# US 10,246,660 B2 · Natural-gas purification apparatus

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- Number: US 10,246,660 B2
- Document ID: US10246660B2
- Status: Granted
- Kind: B2
- Application number: 15/475,944
- Filed: 2017-03-31
- Published: 2018-10-04
- Granted: 2019-04-02
- Earliest claimed: 2017-03-31
- Assignees: Mitsubishi Heavy Industries, Ltd.
- Applicants: Mitsubishi Heavy Industries, Ltd.
- Inventors: Masayuki Eda; Wataru Matsubara; Shintaro Honjo; Susumu Okino; Hiromi Nakatani; Masaki Yushima
- Web page: https://patentgrep.com/patent/US10246660B2

## CPC

- C10L 3/104: {Carbon dioxide}
- B01D 53/22: by diffusion (manufacturing semi-permeable membranes B01D67/00; form, structure or properties of semi-permeable membranes B01D69/00; material for semi-permeable membranes B01D71/00)
- B01D 53/226: {in serial connexion}
- B01D 2256/245: Methane
- B01D 2257/504: Carbon dioxide
- C10L 2290/548: Membrane- or permeation-treatment for separating fractions, components or impurities during preparation or upgrading of a fuel
- Y02C 20/40: of CO2
- 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
- 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)
- Y02C: CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]

## Abstract

A natural-gas purification apparatus includes: a compressor that adjusts the pressure of natural gas from the ground; a cooling unit that liquefies and separates a part of natural-gas liquid by cooling the natural gas after the pressure adjustment by the compressor; a heating unit that heats the natural gas after the separation of the part; a carbon-dioxide separation unit that separates carbon dioxide from the natural gas heated by the heating unit; and an arithmetic control device that adjusts and controls at least one of the compressor, the cooling unit, and the heating unit to a value which has been set in advance according to the composition of the natural gas, such that the cooling unit will liquefy and separate the part of the natural-gas liquid in the natural gas and the carbon-dioxide separator maintains the remaining part of the natural-gas liquid in the natural gas in gaseous form.

## Claims

### Claim 1

A natural-gas purification apparatus for purifying natural gas from ground by separating carbon dioxide from the natural gas, comprising:
a pressure adjuster that adjusts a pressure of the natural gas from the ground;
a natural-gas-liquid separator that liquefies and separates a part of natural-gas liquid by cooling the natural gas after the pressure adjustment by the pressure adjuster;
a heater that heats the natural gas after the separation of the part of the natural-gas liquid by the natural-gas-liquid separator;
a carbon-dioxide separator that separates carbon dioxide from the natural gas heated by the heater through a carbon-dioxide separation membrane; and
a controller that adjusts and controls at least one of a pressure of the natural gas to be achieved by the pressure adjuster, a temperature to which the natural gas is to be cooled by the natural-gas-liquid separator, and a temperature to which the natural gas is to be heated by the heater to a value which has been set in advance according to composition of the natural gas from the ground, such that the natural-gas-liquid separator liquefies and separates the part of the natural-gas liquid in the natural gas and the carbon-dioxide separator maintains a remaining part of the natural-gas liquid in the natural gas in gaseous form.

### Claim 2 (depends on 1)

The natural-gas purification apparatus according to claim 1, further comprising:
a gas-flow-rate detector that detects a flow rate of the natural gas before the pressure adjustment by the pressure adjuster;
a gas-pressure detector that detects the pressure of the natural gas before the pressure adjustment by the pressure adjuster; and
a gas-temperature detector that detects a temperature of the natural gas before the pressure adjustment by the pressure adjuster,
wherein the controller adjusts and controls at least one of the pressure of the natural gas to be achieved by the pressure adjuster, the temperature to which the natural gas is to be cooled by the natural-gas-liquid separator, and the temperature to which the natural is to be heated by the heater to the value which has been set in advance according to the composition of the natural gas from the ground, based on information from the gas-flow-rate detector, the gas-pressure detector, and the gas-temperature detector such that the natural-gas-liquid separator liquefies and separates the part of the natural-gas liquid in the natural gas and the carbon-dioxide separator maintains the remaining part of the natural-gas liquid in the natural gas in gaseous form.

### Claim 3 (depends on 1)

The natural-gas purification apparatus according to claim 1, further comprising:
a membrane-temperature detector that detects a temperature of the carbon-dioxide separation membrane of the carbon-dioxide separator; and
a gas-dew-point detector that detects a dew point of the natural gas after the carbon-dioxide separation by the carbon-dioxide separator,
wherein the controller adjusts and controls at least one of the pressure of the natural gas to be achieved by the pressure adjuster, the temperature to which the natural gas is to be cooled by the natural-gas-liquid separator, and the temperature to which the natural gas is to be heated by the heater to the value which has been set in advance according to the composition of the natural gas from the ground, based on information from the membrane-temperature detector and the gas-dew-point detector such that the natural-gas-liquid separator liquefies and separates the part of the natural-gas liquid in the natural gas and the carbon-dioxide separator maintains the remaining part of the natural-gas liquid in the natural gas in gaseous form.

### Claim 4 (depends on 3)

The natural-gas purification apparatus according to claim 3, wherein
the membrane-temperature detector includes
an upper-limit-membrane-temperature detector that detects a temperature of the carbon-dioxide separation membrane of the carbon-dioxide separator at an upstream portion in a direction of natural-gas flow, and
a lower-limit-membrane-temperature detector that detects a temperature of the carbon-dioxide separation membrane of the carbon-dioxide separator at a downstream portion in the direction of the natural-gas flow, and
the controller
calculates a lower-limit gas temperature Tb and an upper-limit gas temperature Tt based on the dew point Td detected by the gas-dew-point detector; and
controls actuation of the heater based on information from the upper-limit-membrane-temperature detector and the lower-limit-membrane-temperature detector such that an upstream membrane temperature T1 detected by the upper-limit-membrane-temperature detector is lower than or equal to the upper-limit gas temperature Tt (T1≤Tt) and a downstream membrane temperature T2 detected by the lower-limit-membrane-temperature detector is higher than or equal the lower-limit gas temperature Tb (T2≥Tb).

### Claim 5 (depends on 4)

The natural-gas purification apparatus according to claim 4, wherein if the calculated upper-limit gas temperature Tt is higher than or equal to a withstand temperature γ of the carbon-dioxide separation membrane of the carbon-dioxide separator (Tt≥γ), the controller controls actuation of the natural-gas-liquid separator based on information from the gas-dew-point detector such that the upper-limit gas temperature Tt falls below the withstand temperature γ (Tt<γ).

### Claim 6 (depends on 5)

The natural-gas purification apparatus according to claim 5, wherein if the natural-gas-liquid separator reaches a maximum cooling temperature but the upper-limit gas temperature Tt is still higher than or equal to the withstand temperature γ (Tt≥γ), the controller controls actuation of the pressure adjuster based on the information from the gas-dew point detector such that the upper limit gas temperature Tt fall below the withstand temperature γ (Tt<γ).

### Claim 7 (depends on 4)

The natural-gas purification apparatus according to claim 4, wherein
the lower-limit-membrane-temperature detector detects a temperature of a surface on a natural-gas flow side of the carbon-dioxide separation membrane of the carbon-dioxide separator at a downstream portion in the direction of the gas flow, and
the controller figures out the downstream membrane temperature T2 based on a natural-gas-flow downstream membrane temperature T2a detected by the lower-limit-membrane-temperature detector.

### Claim 8 (depends on 4)

The natural-gas purification apparatus according to claim 4, wherein
the lower-limit-membrane-temperature detector detects a temperature of a surface on a carbon-dioxide flow side of the carbon-dioxide separation membrane of the carbon-dioxide separator at a downstream portion in the direction of the gas flow, and
the controller figures out the downstream membrane temperature T2 based on a carbon-dioxide-flow downstream membrane temperature T2b detected by the lower-limit-membrane-temperature detector.

### Claim 9 (depends on 4)

The natural-gas purification apparatus according to claim 4, wherein
the lower-limit-membrane-temperature detector includes
a downstream-natural-gas-temperature detector that detects a temperature of the gas on a natural-gas flow side of the carbon-dioxide separation membrane of the carbon-dioxide separator at a downstream portion in the direction of the gas flow, and
a downstream-carbon-dioxide-temperature detector that detects a temperature of the carbon dioxide on a carbon-dioxide flow side of the carbon-dioxide separation membrane of the carbon-dioxide separator at the downstream portion in the direction of the gas flow, and
the controller figures out the downstream membrane temperature T2 based on a downstream natural-gas temperature T2c detected by the downstream-natural-gas-temperature detector and a downstream carbon-dioxide temperature T2d detected by the downstream-carbon-dioxide-temperature detector.