METHOD FOR REGULATING AND CONTROLLING GENERATED CRYSTAL FORM OF NATURAL GAS HYDRATE

Abstract

A method for regulating and controlling a generated crystal form of a natural gas hydrate is provided. A mixture composed of a salt substance, a surfactant, a water-soluble thermodynamic additive and water is introduced in a generation process of the natural gas hydrate. The salt substance and the surfactant also have a synergistic effect with a water-soluble thermodynamic accelerator. The addition of the salt substance and the surfactant can change a local solubility of the water-soluble thermodynamic additive in water, so that the regulating and controlling process of the hydrate crystal can be realized, thereby improving a hydrate gas storage capacity and solving the problem of low natural gas storage capacity in the generated natural gas hydrate in a water-soluble thermodynamic additive system.

Claims

1. A method for regulating and controlling a generated crystal form of a natural gas hydrate, comprising the following steps: introducing a mixture composed of a salt substance, a surfactant, a water-soluble thermodynamic additive, and water in a generation process of the natural gas hydrate, and then controlling a temperature at 274.15 K-288.15 K and a pressure at 6 MPa-8 MPa.

2. The method according to claim 1, wherein the mixture is subjected to an ultrasonic wave dispersion.

3. The method according to claim 1, wherein the water-soluble thermodynamic additive is selected from one of tetrahydrofuran, tetrabutylammonium bromide, and tetrabutylammonium fluoride.

4. The method according to claim 1, wherein a molar fraction of the water-soluble thermodynamic additive in the water is 1.0%-5.6%.

5. The method according to claim 1, wherein a ratio of a total mass of the salt substance and the surfactant to a mass of the water-soluble thermodynamic additive is between 1:9 and 1:3, and a ratio of a mass of the surfactant to a mass of the salt substance is between 1:2 and 1:6.

6. The method according to claim 1, wherein the surfactant is selected from one of sodium dodecyl sulfate, sodium dodecyl benzene sulfonate, and disodium monolauryl sulfosuccinate.

7. The method according to claim 1, wherein the salt substance is selected from one of sodium chloride, potassium chloride, and potassium nitrate.

8. The method according to claim 1, wherein the method is applied in a natural gas storage and transportation.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure is a PXRD spectrum of a natural gas hydrate obtained in Embodiment 1.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] The following further explains the present invention instead of a limitation to the present invention.

Embodiment 1

[0029] Based on a total mass of 100.00 g, 1.3 g of NaCl, 0.5 g of SDS and 15.00 g of THF were weighed by a balance, and the rest was the mass of water. Firstly, the weighed NaCl, SDS and THF were placed in a closed conical flask and subjected to ultrasonic wave dispersion for 3.5 hours. After completion, the weighed water was added to the dispersed liquid and the ultrasonic wave dispersion was continued for 1.5 hours. After completion, the reaction solution was used for generation reaction of a methane hydrate, and the obtained methane gas storage capacity was 71.43 V/V under the conditions of an initial pressure of 7 MPa and an initial temperature of 274.15 K. At the same time, a pure type I methane hydrate was found in the generated hydrate.

Comparative example 1:

[0030] Referring to Embodiment 1, the difference was that NaCl and SDS were not added. As a result, it was found that the generated hydrate was only a type II THF/CH.sub.4 mixed hydrate (16(CH.sub.4).Math.8(THF).Math.136H.sub.2O) or 16(CH.sub.4).Math.8(THF+CH.sub.4).Math.136H.sub.2O).

Embodiment 2

[0031] Based on a total mass of 100.00 g. 2.4 g of NaCl, 0.6 g of SDBS and 17.00 g of THF were weighed with a balance, and the rest was the mass of water. Firstly, the weighed NaCl, SDS and THF were placed in a closed conical flask and subjected to ultrasonic wave dispersion for 5 hours. After completion, the weighed water was added to the dispersed liquid and the ultrasonic wave dispersion was continued for 2 hours. After completion, the reaction solution was used for generation reaction of a methane hydrate, and the obtained methane gas storage capacity was 90.84 V/V under the conditions of an initial pressure of 7 MPa and an initial temperature of 274. 15 K. At the same time, a pure type I methane hydrate was found in the generated hydrate.

Embodiment 3

[0032] Based on a total mass of 100.00 g. 4.30 g of NaCl, 0.80 g of SDS and 18.00 g of THF were weighed with a balance, and the rest was the mass of water. Firstly, the weighed NaCl, SDS and THF were placed in a closed conical flask and subjected to ultrasonic wave dispersion for 4 hours. After completion, the weighed water was added to the dispersed liquid and the ultrasonic wave dispersion was continued for 1.5 hours. After completion, the reaction solution was used for generation reaction of a methane hydrate, and the obtained methane gas storage capacity was 121.81 V/V under the conditions of an initial pressure of 7 MPa and an initial temperature of 274.15 K. At the same time, a pure type I methane hydrate was found in the generated hydrate, which means that the solution according to the present invention can smoothly realize the regulating and controlling process of the hydrate crystal under the condition that a molar concentration of THF is close to 5.60 mol %.