WO1998037960A1

WO1998037960A1 - Multiphase physico-chemical reactor

Info

Publication number: WO1998037960A1
Application number: PCT/AU1998/000129
Authority: WO
Inventors: Gaetano Russo
Original assignee: Hyperno Proprietary Limited; Russo, Maria
Priority date: 1997-02-28
Filing date: 1998-02-27
Publication date: 1998-09-03
Also published as: AUPO535897A0

Abstract

A process that improves upon the mass transfer of chemicals between phases and which compensates for the slowness in reaction rates inherent in many chemical reactions, wherein a first fluid reactant in a reaction vessel is mixed with a second fluid reactant in a mixing device followed by a reaction vessel so as to allow the chemicals to react together, the mixing being effected by the mixing device, which results in a large surface area between phases, so as to aid in mass transfer.

Description

MULTI-PHASE PHYSICO-CHEMICAL REACTOR

This invention relates to improvements in the process to carry out physico-chemical processes which facilitates physical mass transfer and/or chemical reactions which are normally slow and is directed for use in the pharmaceutical, chemical, petrochemical, refining, mining, metallurgical, textile, and mineral extraction industries .

The object of the invention is to provide a physico-chemical process which improves upon the mass transfer of chemicals between phases and which can also compensate for the slowness in reaction rate inherent in many chemical reactions so as to improve(reduce) on the overall time required to complete the chemical process compared with known conventional means of carrying out the process.

The invention includes a process of accelerating a chemical reaction in which a first fluid reactant in a reaction vessel is mixed with a second fluid reactant so as to allow the chemicals in the two reactants to react together, the mixing being effected by employing a mixing device designed to intimately mix the fluids together whilst providing a large surface area between the phases, in order to aid in mass transfer. This is especially beneficial when chemical reaction is limited by mass transfer across the boundary between the phases.

The invention also includes a process as set out above being a process of treating chemical waste in which the first reactant is a waste fluid in the reaction vessel, is mixed with a second fluid so as to allow the chemicals in the two fluids to react together, the mixing being effected by employing a mixing device designed to intimately mix the fluids together so as to provide a large surface area between the phases, in order to aid in mass transfer.

Preferably the mixing device is a jet compressor or the like. The mixing action results in millions of bubbles resulting in a semi- stable froth forming in the reaction vessel. This froth provides a large surface area for an extended time before bubble/froth collapse occurs thus enhancing the time and surface area available for mass transfer and the reaction. It is the unique interaction between the bubble and aerosol phases mixing within the reaction vessel that allows successful mass transfer and reaction. In this invention the combination of the large surface area, residence time in the froth and bubble phase and the increase in

the gas partial pressure within the mixing device which each act to facilitate the reaction and thus reduce the necessary residence time in the reaction vessel. Because of the efficiency gained by this invention in increasing mass transfer and reducing the overall reaction time, the process can be a continuous one resulting in enhanced capacity and flexibility over the batch processes conventionally employed.

The invention includes a treatment process in which a liquid in a reaction vessel is treated by a gas to substantially remove some of the volatile components in the liquid via a gas stripping mechanism. In some processes, some or all contaminants in the liquid may react with components in the gas being employed for the stripping of the volatile components .

A major feature of the invention is the use of a jet compressor to intimately mix the liquid and gas so that a large surface area is created between the liquid and gas phases. The jet compressor also compresses the gas from the gas inlet of the device to a higher pressure at the discharge of the device. This enhances reaction rate of the gas with compounds in the liquid phase where such reaction is limited by low pressures.

A jet compressor is a device that has a particular geometry in which a high pressure fluid (usually liquid) is passed through a small nozzle into a chamber where it mixes with low pressure fluid (usually gas). The two fluids then flow together along the chamber which converges to a narrow mixing section of the device and then diverges to a chamber of larger diameter. The converging-mixing-diverging geometry gives the jet compressor its characteristic ability to compress the low pressure fluid to a higher pressure at the discharge of the device.

It will be appreciated that the jet compressor is uniquely used as a mixer, aerosol promoter, compressor and gas encapsulating, shearing, de-clumping, heat and mass transfer device.

It is preferred that there is means, whereby the process includes a capability of varying both the liquid phase and gas phase residence times to ensure that low reaction rate steps can proceed substantially to completion. This is achieved in the liquid phase by providing a capability to vary the feed rate of the liquid to the process and/or varying the number of reactor stages used. In this way the residence time can be varied from a few minutes to a number of weeks. Gas phase variation of residence time is achieved by manipulating the operating pressure

at each stage and varying the number of stages. The process, in effect, can be varied from a batch mode to a continuous mode and is very flexible.

Description of the invention with respect to the diagrams;

A specific embodiment of the invention is hereinafter described with reference to Figures 1,2,3,4&5.

With reference to Figure 1, this figure describes the basic reaction stage. Liquid phase to be reacted/treated enters the residence time section of the reactor 8 through inlet line 1. It is taken out of the reactor through liquid line 3 where it has kinetic and pressure energy imparted to it by circulating pump 4.

The high energy liquid is pumped to jet compressor 5 through line 6 where the energy inputted by the pump is dissipated through a nozzle and converted into mixing energy and compression energy within the jet compressor. Gas to the jet compressor is induced

through gas line 7 into the jet compressor and intimately mixed and compressed with the circulating liquid phase. The compression undergone by the gas is up to a 3:1 pressure ratio. In the jet compressor the following takes place:

1. Liquid and gas are intimately mixed.

2. Mass and energy transfer takes place between gas and liquid.

3. Gas is encapsulated to form millions of small bubbles (foam) and droplets in the form of a mist are created leading to an enormous liquid/gas surface area. In addition, some of the liquid phase is converted into an aerosol. The liquid/gas interface thus created through aerosol and bubble formation leads to improved mass transfer to and from the liquid phase versus conventional means of gas/liquid contact, (eg. a tower packing, tower trays, spray nozzles, mixing propellers or gas diffusers).

4. The gas pressure is increased by a ratio of up to 3:1 thereby increasing the gas partial pressure and improving the mass transfer of reactants from the gas to the liquid phase.

5. De-clumping of aggregated particles in the liquid phase (where the liquid phase has a solid precipitate or slurry or a discontinuous liquid phase). This allows reactants from the gas or continuous liquid phase to readily contact molecules/compounds which would otherwise be inaccessible to the reactants if clumps were stable and in some cases can reduce the amount of dispersant chemicals required for this purpose.

6. Encapsulation, homogenisation and/or emulsification of immiscible liquid phases to promote reactant(s) and/or mass transfer between phases.

The mist (aerosol) from the jet compressor coalesces in the reactor 8 and settles out into the liquid phase. The gas/liquid foam created exits the jet compressor into the reactor where, because of its relative stability, gas/liquid mass transfer can continue over an extended time via the surface of the foam bubbles to and from the gas . As mist coalescing and bubble collapse occurs, gas leaner in reactants exits the reactor through line 2. This gas also carries with it organic gases or vapours transferred to it in the gas/liquid exchange that has taken place in the reactor. The reaction stage comprises the combination of the reactor vessel, the pump, the jet compressor and interconnecting piping. Liquid flows into the reaction stage are balanced by liquid outflows from the reaction stage through line 9.

The continuous recycling by the circulating pump, of the liquid phase to the gas through the jet compressor enhances reaction rate over the once through conventional contact processes. The continuous recirculating of liquid allows sufficient gas to contact the inventory of liquid in the reaction vessel so as to reach chemical equilibrium between the phases. The process which uses reaction stages as described is very efficient when mass transfer is limited across the gas/liquid phase boundary and/or when the chemical reaction is slow in the liquid phase; thereby requiring substantial liquid residence times, or slow in the gas phase; thereby requiring substantial gas residence times.

One of the unique features of this invention is that, because of the jet compressors' ability to handle large quantities of gas, the gas phase is not limited to reacting gases only but may incorporate inert gases which in many applications enhances the total process (eg: those involving reaction with reactants from the gas phase in the liquid phase with co-incident removal of noxious products of reaction by desorption into the gas phase for disposal) . This feature enables the efficient removal of volatile compounds from sour water in refineries , chemical and petrochemical plants .

The unique dispersion, intimate mixing and fast recycling characteristics of this invention lend it to enhancement of biological processes such as, but not limited to fermentation, biological drug manufacture and sewage treatment where the reaction time is limited in conventional processes due to the slow availability of reactants to the biological and nutrient species, such as, but no limited to, oxygen and carbon dioxide.

Reactors may be grouped in series and may consist of banks of reactors with the number of reactors in a group being from 1 to 20 depending on the field of application.

They may be combined in a variety of series, parallel or series- parallel combinations depending on application. For convenience a 4 stage reactor group is used to illustrate a selection of the various combinations .

Figures 2 & 3 illustrate series combinations in counter-current and co-current mode respectively. Figure 2 shows a 4 stage counter-current gas phase/liquid phase combination where the liquid phase enters stage 1 and travels through the stage in series fashion to exit at stage 4 with the gas phase entering at stage 4 and exiting at stage 1.

Figure 3 shows a 4 stage co-current gas phase to liquid phase combination where both liquid and gas phases enter stage 1 and exit in stage 4.

Figure 4 illustrates a series-parallel (or cross-flow) configuration.

Figure 4 shows a 4 stage cross - flow operation where liquid enters stage 1 and exits stage 4 whilst fresh gas enters and exits each individual stage. This is used for difficult reactions or physical stripping operations where maximum concentrations of active gas reactant or fresh gas is required to achieve the desired degree of reaction.

Figure 5 illustrates a configuration which combines series, parallel and series-parallel configuration.

Figure 5 shows a liquid phases process combined with gas configuration.

Figure 4 shows a 4 stage cross - flow operation where liquid

phase 10 enters stage 1 and exits stage 4 whilst fresh gas 22

enters and exits each individual stage through line 21 via line 19. This is used for difficult reactions or physical stripping operations where maximum concentrations of active gas reactant or fresh gas 22 is required to achieve the desired degree of reaction.

Figure 5 shows a liquid phases 10 process combined with gas stripping and reabsorption. In this process Stage 1 has liquid phases 10 feeding into it and then going to Stage 2. The liquid phases 10 may be comprised of immiscible liquids containing reactants or components which need to be absorbed or desorbed to and from the immiscible liquids or may comprise liquid/solid slurries to and from which reactants, minerals or compounds are required to be efficiently transferred (eg: leaching or gold ore slurries with cyanide). In these stages the gas used is taken from the gas space in the reactor and is continuously circulated Examples of where these configurations may be used are:

1. Treatment of foul waters (so call "sour water" from refining, petrochemical and chemical installations) to deodorise them by using gases such as flue gas or steam as the reacting gas to take the odours out.

2. Treatment of waters or other liquid phases containing hydrocarbons or volatile compounds such as benzene or other organic compounds such as alcohol, carbonyls, esters and essential oils by stripping into a gas phase of say flue gas, nitrogen, or steam to remove the offending volatile compound(s) from the liquid phase.

3. The reaction in the liquid and/or gas phases between reactants in/from and/or to the liquid and/or gas phases together with the co-incident removal from the liquid phase of undesirable products of reaction and/or undesirable inherent compounds in the liquid phase.

4. Liquid extraction of metals and minerals, in particular gold, from liquid phase or slurries. 2. Treatment of waters or other liquid phases containing hydrocarbons or volatile compounds such as benzene or other organic compounds such as alcohol, carbonyls, esters and essential oils by stripping into a gas phase of say flue gas, nitrogen, or steam to remove the offending volatile compound(s) from the liquid phase.

4. Liquid extraction of metals and minerals , in particular gold, from liquid phase or slurries.

5. Neutralization of liquid seepages from tailings dumps resulting from mining operations . A particular example being seepage from alumina processing tailings dumps.

6. Treatment of waste waters containing cyanide from gold recovery operations . 7. Biochemical reactions such as sewage treatment, fermentation, bacteriological, viral and fungal breeding or culturing processes.

8. Redox reactions requiring intimate contact between several phases.

The essence of this invention is a process of mass transfer across phase boundaries which also compensates for the slowness in reaction rates inherent in many chemical operations and as a result of said process the acceleration in the treatment of contaminants results and it is to be understood that further variations of this concept than here in described can be made.

Claims

The Claims defining the invention are:

1. A process that improves upon the mass transfer of chemicals between phases and which compensates for the slowness in reaction rates inherent in many chemical reactions, wherein a first fluid reactant in a reaction vessel is mixed with a second fluid reactant in a mixing device followed by a reaction vessel so as to allow the chemicals to react together, the mixing being effected by the mixing device, which results in a large surface area between phases, so as to aid in mass transfer.

2. A process as claimed in claim 1 wherein the first fluid reactant is a liquid and the second fluid is gaseous and that the mixing action caused by the mixing device, results in a froth forming in the reaction vessel for substantial time thus enhancing the time and surface area available for mass transfer.

3. A process as claimed in claim 1 wherein the first and second reactants are liquids and that the mixing action caused by the mixing device, results in a froth forming in the reaction vessel for substantial time thus enhancing the time and surface area available for mass transfer.

4. A process as claimed in claim 2 wherein the liquid phase and gas phase residence times are varied to ensure that low reaction rate steps can proceed to completion.

5. A process as claimed in claim 3 wherein the low reaction rate is achieved by providing a capability to vary the feed rate of the liquid to the process and varying the number of reactor stages used.

6. A process as claimed in any preceding claim wherein the combination of a large surface area, residence time in the froth forming stage and an increase in gas partial pressure within the mixing device facilitates the reaction and reduces the necessary residence time in the reaction vessel.

7. A process as claimed in claims 1-5 wherein the mixing device is a jet compressor or similar mixing compression device designed to intimately mix the liquid and gas.

8. A process as claimed in claim 6 wherein the jet mixer acts as a mixer, aerosol promoter, compressor and gas

encapsulating, shearing, de-clumping, heat and mass transfer device.

9. A process as claimed in any preceding claim which comprises the following steps :

(a) mixing of the liquid and gas by means of a mixing device following a reaction vessel resulting in the formation of a froth and an increase in the liquid/gas surface area and mass and energy transfer:

(b) increasing the gas pressure within the reaction vessel by a ratio of at least 3:1 thereby increasing the gas partial pressure and improving the mass transfer of reactants from the gas to the liquid phase;

(c) de-clumping of aggregated particles in the liquid phase, where the liquid phase has a solid precipitate, a slurry or a discontinuous liquid phase, to allow the reactants from the gas or continuous liquid phase to readily contact molecules which would otherwise be inaccessible to reactants; and (d) encapsulation, homogenisation or emulsification of immiscible liquid phases to promote reactant and mass transfer between phases.

10. A process as claimed in claim 2-8 wherein as bubble collapse occurs, gas leaner in reactants exits the reactor, said gas carrying with it organic gases or vapours transferred to it in the gas/liquid exchange that has taken place in the reactor.

11. A process as claimed in claim 9 wherein liquid flows into the reaction stage are balanced by liquid outflows from the reaction stage.

12. A process as claimed in claim 10 wherein the continuous recycling of the liquid phase to the gas through the jet compressor enhances the reaction rate over the conventional contact processes.

13. A process as claimed in any preceding claim wherein the gas phase incorporates reacting gases and inert gases .

14. A process as claimed in claim 12 wherein the process is utilised to remove volatile compounds from sour water.

15. A process as claimed in claims 1 -13 wherein the process is utilised in biological and chemical processes such as fermentation, pharmaceutical manufacture and sewage treatment.

16. A process as claimed in any preceding claim wherein there are a plurality of reaction stages in series, parallel or series-parallel combinations.

17. A process as claimed in claim 15 wherein series combinations are in counter-current or co-current modes .

18. A process as claimed in claim 16 wherein series combinations are in counter-current or co-current modes .

19. A process as claimed in any preceding claim wherein there are up to twenty reaction stages.

20. A process as claimed in claim 18 wherein there are four reaction stages.

21. A process as claimed in claim 19 wherein the four stage reaction is a gas/liquid phase combination where the liquid phase enters stage 1 and travels through stage in series, exiting at stage 4 and with the gas phase entering at stage 4 and exiting at stage 1.

22. A process as claimed in claims 1-19 wherein the four stage reaction is a four stage co-current gas phase to liquid phase combination where both liquid and gas phases enter stage 1 and exit at stage 4.

23. A process as claimed in claims 1-19 wherein the four stage process is a series-parallel combination, such that liquid enters stage 1 and exits stage 4 whilst fresh gas enters and exits each individual stage.

24. A process as claimed in claims 1-19 is a four stage reaction process which combines series, parallel and series -parallel configuration.

25. A process as claimed in claim 23 wherein the liquid phase process is combined with gas stripping and reabsorption, such that stage 1 has liquid phases feeding into it and then proceeding to stage 2, the liquid after treatment flows into stage 3 where it is contacted with in coming gas to strip it of its volatile components before being discharged, said gas phase then exiting stage 3 carrying volatile components into stage 4 where it is continuously contacted with a liquid phase to adsorb volatile components and then finally released, with each reactor in said process acting as a bubble and aerosol producer and de- clumping facilitator.

26. A process as claimed in claim 24 wherein the liquid phase incorporating recovered components is utilised to feed other processes which utilise the volatile components from the original liquid phase from Stage 1.

27. A process as claimed in any one of the preceding claims with reference to the accompanying drawings .