Gas hydrocarbon molecular weight and net heat value detection system

Abstract

The utility model belongs to the technical field of ultrasonic flow meters, and particularly relates to a gas hydrocarbon molecular weight and net heat value detection system which comprises a mobile terminal, an ultrasonic flow meter, a data acquisition module, a temperature sensor, a pressure sensor and an ultrasonic transducer. The data acquisition module is respectively connected with the ultrasonic flowmeter, the temperature sensor, the pressure sensor and the ultrasonic transducer; and the data acquisition module is integrated in the ultrasonic flowmeter. The utility model has the advantages that the hydrocarbon molecular weight in the natural gas is measured and estimated by using the detection system taking the flowmeter, the thermometer, the pressure gauge and the transducer as core function units, the net heat value of the gas is further calculated, and the hydrocarbon molecular weight is quickly measured and calculated through the sound velocity, the temperature and the pressure of the natural gas; hydrocarbon molecular weight and net heat value data of the gas are rapidly obtained; the detection system is wide in application range, and installation cost and time can be saved.

Description

Technical Field

[0001] This utility model belongs to the field of ultrasonic flow meter technology, and in particular relates to a gas hydrocarbon molecular weight and net calorific value detection system. Background Technology

[0002] Currently, natural gas trade settlement primarily uses volumetric measurement, meaning settlement is based on the volume of natural gas. However, this method has limitations. It doesn't reflect the true value of natural gas, as the energy content can vary significantly depending on the origin and composition of the gas. Furthermore, the volume of natural gas changes with temperature and pressure. Under different temperature and pressure conditions, the energy content represented by the same volume of natural gas will also differ. Therefore, using energy-based measurement for natural gas is more conducive to fair trade.

[0003] Natural gas is primarily composed of methane, with small amounts of ethane, propane, butane, and other hydrocarbons. Net Heating Value (NHV) is a key indicator of fuel quality, focusing on the heat released when water vapor exists in a liquid state after combustion. Compared to Higher Heating Value (HHV), which assumes all water vapor in the combustion products exists in a gaseous state, HHV calculates the heat released. For example, with hydrocarbon fuels, the water vapor generated during combustion releases latent heat of vaporization when it changes from a gaseous to a liquid state. NHV calculations subtract this latent heat of vaporization, providing a more accurate reflection of the actual usable heat of the fuel.

[0004] Currently, natural gas energy measurement is divided into direct measurement methods and indirect measurement methods. Indirect measurement methods involve natural gas component analysis, which relies on chromatographs to determine the content ratio of each component. This method has high accuracy, but the equipment is expensive and requires regular maintenance. Direct measurement methods directly measure the heat released by the combustion of natural gas, but this places high demands on the combustion equipment involved.

[0005] According to the formula for calculating the speed of sound It is known that the speed of sound c of a real gas is affected by the gas molar mass M and the gas temperature and pressure. However, since the volume fraction of the mixed gas is unknown, conventional methods cannot obtain the molecular weight information of the mixed gas. Utility Model Content

[0006] The purpose of this invention is to provide a system for detecting the hydrocarbon molecular weight and net calorific value of gases, overcoming the shortcomings of existing technologies. This system uses a detection system with a flow meter, thermometer, pressure gauge, and transducer as core functional units to measure and estimate the hydrocarbon molecular weight in natural gas, and further calculates the net calorific value of the gas. By rapidly measuring the hydrocarbon molecular weight using the sound velocity, temperature, and pressure of natural gas, it provides testing personnel with effective and rapid reference data, helping them to quickly conduct tests and promptly identify problems.

[0007] To achieve the above objectives, this utility model provides the following technical solution:

[0008] A system for detecting the hydrocarbon molecular weight and net calorific value of a gas includes a mobile terminal, an ultrasonic flow meter, a data acquisition module, a temperature sensor, a pressure sensor, and an ultrasonic transducer. The mobile terminal is connected to the data acquisition module via Bluetooth or a digital interface. The data acquisition module is connected to the ultrasonic flow meter, the temperature sensor, the pressure sensor, and the ultrasonic transducer, respectively. The data acquisition module is integrated into the ultrasonic flow meter.

[0009] Furthermore, the ultrasonic transducer is housed within a box, the top and left and right sides of which are covered with stainless steel protective shells, and the bottom of the box is equipped with a high-strength magnet for rapid adsorption to the carbon steel natural gas pipeline; the temperature sensor and pressure sensor are both installed inside the natural gas pipeline.

[0010] Furthermore, the mobile terminal is an Android phone.

[0011] Furthermore, the ultrasonic flow meter is model MT1600CL.

[0012] Furthermore, the temperature sensor is model MT1600CL-T; the pressure sensor is model MT1600CL-P; and the ultrasonic transducer is model MT1600CL-H.

[0013] Compared with the prior art, the beneficial effects of this utility model are:

[0014] 1) By using a detection system with flow meter, thermometer, pressure gauge and transducer as core functional units, the molecular weight of hydrocarbons in natural gas is measured and estimated, and the net calorific value of the gas is further calculated. The molecular weight of hydrocarbons is quickly calculated by measuring the sound velocity, temperature and pressure of natural gas, and the molecular weight and net calorific value of the gas are quickly obtained.

[0015] 2) The detection system has a simple structure, is easy and reliable to install, and has a wide range of applications. It can greatly shorten the installation time and improve the testing efficiency, realize flexible process monitoring and quality control, and save a lot of testing costs, which is conducive to saving installation costs and time.

[0016] 3) Compared with traditional measurement methods, this method reduces the cost of equipment use, installation time and maintenance difficulty, enables effective and rapid online monitoring, provides testers with effective and fast reference data, provides strong support for real-time control and optimization in industrial production processes, and helps testers to quickly conduct tests and identify problems in a timely manner.

[0017] 4) The detection system and calculation method have high applicability and can meet the testing requirements under different conditions. They are mainly applicable to natural gas, liquefied gas, etc. Attached Figure Description

[0018] Figure 1 This is a schematic block diagram of an embodiment of the gas hydrocarbon molecular weight and net calorific value detection system of this utility model;

[0019] Figure 2 This is a schematic diagram of the external structure of an embodiment of a gas hydrocarbon molecular weight and net calorific value detection system according to this utility model;

[0020] Figure 3 This is a schematic diagram of the working state of an embodiment of the gas hydrocarbon molecular weight and net calorific value detection system of this utility model;

[0021] Figure 4 This is a flowchart of the calculation method of an embodiment of this utility model.

[0022] In the diagram: 1-High-strength magnet, 2-Stainless steel protective shell, 3-Ultrasonic flow meter, 4-Carbon steel medium pipeline, 5-Box body. Detailed Implementation

[0023] The technical solution of this utility model will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are some embodiments of this utility model, but not all embodiments.

[0024] To more clearly illustrate the specific embodiments of this utility model or the technical solutions in the prior art, the specific embodiments used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the specific embodiments described below are some embodiments of this utility model. For those skilled in the art, other specific embodiments can be obtained based on these specific embodiments without creative effort.

[0025] The components of the present invention described and shown in the specific embodiments herein can be arranged and designed in numerous different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the specific embodiments is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention.

[0026] like Figure 1-3 The diagram shows a schematic of a gas hydrocarbon molecular weight and net calorific value detection system, which includes a mobile terminal, an ultrasonic flow meter, a data acquisition module, a temperature sensor, a pressure sensor, and an ultrasonic transducer. The mobile terminal is connected to the data acquisition module via Bluetooth or a digital interface. The data acquisition module is connected to the ultrasonic flow meter, the temperature sensor, the pressure sensor, and the ultrasonic transducer, respectively. The data acquisition module is integrated into the ultrasonic flow meter 3.

[0027] The ultrasonic transducer is installed inside the housing 5. The top, left and right sides, and front and back sides of the housing 5 are all covered with stainless steel protective shells 2. The bottom of the housing 5 is equipped with a high-strength magnet 1 for rapid adsorption to the carbon steel natural gas pipeline 4. The temperature sensor and pressure sensor are both installed in the carbon steel natural gas pipeline 4.

[0028] In this embodiment, the mobile terminal is an Android phone, whose functions include calculating hydrocarbon molecular weight and net calorific value, and displaying or setting flow meter-related parameters. It can display parameters such as standard volumetric flow rate, operating volumetric flow rate, standard mass flow rate, operating mass flow rate, temperature, and pressure. It can also set parameters such as pipe diameter, wall thickness, pipe material, transducer frequency, and measurement method. The ultrasonic flow meter 3 is model MT1600CL. The temperature sensor is model MT1600CL-T, used to acquire pipe temperature; the pressure sensor is model MT1600CL-P, used to acquire pipe pressure; and the ultrasonic transducer is model MT1600CL-H, used to send and receive ultrasonic signals. Data acquisition module.

[0029] See Figure 4 This invention discloses a calculation method for a gas hydrocarbon molecular weight and net calorific value detection system. The method involves determining the range of hydrocarbon molecular weight using linear programming, calculating the hydrocarbon molecular weight using historical methane content data from the gas field for compensation, and finally calculating the net calorific value of the natural gas using the corresponding hydrocarbon content information after compensation. The specific calculation steps are as follows:

[0030] 1) Obtain the natural gas sound velocity, temperature, and pressure under the current environment; compensate for the sound velocity using temperature and pressure; as shown by the sound velocity formula, temperature and pressure affect the sound velocity. To eliminate the influence of temperature and pressure, the sound velocity needs to be compensated, converting the sound velocity under all operating conditions to the sound velocity under standard conditions (temperature 0℃, pressure 1 standard atmosphere). The compensation formula is as follows:

[0031]

[0032] Where Z is the compressibility factor, which can be obtained by looking up the natural gas compressibility factor table based on temperature and pressure, and T′ is the temperature in Celsius.

[0033] 2) Establish a linear programming model based on the speed of sound and the characteristics of natural gas; the formula for the linear programming model is:

[0034]

[0035] The formula is called the feasible solution of the linear programming, and the feasible solution that makes the objective function (1) reach the maximum or minimum value is called the optimal solution;

[0036] 3) Model Establishment: Based on existing data, the minimum methane content in natural gas is 61%. Therefore, the molecular weight model for the hydrocarbons of natural gas is as follows:

[0037] y = 16x1 + 30x2 + 44x3 + 58x4

[0038]

[0039] The model is used to obtain the maximum and minimum values ​​of hydrocarbon molecular weight at a certain sound speed; where x1 to x4 are the contents of methane, ethane, propane, and butane, c is the compensated sound speed, and y is the hydrocarbon molecular weight of the natural gas to be determined.

[0040] 4) Result Compensation: The obtained hydrocarbon molecular weights are compensated based on historical data. Through iteration, the maximum and minimum values ​​of the hydrocarbon molecular weights, as well as the corresponding content of each component, can be determined. The range of model parameters can be appropriately narrowed based on past field data. Finally, to obtain more accurate results, result compensation is required. The result compensation formula is as follows:

[0041]

[0042] Where y max y represents the maximum molecular weight of hydrocarbons. min x represents the minimum molecular weight of hydrocarbons. 1max x 1min The methane content corresponds to the maximum and minimum molecular weights of hydrocarbons; k is the compensation coefficient; m is the historical data of the methane content of the natural gas in the pipeline, or 0 if not available.

[0043] 5) Net calorific value calculation: The final net calorific value of natural gas is estimated by averaging the range of net calorific value values. In natural gas energy metering, the lower heating value is generally used because in actual applications, the exhaust gas after combustion is usually discharged at a higher temperature, and water exists in gaseous form.

[0044] The volumetric flow rate and hydrocarbon molecular weight obtained from the flow meter are combined for calculation, and finally the net calorific value of the gas is estimated. The specific steps are as follows:

[0045] 1) The volume fractions of hydrocarbons in natural gas have been obtained by the above method and are x1, x2, x3, and x4, respectively;

[0046] 2) Under standard conditions, the formula for calculating the net calorific value of natural gas is (unit: kJ / m³). 3 ):

[0047] Q = q1x1 + q2x2 + q3x3 + q4x4

[0048] Where q1 to q4 are the net calorific values ​​of methane, ethane, propane, and butane;

[0049] 3) The maximum and minimum net calorific value of natural gas are obtained by calculating the hydrocarbon content corresponding to the maximum and minimum molecular weights of hydrocarbons. Then, the final net calorific value is estimated using the arithmetic mean method, as shown in the following formula:

[0050]

[0051] Since the composition of natural gas produced from different gas fields varies slightly, but the majority of the gas is methane, assuming that the quantity and type of gas components are known but the content of each component is unknown, we first use an ultrasonic flow meter 3 and a temperature and pressure sensor to accurately measure the sound velocity, temperature, and pressure of the natural gas. Then, we substitute the sound velocity after temperature and pressure compensation into a linear programming model to calculate the range of hydrocarbon molecular weight values. Finally, we use the historical data of the methane content of the gas field to perform relevant compensation and obtain the hydrocarbon molecular weight. Finally, we calculate the net calorific value of the natural gas using the corresponding hydrocarbon content information after compensation.

[0052] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A system for detecting the hydrocarbon molecular weight and net calorific value of a gas, characterized in that, The device includes a mobile terminal, an ultrasonic flow meter, a data acquisition module, a temperature sensor, a pressure sensor, and an ultrasonic transducer. The mobile terminal and the data acquisition module are connected via Bluetooth or a digital interface. The data acquisition module is connected to the ultrasonic flow meter, the temperature sensor, the pressure sensor, and the ultrasonic transducer, respectively. The data acquisition module is integrated into the ultrasonic flow meter.

2. The gas hydrocarbon molecular weight and net calorific value detection system according to claim 1, characterized in that, The ultrasonic transducer is housed inside a box, the top and left and right sides of which are covered with stainless steel protective shells. The bottom of the box is equipped with a high-strength magnet for rapid adsorption to the carbon steel natural gas pipeline. The temperature sensor and pressure sensor are both installed inside the natural gas pipeline.

3. The gas hydrocarbon molecular weight and net calorific value detection system according to claim 1, characterized in that, The mobile terminal is an Android phone.

4. The gas hydrocarbon molecular weight and net calorific value detection system according to claim 1, characterized in that, The ultrasonic flow meter is model MT1600CL.

5. The gas hydrocarbon molecular weight and net calorific value detection system according to claim 1, characterized in that, The temperature sensor is model MT1600CL-T; the pressure sensor is model MT1600CL-P; and the ultrasonic transducer is model MT1600CL-H.

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