GB2530611A

GB2530611A - Oscillatory baffled reactor and gas-liquid reaction process

Info

Publication number: GB2530611A
Application number: GB1511922.5A
Authority: GB
Inventors: Nuno Reis; Gianluca Li Puma
Original assignee: Loughborough University
Current assignee: Loughborough University
Priority date: 2014-07-17
Filing date: 2015-07-08
Publication date: 2016-03-30
Also published as: WO2016009177A1; GB201511922D0; GB201412749D0

Abstract

A multi-orifice oscillatory baffled reactor 30 comprises: a reactor tube 301; a baffle 309 within the reactor tube, defining a plurality of orifices having a free area of up to 30%; a gas source having an outlet within the reactor tube; and oscillatory means 316 which, during use, provides oscillatory flow of a fluid relative to the baffle. The reactor may include a plurality of baffles within the reactor tube, each baffle defining a respective plurality of orifices and having a free open area of up to 30%. Also disclosed are: A method of removing contaminants from a fluid by contacting the fluid with an oxidising gas comprising; a method of CO2 sequestration; a method of manufacturing bio product using syngas bioconversion; and the use of the multi-orifice oscillatory baffled reactor are also disclosed.

Description

Oscillatory Baffled Reactor and Gas-Liquid Reaction Process

Technical field

The present invention relates generally to a multi-orifice oscillatory baffled reactor useful in gas-liquid reaction processes, and methods of removing contaminants from fluids using such reactors.

Background of the Invention

Oscillatory baffled reactors (OBRs) have been used to provide a reactor which promotes mixing without the use of stirrers or turbulent flow within the reactor. OBRs usually take the form of an elongated tube containing a number of baffles spaced along the tube. The baffles are usually plates which partially obstruct the internal cross-secUon of the tube, and include one or more orifices for the passage of liquid. It is well known that if a liquid flowing through the tube is oscillated or pulsated, the presence of the baffles causes the formation of vortices within the liquid, thereby providing an excellent mixing mechanism without the use of stirrers.

The most common OBRs include single-orifice baffles equally spaced along the reactor tube. Each baffle is a plate containing a single, central orifice. However, as single-orifice OBRs are scaled up, beyond a certain point the advantageous mixing effects cannot be achieved and therefore different baffle geometries which allow for the OBR effect to be scaled up have been provided, and these include multi-orifice OBRs.

Multi-orifice OBRs contain baffle plates each of which includes a plurality of orifices, usually of equal size and arranged in a regular pattern. The use of multi-orifice OBRs allows the mixing effects observed at laboratory scale to be scaled up to industrial scale.

Abdullah Al-Abduly et a! studied the effects of OBRs on ozone-water mass transfer (Chem. Eng. Process., b LLcccJ«=:gLIQJ.ffl ?J1.$JQ1J2 2014). They found that an OBR was more efficient for ozone-water mass transfer than a standard bubble column (without baffles or oscillation) or baffled column (without oscillation). Their experiments used a single-orifice OBR.

Rao and Baird (J. Chem. TechnoL Biotechnol. 78:134-137, 2003) demonstrated that results achieved with single-orifice OBRs cannot easily be extended to the corresponding multi-orifice OBR, because of the different effects of baffle plate geometries on fluid mechanics.

The efficiency of gas-liquid reactions depends in a large part on the efficiency of mass transfer of the gas to the liquid in dissolution. One important gas-liquid reaction is ozonation, in which ozone reacts with and decomposes organic contaminants of concern from water in water treatment plants. Hellender et S. (2009), Environ. Sd. TechnoL, 2009, 43 (20), pp 7862-7869, showed efficient removal of a large library of 220 contaminants from a municipal wastewater using ozone/oxygen mixture. Pollutants of concern include pharmaceuticals and antibiotics (e.g., ibuprofen, trimethoprim); personal care products (e.g., benzophenone in sunscreens); herbicides (e.g., atrazine, isoproturon); hospital x-ray contrast media (e.g., diatrizoate, iopamidol); recalcitrant industrial (pulp and paper, textile, metal working fluids). Other strong oxidising gases such as chlorine are often also used to remove such contaminants from water supplies.

Pharmaceuticals and Personal Care Products (PPCPs) are rapidly emerging as micro-contaminants or concern in water from wastewater treatment plants (WTPs). It has been shown that WWTPs constitute the most important continuous point source for such micropollutants in the environment, such as in rivers, lakes and groundwater, which has a significant impact on both humans and wildlife. FPCF residues in rivers and lakes are the consequence of an inefficient treatment of municipal wastewater. As such, the Swiss Government and Authorities have approved the implementation of a 1 billion Euro programme over 20 years for upgrading 100 VWVTPS with ozonation technology.

Ozone is very expensive and waste of ozone during ozonation processes represents the biggest cost factor in ozone treatment of contaminated water.

Other applications are also in need of improved gas-liquid mass transfer efficiency.

These include CO2 sequestration by dissolution and syngas bioconversion into biofuels.

The sequestration of carbon dioxide, 002, is a topic of major industrial interest motivated by the recent increased need for reducing greenhouse gas emissions. Conventional gas-liquid contacting technology based on e.g. bubble columns (BCs), stirred tank reactors (STR5) and air-lift reactors (ALR5) are somewhat inefficient and present very modest performance in respect of the dissolution of gases with large gas aeration rates.

Syngas (also known as producer gas or synthesis gas) is produced from the gasification of biomass and other carbonaceous materials. It consists of a mixture of carbon monoxide (00), hydrogen (H2) and carbon dioxide (C02), along with trace amounts of methane (OH4), nitrogen and sulphur containing gases, higher hydrocarbons and particulate matter. The CO and H2 present in syngas can be converted by anaerobic microorganisms into a range of useful bio-based compounds such as bioplastics, ethanol, butanol, acetic and butyric acid and methane. CO and H2 both have low solubility, and it is believed that CO fermentation is controlled by gas-liquid mass transfer rates.

In ozonation, chlorination, 002 sequestration and fermentation of gaseous compounds such as syngas, a high utilisation efficiency of the gaseous compounds in the column is therefore highly desirable. Generally, in order to increase volumetric mass transfer coefficients (kLa) to provide more efficient gas-liquid reactions, the gas flow rate in the OBR has been increased. This increase in gas flow rate is known to increase both the gas hold-up (i.e. the fraction of the total reaction mixture which is gas at any one time) and energy dissipation. However, high gas flow rates are not conducive with high gas utilisation efficiency, which requires low values of gas superficial velocity with resultant low values of gas hold-up and kLa.

No process or device is yet known which can provide the necessary high gas utilisation efficiency while still maintaining an efficient gas-liquid reaction. If this could be achieved, there would be a substantial saving on cost on an industrial scale. For example, at present, ozonation reactions are predominantly carried out in bubble tanks, simple reactors where the gaseous reactant is bubbled through the liquid. Mixing results from internal flow recirculation resulting from differences in density and high superficial flow velocities in the column. Such bubble tanks lead to a waste of ozone and large financial costs, and support only inefficient ozonation reactions.

OBR5 provide a promising solution to the problems associated with existing reactors, but so far no satisfactory reactor design or reaction process has been provided which can substantially increase the efficiency of the gas-liquid reaction.

Summary of the Invention

Any sub-titles herein are included for convenience only, and are not to be construed as

limiting the disclosure in any way.

Multi-Orifice Oscillatory Baffled Reactor A first aspect of the invention is a multi-orifice oscillatory baffled reactor (OBR), comprising; a reactor tube; a baffle within the reactor tube, defining a plurality of orifices and having a free open area of up to 30%; a gas source having an outlet within the reactor tube; and oscillatory means which, during use, provide oscillatory flow of a fluid relative to the baffle.

The free open area is a property of a single baffle. The free open area of a multi-orifice baffle is a percentage value defined as (AD/A) x 100, where A0 is the total area of the orifices within the baffle and A is the total cross-sectional area of the baffle.

Providing a multi-orifice baffle with a free open area of less than or equal to 30% causes the production of a very large quantity of very small bubbles of gas in the sub-millimetre range (microbubbles) within the reactor tube of the OBR when gas is sparged into a fluid present in the OBR and the fluid is subjected to oscillatory flow relative to the baffle. This occurs even at very low gas superficial velocities, and the reactor is therefore made suitable for use in reactions where high gas utilisation efficiency is required.

The use of a small baffle open area in a multi-orifice baffle is responsible for the generation of these microbubbles as the fluid oscillates relative to the baffle. The strong radial mixing which occurs due to the fluid pulsation and/or baffle reciprocation in the reactor tube causes the microbubbles to become trapped within the tube for relatively long periods of time (e.g. for at least 1, at least 2 or at least 3 oscillatory cycles). The result is that a very large gas-liquid interfacial area is created which greatly increases the efficiency of the gas-liquid reaction. Furthermore, the bubbles are trapped within the reactor tube for periods of time long enough to achieve reactant gas consumption close to 100%; that is, little or no reactant gas is wasted and a substantial saving on cost is achieved.

The microbubbles produced within the OBR by the oscillatory motion of fluid relative to the baffle are not simply delayed in their transition through the reactor tube, but are effectively trapped within it. The microbubbles exhibit a downward movement (against the net flow of fluid) which effectively ensures a residence time within the reactor tube sufficient to provide a gas utilisation efficiency of up to 100%.

The gas utilisation efficiency achieved by the OBR may be at least 90%, for example up to 100%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92% or 91%.

The energy costs required for fluid and/or baffle pulsations are more than offset by the energy saving in preventing gas (especially oxidising gas such as ozone) wastage, making the OBR economically viable to provide a means for more efficient gas-liquid reactions, such as in the removal of contaminants from water such as wastewater.

The use of a multi-orifice baffle in the OBR allows the reactor to be scalable, such that it may be used in both small to medium scale applications (laboratory, households, small wastewater treatment plants and hospitals) and large scale industrial applications. Large scale application is not possible with single-orifice OBRs, as explained above.

The effects of a multi-orifice OBR cannot be fully predicted based on the corresponding single-orifice OBR. For example, the effects of baffle free open area do not necessarily translate from single-orifice OBR to multi-orifice OBR. The work of Rao and Baird (J Chem. Technol. BiotechnoL 78:134-137, 2003) suggests that there is little or no correlation between the mass transfer coefficient for the dissolution of oxygen in water and the free open area of a single orifice baffle. The present invention therefore provides unexpected advantages which would not be foreseeable based on work with single-orifice OBRs.

Preferably, the reactor tube contains a plurality of baffles, each baffle defining a respective plurality of orifices and having a free open area of up to 30%. An OBR having two or more baffles provides one or more inter-baffle regions where radial mixing is strong and vortices are generated. The trapping of microbubbles generated by the oscillatory flow is therefore more effective.

The number of baffles within the reactor is not particularly limited and depends upon the dimensions of the reactor tube.

Any number of baffles may be employed within the reactor provided that the appropriate amount of radial mixing is produced to allow for the formation and trapping of microbubbles. It will be clear to the skilled person that the exact number of baffles used within the reactor tube will depend on its design including, inter a/ia, the length and diameter of the tube being used. Thus the number of baffles within the reactor tube may be chosen accordingly.

The OBR may further contain one or more baffles having a free open area greater than 30%, in addition to the one or more baffles having a free open area of up to 30%.

The 0BR may further contain one or more baffles defining a single orifice, in addition to the one or more baffles each defining a plurality of orifices.

Preferably, all baffles within the reactor tube each define a respective plurality of orifices and have a baffle free open area of up to 30%.

The baffle free open area may be up to 25% e.g. up to 20%.

Further reducing the free open area of each baffle within the reactor to at or below 20% produces an even greater quantity of microbubbles, the microbubbles being further reduced in size. The gas-liquid interfacial area is further increased, with a resultant increase in reaction efficiency.

The baffle free open area may be up to 19%, 18%, 17%, 16%, 15%, 14%, 13%, 12%, 11% or 10%. The baffle free open area may be at least 5%, for example at least 6%, 7%, 8%, 9% or 10% The gas source may be an oxidising gas source, a 002 gas source or a syngas gas source. The reactor according to the present invention may therefore find application in processes such as ozonation, 002 sequestration or syngas bioconversion.

The gas source may be an oxidising gas source selected from ozone and chlorine.

As described above, ozonation using standard bubble columns is already employed in the treatment of water, such as wastewater, to remove organic contaminants. The use of an ozone gas source in the present device can provide a highly efficient ozonation reactor to supplement or replace the existing inferior reactors in order to provide a cost efficient water treatment solution in waste water treatment plants and other similar locations.

Similarly, a chlorine gas source could be employed in the disinfection of water supplies.

The device is fully compatible with existent ozonation and chlorination technologies.

The gas source may be an ozone gas source, the oscillatory baffled reactor being adapted for ozonation.

An ozonation reactor is a particularly important device in the treatment of water and wastewater, as described above. The use of the ozonation reactor to decontaminate water and wastewater will make it possible to reuse water and reduce the level of discharge of recalcitrant chemicals into the environment, therefore presenting simultaneously major economic and environmental benefit for local communities and wildlife.

The inventors have found that the chemical reaction for degradation of contaminant with ozone is fast and occurs at the gas-liquid interface, and therefore it is important to produce very small bubbles of ozone and to achieve trapping of those bubbles in order to achieve dissolution and high mass transfer efficiency. The present invention achieves this.

Because of the microbubble production, the OBR provides up to a 10-fold reduction in the amount of reactant gas required to treat a given volume of fluid, with a resultant up to 10-fold reduction in cost per cubic metre of treated fluid.

The gas source may be a sparged gas source. The sparged gas source may comprise a sparger to deliver gas to the internal volume of the reactor tube.

The sparger may comprise a perforated gas delivery element such that gas may pass through the perforation into the reactor tube. The perforated gas delivery element may comprise a tube made from suitable rigid material, such as plastics material, ceramic or other microporous material.

A sparged gas source provides a more controllable introduction of gas into the reactor so that the gas source may be easily adjusted to provide optimal conditions for microbubble production.

The gas source may be adapted to provide a gas aeration rate Qgas during use of between 0.01 and 0.1 vvm, i.e. between 0.1 and 1 L min1.

The multi-orifice oscillatory baffled reactor may have a hydraulic diameter dh between 5 mm and 50 mm, wherein dh is defined as: d,1 =d0/-\'n where d0 is the internal diameter of the reactor tube and n is the number of orifices in the baffle. For multi-orifice baffled reactors this can be shown to be the same as: dh = do/'Ja where do is the diameter of the baffle orifices and a is the baffle free open area.

The hydraulic diameter is a parameter which is often used to predict the performance of baffles with respect to gas-liquid mass transfer rates. A value of dh within this range provides for the optimal production of an increased number of very small diameter microbubbles, leading to a high efficiency gas-liquid reaction.

The baffles within the OBR may be equally spaced along the reactor tube.

When equally spaced, optimal results with regards to microbubble generation and trapping are achieved.

Alternatively, the baffles may be spaced according to a non-regular sequence. The baffles may also be randomly spaced along the reactor tube.

The multi-orifice oscillatory baffled reactor may have a spacing between two consecutive baffles (the inter-baffle spacing, L) of between d,, and 3dh.

An inter-baffle spacing within this range provides the optimal inter-baffle region size to achieve the necessary trapping of the microbubbles produced, leading to an increased gas hold-up, increased time of bubble residence within the reactor tube and therefore enhanced gas utilisation efficiency.

In the multi-orifice oscillatory baffled reactor, the average number of orifices per baffle may be from 2 to 1500 e.g. from 5 to 1000, or from 5 to 750 or from 5 to 500 e.g. from 5 to 250. More preferably, the average number of orifices per baffle may be between 10 and 100, more preferably 15 and 80, more preferably 20 and 60, more preferably 25 and 35. However, the skilled person will be aware that the selection of the average number of orifices per baffle depends upon cI for the reactor and hence the total cross sectional area A of the baffle.

Using a set of baffles having an average number of orifices within this range enhances the generation of microbubbles. The diameter of observed microbubbles also decreases for orifice numbers within this range.

The baffles may be manufactured from any suitable rigid material. Examples of suitable materials include stainless steel, acrylic polypropylene and PVC. The baffles may have a laminate structure comprising a plurality of layers sandwiched together. For example, a baffle may be constructed by sandwiching a suitable rigid polymer between two stainless steel layers. The central rigid polymer layer may be polypropylene.

The baffles may be produced by any suitable method, including machining from sheet material, lamination or 3D printing.

The baffles may be supported within the OBR by suitable supporting means which may fix the position of the baffles relative to the reactor tube. The supporting means may fix the position of the baffles relative to one another.

Alternatively, where oscillation of the baffles rather than the fluid is desired, the supporting means may connect all baffles together and to the oscillatory means, such that all the baffles may be oscillated simultaneously.

The supporting means may be a connecting member which connect all baffles together.

The connecting member may also be connected to the reactor tube, or the oscillatory means.

The connecting member may be a rod fixed within the reactor tube, passing through and connected to each baffle. The rod may be made from any suitable rigid material.

Suitable materials include stainless steel.

The baffles may be designed so as to provide a close fit with the internal wall of the reactor tube. In other words, the diameter of the baffles may be substantially equal to the internal diameter of the reactor tube such that little or no fluid may pass between the outer perimeter of the baffle and the internal wall of the reactor tube.

When such a close fit is provided, the fluid dynamics within the reactor tube may be better controlled and predicted. -10-

All baffles within the OBR may be of identical design. That is, all baffles may have the same baffle free open area a and the same number, size and distribution of orifices.

Furthermore, the baffles may all be manufactured from identical material with identical physical properties. Alternatively, the design of an individual baffle may differ from the design of other baffles within the reactor tube. For example, the distribution of orifices in the baffle may be different, although a and other parameters may be the same.

The OBR may be of the "pulsed" type. The oscillatory means may comprise an axially movable fluid displacement member within the reactor tube at one end, movable to vary the total internal volume of the reactor tube and therefore effect an oscillation of fluid within the reactor tube. The fluid within the reactor is thereby "pulsed" back and forth through the baffle.

The fluid displacement member may be a piston.

Alternatively, the fluid displacement member may be any suitable means for providing displacement of the fluid, such as a diaphragm pump.

Alternatively, the OBR may be of the "reciprocating plate" type. The oscillatory means may be connected to one or more baffles to provide reciprocation of the baffle relative to the reactor tube (and relative to any fluid present in the reactor tube). In this case the oscillatory means may be located either inside or outside the reactor tube. This setup equally provides the strong radial mixing within the reactor tube necessary to produce microbubbles from a gas introduced to the OBR. Whether the OBR is of "pulsed" or "reciprocating plate" type, the net result is similar. The key concern is that there is flow of fluid relative to the baffles (through the baffle orifices), which creates the strong radial mixing and a large number of microbubbles.

The oscillatory means may be connected to a servo-hydraulic system which imparts the oscillatory motion.

Alternatively, any suitable means for providing oscillatory motion may be provided, such as a combustion, wind or solar powered motor.

The oscillatory means may be capable of providing sinusoidal oscillatory motion. -11 -

The oscillatory means can be controlled to produce a desired frequency and amplitude of fluid oscillation and/or baffle oscillation. The result is movement of fluid relative to the baffle through the baffle orifices, which creates the strong radial mixing in the reactor tube, particularly in the inter-baffle region when a plurality of baffles is present. The combination of oscillation and the specific baffle design in the OBR lead to the production and trapping of microbubbles within the reactor tube.

The reactor tube may be made from any suitable material. Suitable materials include rigid plastics materials such as acrylic, PVC or polypropylene, or metallic materials such as steel, or glass. The reactor tube may be made from a transparent material to provide for ease of visual monitoring, which is important to allow the user to ensure that an adequate number and distribution of microbubbles is produced and maintained within the reactor tube during use.

The reactor tube may be sealed at both ends to prevent the unwanted leakage of fluid during operation of the OBR.

The reactor tube may define an opening which acts as a fluid inlet. The opening may be sealable my means of a valve.

The reactor tube may define an opening which acts as a fluid outlet. The opening may be sealable my means of a valve.

The reactor tube may be of a wide range of dimensions depending on the intended application. The size of the reactor tube may range from a size suitable for small scale (e.g. laboratory) use, up to sizes suitable for large scale (e.g. industrial water treatment) use. Clearly, the dimensions of all other components of the reactor will also vary accordingly to correspond with the dimensions of the reactor tube. For example, a suitable size of baffle will be selected depending on the size of the reactor tube.

The multi-orifice oscillatory baffled reactor may include a reactor tube with an internal diameter (d0) of at least 50 mm and up to 1 m.

For small scale use, the reactor tube may have an internal diameter (d0) of less than 300 mm. More preferably the reactor tube has an internal diameter of less than 250 mm, less than 200 mm or less than 150 mm. The total volume of the reactor tube may be less than -12-L, less than 14 L, less than 13 L, less than 12 L or less than 11 L. The height of the reactor tube may be less than 2 m.

For large scale use, the reactor tube may have an internal diameter of up to 1 m. The height of the reactor tube may be less than 2 m The OBR may be a compact modular reactor unit. Such compact modular units are suitable for household use or application in small water and wastewater treatment plants.

They could also be used in small industrial units, hospitals, water purification systems in small to medium sized businesses and car washing stations. They can therefore provide affordable and efficient water decontamination systems for a wide variety of users.

The OBR could also find application in countries where clean and safe drinking water sources are rare. The efficiency of the gas-liquid reaction means that the OBR can provide an affordable source of clean water to supply small communities in such countries.

The multi-orifice oscillatory baffled reactor may be suitable for small to medium scale fluid throughputs, for example up to 10 Us. The OBR may be capable of a fluid throughput of at least 1 Us.

Such small to medium scale fluid throughputs would make the OBR suitable for use in a wastewater treatment plant which serves 10,000 to 20,000 inhabitants.

The reactor tube of the multi-orifice oscillatory baffled reactor may contain between 8 and 10 baffles, each baffle having a free open area of up to 20% and the inter-baffle spacing being between 35 mm and 45 mm, wherein the hydraulic diameter dh is between 25 mm and 30 mm, the hydraulic diameter being defined as above.

The OBR may be connected to a central processing unit (CPU). The CPU may control various functions of the OBR.

The CPU may control the frequency and/or amplitude of oscillation provided by the oscillatory means. For this purpose, the CPU may be connected to a servo-hydraulic unit which is in turn connected to the oscillatory means. The CPU will provide the servo-hydraulic unit with the necessary signal as to the frequency and/or amplitude, and the duration of oscillation. -13-

The CPU may provide a means for monitoring the size and distribution of microbubbles generated within the OBR. For this purpose, the CPU may be connected to a CCD camera or similar device which may record images or video footage of the OBR interior.

The CCD camera may be located either internally or externally of the reactor tube.

Where the CCD camera is located externally, a means for reducing optical distortion may be provided between the reactor tube and the CCD camera. This may be a vessel filled with a distortion reducing medium, such as glycerol. The CPU may be programmed to adjust the frequency and/or oscillation of the oscillatory means in response to data gathered from the CCD camera in order to attain optimal size and/or distribution of microbubbles.

The CPU may provide a means for monitoring the level of dissolved reactant gas and/or the level of contaminants present within a fluid in the reactor tube. For this purpose. The CPU may be connected to a sensor located within the reactor tube. The sensor may monitor the concentration of dissolved gas, such as dissolved ozone or chlorine, present within the reaction fluid. Alternatively, the sensor may monitor the concentration of one or more dissolved contaminants within the reaction fluid. If the OBR is operating in batch mode, such monitoring will be useful in assessing the extent of decontamination and reaction completion. In continuous mode, the effectiveness of the decontamination may be assessed and the throughput or other conditions such as oscillation or gas superficial velocity adjusted accordingly.

The CPU may be connected to a user interface to allow monitoring of the OBR conditions, such as the oscillation frequency and amplitude, the concentration of dissolved reactant gas and/or contaminants, the quantity and distribution of microbubbles etc. The interface may include means for manual adjustment of one or more of these parameters. The interface may be a display monitor.

The OBP may be adapted for the treatment of water.

The OBR may be adapted for the treatment of wastewater.

As described in the background section above, the treatment of water, such as wastewater, with oxidising gases to remove contaminants such as organic contaminants is a very important process which provides a great number of benefits to inter a/ia the environment. -14-

The OBR may be adapted for the removal of organic contaminants from a fluid.

The US EPA list provides details of organic contaminants of concern. These are often present in water and wastewater treatment plants, as well as in other similar industrial facilities. These chemicals are difficult to remove by other physical or chemical processes, but the present OBS offers an effective device for the removal of such contaminants from water, making this process much more efficient and cost-effective.

The OBR may be adapted to carry out a method selected from sanitation treatment of mineral bottled water by ozonation; tertiary treatment to remove micro-contaminants of concern from wastewater; disinfection of drinking water; sanitation of recreational water; decontamination of water used in pulp and paper processing; decontamination of water used in food and beverage production; decontamination of water used in semiconductor manufacture; decontamination of cooling water for antibacterial control; colour removal from textile wastewater; treatment of metal working fluids; decontamination of underground water and decontamination of ballast water for reuse.

The OBR may be adapted to remove Pharmaceuticals and Personal Care Products (PPCPs) from a fluid.

As discussed above, removal of PCPPs is an area of particular importance as these are difficult to remove by existing decontamination methods and can find their way into natural water sources after inefficient treatment of municipal wastewater. The present device is an effective means to remove such contaminants, presenting a major environmental benefit.

The OBR may be adapted to further subject the fluid to one or more additional processes selected from H202 treatment, UV exposure, photo-Fenton processes and sulphate treatment.

Including other known decontamination means in the OBS will ensure effective decontamination of the fluid.

The oscillatory means may be adapted to oscillate at a frequency of up to 20 Hz.

The oscillatory means may be adapted to oscillate at a frequency of up to 10 Hz. -15-

The oscillatory means may be adapted to oscillate at a frequency of up to 19, 18, 17, 16, 15,1413,12,11,10, 9or8Hz.

The oscillatory means may be adapted to oscillate at a frequency of at least 0.5 Hz, for example at least 1 Hz, 1.5 Hz, 2 Hz, 2.5 Hz, 3 Hz, 3.5 Hz, 4 Hz, 4.5 Hz or 5 Hz.

Oscillation within this frequency range provides optimal conditions to establish the strong radial mixing which supports the presence of a large quantity of microbubbles throughout the fluid.

The oscillatory means may be adapted to oscillate with a centre-to-peak amplitude of up to2omm.

The oscillatory means may be adapted to oscillate with a centre-to-peak amplitude of up to 10mm.

The oscillatory means may be adapted to oscillate with a centre-to-peak amplitude of up to 19, 18, 17, 16, 15, 14, 13, 12, 11 or 10mm.

The oscillatory means may be adapted to oscillate with a centre-to-peak amplitude of at least 2.5 mm, for example at least 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, 5.5 mm or 6 mm.

The OBS may be adapted to decontaminate fluid in continuous or batch mode.

The selection of either continuous or batch mode of operation allows the OBR throughput to be adapted to suit the particular application.

The gas source may be adapted to provide a gas superficial velocity of between 0.001 and 10mm -1 The OBS may be adapted to decontaminate fluid in continuous mode with a throughput of between 0.1 and 10 Ls* The OBS may be adapted to carry out decontamination at pH 7 or above.

The OBS may be adapted to carry out decontamination at pH 8, 9, 10 or above. -16-

For ozonation, at low pH (such as pH 4 or below), the enhancement in ozone utilisation efficiency is not as complete as when the reaction is carried out at higher pH values. At higher pH, up to 100% ozone use may be achieved.

The OBR may be adapted to carry out decontamination at atmospheric temperature and pressure. This makes the running of the OBS more cost-efficient.

The OBR may be adapted such that the level of the fluid in the reactor tube during use is kept above the level of the uppermost baffle. This avoids any air from the headspace above the fluid becoming trapped during operation of the CBR.

Method of Removing Contaminants from a Fluid A second aspect of the invention is a method of removing contaminants from a fluid by contacting the fluid with an oxidising gas, the method comprising the steps of: introducing the fluid into the multi-orifice oscillatory baffled reactor according to the first aspect; introducing the oxidising gas into the fluid through the gas source; and oscillating the fluid and/or the one or more baffles with the oscillatory means to provide a dispersion of micro-bubbles within the fluid.

The term "removal" or "removing" refers to the elimination or degradation of one or more contaminants from the fluid, which includes the chemical degradation of contaminants resulting in products which are less harmful to humans, animals and/or the environment than the original contaminants present. The reaction which degrades the contaminants may be oxidation.

When the OBR as defined according to the first aspect is used in this fluid decontamination method, the combination of the OBR design (in particular the baffle design) and the fluid and/or baffle oscillation provides strong radial mixing within the inter-baffle region of the reactor tube. This results in the production of a great quantity of microbubbles which provides a highly efficient gas-liquid reaction, as described above.

Furthermore, the microbubbles are trapped within the inter-baffle region rather than passing through the length of the reactor tube in the direction of net fluid flow, for a period of time sufficient to provide up to 100% use of the oxidising gas, with very little or no wastage. -17-

The fluid may be water.

The fluid may be wastewater.

As described in the background section above, the treatment of water, such as wastewater, with oxidising gases to remove contaminants such as organic contaminants is a very important process which provides a great number of benefits to inter a/ia the environment.

The oxidising gas may be ozone or chlorine.

As described above, ozonation using standard bubble columns is already employed in the treatment of water and wastewater to remove organic contaminants. The use of ozone in the present method can provide a highly efficient ozonation reactor and reaction process to supplement or replace the existing inferior reactors in order to provide a cost efficient water treatment solution in waste water treatment plants and other similar locations.

Similarly, chlorine gas could be employed in the disinfection of water supplies. The method and device are fully compatible with existent ozonation and chlorination technologies.

The oxidising gas may be ozone, such that the reaction occurring in the reactor is ozonation.

Ozonation is a particularly important process in the treatment of water and wastewater, as described above. The use of the ozonation method to decontaminate water and wastewater will make it possible to reuse water and reduce the level of discharge of recalcitrant chemicals into the environment, therefore presenting simultaneously major economic and environmental benefit for local communities and wildlife.

The method may be a method of removing organic contaminants from the fluid.

The US EPA list provides details of organic contaminants of concern. These are often present in water and wastewater treatment plants, as well as in other similar industrial facilities. These chemicals are difficult to remove by other physical or chemical processes, but ozonation offers an effective method to remove such contaminants from water, and the present method makes this process much more efficient and cost-effective. -18-

The method may be selected from sanitation treatment of mineral bottled water by ozonation; tertiary treatment to remove micro-contaminants of concern from wastewater; disinfection of drinking water; sanitation of recreational water; decontamination of water used in pulp and paper processing; decontamination of water used in food and beverage production; decontamination of water used in semiconductor manufacture; decontamination of cooling water for antibacterial control; colour removal from textile wastewater; treatment of metal working fluids; decontamination of underground water and decontamination of ballast water for reuse.

The contaminants may be Pharmaceuticals and Personal Care Products (PCPPs).

As discussed above, removal of PCPPs is an area of particular importance as these are difficult to remove by existing decontamination methods and can find their way into natural water sources after inefficient treatment of municipal wastewater. The present method is an effective means to remove such contaminants, presenting a major environmental benefit.

The method may also subject the fluid to one or more additional processes selected from H202 treatment, UV exposure, photo-Fenton processes and sulphate treatment. These additional processes may occur before decontamination with the oxidising gas, after decontamination with the oxidising gas, or simultaneously with decontamination with the oxidising gas.

Combining the method with other known decontamination processes will ensure effective decontamination of the fluid.

The fluid may be decontaminated in continuous or batch mode.

The selection of either continuous or batch mode of operation allows the throughput of the method to be adapted to suit the particular application.

The fluid may be decontaminated in continuous mode with a throughput of between 0.001 and 10 Ls1.

100% of the oxidising gas introduced to the reactor tube may be consumed by the reaction with contaminants. -19-

Alternatively, up to 100% of the oxidising gas introduced to the reactor tube may be consumed by the reaction, for example at least 90% of the oxidising gas. The reaction may consume up to 99%, 98%, 97%, 96% or 95% of the oxidising gas. The reaction may consume at least 90% of the oxidising gas, for example at least 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99%.

The method may be carried out at pH 7 or above. Preferably, the method is carried out at pH 8,9, 10 or above.

The method may be carried out at atmospheric pressure and room temperature. This ensures a cost-efficient decontamination method.

A third aspect of the invention is a method of CO2 sequestration comprising the steps of introducing a fluid into the multi-orifice oscillatory baffled reactor according to the first aspect; introducing CO2 into the fluid through the gas source; and oscillating the fluid and/or the one or more baffles with the oscillatory means to provide a dispersion of CO2 microbubbles within the fluid.

A fourth aspect of the present invention is a method of manufacturing bioproduct using syngas bioconversion comprising the steps of introducing a fluid into the multi-orifice oscillatory baffled reactor according to any one of claims 1 to 22, the fluid comprising a bioconversion medium; introducing syngas into the fluid through the gas source; and oscillating the fluid and/or the one or more baffles with the oscillatory means to provide a dispersion of syngas microbubbles within the fluid.

The bioconversion medium may be a biomass culture.

The bioproduct may be a biofuel. The bioproduct may be a bioplastic. The bioproduct may be a compound selected from ethanol, butanol, acetic acid, butyric acid and methane.

-20 -In any of the second to fourth aspects, preferably, the oscillatory means may be used to oscillate the fluid directly. Alternatively, the oscillatory means may be used to oscillate the baffles directly. In either case the desired result is the oscillatory movement of fluid relative to the baffles, such that fluid passes through the baffle orifices.

The oscillatory means may be oscillated in a sinusoidal motion.

Sinusoidal oscillation favours dissipation of eddy rings or vortices within the reactor tube.

The oscillatory means may be oscillated at a frequency of up to 20 Hz.

The oscillatory means may be oscillated at a frequency of up to 10 Hz.

The oscillations may be at a frequency of up to 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9 or 8Hz.

The oscillations may be at a frequency of at least 0.5 Hz, for example at least 1 Hz, 1.5 Hz, 2 Hz, 2.5 Hz, 3 Hz, 3.5 Hz, 4 Hz, 4.5 Hz or 5 Hz.

The oscillatory means may be oscillated with a centre-to-peak amplitude of up to 20 mm.

The oscillatory means may be oscillated with a centre-to-peak amplitude of up to 10 mm.

The centre-to-peak amplitude may be up to 19, 18, 17, 16, 15, 14, 13, 12, 11 or 10mm.

The centre-to-peak amplitude may be at least 2.5 mm, for example at least 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, 5.5mm or 6 mm.

The oxidising gas may be introduced through a sparged gas source having an outlet within the reactor tube.

The gas superficial velocity of the oxidising gas may be between 0.001 and 10 mm where the gas superficial velocity, u, is defined as u = 0/S where 0 is the flow rate and S is the cross section of the reactor. -21 -

During performance of the method, the level of fluid in the reactor tube may be kept above the level of the uppermost baffle. This avoids any air from the headspace above the fluid becoming trapped.

Use of the Multi-Orifice Oscillatory Baffled Reactor in Decontamination of Water by Ozonation A fifth aspect of the invention is the use of the multi-orifice oscillatory baffled reactor according to the first aspect in decontamination of water by ozonation, sequestration of GO2, or bioconversion of syngas into a bioproduct.

The use may be in the decontamination of wastewater by ozonation.

The OBR described herein provides particular advantages with respect to ozonation reactions, where ozone is an expensive reactant and the reduction of its wastage is desirable. These advantages have been described in detail above.

Brief Description of the Drawings

Figure 1 is a longitudinal cross-section through a reactor according to the present invention.

Figure 2 is a simplified representation of a batch mode ozonation reactor according to the present invention.

Figure 3 shows plan views of three different baffle designs.

Figure 4 shows six photographs from the optical observation of air bubbles rising in the inter-baffle region in a multi-orifice baffled column in different configurations.

Figure 5 shows bubble size distributions for baffle designs 1 and 2 in different oscillatory conditions.

Figure 6 shows the bubble size distribution within the OBR of the present invention using baffle design 3, in comparison to the equivalent distribution in an un-baffled reactor tube.

-22 -Figure 7 shows time-tracking plots of (a) (x,y) position and (b) instantaneous vertical velocity (V) for four bubbles randomly selected in the inter-baffle region during one oscillatory cycle of the OBR of the present invention.

Figure 8 shows time-tracking plots of (a) (x,y) position and (b) instantaneous vertical velocity (V) for four bubbles randomly selected in the inter-baffle region during one oscillatory cycle of the OBR of the present invention.

Figure 9 shows time-tracking plots of (a) (x,y) position and (b) instantaneous vertical velocity (V) for four bubbles randomly selected in the inter-baffle region during one oscillatory cycle of the OBR of the present invention.

Figure 10 shows time-tracking plots of (a) (x,y) position and (b) instantaneous vertical velocity (V) for four bubbles randomly selected in the inter-baffle region during four oscillatory cycles of the OBR of the present invention.

Figure 11 shows flow visualisation of liquid mixing in the OBR of the present invention using tracing polyamide particles. Images (1), (2) and (3) were respectively taken at three different points on the oscillation cycle.

Figure 12 shows flow visualisation of liquid mixing in the OBR of the present invention using tracing polyamide particles. Columns (1), (2) and (3) indicate images taken at different points on the oscillation cycle and rows (a), (b) and (c) indicate different fluid oscillation conditions.

Figure 13 shows (a) plots of dissolved para-hydroxybenzoic acid (p-HBA) concentration and ozone concentration against time, and (b) a plot of dissolved p-HBA concentration and ozone utilisation efficiency against time.

Figure 14 shows (a) a plot of the amount of p-HBA degraded against cumulative 03 injected, and (b) a plot of dissolved p-HBA concentration and ozone utilisation efficiency against time.

Figure 15 shows (a) plots of dissolved ozone concentration against time for different oscillation conditions, and (b) plots of dissolved p-HBA concentration and ozone utilisation efficiency against time at pH 4 and pH 10.

-23 -Figure 16 shows (a) plots of In (C/C0) against time for two different Ugas values, and (b) plots of the amount of p-HBA degraded against the amount of cumulative 03 injected at two different Uqas values.

Figure 17 shows (a) a plot of Osyngas (in) and Osyngas (out) against time, and (b) plots of instantaneous methane yield from CO and instantaneous methane production rate against time.

Figure 18 shows the effect of specific CO loading rates on (a) the specific reaction rates for CO, H2 and CH4, and (b) the removal efficiency of CO and H2, during continuous syngas fermentation in the CBS.

Figure 19 shows CO and H2 concentration profiles as measured in the CBS headspace.

Figure 20 shows the CBS setup used in continuous syngas fermentation experiments using anaerobic bacteria.

Figure 21 shows (a) the rate of ozone consumption, (b) rate of degradation of p-H BA and (c) TOC reduction in a continuous bubble column (BC) and a continuous mulit-orifice baffled column (MOBC with a mean liquid contacting time of 2.25 minutes.

Figure 22 shows (a) the rate of ozone consumption, (b) rate of degradation of p-H BA and (c) TOC reduction in a continuous bubble column (BC) and a continuous mulit-orifice baffled column (MOBC with a mean liquid contacting time of 11.2 minutes.

Figure 23 shows ozone utilisation efficiency at different ozone dosages.

Figure 24 shows a simplified representation of a continuous mode ozonation reactor according to the present invention.

Detailed Description

The invention will now be further described with reference to the following non-limiting Figures and Examples. Other embodiments of the invention will occur to those skilled in the art in the light of these.

-24 -The disclosure of all references cited herein, inasmuch as it may be used by those skilled in the art to carry out the invention, is hereby specifically incorporated herein by cross-reference.

Multi-Orifice Oscillatory Baffled Reactor Figure 1 shows a longitudinal cross-section of a multi-orifice oscillatory baffled reactor 30 according to one embodiment of the present invention, configured to carry out batch processes.

The OBR includes a transparent cylindrical reactor tube 301 made from glass.

The reactor tube has a maximum internal diameter of 150 mm. At the base of the reactor tube the internal surface extends inwards into an annular lip 302 with an internal diameter of 125 mm. The total reactor tube height (Li) is 540 mm. The total volume of the reactor tube is 10.6 L and the working volume (VL) is 9.6 L. The reactor base 306 includes an inner base flange 307 which abuts the planar annular surface at the end of the tube 301. The reactor tube includes an external lower annular flange 303a close to the lower end of the tube. A series of screws 304 pass through the annular flange 303a and into the base 306. The tightening of these screws seals the annular flange 307 of the base 306 against the reactor tube 301.

At the upper end of the tube 301, the tube opening is sealed by a cap 308. An external upper annular flange 303b is located close to the upper end of the tube. A series of screws 305 pass through the flange 303b and the cap 308. The tightening of these screws seals the opening at the upper end of the tube. The upper end of the tube is not entirely sealed, due to the presence of gas vent 325 which allows for the escape of gas from the headspace within the tube.

Inside the tube 301 is secured a fixed series of baffles 309. Each baffle 309 is fixed at a certain position along a stainless steel connecting rod 310 of 6 mm diameter. The baffles are spaced along the rod at equal intervals of 40 mm. The precise interval may be varied by sliding the baffles along the rod before fixing them in place. Two rods are shown in Figure 1, and a third rod is also used which is not visible.

-25 -Each baffle 309 is of circular geometry having a diameter of 150 mm such that it fits snugly within the reactor tube 301. Each baffle includes a plurality of orifices (not shown) each orifice being circular with a diameter of 10.5 mm. The orifices are distributed in a regular hexagonal array. There are 10 baffles in total, distributed axially along the length of the reactor tube. The average number of orifices per baffle across the 10 baffles is 31.

The free open area of each baffle 309 is 15%.

Each baffle 309 is made from acrylic material and is 3.0 mm thick.

Between each baffle 309 is an inter-baffle region 312 defined by the internal surface of the reactor tube 301 and the surface of two neighbouring baffles 309.

The reactor tube contains a series of equally spaced baffles 302, with 10 baffles in the series. The baffles are connected in series with stainless steel rods 303 of 6 mm diameter. Inter-baffle region 304 is established between neighbouring baffles inside the tube. The inter-baffle spacing is variable by movement of the baffles along the stainless steel rods.

Each baffle is of circular geometry and fits snugly within the reactor tube.

To secure the baffles in place relative to the tube and each other, rods 310 are secured to the floor of the reactor tube, and plastic spacers (not shown) are placed on the rods between two adjacent baffles to maintain the inter-baffle separation.

A piston 313 seals the annular opening at the bottom of the tube 301 defined by the internal surface of the lip 302 and the internal surface of the inner base flange 307. The piston is of 125 mm diameter and therefore fits snugly against the internal surface of the base, sealing the internal volume of the tube 301. The piston 313 is axially slidable within the base 306 and the tube 301, as shown by the double-headed arrow in Figure 1. The piston is connected by drive shaft 314 to a motor 315 which is part of a servo-hydraulic unit 316. This servo-hydraulic unit 316 is controlled by a CPU 317 which is in turn connected to a user interface 318 which in this case is a display monitor. The servo-hydraulic unit can be adjusted to vary the amplitude and frequency of the piston motion.

A gas inlet 320 controlled by a needle valve 321 and connected to a gas delivery line 322 supplies a gas sparger 323 on the inside of the tube 301 with gas. The gas sparger 323 -26 -is an elongate cylindrical PVC tube extending laterally within the reactor tube, with 0.6 mm diameter perforation to allow gas to be sparged into the reactor tube.

A dissolved gas sensor 326 passes through the cap 308 and into the internal volume of the tube 301. The sensor is also connected to and controlled by the CPU 317.

A CCD camera 319 is positioned outside the tube 301, with a view into the transparent tube. A Perspex optical box 324 is positioned around one portion of the tube and filled with glycerol. This reduces optical distortion and allows the internal volume of the tube to be clearly monitored by the CCD camera.

The reactor shown in Figure 1 may be used in the treatment of a fluid to remove contaminants, for example for ozonation of water, such as wastewater, to remove organic contaminants. The reactor may also be used in CO2 sequestration. The OBR shown in Figure 1 is a batch mode OBR, and fluid (not shown) is added to the OBS in batches for treatment. The OBR could easily be modified with fluid inlets and outlets to provide a continuous mode OBR for continuous treatment.

The fluid is introduced to the reactor tube 301 up to a level (not shown) just above the uppermost baffle 309, to prevent any trapping of air from the headspace during oscillation. The height of the liquid phase (hL) is 450 mm. Ozone gas is introduced from an ozone source 320 through the needle valve 213 and the gas line 322 and passes out of the sparger 323 into the water contained within the reactor tube. As the ozone is sparged into the reactor, the piston 313 is oscillated by the servo-hydraulic unit 316. As a result, the fluid contained within the tube oscillates in an axial direction, passing back and forth through the series of baffles 309. Because the baffles have the correct free open area a, as the fluid oscillates through the baffles a large number of microbubbles are generated within the fluid. The size and distribution of these may be monitored by the CCD camera 319. The microbubbles are trapped within the inter-baffle region 312 by the strong radial mixing arising from the oscillatory motion of the fluid. The microbubbles are trapped for a number of oscillatory cycles of the piston.

A consequence of the trapped microbubbles is that up to 100% of the ozone introduced into the reactor can be used in the ozonation reaction. Gaseous ozonation reaction products can be removed through the gas vent 325.

-27 -The user can easily adjust the amplitude and frequency of oscillation of the piston to achieve the optimal generation of microbubbles in the reactor.

Figure 2 shows the setup used for batch ozonation processes. It shows a longitudinal cross section of OBR 50 according to one embodiment of the present invention.

The OBR 50 includes a reactor tube 501 within which is situated a series of equally spaced baffles 502. At the base of the reactor tube is a piston 503 configured to oscillate in the manner shown by the double-headed arrow in Figure 2.

An oxygen cylinder 504 delivers oxygen to an ozone generator 505. Ozone produced by the generator passes through a gas flow meter 506 and into an ozone inlet line 507. The ozone then passes via a gas flow controller 508 to the OBS ozone inlet 509.

Ozone passes through the water 510 contained within the reactor tube 501. The water can be recirculated within the reactor tube by means of the water recirculation line 511, which includes a pump 512. The water recirculation line has a flow capacity of 1 LJmin.

Product gases which may include ozone pass out of gas outlet 513 and where recirculation is required (e.g. before any reaction has occurred and the gas passing out of the outlet is ozone) the gas passes into the ozone recirculation line 514. The ozone recirculation line has a flow capacity of 10 Lfmin.

Where direct recirculation is not possible, e.g. because a reaction is in progress, the outlet gases pass through the outlet line 515 which includes a damper 516. The line also includes mass flow control 517. The gases then pass along the gas line to the ozone analyser 518 via gas flow controller 519, before finally passing along another gas line to an ozone destroyer 520.

Various valves 521 are present along the gas and water lines to allow for proper control over the system.

Figure 20 shows the OBS setup 60 used for continuous syngas bioconversion processes using anaerobic baceria. The setup is very similar to that shown in Figure 1, and the main parts of the OBR and its operation are identical and are therefore not relabelled and not discussed again here. The OBR has however been adapted to be able to perform syngas bioconversion.

-28 -Syngas cylinder 601 supplies syngas consisting of 60 % CO, 30% H2 and 10 % 002. The syngas passes through the inlet gas flow controller 602 and through a ball valve 614 before being sparged into the reactor tube of the OBR as described above in relation to Figure 1.

The reactor tube is surrounded by a water jacket 604 through which water is circulated from the water bath 605 in order to keep the reaction medium within the reactor at the correct temperature for syngas bioconversion.

Liquid from the reaction medium is recirculated through the liquid recirculation line 606 which feeds liquid back into the top of the OBR through the fluid inlet 603. Furthermore, a gas recirculation line 607 is able to feed gas which passes out of the OBR gas outlet 608 back to the gas inlet line. This is useful for example to ensure no waste of syngas which flows through the reactor before any reaction is in progress and is therefore not used up.

Gas exhaust line 609 carries exhaust gases from the gas outlet 608 via a non-return valve 610 and moisture trap 611 to outlet gas flow meter 612 before leaving through gas exhaust 613.

The setup includes various ball valves 614 to provide control over gas flow. The setup also includes two diaphragm pumps 615 and a peristaltic pump 616.

The setup includes two gas sampling ports 617 and a liquid sampling port 618.

Furthermore, pressure gauge 619 and temperature probe 620 provide means for monitoring gas pressure and water temperature within the system.

The system also includes a Dreschel bottle 621 at the OBR gas outlet.

Modified Oscillatory Dimensionless Numbers for a Multi-Orifice Baffled Column In OBRs the oscillatory motion is complex and traditionally the mixing intensity and mass transfer rates in the inter-baffle regions of small diameter single-orifice OBCs is assumed as mainly governed by the oscillatory Reynolds number (Re0) and the Strouhal number (SO: Reo = (2rrfxopdc)/p -29 -St = d0/4rrxo where d0 is the internal diameter of the column (m), f the fluid oscillation frequency (s1), p is kinematic fluid viscosity (kg m1 s1), p is the specific mass of the fluid (kg m3) and xc, is the centre-to-peak fluid oscillation amplitude (m).

The Re0 in the equation above was described in analogy to net flow Reynolds number where the product (2rnxoO represents the peak fluid velocity (m s1) during an oscillation cycle which occurs halfway the piston full stroke. The Stand Re0 dimensionless numbers in the above equations are routinely used in studies involving single-orifice OBRs where there is a direct link between the internal diameter of the column, d0 and the open diameter of the orifice, d0 however they are unsuitable for scaled-up OBRs.

Both Reo and St have been modified to accurately represent the state of mixing in the multi-orifice baffled column and to support scale-up from single-orifice to multi-orifice OBRs. In multi-orifice OBRs, it is d0b5 (the equivalent" diameter of the baffle area surrounding each open orifice) which is the main geometrical parameter controlling the flow separation and eddy formation, as opposed to do and d0 which govern the properties of single-orifice OBRs. This can be defined as: dabs = d(V(1-a) In) where, cI is the internal diameter of the column, Q is the fraction of open area of the baffle, and n is the number of orifices in the baffle. Based on this, a modified Reynolds number (Re0') can be written as follows: Reo' = f(2TTfX0P) //J].dobs.(1 Ia) Which is equivalent to: Re0' = [(2TTfx0p) /jij(d0/'Jn)(1 Ia) Similarly, the Strouhal number St in the equation above has been modified to represent the actual ratio of diameter of column to fluid amplitude in the region around each individual orifice on the baffles in a multi-orifice baffled column. For that, an equivalent hydraulic diameter of a single-orifice column, cJ had to be defined: d,1 =d0/Jn -30 -The modified Strouhal number St can therefore be written as: St' = (d0/4nxo).(1 /.Jn)

Examples

Example 1

Ozone Ut/I/sat/on Efficiency in the Multi-Or/f/ce Baffled Column Figure 13 shows the results of an experiment into ozone utilisation efficiency in the OBR according to the present invention.

The batch column was filled with 9 L of distilled water and spiked with 500 mg of p-hydroxybenzoic acid (p-HBA) yielding a molar concentration of 0.40 mM. The fluid was then oscillated at frequency of 8 Hz, and centre-to-peak amplitude of 5 mm, and continuously sparged with ozone diluted in oxygen at a molar concentration of 0.48 mmolIL (Ugas = 0.93 mm/s). The concentration of p-HBA in the liquid was monitored along the ozonation time using chromatography, and the concentration of ozone was also monitored in the gas phase at both inlet and outlet points from the column.

The results shown in Figure 13 show 100% ozone utilization efficiency at very low superficial gas velocity during p-HBA degradation. Ozone utilization efficiency was calculated based on: E = (C -C0)IC where E is ozone utilisation efficiency, C is the ozone concentration at the ozone inlet and C0 is the ozone concentration at the ozone outlet.

Example 2

Effect of Ozone Concentration on the Inlet Gas Stream Gas was injected continuously at superficial gas velocity of 0.93 mmls, and the ozone content in the inlet gas stream varied from 0.21 to 0.45 mmol/L. The fluid was oscillated at 8 Hz and 5 mm, and spiked with 0.40 mM of p-HBA, and initial pH 10. The yield of p-HBA removed remained constant for varying ozone contents, as well as the ozone -31 -utilisation efficiency, which remained 100% until p-HBA was fully degraded. This shows the rate of ozone degradation is directly proportional to the rate of 03 injection into the column (top pane of Figure 14).

Example 3

Dissolution of Ozone in a Mu/ti-Orifice Osci/latoiy Baffled Column Ozone diluted in oxygen at a concentration of 0.48 mmol/L was injected with a superficial gas velocity of 0.46 mm/s in a batch column containing degassed distilled water with pH adjusted to 4. The dissolved ozone concentration was monitored using a colorimetric assay. The saturation ozone concentration was determined as 0.133 mM at 20°C. The column showed similar performance for different amplitude and frequency combinations as shown in Figure 15(a).

Example 4

Effect of pH on Ozone Degradation of p-I-ISA It is well established in literature that pH strongly affects the rate of ozonation. It was found that pH also strongly affects the ozone utilisation efficiency as shown in Figure 15(b). Ozone diluted in oxygen at a concentration of 0.48 mmol/L was injected with a superficial gas velocity of 0.46 mm/s in a batch column containing distilled water with pH adjusted to 4 to 10. The column was filled with 9L of distilled water and spiked with 500 mg of p-HBA yielding a molar concentration of 0.40 mM. The fluid was oscillated at frequency of 2 Hz, and centre-to-peak amplitude of 10 mm. This shows that the ozonation reaction is fast and occurs at the interface of bubbles with the liquid phase, therefore interfacial area plays a major role in the performance of ozonation systems.

Example 5

Degradation of p-HBA with Ozone in the Mu/ti-Orifice Baffled Column The batch column was filled with 9L of distilled water and spiked with 500 mg of p-HBA yielding a molar concentration of 0.40 mM. The fluid was then oscillated at frequency of 8 Hz, and centre-to-peak amplitude of 5 mm, and continuously sparged with ozone diluted in oxygen at a molar concentration of 0.52 mmol/L (for Ugas = 0.46 mm/s) and 0.48 -32 -mmol/L (for Ugas = 0.93 mm/s). The concentration of p-HBA in the liquid was monitored along the ozonation time using chromatography. Figure 16 shows that the efficiency of decomposition of p-HBA with ozone is similar for different gas flow rates. This shows that the rate of ozone degradation is directly proportional to the rate of Os injection into the column.

Example 6

CO2 Dissolution in a Batch Mu/ti-Orifice Oscil/atory Baffled Column A 150 mm internal diameter column with 9.6L of degassed distilled water and a total height of 540 mm was sparged with 5% v/v 002 in air at atmospheric pressure and room temperature (20°C), at a superficial gas velocity of 0.81 mm/s. Dissolved CO2 concentration was measured using a dissolved CO2 probe.

Table 1 below provides details of the three different baffle designs tested. Baffle designs 1-3 are depicted in Figure 3 (a)-(c) respectively.

Table 1

Baffle design 1 Baffle design 2 Baffle design 3 (comparative) (comparative) Average number of orifices 9 210 31 per baffle Orifice diameter d0, mm 30.0 6.4 10.5 Hydraulic diameter dh, mm 50.0 10.4 26.9 Baffleopenareaa,% 36 42 15 Construction material for Stainless steel Polypropylene Acrylic baffle sandwiched between 2 thin stainless steel layers Table 2 below shows the effect of baffle geometry on volumetric mass transfer coefficient, kLa for CO2 in water.

-33 -Table 2 ____________________________________________ Column kLa Fluid oscillation (Fyi) conditions Unbaffied 24 -Baffle design 1 21 5 Hz 5mm Baffle design 2 23 2 Hz, 10mm Baffle design 3 94 2 Hz, 10mm The inventive baffle design 3 (having a baffle open area of 15% i.e. less than 30%) allowed around 3-fold improvement in ha compared to unbaffled column or other baffle geometries.

Example 7

Effect of Baffle Design on Bubble Size Figure 4 shows six photographs from the optical observation of air bubbles rising in the inter-baffle region in the multi-orifice baffled column. The scale bar coiresponds to 10 mm. The top row (a) includes photos taken of stagnant fluid, i.e. with no oscillations. The bottom row (b) includes photos taken of oscillating fluid. Columns (1)-(3) represent baffle designs 1-3 respectively (as shown in Figure 3). Table 3 below describes the aeration rates Qaji and oscillation conditions used.

Table 3

__________________ __________________ __________________ __________________

Baffle Design Qair IL mirn1 f/Hz xo /mm 1 (comparative) 0.1 3 2.5 2 (comparative) 0.4 2 10 3 (inventive) 0.1 2 10 -34 - (Note that 1 L mm-1 is equivalent to 0.1 vvm).

Figure 5 shows bubble size distributions for the OBR including baffle design 1 (Figure 5(a)-(b)) and baffle design 2 (Figure 5(c)-(d)). Each plot includes a distribution corresponding to bubbles generated in the OBR without oscillation (solid line) and one or more distributions corresponding to various oscillation conditions.

Figure 6 shows a bubble size distribution for inventive baffle design 3 where the OBR is oscillated at 2 Hz with an amplitude of 10 mm, alongside the corresponding distribution for the unbaffled column without oscillation.

Example 8

Effect of Baffle Design on Bubble Residence Time in Inter-Baffle Region Figures 7-10 include plots of time tracking of (x,y) bubble position and instantaneous vertical bubble velocity (Vp) for bubbles in the inter-baffle region using the OBR configured with inventive baffle design 3, in each case the bubbles being selected at random. The column conditions used in each case are given in Table 4 below.

Table 4

Figure Baffle Qqas /L min1 f/Hz xo / mm Reo' Design 7 3 0.4 0 0 0 8 3 0.4 2 10 2314 9 3 0.1 2 10 20216 3 ai 10 2 20216 -35 -In each of Figures 7-10, (a) shows time tracking of (x,y) position and (b) shows instantaneous vertical velocity (Vi). Arrows show the initial position and direction of tracked bubbles.

Figure 11 shows flow visualisation of liquid mixing in the OBR configured with baffle design 2, using tracing polyamide particles. The oscillation conditions employed were f = 4 Hz, x0 = 5 mm and Reo' = 2314. Adjacent baffles can be seen at the top and bottom of each photo, the area covered by the photo representing the inter-baffle region.

Figure 12 shows flow visualisation of liquid mixing in the OBR configured instead with baffle design 3, using tracing polyamide particles. Rows (a)-(c) represent three different fluid oscillation conditions as shown in Table 5 below. Columns (1)-(3) represent three different time points in the oscillation cycle, as shown in the graph at the top right of Figure 12. The horizontal lines which appear white in the photographs are adjacent baffles within the column.

Table 5

____________ ____________ ____________ ___________ ___________

Figure Baffle f I Hz x0 I mm Reo' Design 11 2 4 5 2314 (comparative) 12a 3 5 2 10108 12b 3 8 2 16173 12c 3 8 3 24260

Example 9

Continuous Syngas Bioconversion Using Anaerobic Bacteria The multi-orifice oscillatory baffled bioreactor (MOBS) used to perform syngas bioconversion experiments is shown in Figure 20. The total volume of the column was 10.6 L, with a working volume of 9.1 L, and a total column height of 540 mm. The inlet -36 -gas stream (syngas) consisted of synthetic syngas mixture with the following composition (vlv): 60 % 00, 30 % H2, and 10 % CO2. The gas was fed directly from a pressured cylinder and sparged from the bottom of the MOBB, with flow rates continuously measured and controlled. At the outlet, gas flow rate was also continuously measured.

Gas mixture inside column was continuously recirculated from the headspace at a constant gas flow rate of 600 mL mm-1, in order to enhance gas-liquid contacting and make the syngas continuously available to the anaerobic microorganisms.

Figure 17 shows the syngas fermentation performance in the MOBB during continuous operation: (a) inlet and outlet syngas flow rate (Qsyngas (in), Qsyngas (ovo); (b) instantaneous methane yield from CO (Ycn4/co), expressed as mmol of CH4 produced per mmol of CO consumed (averaged by straight fitting), and instantaneous methane production rate (Fm,cn4), expressed in mmol OH4 produced per gVSS in the liquid medium per day (averaged by exponential line). Five different syngas flow rates were tested: (i) 5, (ii) 10, (iii) 20, (iv) 40, and (v) 100 mL mm-1. Figure 17 shows a high molar yield of conversion of CO to methane, CH4, at a range of syngas flow rates.

Figure 18 shows the effect of specific CO loading rates: (a) on the specific reaction rates (r,1) for 00, H2 and CH4, and (b) on the removal efficiency of CO and H2, during the continuous syngas fermentations, in the MOBB. Lines in graph (a) represent the fitting of data to typical Monod's model (R2 > 0.99), while in graph (b) represent linear regression fitting (R2 > 0.98). Vertical bars represent standard deviation. Figure 18 shows up to 100% dissolution and conversion of CO and H2 to CH4 at low gas inflow rates (the range tested was 0.03-0.63 mm sj.

Example 10

Dissolution of Poorly-Soluble Gases Mass transfer performance of the novel MOBB, evaluated by the results shown in Figure 19, returned kLa values of 39.9 and 24.9 h for CO and H2, respectively. Syngas was injected at a superficial gas velocity of 0.63 mm/s.

Figure 19 shows carbon monoxide and hydrogen concentration profiles as measured in the headspace, during the dynamic gassing-out experiment performed in the M0BB. The inlet superficial syngas velocity was 0.63 mm/s in phase (i) and (iii), and 0 mm/s in phase -37 - (ii), and fluid oscillation conditions were 2 Hz and 5 mm. Baffle design 3 was used.

Vertical dashed lines represent the time at which syngas flow was stopped and resumed.

Example 11

Continuous ozone degradation of p-HBA A multi-orifice baffled column (MCBC) comprising a cylindrical glass column with maximum internal volume of 1OL and internal diameter of O.150m equipped with multi-orifice baffles having an average of 31 holes per baffle with an open orifice diameter of 10.5 mm and free baffle open area of 15% was set up for continuous ozontation. A suitable system is shown in Figure 24. The setup is very similar to that shown in Figure 2, and the main parts of the OBS are identical and are therefore not discussed again here.

Instead of recirculating the within the MOBC, clean water is continuously drawn off from the MOBC.

Baffles were spaced at 40mm, and the column continuously injected with water at pH 10±0.1 (adjusted with NaOH) containing 50 mg/L of a phenolic contaminant, p-hydroxybenzoic acid (p-HBA) and ozone diluted in pure oxygen at a concentration of 23 g/m3. The working volume of the column was kept constant at 9L. The ozone flow rate was varied from 2.1 to 4.7 LJmin (corresponding to mean superficial gas velocities of 2.0 to 4.4 mm/s) and p-HBA flow rate set at 0.8 or 4.0 L/min (corresponding to mean hydraulic time of 2.25 and 11.25 mm, respectively; the mean hydraulic time is defined as the ratio of internal working volume of the column divided by the liquid flow rate).

The experimental conditions are summarised in Table 6 below.

The fluid was oscillated with a 125mm outer diameter piston controlled by a PC and driven by a servo-hydraulic system at a frequency of 2 Hz and amplitude of 10 mm centre-to-peak. The ozone content in both the inlet and outlet gas stream was monitored with an Anseros Ozomat GM-BWA ozone analyser. Liquid samples were collected at appropriate time intervals and filtered through 0.22 m, 33 mm Sterile Millex® Syringe Driven Filters (Millipore) for high performance liquid chromatography (HPLC) and total organic carbon (TOO) analysis.

-38 -The performance of the MOBC was compared to that of the same column without baffles and fluid oscillations, mimicking a bubble column (BC). The rate of ozone used in the ozonation was estimated from a mass balance to ozone between the inlet and outlet gas streams.

Table 6

Liquid Gas Superficial Cumulative supply Cumulative need flow flow gas (mole 03 supplied (mole 03 used per rate rate velocity per mole p-BHA mole p-BHA (Llmin) (LJmin) (mm/s) removed) removed)

MOBC BC MOBC BC

4.0 2.1 2.0 1.3 1.7 1.3 1.2 4.0 2.8 2.7 1.5 1.8 1.5 1.2 4.0 4.0 3.8 1.7 2.1 1.7 1.2 4.0 4.7 4.4 1.9 2.4 1.6 1.3 0.8 0.8 0.8 1.4 2.0 1.0 1.7 0.8 1.5 1.4 2.5* 3.0 0.8 1.5 0.8 2.1 2.0 35* 4.0 0.7 1.7 0.8 2.8 2.7 4.6* 5.1 0.6 2.0 * The MOBC efficiency reduces because full degradation of p-BHA is achieved so the supply is limited by the amount of p-BHA in the liquid inlet stream.

-39 -Surprisingly, with a very low contacting time of 2.2 mm the MOBC utilised all the ozone injected into the column especially, with no ozone being wasted especially at the lowest gas superficial flow velocity (Figure 21(a) -the diagonal line represents 100% ozone utilisation). The MOBC configuration was up to 2 times more efficient than the BC configuration in respect to ozone utilization. The degradation of p-HBA was also more effective in the MOBC configuration, with up to 87% of p-HBA being degraded in the MOBC against up to 69% in the BC (Figure 21(b)). The total reduction in total organic carbon, TOC was up to up to 5.1 times higher in the MOBC compared to the BC (Figure 21(c)). Total degradation of p-HBA and >50% TOC reduction was achievable by extending the mean liquid contacting time has shown in Figure 22 a-c. In Figure 22(a), the diagonal line represents 100% ozone utilisation. In this case there was some ozone wasted as the rate of degradation is limited by the amount of p-HBA injected into the columns.

Overall, it is clear that experimental conditions can be tuned to deliver full use of ozone or full degradation of the contaminant in the MOBC, confirming ozone degradation is limited by mass transfer. The reduced contacting time results in significant footprint savings for ozonation equipment. Conventional ozonation equipment requires extended (>40 mm) contacting time so very large ozonation tanks are required. The use of a contact time of 2 mm represents a 20-fold reduction equipment footprint for the same flow rate of water or wastewater to be treated.

The inventors have compared the cumulative ozone supply and cumulative ozone need for p-HBA removal experiments (the last being a performance parameter for ozonation equipment), and the MOBC required 0.6-1.7 moles of ozone to fully degrade 1 mole of p-HBA, whereas the BC required 1.2-2.0 moles of ozone. Also surprisingly, the ozone cumulative need in the MOBC remains very similar for batch operation (estimated as 1.4 moles ozone per mole of p-HBA degraded as shown in Figure 16) and continuous operation.

Example 12

Effect of ozone dosage on continuous ozonation A 9L working volume MOBC was continuously injected with 0.8 Llmin of water at pH 10.0 containing 50 mg/L of p-HBA and 0.8 LJmin of ozone diluted in pure oxygen, similar to the -40 -experiments described in Example 11 above. The ozone concentration in the inlet gas stream was varied from 10 to 23 g/m3. The efficiency of ozone utilisation remained constant at 100% (Figure 23) independently of the ozone dosage applied, which differs from conventional ozonation contacting technologies, in which ozone utilization efficiency drops linearly with the increase of ozone dosage.

Example 13

Power dissipation calculations The inventors have estimated the required energy input for producing fluid oscillations in the MOBC, based on equations available from literature for sparged oscillatory baffled columns (Baird and Carstang, Chemical Engineering Science, 1972, vol 27, pp 823-833).

Considering a discharge coefficient, Cd equal to 0.7, the estimated power dissipation in the MOBC in Example 11 operating at a frequency of 2 Hz, 10 mm centre-to-peak amplitude and 9L working volume is approximately 8.4W. This demonstrates insignificant energy input required for producing the required fluid pulsations and achieve full ozone utilisation in the MOBC shown in the experimental data. -41 -

Claims

Claims 1. A multi-orifice oscillatory baffled reactor, comprising a reactor tube; a baffle within the reactor tube, defining a plurality of orifices and having a free open area of up to 30%; a gas source having an outlet within the reactor tube; and oscillatory means which, during use, provides oscillatory flow of a fluid relative to the baffle.
2. A multi-orifice oscillatory baffled reactor according to claim 1, wherein there is a plurality of baffles within the reactor tube, each baffle defining a respective plurality of orifices and having a free open area of up to 30%.
3. A multi-orifice oscillatory baffled reactor according to claim 1 or 2, wherein each baffle has a free open area of up to 20%.
4. A multi-orifice oscillatory baffled reactor according to any one of the preceding claims, wherein the gas source is an oxidising gas source, a CO2 gas source or a syngas gas source.
5. A multi-orifice oscillatory baffled reactor according to claim 4, wherein the gas source is an oxidising gas source selected from ozone and chlorine.
6. A multi-orifice oscillatory baffled reactor according to any one of the preceding claims, wherein the gas source is an ozone gas source and the oscillatory baffled reactor is adapted for ozonation.
7. A multi-orifice oscillatory baffled reactor according to any one of the preceding claims, wherein the gas source is a sparged gas source.
8. A multi-orifice oscillatory baffled reactor according to any one of the preceding claims, wherein the hydraulic diameter dh is between 5 mm and 50 mm, wherein dh is defined as d,1 =d/Vn where d is the internal diameter of the reactor tube and n is the number of orifices in the baffle.-42 -
9. A multi-orifice oscillatory baffled reactor according to any one of the preceding claims, wherein the reactor tube has an internal diameter of at least 50 mm and up to 1 m
10. A multi-orifice oscillatory baffled reactor according to any one of the preceding claims, wherein the inter-baffle spacing is from 1db to 3db
11. A multi-orifice oscillatory baffled reactor according to any one of the preceding claims, wherein the average number of orifices per baffle is between 2 and 1500.
12. A multi-orifice oscillatory baffled reactor according to any one of the preceding claims, wherein the reactor tube contains between 8 and 10 baffles, each baffle having a free open area of up to 20% and the inter-baffle spacing being between 35 mm and 45 mm, wherein the hydraulic diameter dh is between 25 mm and 30 mm, the hydraulic diameter being defined as in claim 8.
13. A multi-orifice oscillatory baffled reactor according to any one of the preceding claims, adapted for the treatment of water.
14. A multi-orifice oscillatory baffled reactor according to any one of the preceding claims, adapted for the removal of organic contaminants from a fluid.
15. A multi-orifice oscillatory baffled reactor according to any one of the preceding claims, adapted to carry out a method selected from sanitation treatment of mineral bottled water by ozonation; tertiary treatment to remove micro-contaminants of concern from wastewater; disinfection of drinking water; sanitation of recreational water; decontamination of water used in pulp and paper processing; decontamination of water used in food and beverage production; decontamination of water used in semiconductor manufacture; decontamination of cooling water for antibacterial control; colour removal from textile wastewater; treatment of metal working fluids; decontamination of underground water and decontamination of ballast water for reuse.
16. A multi-orifice oscillatory baffled reactor according to any one of the preceding claims, adapted to remove Pharmaceuticals and Personal Care Products (PPCPs) from a fluid.
17. A multi-orifice oscillatory baffled reactor according to any one of the preceding claims, adapted to further subject the fluid to one or more additional processes selected from H202 treatment, UV exposure, photo-Fenton processes and sulphate treatment.-43 -
18. A multi-orifice oscillatory baffled reactor according to any one of the preceding claims, wherein the oscillatory means is adapted to oscillate at a frequency of up to 10 Hz.
19. A multi-orifice oscillatory baffled reactor according to any one of the preceding claims, wherein the oscillatory means is adapted to oscillate with a centre-to-peak amplitude of uptolomm.
20. A multi-orifice oscillatory baffled reactor according to any one of the preceding claims, adapted to decontaminate fluid in continuous or batch mode.
21. A multi-orifice oscillatory baffled reactor according to any one of the preceding claims, wherein the gas source is adapted to provide a gas superficial velocity of between 0.001 andlomms4.
22. A multi-orifice oscillatory baffled reactor according to any one of the preceding claims, adapted to decontaminate fluid in continuous mode with a throughput of between 0.1 and Ls1.
23. A multi-orifice oscillatory baffled reactor according to any one of the preceding claims, adapted to operate at a modified Reynolds number Reo' of at least 300, at least 1000, at least 2000, at least 5000, at least 10,000 or at least 20,000.
24. A method of removing contaminants from a fluid by contacting the fluid with an oxidising gas, the method comprising the steps of: introducing the fluid into the multi-orifice oscillatory baffled reactor according to any one of claims ito 23; introducing the oxidising gas into the fluid through the gas source; and oscillating the fluid and/or the one or more baffles with the oscillatory means to provide a dispersion of microbubbles within the fluid.
25. A method according to claim 24, wherein the fluid is water.
26. A method according to claim 24 or 25, wherein the oxidising gas is ozone or chlorine.
27. A method according to any one of claims 24 to 26 wherein the oxidising gas is ozone and the reaction is ozonation.-44 -
28. A method according to any one of claims 24 to 27, which is a method of removing organic contaminants from the fluid.
29. A method according to any one of claims 24 to 28, wherein the method is selected from sanitation treatment of mineral bottled water by ozonation; tertiary treatment to remove micro-contaminants of concern from wastewater; disinfection of drinking water; sanitation of recreational water; decontamination of water used in pulp and paper processing; decontamination of water used in food and beverage production; decontamination of water used in semiconductor manufacture; decontamination of cooling water for antibacterial control; colour removal from textile wastewater; treatment of metal working fluids; decontamination of underground water and decontamination of ballast water for reuse.
30. A method according to any one of claims 24 to 29 wherein the contaminants are Pharmaceuticals and Personal Care Products (PPCP5).
31. A method according to any one of claims 24 to 30, wherein the fluid is also subject to one or more additional processes selected from H202 treatment, UV exposure, photo-Fenton processes and sulphate treatment.
32. A method according to any one of claims 24 to 31, wherein the fluid is decontaminated in continuous or batch mode.
33. A method according to any one of claims 24 to 32, wherein at least 90% of the oxidising gas introduced to the reactor tube is consumed by the reaction with contaminants.
34. A method of CO2 sequestration comprising the steps of introducing a fluid into the multi-orifice oscillatory baffled reactor according to any one of claims ito 23; introducing CO2 into the fluid through the gas source; and oscillating the fluid and/or the one or more baffles with the oscillatory means to provide a dispersion of CO2 microbubbles within the fluid.
35. A method of manufacturing bioproduct using syngas bioconversion comprising the steps of -45 -introducing a fluid into the multi-orifice oscillatory baffled reactor according to any one of claims 1 to 23, the fluid comprising a bioconversion medium; introducing syngas into the fluid through the gas source; and oscillating the fluid and/or the one or more baffles with the oscillatory means to provide a dispersion of syngas microbubbles within the fluid.
36. A method according to claim 35, wherein the bioconversion medium is a biomass culture.
37. A method according to any one of claims 24 to 36, wherein the oscillatory means is oscillated at a frequency of up to 10 Hz
38. A method according to any one of claims 24 to 37, wherein the oscillatory means is oscillated with a centre-to-peak amplitude of up to 10mm.
39. A method according to any one of claims 24 to 38, wherein the gas is introduced through a sparged gas source having an outlet within the reactor tube.
40. A method according to any one of claims 24 to 39, wherein the gas superficial velocity is between 0.001 and 10 mm s.
41. A method according to any one of claims 24 to 40, wherein the fluid is decontaminated in continuous mode with a throughput of between 0.1 and 10 [.1*
42. A method according to any one of claims 24 to 41, wherein the modified Reynolds number Reo' is at least 300, at least 1000, at least 2000, at least 5000, at least 10,000 or at least 20,000.
43. Use of the multi-orifice oscillatory baffled reactor according to any one of claims 1 to 23 in the decontamination of water by ozonation, sequestration of 002, or bioconversion of syngas into a bioproduct.
44. Use according to claim 43, in the decontamination of wastewater by ozonation.
45. A multi-orifice baffled reactor substantially as described with reference to, and as illustrated in, Figures 1, 2 and 20.