Applications of ultrasound in the chemical industry?

There are only a few ultrasonic flowmeters at the installation site, and indeed no research has been done on them.

Electrodesalination, ultrasonic demulsification, online ultrasonic descaling of heat exchangers

To the best of my knowledge, the current applications of ultrasound in the chemical industry are mostly still at the laboratory stage; flow meters or pipeline inspection are more commonly used in practice

It is useful during the desorption of the absorption liquid at the bottom of the tower. There is also this assistance during dissolution. . .

I only know about ultrasonic testing after pipeline construction; the more advanced version is the ultrasonic tester that can now record data.

We used ultrasound for defect detection in pipes

Due to its effects in mass transfer, heat transfer, and chemical reactions, ultrasound has become a topic of intense research around the world. In particular, countries such as the United States, the United Kingdom, France, and Japan have made progress in industrial applications, thanks to the unique properties of ultrasound as well as the development and widespread use of ultrasonic power equipment. Russia and other countries have also made some advances in this field. The development of science and technology in our country has given rise to an emerging interdisciplinary field: acoustochemistry. Its development has been driven by the extensive work done by researchers in both theoretical and applied areas. Ultrasonic waves generally refer to sound waves with a frequency range of 20 kHz to 10 MHz, and the driving force for their use in the chemical field stems primarily from ultrasonic cavitation. With intense shock waves and microjets moving at speeds exceeding 100 m/s, the high-gradient shear generated by these shock waves and microjets can produce hydroxyl radicals in aqueous solutions. The resulting physicochemical effects are primarily mechanical in nature; these four effects do not operate in isolation but interact with one another and enhance each other, thereby accelerating the reaction process. This paper reviews the main applications of ultrasound in the chemical industry over recent years, with the aim of promoting research and wider adoption of ultrasound technology in engineering. *1 Cleaning* Ultrasonic cleaning is one of the main applications of ultrasonic waves. Compared with other cleaning methods, it offers high efficiency and good quality; it can remove dirt from complex parts, deep holes, blind holes, and narrow gaps, and it also facilitates the automation of the cleaning process. Currently, the number of ultrasonic cleaner manufacturers has grown from just a few in the early 1990s to several hundred today. With the further development of our country’s national economy, it is bound to become an indispensable technological means for many industries, as well as in medical and environmental protection sectors. The operating frequency of ultrasonic cleaners is broadly divided into three frequency ranges depending on the items to be cleaned: low-frequency ultrasonic cleaning. Low-frequency ultrasonic cleaning is suitable for the surfaces of large components or situations where the adhesion between dirt and the surface of the item to be cleaned is strong. At the low end of frequency, the cavitation intensity is high, which can easily corrode the surface of the parts to be cleaned; it is not suitable for cleaning components with high surface smoothness, and it also generates significant cavitation noise. At a frequency of around 40 kHz, the same sound intensity results in a greater number of cavitation bubbles compared to a frequency of 20 kHz; it thus has stronger penetration power, but lower cavitation intensity. It is suitable for cleaning workpieces with complex surface shapes or blind holes, as well as components where the adhesion between dirt and the surface to be cleaned is weak, and it also produces less cavitation noise. High-frequency ultrasonic cleaning is suitable for the thorough cleaning of microelectronic components, such as disks, drives, read/write heads, liquid crystal glass, flat-panel displays, microcomponents, and polished metal parts. These objects to be cleaned must not suffer from cavitation corrosion during the cleaning process, and they must allow for the removal of contaminants at the micron level. Megahertz ultrasonic cleaning is suitable for cleaning integrated circuit chips, silicon wafers, and thin films, requiring the ability to remove contaminants at the micron and sub-micron levels without causing any damage to the items being cleaned. Since cavitation does not occur at this time, its cleaning mechanism is mainly driven by the sound pressure gradient, particle velocity, and acoustic flow. It is characterized by a strong cleaning direction, with the object to be cleaned generally placed in a direction parallel to the sound beam. Based on the cleaning medium, it can be divided into conventional cleaning and gas-phase ultrasonic cleaning. Conventional cleaning refers to the use of standard cleaning solvents that do not evaporate on a large scale, such as water, water-based cleaners, and certain petroleum-based products used for cleaning. Common cleaning methods used in combination with ultrasound include high-temperature immersion, bubbling, and spraying ； Common drying methods include hot air drying and centrifugal drying. Gas-phase cleaning typically uses volatile cleaning solvents such as Freon, trichloroethylene, and trichloroethane. These solvents have a strong ability to remove oil stains, but their boiling points are low; therefore, a condensation and recovery system is usually employed during use. Common cleaning methods combined with ultrasonics include hot immersion, spraying, and steam bath cleaning ； Freeze drying is generally used for drying. *2 Extraction* Ultrasonic-enhanced solvent extraction primarily relies on the cavitation effect in liquids; therefore, any parameters affecting this cavitation effect—such as ultrasonic power, frequency, treatment time, and the properties of the extraction system—will influence the efficiency of the extraction. The application of ultrasound in extraction processes includes solid-liquid extraction and liquid-liquid extraction; it improves and enhances the mass transfer rate and efficiency of extraction separation more effectively than conventional methods that rely on heat treatment, mechanical stirring, or pressure changes. Ultrasonic extraction can not only enhance the extraction of substances by conventional fluids but also improve the extraction process under supercritical conditions, thereby increasing the yield. Examples of applying ultrasound-enhanced extraction in chemical processes include: when extracting asphaltenes from oil shale using 8 solvents such as benzene, the extraction rate under an ultrasonic field of 50 kHz and 400 W is 24 times that achieved by the Soxhlet extraction method ； When leaching a zinc ore sample containing 17.3% zinc using a mixed solution of sodium hydroxide and ammonium chloride, ultrasonication at 22 kHz and 100 W can **accelerate the leaching rate** ； Acoustic field irradiation at a frequency of 20 kHz and powers of 100 W and 600 W can increase the rate of extracting pyrethroids from powdered chrysanthemum used for pest control, using n-pentane ； At that time, there is an extraction rate that is unmatched by vacuum sublimation ； A high-intensity single-head plug-type ultrasonic field of 18.5 kHz and 250 W can increase the rate of gold leaching using the cyanidation method ； Ultrasonic waves at 20 kHz were used to extract the total alkaloids from Leonurus japonicus, yielding higher yields than those obtained by conventional reflux methods and reducing the extraction time. After 2 hours of extraction using the reflux method, the extraction rate was 0.176%; whereas after 40 minutes of extraction using the ultrasonic method, the extraction rate reached 0.248% ； Ultrasonic irradiation at 20 kHz and 47 W, combined with mechanical stirring, can increase the extraction rate of Ni by 4 to 7 times. At present, ultrasonic extraction technology has been applied to the extraction of small quantities of samples in some industries; however, its application in large-scale production remains limited. The corresponding ultrasonic extraction equipment is not yet mature, and there is a need to further develop such equipment and optimize its process parameters. *3 Crystallization, Grinding* Ultrasound can induce both rapid and gradual precipitation of solid solutes from supersaturated solutions, as well as enhance crystal growth. Solution crystallization plays a very important role in the separation and purification of organically soluble substances and inorganic salts. It can not only separate the solute from the solution in a solid state, but also be used to purify crystalline substances, as different crystals have distinct crystal lattices. Compared with other stimulation nucleation methods and seed nucleation methods, ultrasonic nucleation requires a lower degree of supersaturation, results in faster growth rates, and produces nuclei that are more uniform, intact, and smooth. The size distribution of both the nuclei and the final crystals is narrower, with a lower coefficient of variation. However, the microjets generated by the collapse of ultrasonic cavitation bubbles cause erosion on the crystal surface, and excessive intensity can even shatter the crystals, disrupting their growth. Wang Weining et al. introduced ultrasonic waves 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; the crystallization time was reduced from 12 hours to 4 hours. Moreover, the higher the ultrasonic frequency, the faster the nucleation rate, the shorter the induction period, and the quicker the completion of crystallization. Based on this research, ultrasonic seeders have begun to be put into industrial use. Ultrasonic treatment of molten metal during solidification can refine the grains and improve its physical properties such as ductility and mechanical strength. Ultrasonic treatment of carbon steel shows that it can reduce the grain size from 200 μm to 25–30 μm, increase ductility by 30%–40%, and enhance mechanical strength by 20%–30%. In the pharmaceutical industry, ultrasonic crystallization has been used to produce oral or subcutaneous injection suspension formulations in order to obtain small and uniform particles. There are also other examples of ultrasonic enhancement of the crystallization of solutions such as potassium nitrate, acetamide, and potassium sodium tartrate. For industrial production, an important advantage of ultrasound-assisted crystallization or precipitation is that the precipitates do not deposit on the cooling tubes, thereby ensuring a uniform distribution of the system’s cooling rate. Ultrasonic scale prevention and removal technology requires no changes to the structure or process conditions of heat exchange equipment, nor does it necessitate the addition of any chemical agents; it is one of the best green scale prevention technologies. Ultrasonic vibrations are transmitted to the tube bundle through the metal components, causing the scale accumulated on the tube bundle to peel off continuously and thus slowing down the rate of scaling. At the same time, the ultrasonic waves cause certain hard salts to crystallize in the solution, forming a paste-like precipitate. This technology has been successfully applied in companies such as Shanxi Nanfeng Group. *4 Emulsification and demulsification*** Currently, there are three main theories regarding ultrasonic emulsification: cavitation, surface instability, and microjets induced by the action of ultrasound. Phacoemulsification achieves high emulsification quality compared to conventional emulsification processes and equipment; the resulting emulsion has small average droplet sizes, ranging from 0.2 to 2 μm. The droplet size distribution is narrow, falling within the range of 0.1 to 10 μm or even narrower. The concentration is high, with pure emulsions achieving a concentration of up to 30%, and concentrations with added emulsifiers reaching 70%. Stable emulsions can be produced with little or no emulsifiers; some of these emulsions remain stable for months to over half a year. They require less energy, offer high production efficiency, and have low costs. All types of emulsions can be prepared; however, this is not possible using mechanical emulsification methods. Only the properties of the emulsifier can determine the type of lactic acid. For example, toluene emulsifies in water; at low sound intensities, one type of emulsion can be formed, while at high sound intensities, another type of emulsion may form. Less power is required to produce the emulsion. For example, to produce an emulsion at a rate of 4.55 m³/h with droplet sizes of 1 μm: when using a reed whistle, at an operating pressure of 10.5–14.1 kg/cm², only 5–7 horsepower is required as driving power; whereas when using a high-pressure homogenizer, at an operating pressure of 70.3–351.6 kg/cm², 40–50 horsepower is needed as driving power. Phacoemulsification can also produce emulsions that are impossible to obtain using conventional methods; for example, while ordinary stirring can only yield an emulsion of 5% paraffin in water, a 20% paraffin emulsion can be obtained in an acoustic field. Ultrasonic emulsification of fuel with water followed by combustion has been widely applied in China for many years. No emulsifier is required in this process; the particle size of water droplets in the emulsified oil is around 1 μm. This approach results in a 6%–25% reduction in energy consumption, a 40%–90% decrease in smoke and dust, and a 20%–75% reduction in NOx emissions, thereby saving fuel and being environmentally friendly. By adding a small amount of water to kerosene-based mixed fuels and subjecting the mixture to ultrasonic emulsification, stable kerosene suspensions can be produced with a coal content of over 40%; these suspensions are easy to store and transport, offering significant advantages. On the other hand, at low sound intensities and certain frequencies, ultrasound can cause the demulsification of emulsions. The American company Teksonic has developed an efficient and cost-effective process that uses ultrasound to demulsify oil-water emulsions, achieving good results. In addition, the company also uses ultrasonic technology for the separation of three-phase heterogeneous systems, such as to break down difficult-to-treat oil-water-solid emulsions so that they can be separated. *5 Chemical reactions: Ultrasound is applied to chemical reactions*, primarily by utilizing the phenomenon of ultrasonic cavitation. The collapse of cavitation bubbles generates localized high temperatures, high pressures, as well as intense shock waves and jets, providing a new and very special physicochemical environment for chemical reactions that are difficult or impossible to carry out under normal conditions. It represents an emerging interdisciplinary field at the intersection of acoustics and chemistry. Numerous experiments have shown that ultrasound can be widely applied in various reactions, including those involving powdered solid particles, emulsification reactions, and homogeneous reactions. In polymer chemistry, such as polymerization reactions and polymer degradation reactions. In terms of electrochemistry, by introducing ultrasound directly into the plating tank, cavitation increases the deposition rate and raises the current density. It is more convenient and practical than the magnetic angular spin MAS technique. For example, for aluminum sulfate suspended in carbon tetrachloride using 20 kHz ultrasonic radiation, the half-width at half maximum of its Al quadrupole resonance spectrum is 170 Hz, whereas the half-width at half maximum of the same spectral line obtained using MAS technology is 660 Hz. Using ultrasound degassing to improve the uniformity of stationary phase coating in gas chromatography has become a standard practice. There are many parameters that affect ultrasonic chemical reactions, including the operating frequency, intensity, power, irradiation time, waveform, temperature of the reaction medium, and atmospheric pressure. For example, in synthetic chemistry, ultrasonic frequencies are generally set at several tens of kHz; in polymer chemistry, they are typically below 1 MHz. However, the sound intensity is generally greater than 5 W/cm². *Oil extraction*: During oil well exploitation, blockages often form in the wells due to various reasons. These blockages prevent crude oil from flowing into the wellbore, thereby reducing its permeability and affecting both the later-stage production of the wells and the overall oil recovery rate. Oil wells, water injection wells, and the reservoirs near these wells are treated using sound waves, which alters the physical properties and flow behavior of the fluids in the reservoir. This improves the flow conditions and permeability of the reservoirs near the well bottom, helps to remove blockages, prevents and removes scale, and prevents wax formation, thereby increasing oil production and reducing the viscosity of crude oil. The principle of ultrasonic oil extraction is as follows: when high-power ultrasonic waves enter the oil reservoir, the diameter of the capillaries in that reservoir changes back and forth as a result of the action of these ultrasonic waves. When the capillary diameter changes, its surface tension and capillary force also change. As the capillary radius increases, surface tension decreases by a factor of the square of the radius, while capillary force decreases by a factor of the cube of the radius. This disrupts the original balance between capillary force and gravity; as a result, the residual oil trapped within the capillaries flows into the well under the influence of gravity and ultrasonic vibrations, due to this disruption in force balance. Furthermore, under the action of high-power ultrasound, the oil layer cracks to form fractures, thereby increasing the permeability of the crude oil. The main applications of ultrasonic oil extraction are in oil wells where the mud remains in contact with the well for a long time during drilling, causing severe contamination of the well ； Oil wells with severely clogged reservoirs and sensitivity to water and acid ； Oil wells located close to the oil-water boundary, where fracturing for production enhancement cannot be applied ； Oil wells with good reservoir properties and large reservoir thickness, but poor oil production capacity ； Heavy oil wells, wax-caked wells ； Oil wells in which permeability has decreased sharply due to salt scale, scale blockage, or contamination by mechanical impurities. In the 1960s, American scientists were the first to conduct research on using ultrasound to increase oil production from wells, and field tests of ultrasound-based oil extraction were carried out in wells in Washington County, Oklahoma, with certain successes achieved. Subsequently, the former Soviet Union carried out extensive work in the research and application of ultrasonic oil recovery technology, and has always remained at the world’s forefront. Chinese scientists and technicians have developed a high-power ultrasonic oil extraction machine suitable for use underground in oil fields. Tests on the application of ultrasonic technology for oil extraction were conducted at oil fields such as Yumen and Daqing. These tests led to a notable improvement in the physical properties of the oil-bearing formations; parameters such as flow coefficient, mobility ratio, and specific layer permeability all increased significantly, yielding fairly satisfactory results. Using ultrasound to treat oil wells and reservoirs can increase crude oil production by 40%–50% and boost recovery rates by over 10%; the success rate is around 80%, with the period of increased production lasting more than half a year. Ultrasonic oil extraction equipment is mostly vehicle-mounted, making the operation flexible and convenient. An electrical signal of several tens of thousands of Hz is generated by an ultrasonic transmitter placed on the ground; this signal is transmitted via cables to the ultrasonic transducers located in the oil layer section within the wellbore. The ultrasonic transducers convert the electrical signal into acoustic signals, which are then transmitted through the crude oil in the wellbore to the oil layer. The main advantages of ultrasonic oil extraction are: rapid action and significant oil production increases ； It will not cause pollution to the oil wells, nor will it damage the oil reservoirs ； The equipment cost is relatively low, the construction process is simple, resulting in low costs and high efficiency ； It can be used in combination with other yield-increasing methods to complement each other’s advantages ； Wide range of applications. Currently, the electrical power of ultrasonic generators has reached hundreds of kilowatts. Ultrasonic transducers are generally cylindrical in shape, with a length of about 1–2 meters and a radius of several dozen millimeters. Ultrasonic oil extraction technology has become mature both in terms of process technology and equipment research. This technology has broad development prospects and will undoubtedly play an important role in increasing oil field production in the later stages. *7 Other applications* Ultrasound can also be used in many areas of the chemical industry. When applied in membrane separation, it significantly accelerates mass transfer and reduces concentration polarization, thereby improving the separation efficiency of membrane separation ； Applied in wastewater treatment, it can effectively separate the organic substances present in it and break down harmful substances in the wastewater ； During the fermentation process, ultrasound can facilitate the rapid release of enzymes within cells into the outside of the cells, thereby significantly increasing the overall enzyme activity in the fermentation broth and consequently raising the conversion rate of the substrate ； Used for drying heat-sensitive materials, it enables the removal of water from solids without the need to increase temperature, thereby accelerating the drying process and reducing the residual water content in the solids ； Used for preparing microbubbles, welding, and more. *8 Conclusions* At present, the application of ultrasound in the chemical industry is still in its initial stages, and the development of various applications is uneven. For example, ultrasonic cleaning has seen growing scale of use, while other power ultrasound technologies such as ultrasonic machining and ultrasonic extraction have remained largely unchanged over the past few decades; many of their working principles still require further exploration and investigation. Since the experimental phase of a new ultrasound technology involves high costs and risks, its application in various fields requires the joint efforts of relevant companies in terms of development and research; even significant investment and support are needed. Only in this way can efficient and energy-saving ultrasound technologies and solutions be put into practical use in engineering projects, thereby accelerating their industrialization. Since the introduction of ultrasound has injected new vitality into the field of chemistry and chemical engineering, producing effects that cannot be achieved by conventional methods, and given its simple equipment and absence of secondary pollution, its future prospects are very promising.

There are many applications of ultrasonic equipment or instruments in the chemical industry, such as ultrasonic flowmeters, ultrasonic flaw detectors, ultrasonic devices for prevention and removal of scale, as well as ultrasonic cleaners in laboratories~~

This post was last edited by Fan Gong on 2015-9-8 at 17:04. Laboratory ultrasonic cleaners are used for removing dissolved gases via liquid chromatography with ultrasound. In the machinery industry, ultrasonic cleaning and oil removal are applications of ultrasound; in the petrochemical industry, ultrasound can also be used for demulsifying crude oil

It is widely used in the cleaning industry, and most cleaning tanks are equipped with ultrasound. Additionally, ultrasonic emulsification was used in polymerization experiments in the lab before; its results were much better than those obtained through mechanical stirring for emulsification. I’m not sure whether this technique is now being used in industry.