Efficient energy-saving waste heat recovery system

Abstract

The utility model provides an efficient energy-saving waste heat recovery system which comprises a heating furnace, a fuel heating device, a cold smoke and air mixer, a preheater and a chimney. In the smoke flowing direction, a smoke outlet section of the heating furnace is respectively communicated with a high-temperature medium flow channel of the preheater and a smoke inlet of the fuel heating device; a smoke outlet of the fuel heater is sequentially communicated with the cold smoke and air mixer and a low-temperature medium flow channel of the preheater, an outlet of the low-temperature medium flow channel and a fuel gas outlet of the fuel heater are both connected with a combustor of the heating furnace, and an outlet of the high-temperature medium flow channel is communicated with a chimney; according to the utility model, the content of NOx in combustion tail gas can be reduced, the environment-friendly and energy-saving effects are achieved, the temperature of discharged smoke can be effectively reduced, the efficiency of the heating furnace is improved, the content of solid dust particles in finally discharged smoke is reduced, and the pollution of the discharged smoke to the atmosphere is reduced.

Description

Technical Field

[0001] This utility model relates to the field of waste heat recovery technology, and in particular to a high-efficiency and energy-saving waste heat recovery system. Background Technology

[0002] Energy conservation and emission reduction technologies refer to industrial technologies that reduce energy consumption and pollutant emissions during the production process. Currently, oil refineries, chemical plants, and other work areas with process heating furnaces often require the installation of waste heat recovery systems.

[0003] Taking the oil refining and chemical industry as an example, the flue gas temperature of the traditional waste heat recovery system currently in use is around 150℃. To avoid acid dew point corrosion, the flue gas temperature is generally controlled above the flue gas dew point temperature.

[0004] However, at this time, the flue gas temperature is relatively high. On the one hand, a large amount of waste heat in the flue gas itself cannot be effectively recovered and utilized, and the direct emission of waste heat is a serious waste. According to industry experience, for every 20°C increase in flue gas temperature, the efficiency of the heating furnace decreases by about 1%, which leads to the low efficiency of the existing heating furnace. On the other hand, condensation rarely occurs inside the flue gas above the dew point temperature. The solid particulate matter contained in the flue gas itself will be emitted into the atmosphere along with the flue gas, causing pollution. Utility Model Content

[0005] In view of this, the present invention aims to propose a high-efficiency and energy-saving waste heat recovery system to solve the problems of high flue gas temperature, low heating furnace efficiency, and high content of solid dust particles in flue gas in the existing technology.

[0006] To achieve the above objectives, the technical solution of this utility model is implemented as follows:

[0007] A high-efficiency energy-saving waste heat recovery system includes a heating furnace, a fuel heater, a cold flue gas air mixer, a preheater, and a chimney. In the flue gas flow direction, the flue gas outlet section of the heating furnace is connected to the high-temperature medium flow channel of the preheater and the flue gas inlet of the fuel heater, respectively. The flue gas outlet of the fuel heater is connected to the low-temperature medium flow channel of the cold flue gas air mixer and the preheater in sequence. The outlet of the low-temperature medium flow channel and the fuel gas outlet of the fuel heater are both connected to the burner of the heating furnace. The outlet of the high-temperature medium flow channel is connected to the chimney.

[0008] Furthermore, the system includes a main pipeline, a first branch pipeline, and a second branch pipeline. The inlet of the main pipeline is connected to the flue gas outlet section, and the outlet of the main pipeline is connected to the inlet of the first branch pipeline and the inlet of the second branch pipeline, respectively. The outlet of the first branch pipeline is connected to the inlet of the high-temperature medium flow channel, and the outlet of the second branch pipeline is connected to the flue gas inlet of the fuel heater.

[0009] Furthermore, within a unit of time, the ratio of the flue gas flow rate of the first branch to the flue gas flow rate of the second branch is 9:1.

[0010] Furthermore, the fuel heater is equipped with a heating pipe, the system includes a fuel pipeline, the inlet of the heating pipe is connected to a fuel gas source, and the outlet of the heating pipe is connected to a burner through the fuel pipeline.

[0011] Furthermore, the flue gas outlet of the fuel heater is connected to the flue gas inlet of the cold flue gas air mixer. Along the flue gas flow direction, a first demister and a flue gas fan are sequentially arranged between the flue gas outlet of the fuel heater and the flue gas inlet of the cold flue gas air mixer. The sewage outlet of the first demister is connected to the sewage pipe network.

[0012] Furthermore, the flue gas inlet of the cold flue gas air mixer is connected to a flue gas fan, the air inlet of the cold flue gas air mixer is connected to a blower, the outlet of the cold flue gas air mixer is connected to the inlet of the low-temperature medium flow channel of the preheater, and the cold flue gas air mixer has a mixing chamber inside.

[0013] Furthermore, the system includes an intake pipe, the inlet of which is connected to the outlet of a cryogenic medium flow channel, and the outlet of which is connected to a burner.

[0014] Furthermore, the system includes a flue gas exhaust pipe, the inlet of which is connected to the outlet of a high-temperature medium flow channel, and the outlet of which is connected to a chimney; in the flue gas flow direction, a second demister and an induced draft fan are sequentially installed in the flue gas exhaust pipe, and the wastewater outlet of the second demister is connected to a wastewater network.

[0015] Furthermore, a smoke exhaust valve is installed in the smoke exhaust pipeline, and the smoke exhaust valve is located downstream of the induced draft fan in the direction of smoke flow.

[0016] Furthermore, a drain pipe is provided at the bottom of the preheater, and the drain pipe is connected to the sewage network.

[0017] Compared with existing technologies, the high-efficiency energy-saving waste heat recovery system described in this utility model has the following advantages:

[0018] The present invention discloses a high-efficiency and energy-saving waste heat recovery system. In the first aspect, it heats part of the high-temperature flue gas (flue gas A) to the ambient temperature fuel gas, thereby increasing the temperature of the fuel gas, eliminating liquid water in the fuel gas, and preventing the fuel from burning with liquid, which would affect the combustion safety of the heating furnace.

[0019] Secondly, by mixing the cooled flue gas A with air, the oxygen content in the mixture is lower than that in normal air. Sending such a mixture into the heating furnace for combustion can create a continuous "oxygen-deficient combustion" state. "Oxygen-deficient combustion" can reduce the combustion flame temperature, thereby reducing the NOx content in the combustion exhaust gas, achieving the effect of environmental protection and energy saving, and also helping to reduce the exhaust temperature and improve the efficiency of the heating furnace.

[0020] Thirdly, compared to traditional waste heat recovery technology—"all flue gas exchanges heat with combustion air" and the corresponding amount of gas involved in the heat exchange—this application separates a portion of the flue gas to heat the fuel gas, and then mixes it with air to form a mixed gas. Relatively speaking, in the preheater, while reducing the total amount of high-temperature flue gas involved in the heat exchange, the amount of low-temperature mixed gas is also increased accordingly. As the reduced amount of high-temperature flue gas exchanges heat with the increased amount of mixed gas, the final exhaust temperature is easier to reduce, and can even be reduced to below 80°C or lower, which is far lower than the exhaust temperature in the prior art. This greatly improves the efficiency of the heating furnace, correspondingly reduces fuel consumption, and reduces the carbon emissions of the heating furnace.

[0021] Fourthly, another portion of the high-temperature flue gas (flue gas B) undergoes heat exchange and cooling in a preheater. During this cooling process, the flue gas is forced to undergo intense condensation, causing the water vapor to change from a gaseous state to a liquid state, forming water mist. The small droplets in the water mist adsorb dust particles from the flue gas as condensation nuclei, agglomerating into larger droplets that can be easily collected and processed by the demister. Through this process, the amount of solid dust particles in the final emitted flue gas is significantly reduced, effectively reducing the pollution of the atmosphere caused by the flue gas emissions.

[0022] In addition, this application can retain existing heating furnaces, preheaters, chimneys and other equipment, without the need for major dismantling and modification of existing waste heat recovery equipment, which facilitates the transformation of old equipment and systems in the industry. Attached Figure Description

[0023] The accompanying drawings, which form part of this utility model, are used to provide a further understanding of the utility model. The illustrative embodiments of the utility model and their descriptions are used to explain the utility model and do not constitute an undue limitation of the utility model. In the drawings:

[0024] Figure 1 This is a schematic diagram of the structure of a high-efficiency and energy-saving waste heat recovery system according to an embodiment of the present invention.

[0025] Explanation of reference numerals in the attached figures:

[0026] 1. Heating furnace; 11. Burner; 12. Smoke outlet section; 2. Fuel heater; 21. Heating pipe; 3. First demister; 4. Flue gas fan; 5. Blower; 6. Cold smoke air mixer; 7. Preheater; 71. Second demister; 72. Exhaust fan; 8. Chimney; 81. Adjusting damper; 91. Main valve; 92. Branch valve; 93. Exhaust valve; 101. Main pipeline; 102. First branch; 103. Second branch; 104. Inlet pipeline; 105. Exhaust pipeline; 106. Fuel pipeline. Detailed Implementation

[0027] The inventive concepts of this disclosure will be described below using terminology commonly used by those skilled in the art to convey the essence of their work to others skilled in the art. However, these inventive concepts may be embodied in many different forms and should not be construed as limited to the embodiments described herein.

[0028] It should be noted that, where there is no conflict, the embodiments and features in the embodiments of this utility model can be combined with each other. The path through which the fuel gas flows is uniformly depicted in red for easy distinction. The accompanying drawings show only a portion of the length of the chimney 8 to avoid affecting the overall aspect ratio of the drawings.

[0029] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0030] To address the problems of high flue gas temperature, low furnace efficiency, and high particulate matter content in flue gas in existing technologies, this embodiment proposes a high-efficiency, energy-saving waste heat recovery system, as shown in the attached figure. Figure 1 As shown, the system includes a heating furnace 1, a fuel heater 2, a cold flue gas air mixer 6, a preheater 7, and a chimney 8. In the flue gas flow direction, the flue gas outlet section 12 of the heating furnace 1 is connected to the high-temperature medium flow channel of the preheater 7 and the flue gas inlet of the fuel heater 2, respectively. The flue gas outlet of the fuel heater 2 is connected to the cold flue gas air mixer 6 and the low-temperature medium flow channel of the preheater 7 in sequence. The outlet of the low-temperature medium flow channel and the fuel gas outlet of the fuel heater 2 are both connected to the burner 11 of the heating furnace 1. The outlet of the high-temperature medium flow channel is connected to the chimney 8.

[0031] Based on this system, the flow of each medium is as follows:

[0032] After high-temperature flue gas is generated in the heating furnace 1, at least a portion of the high-temperature flue gas (hereinafter referred to as flue gas A) enters the fuel heater 2 to heat the fuel gas and form a relatively low-temperature "cold flue gas". The cold flue gas (i.e., flue gas A) enters the cold flue gas air mixer and mixes with air to form a "mixed gas". Then, the mixed gas enters the preheater 7 as a low-temperature medium and exchanges heat with another portion of high-temperature flue gas (hereinafter referred to as flue gas B). The flue gas B, after being cooled down by heat exchange, is sent to the chimney 8 for discharge. The mixed gas after heat exchange is sent to the burner 11 as "fuel combustion". At the same time, the fuel gas heated in the fuel heater 2 is also sent to the burner 11 for combustion.

[0033] Thus, this application is made through the system described above:

[0034] Firstly, heating some of the high-temperature flue gas (flue gas A) to the ambient temperature fuel gas increases the temperature of the fuel gas, eliminates liquid water in the fuel gas, and prevents the fuel from burning with liquid, thus affecting the combustion safety of the heating furnace.

[0035] Secondly, by mixing the cooled flue gas A with air, the oxygen content in the mixture is lower than that in normal air. Sending such a mixture into the heating furnace 1 for combustion can create a continuous "oxygen-deficient combustion" state. "Oxygen-deficient combustion" can reduce the combustion flame temperature, thereby reducing the NOx content in the combustion exhaust gas, achieving the effect of environmental protection and energy saving, and also helping to reduce the exhaust temperature and improve the efficiency of the heating furnace.

[0036] Thirdly, compared to traditional waste heat recovery technology—"all flue gas exchanges heat with combustion air" and the corresponding amount of gas involved in the heat exchange—this application separates a portion of the flue gas to heat the fuel gas, and then mixes it with air to form a mixed gas. In contrast, in the preheater 7, while reducing the total amount of high-temperature flue gas involved in the heat exchange, the amount of low-temperature mixed gas is also increased. As the reduced amount of high-temperature flue gas exchanges heat with the increased amount of mixed gas, the final exhaust temperature is easier to reduce, and can even be reduced to below 80°C or lower, which is far lower than the exhaust temperature in the prior art. This greatly improves the efficiency of the heating furnace, correspondingly reduces fuel consumption, and reduces the carbon emissions of the heating furnace 1.

[0037] Fourthly, another portion of the high-temperature flue gas (flue gas B) is cooled down by heat exchange in preheater 7. During the cooling process, the flue gas undergoes intense condensation, causing the water vapor to change from a gaseous state to a liquid state, forming water mist. The small droplets in the water mist adsorb dust particles in the flue gas as condensation nuclei, agglomerating into larger droplets that can be easily collected and processed by the demister. Through this process, the amount of solid dust particles in the final emitted flue gas is significantly reduced, effectively reducing the pollution of the atmosphere caused by the flue gas emissions.

[0038] In addition, this application can retain existing equipment such as heating furnace 1, preheater 7, and chimney 8, without the need for major dismantling and modification of existing waste heat recovery equipment, which facilitates the transformation of old equipment and systems in the industry.

[0039] The system includes a main pipeline 101, a first branch pipeline 102, and a second branch pipeline 103. The inlet of the main pipeline 101 is connected to the flue gas outlet section 12, and the outlet of the main pipeline 101 is connected to the inlet of the first branch pipeline 102 and the inlet of the second branch pipeline 103, respectively. The outlet of the first branch pipeline 102 is connected to the inlet of the high-temperature medium flow channel, and the outlet of the second branch pipeline 103 is connected to the flue gas inlet of the fuel heater 2. Preferably, the main pipeline 101 is equipped with a main valve 91, and the second branch pipeline 103 is equipped with a branch valve 92. By adjusting the opening of the main valve 91 and the branch valve 92, the flow rates of flue gas A and flue gas B can be controlled relatively accurately.

[0040] As a preferred embodiment of this application, the ratio of flue gas flow rate of the first branch 102 to the flue gas flow rate of the second branch 103 is 9:1 per unit time. This allows an appropriate amount of high-temperature flue gas to participate in the circulation of flue gas A throughout the system, satisfying the requirement to reduce exhaust gas temperature while also ensuring good combustion within the heating furnace 1.

[0041] The fuel heater 2 is equipped with a heating tube 21. The system includes a fuel pipeline 106. The inlet of the heating tube 21 is connected to an external fuel gas source, and the outlet of the heating tube 21 is connected to the burner 11 through the fuel pipeline 106. This allows the ambient temperature fuel gas to exchange heat with the high temperature flue gas A in the fuel heater 2 and be heated before being supplied to the burner 11 through the fuel pipeline 106. Preferably, the fuel heater 2 is a glass tube heat exchanger, and correspondingly, the heating tube 21 is a glass tube. In the fuel heater 2, the fuel gas flows through the tube side, and the flue gas A flows through the shell side, exchanging heat to heat the ambient temperature fuel gas.

[0042] The flue gas outlet of the fuel heater 2 is connected to the flue gas inlet of the cold flue gas air mixer 6. Along the flue gas flow direction, a first demister 3 and a flue gas fan 4 are sequentially installed between the flue gas outlet of the fuel heater 2 and the flue gas inlet of the cold flue gas air mixer 6. The wastewater outlet of the first demister 3 is connected to a sewage pipe network. Thus, after the flue gas A is cooled by heat exchange in the fuel heater 2, it first passes through the first demister 3 to remove the mist droplets (including droplets adsorbing solid dust particles) carried by the flue gas A. Then, the demisted flue gas A enters the cold flue gas air mixer 6 under the action of the flue gas fan 4. Preferably, the flue gas fan 4 is made of 316L material, and the first demister 3 is made of 316L material or polypropylene material, which can effectively prevent corrosion.

[0043] The flue gas inlet of the cold flue gas air mixer 6 is connected to the flue gas fan 4, the air inlet of the cold flue gas air mixer 6 is connected to the blower 5, and the outlet of the cold flue gas air mixer 6 is connected to the inlet of the low-temperature medium flow channel of the preheater 7. The cold flue gas air mixer 6 has a mixing chamber inside. Thus, under the action of the flue gas fan 4 and the blower 5, the relatively high-speed flowing flue gas A and air enter the mixing chamber for vigorous and thorough mixing. Then, the mixed gas flows from the cold flue gas air mixer 6 into the preheater 7 to exchange heat with the flue gas B. Preferably, the cold flue gas air mixer 6 is made of 316L material, which can effectively prevent corrosion; the blower 5 is made of carbon steel.

[0044] For preheater 7, a conventional preheater can be directly used, such as the one in the applicant's earlier patent application CN202320883276.3, which may include a high-temperature preheating module and a low-temperature preheating module. The only difference is that the gas entering the low-temperature medium channel of preheater 7 in this application is a mixture of "flue gas + air", rather than pure air. Accordingly, to avoid ambiguity, in the preheater 7 of this application, the heat exchange channel through which flue gas B flows is uniformly referred to as the high-temperature medium channel, and the heat exchange channel through which the mixed gas flows is uniformly referred to as the low-temperature medium channel. In this application, preferably, the high-temperature preheating module can be a plate type, a protruding point type, or a stud-welded plate type heat exchanger, and the low-temperature preheating module can be a glass plate type or a glass tube type heat exchanger.

[0045] The system includes an air inlet pipe 104 and an exhaust pipe 105. The inlet of the air inlet pipe 104 is connected to the outlet of the low-temperature medium flow channel, and the outlet of the air inlet pipe 104 is connected to the burner 11. The inlet of the exhaust pipe 105 is connected to the outlet of the high-temperature medium flow channel, and the outlet of the exhaust pipe 105 is connected to the chimney 8. In the flue gas flow direction, a second demister 71 and an induced draft fan 72 are sequentially installed in the exhaust pipe 105. The wastewater outlet of the second demister 71 is connected to the sewage network. Thus, after the mixed gas and flue gas B exchange heat, the mixed gas is sent to the burner 11. The flue gas B passes through the second demister 71 to remove the mist droplets (including droplets adsorbing solid dust particles) carried by the flue gas B. Then, the demistered flue gas B is sent into the chimney 8 for discharge under the action of the induced draft fan 72. This not only significantly reduces the exhaust gas temperature but also effectively reduces the water content in the discharged flue gas, which helps to eliminate white smoke from the flue gas. Preferably, the induced draft fan 72 is made of 316L material, and the second demister 71 is made of 316L material or polypropylene material, which can effectively prevent corrosion.

[0046] In addition, a smoke exhaust valve 93 can be installed in the smoke exhaust pipe 105. In the direction of smoke flow, the smoke exhaust valve 93 is located downstream of the induced draft fan 72, so as to facilitate the control of the smoke flow rate in the smoke exhaust pipe 105.

[0047] A drain pipe is installed at the bottom of the preheater 7, and the drain pipe is connected to the sewage network. Thus, during the heat exchange and cooling process of flue gas B in the preheater 7, most of the condensate collects at the bottom of the preheater 7 under gravity and is discharged to the sewage network through the drain pipe. Preferably, in this application, the sewage outlets of the first demister 3 and the second demister 71, as well as the drain pipe at the bottom of the preheater 7, can all be equipped with heat-resistant modified PVC drain pipe assemblies and gravity self-priming valves, enabling real-time drainage and completely resisting condensate dew point corrosion.

[0048] In this application, the heating furnace 1 and the chimney 8 can be independent devices or integrated devices. Since they are both prior art, this application will not elaborate on them. The burner 11 of the heating furnace 1 can also directly adopt prior art, and will not elaborate on it.

[0049] This application uses an integrated heating furnace 1 and chimney 8 as an example. The bottom of the chimney 8 is connected to the top of the smoke outlet section 12. An adjusting baffle 81 is installed on the side of the chimney 8 near the smoke outlet section 12 to regulate the connection between the chimney 8 and the smoke outlet section 12. In this application, the connection position of the exhaust pipe 105 to the chimney 8 is higher than the position of the adjusting baffle 81, allowing smoke to be exhausted using the proposed solution when the adjusting baffle 81 is fully closed. Alternatively, the proposed solution can be omitted, and conventional smoke exhaust can be performed by directly opening the adjusting baffle 81.

[0050] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A high-efficiency, energy-saving waste heat recovery system, characterized in that, The system includes a heating furnace (1), a fuel heater (2), a cold smoke air mixer (6), a preheater (7), and a chimney (8). In the direction of flue gas flow, the flue gas outlet section (12) of the heating furnace (1) is connected to the high-temperature medium flow channel of the preheater (7) and the flue gas inlet of the fuel heater (2), respectively. The flue gas outlet of the fuel heater (2) is connected to the cold smoke air mixer (6) and the low-temperature medium flow channel of the preheater (7) in sequence. The outlet of the low-temperature medium flow channel and the fuel gas outlet of the fuel heater (2) are both connected to the burner (11) of the heating furnace (1). The outlet of the high-temperature medium flow channel is connected to the chimney (8).

2. The high-efficiency energy-saving waste heat recovery system according to claim 1, characterized in that, The system includes a main pipeline (101), a first branch (102), and a second branch (103). The inlet of the main pipeline (101) is connected to the smoke outlet section (12), and the outlet of the main pipeline (101) is connected to the inlet of the first branch (102) and the inlet of the second branch (103), respectively. The outlet of the first branch (102) is connected to the inlet of the high-temperature medium flow channel, and the outlet of the second branch (103) is connected to the flue gas inlet of the fuel heater (2).

3. The high-efficiency energy-saving waste heat recovery system according to claim 2, characterized in that, Within a unit of time, the ratio of the flue gas flow rate of the first branch (102) to the flue gas flow rate of the second branch (103) is 9:

1.

4. The high-efficiency energy-saving waste heat recovery system according to claim 1, characterized in that, The fuel heater (2) is equipped with a heating pipe (21). The system includes a fuel pipeline (106). The inlet of the heating pipe (21) is connected to a fuel gas source, and the outlet of the heating pipe (21) is connected to the burner (11) through the fuel pipeline (106).

5. The high-efficiency energy-saving waste heat recovery system according to claim 1, characterized in that, The flue gas outlet of the fuel heater (2) is connected to the flue gas inlet of the cold smoke air mixer (6). Along the flue gas flow direction, a first demister (3) and a flue gas fan (4) are sequentially arranged between the flue gas outlet of the fuel heater (2) and the flue gas inlet of the cold smoke air mixer (6). The sewage outlet of the first demister (3) is connected to the sewage pipe network.

6. The high-efficiency energy-saving waste heat recovery system according to claim 5, characterized in that, The flue gas inlet of the cold smoke air mixer (6) is connected to the flue gas fan (4), the air inlet of the cold smoke air mixer (6) is connected to the blower (5), the outlet of the cold smoke air mixer (6) is connected to the inlet of the low temperature medium flow channel of the preheater (7), and the cold smoke air mixer (6) has a mixing chamber inside.

7. The high-efficiency energy-saving waste heat recovery system according to claim 1, characterized in that, The system includes an intake pipe (104), the inlet of which is connected to the outlet of a cryogenic medium flow channel, and the outlet of which is connected to a burner (11).

8. The high-efficiency energy-saving waste heat recovery system according to claim 1, characterized in that, The system includes a flue gas duct (105), the inlet of which is connected to the outlet of a high-temperature medium flow channel, and the outlet of which is connected to a chimney (8). In the direction of flue gas flow, a second demister (71) and an induced draft fan (72) are sequentially installed in the flue gas duct (105), and the sewage outlet of the second demister (71) is connected to a sewage pipe network.

9. A high-efficiency energy-saving waste heat recovery system according to claim 8, characterized in that, A smoke exhaust valve (93) is provided in the smoke exhaust pipe (105), and the smoke exhaust valve (93) is located downstream of the induced draft fan (72) in the direction of smoke flow.

10. The high-efficiency energy-saving waste heat recovery system according to claim 1, characterized in that, The bottom of the preheater (7) is provided with a drain pipe, which is connected to the sewage network.

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