air enters the smoke inlet of the rotary air preheater 2 from the main smoke gas outlet 51, and the other route enters the tubular air preheater 3 from the bypass smoke gas outlet 52 to heat the primary air for secondary heating, and then passes through the first bypass flue 9 to merge with the smoke from the main smoke gas before entering the rotary air preheater, and enters the rotary air preheater 2 from the smoke inlet of the rotary air preheater; the other route of the cold primary air comes out from the second cold primary air duct 10, merges with the hot primary air of the tubular air preheater coming out from the hot primary air duct 11 of the tubular air preheater, and enters the medium-speed coal mill 4 to adjust the temperature entering the medium-speed coal mill 4. In the present invention, the tubular air preheater 3 includes an upper tubular air preheater tube box 35, a lower tubular air preheater tube box 36 connected to the upper tubular air preheater tube box 35 and arranged in two layers in a vertical staggered manner, and a compensator 37 arranged at the connection between the upper tubular air preheater tube box 35 and the lower tubular air preheater tube box 36. The present invention solves the expansion problem caused by high-temperature flue gas by arranging a compensator. The upper tubular air preheater tube box 35 and the lower tubular air preheater tube box 36 both include a box body 351 and a spiral groove tube 352 arranged in the box body 351. The present invention adopts a spiral groove tube structure to enhance heat exchange. The inner channel of the spiral groove tube 352 is a flue gas duct, and the spiral groove 3521 outside the spiral groove tube 352 is an air duct. The flue gas inlet 34 of the tubular air preheater 3 is arranged at the top of the upper tubular air preheater tube box 35; an adjustable shut-off damper 13 is provided at the flue gas inlet 34 of the tubular air preheater 3, which can adjust the bypass flue gas volume under different loads or coal quality changes to control the heat exchange of the primary air.The flue gas outlet 32 ​​of the tubular air preheater 3 is arranged at the bottom end of the lower tubular air preheater pipe box 36. The tubular air preheater hot primary air inlet 31 is arranged on one side of the lower tubular air preheater pipe box 36; the tubular air preheater hot primary air outlet 33 is arranged on one side of the upper tubular air preheater pipe box 35. In the present invention, the upper tubular air preheater pipe box 35 and the lower tubular air preheater pipe box 36 both include a support frame 353 connected to the box body 351 and used to fix the box body 351 and two legs 354 installed on both sides of the bottom of the box body. The boiler 5 includes a boiler tail shaft 53 and an economizer 54 arranged below the boiler tail shaft 53; the tubular air preheater 3 is arranged behind the boiler tail shaft 53 or on the left and right sides of the boiler tail shaft 53. The boiler bypass flue gas outlet 52 is led out from the outlet of the upper economizer 54 of the boiler rear flue.

[0041] Further, such as Figure 1 As shown, the medium-speed mill direct-blowing pulverizing system suitable for extra-high moisture lignite also includes: a flue gas bypass regulating damper 14 arranged on the second bypass flue 12, and the flue gas bypass regulating damper 14 is used to adjust the flue gas volume entering the tubular air preheater 3 so as to adjust and control the wind temperature entering the medium-speed coal mill 4.

[0042] Specifically, taking the application case of a coal-fired boiler of a 380MW unit in Indonesia as an example, the invention is further explained to be applicable to the medium-speed mill direct-blowing pulverizing system of extra-high moisture lignite.

[0043] The designed coal type receives a base moisture of Mat = 39%, and the verified coal type receives a base moisture of Mat = 48.5%. The tubular air preheater is arranged behind the tail shaft or on the left and right sides. The bypass flue gas is drawn from the outlet of the upper economizer of the rear flue. The flow of the bypass flue gas under BMCR conditions accounts for 7% to 11% of the total flue gas volume. The flue gas temperature at the bypass flue gas extraction point is about 500°C under BMCR conditions. The resistance of the flue gas system will increase by about 140pa. The primary air is heated by a two-stage preheater, namely a rotary air preheater and a tubular air preheater. The air temperature can reach 402°C (moisture Mat = 48.5% coal type, BMCR conditions), and calculated from different load conditions, the requirements of the drying output of the pulverizing system can be met by adjusting the flue gas bypass share. After the primary air pipeline is connected in series with the tubular air preheater, the hot primary air resistance will increase by about 550Pa of air resistance (BMCR conditions).

[0044] The medium-speed mill direct-blowing pulverizing system suitable for extra-high moisture lignite in the embodiment of the present invention increases the temperature of hot primary air by connecting a tubular air preheater in series at the outlet of a conventional rotary air preheater, thereby ensuring the drying output of the medium-speed mill direct-blowing pulverizing system. The present invention adopts a flue gas bypass to enter the tubular air preheater for secondary heating of the primary air, thereby reducing the flue gas temperature at the inlet of the rotary air preheater. At the same time, the boiler exhaust temperature is reduced, which is beneficial to improving boiler efficiency. In addition, when the medium-speed mill direct-blowing pulverizing system suitable for extra-high moisture lignite of the present invention is used to burn ultra-high moisture lignite, the fan mill system can be avoided. The medium-speed mill direct-blowing pulverizing system of the present invention is simple, easy to operate, and requires little maintenance, thereby ensuring higher reliability of the boiler unit.

[0045] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A medium-speed mill direct-blowing pulverizing system suitable for ultra-high moisture lignite, characterized by: It includes: Primary fan, used to provide cold primary air; A rotary air preheater, which is connected to the outlet of the primary fan through a first cold primary air duct, and the smoke outlet of the rotary air preheater is connected to the smoke exhaust duct of the rotary air preheater; A tubular air preheater, wherein the hot primary air inlet of the tubular air preheater is connected to the rotary air preheater through the hot primary air duct of the rotary air preheater, and the flue gas outlet of the tubular air preheater is connected to the flue gas inlet of the rotary air preheater through a first bypass flue; A medium-speed coal mill connected to the primary air fan through a second cold primary air duct and connected to a hot primary air outlet of the tubular air preheater through a hot primary air duct of the tubular air preheater; A boiler, wherein the main flue gas outlet of the boiler is connected to the flue gas inlet of the rotary air preheater, and the bypass flue gas outlet of the boiler is connected to the flue gas inlet of the tubular air preheater through a second bypass flue; The cold primary air comes out of the primary fan, enters the rotary air preheater through the first cold primary air duct for primary heating, and is then introduced into the tubular air preheater from the hot primary air duct of the rotary air preheater for secondary heating to increase the temperature, and finally enters the medium-speed coal mill from the hot primary air duct of the tubular air preheater; the flue gas at the boiler outlet enters the smoke inlet of the rotary air preheater from the main smoke gas outlet, and enters the tubular air preheater from the bypass smoke gas outlet to heat the primary air twice, then passes through the first bypass smoke duct and enters the rotary air preheater before merging with the smoke at the main smoke gas outlet and entering the rotary air preheater from the smoke inlet of the rotary air preheater; the cold primary air comes out of the second cold primary air duct and merges with the hot primary air of the tubular air preheater coming out of the hot primary air duct of the tubular air preheater to enter the medium-speed coal mill to adjust the temperature entering the medium-speed coal mill.

2. The medium-speed mill direct-blowing pulverizing system suitable for extra-high moisture lignite according to claim 1 is characterized in that: The tubular air preheater comprises an upper tubular air preheater pipe box, a lower tubular air preheater pipe box connected to the upper tubular air preheater pipe box and arranged in two layers in a vertical staggered manner, and a compensator arranged at the connection between the upper tubular air preheater pipe box and the lower tubular air preheater pipe box; The upper layer tubular air preheater tube box and the lower layer tubular air preheater tube box both include a box body and a spiral grooved tube arranged in the box body. The inner channel of the spiral grooved tube is a flue gas duct, and the spiral groove outside the spiral grooved tube is an air duct.

3. The medium-speed mill direct-blowing pulverizing system suitable for extra-high moisture lignite according to claim 2 is characterized in that: The flue gas inlet of the tubular air preheater is arranged at the top of the tube box of the upper tubular air preheater; An adjustable shutoff damper is provided at the flue gas inlet of the tubular air preheater; The flue gas outlet of the tubular air preheater is arranged at the bottom end of the tube box of the lower tubular air preheater.

4. The medium-speed mill direct-blowing pulverizing system suitable for extra-high moisture lignite according to claim 2 is characterized in that: The hot primary air inlet of the tubular air preheater is arranged on one side of the tube box of the lower tubular air preheater; The hot primary air outlet of the tubular air preheater is arranged on one side of the tube box of the upper tubular air preheater.

5. The medium-speed mill direct-blowing pulverizing system suitable for extra-high moisture lignite according to claim 2 is characterized in that: The upper tube air preheater tube box and the lower tube air preheater tube box both further include a support frame connected to the box body and used to fix the box body, and two legs installed on both sides of the bottom of the box body.

6. The medium-speed mill direct-blowing pulverizing system suitable for extra-high moisture lignite according to claim 1 is characterized in that: The boiler comprises a boiler tail shaft and an economizer arranged below the boiler tail shaft; The tubular air preheater is arranged behind the boiler tail shaft or on the left and right sides of the boiler tail shaft.

7. The medium-speed mill direct-blowing pulverizing system suitable for extra-high moisture lignite according to claim 6 is characterized in that: The boiler bypass flue gas outlet is led out from the outlet of the upper economizer of the boiler rear flue.

8. The medium-speed mill direct-blowing pulverizing system suitable for extra-high moisture lignite according to claim 1 is characterized in that: Also includes: A flue gas bypass regulating damper is arranged on the second bypass flue, and the flue gas bypass regulating damper is used to adjust the flue gas volume entering the tubular air preheater, thereby adjusting and controlling the wind temperature entering the medium-speed coal mill.

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