Apparatus including rotor and stator having teeth with surfaces of a parabolic profile and method for enhancing phase contact and chemical reactions

Abstract

An apparatus for enhancing phase contact and chemical reactions is provided. The apparatus comprises at least one high-turbulence mixing stage and at least one high-shear-stress and high-cavitation stage. The stages are adapted to cause an increase in relative sliding speeds of phases involved in a multiphase flow passing through the stages. The high-shear-stress and high-cavitation stage comprises a rotor having radial teeth housed in a cavitation chamber surrounded by a stator having radial teeth. The facing surfaces of the radial teeth have a parabolic profile in circumferential direction. For each tooth, the parabolic profile lies along a curve of a parabola of which a vertex is arranged at a rear edge of the tooth, with respect to a direction of rotation of the rotor, and along a radius extending from the rear edge to a center of the rotor. The focus of the parabola is also located on the radius.

Claims

1. An apparatus (11) for enhancing phase contact and chemical reactions, comprising: at least one first high-turbulence mixing stage (13); at least one second high-shear-stress and high-cavitation stage (15); said stages (13, 15) being adapted to cause an increase in relative sliding speeds of phases involved in a multiphase flow passing through said stages (13, 15), wherein said at least one first high-turbulence mixing stage (13) comprises a rotor (17) rotatable within a mixing chamber (19) surrounded by a stator (21), and wherein the rotor (17) comprises at least one radial pin (23) integral with said rotor (17), wherein said at least one radial pin (23) radially extends from an axis of rotation of a shaft (39) of the rotor (17) over such a length that a diameter of an external circumference described by the at least one radial pin (23) is in a range of 0.3 to 0.9D, D being a diameter of the mixing chamber (19), wherein said at least one first high-turbulence mixing stage (13) is adapted to subject the multiphase flow to a high-turbulence regimen with Reynolds number Re>500,000 and said at least one second high-shear-stress and high-cavitation stage (15) is adapted to subject the multiphase flow to a cavitation regimen characterized by a cavitation number <1, where =2(prpv)/((p)(v.sup.2)), pr is reference pressure in pascal, pv is fluid vapor pressure in pascal, p is fluid density in kg/m.sup.3, and v is speed of the flow of the fluid in m/sec, wherein said at least one second high-shear-stress and high-cavitation stage (15) comprises a rotor (25) provided with radial teeth (27) and housed in a cavitation chamber (29) surrounded by a stator (31) provided with radial teeth (33), wherein facing surfaces (35, 37) of the radial teeth (27) of the rotor (25) and the radial teeth (33) of the stator (31) have a parabolic profile in circumferential direction, wherein the parabolic profile of each tooth of said radial teeth (27) of the rotor (25) lies along a curve of a parabola (Pr) of which a vertex (Vr) is arranged at a rear edge (27b) of the tooth (27), with respect to a direction of rotation (F1) of the rotor (25), and along a radius (Rr) connecting said rear edge (27b) to a centre (Cr) of the rotor (25), a focus of the parabola (Pr) being also located on said radius (Rr), and wherein the parabolic profile of each tooth of said radial teeth (33) of the stator (31) lies along a curve of a parabola (Ps) of which a vertex (Vs) is arranged at a rear edge (33b) of the tooth (33), with respect to the direction of rotation (F1) of the rotor (25), and along a radius (Rs) connecting said rear edge (33b) to the centre (Cs) of the stator (31), a focus of the parabola (Ps) being also located on said radius (Rs).

2. The apparatus according to claim 1, comprising a plurality of said first high-turbulence mixing stages (13) and a plurality of said second high-shear-stress and high-cavitation stages (15), said stages (13, 15) being arranged in series and alternated with each other, so that the multiphase flow passes through each of said stages (13, 15), wherein the at least one radial pin (23) of each first high-turbulence mixing stage (13) and the rotor (25) of each second high-shear-stress and high-cavitation stage (15) are integral with the shaft (39).

3. The apparatus according to claim 1, wherein at least two said pins (23) are associated with a same high-turbulence mixing stage (13) and are arranged on a same plane perpendicular to the axis of rotation of the shaft (39) or on parallel planes perpendicular to the axis of rotation of the shaft (39).

4. The apparatus according to claim 1, wherein the at least one first high-turbulence mixing stage (13) comprises injection nozzles (49a, 49b) adapted to inject a flow of a substance or a mixture of substances into the mixing chamber (19).

5. The apparatus according to claim 1, wherein the parabolic profile of the radial teeth (33) of the stator (31) is identical to and a mirror image of the parabolic profile of the radial teeth (27) of the rotor (25).

6. The apparatus according to claim 1, wherein the equation of the parabola of the parabolic profile of the radial teeth (27) of the rotor (25) or of the radial teeth (33) of the stator (31) is Y=0.0062974 X.sup.2.

7. The apparatus according to claim 1, wherein a gap (51) is provided between the radial teeth (27) of the rotor (25) and the radial teeth (33) of the stator (31), which gap is minimum at the rear edges (27b, 33b) of the radial teeth (27) of the rotor (25) and the radial teeth (33) of the stator (31) when said rear edges are substantially aligned along corresponding radiuses (Rr, Rs) of the rotor (25) and the stator (31).

8. The apparatus according to claim 1, wherein the rotor (25) of the at least one second high-shear-stress and high-cavitation stage (15) has a diameter ranging from 50 to 500 mm and an axial length ranging from about 0.05 to 2.5 times the diameter of the rotor (25), and wherein a minimum gap between the radial teeth (27) of the rotor (25) and the radial teeth (33) of the stator (31) ranges from about 0.2 to 5.0 mm.

9. The apparatus according to claim 8, wherein the diameter of the rotor (25) of the at least one second high-shear-stress and high-cavitation stage (15) is 100 to 300 mm.

10. The apparatus according to claim 8, wherein the axial length of the rotor (25) of the at least one second high-shear-stress and high-cavitation stage (15) is 0.1 to 1.0 times the diameter of the rotor (25).

11. The apparatus according to claim 8, wherein the minimum gap between the radial teeth (27) of the rotor (25) and the radial teeth (33) of the stator (31) ranges from 0.5 to 2.5 mm.

12. The apparatus according to claim 1, wherein the diameter (D) of the mixing chamber (19) and a diameter of the cavitation chamber (29) range from about 50 to 500 mm, and wherein an axial length of the at least one first high-turbulence mixing stage (13) ranges from about 0.1 to 2.5 times the diameter (D) of the mixing chamber (19).

13. The apparatus according to claim 12, wherein the diameter (D) of the mixing chamber (19) and the diameter of the cavitation chamber (29) range from 100 to 300 mm.

14. The apparatus according to claim 12, wherein the axial length of the at least one first high-turbulence mixing stage (13) ranges from 0.25 to 1.5 times the diameter (D) of the mixing chamber (19).

15. The apparatus according to claim 1, wherein a rotation speed of the rotor (17) of the at least one first high-turbulence mixing stage (13) ranges from 1000 to 3000 rpm.

16. The apparatus according to claim 1 operating in countercurrent mode, wherein the at least one first high-turbulence mixing stage (13) comprises: a first high-turbulence mixing stage having a first port (165) for inlet of a first substance which is in a first physical state and a second port (167) for outlet of a second substance which is in a second physical state, and a second high-turbulence mixing stage having a first port (173) for inlet of a substance which is in said second physical state and a second port (175) for outlet of a substance which is in said first physical state.

17. The apparatus according to claim 1 operating in equicurrent mode, wherein the at least one first high-turbulence mixing stage (13) comprises: a first high-turbulence mixing stage having a first port (165) for inlet of a first substance which is in a first physical state and a second port (167) for inlet of a second substance which is in a second physical state, and a second high-turbulence mixing stage having a first port (173) for outlet of a substance which is in said second physical state and a second port (175) for outlet of a substance which is in said first physical state.

18. A method for enhancing phase contact and chemical reactions, comprising the steps of: providing the apparatus according to claim 1; and subjecting in the apparatus a multiphase flow to the at least one first high-turbulence mixing stage (13) and to the at least one second high-shear-stress and high-cavitation stage (15), said stages (13, 15) being adapted to cause an increase in relative sliding speeds of phases involved in the multiphase flow passing through said stages (13, 15).

19. The method according to claim 18, wherein said multiphase flow is obtained by feeding substances of different phases in countercurrent mode through said stages (13, 15).

Description

DESCRIPTION OF THE FIGURES

(1) Some preferred embodiments of the invention will be given by way of non-limiting example with reference to the accompanying Figures, in which:

(2) FIG. 1 is a part-sectional perspective view of a preferred embodiment of an apparatus according to the invention;

(3) FIG. 2A is a sectional view of the stages of the apparatus shown in FIG. 1;

(4) FIG. 2B is a cross-sectional view of the stages of the apparatus shown in FIG. 1, in which the nozzles are put in evidence;

(5) FIG. 3A is a schematic view of the rotor and stator teeth of a high-shear-stress and high-cavitation stage of the apparatus shown in FIG. 1;

(6) FIG. 3B is a schematic plan view of a rotor;

(7) FIG. 3C is an enlarged view of the teeth shown in FIG. 3B;

(8) FIG. 4A is a part-sectional, rear perspective view of an apparatus according to the invention, with three high-shear-stress and high-cavitation stages;

(9) FIG. 4B is a part-sectional, front plan view of the apparatus shown in FIG. 4A;

(10) FIG. 4C is a part-sectional, front perspective view of the apparatus shown in FIG. 4A.

(11) FIG. 5 is a graph of cellulose substrate conversion for steam explosion versus the invention as disclosed for Example 1.

(12) In all Figures, the same reference numerals have been used to denote equal or functionally equivalent components.

DESCRIPTION OF SOME PREFERRED EMBODIMENTS OF THE INVENTION

(13) Referring to FIGS. 1 to 3, the apparatus according to the invention has been generally denoted by reference numeral 11. Apparatus 11 illustrated is made in accordance with a preferred embodiment of the invention and it mainly comprises a plurality of serially arranged stages for enhancing phase contact and chemical reactions. More particularly, apparatus 11 comprises high-turbulence mixing stages 13 alternated with high-shear-stress and high-cavitation stages 15. As it will become more apparent from the following description, stages 13, 15 of apparatus 11 are adapted to subject a multiphase flow passing through said stages 13, 15 to an increase of the relative sliding speeds of the phases involved.

(14) In the embodiment illustrated, three high-turbulence mixing stages 13 are provided in the whole and two high-shear-stress and high-cavitation stages are provided in the whole. Other embodiments are possible, comprising at least one high-turbulence mixing stage 13 and at least one high-shear-stress and high-cavitation stage 15.

(15) Always with reference to the preferred embodiment illustrated, stages 13 comprise a rotor 17 rotatable within a mixing chamber 19 surrounded by a stator 21. Moreover, according to the invention, rotor 17 comprises at least one radial pin 23 integral with said rotor 17 rotating within mixing chamber 19. Said pins 23 radially extend from the axis of rotation of shaft 39 of rotor 17, preferably over such a length that the diameter of the external circumference described by pin 23 is in the range of 0.3D to 0.9D, D being the diameter of mixing chamber 19. In the embodiment illustrated, four pins 23 are provided in each mixing stage 13, but embodiments with any number of pins can be envisaged. Moreover, pins 23 associated with a same mixing stage 13 may be arranged on a same plane perpendicular to the axis of rotation of rotor 17 or on parallel planes, as in the embodiment illustrated. Moreover, in the embodiment illustrated, mixing stages 13 are substantially identical and have all the same number of pins 23. However, according to the invention, embodiments with mixing stages 13 different from one another can be envisaged, where moreover the number of pins 23 is different in different stages. In the embodiment illustrated, pins 23 have circular cross-section, substantially constant over the longitudinal pin axis, but pins with a cross-sectional shape different from the circular shape, e.g. an oval or another shape, or pins with variable cross-section along the longitudinal axis, can possibly be provided. Preferably, according to the invention, mixing stage 13 is adapted to subject the multiphase flow to a high-turbulence regimen with Reynolds number (Re)>500,000.

(16) Stages 15 comprise a rotor 25 provided with radial teeth 27 and housed in a cavitation chamber 29 surrounded by a stator 31 provided with radial teeth 33. Preferably, the number of radial teeth 27 in rotor 25 and radial teeth 33 in stator 31 is the same. Moreover, according to the invention, facing surfaces 35, 37 of teeth 27, 33 of rotor 25 and stator 31, respectively, have a parabolic profile in circumferential direction.

(17) As it can be better appreciated from FIGS. 3B and 3C, rotor teeth 27 have a parabolic profile 27a in circumferential direction. According to the invention, profile 27a of tooth 27 lies along the curve of a parabola Pr of which vertex Vr is located at rear edge 27b of tooth 27, with respect to the direction of rotation of rotor 25 (arrow F1), and along radius Rr connecting said edge 27b to centre Cr of rotor 25. The focus of parabola Pr also lies on said radius Rr.

(18) Correspondingly, as it can be appreciated in particular from FIGS. 3B and 3C, stator teeth 33 have a parabolic profile 33a that preferably is identical to and is the mirror image of the profile of teeth 27. More precisely, according to the invention, profile 33a of tooth 33 lies along the curve of a parabola Ps of which vertex Vs is located at rear edge 33b of stator tooth 33, with respect to the direction of rotation of rotor 25, along radius Rs connecting said edge 33b to stator centre Cs, coinciding with centre Cr of rotor 25. The focus of parabola Ps also lies on said radius Rs.

(19) In a preferred embodiment of the invention, the equation of the parabola of the profile of the rotor and/or stator teeth is Y=0.0062974 X.sup.2.

(20) Gap 51 between rotor teeth 27 and stator teeth 33 is minimum at edges 27b, 33b of teeth 27, 33, when said edges are substantially aligned along the corresponding rotor and stator radiuses Rr, Rs.

(21) According to the invention, rotor 17 and rotor 25 are integral with a common rotating shaft 39. Preferably, shaft 39 is made to rotate by an electric motor 41 steadily associated with a supporting frame 43.

(22) In the embodiment illustrated, mixing stages 13 have an inlet port 45a and an outlet port 45b both opening in a corresponding mixing chamber 19. Ports 45a and 45b are associated with ducts 47a, 47b for transporting the substance or mixture of substances into or out of chamber 19.

(23) Moreover, mixing stages 13 can be provided with injection nozzles 49a, 49b adapted to inject a substance or a mixture of substances into mixing chamber 19. At least one injection nozzle 49a, 49b can be provided in each mixing stage 13, and moreover one or more mixing stages 13 can lack the nozzles. In the example illustrated, it is assumed that two consecutive stages 13 are provided with a corresponding nozzle 49a, 49b.

(24) A non-limiting exemplary embodiment of apparatus 11 according to the invention has: diameter of toothed rotors 25 ranging from about 50 to 500 mm and preferably from about 100 to 300 mm; minimum gap between rotor teeth 27 and stator teeth 33 ranging from about 0.2 to 5.0 mm and preferably from about 0.5 to 2.5 mm; axial length of toothed rotors 25 ranging from about 0.05 to 2.5 times the diameter of rotor 25, and preferably ranging from about 0.1 to 1.0 times the diameter of rotor 25; internal diameter of mixing chambers 19 and cavitation chambers 29 ranging from about 50 to 500 mm, and preferably ranging from about 100 to 300 mm; axial length of high-turbulence mixing stages 13 ranging from about 0.1 to 2.5 times the internal diameter of the corresponding mixing chamber 19, and preferably ranging from about 0.25 to 1.5 times the internal diameter of chamber 19; rotation speed ranging from 500 to 5000 rpm, preferably from 1000 to 3000 rpm.

(25) Referring to FIGS. 4A, 4B and 4C, there is shown an apparatus 111 in accordance with a preferred embodiment of the invention, comprising four mixing stages 13 alternated with three high-shear-stress and high-cavitation stages 15. The embodiment illustrated of apparatus 111 is configured for countercurrent operation. Arrow F2 in FIG. 4C denotes the prevailing flow direction of the liquid phase in stages 13, 15, and arrow F3 denotes the prevailing flow direction of the solid phase.

(26) Apparatus 111 is equipped with an inlet hopper 161 for the fresh solid matrix. The configuration illustrated includes, downstream of hopper 161, a motor-driven squeezing device 163 adapted to transfer the material of the solid matrix introduced into hopper 161 to the first mixing stage 13, proximal relative to motor 41. Squeezing device 163 can comprise for instance a conical screw or a conical auger driven by an electric motor 163a. Squeezing device 163 communicates with the proximal first mixing stage 13 through a port 165 provided in stator 21. Moreover, a second port 167 is provided in the proximal first mixing stage 13 for the outlet of the liquid phase from proximal mixing stage 13. Said second port 167 is preferably equipped with a grid 167a for preventing the solid phase from being evacuated, together with the liquid phase, from proximal mixing stage 13 through port 167. Port 167 communicates with a duct 169 for liquid phase evacuation, communicating, for instance, with a collecting tank located downstream of said duct 169.

(27) In the preferred but not exclusive embodiment illustrated, inlet port 165 for solid phase inlet and outlet port 167 for liquid phase outlet are located diametrically opposite and in the upper and lower part of apparatus 111, respectively, when the latter is in working configuration.

(28) Always with reference to the embodiment illustrated, proximal mixing stage 13 further includes a rotatable blade 171, fixedly connected to rotor 17 by means of a pair of parallel arms 171a, 171b radially extending from rotor 17. The purpose of blade 171 is to prevent grid 167a separating stage 13 from evacuation duct 169 from becoming clogged due to the accumulation of solid material, which would prevent liquid phase evacuation through duct 169. Blade 171 keeps said grid 167a free mainly thanks to the circumferential vortex motion imparted to the mixed liquid-solid substance present in proximal stage 13.

(29) According to the invention, in the embodiment illustrated, in which apparatus 111 is configured for countercurrent operation, the amount of liquid phase substance evacuated from proximal mixing stage 13 is prevailing with respect to the amount of solid phase substance evacuated through the grid separating the evacuation duct from the same proximal mixing stage 13.

(30) In the configuration illustrated, mixing stage 13 distal relative to electric motor 41 is provided with a first port 173 for liquid phase inlet and a second port 175 for solid phase evacuation. In the embodiment illustrated, ports 173 and 175 are located diametrically opposite and in the upper and lower part of apparatus 111, respectively, when the latter is in working configuration.

(31) A duct 177 for feeding the liquid phase, e.g. water, is provided upstream of port 173. For instance, duct 177 may be connected, upstream of port 173, to a circuit delivering the liquid substance coming from a suitable tank. Always with reference to the preferred, but not exclusive, embodiment illustrated, a screw press 179, adapted to separate the solid and liquid phases contained in the substance evacuated from distal mixing stage 13, is provided downstream of port 175. Screw press 179 has a first port 179a for the evacuation of the exhausted solid phase or solid matrix and a second port 179b for liquid phase outlet. According to the invention, in the embodiment illustrated, in which apparatus 111 is configured for countercurrent operation, the amount of solid phase substance evacuated from distal mixing stage 13 is prevailing with respect to the amount of liquid phase substance evacuated from the same distal mixing stage 13.

(32) Preferably, apparatus 111 is equipped with a recirculation pump 181 for recovering the residual liquid phase evacuated from screw press 179 through port 179b. Said pump 181 is connected, at its upstream side, to screw press 179 through a first duct 183a for transporting the liquid phase from screw press 179 to pump 181, and, at its downstream side, by means of a pipe tee 177a, to feeding duct 177 through a second duct 183b for transporting the liquid phase towards distal mixing stage 13.

(33) Hereinafter. some examples of application of apparatus 11 made in accordance with the invention will be given.

Example 1

(34) The apparatus according to the invention has been used for pre-treating straw in a method of obtaining sugars at low cost from residual biomass.

(35) In the last decade, there has been a considerable interest in processes for converting lignocellulosic biomasses in biofuels and refinery intermediates, with the aim of identifying a practicable alternative for replacing fossil fuels. The concept of second generation biofuels and second generation biorefinery provides for starting from a raw matter belonging to the field of residual biomasses, and for obtaining a current of sugars (C.sub.5 and C.sub.6, i.e. with 5 or 6 carbon atoms) therefrom. Yet, the structural complexity of the cell walls of plants makes the same biomass highly refractory to chemical or biological attack. Different pre-treatment processes (with different chemical approaches, at different temperature and pressure levels) exist for reducing plant refractoriness to chemical or biological attack. Among such processes, pre-treatments in diluted acidic solution are at present recognised as the most effective processes to make biomass accessible to enzymatic attack with cellulase-type enzymes. In this context, for a given strictness of the operating conditions, the kind of reactor or apparatus in which pre-treatment is carried out has a considerable effect on the properties of the pre-treated material and consequently on the performance of the subsequent enzymatic hydrolysis. This is due to the peculiarities of the reactor or apparatus in terms of capacity of interphase area generation and of increase in the overall size and global volume of the pores, and hence in terms of capacity of devastation of the cell walls in the biomass.

(36) Steam explosion is a known hydrothermal treatment making separation of the three fractions forming the common vegetable substrates (hemicellulose, cellulose and lignin) easier and less severe from the environmental standpoint. The method consists in using high-pressure saturated steam for quickly heating the biomass in a continuous or discontinuous reactor. The material is kept at the desired temperature (180-230 C.) for a short period (1-10 minutes), during which hemicellulose is hydrolysed and made soluble. At the end of this time period, pressure is quickly brought back to atmospheric pressure, thereby obtaining an explosive decompression further fraying the biomass.

(37) The results attainable with the apparatus according to the invention and with an apparatus for steam explosion have been compared in case of a pre-treatment in diluted acidic solution of wheat straw having the following characteristics (% by weight):

(38) TABLE-US-00001 Humidity content 10% Cellulose 38.2% Hemicellulose 24.1% Lignin 7.3% Proteins 3.4% Ashes 7%

(39) The following operating conditions have been adopted for the prior art apparatus: L/S ratio=10; temperature=150 C.; time=6 min; acid concentration=2% by weight H.sub.2SO.sub.4, L/S being the ratio of the liquid phase flow rate to the solid phase flow rate.

(40) The same operating conditions have been adopted for the apparatus according to the invention, except that the temperature was 30 C. The apparatus employed further had the following features: No. of turbulent mixing chambers: 2; No. of rotor-stator stages: 2 (rotor and stator elements having teeth with parabolic profile); Internal diameter of the stators: 195 mm; Rotor-stator gap: 1 mm (1.sup.st stage) and 0.75 mm (2.sup.nd stage); Rotation speed: 2100 rpm.

(41) Thereafter, the specimens of pre-treated biomass have been submitted to an enzymatic digestion method by using a cellulase-type enzymatic complex (in a concentration of 18 mg of enzyme GC 220 produced by Genenco/Danisco per gram of glucancellulose, at pH=5 and in a container stirred at 120 rps), and a diagram of the cellulose substrate conversion versus time has been plotted.

(42) TABLE-US-00002 Incubation Cellulose conversion [% b.w.] time [h] Steam Explosion Invention Untreated material 2 18 25 6 5 33 45 10 10 43 58 12 20 61 83 16 40 68 90 18 60 75 93 20 120 80 96 23

Example 2

(43) In this second example of application, the apparatus according to the invention has been used for a treatment of bacterial inactivation on highly-contaminated raw milk. The apparatus employed had the following features (the numbering of the mixing chambers is referred to the direction of advance of the phase to be processed): No. of turbulent mixing chambers: 2; No. of rotor-stator stages: 2 (rotor and stator elements having teeth with parabolic profile); Diameter of the mixing chambers: 206 mm (D); Axial length of the mixing chambers: 70 mm (i.e. 0.29D); Pins of the first mixing chamber: 4 pins arranged on parallel planes so as to form a spiral with forward thrust when the shaft rotates. Pins with radial size 59.75 mm, i.e. such a size that the circumference described by the pins during rotation is 0.58D; Pins of the second mixing chamber: 6 pins arranged on parallel planes so as to form a spiral with forward thrust when the shaft rotates. Pins with radial size 59.75 mm, i.e. such a size that the circumference described by the pins during rotation is 0.58D; Internal diameter of the stators: 195 mm; Rotor-stator gap (i.e. minimum rotor-stator span): 1 mm (1.sup.st stage) and 0.75 mm (2.sup.nd stage); Axial length of rotors and stators: 40 mm; Rotation speed: 1500 rpm; Motor drive: three-phase electric motor with installed power 15 kW.

(44) The specimen of raw cow milk with high bacterial contamination had the following characteristics:

(45) TABLE-US-00003 Fats 6.6% v/v Proteins 4.0% w/w Lactose 3.7% w/w Total solids 17.25% w/w pH 6.36 Ashes 0.83% w/w
and had the following microbiological content:

(46) TABLE-US-00004 Total count of mesophile 6.35 log cfu/ml aerobic bacteria (TC) Bacterial Endospores (BE) 2.62 log cfu/ml Lactobacilli (LAB) 5.04 log cfu/ml Coliforms (CF) 3.36 log cfu/ml Escherichia Coli (EC) 1.89 log cfu/ml Staphylococcus Aureus (SA) 2.34 log cfu/ml

(47) The set-up or starting step of the method, upstream of the apparatus, included a tank for the liquid phase to be processed (in the specific case, contaminated milk, with the above characteristics), a centrifugal pump for feeding the milk to the apparatus, on the delivery line of which a flow rate adjustment valve was connected, and a flow rate meter or float flowmeter (of the Asametro kind). An outlet line for the processed milk has been provided downstream of the apparatus, which line was equipped with a sampling valve followed by a three-way valve for directing the processed milk either to the milk collecting tank or to a recirculation line (in case of treatments entailing several passes through the apparatus). A plate exchanger (fed with refrigerated water in countercurrent mode, as far as the coolant fluid is concerned: inlet temperature 2 C. and outlet temperature 7 C.) was located on the recirculation line and was adapted to bring back the milk, at the end of each pass to the temperature of 10 C. set for the point of feed to the apparatus.

(48) Three kinds of treatment have been performed: (a) Single pass through the apparatus (permanence time inside the apparatus: 15 s; treatment start temperature: 10 C.; treatment end temperature: 15 C.); (b) Five passes through the apparatus with inter-refrigeration between successive passes (permanence time inside the apparatus: 15 s/pass, 75 s in total; treatment start temperature: 10 C.; treatment end temperature: 15 C.); (c) Single pass through the apparatus with CO.sub.2 injection into the first mixing chamber (permanence time inside the apparatus: 15 s; treatment start temperature: 10 C.; treatment end temperature: 15 C.; CO.sub.2 dosage: 20 g/l).

(49) In all treatments described, the flow rate of the liquid phase (i.e. contaminated milk) fed to the apparatus was 15 l/min.

(50) The bacterial content at the end of the treatment was measured (values expressed in log cfu/ml):

(51) TABLE-US-00005 initial After (a) After (b) After (c) Total count of mesophile 6.35 3.12 1.91 2.21 aerobic bacteria (TC) Bacterial Endospores (BE) 2.62 1.95 0.79 1.17 Lactobacilli (LAB) 5.04 2.47 1.02 1.56 Coliforms (CF) 3.36 1.23 0.51 0.65 Escherichia Coli (EC) 1.89 0.32 0 0.25 Staphylococcus Aureus (SA) 2.34 2.32 1.44 0.66

(52) The effectiveness of the apparatus (with and without the aid of CO.sub.2 injection) in bacterial inactivation treatments has thus been confirmed.

Example 3

(53) In this example the apparatus according to the invention has been employed as extractor.

(54) The apparatus employed had the following features: No. of turbulent mixing chambers: 3; No. of rotor-stator stages: 2 (rotor and stator elements having teeth with parabolic profile); Turbulent mixing chambers alternated with high-shear-stress and high-cavitation stages; Internal diameter of the stators: 195 mm; Rotor-stator gap 1 mm (1.sup.st stage) and 0.75 mm (2.sup.nd stage); Rotation speed: 2000 rpm.

(55) An extraction of carotenes (mainly lycopene) from tomato skins by means of extra virgin olive oil has been performed.

(56) The extra virgin olive oil (EVOO) employed had the following characteristics:

(57) TABLE-US-00006 Density (20 C.) 910 kg/m.sup.3 Viscosity (20 C.) 82 cP Monounsaturated fat content 71.7% w/w Polyunsaturated fat content 15.5% w/w Free acidity 0.221% Peroxide index 3.905 meq O.sub.2/kg Total carotenes 3 mg/kg (of which 0 mg/ kg of Lycopene)

(58) The tomato skins being treated had the following characteristics:

(59) TABLE-US-00007 Morphology flakes Size 1-3 mm Humidity 10% w/w Lycopene content 1140 mg/kg

(60) Two kinds of treatment have been performed: (a) Single pass through the apparatus (permanence time inside the apparatus: 5 s; treatment start temperature: 25 C.; treatment end temperature: 28 C.) with equicurrent feed of tomato skins and EVOO in a ratio 1:5 w/w; (b) Single pass through the apparatus (permanence time inside the apparatus: 5 s; treatment start temperature: 25 C.; treatment end temperature: 28 C.) with countercurrent feed of tomato skins and EVOO in a ratio 1:5 w/w.

(61) The content of total carotenes and lycopene has been measured on the enriched EVOO obtained at the end of the extraction treatment/values expressed in log mg/Kg):

(62) TABLE-US-00008 initial After (a) After (b) Total carotenes 3 94 173 Lycopene 0 73 148

(63) The effectiveness of the apparatus according to the invention as extractor, and above all the possibility of obtaining multistage extractor performance if the solid phase and the extracting liquid phase are fed in countercurrent mode, have been proved.

Example 4

(64) In this example the apparatus according to the invention has been employed as extractor.

(65) The apparatus employed had the following features: No. of turbulent mixing chambers: 4; No. of rotor-stator stages: 3 (rotor and stator elements having teeth with parabolic profile); Turbulent mixing chambers alternated with high-shear-stress and high-cavitation stages; Diameter of the mixing chambers: 206 mm; Axial length of the mixing chambers: 70 mm; Pins of the 1.sup.st mixing chamber: 6 pins arranged on parallel planes so as to form a spiral with forward thrust when the shaft rotates. Pins with radial size 75 mm, i.e. such a size that the circumference described by the pins during rotation is 0.73D, D being the diameter of the mixing chambers; Pins of the 2.sup.nd mixing chamber: 6 pins arranged on parallel planes so as to form a spiral with forward thrust when the shaft rotates. Pins with radial size 75 mm, i.e. such a size that the circumference described by the pins during rotation is 0.73D; Pins of the 3.sup.rd mixing chamber: 6 pins arranged on parallel planes so as to form a spiral with forward thrust when the shaft rotates. Pins with radial size 75 mm, i.e. such a size that the circumference described by the pins during rotation is 0.73D; Pins of the 4.sup.th mixing chamber: 4 pins arranged on parallel planes so as to form a spiral with forward thrust when the shaft rotates. Pins with radial size 59.75 mm, i.e. such a size that the circumference described by the pins during rotation is 0.58D; Internal diameter of the stators: 195 mm; Minimum rotor-stator gap: 2.5 mm (1.sup.st stage), 1.25 mm (2.sup.nd stage) and 0.75 mm (3.sup.rd stage); Axial length of rotors and stators: 35 mm; Rotation speed: 2250 rpm; Motor drive: three-phase electric motor with installed power 22 kW.

(66) The apparatus has been operated in equicurrent mode and countercurrent modes: Equicurrent mode: by feeding the solid phase into the 1.sup.st mixing chamber by means of an auger feeder, and by feeding also the liquid phase into the 1.sup.st mixing chamber by means of a peristaltic positive-displacement pump with flow rate constant in time; by extracting the final suspension from the last mixing chamber (i.e. the 4.sup.th mixing chamber) and then subjecting it to liquid-solid separation by means of decantation, followed by a final pressing. Subsequently, centrifugation on a disc centrifuge and filtration on a polyester bag filter with absolute retention degree 50 microns have been performed on the liquid phase, and then a dehydration of the liquid phase extracted has been carried out by means of a vacuum evaporator of the rotovapor kind, followed by a vacuum cabinet drier, whereby a dry extract in powder form has been obtained. Countercurrent mode: by feeding the solid phase into the 1.sup.st mixing chamber by means of an auger feeder, and by feeding the extracting liquid phase into the 4.sup.th mixing chamber by means of a peristaltic positive-displacement pump with flow rate constant in time; by extracting the exhausted solid phase from the 4.sup.th mixing chamber by means of an auger extractor-squeezer with recirculation of the liquid phase squeezed in the 4.sup.th mixing chamber, and by extracting the liquid phase extracted from the 1.sup.st mixing chamber through a tube surmounted by a mesh grid, with mesh span having a 0.50.5 mm size, adapted to let the liquid phase go out and to retain the solid phase, wherein said grid was kept clean by means of a turbulent flow of a liquid phase current moved by a blade fit onto the machine shaft, the circumference described by the blade having diameter 0.9D. The liquid phase extracted was centrifuged on a disc centrifuge, filtered on a polyester bag filter with absolute retention degree 50 microns and then subjected to dehydration by means of a vacuum evaporator of the rotovapor kind, followed by a vacuum cabinet drier, whereby a dry extract in powder form has been obtained.

(67) Extraction of polyphenols (mainly oleuropein) from olive tree leaves (solid phase) has been performed, by using water as extracting liquid phase.

(68) Water fed to the TURBEX extractor had the following characteristics:

(69) TABLE-US-00009 pH 7.7 Fixed residue 143 mg/l at 180 C. Hardness 21 F. Conductivity 362 micro- siemens/cm at 20 C. Temperature 25 C.

(70) Olive tree leaves fed as the solid phase had the following characteristics:

(71) TABLE-US-00010 Morphology flakes Size 1-2 mm Humidity 10% w/w Oleuropein content 76 g/kg Content of water-extractable 512 g/kg substances other than oleuropein Temperature 5 C.

(72) The operating conditions of the two kinds of treatment are as follows: Equicurrent mode: Single pass through the apparatus (permanence time inside the apparatus: 36 s; treatment start temperature: 25 C.; treatment end temperature: 30 C.), with equicurrent feed of olive tree leaves and water in a ratio 1:7 w/w [Liquid phase (water) flow rate 700 kg/hSolid phase (olive tree leaves) flow rate 100 kg/h]. Countercurrent mode: Single pass through the apparatus (permanence time inside the apparatus: 36 s; treatment start temperature: 25 C.; treatment end temperature: 30 C.), with countercurrent feed of olive tree leaves and water in a ratio 1:7 w/w [Liquid phase (water) flow rate 700 kg/hSolid phase (olive tree leaves) flow rate 100 kg/h].

(73) The solid extract obtained has been weighted, the oleuropein content in the solid extract has been analysed by means of HPLC (High Performance Liquid Chromatography) technique and the oleuropein extraction yield has been calculated.

(74) Result of the Equicurrent Treatment:

(75) Amount of total solid extract obtained: 305 g/kg

(76) of which

(77) Oleuropein content: 16.7% w/w (corresponding to 50.9 g)

(78) Content of other extractable substances: 83.3% w/w (corresponding to 254.1 g)

(79) Oleuropein extraction yield: 50.9/76=67% w/w

(80) Extraction yield of other extractable substances: 254.1/512=49.6% w/w

(81) Result of the countercurrent treatment:

(82) Amount of total solid extract obtained: 375 g/kg

(83) of which

(84) Oleuropein content: 20.05% w/w (corresponding to 75.2 g)

(85) Content of other extractable substances: 79.95% w/w (corresponding to 299.8 g)

(86) Oleuropein extraction yield: 75.2/76=98.9% w/w

(87) Extraction yield of other extractable substances: 299.8/512=58.6% w/w

(88) The results obtained with the apparatus disclosed in this fourth exemplary embodiment of the invention prove the effectiveness of the apparatus as extractor, and above all the possibility of obtaining multistage extractor performance if the solid phase and the extracting liquid phase are fed in countercurrent mode.

INDUSTRIAL APPLICABILITY

(89) The apparatus according to the invention finds advantageous applications in several industrial fields, e.g., as extractor, mixer, homogeniser, reactor, biomass pre-treating apparatus for biorefineries and biofuel installations, etc.

(90) The apparatus can be used for instance as stripper and reactor in the field of the treatment of primary and secondary waters in order to obtain NH.sub.3 removal and to enhance the performance of advanced oxidation techniques for COD removal. Moreover, the apparatus according to the invention can be used as reactor for oxidising paraxylene to terephthalic acid and as reactor for polymerising polyester, enabling attaining the reaction activation energy mainly or exclusively by means of the kinetic component, and consequently conducting the reactions at lower temperatures than in the conventional practice, besides of course attaining a drastic reduction of the reaction times thanks to the enhancement of the generation of the interphase area and the property transport coefficients, with a consequent saving in investment and operating costs.

(91) The invention as described and shown can undergo several alternatives and modifications lying in the same inventive principle.