KR20020042824A - Apparatus And Method For Separating Mixed Liquids - Google Patents

Abstract

In the biomass extraction cycle, an improved evaporator is needed. Evaporator 12 includes an inlet for a liquid solvent / biomass mixture, which includes a spray nozzle 27. Evaporator 12 includes heated vessel walls 20a and 20b. When the solvent / biomass mixture flows through the nozzle 27, some solvent is volatilized due to the pressure drop. The heated walls 20a, 20b volatilize the solvent residue. Solvent vapor is withdrawn from the evaporator 12 upon recycling. The liquid biomass extract is collected at the bottom of the vessel and subsequently used for discharge.

Description

Apparatus And Method For Separating Mixed Liquids

The present invention relates to an apparatus and a method for separating mixed liquids, in particular liquids of different volatility. Such mixtures arise, for example, in a process of extracting "biomass" (the method of which is illustrated next). Typical intermediates in this process include hydrofluorocarbons (“HFCs”) (eg, 1,1,1,2-tetrafluoroethane); Chlorofluorocarbons (“CFCs”); Or a mixture of solvents such as hydrochlorofluorocarbons ("HCFCs") and waxy or oily liquids extracted from naturally occurring substances known as biomass.

The term "hydrofluorocarbon" refers to a substance which contains only carbon, hydrogen and fluorine atoms and therefore does not contain chlorine.

Preferred hydrofluorocarbons are hydrofluoroalkanes and especially C _1-4 hydrofluoroalkanes. Suitable examples of C _1-4 hydrofluoroalkanes that may be used as the solvent are, in particular, trifluoromethane (R-23), fluoromethane (R-41), difluoromethane (R-32), pentafluoro Roetan (R-125), 1,1,1-trifluoroethane (R-143a), 1,1,2,2-tetrafluoroethane (R-134), 1,1,1,2- Tetrafluoroethane (R-134a), 1,1-difluoroethane (R-152a), heptafluoropropane and especially 1,1,1,2,3,3-heptafluoropropane (R-227ea ), 1,1,1,2,3,3-hexafluoropropane (R-236ea), 1,1,1,2,2,3-hexafluoropropane (R-236cb), 1,1, 1,3,3,3-hexafluoropropane (R-236fa), 1,1,1,3,3-pentafluoropropane (R-245fa), 1,1,2,2,3-pentafluoro Lopropan (R-245ca), 1,1,1,2,3-pentafluoropropane (R-245eb), 1,1,2,3,3-pentafluoropropane (R-245ea) and 1, 1,1,3,3-pentafluorobutane (R-365mfc). Mixtures of two or more hydrofluorocarbons may be used as desired.

R-134a, R-227ea, R-32, R-125, R-245ca and R-245fa are preferred.

Particularly preferred hydrofluorocarbons for use in the present invention are 1,1,1,2-tetrafluoroethane (R-134a).

Biomass extraction is the extraction of flavors, fragrances or pharmaceutically active ingredients (herein referred to as "biomass") from natural substances.

Examples of biomass include, but are not limited to, coriander, cloves, star anise, coffee, orange juice, fennel seeds, cumin, ginger and other types of bark, leaves And flavosomes or fragrances such as flowers, fruits, roots, rhizomes and seeds. The biomass may also be extracted in the form of biologically active substances such as insecticides and pharmaceutically active substances or precursors thereof, for example to obtain plant substances, cell cultures or fermentation broths.

There is an increasing technical and commercial interest in using such important solvents as described above in such extraction processes or liquefied carbon dioxide, for example.

The solvent mixture can be used to extract the biomass.

Known extraction processes using such solvents are generally performed in closed-loop extraction equipment. A typical example 10 of such a system is shown schematically in FIG. 1.

In this typical system, the liquefied solvent is osmotically oscillated downward through a bed of biomass fixed to vessel 11. From there it flows into the evaporator 12 where the volatile solvent is volatilized by heat exchange with hot fluid. The vapor from evaporator 12 is then compressed in compressor 13. The compressed steam is then fed to condenser 14 where it is liquefied by heat exchange with cold fluid. The liquefied solvent is then optionally collected in an intermediate storage vessel (receiver) 15 or sent directly to extraction vessel 1 to complete the circulation.

The process is characterized by the pressure difference between the condenser / storage vessel and the evaporator as the main driving force for the solvent to circulate around the biomass and the system. This pressure difference occurs in the compressor. Therefore, in order to increase the solvent circulation rate through the biomass, it is necessary to increase this pressure difference, and a larger and better compressor is required.

The large difference in density of solvent liquid and vapor means that a slow increase in liquid circulation rate can require significant capital and process costs due to the increase in compressor size. This means that the system developer must balance the flow of liquid through the biomass with the rate at which vapor can be compressed.

In such extraction systems, the material is typically extracted as a non-volatile liquid or waxy solid, so solvent evaporators are used for the purpose of separating the solvent from the distillation product and for storing the product. A typical design is a typical jacketed pressure vessel that includes a product and a solvent that forms a liquid or slurry pool. Heat is supplied through the vessel wall to evaporate the solvent and the heat transfer method is to boil the pool. The liquid feed is introduced through a dip-pipe.

Such an arrangement is easy to manufacture, but has many problems.

First, by forming an intimate mixture of solvent and product, the system can be considered similar to thermodynamic equilibrium. This means that as the amount of product in the vessel increases during the extraction process, the concentration of product in the liquid pool of the evaporator steadily increases. Most extracts have very low volatility compared to solvents, which means that the vaporization pressure decreases over time when the evaporation temperature, for example the heat supply temperature, is fixed.

Reducing the steam pressure reduces the vapor density, thus reducing the mass passing through the compressor. If this decrease in density is not compensated for by an increase in vaporization temperature, the overall solvent circulation rate (measured by compressor mass throughput) around the system is reduced.

The vaporization temperature in the evaporator is limited by the temperature supplied by the heat. As is generally the case, using some form of heat integraton (heat recovery) to recycle heat from the condenser to the evaporator, there is a clear upper limit to the heat supply temperature. In the case of heat resistance in the evaporator, this limits the rise of the evaporator temperature to offset the change in vaporization pressure.

Not only is there a maximum temperature difference that can be applied to the evaporator vessel 12, but the boiling scheme beyond this turns into a so-called film boiling in which the heat flow is significantly reduced compared to the full boiling scheme. Thus, any attempt to counteract changes in boiling pressure is significantly limited due to the properties of the device and the thermodynamic properties of the solvent / extraction fluid system.

Secondly, the addition of a second nonvolatile component to the boiling fluid can adversely affect heat transfer rate (generally expressed as a decrease in heat transfer coefficient). This is due to the introduction of the so-called mass transfer resistance as well as the thermal resistance that occurs when pure fluids boil. Thus, as the amount of extract retained in the evaporator increases during extraction, impaired heat transfer may increase. This can reduce the solvent circulation rate as described above.

Both of these problems cause the need to continuously adjust the total solvent circulation rate (to balance the output of the evaporator to the compressor) and to extend the time needed for material extraction to be considered.

The third problem is due to the known design with respect to the thermodynamic properties of the system. Once the extraction is substantially complete, it is necessary to volatize the residual solvent in the extractor vessel, the evaporator and the connecting pipe so that as much solvent as possible can be recovered. If this evaporation occurs completely in the boiling liquid pool mixed with the product, part of the product evaporates as the product extraction concentration increases. This is due to the fact that the concentration in the vapor is considerably low, but still contaminates the solvent.

This loss to the solvent system means that the loss of valuable products requires additional recovery and washing of the solvent before it can be reused. This adds cost because of both the equipment and uptime required.

Evaporation in this way can cause additional problems with some extracts. Many spice and aroma extracts are mixtures of several molecules: therefore, if some are evaporated into the solvent system as described above, the properties of the essential ingredients are lost and their value changes accordingly. This is also undesirable.

In short:

Use of a full boiling evaporator for solvent / extract separation is a standard technique used for closed-loop solvent extraction as described above.

Evaporators such as poor heat transfer which do not separate solvent from the product and prolong circulation time; Thermal degradation of the product; Problems such as partial changes in the extraction due to fractionation and contamination of the solvent system by the extract.

According to one aspect of the invention, the barrier of claim 1 is provided.

The advantages of such a device are:

The evaporation of the solvent occurs in part by the direct contact of the droplet injection and the vapor in the vessel and also partly evaporates from the thin film. Both methods are well known for providing high heat transfer coefficients and therefore good thermal performance.

As the level of extract in the volatilized solvent is always low (e.g., the concentration supplied via the inlet in an extractor vessel, such as vessel 11 of Figure 1), the boiling point temperature or solvent vapor density hardly changes over time. There is almost no reduction in evaporation performance with

Some biomass extracts are known to solidify when concentrated at or near ambient temperature. The present invention allows the extract to remain liquid in the volatilized film (by selecting the temperature of the portion to be heated), thus making it possible to keep the extract in the liquid phase even if the bulk solvent volatilization temperature is lower than the extract's melting point. To be introduced.

Preferred arrangements of the device components to be effectively separated are as shown in claims 2 and 3.

Preferably, the nozzle can be removed at the inlet. The use of removable feed nozzles means that the optimum spray angle and droplet size can be easily changed from extraction to extraction depending on the nature and concentration of the extract being processed.

Optionally, the inlet comprises a preheater used for heating the solvent / liquid mixture. Preferably, the heating by the preheater can be controlled by microprocessor control means in accordance with the exact supply to be processed. This advantageously controls the flash volatilization of the solvent in the device.

Preferred forms of steam outlets are as shown in claims 7 and 8. These forms are beneficial to ensure complete recovery of solvent vapors from the vessel while preventing entrainment of the biomass extract.

The dimming barrier of claim 9 also advantageously prevents the accompanying flow of the biomass extract.

Claims 10 and 11 specify the dimensional form of the vessel which helps to provide good flow and separation effects.

The invention relates to a biomass extraction plant, in particular a pressure vessel, in particular an apparatus as specified herein, when used in operative connection with a plant comprising a closed loop solvent circulation path which forms part of it. It is about.

According to another aspect of the present invention, the method of claim 14 is provided. Preferred implementations of the method are as in claims 15 to 17.

Hereinafter, with reference to the drawings will be described a preferred embodiment of the present invention. However, this does not limit the present invention.

1 is a diagram illustrating a conventional, closed loop biomass extraction cycle in the prior art;

2 shows a cross sectional view of a device according to the invention in the form of an evaporator.

2 shows an evaporator 12 which can replace the conventional evaporator 12 in the circulation of FIG. 1.

Evaporator 12 in FIG. 2 is jacketed pressure vessel 20 with heat source 21 flowing through jacket 22. Another example is the use of an electronic heating element inserted around or surrounding the sides and bottoms 20a, 20b of the vessel 20 in a manner similar to the jacket 22 of FIG.

From extraction step 11 of the process, the liquid solvent containing the extract is fed via feed line 23, any preheater 24, thus providing a short vertical pipe 26 having a removable, angled injection nozzle 27 at the end. Through the container.

As the solvent / biomass extract mixture flows through line 23 and pipe 24 and through nozzle 27, the supply pressure drops at nozzle 27 and thus as part of the feed (typically about 5-7%) flows into vessel 11 Volatilized The so-called amount of flash steam can be controlled by preheating the liquid solvent feed.

The angled nozzle 27 is aimed so that a fine jet of unvolatized liquid is directed towards the wall 20a of the vessel 20, after which the liquid flows down the inner wall 20a of the vessel into a thin film. As the film flows down the solvent evaporates as the wall temperature remains above the evaporation temperature of the solvent at the evaporation pressure. The extract (ie liquid biomass extract) (its dew point temperature is lower than the dew point temperature of the solvent) flows down to bottom 20b of vessel 20 where it is collected during circulation and collected via drain valve 28 at bottom 20b as needed. do.

As mass transfer proceeds by heating and droplet injection, the vaporized vapor rises out of the vessel and is removed through the duct 29 at the top of the vessel by the action of the solvent compressor 13.

The vessel portion 20c, which is above the solvent introduction point, can be used (as a suitable extension of the heating jacket 22 or other heating element) to provide additional superheat to the vapor (to help dry out the steam). It also acts as a disengagement space to minimize the entrainment of liquid droplets.

To aid in the disengagement of the vapor, the vessel inner diameter D is chosen such that the vapor velocity is low enough to substantially eliminate the entrainment of the droplets of particle size formed by the spray nozzle. Additional demister pads or baffle arrays 30 may be mounted as needed at the top of the internal vapor space to further block liquid entrainment.

The vessel length L is chosen to ensure that in the normal operating cycle, the expected amount of product transfers sufficient heat to the surface to ensure complete volatilization of the solvent before reaching the vessel bottom 20.

Claims (19)

A hollow pressure vessel having an inlet, a vapor outlet and a liquid outlet connected to a pressurized source of solvent / liquid mixture; A heater for heating the inside of the pressure vessel; And A spray nozzle connected to the inlet for introducing the solvent / liquid mixture into the pressure vessel with a fine spray, Due to the pressure drop across the nozzle, at least a portion of the solvent is evaporated and the volatile solvent mixed with each other in the liquid state is located relative to each other such that the interior of the nozzle and the heated portion are in contact with the heated portion and the solvent residue is volatilized. And devices for separating less volatile liquids. 2. The apparatus of claim 1, wherein the heated portion is positioned and heated to flow near the liquid outlet into the liquid reservoir along the portion where the liquid is heated with liquid. 3. The injection nozzle as claimed in claim 1 or 2, wherein the injection nozzle and the vapor outlet are located at or near the top of the pressure vessel; The liquid outlet is located at or near the bottom of the pressure vessel; And the heater heats the inner wall of the pressure vessel. The device of claim 1, wherein the nozzle is removable at the inlet. The device of claim 1, wherein the inlet comprises a preheater for the solvent / liquid mixture. 6. The device according to claim 5, wherein the heating of the preheater is adjustable. The device of claim 1, wherein the vapor outlet is connected to a suction tube. The apparatus of claim 1, wherein the steam outlet is located in a disengagement zone and includes a superheater for heating steam in the region of the vessel. 10. The apparatus of claim 8, comprising a defoamer pad or baffle plate that separates the glass region from another portion within the vessel. An apparatus according to any of the preceding claims, wherein the transverse size inside the pressure vessel is such as to ensure a vapor velocity low enough to prevent the microspray droplets from entraining towards the steam outlet. The device according to claim 2, wherein the heated portion is of sufficient length to ensure complete volatilization of the solvent mixed with the liquid before the liquid reaches the reservoir. Apparatus according to any one of the preceding claims, which is included in a biomass extraction plant. 13. The apparatus of claim 12, wherein the biomass extraction plant comprises a closed loop solvent circulation path in which the pressure vessel is part of. Lowering the pressure of the liquid mixture such that a portion of the solvent evaporates and supplying the mixed liquid under pressure through a nozzle to form a fine jet of the liquid mixture into the pressure vessel; Heating the interior of the pressure vessel; Contacting the heated portion with a fine spray such that a solvent residue is evaporated; Allowing the liquid to flow along the heated portion to a low bath; Discharging the liquid from the reservoir; And Evacuating vapor from the vessel; Method for separating the volatile liquid solvent and less volatile solvent mixed with each other comprising a. 15. The method of claim 14, comprising preheating the liquid mixture before the liquid mixture passes through the nozzle. 16. The method of claim 14 or 15, comprising superheating the solvent vapor in the pressure vessel. The method according to any one of claims 14 to 16, wherein the process is carried out as part of a biomass extraction process. A biomass extract obtained by the method of any one of claims 14-17. A solvent obtained by the method of any one of claims 14-17.