Heating furnace waste heat cascade recovery and flue gas purification system

Abstract

The utility model provides a heating furnace waste heat cascade recovery and flue gas purification system which is characterized in that an SNCR (selective non-catalytic reduction) denitration device is arranged at the tail of a heating furnace and is used for carrying out primary denitration treatment on high-temperature flue gas at the tail of the heating furnace; the heating furnace, the high-temperature protection pipe set, the air preheater, the SCR denitration device, the coal gas preheater, the waste heat boiler, the desulfurization device and the smoke exhaust device are sequentially connected, and the high-temperature protection pipe set conducts heat recovery and cooling on smoke subjected to first-time denitration treatment and cooling in the heating furnace. The air preheater is used for recovering and cooling the heat of the cooled flue gas, the SCR denitration device is used for carrying out secondary denitration treatment on the flue gas, the coal gas preheater and the waste heat boiler are used for recovering and cooling the heat of the flue gas, and the desulfurization device is used for purifying the flue gas. According to the system, the flue gas waste heat of the steel rolling heating furnace can be recycled, the flue gas of the heating furnace can be subjected to desulfurization and denitrification purification treatment in a staged purification mode, and the local emission requirement is met.

Description

Technical Field

[0001] The present application relates to the field of flue gas treatment, and in particular to a heating furnace waste heat cascade recovery and flue gas purification system. Background Art

[0002] Flue gas waste heat recovery is an important way to save energy. By reducing exhaust heat loss and recovering flue gas waste heat, the thermal efficiency of equipment such as kilns can be improved, achieving the goal of energy saving and consumption reduction. Flue gas purification aims to reduce pollutant emissions. Especially in industrial production, the emission of high-temperature flue gas contains a large amount of waste heat. If this flue gas waste heat can be fully utilized, it can not only reduce the flue gas exhaust temperature, but also play a positive role in flue gas dust removal and reducing greenhouse effects. It is an important measure to promote the green development of society.

[0003] The significance of flue gas waste heat recovery and flue gas purification lies in improving resource utilization, saving energy and reducing emissions, reducing operating costs, reducing pollutant emissions and promoting sustainable development. In the existing process of flue gas waste heat utilization and purification of steel rolling heating furnaces, the waste heat utilization of flue gas is often not sufficient, and the purification treatment of flue gas cannot meet the increasingly stringent emission requirements. Utility Model Content

[0004] One of the purposes of this application is to provide a heating furnace waste heat cascade recovery and flue gas purification system, aiming to achieve the purpose of recovering and purifying the flue gas waste heat of the steel rolling heating furnace.

[0005] The technical solution of this application is:

[0006] A heating furnace waste heat cascade recovery and flue gas purification system comprises an SNCR denitrification device, a high-temperature protection tube group, an air preheater, an SCR denitrification device, a gas preheater, a waste heat boiler, a desulfurization device and a smoke exhaust device; the SNCR denitrification device is arranged at the tail of the heating furnace and is used to perform a first denitrification treatment on the high-temperature flue gas at the tail of the heating furnace; the heating furnace, the high-temperature protection tube group, the air preheater, the SCR denitrification device, the gas preheater, the waste heat boiler, the desulfurization device and the smoke exhaust device are connected in sequence, the high-temperature protection tube group recovers heat and cools the flue gas in the heating furnace after the first denitrification treatment and cooling, the air preheater is used to recover and cool the flue gas after cooling, the SCR denitrification device is used to perform a second denitrification treatment on the flue gas, the gas preheater and the waste heat boiler are used to recover heat and cool the flue gas, and the desulfurization device is used to purify the flue gas.

[0007] As a technical solution of the present application, the high-temperature protection tube group includes a shell-and-tube heat exchanger.

[0008] As a technical solution of the present application, the air preheater includes a shell and tube heat exchanger or a fully welded plate heat exchanger.

[0009] As a technical solution of the present application, the air preheater is connected to the burner of the heating furnace and is used to send the combustion air preheated by the flue gas into the burner of the heating furnace for combustion.

[0010] As a technical solution of the present application, the gas preheater includes a shell and tube heat exchanger or a heat pipe heat exchanger.

[0011] As a technical solution of the present application, the gas preheater is connected to the burner of the heating furnace and is used to send the gas heated by the flue gas into the burner of the heating furnace for combustion.

[0012] As a technical solution of the present application, the waste heat boiler is connected to a steam network and is used to send the steam generated after being heated by the flue gas into the steam network for secondary utilization.

[0013] As a technical solution of the present application, the smoke exhaust device includes a smoke exhaust fan.

[0014] As a technical solution of the present application, the SNCR denitration device is installed in the range where the flue gas temperature at the tail of the heating furnace is ≥850°C.

[0015] Beneficial effects of this application:

[0016] In the heating furnace waste heat cascade recovery and flue gas purification system of the present application, the high-temperature flue gas at the tail of the heating furnace is subjected to the first denitrification by the SNCR denitrification device, and the cooled flue gas is further cooled by the high-temperature protection tube group, and then sequentially passes through the air preheater, SCR denitrification device, gas preheater, waste heat boiler, and desulfurization device to recover the heat in the flue gas to the maximum extent and purify it before discharge, wherein the combustion-supporting air and gas after the flue gas preheating are respectively sent to the burner of the heating furnace for combustion, and the steam generated by the waste heat boiler can be incorporated into the steam pipeline network for coordinated use; the system can maximize the recovery of the waste heat of the heating furnace by combining the graded utilization of flue gas waste heat with flue gas purification, and at the same time desulfurize and denitrify the flue gas of the heating furnace according to different temperature ranges, and adopts graded purification to meet local emission requirements. It can be seen that it adopts a stepped recovery process according to the different properties of the waste heat source of the heating furnace to maximize the recovery of the waste heat of the heating furnace; and it desulfurizes and denitrifies the flue gas of the heating furnace according to different temperature ranges, and adopts graded purification to meet local emission requirements; in addition, a smoke exhaust fan is installed at the tail end to cool the flue gas to 160°C and then force it to be exhausted, which can maximize the recovery of the waste heat of the flue gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the implementation methods of the present application, the following is a brief introduction to the drawings required for use in the implementation methods. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 Schematic diagram of the heating furnace waste heat cascade recovery and flue gas purification system provided in an embodiment of the present application.

[0019] Icons: 1-heating furnace; 2-SNCR denitrification device; 3-high temperature protection tube group; 4-air preheater; 5-SCR denitrification device; 6-gas preheater; 7-waste heat boiler; 8-desulfurization device. DETAILED DESCRIPTION

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Generally, the components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0021] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments in the present application without making any creative efforts shall fall within the scope of protection of the present application.

[0022] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0023] In the description of this application, it should be noted that the terms "upper" and "lower" etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the utility model product is usually placed when in use. These are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on this application.

[0024] In addition, in this application, unless otherwise expressly specified or limited, the phrase "a first feature is above or below a second feature" may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Furthermore, the phrases "above, above, and above the second feature" may include the first feature being directly above and obliquely above the second feature, or simply indicate that the first feature is higher in level than the second feature. The phrases "below, below, and below the second feature" may include the first feature being directly below and obliquely below the second feature, or simply indicate that the first feature is lower in level than the second feature.

[0025] Furthermore, terms such as "horizontal" and "vertical" do not necessarily mean that a component must be absolutely horizontal or overhanging, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but rather that it can be slightly tilted.

[0026] It should also be noted that, in the description of this application, unless otherwise expressly specified or limited, the terms "disposed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0027] Example:

[0028] Please refer to Figure 1 The present application provides a waste heat cascade recovery and flue gas purification system for a heating furnace 1, comprising an SNCR denitrification device 2, a high-temperature protection tube group 3, an air preheater 4, an SCR denitrification device 5 for treating medium-temperature flue gas, a gas preheater 6, a waste heat boiler 7, a desulfurization device 8, and a smoke exhaust device; wherein the SNCR denitrification device 2 is arranged at the tail of the heating furnace 1, that is, the SNCR denitrification device 2 is arranged at the tail of the heating furnace 1 in a range where the flue gas temperature is ≥850°C, and the flue gas is subjected to the first denitrification by spraying ammonia water or urea at the tail of the furnace; at the same time, the heating furnace 1 , high-temperature protection tube group 3, air preheater 4, SCR denitrification device 5, gas preheater 6, waste heat boiler 7, desulfurization device 8 and smoke exhaust device are connected in sequence. The high-temperature protection tube group 3 recovers heat and cools the flue gas after the first denitrification treatment and cooling in the heating furnace 1. The air preheater 4 is used to recover heat and cool the flue gas after cooling. The SCR denitrification device 5 is used to perform a second denitrification treatment on the flue gas. The gas preheater 6 and waste heat boiler 7 are used to recover heat and cool the flue gas. The desulfurization device 8 is used to purify the flue gas.

[0029] It should be noted that in this embodiment, the high-temperature protection tube group 3 can adopt a shell-and-tube heat exchanger or the like in the prior art, and can cool the flue gas using cooling water or combustion air. The specific structure and working principle thereof are not described in detail. Furthermore, the air preheater 4 can adopt a shell-and-tube heat exchanger or a fully welded plate heat exchanger, etc., depending on the actual process requirements and site layout, and can preheat the combustion air to a maximum of 550°C. The specific structure and working principle thereof are not described in detail. Simultaneously, the air preheater 4 is connected to the burner of the heating furnace 1 to deliver the preheated combustion air into the burner of the heating furnace 1 for combustion. After passing through the air preheater 4, the temperature of the flue gas is reduced to 340°C, where an SCR denitrification device 5 is installed. It can perform secondary denitrification of the flue gas by spraying ammonia water or urea. Therefore, the flue gas purification adopts a SNCR+SCR combination, which can reduce the use of catalysts and the occurrence of ammonia slip.

[0030] It should be noted that in this embodiment, the gas preheater 6 can adopt a shell-and-tube heat exchanger or a heat pipe heat exchanger according to the actual process requirements and site layout. It can preheat the gas to a maximum of 260°C. Its specific structure and working principle will not be repeated here. At the same time, the gas preheater 6 is connected to the burner of the heating furnace 1, and is used to send the gas heated by the flue gas into the burner of the heating furnace 1 for combustion. After passing through the gas preheater 6, the flue gas temperature drops to 220°C, and a waste heat boiler 7 is set there. The waste heat boiler 7 adopts the form of a heat pipe waste heat boiler 7 to continue to recover the waste heat of the flue gas and reduce the flue gas temperature to 160°C; in addition, the waste heat boiler 7 is connected to the steam network, and is used to send the steam generated after the flue gas is heated into the steam network for secondary use.

[0031] Furthermore, the desulfurization device 8 must be placed before the flue gas exhaust. It can purify the flue gas using dry, semi-dry, or fixed-bed desulfurization methods. The exhaust device uses a smoke exhaust fan for exhaust. Its specific structure and operating principle are not detailed here. The smoke exhaust fan cools the flue gas to 160°C before forced exhaust, maximizing the recovery of waste heat from the flue gas.

[0032] The working principle of the device is:

[0033] At the tail of the heating furnace 1, an SNCR denitrification device 2 is installed in the range where the flue gas temperature is ≥850℃, and the flue gas is denitrified for the first time by spraying ammonia or urea at the tail of the furnace; the flue gas outlet of the heating furnace 1 is cooled to 700-750℃ by cold air, and the high-temperature protection pipe group 3 installed thereafter cools the flue gas again, which can reduce the flue gas temperature to 650℃; the flue gas waste heat is recovered by the air preheater 4, which can preheat the combustion air to a maximum of 550℃. After passing through the air preheater 4, the flue gas temperature drops to 340℃; An SCR denitrification device 5 is provided here to carry out secondary denitrification of the flue gas. The SCR denitrification device 5 can purify the flue gas by spraying ammonia or urea. A gas preheater 6 is provided after the SCR denitrification device 5, which can preheat the gas to a maximum of 260°C. A waste heat boiler 7 is then provided, which uses a heat pipe waste heat boiler 7 to continue to recover the waste heat of the flue gas and reduce the flue gas temperature to 160°C. A desulfurization device 8 is subsequently provided, which can desulfurize the flue gas by dry, semi-dry or fixed bed desulfurization, and the flue gas is discharged after desulfurization is completed.

[0034] In summary, it can be seen that in the heating furnace 1 waste heat cascade recovery and flue gas purification system of the present application, the system can maximize the recovery of the waste heat of the heating furnace 1 by combining the graded utilization of the flue gas waste heat with flue gas purification. At the same time, the flue gas of the heating furnace 1 is desulfurized and denitrified according to different temperature ranges, and graded purification is adopted to meet local emission requirements. Therefore, it adopts a cascade recovery process according to the different properties of the waste heat source of the heating furnace 1 to maximize the recovery of the waste heat of the heating furnace 1; and it desulfurizes and denitrifies the flue gas of the heating furnace 1 according to different temperature ranges, and graded purification is adopted to meet local emission requirements; in addition, it adopts a smoke exhaust fan at 160°C to force exhaust, which can maximize the recovery of the waste heat of the flue gas. It can be seen that this system can not only recover the waste heat of the flue gas to the maximum extent but also purify the flue gas in a suitable temperature range, which has important practical significance and good economic value.

[0035] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Those skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A heating furnace waste heat cascade recovery and flue gas purification system, characterized in that: It includes an SNCR denitrification device, a high-temperature protection tube group, an air preheater, an SCR denitrification device, a gas preheater, a waste heat boiler, a desulfurization device and a smoke exhaust device; the SNCR denitrification device is arranged at the tail of the heating furnace, and is used to perform a first denitrification treatment on the high-temperature flue gas at the tail of the heating furnace; the heating furnace, the high-temperature protection tube group, the air preheater, the SCR denitrification device, the gas preheater, the waste heat boiler, the desulfurization device and the smoke exhaust device are connected in sequence, the high-temperature protection tube group recovers heat and cools the flue gas in the heating furnace after the first denitrification treatment and cooling, the air preheater is used to recover and cool the heat of the cooled flue gas, the SCR denitrification device is used to perform a second denitrification treatment on the flue gas, the gas preheater and the waste heat boiler are used to recover heat and cool the flue gas, and the desulfurization device is used to purify the flue gas.

2. The heating furnace waste heat cascade recovery and flue gas purification system according to claim 1 is characterized in that: The high-temperature protection tube group includes a shell-and-tube heat exchanger.

3. The heating furnace waste heat cascade recovery and flue gas purification system according to claim 1 is characterized in that: The air preheater includes a shell and tube heat exchanger or a fully welded plate heat exchanger.

4. The heating furnace waste heat cascade recovery and flue gas purification system according to claim 1 is characterized in that: The air preheater is connected to the burner of the heating furnace and is used to send the combustion air preheated by the flue gas into the burner of the heating furnace for combustion.

5. The heating furnace waste heat cascade recovery and flue gas purification system according to claim 1 is characterized in that: The gas preheater includes a shell and tube heat exchanger or a heat pipe heat exchanger.

6. The heating furnace waste heat cascade recovery and flue gas purification system according to claim 1 is characterized in that: The gas preheater is connected to the burner of the heating furnace and is used to send the gas heated by the flue gas into the burner of the heating furnace for combustion.

7. The heating furnace waste heat cascade recovery and flue gas purification system according to claim 1 is characterized in that: The waste heat boiler is connected to the steam network and is used to send the steam generated after being heated by the flue gas into the steam network for secondary utilization.

8. The heating furnace waste heat cascade recovery and flue gas purification system according to claim 1 is characterized in that: The smoke exhaust device includes a smoke exhaust fan.

9. The heating furnace waste heat cascade recovery and flue gas purification system according to claim 1, characterized in that: The SNCR denitration device is arranged in a region where the flue gas temperature at the tail of the heating furnace is ≥850°C.

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