Apparatus and combined process for carbon dioxide gas separation

Patent metadata

Field	Value
Publication number	US-2018148331-A1
Application number	US-201715487765-A
Country	US
Kind code	A1
Filing date	Apr 14, 2017
Priority date	Nov 25, 2016
Publication date	May 31, 2018
Grant date	—

Abstract

An apparatus and a combined process for carbon dioxide gas separation, combining the hydrate-based process with the chemical absorption process, which reduces secondary pollution and allows the efficient continuous separation of carbon dioxide gas without increasing the pressure and thereby the operating cost is reduced significantly. The apparatus and combined process can be applied in the separation of carbon dioxide in IGCC synthetic gas, natural gas and biogas, and address the issues of the existing processes such as high energy consumption, low throughput, and secondary pollution.

First claim

1 . An apparatus for carbon dioxide gas separation, comprising a gas source, a flow distributor, a gas flow meter, a venturi jet unit provided with two liquid inhaling inlets, a tubular hydrate reaction unit, a gas-liquid-solid three-phase separation unit, a first slurry pump, a hydrate dissociation unit provided with a first pressure maintaining valve at its top, a second slurry pump, and a solution saturation tank provided with a third safety valve at its top, which are communicated sequentially, further comprising a chemical absorption tower, a second corrosion-resistant pump, a heat exchanger, a regeneration tower, a third corrosion-resistant pump, and a reservoir containing a CO 2 chemical absorbent, which are communicated sequentially, wherein,
the reservoir is communicated with an upper portion of the chemical absorption tower through a first corrosion-resistant pump to form a cycle; the flow distributor is communicated with a bottom inlet of the solution saturation tank, and a bottom outlet of the solution saturation tank is communicated with the two liquid inhaling inlets of the venturi jet unit through sequentially a liquid-phase mass flow meter and a ninth stop valve; a second safety valve is disposed at a top of the gas-liquid-solid three-phase separation unit; the gas-liquid-solid three-phase separation unit is communicated with a lower portion of the chemical absorption tower through sequentially a third one-way gas valve, a second pressure maintaining valve and a fourth one-way gas valve. an upper portion of the chemical absorption tower is communicated with a hydrogen collecting tank provided with a first safety valve through a fifth one-way gas valve; the regeneration tower is further communicated with the hydrate dissociation unit, and regenerated carbon dioxide gas is directed to the hydrate dissociation unit in which it will be mixed with the carbon dioxide produced during the dissociation and then subjected to a subsequent processing.

2 . The apparatus according to claim 1 , wherein the venturi jet unit comprises sequentially a body section, a convergent section, a throat section and a divergent section between its inlet and outlet; the body section has a length of 250 mm, and a inner diameter identical with a inner diameter of the tubular hydrate reaction unit; a distance between the narrowest portion of the throat section and an outlet of the divergent section is 80˜100 mm;
one of the two liquid inhaling inlets of the venturi jet unit is disposed between the narrowest portion of the throat section and the inlet of the venturi jet unit at a position 30˜50 mm away from the narrowest portion of the throat section, and communicated with the ninth stop valve; the other one of the two liquid inhaling inlets is disposed at the narrowest portion of the throat section, and communicated with the ninth stop valve through a ball valve;
a Laval nozzle with a length of 100˜120 mm is disposed at a inlet of the body section of the venturi jet unit; the Laval nozzle has a large opening with a maximum outer diameter identical with the inner diameter of the tubular hydrate reaction unit, and an small opening with a maximum diameter equal to ½ of the diameter of the large opening; a diameter of the narrowest portion of the Laval nozzle is ⅙ of the diameter of the large opening.

3 . The apparatus according to claim 1 , wherein the tubular hydrate reaction unit comprises three straight pipe sections and two bent pipes; temperature sensors and pressure sensors are disposed on each straight pipe section; the tubular hydrate reaction unit and the solution saturation tank are respectively provided with an external water-cooled jacket, and the temperature of the tubular hydrate reaction unit and the solution saturation tank is controlled by an external cooling machine.

4 . The apparatus according to claim 1 , wherein the gas source and the flow distributor are communicated through a first one-way gas valve; the gas-liquid-solid three-phase separation unit, the first slurry pump, the hydrate dissociation unit, the second slurry pump, and the solution saturation tank, are sequentially communicated through a first stop valve, a second stop valve, a third stop valve and a fourth stop valve; the heat exchanger, the regeneration tower and the third corrosion-resistant pump are sequentially communicated through a seventh stop valve and an eighth stop valve; the reservoir, the first corrosion-resistant pump and the chemical absorption tower are sequentially communicated through a sixth stop valve and a fifth stop valve; the flow distributor and the bottom inlet of the solution saturation tank are communicated through a tenth stop valve.

5 . A combined process for carbon dioxide gas separation using the apparatus according to claim 1 , comprising the following steps:
(1): distributing a IGCC synthetic gas into two flows via the flow distributor; wherein one flow is directed to the solution saturation tank to sparge a solution containing an hydrate promoter for pre-saturation by bottom-sparging and maintaining a pressure of 3-5 MPa in the solution saturation tank; wherein the other flow is directed to the venturi jet unit; directing the saturated solution in the solution saturation tank to the venturi jet unit and atomizing the saturated solution by spraying and mixing with the IGCC synthetic gas flow; then directing the atomized solution to the tubular hydrate reaction unit to form a hydrate slurry; a temperature of 0-10° C. and a pressure of 3-6 MPa are maintained in the tubular hydrate reaction unit and the solution saturation tank respectively; (2): directing the hydrate slurry formed in the step (1) from the tubular hydrate reaction unit to the gas-liquid-solid three-phase separation unit in which a gas is separated from the hydrate slurry; flowing the hydrate slurry out from a lower portion of the gas-liquid-solid three-phase separation unit, and directing the hydrate slurry to the hydrate dissociation unit via the first slurry pump; after dissociation, discharging an obtained carbon dioxide via the first pressure maintaining valve for subsequent processing, and directing obtained water via the second slurry pump to the solution saturation tank for reuse; directing the gas separated in the gas-liquid-solid three-phase separation unit, in which a molar ratio of carbon dioxide is ranged from 6% to 17%, to the lower portion of the chemical absorption tower via the second pressure maintaining valve, removing carbon dioxide by contacting with the CO 2 chemical absorbent which is directed from the reservoir to the chemical absorption tower, and then directing from the upper portion of the chemical absorption tower to the hydrogen collecting tank in which hydrogen with a purity of 95%-99% is collected; directing the CO 2 chemical absorbent, which has absorbed carbon dioxide, through a second corrosion-resistant pump to the heat exchanger for heat exchanging and then directing to the regeneration tower in which the CO 2 chemical absorbent is regenerated by gas stripping at 100-150° C. to obtain a regenerated carbon dioxide and a regenerated chemical absorbent; directing the regenerated carbon dioxide to the hydrate dissociation unit and mixing with the carbon dioxide obtained from the dissociation for subsequent processing; directing the regenerated chemical absorbent through the third corrosion-resistant pump to the reservoir for reuse.

6 . The combined process according to claim 5 , wherein the hydrate promoter is selected from one or more of tetrahydrofuran, tetrabutylammonium bromide and cyclopentane.

7 . The combined process according to claim 6 , wherein the CO 2 chemical absorbent is ethanolamine or N-methyldiethanolamine.

Assignees

• Guangzhou Inst Energy Conversion Cas

Inventors

• Li Xiaosen
• Xu Chungang
• Yu Yisong
• Chen Zhaoyang
• Huang Ningsheng
• Li Gang

Classifications

• C01B2203/0475

  the impurity being carbon dioxide · CPC title

• B01D2252/20431

  Tertiary amines · CPC title

• B01D2252/20484

  with one hydroxyl group · CPC title

• C01B3/02

  Production of hydrogen; Production of gaseous mixtures containing hydrogen · CPC title

• C01B3/52 Primary

  by contacting with liquids; Regeneration of used liquids · CPC title