System for improving thermal efficiency of large continuous reforming heating furnace

Abstract

The utility model discloses a system for improving the thermal efficiency of a large-scale continuous reforming heating furnace, and belongs to the technical field of continuous reforming devices. The outlet end of the heating furnace outputs high-temperature flue gas; after being subjected to heat exchange through the steam heat exchanger, the combustion gas is conveyed into the heating furnace; the air preheater is arranged on an outlet pipeline of the heating furnace, after cold air exchanges heat with high-temperature flue gas output by the heating furnace, heated air is conveyed to the heating furnace to serve as combustion-supporting air, and meanwhile the cooled flue gas is conveyed to a chimney to be discharged. Fuel gas is preheated through the steam heat exchanger, it is ensured that the fuel gas can be fully combusted in the heating furnace, energy loss and environmental pollution are reduced, high-temperature flue gas output by the heating furnace is used for conducting heat exchange on cold air, the temperature of combustion-supporting air is increased, the combustion efficiency is improved, the exhaust temperature of the flue gas is effectively reduced, and the environment is protected. And the maximum recycling of the flue gas heat is realized.

Description

Technical Field

[0001] This utility model belongs to the technical field of continuous reforming equipment, specifically relating to a system for improving the thermal efficiency of a large continuous reforming heating furnace. Background Technology

[0002] As a core energy-consuming device, the heating furnace of the continuous reforming unit has long been constrained by the high flue gas temperature (usually ≥140℃) and impurities in the fuel gas.

[0003] Traditional designs use natural or forced ventilation to recover waste heat from flue gas through waste heat boilers. However, because the fuel gas contains sulfur (H2S, HCl, etc.), the exhaust gas temperature is forced to be maintained above 150°C to avoid dew point corrosion in the low-temperature section of the air preheater, resulting in a thermal efficiency of less than 93%.

[0004] Furthermore, stringent environmental standards (such as GB 31570-2015) regarding NOx and CO2 emission reduction and acidic condensate discharge have exacerbated the contradiction between high flue gas temperature and low thermal efficiency. Utility Model Content

[0005] This invention addresses the aforementioned problems in the existing technology by proposing a system for improving the thermal efficiency of large continuous reforming furnaces.

[0006] This utility model can be achieved through the following technical solutions:

[0007] A system for improving the thermal efficiency of a large continuous reforming furnace includes:

[0008] The heating furnace outputs high-temperature flue gas from its outlet.

[0009] The combustion gas is heat-exchanged through the steam heat exchanger and then delivered to the heating furnace.

[0010] An air preheater is installed on the outlet pipeline of the heating furnace. After the cold air exchanges heat with the high-temperature flue gas output from the heating furnace, the heated air is delivered to the heating furnace as combustion air, while the cooled flue gas is delivered to the chimney 140 for discharge.

[0011] As a further improvement of this utility model, it also includes a fuel refiner, wherein the steam heat exchanger, the fuel refiner, and the heating furnace are connected in sequence, and the fuel refiner is used to remove hydrogen chloride and organochlorine compounds from the fuel gas.

[0012] As a further improvement of this utility model, the air preheater is internally configured with a multi-pass structure and has a high-temperature section, a medium-temperature section and a low-temperature section. High-temperature flue gas enters from the high-temperature section at the top of the air preheater and flows downward, while cold air enters from the low-temperature section and flows upward. During this process, the cold air and the high-temperature flue gas continuously exchange heat in each pass section and form a flue gas cascade recovery structure.

[0013] As a further improvement of this utility model, the air preheater has a cold flue gas outlet, where the low-temperature flue gas after multi-stage heat exchange forms acidic flue gas condensate.

[0014] As a further improvement of this utility model, the cold flue gas outlet is filled with a neutralizing agent 124, which neutralizes the acidic flue gas condensate.

[0015] As a further improvement of this utility model, the air preheater is provided with a demister at its cold flue gas outlet. The demister is used to remove condensed mist droplets in the cold flue gas. The cold flue gas after the condensed mist droplets are removed by the demister is discharged to the bottom of the chimney through the cold flue.

[0016] As a further improvement of this utility model, the inner wall of the cold flue from the cold flue gas outlet of the air preheater to the chimney is coated with an acid-resistant coating, and an insulation layer is provided on the outer wall of the cold flue.

[0017] As a further improvement of this utility model, the low-temperature section of the air preheater uses a nano-ceramic composite plate as a heat transfer element to transfer the heat of the flue gas to the combustion air.

[0018] As a further improvement of this utility model, the nano-ceramic composite plate forms a dense coating on the surface of the counting substrate by coating a special nano-ceramic coating on the surface of the metal substrate and curing it at high temperature.

[0019] As a further improvement of this utility model, the steam heat exchanger is used to heat fuel gas to 200-230°C.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. The fuel gas is preheated by a steam heat exchanger to ensure that the fuel gas can be fully burned in the heating furnace, reducing energy loss and environmental pollution. The high-temperature flue gas output from the heating furnace is used to exchange heat with cold air. This not only increases the temperature of the combustion air and improves the combustion efficiency, but also effectively reduces the emission temperature of the flue gas, achieving maximum recovery and utilization of flue gas heat.

[0022] 2. By optimizing the fluid path and temperature distribution inside the air preheater, rationally dividing the high-temperature, medium-temperature and low-temperature sections, and adopting a counter-current heat exchange method, efficient energy recovery and heat transfer are achieved, ensuring that heat can be recovered and utilized to the maximum extent, and improving the overall system thermal efficiency.

[0023] 3. By adding a fuel refiner between the steam heat exchanger and the heating furnace, impurities such as H2S and HCl are removed before the fuel gas enters the heating furnace, achieving source control. At the same time, since the steam heat exchanger heats the fuel gas to 200-230℃, it can ensure that the temperature of the fuel gas is higher than the crystallization point of ammonium salt throughout the process, thereby avoiding the precipitation of ammonium salt and solving the problem of ammonium chloride and ammonium sulfide precipitating at low temperatures or dead corners and clogging the heating furnace system's continuous light, flame arrestor and burner metal hose;

[0024] 4. Nano-ceramic composite plates are used as heat transfer elements in the low-temperature section of the air preheater. The high thermal conductivity and corrosion resistance of the nano-ceramic composite plates ensure that the heat of the flue gas can be efficiently transferred to the combustion air, thereby improving the overall thermal efficiency of the system and further solving the problem of dew point corrosion in the low-temperature section of the air preheater.

[0025] 5. Neutralizing agent 124 is filled into the cold flue gas outlet of the air preheater. By neutralizing the acidic flue gas condensate, the corrosion of the air preheater and its downstream equipment is effectively reduced, the service life of the equipment is extended, the maintenance cost is reduced, and the treated flue gas condensate can meet the direct discharge standard.

[0026] 6. Installing a demister at the cold flue gas outlet avoids the potential corrosion risk of condensed mist droplets to downstream equipment and pipelines, extends the service life of the equipment, and reduces maintenance costs. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the system for improving the thermal efficiency of a large continuous reforming furnace according to this utility model.

[0028] In the diagram, 100 is the heating furnace; 110 is the steam heat exchanger; 120 is the air preheater; 121 is the high-temperature section; 122 is the medium-temperature section; 123 is the low-temperature section; 124 is the neutralizing agent; 125 is the demister; 130 is the fuel refiner; and 140 is the chimney. Detailed Implementation

[0029] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings. The technical methods of the present invention will be further described, but the present invention is not limited to these embodiments.

[0030] like Figure 1As shown, this utility model provides a system for improving the thermal efficiency of a large continuous reforming furnace, comprising:

[0031] The heating furnace 100 outputs high-temperature flue gas from its outlet end;

[0032] The combustion gas is preheated to 200-230°C by the steam heat exchanger 110 before being delivered to the heating furnace 100. This not only improves the combustion efficiency but also reduces the incomplete combustion products caused by low-temperature combustion.

[0033] An air preheater 120 is installed on the outlet pipeline of the heating furnace 100. After the cold air exchanges heat with the high-temperature flue gas output from the heating furnace 100, the heated air is delivered to the heating furnace 100 as combustion air, while the cooled flue gas is delivered to the chimney 140 for discharge.

[0034] In other words, the fuel gas is first preheated by the steam heat exchanger 110 to ensure that the fuel gas can be fully burned in the heating furnace 100, reducing energy loss and environmental pollution. Then, the high-temperature flue gas output from the heating furnace 100 is used to exchange heat with the cold air. This not only increases the temperature of the combustion air and improves the combustion efficiency, but also effectively reduces the emission temperature of the flue gas, achieving maximum recovery and utilization of flue gas heat.

[0035] It should also be noted that, due to the presence of impurities such as H2S, NH3 and HCl in the fuel gas components, the reaction produces ammonium chloride and ammonium sulfide, which precipitate out as salt at low temperatures or in dead corners, clogging the heating furnace system's continuous lights, flame arrestors and burner metal hoses. Manual cleaning and unclogging not only affects the stable operation of the equipment, but also increases the workload and the consumption of sealing gaskets. Furthermore, disassembly and cleaning operations in a flammable and explosive gas environment pose safety risks and are prone to causing environmental pollution.

[0036] To solve this problem, a fuel refiner 130 is added between the steam heat exchanger 110 and the heating furnace 100. Before the fuel gas enters the heating furnace, the fuel refiner 130 removes the corresponding impurities, thus achieving source control.

[0037] Meanwhile, since the steam heat exchanger 110 heats the fuel gas to 200-230℃, it can ensure that the temperature of the fuel gas is higher than the crystallization point of ammonium salt throughout the process, thereby avoiding the precipitation of ammonium salt and solving the above-mentioned blockage problem.

[0038] Preferably, the air preheater 120 is configured with a multi-pass structure and has a high-temperature section 121, a medium-temperature section 122 and a low-temperature section 123. High-temperature flue gas enters from the high-temperature section 121 at the top of the air preheater 120 and flows downward, while cold air enters from the low-temperature section 123 and flows upward. During this process, the cold air and the high-temperature flue gas continuously exchange heat in each tube pass and form a flue gas cascade recovery structure.

[0039] This design optimizes the fluid path and temperature distribution inside the air preheater 120, rationally divides the high-temperature, medium-temperature, and low-temperature sections 123, and adopts a counter-current heat exchange method to achieve efficient energy recovery and heat transfer, ensuring that heat can be recovered and utilized to the maximum extent and improving the overall system thermal efficiency.

[0040] Preferably, the low-temperature section 123 of the air preheater 120 uses a nano-ceramic composite plate as a heat transfer element to transfer the heat of the flue gas to the combustion air. The nano-ceramic composite plate is formed by coating a special nano-ceramic coating on the surface of a metal substrate (carbon steel and / or ND steel) and curing it at high temperature. The coating mainly consists of aluminum oxide and silicon carbide, and its acid and alkali corrosion resistance is similar to that of glass. The overall thermal conductivity of the nano-ceramic composite plate is ≥30W / m·K, which is similar to that of ordinary carbon steel, so it has excellent heat transfer performance.

[0041] In other words, the high thermal conductivity and corrosion resistance of the nano-ceramic composite plate ensure that the heat from the flue gas can be efficiently transferred to the combustion air, thereby improving the overall thermal efficiency of the system and further solving the problem of dew point corrosion in the low-temperature section 123 of the air preheater.

[0042] In addition, the thickness of the nano-ceramic composite plate substrate is 1.5 to 2 mm. Due to the heat transfer characteristics of plate heat exchangers, the air preheater 120 made from it is smaller in volume and weight than cast iron and glass types under the same heat transfer capacity.

[0043] Preferably, the air preheater 120 has a cold flue gas outlet. After the high-temperature flue gas has undergone multiple heat exchange and cooling processes, the water vapor and other condensable gases (such as sulfur dioxide, nitrogen oxides, etc.) in it will condense into liquid at a lower temperature, forming acidic condensate. This condensate contains strong acid components such as sulfuric acid and nitric acid, which are highly corrosive.

[0044] To solve this problem, neutralizing agent 124 is filled in the cold flue gas outlet. When neutralizing agent 124 comes into contact with acidic flue gas condensate, a neutralization reaction occurs, generating relatively stable salts and water, thereby eliminating or significantly reducing acidic components and avoiding the risk of corrosion to downstream equipment.

[0045] By neutralizing the acidic flue gas condensate, corrosion of the air preheater 120 and its downstream equipment is effectively reduced, extending the service life of the equipment, reducing maintenance costs, and the treated flue gas condensate can meet the direct discharge standards.

[0046] In addition, the air preheater 120 is equipped with a demister 125 at its cold flue gas outlet. The demister 125 is used to remove condensed mist droplets in the cold flue gas. After the condensed mist droplets are removed by the demister 125, the cold flue gas is discharged to the bottom of the chimney 140 through the cold flue.

[0047] Specifically, after the air preheater 120 completes the multi-stage heat exchange process and the acidic flue gas condensate is treated by the neutralizing agent 124, the cold flue gas may still contain tiny condensate droplets. If these droplets are directly emitted, they will not only affect the emission quality but may also cause corrosion problems in downstream equipment or pipelines. Therefore, a dedicated demister 125 is installed at the cold flue gas outlet to solve this problem, avoiding the potential corrosion risk of condensate droplets to downstream equipment and pipelines, extending the service life of the equipment, and reducing maintenance costs.

[0048] Preferably, the inner wall of the cold flue gas outlet of the air preheater 120 to the chimney 140 is coated with an acid-resistant coating, and the outer wall of the cold flue gas outlet is provided with an insulation layer.

[0049] Specifically, since the cold flue gas after being treated by the air preheater 120 may contain acidic components such as sulfuric acid and nitric acid, these components will form condensate under low temperature conditions, causing severe corrosion to metal pipes. By applying an acid-resistant coating to the inner wall of the cold flue, the corrosion of acidic substances can be effectively resisted, protecting the pipes from damage.

[0050] Installing an insulation layer on the outer wall of the cold flue can effectively slow down the loss of heat to the outside environment, maintain the temperature of the cold flue gas, prevent further condensation, and thus reduce the amount of acidic condensate generated.

[0051] In addition, when the flue gas induced draft fan is located downstream of the air preheater 120, when the flue gas temperature is less than 100℃, the casing and impeller of the flue gas induced draft fan shall be treated with anti-corrosion coating.

[0052] In practical applications, the modified flue gas temperature and thermal efficiency are described below:

[0053] 1. The three-in-one heating furnace 100, after modification, the exhaust gas temperature decreased by 40℃, the thermal efficiency increased by an average of 2.5%, and the average thermal efficiency was 95.3%.

[0054] 2. The combined heating furnace 100, after modification, the exhaust gas temperature decreased by 32℃, the thermal efficiency increased by an average of 2.3%, and the average thermal efficiency was 95.02%. When the air inlet temperature was not within the specified range during calibration, linear conversion was performed based on the air inlet temperature deviating positively by 10℃ corresponding to the flue gas outlet temperature deviating positively by 7.5℃.

[0055] 3. After the modification of the F2106 heating furnace 100, the exhaust gas temperature decreased by 43℃, the thermal efficiency increased by an average of 2.6%, and the average thermal efficiency was 95.8%.

[0056] The technical means disclosed in this utility model are not limited to those described above, but also include technical solutions composed of any combination of the above technical features. The above are specific embodiments of this utility model. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of this utility model, and these improvements and modifications are also considered within the scope of protection of this utility model.

[0057] It should be noted that all directional indicators (such as up, down, left, right, front, back, etc.) in this utility model embodiment are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0058] Furthermore, in this utility model, the use of terms such as "first," "second," and "a" is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this utility model, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified. The terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two elements or the interaction between two elements, unless otherwise explicitly specified. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0059] The technical solutions of the various embodiments of this utility model can be combined with each other, but only if they can be implemented by those skilled in the art. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the protection scope claimed by this utility model.

[0060] The specific embodiments described herein are merely illustrative examples illustrating the spirit of this utility model. Those skilled in the art to which this utility model pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of this utility model or exceeding the scope defined by the appended claims.

Claims

1. A system for improving the thermal efficiency of a large continuous reformer heating furnace, characterized by, include: The heating furnace outputs high-temperature flue gas from its outlet. The combustion gas is heat-exchanged through the steam heat exchanger and then delivered to the heating furnace. An air preheater is installed on the outlet pipeline of the heating furnace. After the cold air exchanges heat with the high-temperature flue gas output from the heating furnace, the heated air is delivered to the heating furnace as combustion air, while the cooled flue gas is delivered to the chimney for discharge.

2. The system for improving the thermal efficiency of a large continuous reforming furnace according to claim 1, characterized in that, It also includes a fuel refiner, wherein the steam heat exchanger, the fuel refiner, and the heating furnace are connected in sequence, and the fuel refiner is used to remove hydrogen chloride and organochlorine compounds from the fuel gas.

3. The system for improving thermal efficiency of a large continuous reforming heating furnace according to claim 1, characterized in that, The air preheater is internally configured with a multi-pass structure and has a high-temperature section, a medium-temperature section and a low-temperature section. High-temperature flue gas enters from the high-temperature section at the top of the air preheater and flows downward, while cold air enters from the low-temperature section and flows upward. During this process, the cold air and high-temperature flue gas continuously exchange heat in each pass section and form a flue gas cascade recovery structure.

4. The system for improving thermal efficiency of a large continuous reforming heating furnace according to claim 1, characterized in that, The air preheater has a cold flue gas outlet, where the low-temperature flue gas, after undergoing multi-stage heat exchange, forms acidic flue gas condensate.

5. The system for improving thermal efficiency of a large continuous reforming heating furnace according to claim 4, characterized in that, The cold flue gas outlet is filled with a neutralizing agent, which neutralizes the acidic flue gas condensate.

6. The system for improving thermal efficiency of a large continuous reforming heating furnace according to claim 4, characterized in that, The air preheater is equipped with a demister at its cold flue gas outlet. The demister is used to remove condensed mist droplets from the cold flue gas. The cold flue gas after the condensed mist droplets are removed by the demister is discharged to the bottom of the chimney through the cold flue.

7. The system for improving thermal efficiency of a large continuous reforming heating furnace according to claim 1, characterized in that, The inner wall of the cold flue from the cold flue gas outlet of the air preheater to the chimney is coated with an acid-resistant coating, and the outer wall of the cold flue is provided with an insulation layer.

8. The system for improving thermal efficiency of a large continuous reforming heating furnace according to claim 2, characterized in that, The low-temperature section of the air preheater uses a nano-ceramic composite plate as a heat transfer element to transfer heat from the flue gas to the combustion air.

9. The system for improving thermal efficiency of a large continuous reforming heating furnace according to claim 8, characterized in that, The nano-ceramic composite plate forms a dense coating on the surface of a counting substrate by coating a special nano-ceramic coating onto the surface of a metal substrate and curing it at high temperature.

10. The system for improving thermal efficiency of a large continuous reforming heating furnace according to claim 1, characterized in that, The steam heat exchanger is used to heat the fuel gas to 200-230°C.

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