ENVIRONMENTALLY FRIENDLY NATURAL GAS HYDRATE INHIBITOR AND APPLICATION

Abstract

The present invention belongs to the technical field of natural gas hydrates (NGHs), and provides an environmentally friendly NGH inhibitor and application. The hydrate inhibitor has a component of nisin, and further comprises chitooligosaccharide and an alcohol thermodynamic hydrate inhibitor, that can enhance the thermostability of the inhibitor and the inhibitory effect for NGHs. The optimal application conditions of the NGH inhibitor of the present invention are: temperatures of −10 to 100° C., pressures of 0.1 to 25 MPa, and a maximum subcooling degree of 12° C. The inhibitor of the present invention has good NGH inhibitory performance and certain antibacterial effects, which is a low-dose, degradable, high temperature resistant, green, environmental protective, safe and efficient NGH inhibitor, that can be used for the fields of oil-gas transportation and NGHs, and provides a new solution for field application of green natural hydrate inhibitors.

Claims

1. An environmentally friendly natural gas hydrate inhibitor, wherein a component of the natural gas hydrate inhibitor is nisin.

2. The environmentally friendly natural gas hydrate inhibitor according to claim 1, further comprises chitooligosaccharide and an alcohol thermodynamic hydrate inhibitor.

3. An environmentally friendly natural gas hydrate complex inhibitor according to claim 1, wherein the mass fraction of the nisin in a system to be regulated does not exceed 5 wt %.

4. The environmentally friendly natural gas hydrate complex inhibitor according to claim 3, wherein the chitooligosaccharide is selected from low-molecular-weight chitosan having water solubility and antibacterial activity with a molecular weight of 500-5000; and the mass fraction of the chitooligosaccharide in the system to be regulated does not exceed 1.5 wt %.

5. The environmentally friendly natural gas hydrate complex inhibitor according to claim 1, wherein the alcohol thermodynamic hydrate inhibitor is one or a mixture of more than one of methanol, ethylene glycol, glycerol, butanol, and polyethylene glycol; and the mass fraction of the alcohol thermodynamic hydrate inhibitor in the system to be regulated does not exceed 3 wt %.

6. The environmentally friendly natural gas hydrate complex inhibitor according to claim 3, wherein the alcohol thermodynamic hydrate inhibitor is one or a mixture of more than one of methanol, ethylene glycol, glycerol, butanol, and polyethylene glycol; and the mass fraction of the alcohol thermodynamic hydrate inhibitor in the natural gas hydrate complex inhibitor does not exceed 3 wt %.

7. An application of the environmentally friendly natural gas hydrate inhibitor in oil-gas transportation and natural gas hydrate, wherein the natural gas hydrate inhibitor is applied under the conditions of absolute pressures of 0.1 to 25 MPa, temperatures of −10 to 100° C., and a maximum subcooling degree of 12° C.

Description

DESCRIPTION OF DRAWINGS

[0016] The sole FIGURE is a schematic diagram of the application of the environmentally friendly NGH complex inhibitor in the present invention.

[0017] In the sole FIGURE: 1 fermentation filler system; 2 fermenter; 3 alkaline solution nozzle; 4 filler port; 5 temperature sensor; 6 pH value sensor; 7 data monitoring system; 8 membrane separation device; 9 titer determination system; 10 compounding filler system; 11 mixing container; 12 inhibitor preparation and control system; 13 annular nozzle; 14 oil-gas pipeline.

DETAILED DESCRIPTION

[0018] Specific embodiments are described below. The following embodiments are intended only to describe implementation modes of the present invention and not to limit all the implementation modes of the present invention.

Embodiment 1

[0019] The NGH complex inhibitor in the present invention can be prepared and applied by the method shown in the sole figure, comprising the following steps:

[0020] Step 1: establishing an NGH inhibitor production facility on a field of NGH inhibitor application demand, comprising a culture system of Lactococcus lactis, a membrane separation system, an inhibitor mixing system and an inhibitor injection system, wherein the culture system of Lactococcus lactis comprises a fermentation filler system 1, a fermenter 2 and a data monitoring system 7; the membrane separation system comprises a membrane separation device 8 and a nisin titer determination system 9; the inhibitor mixing system comprises an inhibitor compounding filler system 10, a mixing container 11 and a stirring blade; and the inhibitor injection system comprises an inhibitor compounding and control system 12 and an annular nozzle 13.

[0021] Step 2: delivering nutrients needed for the culture of Lactococcus lactis through the fermentation filler system 1, comprising 1% sucrose, 1% protein peptone, 2% potassium dihydrogen phosphate, 0.2% sodium chloride, and 0.02% magnesium sulfate; inoculating 5% Lactococcus lactis in the fermenter 2, with cultured fluid accounting for ⅔ of the total volume of the fermenter, and the cultured fluid having an initial pH value of 7; culturing by fed-batch fermentation.; pre-culturing at culture temperature of 35° C. for 24 h; continuously replenishing sucrose and water consumed by fermentation production through a feeding port 4 located at the top of the fermenter; replenishing 1 g of sucrose per liter of cultured fluid per hour; and making a rate of water replenishment consistent with an outflow rate of fermentation broth;

[0022] Step 3: collecting and recording the temperature and pH value in the fermenter in real-time, and maintaining the culture temperature of 35° C. according to the data collected by a temperature sensor 5; evenly spraying the solution of caustic soda into the fermenter from alkaline solution nozzles 3 distributed in several positions on the top of the fermenter according to the data fed back by a pH value sensor 6, so that the pH value of the cultured fluid is maintained at about 7 to prevent the local pH value of the cultured fluid from rising too much; and after full fermenting in the fermenter 2, delivering cultured fluid of Lactococcus lactis to a membrane separation device 8;

[0023] Step 4: conducting stepwise concentration-leaching treatment on the cultured fluid of Lactococcus lactis by the membrane separation device 8 formed by a microfiltration membrane (aperture of 0.2 μm) and a polysulfone hollow fiber ultrafiltration membrane (MWCO 10kDa) under maximum transmembrane pressure difference of 0.1 MPa; intercepting microorganisms and macromolecular impurity protein in the cultured fluid to obtain relatively pure nisin fermentation broth; sampling the fermentation broth, and analyzing and determining titer by an agar diffusion method in the nisin titer determination system 9, wherein nisin titer in the fermentation broth should not be less than 3500 IU/ml; and transporting the nisin fermentation broth to an inhibitor mixing container 11;

[0024] Step 5: adding chitooligosaccharide and alcohol THIs such as glycol into the inhibitor mixing container 11 through the inhibitor compounding filler system 10, with the mass fraction of the chitooligosaccharide as 1 wt % and the mass fraction of THIs as 3 wt %; making a stirring blade fully stirring in a preparation container at the tip speed of 1 m/s to evenly mix all components of the inhibitor; in the case of uninterrupted culture and continuous preparation, considering that the solution located at the bottom of the mixing container 11 is fully mixed to satisfy the composition requirements of the complex inhibitor, to prepare the NGH complex inhibitor of the present invention;

[0025] Step 6: controlling and using the prepared NGH complex inhibitor by the inhibitor compounding and control system 12 through a valve; injecting the hydrate inhibitor into a pipeline through the annular nozzle 13 arranged on the inner wall of an oil-gas pipeline 14, so that the inhibitor can uniformly act on the fluid inside the pipeline; by regulating the injection flow velocity of the inhibitor, adding the prepared NGH complex inhibitor according to a proportion of 5% of the fluid flow in the pipeline, and using the complex inhibitor under a subcooling degree less than 12° C. to realize field preparation and application of the NGH inhibitor.

Embodiment 2

[0026] The present invention provides an environmentally friendly NGH inhibitor and a complex inhibitor. The inhibitory effect of the hydrate inhibitor on the NGH is verified in a high-pressure reactor through the following test:

[0027] The high-pressure reactor used in the test has a volume of 0.1 L and maximum bearing pressure of 10 MPa; the operating range of a water bath is −10 to 30° C.; and the rotating speed of a magnetic rotor is 200 to 300 r/min. Aqueous solutions containing the inhibitors are respectively added to the reactor according to the components shown in Table 1. To ensure that the temperature and the pressure in the reactor before the tests are beyond the phase equilibrium region of the hydrate, pure methane gas is filled to 8 MPa in the high-pressure reactor at 15° C.

TABLE-US-00001 TABLE 1 Solution Components in Reactor Stirring Sample Solution Speed Group Solution Components Concentration 200 rpm S1 Nisin   2 wt % Monoethylene glycol   3 wt % S2 Nisin   5 wt % S3 Nisin  2.5 wt % S4 Nisin 1.25 wt % S5 Nisin (treatment at 50° C.)  2.5 wt % D1 Deionized water — D2 PVP   2 wt % Monoethylene glycol   3 wt % D3 PVP   5 wt % 300 rpm S6 Nisin   2 wt % Monoethylene glycol   3 wt % S7 Nisin  0.5 wt % Monoethylene glycol  1.5 wt % S8 Nisin   5 wt % S9 Nisin  2.5 wt % S10 Nisin   1 wt % S11 Nisin  0.5 wt % S12 Nisin  0.2 wt % S13 Nisin  0.1 wt % D4 Deionized water — D5 PVP   2 wt % Monoethylene glycol   3 wt %

[0028] After the temperature and pressure data in the reactor are stable, the water bath is set to be cooled from 15° C. to 0.5° C. at a constant rate of 2° C./h. The duration time of a single test is 1000 min, and each group of tests is repeated for at least three times to reduce experiment talerror. Test data is shown in Table 2. T.sub.1 is the hydrate onset time in the reactor.

TABLE-US-00002 TABLE 2 Performance Test Results of NGH Inhibitor Stirring Sample Total Speed Group Time/min T.sub.1/min 200 rpm S1 1000 365.18 S2 342.48 S3 299.12 S4 303.78 S5 335.81 D1 226.36 D2 335.98 D3 329.63 300 rpm S6 1000 383.01 S7 363.00 S8 368.16 S9 367.33 S10 330.63 S11 350.50 S12 325.46 S13 262.56 D4 224.70 D5 398.03

[0029] The above test results indicate that the environmentally friendly NGH inhibitor and the application provided by the present invention have a good NGH inhibitory effect, obviously prolong the induction time of NGH nucleation compared with a pure water system, and have an inhibitory effect which exceeds polymeric KHI-PVP.

[0030] The above embodiments are only used for illustrating the feasible specific implementation modes of the present invention. The present invention is not limited to the above embodiments. Various modifications and changes made without departing from the scope of the present invention shall be included in the protection scope of the present invention.