Waste heat recovery system of heating furnace

Abstract

The utility model discloses a heating furnace waste heat recovery system which comprises a main preheater and a front preheater. The main preheater is arranged on a main flue and used for heating air in a main air flue. The standby flue is provided with a branch pipeline, and the front preheater is arranged on the branch pipeline, so that when the main preheater is overhauled, the front preheater replaces the main preheater to work. According to the utility model, the operation of the heating furnace is not influenced by the fault of the preheater in the whole production cycle, when any one of the main preheater and the front preheater is cut out, the other preheater can still work and continuously heat air, an external heat source is saved, flue gas is used for heating air in the main working stage, the energy consumption is saved, the emission is reduced, and the production efficiency is improved. The cost is low. And secondly, multiple working modes can be met, multiple components can be cut out of the system to be overhauled under the non-stop state of the system, the maintenance cost is reduced, and a bypass flue on a chimney in the traditional technology is omitted. In addition, the system does not add too many devices, multiple functions are achieved through pipeline connection optimization, and the device cost is low.

Description

Technical Field

[0001] The utility model belongs to the technical field of heating furnaces and relates to a waste heat recovery system for a heating furnace. Background Art

[0002] Heating furnaces are widely used in petrochemical, chemical and other fields. In order to improve the thermal efficiency of heating furnaces, a flue gas waste heat recovery system is generally configured. Because there are cut-out (non-working) conditions such as preheater failure or maintenance, in order to ensure the normal operation of the heating furnace, a horizontal bypass flue directly connected to the chimney is set on the top of the heating furnace in the traditional waste heat recovery system, so that the high-temperature flue gas does not enter the preheater for heat exchange but is directly discharged into the chimney through the bypass flue at high altitude. This results in two flue branches on the side wall of the chimney, a high-level bypass flue for exhausting smoke when the preheater is cut out, and a low-level induced draft fan exhaust flue under normal working conditions. According to the HJ75 specification, when installing a flue gas continuous emission monitoring system (CEMS) on the chimney, because there is a bypass flue on the chimney, the particulate matter CEMS needs to be installed at a height of 4 times the flue diameter upward from the bypass flue opening, which greatly increases the installation height of the CEMS, increases the investment in the supporting platform ladder and the difficulty of high-altitude operations. In addition, in traditional waste heat recovery systems, a single preheater is generally set up. When a main preheater and a pre-preheater are set up, the two are also connected in series. When one of them stops working, the other cannot be used. The high-temperature flue gas can only be discharged directly into the chimney through the bypass flue, which reduces the thermal efficiency. Summary of the invention

[0003] In order to overcome the shortcomings of the background technology, the utility model provides a waste heat recovery system for a heating furnace, the purpose of which is to set up a waste heat recovery system with multiple working modes to adapt to the maintenance conditions of different equipment cutting out the system, while ensuring the normal operation of the system and eliminating the high-altitude bypass flue, that is, to achieve maintenance without stopping the system, improve adaptability and reduce maintenance costs.

[0004] In order to achieve the above purpose, the utility model provides the following technical solutions:

[0005] A heating furnace waste heat recovery system, comprising a heating furnace with a main air duct and a main flue connected at both ends, the end of the main air duct is connected to a blower; the end of the main flue is connected to an exhaust mechanism; a main preheater is provided on the main flue, and the main air duct runs through the main preheater, and is used to heat the air in the main air duct using the heat of the main flue; it is characterized in that: one end of the spare flue is connected to the main flue between the main preheater and the heating furnace, and the other end is connected to the main flue close to the exhaust mechanism; a pre-preheater is provided on the air inlet duct between the blower and the main preheater; the pre-preheater is connected to an external heat source, and is used to heat the air exhausted by the blower;

[0006] The branch pipe is connected in parallel to the standby flue, and the pre-preheater is connected to the branch pipe to heat the air discharged by the blower using the heat of the standby flue;

[0007] One end of the cold air bypass pipe is connected to the main air duct between the blower and the pre-preheater, and the other end is connected to the main air duct between the main preheater and the heating furnace;

[0008] One end of the hot air bypass pipe is connected to the main air duct between the pre-preheater and the main preheater, and the other end is connected to the main air duct between the main preheater and the cold air bypass pipe;

[0009] One end of the air inlet cross-path air duct is connected to the cold air bypass duct, and the other end is connected to the hot air bypass duct;

[0010] The inlet end of the standby flue is provided with a standby smoke inlet valve; the inlet and outlet ends of the branch pipe connected to the standby flue are respectively provided with a branch inlet valve and a branch outlet valve; the cold air bypass pipe is provided with a cold air bypass valve; the hot air bypass pipe is provided with a hot air bypass valve; the air inlet cross-path duct is provided with an air inlet cross-path valve;

[0011] The main flue is provided with a main preheating smoke inlet valve and a main preheating smoke outlet valve at the inlet and outlet ends connected to the main preheater; the main air duct is provided with a main preheating air inlet valve and a main preheating air outlet valve at the inlet and outlet ends connected to the main preheater; the main air duct is provided with a pre-preheating air inlet valve and a pre-preheating air outlet valve at the inlet and outlet ends connected to the pre-preheater; one end of the cold air bypass pipe is connected to the main air duct between the blower and the pre-preheating air inlet valve; One end of the hot air bypass pipe is connected to the main air duct between the pre-preheating air outlet valve and the main preheating air inlet valve; one end of the cold air bypass pipe and the hot air bypass pipe are both connected to the main air duct between the main preheating air outlet valve and the heating furnace; one end of the air inlet cross-path air duct is connected to the cold air bypass pipe between the cold air bypass valve and the pre-preheating air inlet valve, and the other end of the air inlet cross-path air duct is connected to the hot air bypass pipe between the hot air bypass valve and the pre-preheating air outlet valve.

[0012] Preferably, the exhaust mechanism comprises an induced draft fan, an inlet end of the induced draft fan is connected to the end of the main flue, and an outlet end of the induced draft fan is connected to the lower part of the chimney.

[0013] Preferably, there are two induced draft fans, which are connected in parallel through pipelines.

[0014] Preferably, a furnace air inlet valve and a furnace smoke exhaust valve are respectively provided on the main air duct and the main smoke duct at both ends of the heating furnace.

[0015] Preferably, the backup flue is provided with a backup smoke outlet valve at an interface close to the exhaust mechanism.

[0016] Compared with the prior art, the beneficial effects of the utility model are:

[0017] The utility model can make the operation of the heating furnace unaffected by the failure of the preheater during the entire production cycle, and when any one of the main preheater or the front preheater is cut out, the other preheater can still work and continue to heat the air, and save external heat sources. The main working stage uses flue gas to heat the air, saving energy consumption, reducing emissions, and low cost. Secondly, it can meet a variety of working modes. When the system is not shut down, multiple components can be cut out of the system for maintenance, reducing maintenance costs, and eliminating the bypass flue on the chimney in traditional technology, thereby improving the strength of the chimney and reducing the construction cost of the chimney and the investment in the platform ladder. In addition, the system does not add too much equipment, but uses the connection optimization of the pipeline to achieve multiple functions, and the equipment cost is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the system structure of the utility model;

[0019] Figure 2 It is a structural schematic diagram of the exhaust mechanism of the utility model.

[0020] 1; 2; 3; 4; 5; 6; 7; 8; 9; 10; 11; 12; 13; 14; 15; 16; 17; 18; 19; 20; 21; 22; 23; 24; 25; 26; 27; 28; 29; 30; 31; 32; 33; 34; 35; 36; 37; 38; 39; 40; 41; 42; 43; 44; 45; 46; 47; 48; 49; 50; 51; 52; 53; 54; 55; 56; 57; 58; 59; 60; 61; 62; 73; 74; 75; 80; 81; 82; 83; 84; 85; 86; 87; 88; 89; 90; 91; 92; 93; 94; 95; 96; 97; 98; 99; 100; 110 DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present invention are clearly and completely described below in conjunction with the accompanying drawings of the present invention. Those skilled in the art should understand that these implementation modes are only used to explain the technical principles of the present invention and are not intended to limit the protection scope of the present invention.

[0022] Example 1: Please refer to Figure 1-2 ;

[0023] A heating furnace waste heat recovery system, comprising a heating furnace 1 with a main air duct 2 and a main flue 3 connected at both ends, the end of the main air duct 2 is connected to a blower 21; the end of the main flue 3 is connected to an exhaust mechanism 31; a main preheater 4 is provided on the main flue 3, the main air duct 2 runs through the main preheater 4, and is used to use the heat of the main flue 3 to heat the air in the main air duct 2; it is characterized in that: one end of a spare flue 5 is connected to the main flue 3 between the main preheater 4 and the heating furnace 1, and the other end is connected to the main flue 3 near the exhaust mechanism 31; a preheater 6 is provided on the air inlet duct between the blower 21 and the main preheater 4; the preheater 6 is connected to an external heat exchanger. The branch pipe 51 is connected in parallel to the standby flue 5, and the preheater 6 is connected to the branch pipe 51, and is used to heat the air discharged by the blower 21 by using the heat of the standby flue 5; one end of the cold air bypass pipe 22 is connected to the main air duct 2 between the blower 21 and the preheater 6, and the other end is connected to the main air duct 2 between the main preheater 4 and the heating furnace 1; one end of the hot air bypass pipe 23 is connected to the main air duct 2 between the preheater 6 and the main preheater 4, and the other end is connected to the main air duct 2 between the main preheater 4 and the cold air bypass pipe 22; one end of the air inlet cross-over duct 24 The standby flue 5 is provided with a standby smoke inlet valve 52 at its inlet end; the branch pipe 51 is provided with a branch inlet valve 511 and a branch outlet valve 512 at its inlet and outlet ends connected to the standby flue 5; the cold air bypass pipe 22 is provided with a cold air bypass valve 221; the hot air bypass pipe 23 is provided with a hot air bypass valve 231; the air inlet cross-path duct 24 is provided with an air inlet cross-path valve 241; the main flue 3 is provided with a main preheating smoke inlet valve 41 and a main preheating smoke outlet valve 42 at its inlet and outlet ends connected to the main preheater 4; the main air duct 2 ... The inlet and outlet ends of the main air duct 2 connected to the pre-preheater 6 are respectively provided with a main preheated air inlet valve 43 and a main preheated air outlet valve 44; the inlet and outlet ends of the main air duct 2 connected to the pre-preheater 6 are respectively provided with a pre-preheated air inlet valve 61 and a pre-preheated air outlet valve 62; one end of the cold air bypass pipe 22 is connected to the main air duct 2 between the blower 21 and the pre-preheated air inlet valve 61; one end of the hot air bypass pipe 23 is connected to the main air duct 2 between the pre-preheated air outlet valve 62 and the main preheated air inlet valve 43; one end of the cold air bypass pipe 22 and the hot air bypass pipe 23 are both connected to the main air duct 2 between the main preheated air outlet valve 44 and the heating furnace 1;One end of the air inlet cross-path duct 24 is connected to the cold air bypass pipe 22 between the cold air bypass valve 221 and the front preheated air inlet valve 61, and the other end of the air inlet cross-path duct 24 is connected to the hot air bypass pipe 23 between the hot air bypass valve 231 and the front preheated air outlet valve 62.

[0024] Among them, the pre-preheater is a dual-source heat exchanger, which is provided with an external heat source inlet pipe. The external heat source can be flexibly matched with the hot flue gas in the spare flue to provide heat source for the pre-preheater.

[0025] This embodiment provides a heating furnace waste heat recovery system, which, when in use, includes multiple working modes, as shown below.

[0026] Working mode 1: The flue gas is directly discharged without recovering the waste heat and the air is not preheated. The main preheater 4 and the pre-preheater 6 are both cut out.

[0027] The standby smoke inlet valve 52, the standby smoke outlet valve 53, and the cold air bypass valve 221 are all open;

[0028] The main preheating flue gas inlet valve 41, the main preheating flue gas outlet valve 42, the branch inlet valve 511, the branch outlet valve 512, the pre-preheating air inlet valve 61, the main preheating air outlet valve 44, the hot air bypass valve 231, and the air inlet cross-circuit valve 241 are all closed;

[0029] The air enters the heating furnace 1 through the cold air bypass duct 22, and the flue gas only flows through the spare flue duct 5 but is directly output to the exhaust mechanism 31 without heat exchange with the air. The air inlet and outlet and the flue gas inlet and outlet of the preheater 6 and the main preheater 4 can be closed, and maintenance or replacement can be carried out at the same time. At the same time, the heating furnace 1 works normally without system shutdown.

[0030] Working mode 2: The flue gas is discharged directly without recovering the waste heat, the air temperature is low and needs to be heated, the main preheater 4 is cut out, and the pre-preheater 6 works. At this time, no heat exchange occurs in the main preheater 4, and the air in the pre-preheater 6 is only heated by an external heat source.

[0031] The standby smoke inlet valve 52, the standby smoke outlet valve 53, the preheated air inlet valve 61, the preheated air outlet valve 62, and the hot air bypass valve 231 are all opened;

[0032] The main preheating flue gas inlet valve 41, the main preheating flue gas outlet valve 42, the branch inlet valve 511, the branch outlet valve 512, the main preheating air inlet valve 43, the main preheating air outlet valve 44, the air inlet cross-circuit valve 241, and the cold air bypass valve 221 are all closed.

[0033] The air is heated by the external heat source of the preheater 6 and enters the heating furnace 1. The flue gas only flows through the spare flue 5 but is directly output to the exhaust mechanism 31 without heat exchange with the air. The main preheater 4 can be cut out for maintenance, and the system has good adaptability.

[0034] Working mode 3: The flue gas temperature is high and the air can be preheated. The main preheater 4 is switched off and the preheater 6 is working. At this time, no heat exchange occurs in the main preheater 4, and the air in the preheater 6 is heated by the flue gas without using an external heat source.

[0035] The standby smoke inlet valve 52, the branch inlet valve 511, the branch outlet valve 512, the preheated air inlet valve 61, the preheated air outlet valve 62, and the hot air bypass valve 231 are all opened;

[0036] The air inlet cross-route valve 241, the cold air bypass valve 221, the main preheating air inlet valve 43, the main preheating air outlet valve 44, the main preheating smoke gas inlet valve 41, the main preheating smoke gas outlet valve 42, and the standby smoke outlet valve 53 are all closed.

[0037] The air flows through the preheater 6 and then enters the heating furnace 1 after being heated. The flue gas does not flow through the main flue 3 but through the spare flue 5 and the branch pipe 51, and then flows through the preheater 6 and is discharged to the exhaust mechanism 31. At this time, the external heat source is cut off, and the flue gas is used to transport heat to the preheater 6, which saves the use of the external heat source and reduces the cost. The main preheater 4 can be cut out for maintenance, and the system has good adaptability.

[0038] Working mode 4: The flue gas temperature is high and the air can be preheated. The main preheater 4 works, and the flue gas and air in the main preheater 4 exchange heat, while the pre-preheater 6 does not exchange heat but introduces air.

[0039] The pre-preheated air inlet valve 61, the pre-preheated air outlet valve 62, the main preheated air inlet valve 43, the main preheated air outlet valve 44, the main preheated smoke gas inlet valve 41, and the main preheated smoke gas outlet valve 42 are all opened;

[0040] The standby smoke inlet valve 52, the standby smoke outlet valve 53, the branch outlet valve 512, the air inlet cross-circuit valve 241, the cold air bypass valve 221, and the hot air bypass valve 231 are all closed.

[0041] The air enters the heating furnace 1 after being preheated, but there is no heat exchange. Instead, the air enters the heating furnace 1 after heat exchange with the main preheater 4. The flue gas passes through the main flue 3 and the main preheater 4 instead of the spare flue 5 and is discharged to the exhaust mechanism 31. At this time, the preheater 6 does not work and does not use an external heat source, which saves the heat source cost and increases the life of the preheater 6, thereby reducing the equipment use cost.

[0042] Working mode 5: The flue gas temperature is high and the air can be preheated. The main preheater 4 is working and the preheater 6 is cut out. At this time, the flue gas in the main preheater 4 exchanges heat with the air, and no heat exchange occurs in the preheater 6 and no air is introduced.

[0043] The air inlet cross-way valve 241, the main preheating air inlet valve 43, the main preheating air outlet valve 44, the main preheating flue gas inlet valve 41, and the main preheating flue gas outlet valve 42 are all opened;

[0044] The standby smoke inlet valve 52, the standby smoke outlet valve 53, the branch outlet valve 512, the pre-preheated air inlet valve 61, the pre-preheated air outlet valve 62, the cold air bypass valve 221, and the hot air bypass valve 231 are all closed.

[0045] The air does not enter the preheater 6, but enters the heating furnace 1 after heat exchange with the main preheater 4, and the flue gas passes through the main flue 3 and the main preheater 4 instead of the spare flue 5 and is discharged to the exhaust mechanism 31. At this time, the preheater 6 does not work and can be cut out for maintenance, and the system has good adaptability.

[0046] Working mode 6: The flue gas temperature is high and the air can be preheated. The main preheater 4 and the pre-preheater 6 are both involved in heat exchange.

[0047] The pre-preheated air inlet valve 61, the pre-preheated air outlet valve 62, the main preheated air inlet valve 43, the main preheated air outlet valve 44, the main preheated smoke inlet valve 41, the main preheated smoke outlet valve 42, the standby smoke inlet valve 52, the branch inlet valve 511, and the branch outlet valve 512 are all open;

[0048] The air inlet cross-circuit valve 241, the cold air bypass valve 221, the hot air bypass valve 231, and the standby smoke outlet valve 53 are all closed.

[0049] The air flows through the preheater 6 and the main preheater 4 for two heatings. At this time, the external heat source can be turned on to further increase the heat. The main flue 3 and the standby flue 5 are exhaust in parallel, which makes the exhaust faster, and the exhaust flue gas participates in heating the air, so the waste heat utilization efficiency is high. The standby flue gas inlet valve 52 can also be closed so that the preheater 6 no longer passes flue gas, and only the external heat source is used to heat the air.

[0050] More preferably, the exhaust mechanism 31 is provided with an induced draft fan 311 , the inlet end of the induced draft fan 311 is connected to the end of the main flue 3 , and the outlet end thereof is connected to the lower part of the chimney 312 .

[0051] A seventh operating mode may be included at this time.

[0052] Working mode seven: the blower 21 can be cut out of the system for maintenance, and the burner can be naturally ventilated by using the suction force of the induced draft fan 311 and setting a damper on the burner air duct, and the blower 21 is no longer used.

[0053] Preferably, there are two induced draft fans 311 connected in parallel; one of the two induced draft fans 311 can be used and the other can be used as a backup, or both can be used and not used as a backup; when one of the induced draft fans fails, the other can work to ensure that the system can still exhaust smoke normally.

[0054] Preferably, the main air duct 2 and the main smoke duct 3 at both ends of the inlet and outlet of the heating furnace 1 are respectively provided with a furnace air inlet valve 11 and a furnace smoke exhaust valve 12. When shutting down for overhaul, the heating furnace 1 can be cut out of the system for maintenance.

[0055] Preferably, a spare smoke outlet valve 53 is provided at the interface between the spare smoke duct 5 and the main smoke duct 3. The spare smoke duct 5 can be cut out of the system for maintenance.

[0056] The advantages of this embodiment are:

[0057] This system can make the operation of the heating furnace 1 unaffected by the failure of the preheater during the entire production cycle, and when any one of the main preheater or the front preheater is cut out, the other preheater can still work and continue to heat the air, and save external heat sources. The main working stage uses flue gas to heat the air, saving energy consumption, reducing emissions, and low cost. Secondly, it can meet a variety of working modes. When the system is not shut down, multiple components can be cut out of the system for maintenance, reducing maintenance costs, and eliminating the bypass flue on the chimney in traditional technology, thereby improving the strength of the chimney and reducing the construction cost of the chimney and the investment in the platform ladder. In addition, this system does not add too much equipment, but uses the connection optimization of the pipeline to achieve multiple functions, and the equipment cost is low.

[0058] The parts not described in detail in this utility model are prior art; for ordinary technicians in this field, the technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, all possible combinations of the technical features in the above-mentioned embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification. The scope of this utility model is defined by the attached claims and their equivalents.

Claims

1. A heating furnace waste heat recovery system, comprising a heating furnace (1) having a main air duct (2) and a main flue (3) connected at both ends, the end of the main air duct (2) being connected to a blower (21); the end of the main flue (3) being connected to an exhaust mechanism (31); a main preheater (4) being provided on the main flue (3); the main air duct (2) passing through the main preheater (4) for heating air in the main air duct (2) by utilizing the heat of the main flue (3); characterized in that: One end of the standby flue (5) is connected to the main flue (3) between the main preheater (4) and the heating furnace (1), and the other end is connected to the main flue (3) near the exhaust mechanism (31); a preheater (6) is provided on the air inlet duct between the blower (21) and the main preheater (4); the preheater (6) is connected to an external heat source for heating the air exhausted by the blower (21); The branch pipe (51) is connected in parallel to the standby flue (5), and the pre-preheater (6) is connected to the branch pipe (51) and is used to heat the air discharged by the blower (21) by using the heat of the standby flue (5); One end of the cold air bypass pipe (22) is connected to the main air duct (2) between the blower (21) and the pre-preheater (6), and the other end is connected to the main air duct (2) between the main preheater (4) and the heating furnace (1); One end of the hot air bypass pipe (23) is connected to the main air duct (2) between the pre-preheater (6) and the main preheater (4), and the other end is connected to the main air duct (2) between the main preheater (4) and the cold air bypass pipe (22); One end of the air inlet cross-path air duct (24) is connected to the cold air bypass duct (22), and the other end is connected to the hot air bypass duct (23); The inlet end of the standby flue (5) is provided with a standby smoke inlet valve (52); the inlet and outlet ends of the branch pipe (51) connected to the standby flue (5) are respectively provided with a branch inlet valve (511) and a branch outlet valve (512); the cold air bypass pipe (22) is provided with a cold air bypass valve (221); the hot air bypass pipe (23) is provided with a hot air bypass valve (231); the air inlet cross-path air duct (24) is provided with an air inlet cross-path valve (241); The main flue (3) is provided with a main preheating smoke inlet valve (41) and a main preheating smoke outlet valve (42) at the inlet and outlet ends connected to the main preheater (4); the main air duct (2) is provided with a main preheating air inlet valve (43) and a main preheating air outlet valve (44) at the inlet and outlet ends connected to the main preheater (4); the main air duct (2) is provided with a preheating air inlet valve (61) and a preheating air outlet valve (62) at the inlet and outlet ends connected to the preheater (6); one end of the cold air bypass pipe (22) is connected to the main air duct (2) between the blower (21) and the preheating air inlet valve (61); the hot air bypass pipe (22) is connected to the main air duct (2) between the blower (21) and the preheating air inlet valve (61); One end of the pipe (23) is connected to the main air duct (2) between the pre-preheating air outlet valve (62) and the main preheating air inlet valve (43); one end of the cold air bypass pipe (22) and the hot air bypass pipe (23) are both connected to the main air duct (2) between the main preheating air outlet valve (44) and the heating furnace (1); one end of the air inlet cross-path air duct (24) is connected to the cold air bypass pipe (22) between the cold air bypass valve (221) and the pre-preheating air inlet valve (61), and the other end of the air inlet cross-path air duct (24) is connected to the hot air bypass pipe (231) and the pre-preheating air outlet valve (62).

2. A heating furnace waste heat recovery system according to claim 1, characterized in that: The exhaust mechanism (31) comprises an induced draft fan (311), the inlet end of the induced draft fan (311) is connected to the end of the main flue (3), and the outlet end is connected to the lower part of the chimney (312).

3. A heating furnace waste heat recovery system according to claim 2, characterized in that: There are two induced draft fans (311) connected in parallel via a pipeline.

4. A heating furnace waste heat recovery system according to claim 1, characterized in that: A furnace air inlet valve (11) and a furnace smoke exhaust valve (12) are respectively provided on the main air duct (2) and the main smoke duct (3) at both ends of the heating furnace (1).

5. The heating furnace waste heat recovery system according to claim 1, characterized in that: The standby flue (5) is provided with a standby smoke outlet valve (53) at an interface close to the exhaust mechanism (31).

6. The heating furnace waste heat recovery system according to claim 1, characterized in that: The preheater (6) is a dual-source heat exchanger, which is provided with an external heat source inlet pipe. The external heat source can be flexibly matched with the hot flue gas in the standby flue (5) to provide a heat source for the preheater (6).

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