Dual-channel dual-pressure waste heat boiler system and method for efficiently recycling waste heat of waste gas

Abstract

The invention discloses a dual-channel dual-pressure waste heat boiler system and a method for efficiently recycling waste heat of waste gas. The system at least comprises a high-temperature waste heat boiler unit, a low-temperature waste heat boiler unit, a high-pressure steam pocket, a low-pressure steam pocket, a deaerator and a water feeding pump. A high-pressure superheater, a high-pressure evaporator a, a low-pressure superheater, a high-pressure economizer, a low-pressure evaporator a and a low-pressure economizer are sequentially arranged in the high-temperature waste heat boiler unit in the waste gas flowing direction. A high-pressure evaporator b and a low-pressure evaporator b are sequentially arranged in the low-temperature waste heat boiler unit in the waste gas flowing direction. The double-channel double-pressure steam pocket system is adopted, the exhaust gas temperature of the high-temperature waste heat boiler unit is reduced to the limit, waste gas waste heat is recycled as much as possible, meanwhile, the two waste heat boiler units share one high-pressure steam pocket, one low-pressure steam pocket and the deaerator, energy fluctuation of waste heat of two waste gases is overcome, and engineering investment is also saved.

Description

TECHNICAL FIELD

[0001] The application relates to a waste heat utilization system of a ring cooler, in particular to a double-channel double-pressure waste heat boiler system and a method for efficiently recovering waste heat. BACKGROUND

[0002] At present, waste heat recovery of a domestic sintering ring cooler basically only recovers waste heat of first and second sections, and a small number of steel plants recover waste heat of third and fourth sections, but there are problems of low waste heat resource quantity, low waste heat resource quality and high sintering ore discharge temperature. SUMMARY

[0003] In order to recover waste heat of the cooled sintering ore as much as possible, the application provides a double-channel double-pressure waste heat boiler system and a method for efficiently recovering waste heat.

[0004] To achieve the above purpose, the double-channel double-pressure waste heat boiler system for efficiently recovering waste heat comprises at least a high-temperature waste heat boiler unit, a low-temperature waste heat boiler unit, a high-pressure steam drum, a low-pressure steam drum and a deaerator, and a feed water pump. A high-pressure superheater, a high-pressure evaporator a, a low-pressure superheater, a high-pressure economizer, a low-pressure evaporator a and a low-pressure economizer are sequentially arranged in the high-temperature waste heat boiler unit according to the flow direction of waste gas. The high-temperature waste heat unit and the low-temperature waste heat unit are isolated and not connected.

[0005] Further, the low-pressure economizer inlet is connected with the external feed water, the low-pressure steam drum and the deaerator inlet are connected with the low-pressure economizer outlet, and the low-pressure steam drum and the deaerator are connected with the low-pressure evaporator a and the low-pressure evaporator b through pipelines to form a natural circulation loop. The water side outlet of the low-pressure steam drum and the deaerator is connected with the feed water pump inlet, the steam side outlet of the low-pressure steam drum and the deaerator is connected with the low-pressure superheater inlet, the low-pressure superheater outlet is connected with an external low-pressure steam pipeline, and the feed water pump outlet is connected with the high-pressure economizer inlet. The high-pressure economizer outlet is connected with the high-pressure steam drum water side inlet, the high-pressure steam drum is connected with the high-pressure evaporator a and the high-pressure evaporator b through pipelines to form a natural circulation loop, the high-pressure steam drum steam side outlet is connected with the high-pressure superheater inlet, and the high-pressure superheater outlet is connected with an external high-pressure steam pipeline.

[0006] To achieve the above object, the method for high-efficiency recovery of waste gas residual heat of the double-channel double-pressure waste heat boiler system, which is completed based on the system, comprises the following steps: The external feed water at 0~40℃ first enters the low-pressure economizer, is heated by the waste gas residual heat, and then enters the low-pressure steam drum and deaerator; The pressure in the low-pressure steam drum and deaerator is 0.2~0.8 MPa, and the low-pressure steam drum and deaerator 4 are connected with the low-pressure evaporator a and low-pressure evaporator b respectively through at least two pipelines. The water is heated by the waste gas in the low-pressure evaporator a and low-pressure evaporator b, and then is changed into a steam-water mixture to enter the low-pressure steam drum and deaerator, and the water force circulation is completed by the specific gravity difference of the medium in the inlet and outlet pipelines of the low-pressure evaporator a and low-pressure evaporator b, forming a natural circulation loop; the steam-water mixture is separated in the low-pressure steam drum and deaerator 4, and the saturated steam enters the low-pressure superheater, is heated and changed into high-quality low-pressure superheated steam (0.2~0.8 MPa, 150~250℃) to be sent to an external low-pressure steam pipeline network; Part of the saturated water in the low-pressure steam drum and deaerator enters the low-pressure evaporator a and low-pressure evaporator b again, and the other part of the saturated water is pumped into the high-pressure economizer by a feed water pump, is heated and then enters the high-pressure steam drum, and the pressure in the high-pressure steam drum is 1.0~2.5 MPa; The water in the high-pressure steam drum is heated in the high-pressure steam drum and high-pressure evaporator a and high-pressure evaporator b, and the water force circulation is completed by the specific gravity difference of the medium in the inlet and outlet pipelines of the high-pressure evaporator and high-pressure evaporator, forming a separate natural circulation loop, and the steam-water mixture is separated in the high-pressure steam drum, the saturated water continues to enter the high-pressure evaporator and high-pressure evaporator for heat exchange, and the saturated steam enters the high-pressure superheater, is heated by the exhaust gas of the ring cooling machine, and is changed into high-quality high-pressure superheated steam (1.0~2.5 MPa, 250~420℃) to be sent to an external high-pressure steam pipeline network.

[0007] The application adopts a double-channel double-pressure steam drum system, utilizes the characteristics of the double-pressure waste heat boiler (the higher the inlet exhaust gas temperature, the lower the exhaust gas temperature), reduces the exhaust gas temperature of the high-temperature waste heat boiler unit to the limit, recovers as much waste gas residual heat as possible, and simultaneously shares one high-pressure steam drum and one low-pressure steam drum and deaerator by the two waste heat boiler units, so that the energy fluctuation of the two exhaust gas residual heat is overcome and the engineering investment is saved. BRIEF DESCRIPTION OF DRAWINGS

[0008] Figure 1 It is a structural schematic diagram of a double-channel double-pressure waste heat boiler system. DETAILED DESCRIPTION

[0009] The embodiments of the application will be described in detail below with reference to the drawings.

[0010] In the description of this invention, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0011] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0012] like Figure 1 As shown, the dual-channel dual-pressure waste heat boiler in this embodiment includes a high-temperature waste heat boiler unit 1, a low-temperature waste heat boiler unit 2, a high-pressure steam drum 3, a low-pressure steam drum and deaerator 4, and a feed water pump 5. The high-temperature waste heat boiler unit 1 includes a high-pressure superheater 101, a high-pressure evaporator a102, a low-pressure superheater 103, a high-pressure economizer 104, a low-pressure evaporator a105, and a low-pressure economizer 106. Low-temperature waste heat boiler unit 2 includes a high-pressure evaporator b202 and a low-pressure evaporator b205; High-pressure superheater 101, high-pressure evaporator a102, low-pressure superheater 103, high-pressure economizer 104, low-pressure evaporator a105, and low-pressure economizer 106 are arranged sequentially in the high-temperature waste heat boiler unit 1 according to the direction of waste gas flow. High-pressure evaporator b202 and low-pressure evaporator b205 are arranged sequentially in the low-temperature waste heat boiler unit 2 according to the direction of waste gas flow; the low-temperature waste heat boiler unit 2 and the high-temperature waste heat boiler unit 1 are isolated from each other and not connected.

[0013] This embodiment is divided into two parts: a smoke and air system and a steam and water system.

[0014] Flue gas system: High-temperature exhaust gas of 300~600℃ is connected to high-temperature waste heat boiler unit 1 through pipelines, and after flowing through the heating surfaces arranged therein, the temperature drops to 50~150℃ before being discharged; Low-temperature exhaust gas of 180~400℃ is connected to low-temperature waste heat boiler unit 2 through pipelines, and after flowing through the heating surfaces arranged therein, the temperature drops to 100~200℃ before being discharged.

[0015] The steam-water system: the external water (0-40 DEG C) first enters the low-pressure economizer 106, absorbs the waste heat of the exhaust gas, and then enters the low-pressure steam drum and deaerator 4, the pressure in the low-pressure steam drum and deaerator 4 is 0.2-0.8 MPa (gauge pressure), the low-pressure steam drum and deaerator 4 are connected with the low-pressure evaporator a 105 and the low-pressure evaporator b 205 through at least two pipelines, respectively, the water absorbs the heat of the exhaust gas in the low-pressure evaporator a 105 and the low-pressure evaporator b 205, and then turns into a steam-water mixture to enter the low-pressure steam drum and deaerator 4, the water circulation relies on the specific gravity difference of the medium in the inlet and outlet pipelines of the low-pressure evaporator a 105 and the low-pressure evaporator b 205 to complete, forming a natural circulation loop, the steam-water separation process of the generated steam-water mixture is completed in the low-pressure steam drum and deaerator 4, and the saturated steam enters the low-pressure superheater 103, is heated and turned into high-quality low-pressure superheated steam (0.2-0.8 MPa, 150-250 DEG C) to be sent to the external low-pressure steam pipe network, a part of the saturated water in the low-pressure steam drum and deaerator 4 enters the low-pressure evaporator a 105 and the low-pressure evaporator b 205 again, and the other part of the saturated water is pumped into the high-pressure economizer 104 by the feed water pump 5, is heated and then enters the high-pressure steam drum 3, the pressure in the high-pressure steam drum 3 is 1.0-2.5 MPa (gauge pressure), the water in the high-pressure steam drum 3 is heated in the high-pressure steam drum 3, the high-pressure evaporator a 102 and the high-pressure evaporator b 202, and relies on the specific gravity difference of the medium in the inlet and outlet pipelines of the high-pressure evaporator a 102 and the high-pressure evaporator b 202 to complete, forming a separate natural circulation loop, the steam-water mixture generated in the high-pressure steam drum 3 is separated, the saturated water continues to enter the high-pressure evaporator a 102 and the high-pressure evaporator b 202 to be heated, and the saturated steam enters the high-pressure superheater 101, is heated by the exhaust gas of the ring cooler, and is turned into high-quality high-pressure superheated steam (1.0-2.5 MPa, 250-420 DEG C) to be sent to the external high-pressure steam pipe network.

[0016] The present application recovers the waste heat of the first and second high-temperature exhaust gas and the third and fourth low-temperature exhaust gas of the sintering ore cooled by the ring cooler, arranges the heat receiving surface of the waste heat boiler according to the second law of thermodynamics, and recovers the waste heat of the flue gas in the tail flue in stages to generate two kinds of high-quality superheated steam, so that the exhaust gas discharge temperature limit can be reduced to below 100 DEG C.

[0017] In the description of the present application, it should be noted that, unless otherwise specified and limited, the terms "mounting", "connection" and "connection" should be understood in a broad sense, for example, it can be fixed connection, or detachable connection, or integral connection, it can be direct connection, or indirect connection through an intermediate medium, or internal communication of two elements. For ordinary skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0018] In the description of this specification, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0019] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A dual-channel, dual-pressure waste heat boiler system, characterized in that: The system includes at least a high-temperature waste heat boiler unit, a low-temperature waste heat boiler unit, a high-pressure steam drum, a low-pressure steam drum and deaerator, and a feedwater pump. Inside the high-temperature waste heat boiler unit, arranged in sequence according to the direction of waste gas flow, are: high-pressure superheater, high-pressure evaporator a, low-pressure superheater, high-pressure economizer, low-pressure evaporator a, and low-pressure economizer. The low-temperature waste heat boiler unit is equipped with a high-pressure evaporator b and a low-pressure evaporator b arranged sequentially according to the direction of waste gas flow; the high-temperature waste heat unit and the low-temperature waste heat unit are isolated from each other and are not connected.

2. The dual-channel, dual-pressure waste heat boiler system as described in claim 1, characterized in that: The inlet of the low-pressure economizer is connected to the external water supply; the inlet of the low-pressure steam drum and deaerator is connected to the outlet of the low-pressure economizer; the low-pressure steam drum and deaerator are respectively connected to the low-pressure evaporator a and the low-pressure evaporator b through pipelines to form a natural circulation loop. The water-side outlet of the low-pressure steam drum and deaerator is connected to the feedwater pump inlet; the steam-side outlet of the low-pressure steam drum and deaerator is connected to the low-pressure superheater inlet; the low-pressure superheater outlet is connected to an external low-pressure steam pipeline; and the feedwater pump outlet is connected to the high-pressure economizer inlet. The outlet of the high-pressure economizer is connected to the water-side inlet of the high-pressure steam drum; the high-pressure steam drum is connected to the high-pressure evaporator a and the high-pressure evaporator b through pipelines to form a natural circulation loop; the steam-side outlet of the high-pressure steam drum is connected to the inlet of the high-pressure superheater; the outlet of the high-pressure superheater is connected to an external high-pressure steam pipeline.

3. A method for efficiently recovering waste heat from exhaust gas using a dual-channel, dual-pressure waste heat boiler system, characterized in that: The method described in claim 1 is based on the system described in claim 1 and includes the following steps: External feedwater at 0~40℃ first enters the low-pressure economizer, absorbs the waste heat from the exhaust gas, and then enters the low-pressure steam drum and deaerator. The pressure in the low-pressure steam drum and deaerator is 0.2~0.8MPa. The low-pressure steam drum and deaerator 4 are connected to the low-pressure evaporator and the low-pressure evaporator through at least two pipelines. After absorbing heat from the exhaust gas in the low-pressure evaporator and deaerator, the water is transformed into a steam-water mixture and enters the low-pressure steam drum and deaerator. This part of the hydraulic circulation is completed by the density difference of the medium in the inlet and outlet pipes of the low-pressure evaporator a and low-pressure evaporator b, forming a natural circulation loop. The generated steam-water mixture completes the steam-water separation process in the low-pressure steam drum and deaerator 4. The saturated steam enters the low-pressure superheater, absorbs heat, and becomes high-quality low-pressure superheated steam (0.2~0.8MPa, 150~250℃) which is sent to the external low-pressure steam network. A portion of the saturated water in the low-pressure steam drum and deaerator re-enters low-pressure evaporator a and low-pressure evaporator b, while another portion of the saturated water is pumped into the high-pressure economizer by the feed water pump. After heat exchange and temperature increase, it enters the high-pressure steam drum, where the pressure is 1.0~2.5MPa. The water in the high-pressure steam drum circulates between the high-pressure steam drum and high-pressure evaporators a and b by relying on the density difference of the medium in the inlet and outlet pipes of the high-pressure evaporators 202, forming a separate natural circulation loop. The resulting steam-water mixture is separated in the high-pressure steam drum. The saturated water continues to enter high-pressure evaporators a and b for heat exchange, while the saturated steam enters the high-pressure superheater. After being heated by the exhaust gas of the annular cooler, it becomes high-quality high-pressure superheated steam (1.0~2.5MPa, 250~420℃) and is sent to the external high-pressure steam network.

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