Due to its mass transfer, heat transfer and chemical reaction, ultrasonic has become a hot research topic in the world, especially the United States, Britain, France, unique role and the development and popularization of ultrasonic power equipment. Other countries have made some progress in industrialization. China's science and technology development has become a new interdisciplinary discipline - sonochemistry. Its development has also been done by workers in theory and application.
The so-called ultrasonic wave generally refers to sound waves with a frequency range of 20k to 10MHz , and its application power in the chemical field mainly comes from ultrasonic cavitation. With strong shock waves and micro-jets with speeds higher than 100 m/s , high-gradient shear of shock waves and micro-jets can generate hydroxyl radicals in aqueous solution, and the corresponding physicochemical effects are mainly mechanical effects ( acoustic flow, shock wave) , micro-jet, etc. ) , thermal effects ( local high temperature and high pressure, overall temperature rise ) , light effect ( sound luminescence ) and activation effect ( hydroxyl radicals generated in aqueous solution ) , the four effects are not isolated, but interact, promote each other, accelerate Reaction process.
This paper reviews the main applications of ultrasonic in the chemical industry in recent years, in order to promote the research and application of ultrasonic technology in engineering.
*1 cleaning *
Ultrasonic cleaning is one of the main applications of ultrasonic. Compared with other cleaning, ultrasonic cleaning has high efficiency and good quality. It can clean complex parts, deep holes, blind holes and dirt in slits, and is easy to automate. . Currently, several ultrasonic cleaning machine manufacturers from the early 1990s to today's more than a few hundred. With the further development of China's national economy, it must become an indispensable technological means for many industries, medical and environmental protection departments.
The operating frequency of the ultrasonic cleaner is roughly divided into three frequency bands according to the cleaning object: low frequency ultrasonic cleaning (20 to 50 kHz) , high frequency ultrasonic cleaning (50 to 200 kHz), and megahertz ultrasonic cleaning (700 k to 1 MHz or higher ) . Low-frequency ultrasonic cleaning is suitable for applications where the surface of large parts or the surface of the dirt and cleaning parts is high. The low end of the frequency, high cavitation intensity, easy to corrode the surface of the cleaning part, is not suitable for cleaning parts with high surface finish, and the cavitation noise is large. At a frequency of about 40 kHz , at the same sound intensity, the number of cavitation bubbles generated is more than the frequency of 20 kHz , the penetration force is strong, but the cavitation intensity is low, and the workpiece with complicated surface shape or blind holes should be cleaned and cleaned. The dirt has weak adhesion to the surface of the part to be cleaned, and the cavitation noise is small. High-frequency ultrasonic cleaning is suitable for fine cleaning of microelectronic components such as magnetic disks, drives, read/write heads, liquid crystal glass, flat panel displays, micro-components and polished metal parts. These cleaning objects are required to be free of cavitation corrosion during the cleaning process and to wash off micron-scale dirt. Megahertz ultrasonic cleaning is suitable for the cleaning of integrated circuit chips, silicon wafers and films. It is required to remove micron and submicron dirt without any damage to the cleaning components. Since cavitation does not occur at this time, the cleaning mechanism is mainly the effect of sound pressure gradient, particle velocity and sound flow. The feature is that the cleaning direction is strong, and the cleaning member is generally placed in a direction parallel to the sound beam. According to the cleaning medium, it can be divided into conventional cleaning and gas phase ultrasonic cleaning. Conventional cleaning refers to the use of conventional cleaning solvents that do not evaporate on a large scale, such as water, water-based cleaning agents, and some petroleum products for cleaning. Commonly used cleaning methods combined with ultrasound include high temperature soaking, bubbling, spraying, etc.; drying methods generally use hot air drying, centrifugal drying and the like. Gas phase cleaning generally uses a volatile cleaning solvent such as Freon, trichloroethylene, trichloroethane, etc., and their ability to clean oil is particularly strong, but the boiling point is low, and a condensation recovery system is generally used in use. Commonly used cleaning methods combined with ultrasound include hot dip, spray, steam bath, etc.; the drying method is generally freeze-dried.
*2 extraction *
Ultrasonic enhanced solvent extraction relies mainly on liquid cavitation, so any parameters that affect cavitation effects such as ultrasonic power, frequency, duration of action, and properties of the extraction system will affect the extraction. Ultrasonic application to the extraction process includes solid - liquid extraction and liquid - liquid extraction, which improves and enhances the mass transfer rate and effect of the extraction separation as a whole by conventional methods such as heat treatment, mechanical agitation or pressure change. Ultrasonic extraction can not only enhance the extraction process of substances by conventional fluids, but also enhance the extraction process of substances under supercritical conditions and improve the yield. Examples of applications of ultrasonic enhanced extraction in chemical processes are:
(1) When extracting asphaltenes from oil shale with 8 solvents such as benzene , the extraction rate under the action of 50 kHz and 400 W is equivalent to 24 times that of Soxhlet method ;
(2) When leaching a 17.3% zinc ore sample containing zinc with a mixed solution of sodium hydroxide and ammonium chloride , the leaching rate can be greatly accelerated by using 22 kHz and 100 W of ultrasound;
(3) Sound field irradiation with a frequency of 20 kHz , power of 100 W and 600 W can increase the rate of pyrethroids extracted from powdered pyrethrums by n-hexane;
(4) 24 ± 2.5 kHz , 120W ultrasonic irradiation of methanol extracting benzopyrene (a) in environmental samples , there is an unparalleled extraction rate of vacuum sublimation;
(5) 18.5 kHz , 250 W high-intensity large single-headed insertion ultrasonic field can increase the rate of gold leaching by cyanidation;
(6) Ultrasonic extraction of 20 kHz for the extraction of motherwort total alkali is higher than that of the general reflux method, and the extraction time is shortened. The extraction rate after extraction by reflux method for 2h was 0.176% , and ultrasonic extraction
After 40 minutes , the extraction rate can reach 0.248% ;
(7) Ultrasonic irradiation with 1MHz and 0.2W/cm 2 for 15min can accelerate the phase separation speed of Mo and W by using acidic phosphoric acid extractant by 4 to 5 times; ultrasonic irradiation with 20kHz and 19W/cm can make The extraction rate of Ga is increased by 15 times; (8) Ultrasonic irradiation with 20 kHz and 47 W , accompanied by mechanical stirring, can increase the extraction rate of Ni by 4 to 7 times.
At present, ultrasonic extraction technology has been applied to a small number of samples in some industries, and there are still few large-scale production applications. The corresponding ultrasonic extraction equipment is still immature, and it is necessary to strengthen the equipment development and optimize the process parameters.
*3 crystal, crush *
Ultrasound can both produce a rapid and gentle precipitation of solid solutes in a supersaturated solution and enhance crystal growth. Solution crystallization plays an important role in the separation and purification of organic soluble substances and inorganic salts. It not only separates the solute from the solution in a solid state, but also can be used for purification because different crystals have different crystal lattices. Crystal matter. Compared with other stimulation crystallization and seeding crystallization methods, ultrasonic nucleation requires lower supersaturation and faster growth. The resulting nucleus is more uniform, complete and smooth, and the crystal nucleus and finished crystal size distribution range is better. Small, the coefficient of variation is low. However, the microfluidic jet generated by the collapse of the ultrasonic cavitation bubble has a eclipse effect on the surface of the crystal. If the intensity is too large, the crystal will be broken and the crystal growth will be destroyed. Wang Weining et al . introduced the ultrasonic wave with a frequency of 33 kHz and a power of 250 W into the crystallization process of basic magnesium chloride, which shortened the induction period of the supersaturated solution, and the crystallization process changed from 12 h to 4 h , and the higher the ultrasonic frequency, the faster the nucleation rate and the induction period. The shorter the time, the shorter the time it takes for the crystal to complete. Based on this research, the ultrasonic crystallizer has begun to be put into industrial implementation. The molten metal is sonicated during curing to make the crystal grains finer and to improve physical properties such as elongation and mechanical strength. Sonication indicates that carbon steel, which can make the grain size decreases from 200 μ m to 25 ~ 30 μ m, the ductility increased by 30% to 40%, the mechanical strength increased by 20% to 30%. In the pharmaceutical industry, ultrasonic crystallization has been used to produce oral or subcutaneous suspension suspensions in order to obtain fine, uniform particles. Other examples of ultrasonically enhancing the crystallization of a solution such as potassium nitrate, acetamide or sodium potassium tartrate. An important benefit of ultrasonic assisted crystallization or precipitation for industrial production is that the fixed precipitate does not deposit on the cooling cooling tube, thus ensuring a uniform distribution of the cooling rate of the system. Ultrasonic anti-scaling and descaling technology does not need to change the structure and process conditions of the heat exchange equipment, and does not need to add any chemical agents. It is one of the best green anti-scaling technologies. Ultrasonic vibration is transmitted to the tube bundle through the metal member, so that the scale on the tube bundle is continuously peeled off, which slows down the scale of the tube bundle, and the ultrasonic wave causes the partial hardness salt to crystallize in the solution to form an atheroma precipitate. This technology has been well applied in companies such as Shanxi Southwest Wind Group.
*4 Emulsification, demulsification *
* * There are currently three main theories of phacoemulsification: cavitation, surface instability, and micro-flushing caused by ultrasound. Compared with general emulsification processes and equipment ( such as propellers, colloid mills and homogenizers ) , phacoemulsification has the following characteristics: (1) The emulsification quality is high, and the average droplet size of the formed emulsion is small, which can be
0.2 to 2 μ m , the droplet size distribution range is narrow, which can be
0.1 to 10 μ m or less, high concentration, pure emulsion concentration up to 30% , plus emulsifier up to 70% .
(2) It can produce stable emulsion without or with less emulsifier, and some can be stabilized for several months to more than half a year, with low energy consumption, high production efficiency and low cost.
(3) The type of emulsion can be controlled. Under certain sound field conditions, both o/w ( oil-in-water ) and w/o ( water -in- oil ) emulsions can be prepared. However, it is impossible to use mechanical emulsification. Only the nature of the emulsifier can control lactic acid. Types of. For example, toluene is emulsified in water, forming one type of emulsion under low sound intensity conditions, and another type of emulsion under high sound intensity conditions.
(4) The power required to produce the emulsion is small. Such as: preparation of 4.55m3 / h , droplet size of 1 μ m emulsion, if the reed whistle, when the working pressure is 10.5 ~ 14.1kg / cm2 , only 5 ~ 7 horsepower drive power, and the use of high pressure When the working pressure is 70.3 to 351.6kg/cm2 , the driving power of 40 to 50 horsepower is required . Ultrasonic emulsification can also prepare an emulsion which cannot be obtained by a general method. For example, an ordinary emulsion can only obtain an emulsion of 5% paraffin in water, and in the sound field, a 20% paraffin emulsion can be obtained . The fuel is mixed with water, emulsified and burned, and has been promoted and applied in China for many years. In this process, no emulsifier is needed, and the particle size of the emulsified oil is about 1 μm , and the energy saving is 6% to 25% , the dust is reduced by 40% to 90% , and the NOx is reduced by 20% to 75% . Environmental protection. By adding a small amount of water to the kerosene mixed fuel for phacoemulsification, a stable kerosene suspension can be produced, which contains more than 40% of coal , which is convenient for storage and transportation, and has significant benefits. On the other hand, at low sound intensity and a certain frequency, ultrasound can break the emulsion. Teksonic Corporation of the United States has developed an efficient and economical process that uses ultrasonic waves to break emulsions of oil-water emulsions and achieves good results. In addition, the company uses ultrasonic technology for the separation of three-phase heterogeneous systems, such as the destruction of refractory oil - water - solid emulsions.
*5 Chemical reaction Ultrasonic action on chemical reaction *
The main use of ultrasonic cavitation. Cavitation bubble collapse produces local high temperature, high pressure and strong shock wave and jet, which provides a new and very special physical and chemical environment for chemical reactions that are difficult or impossible to achieve under normal conditions. It is a new one. Interdisciplinary subject between acoustics and chemistry. A large number of experiments have proved that ultrasound can be widely used in various reactions, including:
(1) Synthetic chemistry, especially the application of ultrasound in organic synthesis, has developed rapidly. The main research object is heterogeneous reaction, especially organometallic. Ultrasonic pulverization and surface activation make it possible to replace the phase transfer catalyst (PTC) reaction. Including reactions involving metal surfaces ( such as accelerated catalytic reactions ) , reactions involving powdered solid particles, emulsification reactions, and homogeneous reactions.
(2) Polymer chemistry, such as polymerization, polymer degradation reaction.
(3) In terms of electrochemistry, the ultrasonic wave is directly introduced into the plating bath, and the deposition rate is increased and the current density is increased due to cavitation.
(4) Analytical chemistry. Ultrasound has become a common synthesis technique for many organometallic compounds. For example, in the synthesis of Grignard reagent, the conventional method requires the use of strictly dry diethyl ether, and a small amount of iodine is added as an inducer. Under ultrasonic irradiation, the reaction can be carried out with ordinary reagent grade diethyl ether without drying, and the induction period of the reaction is also shortened to several seconds. This discovery is of great significance for the industrial production of Grignard reagents. The use of ultrasonic radiation for homogeneous and heterogeneous catalytic reactions can continuously strip the reactants adsorbed on the surface of the catalyst and expose a new catalytic surface, thereby effectively maintaining the activity of the catalyst. For example, Moulton of the United States uses ultrasound to catalyze soybean oil. The hydrogenation has been accelerated by more than 100 times; the olefin hydrogenation reaction using nickel powder as a catalyst can accelerate the reaction rate by more than 100,000 times after ultrasonic irradiation. This discovery will have a major impact on petrochemical industry. Ultrasound is currently used in electroplating, which is actually an example of the application of ultrasound in electrochemistry. Ultrasonic radiation is used in electrochemical processes to keep the electrodes clean, degas the electrode surface, and improve mass transfer. The electrochemical process is more effective, the adhesion, hardness and smoothness of the coating can be improved, and the electroplating can be completed at a lower current density, and the electroplating speed is remarkably improved. In recent years, in solid-state nuclear magnetic resonance technology, ultrasonic radiation has been used to narrow the line. This technique is called sonic narrowing (SIN) , which is more convenient and practical than magnetic angle spin MAS technology. For example, aluminum sulfate suspended in carbon tetrachloride with 20 kHz ultrasonic radiation has a half-peak width of 170 Hz in the Al quadrupole resonance spectrum, and a half-value width of 660 Hz in the same line obtained by the MAS technique . Improving the uniformity of stationary phase coating with ultrasonic degassing in gas chromatography has become a routine practice. There are many parameters affecting the ultrasonic chemical reaction, including the working frequency, intensity, power, radiation time, waveform, reaction medium temperature, atmospheric pressure and so on. For example, in synthetic chemistry, the ultrasonic frequency is generally selected to be several tens of kHz , and in the polymerization chemistry, the ultrasonic frequency is generally below 1 MHz , but the sound intensity is generally greater than 5 W/cm.
*6 oil production *
In the process of oil well exploitation, some plugs are often formed in the oil well for various reasons, which hinders the flow of crude oil into the wellbore, reduces the permeability of crude oil, and affects the production of oil wells in the middle and later stages and oil recovery. Produce oil wells, water injection wells and near-well oil layers by sonic processing to change the physical properties and fluidity of fluids in the oil layer, improve the circulation conditions and permeability of near-well oil layers at the bottom of the well, remove clogging, scale and scale, prevent wax and improve The oil recovery reduces the viscosity of the crude oil.
The principle of ultrasonic oil recovery is that when high-power ultrasonic waves enter the oil layer, the capillary diameter in the oil layer changes greatly with the occurrence of ultrasonic waves. When the diameter of the capillary changes, the surface tension and capillary force also change. When the capillary radius becomes larger, the surface tension is reduced by the square of the radius, and the capillary force is reduced by the cube of the radius, which causes the original capillary force and gravity balance relationship to be broken, and the residual oil bound in the capillary due to the force When the equilibrium relationship is broken, it will flow into the well under the action of gravity and ultrasonic vibration. In addition, under the action of high-power ultrasonic waves, the oil layer will also crack, forming cracks and increasing the permeability of crude oil. The scope of application of ultrasonic oil recovery mainly includes:
(1) Oil wells that have long mud immersion time and cause serious pollution to oil wells during drilling;
(2) oil wells with serious oil layer blockage and sensitive to water and acid;
(3) Oil wells that are close to the oil-water boundary and cannot adopt fracturing stimulation measures;
(4) Oil wells with good oil layer properties, large oil layer thickness, but poor oil output;
(5) heavy oil wells and wax wells;
(6) Oil wells whose permeability has dropped drastically due to salt scale, scale blockage or contamination due to mechanical impurities.
In the 1960s , American scientists first conducted research on the stimulation of ultrasonic oil wells, and conducted field tests on ultrasonic oil recovery in oil wells in Washington County, Okla., and the tests achieved certain results. Subsequently, the former Soviet Union carried out a lot of work in the research and application of ultrasonic oil recovery technology, and has been in the world's leading position. China's scientific and technological workers have developed high-power ultrasonic oil extraction machines that can be used in underground oilfields, and have carried out experiments on ultrasonic technology in Yumen, Daqing and other oilfields, which have improved the physical properties of oilfield oil layers, flow coefficient and fluidity ratio. The specific factor permeability ratio has been greatly improved, and the ideal effect has been achieved. Ultrasonic treatment of oil wells and oil layers can increase crude oil production by 40% to 50% and increase oil recovery by more than 10% . The success rate can reach 80% , and the yield increase period can be more than half a year. Ultrasonic oil production equipment is mostly on-board, and the operation is more flexible and convenient. Produced by the tens of thousands of Hz disposed on the ground sonotrode (typically between 16k ~ 30kHz) electrical signal transmitted via a cable to the reservoir section is located within the wellbore ultrasonic transducer, the ultrasonic transducer converts the electrical signal into The acoustic signal, the acoustic signal propagates through the crude oil in the wellbore to the oil layer. The main advantages of ultrasonic oil recovery are:
(1) The effect is rapid and the effect of increasing production is obvious;
(2) It will not pollute the oil well and will not damage the oil layer;
(3) The equipment cost is relatively low, the construction process is simple, the cost is low, and the benefit is high;
(4) It can be combined with other methods of increasing production, and the advantages are complementary;
(5) A wide range of applications. At present, the electric power of the ultrasonic generator has reached hundreds of kilowatts. The shape of the ultrasonic transducer is generally cylindrical, and the length is about 1 to 2 m , and the radius is about several tens of millimeters. Ultrasonic oil recovery technology has matured both in process technology and in equipment research. This technology has broad prospects for development and will certainly play an important role in increasing oil production in the later stage.
*7 other applications *
Ultrasonic
It can also be applied to many aspects of the chemical industry. If it is applied to membrane separation, it has obvious accelerated mass transfer and de-concentration polarization, which can improve the separation efficiency of membrane separation. It can be used in sewage treatment to effectively separate organic matter and harmful in wastewater. The decomposition of the substance; during the fermentation process, the ultrasonic wave can promote the release of the biological enzyme in the cell to the outside of the cell, thereby increasing the overall enzyme activity of the fermentation liquid to a large extent, and correspondingly increasing the conversion rate of the substrate; The drying can remove water from the solid without heating, speed up the drying and reduce the residual water content in the solid; used to prepare microbubbles, welding, and the like.
*8 Conclusion *
At present, the application of ultrasonic in the chemical industry is still in the early stage, and the development of various applications is not balanced, such as ultrasonic cleaning, etc., and its development scale is getting larger and larger, while other power ultrasonic technologies, such as ultrasonic processing, ultrasonic extraction, etc. The scale has not changed much in the past few decades, and many rules of action have yet to be further explored and summarized. Because a new period of ultrasound technology experiment ( including pilot and field experiments ) may involve more risks and risks, applications in different fields require relevant enterprises to participate in development research, and even require government input and support. Only in this way can it be timely Put energy-efficient ultrasound technology and solutions into practical engineering to accelerate industrialization. Since the introduction of ultrasonic waves has injected new vitality into the field of chemistry and chemical industry, it has produced many effects that ordinary methods cannot produce. The equipment is simple and has no secondary pollution, so the development prospect is very considerable.
[Ningbo Xinzhi Biotechnology Co., Ltd.]
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Main production: ultrasonic cell pulverizer, ultrasonic cleaning machine, thermostatic bath, homogenizer, homogenizer
Contact: Ms. Wu 13248546416 ; 0574-88350052
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