A method of estimating changes in the volume mole ratio of components of LNG

Abstract

A method for estimating the volumetric molar ratio changes of LNG components belongs to the field of liquefied natural gas technology. Based on actual requirements, the initial mass m of LNG in the fuel tank is determined. LNG0 And the initial mass m of NG NG0 The mass m of LNG used in the commissioning process LNG1 and NG quality m NG1 The final mass of NG in the fuel tank, m NG2 The initial volume molar ratio X of each component of LNG i0 and molar mass M i ; Calculate the initial mass ratio w of each component of LNG based on the initial conditions. i ; and thus the initial mass m of each component of LNG is obtained. i0 Then, based on the initial mass ratio w of each component of LNG i The mass m of LNG used during commissioning LNG1 The mass m of each component of LNG consumed was obtained. i1 Thus, the final mass m of each component of LNG is obtained. i2， Its molar mass M compared to the components of LNG i Calculations were performed to obtain the final volume molar ratio X of each component of LNG. i2 This method is low-cost, accurate, and efficient, making it more suitable for practical application.

Description

Technical Field

[0001] This invention relates to a method for estimating the volume molar ratio changes of LNG components, belonging to the field of liquefied natural gas technology. Background Technology

[0002] LNG's main component is methane, with other components including small amounts of ethane, propane, and impurities such as nitrogen. After LNG is refueled, its composition changes due to equipment commissioning and the generation of bound gas (BOG), affecting its density, calorific value, and other properties. Currently, resampling is generally used to determine LNG composition changes, but this is resource-intensive and time-consuming. Furthermore, sampling on board after refueling can easily introduce inert gases from the pipelines, leading to inaccurate test results. Therefore, this invention proposes a method for estimating LNG composition changes, providing a simple and quick way to obtain these changes. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a method for estimating the change in the volume molar ratio of each component of LNG. By estimating the change in the volume molar ratio of each component of LNG based on the consumption of NG and LNG, a low-cost, accurate, and efficient estimation method is achieved.

[0004] The technical solution of this invention is: a method for estimating the change in the volume molar ratio of each component of LNG, the method comprising:

[0005] Step 1: Obtain the initial components for LNG bunkering from the LNG supplier, where the volume molar ratio of component i is denoted as X. i0 LNG is composed of methane and non-methane components.

[0006] Step 2: Obtain the initial LNG volume V from the telemetry system of the gas processing system. LNG0 With liquid phase temperature T LNG0 The initial density of LNG was calculated according to the method recommended by ISO 6578. This allows for the determination of the initial mass of LNG in the fuel tank. ;

[0007] Step 3: Based on the initial volume V of the fuel tank NG NG0 The initial temperature T of NG NG0 The initial pressure P of NG NG0 Using the natural gas equation of state, calculate the total mass of NG, i.e., the initial mass of NG. ;in, The density of methane at room temperature (T) and normal pressure (P);

[0008] Step 4: Based on the initial volume molar ratio X of each component of LNGi0 and molar mass M i Calculate the initial mass ratio of each component. ;

[0009] Step 5: Based on the initial mass m of LNG LNG0 and the initial mass ratio w of each component of LNG i Calculate the initial mass of each component of LNG. ;

[0010] Step 6: Install a mass flow meter on the gas supply pipeline to obtain the mass flow rate (m) of the LNG used during the commissioning process. LNG1 and NG quality m NG1 ;

[0011] Step 7: Based on the NG volume V of the fuel tank in the final state. NG2 Temperature T NG2 Pressure P NG2 Based on the natural gas equation of state and referring to step 3, calculate the final mass m of NG in the fuel tank. NG2 ;

[0012] Step 8: Based on the initial mass ratio w of each component of LNG i The mass m of LNG used during commissioning LNG1 Calculate the mass m consumed by each component of LNG. i1 ;

[0013] The consumption of methane is the sum of the methane mass consumed by LNG, the NG consumption, and the change in NG in the fuel tank. ;

[0014] The consumption of non-methane components is the mass of non-methane components consumed in the LNG portion, i.e. ;

[0015] Step 9: Based on the initial mass m of each component of LNG i0 and the mass m of each component consumed by LNG i1 Calculate the final mass of each component of LNG. ;

[0016] Step 10: Based on the molar mass M of each component of LNG i and final mass m i2 The final volume molar ratio of each component of LNG was obtained. .

[0017] Furthermore, the non-methane components include ethane, propane, and nitrogen.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: the method estimates the change in the volume molar ratio of each component of LNG by measuring the consumption of NG and LNG, avoiding the consumption of a large amount of manpower and material resources, realizing a low-cost production process, and at the same time avoiding interference from other substances in the calculation process, thus achieving efficient and accurate estimation results. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of a method for estimating the volume molar ratio changes of LNG components. Detailed Implementation

[0021] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0024] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0025] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention. The directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0026] For ease of description, spatial relative terms such as "above," "over," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation besides the orientation of the device as described in the figures. For example, if the device in the figures is inverted, a device described as "above" or "above" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0027] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0028] Figure 1A method for estimating the volume molar ratio changes of LNG components, the method comprising:

[0029] Step 1: Obtain the initial components for LNG bunkering from the LNG supplier, where the volume molar ratio of component i is denoted as X. i0 LNG is composed of methane and non-methane components.

[0030] Step 2: Obtain the initial LNG volume V from the telemetry system of the gas processing system. LNG0 With liquid phase temperature T LNG0 The initial density of LNG was calculated according to the method recommended by ISO 6578. This allows for the determination of the initial mass of LNG in the fuel tank. ;

[0031] Step 3: Based on the initial volume V of the fuel tank NG NG0 The initial temperature T of NG NG0 The initial pressure P of NG NG0 Using the natural gas equation of state, calculate the total mass of NG, i.e., the initial mass of NG. ;in, The density of methane at room temperature (T) and normal pressure (P);

[0032] Step 4: Based on the initial volume molar ratio X of each component of LNG i0 and molar mass M i Calculate the initial mass ratio of each component. ;

[0033] Step 5: Based on the initial mass m of LNG LNG0 and the initial mass ratio w of each component of LNG i Calculate the initial mass of each component of LNG. ;

[0034] Step 6: Install a mass flow meter on the gas supply pipeline to obtain the mass flow rate (m) of the LNG used during the commissioning process. LNG1 and NG quality m NG1 ;

[0035] Step 7: Based on the NG volume V of the fuel tank in the final state. NG2 Temperature T NG2 Pressure P NG2 Based on the natural gas equation of state and referring to step 3, calculate the final mass m of NG in the fuel tank. NG2 ;

[0036] Step 8: Based on the initial mass ratio w of each component of LNG i The mass m of LNG used during commissioning LNG1Calculate the mass m consumed by each component of LNG. i1 ;

[0037] The consumption of methane is the sum of the methane mass consumed by LNG, the NG consumption, and the change in NG in the fuel tank. ;

[0038] The consumption of non-methane components is the mass of non-methane components consumed in the LNG portion, i.e. ;

[0039] Step 9: Based on the initial mass m of each component of LNG i0 and the mass m of each component consumed by LNG i1 Calculate the final mass of each component of LNG. ;

[0040] Step 10: Based on the molar mass M of each component of LNG i and final mass m i2 The final volume molar ratio of each component of LNG was obtained. .

[0041] The non-methane components include ethane, propane, and nitrogen.

[0042] The specific calculation method is as follows:

[0043] When substance i is methane:

[0044] After composition change, methane mass = initial methane mass - methane mass consumed by LNG - BOG amount.

[0045] BOG quantity = NG consumption + NG change in fuel tank;

[0046] When substance i is of other components:

[0047] The mass of other components after the composition change = the initial mass of other components - the mass of other components consumed by LNG.

[0048] This can be expressed as a formula:

[0049]

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for estimating the change in the volume molar ratio of each component in LNG, characterized in that, The method includes: Step 1: Obtain the initial components for LNG bunkering from the LNG supplier, where the volume molar ratio of component i is denoted as X. i0 LNG is composed of methane and non-methane components. Step 2: Obtain the initial LNG volume V from the telemetry system of the gas processing system. LNG0 With liquid phase temperature T LNG0 The initial density of LNG was calculated according to the method recommended by ISO 6578. This allows for the determination of the initial mass of LNG in the fuel tank. ; Step 3: Based on the initial volume V of the fuel tank NG NG0 The initial temperature T of NG NG0 The initial pressure P of NG NG0 By combining the natural gas equation of state, the total mass of NG is calculated; That is, the initial mass of NG. ; in, The density of methane at room temperature (T) and normal pressure (P); Step 4: Based on the initial volume molar ratio X of each component of LNG i0 and molar mass M i Calculate the initial mass ratio of each component. ; Step 5: Based on the initial mass m of LNG LNG0 and the initial mass ratio w of each component of LNG i Calculate the initial mass of each component of LNG. ; Step 6: Install a mass flow meter on the gas supply pipeline to obtain the mass flow rate (m) of the LNG used during the commissioning process. LNG1 and NG quality m NG1 ; Step 7: Based on the NG volume V of the fuel tank in the final state. NG2 Temperature T NG2 Pressure P NG2 Using the natural gas equation of state, calculate the final mass m of NG in the fuel tank. NG2 ; Step 8: Based on the initial mass ratio w of each component of LNG i The mass m of LNG used during commissioning LNG1 Calculate the mass m consumed by each component of LNG. i1 ; The consumption of methane is the sum of the methane mass consumed by LNG, the NG consumption, and the change in NG in the fuel tank. ; The consumption of non-methane components is the mass of non-methane components consumed in the LNG portion, i.e. ; Step 9: Based on the initial mass m of each component of LNG i0 and the mass m of each component consumed by LNG i1 Calculate the final mass of each component of LNG. ; Step 10: Based on the molar mass M of each component of LNG i and final mass m i2 The final volume molar ratio of each component of LNG was obtained. .

2. The method for estimating the volume molar ratio changes of LNG components according to claim 1, characterized in that, The non-methane components include ethane, propane, and nitrogen.

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