Ultrasonic Reactor
In the ultrasonic reactor method, the ultrasonic waves cause the reaction mixture to produce and collapse bubbles constantly. This cavitation provides simultaneously the mixing and heating required to carry out the transesterification process. Thus using an ultrasonic reactor for biodiesel production drastically reduces the reaction time, reaction temperatures, and energy input. Hence the process of transesterification can run inline rather than using the time consuming batch processing. Industrial scale ultrasonic devices allow for the industrial scale processing of several thousand barrels per day.
Ultrasonic Processing for Fast Biodiesel Production
Biodiesel is biodegradable, non-toxic, renewable, and has reduced emissions of CO, SO2, particulates, and hydrocarbons as compared to conventional diesel. Furthermore its properties are very close to petroleum-based diesel making it a possible substitute of conventional diesel in diesel engines. The most common method for producing biodiesel is transesterification of triglycerides or fatty acids with an alcohol in the presence of a strong catalyst (acid, base, or enzymatic), producing a mixture of fatty acid alkyl esters and glycerol (=glycerine). Glycerine (the heavier phase) will sink to the bottom, while biodiesel (the lighter phase) floats on top and can be separated.
At present, biodiesel is primarily produced in batch reactors in which the required energy is provided by heating accompanied by mechanical mixing. Since fats and alcohols are not totally miscible, the conventional transesterification reaction in batch processing is relatively slow, and phase separation of the glycerin is time-consuming. Whereas, ultrasonic processing used in biodiesel production delivers a biodiesel yield in excess of 99% in five minutes or less, compared to one hour or more using conventional batch reactor systems. This is what the Hielscher Ultrasound Technology offers. Hielscher is a small German company providing ultrasonic processing equipment for a variety of sonochemical applications, biodiesel production being one.
Ultrasonic Processing
Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Ultrasound frequencies range from ~20 kHz to l0 MHz, with associated acoustic wavelengths in liquids of roughly 100-0.15 mm. The application of ultrasound to chemical reactions and processes is called sonochemistry. The chemical effects of ultrasound (sonochemical) in liquids derive from several nonlinear acoustic phenomena, of which cavitation is the most important. Acoustic cavitation is the formation, growth, and implosive collapse of bubbles in a liquid irradiated with sound or ultrasound. Acoustic cavitation can lead to implosive compression if treated under proper conditions which will produce inetense local heating, high pressures, enormous heating and cooling rates, and liquid jet streams. Ultrasonication provides the mechanical energy for mixing and the required activation energy for initiating the transesterification reaction. Ultrasonication can help to reduce the separation time from 5 to 10 hours required with conventional agitation, to less than 15 minutes. The ultrasonication also helps to decrease to amount of catalyst required by 50 to 60% due to the increased chemical activity in the presence of cavitation. Another benefit is the increase in purity of the glycerol.
Since ultrasonication could reduce the transesterification retention times to 5 min compared to over 1 hour or more necessary for conventional batch processing, this method could be effectively used for continuous production of biodiesel using plug-flow or continuous stirred tank reactor systems. In a setup for the continuous processing and continuous separation, the oil is circulated through a heater before it is mixed with the catalyst continuously using adjustable pumps.
In a setup (Fig above) for the continuous processing and continuous separation, the heated oil and the catalyst premix are mixed together continuously using adjustable pumps. The oil/catalyst heated mixture passes the flow cell, where it is being sonicated inline for approximately 5 to 30 seconds. The sonicated mix enters the reactor column with specific volume to give approximately 1 hour retention time in the column, just enough for the transesterification reaction to be completed. The reacted biodiesel/glycerin mix is pumped to the centriguge where it is separated into the biodiesel and glycerin fractions. Post-processing can be done continuously, too.
Cost Effective
The installation of Hielscher ultrasonic reactors into your biodiesel process line reduces your operational for the following reasons:
- Less excess methanol
The reduced methanol levels were able to be achieved due to enhanced reaction kinetics afforded by the Hielscher reactors - Raw material savings
It is possible to switch to cheaper raw materials with poorer quality such as animal fats, recycled restaurant oils or waste oils, because the ultrasonic process intensification improves the conversion results for any feedstock. - Less catalyst
Ultrasonic mixing improves the methanol-in-oil emulsification and generates more and smaller droplets.
This leads to a better distribution and increased catalyst efficiency. As a consequence, you can save up to 50% catalyst when compared with shear mixers or stirrers. - Higher glycerine quality
A higher conversion rate and lower excess methanol lead to a much faster chemical conversion and to a sharper separation of the glycerin. - Electric energy and heating
A comparison in energy consumption between ultrasonic cavitation, high-shear mixing and hydrodynamic cavitation.
The ultrasonic devices require s about 1.4kWh/m³. To achieve a similar result using hydrodynamic magnetic impulse cavitation, requires about 32.0kWh/m³. High-Shear mixing requires about 4.4kWh/m³. This means, that hydrodynamic impulse cavitation requires approx. 23 times more energy and high shear mixing approx. 3 times more energy than ultrasonic devices to provide the same throughput.
Other Aplications
Impact of Homogenization in food process
When ultrasonic processors are used as homogenizers, the objective is to reduce small particles in a liquid to improve uniformity and stability. These particles (disperse phase) can be either solids or liquids.A reduction in the mean diameter of the particles increases the number of individual particles.This leads to a reduction of the average particle distance and increases the particle surface area shows the correlation between individual particle diameter and total surface area.
Surface area and average particle distance can influence the rheology of a liquid.If there is a difference in specific gravity between the particles and the liquid, the homogeneity of the mixture can influence the stability of the dispersion. If the particle size is similar for the majority of the particles, the tendency to agglomerate during settling or rising reduces, because the similar particles have a similar speed of rising or settling.
Ultrasonic Dispersing and Deagglomeration
The dispersing and deagglomeration of solids into liquids is an important application of ultrasonic devices. Ultrasonic cavitation generates high shear forces that break particle agglomerates into single dispersed particles. The mixing of powders into liquids is a common step in the formulation of various products, such as paint, ink, shampoo, beverages, or polishing media.
The individual particles, e.g. nanoparticles are held together by attraction forces of various physical and chemical nature, including van der Waals forces and liquid surface tension. The attraction forces must be overcome on order to deagglomerate and disperse the particles into liquid media. For the dispersing and deagglomeration of powders or nanoparticlese in liquids, high intensity ultrasonication is an interesting alternative to high pressure homogenizers, agitator bead mills, impinging jet mills and rotor-stator-mixers.
Ultrasonic Emulsifying
A wide range of intermediate and consumer products, such as cosmetics and skin lotions, pharmaceutical ointments, varnishes, paints and lubricants and fuels are based wholly or in part of emulsions. Emulsions are dispersions of two or more immiscible liquids. Highly intensive ultrasound supplies the power needed to disperse a liquid phase (dispersed phase) in small droplets in a second phase (continuous phase). In the dispersing zone, imploding cavitation bubbles cause intensive shock waves in the surrounding liquid and result in the formation of liquid jets of high liquid velocity. At appropriate energy density levels, ultrasonic emulsification can well achieve a mean droplet sizes below 1 micron (micro-emulsion).
Ultrasonic Disintegration of Cell Structures
Ultrasonic treatment can disintegrate fibrous, cellulosic material into fine particles and break the walls of the cell structure. This releases more of the intra-cellular material, such as starch or sugar into the liquid. In addition to that the cell wall material is being broken into small debris.This effect can be used for fermentation, digestion and other conversion processes of organic matter. After milling and grinding, ultrasonication makes more of the intra-cellular material e.g. starch as well as the cell wall debris available to the enzymes that convert starch into sugars.
It does also increase the surface area exposed to the enzymes during liquefaction or saccharification. This does typically increase the speed and yield of yeast fermentation and other conversion processes, e.g. to boost the ethanol production from biomass.
Sonochemical Effects of Ultrasound
Sonochemistry is the application of ultrasound to chemical reactions and processes. The mechanism causing sonochemical effects in liquids is the phenomenon of acoustic cavitation.The sonochemical effects to chemical reactions and processes include increase in reaction speed and/or output, more efficient energy usage, performance improvement of phase transfer catalysts, activation of metals and solids or increase in the reactivity of reagents or catalysts
Which system do I need?
It is fundamental for a successful installation and operation of an ASMP inline reactor system. Depending upon the flow, volume will determine which of our reactor product wil suit .
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