Process for component separation utilizing miscibility depression near a freezing point

A process for separating a mixture of components is disclosed. A liquid mixture is provided to a separation vessel substantially near a temperature at which a product component freezes. The liquid mixture comprises the product component and a carrier component. The product component and the carrier component are essentially immiscible substantially near the temperature. The liquid mixture is separated into two or more phases, the two or more phases comprising a product component-rich liquid phase and a product component-depleted liquid phase. In this manner, a mixture of components is separated.

FIELD OF THE INVENTION

This invention relates generally to the field of separations. More particularly, we are interested in separating liquids by reduction of miscibility.

BACKGROUND

A solid crystallizes when it freezes in a solution, which involves molecules of one type falling into a regular orientation with one another to the exclusion of all different molecules. The thermal agitation of the molecules works against this tendency, and freezing occurs when the ordering forces of hydrogen bonding or other intermolecular forces overcome the disordering forces of thermal agitation. Similar intermolecular attractions can lead to the formation of two liquid phases if the intermolecular forces are large enough to exclude other molecules but still too small to completely overcome thermal agitation. Such miscibility gaps form over a broad temperature range when the molecules in a solution exhibit large differences in, for example, dipole moments or even shape and size. More similar liquid-phase molecules, normally partially or completely miscible, can also split into two phases as their temperature approaches the point at which a component freezes, which generally is lower than the pure component freezing temperature. While no liquid mixtures are ever completely immiscible, when a liquid mixture is substantially at the temperature at which a component freezes, the components in the mixture become essentially immiscible. In other words, their partial miscibility approaches zero as the temperature approaches the component freezing temperature. However, the inventors are unaware of any process currently utilizing these near freezing liquid-liquid interactions to separate otherwise partially or fully miscible liquids.

U.S. Pat. No. 3,653,222 to Blair, et al., teaches a method of freezing solution droplets and the like using immiscible refrigerants of differing densities. The invention includes the freezing of liquid dispersions, including dispersions on the ionic scale of salt solutions on through fluid colloidal systems. Appropriate materials that are soluble in a solvent for which two mutually immiscible, denser liquid refrigerants exist, and that are also individually immiscible with the solvent, may be processed. The present disclosure differs from this prior art disclosure in that the purpose of this prior art disclosure is to freeze liquid dispersions, not to separate components from each other nor to do liquid-liquid separations. This prior art disclosure is pertinent and may benefit from the methods disclosed herein and is hereby incorporated for reference in its entirety for all that it teaches.

SUMMARY

A process for separating a mixture of components is disclosed. The mixture comprises a product component and a carrier component. The mixture is brought substantially near a temperature at which the product component freezes such that the mixture becomes a liquid or remains a liquid. Substantially near the temperature is within 20 C above the temperature. The product component and the carrier component are essentially immiscible substantially near the temperature. The mixture is separated in a separation vessel into two or more liquid phases. The two or more liquid phases comprise a product component-rich liquid phase and a product component-depleted liquid phase. In this manner, the mixture of components is separated.

The mixture may be two liquid components that are partially miscible above the temperature at which the product component freezes.

The mixture may be formed by providing a slurry stream. The slurry stream may comprise a suspended solid and a carrier liquid. The suspended solid may comprise the product component and the carrier liquid may comprise the carrier component. The suspended solid may be melted substantially near the temperature to form a liquid mixture.

The mixture may further comprise a gas phase. The gas phase may comprise a vapor form of the product component, a vapor form of the carrier component, or a combination thereof. The gas phase may be not in equilibrium with the product component-rich liquid phase and the product component-depleted liquid phase due to slow transport between a bottom liquid phase and the gas phase. The gas phase may be substantially in equilibrium with the product component-rich liquid phase and the product component-depleted liquid phase. The separating step further may comprise separating the gas phase from the product component-rich liquid phase and the product component-depleted liquid phase. The separating step may be accomplished using a multi-phase separator.

The carrier component may comprise any compound or mixture of compounds with a freezing point below the freezing temperature.

The carrier component and the product component may differ in dipole moment, component solubility, size, shape, hydrogen bonding characteristics, densities, mutual affinities, or combinations thereof, wherein they are prone to form separate phases substantially near the freezing temperature.

The vessel may promote a stable formation of two liquid phases by minimizing turbulence or other forms of mixing. The vessel may avoid the phases coming to complete equilibrium by minimizing molecular transport and mixing rates. The vessel may maximize mass and heat transfer coefficients between or among the two or more phases.

The separating step may be accomplished by a process comprising decanting, centrifuging, gravity settling, enhanced-gravity settling, and combinations thereof.

The carrier liquid may comprise a dissolved portion of the product component.

DETAILED DESCRIPTION

Referring toFIG. 1, a method for separating a mixture of components is shown at100, as per one embodiment of the present invention. A warm liquid mixture, comprising the product component and a carrier component, that is partially miscible is provided to a separation vessel101. The warm liquid mixture is cooled substantially near the temperature at which a product component in the liquid mixture freezes, becoming an immiscible liquid mixture102. The two components are essentially immiscible near the temperature. The two components are separated into two phases comprising a product component-rich liquid phase and a product component-depleted liquid phase103. The phrase “substantially near the temperature” is defined as a temperature above and close enough to the freezing point temperature to cause the product component and the carrier component to be essentially immiscible. This is within 20 C above the temperature. In some embodiments, the temperature above and close enough to the freezing point is within 1 C above the freezing point. In other embodiments, the temperature above and close enough to the freezing point is within 5 C above the freezing point.

Referring toFIG. 2, a method for separating a mixture of components is shown at200, as per one embodiment of the present invention. A slurry stream is provided, containing a suspended solid and a carrier liquid, to a separation vessel201. The suspended solid comprises the product component. The carrier liquid comprises the carrier component. The suspended solid is melted in the separation vessel, forming a liquid mixture of the product component and the carrier component substantially near the temperature at which the product component in the liquid mixture freezes202. The two components are essentially immiscible substantially near the temperature. The two components are separated into two or more phases comprising a product component-rich liquid phase and a product component-depleted liquid phase203. The phrase “substantially near the temperature” is defined as a temperature above and close enough to the freezing point temperature to cause the product component and the carrier component to be essentially immiscible. This is within 20 C above the temperature. In some embodiments, the temperature above and close enough to the freezing point is within 1 C above the freezing point. In other embodiments, the temperature above and close enough to the freezing point is within 5 C above the freezing point.

Referring toFIG. 3, a cross-sectional view of a cooler and vertical liquid-liquid separator for separating a mixture of components is shown at300, as per one embodiment of the present invention. Warm liquid mixture314, a partially miscible mixture comprising a product component and a carrier component, is provided to cooler310through cooler inlet312. Cooler310cools warm liquid mixture314, forming a liquid mixture that passes through separator inlet304into separator302. The liquid mixture is substantially near the temperature at which the product component freezes. In other words, the liquid mixture is close, but not at the freezing point of the product component. This near approach to the freezing point causes the two components to become essentially immiscible in each other, causing the two components to separate into product component-rich liquid phase316and product component-depleted liquid phase318. Separator302separates these components, with product component-rich liquid phase318removed through top outlet306and product component-depleted liquid phase318removed through bottom outlet308. In some embodiments, the phases have opposite densities, resulting in product component-rich liquid phase316being below product component-depleted liquid phase318. The phrase “substantially near the temperature” is defined as a temperature above and close enough to the freezing point temperature to cause the product component and the carrier component to be essentially immiscible. This is within 20 C above the temperature. In some embodiments, the temperature above and close enough to the freezing point is within 1 C above the freezing point. In other embodiments, the temperature above and close enough to the freezing point is within 5 C above the freezing point.

Referring toFIG. 4, a cross-sectional view of a cooler and multi-phase separator for separating a mixture of components is shown at400, as per one embodiment of the present invention. Warm liquid mixture414, comprising a product component and a carrier component, is provided to cooler412through cooler inlet422. Cooler412cools warm liquid mixture414, forming a liquid mixture that passes through separator inlet404into separator402. Liquid mixture414is substantially near the temperature at which the product component freezes. In other words, liquid mixture414is close, but not at the freezing point of the product component. This near approach to the freezing point causes the two components to become essentially immiscible in each other, causing the two components to separate into product component-rich liquid phase416, product component-depleted liquid phase418, and gas phase420. Gas phase420is removed through gas outlet406, product component-rich liquid phase416is removed through first liquid outlet408, and product component-depleted liquid phase418is removed through second liquid outlet410. In some embodiments, the phases have opposite densities, resulting in product component-rich liquid phase416being below product component-depleted liquid phase418. The phrase “substantially near the temperature” is defined as a temperature above and close enough to the freezing point temperature to cause the product component and the carrier component to be essentially immiscible. This is within 20 C above the temperature. In some embodiments, the temperature above and close enough to the freezing point is within 1 C above the freezing point. In other embodiments, the temperature above and close enough to the freezing point is within 5 C above the freezing point.

Referring toFIG. 5, a cross-sectional view of a coalescing separator for separating a mixture of components is shown at500, as per one embodiment of the present invention. A warm liquid mixture is provided to a cooler (not shown) and cooled to form liquid mixture514, comprising product component522and carrier component520. Liquid mixture514is provided to separator502through inlet504. Liquid mixture514is substantially near the temperature at which product component522freezes. In other words, liquid mixture514is close, but not at the freezing point of product component522. This near approach to the freezing point causes the two components to become essentially immiscible in each other. This immiscibility combined with flow through mesh coalescer510and plate coalescer512causes the two components to separate into product component-rich liquid phase516and product component-depleted liquid phase518. Product component-rich liquid phase516is removed through top outlet506and product component-depleted liquid phase518is removed through bottom outlet508. In some embodiments, the phases have opposite densities, resulting in product component-rich liquid phase516being below product component-depleted liquid phase518. The phrase “substantially near the temperature” is defined as a temperature above and close enough to the freezing point temperature to cause the product component and the carrier component to be essentially immiscible. This is within 20 C above the temperature. In some embodiments, the temperature above and close enough to the freezing point is within 1 C above the freezing point. In other embodiments, the temperature above and close enough to the freezing point is within 5 C above the freezing point.

Referring toFIG. 6, a cross-sectional view of a pipe separator for separating a mixture of components is shown at600, as per one embodiment of the present invention. A warm liquid mixture is provided to a cooler (not shown) to form liquid mixture618, comprising a product component and a carrier component. Liquid mixture618is provided to pipe separator602through inlet section604. Liquid mixture618is substantially near the temperature at which the product component freezes. In other words, liquid mixture618is close, but not at the freezing point of the product component. This near approach to the freezing point causes the two components to become essentially immiscible in each other, causing the two components to separate through pipe separator602into product component-rich liquid phase620and product component-depleted liquid phase622. The separation occurs in stages through the pipe, enhanced by the length, allowing for laminar flow to develop and separation to fully occur. Inlet section604has product component and carrier component dispersed in each other. In coalescing section606, the product component begins to coalesce into large bubbles624of the product component. In slug flow section608, large bubbles624come together to form slugs626of the product component. In wavy flow section610, slugs626have combined and settled into nearly laminar layers628and630. In stratified flow section612, the two phases have fully formed under laminar flow conditions. Product component-rich liquid phase620is removed through top outlet614and product component-depleted liquid phase622is removed through bottom outlet616. In some embodiments, the phases have opposite densities, resulting in product component-rich liquid phase620being below product component-depleted liquid phase622. The phrase “substantially near the temperature” is defined as a temperature above and close enough to the freezing point temperature to cause the product component and the carrier component to be essentially immiscible. This is within 20 C above the temperature. In some embodiments, the temperature above and close enough to the freezing point is within 1 C above the freezing point. In other embodiments, the temperature above and close enough to the freezing point is within 5 C above the freezing point.

Referring toFIG. 7, a cross-sectional view of a screw compressor, melter, and separator for separating a mixture of components is shown at700, as per one embodiment of the present invention. Screw compressor702comprises screw inlet704, screw706, and screw outlet708. Screw outlet708feeds melter710. Melter710feeds separator inlet714. Separator712consists of separator inlet714, gas outlet716, first liquid outlet718, second liquid outlet720. Slurry stream722, comprising a suspended solid and a carrier liquid, is provided to screw compressor702through screw inlet704. The suspended solid comprises a product component. The carrier liquid comprises the carrier component. The slurry stream is compressed through screw compressor702and is passed through screw outlet708into melter710. Melter710melts the suspended solids substantially near the temperature at which the product component freezes, producing a liquid mixture. In other words, the liquid mixture is above but not at the freezing point of the product component. This near approach to the freezing point causes the two components to become essentially immiscible in each other, causing the two components to separate into product component-rich liquid phase724, product component-depleted liquid phase726, and gas phase728. Gas phase728is removed through gas outlet716, product component-rich liquid phase724is removed through first liquid outlet718, and product component-depleted liquid phase726is removed through second liquid outlet720. In some embodiments, the phases have opposite densities, resulting in product component-rich liquid phase724being below product component-depleted liquid phase726. In some embodiments, the walls of screw compressor702further comprise pores that allow a portion of the carrier liquid to pass through but prevent passage of the suspended solids. In some embodiments, the carrier liquid further comprises a dissolved portion of the product component. The phrase “substantially near the temperature” is defined as a temperature above and close enough to the freezing point temperature to cause the product component and the carrier component to be essentially immiscible. This is within 20 C above the temperature. In some embodiments, the temperature above and close enough to the freezing point is within 1 C above the freezing point. In other embodiments, the temperature above and close enough to the freezing point is within 5 C above the freezing point.

Referring toFIG. 8, a cross-sectional view of a centrifugal separator for separating a mixture of components is shown at800, as per one embodiment of the present invention. Centrifugal separator802comprises inlets804, rotor806, heavier-phase outlet808, heavier-phase weir810, heavier-phase collector812, lighter-phase outlet814, lighter-phase weir816, lighter-phase collector818, bottom vanes820, diverter disc822, separation vanes824, and rotor inlet826. A warm liquid mixture is provided to a cooler (not shown) forming liquid mixture830, comprising a product component and a carrier component. Liquid mixture830enters centrifugal separator802through inlets804. Liquid mixture830is substantially near the temperature at which the product component freezes. In other words, liquid mixture830is close, but not at the freezing point of the product component. This near approach to the freezing point causes the two components to become essentially immiscible in each other. The centrifugal action of rotor806causes liquid mixture830to separate into product component-rich liquid phase832and product component-depleted liquid phase834. Product component-rich liquid phase832is removed through lighter-phase outlet814. Product component-depleted liquid phase834is removed through heavier-phase outlet810. In some embodiments, the phases have opposite densities, resulting in product component-rich liquid phase832being lighter than product component-depleted liquid phase834. The phrase “substantially near the temperature” is defined as a temperature above and close enough to the freezing point temperature to cause the product component and the carrier component to be essentially immiscible. This is within 20 C above the temperature. In some embodiments, the temperature above and close enough to the freezing point is within 1 C above the freezing point. In other embodiments, the temperature above and close enough to the freezing point is within 5 C above the freezing point.

In some embodiments, the carrier component comprises any compound or mixture of compounds with a freezing point below the temperature. In some embodiments, the carrier component and the product component differ in dipole moment, component solubility, size, shape, hydrogen bonding characteristics, densities, mutual affinities, or combinations thereof, wherein they are prone to form separate phases substantially near the temperature. In some embodiments, the product component comprises carbon dioxide, nitrogen oxide, sulfur dioxide, nitrogen dioxide, sulfur trioxide, hydrogen sulfide, hydrogen cyanide, water, hydrocarbons, mercury, condensed organics, or combinations thereof.

In some embodiments, the vessel promotes a stable formation of two liquid phases by minimizing turbulence or other forms of mixing. In some embodiments, the vessel avoids the phases coming to complete equilibrium by minimizing molecular transport and mixing rates. In some embodiments, the vessel maximizes mass and heat transfer coefficients between or among the two or more phases.

In some embodiments, the separating step is accomplished by a process comprising decanting, centrifuging, gravity settling, enhanced-gravity settling, and combinations thereof.

In some embodiments, the gas phase comprises a vapor form of the product component, a vapor form of the carrier component, or a combination thereof. In some embodiments, the gas phase is not in equilibrium with the product component-rich liquid phase and the product component-depleted liquid phase due to slow transport between a bottom liquid phase and the gas phase. In some embodiments, the gas phase is substantially in equilibrium with the product component-rich liquid phase and the product component-depleted liquid phase. In some embodiments, the separating step further comprises separating the gas phase from the product component-rich liquid phase and the product component-depleted liquid phase. In some embodiments, the separating step is accomplished using a multi-phase separator.

In some embodiments, the gas phase is produced from melting the suspended solids.