Coal-fired unit SCR (Selective Catalytic Reduction) inlet smoke temperature increasing and inferior fuel drying system

Abstract

The utility model relates to the technical field of coal-fired units, and provides a coal-fired unit SCR inlet smoke temperature increasing and inferior fuel drying system which comprises a first unit. The first unit comprises a first steam pipe, a first primary air heat exchanger and a first high-pressure heater, and the first primary air heat exchanger and the first high-pressure heater are both arranged on the first steam pipe. The first primary air heat exchanger and the first high-pressure heater are sequentially arranged on the first steam pipe of the first unit, and steam introduced into the first steam pipe can exchange heat with primary air in the first primary air heat exchanger, so that the temperature of the primary air is increased, burnout of pulverized coal and blending combustion of inferior coal are facilitated, and the utilization rate of the pulverized coal is increased. After heat exchange with primary air, steam still carrying certain waste heat enters the first high-pressure heater to exchange heat with feed water, the temperature of the feed water is greatly increased, and therefore the heat absorption capacity of a coal economizer is reduced, the smoke temperature of an SCR inlet is increased, up-to-standard emission of nitric oxide under the deep peak regulation working condition is guaranteed, and ash deposition on a subsequent tail heating surface is not caused.

Description

Technical Field

[0001] The utility model relates to the technical field of coal-fired units, in particular to a system for increasing the smoke temperature at an SCR inlet of a coal-fired unit and drying inferior fuel. Background Art

[0002] At present, improving the deep peak-shaving capability of coal-fired units is one of the keys for coal-fired power companies to adapt to the new power system, and the flue gas temperature at the inlet of SCR (Selective Catalytic Reduction) is one of the important factors restricting the deep peak-shaving capability. Specifically, the flue gas temperature at the inlet of SCR cannot be lower than 300°C, otherwise it will affect the efficiency of the denitrification reaction, increase the escape of ammonia, and cause the deposition of ammonium bisulfate on the rear heating surface, thereby blocking the air preheater and threatening the safe and stable operation of the unit. Moreover, under the deep peak-shaving condition, the outlet temperature of the pulverizer is low, which is not conducive to the stable combustion of the boiler and the full combustion of coal powder. In addition, hot flushing is required during the startup of the supercritical unit, which involves starting the air duct burner and the pulverizing system, and the combustion is unstable and the operation risk is relatively high.

[0003] In the prior art, when the coal-fired unit is in deep peak regulation, the flue gas temperature at the SCR inlet drops to 300°C, which restricts the coal-fired unit's ability to further regulate the peak. When the system is cold-started and under deep peak regulation conditions, the furnace temperature and wind temperature are both low, and the coal powder burnout is poor, which poses a safety hazard. For supercritical units, when the unit is cold-started, hot flushing requires a large amount of fuel, consumes a lot of energy, and pollutes the environment.

[0004] Therefore, there is an urgent need for a coal-fired unit SCR inlet smoke temperature increase and inferior fuel drying system to solve the above problems. Utility Model Content

[0005] The utility model provides a coal-fired unit SCR inlet smoke temperature improvement and inferior fuel drying system, which is used to solve the defects of low SCR inlet smoke temperature and unstable boiler combustion in the deep peak regulation condition of the existing coal-fired unit.

[0006] The utility model provides a system for increasing the SCR inlet smoke temperature and drying inferior fuel of a coal-fired unit, comprising a first unit;

[0007] The first unit includes a first steam pipe, a first primary air heat exchanger and a first high-pressure heater. The first primary air heat exchanger and the first high-pressure heater are both arranged on the first steam pipe, and the first primary air heat exchanger is located upstream of the first high-pressure heater.

[0008] The SCR inlet smoke temperature raising and inferior fuel drying system for coal-fired units provided by the utility model also includes a second unit and a connecting pipe;

[0009] The second unit comprises a second steam pipe, a second primary air heat exchanger and a second high-pressure heater, the second primary air heat exchanger and the second high-pressure heater are both arranged on the second steam pipe, and the second primary air heat exchanger is located upstream of the second high-pressure heater;

[0010] One end of the connecting pipe is connected to the first steam pipe, and the other end of the connecting pipe is connected to the second steam pipe. The connection point between the connecting pipe and the first steam pipe is located upstream of the first primary air heat exchanger, and the connection point between the connecting pipe and the second steam pipe is located upstream of the second primary air heat exchanger. A main steam pipe communication door is provided on the connecting pipe.

[0011] According to the SCR inlet smoke temperature raising and inferior fuel drying system for coal-fired units provided by the utility model, a first check valve is provided at the outlet end of the first primary air heat exchanger;

[0012] A second check valve is provided at the outlet end of the second primary air heat exchanger.

[0013] According to the SCR inlet smoke temperature raising and inferior fuel drying system for coal-fired units provided by the utility model, the steam inlet end of the first steam pipe is provided with a first electric door and a first electric regulating door in sequence;

[0014] The steam inlet end of the second steam pipe is provided with a second electric door and a second electric regulating door in sequence.

[0015] According to the SCR inlet smoke temperature raising and inferior fuel drying system for coal-fired units provided by the utility model, a third electric door is provided at the inlet end of the first primary air heat exchanger;

[0016] A fourth electric door is provided at the inlet end of the second primary air heat exchanger.

[0017] According to the SCR inlet smoke temperature raising and inferior fuel drying system for coal-fired units provided by the utility model, a fifth electric door is provided at the outlet end of the first primary air heat exchanger;

[0018] A sixth electric door is provided at the outlet end of the second primary air heat exchanger.

[0019] According to the SCR inlet smoke temperature raising and inferior fuel drying system for coal-fired units provided by the utility model, the first unit further includes a first deaerator, which is arranged on the first steam pipe, and the first deaerator is located downstream of the first high-pressure heater;

[0020] The second unit further includes a second deaerator, which is disposed on the second steam pipe and is located downstream of the second high-pressure heater.

[0021] According to the SCR inlet smoke temperature raising and inferior fuel drying system for coal-fired units provided by the utility model, a seventh electric door is provided between the first high-pressure heater and the first deaerator;

[0022] An eighth electric door is provided between the second high-pressure heater and the second deaerator.

[0023] The SCR inlet smoke temperature raising and inferior fuel drying system for a coal-fired unit provided by the utility model also includes a first steam extraction pipe and a second steam extraction pipe, wherein the first steam extraction pipe is connected to the first high-pressure heater, and the second steam extraction pipe is connected to the second high-pressure heater.

[0024] According to the SCR inlet smoke temperature raising and inferior fuel drying system for coal-fired units provided by the utility model, a first steam extraction electric door is provided on the first steam extraction pipe, and a second steam extraction electric door is provided on the second steam extraction pipe.

[0025] The utility model provides a coal-fired unit SCR inlet smoke temperature raising and inferior fuel drying system, by sequentially arranging a first primary air heat exchanger and a first high-pressure heater on the first steam pipe of the first unit, the steam introduced into the first steam pipe can exchange heat with the primary air in the first primary air heat exchanger, thereby raising the primary air temperature, which is beneficial to the combustion of pulverized coal and the blending of inferior coal, and the steam still carrying a certain amount of residual heat after heat exchange with the primary air enters the first high-pressure heater for heat exchange with feed water, greatly raising the feed water temperature, thereby reducing the heat absorption of the economizer, achieving the improvement of the SCR inlet smoke temperature, and ensuring the compliance of nitrogen oxide emissions under deep peak regulation conditions without causing subsequent dust accumulation on the rear heating surface.

[0026] Additional aspects and advantages of the present invention will be given in part in the following description, and in part will become apparent from the following description, or will be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0028] Figure 1 It is a schematic diagram of a system for increasing the smoke temperature at the SCR inlet and drying inferior fuels of a coal-fired unit provided by an embodiment of the utility model.

[0029] Reference numerals:

[0030] 100, first unit; 101, first steam pipe; 102, first primary air heat exchanger; 103, first high-pressure heater; 104, first non-return valve; 105, first electric door; 106, first electric regulating door; 107, third electric door; 108, fifth electric door; 109, first deaerator; 110, seventh electric door; 111, first steam extraction pipe; 112, first steam extraction electric door;

[0031] 200, second unit; 201, second steam pipe; 202, second primary air heat exchanger; 203, second high-pressure heater; 204, second check valve; 205, second electric door; 206, second electric regulating door; 207, fourth electric door; 208, sixth electric door; 209, second deaerator; 210, eighth electric door; 211, second steam extraction pipe; 212, second steam extraction electric door;

[0032] 300. Connecting pipe; 301. Main steam pipeline connecting door. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the utility model clearer, the technical solution of the utility model will be described clearly and completely in conjunction with the drawings in the utility model. Obviously, the described embodiments are part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0034] In the description of the embodiments of the present utility model, it should be noted that the terms "center", "longitudinal", "lateral", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the embodiments of the present utility model. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0035] In the description of the embodiments of the present utility model, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present utility model can be understood according to specific circumstances.

[0036] In the embodiments of the present invention, unless otherwise clearly specified and limited, the first feature being "above" or "below" the second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "above" and "above" the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. The first feature being "below", "below" and "below" the second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0037] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the utility model embodiment. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0038] Combine the following Figure 1 The utility model describes a system for increasing the SCR inlet smoke temperature of a coal-fired unit and drying inferior fuel.

[0039] See also Figure 1 As shown, the utility model provides a system for increasing the inlet smoke temperature of a coal-fired unit SCR and drying inferior fuel, including a first unit 100. The first unit 100 includes a first steam pipe 101, a first primary air heat exchanger 102 and a first high-pressure heater 103, the first primary air heat exchanger 102 and the first high-pressure heater 103 are both arranged on the first steam pipe 101, and the first primary air heat exchanger 102 is located upstream of the first high-pressure heater 103.

[0040] The utility model provides a coal-fired unit SCR inlet flue gas temperature raising and inferior fuel drying system, by sequentially arranging a first primary air heat exchanger 102 and a first high-pressure heater 103 on the first steam pipe 101 of the first unit 100, the steam introduced into the first steam pipe 101 can exchange heat with the primary air in the first primary air heat exchanger 102, thereby raising the primary air temperature, which is beneficial to the combustion of pulverized coal and the blending of inferior coal, and the steam still carrying a certain amount of residual heat after heat exchange with the primary air enters the first high-pressure heater 103 for heat exchange with feed water, thereby greatly raising the feed water temperature, thereby reducing the heat absorption of the economizer, achieving the improvement of the SCR inlet flue gas temperature, and ensuring that nitrogen oxides are discharged in compliance with the standard under deep peak-shaving conditions without causing dust accumulation on the subsequent rear heating surface.

[0041] See also Figure 1 As shown, according to some embodiments of the utility model, the SCR inlet flue gas temperature improvement and inferior fuel drying system of the coal-fired unit also includes a second unit 200 and a connecting pipe 300; the second unit 200 includes a second steam pipe 201, a second primary air heat exchanger 202 and a second high-pressure heater 203, the second primary air heat exchanger 202 and the second high-pressure heater 203 are both arranged on the second steam pipe 201, and the second primary air heat exchanger 202 is located upstream of the second high-pressure heater 203; one end of the connecting pipe 300 is connected to the first steam pipe 101, and the other end of the connecting pipe 300 is connected to the second steam pipe 201, the connection point of the connecting pipe 300 and the first steam pipe 101 is located upstream of the first primary air heat exchanger 102, and the connection point of the connecting pipe 300 and the second steam pipe 201 is located upstream of the second primary air heat exchanger 202, and a main steam pipe communication door 301 is provided on the connecting pipe 300. By setting up the second unit 200, when the first unit 100 is cold-started (the first unit 100 is used as the main unit), the temporary main steam can be introduced into the first unit 100 through the second steam pipe 201 of the second unit 200 (the second unit 200 is used as the temporary unit) through the connecting pipe 300 (the main steam pipeline communication door 301 is open at this time), and flow through the first primary air heat exchanger 102 and the first high-pressure heater 103 in sequence. Through the above process, the local feed water can be heated in the first high-pressure heater 103 of the first unit 100 to reach the hot flushing temperature of 190°C, and a hot flushing method without starting the air and smoke system, the fuel system and the powder making system can be realized, which simplifies the operation process of the operating personnel and saves energy. The same applies when the second unit 200 is used as the main unit and the first unit 100 is used as the temporary unit, and no further details are given.

[0042] At the same time, after the machine is ignited and started, the primary air of the machine absorbs the heat in the temporary main steam, which can further increase the primary air temperature under cold start-up conditions, which is beneficial to the combustion of pulverized coal and stable ignition when the temperature in the furnace is low at the initial stage of ignition.

[0043] See also Figure 1As shown, according to some embodiments of the present invention, a first check valve 104 is provided at the outlet of the first primary air heat exchanger 102; and a second check valve 204 is provided at the outlet of the second primary air heat exchanger 202. By providing the first check valve 104 and the second check valve 204, steam can be prevented from flowing back into the first primary air heat exchanger 102 or the second primary air heat exchanger 202, thereby ensuring normal operation of the system.

[0044] See also Figure 1 As shown, according to some embodiments of the utility model, the steam inlet end of the first steam pipe 101 is provided with a first electric door 105 and a first electric regulating door 106 in sequence; the steam inlet end of the second steam pipe 201 is provided with a second electric door 205 and a second electric regulating door 206 in sequence. By providing the first electric door 105, the first electric regulating door 106, the second electric door 205 and the second electric regulating door 206, the first electric door 105 and the second electric regulating door 205 can be used to control the opening and closing of the first steam pipe 101 and the second steam pipe 201 respectively, and the first electric regulating door 106 and the second electric regulating door 206 can be used to control the flow of steam into the first steam pipe 101 and the second steam pipe 201 respectively, thereby improving the flexibility of the system.

[0045] See also Figure 1 As shown, according to some embodiments of the present invention, a third electric door 107 is provided at the inlet end of the first primary air heat exchanger 102; a fourth electric door 207 is provided at the inlet end of the second primary air heat exchanger 202. By providing the third electric door 107 and the fourth electric door 207, the pipelines at the inlet ends of the first primary air heat exchanger 102 and the second primary air heat exchanger 202 can be opened or closed.

[0046] See also Figure 1 As shown, according to some embodiments of the present invention, a fifth electric door 108 is provided at the outlet end of the first primary air heat exchanger 102 ; a sixth electric door 208 is provided at the outlet end of the second primary air heat exchanger 202 .

[0047] See also Figure 1 As shown, according to some embodiments of the present invention, the first unit 100 further includes a first deaerator 109, which is disposed on the first steam pipe 101 and is located downstream of the first high-pressure heater 103; the second unit 200 further includes a second deaerator 209, which is disposed on the second steam pipe 201 and is located downstream of the second high-pressure heater 203. The first deaerator 109 and the second deaerator 209 are provided to remove oxygen from water.

[0048] See also Figure 1As shown, according to some embodiments of the present invention, a seventh electric door 110 is provided between the first high-pressure heater 103 and the first deaerator 109; an eighth electric door 210 is provided between the second high-pressure heater 203 and the second deaerator 209. By providing the seventh electric door 110 and the eighth electric door 210, the connecting pipelines between the first high-pressure heater 103 and the first deaerator 109 and between the second high-pressure heater 203 and the second deaerator 209 can be opened or closed.

[0049] See also Figure 1 As shown, according to some embodiments of the utility model, the SCR inlet smoke temperature raising and inferior fuel drying system of the coal-fired unit further includes a first steam extraction pipe 111 and a second steam extraction pipe 211, the first steam extraction pipe 111 is connected to the first high-pressure heater 103, and the second steam extraction pipe 211 is connected to the second high-pressure heater 203. The first steam extraction pipe 111 and the second steam extraction pipe 211 are used to connect the steam turbine.

[0050] See also Figure 1 As shown, according to some embodiments of the utility model, a first steam extraction electric door 112 is provided on the first steam extraction pipe 111, and a second steam extraction electric door 212 is provided on the second steam extraction pipe 211. By providing the first steam extraction electric door 112 and the second steam extraction electric door 212, the opening or closing of the first steam extraction pipe 111 and the second steam extraction pipe 211 can be controlled respectively, so as to control the steam in the steam turbine to enter the high-pressure heater.

[0051] The following is a detailed description of the working principle of the SCR inlet smoke temperature increase and inferior fuel drying system for coal-fired units provided by the utility model. Please refer to Figure 1 .

[0052] (1) Operating principle of increasing the SCR inlet flue gas temperature under deep peak load conditions of coal-fired units:

[0053] When the machine (taking the first unit 100 as an example) enters the deep peak load condition, the second electric door 205, the second electric regulating door 206 and the main steam pipeline connecting door 301 are closed, and the first electric door 105, the first electric regulating door 106, the third electric door 107 and the fifth electric door 108 are opened. The main steam of the machine enters the first primary air heat exchanger 102 through the first steam pipe 101 to exchange heat with the primary air, heating the primary air to a certain temperature, and the steam with a certain amount of residual heat is continuously introduced into the first high-pressure heater 103 to exchange heat with the feed water, heating the feed water to a certain temperature.

[0054] After the above process, the primary air exchanges heat with steam in the first primary air heat exchanger 102, further increasing the primary hot air temperature. The increase in primary air temperature is conducive to the complete combustion of coal powder and the blending of inferior coal. It can also achieve the local feed water heating in the first high-pressure heater 103 in the first unit 100 to increase the local feed water temperature, reduce the local economizer heat absorption, thereby increasing the SCR inlet flue gas temperature, and achieving safe and stable denitrification under deep peak load conditions.

[0055] (2) Operation principle of stable combustion and inferior coal blending under deep peak load regulation of coal-fired units:

[0056] The specific operation process is the same as described above (1). Due to the increase in the primary air temperature, it has a certain promoting effect on the stable ignition of inferior coal, and can achieve stable combustion under deep peak load conditions and large-proportion blending of inferior coal under high load.

[0057] (3) Principle of stable combustion during hot flushing and cold start-up of coal-fired units:

[0058] When the machine (taking the first unit 100 as an example) is cold-started, the first electric door 105, the first electric regulating door 106 and the second electric regulating door 205 and 206 of the temporary machine (operating unit, taking the second unit 200 as an example) are opened, the main steam pipeline connecting door 301 is opened, the third electric door 107 is opened, the fourth electric door 207 is closed, the temporary machine main steam enters the first primary air heat exchanger 102, the fifth electric door 108 is opened, and the first steam extraction electric door 112 is closed. The temporary machine main steam enters the first high-pressure heater 103, and the drain water discharged from the first high-pressure heater 103 after heat exchange reaches the seventh electric door 110, and the drain water enters the first deaerator 109.

[0059] Through the above process, the feed water of the machine can be heated in the first high-pressure heater 103 to reach the hot flushing temperature of 190°C. A hot flushing method without starting the air and smoke system, the fuel system and the powder making system is realized. The operation process of the operator is simplified and energy is saved.

[0060] The same applies when the second unit 200 is used as the main unit and the first unit 100 is used as the temporary unit, and no further details are given.

[0061] At the same time, after the machine is ignited and started, the primary air of the machine absorbs the heat in the temporary main steam, which can further increase the primary air temperature under cold start-up conditions, which is beneficial to the combustion of pulverized coal and stable ignition when the temperature in the furnace is low at the initial stage of ignition.

[0062] It can be seen from the description of the above embodiments that the SCR inlet smoke temperature improvement and inferior fuel drying system for coal-fired units provided by the utility model has at least the following advantages:

[0063] The utility model provides a system for increasing the inlet flue gas temperature of the SCR of a coal-fired unit and drying inferior fuels, which solves the problem that the denitrification system cannot be put into operation due to the low inlet flue gas temperature of the SCR during the startup, shutdown and low-load stable combustion of the coal-fired unit. It is beneficial to solve the problem of unstable combustion when the coal-fired unit is mixed with inferior coal, and improves the economic operation of the unit and its adaptability to inferior coal. It reduces the consumption of fuel by the air duct burner during the hot flushing process of the supercritical unit, and the operation is more economical.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the utility model, rather than to limit it. Although the utility model has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the utility model.

Claims

1. A system for increasing the inlet smoke temperature of SCR coal-fired units and drying inferior fuels, characterized in that: Including the first unit; The first unit includes a first steam pipe, a first primary air heat exchanger and a first high-pressure heater. The first primary air heat exchanger and the first high-pressure heater are both arranged on the first steam pipe, and the first primary air heat exchanger is located upstream of the first high-pressure heater.

2. The SCR inlet smoke temperature raising and inferior fuel drying system for coal-fired units according to claim 1 is characterized in that: Also includes a second unit and a connecting pipe; The second unit comprises a second steam pipe, a second primary air heat exchanger and a second high-pressure heater, the second primary air heat exchanger and the second high-pressure heater are both arranged on the second steam pipe, and the second primary air heat exchanger is located upstream of the second high-pressure heater; One end of the connecting pipe is connected to the first steam pipe, and the other end of the connecting pipe is connected to the second steam pipe. The connection point between the connecting pipe and the first steam pipe is located upstream of the first primary air heat exchanger, and the connection point between the connecting pipe and the second steam pipe is located upstream of the second primary air heat exchanger. A main steam pipe communication door is provided on the connecting pipe.

3. The SCR inlet smoke temperature raising and inferior fuel drying system for coal-fired units according to claim 2 is characterized in that: The outlet end of the first primary air heat exchanger is provided with a first check valve; A second check valve is provided at the outlet end of the second primary air heat exchanger.

4. The SCR inlet smoke temperature raising and inferior fuel drying system for coal-fired units according to claim 2 is characterized in that: The steam inlet end of the first steam pipe is provided with a first electric door and a first electric regulating door in sequence; The steam inlet end of the second steam pipe is provided with a second electric door and a second electric regulating door in sequence.

5. The SCR inlet smoke temperature raising and inferior fuel drying system for coal-fired units according to claim 2 is characterized in that: A third electric door is provided at the inlet end of the first primary air heat exchanger; A fourth electric door is provided at the inlet end of the second primary air heat exchanger.

6. The SCR inlet smoke temperature raising and inferior fuel drying system for coal-fired units according to claim 2 is characterized in that: A fifth electric door is provided at the outlet end of the first primary air heat exchanger; A sixth electric door is provided at the outlet end of the second primary air heat exchanger.

7. The SCR inlet smoke temperature raising and inferior fuel drying system for coal-fired units according to claim 2 is characterized in that: The first unit further includes a first deaerator, which is disposed on the first steam pipe and is located downstream of the first high-pressure heater; The second unit further includes a second deaerator, which is disposed on the second steam pipe and is located downstream of the second high-pressure heater.

8. The SCR inlet smoke temperature raising and inferior fuel drying system for coal-fired units according to claim 7 is characterized in that: A seventh electric door is provided between the first high-pressure heater and the first deaerator; An eighth electric door is provided between the second high-pressure heater and the second deaerator.

9. The SCR inlet smoke temperature raising and inferior fuel drying system for coal-fired units according to any one of claims 2 to 8, characterized in that: The invention also includes a first steam extraction pipe and a second steam extraction pipe, wherein the first steam extraction pipe is connected to the first high-pressure heater, and the second steam extraction pipe is connected to the second high-pressure heater.

10. The SCR inlet smoke temperature raising and inferior fuel drying system for coal-fired units according to claim 9, characterized in that: The first steam extraction pipe is provided with a first steam extraction electric door, and the second steam extraction pipe is provided with a second steam extraction electric door.

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