Process for capturing a heavy metal contained in a moist gas, integrating a heat pump to cool the gas before eliminating water

Patent metadata

Field	Value
Publication number	US-2016175771-A1
Application number	US-201414909326-A
Country	US
Kind code	A1
Filing date	Jun 17, 2014
Priority date	Jul 31, 2013
Publication date	Jun 23, 2016
Grant date	—

Abstract

Capturing mercury or arsenic heavy metal from a moist gas containing water vapour, by:
a) cooling the moist gas by heat exchange with a heat transfer fluid produced in e) in order to obtain a gas cooled to a temperature Tf, vaporizing the heat transfer fluid; b) separating condensed water and condensates contained in the cooled gas obtained in a) obtaining a gas depleted in water and a liquid stream containing water; c) compressing vaporized heat transfer fluid obtained from a) obtaining compressed heat transfer fluid; d) heating water-depleted gas by heat exchange with compressed heat transfer fluid obtained in c) obtaining a cooled heat transfer fluid and a gas reheated to a temperature Tc; e) decompressing cooled heat transfer fluid obtained in d), recycling heat transfer fluid to a); f) contacting reheated gas obtained in d) with a capture mass for said heavy metal.

First claim

1 . A process for capturing at least one heavy metal selected from mercury and arsenic, contained in a moist gas comprising water vapour, in which the following steps are carried out:
a) cooling ( 1000 ) the moist gas by heat exchange with a heat transfer fluid produced in step e) in order to obtain a gas cooled to a temperature Tf, the heat transfer fluid being vaporized during step a); b) separating ( 2000 ) at least a portion of the condensed water contained in the cooled gas obtained in step a) in a manner such as to obtain a gas which is depleted in water and a liquid stream containing water; c) compressing ( 4000 ) the vaporized heat transfer fluid obtained from step a) in a manner such as to obtain a compressed heat transfer fluid; d) heating ( 1002 ) the water-depleted gas by heat exchange with the compressed heat transfer fluid obtained in step c) in order to obtain a cooled heat transfer fluid and a gas reheated to a temperature Tc; e) decompressing ( 5000 ) the cooled heat transfer fluid obtained in step d), the decompressed heat transfer fluid being recycled to step a); f) bringing the reheated gas obtained in step d) into contact ( 3000 ) with a capture mass for said heavy metal in order to obtain a gas depleted in heavy metal.

2 . The process according to claim 1 , in which the temperature Tc is determined in a manner such that the reheated moist gas obtained in step d) has a relative humidity of less than 90%.

3 . The process according claim 1 , in which the difference between Tc and Tf is less than 50° C.

4 . The process according to claim 1 , in which the capture mass comprises an active phase selected from at least one metallic sulphide based on a metal selected from the group constituted by copper (Cu), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co) and nickel (Ni).

5 . The process according to claim 1 , in which the capture mass comprises an active phase composed of elemental sulphur.

6 . The process according to claim 1 in which, when the moist gas contains H 2 S, the capture mass comprises an active phase composed of at least one metallic oxide of a metal selected from copper (Cu), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co) and nickel (Ni).

7 . The process according to claim 1 , in which the capture mass comprises an active phase composed of at least one metallic oxide of a metal selected from copper (Cu) and lead (Pb).

8 . The process according to claim 4 , in which the active phase is distributed over a porous support, the porous support being selected from the group constituted by aluminas, phosphorus-containing aluminas, silica-aluminas, silicas, clays, activated carbons, zeolites, titanium oxides, zirconium oxides and mixtures thereof.

9 . The process according to claim 1 , in which the heat transfer fluid is selected from hydrocarbons containing 1 to 7 carbon atoms and optionally one or more heteroatomic ligands.

10 . The process according to claim 1 , in which at least one of the following operations is carried out:
before carrying out step b), carrying out a supplemental step for cooling the cooled gas obtained in step a); before carrying out step c), carrying out a supplemental step for heating the vaporized heat transfer fluid obtained in step a); before carrying out step f), carrying out a supplemental step for heating the reheated gas obtained in step d); before carrying out step e), carrying out a supplemental step for cooling the cooled heat transfer fluid obtained in step d).

11 . The process according to claim 10 , in which exchange of heat from the vaporized heat transfer fluid obtained in step a) to the cooled heat transfer fluid obtained in step d) is carried out.

12 . The process according to claim 1 , in which in step b), a coalescer is used in order to separate the condensed water contained in the cooled gas obtained in step a).

13 . The process according to claim 1 , in which the mercury contained in the aqueous liquid stream obtained from step b) is captured.

14 . The process according to claim 1 , in which the moist gas is selected from one of the following gases: a natural gas, a shale gas, a coal gas, a synthesis gas, combustion fumes, a gaseous hydrocarbon effluent, chlor-alkali plant exhaust gases, and rare earth production exhaust gases.

15 . The process according to claim 1 , in which the moist gas is composed of a natural gas and in which before carrying out step a), the following steps are carried out:
extracting a natural gas from an underground deposit; then introducing the natural gas into a sludge elimination device; then introducing the natural gas into a gas-liquid separation device then sending the natural gas to step a); then, after step f), the following steps are carried out: eliminating at least a portion of the H 2 S and CO 2 contained in the gas depleted in heavy metal; then eliminating at least a portion of the water vapour contained in the gas depleted in heavy metal.

Assignees

• IFP Energies Nouvelles

Inventors

• Guillou Florent
• Porcheron Fabien
• Barthelet Karin
• Baudot Arnaud
• Lepine Yann
• Jubin Clotilde

Classifications

• B01D53/343

  Heat recovery · CPC title

• B01D53/64 Primary

  Heavy metals or compounds thereof, e.g. mercury · CPC title

• B01D2253/1124

  Metal oxides · CPC title

• C10L3/104

  Carbon dioxide · CPC title

• B01D53/81

  Solid phase processes · CPC title