METHODS AND DEVICES FOR DETECTING MERCURY ISOTOPES IN NATURAL GAS

• US 20200132648A1
• Filed: 04/19/2019
• Published: 04/30/2020
• Est. Priority Date: 10/31/2018
• Status: Active Grant

• Current Assignee: Petrochina Company Limited (China National Petroleum Corporation)
• Original Assignee: Petrochina Company Limited (China National Petroleum Corporation)
• Inventors: ZHU, Guangyou, TANG, Shunlin
• Granted Patent: US 11,119,084 B2
• Time in Patent Office: Days
• CPC Class Codes: G01N 21/6404 Atomic fluorescence
• CPC Class Codes: G01N 27/025 a current being generated within the material by induction
• CPC Class Codes: G01N 33/0045 for Hg
• CPC Class Codes: G01N 33/225 Gaseous fuels, e.g. natural gas
• CPC Class Codes: G01N 33/2835 specific substances contained in the oil or fuel
• CPC Class Codes: H01J 49/025 Detectors specially adapted to particle spectrometers data acquisition H01J49/0036; detectors per se G01T, e.g. G01T1/28, G01T1/29

Abstract

The invention provides a method and device for measuring mercury isotopes in natural gas. The method includes the following steps: (1) primary enrichment: subjecting natural gas to a three-stage cascading absorption with an acidic potassium permanganate aqueous solution, and collecting all of the acidic potassium permanganate aqueous solutions in which natural gas is absorbed in step (1); (2) mercury purification and enrichment: reducing the mercury absorbed in the step (1) to mercury vapor with a stannous chloride solution, and then purifying and enriching the mercury vapor by using an acidic potassium permanganate aqueous solution; (3) detecting the acidic potassium permanganate solution in which the mercury vapor is enriched in step (2) to determine the total mercury content therein; and (4) detecting the acidic potassium permanganate solution in which the mercury vapor is enriched in step (2) to determine the composition/content of stable mercury isotopes therein.

Claims

1. A device for detecting mercury isotopes in natural gas, comprising an enrichment-absorption system and a secondary purification-enrichment system for mercury isotopes, wherein:

the enrichment-absorption system comprises an empty impact sampler, a first absorption bottle, a second absorption bottle, and a third absorption bottle each containing an acidic potassium permanganate aqueous solution, and a silica-gel impact sampler containing a silica gel, which are connected in series by pipe lines;

the secondary purification-enrichment system comprises a nitrogen-gas cylinder, a collection bottle with potassium permanganate absorption liquid in which mercury isotope is absorbed, and a secondary enrichment-absorption bottle containing an acidic potassium permanganate aqueous solution, which are connected in series by pipe lines, wherein the secondary purification-enrichment system further comprises a stannous-chloride storage bottle, which is connected to a pipe line between the nitrogen-gas cylinder and the collection bottle with potassium-permanganate absorption liquid via a peristaltic pump and through a pipe line.

2. The device according to claim 1, wherein each of the empty impact sampler, the first absorption bottle, the second absorption bottle, the third absorption bottle, the silica-gel impact sampler, the collection bottle with potassium-permanganate absorption liquid and the secondary enrichment-absorption bottle is a borosilicate glass bottle and is provided with a gas inlet and a gas outlet at the respective top thereof, wherein the gas inlet communicates with the inner space of the bottle through a glass tube which is provided inside the bottle and extends to the lower part of the bottle.

3. The device according to claim 2, wherein in the enrichment-absorption system, the respective gas outlet of the impact sampler, the first absorption bottle, the second absorption bottle, the third absorption bottle and the silica-gel impact sampler is respectively connected to the gas inlet of the adjacent bottle via pipe lines, and the gas inlet of the empty impact sampler is connected to the natural gas well outlet of the natural gas well;

and

in the secondary purification-enrichment system, the gas outlet of the nitrogen-gas cylinder is connected to the gas inlet of the collection bottle with potassium permanganate absorption liquid, and the gas outlet of the collection bottle with potassium permanganate absorption liquid is connected to the gas inlet of the secondary enrichment-absorption bottle.

4. The device according to claim 1, wherein the enrichment-absorption system further comprises a cumulative gas flow meter, which is connected via a pipe line to the gas outlet of the silica-gel impact sampler.

5. The device according to claim 1, wherein the secondary purification-enrichment system further comprises a mercury-trapping gold tube which is disposed on a pipe line connecting the nitrogen-gas cylinder and the collection bottle with potassium permanganate absorption liquid, and approximates to the gas outlet of the nitrogen-gas cylinder.

6. The device according to claim 1, further comprising a detector for detecting the total mercury content of the mercury enriched in the secondary enrichment-absorption bottle and a detector for detecting the composition of stable isotopes of the mercury enriched in the secondary enrichment-absorption bottle.

7. The device according to claim 6, wherein the detector for detecting the total mercury content of the mercury enriched in the secondary enrichment-absorption bottle is a cold atomic fluorescence mercury detector, and the detector for detecting the composition of stable isotopes of the mercury enriched in the secondary enrichment-absorption bottle is a multi-collector inductively-coupled plasma mass spectrometer.

19. The method according to claim 8, which performs the detection by the device for detecting mercury isotopes in natural gas according to claim 1.

8. A method for detecting mercury isotopes in natural gas, comprising the steps of:

(1) primary enrichment;

subjecting natural gas to a three-stage cascading absorption with an acidic potassium permanganate aqueous solution, and collecting all of the acidic potassium permanganate aqueous solutions in which natural gas is absorbed in step (1);

(2) mercury purification and enrichment;

reducing the mercury absorbed in the step (1) to mercury vapor with a stannous chloride solution, and then purifying and enriching the mercury vapor by using an acidic potassium permanganate aqueous solution;

(3) detecting the acidic potassium permanganate solution in which the mercury vapor is enriched in step (2) to determine the total mercury content therein;

(4) detecting the acidic potassium permanganate solution in which the mercury vapor is enriched in step (2) to determine the composition/content of stable mercury isotopes therein.

9. The method according to claim 8, wherein the natural gas in step (1) has a flow rate of 0.5 to 0.7 L/h.

10. The method according to claim 8, wherein step (1) further comprises passing the natural gas firstly into the empty impact sampler and then passing the natural gas out from the empty impact sampler into three cascading acidic-potassium-permanganate absorption bottles to perform the three-stage cascading absorption, and passing the residual natural gas after absorption into a silica-gel impact sampler.

11. The method according to claim 8, wherein step (1) further comprises controlling the time for three-stage cascading absorption for natural gas in step (1), so that the collected acidic potassium permanganate solution has a mercury content of equal to or greater than 1.0 ng/ml.

12. The method of claim 8, wherein step (2) is the step of reducing the mercury absorbed in step (1) to mercury vapor with an aqueous stannous chloride solution having a concentration of 15 to 25 w/v %.

13. The method according to claim 8, wherein the acidic potassium permanganate aqueous solutions used in step (1) have an acid concentration of 10%, and a potassium permanganate concentration of 4% each independently;

and the acidic potassium permanganate aqueous solutions used in step (2) have an acid concentration of 10%, and a potassium permanganate concentration of 1% each independently.

14. The method according to claim 8, wherein the acid in the acidic potassium permanganate aqueous solutions used in step (1) and step (2) is sulfuric acid, respectively.

15. The method of claim 8, wherein step (2) comprises pumping a stannous chloride solution into the acidic potassium permanganate solution in which a natural gas is absorbed, collected in step (1), using nitrogen gas as a carry gas, to reduce mercury to mercury vapor, and feeding the mercury vapor into the acidic potassium permanganate aqueous solution with nitrogen gas to purify and enrich the mercury vapor.

16. The method according to claim 15, wherein the nitrogen gas used as a carry gas in step (2) is subjected to mercury trapping treatment prior to contacting the acidic potassium permanganate solution collected in step (1).

17. The method according to claim 8, wherein step (3) is the step of detecting the acidic potassium permanganate solution in which the mercury vapor is enriched in step (2) with a cold atomic fluorescence mercury detector;

and step (4) is the step of detecting the acidic potassium permanganate solution in which the mercury vapor is enriched in step (2) with a multi-collector inductively coupled plasma mass spectrometer.

18. The method according to claim 8, further comprising a step (5) of:

comparing and analyzing the composition information for the mercury isotopes in mass fractionation and mass-independent fractionation in different types of natural gas based on the detection results in steps (3) and (4), establishing the mercury information characteristics in mass fractionation and mass-independent fractionation in different types of natural gas, and establishing an identification parameter system for natural gas genesis, evaluating the favorable exploration area and providing basis for oil-gas exploration.