the trials below select three points of intervention chosen to demonstrate the claimed invention , namely ( 1 ) ex - screw press ( point 3 in fig2 ); ( 2 ) underflow sludge ( point 5 in fig2 ); and ( 3 ) effluent sludge ( sludge ex - centrifuge ) ( point 6 in fig2 ). three ultrasonic methods were selected to treat selected samples : ultrasound 1 ( us1 ) using a long titanium rod type sonotrode or a short titanium rod sonotrode , ultrasound 2 ( us2 ) and a two - step method ( us1 and us2 ). after mixing and preheating to 70 ° c . the samples were pumped through the ultrasonic system . the mixture was recirculated through the us1 system . in the us2 system , transducers are placed in a water bath at 70 ° c . and indirectly emit sound through the walls of a plastic centrifuge tube holding palm oil material . us1 1 is produced by a long titanium rod type sonotrode using a frequency of 20 khz and power of 238 db us1 s is produced by a short titanium rod type sonotrode using a frequency of 20 khz and power of 238 db us2 uses frequencies of 400 khz and 1 . 6 mhz and power of 231 db . in fig2 points 1 - 5 are separate interventions at selected frequencies . the flow through sonotrode horn utilised for us1 at frequency of 20 khz facilitates breakdown of the plant tissue and oil bearing cells and coalescence of released oil is facilitated with application of higher frequencies . ultrasonic frequencies ( 400 khz - 2 mhz ) obtained with plate transducers ( us2 ) unmix / split oil emulsion through coalescence and oil stripping from solid particulate interfaces by streaming . the decanter ( also called clarifier ) offers a static system where an undisturbed ultrasonic field allows coalescence to occur . increased coalescence promotes separation , decreasing the oil concentration in the underflow sludge at the bottom of the decanter , therefore decreasing residence times . the transducer three dimensional set up can be arranged to bring oil particles together to a point and enhance coalescence . further coalescence can be obtained by pulsing . ultrasonic treated and non - treated samples were placed in a settling tube and left to stand in a water bath at 85 ° c . for 1 hour . the height of the oil from the top layer was measured and the oil separated was removed by pipetting . the remaining sludge was then centrifuged at 1000 g and the height of the oil separated was measured . results are expressed as % oil volume separated from sample on a feed volume basis . tables 1 , 2 and 3 summarise the oil separation after different ultrasonic treatment combinations in the ex - screw press oil and in the sludge ex - centrifuge after ultrasound treatment . the three ultrasonic methods us1 1 , us2 and us1 1 + us2 provided increased yield in the ex - screw press feed sample ( table 1 ). this is partly due to an enhanced separation during settling . the most remarkable case is when using plate transducers ( us2 ) with a 25 % increase with respect to the static control during settling , which also indicates a faster rate of separation . however , ultrasonic method us1 , caused emulsification of the oil and reduced oil separation ( table 2 ). however , the only method that significantly enhanced oil separation in the underflow sludge from the settling tank was us2 showing an additional 7 % oil removal after decanting and an additional oil removal of 4 % with respect to the static control . results show the advantage of using plate transducers alone , as opposed to when the sludge was treated with the flow through low frequency sonotrodes . combination of both plates and sonotrode type transducers also provided negative results . pilot - scale trials further demonstrate other ultrasonic treatment conditions for enhanced oil extraction in various plate transducer configurations and with single frequencies or multiple frequency combinations . ultrasound was applied to the ex - screw press feed ( point 3 in fig2 ): ultrasound 3 ( us3 ), ultrasound 4 ( us4 ), and ultrasound 5 ( us5 ); configurations in fig6 a , b , and c , respectively ). fresh samples were obtained directly from the factory processing line at 85 ° c . and processed directly in an ultrasonic vessel for each configuration . in all cases transducers were held vertically or horizontally inside the vessel and directly emit sound into the palm oil material . us3 uses a frequency of 400 khz and power between 222 to 227 db with two vertical plate transducers arranged perpendicularly in two different planes ; us4 uses frequencies of 400 khz ( only ), or 400 khz and 1 mhz , or 400 khz and 2 mhz and power of 224 to 226 db ; two vertical 400 khz plate transducers were perpendicularly arranged to operate with higher frequency transducers horizontally located at the bottom ; and us5 uses frequencies of 400 khz , or 1 mhz , or 2 mhz and a power of 221 db with transducers placed horizontally at the bottom of the tank . oil separation during settling was followed in two identical tanks filled with the same ex - screw press feed . settling in one of the tanks occurred with operating transducers ( ultrasound on ), while the other tank had no operating transducers ( ultrasound off ). the height of the oil layer in each tank was measured at the end of the run . results are expressed as % oil separation from samples . samples were taken at various heights of the tank , centrifuged at 1000 g , and the volume of oil separated was measured . the oil remaining in the sludge after centrifugation and the oil content in the original feed were analysed using a soxhlet method . table 4 summarises the amount of oil separation from various ultrasonic treatment combinations in the ex - screw press oil and fig7 and 9 represent the increased rate of separation achieved with ultrasound . the three ultrasonic methods us3 , us4 and us5 provided increased oil removal in the ex - screw press oil sample ( table 4 ). a faster oil separation was observed when exposed to all transducer configurations . the most remarkable case is us3 with a 700 % increase in oil separation compared to the respective static control . soxhlet analysis also indicated a 44 % reduction of the oil remaining in the sludge after centrifugation . from the above it can be seen that this invention provides a significant improvement in yield of oil for specific plate transducer arrangements . in particular , benefits can be seen from using a single plate transducer in vertical form , and its combinations with another vertical plate located at a perpendicular plane , either at the same or at different levels of the settling tank . it is worth noticing that even though faster separation of oil was obtained using horizontal plate transducers , these could not provide additional oil yield . nevertheless , acceleration of oil removal entails significant benefits in reducing production times . pilot - scale trials with transducers mounted outside the vessel ( with active face in direct contact with the sample ) additional pilot - scale trials demonstrate that high frequencies are efficient in enhancing oil extraction when using transducers externally mounted on pre - fabricated windows ( or cut outs ) across the vessel walls . this prototype ( fig1 ) has the advantage that only the active area of the transducers is in direct contact with the sample thereby reducing the heat load on the transducer and increasing its lifetime . the pilot - scale systems in fig1 a and 10 b have been designed to accommodate 600 khz and 400 khz transducers , respectively . the system parts are assigned with numbers indicating the following : ( 1 ) spare cut - out cover , ( 2 ) holder clamp bar , ( 3 ) assembly screw , ( 4 ) cut - out support frame , ( 5 ) transducer cooling port , ( 6 ) transducer signal port , ( 7 ) 600 khz plate transducer , ( 8 ) side window , ( 9 ) removable covers , ( 10 ) bottom sampling port , ( 11 ) top sampling port , ( 12 ) upper sampling port , ( 13 ) lower sampling port , and ( 14 ) 400 khz transducer plate . ultrasound was applied to the ex - screw press feed ( point 3 in fig2 ): ultrasound 6 ( us6 ), ultrasound 7 ( us7 ), and ultrasound 8 ( us8 ); configurations in fig1 ). samples were obtained directly from the factory processing line at 85 ° c . and processed directly in an ultrasonic vessel for each sound condition . us6 uses a frequency of 600 khz and power of 230 db with a single transducer plate externally mounted against the side wall of the vessel with a cut - out window ; us7 uses a frequency of 400 khz and power of 220 db with a single transducer plate externally mounted against the side wall of the vessel with a cut - out window ; us8 and us9 use a frequency of 600 khz and power of 220 and 224 db , respectively with a single transducer plate externally mounted against the side wall of the vessel with a cut - out window . table 5 summarises the amount of oil separation from single treatments at the same frequency in the ex - screw press oil . the three replicate runs at us6 provided increased oil removal than the static control in the ex - screw press oil sample after settling ( table 5 ) and also an increase in total decantable oil removal ( table 5 ). table 6 summarises the amount of oil separation in the ex - screw press oil from parallel treatments in two vessels using the same feed at two 400 khz and 600 khz . this comparison demonstrates that higher frequencies ( 600 khz ) are as effective as treatment at 400 khz . from the above it can be seen that this invention provides a significant improvement in yield of oil for specific plate transducer arrangements . in particular , benefits can be seen from using a single plate transducer in vertical form , and its combinations with another vertical plate located at a perpendicular plane , either at the same or at different levels of the settling tank . it is worth noticing that even though faster separation of oil was obtained using horizontal plate transducers , these could not provide additional oil yield . nevertheless , acceleration of oil removal entails significant benefits in reducing production times . those skilled in the art will understand that this invention may be implemented in embodiments other than those described . other likely points of intervention are shown in fig2 . throughout this specification the word “ comprise ”, or variations such as “ comprises ” or “ comprising ”, will be understood to imply the inclusion of a stated element , integer or step , or group of elements , integers or steps , but not the exclusion of any other element , integer or step , or group of elements , integers or steps . any discussion of documents , acts , materials , devices , articles or the like which has been included in the present specification is solely for the purpose of providing a context for the present invention . it is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application . it will be appreciated by persons skilled in the art that numerous variations and / or modifications may be made to the invention as shown in the specific embodiments without departing from the scope of the invention as broadly described . the present embodiments are , therefore , to be considered in all respects as illustrative and not restrictive .
a method of extracting recovering oil from vegetable material in which oil bearing material is heated and subjected to sonication at least one frequency above 400 khz , removing a first yield of oil by decanting and subjecting the retained material to centrifugal separation to separate out a second yield of oil . preferably the raw vegetable material is passed through a screw press and the obtained material is heated and subjected to the ultrasonic treatment and then allowed to settle for a predetermined period before decanting the oil layer . preferably two frequencies above 400 khz are used , one below 1 mhz and the second from 1 mhz . there are many potential transducers arrangements possible for producing standing waves .