# US 9,752,827 B2 · Method and system of maintaining a liquid level in a distillation tower

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- Number: US 9,752,827 B2
- Document ID: US9752827B2
- Status: Granted
- Kind: B2
- Application number: 14/516,686
- Filed: 2014-10-17
- Published: 2015-06-11
- Granted: 2017-09-05
- Earliest claimed: 2013-12-06
- Assignees: ExxonMobil Upstream Research Company
- Applicants: Jaime A. Valencia
- Inventors: Jaime A. Valencia
- Web page: https://patentgrep.com/patent/US9752827B2

## CPC

- F25J 3/0266: {separation of carbon dioxide (production of carbon dioxide in general C01B32/00)}
- B01D 3/324: {Tray constructions}
- C07C 7/05: with the aid of auxiliary compounds
- F25J 1/0022: {Hydrocarbons, e.g. natural gas}
- F25J 1/0027: {Oxides of carbon, e.g. CO2}
- F25J 3/0209: {Natural gas or substitute natural gas}
- F25J 3/0233: {separation of CnHm with 1 carbon atom or more}
- F25J 3/061: {Natural gas or substitute natural gas}
- F25J 3/0635: {separation of CnHm with 1 carbon atom or more}
- F25J 3/067: {separation of carbon dioxide (production of carbon dioxide in general C01B32/00)}
- F25J 3/08: Separating gaseous impurities from gases or gaseous mixtures {or from liquefied gases or liquefied gaseous mixtures}(cold traps B01D8/00)
- C10L 3/101: {Removal of contaminants}
- C10L 2290/543: Distillation, fractionation or rectification for separating fractions, components or impurities during preparation or upgrading of a fuel
- C10L 2290/545: Washing, scrubbing, stripping, scavenging for separating fractions, components or impurities during preparation or upgrading of a fuel
- C10L 2290/58: Control or regulation of the fuel preparation of upgrading process
- F25J 2200/02: in a single pressure main column system
- F25J 2200/30: using a side column in a single pressure column system
- F25J 2200/50: using multiple (re-)boiler-condensers at different heights of the column
- F25J 2200/74: Refluxing the column with at least a part of the partially condensed overhead gas
- F25J 2200/90: Details relating to column internals, e.g. structured packing, gas or liquid distribution
- F25J 2205/04: in the feed line, i.e. upstream of the fractionation step
- F25J 2205/20: using solidification of components
- F25J 2220/66: Separating acid gases, e.g. CO2, SO2, H2S or RSH
- F25J 2235/60: the fluid being (a mixture of) hydrocarbons
- F25J 2280/40: Control of freezing of components
- F25J 2290/12: Particular process parameters like pressure, temperature, ratios
- F25J 2290/40: Vertical layout or arrangement of cold equipments within in the cold box, e.g. columns, condensers, heat exchangers etc.
- Y02C 20/40: of CO2
- F25J: LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS {OR LIQUEFIED GASEOUS} MIXTURES BY PRESSURE AND COLD TREATMENT {OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE (cryogenic pumps F04B37/08; gas storage vessels, gas holders F17; filing vessels with, or discharging from vessels, compressed, liquefied or solidified gases F17C; refrigeration machines, plants, or systems F25B)}
- B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28)
- C07C: ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C10L: FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G OR C10K; LIQUIFIED PETROLEUM GAS; USE OF ADDITIVES TO FUELS OR FIRES; FIRE-LIGHTERS
- Y02C: CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]

## Abstract

The present disclosure provides a distillation tower that may include a stripper section constructed and arranged to separate a feed stream at a temperature and pressure at which the feed stream forms no solid; a controlled freeze zone section constructed and arranged to separate the feed stream at a temperature and pressure at which the feed stream forms a solid; a melt tray assembly in the controlled freeze zone section that includes a liquid; an underflow weir in the controlled freeze zone section that alters a flow of the liquid in the melt tray assembly; an overflow weir in the controlled freeze zone section that works with the underflow weir to alter the flow of the liquid in the melt tray assembly and is adjacent to the underflow weir; and a covering element in the controlled freeze zone section that is connected to and extends from the underflow weir.

## Claims

### Claim 1

A method of maintaining a liquid level in a distillation tower, the method comprising:
forming a freezing zone vapor stream from a feed stream in a stripper section of a distillation tower at a temperature and pressure at which no solid forms in the stripper section;
forming a solid in a controlled freeze zone section of the distillation tower from the feed stream;
preventing accumulation of solid in the controlled freeze zone section by at least providing:
a melt tray assembly in the controlled freeze zone section that includes a liquid, melt tray, and bubble cap;
an underflow weir in the controlled freeze zone section that alters a flow of the liquid in the melt tray assembly;
an overflow weir in the controlled freeze zone section that works with the underflow weir to alter the flow of the liquid in the melt tray assembly and is adjacent to the underflow weir;
a covering element in the controlled freeze zone section that is connected to and extends from the underflow weir, over the overflow weir, and towards the controlled freeze zone wall;
maintaining a predetermined liquid level of liquid in a melt tray assembly of the controlled freeze zone section by:
altering a flow of the liquid in the melt tray assembly such that the liquid flows from a bottom melt tray assembly portion of the melt tray assembly to a top melt tray assembly portion of the melt tray assembly; and
altering the flow of the liquid in the melt tray assembly such that the liquid flows from the top melt tray assembly portion toward the stripper section; and
closing a flow control device that connects the stripper section and the controlled freeze zone section such that the level of the liquid in the melt tray assembly rises and is greater than the predetermined liquid level and such that the liquid acts to melt solids that have accumulated in the controlled freeze zone above the predetermined liquid level.

### Claim 2 (depends on 1)

The method of claim 1, further comprising directing vapor that accumulated while altering the flow of the liquid, upwards toward a top section of the controlled freeze zone section.

### Claim 3 (depends on 1)

The method of claim 1, further comprising producing hydrocarbons from the feed stream.

### Claim 4 (depends on 1)

The method of claim 1, wherein the covering element is at an angle of from 1 to 45 degrees relative to the controlled freeze zone wall.

### Claim 5 (depends on 1)

The method of claim 1, further comprising preventing an accumulation of vapor in the controlled freeze zone section by at least providing an anti-vapor lock that is connected to and extends from the controlled freeze zone wall toward the covering element, where there is a gap between the end of the anti-vapor lock that is closest to the covering element and the covering element.

### Claim 6 (depends on 5)

The method of claim 5, wherein the anti-vapor lock extends from the controlled freeze zone wall at an angle of from 1 to 45 degrees relative to the controlled freeze zone wall.

### Claim 7

A method for modifying a liquid level in a distillation tower, the method comprising:
providing a distillation tower, wherein the distillation tower comprises:
a stripper section constructed and arranged to separate a feed stream at a temperature and pressure at which the feed stream forms no solid;
a controlled freeze zone section constructed and arranged to separate the feed stream at a temperature and pressure at which the feed stream forms a solid, wherein the controlled freeze zone section includes a controlled freeze zone wall;
a melt tray assembly in the controlled freeze zone section that includes a liquid, melt tray, and bubble cap;
an underflow weir in the controlled freeze zone section that alters a flow of the liquid in the melt tray assembly;
an overflow weir in the controlled freeze zone section that works with the underflow weir to alter the flow of the liquid in the melt tray assembly and is adjacent to the underflow weir;
a covering element in the controlled freeze zone section that is connected to and extends from the underflow weir, over the overflow weir, and towards the controlled freeze zone wall;
an anti-vapor lock that is connected to and extends from the controlled freeze zone wall toward the covering element, where there is a gap between the end of the anti-vapor lock that is closest to the covering element and the covering element;
a channel connecting the stripper section to the controlled freeze zone section; and
a flow control device to control the flow of liquid from the controlled freeze zone section to the stripper section;
forming a freezing zone vapor stream from the feed stream in the stripper section;
forming a solid in the controlled freeze zone section from the feed stream;
modifying the liquid level in the melt tray assembly by opening or closing the flow control device, wherein when the flow control device is open the maximum level of liquid in the melt tray assembly is at a predetermined height that is determined by the height of the overflow weir, and wherein when the flow control device is closed the maximum level of liquid in the melt tray assembly is greater than the predetermined height and is greater than the height of the bubble cap; and
closing the flow control device for a period of time that is sufficient to melt solids that have accumulated in the controlled freeze zone above the predetermined height.

### Claim 8 (depends on 7)

The method of claim 7, wherein the period of time is from five minutes to thirty minutes.

### Claim 9 (depends on 7)

The method of claim 7, wherein the channel comprises at least one of an internal channel and an external channel.

### Claim 10 (depends on 9)

The method of claim 9, wherein the internal channel is inside of the controlled freeze zone section and the stripper section and wherein the internal channel includes the overflow weir.