Salt-containing wastewater incineration device

Abstract

The utility model relates to a kind of salt-containing wastewater incinerator, the device includes vertical incinerator and the membrane wall waste heat boiler connected with it, and incinerator top is equipped with low-nitrogen combustor and wastewater lance, inside is divided into combustion chamber and cooling chamber from top to bottom, combustion chamber ensures that flue gas stays above 1100 ℃ for not less than 2 seconds, organic matter is completely decomposed, cooling chamber upper portion is equipped with air distribution ring, low-temperature flue gas is introduced after system rear end, so that high-temperature flue gas is rapidly reduced to about 600 ℃, melt sodium salt is condensed to solid particles, the large cavity passage of membrane wall boiler further cools flue gas and makes solid salt sedimentation, and incinerator and membrane wall bottom are jointly connected with boat-shaped ash bucket, and collected sodium salt is discharged after cooling by water-cooled screw conveyor, and purified flue gas flows through subsequent heating surface to recover waste heat, the utility model effectively solves the problem of sodium salt blockage and corrosion, and realizes long-period stable operation of salt-containing wastewater treatment.

Description

Technical Field

[0001] This utility model relates to the field of saline wastewater incineration and waste heat recovery in the chemical industry, specifically to a saline wastewater incineration device. Background Technology

[0002] Terephthalic acid is a crucial basic raw material in the modern petrochemical industry. Its downstream products are widely used in chemical fibers, bottle chips, films and other fields, with huge market demand. However, the production process of terephthalic acid generates high-concentration organic wastewater with complex composition and difficult treatment. This wastewater usually contains a large amount of inorganic salts such as sodium acetate and sodium bromide, metal catalysts and aromatic organic compounds, etc. If not treated properly, it will cause serious harm to the environment.

[0003] Currently, for this type of high-concentration, high-salt organic wastewater, incineration is considered one of the most effective terminal treatment technologies because it can completely decompose organic matter and achieve harmlessness and significant volume reduction of wastewater. Its basic principle is to oxidize and decompose the organic matter in the wastewater into carbon dioxide and water at high temperature, while inorganic salts form slag or particulate matter and are separated from the flue gas.

[0004] However, the saline wastewater incineration technology has always faced a severe technical bottleneck in practical industrial applications: the problem of sodium salt erosion and clogging. The sodium salts in the wastewater have a low melting point. In the high-temperature zone of the incinerator, these salts melt into a liquid state. When the high-temperature flue gas enters the subsequent waste heat boiler system, the flue gas temperature gradually decreases, and the molten sodium salts will adhere to and deposit on the surface of the heat exchange tubes in a viscous liquid or semi-molten state.

[0005] This deposition can lead to a series of adverse consequences:

[0006] Firstly, the firmly adhered salt scale greatly reduces heat exchange efficiency and affects the waste heat recovery effect;

[0007] Secondly, sediment will continue to accumulate, eventually blocking the flue gas passage, causing a sharp increase in system resistance and preventing normal operation;

[0008] Third, molten salts can cause severe corrosion to refractory materials and metal heating surfaces, shortening equipment lifespan.

[0009] To resolve the blockage, the unit must be shut down frequently for manual coke removal, which not only increases maintenance costs but also prevents the entire production system from achieving long-term, continuous, and stable operation, severely hindering the promotion and application of this technology.

[0010] Therefore, there is an urgent need in this field for an innovative design scheme for saline wastewater incineration devices that can effectively solve the problem of sodium salt adhesion and blockage on subsequent heating surfaces, and ensure the continuity and stability of device operation. Utility Model Content

[0011] The purpose of this invention is to overcome the core technical challenges faced in the incineration treatment of saline wastewater in the existing terephthalic acid and other chemical industries, and to provide a reasonably designed, stable and efficient saline wastewater incineration device. It can ensure that sodium salts complete the transformation from liquid to solid before entering the easily clogged convection heating surface and are effectively separated from the flue gas, thereby fundamentally solving the problems of sodium salt adhesion, clogging and corrosion.

[0012] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0013] A saline wastewater incineration device integrates a vertical incinerator and a membrane wall waste heat boiler to form a synergistic treatment system.

[0014] The vertical incinerator is equipped with a burner and a wastewater spray gun at the top. The burner is preferably a low-NOx burner, which adopts a diffusion combustion mode and effectively suppresses the generation of thermal nitrogen oxides through staged air distribution technology. The wastewater spray gun adopts a dual-fluid atomization form to fully atomize the high-salt wastewater and spray it into the furnace to ensure that it is fully mixed with the high-temperature flue gas and combusted efficiently.

[0015] The incinerator furnace is divided into a combustion chamber and a cooling chamber from top to bottom. The combustion chamber is an insulated structure, and its design height ensures that the flue gas stays in the temperature range of up to 1100°C for no less than 2 seconds. This can completely decompose the organic pollutants in the wastewater. In the key section below the combustion chamber and at the beginning of the cooling chamber, at least one air distribution ring is arranged around the furnace wall. The air distribution ring is connected to the rear of the system through an air duct and is used to circulate and draw back the clean flue gas with a lower temperature. The gas is then evenly and forcibly injected into the furnace through multiple openings on the air distribution ring.

[0016] The high-temperature flue gas and a large amount of low-temperature flue gas from the air distribution ring undergo intense and thorough mixing and heat exchange in the cooling chamber, allowing the flue gas temperature to rapidly drop from over 1100°C to around 600°C. This rapid cooling process causes the sodium salt components in the flue gas, which exist in the form of aerosols or molten droplets, to instantly lose their fluidity, begin to condense, and form tiny solid particles.

[0017] The membrane wall waste heat boiler is directly connected to the outlet of the incinerator cooling chamber. Its radiation cooling section consists of a large cross-section, large cavity structure surrounded by membrane water-cooled walls. After being rapidly cooled, the flue gas enters this large cavity, where the flow rate decreases and the residence time is extended. During the process of radiation and convection heat exchange with the membrane wall, the temperature continues to drop evenly. This ensures that the sodium salt particles are fully cooled and completely solidified, turning into dry, loose solid powder. The solid sodium salt settles naturally under the action of gravity.

[0018] The bottom of the incinerator's cooling chamber is connected to the bottom of the large cavity of the membrane wall boiler via a unified, large boat-shaped ash hopper. This ash hopper adopts an inverted frustum-shaped design that is wider at the top and narrower at the bottom, with a large inclination angle on its inner wall. This structure greatly avoids ash accumulation and bridging on the ash hopper wall, ensuring that solid sodium salt can smoothly slide to the bottom of the ash hopper. The bottom outlet of the boat-shaped ash hopper is sealed to a water-cooled screw conveyor. The water-cooled screw conveyor has a cooling jacket on its outer shell and is circulated with cooling water. While conveying the collected sodium salt particles, it can effectively cool them, preventing the high-temperature salt particles from remelting at the outlet or damaging subsequent conveying equipment. Finally, the cooled sodium salt is continuously and stably discharged from the system.

[0019] The flue gas, cooled by the membrane wall boiler and having most of the solid sodium salt removed, is no longer sticky. It then flows sequentially through a group of convective heating surfaces arranged in the subsequent flue, typically including a superheater, evaporator, and economizer, to exchange heat efficiently with the working fluid and fully recover waste heat to generate steam. Since the sodium salt has been removed in the front section, these convective heating surfaces can effectively avoid clogging and corrosion problems.

[0020] The waste heat boiler system also includes a steam drum, which is connected to the membrane wall and evaporator via downcomers and risers, forming a complete natural circulation loop.

[0021] Beneficial effects:

[0022] In summary, this invention effectively solves the problems of clogging and corrosion caused by sodium salts during the incineration of saline wastewater. Through the integrated design of a vertical incinerator and a membrane-wall waste heat boiler, it achieves high-temperature combustion and rapid cooling, allowing sodium salts to transform from liquid to solid and be effectively separated before entering the convective heating surface. The device employs a low-NOx burner and staged air distribution technology to suppress the generation of nitrogen oxides. The introduction of low-temperature flue gas through the air distribution ring achieves a rapid cooling of the flue gas, causing the sodium salt particles to solidify instantly. The large ship-shaped ash hopper design avoids ash accumulation and bridging, while the water-cooled screw conveyor prevents the salt particles from remelting, ensuring continuous and stable ash discharge. Since the sodium salts are removed in the early stages, the subsequent convective heating surface effectively avoids clogging and corrosion problems, ensuring the stability and efficiency of the device's operation. Simultaneously, it fully recovers waste heat and thoroughly decomposes pollutants. Attached Figure Description

[0023] Figure 1 This is a schematic diagram showing the connection of a saline wastewater incineration device and method.

[0024] In the diagram, 1. Burner, 2. Wastewater spray gun, 3. Combustion chamber, 4. Air distribution ring, 5. Cooling chamber, 6. Ash hopper, 7. Water-cooled screw conveyor, 8. Membrane wall, 9. Steam drum, 10. Superheater, 11. Evaporator, 12. Economizer. Detailed Implementation

[0025] To enhance understanding of this utility model, the present utility model will be further described in detail below with reference to the embodiments and accompanying drawings. These embodiments are only used to explain the present utility model and do not constitute a limitation on the scope of protection of the present utility model.

[0026] 1. Burner, 2. Wastewater spray gun, 3. Combustion chamber, 4. Air distribution ring, 5. Cooling chamber, 6. Ash hopper, 7. Water-cooled screw conveyor, 8. Membrane wall, 9. Steam drum, 10. Superheater, 11. Evaporator, 12. Economizer.

[0027] like Figure 1 As shown, the present invention provides a saline wastewater incineration device, which is mainly composed of two parts: a vertical incinerator and a membrane wall waste heat boiler.

[0028] The vertical incinerator has a steel outer shell and a high-performance refractory lining to form an insulated furnace. A low-NOx burner 1 is installed at the center of the furnace top. The burner 1 can be a commercially available low-NOx model suitable for fuel gas. Through staged air distribution and diffusion combustion technology, it controls the flame center temperature within a reasonable range, effectively suppressing the formation of thermal NOx. On one side of the burner 1, there is one or more wastewater spray guns 2. The spray gun is a dual-fluid atomizing type, which uses high-pressure steam as the atomizing medium to fully atomize the PTA saline wastewater from the wastewater supply pump and spray it into the furnace as tiny droplets.

[0029] The incinerator furnace is divided into a combustion chamber 3 and a cooling chamber 5 from top to bottom. The design volume of the combustion chamber 3 ensures that the residence time of the flue gas in the high-temperature zone of ≥1100℃ is strictly guaranteed to be more than 2 seconds, which is the key to the complete decomposition of organic pollutants. In the transition section between the bottom of the combustion chamber 3 and the top of the cooling chamber 5, an annular air distribution ring 4 is embedded around the furnace wall. The air distribution ring has a cavity inside and several evenly distributed injection holes on the side facing the center of the furnace. The air distribution ring 4 is connected to the rear end of the system through an exhaust pipe, and the low-temperature clean flue gas with the temperature reduced to about 200℃ is forcibly introduced into the air distribution ring 4 by a circulating fan.

[0030] When the high-temperature flue gas descends to the position of the air distribution ring 4, it mixes and exchanges heat intensely with a large amount of low-temperature flue gas injected at high speed from the small holes on the ring. The temperature of the mixed flue gas is rapidly and uniformly reduced to about 600°C. This temperature is lower than the melting point of the sodium salt mixture, causing the molten sodium salt carried in the flue gas to condense instantly and begin to form solid small particles.

[0031] The rapidly cooled flue gas then enters the large cavity radiant cooling chamber enclosed by the membrane wall 8. The membrane wall 8 is made of multiple parallel finned tubes welded together. Boiler water from the steam drum 9 flows inside the tubes, absorbing heat from the flue gas to generate some steam. This large cavity design significantly reduces the flue gas velocity and prolongs the flue gas residence time, ensuring that the sodium salt particles have enough time to further cool and completely solidify into dry powder. The solid sodium salt continues to settle under the action of gravity.

[0032] The bottom of the cooling chamber 5 of the incinerator and the bottom of the large cavity of the membrane wall 8 are connected to a boat-shaped ash hopper 6. The ash hopper is welded from steel plates and its cross-section is an inverted trapezoid or inverted isosceles triangle boat shape with a wider top and a narrower bottom. The angle between the four walls and the horizontal plane is greater than 60°. This large-angle design ensures that the ash hopper wall is smooth and does not accumulate ash. Solid sodium salt can smoothly slide down to the narrow outlet at the bottom of the ash hopper by its own gravity.

[0033] The bottom outlet of ash hopper 6 is flange-sealed to a water-cooled screw conveyor 7. The screw blade shaft of the conveyor rotates inside a housing with a cooling water jacket. The jacket is filled with industrial circulating cooling water. After the high-temperature sodium salt that settles falls into the conveyor, it is fully cooled while being slowly transported outward. Finally, it is continuously and stably discharged from the device at a low temperature of less than 100°C and enters the slag storage bin.

[0034] After being cooled and dusted by the membrane wall 8, the flue gas temperature drops to below about 500°C, and most of the solid sodium salts have been removed, thus solving the adhesion problem. Subsequently, the flue gas flows laterally across the tube bundles of the superheater 10, evaporator 11, and economizer 12. These convective heating surfaces are all composed of finned serpentine tubes. The working fluid flows inside the tubes, and the flue gas flows outside the tubes, efficiently recovering waste heat. The generated steam can be used by the production unit.

[0035] The steam drum 9 supplies water to the membrane wall 8 and evaporator 11 through the downcomer. The steam-water mixture generated in the membrane wall 8 and evaporator 11 returns to the steam drum through the riser for steam-water separation, forming a natural circulation loop. Saturated steam is drawn out from the top of the steam drum and enters the superheater 10 to be heated into superheated steam.

[0036] The entire unit is operated automatically by a distributed control system. By monitoring key parameters such as combustion chamber temperature, flue gas oxygen content, boiler water level, and steam pressure, the system automatically adjusts the fuel quantity, wastewater feed rate, combustion air volume, and circulating flue gas volume to ensure that the system always operates safely, stably, and continuously under optimal conditions.

[0037] Implementation example:

[0038] A chemical plant uses the device of this invention to treat high-concentration saline organic wastewater generated during the production of terephthalic acid. This wastewater contains inorganic salts such as sodium acetate and sodium bromide, as well as various organic pollutants.

[0039] The factory operators first start the device and ignite the low-NOx burner 1 located at the top of the incinerator through the control system. The burner 1 uses staged air distribution technology to effectively control the flame shape and suppress the generation of nitrogen oxides. After the furnace temperature rises to the predetermined level, the operators start the wastewater supply pump and high-pressure steam system. The saline wastewater is finely atomized and sprayed into the combustion chamber 3 through the dual-fluid wastewater spray gun 2 arranged on the top of the furnace.

[0040] The atomized wastewater droplets are fully mixed with the flame in the high-temperature combustion chamber 3 and burn rapidly. Organic pollutants are completely decomposed into carbon dioxide and water. The high-temperature flue gas generated by combustion has a temperature exceeding 1100°C. Its designed residence time in the combustion chamber 3 exceeds two seconds to ensure complete decomposition. Subsequently, the high-temperature flue gas flows downward into the cooling chamber 5.

[0041] In the top area of ​​cooling chamber 5, a circulating fan transports the purified low-temperature flue gas at a temperature of about 200°C from the back end of the system to the air distribution ring 4 through a pipeline. The low-temperature flue gas is evenly and rapidly injected into the furnace from multiple openings in the air distribution ring 4, where it is violently mixed with the descending high-temperature flue gas. The mixing process causes the flue gas temperature to drop sharply to about 600°C in a very short time.

[0042] This rapid cooling process causes the molten sodium salt in the flue gas to condense instantly and transform into tiny solid particles. The flue gas carrying the solid sodium salt particles then enters the large cavity radiative cooling channel surrounded by the membrane wall 8. The flue gas flow rate decreases and exchanges heat with the water inside the membrane wall 8 to further cool down, ensuring that the sodium salt particles are completely solidified into dry powder.

[0043] Solid sodium salt particles continue to settle under gravity and eventually collect in a shared boat-shaped ash hopper 6 located at the bottom of the incinerator and the membrane wall boiler 8. The ash hopper 6 has a steeply inclined wall surface that effectively prevents ash accumulation and ensures that the sodium salt powder slides smoothly to the bottom outlet. The water-cooled screw conveyor 7 connected to the bottom of the ash hopper 6 continuously transports the collected high-temperature sodium salt outward. The circulating cooling water in its cooling jacket reduces the temperature of the sodium salt to below a safe range and eventually discharges it from the system.

[0044] The clean flue gas, after being cooled and having sodium salt removed, then flows sequentially through convection heating surfaces such as heat exchanger 10, evaporator 11, and economizer 12, where it exchanges heat efficiently with the working fluid inside the tubes to recover waste heat and produce steam. Since the sodium salt has been effectively removed in the early stage, these heat exchange devices can avoid clogging and corrosion problems, and the entire system achieves long-term stable and continuous operation of saline wastewater treatment.

[0045] 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 saline wastewater incineration device, characterized in that, include: A vertically mounted incinerator, and a membrane-walled waste heat boiler connected to the incinerator; The incinerator is equipped with a burner and a wastewater spray gun at the top, and its interior consists of a combustion chamber and a cooling chamber from top to bottom. The connection section between the combustion chamber and the cooling chamber is equipped with an air distribution ring, which is connected to the low-temperature flue gas outlet at the rear of the system through a pipe, so as to introduce the purified and cooled low-temperature flue gas into the cooling chamber. The membrane wall waste heat boiler includes a large cavity cooling channel enclosed by a membrane wall; A boat-shaped ash hopper is connected below the cooling chamber of the incinerator and below the large cavity cooling channel to collect the settled solid sodium salt. The bottom outlet of the boat-shaped ash hopper is connected to a water-cooled screw conveyor to transport sodium salt out of the device.

2. The saline wastewater incineration device according to claim 1, characterized in that, The burner is a low-NOx burner that uses a diffusion combustion method and is located at the top center of the incinerator.

3. The saline wastewater incineration device according to claim 1, characterized in that, The combustion chamber is an insulated furnace, and its structural dimensions are configured to allow the flue gas to remain in the temperature range above 1100°C for no less than 2 seconds.

4. The saline wastewater incineration device according to claim 1, characterized in that, The air distribution ring is configured to fully and evenly mix the introduced low-temperature flue gas with the high-temperature flue gas from the combustion chamber, so that the temperature of the mixed flue gas drops to about 600°C.

5. A saline wastewater incineration device according to claim 1 or 4, characterized in that, Low-temperature flue gas is introduced through the air distribution ring, which rapidly reduces the temperature of the high-temperature flue gas in the cooling chamber to below the melting point of sodium salt, causing the liquid sodium salt in the flue gas to transform into solid particles.

6. The saline wastewater incineration device according to claim 1, characterized in that, The boat-shaped ash hopper has a structure that is wider at the top and narrower at the bottom, and its walls have a large inclination angle to facilitate the smooth sliding of solid sodium salt to the bottom outlet.

7. A saline wastewater incineration device according to claim 1 or 6, characterized in that, The water-cooled screw conveyor has a cooling jacket, which can cool the high-temperature sodium salt during the conveying process.

8. The saline wastewater incineration device according to claim 1, characterized in that, The membrane wall waste heat boiler also includes a convective heating surface disposed in the flue after the large cavity cooling channel. The convective heating surface includes, in sequence along the flue gas flow direction, a superheater, an evaporator, and an economizer.

9. The saline wastewater incineration device according to claim 1, characterized in that, The device also includes a steam drum, which is connected to the membrane wall and the evaporator to form a natural circulation loop.

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