An ultrasonic micro-chemical system for synthesizing nanofluid and a method for preparing functional nanofluid from coal-based solid waste

Abstract

The application discloses an ultrasonic micro-chemical system for synthesizing nanofluid and a method for preparing functional nanofluid from coal-based solid waste, and the system comprises at least one temperature-controlled ultrasonic micro-reactor and an ultrasonic leaching reaction kettle; the ultrasonic leaching reaction kettle is connected with a filter, the filter is connected with a reactant preheating unit, the reactant preheating unit is connected with the temperature-controlled ultrasonic micro-reactor, and a reactant storage tank is connected with the reactant preheating unit, and the temperature-controlled ultrasonic micro-reactor is connected. The micro-chemical technology in the application has no amplification effect, the capacity expansion can be realized by increasing the number of micro-reactors in parallel and selectively enlarging the equipment size, the efficient connection from research and development to production can be realized while the heat and mass transfer is strengthened and the consistency of reaction conditions is ensured, and the industrialization cost is greatly reduced. The ultrasonic micro-reactor is used for preparing the functional nanofluid, the cavitation bubbles generated by ultrasonic waves in the liquid working medium can realize multiphase mixing mass transfer strengthening, dredge solid particle blockage and promote uniform dispersion of nanoparticles in the nanofluid.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of chemical industry, and particularly relates to an ultrasonic micro-chemical system for synthesizing nanofluid and a method for preparing functional nanofluid from coal-based solid waste. BACKGROUND

[0002] In the process of coal mining and utilization, various different coal-based solid wastes are generated, including solid waste coal gangue discharged in the process of coal mining and coal washing, fly ash waste residue captured from flue gas after coal combustion, and a large amount of coal gasification slag left over while producing combustible coal gasification gas through coal gasification technology. These solid wastes occupy a large land area and affect land use. The sulfides contained therein and the raised dust seriously pollute the atmosphere, and the solid waste flowing into water systems pollutes the water and causes great harm to aquatic organisms. The chemical composition of these coal-based solid wastes is rich in a large amount of silicon dioxide and aluminum oxide. However, the main utilization form of coal-based solid waste currently still stays in the middle and low value utilization stage such as building materials and roadbed backfilling, and the economic benefit is not strong and the utilization rate is low. If coal gasification ash is used as a silicon source and an aluminum source to prepare high-value silicon dioxide and aluminum oxide nanofluid, a new strategy for broadening the utilization way of coal gasification ash can be provided, and greater economic benefits can be generated while realizing efficient utilization of solid waste. Under the background of rapid development of electronic equipment and high heat transfer load of heat exchange equipment restricting its miniaturization and integration, nanofluid heat transfer enhancement technology has attracted widespread attention. The nanofluid suspension formed by adding nanoscale metal or metal oxide and non-metallic particles into the base fluid can be used as a new type of energy transport working medium with high efficiency and high heat transfer performance to improve the heat transfer performance of the heat dissipation system. At present, the research on high-value utilization of coal-based solid waste is basically in the laboratory stage, and has not yet realized large-scale application. In addition, the traditional process system needs large industrial equipment, and the amplification effect is serious, so it is difficult to realize precise control of the reaction environment. Micro-chemical technology has been widely used due to its small reaction volume, extremely short reaction time and small amount of reagents used, and has been widely used in organic synthesis, biotechnology, pharmaceutical manufacturing and other fields, and has broad application prospects and market potential. Compared with traditional large-scale kettle reactors, micro-chemical reactors have a larger surface area, excellent mixing effect, can quickly and high-throughput synthesize products, and the structure of the reactor itself is variable, which can be adjusted according to the actual production conditions to realize differentiated production under the premise of ensuring quality, efficiency and cost.

[0003] Nanofluids exhibit increased thermal conductivity with decreasing nanoparticle size, but van der Waals forces between small-sized nanoparticles can cause them to aggregate in the fluid. Due to the presence of nanoparticle aggregates, its dispersion stability can decay over time, which will affect its application in various fields. In order to prolong the stable life of nanofluids, ultrasonic waves have been widely used in the preparation of nanofluids. High-frequency ultrasonic waves can generate positive and negative pressure waves in the liquid working medium, thereby achieving uniform distribution of nanoparticles in the continuous liquid phase, and better particle dispersion and smaller aggregate size can be obtained after ultrasonic treatment. At the same time, the mechanical effect caused by the cavitation phenomenon of ultrasonic waves in the liquid phase can produce shear force to break the deposits on the reactor channel wall, thereby overcoming the problem of microreactor blockage. On the other hand, in the process of mineral phase leaching, ultrasonic waves play a strengthening role in many aspects of multiphase reactions involving external and internal diffusion control. The cavitation effect of ultrasonic waves not only can destroy agglomerates and deposits, but also can achieve special stirring of the reaction system. The turbulent effect caused by the collapse of microbubbles can significantly improve the mass transfer in the solid-liquid system, thereby effectively improving the efficiency of mineral leaching.

[0004] At present, there are a large number of studies on the resource utilization of coal-based solid waste. CN102515221A proposes a method for extracting alumina and amorphous silicon dioxide from fly ash or coal gangue. The fly ash or coal gangue is calcined and crushed, mixed with alkali metal sulfate, and then reacted to generate amorphous silicon dioxide after solid-liquid separation by water immersion of the reaction product. The mixed solution is subjected to iron removal, evaporation concentration, calcination, and water immersion to obtain alumina solids after solid-liquid separation. CN110963518A proposes a method for preparing nano-alumina from fly ash. The filter cake after magnetic separation and iron removal is placed in a reaction kettle and heated with acid, then impurities are removed by adsorption, and then nano-sized alumina is generated by high-temperature calcination after long-time stirring of ammonium bicarbonate solution.

[0005] The traditional process used in the above patents requires large reaction kettles to heat for a long time to prepare alumina and silicon dioxide materials from coal-based solid waste. The return mixing in the reaction kettle, the non-uniform reaction environment, and the long reaction time make it difficult to control the uniformity of particle size. In addition, due to the scale-up effect, it is necessary to gradually scale up from small-scale to pilot-scale and industrialization, which consumes a lot of manpower and resources. SUMMARY

[0006] In order to overcome the problems of poor batch-to-batch repeatability and low production efficiency of the existing intermittent reactor, the purpose of the present application is to provide an ultrasonic micro-chemical system for synthesizing nanofluids and a method for preparing functional nanofluids from coal-based solid waste. The method can realize accurate control of reaction parameters and effectively improve production efficiency, and ultimately realize high-value utilization of coal-based solid waste.

[0007] In order to achieve the above-mentioned purpose, the present application realizes the following technical solutions:

[0008] The ultrasonic micro-chemical system for synthesizing nanofluid comprises at least one temperature-controlled ultrasonic micro-reactor, an ultrasonic leaching reaction kettle, a reactant preheating unit, a filter and a reactant storage tank.

[0009] The ultrasonic leaching reaction kettle is connected with the filter, the filter is connected with the reactant preheating unit, and the reactant preheating unit is connected with the temperature-controlled ultrasonic micro-reactor.

[0010] The reactant storage tank is connected with the reactant preheating unit, and the temperature-controlled ultrasonic micro-reactor is connected.

[0011] The further improvement of the present application is that the first fluid conveying device is arranged between the reactant storage tank and the reactant preheating unit, and the second fluid conveying device is arranged between the filter and the reactant preheating unit.

[0012] The further improvement of the present application is that the reactant preheating unit is a coil pipe placed in a constant-temperature water bath, and the product collecting end of the temperature-controlled ultrasonic micro-reactor is provided with a back pressure valve.

[0013] The temperature-controlled ultrasonic micro-reactor comprises an ultrasonic transducer and a temperature-controlled micro-reactor connected with each other.

[0014] The further improvement of the present application is that the ultrasonic transducer is a piezoelectric transducer, a sandwich transducer, a column transducer or an inverted horn transducer, the frequency of the ultrasonic transducer is 10-200 kHz, and the anti-node plane of the highest sound intensity is located at the temperature-controlled micro-reactor.

[0015] The further improvement of the present application is that the temperature-controlled micro-reactor comprises a reaction micro-channel and a heat exchange medium channel, the cross sections of the reaction micro-channel and the heat exchange medium channel are circular, rectangular, trapezoidal, rhombic, oval, triangular or irregular, the hydraulic diameter of the reaction micro-channel and the heat exchange medium channel is 100 μm-10 mm, and the length of the reaction micro-channel and the heat exchange medium channel is 0.1-2 m.

[0016] The material of the reaction micro-channel and the heat exchange medium channel of the temperature-controlled micro-reactor is polymer, metal, glass or ceramic.

[0017] One end of the reaction micro-channel is provided with a reactant inlet, and the other end is provided with a product outlet; one end of the heat exchange medium channel is provided with a heat exchange medium inlet, and the other end is provided with a heat exchange medium outlet.

[0018] Further, the polymer is polycarbonate, polymethyl methacrylate, styrene resin, polydimethylsiloxane or polytetrafluoroethylene, the metal is stainless steel, titanium alloy, zirconium alloy or hastelloy carbon steel, and the ceramic is silicon carbide.

[0019] The further improvement of the present application is that the temperature-controlled micro-reactor comprises a T-shaped, Y-shaped, cross-shaped, U-shaped or parallel-flow connected reactant mixing section channel at the inlet end.

[0020] The channel structure of the temperature-controlled micro-reactor is a circular spiral, a back-shaped spiral or a wave-shaped spiral structure.

[0021] The further improvement of the present application is that the ultrasonic leaching reactor is composed of an overhead impeller, an ultrasonic probe and a temperature-controlled reaction tank; an overhead impeller is arranged at the top of the reactor, and an ultrasonic probe is arranged in the reactor; the impeller is equipped with stainless steel blades, and the working speed is 50-800 rpm; the working frequency of the ultrasonic probe is 10-200 kHz.

[0022] A method for preparing functional nanofluid from coal-based solid waste, comprising the following steps:

[0023] After the coal-based solid waste is pretreated, the acid is introduced into the ultrasonic leaching reactor, the ultrasonic cavitation is used to strengthen the leaching of aluminum elements in the coal-based solid waste, and after the reaction, solid-liquid separation is performed to obtain an aluminum-rich acid leaching solution and a high-silicon acid leaching residue;

[0024] The aluminum-rich acid leaching solution and the alkali solution are preheated in a reactant preheating unit and then introduced into a temperature-controlled ultrasonic micro-reactor to perform a reaction, so as to obtain an aluminum oxide nanofluid;

[0025] After the high-silicon acid leaching residue is washed to a pH of 6-7 and dried, the alkali solution is introduced into the ultrasonic leaching reactor, and after the reaction, solid-liquid separation is performed to obtain a desiliconized leaching solution and a carbon-rich waste residue;

[0026] The desiliconized leaching solution and the acid solution / acid gas are preheated in a preheating unit and then introduced into a temperature-controlled ultrasonic micro-reactor to perform a reaction at 20-120 DEG C, so as to obtain a silicon dioxide nanofluid.

[0027] The further improvement of the present application is that the coal-based solid waste comprises fly ash, coal gangue and coal gasification ash;

[0028] The acid is one of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and acetic acid, the concentration of the hydrochloric acid, the sulfuric acid, the nitric acid and the phosphoric acid is 0.1-12 mol / L, the concentration of the acetic acid is 0.1-6 mol / L, the liquid-solid ratio of the coal-based solid waste and the acid is 5-50 mL / g, the reaction temperature is 20-100 DEG C, and the reaction time is 0.1-48 h.

[0029] The further improvement of the present application is that the alkali solution is one or both of a sodium hydroxide solution and a potassium hydroxide solution, the mass fraction of the alkali solution is 1%-30%, the liquid-solid ratio is 5-50 mL / g, the set temperature is 20-100 DEG C, and the reaction time is 0.1-48 h.

[0030] The alkali liquor is one or two of sodium hydroxide solution, potassium hydroxide solution, sodium carbonate solution and ammonia solution, and the mass fraction of the alkali liquor is 1-10%;

[0031] The acid liquor is one or several combinations of 0.01-1 mol / L of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and acetic acid; and the acid gas is one or several of CO2, HCl, SO2, SO3, NO2, Cl2, Br2 and H2S.

[0032] Compared with the prior art, the present application has the beneficial effects of:

[0033] The temperature-controlled micro-reactor in the present application adopts the method of jointly regulating the micro-channel length in the reactor and the material flow rate to realize the accurate control of the material residence time and the narrow residence time distribution. The temperature-controlled ultrasonic micro-reactor can be based on the parallel number amplification method, and the micro-channels are stacked in parallel to improve the material processing capacity of the micro-reaction unit, realize the amplification of the micro-reaction equipment and move towards industrialization. The micro-chemical system can be multi-stage connected and stacked according to the needs of the preparation process conditions, and has advantages in the aspects of multi-functionality of multiphase reaction, flexibility of reaction amplification, etc.

[0034] Further, the temperature-controlled ultrasonic micro-reactor can parallelly connect multiple ultrasonic transducers according to the process requirements when the channel length or the channel size of the reactor is increased, so as to ensure the ultrasonic cavitation effect in the reaction channel.

[0035] Further, the reactant preheating unit is a coil placed in a constant-temperature water bath to preheat the reactants, thereby effectively controlling the temperature of the reaction unit; and the product collection end of the temperature-controlled ultrasonic micro-reactor is provided with a back pressure valve to regulate the pressure of the reaction unit.

[0036] Compared with the traditional utilization direction of using coal-based solid waste for ground filling and preparing building materials, the coal-based solid waste preparation functional nanofluid method based on the ultrasonic micro-chemical system in the application can realize higher economic benefit of resource recycling of coal gasification ash. In view of the defects of low production efficiency and unstable product quality of the traditional intermittent reaction synthesis system, the continuous synthesis process based on the ultrasonic micro-reactor in the application can realize ultrahigh mixing efficiency by using the micro-channel with large specific surface area of the micro-reactor, and can quickly and high-throughput synthesize aluminum oxide and silicon dioxide nanofluids with uniform particle size distribution. In addition, the material can be finally prepared on a large scale and with stable production performance by flexibly controlling different proportions and flow rates. Since the traditional reaction kettle has a serious amplification effect, the process needs to be continuously adjusted and optimized at the small test, pilot test and industrialization stages. This process needs to consume a large amount of time cost and labor and material cost. The micro-chemical technology in the application has no amplification effect, and the production capacity can be expanded by increasing the number of micro-reactors in parallel and selectively enlarging the equipment size. In addition, the micro-chemical technology can realize efficient connection of research and production while strengthening heat and mass transfer and ensuring consistency of reaction conditions, thereby greatly reducing industrialization cost. The ultrasonic micro-reactor is used to prepare the functional nanofluid in the application. The cavitation bubbles generated by ultrasonic waves in the liquid working medium can realize multiphase mixing mass transfer strengthening, dredge solid particle blockage and promote uniform dispersion of nanoparticles in the nanofluid.

[0037] Further, the micro-reactor structure in the temperature-controlled ultrasonic micro-reactor adopts a compact double-channel spiral structure, which saves volume and reduces excess sound energy consumption. The adjacent channel heat transfer fluid and the reactant flow countercurrently, and the heat transfer area is large, which greatly enhances the heat transfer effect and realizes accurate adjustment of the reaction temperature.

[0038] Further, the coal-based solid waste is first used as a silicon source and an aluminum source in the application, the solid-liquid reaction is intensified based on ultrasonic technology, and the silicon dioxide and aluminum oxide nanofluid is prepared by the temperature-controlled ultrasonic micro-reactor one-step method. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 It is a structure schematic diagram of a reaction unit device of an ultrasonic micro-chemical system of the application

[0040] Figure 2 It is a schematic diagram of a temperature-controlled ultrasonic micro-reactor;

[0041] Figure 3 It is a schematic diagram of a cross, Y-shaped, T-shaped and U-shaped connection mixing structure; wherein (a) is a cross, (b) is a Y-shaped, (c) is a T-shaped, and (d) is a U-shaped;

[0042] Figure 4 It is a schematic diagram of a horizontal cross-sectional structure of a temperature-controlled ultrasonic micro-reactor;

[0043] Figure 5Fig. 1 is a schematic diagram of the channel structure of a temperature-controlled ultrasonic microreactor; wherein (a) is a circular double helix channel, (b) is a wavy double helix channel, and (c) is a back-to-back double helix channel;

[0044] Figure 6 Fig. 2 is a schematic diagram of the ultrasonic transducer integration method for the size amplification of an ultrasonic microreactor;

[0045] Figure 7 Fig. 3 is a TEM image of the silica particles in the silica nanofluid synthesized in Example 2;

[0046] Figure 8 Fig. 4 is a TEM image of the alumina particles in the alumina nanofluid synthesized in Example 1;

[0047] In the figure, 1 is a reactant storage tank; 2 is a first fluid conveying device; 3 is an ultrasonic leaching reactor; 4 is a filter; 5 is a second fluid conveying device; 6 is a reactant preheating unit; 7 is a temperature-controlled ultrasonic microreactor; 8 is a product collection tank; 7-1 is a reaction microchannel; 7-2 is a heat exchange medium channel; 7-3 is an ultrasonic transducer; 4-1 is a heat exchange working medium inlet; 4-2 is a product outlet; 4-3 is a heat exchange working medium outlet; and 4-4 is a reactant inlet. DETAILED DESCRIPTION

[0048] In order to facilitate the understanding of the present application, a more complete description of the present application will be provided below with reference to the relevant drawings. The preferred embodiments of the present application are shown in the drawings. However, the present application can be implemented in various different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0049] In addition, the elements in the present application are referred to as "fixed to" or "disposed on" another element, which can be directly on another element or can have a middle element. When an element is considered to be "connected" to another element, it can be directly connected to another element or can have a middle element. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are only for illustrative purposes and do not represent the only embodiment.

[0050] The method for preparing functional nanofluid from coal-based solid waste of the present application uses an ultrasonic microchemical system for synthesizing nanofluid, which includes at least one temperature-controlled ultrasonic microreactor 7, an ultrasonic leaching reactor 3, a reactant preheating unit 6, a filter 4, a reactant storage tank 1, a product collection tank 8, and two fluid conveying devices (a first fluid conveying device 2 and a second fluid conveying device 5), as shown in Figure 1

[0051] ​The temperature-controlled ultrasonic microreactor 7, as shown in Figure 2 includes an ultrasonic transducer 7-3 and a temperature-controlled microreactor, and the rigid connection between the ultrasonic transducer and the microreactor is achieved by one or more of adhesion, welding, and mechanical structure fixation; the type of ultrasonic transducer 7-3 includes but is not limited to piezoelectric transducer, sandwich transducer, column transducer, or inverted horn transducer, the frequency of the ultrasonic transducer 7-3 is 10-200 kHz, and the highest acoustic intensity anti-node plane is located at the temperature-controlled microreactor;

[0052] The temperature-controlled microreactor contains a reaction microchannel 7-1 and a heat exchange medium channel 7-2, which are separated by a thin wall, and the cross section of the reaction microchannel 7-1 and the heat exchange medium channel 7-2 includes but is not limited to circular, rectangular, trapezoidal, rhombic, oval, triangular, or irregular shape, etc.; the channel hydraulic diameter is 100 μm-10 mm, and by selectively increasing the channel size in one dimension, the size in the other dimension can be kept in the microscale, so as to realize the scale-up of the temperature-controlled ultrasonic microreactor and improve the synthesis efficiency; the channel length is 0.1-2 m.

[0053] The materials of the reaction microchannel 7-1 and the heat exchange medium channel 7-2 of the temperature-controlled microreactor include polymer (polycarbonate (PC), polymethyl methacrylate (PMMA), styrene resin (PS, ABS, etc.), polydimethylsiloxane (PDMS), polytetrafluoroethylene (PTFE), etc.), metal (stainless steel, titanium alloy, zirconium alloy, hastelloy carbon steel, etc.), glass or ceramic (silicon carbide), etc.

[0054] Referring to Figure 3 (a), (b), (c), and (d) of the present application, the channel structure of the reactant mixing section at the front end of the temperature-controlled microreactor is a simple contact structure such as T-shaped, Y-shaped, cross-shaped, U-shaped, and parallel flow connection, so as to improve the mixing efficiency and realize the rapid premixing of two or more streams of materials.

[0055] The reaction microchannel 7-1 and the heat exchange medium channel 7-2 are separated by a thin wall into two spiral channels, and the reactants and the heat exchange fluid exchange heat through the channel wall surface, and the countercurrent flow of the two fluids greatly enhances the heat exchange effect, as shown in Figure 4 The reaction microchannel 7-1 is provided with a reactant inlet 4-4 at one end and a product outlet 4-2 at the other end, and the heat exchange medium channel 7-2 is provided with a heat exchange working medium inlet 4-1 at one end and a heat exchange working medium outlet 4-3 at the other end.

[0056] Referring to Figure 5The channel structure of the temperature-controlled microreactor in (a), (b) and (c) includes but is not limited to a circular spiral, a back-shaped spiral and a wave-shaped spiral structure, and the temperature-controlled microreactor realizes accurate control of the residence time and narrow residence time distribution of the material by jointly regulating the length of the microchannel in the reactor and the flow rate of the material.

[0057] The temperature-controlled ultrasonic microreactor 7 can be connected with multiple ultrasonic transducers 7-3 in parallel as required when the length of the channel of the reactor or the size of the channel is increased, so that the area of the temperature-controlled microreactor in the horizontal direction is greatly increased, as shown in the drawing, thereby ensuring the ultrasonic cavitation effect in the reaction channel. Figure 6

[0058] The temperature-controlled ultrasonic microreactor 7 can be amplified based on the number of parallel methods by stacking the microchannels in parallel, thereby improving the material processing capacity of the microreaction unit and realizing the amplification and industrialization of the microreaction equipment.

[0059] The ultrasonic leaching reaction kettle 3 is a continuous stirring reaction kettle equipped with an ultrasonic probe, which is composed of an overhead impeller, an ultrasonic probe and a temperature-controlled reaction tank; an overhead impeller is arranged at the top of the reaction kettle, and an ultrasonic probe is arranged in the reaction kettle; the impeller is equipped with stainless steel blades, and the working speed is 50-800 rpm; the working frequency of the ultrasonic probe is 10-200 kHz.

[0060] The reactant preheating unit 6 is a coil placed in a constant-temperature water bath to preheat the reactants, thereby effectively controlling the temperature of the reaction unit; the product collection end of the temperature-controlled ultrasonic microreactor 7 is provided with a back pressure valve for regulating the pressure of the reaction unit;

[0061] The microchemical system can be multi-stage connected and stacked according to the needs of the preparation process conditions, and has advantages in multifunctionality of multiphase reaction, flexibility of reaction amplification and the like.

[0062] The method for preparing functional nanofluid from coal-based solid waste based on the ultrasonic microchemical system comprises the following steps:

[0063] 1) After the coal-based solid waste is pretreated by crushing, screening and magnetic separation and iron removal, the coal-based solid waste and acid liquid are fed into the ultrasonic leaching reaction kettle 3, the ultrasonic cavitation strengthens the leaching of aluminum elements in the coal-based solid waste, and after sufficient reaction at a certain temperature for a period of time, the solid-liquid mixture is separated by a filter to obtain an aluminum-rich acid leaching liquid and a high-silicon acid leaching residue;

[0064] The coal-based solid waste includes fly ash, coal gangue and coal gasification slag.

[0065] ​The acid liquor is one of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and acetic acid. Preferably, the concentration of hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid is 0.1-12 mol / L, the concentration of acetic acid is 0.1-6 mol / L, the liquid-solid ratio of coal-based solid waste and acid liquor is 5-50 mL / g, the reaction temperature is 20-100℃, and the reaction time is 0.1-48 h;

[0066] 2) The two materials of the aluminum-rich acid leaching solution and the alkali solution are respectively controlled by the first fluid conveying device 2 and the second fluid conveying device 5 to enter the coil of the reactant preheating unit 6, and the reactants are preheated to a specified temperature by the preheating unit;

[0067] Preferably, the mass fraction of the alkali solution is 1%-30%, the liquid-solid ratio is 5-50 mL / g, the reaction temperature is 20-100℃, and the reaction time is 0.1-48 h;

[0068] 3) The preheated aluminum-rich acid leaching solution and the dilute alkali solution are then introduced into the temperature-controlled ultrasonic microreactor, and pre-mixing of the two streams is realized at the front end. The temperature during the reaction is accurately adjusted by a heat exchange medium. After a period of reaction in the temperature-controlled ultrasonic microreactor, the product is collected in a tank, and an alumina nanofluid is obtained. The introduction of ultrasonic waves into the microreactor solves the risk of solid blockage caused by the small size and curved flow channel structure of the microreactor. The acoustic cavitation effect generated by the ultrasonic waves greatly improves the mass transfer in the solution, allows more uniform growth of the entire particle surface, and increases the nucleation rate;

[0069] Preferably, the mass fraction of the alkali solution is 1%-30%, the liquid-solid ratio is 5-50 mL / g, the reaction temperature is 20-100℃, and the reaction time is 0.1-48 h;

[0070] 4) After washing the high-silicon acid leaching residue to a pH of 6-7 and drying, the residue is placed in an ultrasonic leaching reactor with an alkali solution at a certain temperature for a period of time. After solid-liquid separation through a filter, a desiliconized leaching solution and a carbon-rich waste residue are obtained;

[0071] 5) The desiliconized leaching solution and the dilute acid liquor / acid gas are respectively controlled by the first fluid conveying device 2 and the second fluid conveying device 5, and are introduced into the temperature-controlled ultrasonic microreactor 7 after preheating. After the reaction is completed at a temperature of 20-120℃, a silicon dioxide nanofluid is obtained;

[0072] Preferably, the mass fraction of the alkali solution is 1%-30%, the liquid-solid ratio is 5-50 mL / g, the reaction temperature is 20-100℃, and the reaction time is 0.1-48 h;

[0073] The first fluid delivery device 2 and the second fluid delivery device 5 control the material flow rate to be 0.5-100 mL / min, preferably, the first fluid delivery device 2 and the second fluid delivery device 5 are peristaltic pumps.

[0074] Example 1

[0075] The temperature-controlled ultrasonic microreactor of the present embodiment is formed by bonding a single ultrasonic transducer and a single microreactor with epoxy resin, the ultrasonic transducer is a piezoelectric transducer, and the ultrasonic probe and the ultrasonic transducer have a working frequency of 30 kHz. The temperature-controlled microreactor of the present embodiment is made of Hastelloy, the microreactor has a circular double helix structure, the channel cross section is circular, the mixing structure at the front end of the reaction microchannel is Y-shaped, the hydraulic diameter of the reaction microchannel and the heat exchange medium channel is 1 mm, and the length of the microchannel is 0.1 m. The coal gangue is pretreated by crushing, sieving and magnetic separation to remove iron, mixed with 5 mol / L hydrochloric acid solution in the ultrasonic leaching reactor, and reacted at a liquid-solid ratio of 10 mL / g, a reaction temperature of 90°C and a reaction time of 1 h. The product is filtered to obtain an aluminum-rich acid leaching solution and a high-silicon acid leaching residue. The aluminum-rich leaching solution and a 2% by mass sodium hydroxide solution are used as reactants, and the two materials are transported through a preheating pipeline into the ultrasonic microreactor by a peristaltic pump, the flow rate of the aluminum-rich leaching solution is 0.3 mL / min, the flow rate of the sodium hydroxide solution is 0.3 mL / min, and the temperature is controlled at 30°C by heat exchange medium water. Finally, a semitransparent, uniform and stable water-aluminum oxide nanofluid is obtained.

[0076] Reference Figure 8 It can be seen that the water-based aluminum oxide nanofluid prepared by the one-step method from coal gangue has small aluminum oxide nanoparticles and relatively uniform particle size.

[0077] Example 2

[0078] The temperature-controlled ultrasonic microreactor of the present embodiment is mechanically fixedly connected by a single ultrasonic transducer and a single temperature-controlled microreactor. The ultrasonic transducer is a sandwich transducer, and the ultrasonic probe and the ultrasonic transducer have a working frequency of 50 kHz. The temperature-controlled microreactor of the present embodiment is made of polytetrafluoroethylene, and the microreactor has a wave-shaped double-helix structure. The microchannel cross section is rectangular, the mixing structure at the front end of the reaction microchannel is T-shaped, the hydraulic diameter of the reaction microchannel and the heat exchange medium channel is 2.5 mm, and the length of the microchannel is 0.5 m. The coal gasification ash is pretreated by crushing, screening and magnetic separation to remove iron, mixed with 3 mol / L sulfuric acid solution in the ultrasonic leaching reactor, and reacted at a liquid-solid ratio of 15 mL / g and a reaction temperature of 60°C for 5 h. The product is filtered to obtain an aluminum-rich acid leaching solution and a high-silicon acid leaching residue. The high-silicon acid leaching residue is washed and dried, mixed with a 30% potassium hydroxide solution in the ultrasonic leaching reactor, and reacted at a liquid-solid ratio of 12 mL / g and a reaction temperature of 35°C. After the reaction is completed, the product is filtered to obtain a coal gasification residue desiliconization leaching solution and a carbon-rich waste residue. The desiliconization leaching solution and 0.5 mol / L acetic acid solution are used as reactants, and the two materials are transported to the ultrasonic microreactor through a preheating pipeline controlled by a peristaltic pump. The desiliconization leaching solution has a flow rate of 0.05 mL / min, the acetic acid solution has a flow rate of 0.1 mL / min, and the temperature is controlled at 25°C by heat exchange medium water. Finally, a translucent, uniform and stable water-silica nanofluid is obtained.

[0079] Referring to Figure 7 It can be seen that the water-based silica nanofluid prepared by the one-step method from coal gasification ash has small silica nanoparticles and relatively uniform particle size.

[0080] Example 3

[0081] The temperature-controlled ultrasonic micro-reactor of the embodiment is connected by welding between two ultrasonic transducers and a single micro-reactor. The ultrasonic transducers are piezoelectric transducers. The ultrasonic probe and the ultrasonic transducer have a working frequency of 30 kHz. The temperature-controlled micro-reactor of the embodiment is made of Hastelloy. The micro-reactor has a channel structure in the shape of a back-shaped double helix. The channel cross-section is in the shape of a rhombus. The mixing structure at the front end of the reaction micro-channel is in the shape of a cross. The hydraulic diameter of the reaction micro-channel and the heat exchange medium channel is 5 mm. The length of the micro-channel is 1 m. The fly ash is pretreated by crushing, screening and magnetic separation to remove iron. The fly ash is mixed with 5 mol / L nitric acid solution in an ultrasonic leaching reactor. The liquid-solid ratio is 30 mL / g. The reaction temperature is 30°C. The reaction time is 10 h. The product is filtered to obtain an aluminum-rich acid leaching solution and a high-silicon acid leaching residue. The aluminum-rich acid leaching solution and a 5% sodium hydroxide solution are used as reactants. The two streams of materials are transported to the ultrasonic micro-reactor through a preheating pipeline by a peristaltic pump. The flow rate of the aluminum-rich leaching solution is 50 mL / min. The flow rate of the sodium hydroxide solution is 25 mL / min. The temperature is controlled at 40°C by the heat exchange medium water. Finally, a semi-transparent, uniform and stable water-aluminum oxide nanofluid is obtained.

[0082] Embodiment 4

[0083] The temperature-controlled ultrasonic micro-reactor of the embodiment is mechanically connected between a single ultrasonic transducer and a single temperature-controlled micro-reactor. The ultrasonic transducer is a column-shaped transducer. The ultrasonic probe and the ultrasonic transducer have a working frequency of 100 kHz. The temperature-controlled micro-reactor of the embodiment is made of titanium alloy. The micro-reactor has a channel structure in the shape of a circular double helix. The micro-channel cross-section is in the shape of a triangle. The mixing structure at the front end of the reaction micro-channel is in the shape of a parallel flow. The hydraulic diameter of the reaction micro-channel and the heat exchange medium channel is 10 mm. The length of the micro-channel is 0.5 m. The coal gasification slag is pretreated by crushing, screening and magnetic separation to remove iron. The coal gasification slag is mixed with 10 mol / L sulfuric acid solution in an ultrasonic leaching reactor. The liquid-solid ratio is 40 mL / g. The reaction temperature is 60°C. The reaction time is 7 h. The product is filtered to obtain an aluminum-rich acid leaching solution and a high-silicon acid leaching residue. The high-silicon acid leaching residue is washed and dried. The high-silicon acid leaching residue is mixed with a 30% potassium hydroxide solution in an ultrasonic leaching reactor. The liquid-solid ratio is 40 mL / g. The reaction temperature is 50°C. After the reaction is completed, the product is filtered to obtain a desiliconized leaching solution of the coal gasification slag and a carbon-rich waste residue. The desiliconized leaching solution and CO2 gas are used as reactants. The two reactants are transported to the ultrasonic micro-reactor through a preheating pipeline by a gas pump and a peristaltic pump. The flow rate of the desiliconized leaching solution is 10 mL / min. The flow rate of the CO2 gas is 10 mL / min. The reaction temperature is controlled at 65°C by the heat exchange medium water. Finally, a semi-transparent, uniform and stable water-silicon dioxide nanofluid is obtained.

[0084] Embodiment 5

[0085] The temperature control ultrasonic microreactor of the embodiment is connected by welding from four ultrasonic transducers and a single temperature control microreactor, the type of the ultrasonic transducer is an inverted horn type transducer, and the working frequency of the ultrasonic probe and the ultrasonic transducer is 200 kHz. The temperature control microreactor of the embodiment adopts a stainless steel material, the microreactor inner passage structure is a back-shaped double spiral structure, the passage section is a rhombus, the mixing structure at the front end of the reaction microchannel is cross connection, the hydraulic diameter of the reaction microchannel and the heat exchange medium channel is 5 mm, and the microchannel length is 2 m. The fly ash is pretreated by crushing, screening and magnetic separation to remove iron, mixed with a 5 mol / L phosphoric acid solution in an ultrasonic leaching reactor, the liquid-solid ratio is 50 mL / g, the reaction temperature is 80 DEG C, and the reaction time is 20 h, the product is filtered to obtain an aluminum-rich acid leaching solution and a high-silicon acid leaching residue; the aluminum-rich leaching solution and a 10% ammonia water solution are used as reactants, and the two materials are transported to the ultrasonic microreactor through a preheating pipeline controlled by a peristaltic pump, the flow rate of the aluminum-rich leaching solution is 70 mL / min, the flow rate of the sodium hydroxide solution is 15 mL / min, and the temperature is controlled to 80 DEG C by the heat exchange medium water; and finally a semitransparent, uniform and stable water-aluminum oxide nanofluid is obtained.

[0086] The application has the following advantages:

[0087] Compared with direct stacking and bottom filling of coal-based solid waste, the application realizes high-value utilization of coal-based solid waste.2. Compared with the traditional synthesis process, the large-area ultrasonic microreactor of the application makes the mixture more uniform, and the generated aluminum oxide and silicon dioxide nanomaterials have more uniform and controllable morphology.3. Compared with the traditional drop-in stirring method, the synthesis using the microreactor of the application is faster and can realize high-throughput synthesis.4. The microreactor structure in the application is variable, and can be flexibly selected according to the actual situation.5. The flow rate of the reactants in the application can be adjusted by a microflow pump, so that the residence time of the reactants is accurately controlled, thereby synthesizing aluminum oxide and silicon dioxide nanoparticles with different particle size distributions.6. The functional nanofluid synthesis process based on the microchemical process of the application is more continuous, reduces the manual intervention, and improves the production efficiency.7. The ultrasonic microchemical system is used to prepare the functional nanofluid from coal-based solid waste, and the cavitation bubbles generated by the ultrasonic wave in the liquid working medium can realize multiphase mixing mass transfer intensification, unblock solid particle blockage, and promote uniform dispersion of nanoparticles in the nanofluid.8. The microreactor structure in the temperature control ultrasonic microreactor adopts a compact double-channel spiral structure, the adjacent channel heat exchange fluid and the reactant flow in counterflow, thereby saving the volume, reducing unnecessary energy consumption, and realizing accurate adjustment of the reaction temperature.

[0088] The above description only illustrates the best mode of the present application and is not to be construed as limiting the scope of the claims. The present application is not limited to the above embodiments, and the specific structure allows variations. Any variations made within the scope of the independent claims of the present application are within the scope of the present application.

[0089] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

Claims

1. A method for the preparation of functional nanofluid from coal-based solid waste, characterized by, The application discloses an ultrasonic micro-chemical device for synthesizing nanofluid, which comprises at least one temperature-controlled ultrasonic micro-reactor (7), an ultrasonic leaching reaction kettle (3), a reactant preheating unit (6), a filter (4) and a reactant storage tank (1). The ultrasonic leaching reaction kettle (3) is connected with the filter (4), the filter (4) is connected with the reactant preheating unit (6), the reactant storage tank (1) is connected with the reactant preheating unit (6), and the reactant preheating unit (6) is connected with the temperature-controlled ultrasonic micro-reactor (7). The temperature-controlled ultrasonic micro-reactor (7) comprises an ultrasonic transducer (7-3) and a temperature-controlled micro-reactor connected with each other. The temperature-controlled micro-reactor comprises a reaction micro-channel (7-1) and a heat exchange medium channel (7-2), and the reaction micro-channel (7-1) and the heat exchange medium channel (7-2) are separated into two spiral channels by a thin wall. The method comprises the following steps: The coal-based solid waste is pretreated and then introduced into the ultrasonic leaching reaction kettle (3) together with acid, so that the leaching of aluminum elements in the coal-based solid waste is strengthened by ultrasonic cavitation, and after reaction and solid-liquid separation, an aluminum-rich acid leaching solution and a high-silicon acid leaching residue are obtained. The aluminum-rich acid leaching solution and an alkali solution are introduced into the reactant preheating unit (6) for preheating, and then introduced into the temperature-controlled ultrasonic micro-reactor for reaction, so that an aluminum oxide nanofluid is obtained. The high-silicon acid leaching residue is washed to a pH value of 6-7, dried, and then introduced into the ultrasonic leaching reaction kettle together with an alkali solution, so that after reaction and solid-liquid separation, a desiliconized leaching solution and a carbon-rich waste residue are obtained. The desilicated leaching solution and the acid liquid / acid gas are preheated by a preheating unit and then enter a temperature-controlled ultrasonic microreactor (7) to react, 20-120 o C to obtain a silica nanofluid.

2. The method of claim 1, wherein the coal-based solid waste is prepared functional nanofluid, characterized in that, The coal-based solid waste comprises fly ash, coal gangue and coal gasification ash. The acid is one of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and acetic acid, the concentration of hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid is 0.1-12 mol / L, the concentration of acetic acid is 0.1-6 mol / L, the liquid-solid ratio of coal-based solid waste and acid is 5-50 mL / g, the reaction temperature is 20-100 o C, and the reaction time is 0.1-48 h.

3. The method of claim 1, wherein the coal-based solid waste is prepared functional nanofluid, characterized by, The alkali liquor is one or both of sodium hydroxide solution and potassium hydroxide solution, the mass fraction of the alkali liquor is 1% to 30%, the liquid-solid ratio is 5-50 mL / g, the set temperature is 20 to 100 o C, and the reaction time is 0.1 to 48 h. The alkali solution is one or two of a sodium hydroxide solution, a potassium hydroxide solution, a sodium carbonate solution and an ammonia water solution, and the mass fraction of the alkali solution is 1-10%. The acid solution is one or a combination of several of 0.01-1 mol / L hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and acetic acid, and the acid gas is one or several of CO2, HCl, SO2, SO3, NO2, Cl2, Br2 and H2S.

4. The method of claim 1, wherein the coal-based solid waste is prepared functional nanofluid, characterized by, A first fluid conveying device (2) is arranged between the reactant storage tank (1) and the reactant preheating unit (6), and a second fluid conveying device (5) is arranged between the filter (4) and the reactant preheating unit (6).

5. The method of claim 1, wherein the coal-based solid waste is prepared functional nanofluid, characterized by, The reactant preheating unit (6) is a coil pipe placed in a constant-temperature water bath, and a back pressure valve is arranged at a product collecting end of the temperature-controlled ultrasonic micro-reactor (7).

6. The method of claim 5, wherein the coal-based solid waste is prepared functional nanofluid, characterized by, The ultrasonic transducer (7-3) is a piezoelectric transducer, the frequency of the ultrasonic transducer (7-3) is 10-200 kHz, and the anti-node plane of the highest acoustic intensity is located at the temperature-controlled micro-reactor.

7. The method of claim 5, wherein the coal-based solid waste is prepared functional nanofluid, characterized by, The ultrasonic transducer (7-3) is a sandwich transducer, a column transducer or an inverted horn transducer.

8. The method of claim 5, wherein the coal-based solid waste is prepared functional nanofluid, characterized by, The cross sections of the reaction micro-channel (7-1) and the heat exchange medium channel (7-2) are circular, rectangular, trapezoidal, rhombic, oval, triangular or irregular, the hydraulic diameters of the reaction micro-channel (7-1) and the heat exchange medium channel (7-2) are 100 microns to 10 mm, and the lengths of the reaction micro-channel (7-1) and the heat exchange medium channel (7-2) are 0.1-2 m. The materials of the reaction micro-channel (7-1) and the heat exchange medium channel (7-2) of the temperature-controlled micro-reactor are polymers, metals, glass or ceramics. The reaction microchannel (7-1) is provided with a reactant inlet (4-4) at one end and a product outlet (4-2) at the other end, and the heat exchange medium channel (7-2) is provided with a heat exchange medium inlet (4-1) at one end and a heat exchange medium outlet (4-3) at the other end.

9. The method for preparing functional nanofluid from coal-based solid waste according to claim 5, wherein the temperature-controlled microreactor comprises a T-shaped, Y-shaped, cross-shaped, U-shaped or parallel-flow connected reactant mixing section channel at the inlet end. The channel structure of the temperature-controlled microreactor is a circular spiral, a back-to-back spiral or a wave-shaped spiral structure.

10. The method for preparing functional nanofluid from coal-based solid waste according to claim 5, wherein the ultrasonic leaching reaction kettle (3) comprises a top-mounted impeller, an ultrasonic probe and a temperature-controlled reaction tank; a top-mounted impeller is arranged at the top of the reaction kettle, and an ultrasonic probe is arranged in the reaction kettle; the impeller is provided with stainless steel blades and has a working speed of 50-800 rpm; and the ultrasonic probe has a working frequency of 10-200 kHz.

Images