A method for synergistic treatment of waste gas purification and heat recovery in waste mineral oil regeneration process

Abstract

The application discloses a waste gas purification and heat recovery synergic treatment method in a waste mineral oil regeneration process, and belongs to the technical field of recycling and green production. High-temperature hydrocarbon-containing waste gas is introduced into the shell side of a catalytic heat exchanger, and waste mineral oil to be treated is introduced into the tube side. The outer wall of the tube side is coated with a two-site mesoporous catalytic coating containing first active sites and second active sites. The light components in the waste gas undergo exothermic oxidation reactions at the first active sites, and the heavy gas aerosols absorb heat and products at the second active sites to undergo reforming reactions, so that a self-limiting temperature micro-layer is formed on the outer wall surface through thermodynamic coupling. The phase change vaporization of the light components generates thermal acoustic oscillation to physically detach the attachments on the outer wall. Meanwhile, the feed flow rate is dynamically adjusted based on the oil temperature change rate at the outlet of the tube side. The application blocks chemical cross-linking and coking, solves the contradiction between heat exchange cold traps and anti-coking, and realizes efficient synergy of deep waste gas purification and in-situ recovery of high-grade heat energy.

Description

Technical Field

[0001] This invention belongs to the field of recycling and green production technology, and in particular relates to a method for the synergistic treatment of waste gas purification and heat recovery in the process of waste mineral oil regeneration. Background Technology

[0002] Waste mineral oil generates a large amount of waste gas during regeneration processes such as distillation and cracking. This waste gas is not only at a high temperature, usually between 300°C and 450°C, but also rich in high concentrations of volatile organic compounds and heavy asphaltene aerosols. In order to balance environmental protection and energy conservation, industry urgently needs to carry out in-depth purification and high-grade heat recovery of this type of waste gas.

[0003] Currently, the treatment of waste mineral oil regeneration waste gas mostly adopts a series process of cooling and heat exchange first, followed by end-of-pipe purification. In actual operation, the waste gas first enters the heat exchanger to exchange heat with the cold medium. However, the tube wall of the heat exchanger is very prone to coking and scaling, which causes the thermal resistance of the equipment to increase sharply in a short period of time and the heat transfer efficiency to drop significantly. Ultimately, this forces the production line to frequently stop for physical or chemical cleaning, which restricts the continuity of production.

[0004] Those skilled in the art generally attribute the aforementioned coking phenomenon to a thermodynamic physical condensation process. Based on this understanding, existing improvement schemes mainly focus on the fluid dynamics and macroscopic thermodynamics levels. For example, increasing the operating temperature of the heat exchanger tube wall above the dew point of heavy oil can prevent droplet precipitation; or significantly increasing the flow rate of the exhaust gas can be used to utilize fluid shear force to peel off the droplets adhering to the tube wall. While these conventional methods slow down the scaling rate to some extent, they introduce new technical contradictions: increasing the tube wall temperature means that a large amount of low- and medium-grade heat cannot be effectively recovered, resulting in an extremely low overall system heat recovery rate; while increasing the flow rate increases the system's power consumption and cannot fundamentally prevent the adhesion of substances within the microscopic fluid viscous sublayer.

[0005] In fact, the core reason for coking on the heat exchanger tube wall is not simply physical condensation, but a free radical chain polymerization reaction that occurs within the heat transfer boundary layer. Waste mineral oil regeneration waste gas carries a large number of unsaturated hydrocarbons and free hydrocarbon radicals. When these high-temperature gases come into contact with the lower-temperature heat exchanger tube wall, transition metal elements such as iron, nickel, and chromium in the tube wall matrix act as catalysts. Under the extreme temperature gradient of the heat transfer boundary layer, the trace amounts of condensed unsaturated hydrocarbons undergo strong free radical cross-linking and dehydrogenation condensation reactions under the induction of the transition metals, synthesizing irreversible polymer coke with a three-dimensional network structure in situ on the metal lattice surface.

[0006] Furthermore, to achieve efficient heat transfer, the heat exchanger tube wall must act as a cold trap to maintain a sufficient heat transfer temperature difference; however, to prevent the dehydrogenation condensation reaction of free radicals and the interfacial anchoring of asphaltene, the tube wall needs to be in an inactive or relatively high-temperature state. Existing series processing technologies and their conventional improvement methods cannot simultaneously expand the gas-solid heat transfer temperature difference while breaking the reaction activation energy conditions within the viscous sublayer of the fluid in the micro-region of the heat exchange interface.

[0007] Therefore, there is an urgent need in this field for a novel method for the synergistic treatment of waste gas purification and heat recovery, which can block the free radical condensation reaction induced by transition metals at the level of chemical reaction kinetics, and achieve thermodynamic adaptive coupling of waste gas purification and heat recovery at the microscale, thereby completely resolving the technical contradiction between high recovery rate and high coking rate. Summary of the Invention

[0008] This invention overcomes the shortcomings of the prior art and provides a method for the synergistic treatment of waste gas purification and heat recovery in the process of waste mineral oil regeneration.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is: a method for the synergistic treatment of waste gas purification and heat recovery in the process of waste mineral oil regeneration, comprising the following steps:

[0010] S1. High-temperature hydrocarbon-containing waste gas containing unsaturated hydrocarbons and heavy aerosols is introduced into the shell side of the catalytic heat exchanger, while the waste mineral oil to be treated is introduced into the tube side of the catalytic heat exchanger.

[0011] S2. The high-temperature hydrocarbon-containing waste gas is brought into contact with the outer wall of the tube. The outer wall is coated with a dual-site mesoporous catalytic coating containing a first active site and a second active site. The light components in the high-temperature hydrocarbon-containing waste gas undergo an exothermic oxidation reaction at the first active site, and the heavy aerosol absorbs the heat and products of the exothermic oxidation reaction at the second active site to undergo a reforming reaction, thereby constructing a self-limiting microlayer on the surface of the outer wall.

[0012] S3. The heat from the self-limiting micro-layer and the sensible heat from the exhaust gas work together to heat the waste mineral oil to be treated in the tube, causing the light components in the waste mineral oil to undergo phase change vaporization at the inner wall of the tube and generate thermoacoustic oscillation, so as to physically desorb the deposits on the outer wall.

[0013] S4. Monitor the temperature change rate of the waste mineral oil to be treated at the outlet of the tube, and adjust the feed flow rate of the waste mineral oil to be treated accordingly to maintain the temperature of the self-limiting microlayer within the preset catalytic activity temperature range.

[0014] In a preferred embodiment of the present invention, the first active site comprises a noble metal and the second active site comprises a transition metal; the support for the dual-site mesoporous catalytic coating is a CeO2-ZrO2 solid solution with an average pore size of 5 nm to 15 nm.

[0015] In a preferred embodiment of the present invention, the noble metal is a Pt-Pd alloy and the transition metal is a Ni-Mo alloy.

[0016] In a preferred embodiment of the present invention, in step S2, the preset catalytic activity temperature range is 280°C to 350°C;

[0017] In step S3, the light components in the waste mineral oil to be treated are components with boiling points between 150°C and 180°C, and the phase change vaporization is nucleation boiling.

[0018] In a preferred embodiment of the present invention, a dense barrier layer is further provided between the tube wall substrate of the tube and the two-site mesoporous catalytic coating. The dense barrier layer is an α-Al2O3 crystal layer doped with Y2O3. The thickness of the dense barrier layer is 50 μm to 200 μm and the density is greater than 98%.

[0019] In a preferred embodiment of the present invention, in step S3, the mass percentage of the light components with a boiling point between 150°C and 180°C in the waste mineral oil to be treated is 3% to 8%; the heat flux density of the tube wall in the tube side is controlled at 15 kW / m. 2 Up to 25kW / m 2 between.

[0020] In a preferred embodiment of the present invention, in step S2, the first active site and the second active site coexist in the same mesoporous channel, and the spatial linear distance between the first active site and the second active site is less than 50 nm.

[0021] In a preferred embodiment of the present invention, the specific logic for adjusting the feed flow rate of the waste mineral oil to be treated in step S4 is as follows:

[0022] The basic feed mass flow rate of the waste mineral oil to be treated is set at 1500 kg / (m³). 2 •h) to 2500kg / (m 2 •h), and a control sampling period of 3 to 5 minutes;

[0023] Within each sampling period:

[0024] When the temperature change rate is greater than 2°C / min, the current feed flow rate will be increased by 15% to 20%.

[0025] When the temperature change rate is less than -1℃ / min, reduce the current feed flow rate by 10% to 15%;

[0026] When the feed flow rate reaches 200% of the upper limit or 50% of the lower limit of the basic feed mass flow rate, the system will trigger an audible and visual alarm and maintain a constant flow rate to prevent pressure buildup or dry burning inside the pipe.

[0027] In a preferred embodiment of the present invention, a preprocessing step is included before step S1:

[0028] The initial waste gas is introduced into the insulated cyclone separation zone, and the inlet wind speed of the insulated cyclone separation zone is controlled to be 18m / s to 22m / s, and the insulation temperature is 380℃ to 400℃. The high-temperature hydrocarbon-containing waste gas is obtained by intercepting droplets and solid dust with a particle size greater than 5μm through centrifugal force.

[0029] In a preferred embodiment of the present invention, a tail gas treatment step is included after step S3:

[0030] The exhaust gas discharged from the shell side of the catalytic heat exchanger is introduced into a condensation absorption tower and sprayed with alkaline absorbent; the pH value of the alkaline absorbent is controlled to be between 8.5 and 9.5, and the liquid-to-gas ratio is 3 L / m³. 3 Up to 5L / m 3 This reduces the temperature of the exhaust gas to 60°C to 80°C.

[0031] This invention addresses the shortcomings of the prior art and has the following beneficial effects:

[0032] This invention constructs a dual-site mesoporous catalytic coating containing a first and a second active site on the outer wall of the heat exchange tube. This allows the light components in the exhaust gas to undergo exothermic oxidation reactions, while the heavy aerosols absorb the heat and undergo reforming reactions at adjacent sites, thereby spontaneously constructing a temperature-stable, self-limiting microlayer on the tube wall surface. Compared to existing technologies that rely solely on increasing the macroscopic wall temperature to prevent condensation or using an external combustion chamber, this invention converts the dangerous heat from the combustion of light components into activation energy to absorb the precursors of heavy coking, completely breaking the physical contradiction between the heat exchange cold trap and polymer anchoring. This not only fundamentally blocks irreversible chemical cross-linking and coking but also achieves highly efficient synergy between exhaust gas purification and high-grade chemical heat in-situ recovery.

[0033] By guiding the heat from the self-limiting microlayer outside the pipe and the sensible heat of the exhaust gas to synergistically heat the waste mineral oil inside the pipe, this invention induces nucleation boiling phase transitions in light components within a specific boiling point range of the waste mineral oil near the inner wall of the pipe. This, in turn, excites high-frequency thermoacoustic oscillations. After penetrating the pipe wall, these high-frequency oscillations create a strong nonlinear acoustic-flow effect within the fluid boundary layer on the outer wall of the pipe, physically stripping away trace amounts of ash and heavy matter that have not yet been reformed from the crystal lattice surface. Compared to the inefficient methods of existing technologies that rely on increasing the exhaust gas flow rate to scour the pipe wall through macroscopic fluid shear force, this invention's acoustic-flow desorption mechanism directly acts on the microscopic viscous sublayer with a flow velocity approaching zero. This overcomes the technical bias of flow field scouring, improves anti-fouling performance, and significantly extends the continuous cleaning-free operation cycle of the equipment.

[0034] This invention introduces a negative feedback control logic that dynamically adjusts the feed flow rate based on the temperature change rate of the waste mineral oil at the pipe outlet, transforming the cold waste mineral oil flowing inside the pipe into an adaptive dynamic heat sink. When fluctuations in the concentration of exhaust gas outside the pipe cause drastic changes in chemical exothermics, the system can precisely match the fluctuations in external heat flux through instantaneous increases and decreases in flow rate, strictly controlling the temperature of the micro-regions of the pipe wall within the optimal catalytic activity window. Existing technologies are prone to local thermal runaway or secondary cracking and coking of the oil inside the pipe when dealing with high-concentration VOCs exothermic reactions. However, the dynamic heat sink mechanism of this invention decouples the hysteresis effect between external exothermics and internal endothermics, maximizing the conversion of the latent chemical heat of the exhaust gas into effective heat energy for preheating the feedstock while ensuring the continuous and stable progress of the catalytic reaction, significantly improving the overall thermal efficiency of the entire system.

[0035] By adding a dense α-Al2O3 barrier layer doped with Y2O3 between the tube wall substrate and the catalytic coating, the contact between the d-orbital electrons of the transition metal in the heat exchange tube substrate and the unsaturated hydrocarbons in the exhaust gas is blocked, thereby cutting off the electron transfer path of the catalytic dehydrogenation condensation reaction and eliminating the inducing effect of the metal lattice on the free radical chain polymerization reaction at its source. Existing technologies often overlook the fundamental cause of catalytic coking within the thermal boundary layer of the metal tube wall itself, resulting in conventional physical anti-scaling methods being merely stopgap measures. The dense barrier layer of this invention, combined with the outer dual-site catalytic mechanism, constructs a dual defense line of chemical reaction and physical shielding, completely transforming the originally highly prone chemical coking into a reversible gas-phase reaction, giving the heat exchange equipment an ultra-long service life under extremely harsh operating conditions. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a flowchart of a method for the synergistic treatment of waste gas purification and heat recovery in the process of waste mineral oil regeneration according to the present invention. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein. Therefore, the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0040] Application Overview:

[0041] In the field of waste mineral oil regeneration, the purification and heat recovery of high-temperature hydrocarbon-containing waste gas are key links in achieving a closed-loop process. Existing technologies face a long-standing core technical contradiction when treating such waste gases rich in volatile organic compounds and heavy aerosols: the physical and chemical conflict between the need for a heat exchanger cold trap and the requirement for high-temperature coking prevention. Specifically, to achieve effective recovery of high-grade heat energy, the heat exchanger tube wall must be maintained at a low temperature to create a sufficient heat transfer temperature difference, thus acting as a thermodynamic cold trap. However, when unsaturated hydrocarbons in the waste gas come into contact with the low-temperature tube wall, they undergo a strong free radical dehydrogenation condensation reaction induced by the metal matrix within the heat transfer boundary layer, leading to irreversible chemical cross-linking and coking. To prevent this coking, existing technologies typically force an increase in the operating temperature of the heat exchanger tube wall or the use of an external combustion chamber. This not only significantly sacrifices heat recovery efficiency but also fails to fundamentally prevent polymer anchoring at the microscopic interface.

[0042] To address the aforementioned problems, this invention proposes a waste gas treatment method based on the synergistic effect of microscopic interface thermodynamic self-coupling and phase change acoustic flow desorption. By constructing a dual-site mesoporous catalytic coating containing exothermic oxidation sites and endothermic reforming sites on the outer wall of the heat exchange tube, the exothermic combustion of light components in the waste gas and the endothermic decomposition of heavy aerosols are instantaneously thermodynamically counteracted within micron-level pores, spontaneously constructing a temperature-stable, self-limiting microlayer on the tube wall surface. This not only utilizes the chemical reaction itself to balance the local thermal field and block free radical condensation reactions, but also converts the dangerous latent chemical heat into effective thermal energy for preheating the raw materials. Simultaneously, this invention utilizes the nucleus boiling phase change of specific light components in the waste mineral oil inside the tube to excite high-frequency thermoacoustic oscillations, forming a nonlinear acoustic flow effect within the fluid boundary layer on the outer wall of the tube, achieving the physical stripping of trace ash. Compared to existing technologies, this solution decouples the necessary link between heat exchange cooling and chemical coking. Without sacrificing the heat transfer temperature difference, it achieves the ultimate synergy between deep purification of waste gas and in-situ recovery of high-grade heat energy, significantly improving the overall thermal efficiency of the system and the continuous cleaning-free operation cycle.

[0043] Source of materials:

[0044] Chloroplatinic acid hexahydrate, catalog number C805194, reagent grade, Pt≥37.5%, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0045] Palladium nitrate dihydrate, item number P294583, metal standard purity ≥99.95%, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0046] Nickel nitrate hexahydrate, CAS No. 13478-00-7, purity 99%, purchased from Sinopharm Chemical Reagent Co., Ltd.

[0047] Ammonium molybdate tetrahydrate, product number A597691, purity ≥99%, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0048] Zirconium oxyhydrate nitrate, item number Z104396, purity ≥99.5%, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0049] Aluminum nitrate nonahydrate, product number S492260, purity ≥98%, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0050] Yttrium nitrate hexahydrate, item number Y118878, metal standard purity 99.99%, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0051] Citric acid monohydrate, product number C598654, purity ≥99%, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0052] Ethylene glycol, product number E103323, purity ≥99.9%, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0053] Sodium hydroxide, item number S111498, purity ≥96%, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0054] Nonionic triblock copolymer (polyethylene oxide-polypropylene oxide-polyethylene oxide, abbreviated as P123), CAS No. 9003-11-6, average molecular weight approximately 5800, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0055] Nano-alumina powder (containing α-phase seed crystals), item number A299287, with an average particle size of 30nm and a purity of ≥99.9%, was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0056] The waste mineral oil to be processed was taken from the initial oil discharged from the cracking reactor of a commercially available conventional waste lubricating oil regeneration plant. After pre-distillation and compounding in the laboratory, several batches of samples with a light component mass percentage of 0%, 3%, 5%, 8%, and 10% with a boiling point between 150℃ and 180℃ were prepared for use.

[0057] The preparation steps of the self-made materials involved in the various embodiments and comparative examples of this invention are as follows:

[0058] Preparation of dense barrier layer:

[0059] Aluminum nitrate nonahydrate and yttrium nitrate hexahydrate were dissolved in deionized water at a molar ratio of Al to Y of 95:5. Citric acid monohydrate was added as a complexing agent, and the molar ratio of citric acid to total metal ions was controlled at 1.5:1. Subsequently, nano-sized α-Al2O3 seed crystals accounting for 1% to 2% of the total metal ions were added to the system. The heterogeneous nucleation induction effect of the seed crystals was used to significantly reduce the phase transition activation energy. The mixture was stirred at a constant temperature of 60°C until a transparent sol was formed.

[0060] The heat exchange tubes, which have undergone surface sandblasting and pickling pretreatment, are immersed in the sol and left for 5 minutes. Then, they are pulled up at a uniform speed of 15 mm / min, dried at 120°C for 2 hours, and calcined at 900°C for 3 hours.

[0061] Repeating the above impregnation, pulling and calcination process 3 to 5 times, thanks to the induction effect of the above-mentioned nano-scale α-Al2O3 seeds, the phase transformation that originally required 1200℃ can be completed at 900℃. This not only protects the metal heat exchange tube substrate from high-temperature creep damage, but also forms an α-Al2O3 crystal layer with a thickness of 50μm to 200μm and a density greater than 98% on the surface of the heat exchange tube substrate.

[0062] Preparation of two-site mesoporous catalytic coatings:

[0063] According to the mass percentages set in each embodiment, the molar ratio of cerium to zirconium is controlled to be 1:1 to 1.5:1. Cerium nitrate hexahydrate and zirconium oxynitrate hydrate are accurately weighed and dissolved in deionized water as carrier precursors. The molar ratio of platinum to palladium is controlled to be 1:1 to 2:1, and the molar ratio of nickel to molybdenum is controlled to be 1:3 to 1:5. At the same time, chloroplatinic acid hexahydrate, palladium nitrate dihydrate, nickel nitrate hexahydrate, and ammonium molybdate tetrahydrate are accurately weighed and dissolved in deionized water as active site precursors.

[0064] Nonionic triblock copolymer P123 was dissolved in anhydrous ethanol as a mesoporous structure directing agent and stirred to form a micelle solution with hydrophilic ends and hydrophobic cores.

[0065] First, the carrier precursor and the Pt-Pd-containing first active site precursor are added to the micelle solution, hydrated citric acid and ethylene glycol are added, and the molar ratio of citric acid, ethylene glycol and total metal ions is controlled to be 2:2:1. The solution is heated in a water bath at 80°C and stirred at a speed of 400 r / min to selectively anchor the first active site precursor to the hydrophilic end of the micelle.

[0066] Subsequently, the precursor containing the second active site of Ni-Mo was added dropwise to the system, and hydrophobic interactions were used to allow it to enter the hydrophobic core of the micelles.

[0067] Continuous stirring promotes the complexation and cross-linking of metal ions, forming a gel with a viscosity of 800 mPa·s to 1200 mPa·s. Through the microscopic spatial confinement effect of the triblock copolymer micelles, it is ensured that after the template agent is removed by calcination, the first active site and the second active site coexist in the same mesoporous channel, and the spatial linear distance is strictly limited to within 50 nm, thus avoiding the high-temperature melting and single alloying of multiple metals.

[0068] The heat exchange tube with a dense barrier layer on its surface was coated with the gel using an ultrasonic atomization spraying method. The spraying pressure was controlled at 0.2 MPa. After drying at 25°C for 12 hours, it was subjected to step calcination.

[0069] The stepped calcination process involves first holding the material at 300℃ for 2 hours to remove organic matter, then switching to a hydrogen-argon mixed reducing atmosphere with a hydrogen volume concentration of 5% to 10%, and calcining at a rate of 5℃ / min to 550℃ for 4 hours to decompose and completely reduce the metal precursor. Finally, a dual-site mesoporous catalytic coating with CeO2-ZrO2 solid solution as a carrier and containing Pt-Pd first active sites and Ni-Mo second active sites is generated in situ on the outer wall of the heat exchange tube.

[0070] For coatings lacking specific active sites in the comparative examples, only the addition of the corresponding metal salt needs to be omitted during preparation, while the remaining steps remain completely consistent.

[0071] like Figure 1 As shown, a method for the synergistic treatment of waste gas purification and heat recovery in the waste mineral oil regeneration process includes the following steps:

[0072] S1. High-temperature hydrocarbon-containing waste gas containing unsaturated hydrocarbons and heavy aerosols is introduced into the shell side of the catalytic heat exchanger, while the waste mineral oil to be treated is introduced into the tube side of the catalytic heat exchanger.

[0073] S2. The high-temperature hydrocarbon-containing waste gas is brought into contact with the outer wall of the tube. The outer wall is coated with a dual-site mesoporous catalytic coating containing a first active site and a second active site. The light components in the waste gas undergo an exothermic oxidation reaction at the first active site, and the heavy aerosol absorbs the heat and products of the exothermic oxidation reaction at the second active site to undergo a reforming reaction, thereby constructing a self-limiting microlayer on the surface of the outer wall.

[0074] S3. The heat from the self-limiting micro-layer and the sensible heat from the exhaust gas work together to heat the waste mineral oil to be treated in the tube, causing the light components in the waste mineral oil to undergo phase change vaporization at the inner wall of the tube and generate thermoacoustic oscillation, so as to physically desorb the deposits on the outer wall.

[0075] S4. Monitor the temperature change rate of the waste mineral oil to be treated at the outlet of the tube, and adjust the feed flow rate of the waste mineral oil to be treated accordingly to maintain the temperature of the self-limiting microlayer within the preset catalytic activity temperature range.

[0076] The key technical challenge in applying the above methods lies in ensuring the instantaneous matching of exothermic and endothermic processes at the microscopic scale, and in controlling the internal phase change state. If the exothermic oxidation rate is much greater than the endothermic reforming rate, it can lead to localized thermal stress concentration or even thermal runaway, causing deep cracking and coking of the oil inside the pipe. If the internal phase change vaporization is too intense and enters the film boiling stage, a gas barrier layer will form on the inner wall of the pipe, causing a sharp drop in heat transfer efficiency and blocking the generation of thermoacoustic oscillations. Therefore, it is necessary to overcome these technical gaps through specific microscopic channel structure design and macroscopic dynamic flow rate feedback mechanisms.

[0077] Preferably, in step S1, the high-temperature hydrocarbon-containing waste gas enters the shell side as a heat source along with the object to be purified. The heavy aerosols and unsaturated hydrocarbons it carries are the main precursors that cause coking in conventional heat exchangers.

[0078] Furthermore, the waste mineral oil to be treated enters the tube side as a cold source, and the two form a cross-flow or counter-flow heat exchange flow field in the catalytic heat exchanger, providing the basic physical conditions for subsequent cross-interface heat transfer.

[0079] Preferably, in step S2, when the high-temperature hydrocarbon-containing waste gas enters the fluid boundary layer on the outer wall of the tube, the light volatile organic compounds with low activation energy in the waste gas are preferentially captured by the first active site, undergoing a deep oxidation reaction to generate H2O and CO2 and release a large amount of chemical heat.

[0080] Furthermore, since the first and second active sites coexist in the same mesoporous channel and are very close in space, the released chemical heat and high-temperature H2O and CO2 products rapidly diffuse into the second active site within the channel; the heavy aerosols in the exhaust gas that are difficult to oxidize directly undergo steam reforming or dry gas reforming reactions with H2O and CO2 at the second active site using the diffused heat, and are decomposed into small molecule gases.

[0081] Furthermore, the exothermic oxidation and endothermic reforming achieve spontaneous offsetting in space and time, thereby forming a self-limiting micro-layer with a relatively constant temperature on the outer surface of the tube wall, avoiding excessively high or low local temperatures, and blocking the free radical dehydrogenation condensation coking process from the perspective of chemical reaction kinetics.

[0082] Preferably, in step S3, the chemical heat generated by the self-limiting microlayer is superimposed with the physical sensible heat of the exhaust gas itself, and is transferred to the inside of the tube with high heat flux through the tube wall.

[0083] Specifically, the waste mineral oil to be treated contains a specific proportion of light components with boiling points between 150°C and 180°C. When the temperature of the inner wall of the pipe reaches the boiling point of the light components, the light components undergo nucleation boiling in the micro-regions close to the inner wall of the pipe.

[0084] Specifically, the periodic generation, growth and detachment of bubbles during nucleation boiling, accompanied by the rapid absorption and release of latent heat of vaporization, excites high-frequency thermoacoustic oscillation mechanical waves in the fluid. The high-frequency thermoacoustic oscillation penetrates the metal pipe wall and is transmitted to the outer wall of the pipe, inducing a nonlinear acoustic flow effect in the fluid viscous layer of the outer wall of the pipe.

[0085] To ensure that the aforementioned thermoacoustic oscillation mechanical waves can form stable resonant standing waves without being dissipated by the fluid, the present invention further specifies that: the tube length-to-diameter ratio of the catalytic heat exchanger is controlled between 25 and 40, and the liquid phase Reynolds number of the waste mineral oil to be treated in the tube is maintained in the transition flow to weak turbulence range of 2000 to 4500; the periodic detachment frequency of the nucleated boiling bubbles is coupled with the inherent acoustic resonance frequency of the tube cavity, thereby exciting directional thermoacoustic oscillation waves with an amplitude greater than 150 dB in the micro-region of the tube wall, providing a sufficient energy reference for acoustic flow physical desorption.

[0086] Furthermore, the microscopic shear force generated by the acoustic flow effect disrupts the physical adsorption balance of unreacted trace ash and heavy matter on the surface of the catalytic coating, causing them to desorb and be discharged with the exhaust gas flow, thus maintaining the continuous exposure of the catalytic sites.

[0087] Preferably, in step S4, by monitoring the temperature change rate of the waste mineral oil to be treated at the pipe outlet in real time, the system converts the cold oil flowing in the pipe into a dynamic heat sink.

[0088] Specifically, when the rate of temperature change is positive and exceeds the set threshold, it indicates a surge in external heat release, and the system removes the excess heat by increasing the feed flow rate.

[0089] When the temperature change rate is negative and below the set threshold, it indicates insufficient external heat input. The system reduces heat loss by decreasing the feed flow rate, thereby ensuring that the temperature of the self-limiting microlayer is always maintained within the preset catalytic activity temperature range of 280℃ to 350℃, preventing catalyst deactivation or secondary coking of oil in the pipe.

[0090] Example 1:

[0091] This embodiment provides a method for the coordinated treatment of waste gas purification and heat recovery during the waste mineral oil regeneration process. As the optimal benchmark for verifying various parameters, the specific operating parameters are as follows:

[0092] Pretreatment stage: The initial waste gas is introduced into the insulated cyclone separation zone, the inlet wind speed is controlled at 20m / s, the insulation temperature is 390℃, and high temperature hydrocarbon-containing waste gas is obtained after intercepting large particulate aerosols.

[0093] Step S1: The high-temperature hydrocarbon-containing waste gas is introduced into the shell side of the catalytic heat exchanger, while the waste mineral oil to be treated is introduced into the tube side.

[0094] In step S2, a two-site mesoporous catalytic coating is applied to the outer wall of the tube. The average pore size of this coating is 10 nm. By total coating mass, the Pt-Pd alloy accounts for 0.3% and the Ni-Mo alloy accounts for 3.5%. The linear distance between the first and second active sites is less than 50 nm. The exhaust gas undergoes thermodynamic coupling of exothermic oxidation and endothermic reforming on the coating surface. The target temperature of the self-limiting microlayer on the outer wall surface is set and maintained at 310 °C.

[0095] Step S3: In the waste mineral oil to be treated within the tube, the mass ratio of light components with a boiling point between 150℃ and 180℃ is adjusted to 5%; the heat from the self-limiting microlayer and the sensible heat of the waste gas penetrate the tube wall, and the heat flux density of the tube wall is controlled at 20kW / m³. 2 Light components undergo nucleation boiling on the inner wall of the pipe, generating high-frequency thermoacoustic oscillations, and form acoustic flow effect desorption and attachment on the outer wall of the pipe.

[0096] Step S4: Monitor the temperature change rate of the waste mineral oil to be treated at the tube outlet in real time. The control logic is set as follows: when the temperature change rate is greater than 2℃ / min, increase the feed flow rate by 18%; when the temperature change rate is less than -1℃ / min, decrease the feed flow rate by 12% to maintain the micro-zone temperature stable at 310℃.

[0097] In the tail gas treatment stage, the tail gas discharged from the shell side is introduced into the condensation absorption tower and sprayed with an alkaline absorbent liquid with a pH of 9.0, controlling the liquid-to-gas ratio at 4 L / m³. 3 This reduces the exhaust gas temperature to 70°C.

[0098] Example 2:

[0099] The only difference between this embodiment and Embodiment 1 is that in step S2, the target temperature of the self-limiting micro-layer on the outer wall surface is set and maintained at 280°C; the remaining process steps and parameters are completely consistent with Embodiment 1.

[0100] Example 3:

[0101] The only difference between this embodiment and Embodiment 1 is that in step S2, the target temperature of the self-limiting micro-layer on the outer wall surface is set and maintained at 350°C; the remaining process steps and parameters are completely consistent with Embodiment 1.

[0102] Example 4:

[0103] The only difference between this embodiment and Embodiment 1 is that in step S3, the mass ratio of light components with a boiling point between 150°C and 180°C in the waste mineral oil to be treated in the tube is adjusted to 3%; the remaining process steps and parameters are completely consistent with Embodiment 1.

[0104] Example 5:

[0105] The only difference between this embodiment and Embodiment 1 is that in step S3, the mass ratio of light components with a boiling point between 150°C and 180°C in the waste mineral oil to be treated in the tube is adjusted to 8%; the remaining process steps and parameters are completely consistent with Embodiment 1.

[0106] Comparative Example 1:

[0107] The only difference between this comparative example and Example 1 is that, in preparing the catalytic coating on the outer wall of the tube, nickel nitrate hexahydrate and ammonium molybdate tetrahydrate were not added, and the resulting coating only contained Pt-Pd first active sites and had no Ni-Mo second active sites; the remaining process steps and parameters were completely consistent with those of Example 1.

[0108] Comparative Example 2:

[0109] The only difference between this comparative example and Example 1 is that in step S3, the waste mineral oil to be treated has undergone deep delighting treatment beforehand, and the mass percentage of light components with boiling points between 150°C and 180°C is 0%; the remaining process steps and parameters are completely consistent with Example 1.

[0110] Comparative Example 3:

[0111] The only difference between this comparative example and Example 1 is that in step S2, the target temperature of the self-limiting micro-layer on the outer wall surface is set and maintained at 270°C; the remaining process steps and parameters are completely consistent with Example 1.

[0112] Comparative Example 4:

[0113] The only difference between this comparative example and Example 1 is that in step S3, the mass ratio of light components with boiling points between 150°C and 180°C in the waste mineral oil to be treated in the tube is adjusted to 10%; the remaining process steps and parameters are completely consistent with Example 1.

[0114] To verify the synergistic effect of the dual-site thermodynamic coupling and internal phase change acoustic flow desorption mechanism of this invention, and to avoid using conventional thermal efficiency or apparent coking rate indicators that are easily affected by macroscopic operating conditions, this invention designs the following three customized characterization indicators and corresponding testing methods:

[0115] Micro-area thermal coupling imbalance: This index characterizes the degree of matching between exothermic and endothermic reactions at two sites within the microscopic space. Using a high-frequency infrared thermal imager through a specially designed sapphire observation window, the micro-area temperature of the outer wall of the catalytic heat exchanger tubes was continuously recorded during 100 hours of stable operation. The highest and lowest temperatures per square centimeter were extracted, and the range between the two was calculated and denoted as the micro-area thermal coupling imbalance, expressed in °C. The smaller the value, the more perfect the thermodynamic coupling and the more stable the self-limiting microlayer.

[0116] Acoustic flow desorption critical shear force: This index characterizes the physical desorption capacity generated by the thermoacoustic oscillations induced by internal nucleate boiling on the outer wall of the pipe. A simulated ash layer with standard adhesion strength is pre-coated onto the outer wall of the pipe. After the system stabilizes, a microfluidic interface rheometer combined with a laser Doppler vibrometer is used to measure the average wall shear stress generated by the acoustic flow effect within the viscous fluid layer on the outer wall of the pipe. This stress is denoted as the acoustic flow desorption critical shear force, with units of Pa. The higher the value, the stronger the physical ash removal effect.

[0117] Irreversible chemical crosslinking percentage: This indicator characterizes the degree to which free radical dehydrogenation condensation reactions are blocked. After the system has been running continuously for 500 hours, the adhering material per unit area on the outer wall of the tube is scraped off, and Soxhlet extraction is performed using tetrahydrofuran. The residue insoluble in tetrahydrofuran is dried and weighed, and the percentage of its mass to the total mass of the adhering material is recorded as the irreversible chemical crosslinking percentage, expressed as %. The lower the value, the more the adhering material consists of reversible physical adsorption or unreacted inorganic ash, and chemical coking is effectively inhibited.

[0118] Following the experimental methods described above, Examples 1 to 5 and Comparative Examples 1 to 4 were tested, and the test results are shown in Table 1.

[0119] Table 1. Customized characterization test results for each embodiment and comparative example.

[0120] Group Micro-region thermal coupling imbalance / ℃ Critical shear force for acoustic desorption / Pa Irreversible chemical crosslinking percentage / % Example 1 4.2 18.5 2.1 Example 2 6.5 15.2 4.3 Example 3 7.1 16.8 3.8 Example 4 5.8 12.4 2.9 Example 5 6.2 21.3 2.5 Comparative Example 1 145.6 17.1 89.4 Comparative Example 2 4.5 1.2 15.6 Comparative Example 3 38.4 10.5 62.7 Comparative Example 4 12.3 4.8 8.2

[0121] Comparing Example 1 and Comparative Example 1, it can be seen that when the coating lacks endothermic reforming sites, the micro-region thermal coupling imbalance increases dramatically from 4.2℃ to 145.6℃, and the proportion of irreversible chemical crosslinking soars to 89.4%. This indicates that a single exothermic oxidation site cannot absorb the enormous heat released by the combustion of high-concentration volatile organic compounds, leading to severe temperature runaway in the micro-region. Localized high temperatures not only fail to prevent coking but also accelerate the deep pyrolysis and free radical crosslinking of heavy aerosols on the metal lattice surface, forming extremely difficult-to-remove polymeric dead coke. The data from Example 1 demonstrates that the thermodynamic counterbalancing mechanism of dual sites within micron-sized channels is a necessary prerequisite for constructing self-limiting microlayers and blocking chemical coking.

[0122] Comparing Example 1 and Comparative Example 2, it can be seen that when the waste mineral oil in the pipe lacks light components with a specific boiling point range, the critical shear force for acoustic desorption decreases from 18.5 Pa to 1.2 Pa, and the proportion of irreversible chemical crosslinking also increases to 15.6%. This indicates that without the latent heat of phase change provided by internal nucleation boiling, the scouring of macroscopic fluids alone cannot generate sufficient shear force in the viscous sublayer. The long-term physical retention of trace ash eventually masks the catalytic active sites, leading to the gradual failure of the thermal coupling mechanism and inducing secondary coking. This verifies the decisive synergistic effect of internal phase change oscillation on maintaining external catalytic activity.

[0123] Comparing Example 2 and Comparative Example 3, it can be seen that when the micro-region temperature approaches and falls below the endpoint of 280°C to 270°C, the micro-region thermal coupling imbalance and the proportion of irreversible chemical crosslinking both show nonlinear deterioration. The underlying mechanism is that 280°C is the critical threshold of activation energy for activating the water vapor reforming reaction of heavy aerosols. Below this temperature, the reforming reaction rate decays exponentially and cannot absorb the heat conducted from the oxidation sites in time, leading to the breakage of the thermodynamic coupling chain. The free radical condensation reaction regains dominance, which proves the special nature of the present invention in limiting the temperature range to 280°C to 350°C.

[0124] Comparing Example 5 with Comparative Example 4, it can be seen that when the mass ratio of the light component approaches and exceeds the endpoint of 8% to 10%, the critical shear force for acoustic desorption drops sharply from 21.3 Pa to 4.8 Pa. The underlying mechanism is that the excessively high proportion of the light component causes the boiling state of the inner wall of the tube to change from nucleation boiling to film boiling, crossing the critical heat flux density. The continuous vapor film not only forms a serious thermal resistance, but also blocks the transmission of high-frequency thermoacoustic oscillation mechanical waves to the outside of the tube, causing the acoustic desorption mechanism to completely fail. This proves that strictly controlling the proportion of the light component within the narrow range of 3% to 8% is the key to stimulating specific high-frequency oscillations and achieving nonlinear ash removal effect.

[0125] In summary, this invention breaks through the conventional technical bias in the field of waste gas treatment that relies on macroscopic temperature control and flow field scouring. It innovatively integrates the microscopic thermodynamic self-coupling mechanism of the dual-site mesoporous catalytic coating with the nonlinear acoustic-flow desorption mechanism induced by nucleated boiling of light components within the tube. By achieving instantaneous matching of exothermic oxidation and endothermic reforming within an extremely narrow range of process parameters, this invention successfully constructs a stable self-limiting microlayer on the outer wall of the heat exchange tube, completely blocking the free radical cross-linking and coking process induced by transition metals from a chemical reaction kinetics perspective. Simultaneously, by utilizing the high-frequency thermoacoustic oscillations generated by the internal phase change, physical stripping of adhering substances is achieved within the fluid viscous sublayer. This invention not only resolves the inherent physical contradiction between the heat exchange cold trap and the high-temperature requirements for anti-coking, but also achieves the ultimate synergy between deep waste gas purification and in-situ recovery of high-grade chemical latent heat without sacrificing the heat transfer temperature difference. This provides a novel process path for waste mineral oil regeneration and similar high-concentration hydrocarbon-containing waste gas treatment conditions, characterized by extremely stable operation and a nonlinear leap in overall thermal efficiency.

[0126] Based on the preferred embodiments of the present invention described above, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for the synergistic treatment of waste gas purification and heat recovery in the process of waste mineral oil regeneration, characterized in that, Includes the following steps: S1. High-temperature hydrocarbon-containing waste gas containing unsaturated hydrocarbons and heavy aerosols is introduced into the shell side of the catalytic heat exchanger, while the waste mineral oil to be treated is introduced into the tube side of the catalytic heat exchanger. S2. The high-temperature hydrocarbon-containing waste gas is brought into contact with the outer wall of the tube. The outer wall is coated with a dual-site mesoporous catalytic coating containing a first active site and a second active site. The light components in the high-temperature hydrocarbon-containing waste gas undergo an exothermic oxidation reaction at the first active site, and the heavy aerosol absorbs the heat and products of the exothermic oxidation reaction at the second active site to undergo a reforming reaction, thereby constructing a self-limiting microlayer on the surface of the outer wall. S3. The heat from the self-limiting micro-layer and the sensible heat from the exhaust gas work together to heat the waste mineral oil to be treated in the tube, causing the light components in the waste mineral oil to undergo phase change vaporization at the inner wall of the tube and generate thermoacoustic oscillation, so as to physically desorb the deposits on the outer wall. S4. Monitor the temperature change rate of the waste mineral oil to be treated at the outlet of the tube, and adjust the feed flow rate of the waste mineral oil to be treated accordingly to maintain the temperature of the self-limiting microlayer within the preset catalytic activity temperature range.

2. The method for synergistic treatment of waste gas purification and heat recovery in the waste mineral oil regeneration process according to claim 1, characterized in that, The first active site contains a noble metal, and the second active site contains a transition metal; the support for the dual-site mesoporous catalytic coating is a CeO2-ZrO2 solid solution, and the average pore size is 5 nm to 15 nm.

3. The method for synergistic treatment of waste gas purification and heat recovery in the waste mineral oil regeneration process according to claim 2, characterized in that, The noble metal is a Pt-Pd alloy, and the transition metal is a Ni-Mo alloy.

4. The method for synergistic treatment of waste gas purification and heat recovery in the waste mineral oil regeneration process according to claim 1, characterized in that, In step S2, the preset catalytic activity temperature range is 280°C to 350°C; In step S3, the light components in the waste mineral oil to be treated are components with boiling points between 150°C and 180°C, and the phase change vaporization is nucleation boiling.

5. The method for synergistic treatment of waste gas purification and heat recovery in the waste mineral oil regeneration process according to claim 1, characterized in that, A dense barrier layer is further provided between the tube wall substrate and the two-site mesoporous catalytic coating. The dense barrier layer is an α-Al2O3 crystal layer doped with Y2O3. The thickness of the dense barrier layer is 50 μm to 200 μm and the density is greater than 98%.

6. The method for synergistic treatment of waste gas purification and heat recovery in the waste mineral oil regeneration process according to claim 4, characterized in that, In step S3, the mass percentage of the light components with boiling points between 150°C and 180°C in the waste mineral oil to be treated is 3% to 8%; the heat flux density of the tube wall in the tube side is controlled at 15 kW / m. 2 Up to 25kW / m 2 between.

7. The method for synergistic treatment of waste gas purification and heat recovery in the waste mineral oil regeneration process according to claim 1, characterized in that, In step S2, the first active site and the second active site coexist in the same mesoporous channel, and the spatial linear distance between the first active site and the second active site is less than 50 nm.

8. The method for synergistic treatment of waste gas purification and heat recovery in the waste mineral oil regeneration process according to claim 1, characterized in that, In step S4, the specific logic for adjusting the feed flow rate of the waste mineral oil to be treated is as follows: The basic feed mass flow rate of the waste mineral oil to be treated is set at 1500 kg / (m³). 2 •h) to 2500kg / (m 2 •h), and a control sampling period of 3 to 5 minutes; Within each sampling period: When the temperature change rate is greater than 2°C / min, the current feed flow rate will be increased by 15% to 20%. When the temperature change rate is less than -1℃ / min, reduce the current feed flow rate by 10% to 15%; When the feed flow rate reaches 200% of the upper limit or 50% of the lower limit of the basic feed mass flow rate, the system will trigger an audible and visual alarm and maintain a constant flow rate to prevent pressure buildup or dry burning inside the pipe.

9. The method for synergistic treatment of waste gas purification and heat recovery in the waste mineral oil regeneration process according to claim 1, characterized in that, A preprocessing step is included before step S1: The initial waste gas is introduced into the insulated cyclone separation zone, and the inlet wind speed of the insulated cyclone separation zone is controlled to be 18m / s to 22m / s, and the insulation temperature is 380℃ to 400℃. The high-temperature hydrocarbon-containing waste gas is obtained by intercepting droplets and solid dust with a particle size greater than 5μm through centrifugal force.

10. The method for synergistic treatment of waste gas purification and heat recovery in the waste mineral oil regeneration process according to claim 1, characterized in that, Step S3 is followed by an exhaust gas treatment step: The exhaust gas discharged from the shell side of the catalytic heat exchanger is introduced into a condensation absorption tower and sprayed with alkaline absorbent; the pH value of the alkaline absorbent is controlled to be between 8.5 and 9.5, and the liquid-to-gas ratio is 3 L / m³. 3 Up to 5L / m 3 This reduces the temperature of the exhaust gas to 60°C to 80°C.

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